Note: Descriptions are shown in the official language in which they were submitted.
ATTORNEY DOCIO:T NUMBER 34,814
HYDROCARBON PROCESSING APPARATUS AND METHOD
Field of the Invention
This invention relates generally to the use of momentum-altering
inlet sparger assemblies in chemical reactors, and more particularly to the
use of such assemblies in hydroconversion reactors such as those used to
hydroprocess heavy, hydrocarbonaceousfeedstocks.
Background of the Invention
Modern reactors used to convert heavy hydrocarbonaceous feedstocks
such as petroleum residuum ("resid") to lighter, more valuable products
often employ slurry-type or ebullated bed hydroconversion processes. In
both slurry-type and ebullated bed reactors, feedstock typically is added to a
reactor vessel alone or together with hydrogen through an inlet pipe or
sparger. The pipe or sparger typically is located in a lower portion of the
reactor vessel in a liquid mixing region.
In ebullated bed reactors, a mixture of process liquids and hydrogen
from the liquid mixing region is forced upwardly through a distributor plate
containing a plurality of bubble-capped risers. Feedstock, hydrogen, and
recycled liquid are forced upwardly through the risers to expand a bed of
supported catalyst located above the distributor plate. Maintaining the
catalyst bed in a properly expanded condition requires that the liquids
supporting the bed exhibit a generally symmetric liquid velocity distribution
in the expanded bed region of the reactor.
In slurry-type reactors, a distributor plate and bubble-capped risers are
not needed to prevent supported catalyst from falling into the liquid mixing
region. Nevertheless, many slurry-type reactors resemble ebullated bed
reactors in that fresh feedstock, recycled liquids and liquid or colloidal
catalyst are mixed together in a liquid mixing region in the lows end of a
reactor. The mixture is then forced upwardly through a distributor plate or
other device intended to provide a desired liquid velocity distribution in the
region of the reactor located above the liquid mixing none.
Liquids moving upwardly in slurry-type or ebullated bed reactors
have a velocity that preferably is equal or nearly equal at all points located
within a cross-section of the reactor at a given height. If asymmetries in the
-~.~ 60632
reactor velotity profile occur, mixing will not be uniform within the reactor.
In ebullated'bed reactors, insufficient liquid velocity may prevent the
catalyst
bed from expanding to the desired height or cause catalyst to accumulate or
"slump" in areas of low liquid velocity. Catalyst slumping can in turn result
in the formation of reactor hot spots and coke accumulation.
Various structures have been employed to minimize deviations in
the liquid velocity profile of slurry-type or ebullated bed reactors. For
example, U.S. Patent No. 4,444,653 to Euzen discloses a plurality of inlet
spargers which disperse a reactor feedstock through a plurality of relatively
small discharge orifices located along the spargers. While these sparger
designs may be beneficial in some applications, the use of spargers with large
numbers of relatively small holes such as those disclosed by Euzen can be
problematic when the reactor charge is a heavy hydrocarbonaceous feedstock
such as a petroleum resid, as relatively small holes can easily become
plugged in a resid hydrotreating environment. Euzen's designs also are
subject to the momentum-related problems discussed in depth below.
Another method for improving the flow distribution of liquids in an
ebullated bed reactor is disclosed in U.S. Patent No. 4,702,891 to Li. This
method employs a radially-symmetric recycle liquid inlet nozzle located
along the centerline of a generally cylindrical reactor vessel and in a liquid
mixing region below the reactor's distributor plate. Feedstock and hydrogen
are introduced into the same region through a ring sparger located above the
recycle nozzle. As is common in many such reactors, feedstock appears to be
required to enter the reactor in an asymmetric manner because of
mechanical constraints inherent in the reactor design. While Li's design
may be useful in some instances, our experimental work shows that the use
of a ring sparger such as in the Li patent introduces sufficient unwanted
horimtttal momentum into fluids present below the distributor plate to
cause serious deviations in the liquid velocity profile above the distributor
plate: Specifically, although Li's horizontal sparg~ includes downwardly-
directed discharge apertures, horizontal motion through the sparger causes
the discharged feedstock to retain an undesired horizontal momentum
component. As our experimental data will show, this undesired horizontal
momentum component can seriously degrade the liquid superficial velocity
proC~le in the reactor region located above the inlet sparger. This effect has
been found to occur even though recycled liquids are introduced into the
liquid region in a manner which appears to introduce little unwanted
recycled liquid momentum components. '
-3-_ ~16063~
What is needed is a means for introduang feedstock into a reactor
that minimizes asymmetry in the liquid' velocity profile in a reaction zone
of the reactor.
