ADVANCES IN LIQUID-PHASE ORGANIC-REACTIONS USING HETEROPOLYACID AND CLAY

Zinc ion-exchanged smectite clays, particularly Fe-containing nontroni te clays, were effectively applied as insoluble, readily recoverable s olid acid catalysts to liquid-phase Friedel-Crafts reactions. Mesoporo us montmorillonite K10 and FSM-16 catalyzed the condensation of aldehy des and pyrroles to give porphyrin precursors more efficiently than th e conventional homogeneous acids such as BF, etherate. 12-Tungstophosp horic acid could be included in silica matrix by means of sol-gel tech nique that involves hydrolysis of ethyl orthosilicate to give an insol uble and easily separable solid acid catalyst. The silica-included het eropolyacid was thermally more stable than an ion-exchange resin catal yst such as Amberlyst-15. and catalyzed the hydrolysis of ethyl acetat e in the liquid-phase more efficiently than the resin, H-ZSM-5 and eve n more than aqueous heteropolyacid. (C) 1998 Elsevier Science B.V. All rights reserved.