Three-stage hydrocracking process

Claim 1

A three-stage hydrocracking process adapted for maximizing the yield of naphtha, or of maximizing the yield of certain other distillate fractions from a feedstock containing hydrocarbons boiling at temperatures greater than about 360° F. (180° C.), comprising the steps of: (a) contacting said feedstock in a first hydroprocessing zone with a first hydroprocessing catalyst under conditions comprising a temperature of about 650°-850° F., a total pressure of about 1000-3000 psig, a hydrogen supply of about 500-2000 SCF per barrel of feedstock and a LHSV of 0.3-2.5, (b) fractionating the effluent from said first hydroprocessing zone in a fractionating zone into a first fraction consisting of naphtha and lower boiling components, a second fraction, the residuum, consisting of components having a normal boiling point greater than about 700° F., and a third fraction, the middle and heavy distillate, consisting of the remainder of the effluent of said first hydroprocessing zone, (c) contacting said second fraction in a second hydroprocessing zone with a hydrocracking catalyst under hydrocracking conditions comprising a temperature of about 600°-850° F., a total pressure of about 1000-3000 psig, a hydrogen supply of about 500-1500 SCF per barrel of feed and a total LHSV of about 0.8-3.0, (d) recycling the effluent of said second hydroprocessing zone to said fractionation zone, (e) contacting said third fraction in a third hydroprocessing zone with a zeolite-containing hydrocracking catalyst of higher cracking activity than the catalysts of said first and second hydroprocessing zones, under hydrocracking conditions comprising a temperature of about 550°-850° F., a total pressure of about 800-2500 psig and a hydrogen supply of about 300-1000 SCF per barrel of feedstock, and (f) recycling at least a portion of the effluent from said third hydroprocessing zone to said fractionation zone.