CA1202942A - Activation of zeolites - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method for enhancing the activity of a synthetic crystalline zeolite, including a zeolite having a silica-to-alumina mole ratio greater than 100, which has been synthesized from a reaction mixture containing a diamine as a cation source, is disclosed which involves reacting the zeolite with a dilute aqueous solution of hydrogen fluoride, contacting the hydrogen fluoride reacted zeolite with aluminum chloride, treating the aluminum chloride contacted zeolite by contact with an ammonium salt solution or ammorolysis and calcining the final product.

Description

:L2~29~

ACTIVATION OF ZEOLITES

BACKGROUNO OF THE IN\/I~NT ION
~ Fiel~ of the Invention This invention relates to a method for enhancing the acid activity of certain synthetic porous crystalline zeolites, including high silica-containing synthetic crystalline materials, which involves the sequential steps of reacting the crystalline material with hydrogen ~luoride, contacting the hydrogen fluoride reacted material lo with aluminum chloride vapor, treating the aluminum chloride ccntacted material by contact with a solution of an a~monium salt or by ammonolysis and calcining the resulting material. The resulting zeolite composition exhibits enhd"ce~ Bronsted acidity.
Cescr;~tion of Prior Art Zeolitic materials, both natural and synthetic, have been demonstrated in the past to have catalytic properties for various types of hydrocarbon con~ersions. CeItain zeclitic materials are ordered, porous crystalline aluminosilicates having a definite crystalline structure within which there are a large number of ~ er cavities which may be interconn2cted by a number of still smaller channels. Since the dimensions of these pores are such as to accept for adsorption molecules of certain dimensions while rejection those of larger dimensions, these materials have come to be known as "~olecl~lar sieves" and are utilized in a variety of ways to take advantage of these properties.

Such molecular sieves, both natural and synthetic, include a ~ide variety of positi~/e ion-containing cr~st311ine aluminosilicates.
These aluminosilicates can be described as a risld thrse-dimensional framewor~ SiO4 and A10,~ ln ~hich the tetlahedra are cross-linked ~y the sharing o~ oxygen atoms ~hereby the ratio of the total ~l~minum and silicon atoms to oxygen is 1:~. The electrovalenco or the tet~ahedra con~aining al~minum is balanced by the inclusion in the crystal of a cation, for example, an alkal metal or an alkaline ea~th metal cation. This can be express2d wherein the ratio of aluminum to the number of various cations, such as Ca/2, Sr/2, Na, K or Li is e~ual to unity. ~ne type of cation may ~e exchanged either entirely or partially by another t~/pe of cation utiliz~ng ion exchange techniques in a conventional manner. By means o~ such cation exchange, it has been possible to vary the ~roperties of a given 1~ aluminosilicate 3y suitable selection of the cation. rhe spaces between the tetrahedra are occupied by molecules of ~atsr prior to dehydration.
Prior art techniques have result~d in the formation of a great variety of synthetic aluminosilicates. T~ese aluminosilicates haye come to be designated by convenient symools, as illustrated by zeolite ZSM-5 (U.S. Patont 3,102,886).
High silica-containing synthetic zeolites are well known in the art and it is generally accepted that the ion exchange capacity of the crystalline zeolite is directly dependent on its alLminum content. Thus, lor 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 o~ the acidic type such as hydIogen, they imoart tremendous catalytic activity to the crystalline material. ûn the other hand, high silica-containing zeolites having little or substantially no aluminum, have many important properties and characteristics and a high degree o~
structural stability such that they have become candidates ~or use in various processes Lncluding catalytic processes. ,~aterials o~ this type are known in the art and include high silica-containing aluminosilicates sucn as ZSM-5, ZSM-ll (U.S. Patent 3,709,979), and ZSM-12 (U.S. Patent 3,832,449) to mention a few.

