Reactivation of Steam-Deactivated Catalysts

1. Field of the Invention

This invention relates to a process for reactivating certain catalyst compositions comprising crystalline materials which have been steam-deactivated, said method involving contact with an aluminum compound followed by controlled treatment with an acid solution.

2. Description of Prior Art

Zeolitic materials, both natural and synthetic, have been demonstrated in the past to have catalytic properties for various types of hydrocarbon conversion. Certain zeolitic materials are ordered, porous crystalline aluminosilicates having a definite crystalline structure as determined by X-ray diffraction, within which there are a large number of smaller cavities which may be interconnected by a number of still smaller channels or pores. These cavities and pores are uniform in size within a specific zeolitic material. Since the dimensions of these pores are such as to accept for adsorption molecules of certain dimensions while rejecting those of larger dimensions, these materials have come to be known as "molecular sieves" and are utilized in a variety of ways to take advantage of these properties.

Such molecular sieves, both natural and synthetic, include a wide variety of positive ion-containing crystalline aluminosilicates. These aluminosilicates can be described as a rigid three-dimensional framework of SiO.sub.4 and AlO.sub.4 in which the tetrahedra are cross-linked by the sharing of oxygen atoms whereby the ratio of the total aluminum and silicon atoms to oxygen atoms is 1:2. The electrovalence of the tetrahedra containing aluminum is balanced by the inclusion in the crystal of a cation, for example an alkali metal or an alkaline earth metal cation. This can be expressed wherein the ratio of aluminum to the number of various cations, such as Ca/2, Sr/2, Na, K or Li, is equal to unity. One type of cation may be exchanged either entirely or partially with another type of cation utilizing ion exchange techniques in a conventional manner. By means of such cation exchange, it has been possible to vary the properties of a given aluminosilicate by suitable selection of the cation. The spaces between the tetrahedra are occupied by molecules of water prior to dehydration.

Prior art techniques have resulted in the formation of a great variety of synthetic zeolites. The zeolites have come to be designated by letter or other convenient symbols, as illustrated by zeolite A (U.S. Pat. No. 2,882,243), zeolite X (U.S. Pat. No. 2,882,244), zeolite Y (U.S. Pat. No. 3,130,007), zeolite ZK-5 (U.S. Pat. No. 3,247,195), zeolite ZK-4 (U.S. Pat. No. 3,314,752), zeolite ZSM-5 (U.S. Pat. No. 3,702,886), zeolite ZSM-11 (U.S. Pat. No. 3,709,979), zeolite ZSM-12 (U.S. Pat. No. 3,832,449), zeolite ZSM-20 (U.S. Pat. No. 3,972,983), ZSM-35 (U.S. Pat. No. 4,016,245), ZSM-38 (U.S. Pat. No 4,046,859), and zeolite ZSM-23 (U.S. Pat. No. 4,076,842), merely to name a few.

The silicon/aluminum atomic ratio of a given zeolite is often variable. For example, zeolite X can be synthesized with silicon/aluminum atomic ratios of from 1 to 1.5; zeolite Y, from 1.5 to about 3. In some zeolites, the upper limit of the silicon/aluminum atomic ratio is unbounded. ZSM-5 is one such example wherein the silicon/aluminum atomic ratio is at least 2.5 and up to infinity. U.S. Pat. No. 3,941,871 (Re. 29,948) discloses a porous crystalline silicate made from a reaction mixture containing no deliberately added aluminum in the recipe and exhibiting the X-ray diffraction pattern characteristic of ZSM-5 type zeolites. U.S. Pat. Nos. 4,061,724, 4,073,865 and 4,104,294 describe crystalline silicas of varying aluminum and metal content.

The reactivation of steam-deactivated catalysts comprising such zeolites has been a prime objective of the petrochemical and refining industries. In contrast to coke-deactivated catalysts which can be readily regenerated by air oxidation, no adequate technique has been heretofore developed for reactivation of steam-deactivated catalysts. Steam deactivation apparently involves removal of aluminum from zeolitic framework, a result which until now has been believed to be largely irreversible. The present method provides for the first time a convenient way to reactivate steam-deactivated catalysts. This will prove to be useful and, in fact, valuable in numerous process applications.

It is noted that U.S. Pat. Nos. 3,354,078 and 3,644,220 relate to treating crystalline aluminosilicates with volatile metal halides, including aluminum chloride. Neither of these latter patents is, however, concerned with treatment of catalysts comprising zeolites, especially zeolites having initially a high silicon/aluminum atomic ratio, which have been deactivated by contact with steam.

