Study of the interaction between adsorbed hydrocarbon molecules on graphitized carbon using the chromatographic step-and-pulse method

Abstract

The chromatographic step-and-pulse method has been applied to a study of the adsorption of pure gases and gas mixtures on graphitized carbon black. It is shown how the retention time of a small pulse of a vapour B on a step of preadsorbed vapour A is related to the parameters of an equation of state (two-dimensional van der Waals equation) for the adsorbed gas mixture. The method is used to study the adsorption of isomeric C6-alkanes, cyclohexane and benzene at 343.2 K. The adsorption isotherms derived for the pure vapours are compared with results obtained by static (gravimetric) measurements. The retention results of B on preadsorbed A are analysed and the bestfit values of the interaction parameter αAB are derived. These values are found to be smaller than the geometric mean of αA and αB for the pure gases.