Entropy of adsorption by microcalorimetry. Part 1.—Quasi-ideal chemisorption of CO onto various oxidic systems

Abstract

Reversible adsorption of CO onto ZnO, NO-treated silica supported Cr^II ions and two different sites on transition aluminas is considered. All cases are characterized by the constancy of the heats of adsorption along the coverage and Langmuir-like isotherms, within experimental error. Infrared spectra indicate that in all cases simple coordination onto surface Lewis-acid centres takes place. The standard entropies of adsorption are calculated from both volumetric (and optical) isotherms and calorimetric data at one temperature. The relevant formulae are given. The results do not confirm ideal character for the adsorption process.

The observed correlation between energies and entropies of adsorption is discussed.