Preparation, Surface and Catalytic Properties of Molybdenum Nitrides.

Unsupported and supported molybdenum nitrides are reviewed in the fields of preparation, structure, surface and catalytic properties. The molybdenum nitrides with large surface area were synthesized in a temperature-programmed reactions of MoO3 with NH3 or a N2/H2 mixture. Increased space velocities, reduced reactant particle sizes, and reduced heating rates led to molybdenum nitrides with greater surface area by formation of a MoOxN1-x intermediate. The structure and composition of the molybdenum nitrides and preferential adsorption of N2, H2, and CO are reported. Molybdenum nitrides are effective and active in ammonia synthesis and its decomposition, hydrogenolysis and hydrogenation of aromatics, especially in hydrodenitrogenation, in which molybdenum nitrides, as catalysts, were compatible with sulfided Ni-Mo and Co-Mo catalysts. The nitride catalysts were found significantly active for the direct removal of sulfur from dibenzothiophene, in the hydrodesulfurization of dibenzothiophene. The behavior of adsorbed N2 and NH3 on the Mo catalyst are discussed together with temperature-programmed desorption and reactions. The scheme for transformation of MoO3 to Mo2N via MoO2 was investigated. Active sites on the molybdenum nitrides for HDN are also discussed.