The present invention relates to a novel process for reactivation, i.e. improving acid activity, of certain catalyst compositions comprising crystalline zeolites having a silicon/aluminum atomic ratio of at least 2, especially those zeolites having high silicon/aluminum atomic ratios of greater than 10, such as, for example, greater than 50, which have been deactivated by contact with steam. The present process comprises the steps of contacting said steam-deactivated catalyst composition with an aluminum compound, such as, for example, aluminum halide, e.g. aluminum chloride, at an elevated temperature, followed by contacting said catalyst composition with an aqueous acid solution, such as, for example, an acid solution having a pH of less than about 5, e.g. less than about 2. The resulting reactivated catalyst composition exhibits enhanced Bronsted acidity and, therefore, improved acid activity toward catalysis of numerous chemical reactions, such as, for example cracking of organic, e.g. hydrocarbon, compounds.

The novel process of this invention is concerned with the treatment of catalysts comprising crystalline material having a silicon/aluminum atomic ratio of at least 2, especially those crystalline materials having high silicon/aluminum atomic ratios of greater than 10, such as, for example, greater than 50, which have been steam-deactivated. The expression "high silicon crystalline material" is intended to define a crystalline structure which has a silicon/aluminum atomic ratio greater than about 10, more preferably greater than about 50, still more preferably greater than about 100, up to and including those highly siliceous materials where the silicon/aluminum atomic ratio is as reasonably close to infinity as practically possible. This latter group of high silicon crystalline materials is exemplified by U.S. Pat. Nos. 3,941,871; 4,061,724; 4,073,865 and 4,104,294 wherein the materials are prepared from reaction solutions which involve no deliberate addition of aluminum. Small quantities of aluminum are usually present in reaction solutions from which high silicon crystalline material is to be synthesized. It is to be understood that the expression "high silicon crystalline material" also specifically includes those materials which have other metals besides silicon and/or aluminum associated therewith, such as boron, iron, chromium, etc.

The novel method of this invention is simple and easy to carry out although the results therefrom are unexpected and dramatic. The first necessary step of the present process involves contacting a steam-deactivated catalyst composition comprising crystalline zeolite material, said zeolite material having a silicon/aluminum atomic ratio of at least about 2, with an aluminum compound, such as the halide, e.g. fluoride, chloride or bromide, at a temperature of from about 100.degree. C. to about 850.degree. C., preferably from about 100.degree. C. to about 500.degree. C. The second necessary step of the process involves contacting the aluminum compound contacted composition with an aqueous acid solution of from about 0.001M to about 10M, preferably from about 0.1M to about 2M, at a temperature of from about 20.degree. C. to about 100.degree. C.

Certain optional steps may be employed to tailor reactivation of steam-deactivated catalyst hereby. The first optional step involves hydrolyzing the product catalyst from the above first necessary step. This may be accomplished by contact of the first necessary step product with, for example, water at a temperature of from about 20.degree. C. to about 550.degree. C. When the optional hydrolyzing step temperature is below 100.degree. C. at atmospheric pressure, liquid water may be used. When the boiling point of water is exceeded, such as when the optional hydrolyzing step temperature exceeds 100.degree. C. at atmospheric pressure, the catalyst product of the first necessary step may be purged with water saturated gas, e.g. helium.

Another optional step involves calcining the product catalyst from the above first necessary step or, if hydrolysis has been conducted as a first optional step as above indicated, the product of said optional hydrolysis step. This optional calcination step may be conducted at a temperature of from about 200.degree. C. to about 600.degree. C. in an inert atmosphere of air, nitrogen, etc. at subatmospheric, atmospheric or superatmospheric pressure for from about 1 minute to about 48 hours.

A further optional step involves calcining the product catalyst from the above second necessary step at a temperature of from about 200.degree. C. to about 600.degree. C. in an inert atmosphere of air, nitrogen, etc. at subatmospheric, atmospheric or superatmospheric pressure for from about 1 minute to about 48 hours.

During the first necessary step of contacting the steam-deactivated catalyst composition with an aluminum compound, said aluminum compound may be in vapor or liquid phase at the contacting temperature of from about 100.degree. C. to about 850.degree. C. By liquid phase, it is contemplated that the aluminum compound may be a melt or in aqueous or organic solution at the contacting temperature.

