CA1229838A - High density catalyst and method of preparation and use thereof - Google Patents

Abstract

HIGH DENSITY CATALYST AND METHOD

OF PREPARATION AND USE THEREOF

ABSTRACT

Preparation of a cracking catalyst by mixing silica and alumina solutions at a pH of 3.0 to 4.5 produces a catalyst of high density. Use of the catalyst in the fluidized catalytic cracking (FCC) process reduces SOx emissions from the FCC regenerator.

Description

HIGH DENSITY CATALYST ~ND METHOD
OF PREPARATION .4MD USE T~EREOF

The present invention relates to a rnethod of preparing a high density cracking catalyst which comprises active catalytic fines dispersed in a matrix and the use thereof in a catalytic cracking process.
In fluidized catalytic cracking (FCC) systems a fluidized bed of particulate catalyst is continuously cycled between a cracking zone and a catalyst regeneration zone. Hydrocarbon cracking in the reaction zone deposits coke on the catalyst. The cracked hydrocarbons are separated from the coked catalyst and withdrawn. The coked catalyst is s-tripped of volatiles and passed into the catalyst regenerator ~here coked catalyst contacts an oxygen-containing gas to burn off coke and heat the catalyst. Hot regenerated catalyst then contacts the hydrocarbon stream in the cracking zone. A flue gas is formed by burning coke in the regeneration zone.
The hydrocarbon Eeeds processed in con~ercial FCC units no~mally contain sulfur. A significant portion of this sulfur is deposited on the catalyst in the coke. The flue gas formed by burning coke in the catalyst regenerator contains SOx, i.e., sulfur dioxicle and/or sulfur trioxide.
Known methods of reducing Sx emissions from the FCC catalyst regenerator include desulfurizing the regenerator flue gas by conventional stacX gas scrubbing or desulfurizing the hydrocarbon feed in a separat0 desulfurization unit. I~ese rnethods are expensive.
Catalyst modifica-tion to reduce Sx emissions from FCC
regenerators is much cheaper than currently available methods.
It has been suggestecl in U.S. Paterlt No. 3,835,031 to recluce the amount of sulfur oxides in FCC regenerator flue gas by impregnating a Croup II-A rnetal oxide onto a conventiollal silica-alumina crack;ng catalyst. The attrition encolmtered ihen ~',.

a~ 7 F-173~ - 2 -using unsupported Group II-A metals is thereby reduced. Group II-A
metal oxides, such as magnesia, when used as a component of cracking catalysts, have a highly ~mdesirable effect on the activity and selectivity of the cracking catalyst. The addition of a ~roup II-A
metal reduced the yield of the liquid hydrocarbon fraction and gasoline octane.
Other patents propose reduction of Sx emissions from regenerator flue gas by contacting the sulfur compounds with an oxidation promoter and reactive alumina. The resulting solid a]uminum-sulfate compound, formed in the regenerator9 is reduced to hydrogen sulfide gas and reactive alumina in the reaction zone.
Hydrogen sulfide removal from the reactor effluent is cheaper than feed desulfurization or flue gas desulfurization. The alumina can be impregnated on the standard catalyst, incorporated into the catalyst during manufacture, or admixed with a standard catalyst as a separate particle.
It is known to impregnate standard catalysts with rare earth oxides such as Cr203, MnO, or Co0, alone or in combinations, or rare earth oxide with a platinum group metal oxidation promoter to reduce the sulfur content of coke and shift the sulfur removal to the cracked hydrocarbon effluent.
While the above-mentioned disclosures teach methods of reducing Sx emissions by catalyst modification, the disclosed processes require the addition of elements or compoundS to the cracking catalyst.
Cracking catalysts are solid materials which have acidic properties. Because of -the nature of the reactions taking place, the catalyst mus-t have high porosity. Furthermore, since the catalyst circulates rapidly between reaction zones and burning, or regeneration zones, it must also have resistance to abrasion, temperature changes ancl the like.
Another problem encountered with conventional FCC catalysts is catalyst attrition, aging and loss of activity and selectivity. The trend in commercial fluid catalytic cracking is high density catalysts.
The higher density in conjunction with increased attrition resistance is a major factor in improving catalyst retention in a fluidized cracking unit. As a result, the make-up rate of fresh catalyst can be reduced and dust emissions from the flue gas stacks are lowered. At the same time, however, the characteristic of high density must not result in the loss of product selectivity.
Many FCC catalysts comprise a ~el of silica-alurnina in which is dispersed particles of crystalline zeolitic catalytic material. One method used commercially for rnanufacturing the catalysts involves Eormation of a silica-alumina co-gel7 addition of small particles of zeolite to the co-gel, and forrnation of catalyst particles by spray-drying.
U.S. Patent No. 4,219,446 discloses producing an attrition resistant zeolite-containing catalyst by preparing a zeolite-containing silica-alumina hydro~el. One of the critical aspects of the invention is nozzle-mixing an acid alum solution and an a~ueous solution of sodium silicate which comprises finely dispersed kaolin clay and calcined rare earth exchanged zeolite Y. The mixture has a p~l above 9.
U.S. Patent No. 3,957,689 discloses an attrition resistant zeolite hydrocarborl conversion catalyst made by decreasing the pH of a sodium silicate solu~ion to a p~I of ~.0-3.2 by adding a mixed sulfuric acid-aluminum sulfate solution to form a buffered silica 501, adding clay before, during or after sol formation, preparing a water slurry of a crystalline zeolite and adjusting the p~l to about 3-5, mixing the slurry with the buffered silica sol-clay slurry to prepare a spray dried feed slurry.
U.S. Patent Nos. 3,520,828 and 3,939,05~ disclose preparin~ the sil;ca ancl alumina gel via mozzle mixing of a sodi~ silicate solution and an acid al-nn solution ~o form a hydrosol containing crystallirle aluminosilicate fines. ~le gelled hydrosol has a p~l of about ~Ø
Despite the many advances which have been made, it would be beneficial if FCC catalysts could be produced ~hich would reduce Sx emissions or which would be more attrition resistant alld denser.
Ideally, both improved catalyst properties and reduced Sx emissions could be achieved.

