Graphitic mesoporous carbon-supported molybdenum carbides for catalytic hydrogenation of carbon monoxide to mixed alcohols

Molybdenum carbide (β-Mo₂C) nanoparticles were synthesized in situ on a soft-templated graphitic mesoporous carbon (GMC) and other commercial carbon materials (activated charcoal and carbon black) by carbothermal hydrogen reduction (i.e., carbon supports as carburizing agents). The catalytic activity of these carbon-supported and bulk carbides for carbon monoxide (CO) hydrogenation to mixed alcohols (mainly C₁-C ₃) was investigated at 573 K and 3.0 MPa, showing that their areal specific rates for CO conversion increase with decreasing the carbide particle size, independent of the supports. GMC appears to be a preferable support of β-Mo₂C to activated charcoal and carbon black because of its ability for the formation of smaller carbide particles resulting in higher catalytic activity. Addition of a minor amount of K₂CO₃ into β-Mo₂C/GMC (molar K/Mo = 0.05-0.5) promotes the formation of higher alcohols (C₂₊-OH) considerably, leading to a maximum space time yield (STY) for C₂₊-OH at medium K/Mo ratio of 0.1. Compared with typical Rh/GMC catalyst promoted triply with Mn, Li, and Fe oxides, the K₂CO₃-promoted β-Mo₂C/GMC catalyst shows higher C₂₊-OH selectivity (30 vs. 25 mol-C% on CO₂-free basis) and STY (71 vs. 46 mg (h g_cat)^-1) in spite of its suppressed formation of CH₃OH.