Metal ion-exchanged zeolites as highly active materials for removal of nitrogen monoxide by catalytic decomposition, selective catalytic reduction, or adsorption

Abstract

The removal of nitrogen monoxide (NO) has been tried through three novel methods; catalytic decomposition, selective catalytic reduction by hydrocarbon, and pressure swing adsorption. Copper ion-exchanged zeolite is found to be the most active catalyst for the decomposition among the catalysts used. The present position of catalysts for the direct decomposition is reviewed. During the survey of the effect of coexisting gases on the catalytic activity of Cu zeolites for the NO decomposition, the selective catalytic reduction of NO by hydrocarbon in an oxidizing atmosphere has been found. In this report the catalytic activities of various zeolites are summarized. At last the adsorption properties of NO on various metal ionexchanged zeolites have been investigated by adsorption-desorption measurement: Several metal ion-exchanged zeolites showed high ability for the reversible adsorption of NO. Among these new removal methods, the selective reduction and the pressure swing adsorption are potential ways for removal of NO in emissions and for low concentration NO in air, respectively.