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F-1736 - ~ -Accordingly, the present invention provides a method of preparing a high density FCC catalyst comprising mixing a basic solution containing silica with an acidic solution containing al~nina, continuousl)~ maintaining said mixture at a pH of 3.0 to 4.5 from the initial mixing to the formation oE a gel, homogenizing the gel and spray drying the homogenized gel to produce a high density FCC
catalyst.
In another embodiment, the present invention provides a process for cracking sulfur containing hydrocarbon feed in the presence of a conventional FCC catalyst operated at conventional FCC conversion conditions, wherein at least a portion of the sulfur contained in the Eeed hydrocarbons is deposited on the catalyst in the form of coke, and released to the atmosphere as Sx during coke burnoff, the improvement comprising using as the catalyst a high density FCC
catalyst prepared by mixing a basic solution containing silica with an acidic solution containing alumina, continuously maintaining said mixture at a pH of 3.0 to 4.5 from the initial mixing to the formation of a gel~ homogeni~ing the gel and spray drying the homogenized gel to produce a high density FCC catalyst, whereby the arno~ult of Sx in regenerator flue gas is substantially reduced.

GEL FOR~TION
An acid alurn solution alld a sodiuJn silicate strearn containing a substantial portion of active zeolite fines are purmped to a mixing apparatus where the matrix components are mixed in such a mamler that the mixture is contin-lously maintained at a p~l no greater than 4.5.
l~le reac-tants must be intin~ately mixed to maintain the low pll. ~lixing tlle rnatrix colnponents through a no~zle or vigorously stirring the cornponents sirnultaneously with or immediately following contact maintains the desired lo~ p~l, altllough nozzle mixing is preferred.
~ le acid alum soLution is an acidic solution cornprising an aqueolJs solution of sulfuric acid and aluminum sulfate. ~le sodil~n silicate stream is a hasic solu~ion comprising a mixture of an aqueous socli~ silicate solution.

~L~ 3 After the acid alum solution and sodiurn silicate stream have been mixed, the gel mixture is immediately hcmogenized, as for example, by being passed sequentially through a Charlotte ~ill and Matin-Gaulin homogenizer. The material is then spray dried~ The resulting spray dried product can then be ion exchanged with ammonium ions such as from an aqueous ammonium sulfate solution and then water washed to remove the sulfate. The washed product can then be further ion exchanged with rare earth ions. It will be understood that rare earth iolls include those contained in a salt or a mixture of salt wherein the anion can be a chloride, nitrate or acetate. The rare earth ion rnay be, for example, cerium, lanthanum, praseodyrnium, neodymium, samarium and ytterium. Mixtures of rare earth salts can be used.
The steps o~ ion exchanging and spray drying are conventional and wel]-known in the art. For example, typical ion exchange procedures are described in ~.SO Patent Nos. 39140,249; 3,140,251 and 3,140,253. Such procedures comprise contacting the zeolite with the salt of the desired replacing ion in warm water, followed by drying at 75 to 300C.
Accordin~ to the inven~ion, catalysts ~hich are prepared by continuously maintaining the gelled matrix at a p~l of less than 4.5 and, preferably at a pH of between about 3-!~.5 from initial mixing to completion thereof can be advantageously used as cracking catalysts in conventional FCC units.

