Migration and diffusion of molybdenum catalyst during CO/steam coal hydrogenation

Abstract

CO/steam hydrogenation of an Australian high volatile bituminous coal was carried out at 350–400 °C with molybdenum as catalyst. In most experiments, molybdenum trioxide was mechanically mixed with coal, although impregnation of the coal with a solution of ammonium paramolybdate was also investigated. Naphthalene was used as a vehicle. Microscopic examination of the hydrogenation residues indicated that the molybdenum had migrated towards the coal surface at the early stages of CO/steam hydrogenation. It is thought that molybdenum carbonyl formation is the most likely pathway for molybdenum migration and diffusion. The physical distribution and quantity of catalyst had little influence on conversion yields, as would be expected if only a small proportion of the molybdenum is in highly mobile catalytic form. By itself, molybdenum hexacarbonyl was found to be an excellent CO/steam hydrogenation catalyst.