Zn2+, Fe2+, Cu2+, Mn2+, H+ Ion-exchanged and Raw Clinoptilolite Zeolite Catalytic Performance in the Propane-SCR-NOx Process: A Comparative Study

Abstract

Abstract An investigation on the catalytic performance of various transition-metal ions-exchanged clinoptilolite zeolites in the propane selective catalytic reduction process of NOx (NO+NO2) is reported for the first time. The metallic ions include Zn2+, Fe2+, Cu2+ and Mn2+. The catalytic performance of these materials was compared with the proton form and natural clinoptilolite zeolites. Compared with the raw and H-form clinoptilolite, the ion-exchanged zeolites shift the temperature corresponding to the maximum conversion around 50 °C towards lower temperatures, irrespective of the type of used transition-metal used. The maximum conversion is substantially enhanced especially in the case of Cu2+ and Mn2+-exchanged zeolite. The enhanced activity is attributed to the creation of strong acidic sites, redox centers, enhanced specific surface area and residual extra framework Fe species. Ion-exchange with transition metals results in a distinct effect on the reduction of the CO concentration in the product gas stream. Cu2+ exchanged clinoptilolite resulted in the smallest outlet concentration of CO, i. e. about 81 % reduction with respect to the protonated zeolite form.