CA1209118A - Activation of ultra high silica zeolites - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method for enhancing the activity of high silica crystalline material, e.g. a zeolite having a silica-to-alumina mole ratio greater than 500, is disclosed which involves the sequential steps of calcining the material and treating same with a volatile gallium compound.

Description

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ACTIVATION_OF ULTRA HIGH SILICA ZE~LITES

~AC~C~OUND Ox f l~v~rlo~
Field of the Invention This invention relates to a method for enhancing the catalytic activity of certain high silica-containing crystalline materials which involves the sequential steps of calcining the material and contacting the calcined material with a volatile gallium-containing compound having a minimum vapor pressure of 50 mm at 500C. The gallium-containing compound contacted material may then be subjected to heating, hydrolyzing the heated material and calcining the resulting hydrolyzed material.
Description of Prior Art High silica-containing zeolites are well known in the art and it is generally accepted that the ion exchange capacity of the crystalline aluminosilicate is directly dependent on its aluminum content. Thus, for example, the more aluminum there is in a crystalline structure, the more cations are required to balance the electronegativity thereof, and when such cations are of the acidic type such as hydrogen, they impart tremendous _atalytic activity to the crystalline material. On the other hand, high silica-containing zeolites having little or substantially no aluminum, have many important properties and characteristics and a high degree of structural stability such that they have become candidates for use in various processes including catalytic processes. Materials of this type are known in the art and include high silica-containing aluminosilicates such as ZSM-5 (U.S. Patent 3,702,886), ZSM-ll (U.S. Patent 3,709,979), and zeolite ZSM-12 (U.S. Patent 3,832,449~ to mention a f ew.
The silica-to-alumina ratio of a given zeolite is often variable; for example, zeolite X can be synthesized with a silica-to-alumina ratio of from 2 to 3; zeolite Y
from 3 to about 6. In some zeolites, the upper limit of silica-to-alumina ratio is virtually unbounded. Zeolite 1~91~8 ZSM-5 is one such material wherein the silica-to-alumina ratio is at least 5. U.S. Patent 3,941,871 discloses a crystalline metal organosilicate essentially free of aluminum and exhibiting an x-ray diffraction pattern characteristic of ZSM-5 type aluminosilicate. U.S. Patents 4,061,724;
4,073,865 and 4,104,294 describe microporous crystalline silicas or silicates wherein the aluminum content present is at impurity levels.
Because of the extremely low aluminum content of these high silica-containing zeolites, their ion exchange capacity is not as great as materials with a higher aluminum content. Therefore, when these materials are contacted with an acidic solution or otherwise converted to their acidic forms and thereafter are processed in a conventional manner, they are not as catalytically active as their higher aluminum-containing counterparts.
The novel process of this invention permits the preparation of certain ultra high silica-containing materials which have all the desirable properties inherently possessed by such high silica materials and, yet, have an acid activity which heretofore has only been possible to be achieved by materials having a higher aluminum content in their "as synthesized" form. There is evidence to indicate that the zeolites activated by the present method contain gallium as a structural component. Such a zeolite is shown to be different than a mere mixture of gallium and the zeolite.
It is noted that U.S. Patents 3,354,078 and 3,644,220 relate to treating crystalline aluminosilicates with volatile metal halides. Neither of these latter patents is, however, concerned with the treatment of crystalline materials having an ultra high silica-to-aluminum mole ratio of at least 500. Also, U.S. Patent 4,350,835 teaches a process for converting gaseous paraffinic feedstock to aromatics over a catalyst comprising gallium and a zeolite characterized by a constraint index of 1 to 12 and a silica-to-alumina mole ratio of at least 12. U.S. Patent 4,180,689 _3~

