Adsorption parameters for strongly adsorbed hydrocarbon vapours on some commercial adsorbents

Abstract

High-temperature measurements of the adsorption properties of strongly adsorbed hydrocarbon vapours on a wide range of commercially available adsorbents are presented. These adsorbents include various cationic forms of the type A, X and Y zeolites, activated alumina and carbon, and some clays. The studies are based upon pulse chromatography experiments using low concentrations of hydrocarbon vapours (toluene and methylcyclohexane) in nitrogen carrier gas. The temperature range of investigation was chosen as 400–700 K, which is typical for the catalytic dehydrogenation of methylcyclohexane to toluene. Even at these temperatures, the relatively strong adsorption properties of the hydrocarbons necessitated the use of high carrier gas flow rates. As a consequence, significant deviation from isobaric operation existed. In this work, non-isobaric pulse chromatography theory was applied to the first moment data, and found to describe accurately the adsorption trends. Furthermore, the temperature dependence of the adsorption equilibria parameters could be determined. The data provide a useful reference in the design and assessment of processes in which the simultaneous operations of high-temperature chemical reaction and adsorptive separation take place, as in chromatographic and pressure swing based reactors.