Silica-modified zeolite catalysts

Abstract

An improved method is provided for the production of silica-modified zeolite catalysts. Such catalysts are especially useful in a wide variety of processes including the conversion of methanol to gasoline, methanol to olefins, selective toluene disproportionation, toluene alkylation with methanol, the synthesis of p-ethyl toluene, lubricant hydro-dewaxing and the like. The catalysts formed in accordance with the present invention comprise crystalline aluminosilicate zeolites having a silica to alumina ratio of at least about 12, a constraint index, as hereinafter defined, within an approximate range of 1-12 and having contained within the interior crystalline structure thereof added amorphous silica in an amount of at least about 0.3% and preferably between about 0.5% and about 30 weight percent. The resultant catalyst is characterized by an n-hexane sorption capacity at a temperature of 90.degree. C. and an n-hexane partial pressure of 83 mm. of mercury which is at least 1 percent less than corresponding sorption capacity under identical conditions for the unmodified zeolite. Generally, the n-hexane sorption capacity for the described silica-modified zeolite, at the above specified conditions, is 5 to 60 percent less than that for the zeolite which has not undergone treatment to incorporate amorphous silica therein. The invention described herein also encompasses synthesis of the specified catalyst and use of the same in, for example, selectively converting lower monohydric alcohols and their ethers, especially methanol and dimethyl ether, to a hydrocarbon mixture rich in ethylene and propylene.

Dependencies are inferred from the claim text.