Transesterification of urea and ethylene glycol to ethylene carbonate as an important step for urea based dimethyl carbonate synthesis
Two-step synthesis of dimethyl carbonate (DMC) from urea has been investigated with various solid catalysts. The first step involves reaction of urea with ethylene glycol (EG) to form ethylene carbonate (EC) and the second step transesterification of EC formed with methanol to give DMC and EG. It has been found that ZnO is highly active and selective for the two steps, of which the former should be conducted under reduced pressure. At around ambient pressure, 2-oxazolidone and ethyleneurea are formed in the first step. Similar to EG, other glycols such as 1,2- and 1,3-propanediols can also be transformed to corresponding cyclic carbonates.