METHOD FOR PREPARING CRYSTALLINE ZEOLITE, ZEOLITES PREPARED THEREBY, CATALYSTS CONTAINING THEM AND USE OF SUCH CATALYSTS

Abstract: A method of preparing crystalline zeolite materials having a constraint index between 1 and 12 and a SiO₂/Al₂O₃ mole ratio greater than 12 which comprises crystallizing the substantially pure zeolite material from a mixture of a source of silica, and optionally alumina, in the presence of a trialkylmethylammonium cation, and zeolites so prepared.

Description: METHOD FOR PREPARING CRYSTALLINE ZEOLITE, ZEOLITES PREPARED THEREBY, CATALYSTS CONTAINING THEM AND USE OF SUCH CATALYSTS This invention relates to an improved method of preparing crystalline zeolite materials of the kind which have come to be known as "molecular sieves". Zeolitic materials, both natural and synthetic, have oeen demonstrated to have catalytic properties for various types of hydrocarbon conversions. Certain zeolitic materials are ordered, porous crystalline aluminosilicates having a definite crystalline structure within which there is a large number of uniformly sized channels, the dimensions of the pores of which are such as to accept for adsorption molecules of certain dimensions while rejecting those of larger dimensions. They have been defined as a rigid three-dimensional framework of SiO4 and A104 in which the tetrahedra are cross-linked by the sharing of oxygen atoms whereby the ratio of the total aluminum and silicon atoms to oxygen is 1:2. The electrovalence of the tetrahedra containing aluminum is balanced by the inclusion in the crystal of a cation, for example, an alkali metal or an alkaline earth metal cation. They are susceptible to cation exchange, by which it is possible to vary the properties of a given aluminosilicate by suitable selection of the cation. The spaces between the tetrahedra are usually occupied by molecules of water prior to dehydration. Prior art techniques have resulted in the formation of a great variety of synthetic aluminosilicates. These aluminosilicates have come to be designated by letter or other convenient symbols, as illustrated by zeolite A (U.S. Patent 2,882,243), zeolite x (U.S. Patent 2,882,244), zeolite Y (U.S. Patent 3,130,007), zeolite ZK-5 (U.S. Patent 3,247,195), zeolite ZA-4 (U.S. Patent 3,314,752) zeolite ZSM-5 (U.S. Patent 3,702,886), zeolite ZSM-ll (U.S. Patent 3,709,979), zeolite ZSM-12 (U.S. Patent 3,832,449), zeolite ZSM-20 (U.S. Patent 3,972,983), zeolite ZSM-35 (U.S. Patent 4,016,245), zeolite ZSM-21 and 38 (U.S. Patent 4,046,859), and zeolite ZSM-23 (U.S. Patent 4,076,842), merely to name a few. The present invention relates to an improved method of preparing synthetic crystalline zeolite materials having a constraint index between 1 and 12 and a SiO2/A1203 mole ratio greater than 12 and involves the use, in the preparation, of trialkylmethylammonium compounds. It has applicability in the preparation of zeolites having a constraint index in the range 1 to 12 and a silica/alumina mole ratio greater than 12, such as ZSM-5, ZSM-ll, ZSM-12, ZSM-21, ZSM-23, ZSM-35, ZSM-38 and ZSM-48 (described in our copending European published specification No. 15,132). According to the present invention such crystalline zeolite materials, particularly those designated as ZSM-5, ZSM-ll and ZSM-12, are prepared by crystallizing the substantially pure zeolite material from a mixture of a source of silica and optionally alumina in the presence of a trialkylmethylammonium cation. Constraint Index (CI) values for some known zeolites are: Zeolite C.I. ZSM-5 8.3 ZSM-11 8.7 ZSM-12 2 ZSM-23 9.1 ZSM-35 4.5 ZSM-38 2 ZSM-48 3.4 TMA Ofretite 3.7 The significance and manner of determination of constraint index is set forth in our GB