Glycerol dehydration to hydroxyacetone in gas phase over copper supported on magnesium oxide (hydroxide) fluoride catalysts

Abstract

The dehydration of glycerol to hydroxyacetone was studied over copper-based catalysts using magnesium oxide (hydroxide) fluoride with various F/Mg ratio as support of copper. After calcination at 350 °C, the incorporation of copper, mainly at + II oxidation state, into the support lattice was observed for MgO and MgF(OH) while, copper was stabilized as Cu+1 at the surface of Cu-MgF2. The reaction of dehydration was performed using a mixture of glycerol and water (80%wt of glycerol), in gas phase at 260 °C. Cu-MgF2 was the most active catalyst with a yield in hydroxyacetone of 45.5%, while the catalytic activity was very low for Cu-MgF(OH) and Cu-MgO (yield in HA < 10%). Moreover, the performances obtained for Cu-MgF2 were higher than those obtained with La2CuO4, a reference catalyst. After four hours of reaction, Cu-MgF2 was not significantly modified, while for the two other catalysts, Cu2+ initially present was reduced into metallic copper. The results obtained revealed that the basic properties of the catalysts did not govern the reaction of dehydration of glycerol into HA. The best catalyst (Cu-MgF2) was the one possessing the higher amount of Lewis acid sites, and stabilizing copper at + 1 oxidation state.