In,Fe-Zeolites: active and stable catalysts for the SCR of NOx. Kinetics, characterization and deactivation studies

Abstract

In this work, the addition of Fe2O3 to InH-zeolites (ZSM5 and mordenite) is investigated for the selective catalytic reduction of NOx with both methane and butane as reducing agents. When Fe is added to InHMOR and methane is used, the NOx to N2 conversion increases from 25% to 55% at 20,000 h-1 and 500 8C. An increase is also observed when butane is employed but to a lower extent. The role of Fe could be ascribed to an improvement of the NO to NO2 reaction rate. The presence of iron oxides also improves durability in the presence of 2% water. The catalyst InFeHMOR undergoes a fast initial inhibition after which a reasonable NOx conversion (25%) remains constant during 125 h. TPR, XRD and LRS characterizations indicate that Fe2O3 and Fe3O4 are the iron species present, while InO+ at exchange sites and small amounts of In2O3 are also present. The kinetic plots for the NOx selective catalytic reduction (SCR) with methane with the InFeHMOR catalyst show fractional orders for the NO concentration and ca. first order for methane.