Light-Driven CH Oxygenation of Methane into Methanol and Formic Acid by Molecular Oxygen Using a Perfluorinated Solvent

Light-Driven CH Oxygenation of Methane into Methanol and Formic

Acid by Molecular Oxygen Using a Perfluorinated Solvent

Angew. Chem. Int. Ed. 2017, 56, 1-5 

http://onlinelibrary.wiley.com/doi/10.1002/anie.201710945/epdf

Abstract:

The chlorine dioxide radical (ClO2·) was found to act as an efficient oxidizing agent in the aerobic oxygenation of methane to methanol and formic acid under photoirradiation. Photochemical oxygenation of methane occurred in a two-phase system comprising perfluorohexane and water under

ambient conditions (298 K, 1 atm). The yields of methanol and formic acid were 14 and 85 %, respectively, with a methane conversion of 99% without formation of the further oxygenated products such as CO2and CO. Ethane was also photochemically converted into ethanol (19%) and acetic acid (80%). The methane oxygenation is initiated by the photochemical Cl-O bond cleavage of ClO2· to generate Cl· and O2. The produced Cl· reacts with CH4 to form a methyl radical (CH3·). Finally, the oxygenated products such as methanol and formic acid were given by the radical chain reaction. A fluorous solvent plays an important role of inhibiting the deactivation of reactive radical species such as Cl· and CH3·.

Selective Activation of Methane on Single-Atom Catalyst of Rhodium Dispersed on Zirconia for Direct Conversion

Selective Activation of Methane on Single-Atom Catalyst of Rhodium
Dispersed on Zirconia for Direct Conversion 

Y. Kwon, T. Y. Kim, G. Kwon, J. Yi, and H. Lee

J. Am. Chem. Soc. ASAP
(http://pubs.acs.org/doi/pdf/10.1021/jacs.7b11010)

Abstract:

Direct methane conversion into value-added products has become increasingly important. Because of inertness of methane, cleaving the first C−H bond has been very difficult, requiring high reaction temperature on the heterogeneous catalysts. Once the first C−H bond becomes activated, the remaining C−H bonds are successively dissociated on the metal surface, hindering the direct methane conversion into chemicals. Here, a single-atom Rh catalyst dispersed on ZrO2 surface has been synthesized and used for selective activation of methane. The Rh single atomic nature was confirmed by extended X-ray fine structure analysis, electron microscopy images, and diffuse reflectance infrared Fourier transform spectroscopy. A model of the single- atom Rh/ZrO2 catalyst was constructed by density functional theory calculations, and it was shown that CH3 intermediates can be energetically stabilized on the single-atom catalyst. The direct conversion of methane was performed using H2O2 in the aqueous solution or using O2 in gas phase as oxidants. Whereas Rh nanoparticles produced CO2 only, the single-atom Rh catalyst produced methanol in aqueous phase or ethane in gas phase.

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