ZEOLIT~
The crystalline aluminosil;ca~e zeolite which can be used can be chosen among the na-turally occuring crystalline zeolites such as faujasite, mordenite, erionite, etc. Synthetic crystalline al~nino-silicate zeolites which may be used include large pore materials such as zeolite X and zeolite Y. The preferred crystalline zeolite useful ln the catalyst forming method of the present invention as well as for use in the fluid catalytic cracking process is a calcined rare earth exchanged zeolite Y.

~2~;~3~3~

In addition to the large pore zeolites discussed above3 it will frequently be beneficial to use, as all or only a portion, of the zeolite eventually incorporated into the finished catalyst, a shape selective zeolite.
By shape selective zeolite is meant a catalyst with a constraint index of 1 to lZ~ The constraint index is calculated as ~ollows:
onstraint Index = loglo(fraction of n-hexane remaining) loglo(fraction of 3-methylpentane remaining) The constraint index approximates the ratio of the cracking rate constants for the two hydrocarbons.

ZEOLITES CONSTRAI~T INDE~
ZSM-5 8.3 ZSM-ll 8.7 ZSM-35 4.5 ~A Offretite 3.7 Beta 0.6 ZSM-14 0.5 H-7eolon 0.L~
~EY 0.'~
Amorphous Silica-Alumina f3.6 Erionite 3 The class of ~eolites deEined ilerein is exemplified by ZS~1-5 ZSM-ll, ZSM-12, ZSM-35, ZSM-38 and other similar materials.
Natural ~eolites may sometimes be converted to this type zeolite catalyst by vario~ls activation procedures and other treatmellts such as base exchange, steaming, alumina extraction and calcina~ion.
Natllral minerals ~lhich may be so treated incl~de Eerrierite, brewsterite, stilbite, dachiardite, epistilbite, heulanclite alld clinoptiloliee.
The preferreci shape seLective 7eolites for use herein will have a silica/al~mlina ratio in excess of 12 to 1. Zeolites with very high silica/alumina ratios, e.g., 70 to 1, 100 to 1, 300 to 1, or evell higher, s~lch as 39000 to 1 or 30,000 to 1, may also be l~sed herein.

3~3 In general, higher silica alumina ratio materials have lower acid activities, but better stabili~y.
Other fines that have no effect on the cracking action of the catalyst but whose presence increases the a~trition resistance of a final catalyst may also be added. Among these latter solids can be mentioned the alurnina and kaolin clay matrix components. In addition, recycled fines from the spray drying step may be used.

EXA~1E 1 ~ ,e catalyst consists of 20 wt. ~ rare earth exchanged and calcined zeolite Y (REY) in a silica-alurnina-clay matrix. The REY is formed from ion exchange of the sodium form of zeolite Y such that 68%
of the sodijm cations have been replaced by rare earth cations including Sm, Nd, Pr, Ce, and La having the distribution as indicated in Table 1. After ion exchange, the resulting REY product was calcined for about 10 minutes at 649C (1200F). The chemical composition of the REY is presented in Table 1.
The REY was incorporated in a gel matrix consisting of 60.5 wt. % SiO2, 4.5 wt. % A1203 and 35 wt. % clay. The catalyst was prepared as follows: 2100 grarns of Georgia kaolin clay on a dry basis was mixed with 7.3 grams Q-brand sodium silicate ~8.9 wt. % Na2O, 28.7 wt. % SiO2) and 3750 grams H20 and gro~cd for one hour in a bal] mill. The clay slowly was brought to 30~ solids by adding 1150 grams H2O. 1500 grarns of the REY on a dry basis was mixed with 9 grams of a dispersan-t, '~arasperse N"~and 3000 grams H20 and ground ~or one hour in a ball mill. l~e REY slurry was brought to 25% solids by adding 1500 grarns H2O 1263 kg (27.83 poullcls) ~-brand sodium silicate was mixed well with 7.51 kg (16.56 poullds) H2O and the clay and REY slurries were aclded, stirring continuously ulltil the solution was used. An acid al-~ solution was prepared by mixing 1.65 kg (3.64 pollnds) A12 (SO~)3 (MW=616) with 27.35 kg (61).29 powlds) 1l2n and 0.41 k~ (0.9 pound) 1-1~SO~ (96.2 percent acid).

