(208a) Thermogravimetric and Breakthrough Studies on the Adsorption Reversibility of SO2, NO2 and NO on Type a and X Zeolites

The adsorption reversibility of trace level flue-gas contaminants such as SO₂, NO₂ and NO gas was investigated on type A and X zeolites. The zeolites considered in this work included 13X, calcium exchanged 13X, 5A and 4A. This study was carried out to evaluate the influence of these species on the CO₂ removal from flue gas by PSA using zeolites. Six individual gas mixtures containing these species were utilized that included 74 ppm NO, 74 ppm NO₂, 42 ppm SO₂, 1 vol% NO, 1 vol% NO₂, and 500 ppm SO₂, all using either nitrogen or helium as the balance gas. A 15.03 mol% CO₂ mixture (balance nitrogen) was used to evaluate the effect of SO₂, NO and NO₂ on the adsorption behavior of CO₂ on the selected zeolites. This study included single cycle thermogravimetric analyses (TGA) individually with each gas mixture and each zeolite. It also included consecutive CO₂ breakthrough studies through an adsorption bed containing 5A or 13X before and after saturating the bed with the contaminant gas of interest. The roles of purging with nitrogen and temperature on the contaminated samples were also investigated. All TGA and breakthrough runs were carried at 70 ^oC and 1 atm absolute pressure. The results highlight the importance of the cation (Ca²⁺ versus Na⁺) in the stability of the zeolite against the negative effect exerted by the presence of the contaminant.