Autoxidation of Cyclohexane in the Presence of Fatty Acids and Decomposition of Cyclohexyl Hydroperoxide

Takamitsu, Nagaaki; Hamamoto, Toshikazu

doi:10.1246/nikkashi.1972.1587

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“…January 1988 good agreement with several studies in the literature (Berezin et al, 1966;Takamitsu and Hamamoto, 1972). If a straight-line representation is used for these data also, the resulting lines have slopes very similar to that of total conversion.…”

Section: Aiche Journalsupporting

confidence: 84%

Autocatalytic oxidation of cyclohexane—modeling reaction kinetics

1988

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Liquid phase oxidation of hydrocarbons is a major source of organic chemicals. This paper concerns itself with the oxidation of cyclohexane. The process is one in which gas absorption is accompanied by chemical reaction, but little information has been reported. A major factor has been safety considerations, the Flixborough explosion being a constant reminder. In this paper attention is given to the kinetics and to the interaction of kinetics and mass transfer, showing that in this autocatalytic system the dissolved oxygen level rises to saturation and falls as the rate of reaction increases. Initially zero order in oxygen, the reaction becomes first order at low oxygen levels. Oscillations and enhancement due to reaction within the boundary layer are noted. A kinetic model is developed based on simplification of the accepted free radical scheme and it is reasonably successful in accounting for the results reported. Experiments at temperatures up to 17OOC and 70 bar using uncatalyzed reaction are reported from three different reactors: a homogenous batch reactor, a flat interface reactor, and a sparged agitated bubbling reactor. A. K. Suresh, T. Sridhar, 0. E. PotterDepartment of Chemical Engineering Monash University Clayton, Victoria 3168, Australia lntroduc tionThe liquid phase oxidation of hydrocarbons is a major source of organic chemicals in the chemical industry. Most of the processes of industrial interest are carried out at pressures of 10-30 bar and temperatures of 353-523 K. In terms of the kinetic mechanisms that operate in liquid phase hydrocarbon oxidations, the liquid phase oxidation of cyclohexane is a typical example of this class of reactions. It is also a reaction of considerable industrial importance. The oxidation of cyclohexane supplies much of the raw materials needed for the production of nylon (both nylon-6 and nylon-6,6)-cyclohexanol, cyclohexanone, and adipic acid. Selective production of cyclohexanol and cyclohexanone requires the use of a low-conversion process with muliple stages. A number of catalysts for the reaction have been reported. Cyclohexanol and cyclohexanone are usually subsequently oxidized with nitric acid to adipic acid.The kinetic mechanisms that operate in hydrocarbon oxidations in general and cyclohexane oxidation in particular have been quite extensively studied, especially by Russian kineticists (Berezin et al., 1966;Emanuel et al., 1967). However, these mechanistic studies do not lead to rate expressions with con-A.K. Suresh is presently with Hindusthan Lever Research Center, Bombay, India.stants that can readily be used in the design of industrial reactors. Bearing in mind the way industrial processes operate, these reactions should be studied as gas-liquid reactions in which both mass transfer and reaction kinetics have a role to play. Few studies in the literature have accomplished this. The bulk of available literature (mainly patent literature) discusses the effect on product distribution of operating variables such as temperature, pressure, catalyst, and con...

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Section: Aiche Journalsupporting

confidence: 84%