Synthesis and Hydrodeoxygenation Activity of Carbon Supported Molybdenum Carbide and Oxycarbide Catalysts

Abstract

Carbothermal hydrogen reduction (CHR) of ammonium heptamolybdate impregnated activated charcoal (AC) yields a mixed Mo2C/MoOxCy catalyst. As the CHR temperature increases (from 600 to 800 °C) the Mo2C content increases. At 675 °C graphite networks are generated that attach to the β-Mo2C particles, and at ≥700 °C agglomeration and sintering occur, all of which decrease catalyst activity. An optimal CHR temperature of ∼650 °C is identified based on the catalyst activity for the hydrodeoxygenation (HDO) of 4-methylphenol (4-MP) at 350 °C and 4.3 MPa H2 and the high selectivity for direct deoxygenation (DDO: to yield toluene) versus hydrogenation (HYD: to yield cyclohexane). The Mo2C/MoOxCy catalysts have higher DDO selectivity than MoP, MoO2, or MoS2 when operated at similar conditions. The apparent activation energies for DDO (125 kJ/mol) and HYD (89 kJ/mol) are invariant among the catalysts with varying Mo2C content, but the rate per g Mo correlates with the CO uptake. The fact that the kinetics are not st...