DRIFTS study of the catalytic N2O reduction by SO2 on FeZSM-5

Abstract

Abstract SO 2 has been recognized as an effective reducing agent for N 2 O over iron-containing zeolite catalysts, lowering the operation temperature up to 100 K with respect to the direct N 2 O decomposition. This unique behavior contrasts with the common poisoning effect of SO 2 over other active de-N 2 O metals ( e.g. Co, Cu, Rh, and Ru). The formation of surface sulfates has been generally posed as the main cause for catalyst deactivation by SO 2 . Through the use of in situ infrared spectroscopy (DRIFTS), we show that steam-activated FeZSM-5 indeed builds up stable sulfate species during the N 2 O + SO 2 reaction. Significant amounts of sulfur were detected in the used catalyst by elemental analysis and X-ray photoelectron spectroscopy. However, the enhanced N 2 O conversion is remarkably stable, indicating that the reducing action by SO 2 and the sulfation of the surface are decoupled. The resulting sulfate species are thus spectators in the catalytic process and do not block or alter the structure of the active sites for N 2 O reduction and decomposition.