Ni/silica-based bimetallic catalysts by solid-state co-reduction of admixed metal oxides for acetic acid hydroconversion to ethanol

Consecutive reduction of acetic acid to ethanol was investigated looking for advantageous bimetallic catalysts for the processing of volatile fatty acids that can be produced by thermochemical or biological biomass degradation. The reactant acid was hydrotreated in a flow-through reactor at 21 bar total pressure and 200–380 °C over fumed silica loaded with Ni main metal and Cu, Zn, Cd, Ga, In, Sn modifying metals. By varying these bimetallic composites prepared by solid-state co-reduction of admixed metal oxide precursors, the characteristic hydrodecarbonylation activity of nickel can be completely eliminated and a high ethanol yield can be attained selectively with the exception of Zn and Cd. The low boiling point and high volatility of these two elements in group IIb exclude formation of stable bimetallic composition. Indium and tin doping were found to be the most efficient. The lower reduction temperature of the In2O3 was found to be the advantage of novel In doping compared to well-known Sn-admission using oxide precursors for introduction of the second metal.