GB1585711A

GB1585711A - Cracking catalyst with resistance to poisoning by metals

Info

Publication number: GB1585711A
Application number: GB4778A
Authority: GB
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1977-02-16
Filing date: 1978-01-03
Publication date: 1981-03-11
Also published as: NL7801693A; JPS53100985A; BR7800895A; AU3126577A; DE2756220A1; AU515612B2; CA1108107A

Description

(54) CRACKING CATALYST WITH IMPROVED RESISTANCE TO POISONING BY METALS (71) We, MOBIL OIL CORPORATION, a corporation organised under the laws of the State of New York, United States of America, of 150 East 42nd Street, New York, New York 10017, United States of America, do hereby declare the invention, for which we pray that a patent'may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This application is directed to cracking catalysts having improved resistance to metal poisoning. and to a method of preparing and using same.

The effects of metal poisoning on the cracking performance of amorphous catalysts have been extensively investigated (U.S. 3,234,119); however, only recently have the effects been detailed for zeolitic cracking catalysts. As a result of such studies, it is now known that contaminant coke and hydrogen yields (coke and hydrogen produced by the metal poisoning) are lower on zeolitic than amorphous catalysts, but that metal activity is deactivated more rapidly on amorphous catalysts (Cimbalo et al., Oil & Gas Journal, May, 1972, p. 112).

Therefore, a number of methods have been proposed to overcome the problems associated with the cracking of metal-contaminated feedstocks. For instance. U.S. 3,944.482 proposes the cracking of high metals content feedstock in the presence of a catalyst comprising 1 to 40 wt. %of a zeolite, having cracking characteristics, dis dispersed in a refractory metal oxide matrix having a large pore size distribution (about 50-100A). Also, U.S. 3,711,422 proposes that metal poisoned cracking catalysts can be partially restored with antimony compounds and U.S. 3,977.963 proposes that the effects of metal poisoning can be negated with bismuth or manganese compounds.

U.S. Patent Nos. 3,972.835; 3,957.689 and 3.867.308 advocate a cracking process utilizing a catalyst prepared from a silicate clay and zeolitic components, the patentees apparently neutralize silicates by adjusting their pH, and add clay and zeolites to the resulting solution to form cracking catalysts.

In accordance with the present invention. we provide a method for the preparation of an inorganic oxide gel-containing cracking catalyst which comprises incorporating into the catalyst. subsequent to gel formation and prior to formation of final catalyst particles. a colloidal dispersion of an oxide selected from silica, alumina or silica-alumina to deposit between 0.1 and 50 weight percent of said oxide therein whereby the resulting catalyst composite is characterised by a resistance to metals poisoning greater than that of corresponding catalysts which have not undergone treatment with said colloidal dispersion.

Metal poisoning of cracking catalysts occurs by contact of the circulating catalyst with metals contained in the charge stock. The primary effects of metal poisoning are increased hydrogen and coke yields and catalyst deactivation. all resulting in loss of both conversion and liquid product yields. The development of catalysts that show more resistance to metal poisoning is of considerable importance to current commercial cracking operations and in furture applications to convert less desirable feedstocks containing high metal levels. e.g..

residua or hydrotreated residua. The primary metal contaminants are nickel and vanadium, although other metals such as Fe, Cu and Mo contribute to a lesser extent.

This application is accordingly directed to the incorporation of colloidal dispersions of silica or alumina particles (sometimes referred to as "sols") in a cracking catalyst resulting in dramatic improvement in the resistance of the catalyst to poisoning by metals. The incorporation of the colloidal silica or alumina dispersions apparently reduces the contaminant hydrogen and coke yields when the catalyst is poisoned by metals; the lower hydrogen and coke yields effectively result in higher conversions and liquid product yields in commercial cracking units. The silica or alumina incorporation has no deleterious effects on the catalyst performance in the absence of metal poisons.

This application is further directed to cracking catalysts (e.g., amorphous silica-alumina and/or crystalline aluminosilicate zeolite containing) wherein the above advantages are achieved by having silica and/or alumina added thereto in the form of colloidal dispersibns.

This application is more particularly directed to a process for preparing a cracking catalyst having the aforementioned improved characteristics of high resistance to metal poisoning, high attrition resistance and high selectivity, which comprises preparing a cracking catalyst consisting of crystalline zeolitic and amorphous cracking catalysts and thereafter (but before formation of final catalyst particles) adding silica and/or alumina particles to said catalyst in the form of colloidal dispersions; and to a method of using said catalyst in a process for the catalytic cracking of high metals content charge stock.