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The acid alurn and clay, REY, silicate solutions were mixed through a 0.74 rnn (0.029 inch) diameter nozzle at solution rates of 345 cc/min for the acid alum and 340 cc/min for the clay, REY, silicate solution. The resulting mixture had a pH of 4.0-4.15.
The mixture was i~nediately homogenized and spray dried with an inlet temperature of 371C (700F) and an outlet temperature of 177C
(350F).
l~e resulting spray dried product was ion exchanged with 5%
aqueous ammonium sulfate so]ution and then water washed substantially free of s~l~ate. The washed product was then further ion exchanged with 1% aqueous solution of rare earth chloride, water washed substantially free of chloride and dried at l21C ~250F) for about 40 hours in air. The physical and chemical properties of the final catalyst are given in Table 2.

EXA~LE lA
The catalyst of Example 1 was impregnated with a solution of Pt (NH3)4 C12 containing enough Pt to impregnate the catalyst with 3 ppm. Enough solution was used to fill the catalyst pores. After impregnation, the catalyst was dried in air for 16 hours at 121C
(250F).

EX4~LE 2 l~lis example describes an alternative methocl of forming FCC
catalyst containing 20 wt~ % rare earth exchanged and calcined RY
from Example 1 in a high-density semi-synthetic silica~alumina-clay matrix. The chemical composition of the REY is given in Table 1.
The REY was incorporated in a high-density clay-gel matrix containing 67.9nO SiO2, 10.1% A12O3, 2~ ZrO2 a~ld 20% clay. The matrix was prepared by first dissolving in mixing tcmk A, 2365 grams of alwninum sulfate (17.2% A12O3) in 30.1 kg (66.4 pounds) water, a portion oÇ which was ice. The pH of ~he solution was adjusted to l.4 at UC (32F) by adding 120cc concentrated sulfuric acid.

In mixing tank B, 930 grams of Georgia kaolin clay (86go solids) were added to 24.2 kg (53.4 pounds) water~ a portion of which was ice. To this slurry, 9425 grams of Q-brand sodium silicate tPQ
Corporation, 8.9% NazO, 28.8o SiO2) was added uniformly over a thirty rninute period. The temperature of the resulting slurry was 0C
(3ZP) and the pH was 11.6.
The contents of mixing tank B were then slowly added to mixing tank A. After 7500cc of slurry from mixing tank B had been added, the rnixture had a pH of 3.6 at 4C ~40F). 200cc of concentrated sulfuric acid was added to reduce the pH to 1.7. An additional 7500cc from mixing tank B was added until the mixture pH was 3.4 at 8C (47F).
An additional 200cc of concentrated sulfuric acid was added to mixing tank A, reducing the pH to 1.9 at 11C (52F). The remainder of the slurry from mixing tank B was then added slowly to mixing tank A. The resultant gel-slurry had a pH of 3.6 at 13C ~55F).
Next> a slurry prepared by combining 167 grams of sodium ~irconium silica-te (~8~ ZrO2)~ 108cc of concentrated sulfuric acid and 1620cc water was added to the gel-slurry over a 15 minute period, reducing the pH of the entire mixture to 3.~.
The REY (20 wt. %) was added to the clay-gel mixture so formed. The pH was then adjusted to 4-4.5 by addition of 6S2cc of S0 wt. ~O sodium hydroxide. The mixture was filtered to remove wa~er and dissolved salts and then reslurried with 10.~ kg (23 po~mcls) of water. The gel-2eolite mixture was then homogenized and spray dried at 371C (700F) inlet temperature, 177C (350F) outlet temperature.
The resulting spray dried product was ion exchange~l with 5~0 a~ueous amlnonium sulfate solution, then water washed substantially fre0 of sulEate. The ~shecl product was then Eurther iOII exchanged Wit}l 1 aqueous solution of rare earth chloride, water washed substantially free o~ chlori(le and then dried at 121C (250F). The physical and chemical properties of the final catalyst are given in Table 2.

