Note: Descriptions are shown in the official language in which they were submitted.
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Title: PROCESS FOR TREATING HEAVY OIL
This application claims priority under 35 U.S.C. 119(e) to U.S. Provisional
Application Serial No. 61/250,282, filed October 9, 2009, which is
incorporated
herein by reference in its entirety.
Technical Field
This invention relates to a process for treating heavy oil. More particularly,
this invention relates to a process for upgrading heavy oil by hydroprocessing
the oil
using process intensification techniques.
Background of the Invention
Untreated heavy oils are typically in the form of a dark brown, free-flowing
liquids. Unconventional sources of these heavy oils include those made from
the
gasification, pyrolysis or liquefaction of carbonaceous materials such as
coal, shale,
tar sand, bitumen, biomass, and the like. These unconventional heavy oil
sources
are often distributed in locations far from large central processing
facilities that are
required to upgrade these oils to useful products such as middle distillate
fuels, and
the like. Additionally many of these oils are unstable in long-term storage
and not
miscible with conventional hydrocarbon-based fuels, making transportation to
central processing facilities difficult or uneconomical.
Summary of the Invention
The problem relates to providing a viable process for upgrading heavy oil to
produce useful hydrocarbon products such as middle distillate fuels and the
like,
using equipment that is modular or relatively small in size so that the
process can be
conducted economically at locations closer to the source of the heavy oil and
thus
avoid the problems of storage and transportation incurred when using large
central
processing facilities. It would be advantageous if the equipment could be
readily
adapted to process the heavy oil at any desired production volume. This
invention
provides a solution to this problem. With the present invention, heavy oil is
upgraded to form useful hydrocarbon products by hydroprocessing the oil using
process intensification techniques. Heavy oil in the form of a liquid, vapor
or
combination thereof may be treated using the inventive process.
This invention relates to a process, comprising: flowing heavy oil (that is,
heavy oil in the form of a liquid, vapor, or combination thereof) and hydrogen
(i.e.,
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H2 or reactant streams containing H2) in a reactor in contact with a
hydroprocessing
catalyst under process intensification conditions, the heavy oil comprising
heteroatoms (e.g., sulfur, nitrogen, oxygen and/or metals such as Ni, V, and
the
like); reacting at least some of the heteroatoms with the hydrogen to form one
or
more heteroatom containing compounds; and hydrocracking the heavy oil to form
an
upgraded hydrocarbon product. The hydroprocessing catalyst may be a
hydrotreating catalyst or a hydrocracking catalyst. The heteroatom containing
compounds may be separated from the upgraded hydrocarbon product. In one
embodiment of the invention, the reactor comprises a process microchannel, and
io the heavy oil and hydrogen flow in the process microchannel in contact with
the
hydroprocessing catalyst and undergo reaction. The process may be conducted in
one or more process microchannels or one or more microchannel reactors.
In one embodiment, the heavy oil comprises water, the process further
comprising removing water from the upgraded hydrocarbon product.
is In one embodiment, the heavy oil is reacted in the presence of a
hydrotreating catalyst to form an intermediate hydrocarbon product, and then
the
intermediate hydrocarbon product is reacted in the presence of a hydrocracking
catalyst to form the upgraded hydrocarbon product. In one embodiment, the
reaction with the hydrotreating catalyst is conducted in a process
microchannel and
20 the reaction with the hydrocracking catalyst is conducted in a process
microchannel,
the hydrotreating catalyst and the hydrocracking catalyst being in the same
process
microchannel. In one embodiment, the reaction with the hydrotreating catalyst
is
conducted in a first process microchannel and the reaction with the
hydrocracking
catalyst is conducted in a second process microchannel. In one embodiment, the
25 reaction with the hydrotreating catalyst is conducted in a first
microchannel reactor
and the reaction with the hydrocracking catalyst is conducted in a second
microchannel reactor.
In one embodiment, the pressure in the reactor is in the range from about 0.5
to about 25 MPa.
30 In one embodiment, the temperature in the reactor is in the range from
about
1 00 C to about 500 C.
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In one embodiment, ratio of hydrogen to heavy oil in the reactor is in the
range from about 10 to about 6000 standard cubic centimeters of hydrogen per
cubic centimeter of heavy oil.
In one embodiment, the heavy oil entering the reactor is in the form of a
liquid, a vapor, or a combination of liquid and vapor.
In one embodiment, the reactor comprises one or more process
microchannels, the heavy oil and hydrogen being mixed with each other in the
one
or more process microchannels.
In one embodiment, the reactor comprises a process microchannel and the
io process microchannel is in a microchannel reactor, the microchannel reactor
comprising a reactant stream channel adjacent to the process microchannel, the
process microchannel and the reactant stream channel having a common wall, and
a plurality of openings in the common wall, the process further comprising
flowing
the pyrolysis oil in the process microchannel and flowing the hydrogen from
the
reactant stream channel through the openings in the common wall into the
process
microchannel in contact with the pyrolysis oil.
In one embodiment, the heavy oil and hydrogen are mixed prior to entering
the reactor.
In one embodiment, the reactor comprises a microchannel reactor comprising
a plurality of process microchannels, the microchannel reactor comprising a
manifold providing a flow passageway for the heavy oil and hydrogen to flow
into the
process microchannels.
In one embodiment, the reactor comprises a microchannel reactor comprising
a plurality of the process microchannels, the microchannel reactor comprising
a first
manifold providing a flow passageway for the heavy oil to flow into the
process
microchannels, and a second manifold providing a flow passageway for the
hydrogen to flow into the process microchannels.
In one embodiment, heat is transferred from the reactor to a heat exchanger.
In one embodiment, the reactor comprises a microchannel reactor comprising
3o a plurality of process microchannels, the microchannel reactor further
comprising at
least one heat exchange channel in thermal contact with the process
microchannels,
a heat exchange fluid being in the heat exchange channel, and heat is
transferred
from the process microchannels to the heat exchange fluid in the heat exchange
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channel. The heat exchange fluid may undergo a phase change in the heat
exchange channel. The reactants may flow in the process microchannel in a
first
direction, and the heat exchange fluid may flow in the heat exchange channel
in a
second direction, the second direction being cross current relative to the
first
direction.
In one embodiment, the reactor comprises a process microchannel and a
tailored heat exchange is provided along the length of the process
microchannel to
maintain a substantially isothermal temperature profile along the length of
the
process microchannel.
In one embodiment, the heavy oil entering the reactor comprises heavy oil
vapor, the heavy oil vapor being at least partially condensed in the reactor.
In this
embodiment, the catalyst may be positioned in a distillation column, the
distillation
column comprising a single stage catalytic distillation hydrocracker. Hydrogen
may
be mixed with the heavy oil vapor prior to entering the reactor, or the
hydrogen and
heavy oil may be separately manifolded into the reactor. Further, hydrogen
and/or
another reactive feed or a non-reactive gas or liquid (i.e., a third fluid)
may be fed
downstream of the first manifold region. In one embodiment, a second fluid may
be
used to tailor the reactions or to inhibit unwanted side reactions. The third
fluid may
be added to reduce coking or the formation of longer chain hydrocarbons. The
third
fluid, in one embodiment may be steam or an oxygen containing stream. In one
embodiment, the third fluid may comprise hydrogen or a hydrogen-containing
stream, containing, for example, other carbonaceous matter.
In one embodiment, the reactor comprises a first stage reactor, the
hydroprocessing catalyst comprising a first hydrocracking catalyst, the
process also
employing a second stage reactor containing a second hydrocracking catalyst,
the
heavy oil comprising heavy oil vapor, the process comprising: flowing the
heavy oil
vapor and hydrogen in the first stage reactor in contact with the first
hydrocracking
catalyst, condensing and hydrocracking the heavy oil vapor to form a first
hydrocracked hydrocarbon product comprising a first liquid hydrocarbon product
and
3o a first hydrocarbon vapor, and optionally a first aqueous phase product;
separating
the first hydrocarbon liquid product from the first hydrocarbon vapor, and
optionally
separating the first gaseous phase product from the first hydrocarbon liquid;
flowing
the first hydrocarbon vapor and hydrogen in the second stage reactor in
contact with
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the second hydrocracking catalyst, condensing and hydrocracking the first
hydrocarbon vapor to form a second hydrocracked hydrocarbon product comprising
a second hydrocarbon liquid product and a second hydrocarbon vapor, and
optionally a second aqueous phase product; and separating the second
5 hydrocarbon liquid product from the second hydrocarbon vapor, and optionally
separating the second aqueous phase product from the second hydrocarbon liquid
product. Additional hydroprocessing and/or separation stages may be added.
In one embodiment, the hydroprocessing is conducted in a catalytic
distillation unit (CDU) which contains a hydroprocessing catalyst. The heavy
oil and
1o the hydrogen are fed to the CDU. A portion of the light overhead product is
condensed and recycled to the CDU. At least two product streams exit the CDU,
including at least one product stream which has been converted to an upgraded
hyrocarbon product. Optionally, the heavy oil feed to the CDU may comprise
heavy
oil vapor. Further, the hydrogen for the CDU may be premixed with the heavy
oil
vapor feed prior to being fed to the CDU. The heavy oil vapor feed may be fed
to
the CDU below the catalyst, so that the refluxing liquid may be used to wash
down
entrained solids into the bottom of the CDU to prevent the solids from
entering the
catalyst and causing fouling or plugging. In this embodiment, the
hydroprocessing is
integrated in the heavy oil production flowsheet. As the heavy oil is being
reacted, it
is being upgraded to a more stable, useable product. Further, the heavy oil
may be
upgraded as it is being condensed, a further integration, so that unstable
liquids are
not formed.
In one embodiment, the process comprises a first stage reaction section
containing a first hydroprocessing catalyst, the process also employing a
second
stage reaction section containing a second hydroprocessing catalyst, the first
stage
reaction section and the second stage reaction section being positioned in a
distillation column, the second stage reaction section being positioned above
the
first stage reaction section, the distillation column having a distillate end
and a
bottoms end and being equipped with a distillate condenser; the heavy oil
comprising heavy oil vapor, the process comprising: flowing the heavy oil
vapor and
hydrogen in the first stage reaction section toward the distillate end in
contact with
the first hydroprocessing catalyst, condensing and hydrocracking the pyrolysis
oil
vapor to form a first hydroprocessed hydrocarbon product comprising a first
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hydrocarbon liquid product and a first hydrocarbon vapor; separating the first
hydrocarbon liquid product from the first hydrocarbon vapor, and flowing the
first
hydrocarbon liquid product out of the distillation column; flowing the first
hydrocarbon vapor and hydrogen, with optional addition of hydrogen, in the
second
stage reaction section toward the distillate end in contact with the second
hydroprocessing catalyst, condensing and hydroprocessing the first hydrocarbon
vapor to form a second hydroprocessed hydrocarbon product comprising a second
hydrocarbon liquid product and a second hydrocarbon vapor; separating the
second
hydrocarbon liquid product from the second hydrocarbon vapor, and flowing the
io second hydrocarbon liquid product out of the distillation column; and
condensing at
least part of the second hydrocarbon vapor in the distillate condenser to form
another hydrocarbon liquid product, a portion of the another hydrocarbon
liquid
product being refluxed to the distillation column. One or more of the liquid
products
may subsequently be sent to a phase separation step for removal of immiscible
is water, if present.
In one embodiment, the reactor comprises a first stage reactor, the
hydroprocessing catalyst comprising a first hydrocracking catalyst, the
process also
employing a second stage reactor containing a second hydrocracking catalyst,
the
first stage reactor and the second stage reactor being positioned in a
distillation
20 column, the second stage reactor being positioned above and/or downstream
of the
first stage reactor, the distillation column having a distillate end and a
bottoms end
and being equipped with a distillate condenser; the heavy oil comprising heavy
oil
vapor, the process comprising: flowing the heavy oil vapor and hydrogen in the
first
stage reactor toward the distillate end in contact with the first
hydrocracking catalyst,
25 condensing and hydrocracking at least part of the heavy oil vapor to form a
first
hydrocracked hydrocarbon product comprising a first liquid hydrocarbon oil
product
and a first hydrocarbon vapor; separating the first liquid hydrocarbon oil
product
from the first hydrocarbon vapor, and flowing the first liquid hydrocarbon oil
product
out of the distillation column; flowing the first hydrocarbon vapor and
hydrogen in the
30 second stage reactor toward the distillate end in contact with the second
hydrocracking catalyst, condensing and hydrocracking at least part of the
first
hydrocarbon vapor to form a second hydrocracked hydrocarbon product comprising
a second liquid hydrocarbon oil product and a second hydrocarbon vapor;
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separating the second liquid hydrocarbon oil product from the second
hydrocarbon
vapor, and flowing the second liquid hydrocarbon oil product out of the
distillation
column; and condensing at least part of the second hydrocarbon vapor in the
distillate condenser to provide a liquid reflux back to the distillation
column.
In one embodiment, the hydroprocessing catalyst is positioned in a process
microchannel, the hydroprocessing catalyst being in the form of particulate
solids.
In one embodiment, the hydroprocessing catalyst is supported on a structure
which comprises a foam, felt, wad, honeycomb, monolith, fin, structured
packing, or
a combination of two or more thereof.
io In one embodiment, the hydroprocessing catalyst is in the form of a bed of
particulate solids positioned in a process microchannel, and additional
catalyst is
washcoated and/or grown on one or more interior walls of the process
microchannel.
In one embodiment, the hydroprocessing catalyst is a hydrotreating catalyst
which comprises Ni, Mo, Co, W, or a combination of two or more thereof.
In one embodiment, the hydroprocessing catalyst is a hydrocracking catalyst
which comprises Pt, Pd, Ni, Co, Mo, W, or a combination of two or more
thereof.
In one embodiment, the upgraded hydrocarbon product comprises a middle
distillate oil, a light oil, or a mixture thereof.
In one embodiment, the reactor comprises a process microchannel, the
channel Bond number for the process microchannel being less than about 1.
In one embodiment, the hydroprocessing catalyst is in a process
microchannel, the hydroprocessing catalyst being regenerated in-situ in the
process
microchannel.
In one embodiment, the heat exchange fluid is hydrogen or a hydrogen-
containing fluid that is preheated from the heat of reaction or internal
thermal
recuperation before adding to the hydrocarbon reactant. The hydrogen-
containing
fluid may be combined with the hydrocarbon reactant before the reaction or
distributed along the length of the reactor in two or more discrete locations.
In one embodiment, the inventive process is conducted in a plant facility, the
plant facility comprising an integrated process for producing a heavy oil
vapor
product, the process comprising condensing the heavy oil vapor product, and
hydroprocessing the heavy oil vapor product.
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In one embodiment, the process is conducted in a plant facility, the plant
facility comprising a plurality of process microchannels, or one or more
microchannel reactors containing a plurality of process microchannels, or one
or
more reactor housing vessels containing one or more microchannel reactors, the
hydroprocessing catalyst in one or more process microchannels, microchannel
reactors or reactor housing vessels being regenerated while the process is
carried
out in other process microchannels, microchannel reactors or reactor housing
vessels in the plant facility.
In one embodiment, the heavy oil is derived from the gasification, pyrolysis
or
liquefaction of coal, shale, tar sand, bitumen, biomass, or a combination of
two or
more thereof.
In one embodiment, the heavy oil comprises pyrolysis oil, pyrolysis oil vapor,
or a mixture thereof.
In one embodiment, the heavy oil is formed in a plant, and the reactor is in
the plant, the process comprising forming the heavy oil and transporting the
heavy
oil to the reactor.
With the inventive process, increased process efficiency may be achieved as
a result of relatively high mass and energy transfer rates that can be
achieved as a
result of conducting the process under process intensification conditions.
This may
provide for the following advantages when compared to conventional processing:
= significant increases in productivity,
= significant reductions in process footprint for the same throughput,
= increased processing windows and operational flexibility (opportunities to
operate
at lower pressures and temperatures),
= increased process control (reduced problems with hot spots),
= reduced operating costs,
= reduced energy consumption,
= easy variation in process throughput (by numbering-up scaling approach),
= integration of multiple unit operations in single and movable device
systems,
= optimization of catalyst functionality,
= easy implementation of catalyst regeneration schemes.
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These benefits can eliminate cost and distribution issues that often constrain
operation, allowing energy to be produced on site, adopting readily available,
local
and renewable feedstocks that may include agricultural resources, waste and/or
other biological materials, as well as coal, shale, tar sand, bitumen,
biomass, and
the like.
Brief Description of the Drawings
In the annexed drawings, like parts and features have like designations.
Fig. 1 is a schematic illustration of a microchannel that may be used with the
inventive process.
