AU707435B2 - In situ catalyst formation in fluidized bed syn gas operations - Google Patents

Description

I'/UU/U 1 28/591 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged:

I

*o *o*oo oooo o *o *e Invention Title: IN SITU CATALYST FORMATION IN FLUIDIZED BED SYN GAS

OPERATIONS

The following statement is a full description of this invention, including the best method of performing it known to us -1- 1. FIELD OF THE INVENTION This invention relates to a process for the in situ formation of catalysts useful in FBSG and partial oxidaton processes; catalysts which can be employed in situ or ex situ relative to the reactor in which they are prepared.

2. BACKGROUND Fluidized bed processes are known to provide superior heat and mass transfer characteristics as contrasted with fixed bed processes.

They permit substantially isothermal reactor conditions in conducting both exothermic and endothermic reactions.

For example, in the production of synthesis gas (hydrogen and carbon monoxide) via a known Fluidized Bed Syn Gas, FBSG, :i process, low molecular weight hydrocarbons natural gas (primarily CH4), are fed into the bottom of a reactor containing a mixture of catalyst, a nickel-on-alumina catalyst, and a solids diluent, alumina, to form a fluidized bed of the catalyst and solids diluent. Steam is introduced into the reactor. Oxygen is fed into the fluidized bed through nozzles separate from those through which the natural gas is fed. The oxygen reacts with a portion of the natural gas in a zone near the oxygen :i inlet according to the following partial oxidation reaction:

CH

4 02 CO H 2

H

2 0 (Partial Oxidation) -2- This is a strongly exothermic reaction and produces localized hot spots and burning near the 02 nozzle, or nozzles; the high temperature area around the 02 nozzle constituting a burning zone. The natural gas that does not react directly with the 02 ascends through the reactor where it undergoes a steam reforming reaction to produce hydrogen and carbon monoxide according to the following reaction: CH4 H 2 0 CO 3H2 (Steam Reforming) The steam reforming is highly endothermic, but by having good solids circulation in the fluidized bed, the overall bed temperature becomes quite uniform. The net, or overall reaction (the sum of reactions and supra), described as follows, is slightly exothermic.

2CH 4 02 2CO 4H 2 (Overall) The overall reactions occur in a net reducing atmosphere.

The water gas shift reaction also occurs in the bed; a very rapid reaction which produces only minor heat effects.

CO H 2 0 CO, H2 (Water Gas Shift) The exothermic heat of reaction produced by the oxygen causes burning and severe localized heat near the oxygen inlet zone; and despite the good heat transfer in the fluid bed, the high temperature produces net agglomeration of the catalyst, or catalyst and other solids.

-3- The high localized flame temperature produced by the oxygen in the burning zone of the bed can exceed the melting point of the alumina, or at least produce temperatures which cause the surface of the alumina particles to melt, stick and fuse together as the particles repetitively collide or recycle through the burning zone of the bed. The amount of agglomeration increases with time which adversely affects the fluidization characteristics of the bed, and the activity of the catalyst declines. The active catalytic sites become inaccessible to the reactants due to the agglomeration of the particles; or active surface area lost due to metals agglomeration.

3. DESCRIPTION OF THE INVENTION The present invention relates to the formation in an FBSG operation of catalysts useful in an FBSG process, or process for producing a syn gas, or mixture of hydrogen and carbon monoxide, from a low molecular weight hydrocarbon, steam and oxygen and in a partial oxidation process for producing hydrogen and carbon monoxide i- from a low molecular weight hydrocarbon and oxygen. The catalysts are formed in a reaction zone at FBSG reaction conditions from a fluidized bed of particulate refractory inorganic oxide solids, or (ii) a fluidized bed of a deactivated, or deactivating, catalyst composite, or (iii) mixture of a deactivated, or deactivating, catalyst composite and particulate refractory inorganic oxide solids, by adding, intermittently or continuously to the reaction zone a decomposable compound of a catalytic-metal, or catatyuc metallic metai, to disperse the metal, which at FBSG reaction conditions, will move from particle to particle to form catalytically active :o -4metallic crystallites upon the solids particles of the fluidized bed sufficient, where the bed is constituted of particulate inorganic oxide solids, to produce a catalyst in situ, (ii) where the bed is a deactivated, or deactivating, catalyst composite or (iii) a mixture of a deactivated, or deactivating, catalyst composite and particulate inorganic oxide solids, disperse the metal upon the particulate solids of the bed to increase the catalytic activity of the bed, or stabilize and maintain the catalytic activity of the bed.

