REMOVAL OF NITROGEN MONOXIDE ON COPPER ION-EXCHANGED ZEOLITES BY PRESSURE SWING ADSORPTION

The adsorption properties of nitrogen monoxide (NO) on various metal ion-exchanged zeolites were examined by adsorption-desorption measurements in a fixed bed flow adsorption apparatus. Among the samples used, the copper ion-exchanged ZSM-5 zeolites showed the greatest ability for reversible adsorption of NO; therefore, it has been studied in more detail. The amounts of reversible and irreversible adsorption of NO per copper ion exchanged increased with decreasing aluminum content of the zeolite, and were constant, independent of the ion exchange level. The NO species adsorbed on the zeolite were characterized by infrared (IR) and temperature-programmed desorption (TPD) techniques. Most of the NO reversibly adsorbed is the NO+ adsorbed on Cu2+, and the NO irreversibly adsorbed is the residual of NO+, nitrate (NO3-), nitrite (NO2-), and NO2+. The irreversibly adsorbed species gave the desorption peaks at 400, 463, and 663 K. The total amount of NO desorbed in the TPD experiment is in good agreement with the amount of irreversible adsorption of NO evaluated from the adsorption-desorption measurement.