New efficient and long-life catalyst for gas-phase glycerol dehydration to acrolein

Zirconium and niobium mixed oxides have been shown to be selective catalysts for dehydration of glycerol to acrolein, at 300 °C in the presence of water. The catalysts exhibit a selectivity to acrolein of approximately 72%, at nearly total glycerol conversion. More selective catalysts have been designed for this reaction, but whereas all of these are almost completely deactivated after only 24 h, ZrNbO catalysts still exhibit 82% conversion efficiency after 177 h on stream, its acrolein selectivity remaining unimpaired. Catalysts have been characterized by various techniques, showing that active and selective sites are weak or moderately acid Brønsted sites, whose presence is related to that of polymeric niobium oxide species in interaction with the zirconia support. The key stability of the catalysts has been attributed to the neutralization of Lewis acid of uncovered zirconia, which are unselective coke initiator sites.