GB1588613A

GB1588613A - Zeolite synthesis

Info

Publication number: GB1588613A
Application number: GB15189/78A
Authority: GB
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1977-04-22
Filing date: 1978-04-18
Publication date: 1981-04-29
Also published as: BE866272A; NZ186957A; IT1095609B; IT7822609A0; NL188568B; CA1117512A; NL188568C; FR2442795A1; AU3523778A; JPS53134798A; FR2442795B1; DE2817577C2; AU515185B2; DE2817577A1; JPS624326B2; ZA782292B; NL7804289A

Description

(54) ZEOLITE SYNTHESIS (71) We, MOBIL OIL CORPORATION, a Corporation organised under the laws of the' State of New York, United States of America, of 150 East 42nd Street, New York, New Yorl 10017, Umted States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an improved method for synthesizing crystalline aluminosilicate zeolites requiring a reaction mixture for crystallization thereof which contains an organic nitrogen-containing cation source. Zeolites which may be advantageously synthesized by the present improved method include, for example, ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM34, ZSM-35 and ZSM-38. The present improved process requires a zeolite reaction mixture composition comprising an extremely low mole ratio of hydroxide ions/silica of only at most about 10-2, the presence of acid ions in amount less than the equivalents of organic nitrogen present therein and -a reaction mixture of pH of at least about 7.

This invention further relates to an improved crystalline aluminosilicate zeolite product of the improved method of synthesis and to organic compound conversion in the presence of the improved zeolite as catalyst.

Zeolitic materials, both natural and synthetic, have been demonstrated in the past to have catalytic properties for various types of hydrocarbon conversions. Certain zeolitic materials are ordered, porour crystalline aluminosilicates having a definite crystalline structure within which there are a large number of smaller cavities which may be interconnected 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 rejecting those of large dimensions, these, materials have come to be known as "molecular sieves" and are utilized in a variety of ways to take advantage of these properties.

Such molecular sieves, both natural and synthetic, include a wide variety of positive ion-containing crystalline aluminosilicates. These aluminosilicates can be described 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. This can be expressed wherein the ratio of aluminum to the number of various cations, such as Ca,/2 Sr,/2 Na, K or Li is equal to unity. One type of cation may be exchanged either entirely or partially by another type of cation utilizing ion exchange techniques in a conventional manner. By means of such cation exchange, it has been possible to vary the properties of a given aluminosilicate by suitable selection of the cation. The spaces between the tetrahedra are occupied by molecules of water prior to dehydration.

Prior art techniques have resulted in the formation of a great variety of synthetic aluminosilicates. A number of these aluminosilicates require the presence of a source of organic nitrogen-containing cations in the reaction mixture used to prepare them. Those aluminosilicate zeolites include for example, zeolite ZSM-5 (U.S. Patent 3,702,886), zeolite ZSM-11 (U.S. Patent 3,709,979), zeolite ZSM-12 (U.S. Patent 3,832,449), zeolite ZSM-35 (U.S. Patent 4,016,245), zeolite ZK-4 (U.S. Patent 3,314,752), zeolite ZK-22 (U.S. Patent 3,791,964), zeolite "alpha" (U.S. Patent 3,375,205), zeolite "beta" (U.S. Patent 3,308,069), a synthetic erionite (U.S. Patent 3,699,139) and a synthetic offretite (U.S.

Patent 3,578,398).

Applicant knows of no prior art methods of crystalline aluminosilicate zeolite synthesis, said synthesis requiring a source of organic nitrogen-containing cations in the reaction mixture used therein, utilizing the present improvement.

An improved method for preparing an improved crystalline aluminosilicate zeolite exhibiting enhanced purity as synthesized is provided which comprises forming a reaction mixture containing one or more sources of an alkali metal oxide, any organic nitrogen-containing oxides required for preparation of the particular zeolite to be synthesized, acid ions, an oxide of silicon, an oxide of aluminum and water wherein the mole ratio of hydroxide ions/silica in said reaction mixture is at most about 10-2, preferably from about 10-l to about 10-2, and the acid ions are present in said reaction mixture in amount less than the equivalents of organic nitrogen present therein, and wherein the pH of said reaction mixture is at least about 7, preferably from about 7 to about 12, and maintaining the reaction mixture at a temperature and pressure for a time necessary to crystallize therefrom said crystalline aluminosilicate zeolite.

Reaction conditions include heating the reaction mixture to a temperature of from about 70"F to about 500"F for a period of time of from about 1 hour to about 180 days. At a given reaction temperature, crystallization time can be significantly reduced from that required by the prior art by the present improved method. Further, the amount of organic nitrogencontaining cation source required in the reaction mixture can be reduced from that required by the prior art by the present improved method. Still further, the crystalline aluminosilicate zeolite synthesized by the present improved method can be of higher purity than normally obtainable by prior art methods of synthesis.

The present invention offers a means of synthesizing improved crystalline aluminosilicate zeolites requiring a reaction mixture for crystallization thereof which contains a source of organic nitrogen-containing cations. Improved zeolites which may be prepared in accordance herewith include, for example, ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-34, ZSM-35 and ZSM-38. Each of these is distinguished by a particular crystal structure, as evidenced by X-ray diffraction data.