Figs. 2A, 2B and 2C are illustrations of a microchannel reactor that may be
used to conduct the inventive process. This microchannel reactor comprises a
plurality of process microchannels, reactant stream channels and heat exchange
channels positioned side-by-side. Hydrocarbon reactants (i.e., heavy oil or
intermediate hydrocarbon product) as well as the desired upgraded hydrocarbon
product flow in the process microchannels. Hydrogen flows into the reactant
stream
channels and then from the reactant stream channels into the process
microchannels where it mixes with the hydrocarbon reactants and undergoes a
hydroprocessing reaction. Heat exchange fluid flows in the heat exchange
channels. The reactants and product flow in a direction that is cross-current
to the
flow of the heat exchange fluid. Fig. 2A shows the microchannel reactor
without
headers providing for the flow of fluids into and out of the microchannel
reactor. Fig.
2B shows the headers for providing for the flow of fluid into and out of the
process
microchannels, reactant stream channels and heat exchange channels. Fig. 2C is
an orthographic projection of the reactor shown in Fig. 2B, with the reactor
being
positioned in reactor housing vessel.
Figs. 3 is a flow sheet illustrating the inventive process for hydrotreating
and
hydrocracking heavy oil to form one or more upgraded hydrocarbon products.
Fig. 4 is a schematic illustration of two reactor housing vessels which are
used in sequence, one being identified as a first stage vessel, the other
being
identified as a second stage vessel. Each microchannel reactor housing vessel
contains a plurality of microchannel reactors. In the first stage vessel,
heavy oil is
hydrotreated to form an intermediate hydrocarbon product. In the second stage
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vessel, the intermediate hydrocarbon product from the first stage is
hydrocracked to
form an upgraded hydrocarbon product.
Fig. 5 is a schematic illustration of two layers of process microchannels that
are positioned in the same microchannel reactor. A layer of heat exchange
5 channels is positioned between the process microchannel layers. In the first
layer of
process microchannels heavy oil is hydrotreated to form a intermediate
hydrocarbon
product or hydrotreated product. In the second layer of process microchannels
the
hydrotreated product from the first layer is hydrocracked to form an upgraded
hydrocarbon product or hydrocracked product.
10 Figs. 6 and 7 are schematic illustrations of a microchannel reactor housing
vessel which may be used for housing a plurality of the microchannel reactors
used
with the inventive process. Fig. 7 is a cutaway image of the vessel
illustrated in Fig.
6.
Figs. 8-13 are schematic illustrations of repeating units that may be used in
the microchannel reactors used with the inventive process.
Figs. 14 and 15 are schematic illustrations of surface features that may be
used in the microchannels used with the inventive process.
Figs. 16-24 are schematic illustrations of catalysts or catalyst support
structures that may be used in the microchannels used with the inventive
process.
Fig. 22(b) is a cross sectional view of Fig. 22(a) taken along line (b)-(b) in
Fig. 22(a).
Fig. 23(b) is a cross sectional view of Fig. 23(a) taken along line (b)-(b) in
Fig. 23(a).
Figs. 25 and 26 are schematic illustrations of repeating units that may be
used in the microchannel reactors used with the inventive process. Each of
these
repeating units includes a section for preheating the reactants and a section
for
quenching the product.
Fig. 27 is a flow sheet illustrating a process for gasifying heavy oil to form
a
heavy oil vapor and then hydrocracking the heavy oil vapor using a condenser
hydrocracker.
Figs. 28 and 29 are schematic illustrations of the condenser hydrocracker
shown in Fig. 27.
Fig. 30 is a flow sheet illustrating a two-stage process for hydrocracking
heavy oil vapor.
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Fig. 31 is a flow sheet illustrating a process for hydrocracking heavy oil
vapor
utilizing a distillation column.
Figs. 32 and 33 illustrate the construction of a microchannel reactor using
waveforms.
Detailed Description of the Invention
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,
io 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 "heavy oil" refers to C5+ hydrocarbons produced by the gasification,
liquefaction or pyrolysis of solid carbonaceous materials (e.g., coal, shale,
tar sand,
bitumen, biomass, and the like). Heavy oils may also comprise crude oil
fractions
is with an initial boiling point of about 250 C or above. Heavy oils include
vacuum gas
oils, atmospheric residiuum, vacuum residiuum, light catalytic cracking oil,
heavy
catalytic cracking oil, and the like. Heavy oils may have polyaromatic
concentrations
above about 2% by weight and total aromatic concentrations above about 10% by
weight. Heavy oils may have heteroatom concentrations above about 2% by
weight,
20 the heteroatoms being sulfur, nitrogen, oxygen and/or metal (e.g., Ni, V,
and the
like).
The term "pyrolysis oil" refers to a synthetic oil which is extracted from
biomass as well as other carbonaceous materials using pyrolysis. Pyrolysis oil
has
tar-like characteristics and often contains high levels of heteroatoms such as
sulfur,
25 nitrogen, oxygen and/or metal (e.g., Ni, V, and the like). Pyrolysis oil
may be
referred to as pyrolytic oil or bio-oil.
The term "middle distillate oil" refers to hydrocarbons boiling in the range
of
about 125 C to about 375 C. Middle distillate oils include middle distillate
fuels such
as kerosene, jet fuel, diesel fuel, heating oil, fuel oil, and the like.
30 The term "light oil" refers to hydrocarbons boiling in the range of about
20 C
to about 125 C. Light oils may be referred to as light distillates. Examples
include
liquefied petroleum gas (LPG), gasoline, naphtha, and the like
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The term "biomass" refers to biological material that may be used as fuel.
The biological matter may be living or dead. 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 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" refers 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" refers to a viscous black liquid derived from a carbonaceous
material, for example, by pyrolysis.
The term "process intensification" refers to the miniaturization of unit
operations and processes where a smaller compact piece of equipment takes the
place of a larger piece of equipment or multiple pieces of equipment, but
still
provides for the same capacity or mass flow rate as the larger piece of
equipment or
multiple pieces of equipment. In one embodiment, process intensification may
be
achieved using catalytic distillation in order to conduct reactions and
separations in
integrated equipment. In one embodiment, process intensification may be
achieved
using microchannel process technology where chemical processors are employed
that are characterized by parallel arrays of microchannels. Processes are
intensified using microchannel process technology by decreasing transfer
resistance
between process fluids and channel walls. Process intensification allows for
use of
more active catalysts than conventional processes, greatly increasing the
throughput
per unit volume. As a result of process intensification, overall system
volumes can
be reduced by about ten to one hundred fold or more when compared to
conventional hardware.
The term "process intensification conditions" refers to a process conducted in
a reactor where as a result of enhanced mass and/or energy transfer the volume
of
the reactor is reduced by at least about 2 fold, or at least about 10 fold, or
at least
3o about 50 fold, or at least about 100 fold, as compared to a conventional
reactor and
yet the throughput of product in the reactor is the same or greater than the
throughput of product in the conventional reactor.
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The term "hydroprocessing" process refers to a hydrocracking process or a
hydrotreating process.
The term "hydrotreating process" refers to a process wherein heteroatoms
bonded to one or more hydrocarbon compounds are reacted with hydrogen to form
heteroatom containing compounds. The heteroatom containing compounds may
then be separated from the hydrocarbon compounds. The heteroatoms may include
sulfur, nitrogen, oxygen, and/or metals (e.g., Ni, V, and the like).
The term "hydrocracking" process refers to a process wherein hydrocarbon
molecules are split into smaller molecules. For example, a C12 alkane may be
io hydrocracked to form a C7 alkane and a C5 alkane. The hydrocracked products
may
be isomerized. The hydrocracked products may comprise straight chain
hydrocarbons, branched chain hydrocarbons (e.g., isoparaffins) and/or ring
compounds.
The term "hydrocarbon" refers 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. The term "hydrocarbon" also
refers 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" also refers 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
heteroatoms may include, for example, nitrogen, oxygen, sulfur and/or metals
(e.g.,
Ni, V, and the like).
The term "microchannel" refers 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. An
example of a microchannel that may be used with the inventive process is
illustrated
in Fig. 1. Referring to Fig. 1, microchannel 10 has a height (h), width (w)
and length
(I). Fluid flows through the microchannel 10 in the direction indicated by
arrows 12
and 14. Both the height (h) and width (w) are perpendicular to the bulk flow
direction of the flow of fluid in the microchannel 10. The microchannel may
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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 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 height or
width
may be referred to as the gap between opposed internal walls of the
microchannel.
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
io 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 orwidth 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 0.5 to about 10 meters, and in one
embodiment from about 0.05 to about 6 meters, and in one embodiment from about
0.05 to about 3 meters, and in one embodiment about 0.05 to about 2 meters,
and
in one embodiment from 0.05 to about 1.5 meters, and in one embodiment from
about 0.1 to about 0.7 meter. 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 "process microchannel" refers to a microchannel wherein a process
is conducted. The process may be a hydrocracking or hydrotreating process.
The term "microchannel reactor" refers to an apparatus comprising one or
more process microchannels wherein a reaction process is conducted. The
process
may be a hydrocracking process or a hydrotreating 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 reactants into the one or more process
microchannels, and
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a footer or manifold assembly providing for the flow of product out of the one
or
more process microchannels. The microchannel reactor may further 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 may provide heating
5 and/or cooling for the fluids in the process microchannels. The heat
exchange
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.
10 The term "conventional reactor" refers to a reactor that is not a
microchannel
reactor.
The term "microchannel processing unit" refers to an apparatus comprising
one or more process microchannels wherein a process is conducted. The process
may be a reaction process or it may be any other unit operation wherein one or
15 more fluids are treated.
The term "volume" with respect to volume within a process microchannel
includes 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 means 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 another channel. For example, a process
microchannel may be longer than and extend beyond one or more adjacent heat
exchange channels.
The term "thermal contact" refers 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.
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The term "fluid" refers 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" have the same meaning and are sometimes
used interchangeably.
The term "residence time" or "average residence time" refers 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
io temperature and pressure being used.
The terms "upstream" and "downstream" refer to positions within a reactor or
a channel (e.g., a process microchannel) or in a process or process flow sheet
that
is relative to the direction of flow of a fluid in the reactor, channel,
process or
process flow sheet. For example, a position within a reactor or channel or
process
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 reactor or channel or a process 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 reactor or channels used
herein may
be oriented horizontally, vertically or at an inclined angle.
The term "shim" refers 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. Process microchannels and/or heat exchange channels may be
positioned on or in a shim.
The term "surface feature" refers to a depression in a channel wall and/or
internal channel structure (e.g., fin) and/or a projection from a channel wall
and/or
internal channel structure that disrupts flow within the channel. Examples of
surface
feature designs that may be used are illustrated in Figs. 14, 15 and 24. The
surface
features may be in the form of circles, spheres, hemispheres, frustrums,
oblongs,
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squares, rectangles, angled rectangles, checks, chevrons, vanes, air foils,
wavy
shapes, and the like. Combinations of two or more of the foregoing may be
used.
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 a length. The surface features may be formed on
or
in one or more of the interior walls of the process microchannels and/or heat
exchange channels used in accordance with the inventive process. The surface
features may be referred to as passive surface features or passive mixing
features.
io 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 "waveform" refers 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. 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 copper, aluminum, stainless steel, and the like. The thermal
conductivity of the waveform may be about 1 W/m-K or higher. The waveform may
comprise a composite material which includes two or more layers, where the
thermal
conductivity of the two or more materials may differ by about 20% or more. The
waveform may comprise three layered constructions wherein, for example, an
aluminum or copper layer may be positioned between two stainless steel layers.
A
thermally conductive waveform may be used to remove the heat of reaction while
retaining an inert surface for contacting the catalyst. A composite waveform
may be
used for any exothermic reaction, including a hydroprocessing reactions.
The term "bulk flow direction" refers to the vector through which fluid may
travel in an open path in a channel.
The term "bulk flow region" refers to open areas within a channel (e.g., a
process microchannel). A contiguous bulk flow region may allow rapid fluid
flow
through a channel without significant pressure drop. In one embodiment, the
flow in
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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 term "open channel" refers 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
io fluid may flow through the channel without encountering a barrier to flow.
The gap
may have an internal dimension normal to the flow of fluid through the
microchannel
in the range from about 0.01 to about 10 mm, and in one embodiment from about
0.01 to about 5 mm, and in one embodiment from about 0.01 to about 2 mm, and
in
one embodiment from about 0.01 to about 1 mm.
The term "cross-sectional area" of a channel (e.g., process microchannel)
refers 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 interior channel wall to the
opposite
interior channel wall. These dimensions may be average values that account for
variations caused by surface features, surface roughness, and the like.
The term "open cross-sectional area" of a channel (e.g., process
microchannel) refers 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
refers 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.
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The term "free stream velocity" refers 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" refers to reactants, product, diluent and/or other
fluid
that enters, flows in and/or flows out of a process microchannel.
The term "reactants" refers to hydrocarbon reactants and hydrogen when
io used with reference to the inventive hydroprocessing process.
The term "reaction zone" refers 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 "graded catalyst" refers 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
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
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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
5 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
io 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
15 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 "volume of catalyst" or "cubic meter of catalyst" refers to the
volume
of the catalytically active portion of a catalyst. For a bed of particulate
solids the
terms "volume of catalyst" or "cubic meter of catalyst" may refer to the
volume of the
20 space in which the active catalyst is loaded.
The term "heat exchange channel" refers to a channel having a heat
exchange fluid in it that gives off heat and/or absorbs heat. The heat
exchange
channel may absorb heat from or give off 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 give off
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" refers 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" refers to a fluid that may give off heat and/or
absorb heat.
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The term "heat exchange medium" refers to a substance or device that
absorbs heat or gives off heat and may be used to cool or heat another
substance
or device. The another substance or device may be, for example, a channel that
is
adjacent to or in thermal contact with the heat exchange medium. An example of
a
heat exchange medium would be a heat exchange fluid in a heat exchange
channel.
The term "conversion of reactant" refers to the reactant mole change
between a fluid flowing into a microchannel reactor and a fluid flowing out of
the
microchannel reactor divided by the moles of reactant in the fluid flowing
into the
microchannel reactor.
The term "converted basis yield" or "CBY" is used herein with respect to a
hydrocracking process to refer to the mass of product with 10 to 22 carbon
atoms,
minus the mass of feed with 10 to 22 carbon atoms, divided by the mass of feed
with more than 22 carbon atoms. Converted basis yield or CBY may be
represented
by the expression:
CBY = [(Mass C10-C22 Product) - (Mass C10-C22 Feed)] _ (Mass C22+ Feed)
The term "total basis yield" or "TBY" is used herein with respect to
hydrocracking to refer to the mass of product with 10 to 22 carbon atoms minus
the
mass of feed with 10 to 22 carbon atoms divided by the mass of feed. Total
base
yield or TBY may be represented by the expression:
TBY = [(Mass C10-C22 Product) - (Mass C10-C22 Feed)] _ (Mass Feed)
The term "selectivity" is used herein with respect to a hydrocracking process
to refer to the mass of product with 10 to 22 carbon atoms minus the mass of
feed
with the 10 to 22 carbon atoms divided by the mass of feed with more than 22
carbon atoms minus the mass of product with more than 22 carbon atoms.
Selectivity may be represented by the expression:
Selectivity=[(Mass C10-C22 Product)-(Mass CIO-C22 Feed)] _ [(Mass C22+ Feed)-
(Mass C22 + Product)]
The term "cycle" is used herein to refer to a single pass of the reactants
through a process microchannel.
The term "solid substrate" may refer to a granular particle with a mean
diameter of less than about 2 mm, and in one embodiment less than about 1 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 0.05 to about 2 mm, and in one embodiment
in
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the range from about 0.05 to about 1.5 mm, and in one embodiment in the range
from about 0.05 to about 1 mm, and in one embodiment in the range from about
0.05 mm to about 0.5 mm. The solid substrate may comprise a continuous porous
medium that substantially spans the gap of a microchannel. The porous medium
may be in the form of a foam, wad, strands, and/or monolith with either
regular or
irregular shaped pores. The pores may be interconnected. The porous medium
may comprise a waveform with a porosity throughout the thickness of the
waveform
of from about 5% to about 95% or with a porosity for a portion of the
thickness of the
waveform ranging from about 5% to about 95%. The solid substrate may be housed
io continuously throughout the entire length of a process microchannel or part
of the
length of a process microchannel. The solid substrate may be housed in several
regions along the length of a process microchannel. The width and/or height of
the
process microchannel within the one or more regions may vary along the length
of
the process microchannel.
