New Synthesis of Mo2C 14 nm in Average Size Supported on a High Specific Surface Area Carbon Material

Abstract

A molybdenum carbide supported on active carbon for catalytic hydrotreating was prepared by temperature-programmed reaction (TPR) in flowing H2of an active carbon impregnated by an heptamolybdate. TPR led at 973 K to the formation of supported Mo2C. This new method of preparation avoids the use of methane as carburizing reactant and allowsin situpreparation of supported molybdenum carbide without any contact of this pyrrophoric material with air between preparation and catalytic run. The various steps of the carburization process were studied by trapping the solid intermediates at different temperatures during TPR. Two successive reactions were evidenced: the partial reduction by H2of the initial molybdenum precursor to MoO2, and its subsequent carburization to Mo2C. This last step is mainly due to the reduction of MoO2and carburization with native methane evolved from the reaction of the carbon support with dihydrogen. Solid materials were characterized by elemental analysis, X-Ray diffraction, transmission electron microscopy and specific surface area measurements.