Zeolites X, Y and A enriched with trivalent cations: sorption of carbon dioxide and ammonia. Part 2.—Entropy and physical state of sorbed phase

Abstract

Entropies of CO₂ and NH₃ sorbed in zeolite Y exchanged with Tl⁺, Cr³⁺, Fe³⁺, Y³⁺ and in zeolites X and A exchanged with Cr³⁺ and Y³⁺ are analysed and discussed. CO₂ in Tl-Y is localized, while in zeolites Y and A, CO₂ is mobile at the lower coverages and becomes localized at higher coverages. The physical state of the sorbed ammonia is difficult to determine but in general a localized model with interactions seems to correlate best with the experimental data. Using the Dubinin–Polanyi theory the families of isotherms can be reduced to characteristic curves provided a fixed value for the molar volume is used.