Preparation Of Polymer-Supported Quaternary Phosphonium Salts And Their Applications In The Cycloaddition Reaction Of Carbon Dioxide To Epoxides

In the view of the concepts of"atom economy","sustainable development", and"green chemistry", transformation of carbon dioxide into valuable chemicals is of great importance in terms of greenhouse gas, abundant and cheaper feedstocks. One of the most successful strategies is the synthesis of cyclic carbonates from CO₂ and epoxides. Moreover, cyclic carbonates are widely used as organic syntheses, pharmaceutical intermediates, aprotic solvents, and raw materials for plastics etc.For homogeneous catalysts being used in industrial production of cyclic carbonate resulted in many key problems such as complicated purification process, decomposition of catalyst and formation of by-products, we developed heterogeneous ionic liquids catalysts for the coupling reaction of epoxides and CO₂. In this study, several high-efficiency heterogeneous catalysts were designed and fabricated for the synthesis of cyclic carbonates from CO₂ and epoxides.1. Polymer-supported quaternary phosphonium salts were explored to catalyze the cycloaddition of CO₂ to epoxides. The results indicated that this heterogeneous catalyst was very active and selective for the cycloaddition of CO₂ with epoxides. The catalyst was characterized by thermogravimetric analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. Influences of CO₂ pressure, reaction temperature, time, and catalyst amount on the cycloaddition reaction were investigated. Excellent yield (97.7%) and high selectivity (>99%) of cyclic carbonates were achieved under the conditions of CO₂ pressure of 4.5MPa, 150oC, 6h, and 0.09g catalyst. The catalyst could be recovered easily and reused several times. A plausible mechanism for the synthesis of cyclic carbonate in the presence of polymer-supported quaternary phosphonium salts was discussed. It is believed that the catalyst is of great potential for industrial applications because of its unusual advantages such as easy preparation, high activity, selectivity, and stability, and it can be separated easily from the products. 2. In this study, polymer-supported quaternary phosphonium salts (PS-QPS) was explored as effective catalyst for the coupling reaction of carbon dioxide with epichlorohydrin. The results indicated that cyclic carbonates with high yields (98.6%) and excellent selectivity (100%) could be prepared at the conditions of 5MPa CO₂, 150°C, 6h without the addition of any organic solvents or co-catalysts. The effects of various reaction variables on the catalytic performance were studied in detail. The catalyst is applicable to a variety of epoxides, producing the corresponding cyclic carbonates in good yields. Furthermore, the catalyst could be recovered easily and reused for several times. A plausible mechanism for synthesis of cyclic carbonate in the presence of PS-QPS was discussed. The catalyst was characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectrum. It is believed that PS-QPS is of great potential for industrial applications due to its unusual advantages, such as easy preparation, high activity and selectivity, stability, low cost, and reusability.3. Surface initiated ATRP in the synthesis of polymer-supported copolymers, and applied in the cyclicaddition reaction of carbon dioxide with epxoides. As a result, high yield (95.3%) and excellent selectivity (99.9%) of cyclic carbonates could be achieved at conditions (5MPa, 150℃, 4h, 0.1g) without any co-solvent. In addition, the catalyst recycle test showed that the supported catalyst could be reused for as many as five times without considerable decrease of catalytic activity.