Oxygen as oxidant

TS-1 is a material that perfectly fits the definition of single-site catalyst discussed in the previous Section. It is an active and selective catalyst in a number of low-temperature oxidation reactions with aqueous H2O2 as the oxidant. Such reactions include phenol hydroxylation [9,17], olefin epoxida-tion [9,10,14,17,40], alkane oxidation [11,17,20], oxidation of ammonia to hydroxylamine [14,17,18], cyclohexanone ammoximation [8,17,18,41], conversion of secondary amines to dialkylhydroxylamines [8,17], and conversion of secondary alcohols to ketones [9,17], (see Fig. 1). Few oxidation reactions with ozone and oxygen as oxidants have been investigated. 

For catalytic oxidations opt for hydrogen peroxide or molecular oxygen as oxidant for catalytic reductions opt for molecular hydrogen as reductant. 

Secondary alcohol oxidases catalyze the oxidation of secondary alcohols to ketones using molecular oxygen as oxidant. A secondary alcohol oxidase from polyvinyl alcohol-degrading bacterium Pseudomonas vesicularis var. povalolyticus PH exhibited activity toward several... 

Meanwhile attempts to find an air oxidation route directly from p-xylene to terephthalic acid (TA) continued to founder on the relatively high resistance to oxidation of the /Moluic acid which was first formed. This hurdle was overcome by the discovery of bromide-controlled air oxidation in 1955 by the Mid-Century Corporation [42, 43] and ICI, with the same patent application date. The Mid-Century process was bought and developed by Standard Oil of Indiana (Amoco), with some input from ICI. The process adopted used acetic acid as solvent, oxygen as oxidant, a temperature of about 200 °C, and a combination of cobalt, manganese and bromide ions as catalyst. Amoco also incorporated a purification of the TA by recrystallisation, with simultaneous catalytic hydrogenation of impurities, from water at about 250 °C [44], This process allowed development of a route to polyester from purified terephthalic acid (PTA) by direct esterification, which has since become more widely used than the process using DMT. 

Ley et al. performed oxidations of activated (benzyhc, allylic) alcohols by employing polymer-attached perruthenate catalysts and oxygen as oxidant. Triethylammo-... 

A structured ruthenium catalyst (metal monolith supported) was investigated by Rabe et al. [70] in the ATR of methane using pure oxygen as oxidant. The catalytic activity tests were carried out at low temperature (<800 ° C) and high steam-to-carbon ratios (between 1.3 and 4). It was found that the lower operating temperature reduced the overall methane conversion and thus the reforming efficiency. However, the catalyst was stable during time on-stream tests without apparent carbon formation. 

Platinum supported on carbon (Pt/C) was tested as solid catalysts in the oxidation of sucrose using molecular oxygen as oxidant (Scheme 10). The reaction was carried out in water and under atmospheric pressure. The support strongly influences the reaction and Pt/C was found more efficient than Pt/Alumina at 353 K. Over Pt/C, at a pH of 9, mono-, di-, and tricarboxylate derivatives were mainly obtained with a tricarboxylate yield of 35% [103]. 

Mo containing Y zeolites were also tested for cyclohexene oxidation with oxygen as oxidant and t-butyl hydroperoxide as initiator [86]. In this case the selectivity for cyclohexene oxide was maximum 50%, 2-cyclohexene-l-ol and 2-cyclohexene-l-one being the main side products. The proposed reaction scheme involves a free radical chain mechanism with intermediate formation of cyclohexenyl hydroperoxide. Coordination of the hydroperoxide to Mo + in the zeolite and oxygen transfer from the resulting complex to cyclohexene is believed to be the major step for formation of cyclohexene oxide under these conditions. 

Manson Ferrie (Ref 6) investigated explosive mixtures consisting of combustible hydrocarbons such as C2H2, and natural gas with oxygen as oxidizer. 

Table 9.1 Oxidation of sulfides ArSR to sulfones catalyzed by LDH-OSO4 using molecular oxygen as oxidant.

In a recent study, Xu et al. managed to lower temperatures to 100 °C by using gold catalyst and oxygen as oxidant. The authors compared the Au/C catalyst and supported Pd or Pt catalysts, and concluded that these systems offered similar performance and that selectivity generally depended on cyclohexene conversion [226]. 

TiOi Powders Using Molecular Oxygen as Oxidant — 195... 

Titanium silicates are catalysts for various oxidation reactions. Most of those investigated have been carried out with H202 and hydroperoxides as the oxidants, and a few have been investigated with ozone and oxygen as oxidants. 

Pasta P, Carrea G, Monzani E, Gaggero N, Colonna S (1999) Chloroperoxidase-Catalyzed Enantioselective Oxidation of Methyl Phenyl Sulfide with Dihydroxyfumaric Acid/Oxygen or Ascorbic Acid/Oxygen as Oxidants. Biotechnol Bioeng 62 489... 

The oxidative carbonylation of amines to formamides was also reported in 2001 in up to 94% yield using Ph3PAuTCl as catalyst and oxygen as oxidant in methanol 7... 

Nearly any primary alcohol serves as a substrate with the exception of methanol and ethanol. Ferricyanide (17, 18), porphyrexide (18), and hexachloroiridate(IV) (18) can replace oxygen as oxidant. Hexachloro-iridate(IV) is consumed to the exclusion of oxygen in aerobic mixtures. When hexachloroiridate(IV) and H202 serve as oxidant and reductant respectively, the normal reaction, vis-a-vis H202, is reversed, and oxygen is produced (18). 

Villar, J. C., Caperos, A., and Garcia-Ochoa, F., Oxidation of hardwood kraft-lignin to phenolic derivatives with oxygen as oxidant. Wood Sci Technol 2001, 35 (3), 245 255. 

A stereocontrolled synthesis of the /ra j-tetrahydrofuran units in Annonaceae acetogenins that relies on the Sharpless asymmetric dihydroxylation protocol is outlined in Scheme 60 <1999TA2551>. In the first step, the disubstituted double bond of the starting material is dihydroxylated followed by monoprotection as a methoxymethyl ether. Einally, a cobalt-catalyzed oxidation using molecular oxygen as oxidant furnishes the /ra j-tetrahydrofuran. 

Recent investigation of this reaction indicates that the C-H bond activation necessary for the reaction with CO can also be achieved using metal catalysts [138]. It is surprising that again the Rh/I system was found to be an active catalyst, if the reaction was carried out in water with oxygen as oxidation agent [139], Ethane has also been used as a source for acetic acid [141],... 

Cp—Cp coupling occurs, probably via the first-formed palladium phenolate (315) to give the bisquinone methide (316), and the latter spontaneously undergoes intramolecular Diels-Alder reaction to the natural lignan carpanone (317) in 46% yield, with stereocontrol at five chiral centers. High yields, up to 94%, have been recorded using oxygen as oxidant with a metal(II)-salen complex as catalyst, e.g. cobalt(II) salen. A low yield of carpanone was also obtained in electrooxidation. 8... 

Neumann, R. Levin, M. Molecular Oxygen as Oxidant in Heteropolyanion Catalysed Oxidations. In Dioxygen Activation and Homogenous Catalytic Oxidation, Simandi, L. I., Ed. Elsevier Amsterdam, 1991 pp 121-127. 

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