Summary of the Invention
Each aspect of the present invention is based on novel feedstock
sparger designs useful in liquid-containing chemical reactors, and
particularly useful in resid hydrotreating reactors. These designs exploit our
dasrnvery that a liquid velocity profile asymmetry in the reactor can be
reduced by minimizing undesired momentum components transferred to
the reactor system by entering feedstock.
A first aspect of the invention provides a feedstock inlet sparger
assembly for use in a reactor vessel used to react a mixture rnntaining a
liquid feedstock. The sparger assembly includes a sparger having at least one
discharge aperture for discharging feedstock therethrough into the reactor as
well as one or more baffles for reducing the magnitude of an undesired
momentum component of feedstock discharged from the sparger. The baffle
is located and oriented such that the discharged feedstock impinges on the
baffle, thereby reducing or eliminating undesired momentum components
introduced into the reactor system by the entering feedstock.
A semnd aspect of the invention provides a liquid chemical reactor
incorporating a momentum-altering feedstock inlet sparger assembly. The
reactor includes a reactor vessel; sparger means located within the reactor
vessel for discharging feedstock into the reactor through at least one sparger
discharge aperture; and baffle means for reducing the magnitude of an
undesired momentum rnmponent of feedstock discharged from the sparger
means. The baffle means is located such that the discharged feedstock
impinges on the baffle means to reduce undesired liquid momentum
components introduced into the reactor by the entering feedstock.
Another aspect of the invention provides a method for introducing a
liquid feedstock into a chemical reactor. The method includes the steps of
introducing the liquid feedstock into a liquid mixing region of the reactor
through a sparger having at least two discharge apertures and causing the
introduced feedstock to impinge against a baffle means to seduce an
undesired component of feedstock momentum.
Yet another aspect of the invention provides a method for
hydrotreating a resid feedstock in a resid hydrotreating reactor vessel having
a liquid reaction zone located above a liquid mixing zone. The method
2I~~632
includes the steps of reacting a mixture comprising hydrogen, a liquid
feedstock, and a catalyst in the liquid reaction zone; introducing unreacted
liquid feedstock into the liquid mixing region of the reactor through a
sparger having at least two discharge apertures; impinging the introduced
feedstock against a baffle means to reduce an undesired component of
feedstock momentum; separating a liquid recycle stream from the reacted
mixture; and introducing the recycle stream into the liquid mixing zone.
Brief Description of the Drawings
FIG. 1 is a simplified sectional perspective view of a resid
hydrotreating reactor incorporating a momentum-altering feedstock inlet
sparger assembly in accordance with the present invention;
FIGS. 2a, b and c are simplified sectional views of a bottom portion of
a reactor which are useful in understanding the concept underlying the
present invention;
FIG. 3 is a bottom plan view of the feedstock inlet sparger assembly
shown in FIG. 1 taken along line 3-3 of FIG. I;
FIG. 4 is a partial perspective view of the sparger assembly shown in
FIG. 3 taken along line 4-4 of FIG. 3;
FIG. 5 is a sectional perspective view of the sparger assembly shown in
FIG. 3 taken along line 5-5 of FIG. 3;
FIG. 6 is a perspective view of the sparger assembly shown in FIG. 3
taken along line 6-6 of FIG. 3; and
FIG. 7 is a graphical representation of the liquid velocity distribution
of a reactor employing a prior art feedstock distribution sparger compared to
the liquid velocity distribution of a reactor employing a sparger assembly in
aaoor~dance with the present invention.