teacnes use of galiium-containing aluminosilicate zeolite catalysts to provide improved yields of aromatic hydrocarbons from a feedstock of C3-Cl~ hydrocarbons. The zeoli~e therein has a silica-~o-aijmina mole ratio of frcm 20 to 70 and the saliium ls either deposited on o ; ion-exchanged into the zeolite. U.S. patent 4,1~0,910 teaches use of a ZSM-5 type aluminosilicate zeolite having incorporated therein a minor amount of metal from Group VIII, IIB or IB of the Periodic Table for catalyzins the conversion of paraffinic hydrocarbons to aromatics. Arcmatic hydrocarbons are produced from C3-C8 saturated and unsaturaled hydroca m ons over a cataiyst OT gailium on silica support in U.S. Patent 4,157,3~6. Aromatization is conducted over elemental gallium or a gallium ccmpound on a sLpport material in U.S. Patent 4,056,575. U.S. Patent 3 926,781 teaches us2 of gallia-alLmina catalyst for cracking paraffi.n-containing hydrocarbon feedstocks.
MMARY OF THE INVENTION
The pres2nt invention relates to a novel process for improving catalytio activity of certain ultra hish silica-conta nins crystalline zeolit~s wnich comprises ihe essential steps of calcining the ultra high silica-containins material and contacting the calcined material at an elevated temperature with a volatile gallium-containing comoound having a minimum vapor pressure of 50 mm at 500C, e.g.
gallium halide, triethylgallium, and gallium hydride. The gallium-containing compound contacted 7eolite may then, if desired, be I; subjectcd to heating, hydrolyzing the heated material ar.d caLoi"ing the hydrolyzed material. The resulting zeolite material exhibits enhanced Bronsted acidity and, therefore, improved acid activity toward catalysis of numerous chemical reactions, such as, for example cracking of organic, erg. hydrocarbon, compounds. They also exhibit high selectivites for ar~r,atics production from various feedst~cks, e.g. in dehydrogenation of ethylcyclohexane to aromatic compounds with preferential formation of the para-xylene isomer and preferential dehydrogenation of 1,4-dimethyl cyclohexane relatlve the 1,2-isomer.
Evidence suggests that the zeolites treated in accordance nerewith cortain gallium as structural ccmponent.

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D SCRIPTION_OF SP~_IFIC _MBCDIMENTS
The novel proCcss of this invention is concerned with the t eatment of ultra high silica-containi, î9 crystalline material. Ihe expression "ultra high sillca-containing crystalline material" is intended Jo define a crystalline structure whicn has a silica to-alumina mole ratio greater than 5CO up to and including those highly siliceous materials where the silica-to-alumina mole ratio is infinity or as reasonably close to lnfinity as practically possible. Hishly siliceous materials are exempllfied in U.S. patents 3,~41,871; 4,G61,724; 4,073,865 and 4,104,294 wherein the materials are prepared from reaction solutions which involve no deliberate addition of alLminumO However, t-ace quantities o, aluminum are usually oresent due to the imDurity of the reæ tion solutions. It is to be under~.ood that the expression ultra high silica-containing crystalline material" also specifically includes those materials which have other metals besides silica and/or alumina associated therewith, such as boron, iron, chromium, etc. Thus, a requirement with reward to the starting materials utilized in the novel process of this invention is that they have a silica-to-alumina mole ratio greater than about 5GO (irrespective of what other materials or ,~etals are present in the crystal structure).
The crystalline starting materials for the present process may be synthesized from reæ tion mixtures containing various cation sources9 including as non-limiting examples trialkylammonium compounds I, where ai~yl is from i to about 20 carbon atoms, e.g. tripropyl-ammonium cation sources; quaternary ammonium compounds, e.s.
tetrapropylammonium cation sources; and compounds containing multiple cationic centers, e.g. diquaternary ammonium cation sources. The compounds may be, for example, salts such as halides, e.g. chloride or bromide, nitrates, etc.
The novel process of this lnvention is simple and easy to carry out although the results therefrom are dramatic. The process is carried out by calcining an ultra high silica crystalline zeolite materiai naving a silica-to-alumina mole ratio of at least 500 by he2~ing tne same at a te"perature within .he range of from acout 2C0C
to about 6G0C in an atmosohere of air, nitrosen, etc. at atmospheric, ~Z~
superatmospheric or subatmospheric pressures for between 10 minutes ard 48 hours. rhe calcined zeolite is thereafter treated with a volatile gallium-containing compound (i.e. having a minimum vapor pressure of 50 mm at 500C) at a temperature of from about 100C to about 500C, preferably from about 100C to about 30ûC. If desired, the gallium-containing compound treated zeolite may then be heated to a temperature in the range of from about 300C to about fiOOC in an inert atmosphere of air, nitrogen, etc. for from about 10 minutes to about 48 hours. The heated zeolite may then be hyd m lyzed by contact with water at a temperature of from about ambient room temperature (e.g. 20C) to about 100C. The hyd m lyzed zeolite may then be calcined at a temperature df from about 200C to about 600C in an inert atmosphere of air, nitrogen, etc. at subatmospheric, atmospheric or superatomspheric pressures for from about 10 minutes to about 48 hours.
The gallium-containing compound cont æ ting step may be accomplished by admixture of the gallium-containing compound vapor with an inert gas such as nitrogen or helium at temperatures rangir~
from about 100C to about 500C, preferably from about 100C to about 30ûC. The amount of gallium-com aining compound vapor which is utilized is not nar m wly critical but usually from about 0.01 to about