Zeolite ZSM-5 and the conventional preparation thereof are described in U.S. Patent 3,702,886. Zeolite ZSM-11 and the conventional preparation thereof are described in U.S.

Patent 3,709,979. Zeolite ZSM-12 and the conventional preparation thereof are described in U.S. Patent 3,832,449. Zeolite ZSM-35 and the conventional preparation thereof are described in U.S. Patent 4,016,245.

Zeolite ZSM-23 and the conventional preparation thereof are more particularly described in U.S. Application Serial Number 739,414, filed November 8, 1976. This zeolite can be identified, in terms of mole ratios of oxides and in the anhydrous state, as follows: (0.58-3.4) M20: Al203: (40-250)SiO2 # where M is at least one cation and n is the valence thereof. It will be noticed that the ratio of M2O/n may exceed unity in this material. This is probably due to the occlusion of excess organic species, used in the preparation of ZSM-23, within the zeolite pores.

In a preferred synthesized form, zeolite ZSM-23 has a formula, in terms of mole ratios of oxides and in the anhydrous state, as follows: (0.5-3.0)R2O : (0.08-0.4)M20 : Awl203: (40-250)SiO2 wherein R is an organic nitrogen-containing cation derived from pyrrolidine and M is an alkali metal cation. It will be noticed that in this preferred form the ratio of R2O to Al2O3 may exceed unity, probably due to the occlusion of excess nitrogen-containing organic species (R2O) within the zeolite pores.

The synthetic ZSM-23 zeolite possesses a definite distinguishing crystalline structure whose X-ray diffraction pattern shows substantially the significant lines set forth in Table I.

TABLE I d(A) I/Io 11.2 + 0.23 Medium 10.1 t 0.20; Weak 7.87 + 0.15 Weak 5.59 + 0.10 Weak 5.44 + 0.10 Weak 4.90 + 0.10 Weak 4.53 + 0.10 Strong 3.90 + 0.08 Very Strong 3.72 + 0.08 Very Strong 3.62 + 0.07 Very Strong 3.54 + 0.07 Medium 3.44 + 0.07 Strong 3.36 + 0.07 Weak 3.16 + 0.07 Weak 3.05 + 0.06 Weak 2.99 + 0.06 Weak 2.85 + 0.06 Weak 2.54 + 0.05 Medium 2.47 t 0.05 Weak 2.40 + 0.05 Weak 2.34 + 0.05 Weak Zeolite ZSM-23 can be conventionally synthesized by preparing a solution containing sources of an alkali metal oxide, preferably sodium oxide, sources of nitrogen-containing cation, preferably pyrrolidine, an oxide of aluminum, an oxide of silicon and water and having a composition, in terms of mole ratios of oxides, falling within the following ranges: R+ R+ + M+ 0.85 - 0.95 OH-/SiO2 0.01 - 0.049 H20/OH- 200- 600 SiO2/Al203 55 - 70 wherein R is an organic nitrogen-containing cation and M is an alkali metal ion, and maintaining the mixture until crystals of the zeolite are formed. The quantity of OH- is calculated only from the inorganic sources of alkali without any organic base contribution.

Thereafter, the crystals are separated from the liquid and recovered. Typical reaction conditions consist of heating the foregoing reaction mixture to a temperature above 280 F to about 400 F for a period of time of from about 6 hours to about 14 days. A more preferred temperature range is from about 300 F to about 375 F with the amount of time at a temperature in such range being from about 24 hours to about 11 days.

The digestion of the gel particles is carried out until crystals form. The solid product is separated from the reaction medium, as by cooling the whole to room temperature, filtering and water washing.

The crystalline product is dried, e.g. at 230 F, for from about 8 to 24 hours. Of course, milder conditions may be employed if desired, e.g. room temperature under vacuum.

Zeolite ZSM-34 and the conventional preparation thereof are more particularly described in U.S. Application Serial Number 738,771, filed Ndvember 4, 1976. This zeolite can be identified, in terms of mole ratios of oxides and in the anhydrous state, as follows: (0.5-1.3)R20: (0-0.1 5)Na2O: (0.10-0.50)K20: Al203- XSiO2 where R is the organic nitrogen-containing cation derived from choline [(CH3)3N CH2CH2OH] and X is 8 to 50.

The synthetic ZSM-34 zeolite possesses a definite distinguishing crystalline structure whose X-ray diffraction pattern shows substantially the significant lines set forth in Table II.

