U.S. patent number RE29,315 [Application Number 05/721,419] was granted by the patent office on 1977-07-19 for asphaltene hydrodesulfurization with small catalyst particles utilizing a hydrogen quench for the reaction.
This patent grant is currently assigned to Gulf Research & Development Company. Invention is credited to BY Gulf Science and Technology Company, Edgar Carlson, deceased, Alfred M. Henke, William R. Lehrian, Joel D. McKinney, Kirk J. Metzger.
United States Patent |
RE29,315 |
Carlson, deceased , et
al. |
July 19, 1977 |
Asphaltene hydrodesulfurization with small catalyst particles
utilizing a hydrogen quench for the reaction
Abstract
The hydrodesulfurization of a crude oil or a reduced crude
containing the asphaltene fraction proceeds at unexpectedly low
temperatures by utilizing a catalyst comprising a Group VI and
Group VIII metal on alumina when the catalyst particles are very
small and have a diameter between about 1/20 and 1/10 inch and the
reaction is quenched with hydrogen.
Inventors: |
Carlson, deceased; Edgar (LATE
OF Allison Park, PA), BY Gulf Science and Technology Company
(Pittsburgh, PA), Henke; Alfred M. (Springdale, PA),
Lehrian; William R. (Pittsburgh, PA), McKinney; Joel D.
(Pittsburgh, PA), Metzger; Kirk J. (Pittsburgh, PA) |
Assignee: |
Gulf Research & Development
Company (Pittsburgh, PA)
|
Family
ID: |
27110426 |
Appl.
No.: |
05/721,419 |
Filed: |
September 8, 1976 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
770625 |
Oct 25, 1968 |
03562800 |
Feb 9, 1971 |
|
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Current U.S.
Class: |
208/216R |
Current CPC
Class: |
B01J
8/008 (20130101); B01J 8/0453 (20130101); B01J
2208/025 (20130101); C10G 2300/107 (20130101) |
Current International
Class: |
C10G
45/02 (20060101); C10G 45/02 (20060101); B01J
8/04 (20060101); B01J 8/04 (20060101); B01J
8/00 (20060101); B01J 8/00 (20060101); C10G
45/08 (20060101); C10G 45/08 (20060101); C10G
023/02 () |
Field of
Search: |
;208/216,89 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
"Hydrodesulfurization of Khafii Crude Oil", Ohtsuka et al.,
Bulletin of the Japan Petroleum Institute, vol. 10, May 1968
(English translation)..
|
Primary Examiner: Crasanakis; George
Claims
We claim:
1. A process for the hydrodesulfurization of a crude oil or a
reduced crude containing the asphaltene fraction of the crude
comprising passing a mixture of hydrogen and said oil through a
compact bed of catalyst particles comprising a Group VI metal and
Group VIII metal on alumina, the hydrogen partial pressure being
.[.about.]. 1000 to 5000 pounds per square inch, .[.and.]. said
particles in said bed being between 1/20 and 1/40 inch in diameter
.Iadd.and a throughput of at least 127 volumes of oil per volume of
catalyst is continued for at least 10 days. .Iaddend.
2. The process of claim 1 wherein the particles in said bed are
between about 1/25 and 1/36 inch in diameter.
3. The process of claim 1 wherein the particles in said bed are
between about 1/29 and 1/34 inch in diameter.
4. The process of claim 1 wherein the catalyst comprises
nickel-cobalt-molybdenum on alumina.
5. The process of claim 1 including the step of applying a hydrogen
quench to said bed to control the temperature thereof.
6. A process for the hydrodesulfurization of a crude oil or a
reduced crude containing the asphaltene fraction of the crude
comprising passing a mixture of hydrogen and said oil through a
compact bed of catalyst particles comprising a Group VI metal and
Group VIII metal on alumina, the hydrogen partial pressure being
.[.about.]. 1000 to 5000 pounds per square inch, said particles in
said bed being between about 1/20 and 1/40 inch in diameter,
.[.and.]. applying a hydrogen quench to said bed .Iadd.and a
throughput of at least 127 volumes of oil per volume of catalyst is
continued for at least 10 days.
7. The process of claim 6 wherein the particles in said bed are
between about 1/25 and 1/36 inch in diameter.
8. The process of claim 6 wherein the particles in said bed are
between about 1/29 and 1/34 inch in diameter.
9. The process of claim 6 wherein the catalyst comprises
nickel-cobalt-molybdenum on alumina.
10. The process of claim 6 wherein the charge oil contains between
about 0.002 and 0.03 weight percent of nickel and vanadium.
11. A process for the hydrodesulfurization of a crude oil or a
reduced crude oil containing the asphaltene fraction of the crude
comprising passing a mixture of hydrogen and said oil through
catalyst particles comprising a Group VI metal and Group VIII
metal, said particles being divided into a plurality of compact
beds in series, the hydrogen partial pressure being about 1000 to
5000 pounds per square inch, said catalyst particles in said beds
being between about 1/20 and 1/40 inch in diameter, applying a
hydrogen quench to said catalyst beds, and continuing said process
for at least 10 days and a throughout of at least 127 volumes of
oil per volume of catalyst.
12. The process of claim 11 wherein the particles in said beds are
between about 1/25 and 1/36 inch in diameter.
13. The process of claim 11 wherein the particles in said beds are
between about 1/25 and 1/34 inch in diameter.
14. The process of claim 11 wherein the catalyst comprises
nickel-cobalt-molybdenum on alumina.
15. The process of claim 11 wherein the charge oil contains between
about 0.002 and 0.03 weight percent of nickel and vanadium.
16. The process of claim 1 wherein the hydrogen partial pressure is
1000 to 3000 pounds per square inch.
17. The process of claim 1 wherein the hydrogen partial pressure is
1500 to 2500 pounds per square inch. .[.18. The process of claim 1
wherein throughput is continued for at least 10 days and 127
volumes of oil per
volume of catalyst..]. 19. The process of claim 6 wherein the
hydrogen
partial pressure is 1000 to 3000 pounds per square inch. 20. The
process of claim 6 wherein the hydrogen partial pressure is 1500 to
2500 pounds per square inch. .[.21. The process of claim 6 wherein
throughput is continued for at least 10 days and 127 volumes of oil
per volume of
catalyst..]. 22. The process of claim 11 wherein the hydrogen
partial
pressure is 1000 to 3000 pounds per square inch. 23. The process of
claim 11 wherein the hydrogen partial pressure is 1500 to 2500
pounds per square inch. .Iadd. 24. Claim 1 wherein a throughput of
at least 1,293 volumes of oil per volume of catalyst is continued
for at least 97.6 days. .Iaddend..Iadd. 25. Claim 6 wherein a
throughput of at least 1,293 volumes of oil per volume of catalyst
is continued for at least 97.6 days. .Iaddend..Iadd. 26. Claim 11
wherein a throughput of at least 1,293 volumes of oil per volume of
catalyst is continued for at least 97.6 days. .Iaddend.
