Influence of the Lewis acidity of indium-modified beta zeolite in the m-xylene transformation Original Research Article

The catalytic performance of NH4-beta zeolite containing different amounts of indium, introduced as In+ cations by the method of reductive solid-state ion exchange (RSSIE), has been studied in the m-xylene conversion. It has been shown that In cations regarded as coordinatively unsaturated species possessing Lewis acidity substantially change the catalyst stability and the selectivity of the reaction when performed in an inert atmosphere. An acceleration of the side reactions of disproportionation and coking has been observed on the In-modifications of zeolite beta and a mechanism of hydride ion abstraction and faster benzylic cation formation on them have been supposed. In presence of H2 these reactions are strongly suppressed at the expense of the main reaction of isomerisation. On the completely In-exchanged beta zeolite a partial bimolecular mechanism of isomerisation is suggested.