Study On The Design,synthesis And Catalytic Performance Of Immobilized Ionic Liquids

In recent years,ionic liquids have been widely used in catalysis,organic synthesis and other fields related to chemistry due to their good thermal stability,solubility,non volatility and designability of structure.However,in the traditional chemical reaction process,ionic liquid catalyst also has the disadvantages of large amount,low economic benefit and difficult separation.In order to solve these problems,researchers have found that ionic liquids can be loaded on solid porous materials by physical adsorption,embedding or chemical covalent bonding.In this way,not only the advantages of ionic liquid and porous carrier can be fully utilized,but also the separation and recovery of catalyst can be improved,and the recycling times of catalyst can be increased,which is more economical and environmentally friendly.According to the above concept,we have synthesized different types of porous solid materials and prepared a series of ionic liquids.Ionic liquids were immobilized in porous solid materials by impregnation method to prepare multi-component composite catalysts.The obtained catalysts were used in Acetal reaction or alkylation reaction to test their catalytic performance.The specific work is as follows:（1）Two kinds of mesoporous molecular sieves SBA-16（N）and SBA-16（Q）were prepared by adjusting the crystallization conditions using TEOS as silicon source.At the same time,the monopositive ionic liquid and dicationic ionic liquid with symmetrical structure were prepared by heteropolyacidation.The two kinds of ionic liquids were immobilized in mesoporous molecular sieves by physical adsorption,and finally four kinds of composite catalyst materials were obtained.The internal structure and properties of the materials were characterized by FT-IR,SXRD,SEM,TEM and BET.The catalyst material was applied to acetalization of benzaldehyde with ethylene glycol,and the catalytic performance of the composite was investigated.Due to the structural symmetry and thermal stability of the ionic liquid,the reaction conditions of SBA-16（N）are mild.Therefore,the composite of spherical SBA-16（N）supported diimidazole ionic liquid has better catalytic performance,the conversion of benzaldehyde reaches 83.00%,and the yield of product reaches 66.85%.（2）On the basis of the previous study,bismuth was introduced into the framework and surface of SBA-16 cage to increase the metal sites,and then Bi-SBA-16 catalyst was synthesized.A series of p-toluenesulfonic acidized imidazole ionic liquids were prepared by two-step method,and their molecular structures were characterized by ¹H NMR and MS.Finally,ionic liquids were loaded into Bi-SBA-16mesoporous materials by impregnation.By FT-IR,SXRD,BET,XPS and TG characterization,it was found that the filling of doped Bi metal and ionic liquid only changed the pore volume and pore diameter,while the three-dimensional cubic pore structure of SBA-16 was not destroyed.The composite catalyst was applied to Friedel-Crafts acylation of anisole with acetic anhydride,and its catalytic effect was evaluated.The results showed that ILc@Bi（10）-SBA-16 was used as the catalyst,and the conversion rate of anisole and yield of aromatic ketone reached 85.41%and69.19%respectively under the reaction conditions.After five cycles,the reactant conversion rate and product yield were reduced by no more than 10%,indicating that ILc@Bi（10）-SBA-16 has good stability and reusability.（3）Porous polymers MIL-100（Fe）and MIL-101（Fe）were synthesized by hydrothermal method.A series of novel polysulfonic acid functionalized ionic liquids[Q-PS-HMA]-4Al Cl₄^-and[TEAPS]-Al Cl₄^-modified by Lewis acid and with B-L double acid were supported on metal organic frameworks MIL-100（Fe）and MIL-101（Fe）.The MOFs were characterized by PXRD,SEM,TEM,TGA and BET.The structure and acidity of ionic liquids were characterized by ¹H NMR,MS and Py-IR.Finally,the catalytic activity of the obtained materials was evaluated in the acylation of anisole with acetic anhydride.Under the optimum reaction conditions,the conversion of anisole was 86.78%,and the yield of aromatic ketones was 69.66%.After 5 cycles,the conversion of reactants and the yield of products decreased,but the overall ratio was less than 10%.