In the in situ preparation, or formation of a catalyst, a fluidized bed of particulate inorganic solids, suitably alumina, is contacted at FBSG reaction conditions with a low molecular weight hydrocarbon, steam and oxygen while a decomposable compound of the catalytic metal, or catalytic metallic metal, is added to the reaction zone to form the catalyst. The catalytic metal is deposited on the non-catalytic support solids moving from one particle to another to form crystallites which render the solids of the bed catalytically active for the production in an FBSG process of hydrogen and carbon monoxide from a low molecular weight hydrocarbon feed, steam and oxygen, or in a partial oxidation process from a low molecular weight hydrocarbon feed and oxygen. The catalyst can then be used in sitU, or ex situ, relative to the reactor in which it is prepared. In the formation at FBSG reaction conditions of a catalyst (ii) where the bed is a deactivated, or deactivating, catalyst composite, or (iii) a mixture of a deactivated, or deactivating catalyst composite and particulate refractory inorganic oxide solids, on addition of o **the decomposable compound of the catalytic metal, or catalytic metallic metal, the catalytic metal is deposited on the catalyst composite of the fluidized bed, or on both the catalyst composite and the particulate ao refractory inorganic oxide solids of the fluidized bed, respectively, the metal moving from one solids particle to another to form catalytic metal crystallites. The metal crystallites form reaction sites on the solids particles, whether originally catalytic or non-catalytic, to increase the catalytic activity of catalytic particles, or render the non-catalytic particles catalytic, for use in an FBSG process or partial oxidation process for the production of hydrogen and carbon monoxide. The catalyst can be used in situ or ex situ relative to the reactor in which it is prepared. In a preferred embodiment, the catalyst is employed in situ relative to the reactor in which it is prepared. Pursuant to the latter, a decomposable compound of the catalytic metal, or catalytic metallic metal, is added intermittently or continuously to an operating FBSG process, with the hydrocarbon, steam and oxygen at FBSG reaction conditions at a rate sufficient to increase the catalytic activity of the bed, or to stabilize and maintain the catalytic activity of the bed, during the reaction vis-a-vis a similar catalyst, or fluidized bed of the catalyst and refractory inorganic oxide solids, at similar conditions except that the decomposable compound :i of the catalytic metal, or catalytic metallic metal, is not added to the :reaction zone.

Quite surprisingly, it has thus been found that at FBSG reaction conditions, in an FBSG process, the catalytic metal component of a decomposable compound of the catalytic metal, or the catalytic metallic metal, added to the bed can migrate from particle to particle to disperse itself as metal crystallites which are catalytically active for the production of hydrogen and carbon monoxide. In the operation of the FBSG process, albeit sintering and agglomeration is a continuing ~phenomenon which leads to gradual catalyst deactivation, this adverse -6effect can be compensated for, or overcome by addition of a decomposable compound of the catalytic metal, or catalytic metallic metal, to the fluidized bed at reaction conditions at a rate sufficient to supply fresh catalytic metal reaction sites to the solids of the bed to balance, or exceed the rate of loss of catalytic metal sites which occurs in the bed without such additions. This effect is not found in fixed bed reactors, but occurs in an FBSG reactor. It occurs, it is believed, because the metal component of the decomposable compound of the catalytic metal is liberated, or the catalytic metallic metal per se added to the reactor, is deposited upon the solids particles moving from one solids particle to another and dispersing. The particles containing the metal crystallites are transported from one part of the bed to another, experiencing in an FBSG process both oxidizing and reducing conditions, forming crystallites which become new, fresh catalytically active sites the net effect of which is to increase the catalytic activity of the solids of the fluidized bed on which the sites are formed. By a similar mechanism, a fresh catalyst can be formed by depositing a catalytic metal, or metals, upon a particulate refractory inorganic oxide support to from a catalyst ab initio.

