Environmental-Benign Catalysts for Selective Catalytic Reduction with Ammonia (NH3-SCR) Supported on Natural Clinoptilolite Prepared by Solution Combustion Synthesis Method

Abstract

[EN] The presented research evidenced that natural zeolite, clinoptilolite performs very well as a support of NH3-SCR catalyst. The material was modified with iron or/and copper by solution combustion synthesis method. Fe-modified clinoptilolite showed excellent catalytic performance above 350 degrees C, due to the abundance of oligomeric iron species. On the other hand, relatively poor activity of the sample in the low temperature region resulted from the presence of pore-blocking aggregates of Fe2O3. In contrast to Fe-, the conversion of NO for Cu-modified sample reached 100% at ca. 225 degrees C, confirming outstanding low temperature activity of copper species. This effect was assigned to good dispersion of Cu and the presence of acid sites of medium strength, which were absent in Fe-Clin. However, these sites could possibly promote non-selective reaction of ammonia oxidation, thus, consumption of the reducing agent and generation of N2O. Considering the respective advantages of iron and copper active sites, we prepared bimetallic sample to design catalytic system which is more efficient in a broader temperature window. The results obtained for the FeCu-Clin sample indicated that co-existence of Fe and Cu contributed to low temperature activity due to [Cu(OH)]+ and lowered the formation of N2O due to oligomeric iron species. Such result was also ascribed to the generation of appropriate number of acid sites of medium strength delivered by copper.