PREPARATION OF BIFUNCTIONAL CATALYSTS BY SOLID-STATE ION-EXCHANGE IN ZEOLITES

Bifunctional catalysts containing an acidic as well as a hydrogenation/dehydrogenation function were prepared by solid-state ion exchange. Preparation and properties of Pd-loaded H-ZSM-5 are described in detail. The catalytic behavior of the reduced catalysts was investigated using hydrogenation and hydroisomerisation of ethylbenzene as a test reaction. The catalytic performance of the catalysts could be significantly improved by concomitant incorporation of Ca2+. This was advantageously achieved in a two-step procedure, where first a solid-state ion exchange with CaCl2 and subsequently a second solid-state ion exchange with PdCl2 was carried out. A Ca, H-ZSM-5 with 1.5 wt-% Pd obtained via this two-step procedure and subsequent reduction in H-2 exhibited high activity, long life-time and good selectivity with respect to hydrogenation and hydroisomerisation of ethylbenzene to ethylcyclohexane and dimethylcyclohexanes, respectively. Electron micrographs of the reduced catalyst showed finely dispersed palladium with maximum size of about 2.0 nm.