In the FBSG process, the surface of the catalyst, or surfaces of the catalyst and solids diluent, melts and becomes sticky, gradually forming agglomerates of particles which cover over and hide the original active metal sites, or form metal agglomerates, or both, which lessens the normal activity of the catalyst. As a result, the yield of hydrogen and carbon monoxide gradually decreases. With reduced catalytic activity, less and less of the feed hydrocarbons react to form hydrogen and carbon monoxide (or more and more of the feed hydrocarbons "leak" from the process without reacting with the steam and Co C -7oxygen). However, this loss of catalyst activity or "hydrocarbon leakage" can be offset and the activity of the bed of catalyst gradually increased, or the activity of the bed of catalyst restored, stabilized and maintained throughout the cycle of operation by addition of a decomposable compound of the catalytic metal, or catalytic metallic metal, to the fluidized bed. A catalytic metal compound, or compounds, which decomposes at process conditions, or a finely divided form of the catalytic metal, can thus be added to the fluidized bed to deposit the catalytic metal upon the surface of the catalyst, or upon the surfaces of all of the particles of the bed where a mixture of catalyst and solids diluent is employed to control the heats of reaction. At operating conditions the freshly added catalytic metal, when released, will migrate from the surface of one solids particle to another and become highly dispersed as new catalytically active metal sites to produce activity. In an FBSG operation, the catalytic metal compound, or compounds, or a finely divided form of the catalytic metal, is preferably added to the fluidized bed to disperse fresh catalytic metal upon the surfaces of the agglomerating particles at a rate sufficient to o* *balance the loss of active metal sites within the bed resultant from the agglomerate-forming reactions. Ideally, a steady-state operation is produced wherein the original catalytically active metal sites lost by normal operation, or operation without the added catalytic metal compound, or compounds, or finely divided form of the catalytic metal, oOO• is balanced by the new catalytically active metal sites formed by addition to the reaction zone of the catalytic metal compound, or compounds, or finely divided form of the catalytic metal.

L

-8- Preferably, the decomposable metal compound added to the reaction zone is constituted of a metal, or the added catalytic metal, is similar to that of the fresh, or original catalyst. The rate of addition of the decomposable catalytic metal compound, or added catalytic metal, is selected to supply fresh catalytically active metal sites essentially equal to those lost in the bed by catalyst deactivation.

The catalyst formed in the preferred practice of this invention is constituted of a refractory inorganic oxide carrier, or support, particularly alumina, and more particularly alpha alumina, composited with a metal, or metals, suitably a Group VIII metal of the Periodic Chart of the Elements (Fisher Scientific Company; Copyright 1953) e.g., nickel, platinum, ruthenium, rhodium or the like, catalytic for the production of hydrogen and carbon monoxide from low molecular weight hydrocarbons contacted with a fluidized bed of the catalyst at high temperature hydrothermal conditions. Preferably, the catalyst is a nickelon-alumina catalyst, more preferably a nickel-on-alpha alumina catalyst; especially one containing from about 0.03 percent to about 10 percent *.nickel, preferably from about 0.3 percent to about 1 percent nickel, *o ~composited with the alumina support, based on the total weight of the fluidized bed. Suitably, the catalyst is stabilized with one or more of a lanthanum series metal, or metals, component, lanthanum, cerium, praseodymium, neodymium, etc. or mixture of these one with another, or with these and other components.

