Preparation and catalytic testing of zeolite coatings on preshaped alumina supports

The synthesis of MFI and BEA type coatings on alpha-alumina beads and extrudates is described. Pretreatment of the support by the template solution enhances the surface coverage by both zeolites in sodium rich syntheses. From elemental analysis and probe reactions it is concluded that the supports with low surface area are essentially stable under zeolite synthesis conditions, while the supports with high surface area give rise to dissolution of aluminum and coating instability. The zeolite beta coatings were tested in a fixed bed reactor and a recirculating differential fixed bed reactor. The reactions studied were the transalkylation of benzene with diethylbenzene and the alkylation of benzene with ethylene. The activity of the zeolite beta coatings was compared with the activity of commercial samples of zeolite beta. In both reactions the (initial) observed rate constants and intrinsic rate constants per gram of zeolite for the coatings and the bulk catalysts were of the same order of magnitude. In both reactions the utilization of the bulk catalysts is high, so that in this specific case the possible advantages of coatings on overall catalyst activity are not evident. (C) 1999 Elsevier Science B.V. All rights reserved.