Preparation And Study On Novel Catalysts For The Synthesis Of Cyclic Carbonate Through Expoxides And Carbon Dioxide

Carbon dioxide(CO2) is regarded as both of the main greenhouse gas and an abundant, inexpensive C1 feed stock. Nowadays, affected by the concept of green chemistry and sustainable development, chemical fixation of CO2 has attracted more and more attention. One of the industrial processes is the synthesis of cyclic carbonates via cycloaddition of CO2 to epoxides. In terms of “green chemistry” and“atom economy”, this process is promising and attractive, since CO2 can react with epoxides without formation of any by-product and the substrates are inexpensive.Moreover, cyclic carbonates are valuable compounds. In order to synthesize cyclic carbonates more efficiently through the cycloaddition reaction, a considerable number of homogeneous and hetergeneous catalyst systems, such as alkali metal salts, metal oxide, modified molecular sieve, organometallic complexes, and ionic liquids(ILs)have been explored. However, most of developed catalysts inherit the disadvantages such as low activity or difficultly for catalyst-product separation. Therefore, we developed two novel, efficient and environmentally catalysts for the cycloaddition of carbon dioxide to epoxides.(1) The heterogeneous catalysts which have good catalytic activity were prepared by grafting a series of 1,5,7-Triazabicyclo[4.4.0]dec-5-ene ionic liquids with functional groups on Chloromethyl Polystyrene. Among them, the polymer which loaded carboxyl functioned ionic liquids(P-[TBDC2H4COOH]Br) showed high catalytic activity, good stability and can be recycled in the synthesis of cyclic carbonates through the cycloaddition of CO2 to epoxides without co-catalyst and solvent. The experimental results indicated that with 0.38 mol% amount of the catalyst, the selectivity and yield of propylene carbonate was 96.3 % and 100 % under a mild react condition(140 oC, 2 MPa, 2 h). Moreover, the catalyst showed no significant loss of activity in reusability test after loop five cycles.(2) Cr-MIL-101-NH2 was synthesised by hydrothermal method firstly. Using it as carrier, the catalyst Cr-MIL-101-[BuPh3P]Br was prepared by loading quaternary phosphonium salt on it after grafting method. Since this catalyst has large specific surface areas and pore size, lots of metal unsaturated sites and quaternary phosphonium salt loaded on, it showed high catalytic activity in the synthesis of cyclic carbonates through the cycloaddition of CO2 to epoxides without co-catalyst and solvent. The experimental results indicated the propylene carbonate yield was improved to 97.8% when using Cr-MIL-101-[BuPh3P]Br as catalyst, much higherthen 42.8%(Catalyzed by Cr-MIL-101-NH2).The catalyst showed a little significant loss of activity in reusability test after recycled four times.