Process for Preparing Zeolite Y With Increased Mesopore Volume

This invention relates to zeolites that are useful as catalyst supports. In particular, it involves a zeolite Y product with an increased mesopore volume and the process for preparing such zeolite.

Many conversion processes in the petroleum industry are carried out using catalysts having zeolites with the structure of zeolite Y as a major component. In many cases the zeolite Y has been subjected to certain stabilizing and/or dealumination process steps during its preparation that result in the zeolite having a reduced unit cell constant (a.sub.o) and an increased silica to alumina ratio. In general, there are found three classes of these stabilized zeolites Y; the ultrastable zeolites Y ("USY"), the very ultrastable zeolites Y ("USY"), and the superdealuminated ultrastable zeolites Y ("SDUSY"). These stabilized zeolites, as well as the as-synthesized zeolite Y, do not have many pores that are larger than about 2 nanometers (nm) in diameter, such "mesopores" typically having diameters of 2 to 60 nm. Limited mesopore volume within the 2 to 60 nm pore diameter range can be a decided disadvantage when such catalysts are used for processes that tend to coke the catalysts. Examples of such processes are cracking or hydrocracking of heavy crude oils.

The as-synthesized zeolite Y (referred to herein simply as "Y") has a unit cell constant greater than 24.6 up to 24.85 angstroms (.ANG.). These as-synthesized materials have a mesopore volume of less than about 0.05 cc/g. The ultrastable Y zeolite (USY) has a reduced unit cell constant of 24.5 to 24.6.ANG.. These USY type materials have a mesopore volume of less than about 0.17 cc/g. The very ultrastable zeolite Y (VUSY) has a reduced unit cell constant of greater than about 24.27 (approximately 24.3) to less than 24.5.ANG.. The VUSY type materials have a mesopore volume of less than about 0.22 cc/g. The superdealuminated ultrastable zeolite Y (SDUSY) has a reduced unit cell constant of about 24.27.ANG. or less. These SDUSY type materials have a mesopore volume of less than about 0.25 cc/g.

U.S. Pat. Nos. 5,069,890 and 5,087,348 teach a method of preparing a zeolite with the Y structure with a secondary pore volume as high as 0.20 cc/g. These patents teach that secondary pores are 10 to 60 nm in diameter. The method consists of steam calcining previously dealuminated zeolite Y at high temperatures for long periods of time, typically 16 to 24 hours. Since the dealuminated zeolite Y starting material would have been prepared with one or more steam calcinations, at least two steam calcinations are necessary to provide the product with the slight secondary pore volume increase. In the preparation of these products described in the patent examples, the SiO.sub.2 /Al.sub.2 O.sub.3 ratio of the zeolite is increased as a result of the process.

U.S. Pat. No. 5,112,473 teaches a similar small increase in the so-called secondary pore volume by a method involving the acid treatment of dealuminated zeolite Y having a.sub.o measurements of 24.3 to 24.5.ANG..

It is an object of this invention to prepare zeolites with a structure of zeolite Y having increased mesopore volume in pores having diameters of 2 to 60 nm when compared to similar zeolites prepared using conventional processes. It is also an object of this invention to provide such increased mesopore volume by a process not involving calcining with steam.

We have found that hydrothermal aqueous solution treatment of zeolites with the structure of zeolite Y can increase the number of pores larger than 2 nm so that the mesopore volume is drastically increased. Essentially the zeolite is contacted with an aqueous solution of dissolved solutes at high temperature, above the atmospheric boiling point of the solution, and under sufficient pressure to maintain the solution at least partially in the liquid state for a period of time necessary to provide the desired modification.

Our product differs from the prior art in that the mesopore volumes achieved are greater than zero, say about 0.05 cc/g or greater, for the as-synthesized and unstabilized and/or non-dealuminated zeolite Y; greater than about 0.17 cc/g for the ultrastable zeolites Y (USY); greater than about 0.22 cc/g for the very ultrastable zeolites Y (VUSY); and greater than about 0.25 cc/g for the super-dealuminated ultrastable zeolites Y (SDUSY).

Our process differs from the prior art in that the mesopore volumes are achieved by a process other than steam. Our process allows the SiO.sub.1 /Al.sub.2 O.sub.3 ratio to be maintained or controlled. The most important variables to provide increased mesopore volume appear to be the time/temperature and pH.

The term "hydrothermal treatment or process" as used herein refers to a treatment or process involving contact with an aqueous solution wherein at least part of the solution is maintained in the liquid state. "Liquid hydrothermal" is used synonymously with "hydrothermal" herein.

The term "mesopore volume" as used herein refers to the pore volume found with pores having pore diameters ranging from 2 to 60 nm.

The high mesopore volume products of our invention are prepared from zeolites having the structure of zeolite Y which are synthetic faujasite materials. For the purpose of describing our invention, the zeolites having the structure of Y are divided into four broad classes: (a) the as-synthesized zeolite Y prior to stabilization and/or dealumination (referred to herein as "Y"); (b) ultrastable zeolites Y (referred to herein as "USY"); (c) very ultrastable zeolites Y (referred to herein as "VUSY"); and (d) superdealuminated ultrastable zeolites Y (referred to herein as "SDUSY").

