U.S. patent application number 10/841650 was filed with the patent office on 2005-01-13 for presulfiding ocr catalyst replacement batches.
This patent application is currently assigned to Chevron U.S.A. Inc.. Invention is credited to Bachtel, Robert W., Earls, David E., Johnson, David R., Leung, Pak C., Reynolds, Bruce E., Trimble, Harold J..
Application Number | 20050006283 10/841650 |
Document ID | / |
Family ID | 33567372 |
Filed Date | 2005-01-13 |
United States Patent
Application |
20050006283 |
Kind Code |
A1 |
Leung, Pak C. ; et
al. |
January 13, 2005 |
Presulfiding OCR catalyst replacement batches
Abstract
Catalyst particles are presulfided in a pretreatment zone
separate from a hydroconversion reaction zone. The presulfided
catalyst is then added to a moving bed of catalyst in the
hydroconversion reaction zone at reaction pressure, so that the
reactor is not shut down to replace catalyst. The presulfiding
process is particularly beneficial for use in moving bed reactors
for heavy oil conversion.
Inventors: |
Leung, Pak C.; (Lafayette,
CA) ; Earls, David E.; (Pinole, CA) ;
Reynolds, Bruce E.; (Martinez, CA) ; Johnson, David
R.; (Petaluma, CA) ; Bachtel, Robert W.;
(Livermore, CA) ; Trimble, Harold J.; (Panama City
Beach, FL) |
Correspondence
Address: |
CHEVRON TEXACO CORPORATION
P.O. BOX 6006
SAN RAMON
CA
94583-0806
US
|
Assignee: |
Chevron U.S.A. Inc.
|
Family ID: |
33567372 |
Appl. No.: |
10/841650 |
Filed: |
May 6, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10841650 |
May 6, 2004 |
|
|
|
09839042 |
Apr 20, 2001 |
|
|
|
09839042 |
Apr 20, 2001 |
|
|
|
09465122 |
Dec 16, 1999 |
|
|
|
Current U.S.
Class: |
208/213 ;
208/108; 208/215; 208/251H; 208/254H |
Current CPC
Class: |
C10G 45/04 20130101 |
Class at
Publication: |
208/213 ;
208/215; 208/251.00H; 208/254.00H; 208/108 |
International
Class: |
C10G 045/02; C10G
047/06 |
Claims
What is claimed is:
1. A process for ex-situ sulfiding a catalyst employed in the
hydroprocessing of a heavy hydrocarbon feed stream in a moving bed
reactor system, the system possessing at least one reactor zone and
at least one pretreatment zone, wherein the hydroprocessing occurs
in the reactor zone and the catalyst is sulfided in the
pretreatment zone before being added to the reactor zone.
2. The process of claim 1, wherein the pretreatment zone of the
moving bed reactor system comprises the equipment that is used to
transfer the catalyst from storage to the reactor.
3. The process of claim 1, wherein the feed stream is upflowing
through the reactor zone of the moving bed reactor system, the
moving bed reactor system being selected from the group consisting
of (i) ebullated and expanded types of reactor systems which are
capable of onstream catalyst replacement; (ii) a substantially
packed-bed type reactor system having an onstream catalyst
replacement system.
4. The process of claim 1, wherein the pretreatment zone comprises
at least one high pressure vessel and at least one low pressure
vessel.
5. The process of claim 4, wherein catalyst may be treated in the
low and high pressure vessels in series.
6. The process of claim 4, wherein catalyst may be treated in the
low and high pressure vessels simultaneously, in parallel.
7. The process of claim 1, wherein the catalyst is presulfided in
the pretreatment zone by means of the following steps: a) adding a
volume of hydroprocessing catalyst to the pretreatment zone, which
volume includes fresh hydroprocessing catalyst; b) heating the
volume of hydroprocessing catalyst until the catalyst has a
temperature ranging from 90.degree. C. to 370.degree. C.; and c)
adding a presulfiding agent to the pretreatment zone to prepare
presulfided catalyst.
8. The process of claim 4, wherein hydroprocessing catalyst is
sulfided at a temperature of 125.degree. C. to 325.degree. C.
9. The process of claim 7, wherein the step of adding a volume of
hydroprocessing catalyst to the pretreatment zone comprises: a)
preparing a slurry comprising a hydrocarbon liquid and a volume of
hydroprocessing catalyst; b) adding the slurry comprising the
hydrocarbon liquid and the hydroprocessing catalyst to the
pretreatment zone; and c) removing at least a portion of the
hydrocarbon liquid from the pretreatment zone.
10. The process of claim 7, wherein the step of adding a
presulfiding agent to the pretreatment zone comprises: a)
pressurizing the pretreatment zone which contains the
hydroprocessing catalyst with a presulfiding agent at a pressure in
the range of 0.2 to 24.2 MPa and a temperature in the range of
90.degree. C. to 370.degree. C. to produce at least partially
presulfided catalyst; and b) removing at least a portion of the
presulfiding agent from the pretreatment zone.
11. The process of claim 7, wherein the presulfiding agent
comprises a sulfur containing material selected from the group
consisting of H.sub.2S and sulfur-containing materials which
decompose at temperatures below about 370.degree. C.
12. The process of claim 11, wherein the presulfiding agent
comprises H.sub.2S.
13. The process of claim 11, wherein the presulfiding agent
comprises a gaseous recycle stream containing H.sub.2 and
H.sub.2S.
14. The process of claim 10, wherein the at least partially
presulfided catalyst is produced at a temperature in the range of
125.degree. C. to 325.degree. C. and at a pressure in the range of
5.0 MPa to 20 MPa.
15. The process of claim 10, wherein the at least partially
presulfided catalyst is produced in less than 24 hours.
16. The process of claim 14, wherein the at least partially
presulfided catalyst is produced at a temperature in the range of
150.degree. C. to 285.degree. C.
17. The process according to claim 7, wherein the step of adding a
presulfiding agent to the pretreatment zone comprises: a) adding a
volume of hydroprocessing catalyst to the pretreatment zone, which
volume includes fresh hydroprocessing catalyst; b) flowing a heated
hydrocarbon liquid through the volume of hydroprocessing catalyst
within the pretreatment zone until the catalyst has a temperature
ranging from 90.degree. C. to 145.degree. C.; c) subsequently
pressurizing the pretreatment zone at a pressure ranging from 0.2
MPa to 24.2 MPa; d) continuing to flow the heated hydrocarbon
liquid through the catalyst in the pretreatment zone until the
catalyst has a temperature ranging from 125.degree. C. to
325.degree. C.; e) flowing a presulfiding mixture through the
catalyst in the pretreatment zone to prepare at least partially
presulfided catalyst.
18. A method for hydroprocessing a hydrocarbon feed stream that is
upflowing through a hydroconversion reaction zone comprising the
steps of: a) introducing a hydrocarbon feed stream in the presence
of hydrogen at a reaction pressure into a hydroconversion reaction
zone which contains particulate hydroprocessing catalyst to
commence upflowing of said hydrocarbon feed stream through said
catalyst and to recover a reaction effluent therefrom; b)
presulfiding ex-situ a volume of hydroprocessing catalyst within a
pretreatment zone to produce presulfided catalyst, wherein the
catalyst is presulfided by means of the following steps: (1) adding
a volume of hydroprocessing catalyst to the pretreatment zone,
which volume includes fresh hydroprocessing catalyst; (2) heating
the volume of hydroprocessing catalyst until the catalyst has a
temperature ranging from 90.degree. C. to 370.degree. C.; and (3)
adding a sulfiding agent to the pretreatment zone to prepare
presulfided catalyst; and c) adding at least a portion of the
presulfided catalyst into the hydroconversion reaction zone while
maintaining the reaction zone at the reaction pressure.
19. The process according to claim 18, wherein the reaction zone is
maintained as a substantially packed bed of particulates
hydroprocessing catalyst.
20. The method of claim 19, wherein the step of introducing a
hydrocarbon feed stream into a hydroconversion reaction zone
comprises flowing upwardly said hydrocarbon feed stream into said
substantially packed bed of hydroprocessing catalyst at a rate of
flow such that said substantially packed bed of hydroprocessing
catalyst expands to less than 10% by length beyond a substantially
full axial length of said substantially packed bed of
hydroprocessing catalyst in a packed bed state.
21. A method for hydroprocessing a hydrocarbon feed stream
comprising the steps of: a) introducing a hydrocarbon feed stream
into a hydroconversion reaction zone having a substantially packed
bed of particulate hydroprocessing catalyst to commence upflowing
of said hydrocarbon feed stream through said substantially packed
bed of the catalyst at a rate of flow such that said substantially
packed bed of hydroprocessing catalyst expands to less than 10% by
length beyond a substantially full axial length of said
substantially packed bed of hydroprocessing catalyst in a packed
bed state, and to recover a reaction effluent therefrom; b)
withdrawing a first volume of the hydroprocessing catalyst from the
hydroconversion reaction zone to commence essentially plug-flowing
downwardly said substantially packed bed of hydroprocessing
catalyst within said hydroconversion reaction zone; c) adding a
second volume of a particulate hydroprocessing catalyst to a
pretreatment zone, which second volume includes fresh
hydroprocessing catalyst; d) presulfiding the second volume of
hydroprocessing catalyst within the pretreatment zone to prepare
presulfided catalyst; and e) adding at least a portion of the
presulfided catalyst into the hydroconversion reaction zone to
replace the withdrawn first volume of catalyst.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a Continuation-in-Part of copending
application U.S. Ser. No. 09/839,042, filed on Apr. 20, 2001 which
is a Continuation-in-Part of U.S. Ser. No. No. 09/465,122, filed on
Dec. 16, 1999, now abandoned, and claims priority therefrom.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a method for extending the
catalytic life of catalyst used in hydroprocessing of a hydrocarbon
feed stream. More particularly, the present invention provides for
a method for presulfiding hydroprocessing catalyst in order to
improve operability, reduce catalyst fouling rate, and extend the
catalytic life of a catalyst bed employed in a hydroconversion
reaction zone during hydroprocessing. The present invention more
particularly provides for a method for presulfiding hydroprocessing
catalyst ex-situ before transferring presulfided hydroprocessing
catalyst into a hydroprocessing reactor system. The method is
intended to improve the operability and reduce catalyst fouling
rate, and to extend the catalytic life of a generally "packed
catalyst bed" in the hydroprocessing reactor system that is
preferably capable of onstream catalyst replacement. The methods of
the present invention may also be advantageously practiced in
hydrocarbon reactor systems that utilize an "expanded catalyst
bed", such as the ebullated beds as described in U.S. Pat. No.