Description
The present invention relates to a process for the
hydrodesulfurization of a crude oil or a reduced crude oil in the
presence of a supported Group VI and Group VIII metal
hydrodesulfurization catalyst having an exceptionally small
particle size. Substantially all or a large proportion of the
catalyst particles of the present invention have a diameter of
between about 1/20 and 1/40 inch.
Although nickel-cobalt-molybdenum is the preferred active metals
combination for the catalyst of this invention, other combinations
can be utilized such as cobalt-molybdenum, nickel-tungsten and
nickel-molybdenum. Alumina is the preferred supporting material but
other non-cracking supports can also be used such as silica alumina
and silica magnesia.
Hydrodesulfurization catalysts comprising supported Group VI and
Group VIII metals, such as nickel-cobalt-molybdenum on alumina,
having a particle size as small as the catalyst particles of the
present invention were not heretofore considered advantageous for
use in a large or commercial scale because a bed comprising
particles of the small size of the present invention induces an
extremely high pressure drop, which is highly deleterious to a
hydrodesulfurization process which has a limited inlet pressure
because the temperature required by a catalyst to accomplish a
given degree of desulfurization increases with loss of hydrogen
pressure.
The present invention relates to a hydrodesulfurization process in
which the small particle size catalyst is utilized in a manner
which manifests an unexpectedly high activity so that
hydrodesulfurization of crude oil charge to any desired sulfur
level, such as a 1 percent sulfur level, proceeds at an
unexpectedly low temperature. Although extrapolation of the initial
temperature required to produce a liquid product having a 1 percent
sulfur content with 1/8 inch diameter and 1/16 inch diameter NiCoMo
catalyst particles, which are above the size of the present
invention, indicates that the temperature requirement would be
lower with the small catalyst particles of this invention we have
found that the small size NiCoMo catalyst particles of the present
invention permit the use of a hydrodesulfurization temperature
which is considerably lower than the temperature which would be
expected by extrapolation of the temperature data obtained with
larger size catalyst particles. Moreover, the very discovery that
hydrodesulfurization with the catalyst of the present invention
could be carried out at an unexpectedly low temperature has
heretofore been obscured by the extremely high pressure drop
through a bed of the small size catalyst particles of the present
invention. The reason is that in a hydrodesulfurization process
pressure drop itself increases the temperature requirement to
achieve a given degree of desulfurization usually by an extent
which equals or exceeds the temperature advantage due to the small
particle size of this invention.
It is seen that there are two unexpected features surrounding the
present invention. The first is that there is an unexpectedly great
temperature advantage achievable in a hydrodesulfurization process
by employing a bed of catalyst having a particle size of the
present invention. FIG. 1 (all figures are discussed in detail
herein below) shows that the hydrodesulfurization temperature
required to produce a residual product having 1 percent sulfur with
a 1/32 inch catalyst of the present invention is much lower than
what would be expected by extrapolation of the line connecting the
data obtained with 1/8 and 1/16 inch catalyst particles even though
the surface area defined by the pores of all three catalyst is
about the same. The second feature is that the unexpected
temperature advantage is completely disguised by the ordinary
approach to its determination, i.e. by making a test in a reactor
with relatively large size catalyst particles as a blank and then
making a test in the same reactor under the same conditions except
that the catalyst particle size is within the range of the present
invention (particle size being the only variable changed in the two
tests). In this regard, the vertical dashed line in FIG. 2 shows
that if a 1/16 inch catalyst, which is larger than a catalyst of
this invention, is tested in a 9.5 foot diameter reactor and then a
1/32 inch catalyst of this invention is tested in the same reactor
under unchanged conditions, including an unchanged space velocity,
the pressure drop in the 1/32 inch catalyst bed in the same reactor
is so much greater than that for the 1/16 inch catalyst that the
pressure drop increase itself would easily nullify the temperature
advantage achievable because of particle size and therefore the
advantage of the present invention would be completely masked. The
horizontal dashed line of FIG. 2 shows that if the 1/16 inch
catalyst is tested in a 9.5 diameter reactor a comparable pressure
drop can only be achieved if the 1/32 inch catalyst is tested in an
11 foot diameter reactor, when both tests are performed at a liquid
hourly space velocity of one. Therefore, it is only by making the
tests in two different reactors, to equalize pressure drop, that
the temperature advantage of the 1/32 inch catalyst becomes
apparent. It is clear that not merely one but rather two variables
must be changed to reveal the advantage of the present
invention.
The great effect of pressure drop upon temperature requirements to
produce a hydrocarbon product having a 1 percent sulfur content is
demonstrated by reference to FIG. 3. In FIG. 3 the solid line
represents a hydrodesulfurization process having a constant
hydrogen partial pressure of 1830-1850 p.s.i.a. The dashed line
represents a decreasing hydrogen partial pressure starting with the
1830-1850 p.s.i.a. range to a range of 1720-1740 p.s.i.a. which
reduction is caused by the recycle hydrogen stream becoming
progressively diluted with other gases. FIG. 3 shows that as the
hydrogen partial pressure progressivey decreases the temperature
required to produce a 1 percent sulfur product progressively
increases, so that it is considerably above the temperature
required with constant hydrogen partial pressure. Since pressure
drop due to flow across a catalyst bed similarly reduces partial
hydrogen pressure, FIG. 3 illustrates the detrimental effect upon
reaction temperature of pressure drop through a catalyst bed of
this invention.
The charge to the process of this invention can be a full crude or
a reduced crude containing substantially all of the residual
asphaltenes of the full crude. The residual asphaltenes are
deficient in hydrogen and comprise only about 10 percent of the
charge oil but contain substantially all of the metallic components
present in the crude, such as nickel and vanadium. Since the
desulfurization catalyst has a greater activity for demetalization
than for desulfurization, it removes nickel and vanadium from a
charge stock more rapidly than it removes sulfur. These metals
deposit most heavily on the outermost regions of the catalyst cross
section and tend to reduce the desulfurization activity of the
catalyst. Nickel and vanadium removal constitutes substantially the
entire deactivation of the catalyst while sulfur and nitrogen
removal contributes very little to catalyst deactivations.