The aluminum compound contacting step (first necessary) may be accomplished in the vapor phase by admixture of the aluminum compound vapor with an inert gas such as nitrogen or helium at a temperature of from about 100.degree. C. to about 850.degree. C., preferably from about 100.degree. C. to about 500.degree. C. The amount of aluminum compound vapor which is utilized is not narrowly critical but usually from about 0.2 to about 2 grams of aluminum compound are used per gram of crystalline material in the catalyst composition. The aluminum compound may be an aluminum halide such as, for example, aluminum chloride.

The second necessary step of the present method has been found to be critical in regenerating a catalyst composition comprising a crystalline zeolite material which has been deactivated by steam contact. In fact, when a steam-deactivated catalyst composition comprising a crystalline material, i.e. a high silicon crystalline zeolite, is contacted with an aluminum compound, i.e. aluminum chloride vapor, hydrolyzed and calcined under indicated conditions, no significant activity enhancement is observed. When the above steps are followed by contact with an aqueous acid solution, i.e. 1M hydrochloric acid solution at appropriate coanditions, e.g. 75.degree. C., and thereafter calcined as indicated, a dramatic increase in acid activity of the previously steam-deactivated material occurs.

Of the catalysts comprising crystalline zeolites having a silicon/aluminum atomic ratio of at least 2 which are advantageous reactivated after steam deactivation, those comprising zeolites of intermediate or large pore structure are noted. Intermediate pore structure zeolites provide a selective constrained access to and egress from the intracrystalline free space by virtue of having an effective pore size intermediate between the small pore Linde A and the large pore Linde X, i.e. the pore windows of the structure are of about a size such as would be provided by 10-membered rings of silicon atoms interconnected by oxygen atoms. It is to be understood, of course, that these rings are those formed by the regular disposition of the tetrahedra making up the anionic framework of the crystalline zeolite, the oxygen atoms themselves being bonded to the silicon (or aluminum, etc.) atoms at the centers of the tetrahedra. Intermediate pore structure zeolites freely sorb normal hexane while access in the larger molecules is constrained. It is sometimes possible to judge from a known crystal structure whether such constrained access exists. For example, if the only pore windows in a crystal are formed by 8-membered rings of silicon and aluminum atoms, then access by molecules of larger cross-section than normal hexane is excluded.

A simple determination of "Constraint Index" as herein defined may be made to determine degree of constrained access to molecules larger in cross-section than normal paraffins, and thereby whether a particular zeolite is composed of large or intermediate pores. Constraint Index may be determined by passing continuously a mixture of an equal weight of normal hexane and 3-methylpentane over a sample of zeolite at atmospheric pressure according to the following procedure. A sample of the zeolite, in the form of pellets or extrudate, is crushed to a particle size about that of coarse sand and mounted in a glass tube. Prior to testing, the zeolite is treated with a stream of air at 540.degree. C. for at least 15 minutes. The zeolite is then flushed with helium and the temperature is adjusted between 290.degree. C. and 510.degree. C. to give an overall conversion of between 10% and 60%. The mixture of hydrocarbons is passed at 1 liquid hourly space velocity (i.e. 1 volume of liquid hydrocarbon per volume of zeolite per hour) over the zeolite with a helium dilution to give a helium to (total) hydrocarbon mole ratio of 4:1. After 20 minutes on stream, a sample of the effluent is taken and analyzed, most conveniently by gas chromotography, to determine the fraction remaining unchanged for each of the two hydrocarbons.

While the above experimental procedure will enable one to achieve the desired overall conversion of 10 to 60% for most zeolite samples and represents preferred conditions, it may occasionally be necessary to use somewhat more severe conditions for samples of very low activity, such as those having an exceptionally high silicon/aluminum atomic ratio. In those instances, a temperature of up to about 540.degree. C. and a liquid hourly space velocity of less than one, such as 0.1 or less, can be employed in order to achieve a minimum total conversion of about 10%. ##EQU1##

The Constraint Index approximates the ratio of the cracking rate constants for the two hydrocarbons. Intermediate pore size zeolites include those having a Constraint Index of from about 1 to 12. Large pore size zeolites generally include those having a Constraint Index of less than about 1. Constraint Index (CI) values for some typical materials are:

Zeolite ZSM-20 is described in U.S. Pat. No. 3,972,983, the entire contents of which are incorporated herein by reference. Zeolite Beta is described in U.S. Pat. No. 3,308,069, the entire contents of which are incorporated herein by reference.

