Catalytic reduction of pyrolyzed biomass is required to remove oxygen and produce transportation fuels, but limited knowledge of how hydrodeoxygenation (HDO) catalysts work stymies the rational design of more efficient and stable catalysts, which in turn limits deployment of biofuels. This work reports results from a novel study utilizing both isotopically labeled phenol (which models the most recalcitrant components of biofuels) with D 2 O and DFT calculations to provide insight into the mechanism of the highly efficient HDO catalyst, Ru/TiO 2 . The data point to the importance of interface sites between Ru nanoparticles and the TiO 2 support and suggest that water acts as a cocatalyst favoring a direct deoxygenation pathway in which the phenolic OH is replaced directly with H to form benzene. Rather than its reducibility, we propose that the amphoteric nature of TiO 2 facilitates H 2 heterolysis to generate an active site water molecule that promotes the catalytic C−O bond scission of phenol. This work has clear implications for efforts to scale-up the hydrogen-efficient conversion of wood waste into transportation fuels and biochemicals.

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Pine (Pinus strobus) sawdust was pyrolyzed in a fluidized-bed reactor between the temperatures of 400 and 600 °C. The fixed-bed volume and residence time were optimized to maximize the liquid yield. We report the detailed physical and chemical properties of the bio-oil fraction collected during fast pyrolysis. The liquid yield was maximized at 500 °C, whereas increased gas formation occurred at 600 °C. 13C NMR of the bio-oil fractions indicated a decrease in the carbohydrate fraction and an increase in the aromatic fraction when pyrolysis temperatures were increased from 500 to 600 °C. Over the ranges of our investigation, the effects of the fixed-bed volume and residence time were negligible on the chemical composition of the bio-oil. Toluene and ethyl acetate bio-oil extracts were analyzed by gas chromatography/mass spectrometry following chemical derivatization. At increased reaction temperatures, the process favored conversion of guaiacols to catechols.

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