2.1 Cumene oxidation
CNTs used in the oxidation reaction of cumene were obtained from Zhongshan CNM Plastic Co., Ltd., and the metal impurities in CNTs were tested by ICP-AAS. ZnCl2, ZnBr2 and ZnAc2 were used as additive, which were purchased from Aladdin.
The cumene oxidation reaction was carried out in a three-neck flask (25 mL), supplied with a magnetic stirrer, reflux condenser and the oil bath. Firstly, CNTs (100 mg), additive (10 mg), and cumene (10 mL) were added into the flask, sonicated for 5 min, then heated to preconcerted temperature (80 ℃) followed by the bubbling of 25 mL·min-1 oxygen for 8 h. When the reaction was over, the reaction mixture was cooled to room temperature and filtered to separate the liquid for detection. The concentration of CHP was determined according to the iodometric method.[20] After the reduction of CHP to PP via triphenylphosphine reaction, the other liquid products were detected by gas chromatography (an Agilent GC-7890B) equipped with a DB-1701 capillary column (30 m × 0.25 mm × 0.25 μm) and a flame ionization detector.