Comparison of the catalytic properties of protonic zeolites and exchanged clays for Diels-Alder synthesis

Abstract

Zn 2+ - and Fe 3+ -exchanged K10 montmorillonites have been compared to HY and HBEA zeolites for Diels-Alder condensation of methyl and (−)-menthyl acrylates with cyclopentadiene. In the case of clays, the endo/exo and diastereofacial selectivities of the reaction increase with the temperature of dehydration of the solid. The catalysts dried at 393 K show lower selectivities and some deactivation as a function of time. The initial selectivity of the zeolitic catalysts is good but decreases rapidly with time. This decrease is attributed to the formation of polymers of cyclopentadiene, which deactivate the catalyst. FT-IR studies ofpyridine adsorption on the catalysts showed that this polymerization reaction increases when the proportion of Brønsted acid sites increases.