AMS-1B crystalline borosilicate molecular sieve-based catalyst compositions and process for toluene alkylation

Molecular sieve abstract

Described are catalyst compositions comprising a HAMS-1B crystalline borosilicate molecular sieve incorporated into an inorganic matrix, which have been impregnated with a magnesium compound or with both a phosphorus compound and a magnesium compound, said impregnated compositions having improved para-selectively for toluene alkylation. Such impregnated compositions, when used for the alkylation of toluene using methanol, methylether, ethylene, or propylene yield dialkylbenzene products containing a higher proportion of the para-isomer than corresponding unimpregnated borosilicate-based compositions. When toluene is alkylated with propylene using the impregnated catalyst compositions of this invention, a significant increase in para-selectivity among the cymene isomers is obtained at high total-cymene/n-propyltoluene ratios.

Molecular sieve claims

What is claimed is:

1. A process for making ethyltoluene by reacting ethylene with toluene in the presence of a catalyst composition comprising a HAMS-1B crystalline borosilicate molecular sieve incorporated into an inorganic matrix, said composition (1) impregnated by a magnesium compound and subsequently heated to substantially convert said compound to the oxide form and (2) containing between about 4 and about 25% by weight magnesium.

2. A process for making ethyltoluene by reacting ethylene with toluene in the presence of a catalyst composition comprising a HAMS-1B crystalline borosilicate molecular sieve incorporated into an inorganic matrix, said composition (1) impregnated by a phosphorus compound and a magnesium compound and subsequently heated to substantially convert said compounds to the oxide forms and (2) containing between about 0.5 and about 25% by weight phosphorus and about 4 and about 25% by weight magnesium.

3. The process of claim 1 wherein said HAMS-1B molecular sieve comprises from about 20 to about 80 wt. % incorporated into an alumina, silica, or silica-alumina matrix.

4. The process of claim 2 wherein said HAMS-1B molecular sieve comprises from about 20 to about 80 wt. % incorporated into an alumina, silica, or silica-alumina matrix.

5. A process for making isopropyltoluenes by reacting propylene with toluene in the presence of a catalyst composition comprising a HAMS-1B crystalline borosilicate molecular sieve incoporated into an inorganic matrix, said composition (1) impregnated by a magnesium compound and subsequently heated to substantially convert said compound to the oxide form and (2) containing between about 4 and about 25% by weight magnesium.

6. A process for making isopropyltoluenes by reacting propylene with toluene in the presence of a catalyst composition comprising a HAMS-1B crystalline borosilicate molecular sieve incorporated into an inorganic matrix, said composition (1) impregnated by a phosphorus compound and a magnesium compound and subsequently heated to substantially convert said compounds to the oxide forms and (2) containing between about 0.5 and about 25% by weight phosphorus and about 4 and about 25% by weight magnesium.

7. The process of claim 5 wherein said HAMS-1B molecular sieve comprises from about 20 to about 80 wt. % incorporated into an alumina, silica, or silica-alumina matrix.

8. The process of claim 6 wherein said HAMS-1B molecular sieve comprises from about 20 to about 80 wt. % incorporated into an alumina, silica, or silica-alumina matrix.

9. The process of claim 5 wherein para-cymene is made selectively.

10. The process of claim 6 wherein para-cymene is made selectively.

11. The process of claim 7 wherein para-cymene is made selectively.

12. The process of claim 8 wherein para-cymene is made selectively.

Molecular sieve description

BACKGROUND OF THE INVENTION

This invention relates to improved AMS-1B crystalline molecular sieve-based catalyst compositions, and particularly, to the use of such compositions having improved para selectivity for aromatics alkylation. More particularly, it relates to processes for using these improved compositions to selectively para-propylate toluene to paracymene.

