Ki-Hyouk Choi

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 15xa0ppmxa0S 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 15xa0ppmxa0S over most of the catalysts examined in the present study where the first stage desulfurized the feed oil to be of 300–400xa0ppmxa0S. Two-layer reaction, where two layers were connected directly without gas renewal, suffered severe inhibition of H 2 S and NH 3 . Nevertheless, NiMo sulfides on alumina support with sufficient acidity or zeolite achieved the sulfur level lower than 15xa0ppmxa0S 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.

Properties of adsorbed oxygen on Au/SiO2

Abstract Oxygen adsorption on silica-supported gold catalyst from NO 2 and O 2 exposures were investigated by temperature-programmed desorption spectroscopy under a vacuum condition. NO 2 and O 2 exposures of the surface of the catalyst at room temperature gave adsorbed oxygen in atomic state. Adsorbed oxygen penetrated beneath the gold with lower activation energy for NO 2 exposure than for O 2 exposure. Adsorbed oxygen in oxidic state which was desorbed above 600xa0K altered the surface properties of gold and resulted in the decrease of activation energy for oxygen to penetrate beneath the gold surface.