S S.

S S In start up, as practiced in a typical FBSG operation, a catalyst is admixed with a solids diluent to control the heat of reaction.

ooSS -9- Typically, a catalyst containing from about 1 percent to about 20 percent nickel, preferably from about 5 percent to about 20 percent nickel, based on the weight of the catalyst, is admixed with the solids diluent, suitably a particulate refractory inorganic oxide solids diluent, preferably alumina, and more preferably alpha alumina, of particle size distributions corresponding to that of the catalyst, to form the fluidized bed of the reaction zone. Generally, in terms of bed dynamics, at least about percent by weight to about 95 percent by weight of the particles of the bed are of diameters ranging from about 20 microns to about 130 microns, preferably from about 30 microns to about 110 microns. Generally also, the bed is constituted of from about 10 percent to about 99.9 percent, preferably from about 80 percent to about 99.5 percent, of the solid diluents component and from about 0.1 percent to about 90 percent, preferably from about 0.5 percent to about 20 percent, of the catalyst, based on the total weight of the particulate solids constituting the fluidized bed.

Hydrogen and carbon monoxide are formed in the FBSG .reaction zone by reaction between a low molecular weight hydrocarbon, or hydrocarbons, suitably a mixture of CI-C 4 alkanes, predominantly gee• methane, natural gas, steam, and oxygen, over the fluidized bed of nickel-on-an alumina based catalyst, or catalyst and solids diluent, at i" temperatures ranging from about 1500°F to about 1900'F, preferably "..from about 1600OF to about 1800°F, in a net reducing atmosphere.

A

decomposable nickel compound, or metallic nickel, is added intermittently or continuously to the FBSG reaction zone at a rate sufficient to increase the catalytic activity of the fluidized bed, or stabilize and maintain the catalytic activity of the fluidized bed, throughout the cycle of operation.

In other words, the decomposable nickel compound, or metallic nickel, is added periodically to the reaction zone while the reaction is continued to raise the activity of the bed back to a given level after a decline in catalyst activity, or added continuously to maintain a constant level of catalyst activity for the bed during the operation. Thus, fresh catalytic metal reaction sites are added to the total solids of the bed to exceed, or balance the loss of catalytic metal sites which occurs without such additions.

Exemplary of the catalytic metal compound, or compounds useful as sources of the catalytic metal in the practice of this invention are those which contain, nickel, platinum, rhodium, ruthenium or the like, such oxides and salts as: nickel oxide, nickel acetate, nickel acetylacetonate, nickel carbonate, nickel propionate, nickel formate, nickel nitrate, platinum pentanedionate, platinum oxides, rhodium acetate, rhodium nitrate, ruthenium nitrosylnitrate, ruthenium carbonyl and the like; or a mixture of these and other oxides and salts. Finely divided metallic metals, nickel, ruthenium and the like, can also be employed as a source of the catalytic metal. The catalytic metal source, e.g., catalytic metal compound, or compounds, is added to the fluidized bed of the reaction zone in concentration sufficient that the decomposing compound that is dispersed upon the catalyst, or support, provides sufficient activity to balance the activity lost due to the agglomerating :i solids, and agglomerating original catalytic metals components of the catalyst.

The invention will be better understood by reference to the following demonstration, and non-limiting examples. All parts are given in terms of weight units except as otherwise specified. Pressures are 11 given in terms of pounds per square inch absolute, and temperatures are expressed in terms of degrees Fahrenheit.

The following demonstration shows that in an FBSG reactor, at FBSG operating conditions, nickel has the ability to move from one solids particle to another to disperse, and spread throughout the fluidized solids bed to form catalytically active nickel metal sites on the particles even where the source of nickel is a fresh nickel catalyst.