4,571,326 and U.S. Pat. No. 4,744,887.
[0003] The following three acceptable reactor technologies are
currently available to the industry for hydrogen upgrading of
"heavy" hydrocarbon liquid streams: (i) fixed bed reactor systems;
(ii) ebullated or expanded type reactor systems which are capable
of onstream catalyst replacement and are presently known to
industry under the trademarks H-OilR and LC-FiningR; and (iii) the
substantially packed-bed type reactor system having an onstream
catalyst replacement system, as more particularly described in U.S.
Pat. No. 5,076,908 to Stangeland et al, having a common assignee
with the current inventions and discoveries. A fixed bed reactor
system may be defined as a reactor system having one or more
reaction zone(s) of stationary catalyst, through which feed streams
of liquid hydrocarbon and hydrogen flow downwardly and concurrently
with respect to each other. The current application is not directed
to fixed bed activity, but to moving beds. These include ebullated
and substantially packed beds. An ebullated or expanded bed system
may be defined as a reactor system having an upflow type single
reaction zone reactor containing catalyst in random motion in an
expanded catalytic bed state, typically expanded from 10% by volume
to about 35% or more by volume above a "slumped" bed level which is
the volume of a catalytic bed in an ebullated reactor system in a
non-expanded or non-ebullated state and without a hydrocarbon
stream upflowing therethrough. As particularly described in U.S.
Pat. No. 5,076,908 to Stangeland et al, the substantially
packed-bed type reactor system is an upflow type reactor system
including multiple reaction zones of packed catalyst particles
having little or no movement during normal use under conditions of
no catalyst addition or withdrawal. In the substantially packed-bed
type reactor system of Stangeland et al, when catalyst is withdrawn
from the reactor during normal catalyst replacement, the catalyst
flows in a downwardly direction under essentially plug flow or in
an essentially plug flow fashion, with a minimum of mixing with
catalyst in layers which are adjacent either above or below the
catalyst layer under observation.
[0004] It is well known to those skilled in the art of hydrogen
upgrading of heavy hydrocarbon liquid streams that catalysts
utilized for hydrodemetallation, hydrodesulfurization,
hydrodenitrogenation, hydrocracking, etc., of heavy oils and the
like are generally made up of a carrier of base material, such as
alumina, silica, silica-alumina, or possibly, crystalline
aluminosilicate, with one or more promoter(s) or catalytically
active metal(s) (or compound(s)) plus trace materials. Typical
catalytically active metals utilized are cobalt, molybdenum, nickel
and tungsten; however, other metals or compounds could be selected
dependent on the application. It is also well known to those
skilled in the art of upgrading of heavy oils that potential
catalyst activity and useful life can be substantially influenced
by the manner in which fresh catalyst is prepared and/or
conditioned prior to being exposed to normal reactor operating
conditions. More specifically, promoter or catalytically active
metals contained in fresh catalyst are in an oxide state. During
use for hydroprocessing a sulfur containing feed, the metal oxides
are converted to metal sulfides. Catalytic performance of these
metal sulfides is generally improved when the oxides in the fresh
catalyst are converted to sulfides prior to exposure to reactor
operating conditions, using a process termed catalyst presulfiding.
Specific procedures have been developed over time by those involved
in the industry to presulfide the fresh catalyst charges of fixed
bed type reactor systems in-situ at the start of each run. These
procedures normally involve a gas heatup and catalyst drying
procedure of catalyst in the reactor vessel, followed by catalyst
wetting/soaking with startup oil, and then subsequently proceeding
to a sulfiding step that employs either non-spiked feedstock (a
feedstock containing naturally occurring sulfur compounds) and a
sulfur spiked feedstock (a feedstock to which sulfur compounds are
added). The sulfiding (or presulfiding) step may also and
alternatively employ H.sub.2/H.sub.2S for vapor phase sulfiding.
The techniques, as well as several other approaches, are presented
and discussed in a technical paper by Harman Hallie at a catalyst
symposium in Amsterdam, May 1982, and printed in the Dec. 20, 1982
issue of Oil and Gas Journal, and in another paper presented by
William J. Tuzynski, at the 1989 NPRA Meeting, and entitled
Properties and Application of Commercial Presulfiding Agents. It is
quite clear that the Tuzynski reference is directed to in-situ
sulfiding only, in fixed bed operation. Page 2, second paragraph,
indicates that the catalyst bed must not be damaged during
presulfiding. In ex-situ sulfiding as disclosed in this invention,
sulfiding occurs in a pretreatment zone, not in a catalyst bed.
Tuzynski is a general paper on complete (100%) presulfiding (with
various sulfur containing agents) of fresh catalyst in reactors,
not in pretreatment zones (or catalyst transfer equipment). There
is therefore no motivation to combine Tuzynski, which is directed
to fixed bed presulfiding, with patents directed to moving bed
operation, such as U.S. Pat. No. 5,498,327.
[0005] Generally, non-spiked feedstock presulfiding techniques
involve decomposition of sulfur compounds, which are naturally
present in a selected startup hydrocarbon feed, into H.sub.2S at
reactor temperature conditions ranging from about 300.degree. C.
(572.degree. F.) to about 350.degree. C. (662.degree. F.). Spiked
feedstock presulfiding techniques are carried out by injecting
sulfur-containing organic compounds into a selected startup
hydrocarbon feed such that the injected sulfur-containing organic
may decompose into H.sub.2S at temperatures lower than temperatures
required to decompose the naturally occurring sulfur compounds
present in the startup oil feedstock. Spiking agents currently
preferred by the industry are dimethylsulfide (DMS) and
dimethyldisulfide (MDS) which allow sulfiding procedures to be
accomplished typically at temperatures in the range of from about
250.degree. C. to about 275.degree. C. Vapor phase presulfiding is
difficult to control and, in general, does not achieve the optimum
results in commercial applications, due to several reasons
including poor distribution and uneven sulfiding, poor heat sink of
exothermic reactions, etc.
[0006] Techniques have been developed in which catalyst is
pretreated by impregnation with a sulfur compound (e.g. a
polysulfide) before being charged to a reactor for so-called
ex-situ presulfiding; however, the catalyst must still undergo
drying, wetting, and conversion in-situ from a metal oxide state to
a metal sulfide state within the reactor during startup procedures.
In this case, the major benefit claimed is reduced startup time and
potentially improved activity. U.S. Pat. No. 4,576,710 suggests
presulfiding regenerated catalyst for use in an ebullating bed
reactor, but provides no disclosure of the mechanical details or
operating practice to make such a presulfiding step functional.
[0007] Conventional presulfiding and startup procedures are
tailored to maintain startup oil feed quality and reactor
temperature conditions such that the sulfiding and hydrogenation
reactions do not create deleterious temperature conditions in the
interior of catalyst pellets that result in either carbon
deposition or metal sintering, both of which reduce catalyst
activity. Simply stated, the severity of hydrogenation reactions
during the initial catalyst conditioning and sulfiding period is
limited by startup oil quality (e.g. sulfur content) and reactor
temperature conditions until the sulfiding reactions diminish or
essentially stop. Present-day state-of-the-art techniques allow
in-situ presulfiding to be initiated at temperatures below about
200.degree. C. (392.degree. F.) and completed before temperatures
are elevated above about 300.degree. C. (572.degree. F.). Harman
Hallie's technical paper in the Dec. 20, 1982 issue of Oil and Gas
Journal indicates catalyst activity differences or reductions of
from 7% to about 33% could be experience if sulfiding is carried
out at higher temperature conditions. Such activity losses may
occur when fresh or regenerated catalyst batches with promoter
metal in an oxide state are suddenly loaded into an onstream
reactor operating at temperatures in excess of 300.degree. C.
Therefore, what is needed and what has been invented by us is a
viable, reasonably achievable and economical method for
presulfiding fresh batches of catalyst which are to be added to an
onstream reactor operating at elevated temperatures and hydrogen
pressures. A substantial benefit can be gained from preconditioning
fresh or regenerated catalyst in order to convert a major portion
of the promoter metal oxide into the metal sulfide state prior to
its being loaded into an onstream reactor operating at elevated
temperatures and hydrogen pressures.
[0008] A technical bulletin published by Criterion Catalyst
Company, LLP, entitled "Criterion Hydrotreating Catalysts
Presulfiding Procedures", discusses means of maximizing catalyst
activity in hydrotreating applications by presulfiding the
catalyst. This publication does not discuss presulfiding catalyst
for use in hydroprocessing of "heavy" hydrocarbon liquid streams,
such as atmospheric residuum.
SUMMARY OF THE INVENTION
[0009] The present invention is directed to a process for ex-situ
presulfiding a hydrocarbon conversion catalyst for use in a moving
bed reactor which comprises at least one reaction zone containing
catalytic particulates. Included in the moving bed reactor are
means for removing catalytic particulates from the reaction zone
and means for adding catalytic particulates to the reaction zone
while maintaining the reaction zone at a temperature and at a
pressure selected for hydroconverting a refinery stream. During the
hydroconversion process, a refinery stream in combination with
added hydrogen gas is contacted over catalytic particulates within
the reaction zone for removing contaminants from the refinery
stream, including one or more of nitrogen, sulfur, aromatics and
metals. The effluent from the reaction zone is therefore reduced in
one or more of the contaminants relative to the feedstock to the
reaction zone.
