The Study Of Novel Ionic Liquid Catalysts Applied For The Cycloaddition Of CO₂ To Epoxides

The excess emissions of carbon dioxide is the main reason for leading to more and more serious greenhouse effect, and it is one of the important research subject to take some effective measures for the CO₂ absorption and immobilization. Among them, with100% of atom utilization ratio, the cycloaddition reaction of CO₂ and epoxides becomes one of the significant ways of CO₂ recycling, which conforms to the concept of “green chemistry” and “atom economy”. Meanwhile, cyclic carbonates are also the important synthetic intermediates and chemical products. However, most of the existing homogeneous and heterogeneous catalysts have some imperfections, such as the harsh reaction conditions, poor stability and recycling performance and/or isolating difficulty between catalyst and products. Therefore, our main task is to develop some novel and efficient ionic liquid catalysts for the cycloaddition of CO₂ with epoxides.1. A series of hydroxy and carboxyl groups functionalized isothiouronium ionic liquids?FITILs? were synthesized and used for the cycloaddition of CO₂ with epoxides without solvent and co-catalysts. Most of them show very high catalytic activity and selectivity. Propylene oxide is almost quantitative conversion at 140 oC and 2 MPa in 2h. Meanwhile, the effect of functional groups, the basicity of N atom and counter anions on their catalytic activity were systematically investigated. Furthermore, a possible reaction mechanism was also discussed.2. Polymer nanoparticles grafted with hydroxyl-functionalized phosphonium-based ionic liquid catalyst?PNPs-HPIL? through copolymerization of EGDMA and HPIL were designed and synthesized. The PNPs-HPIL catalysts exhibit good catalytic activity for the synthesis of cyclic carbonates through cycloaddition of CO₂ to epoxides without solvent and co-catalysts. At a catalyst loading as low as 0.47mmol%, the PC yield is above 96.0% and PC selectivity almost 100%. It is noted that the hydroxyl groups of PNPs-HPIL play an important role for facilitating the cycloaddition reaction through the hydrogen bonding between hydroxyl groups and epoxides. Furthermore, the PNPs-HPIL catalysts show good stability and reusability,which are beneficial to practical application industry.3. A promising new strategy for fabricating polymer nanoparticles grafted with bis-imidazolium tetra-halogen zinc ionic liquid catalysts?PNPs-[BPIm IL]ZnX2Y2? by cross-linked polymerization was established. The PNPs-[BPImIL]ZnX2Y2 catalysts exhibit good catalytic activity for the fixation of CO₂ with epoxides without solvent and co-catalysts. The results indicated that at a catalyst loading as low as 0.07 mmol%, and only after 50 min, PC yield is 98.5% and PC selectivity is 99.8%, respectively. It is worth to point out that the PNPs-[BPImIL]ZnX2Y2 catalysts also show some catalytic activity even at room temperature. Meanwhile, the PNPs-[BPImIL]ZnX2Y2 catalysts display good stability and reusability, which has high potential for industrial application.