Note: Descriptions are shown in the official language in which they were submitted.
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1
Process for Upgrading a Carbonaceous Material Using
Microchannel Process Technology
Technical Field
This invention relates to a process for upgrading carbonaceous materials using
microchannel process technology. The process may be used to convert a
carbonaceous
material (e.g., biomass, solid waste, etc.) to one or more hydrocarbons or
alcohols. The
hydrocarbons and alcohols may be used as synthetic fuels.
Background
The U.S. military uses billions of gallons of petroleum-based fuels every
year.
Transporting these fuels to remote military bases is costly and time
consuming, and the
fuel is often a prime target for terrorists. The problem, therefore, is to
provide cheaper and
more secure sources of fuel.
Summary
This invention provides a solution to this problem. The present invention
relates to
a process for converting carbonaceous materials such as biomass, solid-waste,
and the
like, to hydrocarbons and alcohols that may be used as synthetic fuel (e.g.,
automotive
fuel, diesel fuel, aviation fuel, etc.). The inventive process employs the use
of
microchannel reactors which are compact and readily transportable. As such,
the inventive
process may be adapted for use in apparatus that can be readily transported to
remote
locations, such as military bases, and the like. With the inventive process it
is possible to
convert waste products generated at such military bases into fuels such as
automotive
fuel, diesel fuel, aviation fuel, and the like. For example, the inventive
process may be
adapted to produce from about 50 to about 500 barrels per day of synthetic
fuel at such a
base. The inventive process may also be adaptable for use with larger scale
operations
wherein carbonaceous material sources such as municipal solid waste are
converted to
useful products such as synthetic fuel.
2
In an aspect, there is provided a process for converting a carbonaceous
material
to a Fischer-Tropsch product, the carbonaceous material comprising an organic
material and Water and being selected from biomass and organic waste material,
the
process comprising: removing some or all of the water from the carbonaceous
material; (A) gasifying the carbonaceous material in a gasifier at a
temperature of at
least 700 C to form synthesis gas, the synthesis gas comprising CO, H2, water
and
particulate solids, and contaminants; the contaminants being selected from
sulfur,
halogen, selenium, phosphorus, arsenic, or a mixture of two or more thereof;
flowing
the synthesis gas out of the gasifier and reducing the temperature of the
synthesis gas
.. flowing out of the gasifier; flowing the synthesis gas through a scrubber
to separate
the contaminants from the synthesis gas, the contaminant level being reduced
to a
level of up to 5% by volume; separating the particulate solids from the
synthesis gas;
flowing the synthesis gas through a condenser to separate water from the
synthesis
gas; flowing the synthesis gas out of the condenser and compressing the
synthesis
.. gas flowing out of the condenser; adding H2 to the synthesis gas to form an
upgraded
synthesis gas with a molar ratio of H2 to CO in the range from 1.5 to 2.5; and
(B) converting the upgraded synthesis gas to the Fischer-Tropsch product in a
microchannel reactor, the microchannel reactor comprising a plurality of
process
microchannels and a plurality of heat exchange channels, the process
microchannels
containing a Fischer-Tropsch catalyst, the Fischer-Tropsch catalyst comprising
a fixed
bed of particulate catalytic solids, the upgraded synthesis gas being
converted to the
Fischer-Tropsch product by flowing the upgraded synthesis gas in the process
microchannels in contact with the Fischer-Tropsch catalyst to form the Fischer-
Tropsch product; and flowing a heat exchange fluid in the heat exchange
channels,
and transferring heat from the process microchannels to the heat exchange
channels.
The products have various uses including use as synthetic fuels.
Brief Description of the Drawings
In the annexed drawings like parts and features have like references. A number
of
the drawings are schematic illustrations which may not necessarily be drawn to
scale.
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2a
Fig. 1 is a flow sheet illustrating the inventive process in a particular
form, the
process comprising converting a carbonaceous material to one or more
hydrocarbons or
one or more alcohols using a gasifier in combination with a Fischer-Tropsch
(FT) or
alcohol-forming microchannel reactor. The carbonaceous material is converted
to synthesis
gas in the gasifier. The synthesis gas is converted to one or more
hydrocarbons or alcohols
in the microchannel reactor.
Fig. 2 is a flow sheet of a process that is the same as the process
illustrated in
Fig. 1 with the exception that steam, which is used as a heat exchange fluid
in the
microchannel reactor, is also used as a gasification agent in the gasifier.
Fig. 3 is a flow sheet of a process that is the same as the process
illustrated in
Fig. 1 with the exception that the process includes the use of a nitrogen
separator
upstream of the gasifier. Nitrogen is separated from air in the nitrogen
separator. The
remaining oxygen is used as the gasification agent in the gasifier.
Fig. 4 is a flow sheet of a process that is the same as the process
illustrated in
Fig. 1 with the exception that the process illustrated in Fig. 4 employs the
use of a pyrolysis
reactor. The carbonaceous material is converted to pyrolytic oil in the
pyrolysis reactor. The
pyrolytic oil is used as the carbonaceous feed for the gasifier.
Fig. 5 is a flow sheet of a process that is the same as the process
illustrated in
Fig. 4 with the exception that liquid hydrocarbons, such as tar, are separated
from the
synthesis gas flowing out of the gasifier and recycled to the pyrolysis
reactor.
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Fig. 6 is a flow sheet of a process which employs the use of the gasifier and
microchannel reactor illustrated in Fig. 1 in combination with a steam methane
reforming (SMR) microchannel reactor. The SMR microchannel reactor is used to
convert tail gas flowing out of the microchannel reactor to synthesis gas
which is
recycled to the microchannel reactor.
Fig. 7 is a flow sheet of a process that is the same as the process
illustrated
in Fig. 6 with the exception that carbon dioxide is separated from the
synthesis gas
flowing out of the gasifier. The resulting carbon dioxide lean synthesis gas
then
flows into the microchannel reactor.
Fig. 8 is a flow sheet of a process that is the same as the process
illustrated
in Fig. 7 with the exception that the carbon dioxide that is separated from
the
synthesis gas flowing out of the gasifier flows to the SMR microchannel
reactor
where it is combined with tail gas from the microchannel reactor and converted
to
synthesis gas.
Fig. 8A is a flow sheet of a process that is the same as the process
illustrated
in Fig. 1 wherein the microchannel reactor is a Fischer-Tropsch microchannel
reactor except that the product flowing out of the Fischer-Tropsch
microchannel
reactor undergoes a hydrocracking reaction in a hydrocracking microchannel
reactor.
Figs. 9 and 10 are schematic illustrations of a vessel used for housing a
plurality of Fischer-Tropsch or alcohol-forming or microchannel reactors, or a
plurality of SMR microchannel reactors, or a plurality of hydrocracking
microchannel
reactors. In Figs. 9 and 10, five Fischer-Tropsch or alcohol-forming
microchannel
reactors, five SMR microchannel reactors, or five hydrocracking microchannel
reactors are shown.
Figs. 11-14 are schematic illustrations of repeating units that may be used in
the Fischer-Tropsch or alcohol-forming microchannel reactors. Each of the
repeating units illustrated in Figs. 11-14 includes a Fischer-Tropsch or
alcohol-
forming process microchannel that contains a reaction zone containing a
catalyst
and adjacent heat exchange channels. Heat exchange fluid flowing in the heat
exchange channels illustrated in Fig. 11 flows in a direction that is cross-
current
relative to the flow of process fluids in the Fischer-Tropsch or alcohol-
forming
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process microchannel. Heat exchange fluid flowing in the heat exchange channel
illustrated in Fig. 12 may flow in a direction that is co-current or counter-
current to
the flow of process fluid in the Fischer-Tropsch or alcohol-forming process
microchannel. The heat exchange channels illustrated in Figs. 13 and 14
provide for
the flow of heat exchange fluid in a direction that is cross-current relative
to the flow
of process fluid in the Fischer-Tropsch or alcohol-forming process
microchannels.
The heat exchange channels illustrated in Figs. 13 and 14 provide for heat
exchange
zones that cover only part of the length of the reaction zones in the Fischer-
Tropsch
or alcohol-forming process microchannels. Tailored heat exchange profiles may
be
provided with each of these embodiments by controlling the number of heat
exchange channels in thermal contact with different sections of the process
microchannels. With these tailored heat exchange profiles more cooling
channels
may be provided in some parts of the process microchannels as compared to
other
parts of the process microchannels. For example, more cooling channels may be
provided at or near the entrances to the reaction zones as compared to
downstream
parts of the reaction zones. The heat exchange profile may be tailored by
controlling
the flow rate of heat exchange fluid in the heat exchange channels. For
example, a
relatively high rate of flow of heat exchange fluid in the heat exchange
channels in
thermal contact with the entrances to the reaction zones may be used in
combination
with relatively low rates of flow of heat exchange fluid in heat exchange
channels in
thermal contact with downstream sections of the reaction zones.
Figs. 15-20 are schematic illustrations of catalysts or catalyst supports that
may be used in the SMR process microchannels, combustion channels or Fischer-
Tropsch or alcohol-forming process microchannels. The catalyst illustrated in
Fig.
15 is in the form of a bed of particulate solids. The catalyst illustrated in
Fig. 16 has
a flow-by design. The catalyst illustrated in Fig. 17 is a flow-through
structure. Figs.
18-20 are schematic illustrations of fin assemblies that may be used for
supporting
the catalyst.
Figs. 21-25 are schematic illustrations of microchannel repeating units that
may be used in the SMR microchannel reactor. Each of these repeating units
comprises a combustion channel and one or more SMR process microchannels.
The combustion channels illustrated in Figs. 21-25 include staged addition
channels
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for flowing oxygen or a source of oxygen into the combustion channels. Fig. 21
illustrates an upside down U-shaped SMR process microchannel adjacent an M-
shaped combustion channel. Fig. 22 illustrates a single SMR process
microchannel
adjacent an M-shaped combustion channel. Fig. 23 illustrates two SMR process
5
microchannels and an M-shaped combustion channel, one of the SMR process
microchannels being adjacent to the M-shaped combustion channel and the other
SMR process microchannel being adjacent the first-named SMR process
microchannel, both of the SMR process microchannels being in thermal contact
with
the combustion channel. Fig. 24 illustrates a single combustion channel, a
staged
addition channel positioned on one side of the combustion channel and an SMR
process channel positioned on the other side of the combustion channel. Fig.
25
illustrates a repeating unit that is similar to the repeating unit illustrated
in Fig. 24
with the exception that the SMR process microchannel in the repeating unit
illustrated in Fig. 25 is in the shape of an upside down U-shaped
microchannel. In
Figs. 21-25 the channels are illustrated as being spaced from each other for
purposes of clarification, however, in actual practice the channels would be
stacked
on top of each other or positioned side-by-side with no spacing between the
channels. The channels may share common walls at the channel interfaces.
Figs. 26 and 27 are schematic illustrations of surface features that may be
used in the channels employed in the Fischer-Tropsch or alcohol-forming
microchannel reactor and/or in the SMR microchannel reactor used in the
inventive
process.
Fig. 28 is a flow sheet of the process described in Example 1.
Fig. 29 is a schematic illustration of the microchannel reactor described in
Example 2.
Fig. 30 is a schematic illustration of a waveform used to make the
microchannel reactor described in Example 2.
Detailed Description
All ranges and ratio limits disclosed in the specification and claims may be
combined in any manner. It is to be understood that unless specifically stated
otherwise, references to "a," "an," and/or "the" may include one or more than
one,
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and that reference to an item in the singular may also include the item in the
plural.
All combinations specified in the claims may be combined in any manner.
The term "microchannel" may refer to a channel having at least one internal
dimension of height or width of up to about 10 millimeters (mm), and in one
embodiment up to about 5 mm, and in one embodiment up to about 2 mm, and in
one embodiment up to about 1 mm. The microchannel may comprise at least one
inlet and at least one outlet wherein the at least one inlet is distinct from
the at least
one outlet. The microchannel may not be merely an orifice. The microchannel
may
not be merely a channel through a zeolite or a mesoporous material. The length
of
lo the microchannel may be at least about two times the height or width,
and in one
embodiment at least about five times the height or width, and in one
embodiment at
least about ten times the height or width. The internal height or width of the
microchannel may be in the range of about 0.05 to about 10 mm, and in one
embodiment from about 0.05 to about 5 mm, and in one embodiment from about
0.05 to about 2 mm, and in one embodiment from about 0.05 to about 1.5 mm, and
in one embodiment from about 0.05 to about 1 mm, and in one embodiment from
about 0.05 to about 0.75 mm, and in one embodiment from about 0.05 to about
0.5
mm. The other internal dimension of height or width may be of any dimension,
for
example, up to about 3 meters, and in one embodiment about 0.01 to about 3
meters, and in one embodiment about 0.1 to about 3 meters. The length of the
microchannel may be of any dimension, for example, up to about 10 meters, and
in
one embodiment from about 0.1 to about 10 meters, and in one embodiment from
about 0.2 to about 10 meters, and in one embodiment from about 0.2 to about 6
meters, and in one embodiment from 0.2 to about 3 meters. The microchannel may
have a cross section having any shape, for example, a square, rectangle,
circle,
semi-circle, trapezoid, etc. The shape and/or size of the cross section of the
microchannel may vary over its length. For example, the height or width may
taper
from a relatively large dimension to a relatively small dimension, or vice
versa, over
the length of the microchannel.
The term "microchannel reactor" may refer to an apparatus comprising one or
more process microchannels wherein a reaction process is conducted. The
process
may be a Fischer-Tropsch or alcohol-forming reaction process or an SMR
reaction
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process. When two or more process microchannels are used, the process
microchannels may be operated in parallel. The microchannel reactor may
include a
header or manifold assembly for providing for the flow of fluid into the one
or more
process microchannels, and a footer or manifold assembly providing for the
flow of
fluid out of the one or more process microchannels. The microchannel reactor
may
comprise one or more heat exchange channels adjacent to and/or in thermal
contact
with the one or more process microchannels. The heat exchange channels provide
heating and/or cooling for the fluids in the process microchannels. When used
in the
SMR microchannel reactor, the heat exchange channels may be combustion
channels. The heat exchange channels and/or combustion channels may be
microchannels. The microchannel reactor may include a header or manifold
assembly for providing for the flow of heat exchange fluid into the heat
exchange
channels, and a footer or manifold assembly providing for the flow of heat
exchange
fluid out of the heat exchange channels.
The term "process microchannel" may refer to a microchannel wherein a
process is conducted. The process may relate to conducting a Fischer-Tropsch
(FT)
or alcohol-forming reaction or an SMR reaction.
The term "volume" with respect to volume within a process microchannel may
include all volume in the process microchannel a process fluid may flow
through or
flow by. This volume may include volume within surface features that may be
positioned in the process microchannel and adapted for the flow of fluid in a
flow-
through manner or in a flow-by manner.
The term "adjacent" when referring to the position of one channel relative to
the position of another channel may mean directly adjacent such that a wall or
walls
separate the two channels. In one embodiment, the two channels may have a
common wall. The common wall may vary in thickness. However, "adjacent"
channels may not be separated by an intervening channel that may interfere
with
heat transfer between the channels. One channel may be adjacent to another
channel over only part of the dimension of the another channel. For example, a
process microchannel may be longer than and extend beyond one or more adjacent
heat exchange channels.
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The term "thermal contact" may refer to two bodies, for example, two
channels, that may or may not be in physical contact with each other or
adjacent to
each other but still exchange heat with each other. One body in thermal
contact with
another body may heat or cool the other body.
The term "fluid" may refer to a gas, a liquid, a mixture of a gas and a
liquid, or
a gas or a liquid containing dispersed solids, liquid droplets and/or gaseous
bubbles.
The droplets and/or bubbles may be irregularly or regularly shaped and may be
of
similar or different sizes.
The terms "gas" and "vapor" may have the same meaning and are sometimes
.. used interchangeably.
The term "residence time" or "average residence time" may refer to the
internal volume of a space within a channel occupied by a fluid flowing in the
space
divided by the average volumetric flow rate for the fluid flowing in the space
at the
temperature and pressure being used.
The terms "upstream" and "downstream" may refer to positions within a
channel (e.g., a process microchannel) or in a process flow sheet that is
relative to
the direction of flow of a fluid in the channel or process flow sheet. For
example, a
position within a channel or process flow sheet not yet reached by a portion
of a fluid
stream flowing toward that position would be downstream of that portion of the
fluid
stream. A position within the channel or process flow sheet already passed by
a
portion of a fluid stream flowing away from that position would be upstream of
that
portion of the fluid stream. The terms "upstream" and "downstream" do not
necessarily refer to a vertical position since the channels used herein may be
oriented horizontally, vertically or at an inclined angle.
The term "shim" may refer to a planar or substantially planar sheet or plate.
The thickness of the shim may be the smallest dimension of the shim and may be
up
to about 4 mm, and in one embodiment in the range from about 0.05 to about 2
mm,
and in one embodiment in the range of about 0.05 to about 1 mm, and in one
embodiment in the range from about 0.05 to about 0.5 mm. The shim may have any
length and width.
The term "surface feature" may refer to a depression in a channel wall and/or
a projection from a channel wall that disrupts flow within the channel.
Examples of
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surface feature designs that may be used are illustrated in Figs. 26 and 27.
The
surface features may be in the form of circles, spheres, frustrums, oblongs,
squares,
rectangles, angled rectangles, checks, chevrons, vanes, airfoils, wavy shapes,
and
the like, and combinations of two or more thereof. The surface features may
contain
subfeatures where the major walls of the surface features further contain
smaller
surface features that may take the form of notches, waves, indents, holes,
burrs,
checks, scallops, and the like. The surface features may have a depth, a
width, and
for non-circular surface features a length. The surface features may be formed
on or
in one or more of the interior walls of the process microchannels, heat
exchange
channels and/or combustion channels used in accordance with the disclosed
process. The surface features may be referred to as passive surface features
or
passive mixing features. The surface features may be used to disrupt flow (for
example, disrupt laminar flow streamlines) and create advective flow at an
angle to
the bulk flow direction.
The term "heat exchange channel" may refer to a channel having a heat
exchange fluid in it that provides heat and/or absorbs heat. The heat exchange
channel may absorb heat from or provide heat to an adjacent channel (e.g.,
process
microchannel) and/or one or more channels in thermal contact with the heat
exchange channel. The heat exchange channel may absorb heat from or provide
heat to channels that are adjacent to each other but not adjacent to the heat
exchange channel. In one embodiment, one, two, three or more channels may be
adjacent to each other and positioned between two heat exchange channels.
The term "heat transfer wall" may refer to a common wall between a process
microchannel and an adjacent heat exchange channel where heat transfers from
one channel to the other through the common wall.
The term "heat exchange fluid" may refer to a fluid that may give off heat
and/or absorb heat.
The term "waveform" may refer to a contiguous piece of thermally conductive
material that is transformed from a planar object to a three-dimensional
object. The
waveform may be used to form one or more microchannels. The waveform may
comprise a right angled corrugated insert which may be sandwiched between
opposed planar sheets or shims. The right angled corrugated insert may have
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rounded edges. In this manner one or more microchannels may be defined on
three
sides by the waveform and on the fourth side by one of the planar sheets or
shims.
The waveform may be made of any of the thermally conductive materials
disclosed
herein as being useful for making the microchannel reactor. These may include
5 copper, aluminum, stainless steel, and the like. The thermal conductivity
of the
waveform may be about 1 W/m-K or higher.
The term "bulk flow direction" may refer to the vector through which fluid may
travel in an open path in a channel.
The term "bulk flow region" may refer to open areas within a microchannel. A
10 contiguous bulk flow region may allow rapid fluid flow through a
microchannel
without significant pressure drops. In one embodiment, the flow in the bulk
flow
region may be laminar. A bulk flow region may comprise at least about 5% of
the
internal volume and/or cross-sectional area of a microchannel, and in one
embodiment from about 5% to about 100%, and in one embodiment from about 5%
to about 99%, and in one embodiment about 5% to about 95%, and in one
embodiment from about 5% to about 90%, and in one embodiment from about 30%
to about 80% of the internal volume and/or cross-sectional area of the
microchannel.
The terms "open channel" or "flow-by channel" or "open path" may refer to a
channel (e.g., a microchannel) with a gap of at least about 0.01 mm that
extends all
the way through the channel such that fluid may flow through the channel
without
encountering a barrier to flow. The gap may extend up to about 10 mm.
The term "cross-sectional area" of a channel (e.g., process microchannel)
may refer to an area measured perpendicular to the direction of the bulk flow
of fluid
in the channel and may include all areas within the channel including any
surface
features that may be present, but does not include the channel walls. For
channels
that curve along their length, the cross-sectional area may be measured
perpendicular to the direction of bulk flow at a selected point along a line
that
parallels the length and is at the center (by area) of the channel. Dimensions
of
height and width may be measured from one channel wall to the opposite channel
wall. These dimensions may not be changed by application of a coating to the
surface of the wall. These dimensions may be average values that account for
variations caused by surface features, surface roughness, and the like.
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The term "open cross-sectional area" of a channel (e.g., process
microchannel) may refer to an area open for bulk fluid flow in a channel
measured
perpendicular to the direction of the bulk flow of fluid flow in the channel.
The open
cross-sectional area may not include internal obstructions such as surface
features
and the like which may be present.
The term "superficial velocity" for the velocity of a fluid flowing in a
channel
may refer to the velocity resulting from dividing the volumetric flow rate of
the fluid at
the inlet temperature and pressure of the channel divided by the cross-
sectional area
of the channel.
The term "free stream velocity" may refer to the velocity of a stream flowing
in
a channel at a sufficient distance from the sidewall of the channel such that
the
velocity is at a maximum value. The velocity of a stream flowing in a channel
is zero
at the sidewall if a no slip boundary condition is applicable, but increases
as the
distance from the sidewall increases until a constant value is achieved. This
.. constant value is the "free stream velocity."
The term "process fluid" may be used herein to refer to reactants, product and
any diluent or other fluid that may flow in a process microchannel.
The term "reaction zone" may refer to the space within a microchannel
wherein a chemical reaction occurs or wherein a chemical conversion of at
least one
species occurs. The reaction zone may contain one or more catalysts.
The term "yield" may refer to the number of moles of product exiting a
microchannel reactor divided by the number of moles of a reactant entering the
microchannel reactor.
The term "cycle" may refer to a single pass of the reactants through a
.. microchannel reactor.
The term "graded catalyst" may refer to a catalyst with one or more gradients
of catalytic activity. The graded catalyst may have a varying concentration or
surface area of a catalytically active metal. The graded catalyst may have a
varying
turnover rate of catalytically active sites. The graded catalyst may have
physical
properties and/or a form that varies as a function of distance. For example,
the
graded catalyst may have an active metal concentration that is relatively low
at the
entrance to a process microchannel and increases to a higher concentration
near
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the exit of the process microchannel, or vice versa; or a lower concentration
of
catalytically active metal nearer the center (i.e., midpoint) of a process
microchannel
and a higher concentration nearer a process microchannel wall, or vice versa,
etc.
The thermal conductivity of a graded catalyst may vary from one location to
another
within a process microchannel. The surface area of a graded catalyst may be
varied
by varying size of catalytically active metal sites on a constant surface area
support,
or by varying the surface area of the support such as by varying support type
or
particle size. A graded catalyst may have a porous support where the surface
area
to volume ratio of the support is higher or lower in different parts of the
process
microchannel followed by the application of the same catalyst coating
everywhere.
A combination of two or more of the preceding embodiments may be used. The
graded catalyst may have a single catalytic component or multiple catalytic
components (for example, a bimetallic or trimetallic catalyst). The graded
catalyst
may change its properties and/or composition gradually as a function of
distance
from one location to another within a process microchannel. The graded
catalyst
may comprise rimmed particles that have "eggshell" distributions of
catalytically
active metal within each particle. The graded catalyst may be graded in the
axial
direction along the length of a process microchannel or in the lateral
direction. The
graded catalyst may have different catalyst compositions, different loadings
and/or
numbers of active catalytic sites that may vary from one position to another
position
within a process microchannel. The number of catalytically active sites may be
changed by altering the porosity of the catalyst structure. This may be
accomplished
using a washcoating process that deposits varying amounts of catalytic
material. An
example may be the use of different porous catalyst thicknesses along the
process
microchannel length, whereby a thicker porous structure may be left where more
activity is required. A change in porosity for a fixed or variable porous
catalyst
thickness may also be used. A first pore size may be used adjacent to an open
area
or gap for flow and at least one second pore size may be used adjacent to the
process microchannel wall.
The term "biomass" may refer to living and recently dead biological material
that can be used as fuel. The term biomass may refer to plant matter grown for
use
as biofuel. The term biomass may include plant or animal matter used for
production
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of fibers, chemicals or heat. Biomass may include biodegradable wastes that
can be
burnt as fuel. Biomass may comprise plants such as switchgrass, hemp, corn,
poplar, willow, sugarcane, oil palm, and the like.
The term "char" may refer to a solid material that remains after gases have
been driven out or released from a carbonaceous material. Char may be formed
during the combustion of a carbonaceous material.
The term "tar" may refer to a viscous black liquid derived from the
destructive
distillation of a carbonaceous material.
The term "ash" may refer to the. solid residue that remains after a
carbonaceous material is burned.
The term "chain growth" may refer to the growth in a molecule resulting from a
reaction in which the molecule grows with the addition of new molecular
structures
(e.g., the addition of methylene groups to a hydrocarbon chain in a Fischer-
Tropsch
synthesis).
The term "hydrocarbon" may refer to purely hydrocarbon compounds; that is,
aliphatic compounds, (e.g., alkane, alkene or alkyne), alicyclic compounds
(e.g.,
cycloalkane, cycloalkylene), aromatic compounds, aliphatic- and alicyclic-
substituted
aromatic compounds, aromatic-substituted aliphatic compounds, aromatic-
substituted alicyclic compounds, and the like. Examples may include methane,
ethane, propane, cyclohexane, ethyl cyclohexane, toluene, ethyl benzene, etc.
The
term "hydrocarbon" may refer to substituted hydrocarbon compounds; that is,
hydrocarbon compounds containing non-hydrocarbon substituents. Examples of the
non-hydrocarbon substituents may include hydroxyl, acyl, nitro, etc. The term
"hydrocarbon" may refer to hetero substituted hydrocarbon compounds; that is,
hydrocarbon compounds which contain atoms other than carbon in a chain or ring
otherwise containing carbon atoms. The hetero atoms may include, for example,
nitrogen, oxygen, sulfur, and the like. The hydrocarbon compound may comprise
about 10 carbon atoms or more for each non-hydrocarbon substituent or hetero
atom.
