Conversion of carbon dioxide into cyclic carbonates using wool powder-KI as catalyst

Chemical conversion of carbon dioxide (CO2) into usable materials offer opportunities to use carbon dioxide as a sustainable carbon source, but remains difficult to make. In this study, wool powder (WP), fine particles produced from natural wool fibers, was used as a catalyst for cycloaddition coupling of CO2with propylene oxide (PO) to form propylene carbonate (PC) in a solvent free condition. Potassium halide (KCl, KBr and KI), tetrabutylammonium iodide (TBAI), 1, 8-diazabicyclo[5.4.0]-undec-7-ene (DBU), and N, N-dimethylaminopyridine (DMAP) were used separately as co-catalyst. A synergetic effect was found between WP and KI, which shows the optimal efficiency when a low amount of the catalyst (e.g. 1.0 mol% KI relative to PO, WP: KI = 2:1 wt/wt) was employed at 1.5 MPa and 120 °C. The catalyst can be repeatedly used for five cycles without apparently losing the activity. It could be used to catalyze coupling of other mono-substituted terminal epoxides with CO2. Wool powder-KI may serve as an efficient, green catalyst system for the fixation of CO2.