Demonstration A catalyst characterized as a 50 cc sample of 1 wt. Ni on tabular a-A1O03 particles (106 to 150pm) was loaded into a small FBSG reactor, or fluidized bed reactor having a disengaging zone at the top, and an internal filter to limit the loss of solids. Gases were fed to the reactor through small refractory nozzles at the bottom of the reactor; a mixture of steam and natural gas through one set of nozzles and oxygen through a second set of nozzles. The molar ratios of the components of the feed 0.00* .gas were methane/steam/oxygen at about 2/1/1. The reactor was operated at 1800°F and 360 psia. The fluidized bed was operated near equilibrium conditions.

Intermittently the fluidized bed reactor was shut-down, a sample of the bed was removed for activity determination, and the removed sample was replaced with pure, uncatalyzed alumina. The activity of the bed sample removed from the FBSG reactor was determined in a fixed bed reactor operation operating at 1800°F and 360 psig. The fixed bed reactor used a 1 cc sample of catalyst and employed a rapid quench to allow sampling of the product gas without back reaction. Feed -12to this reactor was a post partial oxidation, or POX gas mixture and contained CH 4

/H

2

/CO/H

2 O in a molar ratio of 1//1/2.

The activities of the catalysts taken from the fluidized bed over about a 70 day period showed a drop in activity for the catalyst specimens placed in the fixed bed reactor. However, when the activity was adjusted for nickel loading (some nickel being lost from the fluid bed and also removed and diluted because of sampling), the activity was found to remain constant. An end of run bed sample from the FBSG reactor unit was analyzed on a scanning electron microscope using energy dispersive x-rays to look at nickel dispersion on the solids. It was found that nickel was evenly dispersed on all particles even though over 30% of the bed was replaced with uncatalyzed alumina. In a continuous run with a fresh catalyst in a fixed bed it was found that the catalyst activity decreased by about two orders of magnitude over a 90 day period. This decrease is due to loss of active nickel sites because of sintering. In contrast a relatively stable activity was found in the FBSG, or fluidized bed reactor due to redispersion of the nickel.

In the examples which follow, the effectiveness of various sources of catalytic nickel added to an FBSG reactor are demonstrated.

Examples Activity increases for the steam reforming of methane were observed in an FBSG reactor with the addition to the reactor of nickel from various sources. The FBSG reactor was operated at about 1750°F and 360 psia with an alpha alumina bed material containing from about 0.3 to 1 nickel; the particles of the bed having an average particle 13diameter of about 70 Cjm. The ratios of the molar gas feeds to the unit were methane/steam/oxygen of about 2/1/1. In the operation of this unit, various nickel-containing materials, NiCO 3 and NiO powders and /Lm Ni metal particles, were added to determine their catalytic effectiveness at reducing the methane leak (reducing the methane concentration in the product gas by catalyzing steam reforming). Thus, if the nickel-containing component added is active, the methane concentration will decrease; and the performance of the added component is defined by the observed decrease of methane divided by the quantity of nickel added.

The performance index, CH 4 decrease wt. added Ni, for the various nickel-containing compound additions, and metallic nickel, is shown in the last column of the Table. This performance index was 0.55 for NiCO 3 an average of 0.54 for NiO, and 0.12 for Ni metal particles.

An 8.6 wt.% nickel-on-alumina catalyst was also used as a nickel source, for purposes of comparison. These data show that the performance of these added nickel-containing, or metallic nickel, materials are very good when compared to the performance of the fresh, supported, nickel reforming catalyst. As shown in the Table the performance index for the 8.6 wt.% Ni on a-A1 2 0 3 catalyst was 0.14. The fact that the dduuiLulls of these non-supported nickel materials to the reactor give catalytic performances comparable to supported nickel catalysts is surprising and unexpected.

