Study Of Ionic Liquid Acidic Strength Based On The Alkylation

To the limitation of current ionic liquid’s weak acidic in the alkylation, a scheme ofionic liquid acidic strength is put forward based on the theoretical research. Then thegeneral law of sulfonic acid functionalized ionic liquid acidic strength has beensummarized. This method takes the advantages of simple operation, mild reactionconditions. Due to our study, the serious environmental pollution problems in the processof using traditional liquid acid catalyst can be basically solved. The process route of greencatalytic, better separation and purification conditions of alkylation were established.Taking [C4SO3HPy]HSO4as research object, Its structures, acid content, acid strengthand thermal stability were determined.The precursor compound [C4SO3Py]±, cation [C4SO3HPy]+and the ion pairs of SO3Hfunctionalized acidic ionic liquids [C4SO3HPy]HSO4were studied systematically by DFTtheory. the structure optimization, frequency analysis and energy calculation were obtained,then interaction energy and atomic charge were analyzed. It was found that hydrogenbonding played an important role in the stable structure of the zwitterion, cation and ionicliquid. The strongest interaction in the ionic liquid was found between the anion and thefunctional group. When the strong intramolecular hydrogen bonds were formed, thehydrogen of HSO3-was prone to combined with oxygen atom of HSO4-. The final existingform was the interaction between zwitterion and H2SO4. Further study of charge analysisshow that the hydrogen in anion and functioned cation was acidic, besides,11H in thepyridine ring also show a certain acidic charge.First, the modification of IL using metal chloride and superacid based on thetheoretical research was studied. It is found that both the modified methods have played acertain role in enhancing acid strength of [C4SO3HPy]HSO4, which was equal with98%H2SO4when n(BaCl2): n(IL)=0.305, n(CaCl2)：n(IL)=0.482, n(AlCl3): n(IL)=0.361, and themass content of H2SO4is6.04%. The effects of moldified [C4SO3HPy]HSO4in alkylationof synthesis4-TBC was studied under the same reaction conditions. The research foundthat IL moldified with metal chloride did not obtained preferably catalytic effect. Howere,the results of IL moldified with H2SO4show that when the mass content of H2SO4is7.77%,the selectivities to4-TBC reached92.5%, The catalytic activity was far higher than the pure H2SO4. The universal applicability of two means of modification to sulfonic acidfunctionalized ionic liquids was verified by moidified ILs ([C4HSO3Hmim]HSO4、[C4HSO3HN(CH2CH3)3]HSO4) with BaCl2and H2SO4.A preliminary discussion to [C4SO3HPy] HSO4load in zeolite, such as gamma-Al2O3、Hβ was made, IL had great effects on zeolite, but the effect of zeolite to IL need futherinvestigate. This method provides a new way of thinking on acid strength of ionic liquid.