Detailed Description of the Invention
Each of the inlet sparger assemblies and related processes discussed
herein can improve the superficial liquid velocity distribution in a slurry-
type or ebullated bed resid hydrotreating reactor or other chemical reactor.
The spargers assemblies improve the velocity distribution by damping or
redirecting feedstock having undesired momentum components
introduced into the feedstock by the feedstock's passage through the sparger.
In each case, discharged feedstock impinges on a surface of a baffle oriented
in a plane which is non-parallel to the direction of the undesired
-~_ 216062
momentum component of the discharged feedstock. While the spargers and
processes discussed below are intended for use in an ebullated bed or slurry-
type resid hydrotreating reactor, the invention is also useful in other types
of
chemical reactors.
Turning to FIG. I, an ebullated bed hydrotreating reactor 20 includes a
reactor vessel 22 penetrated by a feedstock inlet sparger assembly 24, a
catalyst
inlet 26, a catalyst outlet 28, an optional vapor outlet 30, and a fluid
product
outlet 32. If desired, vapor outlet 30 may be omitted, with vapor and liquid
products withdrawn from the vessel. together through product outlet 32.
Internal to vessel 22 is a recirculatfon downmmer 34 located along a
radial axis of symmetry 36 of vessel 22. Downcomer 34 extends downwardly
through a distributor plate 38 and terminates into an ebullation or
recirculation pump 40 located at the lower end of downcomer 34.
Distributor plate 38 includes a plurality of bubble-capped risers 42 'which
allow upward liquid flow while preventing the downward flow of liquid
and catalyst.
A recirculation pan 44 is attached to downmmer 34 at downmmer
34's upper end. Pan 44 includes a lower, frustoconical portion 46 attached to
downrnmer 34 at the lower end of portion 46 and an upper, generally
cylindrical pan portion 48 whose upper edge 50 is located typically below a
liquid level LI during operation. A vapor space 52 is located above liquid
level Ll at the upper end of vessel 22.
The reactor of FIG. 1 is generally representative of vertically-oriented
slurry-type and ebullated reactors having an upper half portion
corresponding to the reactor region W located above line H in FIG. I, a
lower half portion corresponding to the reactor region LL located below line
H la FIG. I, an inlet sparger located in lower half portion LL, and in which
total liquid mass flow in the reactor is in a generally vertical direction.
These reactors often include a means for recycling partially-upgraded
materials from region W to LL such as downrnmer 34. It should be noted
that the use of bubble-capped risers 42 in distributor plate 38 is highly
preferred, but that in some reactors, a suitable distributor plate may simply
comprise a plate having a plurality of slots or other apertures.
During operation, feedstock and hydrogen are added to a liquid
mixing region 54 through momentum-altering feedstock inlet sparger
assembly 24. Alternatively, hydrogen may be added to vessel 22 through a
separate sparger or pipe. The added feedstock and hydrogen are mixed with
recirculated reactor liquids drawn downwardly through downcomer 34 by
-s- 2160632
ebullation pump 40. The mixed liquids and hydrogen are forced upwardly
through bubble-capped risers 42. The upward liquid velocity of fluids forced
through bubble-capped risers 42 expands a bed of supported catalyst to level
L2, creating a catalyst-containing liquid region or reaction zone 55 in which
feedstock and recirculated liquids are catalytically upgraded to lighter, more
valuable products. .
A freeboard or catalyst-free liquid region 56 exists between level Ll
and level L2. Freeboard region 56 is catalyst-free because the liquid
superficial velocity of fluids introduced through distributor plate 38 is
insufficient to expand catalyst-containing region 55 above level L2
Proper operation of reactor 20 depends in large part on achieving a
desired liquid superficial velocity distribution within catalyst-containing
region 55. If a proper distribution is not obtained, catalyst may tend to
accumulate or "slump" onto distributor plate 38 below regions of relatively
low velocity. Such catalyst accumulations can result in reactor coking and
"hot spots." Our research has shown that ak the feedstock flow rates typically
used in ebullated bed hydrotreating reactors undesired momentum
components imparted to feedstock introduced in liquid mixing region 54 can
substantially disturb the liquid velocity profile in catalyst-containing
region
55. Spargers in accordance with the present invention employing one or
more baffles such as those disclosed in FIGS. 2-5 below to minimize
undesired momentum components which may disturb the liquid velocity
profile in catalyst-containing region 55.
