Synthesis of Propylene Carbonate from Urea and 1,2-Propylene Glycol over a Zinc Acetate Catalyst

On the basis of thermodynamic analysis for the synthesis of propylene carbonate from urea and 1,2-propylene glycol (PG), the catalytic properties of zinc acetate have been studied. The optimal reaction conditions are as follows: molar ratio of urea to PG, 2:8; reaction time, 3 h; reaction temperature, 170 °C; molar ratio of zinc acetate to PG, 1:148. The highest yield of propylene carbonate is 94%. Then the immobilization of zinc acetate is investigated in order to facilitate recovery and reuse of the catalyst. The suitable support is activated carbon, and the optimal load of zinc acetate is 15 wt %; the highest yield of propylene carbonate is 78%. The analysis of X-ray photoelectron spectroscopy, X-ray diffraction, Brunauer−Emmett−Teller surface area analysis, and atomic absorption spectroscopy for the catalysts used both before and after reaction shows that both some changes and severe loss of zinc acetate have taken place during the process of the reaction.