Specification 1,446,522. Zeolites ZSM-5, ZSM-ll, ZSM-12, ZSM-23, ZSM-35 and ZSM-38 are defined by the X-ray data presented in our U.S. Specifications 3,702,886, 3,709,979, 3,832,449, 4,076,842, 4,016,245 and 4,046,859 respectively. The above zeolites can be used either in the alkali metal form, e.g. the sodium form, the ammonium form, the hydrogen form or another univalent or multivalent form. When used as catalysts they will be subjectea to thermal treatment to remove part or all of any organic constituent. Zeolites ZSM-5, ZSM-l1 and ZSM-12 have been crystallized in the presence of quaternary ammonium compounds or precursors thereof, e.g. in the case of ZSM-5, tetrapropylammonium (TPA) ions;in the case of ZSM-ll, tetrabutylammonium (TBA) ions; and in the case of ZSM-12, tetraethylammonium (TEA) ions. In these cases the functional organic groups in the quaternary have been C2 to C5 compounds and in most cases the quaternary ion has been symmetrical with respect to the organic components, i.e., all organic components are the same. Since in most cases symmetrical C2 to C5 and greater quaternary compounds are not commercially available it is necessary to use precursor materials such as a trialkylamine and the corresponding organic halide. Since reaction of the precursors is not complete the unreacted precursor materials must be recovered from the crystallization mixture at the completion of crystallization for eventual disposal. Therefore, use of precursor materials in zeolite synthesis involves handling toxic and potentially hazardous chemicals, disposal of unreacted materials and it extends the time required for synthesis because an additional period of time is required for the precursors to react. The synthesis of trialkylmethylammonium compounds from trialkylamines and a methyl halide proceeds readily and such materials are commercially available as water solutions. Using such low-cost materials we have been able to synthesize ZSM-5, ZSM-ll, and ZSM-12 of high quality, and the raw material handling problems and related disposal problems have been eliminated. The crystalline zeolites can be prepared from a reaction mixture containing a source of silica, optionally alumina, trialkylmethylammonium (TAMA) ions, an alkali metal oxide, e.g. sodium, and water, and having a composition in terms of mole ratios of oxides, falling within the following ratios: For ZSM-5 REACTANTS BROAD PREFERRED SiO2/A1203 > 5 > 20 M2O/(TAMA)2O O to 1000 0.01 to 100 M2O/SiO2 O to 30 0.01 to 5.0 (TAMA)2/SiO2 1 to 3000 5 to 500 For ZSM-ll REACTANTS BROAD PREFERRED SiO2/A1203 > 5 > 20 M2O/(TAMA)2O 0 to 1000 0.01 to 100 M20/SiO2 0 to 30 0.01 to 5.0 H20/SiO2 1-to 3000 5 to 500 For ZSM-12 REACTANTS BROAD PREFERRED SiO2/A1203 > 5 > 20 M20/(TAMA)20 0 to 1000 0.01 to 100 M20/SiO2 0 to 30 0.01 to 5.0 <RTI ID=4.7> H20/S102 1 to 3000 5 to 500 wherein M in all of the above is alkali or alkaline earth metal, and TAMA is a trialkylmethylammonium ion whose alkyl groups can be C2H5, C3H7, or C4Hg, and maintaining the respective mixtures at crystallization temperature until crystals of the zeolite materials are formed. Crystallization can be carried out at either static or stirred condition. In our examples static conditions, using polypropylene jars at 1000C or teflon-lined stainless steel autoclaves at 160 0C, and stirred conditions using agitated stainless steel autoclaves at 100-160 C, were employed. The total useful range of temperatures is 80 0C to 250 0C for about 2 hours to 150 days. Thereafter, the zeolite crystals are separated from the liquid and recovered. The reaction mixture can be prepared from materials which supply the appropriate oxides. Reaction mixtures can include sodium silicate, silica