US20050006283A1

US20050006283A1 - Presulfiding OCR catalyst replacement batches

Info

Publication number: US20050006283A1
Application number: US10/841,650
Authority: US
Inventors: Pak Leung; David Earls; Bruce Reynolds; David Johnson; Robert Bachtel; Harold Trimble
Original assignee: Chevron USA Inc
Current assignee: Chevron USA Inc
Priority date: 1999-12-16
Filing date: 2004-05-06
Publication date: 2005-01-13

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.

Description

CROSS REFERENCE TO RELATED APPLICATION

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

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.
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.
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 H₂/H₂S 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.
Generally, non-spiked feedstock presulfiding techniques involve decomposition of sulfur compounds, which are naturally present in a selected startup hydrocarbon feed, into H₂S at reactor temperature conditions ranging from about 300° C. (572° F.) to about 350° C. (662° 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 H₂S 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° C. to about 275° 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.
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.
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° C. (392° F.) and completed before temperatures are elevated above about 300° C. (572° 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° 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.
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

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.
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.
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:

- 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;
- ex-situ sulfiding a volume of hydroprocessing catalyst within a pretreatment zone to produce sulfided catalyst; and
- adding at least a portion of the sulfided catalyst into the hydroconversion reaction zone while maintaining the reaction zone at the reaction pressure.

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° C. to 370° C. The preferred temperature for sulfiding the catalytic particulates is in the range from 125° C. to 325° 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.
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:

- adding a volume of hydroprocessing catalyst to the pretreatment zone, which volume includes fresh hydroprocessing catalyst;
- heating the volume of hydroprocessing catalyst until the catalyst has a temperature ranging from 90° C. to 370° C.; and
- adding a sulfiding agent to the pretreatment zone to prepare sulfided catalyst.

In the preferred process of the invention, the method of adding the volume of hydroprocessing catalyst to the pretreatment zone comprises the steps of:

- preparing a slurry comprising a hydrocarbon liquid and a volume of hydroprocessing catalyst;
- adding the slurry comprising the hydrocarbon liquid and the hydroprocessing catalyst to the pretreatment zone; and
- removing at least a portion of the hydrocarbon liquid from the pretreatment zone.
  and the method of adding a sulfiding agent to the pretreatment zone comprises:
- 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° C. to 370° C. to produce at least partially sulfided catalyst; and
- removing at least a portion of the sulfiding agent from the pretreatment zone.

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:

- 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° C. to 145° 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 90° C. to 370° C.;
- flowing a sulfiding mixture through the catalyst in the pretreatment zone to prepare at least partially sulfided catalyst.

The preferred temperature for sulfiding the catalytic particulates is in the range from 125° C. to 325° 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.
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:

- 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.

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:

- 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;
- 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;
- adding a second volume of a particulate hydroprocessing catalyst to a pretreatment zone, which second volume includes fresh hydroprocessing catalyst;
- sulfiding the second volume of hydroprocessing catalyst within the pretreatment zone to prepare sulfided catalyst; and
- adding at least a portion of the sulfided catalyst into the hydroconversion reaction zone to replace the withdrawn first volume of catalyst.

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

FIG. 1 illustrates an embodiment of the invention with a high pressure catalyst transfer vessel only for presulfiding the catalyst according to the invention.
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.
FIG. 3 shows the improved desulfurization performance of a catalyst presulfided according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

