GB2109696A - Method for preparing a zeolite- containing fluid cracking catalyst - Google Patents

Abstract

Zeolite-containing catalysts useful for fluid cracking of hydrocarbons are prepared by forming and drying an aqueous slurry of zeolite and aluminum chlorhydrol to obtain particulate composites that contain in excess of about 1 percent by weight alkali metal oxide. The particulate composites are calcined and subsequently ion exchanged to obtain hard, attrition-resistant catalyst particles which have an alkali metal oxide content of less than 1 percent by weight.

Description

SPECIFICATION Method for preparing a zeolite-containing fluid cracking catalyst The present invention relates to the manufacture of catalysts, and more specifically to the preparation of hard, attrition resistant zeolite-containing catalysts which are highly active for the catalytic conversion of hydrocarbons.

Hydrocarbon conversion catalysts such as fluid cracking catalysts (FCC) which comprise crystalline zeolites dispersed in an inorganic oxide matrix are typically prepared by spray drying an aqueous slurry of zeolite, clay and a suitable binder such as silica-alumina hydrogel, silica sol or alumina sol. The spray dried catalyst particles may be calcined and ion exchanged to remove undesirable alkali metal impurities.

Canadian Patent No. 967,136 describes a hydrocarbon conversion catalyst which comprises zeolite, clay and an alumina sol binder. The catalysts are prepared by spray drying a mixture of low soda ion exchanged zeolite, clay, and alumina sol (chlorhydrol), and calcining the spray dried particles to obtain hard, attrition resistant catalysts.

U.S. Patent No. 3,425,956 describes a method for preparing a zeolite containing cracking catalyst wherein a spray dried composite of partially ion exchanged zeolite and silica-alumina hydrogel is calcined and subsequently ion exchanged. The calcination step stabilizes zeolite and enhances alkali metal oxide removal.

In recent years the cracking catalyst industry has been particularly concerned with regard to the production of catalysts which are highly attrition resistant, active and selective for the production of gasoline fractions.

The present invention therefore provides a process by which highly active, attrition resistant catalysts may be economically prepared. In the new process the need for multiple high temperature calcination steps may be eliminated, and the thermally stable catalytic cracking catalysts obtained are capable of producing a high level of gasoline fractions, and can be made selective for the preparation of high octane gasoline fractions.

Broadly, the present invention provides a process for the production of alumina bound zeolite containing catalysts in which a dried particulate composite comprising an alkali metal containing zeolite and an aluminum chlorhydrol binder is calcined and subsequently ion exchanged to lower the alkali metal content to below about 1 percent by weight.

More specifically, we have found that by calcining an aluminum chlorhydrol bound particulate catalyst composite which includes an alkali metal containing zeolite, the catalyst composite may be simultaneously hardened by conversion of the aluminum chlorhydrol to alumina binder, and activated for sodium removal by subsequent ion exchange.

A more clear understanding of our invention may be obtained by reference to the drawing which outlines a catalyst preparation method which may be used in the practice of our invention.

As shown in the figure, sources of aluminum chlorhydrol solution, zeolite slurry and clay slurry are combined in a mixer device to obtain a uniform aqueous slurry. As indicated in the figure, the mixed chlorhydrol/zeolite/clay slurry is conducted to a spray drying step wherein the slurry is converted to particulate solid composites that comprise zeolite and clay particles bound by aluminum chlorhydrol.

These composites are calcined to obtain hard, attrition resistant particles. During the calcination step, the aluminum chlorhydrol is converted to a strong alumina binder and acid chloride by-products, which are removed from the composite. The calcination step also renders the alkali metal oxide, which is present in the zeolite component, more readily available for removal by subsequent ion exchange.

As shown in the drawing, the calcined catalyst composite is ion exchanged and/or washed to remove excess alkali metal oxide and any other soluble impurities which may be present. The ion exchange step may be conducted using an ammonium salt solution such as ammonium sulfate and/or rare earth chloride solution. The ion exchanged composite is washed with water to remove soluble impurities. Subsequent to ion exchanging and washing, the catalyst composite, which at this point contains less than about 1 percent, preferably less than .5 percent by weight alkali metal oxide, is dried to a level of about 5 to 25 by weight moisture.

