Effect of Fe-zeolite on formation of NO in selective reduction of NO by NH over VO-WO/TiO catalyst.

An approach for significantly suppressing NO formation in reduction of NO by NH over VO-WO/TiO (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 sorption, X-ray diffraction (XRD) analysis, and NH adsorption/desorption techniques to understand the primary role of FeZ in lowering NO production levels. At high temperatures (≥450 °C), VWT gave NO production with high concentrations, while NO formation was noticeably reduced when using FeZ-promoted catalysts, which also showed somewhat lower NO removal activities (<5 %) at all temperatures. N 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 NH on unpromoted and FeZ-promoted catalysts and subsequent desorption yielded very complicated spectra for NO that might primarily come from NH oxidation, and the interaction between V-NO species at temperatures >580 °C. NO on neighboring sites seems to be produced via decomposition of NO generated at lower temperatures. The FeZ in the promoted VWT catalysts could be responsible for NO decomposition and NO reduction with unreacted NH at temperatures >400 °C, thereby significantly lowering NO emission levels. This promotional effect bodes well for use in many industrial deNO applications. [ABSTRACT FROM AUTHOR]