hydrosol, silica gel, silicic acid, clays, and sodium hydroxide, and trialkylmethylammonium salts, e.g. triethylmethylammonium chloride (TEMACL); tripropylmethylammonium chloride (TPMACL), and tributylmethylammonium chloride (TBMACL), merely to name a few. The reaction mixture can be prepared either batch-wise or continuously. Crystal size and crystallization time of the zeolite compositions will vary with the nature of the reaction mixture employed and the crystallization conditions. Catalysts prepared from zeolites synthesized according to the invention are shaped in a wide variety of particle sizes, for instance in the form of a powder, a granule, or a molded product, such as an extrudate having particle size sufficient to pass through a 2 mesh (Tyler) screen and be retained on a 400 mesh (Tyler) screen. In cases where the catalyst is molded, such as by extrusion, the material can be extruded before drying, or dried (or partially dried) and then extruded. The zeolites can also be used as a catalyst in intimate combination with a hyorogenating component such as tungsten, vanadium, molybdenum, rhenium, nickel, cobalt, chromium, manganese, or a noble metal such as platinum or palladium where a hydrogenation-dehydrogenation function is to be performeo. Such component can be exchanged into the composition, impregnated tnerein or physically intimately admixed therewith. Such component can be impregnated into or onto it such as, for example, by, in the case of platinum, treating the zeolite with a solution containing a platinum metal-cbntaining ion. Thus, suitable platinum compounds include chloroplatinic acid, platinous chloride and various compounds containing the tetrammineplatinum complex. Especially in their metal, hydrogen, ammonium and triakylmethylammonium forms the zeolites can be beneficially converted to a catalytically applicable form by thermal treatment. This thermal treatment is generally performed by heating one of these forms in an atmosphere such as air, nitrogen, steam etc., at a temperature of at least 371 C for at least 1 minute and generally not more than 20 hours to remove part or all of the water and the organic constituent. While subatmospheric pressure can be employed for the thermal treatment, atmospheric pressure is desired for reasons of convenience. The thermal treatment can be performed at a temperature up to about 927 0C. The thermally treated product is particularly useful in the catalysis of certain hydrocarbon conversion reactions. Simple dehydration can also be performed at ambient temperatures by placing the zeolite catalyst in a vacuum, but a longer time is required to obtain a sufficient amount of dehydration. In the case of many catalysts it is desired to composite the zeolite with another material resistant to the temperatures and other conditions employed in organic conversion processes, as described in our European Specification 000 1695. Employing a catalytically active form of the zeolite catalysts prepared by the improved method of this invention which may contain additional hydrogenation components, reforming stocks can be reformed. The catalysts can also be used for hydroisomerization of normal paraffins, when provided with a hydrogenation component, e.g., platinum. Other reactions which can be accomplished employing the catalyst of this invention containing a metal, e.g., platinum, include hydrogenation-dehydrogenation reactions and desulfurization reactions, olefin polymerization (oligomerization) and other organic compound conversion such as the conversion of alcohols (e.g. methanol) to hydrocarbon. In the following illustrative examples ZSM-5, ZSM-l1 and ZSM-12 of good crystallinity were prepared. Whenever adsorption