The aluminum chlorhydrol solution used in the practice of the present invention is readily available from commercial sources and typically possesses the formula: Al2+m(0H)3mC16 wherein m has a value of about 4 to 12.

The aluminum chlorhydrol solutions are also frequently referred to in the art as polymeric cationic hydroxy aluminum complexes or aluminum chlorhydroxides which are polymers formed from a monomeric precursor having the general formula Al2(OH)5C1 2H20. For the purpose of the present application, the binder component will be referred to as aluminum chlorhydrol. The preparation of the aluminum chlorhydrol solution is typically disclosed in U.S. 2,196,016, Canadian 967,1 36, and in U.S. 4,176,090. Typically, preparation of aluminum chlorhydrol invoives reacting aluminum metal and hydrochloric acid in amounts which will produce a composition having the formula indicated above.

Furthermore, the aluminum chlorhydrol may be obtained using various sources of aluminum such as alumina (Al203), clay and/or mixtures of alumina and/or clay with aluminum metal. Preferably, the aqueous aluminum chlorhydrol solutions used in the practice of the present invention will have a solids content of from about 1 5 to 30 percent by weight Al203.

The zeolite component used in our invention is typically a synthetic faujasite zeolite such as sodium Type Y zeolite (NaY) which contains from about 10 to 1 5 percent by weight by weight Na20. It is also contemplated that the zeolites may be partially ion exchanged to lower the soda level thereof prior to incorporation in the catalyst. Typically, the zeolite component may comprise a partially ammonium exchanged type Y zeolite (NH4NaY) which will contain about 3 to 4 percent by weight Na20.

Furthermore, the zeolite may be partially exchanged with polyvalent metal ions such as rare earth metal ions, calcium and magnesium. The zeolite component may also be exchanged with a combination of metal and ammonium and/or acid ions. It is also contemplated that the zeolite component may comprise a mixture of zeolites such as synthetic faujasite in combination with mordenite and the ZSM type zeolites. Preferably the zeolite is combined with the aluminum chlorhydrol and a clay component as an aqueous slurry which contains from about 20 to 60 weight percent solids.

The catalysts of the present invention may contain substantial quantities of clay such as kaolin.

The clay component, however, is optional and comprises from about 0 to about 80 weight percent (dry basis) of the overall catalyst composition. While kaolin is the preferred clay component, it is also contemplated that thermally modified kaolin such as metakaolin may be included in the catalyst composition.

During the mixing step, as shown in the figure, a spray-dryer feed slurry is obtained which contains from about 20 to 60 weight percent solids, of which from about 5 to 25 weight percent comprises aluminum chlorhydrol (dry basis) as Awl203, 0 to 60 weight percent zeolite, and from about 0 to 90 weight percent clay. While the drawing illustrates a process by which fluid cracking catalysts are obtained by spray drying the catalyst preparation slurry, it is also contemplated that particulate catalyst of larger particle size, i.e. on the order of from about 1/2 to 2 mm may be obtained by forming beads or pills of the present compositions which are particularly useful for the preparation of hydroprocessing catalysts such as hydrocracking, hydrodesulfurization and hydrodenitrogenation, and demetallization catalysts.

The spray drying step is conducted using inlet temperatures in the range of from about 300 to 4000C and outlet gas temperatures of from about 100 to 2COOC. During the spray drying step, the moisture content of the particles is reduced to about 10 to 30 percent by weight. Catalyst composites have a particle size on the order of 20 to 1 50 microns.

After spray drying the catalyst composites are calcined at temperatures on the order of from about 300 to 7000C for a period of from about 9 to 3 hours, and preferably about 2 to 2 hours. During the calcination step the aluminum chlorhydrol is converted to solid aluminum binder and volatile acid chlorides, which are removed from the calcination zone as part of the off-gas stream. The removal of the acid chlorides at high temperatures converts the aluminum chlorhydrol to an aluminum oxide binder which produces a tough, attrition resistant catalyst particle. Furthermore, the calcination step activates, i.e. loosens, the residual alkali metal oxide present in the zeolite component which is readily removed by subsequent ion exchange and/or washing steps.

