Secondary reactions during CO hydrogenation on zeolite-supported metal catalysts: Influence of alkali cations
Journal
Journal of Catalysis
Journal Volume
107
Journal Issue
2
Pages
471-481
Date Issued
1987
Author(s)
Abstract
The effect of neutralizing cations on the secondary reactions of the primary products from CO hydrogenation over ion-exchanged zeolite-supported Ru catalysts was investigated using zeolites with different alkali cations (Li+, Na+, K+, Rb+, Cs+). The transformation of olefins (propylene and butene) on the zeolites without the metal, under conditions similar to those used for CO hydrogenation, was also studied in order to understand the effect of the various constituents of the support, i.e., the Brønsted acid sites generated during catalyst preparation and the alkali cations, on possible secondary reactions of the primary olefinic products. It was established that secondary acid-catalyzed reactions of these primary products can play a major role in shaping product selectivity during CO hydrogenation over zeolite-supported catalysts. Depending on the concentration and the strength of the acid sites, various competitive reaction paths can be observed for the transformation of the olefinic compounds. These include isomerization, oligomerization, polymerization, and cracking. The strength of the acid sites was found to be a strong function of the nature of the neutralizing alkali cations remaining in the zeolite. The presence of Li+ produced the strongest acid sites resulting in more oligomerization over LiHY than even HY. Acid site strength decreased with the molecular weight of the alkali cation used. © 1987.
Type
journal article