2.1 Materials
All chemicals (AR grade) were purchased commercially and used as received. H2SO4 (A.R, 98 wt%) was bought from Sinopharm Chemical Reagent Co., Ltd. Choline chlorides and carbon tetrachloride (≥99.5%) were purchased from Shanghai Titan Scientific Co., Ltd. Phenol (≥99.0%) and benzoic acid (99.5%) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. P-toluenesulfonic acid (99.0%) and hydroxylamine hydrochloride (98.5%) were purchased from Shanghai MackLin Biochemical Technology Co., Ltd. Isobutane/2-butene mixture (86.9/13.1 wt%)was obtained from Shanghai Weichuang Standard Gas Analysis Technology Co., Ltd. Nitrogen (99.99%) gas was purchased from Air Liquide (Shanghai) Gas Co., Ltd.