Hydrocracking processes yielding a hydroisomerized product for lube base stocks

A process for preparing a lube base stock, the process comprising

• (a) hydrocracking, in a hydrocracking zone containing a hydrocracking catalyst, a heavy hydrocarbon feedstock comprising vacuum gas oil and a recycled portion of an unconverted oil to obtain a hydrocracker effluent comprising at least about 55% by weight of hydrocarbons boiling at a temperature of less than 382° C. (720° F.);
• (b) passing at least a portion of the hydrocracker effluent to a flash separator to obtain, (i) as a liquid bottoms product, an unconverted oil having a pour point of at most about 18° C. (65° F.), and (ii) a vapor overhead product;
• (c) recycling the recycled portion of the unconverted oil to the hydrocracking zone;
• and
• (d) hydrofinishing a non-recycled portion of the unconverted oil to reduce the content of unsaturated hydrocarbons in the non-recycled portion and provide the lube base stock;
• wherein the hydrocracking catalyst comprises a metal selected from the group consisting of nickel, cobalt, tungsten, molybdenum, and mixtures thereof, deposited on a zeolite selected from the group consisting of a Y zeolite, a beta zeolite, and an MFI zeolite.