Quantum Chemical Calculation Of Imidazole Functionalized Ionic Liquids And Their Synthesis And Application

Greenhouse effect is one of the main global environmental problems in the world.Scientists have been devoted to the research of carbon dioxide conversion technology.Converting carbon dioxide into chemical products with industrial application value can not only reduce the effects of greenhouse gases on the environment,but also greatly gets rid of the dependence on fossil fuels in traditional chemical industry,which is expected to develop clean and renewable green energy.Importantly,converting carbon dioxide catalytic into cyclic propylene carbonates is a kind of green atomic economic reaction with 100%atom utilization,and gradually become one of the effective ways of carbon dioxide reclamation.Such technology could allow us obtain high value-added cyclic propylene carbonates,and provided a new method for the emission reduction and utilization of carbon dioxide.In this work,the structure of imidazole ionic liquid was optimized by Gaussian 09W quantum chemistry software.The free energy change process of CO₂ conversion reaction was calculated as a catalyst.On this basis,the functionalized imidazolium-based ionic liquids with novel structure were synthesized,and its influencing factors for the catalytic conversion reaction of CO₂ were also investigated.There are mainly three parts:?1?The structures of ionic liquids,such as[C₃?mim?₂]Br₂,[OH-C₂mim]Br,[OH-C₃mim]Br and[OH-C₃?mim?₂]Br₂,were optimized by Gaussian 09W,and their Natural Population charge distribution?NPA?,Natural Bond Orbital?NBO?second-order stabilization energy?E?2??,interactions between orbitals and the surface electrostatic potentials?ESP?were investigated.The change of free energy in the process of catalyzed cyclization of carbon dioxide and propylene oxide were calculated.The theoretical calculation results displayed that the Br anion and hydrogen bond attack the open ring of propylene oxide cooperatively,which is the decisive step.Employed[OH-C₂mim]Br and[OH-C₃mim]Br with relatively better catalytic effect as the catalyst,the free energy of cyclization of carbon dioxide and propylene oxide using the[OH-C₂mim]Br was much lower down than[OH-C₃mim]Br.It demonstrated that catalytic effect of[OH-C₂mim]Br was better than[OH-C₃mim]Br.?2?Based on step?1?,Six functionalized imidazolium-based ionic liquids such as1,1'-?1,3-trimethylene?-bis-3-methylimidazolium dibromide?[C₃?mim?₂]Br₂?,1-?2-hydroxyet-hyl?-3-methylimidazolium bromide?[OH-C₂mim]Br?,1-?3-hydroxypropyl?-3-methylimidaz-olium bromide?[OH-C₃mim]Br?,1,1'-?2-hydroxypropyl?bis-3-methylimidazolium dibromide?[OH-C₃?mim?₂]Br₂?,1-?2-aminoethyl?-3-methylimidazolium bromide?[NH₂-C₂mim]Br?,1-?3-aminopropyl?-3-methylimidazolium bromide?[NH₂-C₃mim]Br?were synthesized by heating reflux method using 1-methylimidazole as the main ingredients.?3?The synthesized ionic liquids were preliminary characterized by elemental analysis,IR,UV-Vis,and ¹H-NMR,and then were employed to catalyze the synthesis of cyclic propylene carbonate from carbon dioxide and propylene oxide.The experimental results showed that all the as-prepared ionic liquids possess certain catalytic properties.Specifically,the catalytic effect of[OH-C₂mim]Br is best.The effects of reaction conditions on the catalytic performance were investigated.The results showed that the yield of propylene carbonate catalyzed by[OH-C₂mim]Br was up to 72%,when the pressure of carbon dioxide was 2.0 MPa,the temperature was 115?,and the reaction time was 60 min,which was consistent with the experimental results.The experimental results were consistent with the calculated data.