Promoting the aerobic Baeyer-Villiger oxidation of ketones over carboxylic multi-walled carbon nanotubes

• Published in: Molecular catalysis 2017-09, Vol.438, p.152-158
• Main Authors: Chen, Shao-Yun, Zhou, Xian-Tai, Wang, Jie-Xiang, Luo, Rong-Chang, Luo, Qing-Jin, Yu, Liang-Jun, Ji, Hong-Bing
• Format: Article
• Language: English
• Subjects: Baeyer-Villiger oxidation; Dioxygen; Multi-walled carbon nanotubes; Radical
• ISSN: 2468-8231; 2468-8231
• DOI: 10.1016/j.mcat.2017.06.001

[Display omitted] The carboxylic multi-walled carbon nanotubes (c-MWCNTs) can act as metal-free catalyst to against the inhibition, which are in favor of the chain propagation reactions to assure of producing peroxybenzoic acid to the oxidation of cyclohexanone. •c-MWCNTs presented excellent activity in aerobic oxidation ketones.•c-MWCNTs showed good recyclability and reusability.•Mechanism of c-MWCNTs to stabilize the radical species in the reaction. Multi-walled carbon nanotubes (MWCNTs) as metal-free catalysts presented excellent activity and selectivity in the Baeyer-Villiger oxidation of ketones to corresponding lactones in the presence of molecular oxygen and benzaldehyde. Different factors including catalyst, solvents, amount of catalyst were systematically investigated. Compared with MWCNTs, carboxylic multi-walled carbon nanotubes (c-MWCNTs) catalyst exhibited higher performance for the oxidation of ketones, showing good recyclability and reusability. The yield of ε-caprolactone was obtained with 94% under the optimum conditions. Also, c-MWCNTs presented excellent activity towards the oxidation of various cyclic ketones to the corresponding lactones. The introduced carboxyl group on the surface of MWCNTs was favorable to obtain high dispersion in the reaction solution. In addition, the recording of in situ Electron Paramagnetic Resonance (EPR) and Raman spectroscopy indicated that carboxyl group could significantly stabilize the radical species in the reaction.