Selective Catalytic Reduction of NOx by Ammonia: Fe/zeolite Catalyst Development and Reaction Analysis

Content Provider	Semantic Scholar
Author	Iwasaki, Masaoki
Copyright Year	2011
Abstract	Development and characterization of Fe/zeolite, and analysis of the reaction kinetic were conducted to improve the performance for selective catalytic reduction (SCR) of NOx by NH3. The effects of Fe loading (preparation method and Fe content) and the pore structure and Si/Al2 ratio of the zeolite species were investigated. Fe/ZSM-5 prepared by chemical vapor deposition (CVD) with high Fe and Al content was the most suitable catalyst with respect to high reactivity and hydrothermal stability. Characterization of the catalyst revealed that three types of Fe species were present. Of these, ion-exchanged Fe were the active sites and were accurately quantified using temperature-programmed desorption (TPD) of NO2. For reaction kinetics analyses, adsorption/desorption behavior of NO2, elementary SCR kinetics, and the overall reaction mechanism were investigated. At the first stage of NO2 adsorption, the NO evolution reaction occurred over binuclear Fe sites, and the adsorption strength of NO2 on the Fe sites was relatively large (138 kJ/mol). The standard SCR reaction was transiently promoted in the absence of gaseous NH3, because NH3 inhibited the rate-determining step. In the fast SCR, however, promotion did not occur, due to the competitive adsorption of NO2 and NH3. Analysis of the overall reaction presented a general scheme for the SCR mechanism, including the rate-determining step, and common reactions via three SCR and a lowtemperature route for NO2 SCR.
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Language	English
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Resource Type	Article