The reactivity and stability of mixed-sulfide structures in unsupported MoS 2-based hydrodesulfurization catalysts promoted by group VIII metals

Abstract

Unsupported CoMo, NiMo and FeMo catalysts have been prepared by the homogeneous sulfide precipitation method and the coprecipitation method. The presence of a group VIII metal (Me) causes a decrease in the reactivity with O 2 and an increase in the reducibility in H 2. These effects are correlated with the increase in the catalytic activity. The stability of cobalt and iron sulfide species in CoMo and FeMo catalysts was studied by Mössbauer spectroscopy. A significant amount of MeMoS structure remains stable after strong reducing treatment. Catalysts contain also sulfur-rich group VIII metal sulfide species which appear stabilized by MoS 2. The role of these species in promoting HDS activity is evaluated.