CA2061663A1 - Catalytic cracking catalyst additive - Google Patents

Abstract

Abstract of the disclosure Catalytic cracking catalyst additives which contain bayerite and/or eta alumina are added to zeolite containing catalysts that are used to process hydrocarbon feedstocks that contain nickel.

Description

2C'6~S3 The present invention relates to catalytic cracking, and more specifically to catalytic cracking compositions and processes that may be used to catalytically convert high molecular weight nickel containing feedstocks into valuable lower molecular weight products.
It is generally known that catalytic cracking catalysts which comprise seolites such as synthetic faujasite and ZSM-5 dispersed in an inorganic oxide ~matrix such as silica/~alumina hydrogel, sols and clay may be used to economically convert heavy hydrocarbon feedstocks such as gas-oils and/or resid into gasoline and diesel fuel.
More~recently it has been disclosed that the addition of aluminas to cracking catalyst compositions will improve the overall performance of the catalyst particularly when used to process feedstocks that contain significant quantities of sulfur and/or contaminant metals such as vanadium and nickel.
Canadian patent 1,117,511 describes FCC~catalysts which contain~free alumina~ hydrate, particularly alpha-alumina hydrate (boehmite) which may be~used to catalytically crack hydrocarbons that contain sulfur and/or metals încluding nickel and vanadium.~
Japanese Patent Publication 84/1088 discloses catalytic cracking catalysts which contain aluminas such as Bayer Process aluminas (gibbsite), rho, and bayerite that are particularly effective fcr reducing tbe production of coke and hydrogen when used to process hydrodesulfurised Kuwait vacuum gas-oil.
U.S. Patent 4,010,116 discloses FCC catalysts which contain pseudo-boehmite aluminas that may contain crystalline trihydrate components such as bayerite and gibbsite.

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U.S. Patent 3,312,~15 discloses the use of inorganic oxides such as eta alumina in the preparation of FCC catalysts.
EP 0 3~5 246 A1 and copending U.S. Serial No.
533,227 filed June 4, 1990 describe zeolite containing catalysts which include bayerite/eta alumina as a matrix component that are particularly useful for the processing of nickel containing feedstocks.
While it is recognized that aluminas including bayerite, eta, pseudoboehmite and gibbsite may be added to catalytic cracking catalysts to improve the stability and coke/dry gas selectivity thereof~ the industry has not fully developed catalytic cracking catalyst additive compositions that may be used to control the adverse effects of nickel.
It is therefore an object of the present invention to provide an improved catalytic cracking composition and process for converting nickel containing hydrocarbon feedstocks to more valuable low molecular weight products such as gasoline and diesel fuel.
It is a further object to provide a catalytic cracking process wherein hydrocarbon feedstocks containing in excess of about 10 ppm nickel may be economically processed in conventional FCC units.
It is a further object to provide an improved alumina containing FCC catalyst composition which can tolerate large quantities of nickel without producing unacceptable quantities of coke and hydrogen.
'1 It is yet a further object to provide a particulate FCC catalyst additive composition that may be blended with conventional zeolite containing catalysts to control the adverse effect of metal such as nickel.