The term "higher molecular weight hydrocarbon" may refer to a hydrocarbon
having 2 or more carbon atoms, and in one embodiment 3 or more carbon atoms,
and in one embodiment 4 or more carbon atoms, and in one embodiment 5 or more
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carbon atoms, and in one embodiment 6 or more carbon atoms. The higher
molecular weight hydrocarbons may have up to about 100 carbon atoms, and in
one
embodiment up to about 90 carbon atoms, and in one embodiment up to about 80
carbon atoms, and in one embodiment up to about 70 carbon atoms, and in one
embodiment up to about 60 carbon atoms, and in one embodiment up to about 50
carbon atoms, and in one embodiment up to about 40 carbon atoms, and in one
embodiment up to about 30 carbon atoms. The higher molecular weight
hydrocarbons may be aliphatic hydrocarbons. Examples may include ethane,
propane, butane, pentane, hexane, octane, decane, dodecane, and the like.
The term "Fischer-Tropsch" or "FT" may refer to a chemical reaction
represented by the equation:
n CO + 2n H2 ---+ (CHOn + n H20
This reaction is an exothermic reaction which may be conducted in the presence
of a
Fischer-Tropsch catalyst. n may be any number, for example from 1 to about 10,
and in one embodiment from 2 to about 10, and in one embodiment from 2 to
about
8.
The term "Fischer-Tropsch product" or "FT product" may refer to a
hydrocarbon product made by a Fischer-Tropsch process. The FT product may
have a boiling point at or above about 30 C at atmospheric pressure.
The term "FT tail gas" may refer to a gaseous product made by a Fischer-
Tropsch process. The tail gas may have a boiling point below about 30 C at
atmospheric pressure.
The term "alcohol forming reaction" may refer to the synthesis reaction
represented by the equation:
n CO + H2 ---+ CnH2n+1 OH + (n-1) H20
This reaction is an exothermic reaction which may be conducted in the presence
of
an alcohol forming catalyst. n may be any number, for example from 1 to about
10,
and in one embodiment from 2 to about 10, and in one embodiment from 2 to
about
8.
The term "Co loading" may refer to the weight of Co in a catalyst divided by
the total weight of the catalyst, that is, the total weight of the Co plus any
co-catalyst
or promoter as well as any support. If the catalyst is supported on an
engineered
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support structure such as a foam, felt, wad or fin, the weight of such
engineered
support structure may not be included in the calculation. Similarly, if the
catalyst is
adhered to a channel wall, the weight of the channel wall may is not be
included in
the calculation.
5 The term "steam methane reforming" or "SMR" may refer to the reaction:
H20 + CH4 ---* CO + 3 H2
This reaction is endothermic, and may be conducted in the presence of an SMR
catalyst. The product mixture of CO + H2 may be referred to as synthesis gas
or syn
gas. The heat required to effect this reaction may be provided by the
combustion
10 reaction of a mixture of a fuel (e.g., H2) and oxygen or a source of
oxygen (e.g., air
or oxygen enriched air). The combustion reaction is exothermic and may be
conducted in the presence of a combustion catalyst.
The term "hydrocracking process" refers to a process wherein one or more C-
C bonds in a hydrocarbon reactant are ruptured to yield a product comprising
two or
15 more hydrocarbon products having lower molecular weights than the
hydrocarbon
reactant. For example, a C12 alkane may be converted to a C7 alkane and a C5
alkane
The term "mm" may refer to millimeter. The term "nm" may refer to
nanometer. The term "ms" may refer to millisecond. The term "ps" may refer to
microsecond. The term "pm" may refer to micron or micrometer. The terms
"micron"
and "micrometer" have the same meaning and may be used interchangeably.
Unless otherwise indicated, all pressures are expressed in terms of absolute
pressure.
The carbonaceous material that may be used in the inventive process may
comprise any organic or carbon-containing material that can be gasified to
produce
synthesis gas. The carbonaceous material may comprise a food resource such as
corn, soybean, and the like. The carbonaceous material may comprise a non-food
resource. The non-food resource may be referred to as a second generation
biofuel.
The non-food resource may comprise any carbonaceous material not generally
used as a food. The non-food resource may be referred to as a non-food
carbonaceous material. Examples of the non-food carbonaceous materials that
may
be used may comprise coal (e.g., low grade coal, high grade coal, and the
like), oil
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(e.g., crude oil, heavy oil, tar sand oil, and the like), biomass, solid
wastes, or a
mixture of two or more thereof. The non-food carbonaceous material may
comprise
municipal solid waste (MSW), hazardous waste, refuse derived fuel (RDF),
tires,
petroleum coke, trash, garbage, biogas from a digester, sewage sludge, animal
waste (e.g., chicken manure, turkey manure, cow manure, horse manure, as well
as
other animal waste), agricultural waste, corn stover, switch grass, timber,
wood
cuttings, grass clippings, construction demolition materials, plastic
materials (e.g.,
plastic waste), cotton gin waste, landfill gas, natural gas, and the like. The
non-food
carbonaceous material may comprise polyethylene or polyvinyl chloride.
Mixtures of
two or more of any of the foregoing may be used.
The carbonaceous material may be in the form of relatively large solid pieces
and prior to step (A) these relatively large pieces may be shredded into
smaller
pieces using, for example, an auger.
The carbonaceous material may comprise water, and in at least one
embodiment of the invention, it may be advantageous to remove some or all of
the
water prior to the gasification step (A) of the inventive process. This may be
accomplished using conventional drying techniques.
The term "synthesis gas" refers to a gaseous mixture that contains CO and
H2. Synthesis gas is sometimes referred to as syngas. The synthesis gas that
is
formed in the gasification step (A) of the inventive process may comprise a
gaseous
mixture that contains varying amounts of CO and H2. In at least one embodiment
of
the inventive process, it is advantageous to use a synthesis gas during step
(B) with
a molar ratio of H2 to CO that may be in the range from about 0.5 to about 4,
and in
one embodiment in the range from about 1 to about 3, and in one embodiment in
the
range from about 1.5 to about 2.5, and in one embodiment in the range from
about
1.8 to about 2.2. If the amount of H2 produced during step (A) is not
sufficient to
provide for the H2 to CO ratio specified above, additional amounts of H2 may
be
added to the synthesis gas prior to step (B) of the inventive process. The
synthesis
gas may also contain varying amounts of CO2 and water as well as particulate
solids
and other contaminants. The CO2, water, particulate solids and other
contaminants
may be separated out, or at least substantially separated out from the
synthesis gas,
prior to conducting step (B) of the inventive process.
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The inventive process, in its illustrated embodiments, will be described
initially
with respect to Figs. 1-8. Referring to Fig. 1, the process 100 employs the
use of
gasifier 110 and microchannel reactor 200. The microchannel reactor 200 may be
referred to as a Fischer-Tropsch microchannel reactor when employed to convert
synthesis gas to one or more hydrocarbons. The microchannel reactor 200 may be
referred to as an alcohol-forming microchannel reactor when used to convert
synthesis gas to one or more alcohols. In operation, the carbonaceous material
enters the gasifier 110 through line 112. A gasification agent (e.g. steam,
oxygen
and/or air) enters the gasifier 110 through line 114. In the gasifier 110, the
carbonaceous material and the gasification agent are heated and undergo a
gasification reaction to form synthesis gas. The synthesis gas flows from the
gasifier
110 into the microchannel reactor 200 through line 116. The synthesis gas
flowing
out of the gasifier 110 may be at an elevated temperature, for example, in
excess of
about 700 C, and as such it may be advantageous to reduce the temperature of
the
synthesis gas prior to entering the microchannel reactor 200. This temperature
comparable to the desired operating temperature in the microchannel reactor
200 as
discussed below using one or more heat exchangers in the line between the
gasifier
110 and the microchannel reactor 200. These heat exchangers may be
microchannel heat exchangers. The synthesis gas flowing out of the gasifier
110
may contain undesirable levels of water, particulate solids, contaminants
(e.g.,
sulfur, halogen, selenium, phosphorus, arsenic, nitrogen, carbon dioxide, and
the
like), and the like. The concentrations of these may be reduced using one or
more
gas-liquid sorption devices (which may employ the use of one or more ionic
liquid
sorbents), temperature swing adsorption (TSA) devices, pressure swing
adsorption
(PSA) devices, microchannel devises containing layers of nanofibers or nano-
composite films, cyclones, condensers, and the like, in the line between the
gasifier
110 and the microchannel reactor 200. In the microchannel reactor 200, the
synthesis gas flows through one or more process microchannels in contact with
a
catalyst to form the desired product. The catalyst may be a Fischer-Tropsch
catalyst
and the product formed by contacting the Fischer-Tropsch catalyst may comprise
one or more hydrocarbons. Alternatively, the catalyst may be an alcohol-
forming
catalyst and the product resulting from contacting the catalyst may comprise
one or
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more alcohols. Both of these reactions are exothermic reactions. These
reactions
may be controlled using a heat exchange fluid which flows through the
microchannel
reactor 200 as indicated by arrows 204 and 206. In one embodiment, the heat
exchange fluid comprises steam. The resulting product flows out of the
microchannel reactor 200 through line 202.
The process 100A illustrated in Fig. 2 is the same as the process 100
illustrated in Fig. 1, with the exception that steam, which is used as the
heat
exchange fluid in the microchannel reactor 200 is also used as the
gasification agent
in the gasifier 110. The steam flows from the microchannel reactor 200 through
line
206 to the gasifier 110. In the gasifier 110, the steam functions as a
gasification
agent during the gasification of the carbonaceous material.
The process 100B illustrated in Fig. 3 is the same as the process 100
illustrated in Fig. 1 with the exception that the process 100B includes a
nitrogen
separator 300. The nitrogen separator 300 may comprise any device suitable for
separating nitrogen from air. For example, the nitrogen separator 300 may
comprise
an ionic liquid separator, a temperature swing adsorption (TSA) device or a
pressure
swing adsorption (PSA) device. In operation, air enters the nitrogen separator
300
through line 302 where it undergoes a separation process with the nitrogen
being
separated from the air. This results in the formation of oxygen enriched air
or
purified oxygen. The nitrogen flows out of the nitrogen separator 300 through
line
304. The oxygen enriched air or purified oxygen flows from the nitrogen
separator
300 through line 114 into the gasifier 110. The oxygen enriched air or
purified
oxygen functions as a gasification agent in the gasifier 110. The carbonaceous
material and the gasification agent undergo a gasification reaction to form
synthesis
gas. The synthesis gas flows from the gasifier 110 through line 116 to the
microchannel reactor 200 where it undergoes a reaction to form one or more
hydrocarbons or one or more alcohols as discussed above.
The process 100C illustrated in Fig. 4 is the same as the process 100
illustrated in Fig. 1, with the exception that the process 100C employs the
use of
pyrolysis reactor 400. In operation, the carbonaceous material enters the
pyrolysis
reactor 400 through line 112. In the pyrolysis reactor 400, the carbonaceous
material undergoes a pyrolysis reaction with the result being the formation of
a
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pyrolytic oil. The pyrolytic oil flows from the pyrolysis reactor 400 through
line 402 to
gasifier 110. A gasification agent enters the gasifier 110 through line 114.
In the
gasifier 110, the pyrolytic oil and the gasification agent are heated and
undergo a
gasification reaction to form synthesis gas. Synthesis gas flows from the
gasifier
110 through line 116 to the microchannel reactor 200 where it undergoes a
reaction
to form one or more hydrocarbons or one or more alcohols as described above.
The process 100D illustrated in Fig. 5 is the same as the process 100C
illustrated in Fig. 4, with the exception that liquid hydrocarbons, such as
tar, are
separated from the synthesis gas flowing out of the gasifier 110. These liquid
hydrocarbons are recycled back to the pyrolysis reactor 400 from line 116
through
line 118. The recycled liquid hydrocarbons and the carbonaceous material
entering
the pyrolysis reactor 400 through line 112 are combined and subjected to
pyrolysis in
the pyrolysis reactor 400 resulting in the formation of pyrolytic oil. The
pyrolytic oil
flows from the pyrolysis reactor 400 through line 402 to the gasifier 110
wherein it is
combined with a gasification agent which enters the gasifier 110 through line
114.
The pyrolytic oil and gasification agent are heated in the gasifier 110 and
undergo a
gasification reaction to form synthesis gas. The synthesis gas flows from the
gasifier
110 through line 116 to the microchannel reactor 200. In the microchannel
reactor
200, the synthesis gas is converted to one or more hydrocarbons or one or more
alcohols as described above.
The process 100E illustrated in Fig. 6 employs the use of the gasifier 110 and
microchannel reactor 200 discussed above in combination with a steam methane
reforming (SMR) microchannel reactor 500. In the SMR microchannel reactor 500,
an SMR reaction is conducted wherein a tail gas comprising methane reacts with
steam in an endothermic reaction to form synthesis gas. The SMR microchannel
reactor 500 may comprise a plurality of SMR process microchannels in thermal
contact with a plurality of combustion channels. A combustion reaction may be
conducted in the combustion channels to provide the required heat for the
endothermic SMR reaction. In the operation of the process 100E, a carbonaceous
material enters the gasifier 110 through line 112 wherein it is combined with
a
gasification agent which enters the gasifier 110 through line 114. The
carbonaceous
material and the gasification agent are heated and undergo a gasification
reaction to
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form synthesis gas. The synthesis gas flows through line 116 to the
microchannel
reactor 200 wherein it contacts a catalyst and reacts to form one or more
hydrocarbons or one or more alcohols as discussed above. The product flows out
of
the microchannel reactor 200 through line 202. A tail gas, which comprises
5 methane,
is separated from the product and flows from line 202 through line 208 to
the SMR microchannel reactor 500. The remainder of the product (that is, the
product less the tail gas) flows out of the system through line 210, The tail
gas along
with steam flows through the SMR microchannel reactor 500. The tail gas and
steam undergo an SMR reaction and are converted to synthesis gas. The
synthesis
10 gas flows from the SMR microchannel reactor 500 through line 502 to the
microchannel reactor 200 where it is combined with the synthesis gas flowing
from
the gasifier 110. The combined synthesis gas mixture flows in the microchannel
reactor 200 and undergoes reaction as described above.
The process 100F illustrated in Fig. 7 is the same as the process 100E
15
illustrated in Fig. 6 with the exception that carbon dioxide is separated from
the
synthesis gas flowing out of the gasifier 110 through line 116 as indicated by
arrow
120. The carbon dioxide lean synthesis gas (that is, the synthesis gas less
carbon
dioxide) flows through line 122 into microchannel reactor 200 wherein it is
combined
with the synthesis gas from line 502. The combined synthesis gas mixture
20 undergoes
reaction in the microchannel reactor 200 to form one or more
hydrocarbons or one or more alcohols as described above.
The process 100G illustrated in Fig. 8 is the same as the process 100F
illustrated in Fig. 7 with the exception that the carbon dioxide that is
separated from
the synthesis gas flowing out of the gasifier 110 through line 116 flows
through line
120 to the SMR microchannel reactor 500 wherein it is combined with the tail
gas
and reacts to form synthesis gas. This synthesis gas flows out of the SMR
microchannel reactor 500 through line 502 to the microchannel reactor 200. In
the
microchannel reactor 200, the synthesis gas from line 502 is combined with the
synthesis gas from line 122 and undergoes reaction to form one or more
hydrocarbons or one or more alcohols as discussed above.
The process 100H illustrated in Fig. 8A is the same as the process 100
illustrated in Fig. 1 with the exception that the product flowing out of the
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microchannel reactor 200 through line 202 comprises a Fischer-Tropsch product.
The Fischer-Tropsch product may comprise a mixture of liquid and gas. The
gaseous Fischer-Tropsch product may be separated from the liquid Fischer-
Tropsch
product as indicated by arrow 203. The liquid Fischer-Tropsch product may then
undergo a hydrocracking reaction in hydrocracking microchannel reactor 700.
Optionally, the Fischer-Tropsch liquid product may be separated into a light
fraction
and a heavy fraction in a separation unit or a distillation unit. The heavy
fraction may
be fed to the hydrocracking microchannel reactor 700. The light fraction may
be
taken as a final product or processed separately. Alternatively, the light
fraction may
be introduced into the hydrocracking microchannel reactor 700 that is
processing the
heavy fraction. The light fraction may be hydrocracked in a separate
hydrocracking
microchannel reactor. The liquid Fischer-Tropsch product flowing from line 202
may
enter hydrocracking microchannel reactor 700 where it may be combined with a
hydrogen feed stream. The hydrogen feed stream enters the hydrocracking
microchannel reactor 700 as indicated by arrow 702. In the hydrocracking
microchannel reactor 700, the Fischer-Tropsch product and hydrogen contact a
hydrocracking catalyst and react to form the desired hydrocracked product. The
hydrocracked product flows out of the hydrocracking microchannel reactor 700
as
indicated by arrow 704. In an alternate embodiment, the liquid Fischer-Tropsch
product may be separated into a light fraction and a heavy fraction, and then
just the
heavy fraction would be hydrocracked in the hydrocracking microchannel reactor
700. The hydrocracking process is exothermic. This reaction may be controlled
using a heat exchange fluid which flows through the microchannel reactor 700
as
indicated by arrows 706 and 708. However, the use of the heat exchange fluid
may
be optional due to the fact that the hydrocracking reaction may be only
slightly
exothermic.
In an alternate embodiment, the hydrocracking reaction may be conducted in
the same microchannel reactor used to conduct the Fischer-Tropsch reaction. In
this embodiment, the microchannel reactor 200 used to conduct the Fischer-
Tropsch
reaction may be modified to include a hydrocracking reaction zone downstream
of
the Fischer-Tropsch reaction zone. The hydrogen feed would flow into the
hydrocracking reaction zone. The microchannel reactor 200 may also be modified
to
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permit removal of gaseous Fischer-Tropsch products and, optionally, light
fraction
liquid Fischer-Tropsch products, downstream of the Fischer-Tropsch reaction
zone
but upstream of the hydrocracking reaction zone.
The gasification step (A) of the inventive process involves converting the
carbonaceous material to synthesis gas by reacting the carbonaceous material
at a
temperature of at least about 700 C with a gasification agent. The
gasification agent
may comprise oxygen, air and/or steam. The gasification step (A) may be
conducted at a temperature of at least about 800 C, and in one embodiment at a
temperature of at least about 900 C, and in one embodiment at a temperature of
at
least about 1000 C, and in one embodiment at a temperature of at least about
1100 C, and in one embodiment at a temperature of at least about 1200 C. The
gasification step (A) may be conducted at a temperature in the range from
about
700 C to about 2500 C, and in one embodiment in the range from about 800 C to
about 2200 C, and in one embodiment in the range from about 900 C to about
2000 C, and in one embodiment in the range from about 1000 C to about 1800 C,
and in one embodiment in the range from about 1100 C to about 1800 C, and in
one
embodiment in the range from about 1200 C to about 1800 C, and in one
embodiment in the range from about 1300 C to about 1500 C. The elevated
temperatures used during step(A) distinguish it from biological processes such
as
anaerobic digestion that produce biogas.
While not wishing to be bound by theory, it is believed that during step (A)
of
the inventive process, the carbonaceous material may undergo the following
processes:
1. A pyrolysis (or devolatilization) process may occur as the
carbonaceous material heats up. Volatiles may be released and char may be
produced, resulting in, for example, up to about 70% by weight loss. The
process
may be dependent on the properties of the carbonaceous material. These
properties may determine the structure and composition of the char.
2. A combustion process may occur as the volatile products and some of
the char reacts with oxygen to form carbon dioxide and carbon monoxide. This
may
provide heat for the subsequent gasification reactions.
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3. Reaction of the char with carbon dioxide and steam to produce carbon
monoxide and hydrogen.
4. A reversible gas phase water gas shift reaction may reach equilibrium
at the temperatures in the gasifier. This may result in balancing the
concentrations
of carbon monoxide, steam, carbon dioxide and hydrogen
CO+H204-4CO2-1-H2
With these processes, a limited amount of oxygen may be introduced into the
gasifier to allow some of the carbonaceous material to be burned to produce
carbon
monoxide and energy in a first reaction. The molar ratio of oxygen to carbon
may be
in the range from about 0.01:1 to about 5:1, and in one embodiment in the
range
from about 0.2:1 to about 2:1, and in one embodiment in the range from about
0.5:1
to about 1.5:1, and in one embodiment in the range from about 0.5:1 to about
1.2:1,
and in one embodiment about 1:1. This reaction may be used to drive a second
reaction that converts further carbonaceous material to hydrogen and
additional
carbon monoxide.
The gasification step (A) may be conducted in a counter-current fixed bed
gasifier, a co-current fixed bed gasifier, a fluidized bed gasifier, or an
entrained flow
gasifier. The counter-current fixed bed gasifier may comprise a fixed bed of
carbonaceous material through which the gasification agent (e.g., steam,
oxygen
and/or air) flows in counter-current configuration. Ash may be removed either
dry or
as a slag. The slagging gasifiers may require a higher ratio of steam and
oxygen to
carbon in order to reach temperatures higher than the ash fusion temperature.
The
carbonaceous material may require a high mechanical strength and a non-caking
composition so that it may form a permeable bed. The throughput for this type
of
gasifier may be relatively low. Thermal efficiency may be high as the gas exit
temperature may be relatively low. Tar and methane may be produced with this
process.
The co-current fixed bed gasifier is similar to the counter-current type, with
the exception that the gasification agent flows in co-current configuration
with the
carbonaceous material. Heat may need to be added to the upper part of the bed,
either by combusting small amounts of the carbonaceous material or from
external
heat sources. The synthesis gas may leave the gasifier at a high temperature.
Most
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of this heat may be transferred to the gasification agent added in the top of
the bed
to provide for energy efficiency. Tars may pass through a hot bed of char in
this
configuration. However, the tar levels may be lower than with the counter-
current
type.
In the fluidized bed gasifier, the carbonaceous material may be fluidized in
the
gasification agent. Ash may be removed dry or as heavy agglomerates that
defulidize. The temperature may be relatively low in dry ash gasifiers and, as
such,
the carbonaceous material may be relatively highly reactive; low-grade coals
may be
particularly suitable. The agglomerating gasifiers may operate at slightly
higher
temperatures, and may be suitable for higher rank coals. Carbonaceous material
throughput may be higher than for the fixed bed, but not as high as for the
entrained
flow gasifier. The conversion efficiency may be rather low due to elutriation
of
carbonaceous material. Recycle or subsequent combustion of solids may be used
to increase conversion. Fluidized bed gasifiers may be useful for carbonaceous
materials that form highly corrosive ash that may damage the walls of slagging
gasifiers.
In the entrained flow gasifier a dry pulverized solid carbonaceous material,
an
atomized liquid carbonaceous material, or a slurry of the carbonaceous
material may
be gasified with oxygen or air in co-current flow. The gasification reactions
may take
place in a dense cloud of very fine particles. Most coals may be suitable for
this type
of gasifier because of the high operating temperatures and because the coal
particles may be well separated from one another. The high temperatures and
pressures may also mean that a higher throughput may be achieved, however
thermal efficiency may be somewhat lower as the gas may be cooled before it
can
be cleaned. The high temperatures may also mean that tar and methane may not
be present in the product synthesis gas; however the oxygen requirement may be
higher than for the other types of gasifiers. Entrained flow gasifiers may
remove a
major part of the ash as a slag as the operating temperature may be above the
ash
fusion temperature. A smaller fraction of the ash may be produced either as a
very
fine dry fly ash or as a black colored fly ash slurry. Some carbonaceous
materials, in
particular certain types of biomasses, may form slag that is corrosive for
ceramic
inner walls that may serve to protect the gasifier outer wall. However, some
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entrained bed types of gasifiers may not possess a ceramic inner wall but may
have an
inner water or steam cooled wall covered with partially solidified slag. These
types of
gasifiers may not suffer from corrosive slags. Some carbonaceous materials may
have
ashes with very high ash fusion temperatures. In this case limestone may be
mixed with
5 the fuel prior to gasification. Addition of limestone may suffice for
lowering the fusion
temperatures. The carbonaceous material particles may be smaller than for
other types of
gasifiers. This may mean that the carbonaceous material may be pulverized,
which may
require more energy than for the other types of gasifiers.
The gasification step (A) may be conducted in a molten metal reactor. In the
molten
10 metal reactor, the carbonaceous material and steam contact molten metal
and react to
form the synthesis gas. The molten metal may comprise a reactive metal (Me)
that reacts
with a first portion of the steam entering the reactor according to the
following equation:
xMe+yH20-1H2+MexOy
The carbonaceous material may react with a second portion of the steam to form
carbon
15 monoxide and hydrogen. The reactive metal may have an oxygen affinity
that is similar to
the oxygen affinity of hydrogen. The reactive metal may comprise one or more
of the
following metals or their alloys: germanium, iron, zinc, tungsten, molybdenum,
indium, tin,
cobalt or antimony. The reactive metal may be at least partially dissolved in
a second
metal or mixture of metals. The metal into which the reactive metal is
dissolved may be
20 referred to as a diluent metal. The diluent metal may also be reactive
with steam, in which
case it may be selected from the reactive metals disclosed above, provided
that the
diluent metal is less reactive than the reactive metal. The diluent metal may
comprise one
or more of nickel, copper, ruthenium, rhodium, palladium, silver, cadmium,
rhenium,
osmium, iridium, platinum, gold, mercury, lead, bismuth, selenium or
tellurium. More than
25 one diluent metal may be utilized in the molten metal mixture. In one
embodiment, the
reactive metal may comprise iron, and the diluent metal may comprise tin.
Molten metal
reactors that may be used to convert the carbonaceous material to synthesis
gas may
include the molten metal reactors disclosed in U.S. Patents 7,232,472 B2;
6,685,754 B2;
6,682,714 B2; and 6,663,681 B2.
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The gasification step (A) may be conducted in a plasma based gasification
system. With such a system, the carbonaceous material may be fed into a plasma
converter which may comprise a sealed, stainless steel vessel filled with
either
nitrogen or ordinary air. An electric current (e.g., a 650-volt electrical
current) may
be passed between two electrodes; this removes electrons from the nitrogen or
air
and creates plasma. A constant flow of electricity through the plasma
maintains a
field of intense energy powerful enough to disintegrate the carbonaceous
material
into its component elements. The byproducts may comprise a glass-like
substance,
which may be used as a raw material for high-strength asphalt or household
tiles,
and synthesis gas. The synthesis gas may leave the plasma converter at a high
temperature, e.g., about 2200 F (1204 C). The synthesis gas may then be fed
into
a cooling system which generates steam. This steam may be used to drive
turbines
which produce electricity, part of which may be used to power the plasma
converter,
while the rest may be used for the plant's heating or electrical needs, or
sold back to
the utility grid. The synthesis gas may then be advanced to the microchannel
reactor 200.