FIGS. 2a, b and c are simplified sectional views of a bottom portion of
reactor 20 and are useful in understanding the concept underlying the
present invention. In these FIGS., bubble-capped risers 42' and 42" are
located above feedstock inlet sparger 24 on feedstock inlet and outlet sides
of
reactor 20, respectively. Risers 42' and 42" include vertical riser porrions
ST
and 5T' which pass through distributor plate 38 and have bubble caps 58' and
58" located at their upper ends. Vertical riser porfions 5T and 5T' include
lower slots 59' and 59" and upper slots 60' and 60", respectively. During
operation, gas accumulates immediately under distributor plate 38, forming
a gas-liquid interface GLI. Interface GLI occurs partway up lower slots 59'
and 59".
FIG. 2a illustrates an idealized case in which feedstock exits sparger 24
and has only a desired downward momentum component M,~ associated
with the exiting feedstock. Because no undesired momentum components
are imparted to the exiting feedstock, interface GLI occurs at approximately
-7- _ 2160632
the same height on lower slots 59' and 59", and therefore about the same
relative fractions of liquid and gas enter lower slots 59' and 59". When the
same relative fractions of liquid and gas enter slots 59' and 59", the local
liquid velocity above distributor plate 38 above risers 42' and 42" is about
the
same.
FIG. 2b illustrates how the presence o~ undesired feedstock
momentum components affects the liquid velocity distribution. above
distributor plate 38. In this case, feedstock exiting sparger 24 contains a
downward momentum component MX as well as a horizontal momentum
component My imparted to the feedstock as the feedstock travels through
sponger 24. The sum of Mx and My's a net momentum in the direction of
arrow M=,et. The net momentum causes jetting of fluid which drags and tilts
interface GLI upward at the outlet side of reactor 20. The tilted interface
means that a larger fraction of lower slot 59' is exposed to gas than lower
slot
59", thereby causing more gas to enter slot 59' relative to slot 59". This in
turn causes the local liquid velocity to be higher above riser 59' than above
riser 59", resulting in the velocity distribution shown in Curve A of FIG. 7,
which is discussed in detail later in rnnnection with Example 1.
In FIG. 2c, momentum-altering surfaces or baffles 61 are installed
immediately downstream from the points at which feedstock exits sponger
24. Because the exiting feedstock has momentum M"et~ the feedstock
impinges on baffles 61, which redirect the momentum of the exiting
feedstock downwardly and/or otherwise randomize the momentum so that
interface GLI is no longer dragged and tilted by jetting fluid as shown in
FIG.
2b. As a result, the local liquid velocity distribution above distributor
plate
38 more closely resembles that shown in Curve B of FIG. 7, discussed in
detail later in connection with Example 2
A practical application of the rnncepts just explained is shown in
FIGS. 3 - 6. FIG. 3 depicts a momentum-altering feedstock inlet sponger
assembly 24 which includes a feedstock inlet 62 and a pair of sponger arms 63.
Each arm 63 terminates in a sponger outlet nozzle 64 and rnntains a plurality
of downwardly oriented sponger outlet apertures 68 located symmetrically
along the lower surfaces of arms 63. A sponger skirt 70 (depicted and
discussed in detail in conjunction with FIGS. 4-6) surrounds the sides and
top of sponger arms 63. Skirt 70 traps and redistributes in a more uniform
manner gas exiting spargea 24. Fitted within skirt 70 around arms 63 are a
plurality of generally vertical momentum-directing baffles 72. Baffles 72 are
located ~ immediately downstream of each outlet aperture 68. During
CA 02160632 2004-08-11
operation, feedstock exits apertures 68 into liquid mixing region 54.