TABLE II d( ) I/Io 11.5 + .2 Very Strong 9.2 +.2 Weak 7.58 + .15 Medium 6.61 + .13 Strong 6.32 + .12 Weak 5.73 + .11 Medium 5.35 + .10 Weak 4.98 + .10 Weak 4.57 + .09 Strong-Very Strong 4.32 t .08 Very Strong 4.16 t .08 Weak 3.81 # .07 Strong-Very Strong 3.74 # .07 Very Strong 3.59 # .07 Strong-Very Strong 3.30 # .06 Medium-Strong 3.15 + .06 Medium 2.92 + .05 Weak 2.85 # .05 Very Strong 2.80 # .05 Weak 2.67 # .05 Weak 2.52 t .05 Weak 2.48 + .05 Weak-Medium 2.35 + .04 Weak 2.28 + .04 Weak ZSM-34 can be conventionally synthesized by preparing a gel reaction mixture having a composition, in terms of mole ratios of oxides, falling within the following ranges: Broad Preferred SiO2/Al2O3 10-70 10-55 OH-/SiO2 0.3-1.0 0.3-0.8 H2O/OH- 20-100 20-80 K20/ M20 0.1-1.0 0.1-1.0 R+/R+ + M+ 0.1-0.8 0.1-0.50 where R+ is choline [(CH3)3N-CH2CH2OH] and M is Na + K and maintaining the mixture until crystals of the zeolite are formed. The quantity of OH- is calculated from inorganic base (hydroxide ion not neutralized by added mineral acid or acid salt. Resulting zeolite crystals are separated and recovered. Typical reaction conditions consist of heating the foregoing reaction mixture to a temperature of from about 80 C to about 175 C for a period of time of from about 12 hours to 200 days. A more preferred temperature range is from about 90 to 1600C with the amount of time at a temperature in such range being from about 12 hours to 50 days.

The resulting crystalline product is separated from the mother liquor by filtration, water washing and drying, e.g., at 2300F for from 4 to 48 hours. Milder conditions may be employed, if desired, e.g., room temperature under vacuum.

Zeolite ZSM-38 and the conventional preparation thereof are more particularly described in U.S. Application Serial Number 560,412, filed March 20, 1975. This zeolite can be identified, in terms of mole ratios of oxides and in the anhydrous state, as follows: (0.3-2.5)R2O : (0-0.8)M2O : Al2O3 : xSiO2 wherein x is greater than 8, R is an organic nitrogen-containing cation derived from a 2-(hydroxyalkyl) trialkylammonium compound and M is an alkali metal cation, and, is characterized by a specified X-ray powder diffraction pattern.

In a preferred synthesized form, zeolite ZSM-38 has a formula, in terms of mole ratios of oxides and in the anhydrous state, as follows: (0.4-2.5)R2O : (0-0.6)M2O : Al203 : ySiO2 wherein R is an organic nitrogen-containing cation derived from a 2-(hydroxyalkyl) trialkylammonium compound, wherein alkyl is methyl, ethyl or a combination thereof, M is an alkali metal, especially sodium, and y is from greater than 8 to about 50.

The synthetic ZSM-38 zeolite possesses a definite distinguishing crystalline structure whose X-ray diffraction pattern shows substantially the significant lines set forth in Table III.

TABLE III d(A) I/Io 9.8 + 0.20 Strong 9.1 + 0.19 Medium 8.0 + 0.16 Weak 7.1 i 0.14 Medium 6.7 + 0.14 Medium 6.0 + 0.12 Weak 4.37 + 0.09 Weak 4.23 + 0.09 Weak 4.01 + 0.08 Very Strong 3.81 + 0.08 Very Strong 3.69 + 0.07 Medium 3.57 + 0.07 Very Strong 3.51 + 0.07 Very Strong 3.34 + 0.07 Medium 3.17 + 0.06 Strong 3.08 + 0.06 Medium 3.00 + 0.06 Weak 2.92 + 0.06 Medium 2.73 + 0.06 Weak 2.66 + 0.05 Weak 2.60 + 0.05 Weak 2.49 + 0.05 Weak Zeolite ZSM-38 can be conventionally synthesized by preparing a solution containing sources of an alkali metal oxide, preferably sodium oxide, an organic nitrogen-containing oxide, an oxide of aluminum, an oxide of silicon and water and having a composition, in terms of mole ratios of oxides falling within the following ranges: Broad Preferred R+/(R+ + M+) 0.2-1.0 0.3-0.9 OH-/SiO2 0.05-0.5 0.07-0.49 H2O/OH- 41-500 100-250 SiO2/Al203 8.8-200 12-60 wherein R is an organic nitrogen-containing cation derived from a 2-(hydroxyalkyl) trialkylammonium compound and M is an alkali metal ion, and maintaining the mixture until crystals of the zeolite are formed. Thereafter, the crystals are separated from the liquid and recovered. Typical reaction conditions consist of heating the foregoing raction mixture to a temperature of from about 90"F to about 400"F for a period of time of from about 6 hours to about 100 days. A more preferred temperature range is from about 1500F to about 400"F with the amount of time at a temperature in such range being from about 6 hours to about 80 days.

The digestion of the gel particles is carried out until crystals form. The solid product is separated from the reaction medium, as by cooling the whole to room temperature, filtering and water washing. The crystalline product is thereafter dried, e.g. at 2300F for from about 8 to 24 hours.

The values of Tables I, II and III were determined by standard techniques. The radiation was the K-alpha doublet of copper, and a Geiger counter spectrometer with a strip chart pen recorder was used. The peak heights, I, and the positions as a function of 2 times theta, were theta is the Bragg angle, were read from the spectrometer chart. From these, the relative intensities, 100 I/Io, where Io is the intensity of the strongest line or peak, and d(A), the interplanar spacing in Angstrom units, corresponding to the recorded lines, were calculated.

