Alkanes, selective oxidation

Alkanes, selective oxidation, cobalt catalysis, 44 291 Alkene... 

The presence of a large fraction of adsorbed species on the catalyst surface thtis not only decreases the number of available active sites for alkane selective oxidation, but also decreases their s >ecific turnover number, thus increasing the surface lifeiime of adsorbed intermediates on the PVO deactivated surface. This increases the probability of parallel unselective reactions with a decrease in the selectivity to anhydrides. 

Spectroscopy of the PES for reactions of transition metal (M ) and metal oxide cations (MO ) is particularly interesting due to their rich and complex chemistry. Transition metal M+ can activate C—H bonds in hydrocarbons, including methane, and activate C—C bonds in alkanes [18-20] MO are excellent (and often selective) oxidants, capable of converting methane to methanol [21] and benzene to phenol [22-24]. Transition metal cations tend to be more reactive than the neutrals for two general reasons. First, most neutral transition metal atoms have a ground electronic state, and this... 

One of the exciting results to come out of heterogeneous catalysis research since the early 1980s is the discovery and development of catalysts that employ hydrogen peroxide to selectively oxidize organic compounds at low temperatures in the liquid phase. These catalysts are based on titanium, and the important discovery was a way to isolate titanium in framework locations of the inner cavities of zeolites (molecular sieves). Thus, mild oxidations may be run in water or water-soluble solvents. Practicing organic chemists now have a way to catalytically oxidize benzene to phenols alkanes to alcohols and ketones primary alcohols to aldehydes, acids, esters, and acetals secondary alcohols to ketones primary amines to oximes secondary amines to hydroxyl-amines and tertiary amines to amine oxides. 

Comparative activity ofTi-beta and Euro-TS-1 for selective oxidation of different alkanes... 

The selective oxidation and, more generally, the activation of the C-H bond in alkanes is a topic of continuous interest. Most methods are based on the use of strong electrophiles, but photocatalytic methods offer an interesting alternative in view of the mild conditions, which may increase selectivity. These include electron or hydrogen transfer to excited organic sensitizers, such as aryl nitriles or ketones, to metal complexes or POMs. The use of a solid photocatalyst, such as the suspension of a metal oxide, is an attractive possibility in view of the simplified work up. Oxidation of the... 

Scheme 9.1 shows a generalized sequence of reactions for the oxidation of an alkane, via alcohol, ketone and carboxylic acid, to the completely oxidized products, water and carbon dioxide. The latter are often referred to as combustion products as they are the same as those formed by burning hydrocarbons. These are not normally desirable chemical products unless it is necessary to destroy a toxic, hazardous or otherwise unwanted waste material. Oxidation itself is not difficult to achieve, and is a highly exothermic or even explosive process. Selective oxidation, however, is a much greater challenge, as it is important to stop the sequence at the desired product without proceeding further down the oxidation pathway. 

Metal-oxygen bond, 27 195, 196 insertion reactions, 28 136-141 strength and selectivity, oxidative dehydrogenation of alkanes, 40 26-28... 

J. M. Thomas, R. Raja, G. Sankar, and R. G. Bell, Molecular-sieve catalysts for the selective oxidation of linear alkanes by molecular oxygen. Nature 398,227 (1999) J. M. Thomas, Designing a molecular sieve catalyst for the aerial oxidation of n-hexane to adipic acid, Angew. Chem. Int. 

The reaction network for isobutane selective oxidation catalyzed by POMs consists of parallel reactions for the formation of methacrolein, methacrylic acid, carbon monoxide, and carbon dioxide. Consecutive reactions occur on methacrolein, which is transformed to acetic acid, methacrylic acid, and carbon oxides. ° Methacrylic acid undergoes consecutive reactions of combustion to carbon oxides and acetic acid, but only under conditions of high isobutane conversion. Isobutene is believed to be an intermediate of isobutane transformation to methacrylic acid, but it can be isolated as a reaction product only for very low alkane conversion. ... 

He got a Habilitation a diriger les recherches in 2008 and he is now developing his own project that consists of the elaboration of new hybrid metalloprotein catalysts for selective oxidation reactions, by insertion of metal cofactors into xylanases. He then studies their peroxidase, catalase, and monooxygenase activities, in particular in the selective oxidation of sulfides, alkanes, and alkenes. 

Selective oxidation of sulfides, alkanes, and alkenes using iron biocatalysts and mimics. 

The selective oxidations of the terminal positions of -alkanes are an example of substrate-shape selectivity. Product-shape selectivity has been used to enhance the selectivity of the type IIaRH oxidation of cyclohexane [66-68], For example, oxidation of cyclohexane at 373 K for 8 hr using FeAlPO-31 (pore aperture 5.4 A) as a catalyst resulted in 2.5% conversion to a mixture which contained 55.3% of adipic acid and 37.3% of a mixture of cyclohexanol and cyclohexanone [68]. In contrast, oxidation under identical conditions using FeAlPO-5 (pore aperture 7.3 A) resulted in only 9.2% of adipic acid and 89.5%... 

The data in Table 7 show that the selectivity for 2-oxygenated products in the oxidation of alkanes on TS-1 is somewhat higher than could be expected on statistical grounds. Only for 3-methylpentane, this selectivity becomes overcompensated by the higher reactivity of tertiary C-H compared to secondary C-H positions. This indicates that the first step of the oxidation, i.e. the formation of alcohols from alkanes is slightly regioselective. Within the ketone fraction, the selectivity for 2-ketones is even more pronounced, indicating that 2-alcohols are selectively oxidized to 2-ketones in the... 

The selective oxidation of alkanes to ketones using Fe(III)(PA)3 and Fe(III)(PA)2Cl2, Pyr2H (PA = picolinic acid), is performed with BTSP and proceeds by a nonradical mechanism. The Fe -Fe manifold is responsible for the oxidation process (equations 55 and 56). ... 

Activation of Alkanes The selective oxidation of these unreactive hydrocarbons continues to receive attention. Progress in this area is reported by Matsumura, et al, Driscoll, et oL, Banares and Fierro, Erdohelyi, et oL, Owens, et al, and Khouw, et al. 

Selective Oxidation of Alkanes, Alkenes, and Phenol with Aqueous H2O2 on Titanium Silicate Molecular Sieves... 

The selective oxidation of alkanes is cuiTently one of the most widely studied classes of catalytic reactions. This work mainly concentrates on the oxidative dehydrogenation of methane, with some attention paid to the partial oxidation of the product of this reaction, ethane. As regards the latter reaction, higher yields of pai tial oxidation products (acetaldehyde and ethylene) were achieved when N2O was used instead of O2 (1-6). 

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