The term "quench" refers to a process by which a chemical reaction is
terminated using a rapid reduction in temperature of the reaction mixture, a
rapid
introduction of a reactant or non-reactant fluid into the reaction mixture, or
flowing
the reaction mixture through a restricted opening or passageway having a
dimension
at or below the quench diameter.
The term "quench diameter" refers to the internal dimension (e.g., height,
width, diameter) of an opening or passageway for a reaction mixture to flow
through
below which the reaction terminates.
The term "ash" refers to the solid residue that remains after a carbonaceous
material is burned.
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. The term m/s may refer to meters per second. Unless otherwise
indicated, all pressures are expressed in terms of absolute pressure.
The inventive process involves reacting heavy oil and hydrogen in the
presence of a hydroprocessing catalyst in a reactor under process
intensification
conditions to form an upgraded hydrocarbon product. The reactor may be in the
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form of one or more process microchannels, or in the form of a microchannel
reactor
containing a plurality of process microchannels. The hydroprocessing catalyst
may
be a hydrotreating catalyst or a hydrocracking catalyst.
Heavy oil typically contains heteroatoms (e.g., nitrogen, sulfur, oxygen and
or
metals such as Ni, V, and the like) and the hydroprocessing process may be
used to
eliminate or reduce the level of heteroatoms in the product produced by the
process.
The hydrogen reacts with the heteroatoms to produce heteroatom containing
compounds which may then be separated from the hydroprocessed hydrocarbon
product. The process may be used to reduce the concentration of heteroatoms by
io at least about 50% by weight, or at least about 70% by weight, or at least
about 90%
by weight, or at least about 95% by weight, or at least about 99% by weight.
Surprisingly, when the process is conducted under process intensification
conditions
and the hydroprocessing catalyst is a hydrotreating catalyst, the process also
hydrocracks the oil to form a hydrotreated hydrocarbon product which may
comprise
is more useful upgraded hydrocarbon products (e.g., middle distillate oil,
light oil, or a
mixture thereof). .
In one embodiment, the hydrotreated hydrocarbon product may be further
processed in a reactor under process intensification conditions, such as in
one or
more process microchannels, or in one or more microchannel reactors, to
provide
20 further hydrocracking and upgrading of the hydrotreated hydrocarbon
product. In
this embodiment, the hydrotreated hydrocarbon product, which may be referred
to
as an intermediate hydrocarbon product, reacts with hydrogen in the presence
of a
hydrocracking catalyst to further hydrocrack the hydrotreated hydrocarbon
product
and form the desired upgraded hydrocarbon product. The hydrotreating and
25 hydrocracking processes may be conducted in the same process microchannel
or
microchannel reactor, or in different process microchannels or microchannel
reactors.
The hydrotreating reaction requires reaction between hydrogen and heavy oil
in the presence of a hydrotreating catalyst. As indicated above, the product
30 produced by the hydrotreating reaction can be further hydrocracked to form
an
upgraded hydrocarbon product. Each of these reactions may be referred to as
hydroprocessing reactions.
In one embodiment of the invention, the overall process for converting a
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heavy oil source (e.g., coal, shale, tar sand, bitumen, biomass, and the like)
to an
upgraded hydrocarbon product is illustrated in Fig. 3. Referring to Fig. 3,
the heavy
oil source is converted to heavy oil using gasification, pyrolysis or
liquefaction
process. The gasification, pyrolysis or liquefaction processes may be
conducted
using conventional techniques or they may be conducted in a microchannel
reactor.
Gases and char may be separated from heavy oil which can be subjected to an
optional cracking process prior to hydroprocessing in accordance with the
inventive
process. The optional cracking process may be a thermal cracking and/or
catalytic
cracking process. This cracking process may be conducted using microchannel
io process technology or conventional process technology.
The heavy oil is advanced to a Stage 1 microchannel reactor wherein the
heavy oil undergoes hydrotreating. In the hydrotreating process the heavy oil
is
reacted with hydrogen in the presence of a hydrotreating catalyst under
process
intensification conditions. The heavy oil typically contain heteroatoms (e.g.,
sulfur,
nitrogen, oxygen and/or metals such as Ni, V, and the like). The heteroatoms
react
with the hydrogen to form heteroatom-containing compounds which can be
separated from the hydrotreated heavy oil using conventional or microchannel
process techniques (e.g., vaporization, condensation, filtration, ionic liquid
separation, temperature swing adsorption, pressure swing adsorption, and the
like).
At least about 50% by weight of the heteroatoms in the heavy oil may be
reacted
and separated of the heteroatoms in the heavy oil may be reactant and
separated,
or at least about 70% by weight, or at least about 90% by weight, or at least
about
95% by weight, or at least about 99% by weight. Surprisingly, the
hydrotreating
process, when conducted under process intensification conditions such as
provided
when conducting the process in a process microchannel or microchannel reactor,
also results in a hydrocracking of the heavy oil wherein at least some of the
hydrocarbons in the oil are hydrocracked to form upgraded hydrocarbon products
such as middle distillate or light oils. Vapor and water may be separated from
the
hydrotreated product. The hydrotreated product, which may be referred to as an
intermediate hydrocarbon product, may then be further processed during Stage 2
in
a process microchannel or microchannel reactor by reacting the hydrotreated
hydrocarbon product with hydrogen in the presence of a hydrocracking catalyst
to
provide additional hydrocracking with the result being the formation of an
upgraded
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hydrocracked hydrocarbon product, which may be in the form of a hydrocracked
liquid product. Vapor and water may be separated from the hydrocracked liquid
product.
The hydrotreating Stage 1 process and hydrocracking Stage 2 process may
5 be conducted in separate microchannel reactors, with the hydrocracking Stage
2
reactor being connected in series to the hydrotreating Stage 1 reactor, the
Stage 2
hydrocracking reactor is downstream of the Stage 1 hydrotreating reactor. This
is
illustrated in Fig. 4. Referring to Fig. 4, a plurality of Stage 1
microchannel reactors
are housed within a first stage microchannel reactor housing vessel, which may
be
io referred to as a microchannel reactor assembly. In Fig. 4, two Stage 1
microchannel reactors are shown in phantom, although any desired number of
Stage 1 microchannel reactors can be housed within the first stage
microchannel
reactor housing vessel, for example, from 1 to about 50 Stage 1 microchannel
reactors, or from about 3 to about 30 reactors, or from about 3 to about 25
reactors,
15 or from about 5 to about 20 reactors, or from about 10 to about 20
reactors, or about
15 reactors. In the Stage 1 microchannel reactors, heavy oil is reacted with
hydrogen in the presence of a hydrotreating catalyst under process
intensification
conditions to form a hydrotreated product. As indicated above, the heavy oil
contains heteroatoms which during the hydrotreating reaction react with
hydrogen to
20 form heteroatom-containing compounds. The heavy oil also undergoes
hydrocracking wherein at least some of the hydrocarbon compounds are
hydrocracked. The heteroatom-containing compounds can be separated from the
hydrotreated product. This is not shown in Fig. 4. The hydrotreated product is
at
least partially hydrocracked and thus is in the form of a more useable
upgraded
25 hydrocarbon product. The hydrotreated hydrocarbon product may have use, for
example, as a middle distillate or light oil.
The hydrotreated product, which may be referred to as an intermediate
hydrocarbon product, may be further processed during Stage 2 wherein the
hydrotreated product is hydrocracked in the Stage 2 microchannel reactors. The
Stage 2 microchannel reactors are housed within the second stage microchannel
reactor housing vessel, which may be referred to as a microchannel reactor
assembly. The Stage 2 microchannel reactors are shown in phantom in Fig. 4. In
Fig. 4, two Stage 2 microchannel reactors are illustrated, but any desired
number,
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for example, from 1 to about 50 microchannel reactors, or from 1 to about 30
reactors, or from about 3 to about 25 reactors, or from about 5 to about 20
reactors,
or from about 10 to about 20 reactors, or about 15 reactors may be used. In
the
Stage 2 microchannel reactors, the hydrotreated product from Stage 1 and
hydrogen contact a hydrocracking catalyst under process intensification
conditions
and undergo a hydrocracking reaction. The resulting hydrocracked product,
which
may be referred to as an upgraded hydrocarbon product, and may be useful as a
middle distillate or light oil.
The Stage 1 and Stage 2 microchannel reactor housing vessels contain
io internal manifolds for flowing reactants into the microchannel reactors and
flowing
product out of the microchannel reactors. The hydrotreating and hydrocracking
reactions are exothermic, and heat exchange fluid flows in heat exchange
channels
in the Stage 1 and Stage 2 microchannel reactors to control the temperature of
the
reactions. Internal manifolds within the Stage 1 and Stage 2 microchannel
reactor
housing vessels are provided to permit the flow of heat exchange fluid into
the
microchannel reactor housing vessels, through heat exchange channels in the
microchannel reactors, and then out of the microchannel reactor housing
vessels.
The Stage 1 hydrotreating step and Stage 2 hydrocracking step of the
inventive process can be conducted in a single microchannel or microchannel
reactor. These process steps can be conducted in a single microchannel by
positioning separate hydrotreating and hydrocracking catalysts in the same
microchannel, the hydrocracking catalyst being downstream of the hydrotreating
catalyst. Heavy oil and hydrogen flow through the microchannel in contact with
the
hydrotreating catalyst to react under process intensification conditions and
form a
hydrotreated product. Additional hydrogen may be added to the microchannel
downstream of the hydrotreating catalyst. The hydrotreated product and
hydrogen
flow through the microchannel in contact with the hydrocracking catalyst to
react
under process intensification conditions and to form the desired hydrocracked
product, which may be referred to as an upgraded hydrocarbon product.
The Stage 1 hydrotreating process and Stage 2 hydrocracking process may
be conducted in a single microchannel reactor. This is illustrated in Fig. 5.
Referring to Fig. 5, process microchannel layers A and B are positioned one
above
the other with a heat exchange channel layer positioned between the process
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microchannel layers. Heavy oil and hydrogen flow through the process
microchannel layer A in contact with a hydrotreating catalyst to react under
process
intensification conditions and form a hydrotreated product, which may be
referred to
as an intermediate hydrocarbon product. The hydrotreated product flows from
process microchannel layer A to process microchannel layer B where it flows
with
additional hydrogen in contact with a hydrocracking catalyst to react and form
the
desired hydrocracked product, which may be referred to as an upgraded
hydrocarbon product. Heat exchange fluid flows through the heat exchange
channel
layer and is used to control the temperature in the process microchannel
layers.
With enhanced mass and energy transfer characteristics that are available
when conducting the inventive process under process intensification conditions
such
as those available when conducting the process in process microchannels or
microchannel reactors, it is possible to hydroprocess, that is, hydrotreat
and/or
hydrocrack, heavy oil more efficiently using an increased liquid hourly space
velocity
is (LHSV), a reduced temperature, a reduced pressure, and/or a reduced H2 oil
(i.e.,
heavy oil or intermediate hydrocarbon product) feed ratio, as compared to
conventional processing, that is, processes not employing process
intensification
conditions such as available when using microchannels or microchannel
reactors.
When conducting the inventive process under process intensification conditions
in
process microchannel or microchannel reactors, the temperature within the
process
microchannels or microchannel reactors may be in the range from about 100 to
about 500 C, and in one embodiment from about 250 to about 400 C. The pressure
within the process microchannels or microchannel reactors may be in the range
from about 0.5 to about 25 MPa and in one embodiment from about 1 to about 20
MPa. The pressure within the process microchannels or microchannel reactors
may
be in the range from about 100 to about 3000 pounds per square inch gauge
(psig)
(from about 0.69 to about 20.7 MPa), and in one embodiment from about 500 to
about 2000 psig (from about 3.45 to about 13.8 MPa). The LHSV within the
process
microchannels or microchannel reactor may be in the range from about 0.1 to
about
200 hr', and in one embodiment from about 1 to about 100 hr'. As indicated
above, the hydrotreating and hydrocracking processes may be conducted in
separate stages within a process microchannel, or within separate
microchannels
within a microchannel reactor, or within separate microchannel reactors. In
each
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28
case, the reaction may be conducted in a first stage for hydrotreating and a
second
stage for hydrocracking. In the first stage, the LHSV maybe in the range from
about
0.1 to about 50 hr', and in one embodiment from about 5 to about 50 hr'. In
the
second stage the LHSV may be in the range from about 0.1 to about 20 hr', and
in
one embodiment from about 1 to about 20 W.
When the Stage 1 and Stage 2 reactions are conducted in a single process
microchannel, multiple reaction zones within the process microchannel may be
employed. Each zone may contain a different catalyst, or be operated at a
different
temperature, or the fluids flowing in the process microchannel may flow in
different
io zones at different superficial velocities. The employment of different
superficial
velocities within different zones within a process microchannel may be
achieved by
employing different internal dimensions (e.g., different heights and/orwidths)
forthe
microchannel. The ratio of H2 to oil (i.e., heavy oil or intermediate
hydrocarbon
product) may be varied by the addition of additional amounts of H2 between the
separate reaction zones.
With the inventive process employing one or more process microchannels,
one or more microchannel reactors, or one or more microchannel reactor
assemblies, it is possible to conduct the process at any desired production
level.
For example, it is possible to process heavy oil at relatively low levels of
production
and yet conduct the hydroprocessing process at an efficient and cost effective
level.
For example, it is possible to convert a heavy oil source such as biomass to
heavy
oil and then hydroprocess the heavy oil in a single plant at a relatively low
production level of, for example, up to about 5000 barrels per day (bpd) of
heavy oil,
or even less, for example, up to about 500 bpd. The plant site may be used to
both
hydrotreat and hydrocrack the heavy oil to provide an upgraded hydrocarbon
product for transport from the plant, e.g., via truck transport or pipeline,
orfor further
refining at the plant. The plant may also be used to initially convert the
heavy oil
source material, e.g., biomass, to heavy oil and then hydrotreat to form an
intermediate hydrocarbon product at the plant followed by transportation of
the
intermediate hydrocarbon product to another location for further processing.
The
intermediate hydrocarbon product is suitable for transportation although it
may
contain a higher heteroatom content than desired for a finished upgraded
hydrocarbon product. The high heteroatom content can be removed by further
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hydroprocessing. For example, the heavy oil may be converted to a partially
hydrogenated intermediate hydrocarbon product in which more than about 50% by
weight of the heteroatom components are converted on site, and then the
partially
hydrotreated intermediate hydrocarbon product is transported to a facility for
blending with other hydrocarbons for further refining.
The inventive process may be used to convert heavy oil vapor to an upgraded
hydrocarbon product. This process is illustrated in Fig. 27. Referring to Fig.
27,
heavy oil and oxygen are gasified in a heavy oil gasifier. The gasification
step may
be conducted in a counter-current fixed bed gasifier, a co-current fixed bed
gasifier,
io a fluidized bed gasifier or an entrained flow gasifier. In the gasifier,
heavy oil vapor
and char are formed. The char is separated from the heavy oil vapor. In
alternative
embodiments, the heavy oil vapor may be created by pyrolysis. The heavy oil
vapor
is cooled to a temperature in the range of about 200 C to about 500 C, and in
one
embodiment from about 350 C to about 450 C. The cooled heavy oil vapor is
reacted with hydrogen in the presence of a hydrocracking catalyst in a
condenser
hydrocracker under process intensification conditions. The condenser
hydrocracker
comprises one or more process microchannels or one or more microchannel
reactors. The heavy oil vapor and hydrogen may be mixed with each other in the
condenser hydrocracker or upstream of the condenser hydrocracker. In the
condenser hydrocracker, the heavy vapor is condensed and hydrocracked to form
an upgraded hydrocarbon product. Heat exchange fluid flows in and out of the
condenser hydrocracker to provide coolant to control the hydrocracking
reaction,
which is exothermic, and to condense the upgraded hydrocarbon product. The
upgraded hydrocarbon product flows out of the condenser hydrocracker, and then
through a heat exchanger where it is further cooled and flows to a
liquid/vapor
phase separator. In the liquid/vapor phase separator, the upgraded hydrocarbon
product is separated into a vapor and an upgraded hydrocarbon liquid product.
The
vapor may be recycled to the condenser hydrocracker or it may be used as a
valuable hydrocarbon vapor product, or it may be vented to an exhaust.
The condenser -hydrocracker shown in Fig. 27 is illustrated in Figs. 28 and
29. The condenser hydrocracker comprises one or more vertically oriented
process
microchannels containing a hydrocracking catalyst. The heavy oil vapor and
hydrogen flow downwardly through the process microchannels in contact with the
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hydrocracking catalyst, condense and undergo a hydrocracking reaction. Heat
exchange fluid flows through heat exchange channels that are aligned in a
cross-
current direction relative to the flow of fluid in the process microchannels.