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.
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.
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.
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 (H₂S), preferably containing from about 5% by weight to about 80% by weight H₂S. When H₂S is employed as a sulfiding agent in the present process, a preferred H₂S 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 H₂S rich stream, which may be recycled via conduit 328 for use as a sulfiding agent.
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.
Prior to sulfiding, the catalyst is heated to an elevated temperature, such as from 50° C. to 370° C., more preferably from 125° C. to 325° C., still more preferably from 150° C. to 285° C. The heat may be supplied by the catalyst transfer vessel, heated to an elevated temperature, such as between 90° C. and 370° 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.
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° C. and more preferably boiling in the range of from 315° C. to 525° 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.
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 H₂S containing stream. The H₂S 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). H₂S 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° C.-370° C., preferably in the range 125° C.-325° C., more preferably in the range of 150° C.-285° C., and still more preferably in the range of 175° C.-240° 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.
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 H₂to 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 H₂S, 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.
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° 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.
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.
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.
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° C. to 145° 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° C. to 325° C. A sulfiding mixture, delivered via conduit 324 is then flowed through the catalyst in the pretreatment zone to prepare sulfided catalyst.
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.
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 H₂S-rich hydrocarbon gas, the flush oil separator 376 separates mixture(s) of heated hydrocarbon and/or cold hydrocarbon and H₂S-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.
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.
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° C. to 370° 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.
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.
The low pressure feed conduit 320 and the high pressure feed
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.
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.
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.
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.
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° C. to 370° C.; more preferably an operating pressure ranging from 200 KPa to 1140 KPa (15-150 psig) and an operating temperature ranging from 125° C. to 325° 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° C. to 370° 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° C. to 325° C.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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° 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° C., and more preferably in the range of 343° C. to 482° 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).
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.
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° C. to 370° 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 H₂S and H₂, typically in a molar ratio in the range 10:1 to 1:10.
An example method of adding sulfiding agent to the pretreatment zone comprises introducing a H₂S containing gaseous material to the pretreatment zone, pressurizing the pretreatment zone which contains the hydroprocessing catalyst with a H₂containing gas at a pressure in the range of 200 KPa to 20,000 KPa and a temperature in the range of 90° C. to 370° C., preferably in the range of 125-325° C., more preferably in the range of 150-285° 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.
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° C. to 150° 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° C. to 325° C.; flowing a sulfiding mixture through the catalyst in the pretreatment zone to prepare sulfided catalyst.
The sulfided hydroconversion catalyst is added to the hydroconversion reaction zone at a temperature greater than 125° C., preferably greater than 150° 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.
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.
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.
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° C., and preferably above 371° 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° C. (650′-900° F.) and a reaction pressure in a pressure range of 7.0 MPa to 24.2 MPa (1000-3500 psig).
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° C. (650′-900° 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.
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° C. to 370° C., preferably from 125° C. to 325° 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.
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° C. to 145° 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° C. to 325° 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 H₂S, such as the H₂S 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° C., preferably in the temperature range 125-325° C., more preferably in the temperature range 150°-285° 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.
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

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 MoO₃. 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.
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.
A sample of the catalyst was loaded into a sulfiding reactor, heated at 205° 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 % H₂S in H₂for 2.5 hours. The sulfiding reactor containing the catalyst was then depressurized to 790 KPa and cooled to 38° 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° C.

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° C. (e.g. Run D) or at 149° C. (e.g. Run E), or at 204° C. for 1.25 hours followed by 316° 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° C. using a single contacting cycle. The extent of sulfiding was higher at 204° C. than at either 149° C. or at 316° 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° C. for 1.25 hours followed by 316° C. for 1.25 hours (Run F).

TABLE 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° C.	204° C.	204° C.	316° C.	149° C.	204° C./316° 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

Three catalyst samples were tested: an H₂S presulfided catalyst sample prepared as in Run A above (Sample G); a catalyst sample presulfided using a standard dimethyldisulfide liquid presulfiding treatment at 316° C. (Sample H); and a catalyst sample which was not presulfided (Sample I).
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° 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.

Catalyst Sample Sulfur content on catalyst, wt %

G 2.83

H 2.79

I 2.68
These results suggest that the total sulfur content was essentially the same on each of the three catalyst samples.
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

Gravity, ° API 8.9

Sulfur, wt % 4.51

MCR, wt % 16.6

V, ppm 358

Ni, ppm 70

Asphaltenes, wt % 13.6

Viscosity @ 100° C., cSt 285
The atmospheric residuum feedstock was contacted with H₂over 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 H₂/kg oil. For the first 250 hours, the reaction temperature was maintained at 378° C. Between 250 hours and 750 hours the reaction temperature was maintained at 402° C.
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 H₂S treatment was 3.9° C. (7° 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° C. (17° 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.

Claims

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° C. to 370° 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° C. to 325° 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° C. to 370° 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 H₂S and sulfur-containing materials which decompose at temperatures below about 370° C.

12. The process of claim 11, wherein the presulfiding agent comprises H₂S.

13. The process of claim 11, wherein the presulfiding agent comprises a gaseous recycle stream containing H₂and H₂S.

14. The process of claim 10, wherein the at least partially presulfided catalyst is produced at a temperature in the range of 125° C. to 325° 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° C. to 285° 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° C. to 145° 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° C. to 325° 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° C. to 370° 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.