In the application of our process a zeolite from one of the four classes of zeolites having the structure of zeolite Y is contacted hydrothermally with an aqueous solution having dissolved therein one or more salts, acids, bases and/or water soluble organic compounds at a temperature above the boiling point of the solution at atmospheric pressure (referred to herein as "atmospheric boiling point") for a period sufficient to provide said zeolite with an increased mesopore volume in mesopores having diameters of about 2 nm to about 60 nm then separating, washing and recovering the product. The product will generally have unit cell sizes and SiO.sub.2 /Al.sub.2 O.sub.3 ratios in the same general range as the starting materials, although there may be small differences. For example, hydrothermal treatments at low pH may increase the SiO.sub.2 /Al.sub.2 O.sub.3 ratio and can cause a small decrease in unit cell size. The product of our process may be further subjected to stabilization, dealumination and/or other steps which may change the unit cell size and the SiO.sub.2 /Al.sub.2 O.sub.3 ratio.

The temperature of the hydrothermal treatment will be above the atmospheric boiling point of the hydrothermal treating solution. Typically, this will be about 110.degree. C. or more, preferably about 115.degree. C. or more. More elevated temperatures such as about 125.degree. C. and above and about 135.degree. C. and above, such as from about 135.degree. C. to about 250.degree. C., are also suitable. The upper temperature is limited by the equipment used, but temperatures in excess of 250.degree. C. appear to be useful. Since these hydrothermal contacts are carried out above boiling, pressure equipment is required. Ultrahigh pressure condition treatments could provide suitable results at temperatures greater than 200.degree. C. up to 400.degree. C. Accordingly, temperature treatments ranging from 110 to 400.degree. C. could provide suitable materials. While optimum treatment temperature will depend upon the particular class of zeolite Y being processed, the treatment or contact treatment will in general range from above atmospheric boiling point of the hydrothermal treating solution to about 250.degree. C., preferably from about 115.degree. C. to about 250.degree. C. Good results are obtained at a temperature ranging from about 140.degree. C. to about 200.degree. C.

The time of treatment has an inverse relationship to the temperature of treatment, higher temperatures needing shorter time to effect the same degree of mesopore volume increase. At low temperatures, such as 110.degree. C., treatment times as long as 72 hours are required to provide slightly increased mesopore volume compared to those of the prior art processes. At the most elevated temperatures, treatment times as short as 5 minutes can be used. In general, treatment times of about 5 minutes to about 24 hours, more preferably from about 2 hours or more, preferably from about 2 hours to about 10 to 20 hours are used.

The time-temperature applied during the treatment is generally such as to provide a mesopore volume in the final product at least five percent (5%) and preferably at least ten percent (10%) greater than the mesopore volume of the starting zeolite.

The hydrothermal contacting solution in general comprises an aqueous solution having dissolved therein one or more salts, acids, bases and/or water soluble organic compounds. The salts comprise, inter alia, water soluble salts such as ammonium, including quaternary ammonium, alkali and alkaline earth salts of strong and weak acids, both organic and inorganic acids. Non-limiting examples of desirable salts include the nitrate, chloride and sulfate salts of ammonia, and alkali metal, such as sodium and potassium. Non-limiting examples of acids include the inorganic acids such as the strong acids nitric, sulfuric and hydrochloric acid, as well as organic acids such as acetic and formic acids. Non-limiting examples of bases include inorganic bases such as ammonium, alkali and alkaline earth metal hydroxides as well as organic bases such as quaternary ammonium hydroxides, amine complexes, pyridinium salts and the like. Non-limiting examples of water soluble organic compounds include the lower alcohols, ethers and the like. Preferred salts are the ammonium and alkali metal salts, particularly the salts of strong inorganic acids, such as the preferred nitric acid. Preferred acids are the inorganic acids such as nitric, sulfuric and hydrochloric acids, preferably nitric acid. The concentration and amount of the solution contacted with the stabilized zeolite Y is adjusted to provide at least 0.1 part by weight ("pbw") of the dissolved solute for each pbw of zeolite on an anhydrous basis.

The concentration of the solution can be up to about 10 normal.

The process of the invention produces zeolite products having enhanced mesopore volumes and unique pore distribution within the range of mesopores having diameters ranging from about 2 to about 60 nm. In a preferred case the zeolite Y products have mesopore volume contained in mesopores of about 2 nm to about 60 nm in diameter wherein the relationship between the unit cell constant a.sub.o and mesopore volume is defined by the following table:

The different types of zeolite Y will have differing optimum treatment conditions. Some of these treatments that are preferred are discussed below, although it is understood that preferred treatments for one class of zeolite will have application to the other classes.

The as-synthesized zeolite Y typically has a unit cell ranging from above 24.6.ANG. to the theoretical 24.85.ANG. and a SiO.sub.2 /Al.sub.2 O.sub.3 ratio ranging from 3 to about 6, and product materials will have similar parameters. These materials, as synthesized (without additional processing), are highly crystalline with substantially no mesopore volume, say, less than about 0.05 cc/g. The instant process will treat these materials to provide product having mesopore volumes of 0.05 cc/g or greater. Typical mesopore volumes will range from about 0.05 to about 0.5 or 0.6 cc/g, preferably from about 0.1 to about 0.5 or 0.6 cc/g, and more preferably from about 0.2 or 0.3 to about 0.5 or 0.6 cc/g. The zeolite products prepared by the process of our invention from Y have the structure of zeolite Y and a unit cell constant (a.sub.o) of greater than 24.6 to 24.85.ANG., similar to the a.sub.o of the starting Y. These zeolites have SiO.sub.2 /Al.sub.2 O.sub.3 mole ratios of 3 to about 6 and Na.sub.2 O contents ranging from about 12% to about 18% by weight.

