U.S. patent application number 10/310470 was filed with the patent office on 2003-05-08 for extension of catalyst cycle length in residuum desulfurization processes.
Invention is credited to Chabot, Julie.
Application Number | 20030085155 10/310470 |
Document ID | / |
Family ID | 26924424 |
Filed Date | 2003-05-08 |
United States Patent
Application |
20030085155 |
Kind Code |
A1 |
Chabot, Julie |
May 8, 2003 |
Extension of catalyst cycle length in residuum desulfurization
processes
Abstract
Solvent injection in amounts no greater than 2 wt % can
favorably alter the way heavy metals, such as vanadium, are
normally deposited in catalyst particles. Heavy metals may be
stored on the catalyst in a more compact form, saving catalyst pore
volume. Consequently catalyst cycle length is improved, since
capacity for deposition is increased. The instant invention has
also been demonstrated to control the rate of catalyst fouling by
deposition of coke, or microcarbon residue (MCR). In the past,
attempts to increase catalyst activity led to increased rates of
catalyst fouling and shorter catalyst life. In the instant
invention the rate of deposition of microcarbon residue is
decreased, resulting in slower fouling of pores and increased cycle
length.
Inventors: |
Chabot, Julie; (Novato,
CA) |
Correspondence
Address: |
Penny L. Prater
Chevron Corporation
P. O. Box 6006
San Ramon
CA
94583-0806
US
|
Family ID: |
26924424 |
Appl. No.: |
10/310470 |
Filed: |
December 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10310470 |
Dec 3, 2002 |
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09874202 |
Jun 5, 2001 |
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60230646 |
Sep 7, 2000 |
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Current U.S.
Class: |
208/213 ;
208/208R; 208/251R |
Current CPC
Class: |
C10G 45/04 20130101 |
Class at
Publication: |
208/213 ;
208/208.00R; 208/251.00R |
International
Class: |
C10G 045/00; C10G
045/60 |
Claims
What is claimed is:
1. A process for the extension of catalyst cycle length in the
hydrodesulfurization of feeds containing heavy metal contaminants,
said process occurring in one or more reaction zones, where the
feed is contacted with the hydrodesulfurization catalyst, whereby
no more than 2 wt % of a solvent is mixed with the feed prior to
its entry into the initial reaction zone or is subsequently added
to the initial reaction zone or a succeeding reaction zone.
2. The process of claim 1, wherein the solvent is a compound
comprising oxygen which is selected from the group consisting of
water, alcohol, either and other water precursors.
3. The process of claim 1, wherein a heavy metal contaminant is
nickel, vanadium, or a mixture of the two.
4. The process of claim 1, wherein no more than 1.5 wt % of a
solvent is mixed with the feed prior to its entry into the initial
reaction zone or is subsequently added to the initial reaction zone
or a succeeding reaction zone.
5. The process of claim 4, wherein no more than 0.75 wt % of a
solvent is mixed with the feed prior to its entry into the initial
reaction zone or is subsequently added to the initial reaction zone
or a succeeding reaction zone.
6. The process of claim 1, wherein the solvent is injected during
the first 200 hours of the operational cycle.
7. The process of claim 1, wherein the feed is selected from the
group consisting of crude oils, petroleum residua, tar sand
bitumen, shale oil, or liquefied coal or reclaimed oil.
8. The process of claim 7, whereby petroleum, residua is selected
from the group consisting of crude oil atmospheric distillation
column bottoms or vacuum distillation column bottoms.
9. The process of claim 8, crude oil atmospheric distillation
column bottoms. is selected from the group consisting of reduced
crude oil or atmospheric column residuum.
10. The process of claim 1, whereby at least one reaction zone is
designed for onstream catalyst regeneration.
11. The process of claim 1, whereby the operating conditions for
hydrodesulfurization processes include a reaction zone temperature
in the range from 600.degree. F. to 900.degree. F., a pressure in
the range of from 200 to 3000 psig, and a hydrogen feed rate of 500
to 15000 SCF per barrel of oil feed.
12. The process of claim 10, in which at least one catalyst in one
or more of the reaction zones is a macroporous catalyst suitable
for onstream catalyst regeneration.
Description
[0001] This application claims priority from U.S. Provisional
Application Serial No. 60/230,646, filed Sep. 7, 2000.