In U.S. Pat. No. 4532226 a ZSM-5 aluminosilicate zeolite catalyst modified by P and Cr, Mo, or W and used to selectively catalyze formation of the 14-dialkyl isomer during conversion of aromatic compounds is described. U.S. Pat. No. 4518703 teaches a P modified silica polymorph-based catalyst for the methylation of toluene. In U.S. Pat. Nos. 4504690 4128592 and 4086287 is taught modifying a ZSM-5 aluminosilicate zeolite catalyst with P, Mg or P/Mg oxides to obtain high proportions of the 14-dialkyl isomer. Phosphorus modification of a ZSM-5 zeolite catalyst for the alkylation of toluene to form a higher proportion of p-xylene is shown in J. Appl. Polymer Sci. 36 209 (1981) as are P or Mg modified ZSM-5 zeolite catalysts for the disproportionation of toluene. Selective para-alkylation using P modified ZSM-5 zeolite catalysts is again described in J. Cat. 67 159 (1981). Conversion of olefins over the same type of catalyst is shown in J. Cat. 61 155 (1980). Disproportionation of toluene to produce benzene over P, Mg modified crystalline aluminosilicate zeolite catalysts is described in U.S. Pat. No. 4137195. Alkylation or disproportionation of certain monosubstituted benzene compounds to achieve nearly 100% selectivity to paradisubstituted derivates over phosphorous and magnesium compound-modified ZSM-5 type zeolite catalysts is reported in J. Am. Chem. Soc. 101 6783 (1979).

Propylation of toluene with the selective production of cymenes (higher iso/normal ratio) over an unmodified ZSM-5 aluminosilicate of zeolite catalyst is described in U.S. Pat. No. 4049737.

Use of Mg alone or in combination with P to modify a ZSM-5 aluminosilicate of zeolite catalyst is described in U.S. Pat. No. 4049573 and the modified catalyst is used for converting alcohols and ethers to hydrocarbons. Again, Mg is used to modify ZSM-5 zeolite catalysts in U.S. Pat. No. 4002698 which can be used for selective production of p-xylene from charge stocks of toluene and a C.sub.3 -C.sub.10 olefin; P modified catalysts for the methylation of toluene are also described. Phosphorus modified ZSM-5 aluminosilicate zeolite catalysts are again described in U.S. Pat. No. 3972832 and described as useful for the conversion of aliphatics to various products.

Catalyst compositions, generally useful for hydrocarbon conversion, based upon AMS-1B crystalline borosilicate molecular sieve have been described in U.S. Pat. Nos. 4268420; 4269813; 4285919 and Published European Application No. 68796.

As described in the references in the paragraph above, catalyst compositions typically are formed by incorporating an AMS-1B crystalline borosilicate molecular sieve material into a matrix such as alumina, silica or silica-alumina to produce a catalyst formulation. In one method of making AMS-1B crystalline borosilicate, sieve is formed by crystallizing sources for silicon oxide and boron oxide with sodium hydroxide and an organic compound. After crystallization, the resulting sodium form is ion exchanged with an ammonium compound and calcined to yield the hydrogen form of AMS-1B. In another and more preferred method, AMS-1B crystalline borosilicate is crystallized in the hydrogen form from a mixture containing a diamine in place of a metal hydroxide. This method tends to reduce the amount of alkali metal ion, e.g. Na+, in the final catalyst composition. AMS-1B borosilicates in hydrogen form are designated HAMS-1B. Typically, the hydrogen form sieve is gelled with an alumina sol, dried and calcined to yield a catalyst composition.

SUMMARY OF THE INVENTION

Described herein are improved catalyst compositions comprising a HAMS-1B crystalline borosilicate molecular sieve incorporated into a matrix, which have been impregnated with a small amount of a suitable magnesium compound or a small amount of both a suitable phosphorus compound and a suitable magnesium compound, said impregnated compositions showing improved para-selectivity for toluene alkylation. Also described are processes for the alkylation of toluene carried out by contacting such impregnated catalyst compositions and methyl alcohol, dimethyl ether, ethylene or propylene under conversion conditions, which yield dialkylbenzene products containing a higher proportion of the para isomer as compared with unimpregnated borosilicate-based compositions. In particular, when toluene is alkylated with propylene using these impregnated catalyst compositions, a significant increase in para selectivity among the cymene isomers is obtained at high cymene/n-propyltoluene ratios.