One or more of the Fischer-Tropsch (FT) or alcohol-forming microchannel
reactors 200, or one or more of the SMR microchannel reactors 500, or one or
more
of the hydrocracking microchannel reactors 700 may be housed in vessel 220.
Vessel 220 has the construction illustrated in Figs. 9 and 10. Referring to
Figs. 9
and 10, the vessel 220 contains five Fischer-Tropsch or alcohol-forming
microchannel reactors 200, or five SMR microchannel reactors 500, or five
hydrocracking microchannel reactors 700. These are identified in the drawings
as
microchannel reactors 200/500/700. These are identified in Fig. 10 as Fischer-
Tropsch or alcohol-forming microchannel reactors, SMR microchannel reactors,
or
hydrocracking microchannel reactors 200/500/700-1, 200/500f700-2, 200/500/700-
3,
200/500/700-4 and 200/500/700-5. Although five microchannel reactors are
disclosed in the drawings, it will be understood that any desired number of
Fischer-
Tropsch or alcohol-forming microchannel reactors, or SMR microchannel
reactors, or
hydrocracking microchannel reactors may be positioned in vessel 220. For
example,
the vessel 220 may contain from about 1 to about 1000 microchannel reactors
200,
500 or 700, and in one embodiment from 1 to about 750, and in one embodiment
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from 1 to about 500, and in one embodiment from 1 to about 250, and in one
embodiment from 1 to about 100, and in one embodiment from about 1 to about
50,
and in one embodiment from 1 to about 20 microchannel reactors 200, 500 or
700.
The vessel 220 may be a pressurizable vessel. The vessel 220 includes inlets
224
and 228, and outlets 222 and 226.
When the vessel 220 is used with the Fischer-Tropsch or alcohol forming
microchannel reactors 200, inlet 224 is connected to a manifold which is
provided for
flowing synthesis gas to Fischer-Tropsch or alcohol forming process
microchannels
in the microchannel reactors 200. The inlet 228 is connected to a manifold
which is
provided for flowing heat exchange fluid (e.g., steam) to heat exchange
channels in
the microchannel reactors 200. The outlet 222 is connected to a manifold which
provides for the flow of product from the Fischer-Tropsch or alcohol forming
process
microchannels in the microchannel reactors 200. The outlet 226 is connected to
a
manifold to provide for the flow of the heat exchange fluid out of the heat
exchange
channels in the microchannel reactors 200.
When vessel 220 is used with the SMR microchannel reactors 500, the vessel
220 includes outlet 222 and inlets 224, 226 and 228. The inlet 224 is
connected to a
manifold which is provided for flowing the SMR feed (e.g., FT tail gas and
steam) to
the SMR process microchannels in the SMR microchannel reactors 500. The inlet
228 is connected to a manifold which is provided for flowing fuel (e.g.,
natural gas) to
the combustion channels in the SMR microchannel reactors 500. The outlet 222
is
connected to a manifold which provides for the flow of synthesis gas from the
SMR
microchannel reactors 500 out of the vessel 220. The inlet 226 is connected to
a
manifold to provide for the flow of the oxygen or source of oxygen (e.g., air)
to
staged addition channels in the SMR microchannel reactors 500. The vessel 220
also includes an outlet (not shown in the drawings) providing for the flow of
exhaust
gas from the SMR microchannel reactors 500.
When the vessel 220 is used with the hydrocracking microchannel reactors
700, inlet 224 is connected to a manifold which is provided for flowing the
Fischer-
Tropsch product from line 202 to hydrocracking process microchannels in the
microchannel reactors 700. The vessel 220 also includes an inlet (not shown in
the
drawings) for flowing hydrogen through a manifold into the process
microchannels of
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the microchannel reactor 700. The inlet 228 may be connected to a manifold
which
is provided for flowing heat exchange fluid to heat exchange channels in the
microchannel reactors 700. The outlet 222 is connected to a manifold which
provides for the flow of a hydrocracked Fischer-Tropsch product out of the
process
microchannels in the microchannel reactors 700. The outlet 226 may be
connected
to a manifold to provide for the flow of heat exchange fluid out of the heat
exchange
channels in the microchannel reactors 700. The hydrocracking reaction
involving the
Fischer-Tropsch product may be only slightly exothermic and, as such, the use
of
heat exchange channels in the microchannel reactor 700 may not be necessary
and
thus may be considered to be optional. The microchannel reactor 700 may be
used
advantageously, with or without the heat exchange channels, to hydrocrack the
Fischer-Tropsch product due to the fact that when using the microchannel
reactor
700, enhanced mass transfer between the hydrogen feed gas and the Fischer-
Tropsch product may be achieved.
The vessel 220 may be constructed using any suitable material sufficient for
operating under the pressures and temperatures required for operating the
Fischer-
Tropsch or alcohol-forming microchannel reactors 200, the SMR microchannel
reactors 500, or the hydrocracking microchannel reactors 700. For example, the
shell 221 and heads 223 of the vessel 220 may be constructed of cast steel.
The
flanges, couplings and pipes may be constructed of 316 stainless steel. The
vessel
220 may have any desired diameter, for example, from about 10 to about 1000
cm,
and in one embodiment from about 50 to about 300 cm. The axial length of the
vessel 220 may be of any desired value, for example, from about 0.5 to about
50
meters, and in one embodiment from about 1 to about 20 meters.
The Fischer-Tropsch or alcohol-forming microchannel reactors 200 may
comprise a plurality of Fischer-Tropsch or alcohol-forming process
microchannels
and heat exchange channels stacked one above the other or positioned side-by-
side. The Fischer-Tropsch or alcohol-forming microchannel reactors 200 may be
in
the form of cubic blocks. Each of these cubic blocks may have a length, width
and
height, the length being in the range from about 10 to about 1000 cm, and in
one
embodiment in the range from about 20 to about 200 cm. The width may be in the
range from about 10 to about 1000 cm, and in one embodiment in the range from
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about 20 to about 200 cm. The height may be in the range from about 10 to
about
1000 cm, and in one embodiment in the range from about 20 to about 200 cm.
The microchannel reactors 200 as well as the vessels 220 may be sufficiently
small and compact so as to be readily transportable. As such, these reactors
and
vessels along with the other equipment used in the inventive process may be
readily
transported to remote locations, such as military bases, and used to convert
carbonaceous waste products such as solid waste, biomass, etc. to synthetic
fuels
such as automotive fuel, diesel fuel, aviation fuel, and the like.
The Fischer-Tropsch or alcohol-forming microchannel reactors 200 may each
comprise a plurality of repeating units, each of which includes one or more
Fischer-
Tropsch or alcohol-forming process microchannels and one or more heat exchange
channels. The repeating units that may be used include repeating units 230,
230A,
230B and 230C illustrated in Figs. 11-14, respectively. The Fischer-Tropsch or
alcohol-forming microchannel reactors 200 may comprise from about 1 to about
1000 of the repeating units 230, 230A, 230B or 230C, and in one embodiment
from
about 10 to about 500 of such repeating units. The catalyst used in the
repeating
units 230-230D may be in any form including the various catalyst structured
forms
described below.
Repeating unit 230 is illustrated in Fig. 11. Referring to Fig. 11, Fischer-
Tropsch or alcohol-forming process microchannel 232 is positioned adjacent to
heat
exchange layer 234 which contains heat exchange channels 236. The heat
exchange channels 236 may be microchannels. A common wall 237 separates the
process microchannel 232 from the heat exchange layer 234. A catalyst is
positioned in reaction zone 240 of the process microchannel 232. In one
embodiment, the length of heat exchange layer 234 is up to about 200% of the
length of the reaction zone 240, and in one embodiment the length of heat
exchange
layer 234 is from about 50 to about 175% of the length of the reaction zone
240, and
in one embodiment the length of the heat exchange layer 234 is from about 75
to
about 150% of the length of the reaction zone 240. The reactant composition
(i.e.,
synthesis gas) flows into the reaction zone 240 in process microchannel 232 in
the
direction indicated by arrow 250, contacts the catalyst in the reaction zone,
and
reacts to form the desired product. The product (i.e., one or more
hydrocarbons or
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one or more alcohols) flows out of the process microchannel 232 as indicated
by
arrow 252. Heat exchange fluid flows through the heat exchange channels 236 in
a
direction that is cross-current to the flow of reactant composition and
product in the
process microchannel 232. The Fischer-Tropsch or alcohol-forming reactions
5 conducted in the process microchannel 232 are exothermic and the heat
exchange
fluid provides cooling for the reaction.
Alternatively, the process microchannels and heat exchange channels may be
aligned as provided for in repeating unit 230A. Repeating unit 230A, which is
illustrated in Fig. 12, is identical to the repeating unit 230 illustrated in
Fig. 11 with
10 the exception that the heat exchange channels 236 are rotated 90 and
the heat
exchange fluid flowing through the heat exchange channels 236 flows in a
direction
that may be countercurrent to the flow of reactant and product in the process
microchannel 232 or cocurrent relative to the direction of reactant and
product in the
process microchannel 232.
15 Alternatively, the process microchannels and heat exchange channels may
be
aligned as provided for in repeating unit 230B. Repeating unit 230B is
illustrated in
Fig. 13. Referring to Fig. 13, process microchannel 232a is positioned
adjacent to
heat exchange layer 235. Heat exchange layer 235 contains a plurality of heat
exchange channels 236 aligned in parallel relative to one another, each heat
20 exchange channel 236 extending lengthwise at a right angle relative to the
lengthwise direction of the process microchannel 232a. Heat exchange layer 235
is
shorter in length than process microchannel 232a. Heat exchange layer 235
extends lengthwise from or near the entrance 246 to the reaction zone 240 of
process microchannel 232a to a point 247 along the length of the process
25 microchannel 232a short of the outlet 248 of the reaction zone 240. In
one
embodiment, the length of heat exchange layer 235 is up to about 90% of the
length
of the reaction zone 240, and in one embodiment the length of heat exchange
layer
235 is from about 5 to about 90% of the length of the reaction zone 240, and
in one
embodiment the length of the heat exchange layer 235 is from about 5 to about
50%
30 .. of the length of the reaction zone 240, and in one embodiment the length
of the heat
exchange layer 235 is from about 50% to about 90% of the length of the
reaction
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zone 240. The width of the process microchannel 232a is expanded or extended
in
the area downstream of the end 247 of the heat exchange layer 235.
Alternatively, the process microchannels and heat exchange channels may be
aligned as provided for in repeating unit 2300. Repeating unit 230C, which is
illustrated in Fig. 14, is identical to the repeating unit 230B illustrated in
Fig. 13 with
the exception that repeating unit 230C includes heat exchange layer 235a
adjacent
to process microchannel 232a on the opposite side of the process microchannel
232a from the heat exchange layer 235. Heat exchange layer 235a contains a
plurality of parallel heat exchange channels 236a which are the same as or
similar in
size and design to the heat exchange channels 236 discussed above. Heat
exchange layer 235a extends lengthwise from or near the entrance 246 to the
reaction zone 240 of process microchannel 232a to a point 249 along the length
of
process microchannel 232a short of the end 247 of heat exchange layer 235. The
length of the heat exchange layer 235a may be up to about 90% of the length of
the
heat exchange layer 235, and in one embodiment the length of the heat exchange
layer 235a may be from about 5 to about 90% of the length of the heat exchange
layer 235, and in one embodiment the length of the heat exchange layer 235a
may
be from about 5 to about 50% of the length of the heat exchange layer 235, and
in
one embodiment the length of the heat exchange layer 235a may be from about
50% to about 90% of the length of the heat exchange layer 235. The width of
the
process microchannel 232a is expanded in the areas downstream of the ends 247
and 249 of the heat exchange layers 235 and 235a, respectively.
The process microchannels 232 and 232a may have cross sections having
any shape, for example, square, rectangle, circle, semi-circle, etc. The
internal
height of each process microchannel 232 and 232a may be considered to be the
smaller of the internal dimensions normal to the direction of flow of
reactants and
product through the process microchannel. Each of the process microchannels
232
and 232a may have an internal height of up to about 10 mm, and in one
embodiment
up to about 6 mm, and in one embodiment up to about 4 mm, and in one
embodiment up to about 2 mm. In one embodiment, the height may be in the range
of about 0.05 to about 10 mm, and in one embodiment about 0.05 to about 6 mm,
and in one embodiment about 0.05 to about 4 mm, and in one embodiment about
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0.05 to about 2 mm. The width of each process microchannel 232 and 232a may be
considered to be the other internal dimension normal to direction of flow of
reactants
and product through the process microchannel. The width of each process
microchannel 232 and 232a may be of any dimension, for example, up to about 3
meters, and in one embodiment about 0.01 to about 3 meters, and in one
embodiment about 0.1 to about 3 meters. The length of each process
microchannel
232 and 232a may be of any dimension, for example, up to about 10 meters, and
in
one embodiment about 0.2 to about 10 meters, and in one embodiment from about
0.2 to about 6 meters, and in one embodiment from 0.2 to about 3 meters.
The heat exchange channels 236 may be microchannels or they may have
larger dimensions that would classify them as not being microchannels. Each of
the
heat exchange channels 236 may have a cross section having any shape, for
example, a square, rectangle, circle, semi-circle, etc. The internal height of
each
heat exchange channel 236 may be considered to be the smaller of the internal
dimensions normal to the direction of flow of heat exchange fluid in the heat
exchange channels. Each of the heat exchange channels 236 may have an internal
height of up to about 2 mm, and in one embodiment in the range of about 0.05
to
about 2 mm, and in one embodiment about 0.05 to about 1.5 mm. The width of
each
of these channels, which would be the other internal dimension normal to the
direction of flow of heat exchange fluid through the heat exchange channel,
may be
of any dimension, for example, up to about 3 meters, and in one embodiment
from
about 0.01 to about 3 meters, and in one embodiment about 0.1 to about 3
meters.
The length of each of the heat exchange channels 236 may be of any dimension,
for
example, up to about 10 meters, and in one embodiment from about 0.2 to about
10
meters, and in one embodiment from about 0.2 to about 6 meters, and in one
embodiment from 0.2 to about 3 meters.
The number of repeating units 230-230C in the microchannel reactor 200 may
be an desired number, for example, one, two, three, four, six, eight, ten,
hundreds,
thousands, tens of thousands, hundreds of thousands, millions, etc.
In the design and operation of a Fischer-Tropsch or alcohol-forming
microchannel reactor it may be advantageous to provide a tailored heat
exchange
profile along the length of the process microchannels in order to optimize the
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reaction. This may be accomplished by matching the local release of heat given
off
by the Fischer-Tropsch or alcohol-forming reaction conducted in the process
microchannels with heat removal or cooling provided by heat exchange fluid in
heat
exchange channels in the microchannel reactor. The extent of the Fischer-
Tropsch
or alcohol-forming reaction and the consequent heat release provided by the
reaction may be higher in the front or upstream sections of the reaction zones
in the
process microchannels as compared to the back or downstream sections of the
reaction zones. Consequently, the matching cooling requirements may be higher
in
the upstream section of the reaction zones as compared to the downstream
sections
of the reaction zones. Tailored heat exchange may be accomplished by providing
more heat exchange or cooling channels, and consequently the flow of more heat
exchange or cooling fluid, in thermal contact with upstream sections of the
reaction
zones in the process microchannels as compared to the downstream sections of
the
reaction zones. This is shown in Figs. 13 and 14 wherein the heat exchange
layers
235 and 235a extend lengthwise from the entrance 246 to the reaction zone 240
along the length of the process microchannels 230B and 230C to points 247 and
249
short of the outlet 248 of the reaction zone 240. Alternatively or
additionally, a
tailored heat exchange profile may be provided by varying the flow rate of
heat
exchange fluid in the heat exchange channels. In areas where additional heat
exchange or cooling is desired, the flow rate of the heat exchange fluid may
be
increased as compared to areas where less heat exchange or cooling is
required.
For example, a higher rate of flow of heat exchange fluid may be advantageous
in
the heat exchange channels in thermal contact with the upstream sections of
the
reaction zones in the process microchannels as compared to the heat exchange
channels in thermal contact with the downstream sections of the reaction
zones.
Thus, in referring to Fig. 11, for example, a higher rate of flow in the heat
exchange
channels 236 near the inlet to the process microchannel 232 or reaction zone
240
may be used as compared to the heat exchange channels 236 near the outlet of
the
process microchannel 232 or reaction zone 240 where the flow rate may be less.
Heat transfer from the process microchannels to the heat exchange channels may
be designed for optimum performance by selecting optimum heat exchange channel
dimensions and/or the rate of flow of heat exchange fluid per individual or
groups of
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heat exchange channels. Additional design alternatives for tailoring heat
exchange
may relate to the selection and design of the Fischer-Tropsch or alcohol-
forming
catalyst (such as, particle size, catalyst formulation, packing density, use
of a graded
catalyst, or other chemical or physical characteristics) at specific locations
within the
process microchannels. These design alternatives may impact both heat release
from the process microchannels as well as heat transfer to the heat exchange
fluid.
Temperature differentials between the process microchannels and the heat
exchange channels, which may provide the driving force for heat transfer, may
be
constant or may vary along the length of the process microchannels.
The SMR microchannel reactors 500 may comprise a plurality of SMR
process microchannels, combustion channels and staged addition channels
stacked
one above the other or positioned side-by-side. The SMR microchannel reactors
500 may be in the form of cubic blocks as illustrated in Figs. 9 and 10. Each
of
these cubic blocks may have a length, width and height, the length being in
the
range from about 10 to about 1000 cm, and in one embodiment in the range from
about 50 to about 200 cm. The width may be in the range from about 10 to about
1000 cm, and in one embodiment in the range from about 50 to about 200 cm. The
height may be in the range from about 10 to about 1000 cm, and in one
embodiment
in the range from about 50 to about 200 cm.
The SMR microchannel reactors 500 may comprise a plurality of repeating
units, each of which includes one or more SMR process microchannels,
combustion
channels and staged addition channels. The repeating units that may be used
include repeating units 510, 510A, 510B, 510C and 510D illustrated in Figs. 21-
25,
respectively. The SMR microchannel reactors 500 may comprise from about 1 to
about 1000 of the repeating units 510, 510A, 510B, 510C or 510D, and in one
embodiment from about 3 to about 750, and in one embodiment from about 5 to
about 500, and in one embodiment from about 5 to about 250, and in one
embodiment from about 10 to about 100 of such repeating units.
The repeating unit 510 illustrated in Fig. 21 includes SMR process
microchannel 512 and heating section 520. Heating section 520 comprises
combustion channel 530 and staged addition channels 540 and 540A. The process
microchannel 510 is in the form of an upside down U and includes reaction zone
516
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where an SMR catalyst (not shown in the drawing) is positioned. The SMR feed
(e.g., FT tail gas in combination with steam) enters the SMR process
microchannel
512 as indicated by arrow 514, flows through the SMR process microchannel,
contacts the SMR catalyst in the reaction zone 516, undergoes a steam methane
5 reforming reaction with the result being the formation of synthesis gas
comprising
CO and H2. The synthesis gas flows out of the SMR process microchannel as
indicated by arrow 518. The combustion channel 530 is an M-shaped combustion
channel which includes reaction zones 534 wherein a combustion catalyst (not
shown in the drawing) is positioned. The combustion channel 530 also includes
10 apertured sections 538 in its sidewalls to permit oxygen or source of
oxygen to flow
from the staged addition channels 540 and 540A into the combustion channel
530.
A fuel enters the combustion channel 530 as indicated by arrows 532 and flows
into
the reaction zones 534. The oxygen or source of oxygen enters the staged
addition
channels 540 and 540A as indicated by arrows 542 and 542A and flows through
the
15 .. apertu red sections 538 and into the reaction zones 534 in the
combustion channels
530. The fuel is mixed with the oxygen or source of oxygen, contacts the
combustion catalyst, and undergoes a combustion reaction which generates heat
and combustion exhaust. The combustion exhaust flows out of the combustion
channel 530 as indicated by arrows 536.
20 The repeating unit 510A illustrated in Fig. 22 is the same as the
repeating unit
510 with the exception that the SMR process microchannel 512 in repeating unit
510A is a straight-run, flow-through microchannel, rather than an upside down
U-
shaped microchannel.
The repeating unit 510B illustrated in Fig. 23 is the same as the repeating
unit
25 510A with the exception that the repeating unit 510B includes two
adjacent SMR
process microchannels, namely, SMR process microchannels 512 and 512A. The
SMR process microchannel 512 is adjacent to the combustion channel 530. The
SMR process microchannel 512A is adjacent to the SMR process microchannel 512
and in thermal contact with the combustion channel 530.
30 The repeating unit 510C illustrated in Fig. 24 is the same as the
repeating unit
510A illustrated in Fig. 22 with the exception that the combustion channel 530
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illustrated in Fig. 24 is a straight run channel, rather than a M-shaped
channel, and
only one staged addition channel 540 is used.
The repeating unit 510D illustrated in Fig. 25 is the same as the repeating
unit
510C illustrated in Fig. 24 with the exception that the SMR process
microchannel
512 in repeating unit 510D is an upside down U-shaped microchannel, rather
than a
straight run microchannel.
The microchannel reactor 700 may comprise a plurality of hydrocracking
process microchannels and heat exchange channels stacked one above the other.
However, as indicated above, the heat exchange channels may not be necessary
for
the hydrocracking microchannel reactor 700, and thus the use of the heat
exchange
channels may be considered to be optional. The hydrocracking microchannel
reactor 700 may be in the form of a cubic block as illustrated in Figs. 9 and
10. The
cubic block may have a length in the range from about 10 to about 1000 cm, and
in
one embodiment in the range from about 20 to about 200 cm. The cubic block may
have a width in the range from about 10 to about 1000 cm, and in one
embodiment
in the range from about 20 to about 200 cm. The cubic block may have a height
in
the range from about 10 to about 1000 cm, and in one embodiment in the range
from
about 20 to about 200 cm. The Fischer-Tropsch product, or at least the liquid
or
heavy liquid portion of the Fischer-Tropsch product, and hydrogen may enter
the
hydrocracking process microchannels, and a hydrocracked product may flow out
of
the hydrocracking process microchannels. Heat exchange fluid, when used, may
flow through the heat exchange channels. The microchannel reactor 700 may have
a
feed stream header or manifold to provide for the flow of the reactants into
the
process microchannels, a product footer or manifold to provide for the flow of
product out of the process microchannels. When heat exchange channels are
employed with the microchannel heat exchanger 700, a heat exchange inlet
manifold
may be used to provide for the flow of heat exchange fluid into the heat
exchange
channels, and a heat exchange outlet manifold may be used to provide for the
flow
of heat exchange fluid out of the heat exchange channels.
The hydrocracking microchannel reactor 700 may contain one or more
repeating units. Each
repeating unit may contain one or more process
microchannels and, optionally, one or more heat exchange channels. Each of the
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process microchannels may contain one or more reaction zones wherein the
reactants react to form the desired product. A catalyst in solid form may be
present
in the one or more reaction zones. The catalyst may comprise a homogeneous
catalyst immobilized on a solid. In one embodiment, each process microchannel
may be combined with one or more adjacent reactant stream channels to provide
for
the staged addition of hydrogen into the process microchannel. The process
microchannel and the adjacent reactant stream channel may have a common wall
with a plurality of openings in the common wall. These openings may be used to
provide for the flow of hydrogen from the adjacent reactant stream channel
into the
process microchannel. The feed stream header may comprise one or more
manifolds for distributing mixtures of the reactants to the process
microchannels.
Alternatively, the feed stream header may comprise separate manifolds for
distributing the reactants separately to the process microchannels and to the
adjacent reactant stream channels.
The heat exchange channels in the Fischer-Tropsch or alcohol-forming
microchannel reactor 200, the combustion channels and staged addition channels
in
the SMR microchannel reactor 500, and the adjacent reactant stream channels
and
heat exchange channels, when used, in the hydrocracking microchannel reactor
700
may be microchannels or they may have dimensions that would characterize them
as not being microchannels. For example, these channels may have internal
heights
or widths up to about 50 mm, and in one embodiment up to about 25 mm, and in
one
embodiment up to about 15 mm. The Fischer-Tropsch or alcohol-forming process
microchannels, the SMR process microchannels, and the hydrocracking process
microchannels are microchannels. Each of the microchannels may have a cross-
section having any shape, for example, a square, rectangle, circle, semi-
circle, etc.
Each microchannel may have an internal height of up to about 10 mm, and in one
embodiment up to about 5 mm, and in one embodiment up to about 2 mm, and in
one embodiment up to about 2 mm. The height of each of these microchannels may
be in the range of about 0.05 to about 10 mm, and in one embodiment from about
0.05 to about 5 mm, and in one embodiment from about 0.05 to about 2 mm, and
in
one embodiment about 0.05 to about 1.5 mm. The width of each of these
microchannels may be of any dimension, for example, up to about 3 meters, and
in
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one embodiment from about 0.01 to about 3 meters, and in one embodiment about
0.1 to about 3 meters. The length of each microchannel may be of any
dimension,
for example, up to about 10 meters, and in one embodiment about 0.2 to about
10
meters, and in one embodiment from about 0.2 to about 6 meters, and in one
embodiment from 0.2 to about 3 meters.
The Fischer-Tropsch or alcohol-forming process microchannels and heat
exchange channels in the Fischer-Tropsch or alcohol-forming microchannel
reactor
200, the SMR process microchannels, combustion channels and staged addition
channels in the SMR microchannel reactor 500, and the hydrocracking process
microchannels, adjacent reactant stream channels and heat exchange channels,
when used, in the hydrocracking microchannel reactor 700, may have rectangular
cross sections and be aligned in side-by-side vertically oriented planes or
horizontally oriented stacked planes. These planes may be tilted at an
inclined
angle from the horizontal. These configurations may be referred to as parallel
plate
configurations. These channels may be arranged in modularized compact units
for
scale-up.