Feedstock undergoes a large pressure drop in sparger 24, and feedstock
exiting apertures 68 has both a desired downward momentum component
and an undesired horizontal momentum component which was introduced
as the feedstock traveled horizontally through sparger arms 63.~ The
undesired horizontal momentum component causes the discharged
feedstock to impinge on baffles 72. As the feedstock strikes baffles 72, the
undesired horizontal momentum component is dissipated and/or
redirected, thereby preventing the horizontal momentum component from
interfering with the upward superficial liquid velocity profile in the .region
above distributor plate 38.
Also visible in FIG. 3 are a plurality of mounting Lugs 74 which are
attached to shirt 70 and are useful for mounting sparger assembly 24 with
vessel 22.
F'IGS~. 4, 5 and b are sectional perspective views of sparger assembly 24
taken along lines 4-4, 5-5 and 6-6 of FIG. 3, respectively. FIG. 4 shows that
baffle 72 is attached at its periphery to the inter surface of skirt 70 and
that it
is attached to sparger arm 63 around the outer surface of arm 63. Also
visible in FIGS. 4 and 5 but best viewed in the perspective view of FIG. 6 is
a
slotted skirt edge 76. Slotted edge 76 promotes distribution of feedstock and
hydrogen radially inwardly and outwardly through the skirt slots in
directions generally perpendicular to the undesired horizontal momentum
component.
The cooperation of skirt 70, slotted edge 76, and baffles 72 results in a
particularly effective sparger assembly as demonstrated by the following
Examples.
EXAMPLE 1
Itt Exaanpk I, a cold flow pilot plant was used to ateasure the liquid
superficial velodty proFrle present in a reactor eanploying a sparger assembly
like the one shown in FIGS. 1 and 3-6 but lacking the baffle plates used to
redirect feedstxk ~dting apertures 68. The cold #low pilot plant is a one-
quart~ scale model of a single resid hydrotreating reactor of the type
disclosed in our U.S. Patent No. 4,753,721.
The pilot plant reactor vessel is a three foot
diameter clear cylinder. Tlie bottom portion of the cylinder includes a
distributor plate fitted with 110 bubble=capped risers. The reactor vessel
2100632
, , _
includes taps through which pitot tubes may be introduced for measuring
the liquid velocity at various radial locations within the reactor.
Kerosene and nitrogen were used to simulate the oil and hydrogen
phases normally present in a resid hydrotreating reactor. Catalyst extrudates
were not added to the reactor to simplify testing. A liquid flow rate of 60
gallons per minute was introduced into the sparger, corresponding to a
feedstock liquid velocity of 0.02 feet per second in a full scale reactor. Gas
was introduced at a rate of 40 SCFM which corresponds to a gas addition rate
of 2400 SCFM in the full-sized reactor. The feed was introduced through an
inlet sparger of the type disclosed in our '721 pat~t, which corresponds to
the inlet sparger assembly like the one shown in FIGS. 1 and 3 through 6 but
lacks the baffle plates used to redirect flow exiting the sparger discharge
apertures.
Curve A of FIG. 7 is a plot of the distribution of liquid velocity during
the above-described test taken in a reactor region located above the
distributor plate in a vertical plane containing centerline CL of FIG. 3. The
data shows that the veloclty of liquid near the reactor wall on the inlet
(upstream) side of the sparger assembly greatly exceeded the velocity near
the wall at the outlet (downstream) side of the sparger assembly. It is
believed that the asymmetry in veloclty distribution shown on Curve A is
attributable to jetting of liquid and gas in the forward direction as liquid
and
gas exit the sparger apertures. This jetting apparently drags and lifts the
liquid gas interface on the side of the reactor distal from the sparger inlet,
leading to an upflow along the reactor wall on the feed inlet side of the
reactor and a downflow along the opposite reactor wall.
