Application Of Environmentally Friendly Ionic Liquid Catalyst In The Synthesis Of Cyclic Carbonate

The content of carbon dioxide in the natural environment is about 400 ppm,which is equivalent to 0.04 percent of the earth’s atmosphere by volume.It is an important gas for life on earth to survive.However,it becomes very dangerous when it is emitted uncontrolled on Earth from different man-made and natural sources such as fossil fuel power plants,industrial processes,transportation,volcanic eruptions and forest fires.In the past few decades,due to the rapid burning of fossil energy and various human activities,a large amount of carbon dioxide has been released into the atmosphere,which has directly caused and accelerated global climate change.The burning of fossil fuels such as coal,oil,and natural gas has increased dramatically with industrialization and the growth of the global population,which increased energy demand.This excessive consumption of fossil fuels produces about 45%of carbon dioxide emissions and accounts for more than half of global greenhouse gas emissions.The result is uncontrolled carbon dioxide emissions into the atmosphere,causing atmospheric carbon dioxide levels to increase dramatically by 25%over the past century.The 2019 CO₂ concentration of 414.7 ppm is estimated to be equivalent to emitting about 40 billion tons of CO₂ per year.Carbon dioxide concentrations are expected to reach 500 ppm by 2050,which is one of the most serious environmental problems facing the world today.However,the chemical properties of carbon dioxide are very stable,and it is not easy to chemically react with other substances.Therefore,developing efficient catalysts to convert carbon dioxide into high value-added chemical products is an important challenge.In order to meet the requirements of today’s environmental protection,a serious of halogen-free green catalyst was designed.First,we synthesized a series of novel functionalized imidazolyl amino acid ionic liquid catalysts.On the basis of previous studies,we synthesized four ionic liquid catalysts:1-hydroxyethyl-3-butylbenzotriazole butyric acid,1-hydroxyethyl-3-butylbenzotriazole tartaric acid,1-hydroxyethyl-3-butylbenzotriazole lactic acid,1-hydroxyethyl-3-butylbenzotriazole acetic acid.And the synthesized compounds were characterized by proton nuclear magnetic resonance spectroscopy（~1H NMR）,and the number of hydrogen atoms in ionic liquids and the chemical environment of hydrogen atoms were determined.The functional groups and chemical bonds of the compounds were investigated by infrared spectroscopy（IR）.Through the control variates method,the temperature,reaction time,pressure and catalyst dosage were explored to investigate the carbon dioxide cycloaddition of the catalyst,and the optimal reaction conditions were determined.And on the basis of previous studies,we propose a possible mechanism of the catalytic reaction.In this experiment,using epichlorohydrin as the substrate,experimental results show that under the condition that the amount of catalyst is 0.5 mol%,when the pressure is 0.4 MPa,the temperature is95℃,and the reaction time is 12 h,the reaction time of cyclic carbonate is 12 h.In this experiment,using epichlorohydrin as the substrate,we found that the yield of chloropropylene carbonate reached98.6%when the catalyst dosage was 0.5 mol%,the pressure was 0.4 MPa,the temperature was95℃,and the reaction time was 12 h.Three functionalized poly（ionic liquid）s catalysts were also synthesized in this paper.On the basis of previous studies,the hydroxyl-functionalized imidazolium ionic liquid 3-hydroxyethyl-1-vinylimidazolium bromide was synthesized,and then reacted with divinylbenzene（DVB）by radical polymerization and anion exchange reaction.Functionalized poly（ionic liquid）s P（nDVB-[HVim][Br]）,P（nDVB-[HVim][GA]）,P（nDVB-[HVim][LA]）and P（nDVB-[HVim][P-h A]）were synthesized,where n is the ratio of the amount of DVB to the amount of 3-hydroxyethyl-1-vinylimidazolium ionic liquid.The n is equal to 1 in this experiment.The chemical structure of the polymer was determined by infrared spectroscopy（IR）.The microstructure of the polymer was observed by scanning electron microscopy（SEM）.The SEM image showed that the polymer was loosely packed with tiny particles.In this experiment,using epichlorohydrin as the substrate,the experimental results show that the yield of cyclic carbonate reached 98.1%when the catalyst dosage was 0.5 mol%,the pressure was 0.7 MPa,the temperature was 110℃,and the reaction time was10 h.After three cycles,the catalyst activity did not decrease obviously.