The conditions for increasing the mesopore volume appear to be milder for the as-synthesized zeolite Y than for the other types of zeolites, and the techniques for the other types of zeolites below are also usefully applied to Y. Preferred temperatures range from about 115.degree. C. to about 250.degree. C. with times ranging from about 5 minutes to about 24 hours. The product material may be used in catalytic reactions where the enhanced stability of the other zeolite types is not required. Alternatively, the product material may be used as the starting material to which additional stabilizing and/or dealumination steps are applied. The synthesis of zeolite Y is described, for example, in Zeolite Molecular Sieves-Structure, Chemistry and Use, by Donald W. Breck (John Wiley & Sons Inc., 1974), and in U.S. Pat. Nos. 3,671,191; 3,808,326 and 3,957,689. Equivalent zeolites synthesized by other methods can also be used.

The USY material typically has a unit cell ranging from about 24.5.ANG. to about 24.6.ANG. and a SiO.sub.2 /Al.sub.2 O.sub.3 ratio ranging from about 5 to about 12 and product materials will have similar parameters. Mesopore volumes of starting zeolites (prior art materials) are typically less than about 0.17 cc/g. The instant process will increase the mesopore volume of these starting materials by at least about five percent (5%). Thus, treatment of a starting zeolite with mesopore volume of about 0.17 cc/g will provide a product with a mesopore of about 0.18 or greater. Typical mesopore volumes will range from about 0.2 to about 0.6 cc/g.

The as-synthesized zeolites Y are dealuminated and stabilized to produce USY. Such stabilized zeolites have been ammonium exchanged and calcined in the presence of steam. An optional step is to ammonium exchange the steamed zeolite. Such zeolites are known as hydrogen zeolite Y (HY) or ultrastable zeolite Y (USY), respectively. These materials have SiO.sub.2 /Al.sub.2 O.sub.3 ratios of about 5 to about 12, although ratios of about 5 to 10, 5 to 6.5 and 6 to 10 may be present depending on the preparation techniques used. These materials also have Na.sub.2 O contents of less than about 3.5%, unit cell constants (a.sub.o) of about 24.5 to 24.6.ANG., and mesopore volumes of considerably less than about 0.17, usually about 0.1 cc/g in pores of 2 to 60 nm in diameter. The preparation and properties of such ultrastable zeolites are described in numerous patents including Eberly, U.S. Pat. No. 3,506,400 and Ward, U.S. Pat. No. 3,929,672. Equivalent zeolites dealuminated by other methods can also be used.

The starting zeolite is contacted with the hydrothermal solution generally described above, preferably a solution of one or more salts and possibly a pH-altering compound. The mixture is then heated for a time and temperature combination sufficient to provide the increased mesoporosity desired. The temperature is preferably at least about 115.degree. C. We have found here that two or more hours is useful for the time of treatment, and sometimes 10 to 24 hours is used. The pH of the slurry must be about 10 or less. Higher pH values do not provide the desired properties.

One or more of a number of inorganic salts are preferably used in the treating solutions. Alkali metal nitrates or ammonium nitrates are particularly preferred. The concentration and amount of the solution contacted with the stabilized zeolite Y is adjusted to provide at least 0.1 pbw of the dissolved solute for each pbw of zeolite on an anhydrous basis. The concentration of the solution can be up to about 10 normal.

The pH of the slurry of zeolite and solution is very important to the mesopore volume achieved and to control of the extra framework alumina retained in the zeolite, which affects the SiO.sub.2 /Al.sub.2 O.sub.3 ratio. If the pH of the solution is maintained or adjusted to a value between 4.5 and 8 prior to contact with the zeolite, the mesopore volume can be about 0.12 to 0.45 cc/g or more, depending on the temperature. At pH values of about 8 to about 10 the mesopore volume is between about 0.13 and about 0.22 cc/g. The SiO.sub.2 /Al.sub.2 O.sub.3 ratio is not increased substantially at these pH values of 4.5 to 10. If the pH is less than 4.5, the mesopore volume is again between 0.13 and 0.25 cc/g or more, depending on the temperature and time of the hydrothermal treatment. These low pH values are achieved by using any acid, nitric acid being preferred, and the SiO.sub.2 /Al.sub.2 O.sub.3 ratio is increased as the extra framework alumina is eliminated.

The control of time and temperature is extremely important in providing a controlled and significant increase in the mesopore volume of the instant product. At low temperatures such as 110.degree. C., treatment times as long as 72 hours are required to provide mesopore volume of about 0.12 cc/g, similar to or somewhat higher than those of the prior art processes. When the hydrothermal treatments are carried out at 125.degree. C. or more, much shorter times are needed to provide mesopore volumes in excess of 0.12 cc/g. We prefer temperatures of 135.degree. to 250.degree. C. and treatment times of 1 to 5 minutes to 24 hours. We most prefer temperatures of 140.degree. to 200.degree. C. and treatment times of about 1 to 16 hours.

