Rapid conversion of CO2 and propylene oxide into propylene carbonate over acetic acid/KI under relatively mild conditions

Abstract

The coupling of CO₂ and epoxides to form cyclic carbonates has been industrialized since the 1960s. The employment of an efficient and low-cost catalyst is one of the decisive factors to improve the production efficiency. Many catalysts with high activities have been developed; however, those that can convert CO₂ and epoxides into cyclic carbonates in a short time or with high efficiency are still less reported. In this study, we developed such an efficient and low-cost catalytic system of hydrogen bond donor acetic acid (AA) in combination with KI (denoted as AA/KI) for the rapid conversion of CO₂ and propylene oxide (PO). The optimal reaction condition for AA/KI catalyzing the coupling of CO₂ and PO is screened by trial and error. Atime-dependent PO conversion study showed that the AA/KI catalytic system displays quite high activity to completely convert PO within a short time of 15 min under optimized conditions (0.9 MPa CO₂ and 90 °C) for the best case. Moreover, AA/KI is also active for the coupling of other epoxides with CO₂, and the reaction efficiency is significantly influenced by the electronic and steric effects of the epoxide substrates. In addition, the plausible mechanism was deduced. Herein, we provide an efficient and relatively mild route to catalyze the coupling of CO₂ and epoxide within a short time using a non-toxic, cheap and facile catalyst.