DETAILED DESCRIPTION OF THE INVENTION

The AMS-1B borosilicate molecular sieve useful in this invention can be prepared by crystallizing an aqueous mixture, at a controlled pH, of sources for cations, an oxide of boron, an oxide of silicon, and an organic template compound.

wherein R is an organic compound and M is at least one cation having the oxidation state n, such as an alkali or an alkaline earth metal cation or hydrogen. By regulation of the quantity of boron (represented as B.sub.2 O.sub.3) in the reaction mixture, it is possible to vary the SiO/B.sub.2 O.sub.3 molar ratio in the final product.

More specifically, the material useful in the present invention is prepared by mixing a base, a boron oxide source, and an organic template compound in water (preferably distilled or deionized). The order of addition usually is not critical although a typical procedure is to dissolve base and boric acid in water and then add the template compound. Generally, the silicon oxide compound is added with intensive mixing such as that performed in a Waring Blendor and the resulting slurry is transferred to a closed crystallization vessel for a suitable time. After crystallization, the resulting crystalline product can be filtered, washed with water, dried, and calcined.

During preparation, acidic conditions should be avoided. When alkali metal hydroxides are used, the values of the ratio of OH.sup.- /SiO.sub.2 shown above should furnish a pH of the system that broadly falls within the range of about 9 to about 13.5. Advantageously, the pH of the reaction system falls within the range of about 10.5 to about 11.5 and most preferably between about 10.8 and about 11.2.

Examples of materials affording silicon oxide useful in this invention include silicic acid, sodium silicate, tetraalkyl silicates and Ludox, a stabilized polymer of silicic acid manufactured by E. I. DuPont de Nemours & Co. Typically, the oxide of boron source is boric acid although equivalent species can be used such as sodium borate and other boron-containing compounds.

Cations useful in formation of AMS-1B crystalline borosilicate include alkali metal and alkaline earth metal cations such as sodium, potassium, lithium, calcium and magnesium. Ammonium cations may be used alone or in conjunction with such metal cations. Since basic conditions are required for crystallization of the molecular sieve of this invention, the source of such cation usually is a hydroxide such as sodium hydroxide. Alternatively, AMS-1B can be prepared directly and more preferably by the hydrogen form by replacing such metal cation hydroxides with an organic base such as ethylenediamine as described in Published European Application No. 68796.

Organic templates useful in preparing AMS-1B crystalline borosilicate include alkylammonium cations or precursors thereof such as tetraalkylammonium compounds, especially tetra-n-propylammonium compounds. A useful organic template is tetra-n-propylammonium bromide. Diamines, such as hexamethylenediamine, can be used.

In a more detailed description of a typical preparation of this invention, suitable quantities of sodium hydroxide and boric acid (H.sub.3 BO.sub.3) are dissolved in distilled or deionized water followed by addition of the organic template. The pH may be adjusted between about 11.0.+-.0.2 using a compatible acid or base such as sodium bisulfate or sodium hydroxide. After sufficient quantities of a silica source such as a silicic acid polymer (Ludox) are added with intensive mixing, preferably the pH is again checked and adjusted to a range of about 11.0.+-.0.2.

Alternatively and more preferably, AMS-1B crystalline borosilicate molecular sieve can be prepared by crystallizing a mixture of sources for an oxide of silicon, an oxide of boron, an alkyl ammonium compound and ethylenediamine such that the initial reactant molar ratios of water to silica range from about 5 to about 25 preferably about 5 to about 20 and most preferably from about 10 to about 15. In addition, preferable molar ratios for initial reactant silica to oxide of boron range from about 4 to about 150 more preferably from about 5 to about 80 and most preferably from about 5 to about 20. The molar ratio of ethylenediamine to silicon oxide should be above about 0.05 typically below 5 preferably between about 0.1 and about 1.0 and most preferably between about 0.2 and 0.5. The molar ratio of alkylammonium compound, such as tetra-n-propylammonium bromide, to silicon oxide can range from 0 to about 1 or above, typically above about 0.005 preferably about 0.01 to about 0.1 more preferably about 0.01 to about 0.1 and most preferably about 0.02 to about 0.05.