The zeolite products prepared by the process of our invention from USY (and HY) have the structure of zeolite Y but with a contracted cell constant (a.sub.o) of 24.5 to 24.6.ANG., similar to the a.sub.o of the starting HY or USY. These zeolites have SiO.sub.2 /Al.sub.2 O.sub.3 mole ratios of 5 to 10 or even 12 or more and Na.sub.2 O content of less than about 0.25%. The mesopore volumes of these products are in excess of 0.12 cc/g and usually considerably more than 0.15 cc/g.

As the mesopore volume is increased, the surface area of the zeolite degrades, and in some cases the crystal structure of the zeolite decreases as well. The crystallinity can be reduced to about 50% for the products with mesopore volumes approaching 0.4 cc/g.

The USY zeolite products formed from HY and USY are useful as catalyst supports for various hydrocarbon conversions. They are especially useful for such processes when heavy crude oils are involved, since the large hydrocarbon molecules can diffuse to the active catalyst sites more easily through the large mesopores.

The VUSY material typically has a unit cell ranging from greater than about 24.27.ANG. (approximately 24.3.ANG.) to less than about 24.5.ANG. and a SiO.sub.2 /Al.sub.2 O.sub.3 ratio ranging from about 5 to about 25 or 30 or more, and product materials will have similar parameters. Mesopore volumes of starting zeolites (prior art materials) are typically less than about 0.22 cc/g. The instant process will increase the mesopore volume of these starting materials by at least about five percent (5%). Thus, treatment of a starting zeolite with mesopore volume of about 0.22 cc/g will provide a product with a mesopore of about 0.23 or greater. Typical mesopore volumes will range from about 0.3 to about 0.6 cc/g.

The high mesopore volume VUSY products are prepared from previously dealuminated and stabilized zeolite Y. Such starting zeolites are faujasite materials of SiO.sub.2 /Al.sub.2 O.sub.3 mole ratios of 3 to 6 (usually 5 or more) that have been ammonium exchanged and calcined at least twice in the presence of steam. The steam calcination steps are usually two hours or less. These materials are very or super ultrastable zeolites Y having SiO.sub.2 /Al.sub.2 O.sub.3 ratios of 5 to 25 or 30 or more, although ratios of about 5 to 15, 5 to 10, 5 to 9 and 7.5 to 14 may be present depending on the preparation techniques used. These materials also have Na.sub.2 O contents of less than about 0.4%, unit cell constants (a.sub.o) of greater than about 24.3 (24.27) to less than about 24.5.ANG., and mesopore volumes of considerably less than about 0.22 cc/g in pores of 2 to 60 mn in diameter. The preparation and properties of such very ultrastable zeolites Y are described in Eberly, U.S. Pat. No. 3,506,400 among other numerous patents. Equivalent zeolites dealuminated by other methods can also be used.

The starting zeolite is contacted with the hydrothermal solution generally described above, preferably a solution of one or more salts and possibly a pH altering compound. The mixture is then heated for a time and temperature combination sufficient to provide the increased mesoporosity desired. The temperature is preferably at least about 115.degree. C. We have found here that two or more hours is useful for the time for treatment, and sometimes 1 to 5 minutes to 24 hours is used. The pH of the slurry must be about 8 or less. Higher pH values do not provide the desired properties.

One or more of a number of inorganic salts are preferably used in the treating solutions. Alkali metal nitrates or ammonium nitrates are preferred, with the latter being particularly preferred. The concentration and amount of the solution contacted with the very ultrastabilized zeolite Y is adjusted to provide at least 0.1 pbw of the salt for each pbw of zeolite on an anhydrous basis. The concentration of the solution can be up to about 10 normal.

The pH of the slurry of zeolite and solution is very important to the mesopore volume achieved and to control of the extra framework alumina retained in the zeolite, which affects the SiO.sub.2 /Al.sub.2 O.sub.3 ratio. If the pH of the solution is maintained or adjusted to a value between 3 and 8 prior to contact with the zeolite, the mesopore volume can be about 0.23 to 0.45 cc/g or more, depending on the temperature. The SiO.sub.2 /Al.sub.2 O.sub.3 ratio is not increased at these pH values. If the pH is less than about 3, the mesopore volume is between 0.23 and 0.3 cc/g or more, depending on the temperature and time of the hydrothermal treatment. These pH values are achieved by using acid, nitric acid being preferred, and the SiO.sub.2 /Al.sub.2 O.sub.3 ratio is increased as some of the extra framework alumina is removed.

The control of time and temperature is extremely important in providing a controlled and significant increase in the mesopore volume of the instant product. At low temperatures such as 110.degree. C., treatment times as long as 72 hours are required to provide slightly increased mesopore volume compared to those of the prior art processes. When the hydrothermal treatments are carried out at 125.degree. C. or more, much shorter times are needed to provide mesopore volumes in excess of 0.22 cc/g. We prefer temperatures of 135.degree. to 250.degree. C. and treatment times of 1 to 5 minutes to 24 hours.