Of the catalysts comprising high silicon crystalline materials advantageously treated in accordance herwith, steam-deactivated catalysts comprising zeolites ZSM-5 and ZSM-11 are particularly noted. ZSM-5 is described in U.S. Pat. Nos. 3,702,886 and Re 29,948, the entire contents of each being hereby incorporated by reference herein. ZSM-11 is described in U.S. Pat. No. 3,709,979, the entire teaching of which is incorporated herein by reference. Other catalysts comprising high silicon crystalline materials advantageously treated in accordance herewith include steam-deactivated catalysts comprising ZSM-5/ZSM-11 intermediate (U.S. Pat. No. 4,229,424, the entire contents of which are incorporated herein by reference), ZSM-12 (U.S. Pat. No. 3,832,449, the entire contents of which are incorporated herein by reference), ZSM-23 (U.S. Pat. No. 4,076,842, the entire contents of which are incorporated herein by reference), ZSM-35 (U.S. Pat. No. 4,016,245, the entire contents of which are incorporated herein by reference), and ZSM-38 (U.S. Pat. No. 4,046,859, the entire contents of which are incorporated herein by reference). Another such high silicon crystalline material is ZSM-48, described in U.S. Pat. No. 4,375,573, the entire contents of which are incorporated herein by reference. Catalysts comprising crystalline materials having varying amounts of structural aluminum as well as metals such as, for example, boron, chromium, iron, etc. are reactivated after steam deactivation by the present process regardless of what other materials or metals are present in the crystal structure.

The catalyst comprising zeolite which has been steam-deactivated may be composed of the crystalline zeolite alone or said zeolite and a matrix comprising another material normally resistant to the temperature and other conditions employed in a chemical conversion process. Such matrix material is useful as a binder and imparts greater resistance to the catalyst for the severe temperature, pressure and reactant feed stream velocity conditions encountered in many processes, such as, for example, cracking.

Useful matrix materials include both synthetic and naturally occurring substances, as well as inorganic materials such as clay, silica and/or metal oxides such as alumina. The latter may be either naturally occurring or in the form of gelatinous precipitates or gels including mixtures of silica and metal oxides. Naturally occurring clays which can be composited with the zeolite include those of the montmorillonite and kaolin families, which families include the sub-bentonites and the kaolins commonly known as Dixie, McNamee, Georgia and Florida clays or others in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite or anauxite. Such clays can be used in the raw state as originally mined or initially subjected to calcination, acid treatment or chemical modification.

In addition to the foregoing materials, the zeolites employed herein may be composited with a porous matrix material, such as silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, and silica-titania, as well as ternary compositions, such as silica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesia and silica-magnesia-zirconia. The matrix may be in the form of a cogel. The relative proportions of zeolite component and inorganic matrix, on an anhydrous basis, may vary widely with the zeolite content ranging from about 1 to about 99 percent by weight and more usually in the range of from about 5 to about 80 percent by weight of the dry composite.

The catalyst compositions reactivated by the process of the present invention are useful for a variety of organic, e.g. hydrocarbon, compound conversion processes. Such conversion processes include, as non-limiting examples, cracking hydrocarbons with reaction conditions including a temperature of from about 300.degree. C. to about 700.degree. C., a pressure of from about 0.1 atmosphere (bar) to about 30 atmospheres and a weight hourly space velocity of from about 0.1 to about 20; dehydrogenating hydrocarbon compounds with reaction conditions including a temperature of from about 300.degree. C. to about 700.degree. C., a pressure of from about 0.1 atmosphere to about 10 atmospheres and a weight hourly space velocity of from about 0.1 to about 20; converting paraffins to aromatics with reaction conditions including a temperature of from about 100.degree. C. to about 700.degree. C., a pressure of from about 0.1 atmosphere to about 60 atmospheres, a weight hourly space velocity of from about 0.5 to about 400 and a hydrogen/hydrocarbon mole ratio of from about 0 to about 20; converting olefins to aromatics, e.g. benzene, toluene and xylenes, with reaction conditions including a temperature of from about 100.degree. C. to about 700.degree. C., a pressure of from about 0.1 atmosphere to about 60 atmospheres, a weight hourly space velocity of from about 0.5 to about 400 and a hydrogen/hydrocarbon mole ratio of from about 0 to about 20; converting alcohols, e.g. methanol, or ethers, e.g. dimethylether, or mixtures thereof to hydrocarbons including aromatics with reaction conditions including a temperature of from about 275.degree. C. to about 600.degree. C., a pressure of from about 0.5 atmosphere to about 50 atmospheres and a liquid hourly space velocity of from about 0.5 to about 100; isomerizing xylene feedstock components with reaction conditions including a temperature of from about 230.degree. C. to about 510.degree. C., a pressure of from about 3 atmospheres to about 35 atmospheres, a weight hourly space velocity of from about 0.1 to about 200 and a hydrogen/hydrocarbon mole ratio of from about 0 to about 100; disproportionating toluene with reaction conditions including a temperature of from about 200.degree. C. to about 760.degree. C., a pressure of from about atmospheric to about 60 atmospheres and a weight hourly space velocity of from about 0.08 to about 20; alkylating aromatic hydrocarbons, e.g. benzene and alkylbenzenes, in the presence of an alkylating agent, e.g. olefins, formaldehyde, alkyl halides and alcohols, with reaction conditions including a temperature of from about 340.degree. C. to about 500.degree. C., a pressure of from about atmospheric to about 200 atmospheres, a weight hourly space velocity of from about 2 to about 2000 and an aromatic hydrocarbon/alkylating agent mole ratio of from about 1/1 to about 20/1; and transalkylating aromatic hydrocarbons in the presence of polyalkylaromatic hydrocarbons with reaction conditions including a temperature of from about 340.degree. C. to about 500.degree. C., a pressure of from about atmospheric to about 200 atmospheres, a weight hourly space velocity of from about 10 to about 1000 and an aromatic hydrocarbon/polyalkylaromatic hydrocarbon mole ratio of from about 1/1 to about 16/1.