The resulting slurry is transferred to a closed crystallization vessel and reacted usually at a pressure at least the vapor pressure of water for a time sufficient to permit crystallization which usually is about 0.25 to about 20 days, typically is about one to about ten days and preferably is about one to about seven days, at a temperature ranging from about 100.degree. C. to about 250.degree. C., preferably about 125.degree. C. to about 200.degree. C. The crystallizing material can be stirred or agitated as in a rocker bomb. Preferably, the crystallization temperature is maintained below the decomposition temperature of the organic template compound. Especially preferred conditions are crystallizing at about 165.degree. C. for about five to about seven days. Samples of material can be removed during crystallization to check the degree of crystallization and determine the optimum crystallization time.

The crystalline material formed can be separated and recovered by well-known means such as filtration with aqueous washing. This material can be mildly dried for anywhere from a few hours to a few days at varying temperatures, typically about 50.degree.-225.degree. C., to form a dry cake which can then be crushed to a powder or to small particles and extruded, pelletized, or made into forms suitable for its intended use. Typically, materials prepared after mild drying contain the organic template compound and water of hydration within the solid mass and a subsequent activation or calcination procedure is necessary, if it is desired to remove this material from the final product. Typically, mildly dried product is calcined at temperatures ranging from about 260.degree. C. to about 850.degree. C. and preferably from about 425.degree. C. to about 600.degree. C. Extreme calcination temperatures or prolonged crystallization times may prove detrimental to the crystal structure or may totally destroy it. Generally, there is no need to raise the calcination temperature beyond about 600.degree. C. in order to remove organic material from the originally formed crystalline material. Typically, the molecular sieve material is dried in a forced draft oven at 165.degree. C. for about 16 hours and is then calcined in air in a manner such that the temperature rise does not exceed 125.degree. C. per hour until a temperature of about 540.degree. C. is reached. Calcination at this temperature usually is continued for about 4 to 16 hours.

A catalytically active material can be placed onto the borosilicate structure, either before or after incorporation into a matrix, by ion exchange, impregnation, a combination thereof, or other suitable contact means. Before placing a catalytically active metal ion or compound on the borosilicate structure, the borosilicate should be in the hydrogen form, i.e., HAMS-1B If the sieve was prepared using a metal hydroxide, such as sodium hydroxide, the hydrogen form typically, is produced by exchange one or more times with ammonium ion, typically using ammonium acetate, followed by drying and calcination as described above.

The original cation in the AMS-1B crystalline borosilicate can be replaced all or in part by ion exchange with other cations including other metal ions and their amine complexes, alkylammonium ions, ammonium ions, hydrogen ions, and mixtures thereof. Preferred replacing cations are those which render the crystalline borosilicate catalytically active, especially for hydrocarbon conversion. Typical catalytically active ions include hydrogen, metal ions of Groups IB, IIA, IIB, IIIA, VB, VIB and VIII, and of manganese, vanadium, chromium, uranium, and rare earth elements.

Also, water soluble salts of catalytically active materials can be impregnated onto the crystalline borosilicate of this invention. Such catalytically active materials include metals of Groups IB, IIA, IIB, IIIA, IIIB, IVB, VB, VIB, VIIB, and VIII, and rare earth elements.

Examples of catalytically active elements include ruthenium, rhodium, iron, cobalt, and nickel. Mixtures of elements can be used. Other catalytic materials include ions and compounds of aluminum, lanthanum, molybdenum, tungsten, and noble metals such as ruthenium, osmium, rhodium, iridium, palladium, and platinum. Other additional catalytic materials can be ions and compounds of scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, cerium, manganese, cobalt, iron, zinc and cadmium. Specific combinations of non-noble metals of Group VIII and other catalytic materials include ions or compounds of nickel and osmium, nickel and lanthanum, nickel and palladium, nickel and iridium, nickel and molybdenum, and nickel and tungsten.

