Patent ID: 7435335

Claim:
A multi-stage process for reducing the level of sulfur in a distillate feedstock having a sulfur content greater than about 3,000 wppm, the distillate feedstock containing polynuclear aromatics, which process comprises: a) reacting said feedstream in a first hydrodesulfurization stage in the presence of a hydrogen-containing treat gas comprised of i) the hydrogen-containing gas which is cascaded from the second hydrodesulfurization stage of d) below, and ii) a hydrogen-containing gas which is supplied from a source other than the present multi-stage process, said first hydrodesulfurization stage containing one or more reaction zones, each reaction zone operated at hydrodesulfurizing condition and in the presence of a hydrodesulfurization catalyst, thereby resulting in a liquid product stream having a sulfur content less than about 500 wppm; b) passing the liquid product stream to a separation zone wherein a hydrogen-containing product gas stream and a liquid phase product stream are produced; c) passing the liquid phase stream to a second hydrodesulfurization stage; d) reacting said liquid phase product stream in said second hydrodesulfurization stage in the presence of a hydrogen-containing treat gas, wherein the rate of introduction of the hydrogen portion of the treat gas in this second stage is less than or equal to 3 times the chemical hydrogen consumption in this second reaction stage, said second hydrodesulfurization stage containing one or more reaction zones operated at hydrodesulfurization conditions wherein each reaction zone contains a bed of hydrotreating catalyst, thereby resulting in a liquid product stream having less than about 100 wppm sulfur and having a weight ratio of aromatics to polynuclear aromatics of at least about 11; and e) passing the liquid product stream of step d) above to a second separation zone wherein a hydrogen-containing product gas stream and a liquid phase product stream are produced.