Novel Cu and Cu₂In/aluminosilicate type catalysts for the reduction of biomass-derived volatile fatty acids to alcohols

Abstract

This work relates to the consecutive reduction of short chain carboxylic acids (volatile fatty acids, VFAs) to alcohols as main products. Acetic acid (AA) was used as a reactant to model the VFAs that can be produced by either thermochemical or biological biomass degradation. The amorphised zeolite supported copper catalysts (Cu/SiAl), especially the In-modified CuIn/SiAl catalysts, showed high hydroconversion activity and selectivity for alcohol, ester and aldehyde. Catalysts containing dispersed copper particles in amorphous aluminosilicate were obtained by dehydrating and H₂-reducing Cu-forms of low-silica synthetic zeolites (A, X, P). The activity of the highly destructed Cu-aluminosilicates was found to depend on the structure of the zeolite precursor. The formation of ethyl acetate could be suppressed by adding water to the AA feed and by modifying the catalyst, e.g. by In₂O₃ additive. In the catalysts modified by In₂O₃ additive formation of copper-indium alloy phase (Cu₂In intermetallic compound) was detected resulting in a different selectivity than the one recorded for the Cu/SiAl.