Ion exchange and impregnation techniques are wellknown in the art. Typically, an aqueous solution of a cationic species is exchanged one or more times at about 25.degree. C. to about 100.degree. C. A hydrocarbon-soluble metal compound such as a metal carbonyl also can be used to place a catalytically active material. Impregnation of a catalytically active compound on the borosilicate or on a composition comprising the crystalline borosilicate suspended in and distributed throughout a matrix of a support material, such as a porous refractory inorganic oxide such as alumina, often results in a suitable catalytic composition. A combination of ion exchange and impregnation can be used. Presence of sodium ion in a composition usually is detrimental to catalytic activity.

The amount of catalytically active material placed on the AMS-1B borosilicate can vary from about 0.01 weight percent to about 30 weight percent, typically from about 0.05 to about 25 weight percent, depending on the process use intended. The optimum amount can be determined easily by routine experimentation.

The AMS-1B crystalline borosilicate useful in this invention is admixed with or incorporated within various binders or matrix materials depending upon the intended process use. The crystalline borosilicate can be combined with active or inactive materials, synthetic or naturally-occurring zeolites, as well as inorganic or organic materials which would be useful for binding the borosilicate. Well-known materials include silica, silica-alumina, alumina, magnesia, titania, zirconia, alumina sols, hydrated aluminas, clays such as bentonite or kaolin, or other binders well-known in the art. Typically, the borosilicate is incorporated within a matrix material by blending with a sol of the matrix material and gelling the resulting mixture. Also, solid particles of the borosilicate and matrix material can be physically admixed. Typically, such borosilicate compositions can be pelletized or extruded into useful shapes. The crystalline borosilicate content can vary anywhere from a few up to 100 wt. % of the total composition. Catalytic compositions can contain about 0.1 wt. % to about 100 wt. % crystalline borosilicate material and preferably contain about 10 wt. % to about 95 wt. % of such material and most preferably contain about 20 wt. % to about 80 wt. % of such material.

Catalyst compositions impregnated with a magnesium compound and a phosphorus compound or a magnesium compound according to this invention can be in powder form or already in extrudate or pellet form.

To make the impregnated catalyst compositions of this invention, a composition comprising the acid form of the crystalline borosilicate, HAMS-1B, molecular sieve in an inorganic matrix is contacted with a phosphorus compound-containing solution. The resulting mass is then dried at temperatures up to about 150.degree. C. removing in this step essentially all of the impregnation solvent. The resultant composition is then activated by calcination for 3 hours to about 24 hours at about 350.degree. C. to about 650.degree. C., more preferably about 4 hours to about 24 hours at about 400.degree. C. to about 600.degree. C. Care should be taken to avoid catalyst degration during calcination.

The amount of phosphorus incorporated with the catalyst composition should be from about 0.5 to about 25 percent by weight, especially from about 1 to about 15 percent by weight, percents calculated as percent of the element.

Representative phosphorus compounds useful in the impregnation step include derivatives of groups represented by the formulae PX.sub.3 RPX.sub.2 R.sub.2 PX, R.sub.3 P, X.sub.3 PO, (XO.sub.3)PO, (XO).sub.3 P, R.sub.3 P.dbd.O, R.sub.3 P.dbd.S, RPO.sub.2 PPS.sub.2 RP(O)(OX).sub.2 RP(S)(SX).sub.3 R.sub.2 P(O)OX, R.sub.2 P(S)SX, RP(OX).sub.2 RP(SX).sub.2 ROP(OX).sub.2 O, RSP(SX).sub.2 (RS).sub.2 PSP(SR).sub.2 and (RO).sub.2 POP(OR).sub.2 wherein R is alkyl or aryl and X is hydrogen, alkyl, aryl or halide. These compounds include primary, secondary or tertiary phosphines; tertiary phosphine oxides; tertiary phosphine sulfides; primary and secondary phosphonic acids and their corresponding sulfur derivatives; esters of phosphonic acids; the dialkyl alkyl phosphonates; alkyl dialkyl phosphonates; phosphinous acids, primary, second and tertiary phosphites and esters thereof; alkyl dialkylphosphinites, dialkyl alkylphosphonites their esters and sulfur derivatives.