_3_ 1 The silica-to-alumina ratio or a given zeolite is often variable; 'or example, zeolite X (U.S. Patent 2,882,244) can be synthesized with a silica-to-alumina ratio of from 2 ~o 3; zeolitl~ Y
(U.S. Patem ~,130,007) from 3 to about 6. In som2 zeolites, the ; upper limit OT silica-to-alumina ratio ls virtually unbounded.
Zeolite ZSM-5 is one such material wherein the silica-to-alLImina ratio is at least 5. U.S. Patent 3,941,371 discloses a crystalline metal organo silicate essentially free of al minum and ~xhibiting an x-ray diffraction oatt~rn characteristic of ZSM-5 type aluminosilicate.
U.S. ~atents 4,û61,724; 4,073,36~ and 4,104,294 describe microporous crystalllne silicas or organo silicat~s ~her_in the aluminum content present is at impurity levels.
Because of the extremely low aluminum content of these high silica-containing synthetic zeolites, t.~elr ion exchange capacity is l; not as gre~t as mate~ials with a hisher aluminum content. Ther2~0re, when these materials are contacted with an acidic solution and thereafter aro process2d in a conventional manner, they ar~ not as catalytically active as their higher aluminum-containing counterparts.
rhe novel process of this invention permits the prepa~ation of certain synthetic high silica-containing materials which have all the desirable properties ln~erently possessed by such high silica materials and, yet, have an acid activity which heretofore has only been pos-sihle to be achieved by materi~l~ having a higher aluminum content in their "as synthesi~ed" form. It ~urther permits valuable ~, activation of crystalline zeolites having much lower silica-to-alumina mole ratios.
It is noted that U.S. Patents 3,354,078 and 3,~44,220 relate to treating crystalline aluminosilicates with volatile metal halides.
Neither of these latter patents is, however, concerned with treatment of crystalline materials having a high silica-to-alumina mole ratio or with treatment of any crystalline zeolite with hydrogen ~luoride in the present manner. In fact, the use of hydrogen fluoride ~ith aluminosilicates has been aYoided because of resulting lattice damage Hydrogen fluoride in high concentrations, e.g. 5 N or greater, readily attacks both silica and al~mina. Lower concentrations may also damage lattice structures if contact is ~¢34~Z~ L~

