Patent ID: 9546331
Date: 2017-01-17
CPC Classifications: C10G

Claim:
1. A hydrocracking process providing for a reduction of the buildup of polycyclic aromatic hydrocarbons in a heavy oil recycle stream of said hydrocracking process, wherein the process comprises: (a) hydrocracking in a hydrocracker reactor a heavy feedstock to yield a hydrocracked product that is separated into at least two product streams including said heavy oil recycle stream, comprising a concentration of said polycyclic aromatic hydrocarbons; (b) passing a first portion of said heavy oil recycle stream as a recycle feed to said hydrocracker reactor; (c) passing a second portion of said heavy oil recycle stream to a vacuum distillation unit wherein said second portion is separated into at least a light vacuum gas oil stream, a heavier vacuum gas oil stream, a slop oil/wax stream and a vacuum resid stream, and wherein said light vacuum gas oil stream contains a concentration of polycyclic aromatic hydrocarbons greater than the concentration of polycyclic aromatic hydrocarbons in said heavier vacuum gas oil stream; (d) passing said heavier vacuum gas oil stream as a feed to said hydrocracker reactor; (e) using said light gas oil stream containing said higher concentration of polycyclic aromatic compounds as a bleed stream or a product stream that is not returned to said hydrocracking process; (f) passing the slop oil/wax stream and the vacuum resid stream to a solvent deasphalting unit wherein asphaltenes and heavy polycyclic aromatic hydrocarbons are separated from said streams to yield a deasphalted paraffinic oil depleted in polycyclic aromatic hydrocarbons; and (g) passing said deasphalted paraffinic oil depleted in polycyclic aromatic hydrocarbons as a feed to said hydrocracker reactor.