FIELD OF INVENTION
[0002] This invention is concerned with a process for the extension
of catalyst cycle length when employed in residuum
hydrodesulfurization processes.
BACKGROUND OF THE INVENTION
[0003] Catalyst poisoning has long been a problem in
hydrodesulfurization of residuum and heavy oils. These feeds often
contain organometallic compounds, such as nickel and vanadium.
These metallic impurities are thought to deposit on the surface and
in the pores of the hydrodesulfurization catalyst. Catalyst
poisoning has been known to decrease catalyst activity,
particularly if dissolved metals such as nickel and vanadium are
present in amounts greater than 10 to 20 ppm.
[0004] U.S. Pat. No. 5,215,955 (Threlkel) attempted to solve the
problem of fouling by the use of a catalyst having a minimum number
of macropores. Less than 2% of the pore volume of the catalyst of
Threlkel may possess a diameter greater than 1000.ANG.. This
catalyst contains Group VIB and Group VIII metals on a support
comprising alumina. At least 80% of the pore volume comprises pores
having a diameter between 110 and 190.ANG.. In addition to
increased activity, this catalyst was known to have increased life
and increased metals capacity. This solution did limit residuum
processing to the use of specific catalysts, however.
[0005] Other approaches have been used over the years to enhance
catalyst effectiveness in hydrodesulfurization processes, among
them "solvent injection." Though the concept of "solvent injection"
into residuum hydroprocessing units is not new, and has actually
been practiced commercially for many years in a number of units,
its impact on catalyst performance has actually been very poorly
understood. The most common solvent has always been water. If used
in large amounts, however, solvent injection could create
deleterious side effects.
[0006] U.S. Pat. No. 4,013,637 (Eberly, Jr.) discloses a
hydrodesulfurization process in which water is employed. The
effectiveness of the process is improved by injecting 1-32 volume
percent in the gas phase of the reaction zone. The feed however,
contains substantially no metals. The intent of the instant
invention employs water to enhance catalyst life when feeds
containing heavy metals are being desulfurized.
[0007] GB 1468160 and GB 1505886 are commonly owned and disclose
processes for catalytic hydrodesulfurization in the presence of
water vapor of oils containing vanadium and nickel, without
catalyst replenishment. These inventions possess specific
requirements concerning water vapor partial pressure and the ratio
between average pore diameter and average particle diameter for the
catalyst or catalyst combination employed. Another commonly owned
patent, GB 1525508, also discloses catalytic desulfurization
employing water, or another solvent, such as a lower alcohol or
other water precursor.
[0008] U.S. Pat. No. 4,052,295 (Pronk) discloses a process for
catalytic hydrodesulfurization of vanadium-containing heavy
hydrocarbon oils. Heavy hydrocarbon oil containing vanadium is
contacted at elevated temperature and pressure with hydrogen and
with a catalyst. The catalyst is loaded with nickel and/or cobalt
and with about 2.5 to 60 parts by weight of molybdenum and or
tungsten on a porous carrier such as alumina. No water vapor is
added until the average vanadium content of the catalyst has
increased during the contacting by at least 5 parts by weight per
100 parts by weight. Pronk states that the use of water vapor can
be used effectively toward the end of a desulfurization operation
which has been operated in the absence of added water vapor when
the temperature has been raised to the maximum allowable level and
operation under normal circumstances would have to be
terminated.
[0009] Pronk points out problems that arose in its invention with
the use of water vapor in hydrodesulfurization of heavy oils
containing vanadium or other heavy metals. The use of water vapor,
according to Pronk, requires extra energy to evaporate the
requisite quantity of water, resulting in a rise of costs
associated with desulfurization. Furthermore, Pronk found, in order
to ensure that the process be carried out at a constant total
pressure, the hydrogen partial pressure must be reduced if the
desulfurization is carried out in the presence of water vapor.
Reduction of the hydrogen partial pressure generally results in
lower catalyst activity. For these reasons water was added at a
certain stage in the process, but not initially. In the instant
invention it is preferable to add water early in the operational
cycle in order to maximize metals deposition. Metals are deposited
constantly throughout the cycle if water deposition begins
early.