Furthermore, the asphaltenes comprise the highest boiling fraction
of the full crude and contain the largest molecules in the crude.
These large molecules are the ones least able to penetrate catalyst
pores and most likely to plug these pores. The present invention is
directed towards the hydrodesulfurization of a full crude or a
residual oil containing substantially the entire asphaltene
fraction of the crude from which it is derived and which therefore
contains 95 to 99 weight percent or more of the nickel and vanadium
content of the full crude. The nickel, vanadium and sulfur content
of the liquid charge can vary over a wide range. For example,
nickel and vanadium can comprise 0.002 to 0.03 weight percent (20
to 300 parts per million) or more of the charge oil while sulfur
can comprise about 2 to 6 weight percent or more of the charge oil.
If an oil containing smaller quantities of nickel, vanadium and
sulfur is processed, such as a furnace oil, considerably lower
temperature conditions, pressures as low as 1000 pounds per square
inch, lower gas circulation rates and hydrogen of lower purity than
required by this invention, will suffice to produce a liquid
product containing 1 percent sulfur, and therefore the process of
the present invention will not be essential.
As the hydrodesulfurization reaction proceeds, nickel and vanadium
removal from the charge tends to occur preferentially over sulfur
removal. However, deposition of nickel and vanadium upon the
catalyst results in a greater degree of catalyst deactivation than
does sulfur removal because the removed metals deposit upon the
catalyst whereas sulfur removed from the charge escapes as hydrogen
sulfide gas. Low hydrodesulfurization temperatures tend to inhibit
metal removal from the charge and thereby reduce catalyst
deactivation. Since the hydrodesulfurization reaction is
exothermic, it is important to quench the reactor to maintain a
reaction temperature as low as the small catalyst size of this
invention permits to obtain the desired degree of desulfurization
in order to inhibit catalyst deactivation. Unnecessarily high
temperatures by encouraging catalyst deactivation will result in
loss of the initial temperature advantage of the catalyst of this
invention. Quenching is advantageously accomplished by dividing the
total catalyst bed into a plurality of relatively small beds in
series and injecting relatively cool hydrogen between the beds, as
demonstrated below. It is seen that there is a high degree of
interdependence between the use of a high metals content asphaltene
charge, the small size catalyst particles of this invention, and
the use of a quench to insure that the reactor remains at a
temperature as low as the catalyst size permits.
The hydrodesulfurization process of this invention employs
.[.conventional reaction conditions such as, for example,.]. a
hydrogen partial pressure of 1000 to 5000 pounds per square inch,
generally, 1000 to 3000 pounds per square inch, preferably, and
1500 to 2500 pounds per square inch most preferably. Reactor design
limitations usually restrict inlet pressures under the conditions
of the present invention to not more than 2000, 2500, or 3000
p.s.i.g. It is the partial pressure of hydrogen rather than total
reactor which determines hydrodesulfurization activity. Therefore,
the hydrogen stream should be as free of other gases as possible.
Furthermore, since reactor design limitations restrict hydrogen
inlet pressures, hydrogen pressure drop in the reactor should be
held as low as possible.
The gas circulation rate can be between about 2000 and 20,000
standard cubic feet per barrel, generally, or preferably about 3000
to 10,000 standard cubic feet per barrel of gas preferably
containing 85 percent or more of hydrogen. The mol ratio of
hydrogen to oil can be between about 8:1 and 80:1. Reactor
temperatures can range between about 650.degree. and 900.degree.
F., generally, and between about 680.degree. and 800.degree. F.,
preferably. The temperature should be low enough so that not more
than about 10, 15 or 20 percent of the charge will be cracked to
furnace oil or lighter. At temperatures approaching 800.degree. F.
the steel of the reactor walls rapidly loses strength and unless
reactor wall thicknesses of 7 to 10 inches or more are utilized a
temperature of about 800.degree. F. constitutes a metallurgical
limitation. The liquid hourly space velocity in each reactor of
this invention can be between about 0.2 and 10, generally, between
about 0.3 and 1 or 1.25, preferably, or between about 0.5 and 0.6
most preferably.
The catalyst employed in the process is conventional and comprises
sulfided Group VI and Group VIII metals on a support such as
nickel-cobalt-molybdenum or cobalt-molybdenum on alumina.
Hydrodesulfurization catalyst compositions suitable for use in the
present invention are described in U.S. Pat. No. 2,880,171 and also
in U.S. Pat. No. 3,383,301. However, an essential feature of the
catalyst particles of the present invention is that the smallest
diameter of these particles is considerably smaller than the
diameter of hydrodesulfurization catalyst particles of the prior
art. The smallest diameter of the catalyst particles of the present
invention is broadly between about 1/20 and 1/40 inch,
preferentially between 1/25 and 1/36 inch, and most preferably
between about 1/29 and 1/34 inch. Particle sizes below the range of
this invention would induce a pressure drop which is too great to
make them practical. The catalyst can be prepared so that nearly
all or at least about 92 or 96 percent of the particles are within
the range of this invention. The catalyst can be in any suitable
configuration in which the smallest particle diameter is within the
range of the present invention such as roughly cubical,
needle-shaped or round granules, spheres, cylindrically-shaped
extrudates, etc. By smallest particle diameter we mean the smallest
surface to surface dimension through the center or axis of the
catalyst particle, regardless of the shape of the particle. The
cylindrical extrudate form having a length between about 1/10 and
1/4 inch is highly suitable.
Since the asphaltene molecules which are hydrodesulfurized in
accordance with the present invention are large molecules and must
enter and leave the pores of the catalyst without plugging the
pores, in order to obtain good aging properties most of the pore
volume of the catalyst of this invention should be in pores above
50 A. in size. Advantageously 60 to 75 percent or more of the pore
volume should be in pores of 50 A. or more. Most preferably, 80 to
85 percent or more of the pore volume should be in pores above 50
A. in size. Catalysts having smaller size pores have good initial
activity but poor aging characteristics due to gradual plugging of
the pores by the asphaltene molecules. For example, catalyst A
below exhibited good activity in the process of this invention for
about one month while catalyst B below exhibited good activity for
about three months.
