Role of sulfur in hydrotreating catalysis over nickel phosphide

The effect of using a mixture of 10 mol% H2S and H-2 to passivate a Ni2P/MCM-41 catalyst was studied. It was found that H2S 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 H2S-passivated Ni2P/MCM-41 were polysulfide ligands rather than S2- or S2- and the sulfur species were partially oxidized. A treatment with NH3 was also used, and it was found that N species were strongly bonded to the surface sites of Ni2P. Hydrodesulfurization and hydrodenitrogenation/hydrodeoxygenation were carried out in an alternating sequential manner to study the effect of surface sulfur on the catalytic activity of Ni2P/MCM-41. Sulfur analysis of the spent catalysts revealed that the HDS activity correlated with the sulfur content retained on Ni2P/MCM-41. indicating that sulfur is part of the active sites of the HDS reaction. (C) 2008 Elsevier Inc. All rights reserved.