In order to more fully illustrate the nature of the invention and the manner of practicing same, the following examples are presented. In the examples, whenver Alpha Value is examined, it is noted that the Alpha Value is an approximate indication of the catalytic cracking activity of the catalyst compared to a standard catalyst and it gives the relative rate constant (rate of normal hexane conversion per volume of catalyst per unit time). It is based on the activity of the highly active silica-alumina cracking catalyst taken as an Alpha of 1 (Rate Constant =0.016 sec.sup.-1). In the case of zeolite HZSM-5, only 174 ppm of terahedrally coordinated Al.sub.2 O.sub.3 are required to provide an Alpha Value of 1. The Alpha Test is described in U.S. Pat. No. 3,354,078 and in The Journal of Catalysis, Vol. IV, pp. 522-529 (August 1965), each incorporated herein by reference as to that description.

A high silicon crystalline material, i.e. zeolite ZSM-5 having a silicon/aluminum atomic ratio of about 42, was ammonium exchanged by refluxing the calcined crystalline material in 1M NH.sub.4 Cl. The ammonium-exchanged ZSM-5 was then calcined for 60 minutes at 540.degree. C. to provide an acid form zeolite ZSM-5, i.e. HZSM-5. The Alpha Value of this HZSM-5 was measured to be 190.

A first quantity of the high silicon crystalline zeolite product of Example 1 was contacted with 100% steam at 538.degree. C. for 22 hours in order to damage, or deactivate, the zeolite. Examination of the Alpha Value of the steamed zeolite established severe deactivation. The Alpha Value was reduced from the pre-steamed 190 value to only 16.

One-half of the steam-deactivated zeolite of Example 2 was placed in a reactor vessel and contacted with 1M HCl solution for 3 hours at 75.degree. C. The contacted zeolite was washed free of excess hydrochloric acid solution and tested for Alpha Value. It proved to have an Alpha Value of only 15. There was no acid activation of the steam-deactivated high silicon crystalline zeolite by the hydrochloric acid solution contacting.

The zeolite product of Example 3 was contacted with aluminum chloride vapor at 250.degree. C. for 3 hours, and then heated to 500.degree. C. for 1 hour. The aluminum chloride vapor contacted material was then contacted with water at 20.degree. C. for 17 hours. The water contacted material was then calcined at 538.degree. C. in air for 10 hours and again tested for acid activity. Its Alpha Value was only 15. There was no acid activation of the steam-deactivated high silica crystalline zeolite by the steps of hydrochloric acid solution contacting, followed by aluminum chloride vapor contacting, followed by hydrolysis and then calcination.

The product zeolite of Example 4 was then contacted with 1M HCl solution for 3 hours at 75.degree. C. and calcined at 538.degree. C. in air for 10 hours. The Alpha Value of the zeolite was again tested. It was 41, a dramatic increase not expected due to the results of Examples 3 and 4.

