Influence of thermal treatment conditions on the characteristics of Cu-based metal oxides derived from hydrotalcite-like compounds and their performance in bio-ethanol dehydrogenation to acetaldehyde

Abstract The influence of the copper presence on the active sites of catalysts derived from a hydrotalcite-like compound (HTLC) was investigated in bio-ethanol dehydrogenation. It was observed that the presence of copper lead to an inhibition of dehydration and coupling reactions that occurred on the mixed oxide (MgAlO x ) obtained by thermal decomposition of the HTCL, leading to selective formation of acetaldehyde. In situ X-ray absorption experiments revealed that the nature of the copper species depended on the nature of the atmosphere used to promote the HTCL decomposition: when the decomposition was conducted under helium atmosphere at 750 °C a mixture of Cu 0 /Cu +1 species was formed, while when the decomposition was done under an oxygen/helium atmosphere there was only the presence of Cu +2 species. Because the mixed oxide formed after thermal decomposition of the HTCL presents activity for bio-ethanol dehydration, coupling and dehydrogenation reactions, on the studied systems the bio-ethanol conversion into acetaldehyde does not seem to be influenced by the different copper species, even though it is well known that Cu 0 and Cu +1 sites are necessary for the reaction.