The ion exchange step which reduces the alkali metal oxide level of the catalyst composites to less than about 1 percent by weight is conducted using water and/or aqueous ammonium salt solutions such as ammonium sulfate solution and/or solutions of polyvalent metals such as rare earth chloride solutions. Typically, these ion exchange solutions contain from about 1 to 10 weight percent dissolved salts. Frequently, it is found that multiple exchanges are beneficial to achieve the desired degree of alkali metal oxide removal. Typically the exchanges are conducted at temperatures on the order of from 50 to 1 000C. Subsequent to ion exchanging, the catalyst components are washed, typically with water, to lower the soluble impurity level to a desirable level.

Subsequent to ion exchange and washing, the catalyst composites are dried, typically at temperatures ranging from about 100 to 2000C to lower the moisture content thereof to a level of preferably below about 1 5 percent by weight.

Cracking catalysts obtained by our process are highly active for the catalytic cracking of hydrocarbons. Typically, it is found that the activity of these catalysts range from about 60 to 90 volume percent conversion subsequent to deactivation and elevated temperatures. Furthermore, it is found that the catalysts are highly selective for the production of gasoline, and in particular, selective for the production of cracked gasoline fractions which have a high octane rating. Furthermore, the catalysts are extremely tough and attrition resistant.

While the primary components of the catalyst comprise zeolite, aluminum chlorhydrol and optionally, clay, it is also understood that other components such as particulate alumina and rare earth impregnated alumina may be added for the purpose of enhancing the SOx control capabilities of the catalyst. Furthermore, it is understood that the catalyst may be combined with minor quantities (1 to 100 ppm) of platinum and palladium which are added for the purpose of enhancing the CO oxidation characteristics of the catalyst. The attrition properties of the catalyst are expressed in terms of the Davison Index (DI) and the Jersey Index (Jl) which are determined as set forth in U.S. 4,247,420.

Having described the basic aspects of the present invention, the following examples are given to illustrate specific embodiments thereof.

EXAMPLE 1 The following ingredients were combined in a 10 gallon stainless steel mixing kettle: 3,404 g of aluminum chlorhydrol solution possessing the formula Al2Cl(OH)s and containing 23.5 percent by weight Al203; 7500 g (dry basis) kaolin; 1 500 g (dry basis) calcined rare earth exchanged type Y zeolite (CREY); and sufficient water to obtain a slurry which contained 25 weight percent solids. The calcined, rare earth exchanged type Y zeolite was obtained by exchange with aqueous mixed rare earth chloride solution at pH = 5 of NaY followed by calcination for 3 hours at 1 0000 F and contained 1 5.02 weight percent RE203 and 3.8 weight percent Na20.The slurry was thoroughly agitated and spray dried using a gas inlet temperature of 3200C and a gas outlet temperature of 1 500 C. The spray dried catalyst particles which contained about 25 weight percent water and 0.5 weight percent Na2O were calcined (i.e. heated) in a muffle furnace at a temperature of 10000F (5380 C) for 1 hour. Subsequent to calcination the catalyst was dried at a temperature of 1 500 C. The chemical analysis of this catalyst as well as its cracking properties are set forth in Table EXAMPLE 2 The preparation method of Example 1 was repeated. However, 3000 g of the calcined catalyst particles were ion exchanged by contact with 9000 ml of ammonium sulfate solution which contained 3 weight percent by weight ammonium sulfate.The analysis and properties of this catalyst is set forth in Table I.

EXAMPLE 3 The preparation method of Example 1 was repeated. However, the zeolite comprised an ammonium exchanged, calcined type Y zeolite which contained 12.5 weight percent RE203, and 0.5 weight percent Na2O. The catalyst was not ion exchanged subsequent to calcination. The properties of this catalyst sample are set forth in Table I.

EXAMPLE 4 The preparation procedure of Example 1 was repeated. However, a non-calcined rare earth exchanged Y zeolite was utilized (REY) which contained 1 3.4 weight percent Re203 and 3.2 weight percent Na2O. This catalyst sample was not ion exchanged subsequent to calcination. The properties of this catalyst are set forth in Table I.

EXAMPLE 5 The catalyst preparation method of Example 4 was repeated. However, 3000 g of the calcined catalyst was exchanged with 9000 ml of ammonium sulfate solution containing solution containing 3 weight percent by weight ammonium sulfate subsequent to calcination. The properties of this catalyst are set forth in Table I.