EX~MPLE 3 The catalyst of this example, consists of 25 wt. % ZSM-5 in a silica-alumima matrix. The gel matrix consists of 93 wt. % SiO2 and 7 wt. % A12O3.
80.34 pounds of ~-brand sodium silicate ~8.9 wt. ~ Na2O, 28.7 wt. % SiO2) was mixed with 27.8 kg (61.3 pounds) of H2O. An acid-alum solution was prepared by mixing 4.75 kg (10.48 pounds) of A12~SO~)3 (MW-616) with 50.1 kg (110.5 pounds) of H20 and 1.88 kg (4.15 pounds) of H2SO4 (96.3 wt. % acid).
The acid alum and silicate solutions were intimately mixed in a nozzle at rates of 410 and 365 cc/min, respectively. The resulting mixture had a pH of 3.5.
The pH was increased to 4.5 by adding NH4OH (29.6 wt. %) causing the mixture to gel while stirring continuously.
A sufficient quantity of a 20 wt. % slurry of ZSM-5 and water was added to the gel to give 25 wt. % ZSM-5 in the final catalyst, on a dry basis.
The gel matrix-ZSM-5 mixture was filtered to 16 wt. % solids and reslurried to 11 wt. % solids with H2O. This mixtrure was immediately homogenized and spray dried with an inlet temperature o-371C (700F) and an outlet temperature of 177C (350F).
The resulting spray dried product was ion exchanged with 5 wt.
% aqueous ammonium sulfate solution and water washed substantially free of sulfate. lhe product was then dried at 121C (250F) for about 40 hours. The physical and chemical properties of the final catalyst are given in Table 2.

This example describes another process of forming a high-density FCC catalyst containing 25 wt. % ZSM-5 in a semi-synthetic matrix consisting of 74.4 wt. ~ SiO2, 5.6 ~t. %
A12O3 and 20 wt. '~ clay.
The matri~ was prepared by first dissolving, in mixing tank A, 1306 grams of al~mlinum sulfate in 25.6 kg (56.5 pounds) wat~r, a ~Lf~
F-1736 - ll -portion of which was ice. The pH of the solution was adjusted to Q.7 at 25C (77F) by addition of 537cc of concentrated (96.2 wt. %) sulfuric acid.
In mixing tank B, 930 grams of Georgia kaolin clay were added to 28.8 kg (63.4 pounds) water, a portion of which was ice. To this slurry 10,333 grams of Q-brand sodium silicate (PQ Corporation, 8.9 wt. ~ Na20, 28.8 wt. % SiO2) was added uniformly over a 30 minute period. The temperature of the resulting slurry was 6C (43F) and the pH was 11.4.
The contents of mixing dr~n B were then added to mixing drum A
over a one hour period. The final mixture pH was 3.6 at 19C (67F).
The pH of the mixture was adjusted to 4.1 by addition of 330cc of 50 wt. % sodium hydroxide.
The ZSM-5 (25 wt. %) was added to the clay-gel mixture so formed and the zeolite-clay-gel mixture was Eiltered to remove water and dissolved salts. It was then reslurried with water, homogenized and spray dried at 371C (700F) inlet temperature 177C (350F) outlet temperature.
The resulting spray dried product was ion excllanged with S wt.
% aqueous ammonium sulfate solution, then water washed substantially free of sulfate and then dried at 121C (250F). The physical and chemical properties of the final product are given in Table Z.

EXA~LE 5 The catalyst of this example was prepared as follows using REY
from Example l. I~e matrix of this catalyst WRS also a gel matrix consisting of 60.5 wt. % SiO2, 4.5 wt. % A1203 and 35 ~
clay. 1750 grams of Georgia kaolin clay on a dry basis was mixecl with ~9.9 kg (llO.l pounds) H20 10,495 gr~ns of Q-brand socliurn silicat.e was added slowly over a 30 minute period. I~e admi.xture was then heated to 49C (120F) and 541cc of sulfuric acid (96.7 wt. ~ acid~
was added at a uniform rate over one hour to adjust the pH to clbout 10.4. The resulting gel which formed was aged at 49C (20~F) for 30 minutes and then cooled to ambient temperature. Alumina was then ?;3~

incorporated by adding a 20 wt. ~ aqueous solution of aluminum sulfate (17.2 wt. ~ Alz03) over a 30 minute period to a pH of about 3.9.
The pH of the mixture was then adjusted to 4.5 to prevent aging or deterioration of the gel, using 50 wt. ~ NaOH in water. The E~Y (20 wt. %) was added to the clay-gel mixture.
The resulting composite was homogenized and spray dried as described in Example 1 and the spray dried product was ion exchanged and dried again as described in Example 1. The physical and chemical properties of the final product are given in Table 2.