The colloidal silica or alumina addition is applicable to any cracking catalyst, either amorphous (e.g., silica alumina) or crystalline (e.g. aluminosilicate zeolite-containing). The zeolite is usually contained in and distributed throughout an inorganic oxide gel matrix, as more particularly described in, for example U.S. 3,140,249. The colloidal silica or alumina may be added at any point in the catalyst manufacturing process after gel formation and prior to formation of final catalyst particles. Any drying method may be used; spray drying, flash drying, oven or slow rotary drying. The silica or alumina can be added in the form or a dispersion of small particles in water or any other suitable solvent. The silica or alumina particles should be in the colloidal size range, i.e., the particle diameters can be from 10 to 10,000 . Suitable silica dispersions may be obtained from a variety of commercial sources or they may be prepared by appropriate chemical treatment of metal silicates. The amount of added silica and/or alumina sol is generally between 0.1 and 50 weight percent of the final catalyst and preferably from 1 to 10 weight percent.

Suitable amorphous catalytic materials which may be advantageously used in the catalysts embodied herein include silica, alumina, magnesium, zirconia, boria, titania chromia and combinations thereof, combinations of inorganic oxide typified by silica-alumina, silicazirconia, silica-boria, silica-magnesia, silica-titania or ternary combinations such as silicaalumina-zirconia, silica-alumina-magnesia, particularly with silica as silica-alumina and silica-magnesia-alumina.

Suitable zeolite catalytic material useful in the catalysts herein include X and Y aluminosilicate zeolites, ZSM-4, ZSM-5, ZSM-11, ZSM-12, ZSM-35, ZSM-38 and other similar materials, such as erionite, mordenite and faujasite.

Example 1- Base Catalyst A catalyst was prepared having the composition of 15% rare earth Y crystalline aluminosilicate zeolite (REY) and 85% matrix, the matrix being made up of 59.4% silica, 0.6%aluminaand40%clay.

A clay-water slurry was prepared by addition of 1600 grams (dry basis) WP Georgia kaolin to 89.5 Ibs. of deionized (DI) water; 8250.7 grams of sodium silicate, containing 2376 grams SiO2 added with stirring. The mixture was heated to 1200F and concentrated sulfuric acid (97% H2SO4) was added at a uniform rate while mixing to adjust the pH to 10.5. After cooling the mixture to ambient temperature, a 20% aqueous solution of aluminum sulfate was added at a uniform rate over a 30 minute period so as to provide a final alumina content of 0.6 wt. %, based on total dry matrix weight. The mixture was then adjusted to a pH of 4.5 by addition of concentrated sulfuric acid over a 30 minute period.

To the silica-alumina-clay slurry were added 705.9 grams of rare earth exchanged zeolite Y (REY) slurried in 2200 cubic centimeters of water. The REY had previously been 68% exchanged (i.e., 68 % of the sodium content was replaced by rare earth cations) and pretempered by calcining at 1200"F for about 10 minutes (the REY had the following composition: Al203 = 21.7,SiO2 = 6l.4,RE2O3 = 15.9. and Na = 3.2%wt.).TheREY-waterslurrywas homogenized in a blender prior to addition to the matrix slurry.

The catalyst hydrogel composite was then homogenized and spray dried with an air inlet temperature of 700"F and outlet temperature of 350"F. The spray dried product was slurried with water and added to ion exchange columns, then base exchanged with 20 gallons of a 5% aqueous solution of ammonium sulfate. The base exchanged catalyst composite was washed substantially free of sulfate with DI water, then exchanged with rare earth chloride solution containing 175 grams RECI2.6H20 as a 50% aqueous solution dissolved in 20 liters of DI water. The rare earth exchanged catalyst was then washed substantially free of chloride ion with DI water and dried at about 250"F for about 40 hours.

The resultant catalyst had a sodium content of 0.03 wt % Na and a (water) pore volume of 0.73 cc/gram. The mean particle diameter was 58 microns.

Example 2 - Silica SolAdded Prior To Spray Drying A catalyst was prepared in a substantially identical manner to that in Ex. 1, except that the initial matrix gel was prepared containing 5 % less silica (i.e. 54.4%wit. SiO 2) by adjusting the amount of sodium silicate. The remaining 5%SiO2 added to the catalyst hydrogel composite after addition of the REY and just prior to homogenization and spray drying. The added silica was in the form of a commercially prepared colloidal silica containing 30%wtSiO2 and 0.1% Wt. Na2O stabilizer with a silica particle size of about 17 millimicrons and surface area of about 195-215 m2/g. The resultant catalyst had a sodium content of 0.06 %wt Na and a'water pore volume of 0.58 cc/gram; the mean particle diameter was 73 microns.

