Interpretation of limiting rate and of induction period in oxidation of benzaldehyde catalyzed by cobaltous acetate

Abstract

The cobaltous acetate-catalyzed autoxidation of benzaldehyde in acetic acid has been investigated and the nature and the mechanism of the oxidation at high cobaltous concentration (1.2-5 x M) has been studied in detail. The induction period appearing at the beginning of the limiting rate region is explained by the inhibition brought about by the cobaltous ions. The inhibiting effect of the transition metal ions studied has been shown to be due to their electronic structure. The limiting rate of oxidation at high cobalt concentrations could be explained on the basis of the steady-state concentration of perbenzoic acid produced by the catalyst.

Gradientless reactor for gas-liquid reactions

“…A possible distinction can be made between the reaction studies conducted at moderate conditions and those at high oxygen absorption rates. The former include low concentrations of catalyst (Marta et al, 1968), aldehyde (Bawn and Jolley, 1956), and peroxides (Gurmurthy and Govindarao, 1974), and oxygen dispersion intensity; the latter require high catalyst (Marta et al, 1968) or aldehyde (Venugopal et al, 1967) concentration and may result in high peroxides accumulation. The oxidation of propionaldehyde in our study is distinguished by the very fast reaction rate achieved in our reactor.…”

Low Temperature, High Conversion, Liquid‐Phase Benzylic Oxidation with Dioxygen by Metal/NHPI‐Catalyzed Co‐Oxidation with Benzaldehyde

“…Whereas the very low amount of Co that is required to eliminate the induction period underlines the role of Co as a highly efficient radical‐chain initiator,27,28 the necessity of having substantial amounts of Ni in the catalyst system for optimum results is less easy to understand. Co and Ni are both known to be catalysts for PhCH(O) oxidation with O 2 , but they differ in that Co is mainly present in the form of Co III whereas for Ni the lower, divalent oxidation state prevails because oxidation of Ni II to Ni III by intermediate perbenzoic acid is slow compared to the rapid reduction of Ni III by PhCH(O) 29. The large amount of 2 in co‐oxidations by a Cr‐free catalyst system comprising only (Co‐containing) Ni as the metallic catalyst (Table 1, entries 7−9) is in accordance with the slow decomposition of perbenzoic acid by Ni II since the latter is expected to react even slower with alkyl hydroperoxides, which are much weaker oxidants than peracids.…”

“…Any interference in the Cr‐mediated catalytic cycle of the transformation of 2 into 4 that causes a lowering of the concentration of Cr IV results in a reduced rate of decomposition of 2 because the fast path B is replaced by the slower path A , and, consequently, higher levels of 2 are expected in the reaction mixture. The build‐up of 2 above a certain Co concentration is thought to be caused by an enhanced oxidation of Cr IV to less active Cr VI through a twofold oxidation by Co III ,36,37 which is continuously regenerated from Co II via a virtually instantaneous oxidation by the intermediate perbenzoic acid [formed from PhCH(O) and O 2 ] 29,38−41…”

Reaction mechanism and kinetics for the liquid‐phase catalytic oxidation of meta‐xylene to meta‐phthalic acid

“…Oxidation of m-CBA to MPA. Similar to the oxidation of m-TALD to m-TA, the oxidation of m-CBA to MPA also belongs to the oxidation of aldehyde group to carboxy group, and the following radical chain reactions might occur according to that of (20)- (28) Br þ mAHOOCAPhACHO…”

“…The liquid-phase catalytic oxidation of MX to MPA in acetic acid media is a typical aromatic hydrocarbon oxidation process, which belongs to the kind of classical free-radical chain reaction. Researchers such as Kamiya, 5 Hendriks et al, 6 Jones, [7][8][9] Hronec et al, 10,11 Partenheimer et al, [12][13][14][15][16][17][18] Suresh et al, 19,20 Harustiak et al, 21,22 George and Steven, 23 Sheldon and Kochi, 24 Wang et al, 25,26 Emanuel and Gal, 27 Marta et al, 28 Wang et al, 29 and Cheng 30 had studied the mechanism of aromatic hydrocarbon liquid-phase catalytic oxidation for many years. In the oxidation of methyl aromatic hydrocarbon to aromatic carboxylic acid, a mixture of cobalt(II), manganese(II) and bromide salts, which can be called 'Mid-century' catalysts, are used as catalyst species.…”