Oxidation of hydrocarbons by oxygen

Analysis of the results of this series of experiments leads to the conclusion that, in conditions of high-temperature oxidation of hydrocarbons by oxygen, the latter is a less active dehydrogenating agent and splits the process into several parallel reactions. 

OXIDATION OF HYDROCARBONS BY OXYGEN AND HYDROGEN OVER Pd-CONTAINING TITANIUM SILICALITES... 

Whereas this reaction was used to oxidize ethylene (qv) to acetaldehyde (qv), which in turn was oxidized to acetic acid, the direct carbonylation of methanol (qv) to acetic acid has largely replaced the Wacker process industrially (see Acetic acid and derivatives). A large number of other oxidation reactions of hydrocarbons by oxygen involve coordination compounds as detailed elsewhere (25). 

The oxidation of hydrocarbons by atmospheric oxygen to give hydroperoxides is called autoxidation ... 

Liquid phase oxidation of hydrocarbons by molecular oxygen forms the basis for a wide variety of petrochemical processes,3 "16 including the manufacture of phenol and acetone from cumene, adipic acid from cyclohexane, terephthalic acid from p-xylene, acetaldehyde and vinyl acetate from ethylene, propylene oxide from propylene, and many others. The majority of these processes employ catalysis by transition metal complexes to attain maximum selectivity and efficiency. 

The existence of numerous oxygenases that catalyze the direct oxygenation of organic substrates continues to stimulate the search for atom transfer oxidations of hydrocarbons by simple metal-dioxygen complexes. (For a further discussion of reactions of metal-dioxygen complexes with organic substrates via heterolytic pathways, see Section III.C). 

P. Batdoni, J. P. Renaud,]. F. Bartoli, M. Reina-Artiles, M. Fort, D. Mansuy, Monooxygenase-like oxidation of hydrocarbons by hydrogen peroxide catalyzed by manganese porphyrins and imidazole selection of the best catalytic system and nature of the active oxygen species, /. Am. Chem. Soc. 110 (1988) 8462. 

In the selective oxidation of hydrocarbons to oxygenated compounds like acids, water is introduced with the reagents. This additive can create various phenomena in the oxidation mainly kinetic effects and catalyst modification. If there is no definite evidence concerning the second point, it is well known that the addition of water favors the desorption of oxygenated compounds. In the experiment presented in Table 7 this hypothesis is well in evidence the selectivity towards oxygenated compounds particularly towards acrylic acid increasing from 25% to 31% with no change in the propane conversion. We can also notice that the total oxidation of propene to carbon oxides is inhibited by water. 

Ammoxidation refers to the formation of nitriles by oxidation of hydrocarbons with oxygen in the presence of ammonia (Figure 1) [1]. Ammoxidation is best conducted with olefins, or with aromatic or heteroaromatic compounds, containing a readily abstractable H atom (allylic or benzylic intermediates are formed), although the ammoxidation of alkanes (e. g. propane to acrylonitrile [e. g. 2-4] or ethane to acetonitrile [e. g. 5]) is also possible. An exceptional example is the ammoxidation of methane to hydrogen cyanide by the Andrussov reaction [6]. 

This initiation step may occur in a number of ways by thermal decomposition of hydrocarbons with weak C-H bonds, by oxidation of hydrocarbons by metal ions via free radical routes, by reaction with oxygen gas, etc. 

Examples of monocation dimer formation among aromatic hydrocarbons have been confined mostly to alternant hydrocarbons, and the dimer can be regarded as an association of two closed shell molecules which have lost an electron. Recently Paskovich and Reddoch (1972) made a new class of monocation dimers, in which an electron is missing from two associated open shell molecules. Oxidation of phenalene by oxygen led to the phenalenyl radical and, it is thought, to the phenalenyl cation, association of which gave the monocation dimer (93). 

HOMOGENEOUS CATALYTIC OXIDATION OF HYDROCARBONS BY MOLECULAR OXYGEN... 

The oxidation of hydrocarbons by molecular oxygen in the absence of metal complexes has been discussed in Chapter II. The oxidation of hydrocarbons with molecular oxygen, as well as with donors of an oxygen atom (hydrogen peroxide, alkyl hydroperoxides and some other compounds), is a very important field since many industrial processes are based on these reactions [1], In many cases, chain radical non-catalyzed autoxidation of samrated hydrocarbons is not very selective and the yields of valuable products are often low. The use of salts and complexes of transition metals creates great possibilities for solving problems of selective oxidation, as has been demonstrated for a number of important processes. 

Chapter X. Homogeneous Catalytic Oxidation of Hydrocarbons by Peroxides and Other Oxygen Atom Donors... 

Partial Oxidation Reactions. Oxidation is used in industry for producing aliphatic and aromatic alcohols, aldehydes, ketones and acids. Generally, oxidation involves splitting of C-C or C-H bonds and formation of C-0 bonds. For example, the partial oxidation of hydrocarbons by molecular oxygen, to form oxygenates that are used as building blocks in the manufacturing of plastics and synthetic fibers, is an important process in the chemical industry. 

The theory of destructive oxidation of hydrocarbons with oxygen has been tested by oxidizing [l- C]butane with oxygen. According to this theory the oxidation of butane should proceed according to equations 225. 

Gaillon, L., F. Bedioui, P. Battioni, and J. Devynck (1993). Electroassisted biomimetic oxidation of hydrocarbons by molecular-oxygen catalyzed by manganese porphyrin complexes intercalated into montmorillonite. J. Mol. Catal. 78(2), L23-L26. 

The method is direct and based on the use of the chain reaction of liquid-phase oxidation of hydrocarbon by molecular oxygen. 

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