[0010] It is a feature of the moving bed reactor that at least a
portion of the catalytic particulates may be removed from the
reaction zone during hydroconversion, and further catalytic
particulates may be added to the reaction zone during
hydroprocessing. Being able to add and remove catalytic
particulates without the need for shutting down the reaction
process permits the operator to quickly tailor a bed of catalytic
particulates for achieving a desired product slate or catalyst
activity without the burden of a complete reactor shutdown to
replace catalyst. The moving bed reactor also permits the operator
to convert refinery streams, such as metals containing streams,
which would otherwise quickly deactivate a catalyst. Frequent
shutdowns to remove metal fouled catalyst is a major expense for
operators of conventional fixed bed hydroconversion processes.
[0011] In its broadest aspect, the present invention is directed to
a process for hydroprocessing a hydrocarbon feed stream that is
upflowing through a hydroconversion reaction zone, the process
comprising:
[0012] introducing a hydrocarbon feed stream in the presence of
hydrogen at a reaction pressure into a hydroconversion reaction
zone which contains particulate hydroprocessing catalyst to
commence upflowing of said hydrocarbon feed stream through said
catalyst and to recover a reaction effluent therefrom;
[0013] ex-situ sulfiding a volume of hydroprocessing catalyst
within a pretreatment zone to produce sulfided catalyst; and
[0014] adding at least a portion of the sulfided catalyst into the
hydroconversion reaction zone while maintaining the reaction zone
at the reaction pressure.
[0015] The preferred pretreatment zone for the catalyst sulfiding
system comprises one or more treatment vessels which are separate
from the hydroconversion reaction zone contained in the reactor
vessel. The pretreatment zone is preferably part of the equipment
used to transfer the catalyst to the hydroconversion reaction zones
from storage in the catalyst hopper. Typical sulfiding temperatures
range from 90.degree. C. to 370.degree. C. The preferred
temperature for sulfiding the catalytic particulates is in the
range from 125.degree. C. to 325.degree. C. The preferred pressure
is in the range from 200 KPa (15 psig) up to or slightly above
(e.g. less than 450 KPa or 50 psig above) the pressure of the
reaction zone.
[0016] An important aspect of the present invention is the method
of preparation and use of a presulfided catalyst in a moving bed
reactor system. In conventional fixed bed processes, fresh
catalytic particulates are generally sulfided in the reaction
vessel (that is, in-situ) prior to the introduction of a refinery
stream for reaction. In reaction systems permitting catalyst
addition during hydroprocessing, such as moving beds, fresh
catalysts are conventionally added in an unsulfided state to the
reaction zone, and are sulfided by the sulfur compounds present in
the fluids flowing through the catalytic particulates during
reaction. However, the need for more hydroconversion activity while
processing heavy feeds has resulted in the use of catalysts which
benefit from careful sulfiding prior to exposure to the heavy feeds
at reaction conditions. According to the present invention, an
embodiment for sulfiding the volume of hydroprocessing catalyst
within the pretreatment zone comprises the steps of:
[0017] adding a volume of hydroprocessing catalyst to the
pretreatment zone, which volume includes fresh hydroprocessing
catalyst;
[0018] heating the volume of hydroprocessing catalyst until the
catalyst has a temperature ranging from 90.degree. C. to
370.degree. C.; and
[0019] adding a sulfiding agent to the pretreatment zone to prepare
sulfided catalyst.
[0020] In the preferred process of the invention, the method of
adding the volume of hydroprocessing catalyst to the pretreatment
zone comprises the steps of:
[0021] preparing a slurry comprising a hydrocarbon liquid and a
volume of hydroprocessing catalyst;
[0022] adding the slurry comprising the hydrocarbon liquid and the
hydroprocessing catalyst to the pretreatment zone; and
[0023] removing at least a portion of the hydrocarbon liquid from
the pretreatment zone.
[0024] and the method of adding a sulfiding agent to the
pretreatment zone comprises:
[0025] pressurizing the pretreatment zone which contains the
hydroprocessing catalyst with a sulfiding agent at a pressure in
the range of 0.2 to 24.2 MPa and a temperature in the range of
90.degree. C. to 370.degree. C. to produce at least partially
sulfided catalyst; and
[0026] removing at least a portion of the sulfiding agent from the
pretreatment zone.
[0027] In a further embodiment of the invention, the process for
sulfiding the catalyst in the pretreatment zone includes flowing a
fluid comprising the sulfiding agent through the catalyst within
the pretreatment zone, in a process comprising:
[0028] adding a volume of hydroprocessing catalyst to the
pretreatment zone, which volume includes fresh hydroprocessing
catalyst;
[0029] flowing a heated hydrocarbon liquid through the volume of
hydroprocessing catalyst within the pretreatment zone until the
catalyst has a temperature ranging from 90.degree. C. to
145.degree. C.;
[0030] subsequently pressurizing the pretreatment zone at a
pressure ranging from 0.2 MPa to 24.2 MPa (15-3500 psig);
[0031] continuing to flow the heated hydrocarbon liquid through the
catalyst in the pretreatment zone until the catalyst has a
temperature ranging from 90.degree. C. to 370.degree. C.;
[0032] flowing a sulfiding mixture through the catalyst in the
pretreatment zone to prepare at least partially sulfided
catalyst.
[0033] The preferred temperature for sulfiding the catalytic
particulates is in the range from 125.degree. C. to 325.degree. C.
The preferred pressure is in the range from 200 KPa (15 psig) up to
or slightly above (e.g. less than 450 KPa or 50 psig above) the
pressure of the reaction zone.
[0034] The presulfided catalyst produced in the process is added to
a hydroconversion reaction zone while maintaining the reaction zone
at a suitable reaction pressure according to the following:
[0035] adding a hydrocarbon liquid to the sulfided catalyst in the
pretreatment zone;
[0036] forming a slurry comprising the hydrocarbon liquid and at
least a portion of the sulfided catalyst; and
[0037] adding the slurry of the hydrocarbon liquid and the sulfided
catalyst to the hydroconversion reaction zone while maintaining the
reaction zone at the reaction pressure.
[0038] In a more preferred embodiment, the present invention is
directed to a moving bed reaction zone with a substantially packed
bed of catalyst. A method for hydroprocessing a hydrocarbon feed
stream that is upflowing through a hydroconversion reaction zone
having a substantially packed bed of catalyst comprises the steps
of:
[0039] introducing a hydrocarbon feed stream into a hydroconversion
reaction zone having a substantially packed bed of particulate
hydroprocessing catalyst to commence upflowing of said hydrocarbon
feed stream through said substantially packed bed of the catalyst
at a rate of flow such that said substantially packed bed of
hydroprocessing catalyst expands to less than 10% by length beyond
a substantially full axial length of said substantially packed bed
of hydroprocessing catalyst in a packed bed state, and to recover a
reaction effluent therefrom;
[0040] withdrawing a first volume of the hydroprocessing catalyst
from the hydroconversion reaction zone to commence essentially
plug-flowing downwardly said substantially packed bed of
hydroprocessing catalyst within said hydroconversion reaction
zone;
[0041] adding a second volume of a particulate hydroprocessing
catalyst to a pretreatment zone, which second volume includes fresh
hydroprocessing catalyst;
[0042] sulfiding the second volume of hydroprocessing catalyst
within the pretreatment zone to prepare sulfided catalyst; and
[0043] adding at least a portion of the sulfided catalyst into the
hydroconversion reaction zone to replace the withdrawn first volume
of catalyst.
[0044] The present invention is directed to presulfiding a
hydroprocessing catalyst prior to adding the catalyst to a
hydroconversion reaction zone. Processes taught in the art sulfide
the hydroprocessing catalyst in situ, by adding fresh, unsulfided
catalyst to the catalyst bed for sulfiding the catalyst using
sulfur-containing reactants which pass through the fresh,
unsulfided catalyst. Generally, these prior art sulfiding processes
are also run at temperature ranges which are higher than those
employed in the present process. Among other factors, the instant
invention is based on the surprising discovery that catalysts which
are presulfided according to the present process demonstrate
substantially higher performance when used for hydroconversion. The
present method provides for sulfiding catalyst, using sulfur
compounds present in product streams from the hydroconversion
process, at low sulfiding temperatures for preparing a catalyst
which has higher performance in catalyzing conversion reactions,
particularly desulfurization reactions, of heavy feeds. This
discovery is particularly important for operating moving bed
reactors, and in particular reactors operating with substantially
packed bed upflow reactors under plug flow conditions during
catalyst addition and withdrawal.
IN THE FIGURES
[0045] FIG. 1 illustrates an embodiment of the invention with a
high pressure catalyst transfer vessel only for presulfiding the
catalyst according to the invention.
[0046] FIG. 2 illustrates an embodiment of the invention with a low
pressure catalyst transfer vessel and a high pressure catalyst
transfer vessel for presulfiding the catalyst according to the
invention.
[0047] FIG. 3 shows the improved desulfurization performance of a
catalyst presulfided according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0048] Referring in detail now to FIGS. 1, 2 for preferred
embodiments of the present invention, there is seen a catalyst
presulfiding system in communication with the catalyst bed 10 of
the reactor vessel 11. The catalyst sulfiding system functions for
sulfiding catalyst (i.e. the converting of metallic oxide(s) within
the catalyst into metallic sulfide(s)) before the catalyst is
introduced into the reactor vessel 11. In the invention, catalyst
is sulfided (i.e. presulfided) in one or more vessels within
pretreatment zone 50.
