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A kinetic model for the liquid phase oxidation (LPO) of cyclohexane has been derived using a reaction network based on a consistent free radical mechanism. It was demonstrated that on embedding this rate model within the overall model of a semi‐batch gas‐liquid reactor (SBR) one can predict the time variation of the dissolved oxygen concentration and the rate of oxygen absorption which compare fairly closely with some well regarded published experimental data. The model is distinguished by easy extendibility and modularity whereby it could be tailored to predict, in the context of a SBR, cyclohexane conversion and ketone‐alcohol (K‐A) product selectivity levels as observed in commercial plants and in the published data on pilot plant experimentation. The model is expected to be of use in the design and scale‐up of LPO reactors.

Enthalpy of formation of free radicals is often required for the discrimination of reaction mechanisms (for complex processes such as combustion, hydrocarbon oxidation, or decomposition of peroxides and hydroperoxides) involving both molecular species and free radicals. Despite the expanding availability of the experimental measurements, the database for the enthalpy of formation of radicals is still not comprehensive. One of the simplest, efficient, and reliable methods for estimating the quantity for organic radicals from their molecular structure is the group-additivity method due to Benson and co-workers. Perusal of the literature shows that the group-additivity values (GAV) for many radical groups have remained either undetermined or obtained by assignment to the corresponding molecular groups without justification. In this paper, we devise simple methodologies to evaluate GAVs for a number of new oxygen-containing radical groups and re-estimate several alkyl and oxygen-containing radical groups using experimental data on the radical enthalpy of formation. The validity of these GAVs has been established by comparing the predicted enthalpies with experimental data. Finally, some of these updated GAVs were used in estimating the enthalpy change associated with the typical elementary steps in a peroxide decomposition reaction.

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A simple and fairly general kinetic model framework for analyzing the rate data for phasetransfer catalysis reactions has been developed. The model does not a priori assume extractive equilibrium and applies equally well to cases where the pseudo steady state with respect to the active catalytic species in one of the phases is not maintained. Within this framework, complex multistep reactions of comparable rates in both phases along with interphase mass-transfer resistance, if and when present, can be considered. The model was applied to interpret published kinetic data for a number of phase-transfer and inverse phase-transfer catalysis reactions. The model is likely to be useful in rationalizing published or new kinetic data from a general and unified framework and will contribute to the design and development of reactors carrying out phase-transfer catalysis reactions of industrial importance. † NCL Communication No. 6331. ‡ Fax Nos.: (0212) 330233 and (0212) 334761.