The low temperature hydrogenation of light oxygenates in the aqueous fraction of bio-oil (AFBO) was studied using model compounds with a Ru/TiO2 catalyst in a continuous flow reactor. Hydrogenation of hydroxyacetone, acetic acid, and formic acid, in single and multi-compound aqueous mixtures produced 1,2-propanediol, ethanol, and CO2 respectively, as the main products. The order of increasing rate of hydrogenation is the same whether processing single- or multi-component model compounds with the rate decreasing as: formic acid&gt; hydroxyacetone &gt; acetic acid. When present in the model feeds formic acid undergoes dehydrogenation as the main reaction route forming CO2 and H2. The product selectivity to methanol is below 1 %. Hydrogenation of hydroxyacetone gives propylene glycol as the dominant product. Hydrogenation of acetic acid produces ethanol at high selectivity with ethyl acetate as a minor product.<br/>Co-feeding acetic acid and hydroxyacetone increase the hydrogenation rate of hydroxyacetone. A mechanism involving the acid-catalyzed enolization of hydroxyacetone into its enol-form (prop-2-ene-1,2-diol) is proposed. The observation that the total conversion of hydroxyacetone increases with acetic acid concentration implies that formation of the intermediate enol is the rate-determining step. Co-feeding 2 wt% formic acid together with hydroxyacetone completely shuts off hydroxyacetone conversion.The addition of acetic acid increased the rate of hydrogenation of hydroxyacetone by catalyzing the enolization of hydroxyacetone.

Low temperature aqueous phase hydrogenation of light oxygenates over Ru/TiO<sub>2</sub> catalyst: Study of model compounds

2019 Fall National Meeting

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Low temperature aqueous phase hydrogenation of light oxygenates over Ru/TiO2 catalyst: Study of model compounds

Low temperature aqueous phase hydrogenation of light oxygenates over Ru/TiO₂ catalyst: Study of model compounds