The Fischer-Tropsch or alcohol-forming microchannel reactor 200, the SMR
microchannel reactor 500 and the hydrocracking microchannel 700 may be made of
any material that provides sufficient strength, dimensional stability and heat
transfer
characteristics to permit operation of the desired process. These materials
may
include aluminum; titanium; nickel; platinum; rhodium; copper; chromium;
alloys of
any of the foregoing metals; brass; steel (e.g., stainless steel); quartz;
silicon; or a
combination of two or more thereof. Each microchannel reactor may be
constructed
of stainless steel with one or more copper or aluminum waveforms being used
for
forming the channels.
The Fischer-Tropsch or alcohol-forming microchannel reactor 200, the SMR
microchannel reactor 500, and the hydrocracking microchannel 700 may be
fabricated using known techniques including wire electrodischarge machining,
conventional machining, laser cutting, photochemical machining,
electrochemical
machining, molding, water jet, stamping, etching (for example, chemical,
photochemical or plasma etching) and combinations thereof.
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The Fischer-Tropsch or alcohol-forming microchannel reactor 200, the SMR
microchannel
reactor 500 and the hydrocracking microchannel 700 may be constructed by
forming
shims with portions removed that allow flow passage. A stack of shims may be
assembled
via diffusion bonding, laser welding, diffusion brazing, and similar methods
to form an
.5 integrated device. The microchannel reactors may be assembled using a
combination of
shims or laminae and partial sheets or strips. In this method, the channels or
void areas
may be formed by assembling strips or partial sheets to reduce the amount of
material
required.
The Fischer-Tropsch or alcohol-forming microchannel reactor 200, the SMR
microchannel reactor 500 and the hydrocracking microchannel 700 may be
constructed
using waveforms in the form of right angled corrugated inserts. These right
angled
corrugated sheets may have rounded edges rather than sharp edges. These
inserts may
be sandwiched between opposing planar sheets or shims. In this manner the
microchannels may be defined on three sides by the corrugated insert and on
the fourth
side by one of the planar sheets. The process microchannels as well as the
heat
exchange channels may be formed in this manner. Microchannel reactors made
using
waveforms are disclosed in WO 2008/030467.
The Fischer-Tropsch or alcohol-forming process microchannels, SMR process
microchannels and/or combustion channels, and hydrocracking process
microchannels
may contain one or more surface features in the form of depressions in and/or
projections
from one or more interior walls of the process microchannels. Examples are
shown in
Figs. 26 and 27. The heat exchange channels in the Fischer-Tropsch or alcohol-
forming
microchannel reactor 200 and, when used, in the hydrocracking microchannel
reactor 700,
as well as the adjacent reactant stream channels in the hydrocracking
microchannel
reactor 700, may also contain such surface features. The surface features may
be used to
disrupt the flow of fluid flowing in the channels. These disruptions in flow
may enhance
mixing and/or heat transfer. The surface features may be in the form of
patterned
surfaces. The Fischer-Tropsch or alcohol-forming, SMR and/or hydrocracking
microchannel reactors may be made by laminating a plurality of shims together.
One or
both major surfaces of the shims may contain surface features. Alternatively,
the Fischer-
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Tropsch or alcohol-forming, SMR and/or hydrocracking microchannel reactors may
be assembled using some sheets or shims and some strips, or partial sheets to
reduce the total amount of metal required to construct the device. A shim
containing
surface features may be paired (on opposite sides of a microchannel) with
another
5 shim
containing surface features. Pairing may create better mixing or heat transfer
enhancement as compared to channels with surface features on only one major
surface. The patterning may comprise diagonal recesses that are disposed over
substantially the entire width of a microchannel surface. The patterned
surface
feature area of a wall may occupy part of or the entire length of a
microchannel
10 surface.
Surface features may be positioned over at least about 10%, and in one
embodiment at least about 20%, and in one embodiment at least about 50%, and
in
one embodiment at least about 80% of the length of a channel surface. Each
diagonal recesses may comprise one or more angles relative to the flow
direction.
Successive recessed surface features may comprise similar or alternate angles
15 relative to other recessed surface features.
In embodiments wherein surface features may be positioned on or in more
than one microchannel wall, the surface features on or in one wall may have
the
same (or similar) pattern as found on a second wall, but rotated about the
centerline
of the main channel mean bulk flow direction. In embodiments wherein surface
20 features
may be on or in opposite walls, the surface features on or in one wall may
be approximately mirror images of the features on the opposite wall. In
embodiments wherein surface features are on or in more than one wall, the
surface
features on or in one wall may be the same (or similar) pattern as found on a
second
wall, but rotated about an axis which is orthogonal to the main channel mean
bulk
25 flow
direction. In other words, the surface features may be flipped 180 degrees
relative to the main channel mean bulk flow direction and rotated about the
centerline of the main channel mean bulk flow. The surface features on or in
opposing or adjacent walls may or may not be aligned directly with one
another, but
may be repeated continuously along the wall for at least part of the length of
the wall.
30 Surface
features may be positioned on three or more interior surfaces of a channel.
For the case of channel geometries with three or fewer sides, such as
triangular,
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oval, elliptical, circular, and the like, the surface features may cover from
about 20%
to about 100% of the perimeter of the microchannel.
A patterned surface may comprise multiple patterns stacked on top of each
other. A pattern or array of holes may be placed adjacent to a heat transfer
wall and
a second pattern, such as a diagonal array of surface features may be stacked
on
top and adjacent to an open channel for flow. A sheet adjacent to an open gap
may
have patterning through the thickness of the sheet such that flow may pass
through
the sheet into an underlying pattern. Flow may occur as a result of advection
or
diffusion. As an example, a first sheet with an array of through holes may be
placed
over a heat transfer wall, and a second sheet with an array of diagonal
through slots
may be positioned on the first sheet. This may create more surface area for
adhering a catalyst. The pattern may be repeated on at least one other wall of
the
process microchannel. The patterns may be offset on opposing walls. The
innermost patterned surfaces (those surfaces bounding a flow channel) may
contain
a pattern such as a diagonal array. The diagonal arrays may be oriented both
"with"
the direction of flow or one side oriented with the direction of flow and the
opposing
side oriented "against" the direction of flow. By varying surface features on
opposing
walls, different flow fields and degrees of vorticity may be created in the
fluid that
travels down the center and open gap.
The surface features may be oriented at angles relative to the direction of
flow
through the channels. The surface features may be aligned at an angle from
about
10 to about 890, and in one embodiment from about 30' to about 75 , relative
to the
direction of flow. The angle of orientation may be an oblique angle. The
angled
surface features may be aligned toward the direction of flow or against the
direction
of flow. The flow of fluid in contact with the surface features may force some
of the
fluid into depressions in the surface features, while other fluids may flow
above the
surface features. Flow within the surface features may conform with the
surface
feature and be at an angle to the direction of the bulk flow in the channel.
As fluid
exits the surface features it may exert momentum in the x and y direction for
an x,y,z
coordinate system wherein the bulk flow is in the z direction. This may result
in a
churning or rotation in the flow of the fluids. This pattern may be helpful
for mixing.
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Two or more surface feature regions within the process microchannels may
be placed in series such that mixing of the fluids may be accomplished using a
first
surface feature region, followed by at least one second surface feature region
where
a different flow pattern may be used.
The surface features may have two or more layers stacked on top of each
other or intertwined in a three-dimensional pattern. The pattern in each
discrete layer
may be the same or different. Flow may rotate or advect in each layer or only
in one
layer. Sub-layers, which may not be adjacent to the bulk flow path of the
channel,
may be used to create additional surface area. The flow may rotate in the
first level
of surface features and diffuse molecularly into the second or more sublayers
to
promote reaction. Three-dimensional surface features may be made via metal
casting, photochemical machining, laser cutting, etching, ablation, or other
processes where varying patterns may be broken into discrete planes as if
stacked
on top of one another. Three-dimensional surface features may be provided
adjacent to the bulk flow path within the microchannel where the surface
features
have different depths, shapes, and/or locations accompanied by sub-features
with
patterns of varying depths, shapes and/or locations.
An example of a three-dimensional surface feature structure may comprise
recessed oblique angles or chevrons at the interface adjacent the bulk flow
path of
the microchannel. Beneath the chevrons there may be a series of three-
dimensional
structures that connect to the surface features adjacent to the bulk flow path
but are
made from structures of assorted shapes, depths, and/or locations. It may be
further
advantageous to provide sublayer passages that do not directly fall beneath an
open
surface feature that is adjacent to the bulk flow path within the microchannel
but
rather connect through one or more tortuous two-dimensional or three-
dimensional
passages. This approach may be advantageous for creating tailored residence
time
distributions in the microchannels, where it may be desirable to have a wider
versus
more narrow residence time distribution.
The length and width of a surface feature may be defined in the same way as
the length and width of a channel. The depth may be the distance which the
surface
feature sinks into or rises above the microchannel surface. The depth of the
surface
features may correspond to the direction of stacking a stacked and bonded
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microchannel device with surface features formed on or in the sheet surfaces.
The
dimensions for the surface features may refer the maximum dimension of a
surface
feature; for example the depth of a rounded groove may refer to the maximum
depth,
that is, the depth at the bottom of the groove.
The surface features may have depths that are up to about 5 mm, and in one
embodiment up to about 2 mm, and in one embodiment in the range from about
0.01
to about 5 mm, and in one embodiment in the range from about 0.01 to about 2
mm,
and in one embodiment in the range from about 0.01 mm to about 1 mm. The width
of the surface features may be sufficient to nearly span the microchannel
width (for
example, herringbone designs), but in one embodiment (such as fill features)
may
span about 60% or less of the width of the microchannel, and in one embodiment
about 50% or less, and in one embodiment about 40% or less, and in one
embodiment from about 0.1% to about 60% of the microchannel width, and in one
embodiment from about 0.1% to about 50% of the microchannel width, and in one
embodiment from about 0.1% to about 40% of the microchannel width. The width
of
the surface features may be in the range from about 0.05 mm to about 100 cm,
and
in one embodiment in the range from about 0.5 mm to about 5 cm, and in one
embodiment in the range from about 1 to about 2 cm.
Multiple surface features or regions of surface features may be included
within a channel, including surface features that recess at different depths
into one
or more microchannel walls. The spacing between recesses may be in the range
from about 0.01 mm to about 10 mm, and in one embodiment in the range from
about 0.1 to about 1 mm. The surface features may be present throughout the
entire
length of a microchannel or in portions or regions of the channel. The portion
or
region having surface features may be intermittent so as to promote a desired
mixing
or unit operation (for example, separation, cooling, etc.) in tailored zones.
For
example, a one-centimeter section of a channel may have a tightly spaced array
of
surface features, followed by four centimeters of a flat channel without
surface
features, followed by a two-centimeter section of loosely spaced surface
features.
The term "loosely spaced surface features" may be used to refer to surface
features
with a pitch or feature to feature distance that is more than about five times
the width
of the surface feature.
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The surface features may be positioned in one or more surface feature
regions that extend substantially over the entire axial length of a channel.
In one
embodiment, a channel may have surface features extending over about 50% or
less of its axial length, and in one embodiment over about 20% or less of its
axial
length. In one embodiment, the surface features may extend over about 10% to
about 100% of the axial length of the channel, and in one embodiment from
about
20% to about 90%, and in one embodiment from about 30% to about 80%, and in
one embodiment from about 40% to about 60% of the axial length of a channel.
Each surface feature leg may be at an oblique angle relative to the bulk flow
direction. The feature span length or span may be defined as being normal to
the
feature orientation. As an example, one surface feature may be a diagonal
depression at a 45 degree angle relative to a plane orthogonal to the mean
direction
of bulk flow in the main channel with a 0.38 mm opening or span or feature
span
length and a feature run length of 5.6 mm. The run length may be the distance
from
one end to the other end of the surface feature in the longest direction,
whereas the
span or feature span length may be in the shortest direction (that is not
depth). The
surface feature depth may be the distance way from the main channel. For
surface
features with a nonuniform width (span), the span may be the average span
averaged over the run length.
A surface feature may comprise a recess or a protrusion based on the
projected area at the base of the surface feature or the top of the surface
feature. If
the area at the top of the surface feature is the same or exceeds the area at
the
base of the surface feature, then the surface feature may be considered to be
recessed. If the area at the base of the surface feature exceeds the area at
the top
of the surface feature, then it may be considered to be protruded. For this
description, the surface features may be described as recessed although it is
to be
understood that by changing the aspect ratio of the surface feature it may be
alternatively defined as a protrusion. For a process microchannel defined by
walls
that intersect only the tops of the surface features, especially for a flat
channel, all
surface features may be defined as recessed and it is to be understood that a
similar
channel could be created by protruding surface features from the base of a
channel
with a cross section that includes the base of the surface features.
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The Fischer-Tropsch or alcohol-forming process microchannels, SMR
process microchannels and/or combustion channels, and/or hydrocracking process
microchannels may have at least about 20%, and in one embodiment at least
about
35%, and in one embodiment at least about 50%, and in one embodiment at least
5 about 70%,
and in one embodiment at least about 90% of the interior surface of the
channels (measured in cross-section perpendicular to length; i.e.,
perpendicular to
the direction of net flow through the channel) that contains surface features.
The
surface features may cover a continuous stretch of at least about 1 cm, and in
one
embodiment at least about 5 cm. In the case of an enclosed channel, the
10 percentage of surface feature coverage may be the portion of a cross-
section
covered with surface features as compared to an enclosed channel that extends
uniformly from either the base or the top of the surface feature or a constant
value
in-between. The latter may be a flat channel. For example, if a channel has
patterned top and bottom surfaces that are each 0.9 cm across (wide) and
15
unpatterned side walls that are 0.1 cm high, then 90% of the surface of the
channel
would contain surface features.
The Fischer-Tropsch or alcohol-forming process microchannels, SMR
process microchannels, and/or hydrocracking process microchannels may be
enclosed on all sides, and in one embodiment the channels may have a generally
20 square or
rectangular cross-section (in the case of rectangular channel, surface
feature patterning may be positioned on both major faces). For a generally
square
or rectangular channel, the channels may be enclosed on only two or three
sides
and only the two or three walled sides may be used in the above described
calculation of percentage surface features. The surface features may be
positioned
25 on
cylindrical channels with either constant or varying cross section in the
axial
direction.
Each of the surface feature patterns may be repeated along one face of the
channel, with variable or regular spacing between the surface features in the
channel bulk flow direction. Some embodiments may have only a single leg to
each
30 surface
feature, while other embodiments may have multiple legs (two, three, or
more). For a wide-width channel, multiple surface features or columns of
repeated
surface features may be placed adjacent to one another across the width of the
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channel. For each of the surface feature patterns, the feature depth, width,
span, and
spacing may be variable or constant as the pattern is repeated along the bulk
flow
direction in the main channel. Also, surface feature geometries having an apex
connecting
two legs at different angles may have alternate embodiments in which the
surface feature
legs may not be connected at the apex.
The Fischer-Tropsch catalyst may comprise any Fischer-Tropsch catalyst. The
Fischer-Tropsch catalyst may comprise at least one catalytically active metal
or oxide
thereof. In one embodiment, the Fischer-Tropsch catalyst may further comprise
a catalyst
support. In one embodiment, the Fischer-Tropsch catalyst may further comprises
at least
one promoter. The catalytically active metal may comprise Co, Fe, Ni, Ru, Re,
Os, or a
combination of two or more thereof. The support material may comprise alumina,
zirconia,
silica, aluminum fluoride, fluorided alumina, bentonite, ceria, zinc oxide,
silica-alumina,
silicon carbide, a molecular sieve, or a combination of two or more thereof.
The support
material may comprise a refractory oxide. The promoter may comprise a Group
IA, HA, IIIB
or IVB metal or oxide thereof, a lanthanide metal or metal oxide, or an
actinide metal or
metal oxide. In one embodiment, the promoter is Li, B, Na, K, Rb, Cs, Mg, Ca,
Sr, Ba, Sc,
Y, La, Ac, Ti, Zr, La, Ac, Ce or Th, or an oxide thereof, or a mixture of two
or more thereof.
Examples of catalysts that may be used include those disclosed in U.S. Patents
4,585,798; 5,036,032; 5,733,839; 6,075,062; 6,136,868; 6,262,131 Bl; 6,353,035
B2;
6,368,997 B2; 6,476,085 B2; 6,451,864 B2; 6,490,880 Bl; 6,537,945 B2;
6,558,634 BI;
and U.S. Patent Publications 2002/0028853 Al; 2002/0188031 Al; and
2003/0105171 Al.
The Fischer-Tropsch catalyst may comprise Co, and optionally a co-catalyst
and/or
promoter, supported on a support wherein the Co loading is at least about 5%
by weight,
and in one embodiment at least about 10% by weight, and in one embodiment at
least
about 15% by weight, and in one embodiment at least about 20% by weight, and
in one
embodiment at least about 25% by weight, and in one embodiment at least about
28% by
weight, and in one embodiment at least about 30% by weight, and in one
embodiment at
least about 32% by weight, and in one
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embodiment at least about 35% by weight, and in one embodiment at least about
40% by weight. In one embodiment, the Co loading may be from about 5 to about
50% by weight, and in one embodiment about 10 to about 50% by weight, and in
one embodiment about 15 to about 50% by weight, and in one embodiment about 20
to about 50% by weight, and in one embodiment about 25 to about 50% by weight,
and in one embodiment about 28 to about 50% by weight, and in one embodiment
about 30 to about 50% by weight, and in one embodiment about 32 to about 50%
by
weight. The metal dispersion for the catalytically active metal (i.e., Co, and
optionally co-catalyst and/or promoter) of the catalyst may range from about 1
to
about 30%, and in one embodiment about 2 to about 20%, and in one embodiment
about 3 to about 20%. The co-catalyst may be Fe, Ni, Ru, Re, Os, or an oxide
thereof, or a mixture of two or more thereof. The promoter may be a Group IA,
IIA,
IIIB or IVB metal or oxide thereof, a lanthanide metal or metal oxide, or an
actinide
metal or metal oxide. In one embodiment, the promoter is Li, B, Na, K, Rb, Cs,
Mg,
Ca, Sr, Ba, Sc, Y, La, Ac, Ti, Zr, La, Ac, Ce or Th, or an oxide thereof, or a
mixture of
two or more thereof. The co-catalyst may be employed at a concentration of up
to
about 10% by weight based on the total weight of the catalyst (i.e., the
weight of
catalyst, co-catalyst, promoter and support), and in one embodiment about 0.1
to
about 5% by weight. The promoter may be employed at a concentration of up to
about 10% by weight based on the total weight of the catalyst, and in one
embodiment about 0.1 to about 5% by weight.
The Fischer-Tropsch catalyst may comprise Co supported by alumina; the
loading of Co being at least about 25% by weight, and in one embodiment at
least
about 28% by weight, and in one embodiment at least about 30% by weight, and
in
one embodiment at least about 32% by weight; and the Co dispersion is at least
about 3%, and in one embodiment at least about 5%, and in one embodiment at
least about 7%.
The Fischer-Tropsch catalyst may comprise a composition represented by the
formula
COM% M2bOx
wherein: M1 is Fe, Ni, Ru, Re, Os or a mixture thereof, and in one embodiment
M1 is
Ru or Re or a mixture thereof; M2 is Li, B, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc,
Y, La,
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Ac, Ti, Zr, La, Ac, Ce or Th, or a mixture of two or more thereof; a is a
number in the
range of zero to about 0.5, and in one embodiment zero to about 0.2; b is a
number
in the range of zero to about 0.5, and in one embodiment zero to about 0.1;
and x is
the number of oxygens needed to fulfill the valency requirements of the
elements
present.
The Fischer-Tropsch catalyst may be made using multiple impregnation steps
wherein intercalcination steps are conducted between each impregnation step.
The
use of such a procedure, at least in one embodiment, allows for the formation
of
catalysts with levels of loading of catalytic metal and optionally promoter
that are
higher than with procedures wherein such intercalcination steps are not
employed.
In one embodiment, a catalytic metal (e.g., Co) and optionally co-catalyst
(e.g., Re or
Ru) and/or promoter is loaded on a support (e.g., A1203) using the following
sequence of steps: (A) impregnating the support with a composition comprising
a
catalytic metal and optionally a co-catalyst and/or promoter to provide an
intermediate catalytic product; (B) calcining the intermediate catalytic
product formed
in step (A); (C) impregnating the calcined intermediate product formed in (B)
with
another composition comprising a catalytic metal and optionally a co-catalyst
and/or
promoter, to provide another intermediate catalytic product; and (D) calcining
the
another intermediate catalytic product formed in step (C) to provide the
desired
catalyst product. The catalytic metal and optional co-catalyst and/or promoter
may
be impregnated on the support using an incipient wetness impregnation process.
Steps (C) and (D) may be repeated one or more additional times until the
desired
loading of catalytic metal, and optional co-catalyst and/or promoter, is
achieved. The
composition comprising the catalytic metal may be a nitrate solution of the
metal, for
example, a cobalt nitrate solution. The process may be continued until the
catalytic
metal (i.e., Co) achieves a loading level of about 20% by weight or more, and
in one
embodiment about 25% by weight or more, and in one embodiment about 28% by
weight or more, and in one embodiment about 30% by weight or more, and in one
embodiment about 32% by weight or more, and in one embodiment about 35% by
weight or more, and in one embodiment about 37% by weight or more, and in one
embodiment about 40% by weight or more. Each of the calcination steps may
comprise heating the catalyst at a temperature in the range of about 100 C to
about
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500 C, and in one embodiment about 100 C to about 400 C, and in one embodiment
about 250 to about 350 C for about 0.5 to about 100 hours, and in one
embodiment about
0.5 to about 24 hours, and in one embodiment about 2 to about 3 hours. The
temperature
may be ramped to the calcination temperature at a rate of about 1-20 C/min.
The
calcination steps may be preceded by drying steps wherein the catalyst is
dried at a
temperature of about 75 to about 200 C, and in one embodiment about 75 C to
about
150 C, for about 0.5 to about 100 hours, and in one embodiment about 0.5 to
about 24
hours. In one embodiment, the catalyst may be dried for about 12 hours at
about 90 C and
then at about 110-120 C for about 1-1.5 hours, the temperature being ramped
from 90 C
to 110-120 C at a rate of about 0.5-1 C/min.
The Fischer-Tropsch catalyst may comprise a metal, metal oxide or mixed metal
oxide. The metal may be cobalt, iron, ruthenium or a mixture of two or more
thereof. The
catalyst may comprise Co, or a carbide or oxide thereof. These catalysts may
also
comprise one or more alkali metals, alkaline earth metals, transition metals,
rare earth
metals, and/or lanthanides. This catalyst may be supported, and if so, useful
support
materials may include metal oxides, e.g., alumina, titania, zirconia, as well
as silica,
nnesoporous materials, zeolites, refractory metals, or combinations of two or
more thereof.
The support may be modified through the addition of small quantities of one or
more
transition metal oxides. The catalyst may be any of the Fischer-Tropsch
catalysts
disclosed in WO 2008/104793 A2.
The Fischer-Tropsch catalyst may comprise cobalt in an amount of up to about
60% by weight, and in one embodiment from about 10% to about 60% by weight,
and in
one embodiment from about 20% to about 60% by weight, and in one embodiment
from
about 30% to about 60% by weight, and in one embodiment about 35% to about 60%
by
weight, and in one embodiment about 35% to about 50% by weight. These
catalysts may
comprise cobalt and a support.
The Fischer-Tropsch catalyst may comprise cobalt and a support. This catalyst
may be activated using the process disclosed in U.S. Patent 7,183,329 B2. This
process
comprises activating a catalyst precursor comprising a cobalt compound and a
support
with a gas
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comprising at least about 5 mol % of a hydrocarbon.
The term "catalyst" may be used herein to cover both the catalyst in active
form and the catalyst in precursor form since it may undergo change in the
reaction
environment. The term "catalyst precursor" is to be construed widely, covering
not
5 only a
freshly prepared catalyst precursor or a catalyst precursor which is unreduced
or which has not been used in a reaction which it catalyzes, but also any
precursor
which can be used as a catalyst after activation, such as a catalyst which has
already been used in a reaction which it catalyzes. Similarly the term
"activation" is
to be understood as not only including activating as unused or unreduced
catalyst
10 precursor
but also activating a used or reduced catalyst. Therefore the term includes
within its scope any activation, including regeneration of a used catalyst.
The Fischer-Tropsch catalyst may be prepared by activating a catalyst
precursor with a hydrocarbon. The catalyst precursor may contain a cobalt
compound and a support. The support may be any support which is capable of
15 bearing
the catalyst in the desired reaction. The support may be an inert support, or
it may be an active support. Examples of supports that may be used include
alumina, modified alumina, spinel oxides, silica, modified silica, magnesia,
titania,
zirconia, a zeolite, beta-aluminate and forms of carbon. The alumina or
modified
alumina may be, for example, alpha-alumina, beta-alumina or gamma-alumina.
20 Beta-alumina and spinel oxides, such as barium hexaaluminate, may be
advantageous due to their stability. The carbon may be in the form of active
carbon
or carbon nanotubes. A zeolite may be used. The support may contain pores or
channels.
Any cobalt compound may be used with the catalyst precursor. The cobalt
25 compound
may be in the form of a salt, for example, an aqueous soluble salt, or an
oxide. Examples of cobalt salts that may be used may include cobalt nitrate,
acetate, benzoate, oxalate or acetylacetonate. It may be desirable to avoid
the use
of a cobalt halide since the halide may interfere with the support. An example
of a
cobalt oxide that may be used is Co304. One or more cobalt salts and/or oxides
30 may be used.
The catalyst precursor may be formed using any known procedure. The
catalyst precursor may be added to the support in solution using a solvent
such as
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water or an organic solvent such as an alcohol. The alcohol may contain from 1
to
about 4 carbon atoms. These may include methanol and ethanol. The solvent may
be subsequently removed. The solvent may be removed by drying at room
temperature or above room temperature, for example from about 50 C to about
250 C, for about 1 to about 24 hours. A combination of drying steps may be
used.
The supported catalyst precursor may be dried at room temperature for about 2
to
about hours, and subsequently dried at an elevated temperature, for example
from about 100 C to about 200 C, and in one embodiment about 120 C, for about
2
to about 8 hours.
10 The
solution comprising the catalyst precursor may further comprise
additional components if desired. For example, it may also comprise a promoter
or
modifier. The promoters may include alkaline earth salts such as magnesium,
calcium, barium and/or strontium nitrate. The promoters may also include the
oxides
of alkali metal, alkaline earth metal or transition metals which are derivable
from their
aqueous soluble compounds, such as their salts, for example LiNO3, KNO3,
RbNO3,
Ba(NO3)2, Mg(NO3)2, Ca(NO3)2, Sr(NO3)2, Zr(NO3)2.xH20, Ce(NO3)3.xH20 and
UO(NO3)2. The promoters may be loaded onto the support in any manner, for
example by impregnation, especially sequential impregnation or co-impregnation
with the cobalt compound.
