The sorption of krypton and xenon in zeolites at high pressures and temperatures I. Chabazite

Abstract

Isotherms of Kr and Xe in chabazite have been obtained for absolute sorption and for Gibbs excess sorption, in the temperature range 150 to 450 °C and at pressures up to 100 atm. Thermodynamic equilibrium constants for distribution of gas between the crystals and the gas phase, standard state concentrations and heats of sorption have been determined. At the highest pressures differences between absolute sorption and Gibbs excess sorption were large. The change of equilibrium fugacity with temperature for given absolute and Gibbs excess sorptions yielded two differential heats of sorption and two differential entropies of the sorbate. These heats, and the corresponding entropies, differed numerically and in their dependence upon amount sorbed. The thermodynamic relationship between the two heats has been derived and discussed.