Facile ultra-deep desulfurization of gas oil through two-stage or -layer catalyst bed

Abstract

Ultra-deep hydrodesulfurization (HDS) was attempted to achieve the sulfur level less than 15 ppm S by staged and layered catalyst beds over commercially available catalysts. It was confirmed that two-stage and two-layer reaction schemes can attain the targeted sulfur level. Two-stage reaction with hydrogen refreshment between stages could provide the sulfur content lower than 15 ppm S over most of the catalysts examined in the present study where the first stage desulfurized the feed oil to be of 300–400 ppm S. Two-layer reaction, where two layers were connected directly without gas renewal, suffered severe inhibition of H 2S and NH 3. Nevertheless, NiMo sulfides on alumina support with sufficient acidity or zeolite achieved the sulfur level lower than 15 ppm S by two-layer scheme. Nitrogen species survived in the first layer reaction were found to strongly affect the extent of desulfurization in the subsequent second layer reaction.