Vapor phase hydrodeoxygenation (HDO) of anisole over Mo 2 C catalysts at low temperatures (420-520 K) and ambient pressures showed (1) remarkable selectivity for CO bond cleavage, giving benzene selectivity >90% amongst C 6 + 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 selctivity as anisole conversion increased, suggesting that the phenolic CO bond was cleaved preferentially. The concurrent near half/zero order dependence of benzene synthesis rates on H 2 /anisole pressure, and the preferential inhibition of benzene synthesis rates upon introduction of CO relative to isotopic HD exchange suggests that catalytic sites for H 2 activation are distinct from those required for activation of anisole. The involvement of metallic sites on Mo 2 C catalysts for this reaction was demonstrated by the nearly invariant benzene synthesis rate per CO chemisorption site.

Selectively cleaving the C=O bond outside the furan ring of furfural is crucial for converting this important biomass-derived molecule to value-added fuels such as 2-methylfuran. In this work, a combination of density functional theory (DFT) calculations, surface science studies, and reactor evaluation identified molybdenum carbide (Mo2 C) as a highly selective deoxygenation catalyst for converting furfural to 2-methylfuran. These results indicate the potential application of Mo2 C as an efficient catalyst for the selective deoxygenation of biomass-derived oxygenates including furanics and aromatics.

The turnover frequency (TOF) of benzene synthesis from vapor phase anisole hydrodeoxygenation (HDO), estimated via in situ CO titration, was found to be invariant (1.1 ± 0.3 × 10 −3 s −1 ) over molybdenum carbide (Mo 2 C) catalysts with varying CO chemisorption uptakes (∼70 to ∼260 μmol g −1 , measured ex situ at 323 K). Accumulation of oxygen (∼0.29 monolayer) over Mo 2 C catalysts was determined by an oxygen mass balance during the transient of anisole HDO at 423 K under ambient pressure (H 2 /anisole molar ratio ∼ 110). Similar product selectivity, apparent activation energy, and TOF of benzene synthesis for an oxygen treated (with oxygen incorporation: O/Mo bulk (molar ratio) = 0.075) and freshly prepared Mo 2 C catalysts (no exposure to air prior to kinetic measurements) demonstrate that the effect of oxygen at these low concentrations is solely to reduce the number of active sites for anisole HDO, resulting in a lower (∼3 times) benzene synthesis rate per gram of catalyst for the oxygen-modified material. The observed benzene synthesis rates per CO chemisorption site for bulk molybdenum oxide (MoO x ) catalysts were found to be ∼10 times lower than those for Mo 2 C catalysts, suggesting that bulk molybdenum oxide phases are not associated with the dominant active sites for anisole HDO at 423 K under ambient pressure.

No abstract

High aromatics yield (>90%, benzene and toluene) was obtained from vapor phase hydrodeoxygenation (HDO) of phenolic compound mixtures containing m-cresol, anisole, 1,2-dimethoxybenzene, and guaiacol over molybdenum carbide catalysts (Mo2C) under atmospheric pressure at 533-553 K, even with H2 to phenolic compound molar ratios ~3,300. Toluene selectivity increased proportionately (4%-66%) to m-cresol content in HDO of phenolic compound mixtures (molar composition: 0%-70%) at quantitative conversion. Phenol selectivity increased with decreasing conversion, implying that the aryl-methoxyl bond in guaiacol is cleaved first, before the aryl-hydroxyl bond. Low selectivity to cyclohexane and methylcyclohexane (<10%) across the conversions investigated (18-94%) demonstrates that undesired successive hydrogenation reactions of aromatics over Mo2C were inhibited, presumably due to in situ oxygen modification, as inferred from titration studies of aromatic hydrogenation reactions using methanol and water as titrants.

No abstract

No abstract

No abstract