The heat
exchange fluid provides coolant to control the reaction, which is exothermic,
and
5 condense the hydrocracked hydrocarbon product.
The heavy oil vapor may be hydrocracked in a two-stage hydrocracking
process. This is illustrated in Fig. 30. Referring to Fig. 30, heavy oil vapor
and
hydrogen flow into hydrocracking reactor Stage 1 where the heavy oil vapor and
hydrogen contact a hydrocracking catalyst, react under process intensification
io conditions and form a first hydrocracked hydrocarbon product. The first
hydrocracked hydrocarbon product flows to a liquid/vapor separator where heavy
upgraded oil is separated from vaporous oil. The vaporous oil is combined with
hydrogen and flows to hydrocracking reactor Stage 2 where the vaporous oil and
hydrogen react in the presence of a hydrocracking catalyst under process
is intensification conditions to form a second hydrocracked hydrocarbon
product. The
second hydrocracked hydrocarbon product is advanced to a liquid/vapor phase
separator where it is separated into a light upgraded oil and vapor. The vapor
can
be recycled to the Stage 1 or Stage 2 hydrocracking reactor or it can be
vented to
exhaust. The vapor may also be employed as a valuable hydrocarbon product.
20 The heavy oil may be hydrocracked in a catalytic distillation column in
which
one or more catalyst beds comprising hydrotreating or hydrocracking catalysts
are
positioned in a distillation column.
The heavy oil may be hydrocracked in a series of condenser hydrocrackers
positioned in a distillation column. This is illustrated in Fig. 31. Referring
to Fig. 31,
25 heavy oil vapor and hydrogen are advanced to distillation column 500 which,
as
illustrated, contains three condenser hydrocrackers 502, 504 and 506,
positioned
one above another, a distillate end 510 and a bottoms end 512. It will be
understood that any number of condenser hydrocrackers may be employed in the
distillation column 500, for example, from 1 to about 1000 condenser
hydrocrackers
30 may be used, or from 1 to about 100, or from 1 to about 20, or from 1 to
about 10 ,
or from 1 to about 5. The distillation column 500 has a distillate end 510 and
bottoms end 512. Heavy oil vapor and hydrogen flow upwardly through each of
the
condenser hydrocrackers 502, 504 and 506 toward the distillate end 510. In
each
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condenser hydrocracker heavy oil vapor contacts a hydrocracking catalyst, and
condenses and undergoes a hydrocracking reaction under process intensification
conditions. The catalyst in each of the condenser hydrocrackers 502, 504 and
506
may be in the form of a packing (e.g., bales, monoliths, structured packings
comprising catalyst, structured packing coated with catalyst, foams, felts,
honeycombs, and the like). Hydrocarbon vapor flows out of the distillate end
510 of
the distillation column 500. The hydrocarbon vapor flowing out of the
distillation
column 500 is cooled in heat exchanger 514 and advanced to a liquid/vapor
phase
separator 516. In the liquid/vapor phase separator 516, the distillate is
separated
io into a gas and a light oil. The gas contains H2 and may be recycled to a
gasifier
where the heavy oil is vaporized. The light oil is either removed as a
valuable
product or recycled back through the distillation column 500 flowing toward
the
bottoms end 512 for further hydrocracking. At midway points in the
distillation
column Oil Cut Number 1 and Oil Cut Number 2 are removed from the distillation
column. Other oil cuts not shown in the drawings may also be removed. Oil Cut
Numbers 1 and 2 may be referred as middle distillates. A bottoms fraction is
extracted from the bottoms end 512 of the distillation column.
The heavy oil source material may comprise any carbonaceous material that
can be converted to a heavy oil. The carbonaceous material may be a solid
carbon-
containing material. The carbonaceous material may comprise coal, shale, tar
sand,
bitumen or biomass. 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 (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
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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 contain solids or solid forming species.
These may include products derived from coal (which may contain coal ash
constituents) biomass (minerals, etc.), animal derived products (chicken fat,
fryer
oils, etc.), heavy crudes (which often contain Ni and/or V species). It may
therefore
be necessary to remove these species prior to processing, whether using
io conventional or microchannel operations. The removal process may include
filtration (especially for coal or mineral ashes and for animal derived feeds,
for
example, chicken fat may contain feathers, beaks, bones, etc.) or reactive
removal
such as a guard bed, which may comprise a removable cartridge in a
microchannel
reactor system. This may be particularly important for Ni, V, and the like, in
heavy
crudes where the metals may not be formed as a solid until the metal compounds
are decomposed by higher temperatures, with or without additional reactants,
for
example, H2.
Conventional hydrotreating and hydrocracking catalysts may be used.
Examples of conventional hydrotreating and hydrocracking catalysts may include
those with a support which may comprise an amorphous material (e.g., alumina,
silica alumina, titania, zirconia, or a combination of two or more thereof),
zeolite,
layered clay, pillared clay, or any material with acid sites, or a combination
of two or
more of the foregoing materials. The support may be further impregnated with a
metal species which enhances hydrotreating or hydrocracking. The metal species
may comprise platinum, palladium, nickel, molybdenum, tungsten, or a
combination
of two or more of the foregoing metals. As a result of the inventive process
being
conducted under process intensification conditions, the catalyst may be in a
more
active form than those used in conventional processes.
The use of microchannels for hydrotreating and hydrocracking reactions
provides for process intensification conditions on a number of fronts. These
may
include kinetics, pressure drop, heat or energy transfer, and mass transfer.
Conventional hydroprocessing reactions (e.g., hydrocracking reactions and
hydrotreating reactions) not employing microchannel processing may be
constrained
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by heat removal and require catalysts of sufficient but not high activity. On
the other
hand, microchannels may allow for higher activity catalysts than may be
typically
used with conventional reactors. For example, the heat of reaction may be
removed
more effectively with a microchannel reactor than with a conventional reactor
by
' using heat exchange channels interspersed or in thermal contact with process
microchannels in the microchannel reactor. A microchannel processing unit may
be
used as a polishing unit downstream of a conventional hydroprocessing unit in
order
to add additional hydrotreating and/or hydrocracking to the product produced
by the
conventional hydroprocessing unit.
Although the microchannel dimension of height or width may be smaller than
the diameter of a conventional reactor, pressure drop may be dominated by flow
through the catalyst bed, which may comprise a packed bed, porous media, or
other
catalyst form. The catalyst may take the form of pellets, beads, particles,
foam,
wad, felt, honeycomb, or other structure with either regular or irregular
shape or
form. Flow lengths in the process microchannel may range from 0.05 to about 10
meters, and in one embodiment from about 0.05 to about 5 meters, and in one
embodiment from about 0.05 to about 2 meters, and in one embodiment from about
0.1 to about 1.5 meters, and in one embodiment from about 0.1 to about 1
meter,
and in one embodiment from about 0.1 to about 0.7 meter. Shorter flow lengths
may allow for a reduction in catalyst particle diameter to achieve a net
neutral or
lower process pressure drop than with a conventional hydrocracker. In some
embodiments, a higher pressure drop may be useful. Further, the inlet pressure
of
the liquid stream and the gaseous stream may not be the same. A pressure drop
or
pressure let down before the reaction zone within a process microchannel may
be
useful to control the flow distribution of the gas and liquid. The inlet
pressure of the
liquid may be greater than the inlet pressure for gas. The pumping power for a
liquid may be less than the compression required for a gas. Alternatively, the
gas
may be at a higher inlet pressure than the liquid.
For the hydrotreating and hydrocracking reactions, heat release control may
3o require reactor designs with interstage cooling, liquid redistribution,
and/or quench
sections. Microchannel reactors employing process microchannels for conducting
the hydroprocessing reactions may employ local heat removal with heat exchange
or coolant channels interspersed with the process microchannels.
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Microchannel reactors may be used to enable a reduction in both intraparticle
and interparticle mass transfer resistance. When using a catalyst in the form
of
catalyst particles or particulates, the average particle diameter may be in
the range
from about 0.01 to about 1.5 mm, and in one embodiment from about 0.05 to
about
0.5 mm, and in one embodiment from about 0.1 to about 0.3 mm. On the other
hand, a conventional hydrocracker may use a catalyst pellet with an average
diameter that ranges from about 2 to about 10 mm.
The reduction in catalyst particle diameter may improve the effective use of
internal catalyst sites over conventional hydrocracking reactors. The
effectiveness
io factor for a catalyst may be a function of the Thiele modulus. For a
spherical
catalyst particle, the Thiele modulus is proportional to the radius divided by
3. For
equal intrinsic reaction rates on the active catalyst sites, a ten-fold
reduction in the
catalyst diameter will result in a tenfold reduction in the Thiele modulus.
The Thiele
modulus is not directly proportional to effectiveness factor. For a Thiele
modulus
less than one a fairly high effectiveness factor may be expected. If the
Thiele
modulus is greater than one, a much steeper decline in the effectiveness
factor may
be expected. The actual impact of particle size depends upon the intrinsic
reaction
rates, the diffusivity of reactants within the catalyst particle, and the
tortuosity of
mass diffusion within the catalyst particle.
The reduction in interparticle mass transfer resistance may be less
straightforward. The microchannel dimension and associated small catalyst
particles housed therein may promote capillary forces over viscous and body
forces.
The net result may be a well dispersed liquid film that improves the contact
of all
phases with the catalyst to improve the apparent catalyst activity.
The Capillary number (Ca) defines the ratio of viscous to interfacial forces
Ca - ,uvelociry where the viscosity of a liquid feedstock can been
approximated
6
using known high temperature and high pressure hydrocarbon data and surface
tension values. In this formula p velocity refers to viscosity, and 6 refers
to surface
tension. For example, the viscosity of an eicosane fluid at 200 psi and 261 C
is
0.338 cP. Creating a functional dependency on temperature for this fluid
results in
an exponential dependency, where the viscosity is proportional to 3.53 x exp(-
0.0091 x Temperature (in degrees C)). For a 370 C hydrocracking reaction
mixture,
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the viscosity is approximated as 0.12 cP. Measurements of the surface tension
of
the feedstock on the catalyst particle are roughly one-third the surface
tension of
water. For a reaction system with an actual linear velocity of 0.3 m/s, which
corresponds to a hydrocracking process with a LHSV of 30 hr"', a bed void of
0.35,
5 and 1500:1 hydrogen to feed ratio, the estimated capillary number is about
1.5 x
10-3. For this reaction condition, the conversion of a hydrocarbon product
with a
boiling point below 350 C maybe essentially complete, or greater than 99%. In
one
embodiment, the conversion may be greater than 50%, or greater than 80%, per
pass. The capillary number for a multiphase reaction in a microchannel reactor
may
io be in the range from about 10.2 to about 10-6.
The Bond number (Bo) defines the ratio of body forces (e.g., gravity) to
interfacial forces (capillary forces). For low Bond numbers, interfacial
capillary
forces that spread the liquid throughout the reaction chamber may be stronger
than
gravitational forces that force the liquid to coalesce and drip or trickle
through the
15 reactor.
PgL z
Bo = , where the density of the feedstock can be approximated by known high
6
temperature and high pressure hydrocarbon data and surface tension values for
the
liquid hydrocarbon feedstock. In this formula, p refers to density, g refers
to the
gravitational constant, L refers to the critical length, and b refers to
surface tension.
20 A bond number may be calculated for a microchannel, e.g. channel bond
number,
where the critical length is the smallest channel dimension which is typically
the
channel gap or height of the microchannel. A bond number may be calculated for
the particle, e.g. particle bond number, where the critical length is the
particle
diameter. A bond number may be calculated for the microchannel length, e.g.
25 length bond number, where the critical length is the flow length of the
reactor itself.
The three bond numbers may help determine whether the hydrocracker liquid may
preferentially spread via capillary forces in the defined critical length or
fall with
gravity.
The channel bond number may be in the range from about 0.001 to about 2.
3o The bond number may be less than about 1, and in one embodiment in the
range
from about 0.001 to about 0.999, and in one embodiment from about 0.01 to
about
0.95, and in one embodiment from about 0.1 to about 0.9. Using the numbers
from
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the previous example for a microchannel reaction zone with a height of 1.75 mm
and a liquid density of 0.6 gm/cc, the Bond number is 0.75. For smaller
reaction
zones, the Bond number reduces further and is 0.25 for a reaction zone with a
height of 1 mm.
The channel Bond number for a hydroprocessing reaction zone or other
multiphase reaction zones with an internal dimension below about 2 mm may be
less than about 1. This suggests that the interfacial forces to disperse the
liquid
within the microchannel may be greater than gravitational forces thus showing
the
propensity for the liquid to wet the walls of the microchannel rather than
coalesce
io and flow down the channel walls with rivulets. The channel Bond number for
a
conventional hydrocracking reactor bed with a diameter as large as 4.5 meters
may
be greater than about 10, and typically greater than about 100 or greater than
about
1000. This suggests that gravity dominates in flow of liquid within the
reactor vessel.
The conventional hydrocracker or multiphase reaction chamber faces challenges
to
keep the liquid well dispersed and to avoid liquid flow channeling or rivulets
within
the packed bed.
The Bond number for a catalyst particle placed within a microchannel may be
many orders of magnitude below about 1, suggesting the capillary force may be
sufficient to overcome those forces exerted by gravity and thus the liquid may
well
wet the particles rather than coalesce and trickle around the particles in
poorly
dispersed streams. For a conventional hydrocracking reactor particle diameter,
the
particle Bond number may exceed 1 because the catalyst particle exceeds 2 mm
and is typically in the range from about 3 to 50 mm. For the hydrocracking
reaction
fluid properties, the particle Bond number may approach 1 for a particle
diameter of
about 2 mm. The flow of liquid in a conventional hydroprocessing reactor or
other
multiphase reactor may be dominated by gravity and viscous forces rather than
the
capillary forces which may act to spread the liquid laterally throughout the
bed.
Experiments have been conducted with a 1.5 mm particle and a 3 mm particle,
where a liquid oil flows in a downflow orientation with a co-flow of nitrogen
gas under
3o ambient conditions. The experiment with the 3 mm particle forms uneven flow
and
rivulets where the liquid does not fully wet the particle. In comparison, the
experiment with the 1.5 mm particle demonstrates a well wet liquid and stable
flow.
There are no rivulets observed for liquid flow past the 1.5 mm particles where
the
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particle bond number is less than about 1.
In an alternate embodiment with the use of a structured catalyst which is
made of any contiguous porous material unlike a discontinuous particle bed
which is
comprised of discrete particles touching each other but not otherwise joined
or
fused, the critical length is defined by the minimum dimension of the porous
structure. As an example, if a porous felt, foam, wad, regular structure, or
graded
structure with internal porosity has a thickness of 1 mm and a length and
width
greater than 1 mm, the particle bond number would be calculated to be roughly
0.5
for the test conditions of a flowing oil at 370 C. The use of a particle bond
number
io includes the extension to a porous structure with a small critical
dimension such that
the particle bond number is less than about 1.
Laboratory test reactors for conventional hydrocrackers are often tested with
very small particles interspersed around conventional pellets to improve the
lateral
flow of liquid in the reactor. While this dual sized particle solution may not
be
practical from a pressure drop perspective for a conventional hydrocracker, it
shows
the importance of internal liquid distribution on the performance of the
catalyst and
that the large catalyst particles selected for conventional hydrocracking
reactors may
retain poor wetting by the liquid.
The result may be that the small catalyst particles in microchannels may
create a fluidic environment dominated by capillary forces for the reaction.
Unlike
conventional hydrocrackers, where the liquid channels within the bed, liquid
flow in a
microchannel may remain well dispersed across the channel. A conventional
reactor requires periodic collection and redistribution of liquid within the
reactor,
whereas a microchannel may not. Further, a laterally well distributed liquid
flow
allows a gas to shear or thin the liquid film rather than segment the reactor
bed into
unsteady and intermittent zones of gas and liquid films.
The length bond number for a microchannel will typically exceed 1 as it does
for a conventional hydrocracking reactor. The length bond number may not be
the
critical parameter, where the particle and channel bond number are more
important
for establishing well wetted catalyst particles with stable liquid flow. An
additional
component to reducing mass transfer resistance for the contact of the gas,
liquid,
and solid catalyst may be built upon processes with a particle bond number
less
than about 1. The stable and thin films may be further thinned by the high gas
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velocity.