In the present improved method of zeolite synthesis, a reaction mixture is formed containing one or more sources of alkali metal oxide, organic nitrogen-containing cations, acid ions, an oxide of silicon, an oxide of aluminum and water. The composition of the reaction mixture must contain hydroxide ions and silica in the extremely low mole ratio of at most about 10-2, preferably from about 10-l to about 10-2. The composition must also contain acid ions in amount less than the equivalents of organic nitrogen present therein. The reaction mixture, further, must have a pH of at least 7, preferably from about 7 to about 12.

The sources of alkali metal oxide may be, for example, sodium, lithium or potassium hydroxides, oxides, carbonates, halides (e.g. chlorides and bromides), sulfates, nitrates, acetates, silicates, aluminates, phosphates and salts of carboxylic acids.

The sources of organic nitrogen-containing cations, depending, of course, on the particular zeolite product to result from crystallization from the reaction mixture, may be primary, secondary or tertiary amines or quarternary ammonium compounds, examples of which include salts of tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, diethylammonium, triethylammonium, dibenzylammonium, dibenzyldimethylammonium, dibenzyldiethylammonium, benzyltrimethylammonium and choline; or the compounds of trimethylamine, triethylamine, tripropylamine, ethylenediamine, propanediamine, butanediamine, pentanediamine, hexanediamine, methylamine, ethyalmine, propylamine, butylamine, dimethylamine, diethylamine, dipropylamine, benzylamine, aniline, pyridine, piperidine and pvrrolidine.

The sources of acid ions may be, for example, HCl, H2S04, H3PO4, HNO3, carboxylic acids, aluminum sulfates, nitrates, chlorides, phosphates or acid salts of primary, secondary or tertiary amines.

Sources of silicon oxides may be, for example, silica sols, alkali metal silicates, silica gels, silicic acid or aluminosilicates.

Sources of aluminum oxides may be, for example, alkali metal aluminates, aluminum metal, hydrated aluminum oxides or aluminum salts of acids such as H2SO4, HC1 and HNO3.

In general, the reaction mixture for the present improved synthesis process will have a composition, in terms of mole ratios of oxides, as follows: Broadly Most Acceptable Preferred Preferred SiO2/ Al203 5-1000 10-200 15-100 oH-/SiO2 10010-2 10-7-10-2 10-6-10-2 H20/SiO2 5-200 10-100 10-100 M/SiO2 0.01-5.0 0.1-2.0 0.2-1.0 R/SiO2 0.01-3.0 0.04-2.0 0.1-1.0 wherein R is an organic nitrogen-containing cation or organic nitrogen-containing cation source and M is an alkali metal ion.

Specifically, when ZSM-5 is the desired zeolite product of the present improved synthesis process, the reaction mixture will have a composition, in terms of mole ratios of oxides, as follows: SiO2/ Al203 = 5-1000 oH-/SiO2 = 10-'0-10-2 H2O/SiO2 = 5-200 M/SiO2 = 0.01-3.0 R/SiO2 = 0.01-1.0 wherein R is a tetraporpylammonium cation and M is an alkali metal ion. The reaction mixture must be maintained at a temperature of from about 100"F to about 400"F for a period of time of from about 3 hours to about 150 days until crystals form. Thereafter, the crystals arc separated from the reaction medium and recovered. Separation may be accomplished by, for example, cooling the whole to room temperature. filtering and water washing.

When ZSM- 11 is the desired zeolite product of the present improved synthesis process, the reaction mixture will have a composition, in terms of mole ratios of oxides, as follows: SiO2/Al203 = 10-180 oH-/SiO2 = 10-1 10-2 H20/SiO2 = 5-100 M/SiO2 = 0.1-2.0 R/SiO2 = 0.04-1.0 wherein R is a tetrabutylammonium cation and M is an alkali metal ion. The reaction mixture must be maintained at a temperature of from about 100"F to about 400"F for a period of time of from about 4 hours to about 180 days until crystals form. Thereafter, the crystals are separated from the reaction medium and recovered. Separation may be accomp lished by, for example, cooling the whole to room temperature, filtering and water washing.

When ZSM-12 is the desired zeolite product of the present improved synthesis process, the reaction mixture will have a composition, in terms of mole ratios of oxides, as follows: SiO2/Al203 = 40-200 OH-/SiO2 = 10-10-10-2 H2O/SiO2 = 5-100 M/SiO2 = 0.1-3.0 R/SiO2 = 0.1-2.0 wherein R is a tetraethylammonium cation or a cation derived from triethylamine and M is an alkali metal ion. The quantity of hydroxide ions is calculated only from the inorganic sources of alkali without any organic base contribution. The reaction mixture must be maintained at a temperature of from about 100 F to about 400"F for a period of time of from about 6 hours to about 180 days until crystals form. Thereafter, the crystals are separated from the reaction medium and recovered. Separation may be accomplished by, for example, cooling the whole to room temperature, filtering and water washing.

When ZSM-23 is the desired zeolite product of the present improved synthesis process, the reaction mixture will have a composition, in terms of mole ratios of oxides, as follows: SiO2/Al203 = 10-200 OH-/SiO2 = 10-10-10-2 H2O/SiO2 = 5-100 M/SiO2 = 0.1-2.0 R/SiO2 = 0.1-1.0 wherein R is a cation derived from pyrrolidine and M is an alkali metal ion. The quantity of hydroxide ions is calculated only from the inorganic sources of alkali without any organic base contribution. The reaction mixture must be maintained at a temperature of from about 100"F to about 400"F for a period of time of from about 6 hours to about 180 days until crystals form. Thereafter, the crystals are separated from the reaction medium and recovered.