[0010] U.S. Pat. No. 3,501,396 (Gatsis) discloses a process for the
desulfurization of petroleum crude oil, which comprises admixing
the crude oil with hydrogen and from 2 to 30 wt % water and
reacting the resultant mixture in contact with a catalytic
composite at desulfurizing conditions. The patent states that
utilization of water in these comparatively excessive amounts
appears to improve the hydrogen diffusion rate through the liquid
phase on the catalyst, being increased as a result of the reduced
viscosity and surface tension characteristics of the liquid phase.
The difficulty of supplying hydrogen to the active sites of the
catalyst is greatly reduced, and catalytic stability and increased.
There is no mention in U.S. Pat. No. 3,501,396 of extension of
catalyst life. Furthermore, the instant invention obtains its
benefits using no more than 2 wt % water.
[0011] U.S. Pat. No. 3,753,894 (Shoemaker et al.), discloses a
hydrodesulfurization process for processing a sulfur-containing
residuum feed, wherein water is injected between the several
catalyst beds of a multi-bed reactor to quench the products of the
reaction and simultaneously to suppress deactivation of the
catalyst, particularly as occurs during the initial period of a
production run. Water may be added in concentrations as high as 50
wt %. As these references demonstrate, it was commonly believed
that solvent injection induced slight benefits in catalyst
activity, particularly concerning sulfur or heavy metals removal
and to a lesser degree the removal of microcarbon residue.
Conditions, feeds, and catalysts useful in these inventions were
specifically limited, however. Often solvents such as water were
used in large amounts. Finding a process in which the optimal
amount of solvent could be used would reduce the need for process
modifications, simplify downstream processing, decrease operating
costs, and lessen hydrogen partial pressure penalties.
SUMMARY OF THE INVENTION
[0012] Catalyst fouling by heavy metals, such as vanadium, may be
inhibited by the injection of an effective amount of solvent during
the residuum hydrodesulfurization process or just prior to it.
Water injection aids in the control of the temperature increase
requirement over time. Water injection results in a more uniform
deposition of metals such as vanadium within the catalyst pellets,
thereby delaying the onset of pore mouth plugging.
[0013] The most preferred solvent is water. The process of the
instant invention has been found to operate effectively under a
wide variety of conditions and with a wide variety of feeds and
catalysts.
[0014] In the past as the references in the Background of the
Invention demonstrate, water in relatively large quantities was
added in order to increase catalyst activity. Recent findings have
shown that the most interesting aspect of solvent injection in
specific amounts is not actually its relatively minor impact on
catalyst activity, but its significant impact on catalyst cycle
length. Solvent injection in amounts no greater than 2 wt %,
results in a controlled temperature increase across the reactor,
and can favorably alter the way heavy metals, such as vanadium, are
normally deposited in catalyst particles. Heavy metals may be
stored on the catalyst in a more compact form, saving catalyst pore
volume. Consequently catalyst cycle length is improved, since
capacity for deposition is increased.
BRIEF DESCRIPTION OF THE FIGURES
[0015] FIG. 1 demonstrates the effect that the introduction of 2 wt
% water 200 hours into the operation cycle has on the temperature
increase requirement over time, as compared to an operation cycle
with no water injection. The normalized temperature of about
730.degree. F. levels out at approximately 800 hours on stream. The
normalized temperature is the temperature that would be required to
keep the sulfur concentration at 0.55 wt %. Product sulfur
concentration remains constant at 0.55 wt % until the end of the
operation cycle without temperature increase.
[0016] FIG. 2 illustrates the same operational cycles as shown in
FIG. 1. The concentration of vanadium in the product is lower at
lower operating temperatures in the case, in which 2 wt % water was
injected, while in the cycle in which no water was added vanadium
concentrations in the product were higher. This demonstrates that
more vanadium is remaining on the catalyst at the end of the run
and is better penetrating the catalyst.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Solvent injection, as depicted in the instant invention, is
useful in most residuum hydroprocessing applications experiencing
significant vanadium induced catalyst aging. Benefits are generally
most pronounced in applications with very high end of run vanadium
loading, severe processing conditions, and those using catalysts
with low surface to volume ratio. This would include catalysts used
in onstream catalyst replacement (OCR) processes and other large
extrudate catalysts.
[0018] Catalysts with low surface to volume ratio are generally
more sensitive to pore mouth plugging, since access to the pellet
interior (a significant portion of the overall catalyst volume and
surface area) is more restricted. OCR applications combine
utilization of large catalyst pellets, severe operating conditions
and high vanadium loading. The concept of solvent injection (the
preferred solvent is water, although oxygen-containing compounds
such as short chain alcohol, either or other water precursors may
also be used) is particularly well suited to OCR technology.