The zeolite products prepared by the process of our invention from VUSY have the structure of zeolite Y but with a contracted cell constant (a.sub.o) of less than 24.5 to greater than 24.27.ANG., similar to the a.sub.o of the starting VUSY. These zeolites have SiO.sub.1 /Al.sub.2 O.sub.3 mole ratios of 5 to 15 or 25 to 30 or more and Na.sub.2 O content of less than 0.08%. The mesopore volumes of our products are in excess of 0.22 cc/g and usually considerably more than 0.25 cc/g. Zeolites that have been hydrothermally treated with a salt solution but with no acid present tend to have mesopore volumes of about 0.23 to about 0.55 cc/g and SiO.sub.2 /Al.sub.2 O.sub.3 ratios of about 5 to about 9. If the pH of the zeolite/salt solution slurry prior to heating is adjusted to between about 6.5 and 7.5, the mesopore volume is about 0.35 to about 0.55 g/cc. If acid is added to the solution/slurry to lower the pH, our product has a mesopore volume of about 0.23 to about 0.32 cc/g and a SiO.sub.2 /Al.sub.2 O.sub.3 ratio of about 7.5 to about 15 or even up to 25, possibly up to 30 or more.

As the mesopore volume is increased, the surface area of the zeolite decreases, and in some cases the crystal structure of the zeolite degrades as well. The crystallinity can be reduced to about 50% for products with mesopore volumes approaching 0.5 cc/g.

The zeolite products formed from VUSY are useful as catalyst supports for various hydrocarbon conversions. They are especially useful for such processes when heavy crude oils are involved, since the large hydrocarbon molecules can diffuse to the active catalyst sites more easily through the large mesopores.

The SDUSY material defines the material having the smallest unit cell size of all the classes of zeolites Y, and typically has a unit cell size of about 24.27.ANG. or less, more typically from 24.27.ANG. down to the lower limit attainable with zeolites Y, typically about 24.09.ANG., and a SiO.sub.2 /Al.sub.2 O.sub.3 ratio of 20 or greater, more typically ranging from about 20 to about 100 or even 300 or higher. Mesopore volumes of starting zeolites (prior art materials) are typically less than about 0.25 cc/g. The instant process will increase the mesopore volume of these starting materials by at least about five percent (5%). Thus, treatment of a starting zeolite with mesopore volume of about 0.25 cc/g will provide a product with a mesopore volume of about 0.26 or greater. Typical mesopore volumes will range from about 0.3 to about 0.6 cc/g.

The high mesopore volume SDUSY materials are prepared from previously highly dealuminated and stabilized zeolite Y. Such starting zeolites are faujasite materials that have been ammonium exchanged and calcined at least in the presence of steam multiple times as well as subjected to acid treatment to enhance dealumination. These materials are super dealuminated ultrastable zeolites Y having SiO.sub.2 /Al.sub.2 O.sub.3 ratios of 20 or more, and will range up to 200 or even 300 or more and preferably up to 80 or more. These materials also have Na.sub.2 O contents of less than about 0.1%, unit cell constants (a.sub.o) of less than about 24.27 down to the lower limit of SDUSY materials, say, to about 24.09.ANG., and mesopore volumes of considerably less than about 0.25 cc/g in pores of 2 to 60 nm in diameter. The preparation and properties of such very ultrastable zeolites Y are described in Journal of Catalysis, 54, 285 (1978), and U.S. Pat. Nos. 4,477,366 and 5,242,677. Equivalent zeolites dealuminated by other methods can also be used.

The starting zeolite is contacted with the hydrothermal solution generally described above, preferably a solution of one or more salts and possible a pH altering compound. The mixture is then heated for a time and temperature combination sufficient to provide the increased mesoporosity desired. The temperature is preferably at least about 115.degree. C. We have found here that two or more hours is useful for the time of treatment, and sometimes 1 to 5 minutes to 24 hours is used. The pH of the slurry must be about 7 or less. Higher pH values do not provide the desired properties.

One or more of a number of inorganic salts are preferably used in the treating solutions. Alkali metal nitrates or ammonium nitrates are preferred, with the latter being particularly preferred. The concentration and amount of the solution contacted with the very ultrastabilized zeolite Y is adjusted to provide at least 0.1 pbw of salt for each pbw of zeolite on an anhydrous basis. The concentration of the solution can be up to about 10 normal.

The pH of the slurry of zeolite and solution is very important to the mesopore volume achieved and to control of the extra framework alumina retained in the zeolite, which affects the SiO.sub.2 /Al.sub.2 O.sub.3 ratio. If the pH of the solution is maintained or adjusted to a value between 3 and 7 prior to contact with the zeolite, the mesopore volume can be greater than about 0.25 to 0.6 cc/g or more, depending on the temperature. These pH values are achieved by using an acid, nitric acid being preferred, and the SiO.sub.2 /Al.sub.2 O.sub.3 ratio may be increased as some of the external framework alumina is removed.

The control of time and temperature is extremely important in providing a controlled and significant increase in the mesopore volume and the instant product. At low temperatures such as 110.degree. C., treatment times as long as 72 hours are required to provide slightly increased mesopore volume compared to those of the prior art processes. When the hydrothermal treatments are carried out at 125.degree. C. or more, much shorter times are needed to provide mesopore volumes in excess of 0.25 cc/g. We prefer temperatures of 135.degree. to 250.degree. C. and treatment times of 1 to 5 minutes to 24 hours. The SDUSY materials require more stringent conditions, higher temperatures and/or longer times than do the other classes of zeolites to obtain equivalent increased mesoporosity.