[0049] The reaction zone 10 contained within reactor vessel 11 is
preferably an upflow reaction system, with reacting fluids entering
reaction zone 10 through feed inlet 14, passing upward in upflow
mode through reaction zone 10 moving bed reactor, the reaction
effluent exiting through conduit 16. The catalyst presulfiding
process is effective for reaction zones operated as an ebullating
bed reaction system or as a substantially packed-bed type reactor
system having an onstream catalyst replacement system (i.e. having
a capability for transferring catalyst to and from the reaction
zone at substantially reaction pressure). To maintain the reactor
system as a substantially packed-bed type reactor system, the
onstream catalyst replacement system is a counterflow processing
system where the catalyst and fluid velocity combinations limit bed
expansion to less than 10% by length beyond a substantially full
axial length of the bed in a packed bed state. It is more preferred
that the bed expansion be maintained at less than 5% and more
preferred at less than 1% of the substantially full axial length of
the bed in a packed bed state. A preferred substantially packed bed
type reactor system is taught in U.S. Pat. No. 5,076,908, the
disclosure of which is incorporated herein by reference for all
purposes.
[0050] In the embodiment of the invention depicted in FIG. 1, the
catalyst sulfiding system comprises catalyst transfer vessel 304 in
communication with catalyst loading hopper 312 for accepting and
dispensing hydroprocessing catalyst. Catalyst hopper 312 has a
depending conduit 314 communicating therewith and with the high
pressure catalyst feed vessel 304 for conducting hydroprocessing
catalyst from the catalyst loading hopper 312 to the catalyst feed
vessel 304. The depending conduit 314 is conveniently provided with
a valve 318 for regulating catalyst flow therethrough. Catalyst is
preferably transferred from catalyst loading hopper 312 to catalyst
feed vessel 304 as a slurry in a hydrocarbon oil.
[0051] In one embodiment of the invention, the hydroprocessing
catalyst to be sulfided within the catalyst transfer vessel 304 is
treating with a sulfiding agent. The "spiking" or sulfiding agent
may be any suitable spiking or sulfiding agent (e.g. mercaptan
compounds, thiophenic compounds, organosulfides, etc.) but is
preferably a sulfur rich recycle stream recovered from the reaction
effluent. Sulfur containing materials, such as dimethyldisulfide or
dimethylsulfide, may also be used. An example sulfiding agent is a
hydrocarbon gas (e.g. methane, ethane, or the like, etc.) that is
rich in hydrogen sulfide (H.sub.2S), preferably containing from
about 5% by weight to about 80% by weight H.sub.2S. When H.sub.2S
is employed as a sulfiding agent in the present process, a
preferred H.sub.2S is derived from a recycle stream (not shown)
recovered from the reaction effluent 16. For example, the reaction
effluent 16 may be separated into two or more components by boiling
point. Further separations may produce a H.sub.2S rich stream,
which may be recycled via conduit 328 for use as a sulfiding
agent.
[0052] As already stated, the catalyst may be transferred from the
catalyst hopper 312 to the catalyst transfer vessel 304 in a
slurry, where the liquid component of the slurry may be a product
stream from the process, such as a flush oil. At least a portion of
the oil remaining in the catalyst transfer vessel following
transfer of catalyst from the catalyst hopper to the catalyst
transfer vessel is preferentially drained from the catalyst
transfer vessel prior to introduction of the sulfiding agent,
through conduit 310, in cooperation with valve 311. In the
embodiment shown in FIG. 1, sulfiding agent may be introduced to
the catalyst transfer vessel through conduit line 212 in
cooperation with valve 213, or through conduit line 328, in
cooperation with valve 330.
[0053] Prior to sulfiding, the catalyst is heated to an elevated
temperature, such as from 50.degree. C. to 370.degree. C., more
preferably from 125.degree. C. to 325.degree. C., still more
preferably from 150.degree. C. to 285.degree. C. The heat may be
supplied by the catalyst transfer vessel, heated to an elevated
temperature, such as between 90.degree. C. and 370.degree. C.,
using an external heating source, such as a steam jacket.
Alternatively, the catalyst may be heated prior to addition of
catalyst to the transfer vessel, or by using a heated liquid for
flowing through the catalyst in the transfer vessel. In the
embodiment of FIG. 1, heated hydrocarbon oil may be supplied from
flush oil drum, generally illustrated as 356, through conduit 340,
where the heated oil is supplied to the flush oil drum through
conduit 354, in cooperation with valve 357.
[0054] The "hydrocarbon" (e.g. a gas oil or a flushing oil) for the
heated hydrocarbon and the cold hydrocarbon may be any suitable
hydrocarbon but is preferably a heavy distillate fraction boiling
above 315.degree. C. and more preferably boiling in the range of
from 315.degree. C. to 525.degree. C. It will be apparent to one
skilled in the art, however, that hydrocarbon oils boiling below
that immediately specified will be suitable in the subject
preferred embodiment, so long as the oil does not vaporize to any
significant extent at sulfiding conditions during the sulfiding
process in the high pressure catalyst transfer vessel 304.
[0055] In this preferred embodiment, catalyst transfer vessel 304,
with added catalyst from which at least a portion of the liquid oil
used for transporting the catalyst from catalyst hopper 312 is
removed, is pressurized with an H.sub.2S containing stream. The
H.sub.2S containing stream can be at any pressure from ambient
pressure up to the pressure within reactor vessel 11, such as from
0.2 MPa to 24.2 MPa (15-3500 psig). H.sub.2S contained in a recycle
stream will generally have a pressure of from 0.2 MPa to 3.4 MPa
(15-500 psig). The sulfiding agent is introduced to the catalyst
transfer vessel through either conduit 212 or conduit 328, and
valves associated with conduits leading to the catalyst transfer
vessel blocked closed, including valves 307, 311, 323, 318, and
386. Valve 213 remains open, and the catalyst transfer vessel is
pressurized to the desired pressure, including up to the pressure
of the reactor vessel, using hydrogen or a gaseous mixture
containing hydrogen, through conduit 212. At the desired pressure,
valve 213 is closed for a time sufficient to sulfide the catalyst
in the transfer vessel. During sulfiding, the catalyst is
maintained at a temperature in the range of 90.degree.
C.-370.degree. C., preferably in the range 125.degree.
C.-325.degree. C., more preferably in the range of 150.degree.
C.-285.degree. C., and still more preferably in the range of
175.degree. C.-240.degree. C. Generally, less than 24 hours,
preferably less than 10 hours, more preferably less than 5 hours is
sufficient to at least partially sulfide the catalyst. The
presulfiding process results in sulfiding at least 35% and more
preferably at least 50% of the stoichiometric amount of metal oxide
sites available on the catalyst.
[0056] It may be desirable to further sulfide the catalyst with
additional treatments of the sulfiding agent. Additional treatments
beyond the first are performed in essentially the same way as the
first treatment. Thus, at the end of the first treatment, the
catalyst transfer vessel 304 is depressurized, for example through
conduit 212, and additional sulfiding agent is added to the
transfer vessel 304. As before, the vessel is pressurized with
H.sub.2 to the desired pressure, and the catalyst sulfided under
pressure for generally less than 24 hours, preferably less than 10
hours, more preferably less than 5 hours. It will be clear to the
skilled practitioner that a tradeoff will exist between the
concentration of the active sulfur-containing material, such as
H.sub.2S, in the sulfiding agent, the pressure employed during
sulfiding the time that sulfiding is permitted to take place and
the number of sulfiding cycles employed. Greater amounts of
sulfiding will be expected at high concentrations of the sulfur
containing material, at higher pressures in the sulfiding step, or
for processes in which the sulfiding step is conducted for a longer
time. The choice of concentration, pressure and time is largely a
matter of local conditions; all combinations are to be considered
to be within the bounds of the claimed invention, so long as the
sulfided catalyst retains a measurable amount of sulfur at the
conclusion of the sulfiding process.
[0057] Sulfided catalyst which is sulfided in catalyst transfer
vessel 304 is generally transported to reactor vessel 10 in a
slurry with a hydrocarbon oil. Such oil may be supplied from flush
oil drum 356 through conduit 340. It is desirable that the catalyst
be passed to the reactor in a heated state, e.g. 125-325.degree.
C., and so heated oil from flush oil drum 356 is generally used.
Such oil may be supplied though hot oil supply line 354 in
quantities sufficient to immerse at least a portion of the catalyst
in oil at a pressure equal to or slightly higher than the pressure
in the reactor vessel. Valve 307 is then opened and the catalyst is
passed into the reactor vessel at a rate determined by the rate of
oil addition via conduit 324 to the catalyst transfer vessel
304.
[0058] In a separate embodiment, catalyst in transfer vessel 304 is
sulfided using a sulfiding agent which is flowed through the
catalyst in the transfer vessel 304 during the sulfiding process.
Either gaseous or liquid sulfiding agents may be used. As before,
catalyst loading hopper 312 is provided for accepting and
dispensing hydroprocessing catalyst which preferably comprises the
catalyst of the present invention. The catalyst loading hopper 312
has a depending conduit 314 communicating therewith and with the
high pressure catalyst feed vessel 304 for conducting
hydroprocessing catalyst from the catalyst loading hopper 312 to
the catalyst feed vessel 304. The depending conduit 314 is
conveniently provided with a valve 318 for regulating catalyst flow
therethrough. The high pressure catalyst feed vessel 304 is
provided with a high pressure feed conduit 324 with valve 323 for
conducting a feed stream into the high pressure catalyst feed
vessel 304.
[0059] The high pressure feed conduit 324 communicates with various
feed streams that emanate from various conduits. Conduit 328
conducts a "spiking" or sulfiding agent into the high pressure feed
conduit 324. Flow control valve 330 controls the flow of "spiking"
or sulfiding agent in the sulfiding system. Conduit 340 conducts a
heated hydrocarbon (e.g. a hot gas oil) and is capable of feeding
the high pressure feed conduit 324. Line 340 includes flow control
valve 348 for controlling the flow of heated hydrocarbon for
admixing as desired in the feed conduit 324 with the spiking" or
sulfiding agent originating from conduit 328. Conduit 350 contains
a flow/liquid level control valve 360 and functions for
transporting a cold hydrocarbon (e.g. a cold gas oil) to a flush
oil drum, generally illustrated as 356.