data are set forth for comparison of sorptive capacities for water, cyclohexane and n-hexane, they were determined as follows: A weighed sample of the calcined adsorbent was contacted with the desired pure adsorbate vapor in an adsorption chamber, evacuated to < 1 mm and contacted with 12 mm Hg water vapor or 20 mm Hg of cyclohexane or n-hexane vapor, pressures less than the vapor-liquid equilibrium pressure of the respective adsorbate at room temperature. The pressure was kept constant (within about + 0.5 mm) by addition of adsorbate vapor controlled by a manostat during the adsorption period (which did not exceed about eight hours). As adsorption proceeded, the decrease in pressure caused the manostat to open a valve which admitted more adsorbate vapor to the chamber to restore the above control pressures. Sorption was complete when the pressure change was not sufficient to activate the manostat. The increase in weight was calculated as the adsorption capacity of the sample in 9/1009 of calcined adsorbent. Examples 1-6 The following examples, compiled in tabular form as Table 1, immediately hereinbelow, give details as to formulation, reaction conditions, and properties of the products obtained using the trialkylmethylammonium (TAMA) compounds, e.g., TBMA, TPMA, TEMA, as well as using the prior art compounds tetrabutylammonium (TBA) and tetrapropylammonium (TPA) as points of reference. TABLE 1 Zeolite Synthesis with TAMA Compound Example Formulation Silicate Solution Q-Brand g 344 344 344 344 - 172 H2O g 200 200 200 200 - 100 Daxad 27 g 1 1 1 1 - 0,5 HiSil g - - - - 48 Alum. Solution Al2(SO4)3-XH2O g 11.9 11.9 11.9 11.9 - 5.95 H2SO4 (100%) g 34 34 29 29 - 14.5 NaCl g 20 20 40 40 - 20 H2O g 200 200 200 200 - 100 Al(NO3)3-9H2O g - - - - 1 TBMACl (50%) g - 58.6 - - - TBABr g 34 - - - - TPMACl (50%) g - - - 76 - TPABr g - - 44 - - TEMACl (50%) g - - - - 50 18 NaOH g - - - - 4.8 H2O g 70 50 70 40 230 Crystallization Temp., OF 320 Time, days 4 7 4 7 5 5 Agitation None Crystallinity ZSM-11 ZSM-11 ZSM-5 ZSM-5 ZSM-12 ZSM-5 + unidentified crystalline component 90 65 105 85 100 + trace ZSM-5 Examples 7-10 The following examples, compiled in tabular form as Table 2, immediately hereinbelow, give details as to formulation, reaction conditions, and properties of the product obtained with respect to the crystallization-of ZSM-12 in the presence of triethylmethylammonium ions. TABLE 2 PREPARATION OF ZSM-12 WITH TRIETHYLMETHYLAMMONIUM IONS Example 7 8(2) 9 10 Reaction Mixture Composition (g) Al(N03)3 9H20 1.0 80 2.0 1.0 NaOH(50S) 9.6 500 12.25 9.6 TEMAC1(50%) 50 1410 35.25 25 Hi-Sil (90% SiO2) 48 2400 60 48 H20 225 10,500 260 220 SiO2/A1203 540 338 338 540 (Na2O+ (TAMA)2O)/SiO2 0.198 0.151 0.150 0.141 Na2O/(Na2O+ (TAMA)2O) 0.421 0.573 0.568 0.593 H20/ (Na20+ (TAMA)20) 101.8 117.5 120.3 133.7 Aging Time, Hours - 96 24 Temp., C - 25 50 Crystallization Time, Hours 48 69 118 91 Temp., C 160 160 160 160 X-Ray Crystallinity, X ZSM-12(1) 105 105 100 95 ZSM-5 trace 0 0 0 Sorption, g/100g Phenol (2666 kPa) N.A. 5.9 7.2 6.3 n-C6H14 (2666 kPa) N.A. 6.9 6.1 6.3 H20 (1600 kPa) N.A. 6.5 7.2 6.9 SiO2/A1203 N.A. 118 97 147 C/N N.A. 6.58 6.44 6.68 (1) Based on Example 10 (2)Stirred at 90 rpm Examples 11-13 The following examples, compiled in tabular form as Table 3, immediately hereinbelow, demonstrated the n-hexane cracking activity of fresh and steamed ZSM-12 catalyst made according to the method of the invention. TABLE 3 N-HEXANE CRACKING ACTIVITY OF FRESH AND STEAMED ZSM-12 CATALYST Examples 11 12 13 Catalyst Product of Example 8 9 10 Cation TEMA TEMA TEMA SiO2/A1203 118 97 174 * (fresh) 81 92 76 (Steamed 8 Hr at 1000OF, 0 psig) 65 29 49 -values were determined in accordance with the method