Development of highly active Co-Mo catalysts with phosphorus and citric acid for ultra-deep desulfurization of diesel fractions (Part 2) characterization of active sites

MO K-edge EXAFS, TEM and FT-IR of adsorbed NO were performed to further investigate the nature of the active sites on the CoMo/HY-Al2O3 catalyst containing citric acid and phosphorus, which had significantly higher HDS activity compared to the conventional CoMoP/Al2O3 catalyst. The results showed that the new catalyst has multiple layers of MoS2 slabs and the edges of MoS2 are mainly occupied by Co-Mo-S phases. XPS and FT-IR were used to investigate the sulfiding behavior of Co and Mo in the formation process of the active sites during sulfidation. The results showed that addition of citric acid to the impregnation solution postponed the sulfidation of Co at low temperatures, thereby increasing formation of the Co-Mo-S phase.