CuAl2O4–CuO–Al2O3 catalysts prepared by flame-spray pyrolysis for glycerol hydrogenolysis

The catalysts of copper aluminates (CuAl2O4), copper oxide (CuO), and alumina (Al2O3) synthesized via one-step flame-spray pyrolysis (FSP) with various mole ratios of Cu to Al have been studied in the hydrogenolysis of glycerol, a byproduct from the biodiesel industry, to 1,2-propanediol (1,2-PDO) at 220 °C under 50 bar of H2 for 6 h. The studies on the CuAl2O4 nanoparticles reveal that their formation and particle size depend upon the mole ratio of Cu to Al, and they possess a structure analogous to that of the bulk material. The X-ray absorption near edge spectroscopy (XANES) data along with X-ray diffraction (XRD) patterns confirmed the formation of a CuAl2O4–CuO–Al2O3 mixed phases. The characteristic CuAl2O4 species was dominant during the flame process when a low content of Cu to Al, such as a 1:5 mol ratio, was supplied. It was observed that the CuAl2O4 combined with the CuO and Al2O3 phases exerts a strong positive effect on the catalytic activity. A selectivity to 1,2-PDO of 91.7% was observed for the synthesized catalyst with a 1:1 mole ratio of Cu to Al. The developed catalyst was superior to the conventional CuO-based ones in the hydrogenolysis of glycerol process.