Other suitable phosphorus-containing compounds include the phosphorus halides such as phosphorus trichloride, phosphorus tribromide, phosphorus triiodide, alkyl phosphorodichlorides, dialkyl phosphorochlorides and dialkyl phosphonochloridites. Preferred phosphorus-containing compounds include phosphoric acid, phosphite esters such as triethylphosphite, ammonium hydrogen phosphate and ammonium dihydrogen phosphate.

Magnesium compounds can be incorporated with the catalyst compositions in a manner similar to that employed with the phosphorus compounds above. Magnesium impregnation should result in about 4% to 25% by weight magnesium, preferably from about 8% to about 15% by weight magnesium, percents calculated as the element. As with phosphorus, magnesium compound incorporation is effected by contacting the catalyst composition with the solution of an appropriate magnesium compound followed by drying and calcining to substantially convert impregnated magnesium compound to its oxide form. Preferred magnesium-containing compounds include most soluble magnesium salts, more preferably magnesium nitrate or acetate. Drying and calcination times and temperatures are generally the same as recited hereinbefore for drying and calcination of phosphorus-containing catalyst compositions.

The solutions of phosphorus or magnesium compounds used in impregnation may be made from polar or non-polar solvents, including water and organic solvents generally. Solvents that are destructive of either the zeolite or matrix should be avoided. Water and alcohols are preferred solvents.

Generally, the phosphorus compound and the magnesium compound are impregnated in the catalyst composition sequentially with phosphorus impregnation preceding magnesium impregnation.

Methylation of toluene in the presence of the above-described catalyst compositions is effected by contact of the toluene with a methylating agent, preferably methanol or dimethyl ether, at a temperature between about 250.degree. C. and about 700.degree. C. and preferably between about 400.degree. C. and about 600.degree. C. The reaction generally takes place at atmospheric pressure, but the pressure may be within the approximate range of about 1 atmosphere to about 2000 psig. The molar ratio of methylating agent to toluene is generally between about 0.05 and about 5 preferably about 0.1 to about 1. When methanol is employed as the methylating agent a suitable molar ratio of methanol to toluene has been found to be approximately about 0.1-2 moles of methanol per mol of toluene. With the use of other methylating agents, such as acetaldehyde, dimethoxyethane, acetone, and methyl halides, the molar ratio of methylating agent to toluene may vary within the aforenoted range.

Reaction is suitably accomplished utilizing a weight hourly space velocity of between about 0.2 and about 500 and preferably between about 1 and about 100. The reaction product consisting predominantly of para-xylene or a mixture of para- and meta-xylene together with comparatively smaller amounts of ortho-xylene may be separated by any suitable means, such as by passing the same through a fractional crystallization process coupled with distillation.

In effecting the catalyzed alkylation of toluene with ethylene, conversion conditions include a temperature between about 250.degree. C. and about 600.degree. C., pressure between about 1 atmosphere and about 2000 psig, utilizing a feed weight hourly space velocity between about 0.1 and about 100 and a molar feed ratio of toluene/ethylene between about 0.5 and about 50 preferably between about 1 and about 10.

Propylation of toluene in the presence of the above-described catalyst compositions is effected by contact of the toluene with propylene at a temperature between about 200.degree. C. and about 600.degree. C. and preferably between about 250.degree. C. and about 400.degree. C. The reaction generally takes place at atmospheric pressure, but the pressure may be within the approximate range of about 1 atmosphere to about 2000 psig. The molar ratio of toluene to propylene employed is within the approximate range of about 0.5 to about 50. Reaction is suitably accomplished utilizing a weight hourly space velocity of between about 0.1 and about 100 and preferably between about 0.5 and about 50. The reaction product consisting selectively of paracymene with comparatively smaller amounts of n-propyltoluenes may be separated by any suitable means.