Adsorption of nitrogen, carbon monoxide, carbon dioxide and nitric oxide on molecular sieves

Abstract

Adsorption of N 2 , CO, CO 2 and NO has been studied on various molecular sieves using the gas chromatographic method to determine the potential for separation of these common atmospheric contaminants from air. The molecular sieves studied include H-Mordenite, 4A and 5A zeolite, a natural clinoptilolite and an activated carbon. Henry's law constants have been determined over a variety of temperature ranges from 243 to 473 K. Van't Hoff plots are presented for CO on all materials and for NO on all but 4A zeolite. Adsorption of CO 2 on the clinoptilolite was too strong to produce an interpretable response peak. Results of CO adsorption on 4A and 5A zeolites have been compared to and are supported by data available in the literature. Heats of adsorption for CO, NO and N 2 were determined. For CO the heats of adsorption decrease in the order of clinoptilolite > 5A zeolite > 4A zeolite > H-Mordenite > activated carbon. For adsorption of NO the heats of adsorption decrease in the order of clinoptilolite > 5A zeolite > activated carbon. Separation factors are presented for the CO/N 2 and NO/N 2 systems. The natural clinoptilolite shows most promise for the separation of CO and NO from N 2 at the temperature range 273–398 K. Diffusion coefficients for CO and N 2 on clinoptilolite between 348 and 423 K were also determined. Micropore diffusion proved to be the dominant mass transfer mechanism for both CO and N 2 in clinoptilolite under the conditions examined.