EXAMPLE 2
In this Example, a test was rnnducted identical to the one discussed
above in Example 1, except that the sparger included baffles of the type
shown in FIGS. 3-6 above. Curve 8 on FIG. 7 shows the liquid veloclty
distribution obtained with the sparger built in accordance with the present
invention. As can be seen by comparing Curves A and B on FIG. 7, the
liquid velocity profile is much more symmetric around , the reactor
centerline.
The invention is, of course, useful in reactor rnnfigurations other
than those discussed above. For any given reactor and sparger assembly, the
benefits of a momentum-altering spargea assembly in accordance with the
present invention are expected to bernme more apparent as the ratio of
' __1 pr
_216032
feedstock flow to total liquid flow through the reactor's reaction zone
increases. This effect should occur because the larger the unwanted
feedstock momentum component, the less likely that component will be
overwhelmed by total liquid flow. For example, if the feedstock flow used in
the reactor described in conjunction with FIG. I was doubled while the
recirculation flow in the reactor remained constant, it would be expected
that the magnitude of the asymmetry in the superficial liquid velocity
profile would increase. As a rule of thumb, the invention is believed to be
useful in any reactor where the ratio of flow through a sparger to the total
liquid flow through the reactor's reaction zone exceeds 1 to 10, and believed
to be especially useful in those reactors where the ratio of flow through a
sparger to the total liquid flow through the reactor's reaction zone exceeds 1
to 7.
For reactors having the same relative feedstock to total liquid flows,
the benefits of the invention are expected to be more noticeable in
configurations where the angle between the plane containing the sparger
and the direction of overall liquid flow fn the reactor vessel approaches
niatety degrees, such as in the design shown in FIG. 1. As the included angle
between the direction of the unwanted feedstock momentum component
and the overall direction of liquid flow in the reactor changes from 90
degrees, the effect of the unwanted momentum component introduced into
the reactor flow will be likely to decrease.
Spargers useful in the assembly can be of virtually any configuration.
For example, the spargers can consist of multiple pipes, one or more rings,
or a combination of the above. The sparger configuration is non-critical
because any flow disturbances induced in the reactor by undesired feedstock
momentum components can be reduced by proper orientation of the sparger
assembly baffle .
Baffles employed in accordance with the present invention are
believed to be particularly effective when oriented normal to the direction of
flow through the inlet sparger assembly and parallel to the overall mass
flow through the reactor as shown in FIGS. 3-6. Alternatively, baffles may be
oriented at any angle of impingement which theoretically or empirically
reduces an undesired momentum rnmponent of feedstock'entesing the
reactor. Thus, the included angle between direction of the unwanted
momentum rnmponent and baffle surface can be any angle less than 180
degrees, although angles which place baffles normal to the unwanted
--l I-
~~~OG~2
momentum rnmponent and/or forcing the flow in the direction of total
liquid flow through the reactor are preferred.
The baffles need not be planar, as shown in FIGS. 3-6, but instead may
be curved or contain a plurality of angled surfaces for damping or redirecting
the undesired momentum component. For example, the baffles of FIGS. 3-6
could be quarter=circular curved plates for directing exiting fluid
downwardly into the liquid mixing zone of the reactor, or could be
corrugated surfaces which would tend to randomize and damp the
undesired momentum component rather than redirecting that component
downwardly.
The baffles may contain apertures of virtually any size, so long as
sufficient surface area remains to interact with the undesired momentum
component of the entering fluid, and the baffles need not be physically
attached to the sparger arms or skirt as shown in FIGS..2-5 as long as the
baffle surface is located sufficiently near the exiting feedstock to interact
with
the undesired momentum component. The size of a baffle is non-critical,
but it is preferred that at least fifty percent of the feedstock exiting a
discharge
aperture associated with that baffle impinges on the baffle.
