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Functional Br (?) Nsted acidic ionic liquid catalytic synthesis of cyclic carbonate reactivity

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Tutor: WuWei
School: Heilongjiang University
Course: Chemical processes
Keywords: Br(?)nsted acidic ionic liquids,Immobilization,Cyclic carbonates,Epoxides,Carbon
CLC: O643.32
Type: Master's thesis
Year:  2011
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Abstract:
From the standpoint of environmental protection and resource utilization, the chemical fixation of CO2 has become more and more important, it is not only due to the fact that CO2 is one of the green house gas, but also from an increasing interest to use CO2 as an widely distributed and a most abundant C1 building block. The synthesis of cyclic carbonates from carbon dioxide is one of the most minorities of industrialized pathway for the utilization of carbon dioxide. Cyclic carbonates can be used in many applications such as polar solvents, monomers, valuable raw materials and intermediates in the synthesis of pharmaceuticals and fine chemicals. So, the development of an efficient and environmentally benign catalyst for the chemical fixation of carbon dioxide with epoxides under mild conditions has important academic significance and practical value.In this thesis, the Br(?)nsted acidic task-specific ionic liquids were synthesized and used as catalysts for the chemical fixation of carbon dioxide to form cyclic carbonates. The structure and acidity of ionic liquids were characterized by NMR, FT-IR and UV-vis. In the cycloaddition of epoxides and carbon dioxide, the catalytic performance of the Br(?)nsted acidic task-specific ionic liquids was examined and the reaction conditions were optimized. Under the optimal reaction conditions, the reusability of ionic liquids was investigated. Based on the experimental results and the literature, the plausible mechanism in the chemical fixation of CO2 to form cyclic carbonate was proposed.To enhance the catalytic activity, a variety of Br(?)nsted-Lewis acidic ionic liquids had been developed by in-situ addition of Lewis acidic salts in the Br(?)nsted acidic task-specific ionic liquids. The influence of the Br(?)nsted acidic ionic liquids structure, Lewis acid salts and the molar ratio of ionic liquids to ZnBr2 was investigated. The effects of conditions on the reaction results were also investigated and optimized. Because the synergistic effect of the Br(?)nsted acid and Lewis acid in the catalyst for the cycloaddition of carbon dioxide and epoxide, the catalytic activity was increased, the 96.2% yield of propylene carbonate was obtained and the TOF of the catalyst was achieved 4248 h-1. In the meantime, experiments were carried out to test the reusability of the catalyst and the plausible mechanism for the chemical fixation of CO2 was proposed.With using cross-linked polystyrene resin (PS), SiO2 and MCM-41 as the carrier, a variously immobilized Br(?)nsted acidic ionic liquids were synthesized by covalent bonding, and the structure and the loading of the ionic liquids were determined by FT-IR and elementary analysis. The effects of the carrier on the supported ionic liquid were investigated. When the surface of SiO2 and MCM-41were modified by H3PO4, the number of surface hydroxyl groups and the loading of ionic liquid were increased. Using the supported ionic liquid as a catalyst, the synthesis of cyclic carbonates from carbon dioxide and epoxides was carried out and the reaction condition was optimized. Under the optimal reaction conditions, the yield of propylene carbonate was achieved 92.7%. When the catalyst PS-HBIMB was used at the five time, the 91.2% yield of propylene carbonate was obtained.
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