Example 3 - Catalyst Tests The catalysts of Examples 1 and 2 were each steam treated in a fluidized bed for 4 hours at 1400"F in flowing steam at atmospheric pressure. The steamed catalysts were tested for cracking activity and selectivity by cracking a wide-cut Mid-Continent gas oil at 9200F, 3 weights catalyst/oil and 8.33 weight-hourly space velocity in a fixed fluidized bed. The properties of the gas oil chargestock are listed in Table 2; the test results are given in Table 1.

As is evident from the data, the replacement of some matrix silicate with silica in the form of a colloidal dispersion has only minor effects on cracking activity and selectivity. The higher gas yields with the catalyst of Example 3 may be due to gasoline recracking (over-cracking) because of diffusion restrictions caused by the relatively large particle silica in the matrix.

TABLE 1 Product Distributions For Steamed Catalysts Example No. 1 2 Description Base SiO2 Prior Catalyst to S.D. * Conv. %Vol 81.5 79.5 C5 + Gasoline, 65.6 63.2 %Vol Total C4's 17.4 18.4 Dry Gas, %wt. 7.3 7.7 Coke, %wt. 3.96 3.85 H2, %wt. 0.02 0.02 Catalysts steamed 4 hours - 1400"F- 0psig,100%steam Catalysts tested 920"F, 3 C/O, 8.3 WHSV WCMCGO, fixed fluidized bed * Spray drying TABLE 2 Properties of Wide- Cut Midcontinent Gas Oil (WCMCGO) API Gravity 29.2 Sulfur, %wt. 0.51 Nitrogen, %wt. 0.065 Basic Nitrogen, ppm 152 Conradson Carbon, %wt. 0.29 Aniline Point, "F 181 Bromine Number 2.5 Refractive Index at 70"F 1.48852 Pour Point, 0F 85 Viscosity, KV at 2100F 3.55 Molecular weight 328 Hydrogen, %wt. 13.06 Specific Gravity, 60/60"F 0.8767 Metals: Ni, ppm 0.1 V, ppm 0.2 Fe, ppm 32 Distillation, "F: IBP 472 5%Vol. 545 10 578 20 608 30 632 40 665 50 707 60 754 70 796 80 851 90 920 95 958 Example 4 - Metal Poisoning of steamed Catalysts In order to simulate the effects of metal poisoning, the catalysts of Examples 1 and 2, after steaming as described in Example 3, were poisoned with nickel and vanadium as follows: A metal poisoned charge stock containing about 1700 ppm each Ni and V was prepared by dissolving nickel and vanadium naphthenates in WCMCGO. Five parts of steamed catalyst were impregnated with one part of the metal-poisoned charge stock at ambient temperatures; the volume of the charge stock was adjusted with xylene such that the total volume just filled the catalyst pores. The excess xylene in the catalyst was subsequently evaporated at 2500F.

The charge stock impregnated catalyst was then heated in a fixed fluidized bed in a stream of N2 to 9800F and maintained at that temperature for about 10 minutes. This procedure causes the charge stock to crack on the catalysts, depositing both metals and coke on the catalyst.

The coke was subsequently removed by oxidation in air at 1200"F. The clean burnt metal poisoned catalysts, containing about 340 ppm each Ni and V were tested for cracking activity and selectivity as described in Example 4. The results are presented in Table 3.

The effects of metal poisoning on the based catalyst of Example 1 are readily apparent; the metal poisons reduce the cracking activity, produce much higher coke and hydrogen yields in spite of the lower conversion and, as a result, produce much less gasoline product. When the catalyst contains colloidal silica (Example 2), the effects of the metals are considerably reduced: the loss of cracking activity is considerably reduced, as is the increased yield of both coke and hydrogen; as a result, a substantially higher gasoline yield results.

TABLE3 Product Distributions for Metal Poisoned Catalysts Example 1 2 Description Base SiO2Prior Catalyst to S.D.

Conv., %vol 74.5 78.6 Cs+ Gaso., 57.0 60.6 %vol Total C4,s 14.4 15.0 Dry Gas. %wt 6.5 7.8 Coke, %wt 6.7 5.5 H2, %wt 0.66 0.54 Steamed catalysts poisoned with 340 ppm each Ni and V. Catalysts tested at 9200F, 3 C/O, 8.33 WHSV, WCMCGO, fixed fluid bed.

The data detailed in the various tables above clearly substantiate that the added silica, alumina, or mixed silica-alumina can significantly decrease the hydrogen and coke yields caused by metal poisons, thereby resulting in higher liquid product yields. The "enriched" catalysts disclosed herein, resulting from the addition of colloidal silica and/or alumina particles to a catalyst gel, prior to formation of final catalyst particles, therefore results in cracking catalysts of highly improved metal resistance.

