Production of high viscosity index lubricating oil stock

Claim 1

A process for catalytically dewaxing a waxy hydrocarbon fraction boiling within the approximate range of 450° to 1050° F. to provide a lubricating oil of high viscosity index which comprises contacting said fraction at a temperature between about 500° and about 675° F., a pressure between about 100 and about 3000 psig at a liquid hourly space velocity between about 0.1 and about 10 with a catalyst comprising two different types of crystalline aluminosilicate zeolites, one type which possesses particularly characterized pore openings defined by (1) a ratio of sorption of n-hexane to o-xylene, on a volume percent basis, of greater than 3, which sorption is determined at a P/P o of 0.1 and at a temperature of 50° C. for n-hexane and 80° C. for o-xylene and (2) by the ability of selectively cracking 3-methylpentane in preference to 2,3-dimethylbutane at 1000° F. and 1 atmosphere pressure from a 1/1/1 weight ratio mixture of n-hexane/3-methylpentane/2,3-dimethylbutane mixture with the ratio of rate constants k 3MP /k DMB being in excess of about 2 and the other type selected from the group consisting of ZSM-5 and ZSM-11 and mixtures thereof and recovering a dewaxed oil product.