EXAMPLES 6,_7, 8 and 9 The catalysts of these examples~are commercial cracking catalysts sold under the names Super-D (manufactured by Davison C.hemical, E)ivision of W. R. Grace ~ Co.), FS-30, FOC-90 and OPC-4 (all manufactured by Filtrol Corp.), respectively. The physical properties of each are given in Table 2.

~YA~LE 10 The starting material for the catalyst of this example is a commercial catalyst sold under the name HFZ-20 (manufactured by Engelhard Minerals ~ Chemical Corp.). This material was ion exchanged with a solution of rare earth chloride in water containing enough rare eartil chloride to give 3 wt. % RE203 on the final catalyst. After exchange, the catalyst was water washed substantially chloride free and dried in air for about 16 hours at 121C ~250F).

EY~MPIE IOA
[~e startirIg material for this example is the same as for ExanIple lO. This mateIial was exchanged with the same solution as in E.Yample 1() which also incl~(lelI Pt(NI-I3)4CI2, enough to give 3 ppm E't on the final catalyst. ~le catalyst was washed .IIld ~Iriecl as in ExaIlll)le 10.

Z~ 3~

EXA~LE 11 The catalyst of this example consists of 25 wt. % ZS~1-5 in a silica-alumina matrix. The gel matrix consists of 93 wt. % SiO2 and 7 wt. % A1203, percentages by weight.
The catalyst was prepared as follows: 12.95 kg (28.55 pounds) of Q-brand sodium silicate (8.9 wt. % Na2O, 28.7 wt. % SiO2) were mixed with 9.8 kg (21.6 pounds) of H2O. An acid-alum solution was prepared by mixing 1691.0 grams of A12(SO4)3 with 17.8 kg (39.2 pounds) of l-l2O and 670.2 grams of H2SO~ (96.3 wt. % acid).
The acid-alum and silicate solutions were pumped separately but at the same time into a 30 gallon mixing drum at rates of 380 and 365cc/minute, respectively. 6000cc of H2O were placed in the bottom of thè mixing drum so that mixing could begin as soon as the solutions contacted the water. In the bottom of the barrel was placed a stirrer. The resul-ting mixture had a pH of 3.5. Additionally, ice was added to lower the temperature to 13C (55F).
The pH was increased to 4.5 by adding l95cc of NH40H ~29.6 wt. %) causing the mixture to gel while stirring continuously. A
sufficient quantity of a 20 wt. % slurry of ZSM-5 and water was added to the gel to give 25 wt. % ZSM-5 in the final catalyst on a dry basis.
The gel matrix-Z~-5 mixture was filtered to 18 wt. ~ solids and reslurried to 12 wt. % solids with 13.8 kg ~30.38 pounds) of ~l2 This mixture was immediately homogenized and spray dried with an inlet -temperature of 371C (700F) and outlet temperature o~ 177C
(350F).
The resulting spray dried particles were ion e,Ychanged with 5 wt. ~ aqueous c~lmonium sulfate solution and then water washed substantially free of sulfate. Tlle particles were then dried at 121C
(250F) for about ~0 hours. The physical and chemical properties of the final ca-talyst are given in Table 2.

3~3 CHEMICAL C MPOSITION OF CALCINED REY
OF EXAMPLES 1, 2 AND 5 Na, wt. % 3.2 Total RE2O3, wt. ~ 15.9 ~n2O3, wt. % 0.10 Nd2O3, wt. % 3.70 Pr6ll' wt. % 1.05 CeO2, wt. ~ 1.61 La203, wt. % 9.47 SiO2, wt. % 61.4 A123~ wt. % 21.7 From a comparison of the physical and chemical properties of the individual catalysts set forth in Table 2, it can be seen that the packed density and pore vol~e of the catalysts formed in accordance with the present invention~ Exc~mples 1-4 and 11 are comparabl~ to those of a typical commercial catalyst such as the catalyst of Example 6.
In Example 5, a catalyst was formed with the sc~ne chemical composition as the catalyst of Ex~m?le 1, but utilizing a different forming Dlethod.
The ca~alyst of Ex~mple 5 has a more open structure as evidenced by the hiKher surface area and pore vol~ne and lower packed density.

E~ LE 12 Fresh catalysts from Examples 1 and 5-10 were steam treated in a fLuidized bed for 4 hours at 760C (1~00F) with 100~ stearn at atmospheric pressure. The steamed catalysts ~ere used to crack a high-sul~ur sour heavy gas oil, the properties of which are given in 'I'able 3, in a fixed fluidized bed test unit whicil simulated ~:CC
cracking. Tests conditions were 515C ~60~F) 1.0 minute on-s~ream.

