Guerbet condensation of ethanol to n-butanol in liquid phase over Cu-hydrotalcite derived mixed oxides: striking effect of the copper content

n-Butanol (BuOH) is a renewable molecule which can be considered an interesting alternative fuel to replace the gasoline. The synthesis of BuOH has been performed from ethanol by Guerbet condensation carried out in liquid phase in the presence of Cu/Mg/Al hydrotalcite-derived mixed oxides. Different Cu/Mg/Al mixed oxides catalysts, with Cu atomic content in the range 7.6-1.0 % , were synthesized, fully characterized and tested in the condensation tests carried out at temperatures up to 230 °C. The effect of a pre-reduction step on the catalytic performances was also investigated. For the first time appreciable ethanol conversion (up to 30.0 mol % after 6 h with a selectivity of 57.4 mol% BuOH) was ascertained for this batch process at moderate temperature. The catalytic performances resulted significantly influenced by the Cu content which plays a fundamental role on the type and extent of formed byproducts. The obtained results were related to the main characteristics of the different catalytic systems investigated.