described py P.8. weisz and J.N. Miale in Journal of Catalysis, vol. 4, no. 4, August 1965 pp. 527-529 and in U.S. Patent No. 3,354,078. Examples 14-20 The following examples, compiled in tabular form as Tables 4A and 4B, immediately hereinbelow, give details as to formulation, reaction condition and properties of the products obtained with respect to the crystallization of ZSM-5 with various reaction mixtures in the presence of tripropylmethylammonium (TPMA) ions (Examples 14-18 and 20) and tetrapropylammonium bromide (TPABr) as a point of reference (Example 19). TABLE 4A ZSM-5 Synthesis with TPMACl Examples 14 15 16 17 18 19 20 Formulation Silicate Solution Q-Brand, g 6872 6872 --------------------# 6880 H2O, g 3976 3976 --------------------# 4000 Daxad 27, g 20 20 --------------------# 20 Alum Solution Al2((SO4)3#14 H2O, g 238 238 -------------------# 238 H2SO4(100%), g 574 574 574 520 600 - 570 NaCl, g 1289 1289 -------------------# H2O, g 4082 4082 -------------------# 1682 TPMACl (50 %), g 778 778 1556 778 778 - 1238 TPABr (28.5%), 6 - - - - - 1498 TMACl (50%), g - - - - - - 700 Crystallization 1St Stage Temp., F 320 225 220 220 225 215 320 Time, Hr. 12 150 161 145 170 136 17 Agitation, rpm 90 90 90 90 90 90 90 2 Nd Stage Temp., F - 320 --------------------# Time, Hr. - 9 8 8 8 5 Agitation, rpm - 90 --------------------# Crystallinity, % 85 85 85 85 80 90 90 (1) 474 g added to the gel mixture. TABLE 4B Product Properties of ZSM-5 from TPMACl Examples 14 15 16 17 18 19 20 Formulation of Reaction Mixture SiO2, wt% 84.4 82.4 82.1 82.3 83.6 82.5 83.1 Al2O3, wt% 2.1 2.1 2.1 2.1 2.1 2.0 2.1 Na, wt% 0.56 0.51 0.27 0.48 2.86 0.85 0.51 N, wt% 0.84 0.92 0.91 0.87 0.77 0.75 0.92 C, wt% 7.34 7.74 7.68 7.53 6.98 7.21 6.91 Ash, wt% 89.4 87.9 87.9 88.9 88.6 87.8 89.4 Mole Ratios of Product Al2O3 1.0 1.0 1.0 1.0 1.0 1.0 1.0 SiO2 72.4 66.7 66.5 66.6 67.8 70.1 67.3 Na2O 0.59 0.54 0.29 0.51 3.02 0.94 0.54 N 2.91 3.19 3.16 3.02 2.67 2.73 3.19 C 29.7 31.3 31.1 30.5 28.5 30.6 28.0 C/N 10.2 9.8 9.9 10.4 10.6 11.2 8.8 Adsorption, % wt H2O 6.2 10.4 9.2 9.6 14.6 10.0 9.2 CyC6 2.9 7.4 5.8 7.0 6.4 7.2 4.8 nC6 5.7 10.9 .5 10.5 10.0 12.0 9.5

Claims: WHAT IS CLAIMED IS: 1. A method for preparing a synthetic crystalline zeolite material having a constraint index between 1 and 12 and and a SiO2/A1203 mole ratio greater than 12 which comprises preparing a reaction mixture containing a source of an alkali metal oxide, an oxioe of silicon, optionally an oxide of aluminum, TAMA ion, and water and having a composition, in terms of mole ratios of oxides, falling within the following ranges: : SiO2/A1203 > 5 M2O/(TAMA)2O = 0 to 1000 M20/SiO2 = O to 30 HO/SiD2 = 1 to 3000 wherein M is an alkali or alkaline earth metal and TAMA is trialkylmethylammonium whose alkyl groups are C2H5, C H or C H and maintaining said mixture under crystallization conditions until crystals of said zeolite are formed. 2. A method according to Claim 1 wherein said mixture has a composition, in terms of mole ratios of oxides, falling within the following ranges: SiO2/A1203 > 20 M20/(TAMA)20 = 0.01 to 100 M20/SiO2 = 0.01 to 5.0 H20/SiO2 = 5 to 500 wherein M and TAMA are as before. 3. A method according to Claim 1 or Claim 2 wherein said zeolite material is ZSM-5, ZSM-ll or ZSM-12. 4. A zeolite prepared by the method of Claims 1, 2 or 3. 5. A catalyst comprising a zeolite according to claim 4 or a base-exchanged form tnereof. 6. Use of a catalyst according to Claim 5 for the conversion of organic compounds. 1573N

Inventors: CHU, POCHEN, DWYER, FRANCIS GERARD, MCVEIGH, HARRY ALLEN
Applicants: MOBIL OIL CORPORATION
Application year: 1980
Main classification: C01B33
IPC codes: C01B39, B01J29, C07C4, C07C67, C10G11, C10G47, C07C1