4. Conclusion
In the reaction of carbonylation of EG to EC with urea, ZnO is a precursor for the formation of homogenous catalyst Zn(NCO)2(NH3)2 rather than a heterogeneous catalyst. The reaction experienced three periods, the dissolution of ZnO, the homogeneous catalysis, and precipitate formation. To the best of our knowledge, it is the first time on the report of Zn(NCO)2(NH3)2 homogeneously catalyzed this reaction when ZnO is used. The precipitate after reaction has been analyzed to be a mixture of Zn(OH)2, ZnCO3, Zn(NCO)2 with ratio of 8.5:6.1:1.
