Determination of isotherms and initial heat of adsorption of CO2 and N2O in four A zeolites from infrared measurements

Abstract

Measurements of the v₃ band area of CO₂ and N₂O adsorbed on KA, NaA, CaNaA and CaA zeolites at different temperatures and pressures have allowed us to obtain ‘infrared isotherms’ at very low coverage, from which initial heats may be deduced. A measurement of the band intensity for the two sorbates leads to the true isotherms. The advantages of this method are its high sensitivity at low coverage, the verification of the absence of water and the exclusion of chemisorption heat when it occurs, as in the case of CO₂. The results have allowed us to analyse the mobility of both molecules on the four zeolites studied by using different models for the partition function.