Study On The Preparation Of Ionic Liquid Polymer And The Catalytic Synthesis Of Propylene Carbonate

As a chemical,propylene carbonate has many applications,and with the development of human life and technology,green chemical preparation of propylene carbonate has become a necessary trend.CO₂ is a greenhouse gas,and its collection and utilization is a popular subject.Preparation of propylene carbonate through cycloaddition of Propylene oxide（PO）and CO₂ is a reaction with atom utilization of 100%,and there are many related researches in recent years.In these researches,the scholars have developed various catalysts,which have presented great catalysis performance during catalysis and preparation of propylene carbonate.However,there are still some problems,such as rigorous reaction condition,requirement to add additive and difficulty for catalyst separation.Therefore,it is necessary to develop new catalyst.In order to address this issue,we have studied some new functional catalysts.As a new material,the ionic liquid has the advantages of multi-structure,multi-function and high stability,which has attracted great concern from the academic circle.Hence,we conduct research on applying some new functional ionic liquid catalysts to catalyze preparation of propylene carbonate with PO and CO₂.In this paper,first of all,we synthesized the four ionic liquids,conducted materialcharacterization with mass spectrum,infrared spectrum and ¹H-NMR spectrum,and obtained the synthetic target product based on spectral analysis.Then,we employed the free radical polymerization method to polymerize ionic liquid and divinyl benzene to generate the ionic liquid polymer,conducted material characterization using infrared spectrum,element analysis and thermogravimetry,and determined the material structure and performance based on analysis.The ionic liquid polymer was used as catalyst to catalyze the preparation of propylene carbonate with PO and CO₂.Without using the catalysis additive and solvent,the catalysis performances of four catalysts were obtained under specific conditions,and then,the catalysis condition for the catalyst with best performance was optimized to obtain the optimal reaction condition:the reaction temperature of 130℃,the initial CO₂ pressure of 1.8MPa,the reaction time of 4h,the PO weight of 10g and the polyion liquid of 1g.Under this condition,the PO conversion rate could reach 86.6%.In order to further understand the catalysis mechanism of ionic liquid catalystduring the reaction process,we conducted theoretical analysis.Theoretical calculation was conducted using the DFT（Density Functional Theory）in Gauss-Assisted Software and the Multiwfn software,respectively.In the Gaussian calculation,the structural model of material was obtained,related interactions were analyzed,and we also analyzed the change in the bond length between PO and CO₂,the electrostatic potential and frontier orbital.In Multiwfn,the topological calculation of electron density was conducted,the IL and PO generation hydrogen bonds were calculated according to the theoretical model,and the bond energy was also calculated.Finally,the mechanism of using ionic liquid to catalyze the PO cycloaddition reaction was inferred.