The sorption of krypton and xenon in zeolites at high pressures and temperatures II. Comparison and analysis

Abstract

Absolute and Gibbs excess sorption isotherms of Kr and Xe have been measured at a range of temperatures between 0 and 450 °C and at high pressures in zeolites X and Y (near-faujasites); zeolite A; H-Zeolon and Na-Zeolon (near mordenites); chabazite; and an active carbon, to compare their efficiencies in reducing the rare gas pressures in high-temperature, high-pressure systems. At 450 °C the best sorbents for the purpose were chabazite and the carbon. The isotherms have been analysed to give distribution equilibrium constants for absolute sorption and associated standard thermodynamic quantities (Δ A ⊖ , Δ E ⊖ and Δ S ⊖ ). Isosteric heats have been derived and compared as functions of amount sorbed both for absolute and for Gibbs excess uptakes. These heats differ substantially for larger uptakes, but converge as the uptake decreases. Differential entropies of the intracrystalline rare gas have been calculated for absolute sorption. They decline monotonically with amount sorbed and have temperature coefficients which appear not very different from values expected for classical oscillators.