61P 6 6** 96 6 0 06 6*

TABLE

Run Material Added Amount Added, lbs Methane Leak, Mole Dry CH 4 Perfor. Index Material Ni Before After Decrease A&CH 4 /Ni Addition Addition Ni Additions 5/35.1 NiCO 3 1.80 0.88 7.88 7.40 0.48 0.55 5/35.5 NiG 1.14 0.90 7.80 7.22 0.58 0.64 5/36.2 NiO 3.33 2.61 7.80 6.92 0.88 0.34 15/37.8 NiG 3.33 2.61 8.40 7.60 0.65 8.13 7.23_ 18/21.6 Ni Metal 10.0 10.0 6.00 6.00(2) 1.16(2) 0.12 Supported 118/9.7 8F.6%'Y Ni/A1 2 0 3 T250 121.5 14.29 1 2.4()3.53 0.14 Notes: SDecrease in methane leak is the sum of the decreases observed for the partial additions.

STemperature decreased by 29*1F to maintain a constant leak rate; this is equivalent to a decrease in methane of about 1. 16 mole ~Temperature decreased by 27.6'F which is equivalent to a decrease in methane of about 1. 10 mole adding this to the observed decrease of 1.95 mole gives a total decrease in methane leak of 3.05%.

Claims (19)

1. A process for the production of a catalyst useful in fluidized bed syn gas and partial oxidation reactions which includes forming in a reaction zone a fluidized bed of particulate refractory inorganic oxide solids, or (ii) a deactivated, or deactivating, catalyst composite, or (iii) mixture of a deactivated, or deactivating, catalyst composite and particulate refractory inorganic oxide solids, heating the fluidized bed while maintaining temperatures ranging from 1500°F to 1900°F, feeding a low molecular weight hydrocarbon feed, steam and oxygen into the fluidized bed, and CO.o adding, intermittently or continuously, to the fluidized bed of the reaction zone a decomposable compound of a catalytic Group VIII metal, or catalytic Group VIII metallic metal, to disperse said metal upon the surfaces of the particulate inorganic oxide solids, (ii) the :deactivated, or deactivating catalyst composite, or (iii) mixture of a deactivated, or deactivating catalyst composite and particulate refractory inorganic oxide solids, as crystallites which provide catalytic sites sufficient to form a catalyst, to increase the catalytic activity of the fluidized bed, or stabilize and maintain the catalytic activity of the 0 fluidized bed. S

2. The process of Claim 1 wherein the catalytic Group VIII metal is nickel, and the particulate inorganic oxide solids of the fluidized bed is alumina.

3. The process of Claim 1 or 2 wherein at least 80 percent to percent by weight of the solid particles of the fluidized bed on which the catalytic Group VIII metal is deposited is a diameter ranging from microns to 130 microns.

4. The process of Claim 3 wherein the catalytic metal deposited on the solids particles is nickel.

The process of any one of the preceding claims wherein the decomposable compound of the catalytic Group VIII metal added to the fluidized bed is an oxide or salt of nickel.

6. The process of any one of the preceding claims wherein the metal component of the decomposable compound of a catalytic Group VIII, or catalytic Group VIII metallic metal, added to the reaction zone is nickel, the fluidized bed of the reaction zone is particulate refractory inorganic oxide solids, and nickel is deposited on said particulate refractory inorganic oxide solids to form a catalyst useful in situ or ex situ to the reaction zone in which the catalyst is formed.

7. The process of Claim 6 wherein the particulate refractory inorganic oxide solids is alumina, and the catalyst formed is a nickel-on- alumina catalyst. S.

