A study of the catalytic hydroconversion of biocarboxylic acids to bioalcohols using octanoic acid as model reactant

The catalytic hydrodeoxygenation (HDO) of octanoic acid (C7COOH) to octene and octane was found to proceed in consecutive reaction through octyl aldehyde and octyl alcohol intermediates. Aluminosilicate and γ-alumina supported Cu and Cu,In catalysts were applied in a fixed bed flow-through reactor at 21 bar total pressure in the temperature range of 330–380 °C. The feed was 7.1% C7COOH/84.3% H2/He. The WHSV of the acid was 1.82 h−1. The results suggested that at lower temperatures the rate of acid hydrogenation/dehydration determined the rate of the consecutive hydroconversion process and alcohol selectivity. The reduction of aldehyde was facile, thus, the aldehyde selectivity was low under most conditions. At lower temperatures and conversions the acid coverage was high hindering the catalytic dehydration of the product alcohol. At higher temperatures and acid conversions the alcohol dehydration activity of the catalyst determined the alcohol selectivity. The indium additive was found to increase the HDO activity and the alcohol selectivity of the copper catalysts significantly. The favorable effects of indium were attributed to the formation of new catalytically active Cu2In alloy phase.

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► Supported Cu,In catalysts are active in carboxylic acid hydrodeoxygenation (HDO).
► Indium promotes alcohol selectivity of Cu catalysts in carboxylic acid HDO.
► Liquid biofuel can be generated by reducing bio-carboxylic acids to alcohols.
► Promoting effect of indium on Cu catalysts comes from alloy (Cu2In) formation.