Aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by carbon nanotubes without any promoter

摘要

Carbon nanotubes (CNTs) were used as metal-free catalysts for selective oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) with molecular oxygen as the terminal oxidant in the absence of any promoter. The effects of reaction conditions, solvent and surface chemistry of CNTs on the catalytic performances have been investigated. The results showed that the solvent has a remarkable effect on oxidation of BzOH. The effect of the CNTs surface chemistry on the catalytic activity was revealed, and the surface carboxylic groups were particularly detrimental for the catalytic activity. A reasonable mechanism responsible for the liquid-phase oxidation of BzOH on CNTs was proposed, and electron transfer in graph-ene skeletons played an important role. Nitrogen doping efficiently enhanced the catalytic activity of CNTs for aerobic oxidation of BzOH, arising from improving electron transfer. In addition, the NCNTs revealed outstanding recydability and exhibited excellent potential for industrial application of the BzOH oxidation to BzH.