The modifiers may include rare earth modifiers such as transition metal or
rare earth salts or oxides, for example lanthanum and/or cerium nitrate or
acetate, or
oxides of the d-block transition metals such as Mn, W, Nb and Vn. The
modifiers
may be derived from their aqueous soluble compounds such as salts, and may be
impregnated into the catalyst support, followed by calcination in air at a
temperature
in the range from about 300 C to about 1000 C for about 1 to about 24 hours in
air.
The promoters and modifiers may be used singly or in a combination of two or
more
thereof.
The supported catalyst precursor may be formed using a sol gel method.
This method is described, for example, in Gonzalez et al, Catalysis Today, 35
(1997), 293-317 and J. Livage, Catalysis Today, 41 (1998), 3 19. For example,
in an
initial "pregelation" step, an alkoxide or alcohol and a metal precursor may
be
hydrolyzed and condensed to form a gel, for example, in the presence of water.
A
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cobalt compound may then be added in a subsequent "post gelation" step, the
gel
may then be dried and calcined.
The supported catalyst precursor may comprise from about 0.05 to about 30
wt % cobalt, and in one embodiment from about 0.5 to about 15 wt % cobalt. The
supported catalyst precursor may comprise from about 0.5 to about 50 wt % of a
cobalt compound; from 0 to about 10 wt % promoter; and from 0 to about 20 wt %
modifier, or from about 0.01 to about 5 wt % modifier; based on the total
weight of
the supported catalyst precursor. The supported catalyst precursor may
comprise
from about 5 to about 40 wt % of a cobalt compound, from 0 to about 3 wt %
promoter, and from 0 to about 3 wt % modifier.
The supported catalyst precursor may be activated with a gas comprising a
hydrocarbon. The hydrocarbon may be any hydrocarbon. It may be saturated or
unsaturated, for example containing from 1, 2 or 3 or more double and/or
triple
bonds. It may be linear, cyclic or branched. The hydrocarbon may also be
aliphatic
or aryl, or contain both aliphatic and aryl groups. The hydrocarbon may be a
saturated or unsaturated hydrocarbon containing up to about 5 carbon atoms,
and in
one embodiment up to about 4 carbon-atoms. The hydrocarbon may comprise
methane, ethane, acetylene, propane, propene, butane, or a mixture of two or
more
thereof.
The activating gas may comprise at least about 5 mol % of the hydrocarbon,
and in one embodiment at least about 10 mol %, and in one embodiment at least
about 20 mol A), and in one embodiment at least about 40 mol %. The gas
comprising the hydrocarbon may comprise only the hydrocarbon or it may further
comprise up to about 10 mol %, and in one embodiment up to about 20 mol % ,
and
in one embodiment up to about 40 mol % of an inert gas such as nitrogen and/or
argon. It may also comprise a reactive component, such as another component
which may also activate the catalyst precursor. For example, the gas may also
comprise hydrogen. The gas may comprise methane and/or ethane in combination
with hydrogen. If hydrogen is used, any ratio of hydrocarbon to hydrogen may
be
used, for example, the ratio may be in the range from about 0.04:1 or 0.05:1
to about
100:1 on a molar basis, or from about 0.1:1 or about 0.5:1 to about 10:1.
The activation may be carried out by placing the supported catalyst precursor
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in an atmosphere of the activating gas. The activating gas may be passed over
the
supported catalyst precursor. The activation temperature may be about 300 C or
higher,
for example from about 400 C to about 1000 C, or from about 400 C to about 800
C. The
duration of activation may be at least about 30 minutes, and in one embodiment
at least
about 1 hour, for example, from about 1 to about 20 hours, and in one
embodiment from
about 2 to about 5 hours. The activation temperature may vary depending on the
nature of
the catalyst precursor and/or the hydrocarbon. Atmospheric pressure may be
used for the
activation step, although a reduced or elevated pressure may also be used.
The catalyst precursor may be activated in the reaction vessel in which it is
intended to carry out the reaction using the activated catalyst, or it may be
activated in a
different vessel. The activated catalyst may undergo substantial oxidation
when exposed
to air. In order to stabilize the catalyst it may be treated in an atmosphere
containing a
small amount of oxygen, for example about 1% oxygen in an inert gas such as
nitrogen or
argon. The catalyst may be left in the activation reactor while bleeding in a
small amount
of oxygen. Thus, for example, the activated catalyst may be pacified by
treatment in a
reduced oxygen atmosphere, for example comprising less than about 20 mol %
oxygen, or
less than about 10 mol % oxygen, or less than about 5 mol % oxygen, or less
than about 2
mol % oxygen, for at least about 30 minutes, or at least about 1 hour.
The Fischer-Tropsch catalyst may be prepared using the process disclosed in
U.S.
Patent 7,304,012 B2. This process involves preparing a supported catalyst or
catalyst
precursor containing carbon. The process may comprise the steps of: (a)
preparing a
liquid mixture of (i) at least one catalyst support or catalyst support
precursor; (ii) at least
one metal-containing compound, wherein the metal is selected from V, Cr, Mn,
Fe, Co, Ni,
Cu, Mo and W, and (iii) at least one polar organic compound which acts as a
solvent for
the metal-containing compound, the liquid mixture comprising from 0 to about
20 wt % of
water based on the total weight of the mixture; (b) converting the mixture to
a paste or
solid residue; and (c) combusting the residue in an oxygen-containing
atmosphere to at
least partially convert the organic compound to carbon and to form the
supported catalyst
or catalyst precursor.
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In step (a), a liquid mixture may be prepared from at least three components:
(i) a catalyst support or a catalyst support precursor; (ii) one or more metal-
containing compound(s) and (iii) one of more polar organic compound solvents
which act as solvent(s) for the metal-containing compound(s), optionally
together
with water.
All three components may be mixed together simultaneously. The
components may be mixed together at room or elevated temperature, for example,
at about 20 to about 200 C, and in one embodiment from about 40 to about 80 C,
and in one embodiment from about 40 to about 60 C.
In an alternative embodiment, two of the three components may be mixed
together in a preliminary step, before the third component is added to
complete the
liquid mixture. Components (ii) and (iii) may be mixed together in a
preliminary step.
These two components may form a clear solution. Thereafter, component (i) may
be
added to complete the liquid mixture which may contain solid particles if
component
(i) is a solid support. The liquid mixture may be formed at elevated
temperature, for
example, from about 20 to about 200 C, and in one embodiment from about 30 to
about 80 C.
Component (i) may be a catalyst support or catalyst support precursor. A
catalyst support may be in the form of one or more solid particles. The
catalyst
support precursor may initially be in liquid form or in the form of a
solution. The
support precursor may form a solid catalyst support in situ, for example, once
the
catalyst support precursor has been added to the liquid mixture. The catalyst
support precursor may form a catalyst support in the conversion step (b) or
combustion step (c).
The catalyst support may be an inert support or an active support. Examples
of supports that may be used may include solid oxides, carbides, zeolites,
carbon
and boronitride. These may include alumina, modified alumina, spinel oxides,
silica,
modified silica, magnesia, titania, zirconia, a molecular sieve, a zeolite,
beta-
aluminate and forms of carbon. The alumina or modified alumina may be, for
example, alpha-alumina, beta-alumina or gamma-alumina. Beta-alumina and spinel
oxides such as barium hexaaluminate may be particularly useful. The carbon may
be in the form of active carbon or carbon nanotubes. A zeolite may be used.
The
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support may comprise pores or channels. The zeolites may include zeolites A,
X, Y,
ZSMs, MCMs or AlPO4.
The catalyst support precursors may be derived from Al(NO3)3.9H20 or
Mg(NO3)2. Catalyst precursors that may be used are described in further detail
in
5 the above-
mentioned Gonzales eta!, Catalysis Today, 35 (1997), 293-317, and J.
Livage, Catalysis Today, 41 (1998), 3-19.
The catalyst support may be derived from a nitrate of, for example, a Group
HA or Group IIIA metal. For example, aluminium or magnesium nitrate may be
used.
The nitrate may be in a hydrated form. Examples may include Al(NO3)3.9H20 and
10
Mg(NO3)2.6H20. In step (a), the nitrate may be mixed with an organic compound,
such as urea and/or ammonium citrate, to form a clear solution. Water may
optionally be added. To complete the liquid mixture, a metal-containing
compound,
such as cobalt nitrate, may be included in the mixture. During one of the
subsequent
conversion and combustion steps, a supported catalyst or supported catalyst
15 precursor may be formed.
The catalyst may be porous. The particle size may be from about 0.1 pm to
about 20 mm, or from about 0.2 pm to about 5 mm. The surface area may be
greater than about 5 m2/g, or greater than about 10 m2/g , or greater than
about 50
m2/g, or greater than about 200 m2/g. One or a mixture of two or more catalyst
20 supports may be used.
Component (ii) of the liquid mixture may comprise one or more metal-
containing compounds. The catalytically active component of the catalyst may
be
derived from this metal-containing compound. The metal in the metal containing
compound may comprise V, Cr, Mn, Fe, Co, Ni, Cu, Mo, W, or a mixture of two or
25 more
thereof. It is also possible to incorporate a further metal, for example to
act as
a promoter or modifier such as, for example, at least one of Zr, U, Ti, Th,
Hf, Ce, La,
Y, Mg, Ca, Sr, Cs, Rb, Mo, W, Cr, Mg, rare earth metals, noble metals, or a
mixture
of two or more thereof. For example, the metal-containing compound may
comprise
at least one of V, Cr, Mn, Fe, Co, Ni, Cu, Mo or W and at least one metal
selected
30 from the
lanthanide, actinide and transition metal series of the Periodic Table. The
additional metal may be an f-block or d-block metal.
The additional metal may be one or more metals selected from noble metals
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such as Pd, Pt, Rh, Ru, I r, Au, Ag and Os, and transition metal elements such
as Ti,
V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Tc, Cd, Hf, Ta, W, Re, Hg, TI and
the 4f-
block lanthanides such as La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,
Yb
and Lu. Of these metals, Pd, Pt, Ru, Ni, Co, Fe, Cu, Mn, Mo and W may be
particularly useful.
The metal-containing compound may contain other elements. The metal-
containing compound is in the form of a salt. Examples of the metal-containing
salts
may include nitrates, citrates, halides, alkoxides, phenoxides, acetates,
benzoates,
oxalates and acetylacetonates
Component (iii) of the liquid mixture may be a polar organic compound. The
organic compound may function as a solvent for component (ii) and may act as a
solvent for compound (i). The organic compound may be any polar organic
compound that is capable of undergoing combustion in the presence of an oxygen-
containing atmosphere such as air. During combustion the organic compound may
be converted to carbon which may be present either as elemental carbon or as a
carbide, for example a carbide of the metal of the metal-containing compound
(ii).
Some or all of the organic compound may be converted to carbon, and it is also
possible for some of the organic compound to be completely combusted such that
the carbon is converted to carbon monoxide or carbon dioxide and is removed
from
the catalyst or catalyst precursor as a gas. The organic compound may be a
compound that does not produce an ash, in particular an oxide ash, after the
combustion step. The organic compound may be one that does not contain
elements that have a tendency to form residues such as oxides after
combustion.
These elements may include, for example, metals, phosphorus and/or silicon.
Examples of the organic compounds that may be used include organic
amines, organic carboxylic acids and salts thereof such as ammonium salts,
alcohols, ammonium salts of phenoxides and alkoxides, amino acids and
surfactants. The alcohols may be those containing from Ito about 30 carbon
atoms,
or from 1 to about 15 carbon atoms. Examples of the alcohols that may be used
may include methanol, ethanol and glycol. The carboxylic acid may be citric
acid or
oxalic acid. Other organic compounds may be compounds containing functional
groups such as one or more hydroxyl, amine, amide, carboxylic acid, ester,
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aldehyde, ketone, imine or imide groups. These may include urea, hydroamines,
trimethylamine, triethylamine, tetra methylamine chloride and tetraethylamine
chloride. The organic compounds may include EDTA, urea and/or ammonium citrate
The organic compound may be in the form of a liquid at room temperature or
at the temperature at which the mixture is prepared. The organic compound may
be
heated before it is added to the mixture. The organic compound may also be in
the
form of a solid at room temperature or at the temperature at which the mixture
is
prepared, in which case the mixture may be heated after it is prepared to melt
the
organic compound and then dissolve the metal compound. Mixtures of organic
compounds may be used. Water may also be added, for example to assist the
dissolution of the metal compound(s).
When water is employed in the liquid mixture, the amount of water may need
to be controlled. For example, certain catalyst support precursors, such as
Fe(NO3)3.9H20 and Al(NO3)3.9H20 may have a tendency to form gels on coming
into contact with effective amounts of water. Thus, the amount of water
employed in
step (a) should be kept to a minimum, to avoid the formation of a hydrolyzed
gel.
The amount of water may be sufficient to partially hydrolyze the catalyst
precursor,
but not sufficient to convert the catalyst precursor into a polymer. Typically
up to
about 20 wt % water may be used with respect to the total weight of the
mixture.
Water may be added separately or may, for example, be present in one of the
components added as water of crystallization or water of coordination.
The mixture may also comprise other components. These may include
promoters and/or modifiers. The promoters may include alkaline earth salts
such as
magnesium, calcium, barium and/or strontium nitrate. The modifiers may include
rare earth modifiers such as rare earth salts, for example lanthanum and/or
cerium
nitrate or acetate, or oxides of the d-block transition metals. Oxides of
phosphorus,
boron, gallium, germanium, arsenic and antimony may be used. The promoters and
modifiers may be used singly or in a combination of two or more.
The mixture prepared in step (a) may be a liquid mixture. The term "liquid
mixture" refers to the fact that the mixture is in the form of a homogeneous
liquid,
although it may comprise solid particles. For example, after the homogeneous
liquid
mixture of the organic compounds, optionally water, and metal compounds, has
=
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been formed, insoluble particles of the inert support may be added. For
instance, if
a catalyst support rather than a catalyst support precursor is present, the
liquid may
comprise solid support particles. The metal-containing compound should be able
to
contact the support or support precursor, and this may be achieved by the use
of a
liquid mixture.
The weight ratio of component (i): (ii): (iii) employed in step (a) may be
about
0.1-80:1-90:1-99, or about 0.5-60:2-80:10-90. The weight ratios may be varied
depending on the intended use of the final catalyst. The amount of organic
compound may be determined by the atomic ratio of carbon in the organic
compound to metal (C:M) in the dissolved metal containing compound. The atomic
ratio may be at least 0.4:1, or about 1 to about 20:1.
After the liquid mixture is formed, it may be converted to a paste or solid
residue in step (b). This may be achieved by heating the mixture. This heating
step
may be in addition to any heating required to melt the organic compound,
although if
previous heating is required that heating may simply be continued in step (b).
The
heating may transform the liquid mixture into a solid, for example by
evaporating or
decomposing the organic solvent. Any water that may be present in the liquid
mixture may be evaporated. The temperature to which the mixture is heated may
be
any temperature above room temperature, for example from about 50 C to about
250 C, and may be carried out for any time until a solid residue is formed,
for
example for about 1 to about 24 hours. A combination of drying steps may be
used.
The mixture may initially be dried at room temperature for from about 2 to
about 10
hours, and subsequently dried at an elevated temperature, for example from
about
100 C to about 200 C, or about 120 C.
In step (c) the mixture may be combusted. The combustion step may be
carried out in air. Alternatively, pure oxygen or oxygen in an inert
atmosphere of, for
example, nitrogen or another inert gas may be employed. This combustion step
may
be separate from the heating in step (b), or the two steps may be combined,
for
example by simply continuing to heat the mixture after the solvent has been
removed.
The combustion temperature may be from about 200 C to about 1000 C, or
from about 400 C to about 600 C. The combustion step may be performed for any
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period of time, for example, about 60 minutes or less, or about 30 minutes or
less, or
about 15 minutes or less, or from about 5 to about 15 minutes. The combustion
step
may convert the polar organic compound into carbon and volatiles. While not
wishing
to be bound by theory, it is believed that the combustion step may completely
or
partially change the metal-containing compound into a metal and/or one or more
oxides, oxycarbides or carbide forms, or mixtures of two or more thereof. The
combustion step may also convert the promoter and/or modifier to oxide forms
if they
are present.
The preparation of the Fischer-Tropsch catalyst may proceed by first mixing
the metal containing compound(s) and polar organic compound(s). This mixture
may be viscous and addition to a solid catalyst support may coat the external
surface of the support, with only a limited penetration of "internal" surfaces
such as
pores. After the combustion step, a so-called "egg-shell" catalyst in which
all or
substantially all of the catalyst may be present on the surface of the support
may be
obtained. This process may provide a better and more even distribution of the
catalyst on the surface of the support than when only water is used as the
solvent.
The preparation of the Fischer-Tropsch catalyst may also proceed by first
mixing the metal containing compound(s) with the organic compound(s) and then
adding a soluble support. After combustion, the metal catalyst may be
distributed on
both the "external" and "internal" surfaces of the support. This process may
provide
a more homogeneous distribution of the catalyst throughout the support than
with
previously known catalysts.
The Fischer-Tropsch catalyst or catalyst precursor may be distributed in any
desired way on the "external" surface or in the "internal" surfaces of the
support. It
may be distributed substantially throughout the support or only on the
external
surface of the support. The distribution of the active catalyst component or
precursor thereof may be controlled.
The Fischer-Tropsch catalyst or catalyst precursor may contain carbon in all
of its possible forms. For example it may be present as elemental carbon or in
the
form of a metal carbide or oxycarbide. The carbon content may be up to about 8
wt
% based on the total weight of the catalyst precursor or catalyst, or from
about 0.01
to about 8 wt %, or from about 0.01 to about 2 knit %.
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The Fischer-Tropsch supported catalyst or catalyst precursor may comprise
from about 0.5 to about 50 wt % catalyst or catalyst precursor, from 0 to
about 10 wt
% promoter and from 0 to about 5 wt % modifier, based on the total weight of
the
supported catalyst or catalyst precursor. The
supported catalyst or catalyst
5 precursor may comprise from about 5 to about 40 wt % catalyst or catalyst
precursor, from 0 to about 3 wt % promoter, and from 0 to about 3 wt %
modifier.
The Fischer-Tropsch supported catalyst precursor may be activated with
hydrogen or hydrocarbon gas or vapor. The solvent may be removed by heating,
such that the organic compound may be deposited in the pores of the catalyst
10 support. The catalyst support may then be mixed with the metal-containing
compound. Alternatively, the catalyst support may be kneaded with the metal-
containing compound. This process may produce a supported catalyst or catalyst
precursor in which the catalyst or catalyst precursor may be predominantly
situated
on the external surfaces of the porous particles.
15 The alcohol forming catalyst may comprise any catalyst suitable for
converting synthesis gas to one or more alcohols. The alcohol-forming catalyst
may
comprise a catalyst metal of Nb, Ta, Mo, W, Tc, Re or a mixture of two or more
thereof, in free form or combined form. The catalyst metal may be combined
with a
cocatalyst metal of yttrium, a lanthanide series metal, an actinide series
metal, or a
20 combination of two or more thereof, in free form or combined form.
The alcohol
forming catalyst may comprise RhAg, CuCo, CuThOx and/or CoMoS. The term "in
free or combined form" means the metal component of interest may be present as
a
metal, alloy, compound, adduct or combination thereof. Representative
compounds
include hydroxides, oxides, sulfides, sulfates, halides, carbides, cyanides,
nitrides,
25 nitrates, phosphates, borides, suicides, silicates, oxyhalides,
carboxylates such as
acetates and acetylacetates, oxalates, carbonates, carbonyls, hydrides, metal-
bridged and cluster compounds, compounds where the metal is part of an anionic
or
cationic species, and the like. The adducts are chemical addition products.
Molecules of polar or electron-donating solvent, former solvent or ligands
such as
30 ammonia, aliphatic or aromatic amines, imines, amino alcohols,
carboxylic acids,
amino acids, di- and trialkyl- and triarylphosphines, -arsines and stibines
and their
oxides, thiols, amino thiols, and the like, may add to the catalyst metals
with or
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without displacement. These catalysts are described in U.S. Patent 4,762,858.
The alcohol forming catalyst may comprise a copper-based or copper-modified
methanol synthesis catalyst, a copper/cobalt based or copper/cobalt modified
Fischer-
Tropsch catalyst, a precious metal (e.g., Rh) based catalyst, or a Mo or MoS2
based
catalyst. These catalysts are described in U.S. Patents 4,122,110; 4,298,354;
4,492,773;
and 4,882,360; and in Subramani et al., "A Review of Recent Literature to
Search for
Efficient Catalytic Process for the Conversion of Syngas to Ethanol," Energy &
Fuels
XXXX, xxxx, 000-000 (2007).
The alcohol forming catalyst may be used in combination with a dehydration
catalyst to provide a synthesis gas to unsaturated hydrocarbon route. Examples
of the
dehydration catalyst that may be used include acidic oxides such as alumina,
silica-
alumina, zeolite, and silico-alumino-phosphate synthetic molecular sieves.
These are
disclosed in U.S. 2006/0020155 Al and US 2007/0244000 Al. The alcohol forming
catalyst and the dehydration catalyst may be mixed or combined together in the
same
reaction zone. Alternatively, the dehydration catalyst may be positioned
downstream of the
alcohol forming catalyst, either in the same microchannel reactor or in a
separate
microchannel reactor.
The SMR catalyst may comprise any SMR catalyst. The SMR catalyst may
comprise La, Pt, Fe, Ni, Ru, Rh, In, Ir, W, and/or an oxide thereof, or a
mixture of two or
.. more thereof. In one embodiment, the SMR catalyst may further comprise MgO,
Al2O3,
SiO2, TiO2, or a mixture of two or more thereof. In one embodiment, the SMR
catalyst may
comprise 13.8%-Rh/6%-MgO/A1203 on a metal felt of FeCrAlY alloy prepared using
wash
coating of the FeCrAlY felt with a thickness of about 0.25 mm and about 90%
porosity. In
one embodiment, the SMR catalyst may be derived from an aqueous solution of
La(NO3)3-6H20. In one embodiment, the SMR catalyst may be derived from a
solution of
Pt(NH3)4(NO3)2. On one embodiment, the SMR catalyst may be derived from
solutions of
La(NO3) and Rh(NO3) which are deposited on one or more layers of A1203.
The combustion catalyst may comprise Pd, Pr, Pt, Rh, Ni, Cu, and/or an
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oxide thereof, or a mixture of two or more thereof. In one embodiment, the
combustion
catalyst may further comprise A1203, SiO2, MgO, or a mixture of two or more
thereof. In
one embodiment, the combustion catalyst may be derived from a solution of
Pd(NO3)2
which is deposited on a layer of Al2O3. In one embodiment, the combustion
catalyst may
comprise a layer of Pr and Pd using precursors in the form of nitrates, and a
layer of Pt
using a solution of Pt(NH3)4(NO3)2.
The hydrocracking catalyst may comprise any hydrocracking catalyst. These
catalysts may include zeolite catalysts including beta zeolite, omega zeolite,
L-zeolite,
ZSM-5 zeolites and Y-type zeolites. The hydrocracking catalyst may comprise
one or
more pillared clays, MCM-41, MCM-48, HMS, or a combination of two or more
thereof.
The hydrocracking catalyst may comprise Pt, Pd, Ni, Co, Mo, W, or a
combination of two
or more thereof. The hydrocracking catalyst may include a refractory inorganic
oxide such
as alumina, magnesia, silica, titania, zirconia and silica-alumina. The
hydrocracking
catalyst may comprise a hydrogenation component. Examples of suitable
hydrogenation
components include metals of Group IVB and Group VIII of the Periodic Table
and
compounds of such metals. Molybdenum, tungsten, chromium, iron, cobalt,
nickel,
platinum, palladium, iridium, osmium, rhodium and ruthenium may be used as the
hydrogenation component. These catalysts are described in U.S. Patent
6,312,586 B1.
The Fischer-Tropsch, alcohol-forming, SMR, combustion and/or hydrocracking
catalyst may be positioned in a single reaction zone or they may be positioned
in more
than one reaction zone in the process microchannels or combustion channel. The
same or
different catalyst may be used in each reaction zone. The catalyst may be a
graded
catalyst. In each reaction zone the length of one or more heat exchange
zone(s) adjacent
to or in thermal contact with the reaction zone may vary in their dimensions.
For example,
in one embodiment, the length of the one or more of these heat exchange zones
may be
less than about 50% of the length of each reaction zone. Alternatively, the
one or more
heat exchange zones may have lengths that are more than about 50% of the
length of
each reaction zone up to about 100% of the length of each reaction zone.
The Fischer-Tropsch, alcohol-forming, SMR, combustion and/or
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hydrocracking catalyst may have any size and geometric configuration that fits
within
the process microchannels. The catalyst may be in the form of particulate
solids
(e.g., pellets, powder, fibers, and the like) having a median particle
diameter of about
1 to about 1000 pm (microns), and in one embodiment about 10 to about 500 pm,
and in one embodiment about 25 to about 300 pm, and in one embodiment about 80
to about 300 pm. In one embodiment, the catalyst is in the form of a fixed bed
of
particulate solids.
The Fischer-Tropsch or alcohol-forming catalyst, SMR catalyst, combustion
and/or hydrocracking catalyst may be in the form of a fixed bed of particulate
solids
(as shown in Fig. 15). The median particle diameter of the particulate solids
may be
small, and the length of each process microchannel may be relatively short.
The
median particle diameter may be in the range of about 1 to about 1000 pm, and
in
one embodiment about 10 to about 500 pm, and the length of each process
microchannel may be in the range of up to about 500 cm, and in one embodiment
about 10 to about 500 cm, and in one embodiment about 50 to about 300 cm.
Referring to Fig. 15, the catalyst 261, which is in the form of a bed of
particulate solids, is contained in process microchannel 260. Reactants enter
the
fixed bed as indicated by arrow 262, undergo reaction, and product flows out
of the
fixed bed as indicated by arrow 263.