P~NSICAL AND CHEMICAL PROPERTIES OF CATALYSTS

C _ cal ~nalysis Ex. 1 Ex. 2 Ex. 3* Ex. 4* Ex. 5 Ex. 6 Na2O, wt. % 0.15 0.190.03 0.12 0.12 0.70 ~F2O3, wt- ~ 4.83 4.41 --- --- 4.95 3.02 SiO2, wt. % 70.1 71.1 86.6 81.~ 70.1 61.0 A123' Wt- % 18.9 16.5 6.2 11.9 20.1 29.9 Physical Properties Packed ~ensity, gm/cc 0.83 0.97 0.87 0.76 0.61 0.86 Pore Volume, cc/gm 0.22 0.090.23 0.26 0.55 0.23 Surface Area, m /gm 96 96 167 249 181 102 * Physical properties for Examples 3 and ~ were determined after treatmen~
0.5 hours, 649C (1200F), 100~ N2 atmospheric pressure in a fluidi~ed bed. All other ca~alysts were steamed.

~2;~ 3~

~-1736 - 16 -TABLE 2 (cont.) P~SIGAL AND CHEMICAL PROPERTIES OF C~TALYSTS

Chemical Analysis Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 10a Ex. ll Na2O, wt. % 0.52 0.69 0.54 0.92 0.91 0.06 RE2O3, wt- % 2.99 0.49 3.49 3.03 3.41 SiO2, wt. % 51.0 50.5 47.2 37.837.6 87.6 AlzO3~ wt. % 40.3 40.4 43.6 57.457.2 6.4 sical Properties Packed Density, gm/cc 0.85 0.73 0.79 0.90 0.94 0.77 Pore Volume, cc/gm 0.37 0.46 0.41 0.42 0.42 0.24 S~rface AIea, m2/gm 137 141 129 253 239 ---^~22~33~

HIGH SULFUR SOUR HEA~Y GAS OIL

Gravity, API 24~3 Density, g/cc 0.91 Aniline Pt. F/C 171J77 Sulfur, wt. % 1.87 Nitrogen, wt. % 0.10 Basic Nitrogen, ppm 327 Conradson Carbon, wt. % 0.28 Viscosity, KV at 99C ~210F) 3.6 Bromine No. 4.2 Refractive Index at 21C (70~) 1.50~0 Hydrogen, wt~ ~ 12.3 Molecular wt. 358 Pour Point, F 85 Paraffins, wt. % 23.S
Naphthenes, wt. % 32.0 Aromatics, wt. % 44.5 CA, wt. % 18.9 Test conclitions and product distributions are given in Table 4. ~le following abbreviations are used:
G = C5 Gasoline = Gasoline A = Alkylate G~A = Gasoline ~ Alkylate ~Z~3~3 Catalyst Exam~e 1 5 6 Catalyst/oil, wt/wt 2.5 2.0 2.5 W~V, Hr~l 24.0 30.0 24.0 Conversion, % Vol70.8 70.0 70.3 Gasoline, % Vol 55.5 57.5 55.2 Total C4, % Vol 16.4 13.2 15.3 Dry Gas, % Vol 8.5 7.8 8.5 Coke, wt. % 4.0 3.5 4.4 G + A 76.1 76.2 75.0 RON + O, G 88.7 86.9 87.6 RON + 0, G -~ A 90.1 88.6 89.2 Conversion/Coke, Vol/Wt 17.7 20.0 16.0 G/Conversion, Vol/Vol 0.784 0.821 0.785 G/Coke, ~ol/Wt 13.9 16.4 12.5 The catalyst of the present inven~ion ~xample 1) has the sameactivity as the commercial catalyst, Super-D (Example 6) as shown by equivalent conversion at the same catalyst/oil ratio. The catalyst o Example 1 is less active than the catalyst of Example 5 because of the higher diffusional resistance provided by the more closed structure.
The catalyst of Example 1 yields as much gasoline as Super-D. This is accompanied by an increase in the research clear octane number. The total C4 yield of the ca-talyst of the present invention is greater and with less coke formation than Super-D.
Lower secondary cracking rates due to the greater diffusivity are responsible for the higher gasoline yield and lower C4, dry gas and coke yields of Example 5 catalyst. This also causes the octane nL~nber of the gasoline to be lower as the lower octane components of the gasoline are not cracked out.
When the potential akylate of the three catal~sts is included in the analysis, the total gasoline yield of Example 1 is increased to the amount of Example 5. A significant octane advantage still exists for the gasoline of Example 1. The Super-D catalyst has a deficit in both total gasoline yield and octane number.