2 grams of gallium-containing compound are used per gram of ultra high silica crystalline material.
The gallium-containing compound for use herein must have a minimum vapor pressure of about 50 mm at a temperature of 500C. Said compound may be inorganic or organic. Suitable inorganic gallium compounds include, as non-limiting examples, salts such as gallium nitrate, gallium hydride, gallium chloride and gallium b m mide.
Non-limiting examples of organic gallium compounds include those represented by the formula GaR3, wherein R is an organic moiety selected from the group consisting of alkyl of 1 to 4 carbon atoms.
Of course, mixtures of any of the above volatile gallium compounds may be used.
Of the ultra high silica zeolite materials advantageously treated in accordance herewith, zeolites ZSM-5, ZSM- 11 and ZSM-S/ZSM-11 intermediate are particularly noted. ZSM-5 is described in U.S.Patents 3,70~,886 and ye 29,94~. zsM-l~ is described in 12~E3~1&1 U.SO Patent 3,709,979, ZSM-5/ZSM-ll intermediate is described in U.S. Patent 4,229,424.
The activity enhanced high silica crystalline materials preparPd by the present method are useful as catalyst components for a variety of organic, e.g. hydrocarbon, co~oound conversion processes.
Such conversion processes include as non-limiting examples, cracking hydrocarbons with re æ tion conditions including a temperature of from about 300C to about 700C, a pressure of from about 0.1 atmosphere (bar) to about 30 atmospheres ard a weight hourly space velocity of from about 0.1 to about 20; dehydrcgenating hydrocarbon compounds with reaction conditions including a ter~erature of from about 300C to about 700C, a pressure of from about 0.1 atmosphere to about 10 atmospheres ard a weight hourly space velocity of from about 0.1 to about 20; converting paraffins to aromatics with reaction conditions incluoing a .emperature of from about 100C to atout 700C, 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/hyd~ocarbon mole ratio of from about 0 to about 20;
converting olefins to aromatics, e.g. benzene, toluene and xylenes, with reaction cnnditions including a temperature of from about 100C
to about 700C, a pressure of from about 0.1 atmosphere to atout 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 atout 20;
converting alcohols, e.g. methanol, or ethers, e.g. dimethylether, or 2s mixtures thereof to hydrocarbons including aromatics with reæ tion conditions including a temperature of from about 275C to about 600C, 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 re æ tion conditions including a temperature of from about 230C to about 510C, 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 'cemperature of from about 200C to about 760C, a pressure of from I' `..

about atmospheric to about 60 atmospheres and a welght 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. oiefins, formaldehyde, alkyi halides and alcohols, with reaction conditions including a temperature of from about 340C to about 500C, 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 f.om about 1/1 to about 20/1; and transal~ylating aromatic hydrocarbons in the presence of polyalkylaromatic hydrocarbons with reaction conditions including a temperature of from about 340C o abou. 5GûC, a pLessure OT from about atmospheric LO about 200 atmospheres, a weisht hourly space velocity cf f-om about 10 to about lCOû and an aromatic nydrocarbon/polyaikylaromatic hydrocarbon mole s ratio of from about 1/1 to about 16/1.
In practicing a particularly desired chemical conversion process, it may be useful to incorporate the above-described activity enhanced crystalline zeolite with a matrix comprising another material resistant to the temDerature and other conditions employed in the 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, for example, many cracking processes.
Useful matrix materials include both synthetic and naturally occurring substances, as well as inorganic materials sucn as clay, silica and/or metal oxides. 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 familiec 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 alumina, silica-aiumina, silica-magnesia, silica conia, silica-thoria, silica-beIyllia, and silica-titania, as well as tem ary compositions, such as sillca-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 activity enhancPd zeolite component and inorganic oxide gel matrix, on an anhydrous 3asis, may vary widely with the zeolite content ranging from between about 1 to about 99 percent by weight and more usually in the range of about 5 to about 80 percent by weight of the dry composite.
The following examples will illustrate the novel process of the present invention.

l; An ultra high silica-containing ZSM-5 material was prepared from a reaction mixture containing tetrapropylammonium cations, said material having a silica-to-alumina mole ratio of aboul 5~,000. The product zeolite of this example was established to be the ultra high silica-containing ZSM-5 by physical and chemical property evaluations Jo including X-ray diffraction analysis.

An ultra high silica-contai m ng ZSM-5 material was prepared from another reaction mixture containing tetraoropylammonium cations, said material having a silica-to-alumina mole ratio of greater than I; 26~00~ and being identified as such by physical and chemical prcperty evaluations including X-ray diffraction analysis.

