Understanding of the Oxidation Behavior of Benzyl Alcohol by Peroxymonosulfate via Carbon Nanotubes Activation

Abstract

Selective oxidation of benzyl alcohol (BzOH) into benzaldehyde (BzH) is very important in synthetic chemistry. Peroxymonosulfate (PMS) is a cheap, stable, and soluble solid oxidant, holding promise for organic oxidation reactions. Herein, we report the catalytic PMS activation via carbon nanotubes (CNTs) for the selective oxidation of BzOH under mild conditions without other additives. A remarkable promotion of BzH yield with a selectivity over 80% was achieved on modified CNTs, i.e., O-CNTs via the radical oxidation process, and the oxygen functionalities for catalysis were comprehensively investigated by experimental study and theoretical exploration. To understand the different surface oxygen species on CNTs for the activation of PMS, density functional theory (DFT) calculations were performed to investigate the adsorption behavior of PMS on various CNTs. The electrophilic oxygen was identified as the electron captor to activate PMS by O−O bond cleavage to form SO 5•− and SO 4 •− radicals. The nucleophilic carbonyl groups can also induce a redox cycle to generate • OH and SO 4•− radicals, but phenolic hydroxyl groups impede the radical process with antioxidative functionality. The carbocatalysis-assisted PMS activation may provide a cheap process for the selective oxidation of alcohols into aldehydes or ketones. The insight achieved from this fundamental study may be further applied to other organic syntheses via selective oxidation.

Cobalt Single Atoms Embedded in Nitrogen‐Doped Graphene for Selective Oxidation of Benzyl Alcohol by Activated Peroxymonosulfate

“…The reaction conditions were determined based on our previous work. [ 20 ] The catalyst‐free PMS could hardly oxidize BzOH, with the conversion lower than 5% and the BzH yield around 1%. GO showed very limited enhancement of BzH yield (5.0%) while the N doping effectively increased the BzH yield to 30.1% with 86.3% BzH selectivity, indicating that the N species on graphene can serve as active centers to activate PMS.…”

“…[3,22] The sole PMS can yield 87% BzH in homogeneous environment, while extra additives are still needed. [23] The selectivity of SACo@NG is also higher than radical based BzOH oxidation by carbon nanotubes activated PMS (80.1%), [20] suggesting the intrinsic oxidation mechanism over SACo@NG may differ from the metal-free activated PMS oxidation. Compared with Co NPs, the Co SACs exposed more active sites for PMS activation thus the BzOH oxidation rate is greatly enhanced.…”

Au-Pd nanoparticles immobilized on TiO2 nanosheet as an active and durable catalyst for solvent-free selective oxidation of benzyl alcohol

“…Aldehydes are critical chemical intermediates for the production of pharmaceuticals, fragrances, plastics, and fine chemicals et al [1,2]. The traditional processes for benzaldehyde production involved chromates, permanganates, and peroxides together with organic solvents, which are not only expensive but also environmentally-unfriendly [3]. Hence, it is urgent to introduce molecular oxygen or compressed air as an oxi-dant to substitute the traditional stoichiometric oxidants in the selective catalytic oxidation of alcohol for green chemistry approach.…”

Rapid and long-lasting acceleration of zero-valent iron nanoparticles@Ti3C2-based MXene/peroxymonosulfate oxidation with bi-active centers toward ranitidine removal

“…) belongs to a chemically stable and solid oxidant with an asymmetric structure, and serves as a precursor for the generation of sulfate radicals (SO 4 c À ) via activation. 13,14 The standard redox potential of E 0 (SO 4 c À /SO 4 2À ) (2.5-3.1 V) is higher than that of E 0 (HOc/OH À ) (2.7 V), and therefore SO 4 c À has been used as a more aggressive oxidizing agent for aqueous contaminant degradation. 15,16 Various transition metal elements such as Co, Ce, Fe and Ni have been widely applied for PMS activation (eqn (1)), due to the low energy consumption requirements of these activation systems.…”