These and additional objects of the invention will become readily apparent to one skilled in the art from the following detailed description, specific examples and drawing wherein the Figure is a graphic representation of data obtained during the evaluation of a catalyst additive composition of the present invention.
Broadly, our invention contemplates catalytic cracking catalyst additive compositions that contain bayerite and/or eta alumina and the use thereof to process nickel containing hydrocarbon feedstocks.
More specifically, we have discovered that catalyst additive compositions containing from about 10 to 90 wt.% bayerite and/or eta alumina dispersed in a non-zeolite containing inorganic oxide matrix such as silica, alumina and silica-alumina sols and gels and clay are more effective for controlling the adverse effects of Ni.
In particular, we have found that if from about 5 to 50 wt.% of the bayerite and/or eta alumina containing additive is added to conventional particulate zeolite containing fluid catalytic cracking (FCC) catalysts as a separate particulate additive having the same particle size as the conventional FCC catalyst, the catalysts may be used in the catalytic cracking of nickel containing feedstocks.
Catalysts which may be improved hy the addition of our additive compositions typically contain crystalline alumino-silicate zeolites such as synthetic faujasite i.e. type Y zeolite, type X
zeolite, Zeolite Beta, ~SM-5, as w~ll as heat treated (calcined~ and/or rare-earth exchange derivatives thereof. Zeolites which are particularly suited include calcined rare-earth exchanged type Y zeolite (CREY), the preparation of which is disclosed in US
patent 3,402,996, ultrastable type Y zeolite (USY) as disclosed in US patent 3,293,192 as well as various partially exchanged type Y zeolites as disclosed in US
patents 3j60~,043 and 3,676,36~. The catalysts ~ay also contain molecular sieves such as SAPO and ALP0 as disclosed in US patent 4,764,26~. Typical catalyst compositions will include from about S to 50 wt.~
molecular sieve, about 2 to 40 wt.% bayerite and/or eta alumina, and the balance will comprise inorganic oxide binders and additives such as silica, silica alumina and alumina gels and sols as well as clay su~h as kaolin.
The preparation of our catalyst additives involves combining bayerite, and/or eta alumna and the desired matrix components, such as clay and/or inorganic oxide binders, into an aqueous slurry, and forming the slurry into catalyst particles of desired size. To obtain additive suitable for use in fluid catalytic cracking (FCC) operations, the slurry is spray dried to obtain particles having a size range from about 20 to 140 microns. Procedures that may be used in the practice of the invention are disclosed in US
3,957,689, 4,126,579, 4,226,743, 4,458,023 and Canadian patent 967,136.
Using the catalyst preparation pxocedures set forth in U.S. 3,957,689 and U.S. 4,4S8,023, catalysts of the present invention are obtained which are attrition resistant and particularly suited for use in commercial FCC operations. Catalysts of the present invention which include the silica/alumina sol binder matrix described in U.S. 3,957,689 or the alumina sol binder described in U.S. 4,458,023 will possess a Davison ~ttrition Index of 12 or less. The Davison Attrition Index, DI, is determined by the following procedure.
DI Test A 7 g sample of catalyst is screened to remove particles in the 0 to 20 micron size range. The particles above 20 microns are then subjected to a 5 hour test in the standard Roller Particle Size Analyzer using a 0.07 inch jet and 1 inch I.D. U-Tube as supplied by American Instrument Company, Silver Spring, Md. An air flow of 21 liters per minute is used. The Davison Index is calculated as follows.

Davison Index = Wt. 0-20 micron material formed during test x 100 Wt. original 20 + micron fraction Accordingly, the catalyst additive of the present invention are characterized by a DI of about 12 or less and preferably below about 10, and more preferably from about 1 to 10 and an average bulk density (ABD) of about 0.6 to 1 g/cm3 and preferably 0.7 to 1 g/cm3 subsequent to heating in air for 2 hours at 1000F.
The hydrocarbon feedstocks that are used typically contain from about 2 to 10 ppm and as much as 15 ppm nickel. These feedstocks include gas-oils which have a boiling range of from about 340 to 565C as well as residual feedstocks and mixtures thereof.
The catalytic cracking process is conducted in conventional FCC units wherein reaction temperatures that range of from about 400 to 700C and regeneration temperatures from about 500 to 850C are utilized.
The catalyst, i.e. inventory, is circulated through the unit in a continuous reaction/regeneration process ;~r ~ s~

during which nickel i5 deposited on the catalyst. The catalyst inventory is maintained at a nickel level of preferably from 300 to 2500 ppm and in some instances as high as 3000 to 8000 ppm by the addition of fresh catalyst and removal of equilibrium catalyst. During use, some of the bayerite may be converted to eta alumina at reaction temperatures employed during the catalytic cracking process. As indicated in the literature bayerite can be converted to eta alumina by heating to temperatures in excess of about 250C. It is observed that at the equilibrium nickel levels described above the quantity of coke and hydrogen (C + H2) (as mea~ured in a pilot plant) will remain within acceptable levels i.e. from about 3 to 6 wt.% C
and from about 0.3 to 0.8 wt.% H2 based on the weight of fresh feed processed.
The bayerite used to prepare the catalysts can be obtained by processes described in U.S. Patent No.
3,092,454. If it is desired to convert the bayerite to eta alumina prior to incorporation in the catalyst, the Bayerite is heated to a temperature of from about 250 to 400C for a period of 0.5 to 2 hours.
Commercially available bayerite aluminas such as Versal B from La Roche Chemical Inc., Baton Rouge, LA, having a bayerite phase purity of 95 wt.%, and Alcoa C-37 having a bayerite phase purity of greater than 80%, are particularly suited for use in the present invention.
Having described the basic aspects of the invention the following examples are given to illustrate specific embodiments.