8. The process of Claim 7 wherein the catalyst is comprised of from 0.03 percent to 10 percent nickel, based on the weight of the catalyst. 00 17

9. The process of Claim I wherein the metal component of the decomposable compound of a catalytic Group VIII metal, or catalytic Group VIII metallic metal, added to the reaction zone is nickel, the fluidized bed of the reaction zone is a deactivated, or deactivating, catalyst composite, or mixture of a deactivated, or deactivating, catalyst composite and particulate refractory inorganic oxide solids, and nickel is deposited on the particulate solids of the bed to form a catalyst useful in situ or ex situ to the reaction zone in which the catalyst is formed. In a process for the production of hydrogen and carbon monoxide from a low molecular weight hydrocarbon by contact with a fluidized bed of a supported catalytic-metal catalyst at high temperature in the presence of steam and oxygen in a reaction zone operated in a net reducing atmosphere sufficient to progressively deactivate the catalyst during the reaction, S the improvement including adding to the reaction zone a decomposable compound of a catalytic-metal, or catalytic metallic metal, the metal at reaction conditions being dispersed upon the catalyst sufficient to increase the catalytic activity of the fluidized bed, or stabilize and maintain the catalytic activity of the fluidized bed, during the reaction vis-a-vis a fluidized bed of a similar catalyst at similar reaction conditions except that the decomposable compound of the catalytic-metal, or catalytic metallic metal, is not added to the reaction zone.

S*S 18

11. The improvement of Claim 10 wherein the catalytic metal catalyst is a Group VIII metal-on-alumina, the decomposable compound of a catalytic metal is a Group VIII metal compound decomposable at process conditions, and the catalytic metallic metal is a metallic Group VIII metal.

12. The improvement of Claim 11 wherein the Group VIII metal is nickel.

13. The improvement of any of Claims 10 to 12 wherein the fluidized bed is constituted of a mixture of the supported catalyst and a *t particulate solids diluent.

14. The improvement of Claim 13 wherein at least 80 percent to percent by weight of the particles of the bed are of diameters ranging from 20 microns to 130 microns, and the bed is comprised of from percent to 99.9 percent of the solids diluent component and from 0.1 percent to 90 percent of the catalyst component.

15. The improvement of any one of Claims 10 to 14 wherein the temperature of the reaction zone ranges from 1500OF to 1900 0 F.

16. In a process for the production of hydrogen and carbon monoxide from a low molecular weight hydrocarbon by contact with a fluidized bed of a nickel-on-alumina catalyst, or mixture of said catalyst and a particulate solids diluent, at temperature ranging from 1500OF to 1900OF in the presence of steam and oxygen in a reaction zone operated in a net reducing atmosphere sufficient to progressively deactivate the catalyst during the reaction 19 the improvement including adding, intermittently or continuously, to the reaction zone a decomposable nickel compound, or metallic nickel, which at reaction conditions causes the nickel to become dispersed upon the catalyst, or solids diluent, or both the catalyst and solids diluent, sufficient to increase the catalytic activity of the fluidized bed, or stabilize and maintain the catalytic activity of the fluidized bed, during the operation vis-a-vis a fluidized bed of a similar catalyst at similar reaction conditions except that the decomposable nickel compound, or metallic nickel, is not added to the :reaction zone during the operation.

17. The improvement of Claim 16 wherein at least 80 percent to 95 percent by weight of the particles of the bed are of diameters ranging from 20 microns to 130 microns, and the bed is comprised of from percent to 99.9 percent of the solids diluent component and from 0.1 percent to 90 percent of the catalyst component.

18. The improvement of Claim 17 wherein the particles of the bed are of diameter ranging from 30 microns to 110 microns, and the bed is comprised of from 80 percent to 99.5 percent of the solids diluent and from percent to 20 percent of the catalyst component.

19. The improvement of Claim 17 or 18 wherein the catalyst is comprised of nickel stabilized with one or more of a lanthanum series metal. The improvement of any one of Claims 16 to 19 wherein the decomposable nickel compound added to the fluidized bed is an oxide or salt of nickel. DATED this 9th day of March 1999. EXXON RESEARCH AND ENGINEERING COMPANY WATERMARK PATENT TRADEMARK ATTORNEYS 4TH FLOOR, "DURACK CENTRE" 263 ADELAIDE TERRACE PERTH W.A. 6000 AUSTRALIA DOC 26 AU5054596.WPC RHB:JAH