NO Oxidation Kinetics on Iron Zeolites: Influence of Framework Type and Iron Speciation |
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Authors: | R Brosius D Habermacher JA Martens L Vradman M Herskowitz L apek Z Sobalík J Ddeek B Wichterlová V Tokarová and O Gonsiorová |
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Affiliation: | (1) C.O.K., K.U. Leuven, Kasteelpark Arenberg 23, 3001 Leuven, Belgium;(2) Blechner Center for Industrial Catalysis and Process Development, Ben-Gurion University, Beer-Sheva, B.G.U, Israel;(3) Academy of Sciences, J. Heyrovský Institute of Physical Chemistry, Prague, Czech Republic;(4) Unipetrol Group, Research Institute of Inorganic Chemistry, Ústí nad Labem, Czech Republic |
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Abstract: | Zeolites having MFI, FER and *BEA topology were loaded with iron using solid state cation exchange method. The Fe:Al atomic ratio was 1:4. The zeolites were characterized using nitrogen adsorption, FTIR and DR UV–Vis–NIR spectroscopy. The catalytic activity in NO oxidation and the occurrence of NO
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adsorption was determined in a fixed-bed mini reactor using gas mixtures containing oxygen and water in addition to NO and NO2 and temperatures of 200–350 °C. Under these reaction conditions, the NO
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adsorption capacity of these iron zeolites was negligible. The kinetic data could be fitted with a LHHW rate expression assuming a surface reaction between adsorbed NO and adsorbed O2. The kinetic analysis revealed the occurrence of strong reaction inhibition by adsorbed NO2. FER and MFI zeolites were more active than *BEA type zeolite. MFI zeolite is most active but suffers most from NO2 inhibition of the reaction rate. FTIR and UV–Vis spectra suggest that isolated Fe3+ cations and binuclear Fe3+ complexes are active NO oxidation sites. Compared to the isolated Fe3+ species, the binuclear complexes abundantly present in the MFI zeolite seem to be most sensitive to poisoning by NO2. |
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Keywords: | SCR NO
x
NO oxidation iron Fe-MFI zeolite ferrierite beta zeolite |
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