With a laterally well dispersed liquid film within a microchannel reactor,
that
has sufficient capillary force to resist segmentation orflow rivulets, the
film thickness
may be further thinned by high gas velocity in the microchannel. The reduction
in
liquid film around the particle may reduce the mass transfer resistance for a
gas
such as hydrogen to access the catalyst particle. For a hydroprocessing
reaction,
the mean film thickness for the liquid when using hydrogen gas with a 0.24 m/s
superficial velocity may be about 5 microns. For a hydrogen gas with a
velocity of
0.009 m/s passing against a thin film of the hydrocarbon liquid, a mean film
1o thickness of about 20 microns may be expected. For these two cases, a four-
fold
reduction in liquid film thickness may correspond to a 16 fold reduction in
time for
the gaseous hydrogen to diffuse through the liquid film to the catalyst
surface.
Further, the time for the liquid reactant to diffuse within the liquid film to
the catalyst
on and in the catalyst particles or surface may also be reduced roughly with
the
square of the film thickness. Given that diffusivity of a liquid may be two to
three
orders of magnitude greater than the diffusion of a gas, the liquid diffusion
within the
liquid layer to the catalyst surface may dominate the transport resistance
contribution to the overall apparent rate of reaction. The surface rate of
reaction on
the catalyst may be rate limiting. From a control volume analysis around a
catalyst
particle, a comparison of diffusion time to convection time may suggest the
importance of reduced film thickness on the hydroprocessing reaction rate. As
the
amount of time available for a gas such as hydrogen to diffuse through a
thicker
liquid film increases, the corresponding amount of additional gas fed to the
reaction
system in excess may decrease thus providing surprising results with a lower
excess
hydrogen required for a microchannel hydrocracker.
The diffusion time for a thin film may be the square of the diffusion distance
divided by the diffusivity. The diffusivity for hydrogen in a hydrocarbon
liquid may be
about 4.3 x 10-4 cm2/s. For a 20 micron film thickness, the diffusion time may
be
about 10 ms. For a 5 micron film thickness, the time for diffusion across the
thin film
surrounding a catalyst particle may be about 0.5 ms.
The convection time in a control volume around a catalyst particle of about
110 microns diameter for a superficial gas velocity of about 0.3 m/s may be
about 1
ms. For the same microchannel dimensioned particle size of a mean diameter of
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about 110 microns, the impact of a film thickness ranging from about 5 microns
to
about 20 microns imparts a capture number difference of about 2 to about 0.1.
The
capture number is the time for convection divided by the time for diffusion.
For the 5
micron thin film, the gas spends roughly twice the amount of time around the
catalyst as it takes to diffuse to the active catalyst sites. For the 20
micron film at
equal superficial gas velocity, the gas requires roughly ten times more time
to diffuse
to the catalyst sites (10 ms) than available as it flows around the particle
(1 ms). In
this latter case, there may be much more catalyst required to achieve the same
level
of reaction. This excess catalyst may range from about 2 to about 200 times
more
io catalyst as compared to a high velocity microchannel. The result may be
that a
higher excess amount of hydrogen is required as the capture number drops below
1.
For a larger particle size, as expected in a conventional reactor (where
roughly 2 mm is near the low end of diameter), the convection time in a
control
volume around a catalyst particle is longer. However, the flow dynamics of the
lower
velocity gas around this larger particle also give rise to much thicker films.
Fora 100
micron liquid film that is either regular or intermittent flowing or trickling
down a
conventional reactor, the required time for diffusion across the film is
roughly about
200 milliseconds. Correspondingly, for a superficial velocity of about 0.02
m/s, the
convection time in a control volume around a 2 mm particle is roughly 100 ms.
The
capture number may remain less than 1, near 1 or even greater than 1,
suggesting
the importance of excess hydrogen that may remain in the liquid film to
conduct the
reaction in a conventional hydrocracker. The thick films found in a
conventional
hydrocracker may require substantially more mass transfer time for the
hydrogen
and liquid reactants to reach the solid catalyst particle to react.
The result of this may be less access of the hydrogen to the catalyst. A
conventional hydrocracker may overcome this limitation by increasing the
amount of
hydrogen excess fed to the system. A microchannel reaction system offers the
potential to reduce the amount of excess hydrogen.
The inventive process is applicable to any hydroprocessing reaction
conducted in a microchannel when the particle Bond number is less than about 1
and/or the reaction chamber Bond number is less than about 1.
The heavy oil feed, intermediate hydrocarbon product feed and/or H2 feed
may be introduced into a manifold on one side of the reactor. Flow may
traverse
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laterally across the reactor or a shim through a submanifold. From the
submanifold,
flow may pass through a flow restriction section, where pressure drop may be
imparted to improve the uniformity of the flow in each of the mating
microchannels.
The flow may then pass through connection apertures to enter the reactor. The
5 connection apertures may be positioned upstream from the catalyst, but in
alternate
embodiments the connection apertures may be adjacent to the catalyst. In one
embodiment, the liquid may flow through the submanifold and through adjacent
connection apertures. The connection apertures may be regular or irregular in
shape.
10 The heavy oil feed composition and/or intermediate hydrocarbon product feed
composition may include one or more diluent materials. Examples of such
diluents
may include inert compounds such as nitrogen or 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 hydrocarbon reactant, and in
one
15 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. An advantage of at least one embodiment of the invention is
that
the use of such diluents is avoided, and operation of the inventive process is
more
efficient and compact.
20 The viscosity of the heavy oil feed composition and/or intermediate
hydrocarbon product feed composition may be in the range from about 0.001 to
about 1000 centipoise, and in one embodiment from about 0.01 to about 100
centipoise, and in one embodiment from about 0.1 to about 10 centipoise. The
heavy oil feed composition and/or intermediate hydrocarbon product feed
25 composition may be in the form of a liquid, a gas, or a combination
thereof.
The ratio of hydrogen to oil in the heavy oil feed composition and/or
intermediate hydrocarbon product feed composition may be in the range from
about
10 to about 6000 standard cubic centimeters (sccm) of hydrogen per cubic
centimeter (ccm) of oil, and in one embodiment from about 50:1 to about 4000:1
30 sccm/ccm, and in one embodiment from about 100:1 to about 2000:1 sccm/ccm,
and in one embodiment from about 300:1 to about 1500:1 sccm/ccm. The hydrogen
feed may further comprise water, methane, carbon dioxide, carbon monoxide or
nitrogen.
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41
The H2 in the hydrogen feed may be derived from another process such as a
steam reforming process .(product stream with H2 /CO 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/CO mole ratio of about
2.5),
a CO2 reforming process (product stream with H2/CO mole ratio of about 1), a
coal
gasification process (product stream with H2/CO mole ratio of about 1), and
combinations thereof. With each of these feed streams the concentration of H2
may
be increased through the use of water-gas shift and/or the H2 may be separated
from the remaining ingredients using conventional techniques such as membranes
io or adsorption.
The upgraded hydrocarbon product made by the inventive process may be a
middle distillate fraction boiling in the range of about 260-700 F (127-371
C). The
term "middle 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
is 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 product may be a gasoline or naphtha fraction. These are
normally considered to be the C5 to 400 F (204 C) endpoint fractions.
The product produced from the inventive process may comprise C5+
20 hydrocarbons with an iso/normal ratio greater than about 0.5. The product
may
comprise C20+ hydrocarbons with an iso/normal ratio that is greater than about
1.
The product may comprise C10+ hydrocarbons with an iso/normal ratio greater
than
about 1 when the weight hourly space velocity (WHSV) for the flow of liquid
product
is less than about 20 hr 1. The cloud point for the product may be less than
about
25 -10 C.
When the inventive process is conducted using, for example, a low operating
pressure or low hydrogen partial pressure, the resulting product that is
formed may
comprise straight chain aliphatic compounds as well as alicyclic and aromatic
compounds. The formation of alicyclic and aromatic compounds is undesirable
and
30 is typically avoided in conventional processing using non-microchannel
reactors due
to the fact that these compounds tend to interfere with the catalyst. However,
the
formation of these compounds is permissible with the inventive process due to
the
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42
fact that the catalyst can be regenerated periodically without causing
significant
production disruptions.
The reactants or process feed may further comprise a recycle stream from
which the hydrocracked products, and optionally other components, have been
separated out, for example, by distillation or partial condensation.
The reactants may comprise one or more gases at reaction conditions which
react to form a liquid. The reactants may comprise one or more gases that form
a
liquid that continues to react. The reactants may comprise a liquid and gas at
reaction conditions that flow concurrently through the process microchannel.
The
io reactants may comprise one or more liquids that are fed with an inert gas
to improve
interfacial contact with the catalyst to enhance the reaction rate.
The local conditions in a process microchannel or a microchannel reactor
may be controlled via tailoring temperature and/or composition profiles via
one or
more of the following: heat exchange with heat exchange channels adjacent to
or in
thermal contact with the one or more process microchannels in the microchannel
reactor; heat exchange with multiple combinations of heat exchange channels
strategically placed to correspond to individual reaction sections within the
process
microchannels; addition of one or more reactants and/or diluents using staged
addition along the axial length of the process microchannels. An isothermal
reactor
profile may be employed. With such a thermal profile, a partial boiling heat
exchange fluid may be used. A tailored temperature profile along the length of
the
process microchannels may be used. Heat may be removed with a single phase
fluid, such as a hot oil, steam, a gas or the like. The heat exchange fluid
may flow in
a direction that is co-current, counter-current or cross-current to the flow
of the
process fluids in the process microchannels. The heat exchange fluid may
comprise
one of reacting species or non-reacting species that subsequently joins the
reaction
mixture after receiving heat from the reaction. The heat exchange fluid may be
used
to remove exothermic reaction heat from the process microchannels, and to
preheat
the reactants entering the process microchannels. The reactants may be
preheated
to substantially the reaction conditions or they may be partially preheated
from the
inlet temperature of the feed to an intermediate temperature between the
average
reaction temperature and the inlet temperature. The heavy oil or intermediate
hydrocarbon reactant may enter the reactor at a temperature below the reaction
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temperature to minimize coking and then be heated to the reaction temperature
in
the reactor. The heavy oil or intermediate hydrocarbon reactant entering the
microchannel reactor may be at a temperature that is about 10 C, or about 50
C, or
about 100 C, or more, less than the reaction temperature. In one embodiment,
the
heavy oil or intermediate hydrocarbon reactant entering the microchannel
reactor
may be at a temperature that is in the range from about 200 C to about 250 C,
and
the reaction temperature in the microchannel reactor may be in the range from
about 300 C to about 400 C.
In order to control the exothermic reaction via heat exchange with a heat
io exchange medium, for example, a heat exchange fluid, the process may employ
a
heat flux at or near the entrance to the microchannel reactor that is higher
than the
heat flux near the outlet of the microchannel reactor.
The microchannel reactor used with the inventive process may contain one or
more repeating units, as discussed below. Each of the repeating units
discussed
below contains one or more process microchannels and one or more heat exchange
channels. Examples of some of the repeating units that may be used are
illustrated
in Figs. 8-13 and 25-26. Each of the 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. Each
repeating unit may contain one or more heat exchange channels. 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. A
feed
stream header may be used for distributing mixtures of the reactants to the
process
microchannels. Alternatively, one feed stream header may be used for
distributing
3o hydrocarbon reactants (i.e., heavy oil or intermediate hydrocarbon
reactant) to the
process microchannels, and another header may be used to distribute H2 to the
adjacent reactant stream channels.
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Although an advantage of the inventive process is that a high converted basis
yield to the desired intermediate hydrocarbon product or upgraded hydrocarbon
product may be obtained with one pass through the microchannel reactor, in one
embodiment, one or more hydrocarbon reactants may be separated from the
hydrotreated or hydrocracked product using conventional or microchannel
techniques and recycled back through the microchannel reactor. The
hydrotreated
or hydrocarbon reactants may be recycled through the microchannel reactor any
number of times, for example, one, two, three, four times, etc.
The reactants may be preheated prior to entering the microchannel reactor.
io The reactants may be preheated to the average temperature employed in the
reaction zone of the one or more process microchannels used in the
microchannel
reactor or to a temperature that is less than the average temperature employed
in
the reaction zone. The hydrotreating and hydrocracking processes are
exothermic.
In order to control the reaction, heat may be transferred from the process
microchannels to a heat exchange medium. That is, during the inventive process
the process microchannels may be cooled using a heat exchange medium. The
heat exchange medium may comprise a heat exchange fluid in one or more heat
exchange channels. The heat exchange channels may be adjacent to and/or in
thermal contact with the process microchannels. The heat exchange channels may
be microchannels. Heat transfer between the process fluids and heat exchange
fluid may be effected using convective heat transfer. In one embodiment, heat
transfer may be enhanced using a heat exchange fluid wherein the heat exchange
fluid undergoes an endothermic reaction and/or a full or partial phase change
(e.g.,
partial boiling). Multiple heat exchange zones may be employed along the
length of
the process microchannels to provide for different temperatures at different
locations
along the axial lengths of the process microchannels. Also, at the end of the
reaction the product may be quenched in order to reduce or eliminate the
formation
of undesired by-products. Quenching may be effected in the microchannel
reactor
or downstream of the microchannel reactor.
With the inventive process, intermixing of the gaseous and liquid phases may
be enhanced using catalyst beds employing relatively small particulate solids,
for
example, particulate solids with average diameters in the range from about
0.01 to
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about 1.5 mm, and in one embodiment from about 0.05 to about 0.5 mm, and in
one
embodiment from about 0.1 to about 0.3 mm.
The microchannel reactor may be used in combination with one or more
storage vessels, pumps, compressors, valves, microprocessors, flow control
5 devices, and the like, which are not shown in the drawings, but would be
apparent to
those skilled in the art.
The microchannel reactor may be constructed as illustrated in Figs. 2A-2C.
Referring to Fig. 2A, microchannel reactor 100 comprises a plurality of
process
microchannels 110, reactant stream channels 150 and heat exchange channels 170
io positioned side-by-side to provide microchannel reactor 100 in the form of
a cubic
block. 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
15 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 heavy oil or intermediate
hydrocarbon enters the process microchannels 110 as indicated by arrow 112. H2
enters reactant stream channels 150 as indicated by arrow 152. The H2 flows
from
the reactant stream channels 150 into the process microchannels 110 where it
20 contacts the heavy oil or hydrocarbon intermediate product. The reactants
react
and product flows out of the process microchannels 110 as indicated by arrow
118.
Heat exchange fluid enters the heat exchange channels 170 as indicated by
arrow
172. Heat exchange fluid flows out of the heat exchange channels 170 as
indicated
by arrow 174.
25 Referring to Figs. 2B and 2C, the microchannel reactor 100 has a feed
stream header 114 to provide for the flow of the heavy oil or intermediate
hydrocarbon reactant into the process microchannels 110, a reactant stream
channel header 154 to provide for the flow of H2 into the reactant stream
channels
150, a product footer 120 to provide for the flow of product out of the
process
30 microchannels 110, and a heat exchange inlet header 176 to provide for the
flow of
heat exchange fluid into the heat exchange channels 170. As shown in Figs. 2C
and 6, the heat exchange fluid flows out of heat exchange channels through
side
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111 of the microchannel reactor 100 into the interior of the microchannel
housing
vessel.
The microchannel reactor may contain a plurality of repeating units, each of
which may include one or more process microchannels and one or more heat
exchange channels. Staged addition of the H2 may be used (as indicated in
Figs.
2A, 2B and 2C), and when used, the repeating units contain one or more
reactant
stream channels positioned adjacent to each process microchannel. The
repeating
units that may be used include repeating units 200, 200A, 2008, 200C, 200D,
200E,
200F and 200G illustrated in Figs. 8-13 and 25-26, respectively. The
microchannel
io reactor may comprise from 1 to about 1000 or more of the repeating units
200,
200A, 200B, 200C, 200D, 200E, 200F or 200G, and in one embodiment from about
to about 500 of such repeating units. The catalyst used in the repeating units
200, 200A, 200B, 200C, 200D, 200E, 200F or 200G may be in any form, including
particulate solids or the various catalyst structured forms described below.
Repeating unit 200 is illustrated in Fig. 8. Referring to Fig. 8, process
microchannel 210 is positioned adjacent to heat exchange channel 230. The heat
exchange channel 230 may be a microchannel. A common wall 232 separates the
process microchannel 210 and the heat exchange channel 230. The common wall
232 may be referred to as a heat transfer wall. The process microchannel 210
includes reaction zone 212. A catalyst (not shown in the drawing) is
positioned in
the reaction zone 212. The reactants or reactant composition (i.e., heavy oil
or
intermediate hydrocarbon product, and hydrogen) flow into the reaction zone
212,
as indicated by arrow 214, contact the catalyst in reaction zone 212, and
react to
form the desired product. The product comprises an intermediate hydrocarbon
product or upgraded hydrocarbon product. The product flows out of the process
microchannel 210 as indicated by arrow 216. Heat exchange fluid flows in the
heat
exchange channel 230 in a direction that is cross-current to the flow of
reactants and
product in the process microchannel 210 (that is, into or out of the page, as
illustrated in Fig. 8). The process conducted in the process microchannel 210
is
3o exothermic and the heat exchange fluid provides cooling for the reaction.