maintained r~or too long a time. ~ith some zeolitic materials, hydrosen rluoride tre7tment under controlled conditions has been used to alter pore si2e. U.S. ?atents 3,997,474 and 4,û54,511 relate to altering e~fective pcre si7e of ~atural rerrierite ore with very dilute hydrogen fluoride t eatment. However, the same treatment of erionite resulted in a large loss in activity and crystallinity.
SUMMARY ûf T~E INV~TION
The present lnvention relates to a novel process for improving acid activity of certain synthetic crystall.ine aluminosilicate zeolltes having been synthesized rrom reaction mixtures containin~ a diamine as a cation source, ineluding high silica-containing synthetic crystalline zeolites, which comprises the sequential steps of reacting the zeolite ~ith a dilute aqueous solution or hydrogen f'uoride (e.g. less ~han about 1.5 weight pe~cent l~ HF) for a time or less than about one hour, contacting the hydrogen fluoride react2d zeoli.e ~ith aluminum chloride vapor~ treating the aluminum chloride contacted zeolite ~y contact with an ammonium salt solution or by ammonolysis, and calcining ~he resulting material. The resulting calcined material exhibits enhanced 3ronsted acidity ~nd, ~0 theIefore, improved acid activity toward catalysis o~ nume~ous chemical reactions, such as, for example, crac~ing of organic, e.g.
hydrocarbon t compounds.
oEs~RIprIûN Of SPFCIFIC ~eCOI~ENTS
The novel process of this invention is concerned ~ith the 2i treatment of certain synthetic porous crystalline zeolites, including high silica-containins synthetic c~ystalline material. The expression "hi~h silica-containin~ orystalline material'' is intended to derine a crystalline structure ~hich has a silica-to-alumina ratio greater than 100 and more preferably greater than SCO, up to and including those highly siliceous mate~ials ~here the silica-to-alumina ratio is infinity or as reasonably close to infinit~J as practically possible.
This latter group of highly siliceous mate~ials is exemplified by U.S. patents 3,941,871; 4,û61,724; 4,07~,865 an~ 4,1Q4,~54 wherein the materials are prepared ~rom reaction solutions ~hich involve no 4j deliberate addition of aluminum. However, trace ~uantities of aluminum are usually present due to the impurity of the synthesis ~1 2V~
-reaction soluticns. It is to be unders~30d that the expression ~high silica-containing crystalline material" alsa specifically includes those materials ~nioh have other metals besides silica and/or alumina assorjated therewith, such as boron, lron, chromium, etc. Thus, the starting materials utilized in the nûvel procoss of this invention may havc a silica-to-alumina ratio greater than about 100 (irrespe~ive of what other materials or metals are pres2nt in the crystal structure).
The synthetic zeolite starting materials utilized herein, including those having a silica-to-alumina mole ratio g~eater than about lûO, are synthesi~ed from reaction mixt~res containing diamines as cation sources. Zeolites prepared ~ith other sources of cations in the reaction mixture may be activated by exposure to aluminum halide vapor at elevated temperature. ~owever, zoolites synthesi~ed from rPaction mixtures containing diamines as ca~ion sources ~ill not be 1, activated by such a method as hereinafter exemplified. The pres2nt me~hod sisnificantly activates such ~eolito materials as ~ill also be exemplified. i~or-limiting examples af diamines used as cation sources in zeolite synthesis reaction mixtures lnclude C4 to C10 diamines, e.g. l,S-diaminopentane.
The novel proc~ss o~ this inveniion is simple and ~asy to carry out althou~h tne results theref-om are d~amatic. It is c~rried out by reacting the zeolite with a dilute aqueous solution cf hy~rogen fluoride o~ rrom about 0.1 to about ~ Normal, said re3ction being conducted at a temperature of from about 0C to about 30C, pr~ferably at a~cut amoient temperature, for a time of less than a~out 60 minutes, preferably from about 5 minutes to less than about 60 ~inutes. The hydrogen fluori~e reacted zeolite is washed, usually with cold ~Nater, dried, usually ~y heating to about 130qC, and then contacted with volatile aluminum chloride at a t~mperature of from a~out lCOqC ta about 850qC, prefeIably from about 100CC to about 550~C. The aluminum chloride contacted zeolite iâ dried, again usually by heating to about 130qC, and contacted with an ammonium salt solution, e.g. lN NH4N03, or ~ith ammonium hydroxide or ammonia, and thereafter calcined at a temperature of from about 200C to about 600C in an inert atmosphere of air, nitrogen, etc. at subatmospheric, atmospheric or superatmospheric pressures for from about 1 minute to about 48 hours.

~29i~

The amount of hydrogen fluoride which is utilized in the process of this invention is from about 0.02 to about 0.2 grams of hydrogen fluoride per gram of crystalline zeolite material being treated.
The ammonium salt solution contacting step may be conducted for a period of time of from about 1 hour to about 20 hours at a temperature of from about 0C to about goaC. The ammonium salt used is not narrowly criticai and will normally be an inorganic salt such as ammonium nitrate, ammonium sulfate, ammonium chloride1 etc. If the ammonium salt solution is aqueous, it will be from about 0.1 to about 5 Normal, preferably about 1 Normal.
If instead of contacting the aluminum chloride contacted zeolite with an ammonium salt solution, ammonolysis is conducted, the zeolite will be contacted with 0~1 to 5 Normal ammonium hydroxide at a temperature of from aoout 0C to about 90C for a time of from about 1 hour to about 20 hours, or ~ith moist or dry gaseous ammonia at a temperature of from about 50C to about 200C for a time of from about 10 minutes to about 2 hours.
Of the zeolite materials having been synthesized from a reaction mixture containing a diamine as a cation source advant~g~olJsly treated in accordance herewith, zeolites ZSM-5, ZSM-ll, ZSM-35 and ZSM-48 are particularly noted. ZSM-5 is described in U.S. 4,139,600, ZSM-ll is described in U.S.
Patent 4,108,881. ZSM-35 is described in U.S. 4,016,245 and 4,107,195.
Z5M-48 can be identified, in terms of moles of anhydrous oxides per 100 moles of silica as follows:
(0.05 to 5) N20: (0.1 to lO)M2/nO : (0 to 4)A1203 : (lOO)SiO2 wherein M is at least one cation having a valence n, N is a mixture of a C2-C12, and mcre preferably of a C3-C5, alkylamine and a tetramethylammonium compound and wherein the composition is characterized by the distinctive X-ray diffraction pattern as shown below:

