Design And Preparation Of Novel Supported Ionic Liquids And Their Synergistic Catalysis For Biginelli And Knoevenagel Reactions

Ionic liquids are rich in anions and cations,and have excellent physical and chemical properties,such as adjustable structure,good chemical and thermal stability,low vapor pressure and strong solubility.As"clean solvents"and catalysts,ionic liquids have broad application prospects in chemical and catalytic fields.However,it is difficult to use ionic liquids in catalytic reactions because of the large dosage of ionic liquids,the low atomic utilization rate and the difficulty of recovery.Based on the unique advantages of supported ionic liquids in the area of catalysis and separation,imidazole ionic liquids were loaded on the pore surface of silicon-based materials by grafting method,and a series of mesoporous silicon-supported ionic liquids were designed and prepared in this thesis.A series of MCM-41 supported monoimidazole ionic liquids IL-anion@MCM-41@Cu were prepared by grafting monoimidazole ionic liquids onto the surface of mesoporous materials MCM-41.A series of PMO-IL-anion ionic liquids were prepared by grafting diimidazole ionic liquids onto the surface of PMO channels.The structure and properties of catalysts were confirmed by characterization method of FT-IR,UV-Vis,XRD,SEM,N₂adsorption-desorption,EDS and TG,etc.The results show that imidazole ionic liquids have been successfully grafted onto the surface of the material pore without affecting the pore characteristics of the carrier.In addition,the catalyst has good thermal stability.A series of MCM-41 supported monoimidazole ionic liquids IL-anion@MCM-41showed good catalytic activity in Biginelli reaction with ethanol as the solvent.Among them,the catalyst IL-HSO₃@MCM-41 containing HSO₃^-has better catalytic performance,which may be due to its ability to provide hydrogen protons,stabilize and activate substrates,thus increasing the active sites of the molecular reactions of substrates and promoting the reaction.After IL-HSO₃@MCM-41 was doped with Cu by impregnation method,the catalytic performance of the catalyst was further improved,because the good dispersion of Cu on the support increased the active center of the catalyst.In the optimum reaction conditions and catalytic system,the conversion and yield of the reaction were over 90%.The cyclic experiment of the catalyst showed that IL-HSO₃@MCM-41@Cu could be effectively reused for 6 times.In Knoevenagel reaction using ethanol as solvent,catalytic activities of a series of PMO supported bisimidazole ionic liquids PMO-IL-anion were investigated.Among them,the catalysts PMO-IL-PF₆ and PMO-IL-NTf₂ have the best catalytic performance,which may be due to the synergistic catalysis of basic sites and mesoporous support.Under the optimum reaction conditions and catalytic system,the conversion and yield of the reaction were over91%.Cyclic experiments of the catalyst showed that PMO-IL-PF₆?PMO-IL-NTf₂?could be effectively reused for five times.In addition,the structure of the target product was confirmed by melting point test and ¹HNMR and LC-MS analysis.The novel supported ionic liquids designed above have the advantages of both homogeneous and heterogeneous catalytic systems:while reducing the dosage of ionic liquids and improving the utilization rate of ionic liquids,they can also be separated from the products very well without causing environmental pollution,which provides a new idea for industrial catalytic synthesis.