Swelling Poly(Ionic Liquid)s Catalyzed The Transesterification Of Ethylene Carbonate And Methanol

Dimethyl carbonate（DMC）has been widely used in industrial fields owing to its low toxicity,high reactivity and excellent solubility.The transesterification of CO₂-derived ethylene carbonate（EC）with methanol（Me OH）to synthesize DMC was a more promising approach.Recently,ionic liquids（ILs）were considered to be highly efficient and non-corrosive homogeneous catalysts for catalyzing the transesterification reaction.Nevertheless,the thorny issue associated with ILs was the difficulty of catalyst-product separation.In this thesis,a serious of poly（ionic liquids）（PILs）with swelling ability in Me OH were designed and synthesized,and applied as highly efficient catalysts to catalyze the transesterification of EC and Me OH.The main contents of the dissertation were as follows:（1）The application of DMC and the research advance of the synthesis of DMC,as well as the swelling performance and application of swelling PILs were summarized.（2）PILs containing fatty acid anions were successfully synthesized by free radical copolymerization,which mainly include PILs with fatty acid anion directly fixed on the polymer chain,PILs with free fatty acid anion,and PILs with fatty acid anion in the 3-substituent on imidazolium.The swelling abilities of PILs in various solvents were measured.PILs could swell in Me OH and exhibite obvious swelling abilities in solvents with Hansen solubility parametersδ_T≥24.4 MPa^1/2.The influence of the structure of PILs on their swelling abilities was analyzed.PILs with ionic cross-linker,the carboxylate anions and the long-chain substituents on imidazolium exhibited the higher swelling ratio.The swelling PILs were used to catalyze the transesterification of EC and Me OH,and the catalytic activities were correlated with the swelling ratio of PILs containing carboxylate anions in the mixture solvent of Me OH and EC.Poly[VOIm-AA-DVIm]with the largest swelling ratio(Q_{Me OH/EC}=25.9（g/g）)exhibited similar activity（76.6%DMC yield,90.1%selectivity）with the homogeneous ionic liquid[BMIm]OAc（77.9%DMC yield,96.2%selectivity）.（3）Swelling PILs containg benzoate anion were successfully synthesized by free radical copolymerization.The PILs exhibited obvious swelling abilities in solvents with Hansen solubility parametersδ_T≥26.5 MPa^1/2,and the swelling ratio was increased with an increase in the Hansen solubility parameters.The swelling abilities of PILs with different structures in Me OH were studied in detail.The lower cross-linker content was beneficial to the swelling of PILs,and the PIL with n-butyl on imidazolium exhibited the highest molar swelling ratio（Q_M=527 mmol/g）.The swollen state of PILs in Me OH presented a porous cross-linked network structure observed by the cryo-scanning electron microscope（cryo-SEM）.The swelling PILs were used to catalyze the transesterification of EC and Me OH,and the catalytic activities were correlated to the swelling abilities of PILs.poly[VBIm-VBA-DVIm]-2.5%with the highest swelling ratio in Me OH and EC mixed solvents exhibited excellent catalytic activities（78.6%DMC yield,98.1%selectivity）,which was similar to the corresponding homogeneous ionic liquid[BMIm]BA（77%DMC yield,96.3%selectivity）.In addition,the catalyst could be reused up to seven runs without any considerable loss of its initial activity.