Selective vapor-phase hydrodeoxygenation of anisole to benzene on molybdenum carbide catalysts

Vapor-phase hydrodeoxygenation (HDO) of anisole over Mo₂C catalysts at low temperatures (420-520 K) and ambient pressure showed (1) remarkable selectivity for C-O bond cleavage, giving benzene selectivity >90% among C₆⁺products, (2) high hydrogen efficiency for the HDO reaction as indicated by low cyclohexane selectivity (<9%), and (3) good stability over ∼50 h. Methane selectivity increased at the expense of methanol selectivity as anisole conversion increased, suggesting that the phenolic C-O bond was cleaved preferentially. The concurrent near half-/zero-order dependence of benzene synthesis rates on H₂/anisole pressure, and the preferential inhibition of benzene synthesis rates upon introduction of CO relative to isotopic HD exchange suggest that catalytic sites for H₂activation are distinct from those required for the activation of anisole. The involvement of metallic sites on Mo₂C catalysts for this reaction was demonstrated by the nearly invariant benzene synthesis rate per CO chemisorption site.