In order to obtain evidence establishing reactivation steps necessary for the present method, the second half of the steam-deactivated zeolite of Example 2 was placed in a reactor vessel and contacted with aluminum chloride vapor at 250.degree. C. for 2 hours, and then heated to 500.degree. C. for 1 hour. The aluminum chloride vapor contacted material was contacted with water at 20.degree. C. for 17 hours and then calcined at 538.degree. C. in air for 10 hours. The calcined material was then contacted with 1M HCl solution for 3 hours at 75.degree. C. and again calcined at 538.degree. C. in air for 10 hours. The Alpha Value of the product zeolite was measured to be 57. This was a 256 percent increase in activity.

For further evidence of reactivation method step sequence and effect, the following experiments were conducted.

A second quantity of the high silicon crystalline zeolite product of Example 1 was contacted with 100% steam at 500.degree. C. for 22 hours in order to damage, or deactivate, the zeolite. The Alpha Value of the product zeolite was 29, establishing severe deactivation.

One-half of the steam-deactivated zeolite product of Example 7 was placed in a reactor vessel and contacted with 1M HCl solution for 3 hours at 75.degree. C. The hydrochloric acid solution contacted zeolite was calcined at 538.degree. C. for 10 hours and then tested in the Alpha Test. Its Alpha Value was only 30.

The second half of the steam-deactivated zeolite product of Example 7 was placed in a reactor vessel and treated by the sequential steps of (1) contacting said deactivated zeolite with aluminum chloride vapor at 300.degree. C. for 2 hours, and then heated to 500.degree. C. for 1 hour, (2) contacting the step (1) product with water at 20.degree. C. for 17 hours, (3) calcining the step (2) product at 538.degree. C. in air for 10 hours, (4) contacting the step (3) product with 1M HCl solution for 3 hours at 75.degree. C., and (5) calcining the step (4) product in air for 10 hours at 538.degree. C. The Alpha Value of the final product zeolite was measured to be 123. This was a 324 percent increase in activity.

A high silicon crystalline material, i.e. zeolite ZSM-5 having a silicon/aluminum atomic ratio of about 35, was ammonium exchanged as in Example 1, combined with 35 wt. % alumina matrix and extruded into extrudate particles (65 wt. % ZSM-5, 35 wt. % alumina). The extrudate product was calcined for 60 minutes in air at 538.degree. C. to provide HZSM-5 extrude established to have an Alpha Value of about 200.

The extrudate of Example 10 was contacted with 1 atmosphere steam at 600.degree. C. for 2 hours. The Alpha Value of this steam damaged, or deactivated, zeolite extrudate was established to be only 14.

The steam deactivated extrudate of Example 11 was washed with 0.1M sodium hydroxide solution to convert same to sodium form, then contacted with aluminum chloride vapor at 150.degree. C. to 500.degree. C. while hating at 2.degree. C./minute, then contacted with water at 20.degree. C. for 2 hours and then calcined at 538.degree. C. in air for 10 hours. The extrudate treated in this manner was then tested for Alpha activity. Its Alpha Value was only 13.

The product extrudate of Example 12 was contacted with 1M hydrochloric acid solution at 75.degree. C. for 3 hours and then calcined in air at 538.degree. C. for 10 hours. The Alpha Value of the product of this example was established to be 78, a 457 percent increase from the value of 14 obtained for the steam-deactivated extrudate material of Example 11.

The following experiments were conducted to further establish effect of the present method upon steam-deactivated catalyst comprising a zeolite and a matrix.

A high silicon crystalline material, i.e. zeolite ZSM-5 having a silicon/aluminum atomic ratio of about 35, was ammonium exchanged as in Example 10 and then extruded with alumina binder to yield extrudate particles composed of 65 weight percent zeolite and 35 weight percent alumina.

The extrudate catalyst of Example 14 was steamed (100% steam) for 16 hours at 454.degree. C. Its Alpha Value was measured to be about 70. It was further steamed (100% steam) at 538.degree. C. for 22 hours. Its Alpha Value was then measured to be only 14.

The steam-deactivated catalyst extrudate of Example 15 (Alpha Value of 14) was placed in a reactor vessel and treated by the sequential steps of (1) contacting said deactivated extrudate catalyst with aluminum chloride vapor at 300.degree. C. for 2 hours and then at 500.degree. C. for 1 hour, (2) contacting the step (1) product with water at 20.degree. C. for 17 hours, (3) calcining the step (2) product at 538.degree. C. in air for 10 hours, (4) contacting the step (3) product with 1M HCl solution for 3 hours at 75.degree. C., and (5) calcining the step (4) product in air for 10 hours at 538.degree. C. The Alpha Value of the final product catalyst extrudate was measured to be 78. This was a 457 percent increase in activity.