Synthesis of diethyl carbonate from urea and ethanol over lanthanum oxide as a heterogeneous basic catalyst

The catalytic synthesis of diethyl carbonate from urea and ethanol was investigated over various metal oxide catalysts. Among them, the lanthanum oxide prepared by precipitation method exhibited much higher catalytic activity. In particular, 38.6% of DEC yield could be achieved at the reaction conditions of ethanol/urea molar ratio of 10, reaction temperature of 210 °C within 3 h over La2O3-500. The catalyst structures and surface properties were studied by N2 adsorption, XRD, FT-IR and CO2-TPD. On the basis of these results, it can be inferred that the high catalytic activity could be attributed to the abundant medium basicity of lanthanum oxide. Importantly, as confirmed by ICP-OES test, there was no obvious leaching of La into the resulting mixture. This phenomenon indicated that La2O3-500 was very stable during the reaction and behaved as a heterogeneous basic catalyst. In addition, the facile calcination of the used catalyst could provide an efficient way to regenerate the catalytic activity.