The Fischer-Tropsch catalyst, alcohol-forming catalyst, SMR catalyst,
combustion catalyst and/or hydrocracking catalyst may be supported on a porous
support structure such as a foam, felt, wad or a combination thereof. The term
"foam" is used herein to refer to a structure with continuous walls defining
pores
throughout the structure. The term "felt" is used herein to refer to a
structure of
fibers with interstitial spaces therebetween. The term "wad" is used herein to
refer to
a structure of tangled strands, like steel wool. The catalyst may be supported
on a
honeycomb structure. The catalyst may be supported on a flow-by support
structure
such as a felt with an adjacent gap, a foam with an adjacent gap, a fin
structure with
gaps, a washcoat on any inserted substrate, or a gauze that is parallel to the
flow
direction with a corresponding gap for flow.
An example of a flow-by structure is illustrated in Fig. 16. In Fig. 16, the
catalyst 266 is contained within process microchannel 265. An open passage way
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267 permits the flow of fluid through the process microchannel 265 as
indicated by
arrows 268 and 269. The reactants contact the catalyst and undergo reaction to
form product.
The Fischer-Tropsch catalyst, alcohol-forming catalyst, SMR catalyst,
combustion catalyst, and/or hydrocracking catalyst may be supported on a flow-
through support structure such as a foam, wad, pellet, powder, or gauze. An
example of a flow-through structure is illustrated in Fig. 17. In Fig. 17, the
flow-
through catalyst 271 is contained within process microchannel 270, the
reactants
flow through the catalyst 271 as indicated by arrows 272 and 273, and undergo
reaction to form the product.
The support structure for a flow-through catalyst may be formed from a
material comprising silica gel, foamed copper, sintered stainless steel fiber,
steel
wool, alumina, or a combination of two or more thereof. In one embodiment, the
support structure may be made of a heat conducting material, such as a metal,
to
enhance the transfer of heat to or from the catalyst.
The Fischer-Tropsch catalyst, alcohol-forming catalyst, SMR catalyst,
combustion catalyst, and/or hydrocracking catalyst may be directly wash coated
on
the interior walls of the process microchannels or combustion channels, grown
on
the channel walls from solution, or coated on a fin structure. The catalyst
may be in
the form of a single piece of porous contiguous material, or many pieces in
physical
contact. In one embodiment, the catalyst may comprise a contiguous material
and
have a contiguous porosity such that molecules can diffuse through the
catalyst. In
this embodiment, the fluids flow through the catalyst rather than around it.
The
cross-sectional area of the catalyst may occupy from about 1 to about 99%, and
in
one embodiment about 10 to about 95% of the cross-sectional area of the
process
microchannels and/or combustion channels. The catalyst may have a surface
area,
as measured by BET, of greater than about 0.5 m2/g, and in one embodiment
greater than about 2 m2/g.
The Fischer-Tropsch catalyst, alcohol-forming catalyst, SMR catalyst,
combustion catalyst, and/or hydrocracking catalyst may comprise a porous
support,
an interfacial layer on the porous support, and a catalyst material on the
interfacial
layer. The interfacial layer may be solution deposited on the support or it
may be
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deposited by chemical vapor deposition or physical vapor deposition. In one
embodiment the catalyst has a porous support, a buffer layer, an interfacial
layer,
and a catalyst material. Any of the foregoing layers may be continuous or
discontinuous as in the form of spots or dots, or in the form of a layer with
gaps or
5 holes. The
porous support may have a porosity of at least about 5% as measured
by mercury porosimetry and an average pore size (sum of pore diameters divided
by
number of pores) of about 1 to about 1000 microns. The porous support may be a
porous ceramic or a metal foam. Other porous supports that may be used include
carbides, nitrides, and composite materials. The porous support may have a
10 porosity
of about 30% to about 99%, and in one embodiment about 60% to about
98%. The porous support may be in the form of a foam, felt, wad, or a
combination
thereof. The open cells of the metal foam may range from about 20 pores per
inch
(ppi) to about 3000 ppi, and in one embodiment about 20 to about 1000 ppi, and
in
one embodiment about 40 to about 120 ppi. The term "ppi" refers to the largest
15 number of
pores per inch (in isotropic materials the direction of the measurement is
irrelevant; however, in anisotropic materials, the measurement is done in the
direction that maximizes pore number).
The buffer layer, when present, may have a different composition and/or
density than both the porous support and the interfacial layers, and in one
20 embodiment
has a coefficient of thermal expansion that is intermediate the thermal
expansion coefficients of the porous support and the interfacial layer. The
buffer
layer may be a metal oxide or metal carbide. The buffer layer may comprise
A1203,
TiO2, SiO2, ZrO2, or combination thereof. The Al2O3 may bq a-A1203, y-A1203 or
a
combination thereof. The buffer layer may be formed of two or more
compositionally
25 different
sublayers. For example, when the porous support is metal, for example a
stainless steel foam, a buffer layer formed of two compositionally different
sub-layers
may be used. The first sublayer (in contact with the porous support) may be
TiO2.
The second sublayer may be 2-A1203 which is placed upon the T102. In one
embodiment, the g -Al2O3 sublayer is a dense layer that provides protection of
the
30 underlying
metal surface. A less dense, high surface area interfacial layer such as
alumina may then be deposited as support for a catalytically active layer.
The porous support may have a thermal coefficient of expansion different
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from that of the interfacial layer. In such a case a buffer layer may be
needed to
transition between the two coefficients of thermal expansion. The thermal
expansion
coefficient of the buffer layer can be tailored by controlling its composition
to obtain
an expansion coefficient that is compatible with the expansion coefficients of
the
porous support and interfacial layers. The buffer layer should be free of
openings
and pin holes to provide superior protection of the underlying support. The
buffer
layer may be nonporous. The buffer layer may have a thickness that is less
than one
half of the average pore size of the porous support. The buffer layer may have
a
thickness of about 0.05 to about 10 pm, and in one embodiment about 0.05 to
about
5 pm.
In one embodiment adequate adhesion and chemical stability may be
obtained without a buffer layer. In this embodiment the buffer layer may be
omitted.
The interfacial layer may comprise nitrides, carbides, sulfides, halides,
metal
oxides, carbon, or a combination thereof. The interfacial layer provides high
surface
area and/or provides a desirable catalyst-support interaction for supported
catalysts.
The interfacial layer may be comprised of any material that is conventionally
used as
a catalyst support. The interfacial layer may comprise a metal oxide. Examples
of
metal oxides that may be used include a-A1203, SiO2, ZrO2, T102, tungsten
oxide,
magnesium oxide, vanadium oxide, chromium oxide, manganese oxide, iron oxide,
nickel oxide, cobalt oxide, copper oxide, zinc oxide, molybdenum oxide, tin
oxide,
calcium oxide, aluminum oxide, lanthanum series oxide(s), zeolite(s) and
combinations thereof. The interfacial layer may serve as a catalytically
active layer
without any further catalytically active material deposited thereon. The
interfacial
layer may be used in combination with a catalytically active layer. The
interfacial
layer may also be formed of two or more compositionally different sublayers.
The
interfacial layer may have a thickness that is less than one half of the
average pore
size of the porous support. The interfacial layer thickness may range from
about 0.5
to about 100 pm, and in one embodiment from about 1 to about 50 microns. The
interfacial layer may be either crystalline or amorphous. The interfacial
layer may
have a BET surface area of at least about 1 m2/g.
The Fischer-Tropsch catalyst, alcohol-forming catalyst, SMR catalyst,
combustion catalyst, and/or hydrocracking catalyst may be deposited on the
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interfacial layer. Alternatively, the catalyst material may be simultaneously
deposited
with the interfacial layer. The catalyst layer may be intimately dispersed on
the
interfacial layer. That the catalyst layer is "dispersed on" or "deposited on"
the
interfacial layer includes the conventional understanding that microscopic
catalyst
particles are dispersed: on the support layer (i. e., interfacial layer)
surface, in
crevices in the support layer, and in open pores in the support layer.
The Fischer-Tropsch catalyst, alcohol-forming catalyst, SMR catalyst,
combustion catalyst, and/or hydrocracking catalyst may be supported on an
assembly of one or more fins positioned within the process microchannels.
Examples are illustrated in Figs. 18-20. Referring to Fig. 18, fin assembly
280
includes fins 281 which are mounted on fin support 283 which overlies base
wall 284
of process microchannel 285. The fins 281 project from the fin support 283
into the
interior of the process microchannel 285. The fins 281 may extend to and
contact
the interior surface of upper wall 286 of process microchannel 285. Fin
channels
287 between the fins 281 provide passage ways for reactant and product to flow
through the process microchannel 285 parallel to its length. Each of the fins
281 has
an exterior surface on each of its sides. The exterior surface provides a
support
base for the catalyst. The reactants may flow through the fin channels 287,
contact
the catalyst supported on the exterior surface of the fins 281, and react to
form
product. The fin assembly 280a illustrated in Fig. 19 is similar to the fin
assembly
280 illustrated in Fig. 18 except that the fins 281a do not extend all the way
to the
interior surface of the upper wall 286 of the microchannel 285. The fin
assembly
280b illustrated in Fig. 20 is similar to the fin assembly 280 illustrated in
Fig. 18
except that the fins 281b in the fin assembly 280b have cross sectional shapes
in the
form of trapezoids. Each of the fins may have a height ranging from about 0.02
mm
up to the height of the process microchannel 285, and in one embodiment from
about 0.02 to about 10 mm, and in one embodiment from about 0.02 to about 5
mm,
and in one embodiment from about 0.02 to about 2 mm. The width of each fin may
range from about 0.02 to about 5 mm, and in one embodiment from about 0.02 to
about 2 mm and in one embodiment about 0.02 to about 1 mm. The length of each
fin may be of any length up to the length of the process microchannel 285, and
in
one embodiment up to about 10 m, and in one embodiment about 0.5 to about 10
m,
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and in one embodiment about 0.5 to about 6 m, and in one embodiment about 0.5
to about 3 m. The gap between each of the fins may be of any value and may
range
from about 0.02 to about 5 mm, and in one embodiment from about 0.02 to about
2
mm, and in one embodiment from about 0.02 to about 1 mm. The number of fins in
the process microchannel 285 may range from about 1 to about 50 fins per
centimeter of width of the process microchannel 285, and in one embodiment
from
about 1 to about 30 fins per centimeter, and in one embodiment from about 1 to
about 10 fins per centimeter, and in one embodiment from about 1 to about 5
fins
per centimeter, and in one embodiment from about 1 to about 3 fins per
centimeter.
Each of the fins may have a cross-section in the form of a rectangle or square
as
illustrated in Figs. 18 or 19, or a trapezoid as illustrated in Fig. 20. When
viewed
along its length, each fin may be straight, tapered or have a serpentine
configuration.
The fin assembly may be made of any material that provides sufficient
strength,
dimensional stability and heat transfer characteristics to permit operation
for which
the process microchannel is intended. These materials include: steel (e.g.,
stainless
steel, carbon steel, and the like); aluminum; titanium; nickel; platinum;
rhodium;
copper; chromium; alloys of any of the foregoing metals; monel; inconel;
brass;
polymers (e.g., thermoset resins); ceramics; glass; quartz; silicon; or a
combination
of two or more thereof. The fin assembly may be made of an A1203 or a Cr2O3
forming material. The fin assembly may be made of an alloy comprising Fe, Cr,
Al
and Y, or an alloy comprising Ni, Cr and Fe.
The Fischer-Tropsch catalyst, alcohol-forming catalyst, SMR catalyst,
combustion catalyst, and/or hydrocracking catalyst may be in the form of a bed
of
particulates which may be graded in composition or graded with a thermally
conductive inert material. The thermally conductive inert material may be
interspersed with the active catalyst. Examples of thermally conductive inert
materials that may be used include diamond powder, silicon carbide, aluminum,
alumina, copper, graphite, and the like. The catalyst bed fraction may range
from
about 100% by weight active catalyst to less than about 50% by weight active
catalyst. The catalyst bed fraction may range from about 10% to about 90% by
weight active catalyst, and in one embodiment from about 25% to about 75% by
weight. In an alternate embodiment the thermally conductive inert material may
be
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deployed at the center of the catalyst or within the catalyst particles. The
active
catalyst may be deposited on the outside, inside or intermittent within a
composite
structure that includes the thermally conductive inert. The resultant catalyst
composite structure may have an effective thermal conductivity when placed in
a
process microchannel or combustion channel that is at least about 0.3 W/m/K,
and in
one embodiment at least about 1 W/m/K, and in one embodiment at least about 2
W/m/K.
The Fischer-Tropsch catalyst, alcohol-forming catalyst, SMR catalyst,
combustion catalyst, and/or hydrocracking catalyst bed may be graded only
locally
within the process microchannels or combustion channels. For example, a
process
microchannel may contain a catalyst bed with a first reaction zone and a
second
reaction zone. The top or bottom (or front or back) of the catalyst bed may be
graded in composition whereby a more or less active catalyst is employed in
all or
part of the first or second reaction zone. The composition that is reduced in
one
reaction zone may generate less heat per unit volume and thus reduce the hot
spot
and potential for the production of undesirable by-products, such as methane
in a
Fischer-Tropsch reaction. The catalyst may be graded with an inert material in
the
first and/or second reaction zone, in full or in part. The first reaction zone
may
contain a first composition of catalyst or inert material, while the second
reaction
zone may contain a second composition of catalyst or inert material.
Different particle sizes may be used in different axial regions of the process
microchannels or combustion channels to provide for graded catalyst beds. For
example, very small particles may be used in a first reaction zone while
larger
particles may be used in a second reaction zone. The average particle
diameters
may be less than half the height or gap of the process microchannels. The very
small particles may be less than one-fourth of the process microchannel height
or
gap. Larger particles may cause lower pressure drops per unit length of the
process
microchannels and may also reduce the catalyst effectiveness. The effective
thermal conductivity of a catalyst bed may be lower for larger size particles.
Smaller
particles may be used in regions where improved heat transfer is sought
throughout
the catalyst bed or alternatively larger particles may be used to reduce the
local rate
of heat generation.
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Relatively short contact times, high selectivity to the desired product and
relatively low rates of deactivation of the catalyst may be achieved by
limiting the
diffusion path required for the catalyst. This may be achieved when the
catalyst is in
the form of a thin layer on an engineered support such as a metallic foam or
on the
5 wall of
the process microchannel. This may allow for increased space velocities.
The thin layer of catalyst may be produced using chemical vapor deposition.
This
thin layer may have a thickness in the range up to about 1 micron, and in one
embodiment in the range from about 0.1 to about 1 micron, and in one
embodiment
in the range from about 0.1 to about 0.5 micron, and in one embodiment about
0.25
10 micron.
These thin layers may reduce the time the reactants are within the active
catalyst structure by reducing the diffusional path. This may decrease the
time the
reactants spend in the active portion of the catalyst. The result may be
increased
selectivity to the product and reduced unwanted by-products. An advantage of
this
mode of catalyst deployment may be that, unlike conventional catalysts in
which the
15 active
portion of the catalyst may be bound up in an inert low thermal conductivity
binder, the active catalyst film may be in intimate contact with either an
engineered
structure or a wall of the process microchannel. This may leverage high heat
transfer rates attainable in the microchannel reactor and allow for close
control of
temperature. This may result in the ability to operate at increased
temperature
20 (faster
kinetics) without promoting the formation of undesired by-products, thus
producing higher productivity and yield and prolonging catalyst life.
The configuration of the SMR microchannel reactor 500, hydrocracking
microchannel reactor 700 and/or Fischer-Tropsch or alcohol-forming
microchannel
reactor 200 may be tailored to match the reaction kinetics. Near the entrance
or top
25 of a first
reaction zone of a process microchannel, the microchannel height or gap
may be smaller than in a second reaction zone near the exit or bottom of the
process
microchannel. Alternatively, the reaction zones may be smaller than half the
process microchannel length. For example, a first process microchannel height
or
gap may be used for the first 25%, 50%, 75%, or 90% of the length of the
process
30
microchannel for a first reaction zone, while a larger second height or gap
may be
used in a second reaction zone downstream from the first reaction zone. This
configuration may be suitable for conducting Fischer-Tropsch or alcohol-
forming
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reactions. Other gradations in the process microchannel height or gap may be
used.
For example, a first height or gap may be used near the entrance of the
microchannel to provide a first reaction zone, a second height or gap
downstream
from the first reaction zone may be used to provide a second reaction zone,
and a
third height or gap may be used to provide a third reaction zone near the exit
of the
microchannel. The first and third heights or gaps may be the same or
different. The
first and third heights or gaps may be larger or smaller than the second
height or
gap. The third height or gap may be smaller or larger than the second height
or gap.
The second height or gap may be larger or smaller than the third height or
gap.
The Fischer-Tropsch catalyst, alcohol-forming catalyst, SMR catalyst,
combustion catalyst, and/or hydrocracking catalyst may be regenerated by
flowing a
regenerating fluid through the channels in contact with the catalyst. The
regenerating fluid may comprise hydrogen or a diluted hydrogen stream. The
diluent
may comprise nitrogen, argon, helium, methane, carbon dioxide, steam, or a
mixture
of two or more thereof. The temperature of the regenerating fluid may be from
about 50 to about 400 C, and in one embodiment about 200 to about 350 C. The
pressure within the channels during this regeneration step may range from
about 1
to about 40 atmospheres, and in one embodiment about 1 to about 20
atmospheres,
and in one embodiment about 1 to about 5 atmospheres. The residence time for
the
regenerating fluid in the channels may range from about 0.01 to about 1000
seconds, and in one embodiment about 0.1 second to about 100 seconds.
When the catalyst is a Fischer-Tropsch catalyst, it may be regenerated by
increasing the molar ratio of H2 to CO in the reactant composition to at least
about
2.5:1, and in one embodiment at least about 3:1, and flowing the resulting
adjusted
feed composition through the process microchannels in contact with the
catalyst at a
temperature in the range from about 150 C to about 300 C, and in one
embodiment
in the range from about 180 C to about 250 C, for a period of time in the
range from
about 0.1 to about 100 hours, and in one embodiment in the range from about
0.5 to
about 20 hours, to provide the regenerated catalyst. The feed composition may
be
adjusted by interrupting the flow of all feed gases except hydrogen and
flowing the
hydrogen through the process microchannels in contact with the catalyst. The
flow
of H2 may be increased to provide for the same contact time used for the
reactant
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composition comprising H2 and CO. The adjusted feed composition may comprise
H2 and is characterized by the absence of CO. Once the catalyst is
regenerated, the
Fischer-Tropsch process may be continued by contacting the regenerated
catalyst
with the original reactant composition comprising H2 and CO.
The Fischer-Tropsch or alcohol-forming process microchannels, SMR
process microchannels, combustion channels, and/or hydrocracking process
microchannels may be characterized by having bulk flow paths. The term "bulk
flow
path" refers to an open path (contiguous bulk flow region) within the process
microchannels or combustion channel. A contiguous bulk flow region allows
rapid
fluid flow through the channels without large pressure drops. In one
embodiment,
the flow of fluid in the bulk flow region is laminar. Bulk flow regions within
each
process microchannel or combustion channel may have a cross-sectional area of
about 0.05 to about 10,000 mm2, and in one embodiment about 0.05 to about 5000
mm2, and in one embodiment about 0.1 to about 2500 mm2. The bulk flow regions
may comprise from about 5% to about 95%, and in one embodiment about 30% to
about 80% of the cross-section of the process microchannels or combustion
channel.
The contact time of the reactants with the Fischer-Tropsch or alcohol-forming
catalyst, SMR catalyst and/or combustion catalyst may range up to about 2000
milliseconds (ms), and in the range from about 10 to about 2000 ms, and in one
embodiment from about 10 ms to about 1000 ms, and in one embodiment about 20
ms to about 500 ms. In one embodiment, the contact time may range up to about
300 ms, and in one embodiment from about 20 to about 300 ms, and in one
embodiment from about 50 to about 150 ms, and in one embodiment about 75 to
about 125 ms, and in one embodiment about 100 ms. In one embodiment, the
contact time may be up to about 100 ms, and in one embodiment from about 10 to
about 100 ms.
The space velocity (or gas hourly space velocity (GHSV)) for the flow of fluid
in the Fischer-Tropsch or alcohol-forming process microchannels, SMR process
microchannels and/or combustion channels may be at least about 1000 hr-1
(normal
liters of feed/hour/liter of volume within the process microchannels) or at
least about
800 ml feed/(g catalyst) (hr). The space velocity may range from about 1000 to
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about 1,000,000 hrl, or from about 800 to about 800,000 ml feed/(g catalyst)
(hr).
In one embodiment, the space velocity may range from about 10,000 to about
100,000 hrl, or about 8,000 to about 80,000 ml feed/(g catalyst) (hr).
The liquid hourly space velocity (LHSV) for the flow of fluid in the
hydrocracking microchannel reactor may be in the range from about 0.1 to about
100
hrl (volume of feed/hr/volume of catalyst), and in one embodiment from about 1
to
about 100 hrl, and in one embodiment from about 5 to about 100 hrl, and in one
embodiment from about 10 to about 100 hr', and in one embodiment from about 1
to about 50 hrl, and in one embodiment from about 5 to about 50 Fe .
The pressure within the Fischer-Tropsch or alcohol-forming process
microchannels, SMR process microchannels and/or hydrocracking process
microchannels may be up to about 100 atmospheres, and in one embodiment in the
range from about Ito about 100 atmospheres, and in one embodiment from about 1
to about 75 atmospheres, and in one embodiment from about 2 to about 40
atmospheres, and in one embodiment from about 2 to about 10 atmospheres, and
in
one embodiment from about 10 to about 50 atmospheres, and in one embodiment
from about 20 to about 30 atmospheres.
The pressure drop of fluids as they flow in the Fischer-Tropsch or alcohol-
forming process microchannels, SMR process microchannels, combustion channels,
and/or hydrocracking process microchannels may range up to about 10
atmospheres per meter of length of channel (atm/m), and in one embodiment up
to
about 5 atm/m, and in one embodiment up to about 3 atm/m.
The Reynolds Number for the flow of fluid in the Fischer-Tropsch or alcohol-
forming process microchannels, SMR process microchannels, combustion channels,
and/or hydrocracking process microchannels may be in the range of about 10 to
about 4000, and in one embodiment about 100 to about 2000.
The average temperature in the Fischer-Tropsch process microchannels may
be in the range from about 150 to about 300 C, and in one embodiment in the
range
from about 200 to about 300 C.
The average temperature in the alcohol-forming process microchannels may
be in the range from about 200 to about 500 C, and in one embodiment in the
range
from about 200 to about 350 C.
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The average temperature in the SMR microchannels may be in the range
from about 100 to about 400 C, and in one embodiment in the range from about
150
to about 350 C.
The average temperature in the hydrocracking process microchannels may
be in the range from about 100 C to about 700 C, and in one embodiment from
about 250 C to about 500 C, and in one embodiment from about 350 C to about
450 C, and in one embodiment from about 370 C to about 400 C.
The heat exchange fluid entering the heat exchange channels of the Fischer-
Tropsch or alcohol-forming microchannel reactor 200 and, optionally,
hydrocracking
microchannel reactor 700 may be at a temperature of about 100 C to about 400
C,
and in one embodiment about 200 C to about 300 C. The heat exchange fluid
exiting the heat exchange channels may be at a temperature in the range of
about
150 C to about 450 C, and in one embodiment about 200 C to about 350 C. The
residence time of the heat exchange fluid in the heat exchange channels may
range
from about 1 to about 2000 ms, and in one embodiment about 10 to about 500 ms.
The pressure drop for the heat exchange fluid as it flows through the heat
exchange
channels may range up to about 10 atm/m, and in one embodiment from about 1 to
about 10 atm/m, and in one embodiment from about 2 to about 5 atm/m. The heat
exchange fluid may be in the form of a vapor, a liquid, or a mixture of vapor
and
liquid. The Reynolds Number for the flow of the heat exchange fluid in heat
exchange channels may be from about 10 to about 4000, and in one embodiment
about 100 to about 2000.
The heat exchange fluid used in the heat exchange channels in the Fischer-
Tropsch or alcohol-forming microchannel reactor 200 and, optionally,
hydrocracking
microchannel reactor 700 may be any heat exchange fluid suitable for cooling a
Fischer-Tropsch exothermic reaction. These may include air, steam, liquid
water,
gaseous nitrogen, other gases including inert gases, carbon monoxide, oils
such as
mineral oil, and heat exchange fluids such as Dowtherm A and Therminol which
are
available from Dow-Union Carbide.
The heat exchange channels used in the Fischer-Tropsch or alcohol-forming
microchannel reactor 200 and, optionally, in the hydrocracking microchannel
reactor
700 may comprise process channels wherein an endothermic process is conducted.
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These heat exchange process channels may be microchannels. Examples of
endothermic processes that may be conducted in the heat exchange channels
include steam reforming and dehydrogenation reactions. Steam reforming of an
alcohol that occurs at a temperature in the range from about 200 C to about
300 C
5 is an
example of an endothermic process that may be used. The incorporation of a
simultaneous endothermic reaction to provide an improved heat sink may enable
a
typical heat flux of roughly an order of magnitude above the convective
cooling heat
flux.
The heat exchange fluid may undergo a partial or full phase change as it
10 flows in the heat exchange channels of the Fischer-Tropsch or alcohol-
forming
microchannel reactor 200 and, optionally, in the hydrocracking microchannel
reactor
700. This phase change may provide additional heat removal from the process
microchannels beyond that provided by convective cooling. For a liquid heat
exchange fluid being vaporized, the additional heat being transferred from the
15 Fischer-
Tropsch process microchannels and, optionally, from the hydrocracking
process microchannels may result from the latent heat of vaporization required
by
the heat exchange fluid. In one embodiment, about 50% by weight of the heat
exchange fluid may be vaporized, and in one embodiment about 35% by weight may
be vaporized, and in one embodiment about 20% by weight may be vaporized, and
20 in one
embodiment about 10% by weight may be vaporized. In one embodiment,
from about 10% to about 50% by weight may be vaporized.
The heat flux for heat exchange in the Fischer-Tropsch or alcohol-forming
microchannel reactor 200, the SMR microchannel reactor 500, and/or
hydrocracking
microchannel reactor 700 may be in the range from about 0.01 to about 500
watts
25 per square
centimeter of surface area of the one or more heat transfer walls of the
process microchannels (W/cm2) in the microchannel reactor, and in one
embodiment
in the range from about 0.1 to about 250 W/cm2, and in one embodiment from
about
1 to about 125 W/cm2. The heat flux for convective heat exchange in the
microchannel reactor may be in the range from about 0.01 to about 250 W/cm2,
and
30 in one embodiment in the range from about 0.1 to about 50 W/cm2, and in one
embodiment from about 1 to about 25 W/cm2, and in one embodiment from about 1
to about 10 W/cm2. The heat flux for phase change and/or an exothermic or
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endothermic reaction of the heat exchange fluid may be in the range from about
0.01
to about 500 W/cm2, and in one embodiment from about 1 to about 250 W/cm2, and
in one embodiment, from about 1 to about 100 W/cm2, and in one embodiment from
about 1 to about 50 W/cm2, and in one embodiment from about Ito about 25
W/cm2,
and in one embodiment from about 1 to about 10 W/cm2.