Momentum-altering spargers in accordance with the present
invention are most effectively used in systems where all fluids added to a
liquid mixing region of the reactor are substantially devoid of momentum
rnmponents which degrade the liquid velocity profile in the reactor. For
example, in a reactor which recycles reactor fluids into the liquid mixing
region, the recycled liquids preferably are introduced through a sparger in
accordance with the present invention or in any other manner which
prevents the introduction of unwanted recycle liquid momentum
components, such as through a recycle or ebullition pump having
syrnr~atrically-oriestted outlets. Any other fluid added to the region such as
a soluble catalyst-containing liquid or a gas should be added in a similar
manner if the momentum of the added fluid is sufficient to introduce
velocity profile-degrading momentum rnmponents.
Spargers of the type discussed above are especially useful in the
hydroconversion of relatively heavy hydrocarbonaceous feedstocks to
relatively lighter products. Suitable feedstocks can be derived from
naturally-occurring materials such as petroleum, coal, tar sands, and oil
shales as well as waste plastics and waste streams from various
petrochemical processes. Operating conditions generally should be at
pressures from atmospheric to about 8000 psi, at hydrogen partial pressures
CA 02160632 2004-08-11
--12--
ranging from 10 to 100 percent of the total pressure, and at temperatures
ranging from about 200° to 1200°F.
Catalysts suitable for use in the hydroconversion processes include
supported and oil-soluble, metal-containing catalysts. Suitable supported
catalysts typically will comprise a hydrogenation metal such as nickel or
cobalt and one or more promoters such as molybdenum which are deposited
on a porous, refractory, inorganic oxide support. Suitable oil-soluble
catalysts include virtually any metal-containing organic compound soluble
in the feedstock which contains a hydrogenation metal. Preferred soluble
catalysts include organophosphorodithioate compounds such as the
lubricant Molyvan L*available from the Vanderbilt Chemical Company of
Norwalk, Corn.
If an oil-soluble catalyst is used, the catalyst may . be added directly to
the reactor or mixed with the feedstock at a location immediately upstream
of the reactor. If a soluble catalyst is used, sufficient catalyst should be
added
to provide a molybdenum metal concentration in the feedstock/catalyst
mixture of between about 20 and 1000 parts per million. If a supported
catalyst is used, catalyst should be added in an amount of about 0.05 to 1.0
pounds of catalyst per barrel of feedstock.
Oil-soluble catalysts in accordance with the present invention are
particularly well-suited to catalyzing the conversion of petroleum reside to
tighter, more valuable products. As used in this application, the term
"petroleum resid" or "resid" refers to feedstocks containing at least 50
weight
percent of material boiling above about 650°F at atmospheric pressure
without regard _ for 'whether the feedstock is the product of a distillation
process. Typically, resid will contain at least seventy weight percent of
mate~al boiling above about 1000°F at atmospheric pressure and will be
the
botbonns product from one or more atmospheric or vacuum distillations.
When the feedstock is atmospheric or vacuum petroleum resid, the
conversion preferably occurs in the presence of hydrogen gas at total
pressures between about 200 and 8000 psi, at hydrogen partial pressures
ranging from 20 to 95 percent of the total pressure, and at temperatures
ranging from about 200° to 1200°F. More preferably, the
conversion occurs at
total pressures between about 1000 and 3000 psi at hydrogen partial pressures
ranging from 20 to 95 percent of the total pressure and at temperatures
between about 500° and 1000°F. Most preferably, the conversion
occurs at
total pressures between about 1500 and 2700 psi, at hydrogen partial
pressures ranging from 50 to 95 percent of the total pressure and at
Trademark*
__I~_ 21 ~ 0 6 3 2
temperatures between about 700° and 900°F. If a soluble or
colloidal metal
catalyst is used, catalyst concentration in the resid feedstock should be such
as to provide between about 20 to 800 parts per million of molybdenum
metal in the catalyst/resid mixture, and preferably between about 15 and I00
parts per million of molybdenum metal in the resid/feedstock mixture. If a
supported catalyst is used, catalyst should be added in an amount of 0.1 to
0.5
pounds of catalyst per barrel of feedstock.
Many modifications can be made to the sparger and processes
described above without departing from the spirit of the invention. The
scope of the invention is therefore intended to be limited only by the
following claims.