Separation may be accomplished by, for example, cooling the whole to room temperature, filtering and water washing.

When ZSM-34 is the desired zeolite product of the present improved synthesis process, the reaction mixture will have a composition, in terms of mole ratios of oxides, as follows: SiO2/Al2O3 = 5-100 OH-/SiO2 = 10-l 10-2 H2O/SiO2 = 5-100 M/SiO2 = 0.1-2.0 R/SiO2 = 0.1-1.0 wherein R is a cation derived from choline and M is an alkali metal ion. The reaction mixture must be maintained at a temperature of from about 100"F to about 400"F for a period of time of from about 3 hours to about 150 davs until crvstals form. Thereafter. the crystals are separated from the reaction medium and recovered. Separation may be accomplished by, for example, cooling the whole to room temperature, filtering and water washing.

When ZSM-35 is the desired zeolite product of the present improved synthesis process, the reaction mixture will have a composition. in terms of mole ratios of oxides, as follows: SiO2/Al2O3 = 8.8-200 oH-/SiO2 = 10-'0-10-2 H20/ SiO2 = 5-100 M/SiO2 = 0.1-3.0 R/SiO2 = 0.05-2.0 wherein R is a cation derived from ethylenediamine or pyrrolidine and M is an alkali metal ion. The quantity of hydroxide ions is calculated only from the inorganic sources of alkali without any organic base contribution. The reaction mixture must be maintained at a temperature of from about I 000F to about 400"F for a period of time of from about 6 hours to about 180 days until crystals form. Thereafter, the crystals are separated from the reaction medium and recovered. Separation may be accomplished by. for example, cooling the whole to room temperature, filtering and water washing.

When ZSM-38 is the desired zeolite product of the present improved synthesis process. the reaction mixture will have a composition, in terms of mole ratios of oxides, as follows: SiO2/Al2O3 = 8.8-200 oH-/SiO2 = 10-'0-10-2 H2O/SiO2 = 5-100 M/SiO2 = 0.1-3.0 R/SiO2 = 0.1-2.0 wherein R is derived from a 2-(hydroxyalkyl) trialkylammonium compound wherein alkyl is methyl, ethyl or a combination thereof, and M is an alkali metal ion. The reaction mixture must be maintained at a temperature of from about 1 OO"F to about 400"F for a period of time of from about 6 hours to about 180 days until crystals form. Thereafter, the crystals are separated from the reaction medium and recovered. Separation may be accomplished by, for example, cooling the whole to room temperature, filtering and water washing.

It is recalled that in calculating the mole ratio of hydroxide ions/silica, it is conventional to calculate hydroxide by summing moles of OH-, whether added as NaOH, as quaternary ammonium hydroxide, as sodium silicate (NaOH + SiO2), as sodium aluminate (NaOH + Al2O3), or the like, and to subtract from that sum any moles of acid added. Acid may be added simply as HC1, HNO3, H2SO4, acetic acid, and the like or it may be added as an aluminum sulfate (awl203 + H2SO4), chloride (Al203 + HC1), nitrate (A1203 + HNOs), etc. In particular, no contribution is assigned to organic bases such as amines in this calculation.

Although the usefulness of this invention is to be found with quaternary ammonium cations at OH-/SiO2 ratios below those recognized earlier, it is with the amines that this invention is ideally suited. Amines present in reaction mixtures having an OH-/SiO2 ratio of 0.01 are protonated when further acid is added. Until said additional acid exceeds the amine present, the pH remains above 7.

In a conventional calculation which does not consider amines, the total moles of acid could thereby exceed the moles of hydroxide added in said reaction mixture and subtraction would thereby lead to apparent "negative" OH-/SiO2 ratios. A negative ratio is, of course, not possible since the true moles of hydroxide (per liter) in an aqueous mixture are always positive and equal to 10-l4 divided by the moles per liter of acid. Calculated from the true moles of hydroxide, the present invention would include an OH-/SiO2 range of about 10-'0 to about 10-2. Maintaining the convention which has been established in describing reaction mixture compositions, we define the quantity of acid added in excess of the hydroxide added by the ratio H+(additional)/SiO2.

The improved zeolites prepared by the present improved method may be used for organic compound conversion in the hydrogen form or they may be base exchanged or impregnated to contain ammonium or a meta silica-magnesia-zirconia. The matrix can be in the form of a cogel. A mixture of these components, one with the other and/or with a clay, could also be used. The relative proportions of zeolite and inorganic oxide gel matrix and/or clay vary widely with the crystalline aluminosilicate content ranging from about 1 to about 90 percent by weight and more usually in the range of about 2 to about 50 percent by weight of the composite.

Zeolites prepared by the present improved method are valuable catalysts in various organic compound, e.g. hydrocarbon compounds and oxygenates such as methanol, conversion processes. Such processes include, for example, alkylation of aromatics with olefins, aromatization of normally gaseous-olefins and paraffins, aromatization of normally liquid low molecular weight paraffins and olefins, isomerization of aromatics, paraffins and olefins, disproportionation of aromatics, transalkylation of aromatics, oligomerization of olefins and cracking and hydrocracking. All of the foregoing catalytic processes are of value since they result in upgrading of the organic charge being processed.

