Silicalite-1 deactivation in vapour phase Beckmann rearrangement of cyclohexanone oxime to caprolactam

Abstract

Defective silicalite-1 is an efficient and selective catalyst in gas phase Beckmann rearrangement. A kinetic study of catalyst decay applied to Beckmann reaction of cyclohexanone oxime into ɛ-caprolactam performed with silicalite-1 as catalyst was carried out with reference to time on stream theory. Information about kinetic deactivation constant was obtained. Kinetic deactivation expressions based on the Wojciechowski model were developed by regressing the experimental data over the silicalite-1 catalyst. The kinetic reaction constant for fresh catalyst k o, the catalyst site deactivation constant k d , the sites deactivation reaction order m and the deactivation reaction order n′ with respect to cyclohexanone oxime were determined. It was established that k d was independent from residence time and only was affected by temperature and cyclohexanone oxime concentration. The model suggested a deactivation rate established on a second order reaction kinetic both for active centre and cyclohexanone oxime concentration.