EXA~LE 13 The sulfur emissions from coke burnof were determined by oxidizing spent catalyst in oxygen at 649C (1200F) and passin~ the effluent gas through a 3% solution of hydrogen peroxide in ~ater, thus converting SO2 to SO3 and absorbing all of the SO3. ~le sulfate formed was ~itrated as sulfuric acid with standard base ~aOH.
Table 5 presents the sulfur emissions of the example catalysts in several ways. The sulfur on-catalyst (S/CAT) fixures give an indication of the anlount of sulfur released per weight of catalyst while the sulfur in coke (~ S/C) values relate the sulfur released to the amount of coke hurned. The third set of figures, sulfur per vol~Dne o~ feed converted, is influenced by the activity of the catalysts.

~2;~3~

SUL~ EMISSIONS OF COKED CATALYSTS

Catalyst lb S/bbl Example % C/Cat S/CAT, ppm % S/C feed converted ~g S/m3 1 1.338 71 0.53 0.093 0.27 1.378 79 0.57 0.089 0.25 la 1.399 69 0.49 0.092 0.26 1.562 151 0.96 0.189 0.54 6 1.487 280 1.88 0.366 1.05 7 1.511 184 1.18 0.230 0.66 8 0.983 157 1.72 0.215 0O61 9 l.962 324 1.65 0.398 1.14

2.257 155 0.69 0.179 0.51 10a 2.259 242 7.07 0.285 0.81 From Table 5, it can be seen that when the matrix components of a fluid cracking catalyst are intimately mixed as previo~sly described such that the pH is maintained at 3.0-4~5, a very substantial reduction of sulfur emissions results. At least a 50~ reduction occurs compared to all catalysts in sulfur on catalyst. The effect of a platinum oxidation promoter in this example is demonstratad by the catalyst of Example 10a. Compared to the catalyst of Example 10, an increase in the sulfur emissions is measured. This has not been the case in commercial measurements of Sx emissions Eor ~its operating with some degree of promoted CO combustion.

Claims (12)

CLAIMS:

1. A method of preparing a high density FCC catalyst comprising mixing a basic solution containing silica with an acidic solution containing alumina, continuously maintaining said mixture at a pH of 3.0 to 4.5 from the initial mixing to the formation of a gel, homogenizing the gel and spray drying the homogenized gel to produce a high density FCC catalyst.

2. The method of Claim 1 wherein the basic solution containing silica is an aqueous sodium silicate solution.

3. The method of Claim 1 wherein the acidic solution containing alumina is an aqueous acid-alum solution.

4. The method of Claim 1 wherein a zeolite is added to the catalyst before spray drying.

5. The method of Claim 4 wherein the zeolite is added to the basic solution containing silica.

6. The method of Claim 4 wherein the zeolite is added to a mixture of silica and alumina.

7. The method of Claim 4 wherein a large pore zeolite is added to the catalyst before spray drying.

8. The method of Claim 4 wherein a rare earth exchanged zeolite Y is added to the catalyst before spray drying.

9. The method of Claim 1 wherein a zeolite having a constraint index of 1 to 12 and a silica to alumina mole ratio above 12 is added to the catalyst prior to spray drying.

10. A fluidized catalytic cracking catalyst prepared by the method of claim 1, 2 or 3.

11. In a fluidized catalytic cracking process wherein a conventional feed stock contacts a conventional FCC catalyst at conventional FCC operating conditions, the improvement comprising use of a cracking catalyst prepared by the method of claim 1, 2 or 3.

12. In a process for cracking sulfur containing hydrocarbon feed in the presence of a conventional FCC catalyst operated at conventional FCC conversion conditions, wherein at least a portion of the sulfur contained in the feed hydrocarbons is deposited on the catalyst in the form of coke, and released to the atmosphere as SOx during coke burnoff, the improvement comprising using as the catalyst a high density FCC catalyst prepared by mixing a basic solution containing silica with an acidic solution containing alumina, continuously maintaining said mixture at a pH of 3.0 to 4.5 from the initial mixing to the formation of a gel, homogenizing the gel and spray drying the homogenized gel to produce a high density FCC catalyst, whereby the amount of SOx in regenerator flue gas is substantially reduced.