[0060] Line 362 contains a flow control valve 358 and interconnects
the sulfiding system and the conduit 350 for dispensing a cold
hydrocarbon from conduit 350 into the sulfiding feed conduit 324
for admixing with the "spiking" or sulfiding agent and the heated
hydrocarbon for lowering the overall temperature of a sulfiding
agent/heated hydrocarbon mixture, or for flushing or washing
through a catalytic bed (not shown) within the high pressure
catalyst feed vessel 304 after the catalyst has been presulfided.
In a preferred embodiment, the hydroprocessing catalyst is heated
by flowing a heated hydrocarbon liquid through the volume of
hydroprocessing catalyst within the pretreatment zone 50 until the
catalyst has a temperature ranging from 90.degree. C. to
145.degree. C. The pretreatment zone is subsequently pressurizing
at a pressure ranging from 0.2 MPa to 24.2 MPa (15-3500 psig), and
heated hydrocarbon liquid is continued to flow through the catalyst
in the pretreatment zone until the catalyst has a temperature
ranging from 125.degree. C. to 325.degree. C. A sulfiding mixture,
delivered via conduit 324 is then flowed through the catalyst in
the pretreatment zone to prepare sulfided catalyst.
[0061] The high pressure catalyst feed vessel 304 is formed with a
screen 382 in communication with a conduit 384. Any mixture of
heated hydrocarbon and/or cold hydrocarbon and residual (unreacted)
"spiking" or sulfiding agent overflowing the high pressure catalyst
feed vessel 304 passes through screen 382 and into the conduit 384
for transportation to and dispensing into a flush oil separator
376. Conduit 384 comprises a flow/pressure control valve 386 for
controlling mixture flow through conduit 384 and for controlling
operating or working pressures within the high pressure catalyst
feed vessel 304.
[0062] The flush oil separator 376 separates any mixture of heated
hydrocarbon and/or cold hydrocarbon and residual (unreacted)
"spiking" or sulfiding agent into various components. In a
preferred embodiment of the invention where the "spiking" or
sulfiding agent is an H.sub.2S-rich hydrocarbon gas, the flush oil
separator 376 separates mixture(s) of heated hydrocarbon and/or
cold hydrocarbon and H.sub.2S-rich hydrocarbon gas into an overhead
gas (e.g. methane, ethane, nitrogen, etc. and mixtures thereof),
which exits through an exit conduit 396, having flow/pressure
control valve 398, and a recovered liquid hydrocarbon which exits
the flush oil separator 376 through an exit conduit 390 that
extends from the flush oil separator 376 to conduit 352 where the
recovered liquid hydrocarbon is mixed with heated hydrocarbon
and/or cold hydrocarbon for introduction into the flush oil drum
356. A liquid/flow control valve 392 in exit conduit 390 controls
the flow of recovered liquid hydrocarbon from the flush oil
separator 376 through the exit conduit 390.
[0063] The recovered liquid hydrocarbon from the flush oil
separator 376 typically contains residual overhead gas that did not
separate out in the flush oil separator 376. In those typical
occurrences, when a mixture of recovered liquid hydrocarbon and
heated hydrocarbon and/or cold hydrocarbon is introduced into the
flush oil drum 356 from conduit 352, residual overhead gas
separates in the flush oil drum 356 from the mixture and is
dispensed through a conduit 414. Conduit 414 contains a
flow/pressure control valve 420 for regulating residual overhead
gas flow and for regulating working or operating pressures within
the flush oil drum 356.
[0064] In the embodiment of the invention depicted in FIG. 2, the
pretreatment zone for the catalyst sulfiding system comprises two
vessels which are separate from the hydroconversion reaction zone
contained in the reactor vessel, a low pressure catalyst feed
vessel, generally illustrated as 302, communicating with a high
pressure catalyst transfer vessel, generally illustrated as 304,
via a conduit 306 having a valve 308 for controlling the transfer
of at least partially sulfided catalyst from the low pressure
catalyst feed vessel 302 to the high pressure catalyst transfer
vessel 304. In this embodiment of the invention, the low pressure
catalyst feed vessel 302 is provided as an initial vehicle for
wetting, preheating, and at least partially presulfiding the
hydroprocessing catalyst before the transfer of at least partially
presulfided hydroprocessing catalyst from the low pressure catalyst
feed vessel 302 through conduit 306 and into the high pressure
catalyst transfer vessel 304. As will be readily apparent from the
following description, the high pressure catalyst transfer vessel
304 is provided with sources for continuing to wet, preheat and
further sulfide the at least partially presulfided hydroprocessing
catalyst, but at higher temperatures and/or pressures which
approximate reaction conditions within the reactor vessel 11.
Presulfiding of hydroprocessing catalyst is performed at lower
temperatures and pressures than temperatures and pressures required
for directly transferring presulfided catalyst into a
hydroconversion reaction zone such as that existing within the
reactor vessel 11. Example sulfiding conditions in the low pressure
catalyst transfer vessel 302 include a pressure of greater than 200
KPa (15 psig), preferably between 200 KPa and 7000 KPa (15 psig and
1000 psig), and a temperature of 90.degree. C. to 370.degree. C. It
is to be understood that the spirit and scope of the present
invention as depicted in FIG. 1 includes disposing fresh (to be
sulfided) hydroprocessing catalyst in both the low pressure
catalyst feed vessel 302 and the high pressure catalyst transfer
vessel 304, and subsequently sulfiding simultaneously both batches
of hydroprocessing catalyst positioned in the two vessels 302 and
304.
[0065] Sulfided catalyst passes from the high pressure catalyst
transfer vessel 304 through conduit 305 for deposit into the
reactor vessel 11. The conduit 305 contains a block valve 307. A
catalyst loading hopper 312 is provided for accepting and
dispensing hydroprocessing catalyst which preferably comprises the
catalyst of the present invention. The catalyst loading hopper 312
has a depending conduit 314 communicating therewith and with the
low pressure catalyst feed vessel 302, or with the high pressure
catalyst feed vessel 304 for conducting hydroprocessing catalyst
from the catalyst loading hopper 312 to the catalyst feed vessels
302 or 304. The depending conduit 314 is conveniently provided with
a valve 318 for regulating catalyst flow therethrough. The low
pressure catalyst feed vessel 302 is provided with a low pressure
feed conduit 320 with associated valve 321 for conducting a feed
stream into the low pressure catalyst feed vessel 302. A high
pressure feed conduit 324 communicates with the high pressure
catalyst transfer vessel 304 for furnishing a feed stream that is
to upflow therethrough.
[0066] The low pressure feed conduit 320 and the high pressure
feed
[0067] conduit 324 communicate with various feed streams that
emanate from various conduits. Conduit 328 conducts a "spiking" or
sulfiding agent into the low pressure feed conduit 320 and the high
pressure feed conduit 324 via line 329. Flow control valve 330
controls the flow of "spiking" or sulfiding agent in the sulfiding
system. Conduit 340 conducts a heated hydrocarbon (e.g. a hot gas
oil) and is capable of feeding the low pressure feed conduit 320
and the high pressure feed conduit 324 through line 329. Line 340
includes flow control valve 348 for controlling the flow of heated
hydrocarbon for admixing as desired in the feed conduits 320 and
324 respectively with the spiking" or sulfiding agent originating
from conduit 328. Conduit 350 contains a flow/liquid level control
valve 360 and functions for transporting a cold hydrocarbon (e.g. a
cold gas oil) to a flush oil drum, generally illustrated as
356.
[0068] Line 362 contains a flow control valve 358 and interconnects
the sulfiding system and the conduit 350 for dispensing a cold
hydrocarbon from conduit 350 into the sulfiding feed conduit 329
for admixing with the sulfiding agent and the heated hydrocarbon
for lowering the overall temperature of a sulfiding agent/heated
hydrocarbon mixture, or for flushing or washing through a catalytic
bed (not shown) within the low pressure catalyst feed vessel 302
and/or the high pressure catalyst feed vessel 304 after the
catalyst has been presulfided.
[0069] Another feature of the invention depicted in FIG. 2 is that
fresh (to be sulfided) hydroprocessing catalyst may be dispensed
into both the low pressure catalyst feed vessel 302 and the high
pressure catalyst transfer vessel 304 and subsequently
simultaneously sulfided in the two vessels 302 and 304. Such
positioning of fresh (to be sulfided) hydroprocessing catalyst may
be accomplished in any suitable manner such as initially adding a
batch of fresh (to be sulfided) hydroprocessing catalyst into the
low pressure catalyst feed vessel 302 from the catalyst loading
hopper 312 and subsequently transferring via conduit 306 such
initially added batch of fresh hydroprocessing catalyst to the high
pressure catalyst transfer vessel 304 and refilling the low
pressure catalyst feed vessel 302 from the catalyst loading hopper
312 with another batch of fresh (to be sulfided) hydroprocessing
catalyst. Alternatively, a second catalyst loading hopper (not
shown) may be provided and dedicated to the high pressure catalyst
transfer vessel 304 for dispensing fresh (to be sulfided)
hydroprocessing catalyst directly into the high pressure catalyst
transfer vessel 304 instead of through the low pressure catalyst
feed vessel 302. If two batches of hydroprocessing catalyst are to
be sulfided simultaneously in vessels 302 and 304, flow control
valves 330, 348, 358, and in lines 328, 340, 362, respectively, are
all opened and regulated as necessary and as would be well known to
artisans in the art such that mixtures of sulfided agent and heated
hydrocarbon and/or cold hydrocarbon are introduced simultaneously
into conduits 320 and 324 for simultaneous upflow through fresh (to
be sulfided) hydroprocessing catalyst that has been previously
positioned in vessels 302 and 304.
