Ammoximation of Cyclohexanone on Titanium Silicalite: Investigation of the Reaction Mechanism

In a series of combined adsorption, reactivity and spectroscopic experiments in solution with ketones of different size and shape, the fundamental role of the hydroxylamine pathway in the cyclohexanone ammoximation is established. In presence of H2O2 and NH3, framework Ti(IV) forms octahedrally distorted aquohydroperoxo and ammonia-hydroperoxo mixed complexes: the latter one being the precursor of the hydroxylamine formation. This intermediate immediately reacts with cyclohexanone in the channels or diffuses to the external solution where it gives oximation reaction with larger ketones which could not penetrate the channels.