Polymeric Ionic Liquids For The Catalytic Synthesis Of Cyclic Carbonates

Research scientists have always been trying to develop highly efficient methods to transforming carbon dioxides into value-added chemicals.Among a myriad of practical ways,the route concerning the synthesis of cyclic carbonates via carbon dioxide and epoxides outshines others with high atom economy and efficient utilization of carbon dioxide.The cornerstone of this way lies in the development of efficient catalysts.Herein,our work is aiming to provide solutions to the hindrances caused by using homogeneous catalysts.In order to address these defects,we've developed a series of novel catalysts based on the principle of being eco-friendly and cost-efficiency.The detailed contents and studies are presented as follows.1.Six types of ionic liquids containing hydrogen and sulfonic groups and different carbon chain lengths are designed and synthesized based on the precursor DMAEMA for the aim of efficient activation of epoxides.Through analytical characterization and activity evaluation,DMAEMA ionic liquid tailored by hydroxyethyl group has the highest activity among prepared ionic liquid monomers,achieving 99%conversion of propylene oxide under the condition of 110 ?,2.5 MPa.2.In order to simplify the separation process and realize multi-sites grafting,we then selected silica gel,known for its multiple hydroxyl groups,as the supports to load quantity-controllable polymeric ionic liquids which is tailored by hydroxyethyl group,selected from the previous work.Different kinds of polymeric methods are being investigated to optimize the loading amount and the highest activity is 91%under the condition of 110 ?,2.5 MPa.Afterward,various types of characterization methods,including FT-IR,XRD,TGA and SEM etc.are employed to confirm the successful grafting of polymeric ionic liquids.Moreover,Subsequent studies concerning recyclability and EA analysis affirm the as-prepared catalyst is stable after 5 times reuse without obvious loss in activity.Finally,a plausible mechanism,called H-bond and electrostatic interaction,is proposed based on the H-NMR experiment,which reveals the interaction between reactant and grafted polymeric ionic liquids.2.To realize high utilization ratio and easy recyclability of catalysts,polymeric ionic liquids containing DMAEMA components as the heterogeneous catalysts,without grafting,are tailored for the transformation of CO2 into cyclic carbonates.Based on the synthesized ionic liquids,six types of self-polymerized polymeric ionic liquids are successfully synthesized by radical polymerization method.Amongst those catalysts,hydroxyl-rich polymeric ionic liquid,especially P(DMAEMA-EtOH)Br exhibits the highest conversion(96%)of propylene carbonate under the condition of 110 'C,2.5 MPa,which is almost comparable to the reactivity of its ionic liquid monomer,being the quasi-homogeneous catalysts.Recyclable researches rectify the chemical stability and stable reactivity of 96%after 5 times of recycle experimentation.Not only does the presence of hydroxyl group considerably boost the reactivity,but also enhance the thermal stability.Studies including molecular dynamics calculations and XPS analysis prove that the combining ability of P(DMAEMA-EtOH)Br to epoxide is equivalent to that of its monomer.Dynamic light scattering data reveal that decreased hydrodynamic radius of polymer particles contributes to the increasing exposure of active sites,resulting in a comparable reactivity.Finally,synergistic catalysis mechanisms are proposed on the basis of the H-NMR studies.This work provides insight for the design of quasi-homogeneous catalysts for the substitution of homogeneous ionic liquids.