Monte-Carlo simulation and mean-field theory interpretation of adsorption preference reversal in isotherms of alkane binary mixtures in zeolites at elevated pressures

In this Letter the phenomenon of `Adsorption Preference Reversalʹ observed in Monte-Carlo simulations of ethane–methane mixture adsorption in silicalite at high pressure is introduced and discussed. To interpret this we discuss a simple mean-field theory for a lattice gas model of the mixture which reproduces the essential features of the effect. A clear picture of the important features of the process is obtained and it appears that there is a simple entropically driven balance between various terms in the gas and adsorbed phase chemical potentials driving the preferential displacement.