Synthesis of cyclic carbonates from CO2 and epoxides with metalcontaining deep eutectic solvents

Abstract

In the introductory chapter, a brief overview of the chemistry of ionic liquids is presented. Ionic liquids have been a very popular alternative reaction media in recent decades because of their very low vapor pressure and non-flammability compared to conventional organic solvents. Ionic liquids have also been widely used in chemical synthesis and catalysis. A deep eutectic solvent (DES) is an ionic solvent which is easily prepared, air/moisture insensitive and frequently environmentally benign. Physical properties of the DES depend on the ratio of the two components from which it is prepared. DESs containing metals can be prepared and some have been used in catalytic reactions. Carbon dioxide utilization is important for sustainable development. At the end of Chapter 1, the use of ionic liquids and metal complexes in the catalytic synthesis of cyclic carbonates from carbon dioxide and epoxides is introduced. Six metal-containing DESs were synthesized from choline chloride (ChCl) and MClₓ·yH₂O where M = Co (x = 2, y = 6), Cr (x = 3, y = 6), Ni (x = 2, y = 6), Cu (x = 2, y = 2), Fe (x = 3, y = 0), Mn (x = 2, y = 4). Physical properties of the DESs were studied by TGA and DSC. The solubility of the Co(II) DES was also tested. These results are presented in Chapter 2. In Chapter 3, the metal-containing DESs catalyzed coupling reactions of CO₂ and styrene oxide to produce styrene carbonate under solvent-free conditions are described. ¹H NMR and GC-MS were used to confirm product formation and the resulted indicated that a high level of selectivity was achieved in this reaction. The effects of reaction parameters like temperature, CO₂ pressure, reaction time and DESs of different ratios were investigated.