The Catalytic Activity of Transition Metal Compounds in the Liquid‐Phase Oxidation of Hydrocarbons

Emanuel, N.M.; Maizus, Z. K.; Skibida, I. P.

doi:10.1002/anie.196900971

Cited by 49 publications

(14 citation statements)

References 16 publications

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“…The radical-chain mechanisms proposed in the literature usually stop at this point, [3,5,13] often attributing the formation of the major reaction products, CyOH and Q=O, to the radical termination step (1). However, the long radical chain, of the order of 100, [5] clearly implies that major products can only result from chain-propagation steps.…”

Section: Introductionmentioning

confidence: 99%

Autoxidation of Cyclohexane: Conventional Views Challenged by Theory and Experiment

et al. 2005

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In spite of its industrial importance, the detailed reaction mechanism of cyclohexane autoxidation by O2 is still insufficiently known. Based on quantum chemical potential energy surfaces, rate coefficients of the primary and secondary chain propagation steps involving the cyclohexylperoxyl (CyOO) radical were evaluated using multiconformer transition-state theory. Including tunneling and hindered-internal-rotation effects, the rate coefficient for hydrogen-atom abstraction from cyclohexane (CyH) by CyOO was calculated to be k(T)= 1.46 x 10(-11) x exp(-17.8 kcal mol(-1)/ RT) cm3s(-1) (300-600K), close to the experimental data. A "Franck-Rabinowitch cage" reaction between the nascent cyclohexylhydroperoxide (CyOOH) and cyclohexyl radical, products from CyOO + CyH, is put forward as an initially important cyclohexanol (CyOH) formation channel. alphaH abstraction by CyOO. from cyclohexanone was calculated to be only about five times faster than that from CyH, too slow to explain all the observed side products. The a-hydrogen (alphaH) abstractions from CyOH and CyOOH by CyOO. are predicted to be about 10 and 40 times faster, respectively, than the CyOO. +CyH reaction. The very fast CyOO.+CyOOH reaction proceeds through the unstable Cy-alphaH .OOH radical that decomposes spontaneously into the ketone (Q=O) plus the OH radical; the "hot" .OH is found to produce the bulk of the alcohol via a second, "activated cage" reaction analogous to that above. It is thus shown how the very reactive CyOOH intermediate is the predominant source of ketone and alcohol, while it also leads to some side products. The alpha-hydroxycyclohexylperoxyl radical formed during the moderately fast oxidation of CyOH is shown to decompose fast into HO2 + cyclohexanone in a rapidly equilibrated reaction, which constitutes a smaller, second ketone source. These two fast cyclohexanone forming routes avoid the need for unfavorable molecular routes hitherto invoked as ketone sources. The theoretical predictions are supported and complemented by experimental findings. The newly proposed scheme is also largely applicable to the oxidation of other hydrocarbons, such as toluene, xylene, and ethylbenzene.

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Section: Introductionmentioning

confidence: 99%

Autoxidation of Cyclohexane: Conventional Views Challenged by Theory and Experiment

et al. 2005

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“…[1] The synthesis of cyclohexanone (QO) is of special interest, [2] as it is a key chemical for the production of polyamides such as nylon 6 and nylon 6,6. It is generally recognized that the thermal reaction of CyH with O 2 proceeds via a complex radical chain mechanism, with a limit of 5 % on the conversion to prevent overoxidation of the desired products.…”

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confidence: 99%

Silica‐Immobilized Chromium Colloids for Cyclohexane Autoxidation

et al. 2006

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“…Allara and Edelson (1977) denote such phenomena as "inhibition-catalysis switching". Many previous results about the oxidation of hydrogen and hydrocarbons (Marsal-Bonnernaison, 1971;Marsal et al, 1972;Rust and Vaughan, 1949;Babaeva et al, 1959;Knorre et al, 1959;Ingold, 1961;Shlyapnikov et al, 1961;Cullis et al, 1963;Vetchinkina et al, 1967;Emanuel et al, 1969;Smurova et al, 1971;Morrison and Scheller, 1972;Nettleton and Stirling, 1974;Herzberg et al, 1976) revealed either the absence of inhibition or catalysis in the presence of inhibitors, or else inhibition-catalysis switching.…”

Section: Introductionmentioning

confidence: 91%

Kinetics; of Hydrogen Oxidation Part 5. Inhibition and Catalysis at Low Pressures

Lovachev¹,

Lovachev²

1980

Combustion Science and Technology

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The Catalytic Activity of Transition Metal Compounds in the Liquid‐Phase Oxidation of Hydrocarbons

Abstract: A and B', and the nepbelauxetic ratio P = B'/Bo of octahedral diethyldithiophosphinato complexes KCzHs)2P(S)Sl&f.BrO < CIO = (C2H&P(S)SG < (CzH50)2P(S)SQ < F O < H20 < NH3 < H2N-(CH&-NH* > CNo whereas its position in the nephelauxetic series is as follows:

Cited by 49 publications

References 16 publications

Autoxidation of Cyclohexane: Conventional Views Challenged by Theory and Experiment

Autoxidation of Cyclohexane: Conventional Views Challenged by Theory and Experiment

Silica‐Immobilized Chromium Colloids for Cyclohexane Autoxidation

Kinetics; of Hydrogen Oxidation Part 5. Inhibition and Catalysis at Low Pressures

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