Solvent-free aerobic epoxidation of 1-decene using supported cobalt catalysts

Selective Oxidation of Alcohols and Alkenes with Molecular Oxygen Catalyzed by Highly Dispersed Cobalt (II) Decorated 12-Tungstosilicic Acid-Modified Zirconia

Traditional procedures for oxidation processes suffer from a lack of selectivity, the use of organic solvents, the toxicity of the reagents, and waste production. As a cleaner alternative, highly dispersed Co over 12-tungstosilicicacid modified zirconia was synthesized and used for the selective oxidation of benzyl alcohol and styrene with molecular oxygen to carbonyl compounds under environmentally benign solvent-free conditions. The supremacy of the present catalyst lies in achieving excellent selectivity (>90%) for products with a very high turnover number. The catalytic activity of the recycled catalysts was also explored under optimized conditions to confirm sustainability. Further, the viability of the catalyst was studied via oxidation of various alcohols and alkenes under optimized conditions as well as superiority by comparison with the reported catalysts.

Direct Propylene Epoxidation with Molecular Oxygen over Cobalt-Containing Zeolites

Direct propylene epoxidation with molecular oxygen is a dream reaction with 100% atom economy, but aerobic epoxidation is challenging because of the undesired over-oxidation and isomerization of epoxide products. Herein, we report the construction of uniform cobalt ions confined in faujasite zeolite, namely, Co@Y, which exhibits unprecedented catalytic performance in the aerobic epoxidation of propylene. Propylene conversion of 24.6% is achieved at propylene oxide selectivity of 57% at 773 K, giving a state-of-the-art propylene oxide production rate of 4.7 mmol/g_cat/h. The catalytic performance of Co@Y is very stable, and no activity loss can be observed for over 200 h. Spectroscopic analyses reveal the details of molecular oxygen activation on isolated cobalt ions, followed by interaction with propylene to produce epoxide, in which the Co²⁺-Co^δ+-Co²⁺ (2 < δ < 3) redox cycle is involved. The reaction pathway of propylene oxide and byproduct acrolein formation from propylene epoxidation is investigated by density functional theory calculations, and the unique catalytic performance of Co@Y is interpreted. This work presents an explicit example of constructing specific transition-metal ions within the zeolite matrix toward selective catalytic oxidations.

Bromine and oxygen redox species mediated highly selective electro-epoxidation of styrene

Olefin epoxidation is an essential transformation and arouses great interest among the scientific community for the key role of epoxide in the chemical industry.

Ag supported on alumina for the epoxidation of 1-hexene with molecular oxygen: the effect of Ag+/Ag0

The catalytic liquid-phase oxidation of 1-hexene with O2 using Ag/porous bowl-shaped alumina shows good selectivity for the epoxidation product.

A new and efficient methodology for olefin epoxidation catalyzed by supported cobalt nanoparticles

A new heterogeneous catalytic system consisting of cobalt nanoparticles (CoNPs) supported on MgO and tert-butyl hydroperoxide (TBHP) as oxidant is presented. This CoNPs@MgO/t-BuOOH catalytic combination allowed the epoxidation of a variety of olefins with good to excellent yield and high selectivity. The catalyst preparation is simple and straightforward from commercially available starting materials and it could be recovered and reused maintaining its unaltered high activity.

Kinetic investigation of aerobic epoxidation of limonene over cobalt substituted mesoporous SBA-16

Incorporation of low coordination Co²⁺ within the structure of mesoporous silica SBA-16 has been accomplished through a facile and green “pH adjusting” method.