The zeolite products prepared by the process of our invention from SDUSY have the structure of zeolite Y but with a contracted cell constant (a.sub.o) of less than about 24.27 down to the lower limit of the SDUSY materials, say about 24.09.ANG., similar to the a.sub.o of the starting SDUSY. These zeolites have SiO.sub.2 /Al.sub.2 O.sub.3 mole ratios of 20 to 100 or more, say 300 or more, and Na.sub.2 O content of less than about 0.05% and mesoporosities usually more than 0.25 cc/g.

The zeolite products formed from SDUSY are useful as catalyst supports for various hydrocarbon conversions. They are especially useful for such processes when heavy crude oils are involved, since the large hydrocarbon molecules can diffuse to the active catalyst sites more easily through the large mesopores.

The following examples illustrate certain embodiments of our invention. These examples are not provided to establish the scope of the invention, which is described in the disclosure and recited in the claims. The proportions are in parts by weight (pbw), percent by weight (% wt/wt) or parts per million (ppm) unless otherwise indicated.

The unit cell constant (a.sub.o) is determined as described in ASTM method D 3942-80, entitled "Determination of Unit Cell Dimension of a Faujasite-type Zeolite." The % crystallinity is determined by comparing x-ray data of modified zeolite with the same data for a standard corresponding zeolite of the prior art. The surface properties (surface area, pore volume and pore size distribution) were determined using N.sub.2 sorption at 77.degree. K.

Zeolite HY (9.0 g) was added to 62.5 ml of a 4N solution of NH.sub.4 NO.sub.3 to provide 2.2 pbw of salt per pbw of zeolite on an anhydrous basis. The slurry was placed in a pressure vessel and heated at 82.degree. C. for 2, 16 and 72 hours. The preparation was completed by filtering and washing with 200 ml of deionized water at 66.degree. C. The starting zeolite and the products have the following properties.

These results show that treatment at low temperatures does not result in the desired increase in mesopore volume, even if treated for a long time.

The process of Example 1 was followed, except that the zeolite was treated at different temperatures in a pressure vessel. The time of treatment was 16 hours. The conditions of treatment and the resulting properties are summarized in Table 3.

These results show that as the temperature is increased, the mesopore and total pore volume are increased, and the silica to aluminum mole ratio (SiO.sub.2 /Al.sub.2 O.sub.3) is not greatly changed.

The procedure of Example 2 was followed except that a solution of NaNO.sub.3 was substituted for NH.sub.4 NO.sub.3. The temperature of the treatment and the resulting properties are summarized in Table 4.

These results show that hydrothermal treatment with NaNO.sub.3 solution is effective in increasing mesopore volume, but a relatively high sodium content is maintained.

The treatments used in Examples 7, 8 and 9 were repeated except that a solution of (NH.sub.4).sub.2 SO.sub.4 was used instead of NaNO.sub.3. The conditions and results are summarized in Table 5.

These results show that treatment with sulfates appears to require somewhat higher temperatures to provide the desired increase in mesopore volume.

The process described in Example 3 was repeated, except that acid (4N HNO.sub.3) was added to the zeolite-salt solution slurry to provide two different levels of acid treatment. Table 6 summarizes the treatment conditions and the results.

These results show that the addition of acid to the zeolite-salt solution provides for an increase in the SiO.sub.2 /Al.sub.2 O.sub.3 mole ratio while the mesopore volume is changed slightly when compared to the results from the process without acid.

The process of Example 13 was repeated except the time was varied to provide three different times of treatment. Table 7 summarizes the treatment conditions and the results.

These results indicate that the mesopore volume increases as the time of treatment increases.

The process of Example 2 was followed except that the time of treatment was 2, 6 and 18 hours, respectively. Table 8 summarizes the treatment conditions and the results.

These results show that as the time of treatment increases the mesopore volume also increases.

The procedure of Example 3 was followed except that the pH of the salt solution was varied. Sufficient ammonium hydroxide was added to provide the desired pH. The treatment conditions and results are summarized in Table 9.

These results show that the increase in mesopore volume is greatest at pH values of 8 or less. They also show that at pH values of 8 to 10, mesopore volumes greater than those of the prior art can be obtained.

The procedure of Example 5 was followed except that the pH of the salt solution was varied by adding sufficient ammonium hydroxide to provide the desired pH. The treatment conditions and results are summarized in Table 10.

These results also show that as the pH is increased to 10 or 12, the desired high mesopore volume is not obtained even if the treatment temperature is 180.degree. C. These results also show a considerable increase in mesopore volume at 10 to 60 nm when a pH of 7 and a temperature of 180.degree. C. are used. Compare the 10 to 60 nm volumes of Examples 25 and 20.

Zeolite HY (3 g) was slurried with 30 ml of deionized water, then sufficient 4N HNO.sub.3 was added to provide 1 and 4 Meq H.sup.+ per gram of zeolite, respectively. The slurries were heated at 149.degree. C. for 1 hour. Table 11 summarizes the results. A comparative example at a lower temperature heated for 2 hours is included.

