Transformation of CO2 and glycerol to glycerol carbonate over CeO2ZrO2 solid solution —— effect of Zr doping

Ce1-xZrxO2 (0 ≤ x ≤ 0.2) solid solutions were prepared by hydrothermal method and applied for the synthesis of glycerol carbonate from glycerol and CO2 in the presence of 2-cyanopyridine (dehydrant) with dimethyl formamide (DMF) as a solvent. The physicochemical properties of the catalysts were characterized by ICP, XRD, BET, H2-TPR, CO2/NH3-TPD, TEM and XPS. The activation route of CO2 and glycerol were measured by DRIFTS and FT-IR. Compared to pure CeO2, Ce1-xZrxO2 solid solutions exhibited enhanced activity in the present reaction system, and the improved catalytic activity was associated with the BET surface area and the acid-base properties. DRIFTS results showed that the chelating bidentate carbonate species was the main adsorption pattern for CeO2 and no striking differences between Ce0·98Zr0·02O2 and CeO2. FT-IR spectra of the spent catalysts revealed that glycerol and 2-cyanopyridine could be activated on CeO2-based catalysts, and an ester intermediate was formed for the production of glycerol carbonate. Thus, a plausible mechanism is proposed for the synthesis of glycerol carbonate from glycerol and CO2 in the presence of 2-cyanopyridine in DMF solvent over CeO2-based catalysts. Moreover, the recyclability of Ce0·98Zr0·02O2 was measured and the catalysts could be regenerated through a simple calcination process at 400 °C for 5 h in air.