EXAMPLE 6 The catalyst preparation method of Example 1 was repeated. However, the finished catalyst contained 25 weight percent of a sodium ammonium Y zeolite which contained 3.8 weight percent Na2O which was obtained by exchanging a sodium Y zeolite with ammonium sulfate. 3000 g of this catalyst was washed with 9000 ml of water subsequent to calcination. The properties of this catalyst are set forth in Table II.

EXAMPLE 7 The catalyst preparation procedure of Example 6 was repeated. However, subsequent to calcination 3000 g of the catalyst was exchanged with 9000 ml of ammonium sulfate solution which contained 3 weight percent by weight ammonium sulfate. The properties of these catalysts is described in Table II.

EXAMPLE 8 The catalyst preparation method of Example 1 was repeated. However, the zeolite comprised 25 weight percent by weight of an ammonium exchanged, calcined, stabilized Type Y zeolite (Z14US zeolite) which was prepared in accordance with the process set forth in U.S. 3,449,070. The Z14US zeolite, at the time of incorporation in the catalyst, contained about 3.8 weight percent Na20. 3000 g of the catalyst subsequent to calcination was exchanged with 9000 ml of ammonium sulfate solution. The properties of this catalyst are set forth in Table II.

EXAMPLE 9 The catalyst preparation method of Example 1 was followed. However, a catalyst was prepared which contained 40 weight percent ammonium exchanged type Y zeolite which contained 3.8 weight percent Na2O. Furthermore, the quantity of chlorhydrol was adjusted to provide an alumina binder content of 1 5 weight percent and the kaolin content was adjusted to 45 weight percent. This catalyst was not washed subsequent to calcination. The properties of the catalyst are set forth in Table Ill.

EXAMPLE 10 The catalyst preparation method of Example 9 was repeated. However, subsequent to calcination 3000 g of the catalyst was washed with 9000 ml of water. The properties of this catalyst are set forth in Table Ill.

EXAMPLE 11 The catalyst preparation method of Example 9 was repeated. However, subsequent to calcination 3000 g of the catalyst was washed with 9000 ml of ammonium sulfate solution which contained 3 weight percent of ammonium sulfate. The properties of this catalyst are set forth in Tables Ill and IV.

EXAMPLE 12 A commercial comparison catalyst which contained 40 weight percent Z14US zeolite, 23 weight percent of a silica sol binder, and 37 weight percent kaolin clay was prepared by the method set forth in U.S. 3,957,689. This catalyst was washed with ammonium sulfate and the properties thereof are described in Table IV.

EXAMPLE 13 A catalyst was prepared by the method set forth in Example 9. However, the zeolite component comprised 40 weight percent of a Z14US type zeolite which had been exchanged with ammonium sulfate to a level of about 0.2 percent by weight Na20. This catalyst was not ion exchanged or washed subsequent to calcination. The properties of this catalyst are set forth in Table IV.

EXAMPLE 14 In this example the properties of the catalysts prepared in Examples 1 through 5 were determined and tabulated in Table I below: TABLE I Catalyst of Example No. 1 2 3 4 5 Analyses Wot. % NaY 0.51 0.14 0.18 0.44 0.18 Wt. % RE203 2.26 2.33 2.43 2.77 2.74 Wt.%SO4 0.18 1.31 0.15 0.13 0.67 Surface Area m2/g 133 133 148 148 146 Density g/cm2 0.84 0.84 0.84 0.87 0.87 Davison Index/Jersey Index 6/0.8 36/3.5 3/0.1 3/0.9 16/1.7 Microactivity (Vol. % Conv.) 72 73 71 76 76 Deactivation (s-13.5)(1) Deactivation (1500)(2) 54 68 65 62 72 (t) S-1 3.5: : 3 hours at 10000F (538"C) in air followed by 8 hours at 1 350" F (7320C) in 100% steam at 1 5 psig (103 KPa gauge).

(2) 1500: 5 hours at 1 5000F (81 60C) in 100% steam at 0 psig (i.e. atmospheric pressure).

