Abstract
We aimed to develop new effective catalysts for the synthesis of propylene carbonate from propylene oxide and carbon dioxide. A kind of Mx+LClx coordination complex was fabricated based on the chelating tridentate ligand 2,6-bis[1-(phenylimino)ethyl] pyridine (L). The obtained products were characterized by elemental analysis, infrared spectroscopy, ultraviolet spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. It was found that the catalytic activity of the complexes with different metal ions, the same ligand differed and co-catalyst, where the order of greatest to least catalytic activity was 2 > 3 > 1. The catalytic system composed of complex 2 and DMAP proved to have the better catalytic performance. The yields for complex 2 systems was 86.7% under the reaction conditions of 100 °C, 2.5 MPa, and 4 h. The TOF was 1026 h−1 under the reaction conditions of 200 °C, 2.5 MPa, and 1 h. We also explored the influence of time, pressure, temperature, and reaction substrate concentration on the catalytic reactions. A hypothetical catalytic reaction mechanism is proposed based on density functional theory (DFT) calculations and the catalytic reaction results.
Highlights
Considerable attention has been paid to the fixation of carbon dioxide, due to its key role as a greenhouse gas
Three different metal complexes 1–3 were synthesized from the selected tridentate nitrogen-containing ligand 2,6-bis[(1-phenylimino)ethyl] pyridine (L)
It is worth highlighting that these widely used metal complexes for ethylene oligomerization were applied for the first time to the synthesis of cyclic propylene carbonate from propylene oxide and carbon dioxide
Summary
Considerable attention has been paid to the fixation of carbon dioxide, due to its key role as a greenhouse gas. Many methods have been developed for the synthesis of propylene carbonate, including urea alcoholysis, phosgene (carbonyl chloride), chloropropanols, cycloaddition, and ester exchange Among these methods, ester exchange is the simplest and easiest one to operate, with low cost, high product yield, good selectivity, and high. Among these methods, ester exchange is the simplest and easiest one to operate, with low cost, high product yield, good selectivity, and high quality [16,17,18].
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