Reaction parameters dependence of the CO2/epoxide coupling reaction catalyzed by tunable ionic liquids, optimization of comonomer-alternating enhancement pathway

Abstract

Glycerol based symmetrical cations with different anions accommodated ionic liquids (ILs) was found to be the most prominent catalyst system to produce cyclic carbonate (CC) from carbon dioxide (CO2) and propylene oxide (PO) for the first time. The synthesized ILs was analyzed by different spectroscopic technique, the thermal stability of ILs was analyzed by TGA, DSC. The mole ratio of IL/DBU gives a positive effect towards the product yield and selectivity. The best catalytic activity and long-term durability of ILs could be due to the synergistic combination of cation and anion makes an ideal catalyst for title reaction. The effect of ILs loading, temperature, pressure, and time on the production of cyclic carbonate was also investigated to determine the best reaction conditions (final 2 MPa CO2 pressure, 4 h, and 110 °C) the propylene carbonate (PC) selectivity and yield was 98.2 and 91.9%. Moreover, based on TGA and FT-IR analysis the catalyst system could be reusable up to four times (16 h) with no change in catalyst performance and product selectivity. In addition, the probable mechanism of this reaction was also proposed with the help of 13C NMR analysis.