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The heterogeneous catalyzed ammoximation of cyclohexanone on titanium silicalite catalyst has been studied. Cyclohexanone oxime is formed by reaction of cyclohexanone with ammonia and hydrogen peroxide. The organic by-products formed in the reaction have been studied and the following products were identified: nitrocyclohexane, cyclohexenylcyclohexanone, cyclohexenone oxime and cyclohexanone azine. The effect of some reaction parameters on by-products formation have been investigated. Experiments have been performed to verify if these by-products are due to side or consecutive reactions and derive from non-catalyzed or catalyzed reactions.

The catalytic behaviour in the liquid phase and in the gas phase ammoximation of cyclohexanone on amorphous silicas containing different amounts of titanium has been investigated. The silicas were prepared by impregnation and the sol-gel method. The behaviour of the silicas with and without titanium was different in the liquid and gas phases. The presence of titanium sites was found to be essential for the development of selectivity to oxime in the liquid phase. In the gas phase the paramount parameters are the textural and structural features of the silica and the introduction of titanium can only enhance the activity in both impregnated and sol-gel catalysts. It is proposed that the role of titanium in the gas phase is to favour the oxidation of imine, an intermediate in the vapour phase reaction, due to its ability to activate molecular oxygen.

In the new EniChem process cyclohexanone oxime is directly synthesized by ammoximation of cyclohexanone with ammonia and hydrogen peroxide on titanium silicalite catalyst. The ammoximation reaction is suitable for the synthesis of several oximes by reaction of the corresponding ketones with ammonia and hydrogen peroxide on titanium silicalite. New results on ketones ammoximation and on reaction byproducts are reported. The effect of some reaction parameters on the oxime yield and on byproducts formation is discussed.