Alternatively, the heat exchange fluid may flow through the heat exchange
channel
230 in a direction that is counter-current to the flow of reactants and
product in the
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process microchannel 210 or co-current to the flow of the reactants and
product in
the process microchannel 210.
Repeating unit 200A is illustrated in Fig. 9. Referring to Fig. 9, process
microchannel 210 is positioned adjacent to reactant stream channel 250. The
process microchannel 210 includes reaction zone 212. The process microchannel
210 and reactant stream channel 250 have a common wall 252. The common wall
252 has a plurality of openings 254 that are of sufficient dimension to permit
the flow
of hydrogen from the reactant stream channel 250 into the process microchannel
210 as indicated by arrows 256. This hydrogen reactant may be referred to as a
io staged addition reactant or the second reactant. The openings 254 may be
referred
to as apertures. The section 258 in the common wall 252 containing the
openings
254 may be referred to as an apertured section. Heat exchange channel 230 is
positioned adjacent to the process microchannel 210. The heat exchange channel
230 and the process microchannel 210 have a common wall 232. The common wall
232 may be referred to as a heat transfer wall. In operation, the hydrocarbon
reactant (i.e., heavy oil or intermediate hydrocarbon product) flows into the
process
microchannel 210 as indicated by arrow 217. The hydrogen reactant flows into
the
reactant stream channel 250 as indicated by arrow 218, and from the reactant
stream channel 250 through the openings 254 into the process microchannel 210.
In the process microchannel 210, the reactants contact the catalyst in the
reaction
zone 212 and react to form the desired product which comprises an intermediate
hydrocarbon product or an upgraded hydrocarbon product. The reaction is
exothermic, and the heat exchange channel 230 provides cooling to control the
temperature of the reaction. The heat exchange fluid may flow in the heat
exchange
channel 230 in a direction that is cross-current relative to the flow of
reactants and
product in the process microchannel 210. Alternatively, the heat exchange
fluid may
flow in a direction that is counter-current or co-current to the flow of
reactants and
product in the process microchannel 210.
The repeating unit 200B illustrated in Fig. 10 is similar to the repeating
unit
200A illustrated in Fig. 9, with the exception that the process microchannel
210 is an
E-shaped or M-shaped microchannel which includes two reaction zones. Also, two
adjacent reactant stream channels are used. With this embodiment, staged
addition
of the hydrogen is provided for the reaction process. The process microchannel
210
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has an E-shape or M-shape with entrances indicated by arrows 217 and 217A and
an outlet indicated by arrow 216. The process microchannel 210 includes
reaction
zones 212 and 212A. Reactant stream channels 250 and 250A are positioned
between the legs of the E-shaped or M-shaped process microchannel 210. The
reactant stream channel 250 and process microchannel 210 have a common wall
252 which contains a plurality of openings 254. The reactant stream channel
250A
and the process microchannel 210 have a common wall 252A which contains a
plurality of openings 254A. The hydrocarbon reactant (i.e., heavy oil or
intermediate
hydrocarbon product) enters the process microchannel 210 as indicated by
arrows
io 217 and 217A, and flows into the reaction zones 212 and 212A, respectively.
The
hydrogen enters the reactant stream channels 250 and 250A as indicated by
arrows
218 and 218A, respectively. The hydrogen flows from the reactant stream
channels
250 and 250A to and through openings 254 and 254A into the reaction zones 212
and 212A, contacts the hydrocarbon reactant and the catalyst, and reacts to
form
the desired product. The product flows out of the E-shaped or M-shaped process
microchannel 210 as indicated by arrow 216. Heat exchange fluid flows in the
heat
exchange channel 230 in a direction that is cross-current relative to the flow
of
reactants and product in the process microchannel 210 and provides cooling for
the
exothermic reaction. Alternatively, the heat exchange fluid may flow in a
direction
that is co-current or counter-current relative to the flow of reactants and
product in
the reaction zones 212 and 212A.
Repeating unit 200C is illustrated in Fig. 11. Referring to Fig. 11, repeating
unit 200C comprises process microchannel 210, heat exchange channel 230,
reactant stream channel 250, and apertured section 258. A common wall 252
separates process microchannel 210 and reactant stream channel 250. The
apertured section 258, which contains openings 254, is positioned in common
wall
252. The apertured section 258 extends partially along the axial length of
process
microchannel 210. The process microchannel 210 has a mixing zone 211, and a
reaction zone 212. A catalyst 215 is positioned in the reaction zone 212. The
mixing zone 211 is upstream from the reaction zone 212. The hydrocarbon
reactant
(i.e., heavy oil or intermediate hydrocarbon product) flows into process
microchannel
210, as indicated by the arrow 217, and then into the mixing zone 211. The
hydrogen flows into reactant stream channel 250, as indicated by arrow 218,
and
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from the reactant stream channel 250 through the openings 254 into mixing zone
211, as indicated by arrows 256. The hydrocarbon reactant and the hydrogen
contact each other in the mixing zone 211 and form a reactant mixture. The
reactant mixture flows from the mixing zone 211 into the reaction zone 212,
contacts
the catalyst 215, and reacts to form the desired product which comprises an
intermediate hydrocarbon product or an upgraded hydrocarbon product. The
product flows out of the process microchannel 210, as indicated by arrow 216.
Heat
exchange fluid flows in heat exchange channel 230 in a direction that is cross-
current to the flow of fluid flowing in process microchannel 210.
Alternatively, the
1o heat exchange fluid may flow in a direction that is counter-current or co-
current to
the flow of fluid in the process microchannel 210.
In an alternate embodiment of the repeating unit 200C illustrated in Fig. 11,
a
supplemental mixing zone may be provided in the process microchannel 210
between the mixing zone 211 and reaction zone 212. The residence time for
mixing
in the supplemental mixing zone may be defined using the sum of the total of
the
flow through the openings 254 and the flow of the first reactant in process
microchannel 210, at standard conditions of temperature (i.e., 0 C) and
pressure
(i.e., atmospheric pressure), and the volume defined by the process
microchannel
210 between the end of the mixing zone 211 and the beginning of the reaction
zone
212. This residence time for mixing in the supplemental mixing zone may be in
the
range up to about 500 milliseconds (ms), and in one embodiment from about 0.25
ms to about 500 ms, and in one embodiment from about 0.25 ms to about 250 ms,
and in one embodiment from about 0.25 to about 50 ms, and in one embodiment
from about 0.25 to about 2.5 ms.
The repeating unit 200D illustrated in Fig. 12 is the same as the repeating
unit 200C illustrated in Fig. 11 with the exception that the repeating unit
200D does
not contain the separate mixing zone 211. With repeating unit 200D, the
hydrogen
flows through the openings 254 into the reaction zone 212 where it contacts
the
hydrocarbon reactant (i.e., heavy oil or intermediate hydrocarbon product) and
the
catalyst 215, and reacts to form the desired product which comprises an
intermediate hydrocarbon product or an upgraded hydrocarbon product. The
product then flows out of the process microchannel 210, as indicated by arrow
216.
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The repeating unit 200E illustrated in Fig. 13 is the same as the repeating
unit
200C illustrated in Fig. 11 with the exception that part of the hydrogen mixes
with the
hydrocarbon reactant (i.e., heavy oil or intermediate hydrocarbon product) in
the
mixing zone 211, and the remainder of the hydrogen mixes with the resulting
5 reactant mixture in the reaction zone 212. The amount of the hydrogen that
mixes
with the heavy oil or hydrotreated product in the mixing zone 211 may be from
about
1 % to about 99% by volume of the hydrogen used in the overall reaction, and
in one
embodiment from about 5% to about 95% by volume, and in one embodiment from
about 10% to about 90% by volume, and in one embodiment from about 20% to
io about 80% by volume, and in one embodiment from about 30% to about 70% by
volume, and in one embodiment from about 40% to about 60% by volume of the
hydrogen used in the overall reaction. The remainder of the hydrogen mixes
with
the resulting reactant mixture in the reaction zone 212.
The repeating unit 200F illustrated in Fig. 25 is the same as the repeating
unit
15 200 in Fig. 8 with the exception that the process microchannel 210
illustrated in Fig.
26 includes a reaction zone 212, a preheating zone 240 and a quenching zone
245.
The preheating zone 240 is upstream of the reaction zone 212. The quenching
zone 245 is downstream of the reaction zone 212. The preheating zone 240 is
heated by heating section 236. The reaction zone 212 is cooled by cooling
section
20 234. The quenching zone 245 is cooled by cooling section 238. The heating
section 236, and the cooling sections 234 and 238 may each comprise heat
exchange channels with appropriate heat exchange fluids flowing in the heat
exchange channels. The reactants (i.e., heavy oil or intermediate hydrocarbon
reactant, and hydrogen) enter the preheating section 240, as indicated by 214,
and
25 flow through the preheating section 240 where they are preheated to a
desired
temperature for entering the reaction zone 212. The reactants flow from the
preheating section 240 into the reaction zone 212 where they undergo reaction
to
form the desired product. The product flows from the reaction zone 212 through
the
quenching zone 245 wherein the product is quenched. The product flows from the
3o quenching zone 245 out of the process microchannel 210 as indicated by
arrow 218.
The repeating unit 200G illustrated in Fig. 26 is similar to the repeating
unit
200F with the exception that the process microchannel 210 is in the form of a
U
laying on its side. Also, the preheating zone 240 and the quenching zone 245
are
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adjacent to each other and exchange heat with each other. The reaction zone
212
of the process microchannel 210 is cooled by the cooling section 234 of heat
exchange channel 230. The reactants (i.e., heavy oil or intermediate
hydrocarbon
reactant, and hydrogen) enter the process microchannel 210 as indicated by
arrow
214, flow through preheating section 240 where they are preheated and then
through reaction zone 212 where the reactants undergo reaction to form the
desired
product. The product flows from the reaction zone 212 through the quenching
zone
245 where the reaction is quenched. The product flows out of the process
microchannel 210 as indicated by arrow 218. The relatively cool reactants
flowing in
io the preheating zone 240 are heated by the relatively hot product flowing
through the
quenching zone 245. As a result, heat transfers from the quenching zone 245 to
the
preheating zone 240.
The repeating units 200F and 200G provide for quenching the product in the
microchannel reactor 100. Alternatively, the product may be quenched
downstream
of the microchannel reactor 100. The product quenching may involve reducing
the
temperature of the product by at least about 200 C within a period of up to
about
500 milliseconds (ms). The temperature may be reduced by at least about 150 C,
and in one embodiment at least about 100 C, within a time period of up to
about
500 ms, and in one embodiment up to about 400 ms, and in one embodiment up to
about 300 ms, and in one embodiment up to about 200 ms, and in one embodiment
up to about 100 ms, and in one embodiment up to about 50 ms, and in one
embodiment up to about 35 ms, and in one embodiment up to about 20 ms, and in
one embodiment up to about 15 ms, and in one embodiment up to about 10ms, and
in one embodiment within a time period of up to about 5 ms. The temperature
may
be reduced by at least about 200 C, and in one embodiment at least about 100
C,
and in one embodiment at least about 50 C, within a time period of about 5 to
about
100 ms, and in one embodiment about 10 to about 50 ms. The product may be
quenched in the microchannel reactor as illustrated in Figs. 25 and 26, or it
may be
quenched in a quenching device that is separate from the microchannel reactor.
3o The quenching device may comprise a microchannel heat exchanger. The
quenching device may comprise a heat exchanger that is adjacent to or
interleaved
with the product stream exiting the microchannel reactor. The quenching device
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may comprise a mixer capable of rapidly mixing the product with a secondary
cooling fluid. The secondary cooling fluid may be a low temperature steam.
The quenching device may comprise a narrow gap or passageway for the
process fluids to flow through. The gap or passageway may have a dimension
equal to or below the quench diameter for the reaction. In this embodiment,
the
reaction may terminate as the reactants flow through the gap or passageway as
a
result of wall collisions. The gap or passageway may have a height or width of
up to
about 5 mm, and in one embodiment up to about 3 mm, and in one embodiment up
to about 1 mm, and in one embodiment up to about 0.5 mm, and in one
io embodiment up to about 0.1 mm, and in one embodiment up to about 0.05 mm.
This quenching device may comprise a microchannel or a plurality of parallel
microchannels. This quenching device may comprise part of the process
microchannels used with the inventive process downstream of the catalyst
contained within the microchannels. The narrow gap or passageway may be used
in conjunction with one or more of the other quenching devices (e.g., heat
exchangers).
The heat exchange channels and reactant stream channels 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 process microchannels are microchannels.
Each of the channels 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 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 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 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 from about 0.05 to about 10 meters, and in one embodiment from
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about 0.05 to about 5 meters, and in one embodiment from about 0.05 to about 2
meters, and in one embodiment from about 0.1 to about 2 meters, and in one
embodiment from about 0.1 to about 1.5 meters, and in one embodiment from 0.1
to
about 1 meter, and in one embodiment from about 0.1 to about 0.7 meter.
The process microchannels, heat exchange channels and reactant stream
channels 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
io modularized compact units for scale-up.
The microchannel reactor may be made of any material that provides
sufficient strength, dimensional stability and heat transfer characteristics
to permit
operation of the inventive process. These materials may include aluminum;
titanium; nickel; copper; chromium; alloys of any of the foregoing metals;
brass;
steel; quartz; silicon; or a combination of two or more thereof. Use of non-
metal
materials of construction, (e.g., plastic, glass or ceramic materials) may be
employed.
The microchannel reactor 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.
The microchannel reactor may be constructed by forming shims with portions
removed that allow flow passage. A stack of shims may be assembled via
diffusion
bonding, welding, diffusion brazing, and similar methods to form an integrated
device. The microchannel reactor 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 microchannel reactor may be constructed using waveforms in the form of
right angled corrugated inserts. The small width between the tines of the
waveform
may provide the characteristic microchannel dimensions. The waveforms may be
made of copper, stainless steel, and the like. These inserts may be sandwiched
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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 reactant stream
channels and heat exchange channels may be formed in this manner. This is
shown in Figs. 32 and 33. The hydroprocessing catalyst may be coated on or
packed around each waveform either before or after stacking and bonding the
layers. Microchannel reactors made using waveforms are disclosed in WO
2008/030467, which is incorporated herein by reference.
The feed entering the first microchannel reactor for conducting the
io hydrotreating process may comprise liquid or vaporous heavy oil, or a
mixture of
liquid and vaporous heavy oil, and gaseous or vaporous hydrogen. The feed
entering the second microchannel reactor conducting the hydrocracking process
may comprise the hydrotreated product from the first microchannel reactor, and
hydrogen. The microchannel reactor may comprise a manifold providing a flow
passageway for the reactants to flow into the process microchannels. The
microchannel reactor may comprise separate manifolds for flowing the reactants
into
the process microchannels, one of the manifolds being for the hydrocarbon
reactant
(i.e., heavy oil or intermediate hydrocarbon product), and the other manifold
being
for the hydrogen.
Hydroprocessing may be achieved where there is superior wetting of the
catalyst due to the assistance of capillary forces. These may be further
assisted by
thin layers of liquid on the catalyst for enhanced mass transfer. The
architecture for
conducting hydroprocessing may include structures such as honeycomb monoliths
(metal and/or ceramic), which may be filled or coated with catalyst particles.
An assembly for microchannel mixing of hydrogen and liquid may be
installed upstream of or inside a conventional trickle bed reactor in order to
achieve
improved contacting.
One or more of the microchannel reactors 100 may be housed in
microchannel reactor housing vessel 300 which is illustrated in Figs. 6 and 7.
3o Referring to Figs. 2A, 2B, 2C, 6 and 7, the vessel 300 contains twelve
microchannel
reactors 100. These are identified in Fig. 7 as microchannel reactors 100-1,
100-2,
100-3, 100-4, 100-5, 100-6, 100-7, 100-8, 100-9, 100-10, 100-11 and 100-12.
Although twelve microchannel reactors 100 are disclosed in the drawings, it
will be
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understood that the vessel 300 may contain any desired number of microchannel
reactors. For example, the vessel 300 may contain from about 1 to about 1000
or
more microchannel reactors, and in one embodiment from 1 to about 750, and in
one embodiment from 1 to about 500, and in one embodiment from 1 to about 250,
5 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,
and
in one embodiment from 5 to about 20 microchannel reactors 100, and in one
embodiment from about 10 to about 20 microchannel reactors. The vessel 300 may
be a pressurizable vessel. The vessel 300 includes inlets 310 and 320, and
outlets
10 330 and 340. The inlet 310 is connected to a header 114 which is provided
for
flowing hydrocarbon reactants into the microchannel reactors 100. An inlet
(now
shown in Figs. 6 or 7) is provided for flowing H2 into the microchannel
reactors 100.
