New synthesis of Mo2C 14 nm in average size supported on a high specific surface area carbon material

A molybdenum carbide supported on active carbon for catalytic hydrotreating was prepared by temperature-programmed reaction (TPR) in flowing H-2 of an active carbon impregnated by an heptamolybdate, TPR led at 973 K to the fo rmation of supported Mo2C. This new method of preparation avoids the use of methane as carburizing reactant and allows in situ preparation of supporte d molybdenum carbide without any contact of this pyrrophoric material with air between preparation and catalytic run. The various steps of the carburi zation process were studied by trapping the solid intermediates at differen t temperatures during TPR, Two successive reactions were evidenced: the par tial reduction by H-2 of the initial molybdenum precursor to MoO2, and its subsequent carburization to Mo2C. This last step is mainly due to the reduc tion of MoO2 and carburization with native methane evolved from the reactio n of the carbon support with dihydrogen, Solid materials were characterized by elemental analysis, X-Ray diffraction, transmission electron microscopy and specific surface area measurements. (C) 1998 Academic Press.