Metal oxide mediated oxidation

Metal oxide-mediated oxidation of methane using air as a primary oxidant is an alternative way to produce N2-free syngas. The concept is based on the oxidation of methane by transition metal oxides in high-oxidation state yielding syngas and corresponding metal oxide in a low-oxidation state ... 

The field of surface-mediated synthesis of metal carbonyl clusters has developed briskly in recent years [4-6], although many organometallic chemists still seem to be unfamiliar with the methods or consider themselves ill-equipped to carry them out. In a typical synthesis, a metal salt or an organometallic precursor is brought from solution or the gas phase onto a high-area porous metal oxide, and then gas-phase reactants are brought in contact with the sample to cause conversion of the surface species into the desired products. In these syntheses, characteristics such as the acid-base properties of the support influence fhe chemisfry, much as a solvenf or coreactant influences fhe chemisfry in a convenfional synfhesis. An advanfage of... 

Kidney Metal ion-mediated nephrotoxicity Protoporphyrin photo-oxidation... 

As different research groups have shown, electrochemical reactions can be mediated by metal powders, metal ions, metal oxides, semi-metals, halogens, inter halogens, halogen oxides, organics, or organometallics [123]. 

The rates of Mn(II) oxidation in natural waters, although slow, are typically orders of magnitude faster than the rate of oxidation of Mn(II) in solution (8,12). It has been suggested that the enhanced rate of Mn(II) oxidation in natural waters is due either to bacterial oxidation (13-16) or to the "catalytic" effects of surfaces such as metal oxides (8, 17-19). The existing evidence suggests that in certain environments bacterial mediation of the reaction is important (13-15). But in many cases the relative importance of bacterial and abiotic "catalysis" in natural waters has not been clearly defined. 

A different approach to the metal peroxo-mediated asymmetric oxidations of sulfides was proposed by Chmielewski and coworkers and more recently by Korb, Adam and coworkers based on the use of optically active hydroperoxides. First attempts to use... 

In the development of effective catalytic oxidation systems, there is a qualitative correlation between the desirability of the net or terminal oxidant, (OX in equation 1 and DO in equation 2) and the complexity of its chemistry and the difficulty of its use. The desirability of an oxidant is inversely proportional to its cost and directly proportional to the selectivity, rate, and stability of the associated oxidation reaction. The weight % of active oxygen, ease of deployment, and environmental friendliness of the oxidant are also key issues. Pertinent data for representative oxidants are summarized in Table I (4). The most desirable oxidant, in principle, but the one with the most complex chemistry, is O2. The radical chain or autoxidation chemistry inherent in 02-based organic oxidations, whether it is mediated by redox active transition metal ions, nonmetal species, metal oxide surfaces, or other species, is fascinatingly complex and represents nearly a field unto itself (7,75). Although initiation, termination, hydroperoxide breakdown, concentration dependent inhibition... 

The oxidation of CO to CO2 by metal-oxide clusters has received quite some attention, in part due to its relevance for the catalytic converters in automobiles, in part also because carbon monoxide is often used as a probe molecule in surface science and the reasonable simplicity of the system may still permit adequate theoretical treatments. In addition to the various systems involving PtmO cations as well as PtmO anions (see above), considerable efforts have been devoted to cluster anions of silver and gold, as reviewed recently [87]. A particular highlight is a conceptual catalytic cycle for the Au2 -mediated oxidation of CO with molecular oxygen, for which... 

A systematic study to identify solid oxide catalysts for the oxidation of methane to methanol resulted in the development of a Ga203—M0O3 mixed metal oxide catalyst showing an increased methanol yield compared with the homogeneous gas-phase reaction.1080,1081 Fe-ZSM-5 after proper activation (pretreatment under vacuum at 800-900°C and activation with N20 at 250°C) shows high activity in the formation of methanol at 20°C.1082 Density functional theory studies were conducted for the reaction pathway of the methane to methanol conversion by first-row transition-metal monoxide cations (MO+).1083 These are key to the mechanistic aspects in methane hydroxylation, and CuO+ was found to be a likely excellent mediator for the reaction. A mixture of vanadate ions and pyrazine-2-carboxylic acid efficiently catalyzes the oxidation of methane with 02 and H202 to give methyl hydroperoxide and, as consecutive products, methanol and formaldehyde.1084 1085... 

Solid/solid redox couples, as defined by metal oxides of metals exhibiting different valencies (e.g. PbOj/PbS04, Mn02/Mn00H, NiOOH/NiO), are used as oxidants in preparative organic syntheses and may be used as heterogeneous mediators for the anodic oxidation of organics, provided ... 

Metal/Metal-Oxide Couples Capable of Acting as Heterogeneous Mediators for the Oxidation of Organic Substrates Dissolved in Aqueous Solution... 

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