Adsorption properties of zeolitic ruthenium and of chromium, iron and lanthanum mordenites. Part 1.—Equilibria and affinities

Abstract

The preparation of a number of zeolite samples containing trivalent ruthenium and the identification of the intrazeolitic ruthenium species is reported. The sorptive properties of ruthenium forms of the X, Y, A and L zeolites towards carbon dioxide and of mordenite samples enriched with Ru³⁺, La³⁺, Cr³⁺ and Fe³⁺ towards carbon dioxide and ammonia are discussed. Hydrolysis was found to occur in the Ru(H₂O)³⁺₆ complex both during and after ion exchange to give a hydroxylated intrazeolitic ruthenium(III) species in all samples. Mordenite samples prepared by ion exchange from low pH exchange solutions were found to contain protons which had a pronounced effect on the sorption characteristics of the samples both toward CO₂ and NH₃. Irreversible chemisorption of NH₃ on these samples was found to be associated with the protons. Consideration of the sorption equilibria indicates that there is no major difference between the behaviour of intrazeolitic ruthenium and other trivalent transition metal ions toward CO₂ and NH₃ adsorption. Analysis of the affinity curves suggests that the thermodynamics of CO₂ sorption on the RuY sample may differ significantly from that of other ruthenium samples and also that differences between the data for CO₂ and NH₃ sorption are due to the manner in which each sorbate interacts with an electrostatic field.