The control of heat exchange during the Fischer-Tropsch or alcohol-forming
reaction processes, SMR process, and/or optionally the hydrocracking process
may
be advantageous for controlling selectivity towards the desired product due to
the
fact that such added cooling and/or heating may reduce or eliminate the
formation of
undesired by-products from undesired parallel reactions with higher activation
energies.
The pressure within each individual heat exchange channel in the Fischer-
Tropsch or alcohol-forming microchannel reactor 200 and, optionally, in the
hydrocracking microchannel reactor 700 may be controlled using passive
structures
(e.g., obstructions), orifices and/or mechanisms upstream of the heat exchange
channels or in the channels. By controlling the pressure within each heat
exchange
microchannel, the temperature within each heat exchange microchannel can be
controlled. A higher inlet pressure for each heat exchange channel may be used
where the passive structures, orifices and/or mechanisms let down the pressure
to
the desired pressure. By controlling the temperature within each heat exchange
channel, the temperature in the Fischer-Tropsch or alcohol-forming process
microchannels or hydrocracking process microchannels can be controlled. Thus,
for
example, each Fischer-Tropsch or alcohol-forming process microchannel may be
operated at a desired temperature by employing a specific pressure in the heat
exchange channel adjacent to or in thermal contact with the process
microchannel.
This provides the advantage of precisely controlled temperatures for each
Fischer-
Tropsch or alcohol-forming process microchannel. The use of precisely
controlled
temperatures for each Fischer-Tropsch or alcohol-forming process microchannel
provides the advantage of a tailored temperature profile and an overall
reduction in
the energy requirements for the process.
In a scale up device, for certain applications, it may be required that the
mass
of the process fluid be distributed uniformly among the microchannels. Such an
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application may be when the process fluid is required to be heated or cooled
down
with adjacent heat exchange channels. The uniform mass flow distribution may
be
obtained by changing the cross-sectional area from one parallel microchannel
to
another microchannel. The uniformity of mass flow distribution may be defined
by
Quality Index Factor (0-factor) as indicated below. A 0-factor of 0% means
absolute
uniform distribution.
¨
Q= ____________ xrniflX 100
n2 max
A change in the cross-sectional area may result in a difference in shear
stress on the
wall. In one embodiment, the Q-factor for the hydrocracking microchannel
reactor
700, SMR microchannel reactor 500 and/or Fischer-Tropsch or alcohol-forming
microchannel reactor 200 may be less than about 50%, and in one embodiment
less
than about 20%, and in one embodiment less than about 5%, and in one
embodiment less than about 1%.
The superficial velocity for fluid flowing in the Fischer-Tropsch or alcohol-
forming process microchannels, SMR process microchannels, and/or hydrocracking
process microchannels may be at least about 0.01 meters per second (m/s), and
in
one embodiment at least about 0.1 m/s, and in one embodiment in the range from
about 0.01 to about 100 m/s, and in one embodiment in the range from about
0.01 to
about 1 m/s, and in one embodiment in the range from about 0.1 to about 10
m/s,
.. and in one embodiment in the range from about Ito about 100 m/s.
The free stream velocity for fluid flowing in the Fischer-Tropsch or alcohol-
forming process microchannels, SMR process microchannels, and/or hydrocracking
process microchannels may be at least about 0.001 m/s, and in one embodiment
at
least about 0.01 m/s, and in one embodiment in the range from about 0.001 to
about
200 m/s, and in one embodiment in the range from about 0.01 to about 100 m/s,
and
in one embodiment in the range from about 0.01 to about 200 m/s.
The conversion of CO in the Fischer-Tropsch or alcohol forming microchannel
reactor may be about 40% or higher per cycle, and in one embodiment about 50%
or
higher, and in one embodiment about 55% or higher, and in one embodiment about
60% or higher, and in one embodiment about 65% or higher, and in one
embodiment
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about 70% or higher. The term "cycle" is used herein to refer to a single pass
of the
reactants through the process microchannels.
The selectivity to methane in the Fischer-Tropsch (FT) product may be about
25% or less, and in one embodiment about 20% or less, and in one embodiment
about 15% or less, and in one embodiment about 12% or less, and in one
embodiment about 10% or less.
The yield of Fischer-Tropsch product may be about 25% or higher per cycle,
and in one embodiment about 30% or higher, and in one embodiment about 40% or
higher per cycle.
In one embodiment of the Fischer-Tropsch process, the conversion of CO is
at least about 50%, the selectivity to methane is about 15% or less, and the
yield of
product is at least about 35% per cycle.
The nitrogen separator 300 may comprise a microchannel separator
employing an ionic liquid as a liquid absorbent. The microchannel separator
may
comprise a thin film separator wherein the flow of the liquid absorbent (i.e.,
the ionic
liquid) is retained or constrained within a channel or structure by the use of
capillary
forces that minimize the mixing or back mixing of a liquid and a gas (e.g.,
air) in a
microchannel. The microchannel separator may comprise a device wherein a fluid
mixture of the liquid absorbent and gas are co-fed either inside or outside of
the
microchannel device and flow in a co-flow arrangement. The fluid may flow into
and
out of surface features in the device. The microchannel separator may comprise
a
device wherein the gas and liquid absorbent flows in a co-flow arrangement and
are
mixed to create a high interfacial area by flowing past a series of
obstructions in the
form of a porous packed bed of rings, spheres, or other shapes. The
microchannel
separator may comprise a device wherein a thin contactor plate separates the
phases to assist with countercurrent flow. The contactor plate may have
sufficiently
small apertures such that capillary pressure of the liquid retains the liquid
on one
side of the contactor plate and the gaseous stream on the other side of the
contactor
plate. The ionic liquid that may be used as the liquid absorbent may comprise
one or
more quaternary imidazolium salts, and/or one or more quaternary aromatic 5-
or 6-
membered-ring heterocyclic compounds such as imidazolium salts, pyridinium
salts,
and the like. These may include 1-butyl-3-methylimidazolium
hexafluorophosphate,
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1-octy1-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium
nitrate, 1-
octy1-3-methylimidazolium tetrafluoroborate, 1-ethy1-3-methylimidazolium
ethylsulfate,
and/or N-butylpyridinium tetrafluoroborate. Ionic liquids that may be used are
disclosed in
U.S. Patents 6,579,343 B2 and 6,623,659 B2, U.S. Patent Publication
2006/0251588 Al,
and international publication WO 02/34863 Al.
The temperature swing adsorption (TSA) or pressure swing adsorption (PSA)
techniques may be used in the nitrogen separator 300. TSA and PSA processes
employing microchannel technology that may be used for the foregoing
separations are
disclosed in U.S. Patents 6,508,862 B1 and 6,652,627 B1, and U.S. Patent
Publication US
2005/0045030 Al.
The ionic liquid separators, TSA separators and/or PSA separators discussed
above may also be used in the line between the gasifier 110 and the
microchannel
separator 200 to separate out contaminant gases and materials (e.g. CO2,
sulfur
compounds such as H2S, particulate solids, and the like) from the synthesis
gas formed in
the gasifier 110.
Microchannel devices employing layers of nanofibers or nano-composite films
may
be employed in the line between the gasifier 110 and the microchannel reactor
200 to
separate out contaminant materials from the synthesis gas. Nanofibers and nano-
composite films that may be used are disclosed in U.S. Patents 6,326,326 Bl;
6,531,224
BI; 6,733,835 B2; 6,753,038 B2; 6,846,554 B2; and 7,122,106 B2.
The presence of contaminants such as sulfur, halogen, selenium, phosphorus,
arsenic, and the like, in the synthesis gas flowing out of the gasifier 110
may be
undesirable. The foregoing contaminants may be removed from the synthesis gas
or have
their concentrations reduced prior to conducting the reaction in the
microchannel reactor
200. Techniques for removing or reducing the level of these contaminants are
well known
to those of skill in the art. For example, ZnO guardbeds may be used in the
line between
the gasifier 110 and the microchannel reactor 200 for removing sulfur
impurities. The
contaminant level in the synthesis gas may be reduced to a level of up to
about 5% by
volume, and in one embodiment up to about 1% by volume, and in one embodiment
up to
about 0.1% by volume, and
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in one embodiment up to about 0.05% by volume.
The pyrolysis process that is conducted in the pyrolysis reactor 400 may
comprise heating the carbonaceous material in the absence of oxygen or any
other
reagent, except possibly steam. The pyrolysis process may comprise an
anhydrous
5 process. The pyrolysis process may comprise a fast or flash pyrolysis
process
wherein the carbonaceous material is heated at temperature in the range from
about
350 C to about 500 C over a relatively short period of time of up to about 2
seconds,
and in one embodiment in the range from about 0.5 to about 2 seconds. The
pyrolysis process may be used to produce a liquid product which may be
referred to
10 as pyrolytic oil. The pyrolysis process may be conducted in an auger
reactor,
ablative reactor, rotating cone, fluidized bed or circulating fluidized bed.
The pyrolysis reaction that is conducted in an auger reactor involves the use
of a feed of hot sand and carbonaceous material particles at one end of a
screw.
The screw mixes the sand and carbonaceous material and conveys it along as the
15 pyrolysis process proceeds.
The ablative process involves projecting carbonaceous material particles at
high speed against a hot metal surface. This can be achieved by using a metal
surface spinning at high speed within a bed of carbonaceous material
particles. As
an alternative, the particles may be suspended in a carrier gas and introduced
at
20 high speed through a cyclone whose wall is heated.
The rotating cone process involves heating a mixture of sand and
carbonaceous material particles and introducing the mixture into a rotating
cone.
Due to the rotation of the cone, the mixture of sand and carbonaceous material
is
transported across the cone surface by centrifugal force as the pyrolysis
process
25 proceeds.
With the fluidized bed reactor, carbonaceous material particles are introduced
into a bed of hot sand fluidized by a gas. High heat transfer rates from the
fluidized
sand result in rapid heating of the carbonaceous material particles. Heat may
be
provided by heat exchanger tubes through which hot combustion gas may flow.
30 With the
circulating fluidized beds, carbonaceous material particles are
introduced into a circulating fluidized bed of hot sand. Gas, sand and
carbonaceous
material particles move together. The transport gas may be a recirculated
product
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gas, although it may also be a combustion gas. High heat transfer rates from
the
sand provide for rapid heating of carbonaceous material particles. A separator
may
separate the product gases and vapors from the sand and char particles. The
sand
particles may be reheated in a fluidized burner vessel and recycled to the
reactor.
The Fischer-Tropsch product formed in the microchannel reactor 200 may
comprise a gaseous product fraction and a liquid product fraction. The gaseous
product fraction may include hydrocarbons boiling below about 350 C at
atmospheric pressure (e.g., tail gases through middle distillates). The liquid
product
fraction (the condensate fraction) may include hydrocarbons boiling above
about
350 C (e.g., vacuum gas oil through heavy paraffins).
The Fischer-Tropsch product fraction boiling below about 350 C may be
separated into a tail gas fraction and a condensate fraction, e.g., normal
paraffins of
about 5 to about 20 carbon atoms and higher boiling hydrocarbons, using, for
example, a high pressure and/or lower temperature vapor-liquid separator, or
low
pressure separators or a combination of separators. The fraction boiling above
about
350 C (the condensate fraction) may be separated into a wax fraction boiling
in the
range of about 350 C to about 650 C after removing one or more fractions
boiling
above about 650 C. The wax fraction may contain linear paraffins of about 20
to
about 50 carbon atoms with relatively small amounts of higher boiling branched
paraffins. The separation may be effected using fractional distillation.
The Fischer-Tropsch product formed in the microchannel reactor 200 may
include methane, wax and other heavy high molecular weight products. The
product
may include olefins such as ethylene, normal and iso-paraffins, and
combinations
thereof. These may include hydrocarbons in the distillate fuel ranges,
including the
jet or diesel fuel ranges.
Branching may be advantageous in a number of end-uses, particularly when
increased octane values and/or decreased pour points are desired. The degree
of
isomerization may be greater than about 1 mole of isoparaffin per mole of n-
paraffin,
and in one embodiment about 3 moles of isoparaffin per mole of n-paraffin.
When
used in a diesel fuel composition, the product may comprise a hydrocarbon
mixture
having a cetane number of at least about 60.
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The Fischer-Tropsch product may be further processed to form a lubricating
base
oil or diesel fuel. For example, the product made in the microchannel reactor
200 may be
hydrocracked and then subjected to distillation and/or catalytic isomerization
to provide a
lubricating base oil, diesel fuel, aviation fuel, and the like. The Fischer-
Tropsch product
may be hydroisomerized using the process disclosed in US Patents 6,103,099 or
6,180,575; hydrocracked and hydroisomerized using the process disclosed in
U.S.
Patents 4,943,672 or 6,096,940; dewaxed using the process disclosed in U.S.
Patent
5,882,505; or hydroisomerized and dewaxed using the process disclosed in U.S.
Patents
6,013,171, 6,080,301 or 6,165,949.
The hydrocracking reaction conducted in the hydrocracking microchannel reactor
700 may involve a reaction between hydrogen and the Fischer-Tropsch product
flowing
from the microchannel reactor 200, or one or more hydrocarbons separated from
the
Fischer-Tropsch product (e.g., one or more liquid or wax Fischer-Tropsch
hydrocarbons).
The Fischer-Tropsch product may comprise one or more long chain hydrocarbons.
In the
hydrocracking process, a desired diesel fraction, for example, may be
increased by
cracking a C23 fraction to mid range carbon numbers of C12 to C22. A wax
fraction
produced from the Fischer-Tropsch microchannel reactor 200 may be fed to the
hydrocracking microchannel reactor 700 with excess hydrogen for a triple phase
reaction.
Under reaction conditions at elevated temperatures and pressures, a fraction
of the liquid
feed may convert to a gas phase, while the remaining liquid fraction may flow
along the
catalyst. In conventional hydrocracking systems, a liquid stream forms. The
use of a
microchannel reactor for the hydrocracking reaction enables unique advantages
on a
number of fronts. These may include kinetics, pressure drop, heat transfer,
and mass
transfer.
The Fischer-Tropsch hydrocarbon products that may be hydrocracked in the
hydrocracking microchannel reactor 700 may comprise any hydrocarbon that may
be
hydrocracked. These may include hydrocarbons that contain one or more C-C
bonds
capable of being broken in a hydrocracking process. The hydrocarbons that
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may be hydrocracked may include saturated aliphatic compounds (e.g., alkanes),
unsaturated aliphatic compounds (e.g., alkenes, alkynes), hydrocarbyl (e.g.,
alkyl)
substituted aromatic compounds, hydrocarbylene (e.g., alkylene) substituted
aromatic compounds, and the like.
The feed composition for the hydrocracking microchannel reactor 700 may
include one or more diluent materials. Examples of such diluents may include
non-
reactive hydrocarbon diluents, and the like. The diluent concentration may be
in the
range from zero to about 99% by weight based on the weight of the Fischer-
Tropsch
product, and in one embodiment from zero to about 75% by weight, and in one
embodiment from zero to about 50% by weight. The diluents may be used to
reduce
the viscosity of viscous liquid reactants. The viscosity of the feed
composition in the
hydrocracking microchannel reactor 700 may be in the range from about 0.001 to
about 1 centipoise, and in one embodiment from about 0.01 to about 1
centipoise,
and in one embodiment from about 0.1 to about 1 centipoise.
The ratio of hydrogen to Fischer-Tropsch product in the feed composition
entering the hydrocracking microchannel reactor 700 may be in the range from
about
10 to about 2000 standard cubic centimeters (sccm) of hydrogen per cubic
centimeter (ccm) of Fischer-Tropsch product, and in one embodiment from about
100 to about 1800 sccm/ccm, and in one embodiment from about 350 to about 1200
sccm/ccm. The hydrogen feed may further comprise water, methane, carbon
dioxide, carbon monoxide and/or nitrogen.
The H2 in the hydrogen feed may be derived from another process such as a
steam reforming process (product stream with H2/C0 mole ratio of about 3), a
partial
oxidation process (product stream with H2 /CO mole ration of about 2), an
autothermal reforming process (product stream with H2/C0 mole ratio of about
2.5),
a CO2 reforming process (product stream with H2/C0 mole ratio of about 1), a
coal
gassification process (product stream with H2/C0 mole ratio of about 1), and
combinations thereof. With each of these feed streams the H2 may be separated
from the remaining ingredients using conventional techniques such as membranes
or adsorption.
The hydrocracked Fischer-Tropsch product may comprise a middle distillate
fraction boiling in the range of about 260-700 F (127-371 C). The term "middle
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distillate" is intended to include the diesel, jet fuel and kerosene boiling
range
fractions. The terms "kerosene" and "jet fuel" boiling range are intended to
refer to a
temperature range of 260-550 F (127-288 C) and "diesel" boiling range is
intended
to refer to hydrocarbon boiling points between about 260 to about 700 F (127-
371 C). The hydrocracked Fischer-Tropsch product may comprise a gasoline or
naphtha fraction. These may be considered to be the C5 to 400 F (204 C)
endpoint
fractions.
The desired product for the alcohol-forming process may comprise one or
more alcohols having from 1 to about 10 carbon atoms, and in one embodiment
from
1 to about 5 carbon atoms, and in one embodiment from 2 to about 5 carbon
atoms.
The product may comprise methanol. The product may comprise methanol,
ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-
methyl-2-propanol, 1-pentanol, 2-pentanol, or a mixture of two or more
thereof.
These alcohols and alcohol mixtures may be used as fuels and fuel supplements.
For example, these alcohols can be added to gasoline to supplement the
gasoline.
Example 1
A process simulation using Chem CAD is conducted. The process is
illustrated in Fig. 28. Referring to Fig. 28, the process 600 involves the use
of dryer
601, mixer 607, gasifier 610, tempering chamber 615, super heater 620, quench
chamber 625, scrubber 630, cyclone 635, condensers 640, 645 and 650, mixer
655,
Fischer-Tropsch (FT) microchannel reactor 660, heat exchange steam circuit
663,
separators 670 and 675, mixer 680, and fractionators 685 and 690. The process
also employs the use of heat exchangers 636, 641, 646, 656, 673 and 674. These
heat exchangers may be microchannel heat exchangers. Compressors 642, 647
and 652 are also employed in the illustrated process. The temperature,
pressure,
flow rate and composition of various flow streams employed in the process 600
are
disclosed in the following Tables 1-3.
The operation of the process 600 illustrated in Fig. 28 will now be described.
In the following description, temperatures and pressures of various flow
streams are
indicated within parentheses. The temperatures are in C and the pressures are
in
bars. In some instances, these values have been rounded off from what was
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produced by the Chem CAD simulation. The full values produced by Chem CAD are
shown in Tables 1-3. Municipal solid waste (MSW) with a water content of 70%
by
weight flows through line 602 (15 C, 1 bar) into dryer 601 wherein the MSW
undergoes condensation. Separated water flows out of the dryer 601 through
line
5 604 (89 C,
1 bar). Steam flows through line 603 (250 C, 25 bars) into the dryer 601,
heats the MSW, and flows out of the dryer 601 through line 605 (225 C, 25
bars).
Condensed MSW with a water concentration of 14.2% by weight flows through line
606 (89 C, 1 bar) into mixer 607 wherein it is combined fractionator light
ends from
line 687 (121 C, 18 bars) and fractionator bottoms from line 692 (121 C, 18
bars).
10 The combined flow of condensed MSW, fractionator light ends and
fractionator
bottoms (which may be referred to as a combined carbonaceous feed) flows from
mixer 607 through line 608 (94 C, 1 bar) to gasifier 610. Oxygen (15 C, 1 bar)
flows
through line 609 to gasifier 610. In gasifier 610, the combined carbonaceous
feed
and the oxygen are heated and undergo a gasification reaction to form
synthesis
15 gas. Ash is removed from the gasifier 610 as indicated by arrow 617.
The synthesis gas flows from the gasifier 610 through line 611 (1480 C, 1
bar) to tempering chamber 615. Water flows through lines 612 and 614 (15 C, 1
bar) to tempering chamber 615. Steam flows out of the tempering chamber 615
through line 619. The synthesis gas flows from tempering chamber 615 through
line
20 616 (1013
C, 1 bar) to superheater 620. Steam flows through line 618 (225 C, 25
bars) to and through superheater 620, and then out of superheater 620 through
line
621 (450 C, 25 bars). The synthesis gas flows from superheater 620 through
line
622 (235 C, 1 bar) to and through quenching chamber 625. Water flows through
lines 612 and 613 (15 C, 1 bar) to and through quenching chamber 625, and then
25 out of
quenching chamber 625 through line 627 (67 C, 1 bar). The synthesis gas
flows from the quenching chamber 625 through line 626 (67 C, 1 bar) into
scrubber
630. Contaminants are separated from the synthesis gas in the scrubber 630 and
flow out of the scrubber through line 632 (67 C, 1 bar). The synthesis gas
flows
from scrubber 630 through line 631 (67 C, 1 bar) into cyclone 635. Solid
particulates
30 are
separated from the synthesis gas in cyclone 635. The solid particulates are
removed through line 638. The synthesis gas flows from cyclone 635 through
line
637 (67 C, 1 bar) to and through heat exchanger 636, and then through line
637a
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(24 C, 1 bar) into condenser 640 where it is condensed. Water flows out of
condenser 640 through line 644 (24 C, 1 bar). The synthesis gas flows from
condenser 640 through line 643 (24 C, 1 bar) to and through compressor 642,
and
then from compressor 642 through line 643a (125 C, 2.6 bars) to and through
heat
exchanger 641. The synthesis gas flows from heat exchanger 641 through line
643b
(24 C, 2.6 bars) to condenser 645 where it is condensed. Water is removed from
the synthesis gas in condenser 645 and flows out of the condenser through line
648
(24 C, 2.6 bars). The synthesis gas flows from condenser 645 through line 649
(24 C, 2.6 bars) to and through compressor 647, and then from compressor 647
113 through
line 649a (101 C, 5.5 bars) to and through heat exchanger 646. The
synthesis gas flows from heat exchanger 646 through line 649b (24 C, 5.5 bars)
to
condenser 650 where it is condensed. Water flows out of the condenser 650
through line 651a (24 C, 1 bar). The synthesis gas flows out of condenser 650
through line 651 (24 C, 5.5 bars) to and through compressor 652.
The synthesis gas flows from compressor 652 through line 653 (234 C, 25
bars) to mixer 655. The synthesis gas flowing through line 653 has a H2:CO
ratio of
0.989. Hydrogen flows through line 654 (37 C, 15 bars) to mixer 655 wherein it
is
combined with the synthesis gas. The combined mixture of synthesis and
hydrogen
may be referred to as upgraded synthesis gas. The upgraded synthesis gas has a
H2:CO ratio of 1.896. The upgraded synthesis gas flows from mixer 655 through
heat exchanger 656, and from the heat exchanger 656 through line 657 (220 C,
25
bars) to and through Fischer-Tropsch (FT) microchannel reactor 660 wherein the
synthesis gas undergoes an exothermic FT reaction to form a FT product.
The FT microchannel reactor 660 is cooled by steam which flows through
coolant steam loop 663. Steam enters the coolant steam loop 663 through line
664
(150 C, 26 bars) and flows into mixer 664a. Steam flows from mixer 664a
through
line 664b (222 C, 26 bars) to and through heat exchanger 668. The heat
exchanger
668 is in thermal contact with the FT microchannel reactor 660 and exchanges
heat
with the FT microchannel reactor. The steam cools the FT microchannel reactor
660
as the synthesis gas is converted to the FT product in the FT microchannel
reactor
660. Steam flows out of the heat exchanger 668 through line 664c (225 C, 25
bars)
to vessel 666. Steam flows out of the vessel 666 through line 665 (225 C, 25
bars)
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and out of the coolant steam loop 663. Steam flows from the vessel 666 through
line
664d (225 C, 25 bars) to and through pump 667. The steam flows from pump 667
through line 669 (225 C, 27 bars) to mixer 664a.
The FT product flows from the FT microchannel reactor 660 through line 661
(230 C, 18 bars) to separator 670 where it undergoes a separation. A gaseous
FT
product flows out of separator 670 through line 671 (230 C, 18 bars). A liquid
FT
product flows out of separator 670 through line 672 (230 C, 18 bars) to mixer
680.
The gaseous FT product flows through heat exchanger 673 to line 671a (80 C, 18
bars). Coolant water flows from line 682 (30 C, 5 bars) to and through heat
exchanger 673 and out of heat exchanger 673 through line 683 (34.2 C, 3.5
bars).
The gaseous FT product flows through line 671a (80 C, 18 bars) to and through
heat exchanger 674 and from the heat exchanger 674 to and through line 671b
(35 C, 18 bars) to three-way separator 675. A gaseous mixture flows out of the
three-way separator 675 through line 676 (35 C, 18 bars). This gaseous mixture
may be referred to as an FT tail gas. A liquid mixture flows out of the three-
way
separator 675 through line 677 (35 C, 18 bars). This liquid mixture may be
referred
to as process condensate.
A liquid FT product flows from the three-way separator 675 through line 678
(35 C, 18 bars) to mixer 680 where it is combined with the liquid FT product
from line
.. 672. The combined liquid FT product flows from mixer 680 through line 681
(121 C,
18 bars) to fractionator 685 where the combined liquid FT product undergoes
fractionation. A light ends product flows out of fractionator 685 through line
687
(121 C, 18 bars) to mixer 607. A liquid FT product flows from fractionator 685
through line 686 (121 C, 18 bars) to fractionator 690 wherein the liquid FT
product
undergoes fractionation. Liquid FT product flows out of fractionator 690
through line
691 (121 C, 18 bars). This liquid FT product may be referred to as synthetic
fuel. A
bottoms product flows out of fractionator 690 through line 692 (121 C, 18
bars) to
mixer 607.