It is noted from the data set forth in Table I that the activity of catalysts which contained the noncalcined Y zeolite (Examples 4 and 5) are superior to those which contained the precalcined zeolite (Examples 1,2 and 3).

EXAMPLE 15 In this example the properties of the catalysts prepared in Examples 6,7 and 8 were determined and are compared in Table II below.

TABLE II Catalyst of Example No. 6 7 8 Wt. % Na20 0.58 0.13 0.27 Unit Cell (AO) 24.62 24.62 24.50 Microactivity (Vol. % Conversion after 60 59 57 S-i 3.5 deactivation) Pilot Unit Data Microactivity (Vol. % Conversion) after 58.5 62.0 60.5 S-20 deactivation13 Research Octane No. 89.5 90.3 90.6 Motor Octane No. 78.2 79.0 79.3 (3) S-20: 18 hours at 1 5200F (8270C), 20% steam, 80% air, 0 psig (atmospheric pressure).

It is noted from the data set forth in Table II that the octane selectivity for the catalysts prepared in accordance with the teachings of the present invention (Examples 6 and 7) are almost equal to the catalyst which contained the precalcined Z14US type Y zeolite (Example 8).

EXAMPLE 16 In this example the properties of the catalysts obtained in Examples 9, 10 and 11 are compared, as set forth in Table Ill below.

TABLE Ill Catalyst Example No. 9 10 11 Ammonium No Sulfate Wash/Exchange Water Wash Exchange Wot. % NaY 2.11 0.91 0.54 Microactivity after S-i 3.5 16 50 67 Deactivation The above data indicates that substantial soda removal may be obtained through use of the practice of the present invention, even though only water (Example 10) is used in lieu of ammonium sulfate solution (Example 11).

EXAMPLE 17 The properties of the catalysts described in Examples 11, 12 and 13 are compared and summarized in Table IV below.

TABLE IV Catalyst Example No. 11 12 13 Wt. % Na2O 0.22 0.54 0.04 Microactivity after S-13.5 69 67 69 Deactivation Microactivity (Vol. % Conversion) after 55.0 68.0 71.0 1400 Deactivation'4' Research Octane No. 92.8 92.7 93.0 Motor Octane No. 81.3 80.2 81.8 * USY exchanged to 0.20% Na20.

'4' 1400: 16 hours at 10000F (5380C) in air followed by 16 hours at 1 4000F (7600C), 100% steam, 0 psig (atmospheric pressure).

The above data indicate that use of the process described in the present invention (Examples 11 and 13) provides catalysts of high activity and good octane selectivity when compared to a prior art catalyst (Example 12).

Claims (10)

1. A method for preparing a catalyst composition which comprises: (a) preparing an aqueous mixture of an alkali metal containing zeolite and aluminum chlorhydrol: (b) forming said mixture to obtain particulate zeolite/aluminum chlorhydrol composites which contain in excess of about 1 percent by weight alkali metal oxide: (c) calcining said composites at a temperature in excess of about 5000 C; and (d) ion exchanging and washing the calcined composites to obtain catalyst particles having an alkali metal oxide content of below about 0.5 weight percent.

2. The method of claim 1 wherein said aluminum chlorhydrol has the formula Alz+m(OH)3mCl6 wherein m has a value of about 4 to 12.

3. The method of claim 1 or 2 wherein the zeolite is a type Y zeolite.

4. The method of any of claims 1 to 3 wherein the said aqueous mixture prepared in slep (a) includes clay.

5. The method of any of claims 1 to 4 wherein the said mixture is formed at step (b) by spray drying.

6. The method of any of claims 1 to 3 wherein said ion exchange step (d) includes contacting the calcined particles with a solution which includes ammonium ions and/or rare earth ions.

7. The method of claim 1 substantially as described in any one of the foregoing Examples 2, 5, 6, 7, 10or11.

8. A catalyst composition prepared by the method of any of claims 1 to 7.

9. The composition of claim 8 wherein said catalyst contains from about 0 to 60 weight percent zeolite, 5 to 25 weight percent alumina binder, and up to about 90 weight percent clay.

10. A method for the catalytic cracking of hydrocarbons in which a catalyst composition as claimed in claim 8 or 9 is used as the fluid cracking catalyst.