Catalytic Synthesis of Cyclic Carbonates A Green Chemistry Approach

This work is focused on the development and optimization of sustainable catalytic systems for the production of cyclic carbonates from epoxides and CO2. Herein, the performance of novel supported ionic liquid aerogel-based catalysts is evaluated for the synthesis of cyclic carbonates directly from propylene oxide and CO2, at 353.15 K and 4 MPa. The catalysts are made from bio-based materials, alginate with or without cellulose, and comprise either methyltrioctylammonium chloride or tetrabutylammonium bromide in their structure. The maximum 93 mol% conversion was obtained for a methyltrioctylammonium chloride supported alginate aerogel catalyst, with up to 6 reaction cycles. Furthermore, it is studied the optimization of the synthesis of styrene carbonate from CO2 and styrene oxide coupling reaction, using a binary catalytic system composed of a Zn(II) complex of arylhydrazones of β-diketones (0.05, 0.10, or 0.25 mol%) and tetrabutylammonium bromide (0.2, 0.4, or 1.0 mol%) as catalyst. Experiments were performed at three temperatures (313.15, 333.15 and 353.15 K) and pressures of 4, 8, and 12 MPa. The optimum reaction conditions were established to be 353.15 K and 4 MPa, using 0.05 and 1.0 mol% of catalyst and co-catalyst, respectively, resulting in a 99 mol% conversion (1980 TON). This work offers alternative strategies to be employed in the production process of cyclic carbonates from epoxides and CO2.