The process for upgrading reformates wherein a zeolite prepared in accordance herewith is employed as catalyst generally involves contact during processing with a reformate or reformer effluent, with or without added hydrogen, at a temperature between 500"F and about 1100 F and preferably between about 550"F and about 1000 F. The reaction pressure in such operation is generally within the range of about 25 and about 2000 psig and preferably about 50 to about 1000 psig. The liquid hourly space velocity, i.e. the liquid volume of hydrocarbon per hour per volume of catalyst, is between about 0.1 and about 250, and preferably' between about 1 and 100. Although hydrogen is not essential to this process, when it is used the molar ratio of hydrogen to hydrocarbon charge employed is between about 0.1 and about 80 and preferably between about 1 and about 10.

Oligomerization of olefins, i.e. olefins having 2 to 10 carbon atoms, is effectively carried out with the zeolite prepared in accordance herewith as catalyst. Such reaction is suitably effected at a temperature between about 550"F and about 1150"F, a pressure between about 0.01 and about 1000 psig utilizing a weight hourly space velocity within the approximate range of 0.1 to 1000.

Alkylation of aromatic hydrocarbons, e.g. benzene, with an alkylating agent such as an alkyl halide, an alcohol or an olefin, is also readily effected in the presence of the presently made zeolite as catalyst with reduced aging.

Alkylation conditions include a temperature between about 400 F and about 1000 F, a pressure between about 25 and about 1000 psig utilizing an aromatic hydrocarbon/alkylating agent mole ratio of 2 to 200 and an alkylating agent weight hourly space velocity within the approximate range of 0.5 to 50.

Xylene isomerization is another reaction suitably conducted in the presence of the zeolite made in accordance herewith as catalyst. Isomerization conditions include a temperature between about 300"F and about 900"F, a pressure between about 25 and about 1000 psig utilizing a weight hourly space velocity within the approximate range of 0.2 to 100.

Aromatics, such asj for example, toluene, may be disproportionated in the presence of the presently made zeolite under a temperature of from about 450"F to about 1100 F, a pressure of from about 50 psig to about 800 psig and a liquid hourly space velocity within the approximate range of about 0.1 to about 20. Aliphatic hydrocarbons may also be disproportionated in the presence of zeolite prepared by the present improved method at a temperature of from about 350"F to about 900"F, a pressure between 0 and 3,000 psig and a liquid hourly space velocity of between about 0.01 and about 5.

When the conversion of organic compounds with the presently made zeolite as catalyst is cracking, catalytic conversion conditions should be maintained within certain ranges, including a temperature of from about 700"F to about 1200"F, preferably from about 800"F to about 1000 F, a pressure of from about atmospheric to about 200 psig, and a liquid hourly space velocity of from about 0.5 hr-1 to about 50 hr-1, preferably from about 1 hr-1 to about 10 hr-1. When the conversion is hydrocracking, catalytic conversion conditions should be maintained within somewhat different ranges, including a temperature of from about 400"F to about 1000"F, preferably from about 500"F to about 850"F, a pressure of from about 500 psig to about 3500 psig, a liquid hourly space velocity of from about 0.1 hr-1 to about 10 hr-1, preferably from about 0.2 hr-1 to about 5 hr-1, and a hydrogen/hydrocarbon ratio of from about 1000 scf/bbl to about 20,000 scf/bbl, preferably from about 3,000 scf/bbl to about 10,000 scf/bbl.

It may be desirable in some instances to add a hydrogenation/dehydrogenation component to the zeolite prepared in accordance herewith for use as catalyst. The amount of the hydrogenation/dehydrogenation component employed is not narrowly critical and can range from about 0.01 to about 30 weight percent based on the entire catalyst. A variety of hydrogenation components may be combined with either the zeolite and/or matrix in any feasible manner which affords intimate contact of the components, employing well known techniques such as base exchange, impregnation, coprecipitation, cogellation, mechanical admixture of one component with the other and the like. The hydrogenation component can inclilde metals, oxides and sulfides of metals of the Periodic Table which fall in Group VI-B including chromium, molybdenum, tungsten and the like; Group II-B including ziric and cadmium; Group VIII including cobalt, nickel, platinum, palladium, ruthenium, rhodium, osmium and iiidiuin; Group IV-A such as germanium and tin and combinations of metals, sulfides and oxides of metals of Group VI-B and VIII, such as nickel-tungsten-stilfide, cobalt oxide-molybdenum oxide arid the like. Pre-treatment before use varies depending on the hydrogenation component present. For example, with components such as nickel-tungsten, cobalt-molybdenum, platinum and palladium, the catalyst may desirably be sulfided. With metals like platintim or palladium, a hydrogenation step may also be employed. These techniques are well known in the art and are accomplished in a conventional manner.

In order to more fully illustrate the nature of the invention and the manner of practicing same; the following examples are presented.

