Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (06): 1386-1392.doi: 10.3866/PKU.WHXB20110615


Reaction Mechanism for Propylene Carbonate Prepared by KI/NH3 Catalysis from Propylene Oxide and CO2

DENG Ping1, ZHANG Hai-Dong2, JIANG Jun-Hao1, JIANG Qi-Hua1   

  1. 1. Pharmaceutical School, Chongqing Medical University, Chongqing 400016, P. R. China;
    2. Engineering Research Centre for Waste Oil Recovery Technology and Equipment, Ministry of Education, Chongqing Technology and Business University, Chongqing 400067, P. R. China
  • Received:2011-02-11 Revised:2011-04-11 Published:2011-05-31
  • Contact: JIANG Qi-Hua


The reaction mechanisms for the preparation of propylene carbonate (PC) from propylene oxide (PO) and CO2 in the absence of a catalyst or by catalysis using KI or KI/NH3 were studied in detail using density functional theory (DFT) at the B3LYP/6-311++G** level (I atom using the MIDIX basis set). The geometric configurations of the reactants, intermediates, transition states, and products were optimized. Vibration analysis and the intrinsic reaction coordinate (IRC) of the reactions proved that the intermediates and transition states predicted were present. The natural bond orbital (NBO) and atoms in molecules (AIM) theories were used to determine the orbital interactions and the bond nature at the same level. The results reveal that PO+CO2→M0a→TS0c→M0c→TS0c′→PC is the main reaction channel in the absence of the catalyst and it has a high energy barrier of 200.65 kJ·mol-1. The energy barrier is reduced to 187.40 kJ·mol-1 in the presence of KI, and it has a slow reaction rate. However, the energy barrier is reduced to 154.64 kJ·mol-1 and the reaction rate increases considerably upon promotion by KI/NH3, possibly because of the formation of hydrogen bonds between H in NH3 and O in CO2 or PO, which is in good agreement with the experimental results.

Key words: KI, NH3, Catalysis, Propylene oxide, Propylene carbonate, Reaction mechanism