Preparation Of Ionic Liquids And Its Applications In The Oxidation Of Trimethylphenol

2, 3, 5-Trimethyl-1, 4-benzoquione(TMBQ) is a key intermediate for thesynthesis of vitamin E, which can be obtained from the oxidation of2, 3, 6-trimethylphenol (TMP). However, the low catalytic activity, large amount ofcatalyst, environmental and safe problem caused by use of organic solvent aregeneral problems encountered in the oxidation. In this dissertation, ionic liquids,which are featured as negligible volatility, nonflammability, excellent chemical andthermal stability, good catalytic ability and dissolvability, were introduced to providean alternative process for the clean production of TMBQ.Six kinds of ammonium salts and imidazolium-based ionic liquids have beensynthesized and characterized firstly. The single crystal of dipropylammomiumhydrosulfate was obatained by solvent diffusion method. Furthermore, the structureof dipropylammomium hydrosulfate indicated by the X-ray diffraction is featured bylayered reticulation linked by hydrogen bond.Ionic liquids were then used as co-catalyst for the oxidation of TMP inconventional organic solvent, which reduced the amount of catalyst to 10mol% ofsubstrate. Additionally, the results demonstrated that the nature of cations and anionsof ionic liquids had significant effects on the selectivity of TMBQ. Among variouscations with fixed anion examined, imidazolium-based ionic liquids showed betterselectivity to TMBQ than ammonium-based ionic liquids. As for the different anionsstudied, it followed the same order: BF₄＞Cl^-＞≈Br^-＞NO₃^-HSO₄^-＞CH₃COO^-. Whenthe amount of catalyst composed by 1-butyl-3-methylimidazolium tetrafluoroborate([Bmim]BF₄) and copper(â…¡) chloride was equivalent with 10mol% of TMP, theselectivity of 94.7% at full conversion could be obtained within 5h at 85℃.Ionic liquids were finally performed as solvent and co-catalyst for the oxidationof TMP to eliminate the use of volatile and flammable organic solvent. The conversion of 100% and selectivity of 88.3% could be achieved in [Bmim]BF₄within 1h at 60℃, which were significantly improved in comparison with those intraditional organic solvents. Additionally, according to the results determined byHPLC and GC-MS, the oxidation of TMP was proposed to be a free radical reaction.