New perspectives on basic zeolites as catalysts and catalyst supports

Zeolites are aluminosilicate molecular sieves that have great potential as basic catalysts and catalyst supports. In particular, this paper discusses recent work and future directions with zeolite X containing exchanged alkali metal cations, occluded alkali metal oxides, and occluded alkali metals. Probe reactions such as alkylation of toluene with methanol, cyclo-addition of carbon dioxide to ethylene oxide, isomerization of I-butene, and alkylation of toluene with ethylene are catalyzed by the basic X zeolites, depending on the preparation method. Basic zeolites are also excellent supports for nanometer-sized Ru metal clusters used to catalyze the ammonia synthesis reaction. In that case, occluded barium oxide effectively promotes the reaction on Ru-loaded Ba-exchanged zeolite X. These examples illustrate important principles that can be used to guide future design of shape-selective base catalysts. (C) 2003 Elsevier Science (USA). All rights reserved.