New Understanding of Selective Aerobic Oxidation of Ethylbenzene Catalyzed by Nitrogen-doped Carbon Nanotubes

Selective aerobic oxidation of hydrocarbons undergoes a free-radical chain reaction to yield corresponding value-added products is the significant process in the chemical industry. Nanocarbons with heteroatoms doping as free-metal catalysts have been proved to be excellent alternatives in various fields of reactions. In this work, nitrogen doped carbon nanotubes (NCNTs) were applied for the aerobic oxidation of ethylbenzene (EB) in the liquid-phase. The catalytic performance was unexpectedly suppressed, even lower than the control experiment, which is totally different from earlier publications. Mechanistic studies demonstrated that N doping would inhibit the abstraction of alpha-H from EB molecule and end the radical propagation, thus suppressing the overall activity. Addition of TBHP would be helpful for the alpha-H abstraction and forming alkyl radicals, which start the Franck-Rabinowitch cage reaction and promote radical propagation in the presence of carbon catalysts. Herein, a higher catalytic efficiency with 46 % EB conversion and 72 % AcPO selectivity were obtained over NCNTs with O-2 and TBHP as dual-oxidants.