GB2065090A - Method for producing zeolites - Google Patents

Abstract

As synthesized by previous methods, ZSM-5 or ZSM-11 zeolites are crystallized in the presence of substantial amounts of a nitrogen-containing compound and contain an organic ammonium cation as well as a metal cation such as sodium. To obtain a more active form, the sodium ion must be exchanged out. Such exchange is difficult unless there is calcination of the zeolite to remove the obstructing organic compounds. By making these zeolites in the presence of seeds of the desired zeolite, optionally also with ammonium hydroxide and possibly with an alcohol, as a still further component a product substantially deficient in organic ammonium cation is obtained which can be exchanged directly without any calcination.

Description

SPECIFICATION Method for producing zeolites The invention relates to a method for synthesizing zeolite ZSM-5 or ZSM-1 1.

Zeolites ZSM-5 and ZSM-11, like zeolites Beta, TEA mordenite and ZSM-12, are usually crystallized from a solution containing organic cations, particularly alkyl ammonium cations, as described in U.S.

Specifications 3,702,886 and 3,709,979 respectively.

In accordance with the invention, there is provided a method for synthesizing a ZSM-5 or ZSM-11 crystalline aluminosilicate containing no more than about 0.2% by weight of nitrogen, which comprises carrying outthe reaction for form said zeolite in the presence of a member selected from the group consisting of ZSM-5 seeds, ZSM-1 1 seeds and mixtures thereof with NH40H and optionally alcohol, also, when seeds are used, ZSM-5 seeds produce ZSM-5 and ZSM-11 seeds produce ZSM-11, whether used alone or in a mixture.

The aliphatic alcohol preferably is an alcohol containing 2 to 5 carbon atoms. Illustrative are ethanol, propanol, butanol and pentanol. It is contemplated that the alcohols may be straight or branch chain.

ZSM-5 and ZSM-11 seeds may be from previously prepared batches of ZSM-5 and ZSM-11 made by prior art methods. Alternatively, seeds of ZSM-5 or ZSM-11 prepared by the method of this invention may be used. Furthermore, it has been discovered that when subsequent batches of ZSM-5 or ZSM-1 1 zeolites are made in the same equipment, the residual zeolite can be sufficient to supply the requisite amount of seeds.

Only a small amount of seeds are needed for the practice of this invention. Generally, from about 0.01% by weight to about 10% by weight of final product is sufficient. We prefer, however, to use from about 1% by weight to 6% by weight ZSM-5 has the characteristic X-ray diffraction pattern set forth in Table 1 of U.S. 3,702,866, whether produced by prior art methods or by the method of this invention. ZSM-5 compositions (as well as ZSM-11 compositions) can also be identified in terms of mole ratios of oxides as follows: 0.9 t 0.2 M2O : W2O3 : X YO2 : ZH2O wherein M is a cation, n is the valence of said cation, W is selected from the group consisting of alumina and gallium, Y is selected from the group consisting of silicon and germanium, Xis from about 5 to about 3000 and Z is from 0 to 40.In a preferred form as synthesized by prior art methods the zeolite has a formula, in terms of mole ratios of oxides as follows: 0.9 t 0.2 M2O : AI2O3: X SiO2 : ZH2O I wherein M is selected from the group consisting of a mixture of alkali metal cations, especially sodium, and tetraalklammonium cations, the alkyl groups of which preferably contains 2-5 carbon atoms. In this preferred embodiment of ZSM-5, W is aluminium and Y is silicon. Also the preferred silica/alumina ratio is from about 15 to about 900. More preferably, the silica/alumina ratio is from about 30 to about 350.

According to the prior art zeolite ZSM-5 is prepared by forming a solution containing water, tetrapropyl ammonium hydroxide and the elements of sodium oxide, an oxide of aluminium or gallium and an oxide of silica, and having a composition, in terms of mole ratios of oxides, falling within the following ranges: TABLEA Particularly Broad Preferred Preferred OH SiO2 0.07-1.0 0.1-0.8 0.2-0.75 R41V+ (R4N' + Nai) ) 0.2-0.95 0.3-0.9 0.4-0.9 H20 OH- 10-300 10-300 10-300 YO2 W203 5-100 10-60 10-40 The solution is maintained at reaction conditions until the crystals of the zeolite are formed. Thereafter the crystals are separated from the liquid and recovered.Typical reaction conditions consist of a temperature of from about 75"C to 175"C for a period of about six hours to 60 days. A more preferred temperature range is from about 90 to 1 500C, with the amount of time at a temperature in such range being from about 12 hours to 20 days.

