Acetic acid hydroconversion to ethanol over novel InNi/Al2O3 catalysts

Consecutive reduction of acetic acid (AA) to ethanol was studied looking for an advantageous catalyst for the processing of VFAs (volatile fatty acids) that can be produced by thermochemical or biological biomass degradation. A fixed bed flow-through reactor was applied with hydrogen stream at 21 bar total pressure in the temperature range of 220–380 °C. AA hydroconversion activity of the parent alumina supported Ni catalyst and the yield of selectively produced alcohol can be increased drastically by In2O3 addition. Efficient catalysts, containing finely dispersed metal particles were obtained by reduction with H2 at 450 °C. In the catalysts modified with In2O3 additive formation of indium metal and/or an intermetallic compound (InNi2) was observed resulting in a different catalytic behavior as for pure nickel particles supported on alumina. Appearance of metallic indium can direct the step by step catalytic reduction to ethanol formation inhibiting decarbonylation, decarboxylation, and additional dehydration. On comparing the commercial, conventionally used catalysts with the bimetallic alumina supported composite (InNi/Al2O3) the novel catalyst proved to be much more active and selective for producing ethanol.

► Novel InNi/Al2O3 catalyst was obtained for acetic acid hydroconversion.
► The new catalyst is much more active and selective for producing ethanol.
► Activity and selectivity can be significantly modified by In addition.
► Ni2In alloy is obtained which have a moderated hydrogenation activity.