SOME FUNDAMENTAL AND PRACTICAL ASPECTS OF THE AMMOXIDATION OF ALKYLBENZENES

Various aspects of the ammoxidation of the alkylbenzenes are discussed, with emphasis being placed on the reaction kinetics and mechanism, dependent on the chemical nature of the catalyst. Over one group of catalysts based on vanadium pentoxide, ammoxidation occurs via the benzoate-like surface intermediate. All of them are active in both ammoxidation and partial oxidation of alkylaromatic hydrocarbons. Over another group of catalysts active in oxidative dehydrogenation as well as in ammoxidation reactions, the latter reaction proceeds via the amine and imine-like intermediates. Irrespective of the reaction mechanism, the rate-limiting step is related to the alkyl C-H bond dissociation, occurring by either the homolytic or the heterolytic process. From this point of view, different possibilities for controlling the ammoxidation process are discussed. The most effective one is a modification of the catalyst with acid-base or redox additives. In conclusion, industrial applications and technologies for these reactions are briefly reviewed.