According to the prior art zeolite ZSM-11 can be prepared by forming a solution of (R4X)2O, sodium oxide, an oxide of aluminium or gallium, an oxide of silicon or germanium and water and having a composition, in terms of mole ratios of oxides, falling within the following ranges: TABLE B Broad Preferred YO2 W203 10-150 20-90 Na2O YO2 0.05-0.70 0.05-0.40 (R4x)2O YO2 0.02-0.20 0.02-0.15 H20 Na2O 50-800 100-600 wherein R4X is a cation of a quaternary compound of an element of Group 5A of the Periodic Table, W is aluminium or gallium and Y is silicon or germanium maintaining the mixture until crystals of the zeolite are formed. Preferably, crystallization is performed under pressure in a stirred autoclave or static bomb reactor.The temperature ranges from 1 OO"C to 200 C generally, but at lower temperatures, e.g., about 10000, crystallization time is longer. Thereafter the crystals are separated from the liquid and recovered.

The zeolite is preferably an aluminosilicate, having the formula: 0.9 + 0.3 M2O : Al203: 30-350 SiO2: ZH2O n wherein M is an alkali metal or an alkaline earth metal and Z isO to 40.

The ZSM-5 made by the method of this invention is, as is the same zeolite made according to the prior art, preferably formed as the aluminosilicate, and it can be prepared utilizing materials which supply the elements of the appropriate oxide. Such materials include aluminium sulfate, a mineral acid such as sulfuric acid, sodium aluminate, alumina, sodium silicate, silica hydrosol, silica gel, silicic acid, sodium hydroxide, along with the reagents of the improved method of this invention. It will be understood that each oxide component utilized in the reaction mixture for preparing ZSM-5 can be supplied by one or more initial reactants, and they can be mixed together in any order. For example, sodium oxide can be supplied by an aqueous solution of sodium hydroxide or an aqueous solution of sodium silicate.

The reaction mixture can be prepared in either a batchwise or continuous manner. Crystal size and crystallization time of the ZSM-5 composition will vary with the nature of the reaction mixture employed.

ZSM-11 made by the method of this invention is also preferably made as the aluminosilicate utilizing reactants which supply the needed oxides. Thus, the reaction mixture may comprise reactants to yield an alkalimetal oxide, e.g., sodium oxide, alumina and silica.

ZSM-5 and ZSM-11 zeolites are useful as cracking and hydrocracking catalysts as well as catalysts for isomerization and dewaxing. However, in order to increase their range of activities and their stability, it is necessary to remove the original metal ion, usually sodium. The original metal of most zeolites can be removed by conventional exchange procedures, as by multiple exchanges. Some zeolites, ZSM-5 and ZSM-11 included, are not susceptible to this method of exchange, the sodium content reaching a plateau and remaining there regardless of the number of additional exchanges. It has been previously discovered that calcination of the zeolite by removing the organic N-containing cations "frees" the sodium so it can thereafter be removed easily. Typical replacing cations would include hydrogen, ammonium and metal cations, including mixtures of the same.Of the replacing cations, particular preference is given to cations of hydrogen, ammonium, rare earth, magnesium, zinc, calcium, nickel, and mixtures thereof, generally employed in the form oftheirsalts, preferably the chlorides, nitrates or sulfates. Although not necessary, calcination may still be assist in removing the sodium cation from the products of this invention.

Following contact with the salt solution of the desired replacing cation, the zeolites prepared in accordance with this invention may be washed with water and dried at a temperature ranging from 150"F to about 600"F and thereafter may be heated in air or other inert gas at temperatures ranging from about 5000to 1500 F for periods of time ranging from 1 to 48 hours or more.

It is also possible to treat the zeolite with steam at elevated temperatures ranging from 8000to 1800"F and preferably 1000"F and 1500"F, if such is desired.

