Adsorption properties of nitrogen monoxide on silver ion-exchanged zeolites

The adsorption properties of nitrogen monoxide (NO) on various silver ion-e xchanged zeolites were examined by adsorption-desorption measurements in a fixed bed flow apparatus. Both reversible (q(rev)) and irreversible (q(irr) ) adsorption of NO is dependent on the aluminum content in the zeolites and the zeolite structure. The amounts of reversible and irreversible adsorpti on of NO per silver ion increased with decreasing aluminum content of the z eolites and were constant, independent of the ion exchange level for ZSM-5 zeolites, but increased with the ion exchange level for mordenite zeolites (MOR). It was also found that the adsorption properties are dependent on th e temperature and pressure of adsorption: q(irr) and q(rev) of Ag-MOR incre ased with decreasing adsorption temperature and increasing adsorption press ure. Furthermore, the influence of preadsorbed gases on the Ag-MOR zeolite was investigated, and an enhancement of q(rev) was observed when NO2 was pr eadsorbed. The NO species adsorbed on the Ag-MOR zeolite were characterized by infrared (IR). Most of the reversibly adsorbed NO species are NOdeltaand some N2O adsorbed on Ag+, and the irreversibly adsorbed NO species are some N2O, NOdelta+, and a small amount of NOdelta-, NO2delta+.