Research On Green Synthesesis Of Epoxidefrom The Decarboxylation Of Cyclic Carbonate Catalyzed By Ionic Liquids/poly(Ionic Liquid)s

Epoxide is a kind of important organic chemical and fine chemical intermediate.At present,the use of direct decarboxylation process to produce epoxide suffers from the drawbacks such as the separation problems in homogeneous catalytic system and the undesirable catalytic activity in heterogeneous catalytic system.Herein,ionic liquids with multiple active sites were first designed and synthesized,then they were covalently bonded with crosslinker to form a porous polymer network with high density of ionic sites.This work provided a new idea for the heterogeneous catalytic synthesis of epoxide with ionic liquid based catalysts.The main work and innovations are as follows:(1)Imidazole-based ionic liquids,[Bmim]Br,[C4bim]Br,and[PhTbim]Br,with different numbers of active centers were designed and synthesized,and then used to catalyze the decarboxylation reaction of butylene carbonate.1H/13CNMR、FT-IR and TGA results showed that the target ionic liquids were successfully synthesized.The catalytic activity evaluation results show that the tricenter ionic liquid catalyst[PhTbim]Br has the best catalytic performance.Under the optimal conditions of 200℃,90 min and[PhTbim]Br dosage of 1.5 g,reached a butylene oxide yield of 82.6%,and TOF value of 46.1 h-1.In addition,the results of long-term performance investigations showed that the catalytic activity of[PhTbim]Br remained stable under 12 h of continuous reaction.Substrate scope investigations showed that[PhTbim]Br has excellent substrate compatibility.(2)A series of porous poly(ionic liquid)s catalysts with different anions were prepared by copolymerization between the vinylfunctionalized tris-imidazolinium-based ionic liquids monomer and DVB,and then used to catalyze the decarboxylation reaction of butylene carbonate.The results of BET,SEM,TEM,TGA and elemental analysis showed that these poly(ionic liquid)s have abundant ionic sites,excellent thermal stability and stable meso-macroporous structure.Meanwhile,the density of the ionic sites and the pore structure of these poly(ionic liquid)s can be effectively controlled by adjusting the DVB content.The catalytic activity evaluation results indicated that the anionic nucleophilicity of poly(ionic liquid)s were positively correlated with catalytic activity.Among them,PDVB-[PhTVIM]Cl-1 with chloride anion-enriched skeleton displayed the best catalytic performance.Under the optimal conditions of 0.6 g catalyst,120 min and 195℃,reached a yield of butylene oxide 89.6%and the TOF value of 108.1 h-1.The reusability,FTIR and SEM results showed that the activity and structure of the catalyst remained unnoticeable changes during 5 cycles.In addition,based on the results of 1H NMR studies,the hydrogen-bond interaction between PDVB[PhTVIM]Cl-1 and the substrate was preliminarily investigated,and the corresponding anion and cation cooperative ring-opening mechanism was proposed.