The treatment may be accomplished in atmospheres consisting partially or entirely of steam. A similar treatment can be accomplished at lower temperatures and elevated pressures, e.g., 350-700"F at 10 to about 200 atmospheres.

The zeolites produced in the method of this invention may be used in a porous matrix. The zeolites can be combined, dispersed or otherwise intimately admixed with a porous matrix in such proportions thatthe resulting product contains from 1%to95% by weight, and preferably from 1 to 70% by weight of the zeolite in the final composite.

The term "porous matrix" includes organic com positions with which the aluminosilicates can be combined, dispersed or otherwise intimately admixed wherein the matrix may be active or inactive. It is to be understood that the porosity of the compositions employed as a matrix can either be inherent in the particular material or it can be introduced by mechanical or chemical means. Inorganic compositions especially those of a siliceous nature are preferred. Of these matrices inorganic oxides such as ctay, chemically treated clay, alumina, silica, siiica-alumina, etc. are particularly preferred because of their superior porosity, attrition resistance and stability. More preferably, alumina is the matrix, and it is preferably combined with the zeolite prior to calcination.

Techniques for incorporating the zeolites in a matrix are conventional in the art and are set forth in U.S. Specification 3,140,253.

The following Examples serve to illustrate the scope of the invention showing that ZSM-5 crystalline aluminosilicates containing very low levels of organic nitrogen can be made by various techniques. It will be understood that the examples are not intended in any way to place a limitation on the invention.

Atypical preparation of ZSM-5 according to the invention is given hereinbelow. The details and results for the product are listed in the Tables. An acid alumina solution comprising Al2(SO4)s 1 8H2O.

98% H2SO4 and of H20 was added to a sodium silicate solution made by mixing Cl-brand sodium silicate (28.8% SiO2, 8.9% Na2O, 62.4% H2O) and water.

To the resultant gel was added the further component by which the invention is characterized. The gel was mixed until homogeneous and crystallized at autogeneous pressure in a stirred autoclave at350 F for 24 hours. The resultant solid material was water washed and dried at 230"F.

Several of these examples were ion exchanged with ammonium salts without any prior calcination to show that sodium was easily replaced in such a procedure. Results were excellent as indicated in the appropriate tables.

Table 1 Seeds in absence of alcohol or hydroxide Examples 1 2 Starting Components, gms.

A. Cl-Brand 45.0 450 H2O 56.3 563 B. Al2(SO4) 1 8H2O 1.54 15.4 H2SO4 (98%) 3.75 37.5 H2O 77.0 770 C. ZSM-5 seeds (19.3% Solids) 3.25 32.5 Mixed Ratio-Moles Na2O 8.6 8.6 Na2SO4 19.0 19.0 Al2O3 1.0 1.0 SiO2 94.0 94.0 H2O 3870 3870 ZSM-5, % Final Product 5.7 5.7 Crystallization Static Stirred Temp. F 350 350 Time, hrs. 96 24 Product X-Ray Analysis ZSM-5 ZSM-5 % Crystallinity 90 105 Composition, wt % N 0.02 0.03 Na 1.50(1) 1.79(1) Al203 2.40 2.44 SiO2 97.2 Composition, Molar Ratio Na2O 1.38 1.63 Al203 1.0 1.0 SiO2 67.8 Catalytic Properties (M-Forming Screening Test) (600 F, 400 psig, 15 WHSV, 3/1 H2HC, 1.5 gms. cat.) Type Catalyst Hs (2) n-Heptane Conv., wtO/o 89.6 Benzene, Conv., wt% 30.8 C7 Aromatics Prod., wtO/o 29.2 Selectivity 0.31 (1) This value is reduced to 0.087% on Example 1 and 0.04% on Example 2 when exchanged with NH4CI without any precalcination.

