Studies of Some Catalytic Properties of Zeolites

Abstract

The use of Yetype zeolites as catalysts for the vapour
phase Beckmann rearrangement of alicyclic oximes has been
investigated, particularly for the conversion of cyclopentanone
oxime to 2-piperidone. The rearrangements of cyclopentanone oxime
and cyclohexanone oxime were studied spectroscopically, and the
conversion of cyclopentanone oxime studied further using a flow
system. The active sites for the Beckmann rearrangement have been
identified as surface hydroxyl groups located at specific sites
within the zeolitic lattice. The most efficient catalysts for the
rearrangement, therefore, are the decationated or hydrogen zeolites.
The interaction of cyclohexanone oxime with zeolites containing no
surface hydroxyl groups has also been studied, and the nature of
the interaction inferred. The formation of an alkene-nitrile on
this catalyst is indicated by the infrared spectra obtained.

Using a flow system, the rearrangement of cyclopentanone
oxime to 2-piperidone was studied as a function of the catalyst,
temperature, solvent and carrier, and the results of the
spectroscopic studies were confirmed and extended. The formation
of 2-piperidone has been shown to be a function of catalyst acidity,
and the reaction on zeolites containing no surface hydroxyl groups
was shown to result in the formation of an alkene-nitrile. The
formation of the latter is a function of the electrostatic
potential of the zeolitic cation. Cyclopentanone, which is formed
in small amounts for all catalysts studied, probably results from
hydrolysis of the oxime by residual zeolitic water.

The reason for the short catalyst lifetimes for the
rearrangement of cyclopentanone oxime to 2-piperidone is formation
of carbon on the catalyst surface. This results from decomposition
of the rearrangement product, which is strongly held on the surface.
It is predicted that decationated zeolites should be efficient
catalysts for the rearrangement of oximes which are stable, and
which produce stable products.

Date of Award	1972
Original language	English
Awarding Institution	Aston University