The inlet 320 is connected to header 176 which is provided for flowing heat
exchange fluid (e.g., steam) into the microchannel reactors 100. The outlet
330 is
is connected to footer 120 which provides for the flow of product out of the
microchannel reactors 100. The outlet 340 provides for the flow of the heat
exchange fluid out of the heat exchange channels in the microchannel reactors
100.
The vessel 300 also includes a manway with demister 360, steam outlet 362,
blowdown 364, pressure relief valve 366, level transmitter 368, and
temperature
20 control device 370.
The housing vessel 300 may be constructed using any suitable material
sufficient for operating under the pressures and temperatures required for
operating
the microchannel reactors 100. For example, the shell 350 and heads 352 of the
vessel 300 may be constructed of cast steel. The flanges, couplings and pipes
may
25 be constructed of 316 stainless steel. The vessel 300 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, and in one embodiment from about 100 to about
200 cm. The axial length of the vessel 300 may be of any desired value, for
example, from about 0.5 to about 50 meters, and in one embodiment from about 1
30 to about 20 meters, and in one embodiment from about 5 to about 20 meters,
and in
one embodiment from about 5 to about 10 meters.
In the design and operation of the microchannel reactor it may be
advantageous to provide a tailored heat exchange profile along the length of
the
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process microchannels in order to optimize the reaction. This may be
accomplished
by matching the local release of heat given off by the hydrotreating or
hydrocracking
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 hydrotreating or hydrocracking 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
io 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.
is 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
20 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. Heat transfer from the process microchannels to the heat
exchange channels may be designed for optimum performance by selecting
25 optimum heat exchange channel dimensions and/or the rate of flow of heat
exchange fluid per individual or groups of heat exchange channels. Additional
design alternatives for tailoring heat exchange may relate to the selection
and
design of the catalyst (such as, particle size, catalyst formulation, packing
density,
use of a graded catalyst, or other chemical or physical characteristics) at
specific
30 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
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transfer, may be constant or may vary along the length of the process
microchannels.
The process microchannels and/or heat exchange channels may contain one
or more surface features in the form of depressions in and/or projections from
one
or more interior walls or interior structures of the process microchannels
and/or heat
exchange channels. Examples are shown in Figs. 14, 15 and 24. 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 microchannel reactors may be
made
io by laminating a plurality of shims together. One or both major surfaces of
the shims
may contain surface features. Alternatively, the 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. In one embodiment,
a
shim containing surface features may be paired (on opposite sides of a
microchannel) with another 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. In one embodiment, 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 surface. In one embodiment,
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 recess may
comprise one or more angles relative to the flow direction. Successive
recessed
surface features may comprise similar or alternate angles 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
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
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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 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. 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
io triangular, oval, elliptical, circular, and the like, the surface features
may cover from
about 20% to about 100% of the perimeter of the microchannel.
In one embodiment, 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. In one embodiment, 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 1 to about 89 , 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
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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 direction
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 direction 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.
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-
3o 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
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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.
5 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
microchannel device with surface features formed on or in the sheet surfaces.
The
io dimensions forthe 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
15 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
20 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
25 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
30 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
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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.
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
io 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
3o 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
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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.
The process microchannels and/or heat exchange channels 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 about 70%, and
in
one embodiment at least about 90% of the interior surface of the channel
(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
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
unpatterned side walls that are 0.1 cm high, then 90% of the surface of the
channel
would contain surface features.
The process microchannel may be enclosed on all sides, and in one
embodiment the channel may have a generally 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 channel
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. In
one
embodiment, the surface features may be positioned 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
surface feature, while other embodiments may have multiple legs (two, three,
or
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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
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.
An advantage of the inventive process, at least in one embodiment, is that
the gap distances between the process microchannels, optional reactant stream
io channels, and heat exchange channels may be the same whether the process is
intended for laboratory or pilot plant scale or for full production scale. As
a result,
the dispersion of the hydrogen reactant into the reaction mixture used in the
inventive process may be substantially the same whether the microchannel
reactor
is built on a laboratory, pilot plant scale or as a full scale plant unit.
is The catalyst may be segregated into separate reaction zones in the process
microchannels in the direction of flow through the process microchannels. The
same or different catalyst or catalyst composition may be used in each
reaction
zone. In each reaction zone the length of one or more adjacent heat exchange
zone(s) may vary in their dimensions. For example, in one embodiment, the
length
20 of the one or more adjacent 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 catalyst may be in the form of a catalyst bed that is graded in
25 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 bed
fraction
may range from 100% by weight active catalyst to less than about 10% by weight
3o active catalyst. In an alternate embodiment the thermally conductive inert
material
may be deployed at the center 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 resulting catalyst composite
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structure may have an effective thermal conductivity when placed in a process
microchannel that is at least about 0.5 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 catalyst may be in the form of a catalyst bed that is graded only locally
within the reactor. 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
io volume and thus reduce the hot spot and potential for the production of
undesirable
by-products. 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.
In one embodiment, different particle sizes may be used in different axial
length regions of the process microchannels 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 the 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.
In one embodiment, 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
3o achieved when the catalyst is in the form of a thin layer on an engineered
support
such as a metallic foam or on the wall of the process microchannel. This
allows for
increased space velocities. In one embodiment, the thin layer of catalyst may
be
produced using chemical vapor deposition or by a chemical reaction in a
solution,
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for example, electroless plating. This thin layer may have a thickness in the
range
up to about 5 microns, and in one embodiment from about 0.1 to about 5
microns,
and in one embodiment from about 0.5 to about 3 microns, and in one embodiment
from about 1 to about 3 microns, and in one embodiment about 2.5 microns.
These
5 thin layers may reduce the time the reactants are within the active catalyst
structure
by reducing the diffusional path. This decreases 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 is that, unlike conventional catalysts in which the active portion
of the
1o catalyst may be bound up in an inert low thermal conductivity binder, the
active
catalyst film may be in intimate contact with either the engineered structure
or the
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 (faster
kinetics)
15 without promoting the formation of undesired by-products, thus producing
higher
productivity and yield and prolonging catalyst life.
The microchannel reactor configuration may be tailored to match the reaction
kinetics. For example, near the entrance or top of a first reaction zone of
the
reactor, the microchannel height or gap may be smaller than in a second
reaction
20 zone near the exit or bottom of the reactor. Alternatively, the zones may
be much
smaller than half the reactor 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 microchannel, while a larger second height or gap may be used in a
second
reaction zone downstream from the first reaction zone. Alternatively,
different
25 configurations may be used. For example, a larger process microchannel
height or
gap may be used near the entrance of the process microchannels and a smaller
process microchannel height or gap may be used near the reactor exit. In one
embodiment, 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
30 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
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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 openings or apertures 254 (Figs. 9-13) may be of sufficient size to permit
the flow of the hydrogen reactant through the apertured sections. The openings
254
may be referred to as pores. The apertured section 258 may have thicknesses in
the
range from about 0.01 to about 50 mm, and in one embodiment about 0.05 to
about
mm, and in one embodiment about 0.1 to about 2 mm. The openings 254 may
io have average diameters in the range up to about 1000 microns, and in one
embodiment up to about 250 microns, and in one embodiment up to about 50
microns, and in one embodiment in the range from about 0.001 to about 50
microns,
and in one embodiment from about 0.05 to about 50 microns, and in one
embodiment from about 0.1 to about 50 microns. In one embodiment, the openings
254 may have average diameters in the range from about 0.5 to about 10
nanometers (nm), and in one embodiment about 1 to about 10 nm, and in one
embodiment about 5 to about 10 nm. The number of openings 254 in the apertured
section 258 may be in the range from about 1 to about 5 x 108 openings per
square
centimeter, and in one embodiment about 1 to about 1 x 106 openings per square
centimeter. The openings 254 may or may not be isolated from each other. A
portion or all of the openings 254 may be in fluid communication with other
openings
254 within the apertured section 258; that is, a fluid may flow from one
opening to
another opening. The ratio of the thickness of the apertured section 258 to
the
length of the apertured section along the flow path of the fluids flowing
through the
process microchannels 210 may be in the range from about 0.001 to about 1, and
in
one embodiment about 0.01 to about 1, and in one embodiment about 0.03 to
about
1, and in one embodiment about 0.05 to about 1, and in one embodiment about
0.08 to about 1, and in one embodiment about 0.1 to about 1.
The apertured section 258 may be constructed of any material that provides
sufficient strength and dimensional stability to permit the operation of the
inventive
process. These materials include: steel (e.g., stainless steel, carbon steel,
and the
like); monel; inconel; brass; aluminum; titanium; nickel; copper; chromium;
alloys of
any of the foregoing metals; polymers (e.g., thermoset resins); ceramics;
glass;
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composites comprising one or more polymers (e.g., thermoset resins) and
fiberglass; quartz; silicon; microporous carbon, including carbon nanotubes or
carbon molecular sieves; zeolites; or a combination of two or more thereof.
The
openings 254 may be formed using known techniques such as laser drilling,
s microelectro machining system (MEMS), lithography electrodeposition and
molding
(LIGA), electrical sparkling, or electrochemical or photochemical etching. The
openings 254 may be formed using techniques used for making structured
plastics,
such as extrusion, or membranes, such as aligned carbon nanotube (CNT)
membranes. The openings 254 may be formed using techniques such as sintering
io or compressing metallic powder or particles to form tortuous interconnected
capillary
channels and the techniques of membrane fabrication. The openings 254 may be
reduced in size from the size provided by any of these methods by the
application of
coatings over the apertures internal side walls to partially fill the
apertures. The
selective coatings may also form a thin layer exterior to the porous body that
15 provides the smallest pore size adjacent to the continuous flow path. The
smallest
average pore opening may be in the range from about one nanometer to about
several hundred microns depending upon the desired droplet size for the
emulsion.
The apertures may be reduced in size by heat treating as well as by methods
that
form an oxide scale or coating on the internal side walls of the apertures.
These
20 techniques may be used to partially occlude the apertures to reduce the
size of the
openings for flow.
The apertured section 258 may be made from a metallic or nonmetallic
porous material having interconnected channels or pores of an average pore
size in
the range from about 0.01 to about 200 microns. These pores may function as
the
25 openings 254. The porous material may be made from powder or particulates
so
that the average inter-pore distance is similar to the average pore size. When
very
small pore sizes are used, the inter-pore distance may also be very small. The
porous material may be tailored by oxidization at a high temperature in the
range
from about 300 C to about 1000 C for a duration of about 1 hour to about 20
days,
30 or by coating a thin layer of another material such as alumina by sol
coating or
nickel using chemical vapor deposition over the surface and the inside of
pores to
block the smaller pores, decrease pore size of larger pores, and in turn
increase the
inter-pore distance.
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The cooling of the process microchannels during the inventive process, in
one embodiment, is advantageous for reducing the formation of undesired coke.
As
a result of this cooling, in one embodiment, the temperature of the feed
streams
entering the entrance to the process microchannels may be within about 200 C,
and
in one embodiment within about 100 C, and in one embodiment within about 50 C,
and in one embodiment within about 20 C, of the temperature of the product
exiting
the process microchannels.
The hydrotreating catalyst may be any hydrotreating catalyst. The
hydrotreating catalyst may comprise Ni, Mo, Co, W, or combinations of two or
more
1o thereof. These may be supported on alumina. The catalyst may comprise Mo-
W/AI203.
The hydrocracking catalyst may be 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 6,312,586 131, which is
incorporated
herein by reference.
The hydrotreating and hydrocracking catalysts that are used in the
microchannel reactor 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
3o about 1 to about 1000 pm (microns), and in one embodiment from about 10 to
about
500 pm, and in one embodiment from about 25 to about 300 pm, and in one
embodiment from about 80 to about 300 pm.
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The catalyst may be in the form of a bed of particulate solids. The median
particle diameter may be in the range from about 1 to about 1000 pm, and in
one
embodiment from about 10 to about 500 pm. This is shown in Fig. 16 wherein a
bed
of particulate solids 400 is packed in process microchannel 402. Reactants
flow into
the process microchannel as indicated by arrow 404 and product flows out of
the
process microchannel as indicated by arrow 406. Microfibers (e.g. within a
catalyst
bed or catalyst bale and/or coated with catalyst) to promote good liquid
distribution
across a catalyst may be used.
Foams for retaining catalyst particles and/or coated foams, including graphite
io foams, silicon carbide, metal (e.g., Fecralloy), ceramic, and/or internal
coatings of
grapheme for high thermal conductivity coating may be used.
The 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 that include pores positioned along the length
or the
structure or throughout the structure. The pores may be on the surface of the
continuous walls and used for adhering catalyst material (e.g., catalyst metal
particles) to the walls of the foam structure. The term "felt" is used herein
to refer to
a structure of fibers with interstitial spaces there between. The term "wad"
is used
herein to refer to a structure of tangled strands, like steel wool. The
catalyst may be
supported on a monolith or 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. 17. In Fig. 17, the catalyst 410 is contained within process microchannel
412.
An open passage way 414 permits the flow of fluid through the process
microchannel 412 in contact with the catalyst 410 as indicated by arrows 416
and
418.
The 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. 18. In Fig. 18, the flow-through catalyst 420 is contained
within
process microchannel 422 and the fluid flows through the catalyst 420 as
indicated
by arrows 424 and 426.
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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, poly(methyl methacrylate), polysulfonate,
poly(tetrafluoroethylene),
iron, nickel sponge, nylon, polyvinylidene difluoride, polypropylene,
polyethylene,
5 polyethylene ethylketone, polyvinyl alcohol, polyvinyl acetate,
polyacrylate,
polymethylmethacrylate, polystyrene, polyphenylene sulfide, polysulfone,
polybutylene, 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 away from the catalyst.
10 The catalyst may be directly washcoated on the interior walls of the
process
microchannels, grown on the walls from solution, or coated in situ on a fin
structure
or other support structure. The catalyst may be in the form of one or more
pieces of
porous contiguous material. In one embodiment, the catalyst may be comprised
of
a contiguous material and has a contiguous porosity such that molecules can
diffuse
15 through the catalyst. In this embodiment, the fluids flow through the
catalyst rather
than around it. In one embodiment, the cross-sectional area of the catalyst
occupies about 1 to about 99%, and in one embodiment about 10 to about 95% of
the cross-sectional area of the process microchannels. The catalyst may have a
surface area, as measured by BET, of greater than about 0.5 m2/g, and in one
20 embodiment greater than about 2 m2/g.
The catalyst may comprise a porous support, an interfacial layer on the
porous support, and a catalyst material deposited on or mixed with the
interfacial
layer. In one embodiment, a buffer layer may be positioned between the porous
support and the interfacial layer. The buffer layer may be grown or deposited
on the
25 porous structure. For example, the porous support may be made of an alumina
forming material such as Fecralloy (an alloy of Fe, Cr. Al and Y), and the
porous
structure may be heat treated in air to form an alumina layer on the surface
of the
porous support. This alumina layer would be a buffer layer. The interfacial
layer
may be coated or solution deposited on the surface of the porous support or it
may
3o be deposited by chemical vapor deposition or physical vapor deposition. 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 holes.
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The porous support may have a porosity of at least about 5% as measured
by mercury porosimetry. The porous support may have an opening or gap with a
height or width normal to the bulk flow direction of reactants flowing through
the
catalyst in the range from about 1 to about 2000 pm, and in one embodiment
from
about 1 to about 1500 pm. The reactants flowing through the opening or gap may
contact catalyst on the walls of the porous support. The porous support may be
a
ceramic or a metal support. Other porous supports that may be used include
carbides, nitrides, and composite materials. The porous support may have a
porosity of about 30% to about 99%, and in one embodiment about 60% to about
io 98%. The porous support may be in the form of a foam, felt, wad, or a
combination
thereof. The foam may have a porous construction on the surface of its walls
with
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 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
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 be comprised
of
A1203, Ti02, Si02, ZrO2, or combination thereof. The A1203 may be a-AI203, y-
AI203
or a combination thereof. a-A1203 provides the advantage of excellent
resistance
to oxygen diffusion. When the porous support is made of an alumina forming
material such as Fecralloy (an alloy of Fe, Cr, Al and Y), the buffer layer
may be
A1203 on the surface of the porous support formed by heating the porous
support in
air.