_7_ ~2~2~

Characteristics Lines of Zeolite Z5~ 8 d _ Relative Intznsity (I/Io) 11.8 + 0.2 S
10.2 ~ 0.2 7.2 + 0.15 W
4.~ + 0.08 VS
3.9 + 0.08 VS
-3.6 + 0.06 ~
3.1 + 0.05 W

2.85 + 0 05 ,~
These values were determined by standard techniques. The radiation ~as the K-alpha dcublet of copper, and a diffractometer e~uipped with a scintillation counter and a strip chart oen recorder ~as uszd. The pea~ heights, I, and the positions as a function of two l; ti~es theta, where theta is the 8ragg angle, wer r~ad from the spect m met~r chart. From these, the relative intensities, 100 I/I
where Io is the intensit~ of the st~onge~t line or peak, and d (obs.), the interplanar spacing in Angstroms (A) corTesponding to the recorded lines, were calculated. In the fore~oing table the relative intensities are given in terms of the symbols W = weak, VS = very strong, M = medium and W~ eak-to-medium (depending on the cationic form). Ion exchange o~ the sodium ion ~ith cations reveals suhstantially the same pattern with 33me minar shift, in interplanar spacing and va~iation in relative intensity. Other minor variations can occur depending on the sillcon to aluminum -atio of the particular sample, as well as if it has been subjected to thermal tTeatment.
ZSM-48 can be prepared from a reaction mixture containing a sourc~ of silica, tetramethylammonium compound, C2-C12 alky!amine, an alkali metal oxide, e.g. sodium, with or without a source of alumina, and water, and having a comoosition, in terms of mole ratios of oxides, falling ~ithin the following ranges:
~EACTANT5 BROAD YKt~ tK~
A1203/SiO2 0 to O.OS 0 to 0.02 Na20/SiO2 0.01 to 1.0 0.1 to 0.5 N2o/sio2 0.005 to 0 5 0.005 to 0.25 OH /SiO2 0.01 to 0.5 0.05 to 0.2 H20/Sio2 10 to 2ûO 20 to 100 where-n N is a mix~ure of a C2-~12 alkylamine and tetramethyl-ammonium compound, and maintaining the mixture at 8C-2~0CC until crystals o~ Z~M-48 are formed.
he molar ratio or C2-C12 alkylamine to tetramethyl ammonium compound is not narrowl~ critical and can range from L:1 to 10:1. The tetrame~hylammonium compound can include t,~e hydroxide or halide ~ith the chloride being particular-y preferred.
The original cations o~ ZSM-48 can ~e replaced, at least in part, by calcination and/or ion exchange ~ith another cation ~hus, the original cations are exchanged into a hydrogen or hydrogen ion precursor form or a form in whicn the original cation has been replaced by a metal or Groups ~I through VII~ of the Poriodic Table.
Thus, for example, it is contemplated that ~he original cations can be r~pla~ad with ammonium ions or with hydronium ions. Catalytically l; active forms of thes2 ~ould include, in p~Iticular, hydrcgen, rar~
earth metals, aluminum, metals of Groups II and VIII of the Periodic Table and manganese.
The activity en~anced materials propa~ed oy the present orocess are useful as catalyst componentâ for acid catalyz~d organic ~o compourd conversion reactions. 5uch reactions include, as n~n-limiting examples, crac~ing of hydrocar~ons, wherein the reaction conditions lnclude a temperature o~ from acout 300C to about aoooc, a pressure of from aoout 15 psia to about 5C0 psia, and a wei~ht hourly space velocity of from about 0.1 to ahaut 20; and conversion o~
~S methanol to ~asoline wherein the reaction conditions include a temperature of from about 300C to about 550C, a pressure of from about 5 psia to about 5C0 psia, and a weight hourly space velocity of from about 0.1 to abcut 100.
In practicing a particularly desi~ed chemical conversion process, it may be useful to incûrporate the a~ove-described activity enhanced matPrial with a matri~ comprising a material resistant to the temperature and other conditions employed in the process. Such matri~
~aterial is useful as a birder and imparts additional resistance to the catalyst for the severe temperature, pressure and reactant feed stream velocity corditions encountered in many cracking processes.