______________________________________ Catalyst A, Catalyst B,
percent of percent of pore volume pore volume
______________________________________ Pore size, A.: 200-300 1.2
2.3 100-200 4.2 41.7 50-100 16.2 43.3 Total 21.7 87.3 40-50 16.4
6.4 30-40 22.6 5.6 20-30 26.6 1.0 7-20 12.5 0.0
______________________________________
As indicated above, as the diameter of conventional
hydrodesulfurization catalyst particles progressively decreases
within a range which is above the range of the present invention,
hydrosulfurization of a crude oil to a one percent sulfur level
proceeds at progressively lower temperatures. However, the
following tests show that the diminishing of catalyst diameter size
to a level within the range of the present invention results in an
unexpectedly great reduction in hydrodesulfurization temperature
which is much greater than indicated by the particle
diameter-temperature relationship exhibited by larger size
particles. However, counteracting this temperature advantage is the
fact that the small catalyst particle diameters of the present
invention result in a large pressure drop through a catalyst bed
comprising them, and this pressure drop tends to nullify the
temperature advantage achievable with the catalyst of the present
invention because hydrodesulfurization temperature requirements
increase as hydrogen partial pressures decrease.
Although it is expected that reduction in catalyst particle size
will increase pressure drop, we have found that under
desulfurization conditions the increase in pressure drop occasioned
by using a bed of catalyst particles of the size of this invention
as compared to a bed of catalyst particles only slightly larger
than those of this invention is great within reactors having
moderate diameters. As shown in FIG. 2 the increase in pressure
drop occasioned by utilizing the catalyst size of the present
invention as compared to slightly higher catalyst sizes can be
greatly moderated by utilizing a reactor having a very high
diameter such as 10 or 11 feet or more. However, high pressure
reactors having large diameters require extremely thick walls,
especially under the elevated temperature conditions of the present
process.
As indicated above, in the temperature vicinity of 800.degree. F.
which is required for hydrodesulfurization of crude oil or reduced
crude oil a considerable metallurgical weakening occurs in the
steel reactor walls. In order to guard against reactor failures at
the 2000 or 2500 + pounds per square inch operating pressures of
the process extremely thick steel walls are required, for example,
a thickness of 8, 10 and 12 inches. At the reaction temperatures of
this invention the required reactor wall thickness increases
appreciably with relatively small increases in reactor inlet
pressure. Furthermore, at any temperature or pressure of this
invention the wall thickness required also increases with reactor
diameter. Therefore the excessive increase in reactor wall
thickness which is required upon any increase in reactor diameter
or reactor temperature exerts a practical design limitation upon
maximum allowable pressure in a reactor of the present
invention.
The existence of a maximum pressure limitation tends to be
prohibitive to the use of a hydrosdesulfurization catalyst having a
small diameter because a bed comprising such a small catalyst
induces a very high pressure drop, diminishing still further the
average pressure within the reactor, and the magnitude of this
pressure drop is closely related to reactor diameter. For example,
FIG. 2 shows that the pressure drop curves for 1/12 inch, 1/16 inch
and 1/32 inch catalyst beds are roughly parallel at reactor
diameters of 11 feet or greater. However, the pressure drop curve
for the 1/32 inch catalyst of this invention is much steeper at
reactor diameters less than 11 feet than the pressure drop curves
for the 1/12 inch and 1/16 inch catalyst. Therefore, for a catalyst
of the present invention the diameter of the reactor within the
range of conventional reactor sizes has an important effect upon
pressure drop.
Since there is a practical limit on reactor inlet pressure, as
explained above, due to reactor wall thickness requirements, it is
important to hold pressure drop in the reactor as low as possible.
In effect there is a pressure squeeze in the system in that inlet
hydrogen pressure should be held down while reactor outlet pressure
should be as high as possible. Therefore, in reactors having an
inlet pressure limitation of about 2000, 2500 or 3000 p.s.i.g., the
diameter to depth ratio of the catalyst bed should be high enough
to reduce pressure drop so that the reactor outlet pressure is not
more than about 150, 250 or 350 p.s.i.g. lower than the inlet
pressure. Control of reactor pressure differential with a high
diameter to depth ratio catalyst bed is especially important in
single reactor systems capable of accepting only relatively low
inlet pressures. The diameter to depth ratio becomes less important
in reactors which can accept relatively high inlet pressures or in
parallel reactor systems wherein pressure drop can be reduced by
diverting a portion of reactant flow to another reactor.
There is an additional problem relating to pressure drop arising
when utilizing the very small catalyst particles of this invention
that is alleviated considerably by utilizing a large diameter
reactor or parallel reactors. When catalyst particles have the very
small size within the range of this invention, reactant flow
through them causes them to shift and scrape against each other in
a process of compaction. Scraping of particles against one another
result in production of fines which further increases pressure
drop. Since a catalyst bed may be in continuous operation for long
periods of time, production of fines can be considerable. The use
of a large diameter reactor or a parallel reactor system, by
permitting a greater catalyst cross-section per volume of reactor
flow, inhibits fines formation and thereby inhibits an increasing
pressure drop across the catalyst field due to this cause.
In accordance with the present invention a hydrodesulfurization
catalyst whose diameter is between 1/20 and 1/40 inch which
provides an unexpected and substantial temperature advantage due to
its size is advantageously divided into separate beds arranged in
series to form a reactor train with each succeeding bed in series
containing a greater quantity of catalyst than its preceding bed.
The total liquid charge stream comprising crude oil or reduced
crude oil together with a portion of total hydrogen requirements is
charged to the reactor inlet. An effluent stream comprising
desulfurized liquid together with gases is withdrawn from the
reactor and cooled. Liquid and gases are separated from each other
in the cooled effluent stream. Impurities are removed from said
effluent gases to provide a recycle hydrogen stream having an
increased proportion of hydrogen. The recycle hydrogen is recycled
to a plurality of positions in series in the reactor train between
the separate catalyst beds therein.
The apportioning of the recycle hydrogen so that it is injected
between the separate catalyst beds permits it to serve as a quench
to cool the flowing stream as it passes between catalyst beds,
thereby permitting reaction temperature to remain near the low
temperature level permitted by the small catalyst size. In the
absence of a hydrogen quench as described the temperature increase
of reactants across each bed would become cumulative so that
neither deep beds nor a number of beds in series could be used.
Temperatures even slightly higher than necessary are detrimental
because, as shown in FIG. 4, moderate temperature elevations
considerably enhance thermal cracking of liquid producing among
other products light hydrocarbon gases which dilute the hydrogen
stream and reduce the partial pressure of hydrogen therein.
