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

The influence of the copper presence on the active sites of catalysts derived from a hydrotalcite-likecompound (HTLC) was investigated in bio-ethanol dehydrogenation. It was observed that the presenceof copper lead to an inhibition of dehydration and coupling reactions that occurred on the mixed oxide (MgAlOx) 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 dependedon the nature of the atmosphere used to promote the HTCL decomposition: when the decompositionwas conducted under helium atmosphere at 750 degrees 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 activityfor bio-ethanol dehydration, coupling and dehydrogenation reactions, on the studied systems the bioethanol 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. (c) 2017 Elsevier B.V. All rights reserved.