The buffer layer may comprise two or more compositionally 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 a-A1203 which is placed upon the Ti02. In one
embodiment, the a-A1203 sublayer is a dense layer that provides protection of
the
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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
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
io 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
5pm.
The buffer layer may be used to increase the adhesion of the interfacial layer
is to the surface of the porous support. However, in one embodiment of the
invention,
adequate adhesion and chemical stability may be obtained without a buffer
layer
and, consequently, 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
20 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 be comprised of a metal oxide.
Examples of metal oxides that may be used include AI203, Si02, Zr02, Ti02,
tungsten oxide, magnesium oxide, vanadium oxide, chromium oxide, manganese
25 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.
Usually, however, the interfacial layer is used in combination with a
catalytically
3o 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
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about 50 pm. 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 catalyst may be deposited on the 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 catalyst may be in the form of a bed of particulate solids positioned in a
reaction zone wherein one or more interior walls of the reaction zone includes
additional catalyst washcoated and/or grown thereon. The catalyst in the bed
of
particulate solids may be the same as the catalyst washcoated and/or grown on
the
interior walls of the reaction zone, or it may be different.
The catalyst may be supported on an assembly of one or more fins or other
structures positioned within the process microchannels. Examples are
illustrated in
Figs. 19-21. Referring to Fig. 19, fin assembly 430 includes fins 432 which
are
mounted on fin support 434 which overlies base wall 436 of process
microchannel
438. The fins 432 project from the fin support 434 into the interior of the
process
microchannel 438. The fins 432 extend to and may contact the interior surface
of
upper wall 440 of process microchannel 438. Fin channels 442 between the fins
432 provide passage ways for fluid to flow through the process microchannel
438
parallel to its length. Each of the fins 432 has an exterior surface on each
of its
sides, this exterior surface provides a support base for the catalyst. With
the
inventive process, the reactant composition flows through the fin channels
442,
contacts the catalyst supported on the exterior surface of the fins 432, and
reacts to
form the product. The fin assembly 430a illustrated in Fig. 20 is similar to
the fin
assembly 430 illustrated in Fig. 19 except that the fins 432a do not extend
all the
way to the interior surface of the upper wall 440 of the microchannel 438. The
fin
3o assembly 430b illustrated in Fig. 21 is similar to the fin assembly 430
illustrated in
Fig. 20 except that the fins 432b in the fin assembly 430b 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 438, and in one
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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 438, and in one embodiment up to about 10 m, and in one
embodiment about 0.5 to about 10 m, 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
io 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 438 may
range from about 1 to about 50 fins per centimeter of width of the process
microchannel 438, 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.
19 or 20, or
a trapezoid as illustrated in Fig. 21. 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; composites comprising one or more polymers (e.g., thermoset
resins) and fiberglass; quartz; silicon; or a combination of two or more
thereof. The
fin assembly may be made of an A1203 forming material such as an alloy
comprising
Fe, Cr, Al and Y, or a Cr203 forming material such as an alloy of Ni, Cr and
Fe.
The catalyst may be supported by a microgrooved support strip. Examples of
these support strips are illustrated in Figs. 22 and 23. Referring to Fig. 23,
process
microchannel 450 includes support strip 452 mounted on interior wall 454 of
the
process microchannel 450. Bulk flow region 456 is defined by the space within
the
process microchannel 450 between the support strip 452 and the top channel
wall
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457. Process fluid flows through the process microchannel 450 as indicated by
arrows 458 and 460. In flowing through the process microchannel 450, the
process
fluid flows through the bulk flow region 456 in contact with the catalyst
support strip
452. The catalyst may be in the form of microsized particulates positioned in
the
5 microgrooves 462. The support strip 452 is a flow-by support strip. However,
some
of the process fluid may flow in the microgrooves 462 in contact with the
catalyst.
The flow of the process fluid through the microgrooves 462 may be in the
general
direction from the front edge 463 and the first side edge 464 toward the
second side
edge 466 and the back edge 468. The process microchannel illustrated in Fig.
23 is
io similar to the process microchannel illustrated in Fig. 22 with the
exception that the
process microchannel 450 illustrated in Fig. 23 contains opposite interior
walls 454
and 457 and a catalyst supporting support strip 452 mounted on each of the
opposite interior walls. Additional details concerning the construction and
use of the
microgrooved support strip 452 can be found in US Patent Publication No. U.S.
15 2007-0225532A1, which is incorporated herein by reference.
Surface features can be used in combination with a supported catalyst to
enhance contact between the reactants and the catalyst. This is shown in Fig.
24.
Referring to Fig. 24, process microchannel 450 which has support strip 452
mounted on interior wall 454 and surface features 470 formed in the opposite
20 interior wall 457. Process fluid flows through the process microchannel 450
as
indicated by arrows 472. The flow of the process fluid is modified as the
process
fluid flows through surface features 470. The surface features 470 illustrated
in Fig.
24 are in the form of hemispherical depressions in the microchannel wall 457.
The
modification of the flow of the process fluids by the surface features 470
enhances
25 contact between the process fluid and the catalyst supported by the support
strip
452.
A sintered ceramic or metal material (e.g., one micron, Inconel sintered
metal) may be used to contact the catalyst or to support the catalyst in the
microchannel reactor. The sintered material may be contained or attached to
30 interior walls of solid metal "sleeves" to form a unit, which may serve as
individual
pressure vessels and may be added for capacity/replacement. The sintered metal
and/or metal sleeves may comprise a high thermal conductivity metal such as
copper, aluminum or titanium. Catalyst particles may be loaded into the
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subassemblies. The catalyst may be coated using solution coating, slurry
coating,
sol-gel coating, physical vapor deposition, chemical vapor deposition or
electroless
plating onto the sintered metal.
The catalyst may be regenerated. This may be done by flowing a
regenerating fluid through the process microchannels in contact with the
catalyst.
The regenerating fluid may comprise hydrogen or a diluted hydrogen stream,
hydrogen sulphide (or other sulphur containing compound) or a diluted hydrogen
sulphide (or other sulphur containing compound) stream, oxygen or an oxygen
containing stream, or a stream containing a halogen containing gas or a
mixture of
oxygen and a halogen containing gas. Halogen compounds may include metal
halides and organic halides. The diluent may comprise nitrogen, argon, helium,
methane, ethylene, carbon dioxide, steam, or a mixture of two or more thereof.
The
regenerating fluid may flow from the header through the process microchannels
and
to the footer, or in the opposite direction from the footer through the
process
microchannels to the header. The temperature of the regenerating fluid may be
from about 20 to about 600 C, and in one embodiment about 150 to about 400 C.
The pressure within the process microchannels during this regeneration step
may
range from about 0.1 to about 4 MPa, and in one embodiment about 0.1 to about
2
MPa, and in one embodiment about 0.1 to about 0.5 MPa. The residence time for
the regenerating fluid in the process microchannels may range from about 0.01
second to about 3 hours, and in one embodiment about 0.1 second to about 100
seconds.
The catalyst may be regenerated in-situ in the process microchannels by
oxidizing a carbonaceous material on the surface of the catalyst or by
removing
carbonaceous materials via hydrogenation. The catalysts may be regenerated via
sulphiding. The regeneration process may also occur ex situ, whereby the feed
is
bypassed from the reactor, the temperature is dropped to ambient, and a liquid
or
gaseous fluid is used to remove carbonaceous materials. In one embodiment, the
regeneration process utilizes a dissolution process to remove the carbonaceous
material. The pressure drop through the reactor may be lower after
regeneration
than before by about 10% or more
The plant facility used for conducting the inventive process may comprise a
plurality of process microchannels, microchannel reactors, or reaction vessels
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containing one or more microchannel reactors. The catalyst in one or more of
the
process microchannels, microchannel reactors or reaction vessels may be
regenerated, while the inventive process may be carried out simultaneously in
other
process microchannels, microchannel reactors or reaction vessels in the plant
facility.
The inventive process may be conducted using a regenerated catalyst at
relatively high liquid hourly space velocities (LHSV), for example, at about 5
hr 1 or
above, or about 10 hr' or above. The process may be conducted under stable
operating conditions using the regenerated catalyst for extended periods of
time, for
io example, periods in excess of about 1000 hours.
The process microchannels may be characterized by having a bulk flow path.
The term "bulk flow path" refers to an open path (contiguous bulk flow region)
within
the process microchannels. A contiguous bulk flow region allows rapid fluid
flow
through the microchannels without large pressure drops. In one embodiment, the
is flow of fluid in the bulk flow region is laminar. Bulk flow regions within
each process
microchannel 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
20 of the process microchannels.
The heat exchange fluid may be any fluid. These may include air, steam,
liquid water, steam, gaseous nitrogen, other gases including inert gases,
carbon
monoxide, molten salt, oils such as mineral oil, a gaseous hydrocarbon, a
liquid
hydrocarbon, heat exchange fluids such as Dowtherm A and Therminol which are
25 available from Dow-Union Carbide, or a mixture of two or more thereof.
"Dowtherm"
and "Therminol" are trademarks.
The heat exchange fluid may comprise a stream of one or more of the
reactants and/or the product. This can provide process cooling for the process
microchannels and/or pre-heat for the reactants and thereby increase the
overall
30 thermal efficiency of the process.
The heat exchange channels may comprise process channels wherein an
endothermic process is conducted. These heat exchange process channels may be
microchannels. Examples of endothermic processes that may be conducted in the
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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 is an example of an endothermic process suited for an
exothermic reaction such as an ethylene oxide synthesis reaction in the same
temperature range. 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
flows through the heat exchange channels. This phase change may provide
io 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 process microchannels would result from the
latent
heat of vaporization required by the heat exchange fluid. An example of such a
phase change would be a heat exchange fluid such as oil or water that
undergoes
partial boiling. In one embodiment, up to about 50% by weight of the heat
exchange
fluid may be vaporized.
The gaseous fraction of reactants and products may flow in the reaction zone
in contact with the catalyst to produce a Reynolds number up to about 100000,
and
in one embodiment up to about 10000, and in one embodiment up to about 100,
and in one embodiment in the range from about 10 to about 100, and in another
in
the range from about 0.01 to about 10, and in one embodiment in the range from
about 0.1 to about 5.
The heat flux for heat exchange in the microchannel reactor may range from
about 0.01 to about 500 watts per square centimeter of surface area of the
heat
transfer walls (W/cm2) in the microchannel reactor, and in one embodiment from
about 0.1 to about 350 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 1
to about 25 W/cm2, and in one embodiment from about 1 to about 10 W/cm2.
The cooling of the process microchannels during the inventive process, in
one embodiment, is advantageous for controlling selectivity towards the main
or
desired product due to the fact that such added cooling reduces or eliminates
the
formation of undesired by-products from undesired parallel reactions with
higher
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activation energies. As a result of this cooling, in one embodiment, the
temperature
of the reactants at the entrance to the process microchannels may be within
about
20 C, and in one embodiment within about 10 C, and in one embodiment within
about 5 C, and in one embodiment within about 3 C, and in one embodiment
within
about 2 C, and in one embodiment within about 1 C, of the temperature of the
product (or mixture of product and unreacted reactants) at the outlet of the
process
microchannels. In one embodiment, the process microchannels may be operated
with an isothermal or substantially isothermal temperature profile.
The contact time of the reactants with the catalyst in the process
io microchannels may range from about 1 to about 2000 milliseconds (ms), and
in one
embodiment from about 10 to about 1000 ms, and in one embodiment from about
100 to about 500 ms.
The liquid hourly space velocity (LHSV) for the flow of liquid reactant in the
process microchannels may be at least about 0.1 liters of liquid reactant per
hour
per liter of volume in the process microchannel (hr'), and in one embodiment
at
least about 1 hr', and in one embodiment at least about 5 hr', and in one
embodiment at least about 10 hr', and in one embodiment at least about 20 hr',
and in one embodiment at least about 30 hr', and in one embodiment at least
about
35 hr', and in one embodiment at least about 40 hr', and in one embodiment
from
about 0.1 to about 40 hr', and in one embodiment from about 1 to about 40 hr'.
The LHSV may be in the range from about 0.1 to about 200 hr', and in one
embodiment from about 1 to about 100 hr', and in one embodiment from about 2
to
about 100 hr'.
The gas hourly space velocity (GHSV) for the flow of gases (e.g., vapor, H2)
in the process microchannels may be in the range from about 500 to about
500,000
hr'.
In the hydrotreating and hydrocracking processes, the conversion of
hydrocarbon fractions with boiling points above about 350 C to hydrocarbons
with
boiling points below about 350 C may be at least about 50% by weight, and in
one
3o embodiment at least about 55% by weight, and in one embodiment at least
about
60% by weight, and in one embodiment at least about 65% by weight, and in one
embodiment at least about 70% by weight, and in one embodiment at least about
75% by weight, and in one embodiment at least about 80% by weight, and in one
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embodiment at least about 85% by weight, and in one embodiment at least about
90% by weight.
The pressure drop for the process fluids as they flow in the process
microchannels may range up to about 50 bars per foot of length of the process
5 microchannel (bars/ft) (0.16 MPa/cm), and in one embodiment up to about 10
bars/ft
(0.032 MPa/cm), and in one embodiment up to about 1.5 bars/ft (0.005 MPa/cm),
and in one embodiment up to 1 bar/ft (0.0033 MPa/cm), and in one embodiment up
to about 0.5 bar/ft (0.0016 MPa/cm).
The flow of the process fluids in the process microchannels may be laminar
io or in transition, and in one embodiment it is laminar. The Reynolds Number
for the
flow of process fluids in the process microchannels may be up to about 10,000,
and
in one embodiment up to about 4000, and in one embodiment up to about 2300,
and in one embodiment in the range of about 1 to about 2000, and in one
embodiment in the range from about 100 to about 1500.
15 The superficial velocity for process gas flowing in the process
microchannels
may be at least about 0.01 meters per second (m/s), and in one embodiment in
the
range from about 0.01 to about 5 m/s, and in one embodiment in the range from
about 0.01 to about 2 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 0.05 to about 0.5
m/s.
20 The heat exchange fluid in the heat exchange channels may have a
temperature in the range from about 100 C to about 800 C, and in one
embodiment
from about 250 C to about 500 C. The difference in temperature between the
heat
exchange fluid and the process fluids in the process microchannel may be up to
about 50 C, and in one embodiment up to about 30 C, and in one embodiment up
25 to about 10 C. The residence time of the heat exchange fluid in the heat
exchange
channels may range from about 1 to about 1000 ms, and in one embodiment about
1 to about 500 ms, and in one embodiment from 1 to about 100 ms. The pressure
drop for the heat exchange fluid as it flows in the heat exchange channels may
be
up to about 3 bar/ft, and in one embodiment up to about 1 bar/ft. The flow of
the
3o heat exchange fluid in the heat exchange channels may be laminar or in
transition,
and in one embodiment it is laminar. The Reynolds Number for the flow of heat
exchange fluid in the heat exchange channels may be up to about 50,000, and in
one embodiment up to about 10,000, and in one embodiment up to about 2300, and
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in one embodiment in the range of about 10 to about 2000, and in one
embodiment
about 10 to about 1500.
The control of heat exchange during the hydrotreating and hydrocracking
processes may be advantageous for controlling selectivity towards the desired
product due to the fact that added cooling 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
microchannel reactor may be controlled using passive structures (e.g.,
obstructions),
io orifices and/or mechanisms upstream of the heat exchange channels or in the
channels. By controlling the pressure within each heat exchange channel, the
temperature within each heat exchange channel 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
is pressure. By controlling the temperature within each heat exchange channel,
the
temperature in the process microchannels may be controlled. Thus, for example,
each 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 may provide the advantage of precisely
20 controlled temperatures for each process microchannel. The use of precisely
controlled temperatures for each 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
25 of the process fluid be distributed uniformly among the microchannels. Such
an
application may be when the process fluid is required to be 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
30 Quality Index Factor (Q-factor) as indicated below. A Q-factor of 0% means
absolute
uniform distribution.
Q = mmax - mmin X100
l max
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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 microchannel reactor 100
maybe
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 free stream velocity for process fluid flowing in the 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.
Advantages of the inventive process may include the potential for process
intensification. Conventional processes of the prior art (that is, non-
microchannel
processes) often operate under conditions of reactant dilution to prevent
runaway
reactions, while the inventive process may be operated, if desired, under more
intense conditions leading to greater throughput.
30 While the invention has been explained in relation to various embodiments,
it
is to be understood that various modifications thereof will become apparent to
those
skilled in the art upon reading the specification. Therefore, it is to be
understood
that the invention disclosed herein is intended to cover such modifications as
fall
within the scope of the appended claims.