(2) Pre-calcination, 1000 F + NH4 exchange. Table2 Ethanol +NH4OH Example 3 Mix Components, gms A. Q-Brand 362 H2O 478 B. Al2(SO4)3 . 18H20 13.1 H2SO4(98%) 31.9 H2 658 C. Ethanol 131 NH40H, Conc., ml 148 Mole Ratio of Mix Ethanol 146 NH40H 114 Na2O 8.6 Al2O3 1.0 SiO2 94.0 H2O 3870 Na2SO4 19.0 Crystallization Stirred Temp., F 350 Time, hrs 21 Product X-Ray Analysis ZSM-5 %Cryst. 110 Composition, wt % N 0.044 Na 0.94 Al2O3 2.41 SiO2 96.1 Composition, mole Ratio N2O 0.07 Na2O 0.87 Al2O3 1.00 SiO2 67.8 Catalytic Properties M-Forming Screening Test (600 F, 400 psig, 15 WHSV, 3/1 H2/HC) (1.5 g catalyst-charged 50/50 wt n-heptane/benzene) Type Catalyst H (1) n - Heptane Conv., wt% 76.6 Benzene Conv., wt% 26.4 C7 + Aromatics Prod., wt% 24.9 Selectivity 0.31 (1) NH4 Exch., 21 00F without pre-calcination Na4 = 0.01% Table3 Ethanol + NH4OH + Seeds Example 4 5 6 7 8 Mix Components - gms.

A. Cl-Brand 360 45 45 255.2 45 H2O 450 56.3 56.3 280 56.3 Ludox (29.5% SiO2) 450 56.3 56.3 280 56.3 B. Al2(SO4)3 1 8H2O 12.42 1.54 1.54 20.0 6.0 H2SO4 30.0 3.75 3.75 20.0 2.25 H2O 616 77.0 77.0 480 77.0 C. Ethanol 124 15.5 15.5 124 15.5 NH4OHconc., ml. 140 17.5 17.5 140 17.5 D.ZSM-5 seeds (19.3% solids) 26.0 3.25 3.25 21.0 3.25 Mole Ratio of Mix Ethanol 73 73 146 90 336 NH4OH 115 115 115 69 28.5 Na,O 8.6 8.6 8.6 2.56 1.66 Al2O3 1.0 1.0 1.0 1.0 1.0 SiO2 94.0 94.0 94.0 40.8 23.9 H2O 3870 2870 3870 1700 990 Na2SO4 19.0 19.0 19.0 9.7 5.4 ZSM-5 Seeds, % Final Product 5.7 5.7 5.7 5.5 4.5 Crystallization stirred static static stirred static Temp., "F 350 446 255 350 400 Time, hrs. 17 22 334 120 96 Product X-Ray Analysis ZSM-5 ZSM-5 ZSM-5 ZSM-5 ZSM-5 %Cryst. 95 110 95 80 65 Composition,wt% 0.053 0.13 0.19 0.011 0.016 N 0.42 C 1.3(1) 0.98 1.7(1) 3.2 Na 2.53 2.13 4.36 6.40 Awl203 97.2 95.6 92.8 88.2 SiO2 Composition, mole ratio N2O 0.08 0.24 0.01 Na2O 1.14 1.02 0.87 1.1 Al2O3 1.0 1.0 1.00 1.0 SiO2 65.3 76.2 36.1 23.4 Catalytic Properties M-Forming Screening Test (600"F, 400 psig, 15 WHSV, 3/1 H2/HC, 1.5 g. catalyst-charge 50/50 wt. N - Heptane/Benzene) Type Catalyst H (2) K (2) n - Heptane Conv., wtO/o 80.2 95.0 Benzene Conv., Wt% 32.0 27.8 C7 Aromatics Prod., wt 28.9 27.4 Selectivity 0.32 0.28 (1) These values are reduced to 0.03% for Example 4 and 0.05% for Example 7. When uncalcined samples are exchanged with NH4CI.

(2) Calcination 1000oF + NH41 Exchange

Claims (3)

1. Amethod of synthesizing zeoliteZSM-5 or ZSM-11 comprising reacting a mixture comprising sources of silica and alumina, alkali metal and water until crystals of the zeolite form characterised by the fact that said mixture further comprises from 0.01 to 10 weight percent, relative to product zeolite, of seeds of that zeolite, said product containing no more than 0.2 weight percent of organic nitrogen.

2. A method according to claim 1 further characterized in that the reaction mixture contains ammonium hydroxide.

3. A method according to claim 2 further characterized in that the reaction mixture contains a two-to five-carbon atom alcohol.