The hydrogen quench by reducing the actual temperature also reduces
the required temperature and therefore cooperates interdependently
with the small catalyst particles of this invention. By lowering
the temperature, the hydrogen quench reduces cracking which would
consume hydrogen and produce light hydrocarbon gases leading to a
lower hydrogen concentration, which in turn would reduce the
hydrogen partial pressure and increase the required reaction
temperature.
As shown in FIG. 2, at reactor diameters below about 11 feet, the
pressure drop through the 1/32 inch catalyst bed of the present
invention increases extremely rapidly with reduction in reaction
diameter at the indicated space velocity. However, in the diameter
range shown the pressure drops through a 1/16 inch catalyst bed and
a 1/12 inch catalyst bed, which are both above the range of this
invention, are not nearly as sensitive to reduction in reactor
diameter below 11 feet. FIG. 2 also shows that at reactor diameters
above 11 feet the pressure drop through a 1/32 inch catalyst bed is
not significantly more sensitive to changes in reactor diameter
than are the pressure drops through the 1/12 inch and 1/16 inch
catalyst beds. Therefore, there is a much more sensitive pressure
drop relationship between a 1/32 inch catalyst bed of this
invention at the reactor diameters shown in FIG. 2 than there is
with beds of larger size catalyst particles. However, at the high
temperature and pressure conditions of the hydrodesulfurization
process of this invention metallurgical requirements require
reactor walls of great thickness at reactor diameters of 11 feet or
more, reactor wall thickness requirements increasing with
increasing reactor diameter so that economic considerations
prohibit reactor diameters much larger than 11 feet in the process
of this invention. FIG. 2 clearly indicates that at the indicated
space velocity and with the reactor diameters shown an importance
regarding pressure drop sensitivity arises when employing a 1/32
inch catalyst bed which is far greater than in the case of the 1/12
inch and 1/16 inch catalyst bed.
All of the tests indicated in FIG. 2 for the various catalyst sizes
were made at the same liquid hourly space velocity. Therefore, in
the tests within a reactor of relatively large diameter, the
catalyst bed depth was relatively shallow. In the tests within a
reactor of relatively small diameter, the catalyst bed was
deeper.
EXAMPLE 1
A series of tests were conducted to illustrate the temperature
advantage of a small particle size catalyst of the present
invention. These tests were conducted by employing NiCoMo on
alumina catalyst of various sizes for hydrodesulfurizing a 36
percent Kuwait reduced crude from which furnace oil having an
800.degree. F. TBP had been removed at a 2000 p.s.i.a. partial
pressure of hydrogen and a space velocity of 3.0 liquid volumes per
hour per volume of catalyst. The charge was 78 percent desulfurized
to a 1.0 percent product sulfur content. The arrangement of the
reactor was such that there was no significant or readily
detectable pressure drop in any of the tests. FIG. 1 shows the
effect of catalyst size upon the initial temperature required to
produce a product containing 1 percent sulfur. The solid line is
based upon initial temperatures determined in tests with 1/8 inch
and 1/16 inch diameter extrudate catalyst whose particle size is
above the range of this invention. The dashed extrapolation of the
solid line indicates that a 1/32 inch diameter extrudate catalyst
would be expected to require an initial temperature of about
775.degree. F. However, FIG. 1 surprisingly shows that the 1/32
inch diameter extrudate catalyst requires an initial temperature of
only 750.degree. F. It is noted that the surface area defined by
the pores of all three catalysts tested is about the same. The
position of the data point for the 1/32 inch catalyst is highly
surprising because if the dashed line in FIG. 1 were curved
downwardly towards the 1/32 inch catalyst data point the resulting
curve would tend to indicate that as catalyst particle size becomes
very small the activity of the catalyst becomes unlimited, which is
obviously unreasonable. Therefore, the straight configuration of
the dashed extension of the curve in FIG. 1 is a reasonable
extrapolation of the solid line and the position of the 1/32 inch
data point is highly unexpected.
EXAMPLE 2
When catalyst similar to the 1/32 inch catalyst of Example 1 except
that the particle size is smaller within the range of this
invention, such as 1/34 or 1/40 inch, or except that the particle
size is larger within the range of this invention, such as 1/29 or
1/20 inch, are utilized under the conditions of Example 1, the
initial temperature in each instance to achieve
hydrodesulfurization to one percent sulfur is at about the same
level as that shown in FIG. 1 for the 1/32 inch catalyst.
EXAMPLE 3
When catalyst compositions other than NiCoMo on alumina, such as
NiCoMo on silica alumina, CoMo on alumina, NiW on alumina, NiW on
silica alumina, NiW on silica magnesia or NiMo on alumina having a
particle size within the range of this invention are utilized under
the conditions of Example 1 to achieve hydrodesulfurization to one
percent sulfur, a similar unexpected temperature advantage is
realized as compared to the extrapolated temperature based on
larger size particles of the same composition.
EXAMPLE 4
Tests were made which demonstrate that a 1/32 inch
nickel-cobalt-molybdenum on alumina extrudate is not only capable
of hydrodesulfurizing a reduced crude oil to a one percent sulfur
level at a considerably lower initial temperature than a similar
catalyst in the form of a 1/16 inch extrudate but also is capable
of maintaining a lower hydrodesulfurization temperature with age.
The tests with the 1/32 inch catalyst were based on a 0.55 liquid
hourly space velocity and a hydrogen partial pressure of 1830
pounds per square inch. The reactor pressure drop was about 50
pounds per square inch. The charge was a 50 percent Kuwait reduced
crude. The reaction was performed in a single reactor having three
separate beds and recycle hydrogen gas was used as a quench after
each bed. There was no separate guard chamber before the reactor.
The first, second and third beds contained 13.3 percent, 41.6
percent and 45.1 percent of the total catalyst, respectively.
Typical data for the test utilizing the 1/32 inch catalyst are
shown below and the general data is illustrated in FIGS. 5 and 6.
FIG. 5 shows the aging characteristics for the entire 1/32 inch
catalyst reactor as compared with a comparable aging run with a
1/16 inch catalyst reactor. FIG. 6 shows the aging characteristics
for the individual beds within the 1/32 inch reactor and shows that
when the first bed becomes deactivated the second bed assumes a
greater desulfurization load.
