Role of sulfur in hydrotreating catalysis over nickel phosphide

The effect of using a mixture of 10 mol% H 2 S and H 2 to passivate a Ni 2 P/MCM-41 catalyst was studied. It was found that H 2 S passivation was superior to conventional O 2 passivation because it gave a higher HDS activity and required no post re-reduction. Chemisorption of CO indicated that the passivation layer covered or replaced the surface active sites. Characterization of X-ray photoelectron spectroscopy revealed that the sulfur species on the surface of the H 2 S-passivated Ni 2 P/MCM-41 were polysulfide ligands rather than S 2− or S 2− 2 and the sulfur species were partially oxidized. A treatment with NH 3 was also used, and it was found that N species were strongly bonded to the surface sites of Ni 2 P. Hydrodesulfurization and hydrodenitrogenation/hydrodeoxygenation were carried out in an alternating sequential manner to study the effect of surface sulfur on the catalytic activity of Ni 2 P/MCM-41. Sulfur analysis of the spent catalysts revealed that the HDS activity correlated with the sulfur content retained on Ni 2 P/MCM-41, indicating that sulfur is part of the active sites of the HDS reaction.