Metal-Free Mesoporous SiO₂ Nanorods as a Highly Efficient Catalyst for the Baeyer–Villiger Oxidation under Mild Conditions

Abstract

The development of efficient and environmentally friendly catalysts for oxidative reaction is of great importance in applied catalysis. In this work, a simple and environmentally benign approach for highly selective preparation of ε-caprolactone by oxidation of cyclohexanone has been carried out, which employed metal-free mesoporous silica (mSiO2) nanorods as catalyst under atmospheric pressure. The metal-free silica catalyst was applied for the first time in the Baeyer–Villiger (B–V) oxidation reaction. It showed efficient catalytic performance for the B–V oxidation of various cyclic ketones and aliphatic ketones with O2/benzaldehyde as oxidant. The catalyst could be easily separated from the reaction system by filtration and reused several times without significance loss of activity. Moreover, electron paramagnetic resonance (EPR) spectra of the reaction were obtained, indicating the existence of benzoyloxyl radical. The mechanism study of the reaction demonstrated that the super large surface area diluted the concentration of radicals and the adsorption of radicals could protect the radical species from inhibition.

Sn‐Ti Submicrospheres with Tunable Particle Size for Cyclohexanone Baeyer‐Villiger Oxidation

“…[6,7] Oxygen, as a green, safe and cheap oxidant, is a very promising substitution for the ε-caprolactone preparation by co-oxidation in the presence of aldehydes. [8][9][10][11][12] Up to now, catalysts used for oxygen/aldehyde oxidation mainly include Fe-based, [8] Cubased, [13] and Sn-based materials, [14] etc. Among them, Sn-based materials have been widely studied because of its Lewis acid, which can activate the carbonyl group of cyclohexanone and is more favorable to the cyclohexanone conversion.…”

Cobalt-Tetraamide-Phthalocyanine Immobilized on Fe3O4/Chitosan Microspheres as an Efficient Catalyst for Baeyer–Villiger Oxidation

“…High concentration of hydrogen peroxide has a good oxidation effect on the B–V reaction, but the water produced by the reaction is prone to hydrolyze lactones, and high concentration has a higher risk in industrial production. , Based on the above-mentioned factors, the harmfulness and high economic cost of peroxide limit its practical application. Another strategy uses aldehydes and molecular oxygen as green oxidants, known as the Mukaiyama method . Many research studies have been focused on the aldehyde/O 2 oxidation system because the use of O 2 fulfills the considerations of environment, economy, and safety.…”

“…Another strategy uses aldehydes and molecular oxygen as green oxidants, known as the Mukaiyama method. 8 Many research studies have been focused on the aldehyde/O 2 oxidation system because the use of O 2 fulfills the considerations of environment, economy, and safety.…”

Kinetics study and process simulation of reactive distillation for the synthesis of ε‐caprolactone

“…In addition, this synthesis process took a long time due to the weak ability of hydrogen peroxide. [ 15 ] Therefore, a two‐step indirect oxidation method was proposed. In this method, organic acid was employed and oxidized by hydrogen peroxide to peracids, and then peracids oxidized cyclohexanone to ε‐CL.…”

“…Currently, how to choose a catalyst and oxidizing agent is a research focus for the synthesis of ε‐CL, and most processes of production are based on batch reactors. [ 15,18–20 ] An airlift loop sonochemical batch reactor was studied for oxidizing cyclohexanone to ε‐CL, which intensified the reaction rate and increased the yield of product. [ 21 ] Nevertheless, there are some shortcomings in the batch reactor processes.…”