Example 1 In accordance with the prior art method of preparing zeolite ZSM-5, to a solution of 63.3 grams Q-brand sodium silicate (28.5 wt. % SiO2, 7.75 wt, % Na2O and 63.75 wt. % H2O) in 79.2 grams of water in a polypropylene bottle was added a solution of 2.05 grams Al2(SO4)3.16H20, 3.8 grams H2SO4 and 7.85 grams tetraporpylammonium bromide in 108.3 grains of water. After vigorous mixing the pH of the mixture was measured to be z 10.

The bottle was placed in a steam chest at 90-950C. The reaction mixture had a molar composition as follows: SiO2/Al2O3 = 92 OH-/SiO2 = 0.20 H20/SiO2 = 42 M/SiO2 = 0.53 R/SiO2 = 0.10 After 30 days, a sample of the gel was taken, washed with water, and dried. An X-ray diffraction pattern showed the sample to contain about 40% ZSM-5 together with amorph dus material.

Example 2 In accordance with the present improved method of preparing zeolite ZSM-5, to a solution of 63.3 grams Q-brand sodium silicate in 79.2 grams of water in a polypropylene bottle was added a solution of 2.05 grams A12(SL)3.16H2O, 7.2 grams H2SO4 and 7.85 grams tetrapropylammonium bromide in 108.3 grams of water. The acid ions in this reaction mixture were present in amount sufficient to reduce the OG-/ SiO2 ratio below 10-2. After vigorous rnixing the pH was determined to be 7. The bottle was then placed in a steam chest at 90-950C. The reaction mixture had a molar composition as follows: SiO2/Al203 = 92 oH-/SiO2 = < 10-2 H20/SiO2 = 42 M/SiO2 = 0.53 R/SiO2 = 0.10 Although successful crystallization was noted earlier, the produce ZSM-5 was removed, washed, and dried after 30 days in the steam chest. The X-ray diffraction pattern showed 100% ZSM-5. Scanning electron micrograms showed the material to be relatively uniform crystals of 6-12 micron diameter.

Examples 3-6 In these examples, prior art and present improved methods of syntheses of zeolite ZSM-35 were conducted. Crystallization at 100 C was conducted in polypropylene bottles under static condicitions in a steam chest. The silicate source was Q-brand (27.8 % SiO2, 8.42 % Na2O) and the alumina source was Al2(SO4)2.16H2O. The organic nitrogen-containing cation source was pyrrolidine. Reaction mixture compositions (mole ratios), total days in a steam chest for crystallization to occur and zeolite product compositions are tabulated in Table IV, hereinafter presented. It is observed from these examples that prior art methods Examples 5 and 6) fail to compare favorably with the present improved method of synthesis Examples 3 and 4) for zeolite ZSM-35. After only 35 and 39 days in the steam chest, 100% ZSM-35 was obtained from the improved method of Examples 3 and 4. After as many as 85 days in the steam chest for the reaction mixture of Example 5, the product contained 50% ZSM-35 and 50% mordenite. After 70 days in the steam chest for the reaction mixture of Example 6, only 10% ZSM-35 resulted.

TABLE IV Reaction Mixture Composition Example SiO2/Al2O3 H2O/SiO2 OH-#SiO2 Na/SiO2 H+(additional)/SiO2 R2SiO2 pH 3 30 39 < 10-2 0.59 0.15 0.68 11-12 4 30 39 < 10-2 0.59 0.02 0.27 11-12 5 30 40 0.29 0.59 0 0.30 13-14 6 30 39 0.29 0.59 0 0.19 13-14 TABLE IV (Continued) Product Composition Example Days Zeolite SiO2/AI203 Al/uc * Na/uc*N/uc* C/N 3 35 100SoZSM-35 29.1 2.3 0.1 4.1 4.5 4 39 100%ZSM-35 26.6 2.5 0.2 3.9 4.5 5 85 50SoZSM-35 + 50% Mordenite - - - - 6 70 10SoZSM-35 * uc = Unit cell, assumed to contain 36 Si and Al tetrahedra.

Example 7 A sample of crystalline aluminosilicate zeolite ZSM-5 prepared as in Example 2 was evaluated for catalytic activity with a five-component feedstock of n-hexane, 3-methylpentane, 2,3-dimethylbutane, benzene and toluene at 200 psig, a weight hourly space velocity (WHSV) of 2.9 he~', a temperature of 427"C and a hydrogen/hydrocarbon mole ratio of 3.6. This zeolite, after exchange, provided 94% conversion of n-hexane and 46% conversion of 3-methylpentane. Of the converted paraffin charge, 11% reacted with benzene and toluene to produce alkyl aromatics.

Example 8 A sample of ZSM-35 was prepared as in Example 3, but at a temperature of 1600C and with R/SiO2 = 0.14 and H+(additional)/SiO2 = 0.03. The ZSM-35 product was evaluated for catalytic activity with a feedstock as in Example 7. Test conditions were 200 psig, 3.2 hr-1 WHSV, 427"C and a hydrogen/hydrocarbon mole ratio of 4.8. This ZSM-35 converted 96% n-hexane and 20% 3-methylpentane.

