Hydrogen-free synthesis of 1,2-propanediol from glycerol over Cu–Mg–Al catalysts

Hydrogen-free synthesis of 1,2-propanediol (1,2-PDO) from glycerol was carried out over a series of Cu–Mg–Al catalysts with different (Cu + Mg)/Al ratios. Several hydrogen donors were tested and it was found that ethanol was the best donor for this process, the efficiency of the ethanol donor reached 79.8%. Cu0.4/Mg6.28Al1.32O8.26 showed the best performance among these tested catalysts. The conversion of glycerol and selectivity of 1,2-PDO reached 95.1% and 92.2%, respectively, at 210 °C. Characterizations indicated that the activity of Cu–Mg–Al for this hydrogen-free synthesis of 1,2-PDO depended mainly on the basicity of the catalysts. Both the conversion of glycerol and selectivity to 1,2-PDO could be improved with prolonged time, reaction temperature and the amount of hydrogen donor. The reaction mechanism was proposed.