Oximes vapor-phase cyclohexanone reaction

There is, as is well known, a close similarity between the crystalline and porous structures of silicalite-1 and silicalite-2. The same similarity therefore exists between TS-1 and TS-2, and it appears logical that they should have very similar catalytic properties. TS-2 has been evaluated as a catalyst for many different reactions, such as Beckmann rearrangement of cyclohexanone oxime with vapor-phase reactants H202 oxidation of phenol, anisole, benzene, toluene, n-hexane, and cyclohexane and ammoximation of cyclohexanone. As described in detail in Section V.C.3, differences that had been claimed between the catalytic properties of TS-1 and those of TS-2 have not been substantiated. Later investigations have shown that, when all the relevant parameters are identical, the catalytic activities of TS-1 and TS-2 are also identical. The small differences in the crystalline structure between the two materials have no influence on their catalytic properties (Tuel et al., 1993a). 

A simple oxide catalyst can be used in either the bulk state or supported on an inert oxide support material. The bulk oxides are usually prepared using a precipitation-calcination sequence similar to those described in Chapter 9 for the preparation of support oxides. " In general, the simple semiconductor oxides are not very good catalysts for synthetic reactions. The insulator oxides, however, can be used as solid acids and bases for a number of reactions. Alumina has been used as an acid catalyst for the vapor phase rearrangement of cyclohexanone oxime to caprolactam (Eqn. 10.9). Modification of the y-alumina surface by the addition of 10-20% of B2O3 increased its activity for this reaction, giving caprolactam in 80% selectivity even after several hours of continuous operation. "... 

The control of selectivity in the vapor phase Beckmann rearrangement seems to be difficult this can be ascribed to the drastic experimental conditions required. Liquid-phase reactions over heterogeneous catalysts have been investigated. The Beckmann rearrangement of cyclohexanone oxime in the liquid phase was performed under reflux conditions in a variety of solvents [44]. When chlorobenzene was used solvent conversion and selectivity increased with temperature up to 405 K. From plots of conversion against time it was concluded that catalyst deactivation under liquid-phase conditions is small, in contrast with the rapid deactivation observed when the reaction was conducted in the vapor phase. 

Vapor-phase Beckmann rearrangement of cyclohexanone oxime over AIPO4 (AP) and AlP04-Ti02 (APTi, 25-75 wt%) catalysts was investigated. Apparent rate constants and activation parameters were calculated in terms of the kinetic model of Bassett and Habgood for first order reaction processes. In all cases the selectivity to e-caprolactam increased with reaction temperature and,... 

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