_9_ Useful matrix materials include both synthetic and naturally occurring substances, as ~ell as inorganic materials such as clay, siLica anc/or metal oxides. The latter may be either naturally occurring or in the form of gelatincus precipitat3s or gels inclu~ing mixtures of silica and metal oxides. ,~aturally occurring clays which can be composi~ed with the zeolite include those of the montmorillonite and kaolin families, which r^amilies include the sub-~entonites and the kaolins commoniy known as Oixie, McNamee, Georgia and florida clays or others in wnlch t~e main mineral constituent is halloysite, kaolinits, dickite, nacrite or anauxite.
Such clays can be used in the raw state as originally mined or initially subjected to calcination, acid treaL",en~ or chemical modi~ication.
In addition to the foreqoing mairix materials, the catalys-~mployed herein may oe co~co-~ited with a ma erial such as alumina, i, silica-alumina, silica_~agnesia, silica-zirconia, silica-thoria, silica-beryllia? and silica-titania, as well as ternary compositions, âuch as silica-alumina-thoria, silica-alLmina-zirconia, silica alumina-ma~nesia and silica-nagnesia-zi~ccnia. The matrix may oe in the form o~ a cosel. The relative procorti3ns o~ activity ~o enhanced zeolite co",ponent and matrix, on an anhyd~ous hasis, may vary widely with the zPolite content ranging r^rom aoout 1 to about 99 percent by weight and more usually in the range of aoout 5 to about 80 percent by weisht of the total dry com~osite.
The following examples will illustrate the novel method or the present invention.
E~ E
A six gram quantity o~ zeolite ZSM-48 ~as synthesized as above indicated witn the reaction mixture containing 1,5 -diaminopentane as the source of cations. The zeolite product had a silica-to-alumina mole ratio of 870. It was calcined at 538~C for one hour with helium rlow and for ~our hours in air.
\

29'1~

~XPMfLE 2 A 4.5 gram portion or the calcined zeolite ZSM-4~ from ~xample 1 was reacted ~ith S0 ml of 1 percent (0.5N~ hydrogen fluoride solution for ten ~inutes at 20CC and then ~ater ~asned ~ith cQld ; water. The hydrogen ~luoride reacted zeolite was dried at about 1303C
and then contacted ~ith !~ aqueous solution of NH4N03 (no aluminum chloride contacting) for 4 hours at ~o~r and calcined at 5380 in air for 6~ minutes.
FXAMPL~ 3 A l.S gram portion of the calcined zeolite Z~-48 from Example 1 l~as reactod ~ith 50 ml o~ 1 percont (a.5N) hydrogen fluoride solution for ten minutes at 2û~C and then ~ater washed with cold ~ater. The hyd~ogen fluoride reacted zeolito was dried at about 130CC
and loaded into a glass tube ~ith 3 grams of an~ydrous aluminum lS chloride on the upstream end. The tube ~Nas heated slowly (about 2CC
~er minute) ,rom lûO~C to 550~C with helium flo~ing at abcut 20 ml/minute. This caused aluminu~ chloride vapor to pass through the zeolitP for about 240 minutes. The aluminum chloride c~ntacted zeolite was remoYed rrom tne tube, dried at about L30C, ~reated with lN ~H~N03 and calcined as in Exa~ple 2.
ExaM Q E 4 rhe final products of xamples 2 and 3 ~ere subje~tod to the Alpha Test to ~easuIe catalytic actiY-ty. As is known in the art, the Alpha Value is an ap,oroximate indication of the catalytic cracking activity of the catalyst compaIed 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-al~mina crac~ing catalyst taken as an Alpha of 1 (rate constant = 0.016). 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 results of this test are listed below:
Product of T~e~L~ nL
Example ~ Calcination Alpha Vaiue 2 Hf+NH4N03 4.4 3 ~f+AlC13~NH4N03 13 cX~M~c ~
A sample ~f zeolite Z~M-48 was synthesized as above indicated ~ith the reaction mixture containing 1,8-octanedi~mine as the cation source. This zeolite product had a sillca-to-alumina mole ratio of ; 180. It ~as calcined as in Example 1.
EX~ Q 6 An aliquot or the zeol.ite product of xample 5 ~as contacted ~ith lN NH4i~03 for 18 hours at 20qC (no hydrogen fluoride or aluminum cnlor~de tr~atment) and then calrined as in ~xample 1.
EXAMPL' 7 Another aliquot of the Example ~ zeolite product ~!~as contacted ~ith aluminum chloride Yapor as in Example 3 (no hydrogen ~luoride treatment), dried at about L30C, treated ~ith lN NH4N03 and calcined as in Examole 3.

