Process for maximum middle distillate production with minimum hydrogen consumption.

摘要

A process for the conversion of an aromatic-rich, distillable gas oil charge stock to selectively produce large quantities of high quality middle distillate while minimizing hydrogen consumption which process comprises the steps of reacting the charge stock with hydrogen, in a catalytic hydrocracking reaction zone, at hydrocracking conditions including a maximum catalyst bed temperature in the range of 315 to 454oC selected to convert at least a portion of the charge stock to middle distillate and to convert at least about 10 volume percent of the aromatic hydrocarbon compounds contained in the charge stock to paraffin hydrocarbons; separating a hydrocracking zone effluent to provide a middle distillate product stream and a paraffin-rich hydrocarbonaceous stream boiling at a temperature greater than 371oC; recovering the middle distillate product stream; reacting the paraffin-rich hydrocarbonaceous stream in a non-catalytic thermal reaction zone at mild thermal cracking conditions including an elevated temperature from 371 to 526oC, a pressure from 207 to 6895 kPa gage and an equivalent residence time at 482oC from about 1 to about 60 seconds to provide a non-catalytic thermal reaction zone effluent; and separating the thermal reaction zone effluent to provide a middle distillate fraction boiling in the range from 149 to 371oC and a heavy fraction boiling at a temperature greater than 370oC wherein the middle distillate fraction recovered from the thermal step can be either recycled to the hydrocracking step or blended with the middle distillate product stream to increase the yield thereof and wherein the heavy fraction recovered from the thermal step is an excellent charge stock for an FCC unit.