Glycerol hydrogenolysis on heterogeneous catalysts

Abstract

Aqueous solutions of glycerol were hydrogenolysed at 180 °C under 80 bar H₂-pressure in the presence of supported metal catalysts in an attempt to selectively produce 1,2- and 1,3-propanediol. Catalysts (Cu, Pd, Rh), supports (ZnO, C, Al₂O₃), solvents (H₂O, sulfolane, dioxane) and additives (H₂WO₄) were tested to improve reaction rate and selectivity to the target molecules. The best selectivity (100%) to 1,2-propanediol was obtained by hydrogenolysis of water solution of glycerol in the presence of CuO/ZnO catalysts. To improve the selectivity to 1,3-propanediol the reaction was conducted with rhodium catalysts with tungstic acid added to the reaction medium. The best result in terms of conversion and selectivity to 1,3-propanediol (1,3-PDO/1,2-PDO = 2) was obtained by operating in sulfolane. The presence of iron dissolved in the reaction medium was also beneficial for the selectivity to 1,3-PDO. A mechanism was proposed to account for the effect of these different parameters.