These results show that the mesopore volume can be increased by hydrothermal treatment with acid if the temperature is elevated above about 115.degree. C. and about 4 Meq H.sup.+ /g of zeolite is used.

The procedure of example 3 was carried out except that NH.sub.4 Cl was used instead of NH.sub.4 NO.sub.3 and the pH was varied by adding acid or NH.sub.4 OH. The conditions and results are summarized in Table 12.

These results indicate that the mesopore volume is increased when NH.sub.4 Cl is substituted for NH.sub.4 NO.sub.3. Compare the results of Examples 34 and 3.

The procedure of Example 25 was carried out except that the pH was adjusted to 7.2, the temperature was 82.degree. C. and the time of treatment was 72 hours. The mesopore volume of the product zeolite was 0.101 cc/g. This result indicates that temperatures of less than 115.degree. C. do not provide the desired increase in mesopore volume even if the best pH conditions and long heating times are used.

A dealuminated zeolite Y with a considerably contracted a.sub.o (24.33.ANG.) was contacted with 3N NH.sub.4 NO.sub.3 for 48 hours. The proportions provided 1 pbw of NH.sub.4 NO.sub.3 per 1 pbw of anhydrous zeolite. The variable process conditions and results are summarized in Table 13.

These results show that higher temperatures provide increased mesopore volumes, while the SiO.sub.2 /Al.sub.2 O.sub.3 ratio is relatively unchanged. These results also show that the temperature should be greater than about 110.degree. C. to provide the desired increase in mesopore volume.

A dealuminated zeolite having an a.sub.o of 24.33.ANG. was contacted with 6N NH.sub.4 NO.sub.3 for 18 hours at various temperatures. The proportions were such that there was 2.1 pbw of NH.sub.4 NO.sub.3 for each pbw of anhydrous zeolite. The conditions of treatment and the resulting properties are summarized in Table 14.

These results show that higher temperatures provide higher mesopore volume. The results further indicate that temperatures of about 100.degree. C. do not provide the desired mesopore volume even though 2 pbw of NH.sub.4 NO.sub.3 was substituted for the 1 pbw of NH.sub.4 NO.sub.3 used in the experiments summarized in Table 13.

A dealuminated zeolite having an a.sub.o of 24.37.ANG. was contacted with 6NNH.sub.4 NO.sub.3 for 6 hours at various temperatures. The proportions were 2.1 pbw of NH.sub.4 NO.sub.3 for each pbw anhydrous zeolite. The conditions of treatment and the resulting properties are summarized in Table 15.

These results show again that higher temperatures provide higher mesopore volume.

A dealuminated zeolite Y with a considerably contracted a.sub.o (24.33.ANG.) was contacted with 3N NH.sub.4 NO.sub.3 at 149.degree. C. for various times. The proportions of zeolite and solution provide 1 pbw of NH.sub.4 NO.sub.3 per pbw of zeolite. Table 16 summarizes the total heating time, time at 149.degree. C. and the characterization data for the starting zeolite and the products.

These results show that as the time of the hydrothermal treatment increases, the mesopore volume also increases. In addition, the results show that the mesopore volume can be increased without substantial changes in the SiO.sub.2 /Al.sub.2 O.sub.3 ratio. The results also indicate that as the mesopore volume increases, the micropore volume tends to decrease.

A dealuminated zeolite Y having an a.sub.o of 24.37.ANG. was contacted with 6N NH.sub.4 NO.sub.3 at 150.degree. C. for various times. The proportions were 2.1 pbw of NH.sub.4 NO.sub.3 per each pbw of zeolite. Table 17 shows the total heating time and the characterization data for the zeolites.

These results also show that mesopore volume increases as the time of treatment increases.

A dealuminated zeolite Y having an a.sub.o of 24.35.ANG. was contacted at 120.degree. C. or 150.degree. C. with a 6N solution of either NH.sub.4 NO.sub.3 or (NH.sub.4)2SO.sub.4. The total heating time was 3 hours. The proportions were 2.1 pbw NH.sub.4 NO.sub.3 or 1.7 pbw (NH.sub.4).sub.2 SO.sub.4 per 1 pbw zeolite. Table 18 shows the salt anion and temperature conditions and the characterization data for the product zeolites.

These results show that sulfate is not as effective as nitrate in increasing the mesopore volume. The x-ray crystallinity measurement shows that a crystalline basic aluminum sulfate is formed when using (NH.sub.4).sub.2 SO.sub.4 as the salt, and this material apparently occupies space in the internal volume of the zeolite crystals.

A dealuminated zeolite Y having an a.sub.o of 24.37.ANG. was contacted at 150.degree. C. with a 6N solution of NH.sub.4 NO.sub.3, (NH.sub.4).sub.2 SO.sub.4, or NH.sub.4 Cl. Prior to contact with the zeolite, the ammonium salt solutions were mildly acidified. The total heating time was 6 hours. The respective salt-to-zeolite contact ratios in parts by weight were 2.1, 1.7, and 1.4, for the nitrate, sulfate, and chloride preparations. These contact ratios provide the same equivalent NH.sub.4 /zeolite contact ratio. Table 19 shows the salt anion and characterization data for the zeolites.

