Complete oxidation of benzene

Co/A1203 [35] Reaction tested was complete oxidation of benzene to C02... 

In addition, complete oxidation of benzene [118, 119] and 2-propanol [118, 120] over Au catalysts was reported. In this case, Au/CeOx was often used and showed high activity [119,120], indicating that the redox properties ofceria phase may play an important role in the formation of surface oxygen species, which results in the complete oxidation of benzene and 2-propanol. 

Naydenov, A. and Mehandjicv, D. Complete oxidation of benzene on manganese dioxide by ozone 4ppA Catai. 1 General, 1993, 97. 17-22... 

Reaction (F) represents one of the uses of methanol (reaction (C)), and is also an example in which reaction selectivity is an important issue. The reaction cannot be allowed to go to ultimate completion, since the complete oxidation of CH3OH would lead to C02 and HzO as products. Similarly, in reaction (D), benzene and other (unwanted) products are produced by dealkylation reactions. 

In another definitive study, Lovely et al. (1995) demonstrated the complete mineralization of, 4C-benzene by enrichment cultures from San Diego Bay sediments. Their cultures clearly coupled the reduction of sulfate to the oxidation of benzene with no detectable extracellular intermediates. 

The gas phase oxidation of benzene with air is an important process for the production of maleic anhydride, which is the major partial oxidation product, besides products of complete oxidation. By-products are benzo-quinone, in particular at low conversion, and fumaric acid which is formed at the high conversion levels used in industrial installations [28]. Only traces of phenol and other by-products are formed. The important catalysts are based on V2Os and a maximum yield of 60—80% maleic anhydride is obtained at 350—500° C. 

The oxidation of benzene to maleic anhydride is generally described by the simplified reaction scheme (Scheme 1, p. 198). Complete oxidation products (CO, C02) are mainly formed from benzene and not by combustion of maleic anhydride itself. Therefore, the parallel character of the reaction scheme predominates, which implies that a high initial selectivity enables high yields to be obtained. 

Even though details of the oxidation chemistry of even the simplest aromatic species, benzene and toluene, remain uncertain, reaction mechanisms are useful in evaluating the overall oxidation behavior of these fuels. Taking benzene as a characteristic compound, evaluate whether the conditions ensure complete oxidation of aromatic species. Use the supplied mechanism (benzen. mec [12]) or another recent mechanism for benzene oxidation, and assume plug flow. Assess whether the regulation could be less severe in terms of temperature or residence time if the reactants are completely mixed. 

The times of the complete oxidation of alkanes with oxygen or air under the action of nanosecond pulsed discharges have been determined 222 The kinetics of liquid-phase oxidation of isomeric methoxy(l-methylethyl)benzenes with oxygen to the corresponding hydroperoxides has been studied. The overall activation energies of the oxidation and initiating properties of some of the hydroperoxides were determined 223... 

Vassileva, M., A. Andreev, and S. Dancheva. 1991. Complete catalytic oxidation of benzene over supported vanadium oxides modified by silver. Appl. Catal. 69 221-234. 

The effect of water addihon on the complete oxidahon of benzene and propane VOCs by uranium oxide catalysts has been inveshgated [37]. Benzene oxidahon was studied using a silica-supported U3O8 catalyst Complete oxidahon was promoted by the addition of 2.6% water compared with the reachvity when no water was added to the reactant feed. Increasing the water concentrahon to 12.1% resulted in a suppression of oxidahon achvity. Inveshgahon of propane oxidahon using U3O8 showed a dramatic promohon of achvity. Propane conversion was ca 50% at 600 °C without added water, whilst it increased to 100% at 400 °C with the... 

Clearly the only tri-methyl benzene that can thus always yield 1-3-dimethyl benzene is the one in which the three methyl groups are in the symmetrical positions, the 1-3-5 positions, so that whichever methyl group is oxidized the remaining two will be in the 1-3 positions. Further oxidation of mesitylene gives a di-basic acid which yields toluene, and complete oxidation of the methyl groups gives finally a tri-basic acid which yields benzene. 

A less complete oxidation of hexa-hydro benzene than that represented by the relationship of the tri-ketone compound above yields a series of cyclic secondary alcohols some of which are natural substances. Their relationship to hexa-hydro benzene is as follows ... 

Using FeS04 (1.67 x 10 M) in conjunction with equimolar amounts of methyl-pyrazine-5-carboxylic acid N-oxide and trifluoroacetic acid, in a water-acetonitrile-benzene (5 5 1 v/v/v) biphasic system, with benzene-H202-FeS04 = 620 60 1, a benzene conversion of 8.6% is achieved (35 °C 4h). Hydrogen peroxide conversion is almost complete (95%) and selectivities to phenol are 97% (based on benzene) and 88% (based on H2O2) [13]. These values are definitely higher than those described in the literature for the classical Fenton system [14], whereas iron complexes with pyridine-2-carboxylic acid derivatives are reported to be completely ineffective in the oxidation of benzene under the well-knovm Gif reaction conditions [15]. 

In the vapor phase oxidation of benzene to maleic anhydride an active catalyst is necessary to force oxidation to rupture the ring without leading to complete destruction. Vanadium pentoxide or vanadium compounds such as tin vanadate have been successfully used for this purpose.26 In the oxidation of alkylated benzene compounds to benzaldehyde, benzoic acid, or phthalic anhydride, a milder form of catalyst is effective. The oxidation of naphthalene to naphthaquinone would also require a mild form of catalyst to prevent ring rupture caused by too severe oxidation. However, oxidation to phthalic anhydride may be realized under ordinary conditions by the use of such catalysts as have been found effective in benzene oxidation, i.e., oxides of the metals of the fifth and sixth groups of the periodic system, especially the oxides of vanadium and molybdenum. 

The heat theoretically liberated in the oxidation of benzene to maleic acid is about 10,500 Btu per lb,of benzene reacting, and the heat liberated in the complete combustion of benzene is approximately 18,000 Btu per lb. In practice, where 40 per eent or more of the benzene may undergo complete combustion during reaction, the heat liberated would be 13,500 Btu or more per pound of benzene reacted. It is imperative that this reaction heat be removed from the catalyst zone and that the catalyst tempterature be maintained at the proper operating level. Special means have been provided for this in commercial opteration. 

Kim, H. H. Oh, S. M. Ogata, A. and Futamura. S. Decomposition of gas-phase benzene using plasma-driven catalyst reactor Complete oxidation of adsorbed benzene using oxygen plasma J. Ad O.xid. Technoi, 2005, 5, 226-233... 

Vassileva, M., Andreev, A., Dancheva, S. etal. (1989). Complete Catalytic Oxidation of Benzene Over Supported Vanadium Oxides Modified by Palladium, Appl. Catal. A Gen., 49, pp. 125-141. 

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