[0070] The low pressure catalyst feed vessel 302 is formed with a
screen 370 in communication with a conduit 372. Any mixture of
heated hydrocarbon and/or cold hydrocarbon and residual (unreacted)
"spiking" or sulfiding agent overflowing the low pressure catalyst
feed vessel 302 passes through screen 370 and into the conduit 372
for transportation to and dispensing into a flush oil separator
376. Conduit 372 comprises a flow/pressure control valve 380 for
controlling mixture flow through conduit 372 and for controlling
operating or working pressures within the low pressure catalyst
feed vessel 302. The high pressure catalyst transfer vessel 304 is
formed with a screen 382 wherethrough any mixture of heated
hydrocarbon and/or cold hydrocarbon and residual (unreacted)
"spiking" or sulfiding agent may pass and be introduced into a
conduit 384 for transportation through conduit 374 to the flush oil
separator 376. The conduit 384 contains a flow/pressure control
valve 386 for controlling mixture flow through conduit 384 from the
high pressure catalyst transfer vessel 304 and for controlling
operating and working pressures within the latter.
[0071] Preferably, the sulfiding process conditions within the low
pressure catalyst feed vessel 302 include an operating pressure
ranging from 0.7 KPa to 1480 KPa (0.1-200 psig) and an operating
temperature ranging from 90.degree. C. to 370.degree. C.; more
preferably an operating pressure ranging from 200 KPa to 1140 KPa
(15-150 psig) and an operating temperature ranging from 125.degree.
C. to 325.degree. C. Sulfiding process conditions within the high
pressure catalyst transfer vessel 304 include an operating pressure
ranging from 0.7 KPa to 24.2 MPa (0.1-3500 psig) and an operating
temperature ranging from 90.degree. C. to 370.degree. C.; more
preferably an operating pressure ranging from 7.0 MPa to 24.2 MPa
(1000-3500 psig) and an operating temperature ranging from
125.degree. C. to 325.degree. C.
[0072] In the process, presulfided catalyst from high pressure
transfer vessel 304 may be added to the hydroconversion reaction
zone through conduit 305. While not required, it may be desirable
to remove a volume of catalyst from the reaction zone 10, the
volume removed being approximately equal to the volume of
presulfided catalyst to be added to the reaction zone 10. The order
of operation, whether adding presulfided catalyst followed by
removal of at least partially spent catalyst from the reaction
zone, or, alternatively, removing at least partially spent catalyst
particulates from the reaction zone followed by adding presulfided
catalyst to the reaction zone, or, alternatively, removing at least
partially spent catalyst particulates from the reaction zone and
adding presulfided catalyst particulates to the reaction zone
simultaneously, is not critical to the invention, so long as the
catalyst volume in the reaction zone does not exceed design
capacity. Methods for transferring catalyst to and from a reaction
zone which are useful in the present process are disclosed, for
example, in U.S. Pat. No. 5,498,327, the entire disclosure of which
is incorporated herein by reference for all purposes. U.S. Pat. No.
5,498,327 is directed to transferring catalyst to and from moving
beds such as those of the instant invention. There is no teaching
in this patent of presulfiding techniques for catalyst being added
to moving beds.
[0073] The at least partially spent catalyst to be withdrawn from
the hydroconversion reaction zone 10 is either intermittently or
semi-continuously or continuously withdrawn in the hydrocarbon
liquid, as defined above, from the reactor vessel 11 and discharged
into conduit 198 via valve 94 for transfer to the high pressure
catalyst recovery vessel 304. The withdrawn catalyst will typically
be from about 50% to about 95% expended, more preferably from about
70% to about 80% expended, where a 100% presulfided expended
catalyst will be fully fouled and will possess essentially no
useful hydroconversion activity at reaction conditions in the
hydroconversion zone.
[0074] The at least partially spent catalyst in the hydrocarbon
liquid has a high concentration of catalyst to hydrocarbon liquid,
preferably from about 0.2 to about 1.0 pounds of particulate
catalyst per pound of catalyst slurry (i.e. weight of withdrawn
catalyst plus weight of hydrocarbon liquids), more preferably from
about 0.25 to about 0.8 pounds of particulate catalyst per pound of
catalyst slurry, most preferably about 0.5 pounds of particulate
catalyst per pound of catalyst slurry. The hydrocarbon liquids may
comprise a liquid hydrocarbon component which has not been
converted (into lighter products) or partly converted or a mixture
of partly converted and unconverted liquid hydrocarbon components
or a mixture of a hydrogen-containing gas component and any of the
liquid components.
[0075] In the preferred embodiment of a substantially packed
catalyst bed, the withdrawn at least partially spent catalyst is a
volumetric layer (i.e. the lowermost volumetric layer) of catalyst
from the catalyst bed 10 of reactor vessel 11. As withdrawal
commences the particulate catalyst in the catalyst bed 10 plug
flows downwardly. As previously indicated, the withdrawn at least
partially expended catalyst is transferred in the hydrocarbon
liquid (as defined above) to the high pressure catalyst transfer
vessel 304 as a concentrated highly dense liquid slurry in laminar
flow, in order to avoid undue abrasion of the withdrawn at least
partially expended catalyst particles that are being transferred
into the catalyst transfer vessel 304 by conduit 198.
[0076] Catalysts useful in the present process are described in
detail in U.S. Pat. No. 5,472,928, the entire disclosure of which
is incorporated herein by reference for all purposes. A preferred
catalyst comprises an inorganic support which may include zeolites,
inorganic oxides, such as silica, alumina, magnesia, titania and
mixtures thereof, or any of the amorphous refractory inorganic
oxides of Group II, III or IV elements, or compositions of the
inorganic oxides. The inorganic support more preferably comprises a
porous carrier material, such as alumina, silica, silica-alumina,
or crystalline aluminosilicate. Deposited on and/or in the
inorganic support or porous carrier material is one or more metals
or compounds of metals, such as oxides, where the metals are
selected from the groups IB, VB, VIIB, VIIB, and VIII of the
Periodic System. Typical examples of these metals are iron, cobalt,
nickel, tungsten, molybdenum, chromium, vanadium, copper,
palladium, and platinum as well as combinations thereof. Preference
is given to molybdenum, tungsten, nickel, cobalt, platinum, and
palladium and combinations thereof. Suitable examples of catalyst
of the preferred type comprise nickel-tungsten, nickel-molybdenum,
cobalt-molybdenum or nickel-cobalt-molybdenum deposited on and/or
in a porous inorganic oxide selected from the group consisting of
silica, alumina, magnesia, zirconia, thoria, boria or hafnia or
compositions of the inorganic oxides, such as silica-alumina,
silica-magnesia, alumina-magnesia and the like.
[0077] The catalyst of the present invention may further comprise
additives, such as phosphorus, boron, clays (including pillared
clays), boron phosphate or phosphor, and/or halogens, such as
fluorine and chlorine. The boron phosphate compound may be present
in an amount ranging from about 10 to about 40 percent by weight
calculated on the weight of the total catalyst (i.e. inorganic
oxide support plus metal oxide(s)), and more preferably ranging
from about 15 to about 30 percent by weight, whereas the halogens
and phosphor are used in an amount of less than about 10 percent by
weight of the total catalyst.
[0078] Although the metal components (i.e. cobalt, nickel,
molybdenum, etc.) may be present in any suitable amount, the
catalyst of the present invention preferably comprises of from
about 0.1 to about 60 percent by weight of metal component(s)
calculated on the weight of the total catalyst (i.e. inorganic
oxide support plus metal oxides) and more preferably of from about
5 to about 50 percent by weight of the total catalyst. The metals
of Group VIII are generally applied in a minor quantity ranging
from about 0.1 to about 30 percent by weight, and the metals of
Group VIB are generally applied in a major quantity ranging from
about 1.25 to about 50 percent by weight. The atomic ratio of the
Group VIII and Group VIB metals may vary within wide ranges,
preferably from about 0.01 to about 15, more preferably from about
0.05 to about 10, and most preferably from about 0.1 to about
5.
[0079] The groups in the Periodic System referred to above are from
the Periodic Table of the Elements as published in Lange's Handbook
of Chemistry (Twelfth Edition) edited by John A. Dean and
copyrighted 1979 by McGraw-Hill, Inc., or as published in The
Condensed Chemical Dictionary (Tenth Edition) revised by Gessner G.
Hawley and copyrighted 1981 by Litton Educational Publishing
Inc.
[0080] In a more preferred embodiment for the catalyst, the oxidic
hydrotreating catalyst or metal oxide component carried by or borne
by the inorganic support or porous carrier material is molybdenum
oxide (MoO3) or a combination of MoO3 and cobalt oxide (CoO) or a
combination of MoO3 and nickel oxide (NiO) where the MoO3 is
present in the greater amount. The porous inorganic support is more
preferably alumina. The MoO3 is present on the catalyst inorganic
support (alumina) in an amount ranging from about 1 to about 60
percent by weight, preferably from about 1 to about 35 percent by
weight, more preferably from about 2 to about 8 percent by weight
based on the combined weight of the inorganic support and metal
oxide(s). When CoO (or NiO) is present it will be in amounts
ranging up to about 30 percent by weight, preferably from about 0.5
to about 20 percent by weight, more preferably from about 1 to
about 6 percent by weight based on the combined weight of the
catalyst inorganic support and metal oxide(s). The oxidic
hydrotreating catalyst or metal oxide component may be prepared by
depositing aqueous solutions of the metal oxide(s) on the porous
inorganic support material and thoroughly drying, or such catalyst
may be purchased from various catalyst suppliers. Catalyst
preparative techniques in general are conventional and well known
and can include impregnation, mulling, co-precipitation and the
like, followed by calcination.
[0081] In a preferred embodiment of the present invention, the
catalyst will have a uniform size which is preferably spherical
with a diameter as a mean of a normal Gausian distribution curve
ranging from about {fraction (1/64)} inch to about {fraction (1/4)}
inch, more preferably ranging from about {fraction (1/16)} inch to
about {fraction (1/8)} inch. To maintain a uniform size particle,
it is preferred that at least about 70%, preferably at least about
80%, and more preferably at least about 90% of the catalyst
particles be of a size within about 20%, preferably within about
10%, and more preferably within about 5% of the mean catalyst
particle size, where the mean particle size is based on the longest
dimension of the particle.
