Adsorption properties of zeolitic ruthenium and of chromium, iron and lanthanum mordenites. Part 2.—Heats and entropies

Abstract

Isosteric heats and entropies of CO₂ sorption on ruthenium forms of A, X, Y and L zeolites and of CO₂ and NH₃ sorption on mordenite samples containing Ru³⁺, La³⁺, Cr³⁺ and Fe³⁺ cations are analysed and discussed. Analysis of the heats indicates that hydroxylated ruthenium species exist in the outgassed X, Y and mordenite samples but Ru³⁺ cations are found in the A and L samples; this condition is shown to be related to both the preparative conditions and zeolite structure. Both La³⁺ and Ru(OH)⁺₂ species interact specifically with sorbed CO₂ but Cr³⁺ and Fe³⁺ do not, whereas all M³⁺ species interact with sorbed NH₃. Strong energetic heterogeneity in all samples is suggested by the analysis of integral sorption entropies and by the failure of ideal model isotherms to describe the sorption equilibria. This is verified by application of the analysis of Ross and Olivier to these systems.