The results show that mesopore volume is increased in the nitrate system, but not in the chloride or sulfate systems. In the latter, a crystalline basic aluminum sulfate is formed, apparently residing in the internal pores of the zeolite, thus leading to lower pore volume and crystallinity. This basic aluminum sulfate is formed even in the presence of the mildly acidified condition.

A dealuminated zeolite Y having an a.sub.o of 24.33.ANG. was contacted with 4N NH.sub.4 NO.sub.3 at 130.degree. C. for a total heating time of 4 hours. In each of several experiments, the NH.sub.4 NO.sub.3 was mildly acidified at a different level with HNO.sub.3 prior to contact with the zeolite. The contact ratio of NH.sub.4 NO.sub.3 to zeolite in parts by weight was 2.1 in all cases. Table 20 shows the acidification level and the characterization data for the zeolites.

These results show that at 130.degree. C., the mesopore volume and SiO.sub.2 /Al.sub.2 O.sub.3 ratio both increase as the acidification level is increased. These increases are larger than those realized when similar treatments were carried out at 93.degree. C.

The dealuminated zeolite Y used as stock for Examples 38-41 was contacted with 3N NH.sub.4 NO.sub.3 at 130.degree. C. for 4 hours (total heating time). The proportions were 1 pbw NH.sub.4 NO.sub.3 per 1 pbw zeolite. In one experiment the NH.sub.4 NO.sub.3 was mildly acidified with HNO.sub.3. The acidification conditions and characterization data are shown in Table 21.

These results show again that at 130.degree. C., the mesopore volume and SiO.sub.2 /Al.sub.2 O.sub.3 ratio are higher for the product of the acidified system than for the unacidified system.

The dealuminated zeolite having an a.sub.o of 24.37.ANG. was contacted with 6N NH.sub.4 NO.sub.3 at 180.degree. C. for 6 hours (total heating time). The NH.sub.4 NO.sub.3 -to-zeolite contact ratio in parts by weight was 2:1. In one experiment, the NH.sub.4 NO.sub.3 solution was mildly acidified with HNO.sub.3. The acidification conditions and characterization data are shown in Table 22.

These results show that after these 180.degree. C. treatments, the mesopore volume increases significantly but is lower from the acidified system than for the non-acidified system. The SiO.sub.2 /Al.sub.2 O.sub.3 is not significantly changed, as it is for comparable 130.degree. C. treatments.

The dealuminated zeolite having an a.sub.o of 24.37.ANG. was contacted with 6N NH.sub.4 NO.sub.3 at a ratio of 2.1 pbw NH.sub.4 NO.sub.3 per 1 pbw of zeolite. In separate experiments, the pH was varied by adding ammonium hydroxide or HNO.sub.3 to provide the desired pH. The treatment conditions were 150.degree. C. for 6 hours of total heating time. The characterization data are shown in Table 23.

These results show that the highest mesopore volume is obtained at about pH 7. Above about pH 8, the crystallinity, surface area, and pore volume fall significantly from the maximum values seen in the pH 7 treatment. The SiO.sub.2 /Al.sub.2 O.sub.3 ratio of the products from the ammonium hydroxide treated experiments do not vary dramatically from that of the starting Y zeolite.

The procedures of Examples 76-79 were followed except NH.sub.4 Cl salt was used instead of NH.sub.4 NO.sub.3. The treatment conditions and results are summarized in Table 24.

These results also show that pH about 7 produces the highest mesopore volume. Above about pH 8, the crystallinity, surface area and pore volume fall significantly from the maximum values seen in the pH 7 treatment.

The procedures of Examples 46 and 47 were followed, except that a solution of 6N NaNO.sub.3 was substituted for 6N NH.sub.4 NO.sub.3. Two treatment temperatures, 150.degree. and 180.degree. C., were used, with total heating time of 6 hours. The conditions and resulting properties are summarized in Table 25, along with the comparable NH.sub.4 NO.sub.3 prepared products.

These results show that NH.sub.4 NO.sub.3 is more effective than NaNO.sub.3 in generating high mesopore volume.

A dealuminated zeolite Y, SDUSY, with a considerably contracted a.sub.o (24.26.ANG.) was contacted with 4N NH.sub.4 NO.sub.3 for 6 hours at 200.degree. C. The proportions provided 1.5 pbw of NH.sub.4 NO.sub.3 per 1 pbw of anhydrous zeolite. The results are summarized in Table 26.

These results show that the high temperature (200.degree. C.) provides increased mesopore volume, while the SiO.sub.2 /Al.sub.2 O.sub.3 ratio is relatively unchanged.

Zeolite NaY (3.5 g) was added to 80 ml of a 2N solution of NH.sub.4 NO.sub.3 to provide 3.6 pbw salt per pbw zeolite on an anhydrous basis. The slurry was placed in a pressure vessel and heated to 200.degree. C. for 16 hours. The preparation was completed by filtering and washing with 200 ml of deionized water at 66.degree. C. The properties of the starting zeolite and the final product are shown in Table 27.

This result shows that treatment of zeolite Y at elevated temperature results in the desired increase in mesopore volume even when the starting feedstock has not been subjected to a steam stabilization step.