THIOPHENE HYDRODESULFURIZATION OVER ALUMINA-SUPPORTED MOLYBDENUM CARBIDE AND NITRIDE CATALYSTS - EFFECT OF MO LOADING AND PHASE

Alumina-supported beta-Mo2C, alpha-MoC(1-x) (x approximate to 0.5) and gamma-Mo2N catalysts with Mo loadings in the range 1.5-20 wt% have be en synthesized and characterized by X-ray diffraction and pulsed chemi sorption (CO and O-2) measurements. Thiophene hydrodesulfurization (HD S) activities were measured for the alumina-supported Mo carbide and n itride catalysts as well as sulfided Mo/Al2O3 catalysts with the same Mo loadings. The HDS activities of the catalysts after 24 h at 693 K w ere observed to increase according to the trend: sulfided Mo approxima te to alpha-MoC(1-x) < gamma-Mo2N < beta-Mo2C. The HDS activities of t he different catalysts were found to correlate in a linear fashion wit h their CO and O-2 chemisorption capacities for the wide range of Mo l oadings investigated. Thiophene HDS turnover frequencies for the Mo ca rbide, nitride, and sulfided Mo catalysts are nearly identical, provid ing further evidence that the higher HDS activity of alumina-supported beta-Mo2C and gamma-Mo2N catalysts stems from a higher density of act ive sites. (C) 1997 Academic Press.