Effect of Fe-zeolite on formation of N2O in selective reduction of NO by NH3 over V2O5-WO3/TiO2 catalyst

摘要

An approach for significantly suppressing N2O formation in reduction of NO by NH3 over V2O5-WO3/TiO2 (VWT) catalyst has been studied by coating different amounts of a Fe-exchanged zeolite (FeZ) onto the catalyst. FeZ-promoted VWT samples were characterized using N-2 sorption, X-ray diffraction (XRD) analysis, and NH3 adsorption/desorption techniques to understand the primary role of FeZ in lowering N2O production levels. At high temperatures (a parts per thousand yen450 A degrees C), VWT gave N2O production with high concentrations, while N2O formation was noticeably reduced when using FeZ-promoted catalysts, which also showed somewhat lower NO removal activities (< 5 %) at all temperatures. N-2 sorption and XRD measurements revealed no perceptible physical or chemical alterations of each constituent, even in VWT catalysts after FeZ coating following high-temperature calcination. Adsorption of NH3 on unpromoted and FeZ-promoted catalysts and subsequent desorption yielded very complicated spectra for N2O that might primarily come from NH3 oxidation, and the interaction between V-NO species at temperatures > 580 A degrees C. NO on neighboring sites seems to be produced via decomposition of N2O generated at lower temperatures. The FeZ in the promoted VWT catalysts could be responsible for N2O decomposition and N2O reduction with unreacted NH3 at temperatures > 400 A degrees C, thereby significantly lowering N2O emission levels. This promotional effect bodes well for use in many industrial deNO (x) applications.