A quantity of the product of 'cxamDle 7 was reacted with 40 ml of 1 perc~nt (0.5N) hydrogen fluoride solution for ten minutes at 20~C
and then washed with cold water. It ~as then treated with lN
NH4N03 as in E~ample 3 ~no aluminum chloride treatment subs~quent to hydrogen fluoride tr~atment), ~ashed~ dried and calcined for 30 minutes at ~38aC in air.

A quantity o~ product of ~xample 7 was treated with hydrogen fluoride as in ExamDle 8 and washed with ~Nat2r. It was then, however, oontacted with aluminum chloride, contacted with NH4N03 and calcined as in Example 3.
EXAMFLE lû
Quantities of the final products of Examples 5, 6, 7, 8 and 9 were subjected to ~he Alpha Test. The ~esults of this test are listed below:
Product of ~reatment Alpha ExamDle + Calcination Value (base) less than 1 6 NH41~03 31 7 AlC13+NH4No3 30 8 cx.7~HF+NH4N03 28 ; 9 Cx.7+~F+AlC13~NH41~03 65 -12-2~ ~

All o~ the above experlments demonstrate that there is a respons2 to the alLminum chloride treatment for these zeolites having be~n prepa~ed from a reaction mixtu~e ccntaining a diamine as the cation source only ~ren a hyd~ogen fluoride treatment st~p prec~des the aluminum chloride treatment step. Note Ln 'xample 9 that the zeolite not previously activated ~y cont ct ~ith alLminum chloride (Examplo 7) was substantially activated wnen it ~as treated with hydrogen fluoride prior to al~minum chl3rlde 'reatment.

Claims (11)

WHAT IS CLAIMED IS:

1. A method for enhancing the activity of a synthetic porous crystalline zeolite, said zeolite having been synthesized from a reaction mixture containing a diamine as a cation source, which comprises the steps of reacting the zeolite with a diluts aqueous solution of hydrogen fluoride at a temperature or from about 0°C to about 30°C for a time or less than about 60 minutes, contacting the hydrogen fluoride reacted zeolite with aluminum chloride vapor at a temperature or from about 100°C to about 850°C, treating the aluminum chloride contacted zeolite by contact with an ammonium salt solution or ammonolysis, and calcining the resulting material at a temperature of from about 200°C to about 600°C.

2. The method of Claim 1 wherein said zeolite has a silica-to-alumina mole ratio greater than about 100.

3. The method of Claim 1 wherein said zeolite has a silica-to-alumina mole ratio greater than about 500.

4. The method of Claim 1 wherein said aluminum chloride contacted zeolite is thereafter treated by contact with an ammonium salt solution.

5. The method of Claim 4 wherein the ammonium salt is selected from the group consisting of ammonium nitrate, ammonium sulfate and ammonium chloride.

6. The method of Claim 5 wherein said ammonium salt is ammonium nitrate.

7. The method of Claim 1 wherein said aluminum chloride contacted zeolite is thereafter treated by ammonolysis.

8. The method of Claim 1 wherein said zeolite is ZSM-5, ZSM-11, ZSM-35 or ZSM-48.

9. The method of Claim 2 wherein said zeolite is ZSM-5, ZSM-11, ZSM-35 or ZSM-48.

10. A zeolite composition having enhanced activity prepared by the method of Claim 1.

11. A method for converting an organic compound which comprises contacting said organic compound at conversion conditions with a catalyst comprising a zeolite composition having enhanced activity of Claim 10.