Claims

WHAT WE CLAIM IS:

1. A method for synthesizing a crystalline aluminosilicate zeolite which comprises forming a reaction mixture containing one or more sources of alkali metal oxide, organic nitrogen-containing cations, acid ions, an oxide of silicon, an oxide of aluminium and water wherein the mole ratio of hydroxide ions/silica in said reaction mixture is at most about 10-2 and the acid ions are present in said reaction mixture in amount less than the equivalents of organic nitrogen present therein, and wherein the pH of said reaction mixture is at least about 7, and maintaining the reaction mixture at a temperature and pressure for a time necessary to crystallize therefrom said crystalline aluminosilicate zeolite.

2. The method of Claim 1 wherein said reaction mixture has a composition in terms of mole ratios of oxides as follows: SiO2/Al203 = 5-1000 OH-/SiO2 = 10-'0-10-2 H20/SiO2 = 5-200 M/SiO2 = 0.01-5.0 R/SiO2 = 0.01-3.0 wherein R is an organic nitrogen-containing cation or an organic nitrogen-containing cation source and M is an alkali metal ion.

3. The method of Claim 2 wherein the zeolite prepared is ZSM-5 and said reaction mixture has a composition in terms of mole ratios of oxides as follows: SiO2/Al203 = 5-1000 OH-/SiO2 = 10-'0-10-2 H20/SiO2 = 5-200 M/SiO2 = 0.01-3.0 R/SiO2 = 0.01-1.0 wherein R is a tetrapropylammonium cation and M is an alkali metal ion.

4. The method of Claim 2 wherein the zeolite prepared is ZSM-11 and said reaction mixture has a composition in terms of mole ratios of oxides as follows: SiO2/Al203 = 10-180 oH-/SiO2 = 10-1 10-2 H20/SiO2 = 5-100 M/SiO2 = 0.1-2.0 R/SiO2 = 0.04-1.0 wherein R is a tetrabutylammonium cation and M is an alkali metal ion.

5. The method of Claim 2 wherein the zeolite prepared is ZSM-12 and said reaction mixture has a composition in terms of mole ratios of oxides as follows: SiO2/Al203 -= 40-200 OH-/SiO2 = 10-10-10-2 H2O/SiO2 = 5-100 M/SiO2 = 0.1-3.0 R/SiO2 = 0.1-2.0 wherein R is a tetraethylammonium cation or a cation derived from triethylamine and M is an alkali metal ion.

6. The method of Claim 2 wherein the zeolite prepared is ZSM-23 and said reaction mixture has a composition in terms of mole ratios of oxides as follows: SiO2/A1203 = 10-200 OH-/SiO2 = 10-10-10-2 H2O/SiO2 = 5-100 M/SiO2 = 0.1-2.0 R/SiO2 = 0.1-1.0 wherein R is a cation derived from pyrrolidine and M is an alkali metal ion.

7. The method of Claim 2 wherein the zeolite prepared is ZSM-34 and said reaction mixture has a composition in terms of mole ratios of oxides as follows: SiO2/Al203 = 5-100 OH-/SiO2 = 10-10-10-2 H20/SiO2 = 5-100 M/SiO2 = 0.1-2.0 R/SiO2 = 0.1-1.0 wherein R is a cation derived from choline and M is an alkali metal ion.

8. The method of Claim 2 wherein the zeolite prepared is ZSM-35 and said reaction mixture has a composition in terms of mole ratios of oxides as follows: SiO2/Al203 = 8.8-200 OH-/SiO2 = 10-10-10-2 H20/SiO2 = 5-100 M/SiO2 - 0.1-3.0 R/SiO2 = 0.05-2.0 wherein R is a cation derived from ethylenediamine or pyrrolidine and M is an alkali metal ion.

9. The method of Claim 2 wherein the zeolite prepared is SZM-38 and said reaction mixture has a composition in terms of mole ratios of oxides as follows: SiO2/Al203 = 8.8-200 OH-/SiO2 = 10-10-10-2 H2O/SiO2 = 5-100 M/SiO2 = 0.1-3.0 R/SiO2 = 0.1-2.0 wherein R is a cation derived from a 2-(hydroxyalkyl) trialkylammonium compound, wherein alkyl is methyl, ethyl or a combination thereof, and M is an alkali metal ion.

10. The crystalline aluminosilicate zeolite resulting from the method of Claim 1.

11. The crystalline aluminosilicate zeolite resulting from the method of any one of the preceding claims.

12. A crystalline aluminosolicate zeolite comprising a zeolite of Claim 10 having its original cations replaced, at least in part, by ion exchange with a cation or a mixture of cations selected from the group consisting of hydrogen and hydrogen precursors and metals of Groups I through VIII of the Periodic Table of Elements.

13. A process of catalytically converting an organic compound charge which comprises contacting said charge under organic compound conversion conditions with a catalyst comprising a zeolite as defined in Claim 10 or 11 or a product of calcination thereof.

14. A method of synthesizing a crystalline aluminosilicate zeolite according to Claim 1 substantially as described herein.

15. A method of synthesizing a crystalline aluminosilicate zeolite substantially as described herein with reference to any one of Examples 2, 3, 4 and 8.

16. A crystalline aluminosilicate zeolite prepared by the method of Claim 13 or 14.

17. A process according to Claim 12 substantially as described herein.

18. A process of catalytically converting an organic compound charge substantially as described herein with reference to Example 7 or 8.