[0019] The minimal amount of water (no greater that 2 wt % in the
instant invention) necessary to trigger the beneficial chemical
reactions is injected into the OCR reactor. Minimizing the
injection of excess solvent to the OCR (or to a reactor in any
hydrodesulfurization process) is important to avoid significant
process modifications, simplify downstream processing, decrease
operating costs, lessen hydrogen partial pressure penalties and
minimize gas rate to maintain good flow conditions. The OCR process
is more completely disclosed in U.S. Pat. No. 5,076,908 (Stangeland
et al) which is hereby incorporated by reference. As illustrated in
the Examples below, highly effective results are obtained when a
solvent such as water is added early in the operating cycle.
Solvent may be added at any time during the operating cycle but
addition at the beginning of the cycle is preferable. The Examples
demonstrate addition of water in the first 200 hours of the
operational cycle.
[0020] Feeds suitable for use in the instant invention include
"heavy" hydrocarbon liquid streams, and particularly crude oils,
petroleum residua, tar sand bitumen, shale oil or liquefied coal or
reclaimed oil. Petroleum residua may be crude oil atmospheric
distillation column bottoms (reduced crude oil or atmospheric
column residuum), or vacuum distillation column bottoms (vacuum
residua).
[0021] These feed streams generally contain product contaminants,
such as sulfur, and/or nitrogen, metals, including heavy metals
such as vanadium and organo-metallic compounds possibly in
porphyrin or chelate-type structures. Residua typically contain
greater than 10 ppm metals. These contaminants tend to deactivate
catalyst particles during contact by the feed stream and hydrogen
under hydroprocessing conditions. This invention is particularly
effective with residuum feeds, such as the Maya residuum employed
in the Examples below.
[0022] The high reactivity of the Maya/Arabian Heavy Atmospheric
Residua blend, coupled with high temperatures of operation, usually
promotes significant vanadium deposition on the outside of the
catalyst pellets. Such deposition tends to block access of the
crude to the interior catalytically active portion of the catalyst.
In the instant invention, significant vanadium deposition has been
found within the catalyst itself. Catalyst life is extended
significantly because the pores are not blocked as quickly.
[0023] As further described in U.S. Pat. No. 5,215,955, typical
operating conditions for hydrodesulfurization processes include a
reaction zone temperature of 600.degree. F. to 900.degree. F., a
pressure of 200 to 3,000 psig, and a hydrogen feed rate of 500 to
15,000 SCF per barrel of oil feed. Generally such
hydrodesulfurization is in the presence of a catalyst or
combination of catalysts which contain Group VI or VII metals such
as platinum, molybdenum, tungsten, nickel, cobalt, etc. These
metals may be loaded onto refractory supports such as alumina,
silica, magnesia and so forth. A high surface to volume ratio is
preferable for the catalysts employed in this invention.
[0024] Alumina is the preferred catalytic support material although
alumina may be combined with silica or magnesia. The support
materials are available from a variety of commercial sources, or
they may be prepared as disclosed in Tamm '661. The preparation of
catalysts suitable for use in the hydroprocessing of residuum is
further disclosed in U.S. Pat. No. 5,620,592, U.S. Pat. No.
5,215,955 and U.S. Pat. No. 5,177,047. It is notable that the
catalysts disclosed in these patents preferably have few
macropores. The catalysts of the OCR process are highly
macroporous. The instant invention may thus be employed with
catalyst possessing wide variation in pore structure.
[0025] The hydrocarbon hydrodesulfurization catalysts of the
present invention contain at least one hydrogenation agent, and
preferably contain a combination of two such agents. One or more
catalysts may be used in any of the reaction zones. The metals
and/or the compounds of the metals, particularly the sulfides and
oxides of Group VIB (especially molybdenum and tungsten) and Group
VII (especially cobalt and nickel) of the elements are in general
satisfactory catalytic agents. The combinations of cobalt, nickel
and molybdenum catalytic agents are preferred. Suitably, the Group
VII metal is present in the catalyst in the range of about 0.1 wt.
% to about 5 wt. %, calculated as the metal and based upon the
total catalyst weight, and the Group VIB metal is present in an
amount within the range of about 4 wt. % to about 20 wt. %,
calculated as the metal and based upon the total catalyst weight.