The use of a metal resistant catalyst in current commercial operations can be quite beneficial. Typical fresh feeds contain as much as 1 ppm metals (Ni, V, Cu). The use of a catalyst such as described above can significantly reduce the additional coke and hydrogen yields caused by these metals, resulting in better liquid yields. Alternatively, the same yields could be attained with feeds of higher metal content, allowing a larger fraction of the total crude to be converted. In addition, such catalysts would allow improved processing of residua, which contain much higher metal levels.

WHAT WE CLAIM IS: 1. A method for the preparation of an inorganic oxide gel-containing cracking catalyst which comprises incorporating into the catalyst, subsequent to gel formation and prior to formation of final catalyst particles, a colloidal dispersion of an oxide selected from silica, alumina or silica-alumina to deposit between 0.1 and 50 weight percent of said oxide therein whereby the resulting catalyst composite is characterized by a resistance to metals poisoning greater than that of corresponding catalyst which have not undergone treatment with said colloidal dispersion.

2. The method of Claim 1 wherein said colloidal dispersion is a silica sol.

3. The method of Claim 1 wherein said colloidal dispersion is an alumina sol.

4. The method of Claim 1 wherein said colloidal dispersion is a silica-alumina sol.

5. The method of Claim 1 wherein the amount of deposited oxide is between 1 and 10 weight percent.

6. The method of Claim 1 wherein said cracking catalyst contains a crystalline aluminosilicate zeolite in finely divided form contained in and distributed throughout an inorganic oxide gel matrix.

7. The method of Claim 1 wherein said cracking catalyst is an amorphous silica-alumina gel.

8. The method of Claim 6 wherein said colloidal dispersion is a silica sol.

9. The method of Claim 6 wherein said colloidal dispersion is an alumina sol.

10. The method of Claim 6 wherein said colloidal dispersion is a silica-alumina sol.

11. The method of Claim 6 wherein said crystalline aluminosilicate zeolite is zeolite X or zeolite Y.

12. The method of Claim 1 wherein said cracking catalyst is in fluid form.

13. A cracking catalyst prepared by the method of Claim 1.

14. A cracking catalyst prepared by the method of Claim 6.

15. A process for cracking a hydrocarbon charge stock containing metal contaminants which comprises contacting said charge stock, under catalytic cracking conditions, with the catalyst of Claim 13.

16. A process for cracking a hydrocarbon charge stock containing metal contaminants which comprises contacting said charge stock under catalytic cracking conditions with the catalyst of Claim 14.

17. The method of using a catalyst as defined in Claim 1 in a cracking process which

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. TABLE3 Product Distributions for Metal Poisoned Catalysts Example 1 2 Description Base SiO2Prior Catalyst to S.D. Conv., %vol 74.5 78.6 Cs+ Gaso., 57.0 60.6 %vol Total C4,s 14.4 15.0 Dry Gas. %wt 6.5 7.8 Coke, %wt 6.7 5.5 H2, %wt 0.66 0.54 Steamed catalysts poisoned with 340 ppm each Ni and V. Catalysts tested at 9200F, 3 C/O, 8.33 WHSV, WCMCGO, fixed fluid bed. The data detailed in the various tables above clearly substantiate that the added silica, alumina, or mixed silica-alumina can significantly decrease the hydrogen and coke yields caused by metal poisons, thereby resulting in higher liquid product yields. The "enriched" catalysts disclosed herein, resulting from the addition of colloidal silica and/or alumina particles to a catalyst gel, prior to formation of final catalyst particles, therefore results in cracking catalysts of highly improved metal resistance. The use of a metal resistant catalyst in current commercial operations can be quite beneficial. Typical fresh feeds contain as much as 1 ppm metals (Ni, V, Cu). The use of a catalyst such as described above can significantly reduce the additional coke and hydrogen yields caused by these metals, resulting in better liquid yields. Alternatively, the same yields could be attained with feeds of higher metal content, allowing a larger fraction of the total crude to be converted. In addition, such catalysts would allow improved processing of residua, which contain much higher metal levels. WHAT WE CLAIM IS:

1. A method for the preparation of an inorganic oxide gel-containing cracking catalyst which comprises incorporating into the catalyst, subsequent to gel formation and prior to formation of final catalyst particles, a colloidal dispersion of an oxide selected from silica, alumina or silica-alumina to deposit between 0.1 and 50 weight percent of said oxide therein whereby the resulting catalyst composite is characterized by a resistance to metals poisoning greater than that of corresponding catalyst which have not undergone treatment with said colloidal dispersion.