Abstract
Publisher Summary This chapter discusses the roles of basic sites in adsorption and catalysis by zeolites. Zeolites usually act as acidic catalysts, having very high catalytic activity for major carbonium ion hydrocarbon transformations such as cracking, alkylation, and isomerization. The large-scale industrial application of these reactions has prompted very intensive studies on the acidic nature of zeolites, and extensive data have been accumulated. On the contrary, much less attention has been directed to the zeolites as basic catalysts. There are, however, some reactions for which basic sites play a primary role in the catalysis. The acid-catalyzed reactions of aromatic hydrocarbons with olefins result almost exclusively in the addition of an alkyl group to the aromatic ring, while the base-catalyzed reactions of alkyl aromatics with olefins are unique in that they allow the enlargement of the alkyl groups of arylalkane. Similar phenomena have been observed in the alkylation of alkylaromatics over zeolites. The alkylation of toluene with methanol over acidic zeolites produces xylenes. Dehydration and dehydrogenation of alcohols are catalyzed by the acidic and the basic sites, respectively, and the reactions give a diagnostic means of knowing acid–base character of solid surfaces.
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