An ultra high silica-containing ZSM-ll material was prepared from a reaction mixture containin3 tetrabutylammonium cations, said material having a silica-to-alumina mole ratio of 1,056 and being identified as such by physical and chemical property evaluations including X-ray diffraction analysis.

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An aliquot of each zeolite prepared in ExGmples 1, 2 and 3, as synthesized, was separately treatecl in accordance with the present invention by calcining same at 540C in air for 2 hours and contacting the calcined zeolite with gallium chloride vapor in flowing nitrogen at 200~C for 2 hours. The gallium chloride vapor contacted zeolite, in eæ h case, was further subjected to heating at 500C in nitrogen for 1 hour, hyd m lyzing the heated zeolite in water at room temperature (20~) and then calcining the hydrolyzed zeolite at 500C
in air for about 8 hours. The gallium content of the zeolite material from example 1 treated in accordance herewith was 3.5 weight percent;
4.1 weight percent for the treated zeolite from Example 2 and 4.2 weight percent for the treated zeolite from Ex2mple 3. These amounts of incorporated gallium are far greater than would be anticipated from simple ion-exchange based on original aluminum content of the zeolites used.

Portions of the prodLct ultra hish sili^a-containing zeolite materials of Examples 1, 2 and 3 without treatment as in Example 4 (but converted to acid form by ammonium exchange and calcination) and with treatment as in Example 4 were evaluated for acid activity by the Alpha Test. As is known in the art, the Alpha Value is an approximate indication of the catalytic crac K ng 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 highly active silica-alumina cracking catalyst taken as an Alpha of 1. The Alpha Test is described in U.S.
Patent 3,354,078 and in The Journal of Catalysis, Vol. IV, pp. 522-529 (August 1965). The Alpha Test here conducted was maintained at about 538C. Extensive activity enhancement by way of the present method was observed as shown in Table 1 below:

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Zeolite xample 1 Examole 2 Example 3 Aloha Value, acid 'orm but untreated less than 0v2 less than 0.2 less than 10 (est.) Alpha Value, treated After 5 minutes - 131 after 20 minutes 101 84 62 After 60 minutes 50 - 35 After 120 minutes 35 - 25 After 130 minutPs - 32 The portion of ultra ni3h silica-containing zeoli~e material from Example 2, having been treated as n Example 4 and tested in Example 5, arter regeneration by calcination in air for 60 minutes at ~38C, was reevaluated by the Alpha Test as ln Exanple 5. The regenerated material exhibited an Alpha Value or 131 after ; minutes, 89 after 21 minutes and 53 after 68 minutes.
It is observed from the results of Examples 5 and 6 that tne ultra high silica-cont2inir~ 7eolite materials treatcd by the present o invention exhibit vastly enhanced acidi_ cracking activity. It ls also noted here that durins the above Alpha Testing, the activity enhanced materials provided by the present invention demonstrated dehydrogenative activity, uncharacteristic of a non-g311ium-containing, lower silica/alumina zeolite, as indicated by high yields 2; of benzene formed under the Alpha Test conditions where selectivity for benzono retained constanl througnout the tests at sreater tnan about 20 percent.
To demonstrate the observed dehydrogenative activity more fully, the following two experiments were conducted:

A mixture feed of 5C percent 1,2-dimethylcyclohexane and 50 percent 1,4-dimethylcyclohexane was contacted with a zeolite material product of Example 1 which was treated in accordance with Example 4 at conversion conditions including atmospheric pressure, 538C ana 2

3 WHSV. Conversion of 25 weisht percent was achieveG. procuc~
profile for this example demonst-ating the shape-selectlve dehydrogenative activity of the ultra hish silica-containing zeolite treated by the present invention is presented in Table 2 below:

~Z~91~8 Products, wt. %
Benzene 1.5 Toluene 4~6 Ethylbenzene 2.1 p~Xylene 5.6 m-Xylene 4 5 o-Xylene 3.4 The preferential dehydrogenation of 1,4-dimethylcyclohexane (50% converted) relative to the 1,2-isomer (4% converted) confirms the intra-z~olitic structure position of the gallium by way of the preseni invention.

A feed of ethylcyclohexane was contacted with a zeolite , material product of Example 1 which was treater in acrordance with Example 4 at conversion conditions including atmospheric pressure, 538C and 2 ',~SV. Conversion of weight percent was achieved. A
prcduct profile for this example demonstrating the shape-selective dehydrogenative activity of the ultra high silica-contai m ng zeolite treated by the present invention is presented in Table 3 below:
TA8Lc 3 Products, wt.
Benzene 4-3 Toluene 4-9 Ethylbenzene 8.7 p-Xylene 8.0 m-Xylene 5-5 o-Xylene 2.C
The preferential fonmation of p-xylene isomer (52% of xylenes formed) from ethylcyclohexane agaln confirms the structural position of the gallium in the zeolite treated hereby.

