Kinetics of alkane adsorption on a solid cracking catalyst

Abstract

A microreactor technique is developed for a study of alkane chemisorption on solid cracking catalysts. Kinetics of adsorption–desorption processes can be observed at ca. 200°C; it manifests itself as extensive tailing of alkane peaks in gas chromatograms. A kinetic model of the adsorption process is developed. The model allows calculation of two kinetic parameters, those of alkane adsorption, k a[ C *], and desorption, k d. Both these values decrease as the carbon atom number of an alkane increases. In a first approximation, both the k a and k d values for an alkane with a given carbon atom number do not depend on the degree of chain branching. All these features are typical for chemisorption, i.e. strong, non-specific interaction of alkane molecules with particular areas on the catalyst surface situated within its zeolite component. The experimental technique and the kinetic approach for measuring rapid adsorption–desorption phenomena described in this article can be applied to a variety of catalytic processes involving gas/solid interactions.