The most preferred catalyst contains between about 2% and about 4%
nickel and between about 7% and about 9% molybdenum. The catalysts
used in the Examples (Table 3) are typical.
[0026] The catalytic agents required for the present catalyst
compositions may be incorporated into the calcined carrier by any
suitable method, particularly by impregnation procedures ordinarily
employed in general in the catalyst preparation art. It has been
found that an especially outstanding catalyst is made by a single
step impregnation of the alumina using a solution of a cobalt or
nickel salt and a heteropolymolybdic acid, for example,
phosphomolybdic acid.
EXAMPLES
Example I
[0027] A reactor system, consisting of three reactors connected in
series for downflow operation, was loaded with commercially
available catalyst comprising Al/Mo/P/Ni (See Table 3). The reactor
system was run at 57% MCR conversion based on a target material
balance. A similar adiabatic temperature profile was established in
each of the reactors. The temperature increase across each reactor
was set to 50-55.degree. F. with an overall maximum temperature of
780.degree. F. The reactor system total pressure was maintained at
2200 psig with a hydrogen partial pressure of 1800 psia & a
hydrogen flow rate of 5000 scf/bbl. The feed consisted of Arabian
Heavy/Maya atmospheric residuum (See Table 1 for Feed 2 physical
properties) fed at a liquid hourly space velocity (LHSV) of 0.46
hr.sup.-1.
[0028] After 1,508 hrs on-stream in this accelerated aging regime,
water was continuously injected at 3 wt % or 3.2 gms/hr into the
feed for the remainder of the run ending at 2,806 hrs. The results
from this run clearly show a significant improvement of catalyst
cycle length and metal loading. The cycle length increased by 27%
as compared to the base case reactor system, and the metal loading
increased by 28% as compared to the base case reactor system.
Example II
[0029] The reactor system and conditions were identical to Example
I above except that the LHSV was 0.22 hr.sup.-1, and Feed 2 was
used. (See Table 1 for feed 1 physical properties).
[0030] In this example, water was continuously injected at 2.0 wt %
or 2.2 gms/hr into the feed at the start of the run and ending
after 2380 hrs. The cycle length improved by 31% and the metal
loading increased by 34% as compared against the base case reactor
system.
Example III
[0031] The reactor system was a single stage reactor with the same
conditions as Example I except the feed was a different feed (See
Table 1 for feed 3 physical properties ) and only catalyst 2 (See
Table 3) was used for this run.
[0032] In this example, water was continuously injected at 1.5 wt %
or 1.7 gms/hr into the feed throughout the 750 hrs of run time.
However, despite the short duration of this run and the relatively
low catalyst metal loading there was a clear indication that a
water-induced catalyst metal capacity and a lower catalyst aging
rate was starting to develop as compared to the base case reactor
system.
Example IV
[0033] The reactor system was a single stage reactor with the same
conditions as Example I except the feed was a different feed (See
Table 1 for feed 3 physical properties) and only catalyst 2 (See
Table 3) was used for this run.
[0034] In this example, water was continuously injected at 1.0% or
1.2 gms/hr into the feed throughout the 750 hrs of run time. Here
again, given the short duration of this run, there was an
indication that the water injection was starting to improve the
metal loading capacity & the aging rate of the catalyst.
1TABLE 1 Feed: Arab Heavy/Maya Atmospheric Residuum Feed 1 Feed 2
Feed 3 Sulfur, wt % 4.660 4.620 4.551 Nitrogen, ppm 4087 4024 4260
MCR, wt % 18.9 704.8 284.5 API 7.5 7.4 8.9 Iron, ppm 5.6 8.2 7.3
Nickel, ppm 58.9 59.6 70.2 Vanadium, ppm 264.0 265.0 358.0 IBF
(.degree. F.) 684 676 641
[0035]
2TABLE 2 Water % Run Length % Metal Load Injection Wt. Improvement
Improvement 0.75% 1.5% 2.0% +30.8% +34.0% 3.0% +26.6% +28.0%
Estimated values
[0036]
3 TABLE 3 Composition Catalyst 1 Catalyst 2 Catalyst 3
Al.sub.2O.sub.3 79% 86% 80% MoO.sub.3 13% 9% 12% P.sub.2O.sub.5 4%
2% 4% NiO 4% 3% 4%
* * * * *