Aspects of structure and activity in USboxide acrylonitrile catalysts

Abstract

A uranium-antimony-oxide catalyst, known to be particularly efficient for the synthesis of acrylonitrile, has been studied in order to develop an understanding of structural features related to catalytic activity. The formation of an active and highly selective phase, USb3O10, of this catalyst and its equally active but less selective precursor, USbO5, were followed by X-ray and low frequency infrared measurements in controlled temperature experiments. Verification of the USb3O10 phase as the catalytically most important was made. Pulse microreactor studies show that there are at least two types of lattice oxygen operative in the reaction. The more labile but less abundant type is mainly involved in the formation of desired products (acrylonitrile and acrolein). Oxygen transfer through the lattice is an important aspect of the oxidation reaction.A mechanism for the oxidation and ammoxidation of propylene is proposed involving allylic intermediates. The active catalyst site is believed to involve pentavalent antimony, which is stabilized and regenerated through the action of uranium.