Synthesis of diethylcarbonate by ethanolysis of urea catalysed by heterogeneous mixed oxides

Abstract

New Zn- and Ca-based mixed oxides have been tested in the ethanolysis of urea. Cerium and magnesium have revealed to be able to stabilize and enhance the activity of Zn and Ca. All the used compounds act as heterogeneous catalysts in a batch reactor and can be easily recovered and re-used in several catalytic runs. However, although ZnO dissolves as Zn(NCO)₂(NH₃)₂ in the reaction medium under the operative conditions and then partly precipitates at room temperature ensuring a modest immediate recoverability and recyclability, 2CaO/CeO₂ is insoluble also at the reaction temperature that makes it well suited even for the use in a flow reactor. MgO–ZnO and SiO₂–ZnO have also been tested. The former has an interesting performance, but still not equal to that of 2CaO–CeO₂. Interestingly, the latter catalyst is able to convert urea and ethanol into DEC with 91% conversion of urea and 98% selectivity in the long term.