Direct synthesis of diethyl carbonate from ethanol and carbon dioxide over ceria catalysts

Direct synthesis of diethyl carbonate (DEC) by carboxylation of ethanol with CO 2 was investigated over ceria catalysts. 2-Cyanopyridine (2-CP) was used for trapping water formed in the reaction and to shift the equilibrium towards the product side. An optimal dependence ("volcanic plot") of the catalytic activity on the acidity/basicity molar ratio was observed. "Neat" ceria (procured from Daiichi Kigenso Kagaku Kogyo Co. Ltd, Japan) showed higher catalytic activity than metal incorporated ceria catalysts. CeO 2 had the right kind of acidity/basicity ratio to activate ethanol and CO 2 simultaneously, yielding DEC. The catalyst was reusable. The yield of DEC obtained in this study using the commercial catalyst was higher than that reported by others using ceria catalysts prepared by other methods. Under optimum conditions (ethanol : 2-CP molar ratio = 2 : 1, catalyst = 2.17 wt% with respect to ethanol, CO 2 pressure = 40 bar, reaction temperature = 150 °C and reaction time = 3 h) in a batch reaction, a DEC yield as high as 45 mol% ( i.e. , 38.7 mmol mmol −1 of CeO 2 ) was obtained. Direct synthesis of diethyl carbonate (DEC) from ethanol and CO 2 was investigated over "neat" and metal incorporated ceria catalysts. An optimal dependence ("volcanic plot") of the catalytic activity on the acidity/basicity molar ratio was observed.