The test utilizing the 1/16 inch nickel-cobalt-molybdenum on
alumina catalyst was performed as a 1.1 liquid hourly space
velocity, but is illustrated in FIG. 5 on a basis comparable to the
0.55 space velocity of the test made with the 1/32 inch catalyst.
The total pressure for the 1/16 inch catalyst test was 2500 pounds
per square inch gauge. 5000 s.c.f./bbl. of gas was charged to the
reactor. The reactor contained four catalyst beds and recycle gas
was used as a quench after each bed. The average reactor
temperature was increased throughout the test to maintain a 1.0
percent by weight sulfur level in the 660.degree. F. + residual
product. Typical data for both the 1/32 inch and the 1/16 inch
catalyst tests are shown below.
______________________________________ 1/32 inch 1/16 inch catalyst
catalyst ______________________________________ Oil charge (.sup.1)
(.sup.1) Catalyst (.sup.2) (.sup.3) Volume, cc. 2,294 2,254 Weight,
grams 1,543.0 1,768.0 Age, days this measurement 97.6 87.6 Total
throughput volume oil per volume catalyst 1,203 2,323 Operating
conditions Reactor hcd temp., .degree. F.(inlet, outlet) 694,716
Reactor pressure 2,050 2,619 Average reactor temp., .degree. F. 703
781 Space velocity: Vol./hr./vol. 0.51 1.11 Wt./hr./wt. 0.78 1.36
Reactor gas charge: S.c.f./bbl. 4,385 4,920 Percent H.sub.2 91 81
Makeup gas: S.c.f./bbl. 890 735 Percent H.sub.2 93 95 Recycle gas:
S.c.f./bbl. 3,495 4,233 Percent H.sub.2 89 80 Product yields, wt.
percent: Bottoms (660.degree. F. + ) 91.1 81.7 Furnace oil (380
660.degree. F.) 4.9 9.1 Naphtha (IBP. 380.degree. F.) 0.8 2.2 Gas
5.1 6.1 Chemical hydrogen consumption, s.c.f./bbl. 476 617 Hydrogen
sulfide, s.c.f./bbl. 139 127 ______________________________________
(.sup.1) Kuwait 50 percent reduced crude. (.sup.2) 1/32 Inch
diameter NiCoMo on alumina extrudates having 0.5 wt. percent
nickel, 1.0 wt. percent cobalt and 8.0 wt. percent molybdenum, a
surface area of 200 m 2/g and a pore volume of 0.5 cc./g. (.sup.3)
1/16 Inch diameter NiCoMo on alumina extrudates.
The charge and product inspections for the test employing the 1/32
inch catalyst are as follows:
______________________________________ Product Change bottoms
______________________________________ Gravity, .degree. API 11.6
20.1 Sulfur, percent by wt. 4.07 1.03 Nitrogen, percent by wt. 0.22
0.17 Carbon residue, percent by wt. 8.59 4.97 Nickel, p.p.m. 16 5.1
Vanadium, p.p.m. 55 9.3 Heat of comb. B.t.u./lb 18,360 19,091
Distillation, vacuum, .degree. F.: At 10% 715 716 At 30% 809 807 At
50% 918 At 60% 942 ______________________________________ Note:
Charge, cracking at 995.degree. F.
The 660.degree. F. + residual oil product inspections for the 1/16
inch catalyst test are as follows:
______________________________________ Gravity, .degree. API 21.4
Sulfur, percent 1.08 Nitrogen, percent 0.17 Pour point, D97,
.degree. F. 65 Viscosity, kin. D445,cs.: 122.degree. F. 104.9
210.degree. F. 16.36 Carbon residue, Rams. D524, percent by wt.
4.86 Vanadium, p.p.m. 14 Nickel, p.p.m. 6.8 Flash point, D93,
.degree. F. 390 Distillation vacuum, D1160, .degree. F.: At 10% 719
At 30% 788 At 50% 874 At 70% 1010 At 90% --
______________________________________
EXAMPLE 5
Tests were made to show the effect of temperature upon liquid yield
in a hydroesulfurization process. The tests were made in a pilot
plant equipped with a four-bed 2254 cc. adiabatic reactor. Reactor
charge gas was used as quench between the catalyst beds for
temperature control. The charge stock passed through a cotton fiber
cartridge filter before it was preheated and charged to the
reactor. The filter which was at steam tracing temperature takes
out most of any solid contaminants in the feed, but does very
little in removing any small or organically combined metals present
in the charge stock.
The reactor effluent flowed into a high pressure separator where
hydrogen-rich gas was separated from the hydrocarbon liquid. The
hydrogen-rich gas was scrubbed with 3 percent to 5 percent
diethanolamine and water and recycled to the reactor. After high
pressure separation of high pressure hydrogen-containing gas, the
liquid product flowed to distillation towers where gases, naphtha,
furnace oil, and residual were removed from the unit.
The charge to the unit was a 50 percent Kuwait reduced crude. The
operation was designed to produce a 660.degree. F. + product having
a 1.0 percent sulfur level. The catalyst was 1/16 inch extruded
NiCoMo on alumina. The operating conditions were 2500 pounds per
square inch gauge total pressure, 1.1 liquid hourly space velocity
and 5000 s.c.f/bbl. of 80 percent hydrogen with recycle gas quench
as required for temperature control. The results of the tests are
illustrated in FIG. 4 and in the following data.
______________________________________ Catalyst: NiCoMo on alumina
having 0.97 wt. per- cent cobalt, 8.6 wt. percent molybdenum and
0.59 wt. percent nickel. Age: Days at this measurement 45.9
Bbl./lb. 4.43 Space velocity, LHSV 1.1 Average reactor temp.,
.degree. F. 760 Reactor gas: Inlet S.c.f./bbl. 5008 Percent H.sub.2
82 Quench S.c.f./bbl. 2920 Percent H.sub.2 82 Reactor pressure,
p.s.i.g. 2500 Hydrogen consumption, s.c.f./bbl. 623 Product yields:
Percent by weight ______________________________________ H.sub.2 S
3.4 C.sub.1 0.2 C.sub.2 0.1 C.sub.3 0.2 C.sub.4 0.2 C.sub.5
-380.degree. F. 1.5 380-460.degree. F. 1.4 460-600.degree. F. 2.8
600-660.degree. F. 2.5 660.degree. F. + 88.6
______________________________________
EXAMPLE 6
Tests were conducted to illustrate the effect of a change in
hydrogen partial pressure upon the temperature required to
hydroesulfurize a reduced crude to 1 percent sulfur in the residual
product. The comparative tests were performed by, in one case, not
recycling hydrogen containing light hydrocarbons which build up in
the hydrogen stream and reduce the partial pressure of the hydrogen
in the stream but instead charging to the hydrodesulfurizer only
fresh hydrogen charge having a uniform hydrogen purity. In the
other case, a recycle hydrogen stream which was not subjected to
naphtha scrubbing to remove light hydrocarbons so that the hydrogen
partial pressure therein continually decreased throughout the test
was recycled to the hydrodesulfurizer. The reactor system catalyst
and operating conditions for both tests are generally the same as
that described in the tests of Example 4. The results are
illustrated in FIG. 3. The solid line in FIG. 3 represents the test
utilizing only fresh hydrogen at 1830-1850 pounds per square inch
of hydrogen pressure. The broken line in FIG. 3 represents the
tests wherein non-naphtha scrubbed recycle gas is recycled causing
hydrogen partial pressure to continually decrease so that at the
last data point shown the hydrogen partial pressure was 1720-1740
pounds per square inch. The following data are representative of
the test represented by the broken line.