[0082] From the foregoing discussion it will be clear to the
skilled practitioner that, though the catalyst particles of the
present process have a uniform size, shape, and density, the
chemical and metallurgical nature of the catalyst may change,
depending on processing objectives and process conditions selected.
For example, a catalyst selected for a demetallation application
with minimum hydrocracking desired could be quite different in
nature from a catalyst selected if maximum hydrodesulfurization and
hydrocracking are the processing objectives. The type of catalyst
selected in accordance with and having the properties mentioned
above, is disposed in any hydroconversion reaction zone. A
hydrocarbon feed stream is passed through the catalyst, preferably
passed through such as to upflow through the catalyst, in order to
hydroprocess the hydrocarbon feed stream. More preferably, the
catalyst is employed with the various embodiments of the present
invention.
[0083] The process of the present invention is further illustrated
with the following specific example of the invention. In the
example process, a hydrocarbon feed stream having a boiling point
of greater than about 343.degree. C. and containing greater than 1
ppm metals and greater than 500 ppm sulfur is introduced into a
hydroconversion reaction zone which contains particulate
hydroprocessing catalyst maintained at a reaction pressure, to
commence upflowing of said hydrocarbon feed stream through said
catalyst and to recover a reaction effluent therefrom. The
properties of the feed stream, the properties of the catalyst and
reaction conditions, including flow rate, reaction temperature and
reaction pressure, are selected to maintain the reactor system as a
substantially packed-bed type reactor system, where the catalyst
and fluid velocity combinations limit bed expansion to less than
10% by length beyond a substantially full axial length of the bed
in a packed bed state. It is more preferred that the bed expansion
be maintained at less than 5% and more preferred at less than 1% of
the substantially full axial length of the bed in a packed bed
state. A preferred reaction pressure in the hydroconversion
reaction zone is greater than 343.degree. C., and more preferably
in the range of 343.degree. C. to 482.degree. C. A preferred
reaction pressure in the hydroconversion reaction zone is greater
than 7.0 MPa (1000 psig), and more preferably in the range of 7.0
MPa to 24.2 MPa (1000-3500 psig).
[0084] During the hydroprocess, a volume of hydroprocessing
catalyst within a pretreatment zone is sulfided to produce sulfided
catalyst, and at least a portion of the sulfided catalyst is added
into the hydroconversion reaction zone while maintaining the
reaction zone at the reaction pressure.
[0085] The hydroprocessing catalyst to be sulfided is either fresh
hydroprocessing catalyst or combinations of fresh hydroprocessing
catalyst and regenerated hydroprocessing catalyst. While additional
components other than catalyst to be sulfided may be included in
the volume of hydroprocessing catalyst, it is generally not
preferred. A volume of the hydroprocessing catalyst is added to a
pretreatment zone, such as by adding a slurry comprising a
hydrocarbon liquid and the volume of hydroprocessing catalyst to
the pretreatment zone and removing at least a portion of the
hydrocarbon liquid from the pretreatment zone., and the volume is
heated until the catalyst has a temperature ranging from 90.degree.
C. to 370.degree. C. When the desired temperature is achieved, a
sulfiding agent is added to the pretreatment zone to prepare
sulfided catalyst. A suitable sulfiding agent includes H.sub.2S and
H.sub.2, typically in a molar ratio in the range 10:1 to 1:10.
[0086] An example method of adding sulfiding agent to the
pretreatment zone comprises introducing a H.sub.2S containing
gaseous material to the pretreatment zone, pressurizing the
pretreatment zone which contains the hydroprocessing catalyst with
a H.sub.2 containing gas at a pressure in the range of 200 KPa to
20,000 KPa and a temperature in the range of 90.degree. C. to
370.degree. C., preferably in the range of 125-325.degree. C., more
preferably in the range of 150-285.degree. C. The catalyst in the
pretreatment zone is maintained at the given pressure in contact
with the sulfiding agent for a sufficient time, generally less than
24 hours, preferably less than 10 hours, more preferably less than
5 hours, to at least partially sulfide the catalyst. The pressure
in the pretreatment zone is then reduced and at least a portion of
the sulfiding agent is removed from the pretreatment zone.
[0087] An alternative example method of adding sulfiding agent to
the pretreatment zone comprises adding a volume of hydroprocessing
catalyst to the pretreatment zone, which volume includes fresh
hydroprocessing catalyst; flowing a heated hydrocarbon liquid
through the volume of hydroprocessing catalyst within the
pretreatment zone until the catalyst has a temperature ranging from
90.degree. C. to 150.degree. C.; subsequently pressurizing the
pretreatment zone at a pressure ranging from 0.2 MPa to 24.2 MPa
(15-3500 psig); continuing to flow the heated hydrocarbon liquid
through the catalyst in the pretreatment zone until the catalyst
has a temperature ranging from 125.degree. C. to 325.degree. C.;
flowing a sulfiding mixture through the catalyst in the
pretreatment zone to prepare sulfided catalyst.
[0088] The sulfided hydroconversion catalyst is added to the
hydroconversion reaction zone at a temperature greater than
125.degree. C., preferably greater than 150.degree. C. and at a
pressure of no less than the reaction pressure of the
hydroconversion reaction zone. The method of adding the sulfided
hydroconversion catalyst to the hydroconversion reaction zone
comprises adding a hydrocarbon liquid to the sulfided catalyst in
the pretreatment zone; forming a slurry comprising the hydrocarbon
liquid and at least a portion of the sulfided catalyst; and adding
the slurry of the hydrocarbon liquid and the sulfided catalyst to
the hydroconversion reaction zone while maintaining the reaction
zone at the reaction pressure.
[0089] The reaction zone 10 contained within reactor vessel 11 is
preferably an upflow reaction system, with reacting fluids entering
reaction zone 10 through feed inlet 14, passing upward in upflow
mode through reaction zone 10 moving bed reactor, the reaction
effluent exiting through conduit 16. The catalyst presulfiding
process is effective for reaction zones operated as a ebullating
bed reaction system or as a substantially packed-bed type reactor
system having an onstream catalyst replacement system (i.e. having
a capability for transferring catalyst to and from the reaction
zone at substantially reaction pressure). To maintain the reactor
system as a substantially packed-bed type reactor system, the
onstream catalyst replacement system is a counterflow processing
system where the catalyst and fluid velocity combinations limit bed
expansion to less than 10% by length beyond a substantially full
axial length of the bed in a packed bed state. It is more preferred
that the bed expansion be maintained at less than 5% and still more
preferred at less than 1% of the substantially full axial length of
the bed in a packed bed state. A preferred substantially packed bed
type reactor system is taught in U.S. Pat. No. 5,076,908, the
disclosure of which is incorporated herein by reference for all
purposes.
[0090] In carrying out the process of a preferred embodiment of the
present invention as broadly illustrated in FIGS. 1, 2, a minimum
average level of catalytic feed upgrading activity for the
countercurrently moving catalyst bed (e.g. catalyst bed 10) as a
whole is selected for the particular catalytic upgrading reaction.
For a moving bed (e.g. catalyst bed 10) in a demetallation reaction
system, for example, the minimum average upgrading activity level
for the catalyst bed is one which removes the necessary amount of
metals from the hydrocarbon feed stream when it passes through the
moving bed at demetallation conditions. Similarly, for a
desulfurization reaction system, the moving catalyst bed (e.g.
catalyst bed 10) removes the necessary amount of sulfur from the
hydrocarbon feed stream when it passes through the moving bed at
desulfurization conditions. Thus, as will be apparent to those
skilled artisans, the minimum average upgrading activity level for
a particular reaction system will depend on the desired degree of a
contaminant, such as metals, sulfur, nitrogen, asphaltenes, etc.,
which the refiner desires to remove from the heavy oil feed. The
degree of demetallation or desulfurization (or etc.) will typically
be set by economics and the downstream processing that the heavy
feed will undergo.
[0091] A preferred upgrading use of the present invention is for
feed demetallation. For such upgrading, the temperatures and
pressures within the reaction zone can be those typical for
conventional demetallation processing. The pressure is typically
above 3.45 MPa (500 psig). The temperature is typically greater
than 315.degree. C., and preferably above 371.degree. C. Generally,
the higher the temperature, the faster the metals are removed; but
the higher the temperature, the less efficiently the metals
capacity of the demetallation catalyst is used. While demetallation
reaction can be conducted in the absence of added hydrogen,
hydrogen is generally used and therefore requires full and equal
distribution into the moving bed along with any gases evolving from
the feed. More preferred hydroprocessing conditions within the
hydroconversion reaction zone to hydroprocess the hydrocarbon feed
stream include a reaction temperature in a temperature range
343'-482.degree. C. (650'-900.degree. F.) and a reaction pressure
in a pressure range of 7.0 MPa to 24.2 MPa (1000-3500 psig).
[0092] The invention is illustrated by the following example of a
preferred embodiment. A hydrocarbon feed stream in the presence of
hydrogen is introduced into a hydroconversion reaction zone which
contains particulate hydroprocessing catalyst maintained at a
reaction pressure, to commence upflowing of said hydrocarbon feed
stream through said catalyst and to recover a reaction effluent
therefrom. The reaction pressure is preselected for the particular
process and reactions desired, and is typically greater than 3.6
MPa (500 psig), preferably in the temperature range of 7.0 MPa to
24.2 MPa (1000-3500 psig). The reaction temperature, which is
sufficient to hydroprocess the hydrocarbon feed stream, is in a
temperature range of 343'-482.degree. C. (650'-900.degree. F.). In
the process, a first volume of the hydroprocessing catalyst from
the hydroconversion reaction zone is withdrawn while maintaining
the reaction zone at the reaction pressure. Desirably, the
hydroconversion reaction zone contains a substantially packed bed
of catalyst, which commences to essentially plug-flow downwardly
within the hydroconversion reaction zone when the first volume of
hydroprocessing catalyst is withdrawn therefrom.