. .
The conversion of paraffins, e.g. propane, to aromatics was also accomplished over an ultra high silica-containing zeolite ZSM-5 3~ prepared as in Exanple 2 and treated as in Example 4 at conversion -12- ~Z~9~

conditions including 540C, 0.6 WHSV and atmospheric pressure. A
conversion of 40 weight percent propane yielded C6-C8 aromatics with 45 weight percent selectivity.

The conversion of n-hexane to aromatics was also conducted over an ultra high silica-contaLning zeolite ZSM 5 p-epared as in Exam4le 2 and treated as in Example 4 at conversion conditions including ~38C, and 150 mm n-hexane in nitrogen. At greater than 95%
conversion of n-hexane, the C10 ammatics yield showed greater than 50 weight percent selectivity, with benzene predominating.

The conversion of propylene to paraffins and alomatics was conducted over an ultra high siiica-containing zeoilte Z~M-5 precared as in Example 2 and treated as in Example 4 at conversion conditions including 450C, atmospheric pressure and a weight hourly space velocity of 25. Ccnversion of 50~ resulted with the product being comDosed of Cl-C10 paraffins and aromatic hydrocarbons.

Dimethylether (DME) was converted to hydrocarbon compounds over an ultra high silica-containing zeolite ZSM-ll prepared as in Example 3 and treated as in Example 4 at conversion conditions including 450C, atmospheric pressure and 8 WHSV. The DME was lOQ%
converted to a Cl-C10 paraffin, olefin and aromatic product including 11.4 weight percent ethylene, 4.0 weight percent toluene, ~5 9.4 weight percent C8 aromatics and 8.2 weight percent C9 aromatics.

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In order to demonstrate further evidence that the gallium content of an ultra high silica-containing zeolite treated by the present invention is structurally located, an experiment was conducted to measure ion exchange capacity of such a zeolite before and after treatment. The ultra high silica-containing zeolite of Example 2 was chosen for this experiment. A quantity of the zeolite prepared as in Example 2 having been calcined and a quantity of zeolite prepared 2S
in Example 2 and treated in accordance with Example were subjected to ion exchange by contacting each with lM NH4Cl and adjusting the -13~ 3~

pH of each contacting solution to 9 with addition of NH40H. The solutions were each stirred overnight at room temperature (about 20C). aoth ion exchanged zeolites were then separated rrom solution in the normal way and tested for ion exchange capacity. That ca4acity for the Example 2 zeolite without the benefit of treatment in accordance with the present invention was less than 0.01 meq N/gram.
The ion exchange capacity for the Example 2 zeolite having been treated by the method of this invention was 0.5 ,meq N/gram. The increase ln ion exchange capacity of the treated zeolite in comparison with the untreated zeolite demonstrates the structural disposilion of the gallium.

Claims (9)

Claims:

1. A method for enhancing the activity of a silica-containing crystalline material having a silica-to-alumina mole ratio greater than about 500 which comprises calcining said crystalline material at a temperature of from about 200°C to about 600°C and contacting said calcined crystalline material at a temperature of from about 100°C to about 500°C
with a volatile gallium-containing compound having a minimum vapor pressure at 500°C of 50 mm.

2. The method of claim 1 which comprises heating said gallium-containing compound contacted crystalline material at a temperature of from about 300°C to about 600°C, hydrolyzing said heated crystalline material at a temperature of from about ambient to about 100°C and thereafter calcining said hydrolyzed crystalline material at a temperature of from about 200°C to about 600°C.

3. The method of claim 1 wherein said crystalline material is ZSM-5, ZSM-11 or ZSM-5/ZSM-11 intermediate.

4. The method of claim 2 wherein said crystalline material is ZSM-5, ZSM-11 or ZSM-5/ZSM-11 intermediate.

5. The method of claim 1 wherein said gallium-containing compound is an inorganic compound.

6. The method of claim 5 wherein said inorganic compound is selected from the group consisting of gallium mitrate, gallium hydride, gallium chloride and gallium bromide.

7. The method of claim 6 wherein said compound is gallium chloride.

8. The method of claim 1 wherein said gallium-containing compound is represented by the formula GaR3, wherein R is an organic moiety.

9. The method of claim 8 wherein said organic moiety is selected from the group consisting of alkyl of from 1 to 4 carbon atoms.