Katalytische Wirkung von Übergangsmetallverbindungen bei der Flüssigphasen‐Oxidation von Kohlenwasserstoffen

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

doi:10.1002/ange.19690810302

Cited by 40 publications

(6 citation statements)

References 14 publications

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“…Transition Metal Ion Catalysis. Co II ions are known to catalyze the rate-determining initiation step of autoxidations via a fast redox reaction with CyOOH, − ,− producing CyO • radicals (reaction 25). This so-called Haber−Weiss catalytic cycle is assumed to close via the reaction of Co III OH with an additional CyOOH molecule, regenerating Co II (reaction 26).…”

Section: Resultsmentioning

confidence: 99%

Origin of Byproducts during the Catalytic Autoxidation of Cyclohexane

2008

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The formation of byproducts during the Co(acac)2 and Cr(acac)3-catalyzed cyclohexane autoxidation is compared with the noncatalyzed thermal process. CoII ions seem to cause only a moderate perturbation of the reaction mechanism, causing a fast conversion of the cyclohexyl hydroperoxide via a redox cycle, rather than via abstraction of the alphaH-atom by chain carrying peroxyl radicals. Nevertheless, both the radical propagation and the CoII-induced decomposition of the hydroperoxide cause the formation of cyclohexoxy radicals that are partially transformed to 6-hydroxyhexanoic acid, the major primary byproduct for these systems. However, during the CoII-catalyzed reaction, the concentration of cyclohexanone increases much faster than that of the hydroperoxide, causing the ketone to take over the role of dominant byproduct source. A mechanism for the conversion of cyclohexanone to ring-opened byproducts is put forward. Cr(acac)3 seems to catalyze additional reactions, some of them probably leading directly to byproducts. Indeed, the evolution of (by)products is significantly different from the CoII-catalyzed and the thermal systems, in the sense that they all seem to be primary in origin.

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Section: Resultsmentioning

confidence: 99%

Origin of Byproducts during the Catalytic Autoxidation of Cyclohexane

2008

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“…Therefore wear protection will be reduced or conversely, if the ZDDP is protected from oxidation by using alternative antioxidants, the overall anti-wear performance of the lubricant may be improved. Inhibition of peroxide formation, Reaction (3.2(ii)), is very difficult because of the high rate constant value, 10 8 1 mol −1 s −1 [59]. Zinc dialkyldithiocarbamates are alternative peroxide radical scavengers and like the usual antioxidants, sterically hindered phenols and aromatic amines, they terminate peroxide radicals by Reaction (3.3).…”

Section: Influence Of Antioxidantsmentioning

confidence: 99%

Friction, Wear and the Role of Additives in Controlling Them

Bovington

2009

Chemistry and Technology of Lubricants

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The laws of friction are described. Abrasive, adhesive, contact fatigue and corrosive wear mechanisms are explained. The tribological regime of boundary lubrication is discussed in the context of the Stribeck curve and surface film formation. Physical processes for surface film formation and their properties are examined for oxygen-, nitrogen-, sulphur-, phosphorus, boron, molybdenum-containing organic compounds and ZDDP in particular. ZDDP film formation is discussed in depth and the influence of dispersants described. Interactions between reduced ZDDP levels and molybdenum compounds to maintain wear protection and antioxidancy are considered for the requirements of lower SAPS formulations in future formulations.

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“…The occurrence of CIDNP signals could be explained by the formation of the phenylcarbonyl/a-hydroxybenzyl radical pair. Emanuel et al (9) propose, as thermal initiation, the termolecular reaction 111, which has a much higher exothermal effect than the bimolecular reaction 11. Based on these results photochemical initiation, as has been observed by Zaikov et al (151, can be explained by hydrogen abstraction from the aldehyde by a photo-exited aldehyde molecule (reaction I).…”

Section: Introductionmentioning

confidence: 99%

Autoxidation of Aldehydes in Acetic Acid Solution

Hendriks¹,

Beek²,

Heertjes³

1977

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chemical engineering since Decem.ber 1969. He studied at the same Uniuersity and obtained the degree in chemical engineering i n 1955: in 1960 he receiued the emee of doctor of tech-Zd,, , nical sciences on the subject: fading by light of anthraquinoid mordant dyes. He authored several papers, for example, in the fields ofphotoreduction of azo dyes and fading by light of organic dyes o f textiles. He is a member of the Royal Dutch Chemical Society. Pieter M. Heertjes studied at the Uniuersity of Technology, Delft, obtained the degree in chemical engineering in 1932 and the degree of doctor of technical sciences in 1938. I n 1973 h e became Doctor H.C. o f Loughborough Uniuersity of Technology. After a short period as a lecturer he took the chair o f ordinary Professor in chemical engineering at the Uniuersity of Technology, Delft, i n 1946. He was President of the Roval Dutch Chemical Societv and is a member of several societies including The Institution of Chemical Engineers and the Chemical Society. His scientific field.? of interest are chemical engineering and dyestuffs. 270 Ind. Eng. Chem.. Prod. Res. De"., VoI. 16, No. 4, 1977The initiation of aldehyde autoxidations in acetic acid has been investigated under circumstances where the radical chain processes were inhibited. Phenol, 4-methylphenol, and 2,6-di-feff-butyl-4-methylphenol were used as inhibitors. It was found that the initiation reactions were combinations of a photochemical and, particularly at higher temperatures, a bimolecular thermal process. The thermal reaction is responsible for the influence of oxygen on the overall autoxidation rates. Oxidation of benzaldehyde in the presence of 2,6-di-tert-butyl-4-methylphenol led to the conversion of the latter into its hydroperoxy-and benzoylperoxy derivatives, thus confirming its activity as scavenger of peroxy chain radicals. Uninhibited autoxidations were second order in the aldehyde concentrations for cyclohexanecarboxaldehyde and halogen substituted aldehydes. Other aldehydes gave firstorder reactions. These results, together with those obtained for the initiation reaction, give information regarding the nature of the chain termination reactions.

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Katalytische Wirkung von Übergangsmetallverbindungen bei der Flüssigphasen‐Oxidation von Kohlenwasserstoffen

Cited by 40 publications

References 14 publications

Origin of Byproducts during the Catalytic Autoxidation of Cyclohexane

Origin of Byproducts during the Catalytic Autoxidation of Cyclohexane

Friction, Wear and the Role of Additives in Controlling Them

Autoxidation of Aldehydes in Acetic Acid Solution

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