[0093] The preferred process further comprises sulfiding a second
volume of hydroprocessing catalyst within a pretreatment zone to
produce sulfided catalyst. In one preferred embodiment of the
process, sulfided catalyst is produced by adding a second volume of
hydroprocessing catalyst to the pretreatment zone, which second
volume includes fresh hydroprocessing catalyst; heating the second
volume of hydroprocessing catalyst until the catalyst has a
temperature ranging from 90.degree. C. to 370.degree. C.,
preferably from 125.degree. C. to 325.degree. C.; and adding a
sulfiding agent to the pretreatment zone to prepare sulfided
catalyst. If catalyst is added to the pretreatment zone as a slurry
in, e.g. a hydrocarbon stream, it may be desired to remove at least
a portion of the hydrocarbon stream prior to sulfiding. Sulfiding
agent may be added by flowing the agent, or a liquid stream
containing the agent, through the catalyst. Alternatively,
sulfiding agent may be added by pressurizing a vessel containing
the hydroprocessing catalyst in the pretreatment zone with the
sulfiding agent. A sulfiding procedure involving pressurizing the
catalyst in the pretreatment zone with a sulfiding agent for a time
sufficient to sulfide the catalyst may include a step of reducing
the pressure in the pretreatment zone, and repressurizing the
catalyst in the pretreatment zone with a second quantity of
sulfiding agent, to further sulfide the catalyst. This cycle may be
repeated until the catalyst is adequately sulfided for the use
desired.
[0094] To heat and/or sulfide the catalyst using flowing liquid
streams, one preferred embodiment of the invention includes flowing
a heated hydrocarbon liquid through the second volume of
hydroprocessing catalyst within the pretreatment zone until the
catalyst has a temperature ranging from 90.degree. C. to
145.degree. C.; subsequently pressurizing the pretreatment zone;
continuing to flow the heated hydrocarbon liquid through the
catalyst in the pretreatment zone until the catalyst has a
temperature ranging from 125.degree. C. to 325.degree. C.;
subsequently adding a sulfiding agent into the heated hydrocarbon
liquid to produce a sulfiding mixture; flowing the sulfiding
mixture through the catalyst in the pretreatment zone to prepare
sulfided catalyst. Preferred sulfiding agents include H.sub.2S,
such as the H.sub.2S derived from a recycle stream recovered from
the reaction effluent, dimethylsulfide and dimethyldisulfide.
Catalyst may be sulfided in the present process at low temperature,
e.g. at less than 370.degree. C., preferably in the temperature
range 125-325.degree. C., more preferably in the temperature range
150.degree.-285.degree. C. Catalyst may be sulfided in a low
pressure vessel in the pretreatment zone at a pressure of 200 KPa
(15 psig) or higher; in a high pressure vessel in the pretreatment
zone at a pressure in the range of, for example, 7.0 MPa to 24.2
MPa (1000 psig to 3500 psig), or in both.
[0095] Sulfided catalyst is added to the hydroconversion reaction
zone at a pressure higher than the reaction pressure, in order for
the catalyst to flow into the reaction zone. Suitably, the catalyst
is added to the reaction zone as a slurry in a hydrocarbon stream
by adding a hydrocarbon liquid to the sulfided catalyst in the
pretreatment zone; forming a slurry comprising the hydrocarbon
liquid and at least a portion of the sulfided catalyst; and adding
the slurry of the hydrocarbon liquid and the sulfided catalyst to
the hydroconversion reaction zone.
EXAMPLES
[0096] The catalytic particulates comprised an alumina porous
carrier material or alumina inorganic support. Deposited on and/or
in the alumina porous carrier material was an oxidic hydrotreating
catalyst component consisting of NiO and/or MoO.sub.3. The Mo was
present on and/or in the alumina porous carrier material in an
amount of about 3% by wt., based on the combined weight of the
alumina porous carrier material and the oxidic hydrotreating
catalyst component(s). The Ni was present on and/or in the alumina
porous carrier material in an amount of about 1% by wt., based on
the combined weight of the alumina porous carrier material and the
oxidic hydrotreating catalyst component(s). The surface area of the
catalytic particulates was about 120 sq. meters per gram.
[0097] The plurality of catalytic particulates were generally
spherical with a mean diameter having a value ranging from about 6
Tyler mesh to about 8 Tyler mesh and an aspect ratio of about 1.
The mean crush strength of the catalytic particulates was about 5
lbs. force. The metals loading capacity of the catalyst or
plurality of catalytic particulates was about 0.3 grams of metal
per cubic centimeter of catalytic particulate bulk volume.
[0098] A sample of the catalyst was loaded into a sulfiding
reactor, heated at 205.degree. C., and flooded with medium cycle
oil (MCO). After 30 minutes the medium cycle oil was drained, and
MCO continued to pump over the catalyst with the drain open for an
additional 30 minutes. The flow of MCO was stopped and the excess
oil allowed to drain from the catalyst. The catalyst in the
sulfiding reactor was then pressurized with 13.2 MPa of 5.0 vol %
H.sub.2S in H.sub.2 for 2.5 hours. The sulfiding reactor containing
the catalyst was then depressurized to 790 KPa and cooled to
38.degree. C. The catalyst was flushed with heptane to remove the
remaining MCO, dried and recovered for analysis. The sulfur content
as shown in Run A of Table I is a percent of the amount of sulfur
present on a catalyst which was sulfided using dimethyldisulfide in
a standard liquid sulfiding procedure at 316.degree. C.
[0099] Table I also lists the sulfur content on catalysts sulfided
using the procedure of Run A as described (e.g. Run B), using the
procedure of Run A but without flooding the catalyst initially with
MCO (e.g. Run C), using the procedure of Run A but sulfiding at
316.degree. C. (e.g. Run D) or at 149.degree. C. (e.g. Run E), or
at 204.degree. C. for 1.25 hours followed by 316.degree. C. for
1.25 hours (e.g. Run F). The results in Table I show that, at the
conditions of the experiment, the catalyst was adequately sulfided
at 204.degree. C. using a single contacting cycle. The extent of
sulfiding was higher at 204.degree. C. than at either 149.degree.
C. or at 316.degree. C. Two sulfiding cycles gave slightly better
results than one cycle. The best results, in terms of extent of
sulfiding of the catalyst, occurred with the sulfiding temperature
maintained at 204.degree. C. for 1.25 hours followed by 316.degree.
C. for 1.25 hours (Run F).
1TABLE I Run B C A E F Catalyst Wetted with Wetted with Dry Wetted
with Wetted with Wetted with Pretreatment medium cycle medium cycle
medium cycle medium cycle medium cycle oil oil oil oil oil
Sulfiding 204.degree. C. 204.degree. C. 204.degree. C. 316.degree.
C. 149.degree. C. 204.degree. C./316.degree. C. temperature Number
of 1 2 1 1 1 1 sulfiding cycles Sulfiding time, 2.5 hours 2.5 hours
2.5 hours 2.5 hours 2.5 hours 2.5 hours each cycle Sulfur content
76% 82% 77% 62.5% 69.1% 90.5% of the sulfided catalyst 1
[0100] Three catalyst samples were tested: an H.sub.2S presulfided
catalyst sample prepared as in Run A above (Sample G); a catalyst
sample presulfided using a standard dimethyldisulfide liquid
presulfiding treatment at 316.degree. C. (Sample H); and a catalyst
sample which was not presulfided (Sample I).
[0101] Each catalyst sample was dropped into an Arab Heavy
Atmospheric Residuum (4.3% Sulfur, 24.6 ppm nickel, 82.4 ppm
vanadium and 11.3 API gravity) heated to 371.degree. C. to simulate
dropping catalyst into a moving bed reactor at reaction
temperature. The catalyst was removed from the residuum after 24
hours, flushed with solvent, dried, and analyzed for the sulfur
content remaining.
2 Catalyst Sample Sulfur content on catalyst, wt % G 2.83 H 2.79 I
2.68
[0102] These results suggest that the total sulfur content was
essentially the same on each of the three catalyst samples.
[0103] Following the hot oil treatment, catalyst samples G, H and I
were tested for desulfurization activity, using an atmospheric
residuum feedstock having the following properties
3 Gravity, .degree. API 8.9 Sulfur, wt % 4.51 MCR, wt % 16.6 V, ppm
358 Ni, ppm 70 Asphaltenes, wt % 13.6 Viscosity @ 100.degree. C.,
cSt 285
[0104] The atmospheric residuum feedstock was contacted with
H.sub.2 over each catalyst at 13.9 MPa pressure, a flow rate of
0.75 hr-1, and with a once-through hydrogen flow of 760 liters
H.sub.2/kg oil. For the first 250 hours, the reaction temperature
was maintained at 378.degree. C. Between 250 hours and 750 hours
the reaction temperature was maintained at 402.degree. C.
[0105] FIG. 3 is a normalized temperature plot showing the
normalized reaction temperature required to maintain a product
sulfur content of 2.2 wt % in the stripper bottoms product at 0.75
LHSV, assuming 1.5th order kinetics and an activation energy of 30
kcal/gmole. As shown in FIG. 3, the catalyst presulfided using the
H.sub.2S treatment was 3.9.degree. C. (7.degree. F.) more active
(i.e. lower reaction temperature) than the conventional unsulfided
catalyst. The catalyst presulfided using the more costly
dimethyldisulfide presulfiding was 9.4.degree. C. (17.degree. F.)
more active than the conventional unsulfided catalyst. These data
show the surprising benefit of presulfiding the catalyst prior to
adding the catalyst to a moving bed reaction system, even though
the catalyst is presumed to be quickly sulfided once it is added to
the reaction zone by the sulfur containing components of the feed
which is being processed.
* * * * *