______________________________________ Oil charge 50 percent Kuwait
re- duced crude. Catalyst 1/32 inch NiCoMo on alumina. Volume, cc.
2296. Weight, grams 1771. Age, days at time of this measurement
7.2. Throughput, vol. oil per vol. cat. 96. Reactor bed temp.,
.degree. F. (inlet, outlet) 668. 690. Operating conditions: Reactor
pressure, p.s.i.g. 2058. Avg. reactor temp., .degree. F. 676. Space
velocity Vol./hr./vol. 0.53. Wt./hr./wt. 0.66. Reactor gas charge
S.c.f./bbl. 4462. Percent H.sub.2 88. Makeup gas S.c.f./bbl. 587.
Percent H.sub.2 94. Recycle gas S.c.f./bbl. 3874. Percent H.sub.2
85. Product yields, wt. percent: Stripper bottoms 92.5. Furnace oil
4.7. Naphtha 0.6. Gas 3.7. Net hydrogen sulfide, s.c.f./ bbl. 108.
______________________________________
______________________________________ Product Charge stripper oil
bottoms ______________________________________ Gravity, .degree.
API. 15.7 20.6 Viscosity, SUS D2161: 100.degree. F. 4.906 2.181
210.degree. F. 171.8 114.8 Carbon, wt. percent 84.52 85.52
Hydrogen, wt. percent 11.43 11.68 Nitrogen, wt. percent 0.20 0.17
Sulfur, wt. percent 4.06 1.11 Carbon residue, wt. percent 8.16 5.12
Nickel, p.p.m. 16 4.7 Vanadium, p.p.m. .54 6.1 Heat of combustion,
b.t.u./lb. 18,423 19,908 Distillation, vacuum, .degree. F.: At 5%
608 654 At 10% 674 692 At 20% 762 760 At 30% 829 807 At 40% 866 At
50% 925 At 60% 992 ______________________________________ Note:
Charge oil, cracking at 888.degree. F. Product stripper bottoms,
cracking at 1.011.degree. F.
The above data state that the space velocity is 0.53 vol./hr./vol.
so that after 10 days (240 hours) the throughput is 0.53.times. 240
or 127 vol./vol. FIG. 3 shows that at the 10 day data point the bed
outlet temperature is higher for the decreasing hydrogen pressure
test as compared to the constant hydrogen pressure test.
EXAMPLE 7
Simulation experiments were conducted to show the effect of
catalyst particle size on pressure drop in hydrodesulfurization
process in reactors of various diameters. All tests were made with
the same liquid hourly space velocity in a single bed reactor,
charging a 75 percent reduced Kuwait crude, using recycle hydrogen
and maintaining a hydrogen purity of 77 percent, using reactor
inlet and outlet temperatures of 780.degree. and 815.degree. F.,
respectively, a reactor inlet pressure of 2500 p.s.i.g., and a 1.0
liquid hourly space velocity. Three series of tests were made
utilizing reactors of various diameters with 1/12 inch, 1/16 inch
and 1/32 inch NiCoMo on alumina catalyst particles. The results are
illustrated in FIG. 2.
The following description of the process of this invention is made
in reference to FIG. 7. FIG. 7 itself indicates suitable
temperature and pressure conditions at various points in the
process, and these indicated conditions are not reiterated in the
following description.
Referring to FIG. 7, a full crude or a reduced crude, such as a 50
percent reduced Kuwait crude which contains the entire asphaltene
content of the full crude and therefore also contains substantially
all of the nickel, vanadium and sulfur content of the full crude,
is charged to the process through line 10 and is pumped by pump 12
through line 14, preheater 16, line 18, solids filter 20 and line
22 to drum 24. From drum 24 the liquid oil charge is passed through
line 26 to feed pump 30.
Liquid from pump 30 is admixed with hydrogen from line 52 and
passed through line 32, valve 34, preheater 36, line 38 and furnace
40. Liquid flow valve 34 is disposed in a nonfully preheated liquid
hydrocarbon line but no valves are utilized in any fully preheated
liquid hydrocarbon lines because at the reaction temperatures of
this invention if any hydrocarbon should descend into any
indentation or crevice of a valve and become stagnant therein for
even a brief period of time without full exposure to hydrogen,
coking would occur and render the valve inoperative. Therefore,
there is no other valve in any liquid line in the vicinity of the
reactor until the hot reactor liquid has been cooled downstream
from the reactor, as will be shown subsequently.
A mixture of fresh and recycle hydrogen is introduced into the
liquid charge to the reactor prior to preheating thereof. Recycle
hydrogen is admitted to the liquid charge through line 42 and valve
44. Makeup hydrogen is charged through line 46, compressor 48 and
valve 50. A mixture of fresh and recycle hydrogen is introduced to
the relatively cool liquid charge through line 52.
The preheated mixture of liquid charge and hydrogen is charged
through line 54 to guard reactor 56 containing a bed of catalyst
58. An effluent stream from the guard reactor is charged to main
reactor 60 containing catalyst beds 62, 64, and 66. The catalyst
beds each contain NiCoMo on alumina catalyst as 1/32 inch
extrudates which have the following typical specifications:
Surface area--150 meters.sup.2 /gram
Pore volume in 50-300 A. radius--60% to 90% of total pore
volume
Pore volume--0.5 to 0.8 cc./gram
Compacted density--0.45 to 0.65 gram/cc.