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Table 1
Eream No. 602 , 606 608 611 616 622 626 631
Tamp C 15 89 93.9883 1480 1013.054 235 66.7115
66.7115
Pes bar 1 1 1 1 1 1 1 1
Elth MW -7.4219 -3.2923 -3.5602 0.14156 -3.3517 -
5.2457 -7.3836 -7.5537
V3por mole 0.3192 0 0.17438 1 1 1 1
0.99112
fnction
"Nal kmol/h 98.1637 25.8081 28.1409 195.2389 240.0912
240.0912 266.6482 260.3062
"Nal kg/h 3559.074 2279.7353 2789.0026 3279.5127 4069.5129 4069.5129
4547.9342 4184.5017
Mtal std L m3/h 1.9979 0.4612 1.1084 6.6447 7.4347 7.4347
7.9131 7.4862
"Nal std V m3/h 2200.21 578.45 630.74 4398.43 5381.32
5381.32 5976.56 5834.41
Fpwrates in
knol/h
r\SVV 22.1358 22.1358 22.1358 0 0 0 0 0
Fltdrogen 0 0 0.0379 91.761 91.761 91.761 91.761
91.761
Carbon 0 0 0.0495 92.8783 92.8783 92.8783
92.8783 92.8783
116noxide
Vater 51.4844 3.6677 3.9381 0.0002 43.8525 43.8525 70.4096 70.4096
Carbon Dioxide 0 0 0.0142 0 0 0 0 0
Nethane 0 0 0.05 3.12116 3.2116 3.2116 3.2116
3.2116
Ehane 0 0 0,0086 0.0009 0.0009 0.0009 0.0009
0.0009
Ehylene 0 0 0.0191 1.3367 1.3367 1.3367 1.3367
1.3367
Popane 0 0 0,0187 0 0 0 0 0
Popylene o 0 0.0002 0.0035 0.0035 0.0035 0.0035
0.0035
NButane 0 0 0.0037 0 0 0 0 0
NPentane 0 0 0.0093 0 0 0 0 0
NDodecane 0 0 0.154 0 0 0 0 0
NTridecane 0 0 0.1913 0 0 0 0 0
NTetradecane , 0 0 0.1782 0 0 0 0 0
NPentadecane 0 o 0.1412 0 0 0 0 0
NHexadecane 0 0 0.1186 0 0 0 0 0
NHeptadecane 0 0 0.102 0 0 0 0 0
NOctadecane 0 0 0.1204 0 0 0 o 0
NNonadecane 0 0 0.0983 0 o 0 0 0
NEicosane 0 0 0.1801 0 0 0 0 o
n-Docosane 0 0 0.1402 0 0 0 0 0
nTetracosane 0 0 0.1197 0 0 0 o 0
n-lexacosane 0 0 0.0845 0 0 0 0 0
nOctacosane 0 0 0.0697 0 0 0 0 0
NTricontane 0 0 0.0513 0 0 0 0 0
NDotriacontane 0 0 0.054 0 0 0 0 0
Ffixatriacontane 0 0 0.0478 0 0 0 0 0
Hdrogen 0 0 0 0.6119 0.6119 0.6119 0.6119
0.0612
Ciloride
Anmonia 24.5435 0.0046 0.0046 0.0001 0.0001 0.0001 0.0001 0
N:rogen o o 0 0.265 0.265 0.265 0.265
0.0265
H drogen 0 0 o 2.0347 2.0347 2.0347 2.0347
0.2035
Ganide
lidrogen o o 0 0.0846 0.0846 0.0846 0.0846
0.0085
&fide
arbonyl 0 0 0 0.0042 0.0042 0.0042 0.0042
0.0004
Silfide
C,rbon 0 0 o 0.0523 0.0523 0.0523 0.0522
0.0052
Dsulfide
Bmzene 0 0 0 3.9939 3.9939 3.9939 3.9939
0.3994
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Table 2
Stream No. 653 654 651 661 672 671 676
Temp C 233.7769 15 220 230 230 230 35
Pres bar 25.17 25.17 25.17 18.25 18.25 18.25 1795
Enth MW -2.6217 -0.006469 -2.5101 -5.5514 -0.13693
-5.4144 -1.2426
Vapor mole fraction 1 1 1 0.99172 0 1 1
Total kmol/h 190.9299 84.3338 275.2637 146.281
1.2117 145.0693 78.2589
Total kg/h 2934.6853 170 3104.6854
3104.6994 308.7789 2795.9199 1198.5036
Total std L in3/h 6.2364 2.4286 8.665 5.0348 0.384, 4.6508
2.9014
Total std V m3/h 4279.44 1890.23 6169.66 3278.69
27.16 3251.53 1754.07
Flowrates in kmol/h
Hydrogen 91.761 84.3338
176.0948 33.7124 0.012 33.7004 33.6744
Carbon Monoxide 92.8783 0 92.8783 27.8635
0.0104 27.8531 27.8139
Water 1.0333 0 1.0333 63.7726
0.1997 63.5729 0.2657
Carbon Dioxide o o 0 0.9005 0.0007 0.8998
0.8806
Methane 3.2116 0 3.2116 12.9638
0.0056 12.9583 12.9137
Ethane 0.0009 0 0.0009 0.4203
0.0004 0.4198 0.4116
Ethylene 1.3367 0 1.3367 1.3367
0.0012 1.3355 1.3175
Propane o o 0 0.2926 0.0005
0.2921 0.2739
Propylene 0.0035 0 0.0035 0.0035 0 0.0035 0.0033
N-Butane 0 o 0 0.0203 0.0001
0.0203 0.0166
N-Pentane 0 0 0 0.0767 0.0003
0.0763 0.0457
N-Hexane 0 0 0 0.1415 0.001 0.1405 0.0465
N-Heptane o o 0 0.223 0.0024
0.2206 0.0319
N-Octane o o 0 0.2922 0.0047
0.2875 0,0165
N-Nonane o 0 0 0.302 0.0074
0.2946 0.0057
N-Decane 0 0 0 0.2829 0.0103
0.2726 0.0018
N-Undecane 0 o 0 0.2698 0.0144
0.2553 0.0006
N-Dodecane o o 0 0.2568 0.02
0.2368 0.0002
N-Tridecane 0 0 0 0.2126 0.0237
0.189 0.0001
N-Tetradecane 0 0 0 0.1876 0.0293 0.1583
0
N-Pentadecane 0 0 0 0.1471 0.0316 0.1155
0
N-Hexadecane o o 0 0.1235 0.0376 0.0859
o
N-Heptadecane o o 0 0.1062 0.0396 0.0666
o
N-Octadecane o o 0 0.1254 0.0564 0.0691
0
N-Nonadecane 0 o 0 0.1024 0.0549 0.0475
0
N-Eicosane o o 0 0.1876 0.1242 0.0634
o
n-Docosane o o 0 0.1402 0.1105 0.0297
o
n-Tetracosane 0 0 0 0.1197 0.1068 0.013
0
n-Hexacosane 0 0 0 0.0845 0.0798 0.0046
0
n-Octacosane 0 0 0 0.0697 0.0677 0.0019
0
n-Tricontane 0 0 0 0.0513 0.0506 0.0007
0
n-Dotriacontane 0 0 0 0.054 0.0536 0.0004
0
Hexatriacontane 0 0 0 0.0478 0.0477 0.0001
0
Methanol o o o 0.13 0.0005
0.1296 0.0051
Ethanol o 0 0 0.5201 0.0023
0.5178 0.1664
Isopropanol 0 0 0 0.0033 0 0.0032 0.0007
N-Propanol 0 0 0 0.0325 0.0002
0.0323 0.0051
HydrogenChloride 0.0612 0 0.0612 0.0612 0.0001 0.0611 0.0598
Nitrogen 0.0265 0 0.0265 0.0265 0
0.0265 0.0265
Hydrogen Cyanide 0.2035 0 0.2035 0.2035 0.0006 0.2029
0.1449
Hydrogen Sulfide 0.0085 0 0.0085 0.0085 0, 0.0084
0.0081
Carbonyl Sulfide 0.0004 0 0.0004 0.0004 0 0.0004 0.0004
Carbon Disulfide 0.0052 0 0.0052 0.0052 0 0.0052 0.0032
Benzene 0.3994 0 0.3994 0.3994
0.0031 0.3963 0.1184
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Table 3
Stream No. 677 678 681 692 686 691 687
Temp C 35 35120.8143
120.8143120.8143120.8143120.8143
Pres bar 17.95 17.95 17.95 17.95 17.95 17.95
17.95
Enth MW -5.0226 -
0.26163 -0.39856-0.025453 -0.37262 -0.13048 -0.24245
Vapor mole fraction 0 0 0 0.49977 0 0 0.2
Total kmol/h 63.402 3.4085 4.6202 0.4815 4.1387
2.2875 1.8512
_
Total kg/h
1145.1263452.2904761.0694 10.2715750.7979251.8024498.9954
Total std L m3/h 1.1466 0.6028 0.9869 0.0164 0.9704
0.3397 0.6307
Total std V m3/h 1421.07 76.4 103.56 10.79 92.76 51.27
41.49
Flowrates in kmol/h -
Hydrogen 0.0001 0.0259 0.0379 0.0379 0
0 0
Carbon Monoxide 0 0.0391 0.0495 0.0495 0 0
0
Water 63.2365 0.0707 0.2704 0.2704 0
0 P.
Carbon Dioxide 0.0057 0.0135 0.0142 0.0142 0 0
0
Methane 0.0001 0.0444 0.05 0.05 0 0
0
Ethane 0 0.0082 0.0086 0.0086 0 0
0
Ethylene 0 0.0179 0.0191 0.0191 0 0
0
Propane 0 0.0182 0.0187 0.0187 0 0
0
Propylene 0 0.0002 0.0002 0.0002 0 0
0
N-Butane 0 0.0036 0.0037 0.0037 0 0
0
N-Pentane 0 0.0306 0.0309
0.0093 0.0217 0.0217 0
N-Hexane 0 0.0941 0.0951 0 0.0951 0.0951 0
N-Heptane 0 0.1887 0.1911 0 0.1911 0.1911 0
N-Octane 0 0.271 0.2757 0 0.2757 0.2757 0
N-Nonane 0 0.2889 0.2963 0 0.2963 0.2963 0
N-Decane 0 0.2708 0.2811 0 0.2811 0.2811 0
N-Undecane 0 0.2547 0.2692 0 0.2692 0.2692 0
N-Dodecane 0 0.2366 0.2566 0 0.2566 0.1026
0.154
N-Tridecane 0 0.1889 0.2126 0 0.2126 0.0213
0.1913
N-Tetradecane 0 0.1583 0.1876 0 0.1876 0.0094
0.1782
N-Pentadecane 0 0.1155 0.1471 0 0.1471 0.0059
0.1412
N-Hexadecane 0 0.0859 0.1235 0 0.1235 0.0049
0.1186
N-Heptadecane 0 0.0666 0.1062 0 0.1062 0.0042
0.102
N-Octadecane 0 0.0691 0.1254 0 0.1254 0.005
0.1204
N-Nonadecane 0 0.0475 0.1024 0 0.1024 0.0041
0.0983
N-Eicosane 0 0.0634 0.1876 0 0.1876 0.0075
0.1801
n-Docosane 0 0.0297 0.1402 0 0.1402 0
0.1402
n-Tetracosane 0 0.013 0.1197 0 0.1197 0 0.1197
n-Hexacosane 0 0.0046 0.0845 0 0.0845 0
0.0845
n-Octacosane 0 0.0019 0.0697 0 0.0697 0
0.0697.
n-Tricontane 0 0.0007 0.0513 0 0.0513 0
0.0513
n-Dotriacontane 0 0.0004 0.054 0 0.054 0 0.054
Hexatriacontane 0 0.0001 0.0478 0 0.0478 0
0.0478
Methanol 0.1205 0.0039 0.0043 0 0.0043 0.0043
0
Ethanol 0.0378, 0.3136 0.3159 0 0.3159 0.3159
0
Isopropanol 0 0.0025 0.0025 0 0.0025 0.0025 0
N-Propanol 0.0003 0.0269 0.0271 0 0.0271 0.0271
0
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Stream No. 677 678 681 692 686 691 637
HydrogenChloride 0.0002 0.0011 0.0012 0 0.0012 0.0012
0
Hydrogen Cyanide 0.0002 0.0578 0.0583 0 0.0583
0.0583 0
Hydrogen Sulfide 0.0001 0.0003 0.0003 0 0.0003
0.0003 0
Carbon Disulfide 0.0003 0.0017 0.0017 0 0.0017
0.0017 0
Benzene 0 0.2779 0.231 0 0.281 0.281
0
Example 2
A Fischer-Tropsch reaction is conducted in a microchannel reactor employing
a fixed catalyst bed. The process is conducted at a high capacity (contact
times on
the order of about 290 to about 214 milliseconds) and provides for high CO
conversions (up to about 80%). The reactor is operated with a two phase flow
and
shows little pressure drop variation, with a standard deviation less than 3%
of the
total pressure drop. The high CO conversions and stable pressure drops are
also
associated with low CH4 selectivities, less than 15% for all cases, and less
than 10%
for most cases, coupled with high C6+ hydrocarbon selectivities of greater
than 75%
for all cases and greater than 80% for most cases.
The microchannel reactor has two process repeat units interleaved between
three coolant repeat units. Process microchannels in the process repeat units
are in
a cross-flow orientation to coolant channels in the coolant repeat units. This
is
shown in Fig. 29. The active reactor core has an area that is 15.2 cm (6
inches) by
15.2 cm (6 inches). The overall stack size of the reactor is 25.4 cm (10
inches) by
19.1 cm (7.5 inches) by 6.17 cm (2.43 inches). The coolant channels are formed
from multiple shims which include flow distribution features. The process
microchannels are formed from a copper waveform. This is shown in Fig. 30.
This
waveform has the dimensions of 19.1 cm (7.5 inches) by 15.2 cm (6 inches) by
3.18
mm (0.125 inch). The thickness of the waveform is 0.15 mm (0.006 inch). The
resulting microchannel reactor has 276 process microchannels formed in two
layers.
Each of the process microchannels has the average dimensions of 0.95 mm
(0.0375 inch) in width, 3.18 mm (0.125 inch) in height and 19.1 cm (7.5
inches) in
length. Headers and footers are connected to the coolant channels and process
microchannels to provide for connection to larger external piping.
A catalyst bed is loaded into the microchannel reactor as described below.
The assembly is then enclosed within a process confinement shell (PCS). The
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catalyst bed contains SiC particles and particles of an FT catalyst.
The SiC particles are suppled by Atlantic Equipment Engineers of Bergen
New Jersey, catalogue number SI-312. A Malvern Hydro 2000 G light scattering
particle distribution analyzer is used to measure the volume average d(50)
diameter
for the SiC particles. The SiC particles have an average diameter of 281
microns.
The packed apparent bulk density (PABD) for the SiC particles is 1.62 grams
per
cubic centimeter (g/cc) in triplicate, and the void fraction at PABD is 0.31.
The FT catalyst is supplied by Oxford Catalyst Limited. This catalyst
comprises cobalt and a support. The volume averaged particle size for the
catalyst
particles is 261 microns as determined using the Malvern Hydro 2000 G
analyzer. A
later sieving of the catalyst shows most of the catalyst mass between 210 to
250
microns with more at higher mesh sizes than at lower mesh sizes. The PABD for
the
catalyst is 1.08 g/cc in triplicate. The void fraction for PABD packing is
0.362.
Deionized water is added in 100 microliter aliquots using a pipette until the
water
breaks the surface. The wetted catalyst is placed on a vibrating table for 30
seconds
at medium power to displace trapped air, settle the bed, and bring excess
water to
the surface. Excess water is removed using a pipette. The sample is allowed to
dry
in air. The sample is then dried at 200 C for one hour at ambient pressure.
The volume of the reactor is determined by the addition of methanol at room
-- temperature. 151.5 cc of methanol fills the reactor waveform channels to
the top.
A 100 ppi foam that has a thickness of 0.635 cm (0.25 inches) is inserted in
the bottom of the reactor.
The FT catalyst is added to the waveform and densified using vibration from a
rubber covered mallet. The total mass added is 143.22 grams. The depth filled
is
measured at each waveform channel with measured length pins whose distance
above the waveform opening is measured with a graded sheet and digital
photography. The average difference of FT catalyst fill height and the desired
fill
height of 17.145 cm (6.75 inches) is 0.467 cm (0.184 inch) below the desired
level.
The standard deviation for the fill height is 0.483 cm (0.190 inche. The
density of the
packing, assuming the volume of the process waveform channels are the same
throughout the packing height, is 1.068 g/cc, or 1.1% lower than the measured
PABD of 1.08 g/cc. The total volume of the catalyst is 134.1 cc.
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The SIC layer is added to the top of the reactor and densified to fill the
reactor. A 100 ppi foam with a thickness of 0.635 cm (0.25 inch) is inserted
in the
top of the reactor.
The flow and composition of syn gas fed to the microchannel reactor is
controlled using Brooks 5850E mass flow controllers. Hydrogen, carbon monoxide
and nitrogen gases are supplied by Praxair, Matheson Tr-gas and DeliIle. These
are fed through both activated carbon and molsieve 13X traps. A sample port is
located downstream of the mixing point to measure the inlet gas composition.
The
gases are heated to >300 C in a stainless steel microchannel heat exchanger,
which is heated with nitrogen gas, before being fed to the microchannel
reactor.
The inlet pressure is measured using a Yokogawa EJA430A-H model
pressure transmitter. The process fixed bed pressure drop is measured by a
Yokogawa model EJA110A-H differential pressure transmitter. The inlet and
outlet
streams are analyzed using an Agilent 3000A RGA refinery gas analyzer gas
chromatograph (GC) with extra channel for higher hydrocarbons. Tail gas
samples
are collected through a sample port located downstream from the reactor and
upstream from the first product collection tank. The sample conditioner
consists of
a Neptune SC-316 sample cooler and a Swagelok 300 cc condensate trap. Flow
through the sample conditioner is set with a pressure regulator and needle
valve and
turned on only while sampling. Five to seven GC samples are collected for each
gas
measurement, with the first two discarded and the remainder averaged.
The product stream is routed through three collection vessels at elevated
pressure, and cooled in stages to provide a rough separation of lighter
hydrocarbon
products from heavier hydrocarbon products along with an aqueous phase. A
first
drum is heated with two Watlow band heaters to a local surface temperature of
120 C to135 C. Aqueous phase and heavier hydrocarbon products are drained
from the bottom and weighed. Gases leave the first drum at a temperature
between
120 C and 140 C and are cooled to less than 30 C in the first Sentry model
1253C57-EW6-H35X heat exchanger, which is cooled with Dow Dowfrost HD
coolant. A second drum is at ambient temperature and is used to collect an
aqueous
phase and a clear liquid hydrocarbon phase. The remaining gases flow to a
second
model 1253C57-EW6-H35X heat exchangers, which is cooled to 10 C with
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propylene glycol coolant and then to a third collection tank, which collects
less than
1% of total condensate. After the third tank the tail gas reaches a pressure
control
device for the process side. This devices is a Kammer model 030000 globe
valve.
The product is measured with an American Meter Company 100 liter/revolution
dry
test meter equipped with a relay for signal transmission. A second tail gas
sample
port is located downstream of the dry test meter for additional sampling.
The reactor is heated and catalyst activation is carried out under a reducing
atmosphere of hydrogen at 400 C and near ambient pressure. The reactor is then
cooled down and the start-up is initiated by increasing the pressure within
the reactor
to the operating pressure, gradually turning on the flow of coolant, as well
as the flow
of the reactant feed mixture, and increasing the reactor temperature. The
reactant
feed mixture contains H2 and CO at an H2:CO mole ratio of 2:1. The reactant
feed
mixture also contains 16.6% by volume N2. At a contact time of 290 ms, the
reactor
temperature is gradually raised to 210 C to reach a steady state CO conversion
of
.. greater than 70%.
The standard deviation of the pressure drop is high as the reaction conditions
are established, and it then settles out to a lower value as the system
stabilizes.
Pressure drop at selected time-on-stream conditions illustrate stability over
short and
long periods of time:
At around 1500 hours on stream, the reactor operating conditions are set to
an inlet H2:CO ratio of 2.01, and 4% by volume N2 in the feed at an inlet
pressure of
350 psig and an inlet temperature of 222 C and a contact time of 214 ms. These
conditions are maintained for 190 hours. The reactor performance shows a
steady
CO conversion of 68.8 0.3%. The average selectivity to CH4 is 13.3 0.1%
and
the selectivity to C6+ hydrocarbons is 74.8 0.2%.
The reactor pressure drop is steady as evidenced by a low standard deviation
in the pressure drop measurements. The average pressure drop during this
operation is 1.75 0.01 psi.
The catalyst is re-reduced at around 1890 hours on stream and the reactor re-
started to the target condition with an inlet H2:CO ratio of 2.0, and 16.6% N2
in the
feed. The inlet pressure is 350 psig, and the average inlet temperature is 211
C.
The contact time is 290 ms. This set of reaction conditions is maintained for
420
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hours. The CO conversion in the reactor is initially high at around 75% and
gradually stabilizes over the course of a few hundred hours to a steady value
of 68.8
0.3%. The average selectivity to CH4 is 8.9 0.1% and that to C6+
hydrocarbons is
77.8 0.2%.
Corresponding to the stabilization of the CO conversion described above, the
pressure drop increases initially and then stabilizes as the CO conversion
drops to
its final stable value. The reactor pressure drop during this operation
remains
steady as evidenced by the low standard deviation in the pressure drop
measurements. The average pressure drop during this condition is 1.46 0.04
psi.
10 Prior to data being collected, a leak between the coolant side and
the fixed
bed (process) side is detected during normal pressure checking. From that time
forward the coolant side is operated at a pressure higher than the process
side so
that any leaking would be liquid water or steam from the coolant side into the
process side. Hence a larger standard deviation for the process side pressure
drop
15 (two to fourfold) is seen here compared to the previous run.
The details of the performance of the microchannel reactor throughout its
operational life is summarized below.
After the completion of the initial start-up, a target condition with H2:CO
ratio
of 2:1 and 16.6% N2 in the feed at an average reactor temperature of 210 C and
a
20 contact time of 290 ms is reached which gives an average CO conversion
of 71.7%.
These process conditions are maintained from start-up to around 1140 hours on
stream. The CO conversion stabilizes gradually to an average value of about
71.7% and the corresponding average CH4 selectivity is 8.9%.
The contact time is then decreased to 214 ms and the reactor temperature
25 gradually increased to 222 C to increase the CO conversion to its
previous steady
value. At these conditions the average CO conversion is 71.9% with a 77.2%
selectivity to C6+ hydrocarbons. The corresponding steady state pressure drop
is
1.843 0.004 psi.
At around 1500 hours on stream the feed dilution is then decreased to 4% by
30 volume N2, the reactor temperature is maintained at 222 C, and the
average CO
conversion is 68.8%. The corresponding average pressure drop is 1.75 psi.
The reactor conditions are then reverted to the initial start-up condition by
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decreasing the temperature to 210 C, increasing dilution with N2 to 16.6% and
increasing the contact time to 290 ms. The average CO conversion is 66.4%.
This
is about 5% lower the initial performance. This highlights a minimal catalyst
deactivation with time on stream. The corresponding average pressure drop of
1.46
0.01 psi is higher than the 1.41 0.01 psi initially seen. This increase in
pressure
drop is commensurate with the decrease in conversion. The standard deviation
of
the pressure drop indicating the stability of the flow development in the
process
microchannels remains virtually unchanged during the 1880 hours on stream.
The catalyst is re-redued at 1890 hours on stream with the catalyst spending
a half hour above 400 C and about 2 hours above 390 C. A cross-leak between
the
coolant and process sides is discovered after the reduction. During the start-
up
process the chiller pump fails causing an interlock shut down event. When the
reactor reaches the target temperature, the CO conversion is only 39%, well
below
the previous values. The catalyst is reduced again.
The catalyst is then restarted to reach a condition with an H2:CO ratio of 2:1
and 16.6% N2 in the feed at an average reactor temperature of 210 C and a
contact
time of 290 ms which corresponds to the first steady condition after the
initial start-
up. The initial CO conversion is slightly higher than the previous start-up
but it
steadies out at a slightly lower value of 69.5%. The corresponding average
pressure
drop is 1.47 0.04 psi. The standard deviation of the pressure drop increases
compared to the original start-up of the reactor. This also corresponds to the
increase in a deactivation rate for the catalyst. The increase in the standard
deviation may be a result of the leak described above.
The contact time is then decreased to 214 ms and the reactor temperature
gradually increased to 223 C. This results in an average CO conversion of
70.4%
and a C6+ selectivity of 76.0%.
The H2:CO ratio is then changed to 1.5:1 and the contact time increased to
255 ms. The reactor pressure is then increased to 384 psig and the reactor
temperature gradually increased to 228 C leading to an average CO conversion
of
60.9% at a 7.1% CH4 selectivity. The pressure drop decreases as the CO
conversion increases at the higher pressure.
The H2:CO ratio is changed to 1.5, and the dilution with N2 is increased to
CA 02719382 2010-09-22
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97
40%. The reactor pressure is increased to 420 psig and the reactor temperature
increased to 232 C. As the contact time is increased from 184 ms to 250 ms,
the
CO conversion increases from 56.1% to 64.0%. The corresponding pressure drop
decreases from 2.256 psi to 1.545 psi. The pressure drop decreases as the
contact
time increases which reduces flow and increases CO conversion.
The reaction conditions are then reverted to an H2:CO ratio of 2:1 with 16.6%
N2 in the feed. The average reactor temperature is 211 C and the contact time
is
290 ms. The CO conversion decreases to an average value of 59.6%. The average
pressure drop is 1.52 0.04 psi. This is higher than that at the restart due
to the
catalyst deactivation.
The catalyst is then reduced again and restarted to the same reaction
conditions of an H2:CO ratio of 2:1, 16.6% N2 in the feed, average reactor
temperature of 211 C and contact time of 290 ms. The CO conversion reaches a
steady value of about 69.2% which is comparable to that attained after the
previous
reduction. The corresponding average pressure drop is 1.50 0.04 psi.
The standard deviation of the pressure drop, which is indicative of flow
stability, indicates a stable flow in the process microchannels that remains
virtually
unchanged during the 1800 hours on stream.
While the invention has been explained in relation to various embodiments, it
is to be understood that various modifications thereof may become apparent to
those
skilled in the art upon reading this specification. Therefore, it is to be
understood
that the invention includes all such modifications that may fall within the
scope of the
appended claims.