2(``~ S3 Example 1: (Invention) 4.96 kg of bayerite (LaRoche Versal B) was slurried in 11 kg of water and acidified with 20 wt.%
H2S0~ to a pH of 3.8. Silica sol, having 10% solids, was prepared by mixing sodium silicate and a solution of H2S0~ and aluminum sulfate to a pH of 3Ø 20 kg of the silica sol was mixed with 10.5 kg of bayerite slurry and spray dried. The spray dried catalyst was washed to low Na and Cl and oven dried. Analysis of this sample is shown in Table I. This sample will be designated Catalyst A.
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Example 2: tComparative) 3.56 kg of a flash calcined gibbsite (Alcoa CP-100) was slurried in 12.4 kg of water and acidified to a pH 3.8 with 20% HaS04. 10.5 kg of the alumina slurry was mixed with 20 ~g of silica sol (described in Example 1) and spray dried. This catalyst was washed as in Example 1. Properties of this catalyst are shown in Table I. This sample will be designated Catalyst B.

Example 3: (Evaluation) Catalysts A and B were steamed for 2 hours at 1500F under atmospheric pressure of steam, impregnated with nickel naphthenate to 8000 ppm nickel, calcined in air at 1450F and resteamed for 2 hours at atmospheric pressure and 1500F under 20%
steam. The nickel-impregnated and steamed catalysts were analyzed by Temperature Programmed Reduction (TPR). In TPR, a 5% H2 in Ar gas mixture is passed at 30 ml~min over 0.4 g of catalyst as the temperature is raised linearly from 400C to 1000C at 5 C/min. The consumption of H2 i.s a direct measure of the reduction of nickel. The TPR profiles of Catalysts A and B are shown in the Figure. As can be seen clearly, the extent of nickel reduction of Catalyst B is about 2.5 times higher than that on Catalyst A. Furthermore, the t~mperature maxima of the reduction peaks on Catalyst B are lower than those of Catalyst A. These results indicate that nickel on Catalyst B is bound less strongly to the matrix and more readily reduced than nickel on Catalyst A. In other words, Catalyst A
is more effective than Catalyst B for passivating nickel.

TABLE I
Properties of Bottoms Crackinq Additive Example 1 Example 2 (Invention) (Comparative) Chemical Analysis AlzO3 54.9 54.1 NazO 0.05 0-05 S04 1.44 3.57 ; Physical Properties 2 at 1000F
'.BET Area 214 161 N2 Pore Volume 0.23 0.20

Claims (14)

1. A catalytic cracking catalyst additive composition which comprises bayerite and/or eta alumina dispersed in a non-zeolite containing inorganic oxide matrix.

2. The composition of claim 1 having a DI of 1 to 10 and a particle size of 20 to 140 microns.

3. The composition of claim 1 which contains from about 10 to 90 wt.% bayerite and/or eta alumina, and from about 10 to 50 wt.% of an inorganic oxide matrix selected from the group consisting of silica, alumina and silica-alumina, hydrogels and sols and clay.

4. The composition of claim 1 wherein the phase purity of said bayerite and/or eta alumina is above 80%.

5. The composition of claim 1 which contains from about 20 to 60 weight percent of said bayerite and/or eta alumina.

6. The composition of claim 3 wherein said binder is silica/alumina sol.

7. The composition of claim 3 wherein said binder is alumina sol.

8. A catalytic cracking catalyst composition comprising a molecular sieve dispersed in an inorganic oxide matrix and from about 5 to 50 wt.% of the additive composition of claim 1.

9. The composition of claim 8 which contains from about 300 to 2500 ppm Ni.

10. The composition of claim 8 wherein the Ni content of said catalyst ranges from about 300 to 8000 ppm.

11. The composition of claim 8 having a Davison Attrition Index (DI) of 12 or less and a particle size range of about 20 to 140 microns.

12. A method for the catalytic cracking of hydrocarbons which comprises reacting a hydrocarbon feedstock with the catalyst of claim 8.

13. A method for catalytically cracking Ni containing hydrocarbon feedstocks which comprises (a) reacting a hydrocarbon which contains in excess of about 2 ppm Ni under catalytic cracking conditions in the presence of a catalytic cracking catalyst of claim 8, and (b) adding the catalyst additive of claim 1 to maintain a desired level of catalytic conversion.

14. The method of claim 13 wherein the cracking reaction is conducted at a temperature of 400 to 700°C