Patent ID: 8343334

Claim:
A method of hydrocracking an oil feedstock to produce a light oil stream without build-up of heavy polynuclear aromatic (HPNA) hydrocarbons in the recycle stream, the method comprising the steps of: a. hydrocracking the oil feedstock with a first stage hydrocracking catalyst possessing hydrotreating and hydrocracking functionality in a first reactor to produce an effluent stream; b. fractionating the effluent stream into first, second and third product streams ( 21 , 22 , 23 ), wherein the first product stream comprises C 1 -C 4 , naphtha, and diesel boiling in the range of 36-370° C., the second product stream comprises hydrocarbon components having an initial nominal boiling point of 370° C. and a final boiling point ranging from 420-480° C., and the third product stream comprises HPNA hydrocarbons and other hydrocarbons boiling above 420° C. to 480° C., depending upon the final boiling point of the second product stream; c. cracking the second product stream in a second reactor; and d. cracking the third product stream in a third reactor; wherein the third reactor operates at a higher operational pressure than the second reactor.