AMINATION OF 2-METHYLPROPENE OVER PROTON-EXCHANGED ZSM-5 ZEOLITE CATALYSTS

The reaction between 2-methylpropene and ammonia over various zeolite catalysts having a wide range of silica/alumina ratios from 5.6 to 1340, and over solid acid catalysts (CsxH3-xPW12O40 (x = 0.15, 0.5), SiO2-Al2O3, and SiO2-TiO2) and the solid base MgO was investigated. The significant decrease of activity following substitution of Na+ for H+ in H-MFI-40 or by preadsorption of diisopropylamine showed that amination is catalyzed by the acid sites. A similar change in the catalytic activity of H-MFI-40 with the number of Bronsted acid sites at elevated temperatures, as well as the appearance of activities of CsH3-xPW12O40 (X = 2.5, 2.85), which has only Bronsted acid sites, indicated amination on the Bronsted acid site. The dependence of conversion into t-butylamine, the number of Bronsted acid sites, and the turnover frequencies on the SiO2/Al2O3 ratio suggested that the number and strength of the Bronsted acid sites are the factors controlling the title reaction. Due to the above two factors having the proper values, proton-exchanged ZSM-5 zeolite with a silica/alumina ratio of 81 was the most active for amination among the catalysts tested. (C) 1994 Academic Press, Inc.