Study On The Effect Of The Structure Of Imidazolyl Acidic Ionic Liquid And Surface Modified ?-Al₂O₃ On Catalytic Synthesis Of Tributyl Citrate

Tributyl citrate(TBC)is a new non-toxic plasticizer,which is of great significance to replace the widely used toxic plasticizer phthalate.In this paper,1,3 propane sultone was reacted with spherical ?-Al2O3 with millimeter particle size to prepare solid acid catalysts PrSO3H@?-Al2O3 firstly.And then,three imidazolyl acidic functionalized ionic liquids(1-methyl-3-(3-sulfopropyl)imidazole p-toluenesulfonic acid ionic liquid([MIMPS]OTs),1-ethyl-3-(3-Sulfopropyl)imidazole p-toluenesulfonic acid ionic liquid([EIMPS]OTs)and 1-propyl-3-(3-sulfopropyl)imidazole p-toluenesulfonic acid ionic liquid([PIMPS]OTs))were selected,and the catalytic performance of PrSO3H@?-Al2O3 and three acidic ionic liquids for the synthesis of TBC was discussed.The main research results of the paper are as follows:(1)A surface-modified catalyst PrSO3H@y-Al2O3 with millimeter-level particle size was synthesized using spherical mesoporous?-Al2O3 with millimeter-scale particle size and 1,3-propane sultone as reactants,heated and refluxed in anhydrous toluene.The composition and structure of the catalyst were determined by FT-IR,PXRD and SEM-EDS respectively,and the catalytic performance of the catalyst for the synthesis of TBC under different conditions was gradually investigated by the control variable method.The reaction conditions are controlled as follows:the reaction temperature is the reflux temperature,the amount of catalyst is 6%of the total mass of the reactant material,the molar ratio of acid to alcohol n(CA):n(n-BuOH)=1:5,the reaction time is 4.0 h,the spherical mesopores PrSO3H@?-Al2O3 with millimeter-scale particle size can catalyze the TBC synthesis to achieve that the conversion rate of CA is 90.41%,and the conversion rate of CA should not be less than 86%after reuse 4 times.(2)Three precursors of ionic liquid 1-methyl-3-(3-sulfopropyl)imidazole internal salt(MIMPS),1-ethyl-3-(3-sulfopropyl)imidazole internal salt(EIMPS)and 1-propyl-3-(3-sulfopropyl)imidazole internal salt(PIMPS)were selected,then three acidic ionic liquids[MIMPS]OTs,[EIMPS]OTs and[PIMPS]OTs were synthesized by the reaction of p-toluenesulfonic acid(TsOH)with three ionic liquid precursors respectively.Three acidic ionic liquids were identified by FT-IR and 1H-NMR characterization methods.Through the control variable method,the effects of catalyst dosage,reactant acid-alcohol molar ratio and reaction time on[EIMPS]OTs catalytic synthesis of TBC were systematically investigated,and the differences of catalytic performance and reusability of three acidic ionic liquids under the same conditions were experimented.The experimental results prove that the reaction conditions are controlled as follows:the reaction temperature is the reflux temperature,the catalyst dosage is 4.0%of n(CA),the reactant acid-alcohol molar ratio is 1:6,the reaction time is 2.5 h,the conversion rate of CA during the catalytic synthesis of TBC is above 99%.Repeated use experiments show that[EIMPS]OTs can be reused 3 times under the above reaction conditions,and the conversion rate is not less than 90%.[PIMPS]OTs can only be reused twice and the conversion rate is above 90%.[MIMPS]OTs are precipitated in the form of white liquid beads in the product system,which makes it difficult to recycle.Control the reaction temperature,acid-alcohol molar ratio and reaction time unchanged,and expand the amount of[EIMPS]OTs to 28%of n(CA)for catalytic reaction.The experiment proves that the conversion rate of CA can still be maintained about 99%when the catalyst is reused 15 times.