Cyclohexene Epoxidation with Cyclohexyl Hydroperoxide: A Catalytic Route to Largely Increase Oxygenate Yield from Cyclohexane Oxidation

Photocatalytic cyclohexane oxidation and epoxidation using hedgehog particles

Inorganic particles are effective photocatalysts for the liquid-state production of organic precursors and monomers at ambient conditions. However, poor colloidal stability of inorganic micro- and nanoparticles in low-polarity solvents limits their utilization as heterogeneous catalysts and coating them with surfactants drastically reduces their catalytic activity. Here we show that effective photo-oxidation of liquid cyclohexane (CH) is possible using spiky particles from metal oxides with hierarchical structure combining micro- and nanoscale structural features engineered for enhanced dispersibility in CH. Nanoscale ZnO spikes are assembled radially on α-Fe₂O₃ microcube cores to produce complex 'hedgehog' particles (HPs). The 'halo' of stiff spikes reduces van der Waals attraction, preventing aggregation of the catalytic particles. Photocatalysis in Pickering emulsions formed by HPs with hydrogen peroxide provides a viable pathway to energy-efficient alkane oxidation in the liquid state. Additionally, HPs enable a direct chemical pathway from alkanes to epoxides at ambient conditions, specifically to cyclohexene oxide, indicating that the structure of HPs has a direct effect on the recombination of ion-radicals during the hydrocarbon oxidation. These findings demonstrate the potential of inorganic photocatalysts with complex architecture for 'green' catalysis.

Peroxide activation by selenium-doped graphite

Selenium-doped graphitic material has shown GPx-like activity and carried out epoxidation of various aromatic and aliphatic alkenes using H2O2, a green oxidant.

Liquid-Phase Cyclohexene Oxidation with O2 over Spray-Flame-Synthesized La1-x Srx CoO3 Perovskite Nanoparticles

La_1−xSr_xCoO₃ (x=0, 0.1, 0.2, 0.3, 0.4) nanoparticles were prepared by spray‐flame synthesis and applied in the liquid‐phase oxidation of cyclohexene with molecular O₂ as oxidant under mild conditions. The catalysts were systematically characterized by state‐of‐the‐art techniques. With increasing Sr content, the concentration of surface oxygen vacancy defects increases, which is beneficial for cyclohexene oxidation, but the surface concentration of less active Co²⁺ was also increased. However, Co²⁺ cations have a superior activity towards peroxide decomposition, which also plays an important role in cyclohexene oxidation. A Sr doping of 20 at. % was found to be the optimum in terms of activity and product selectivity. The catalyst also showed excellent reusability over three catalytic runs; this can be attributed to its highly stable particle size and morphology. Kinetic investigations revealed first‐order reaction kinetics for temperatures between 60 and 100 °C and an apparent activation energy of 68 kJ mol⁻¹ for cyclohexene oxidation. Moreover, the reaction was not affected by the applied O₂ pressure in the range from 10 to 20 bar. In situ attenuated total reflection infrared spectroscopy was used to monitor the conversion of cyclohexene and the formation of reaction products including the key intermediate cyclohex‐2‐ene‐1‐hydroperoxide; spin trap electron paramagnetic resonance spectroscopy provided strong evidence for a radical reaction pathway by identifying the cyclohexenyl alkoxyl radical.

Interfacial charge shielding directs the synthesis of dendritic mesoporous silica nanospheres by a dual-templating approach

A unique ethylene oxide (EO) layer coated core–shell structured spherical micelle was used as a building unit to synthesize dendritic mesoporous silica nanospheres (DMSNs) by a dual-templating approach.

Surface organometallic chemistry in heterogeneous catalysis

Surface organometallic chemistry has been reviewed with a special focus on environmentally relevant transformations (C–H activation, CO₂conversion, oxidation).

Oxidation mechanism of molecular oxygen over cyclohexene catalyzed by a cobalt l-glutamic acid complex

We introduce a new strategy towards the cyclohexene oxidation reaction, which is driven by molecular oxygen with a cobalt(ii)/amine acid complex as the catalyst without any solvents.

Effect of L-cysteine on the oxidation of cyclohexane catalyzed by manganeseporphyrin

Effect of L-cysteine as the cocatalyst on the oxidation of cyclohexane by tert-butylhydroperoxide (TBHP) catalyzed by manganese tetraphenylporphyrin (MnTPP) has been investigated. The results showed that L-cysteine could moderately improve the catalytic activity of MnTPP and significantly increase the selectivity of cyclohexanol. Different from imidazole and pyridine, the L-cysteine may perform dual roles in the catalytic oxidation of cyclohexane. Besides as the axial ligand for MnTPP, the L-cysteine could also react with cyclohexyl peroxide formed as the intermediate to produce alcohol as the main product.

Hollow TS-1 mesocrystals: hydrothermal construction and high catalytic performances in cyclohexanone ammoximation

Hollow TS-1 mesocrystals were obtained by the hydrothermal treatment. The hollow mesocrystalline structure significantly affects their catalytic activity in cyclohexanone ammoximation.

Indium oxide nanocluster doped TiO2 catalyst for activation of molecular O2

The In₂O₃ nanocluster doped faceted nanosize anatase TiO₂ can activate molecular O₂ for styrene epoxidation reaction.

A simple and convenient approach for preparing core–shell-like silica@nickel species nanoparticles: highly efficient and stable catalyst for the dehydrogenation of 1,2-cyclohexanediol to catechol

A simple and convenient approach for the preparation of core–shell-like silica@nickel species nanoparticles.