Specific volume of pores--30-40 cc./100 cc.
Each succeeding catalyst bed has a larger volume than the bed just
prior to it. If desired there can be four, five, six or more
catalyst beds in the reactor. Also, if desired, each reactor bed
can have 25 percent, 50 percent, 100 percent, or more, catalyst
than the bed just prior to it.
If desired, guard chamber 56 can be omitted in which case line 54
will lead directly into the reactor.
The effluent from the guard reactor is charged through line 68 to
which a temperature quenching hydrogen stream is charged through
line 70 and valve 72 so that a quenched hydrocarbon and hydrogen
stream is charged to the top of the reactor through line 74. The
reaction stream is passed through catalyst bed 62 and due to the
exothermic nature of the hydrodesulfurization reaction it is heated
in passage therethrough and is quenched by recycle hydrogen
entering through line 76, valve 78, and sparger 80. The cooled
reaction stream is then passed through catalyst bed 64 wherein it
increases in temperature so that it is then cooled by a quenching
hydrogen stream entering through line 82, valve 84 and sparger 86.
Temperatures between the various catalyst beds are controlled by
regulating the valves in the various hydrogen quench lines to
apportion hydrogen recycle flow. Finally, the reaction mixture
passes through catalyst bed 66 and then leaves the reactor in a
desulfurized condition through line 88. The reactor effluent stream
then gives up some heat at charge preheater 36 and passes through
line 90 to air cooler 92 where the effluent is sufficiently cooled
so that the valve 94 can be utilized. Because it is disposed after
the air cooler, valve 94 is the first valve in a liquid-containing
line downstream from the reactor which can be employed without the
danger of coking therein rendering the valve inoperative. Reactor
effluent enters flash chamber 96 whence desulfurized liquid is
discharged through line 98 to a distillation column 102. A gaseous
stream comprising primarily hydrogen together with ammonia and
hydrogen sulfide formed by nitrogen and sulfur removal from the
charge and light hydrocarbons formed by thermal hydrocracking of
some of the charge is discharged from flash chamber 96 through line
99.
The gaseous effluent stream passes through unit 106 to which water
is added through line 108 and from which aqueous ammonia is removed
through line 110. The gaseous effluent from unit 106 is passed
through line 112 to light hydrocarbon wash unit 114 to which
naphtha from distillation column 102 is pumped in order to wash
light hydrocarbons from the hydrogen stream. The wash naphtha is
removed through line 116 and passed to flash chamber 118 where some
of the dissolved hydrocarbons are flashed off through line 120.
Then the naphtha is passed through line 122, heater 124 and hot
naphtha flash chamber 126 from which additional light hydrocarbons
are flashed through line 128. The regenerated naphtha is recycled
through line 130 with makeup naphtha entering through line 132.
The hydrogen stream is then passed through line 134 to hydrogen
sulfide removal unit 136 to which an amine such as monoethanolamine
is added through line 138. Hydrogen sulfide-rich amine is removed
through line 140 and passed to amine regenerator 142 from which
hydrogen sulfide is discharged through line 144 and recycle amine
exits through line 146. Makeup amine is charged through line 148. A
recycle hydrogen stream is then returned to the reactor through
line 150.
It is important to remove a substantial amount of the ammonia,
hydrogen sulfide and light hydrocarbons from the hydrogen stream
prior to recycle because these gases reduce the partial pressure of
hydrogen in the reactor. It is the partial pressure of hydrogen
rather than the total pressure in the reactor which affects
hydrodesulfurization activity. It is not possible to arbitrarily
increase total hydrogen pressure in the reactor to compensate for a
low hydrogen partial pressure because of severe design pressure
limitations in the reactor, as explained above. The recycle
hydrogen passes through compressor 154 for increasing the pressure
of the hydrogen stream to the reactor.
Hydrodesulfurized residual oil is removed from distillation column
102 through line 156 and is used to supply heat to inlet crude oil
heat exchanger 16 prior to its discharge from the system through
line 158. Hydrodesulfurized furnace oil is removed from the
distillation column through line 160 while naphtha product is
removed from the system through line 162.
FIG. 8 is a cutaway segment of a multibed reactor in which the
lower two catalyst beds are shown. FIG. 8 shows that a bed of the
small size catalyst of the present invention is prepared in a
manner to secure the particles from excessive relative movement and
to prevent the particles from producing fines and plugging screens,
both of which conditions would greatly increase the pressure drop
in the reactor and tend to further nullify the temperature
advantage of the small size catalyst particles.
FIG. 8 shows a steel reactor wall 1000 which may be 7 to 10 inches
thick. One bed of catalyst lies above hydrogen quench line 1002 and
another catalyst bed lies below this line, each bed filling the
entire cross-section of the reactor. The greatest volume of the
upper bed comprises 1/32 inch catalyst bed 1004 which rests upon a
smaller bed of 1/12 inch catalyst 1005 and 1/4 inch aluminum balls
1006 which in turn rests upon a bed of 1/2 inch aluminum balls
1008. Beds 1005, 1006 and 1008 prevent the 1/32 inch catalyst
particles from surrounding and plugging the sparger openings of
hydrogen quench line 1002. Above catalyst bed 1004 is a bed 1010 of
1/4 inch aluminum balls and a bed 1012 of 1/2 inch aluminum balls.
These latter two beds contribute stabilizing weight to the 1/32
inch catalyst bed to prevent shifting of particles therein during
the flow of reactants, which shifting would tend to cause catalyst
disintegration and fines formation and thereby greatly enhance
pressure drop through the 1/32 inch bed.
The lower bed of catalyst rests upon screen 1014. Screen 1014 is
protected from plugging by 1/32 inch catalyst bed 1016 by a gradual
increase in particle size between it and the 1/32 inch catalyst bed
as indicated by 1/12 inch catalyst bed 1018, 1/4 inch aluminum
balls bed 1020 and 1/2 inch aluminum balls bed 1022. Proper
distribution of hydrogen and liquid reactant as they approach lower
catalyst bed 1016 is insured by bed 1024 of 1/4 inch aluminum balls
and bed 1026 of 1/2 inch aluminum balls.
FIG. 8 shows that an elaborate arrangement is required in preparing
a catalyst bed of the present invention in order that nearly all
the pressure drop through the bed can be confined to the 1/32 inch
catalyst beds themselves with very little pressure drop at
retaining screens and with a minimum of pressure increase occurring
due to fines formation during the reaction.
* * * * *