The studies of the natural zeolite - clinoptylolite in reduction of nitrogen

This article presents the results of the research in the area of the possibilities of the utilization of natural zeolite- clinoptylolite for reduction of oxide nitrogen. The clinoptylolite type zeolite has the unique structure, high resistance against hydrothermal conditions and the ability to form strong acid centers. Various kinds of metals ions were inserted into the samples of zeolite using ion-exchange method. The effect of metals content was shown for clinoptylolite matrix and related to the performance of its pure hydrogen form. A comparison of the catalytic properties of Cu-, Co-, Fe-, Mn- and Ni-CLI was carried out for the NO reduction with methane. A eries of doubly substituted CoCu-CLI catalysts with different metal loading were studied too. Over the copper and cobalt-CLI was observed high nitric oxide conversion, especially at temperatures between 400 and 500°C. It was confirmed that the copper-cobalt-CLI catalysts have higher activity and durability than catalysts composed of iron, nickel and manganese supported on clinoptylolite. Moreover, the iron, nickel and manganese containing catalysts produced more nitrous oxide than nitrogen. The presence of both copper and cobalt species seems to be an indispensable condition for the high activity and selectivity in the NO reduction.