Mg/Al and Cu-Mg/Al mixed oxides derived from hydrotalcites as catalysts to produce 1-butanol from ethanol

Abstract

The interaction between ethanol molecules to produce 1-butanol over surfaces of Mg/Al and Cu-Mg/Al oxides derived from hydrotalcites (HT) was studied experimentally and computationally. For Mg/Al catalyst, the insertion of Al in the MgO lattice generates a selectivity of 11.7 % for 1-butanol and of 5.8 % for diethyl ether at 300 °C, indicating the importance of the presence of acid sites for dehydration. For Cu-Mg/Al catalyst, Cu²⁺ cations have been structural substituted, instead of superficial substituted, exhibiting the highest selectivity for 1-butanol at 250 °C (16.5 %). The inclusion of copper increases the number of acid-base pairs, which are important in the dehydrogenation of ethanol molecules, the aldol condensation of acetaldehyde molecules and the subsequent steps to get 1-butanol. According to DFT results, the presence of copper favors the adsorption of ethanol on the surface, weakening the C_α-H_α bond of the molecule, contributing to the formation of acetaldehyde.