Transformation of CO2 with glycerol to glycerol carbonate by a novel ZnWO4-ZnO catalyst

ZnWO4-ZnO catalysts with different W content were prepared by conventional hydrothermal and wet impregnation methods and applied in the direct synthesis of glycerol carbonate from CO2 and glycerol. The crystallite structure, texture property, morphology, redox and acid-base properties and the surface chemical situation of the catalysts were characterized by XRD, BET, TEM, H-2-TPR, NH3/CO2-TPD and XPS. The possible activation routes of CO2 and glycerol were analyzed with DRIFTS and FTIR. ZnWO4-ZnO composite catalysts showed better catalytic performances with respect to ZnO in the carbonylation of glycerol with CO2. The improved activity of ZnWO4-ZnO catalysts was associated with the formation of ZnWO4, the interaction between ZnWO4 and ZnO, and the enhanced moderate acidic property. DIRFTS results showed that chelating bidentate carbonate species was the main adsorption pattern for CO2 on ZnO, while the introduction of W led to the bridged bidentate carbonate, which became the main adsorption pattern on ZnWO4-ZnO. As for the activation of glycerol, zinc glycerolate played an important role in the reaction process. Based on the reaction and characterization results, a plausible reaction route involved a seven-membered ring esters intermediate was suggested for the reaction of CO2 and glycerol over ZnWO4-ZnO catalysts.