Beneficial Modification of HC-SCR DeNOx Catalysts to Improve Hydrothermal Stability

3 Beneficial Modification of HC-SCR DeNO Catalysts to Improve Hydro-thermal Stability. - Impairment of the hydrothermal durability of HC-SCR catalysts, particularly metal-exchanged zeolites which are of interest in high-temperature deNOx applications, can be either prevented or at least reduced by selecting appropriate parent zeolite structure, employing suitable preparation technique, modifying physicochemical properties, and adding subsequent cation. The former two approaches have been extensively described in the previous section and the other ones will be mainly discussed. 

Second ingredients including Co, Ca, Cr, Sr, Ag, Ce, Ba, Mg, Mo, Fe, Sn and so forth can be simultaneously employed to improve hydrothermal durability of SCR catalysts such as metal-exchanged zeolites, supported metals and their 

1 Fe-Exchanged Zeolites. Since overexchanged Fe-MFI containing a ratio of Fe/Al 1 appeared to exhibit extremely high catalytic activity and strong hydrothermal durability for the selective reduction of NOx with iso-butane as 

An overexchanged Fe-MFI catalyst prepared by the CVD route was characterized by acquiring FTIR, HRAEM and TPD. All the Bronsted sites could be completely removed upon subliming FeCL, probably by exchange with (Fe2Cl4) entities via the following reaction. 

Cu-Exchanged Zeolites. Copper ions and/or complexes exchanged into such commercially manufactured zeolites as MFI, MOR, FAU, FER, BEA and so forth have been shown to be active for deNOx catalysis with HCs. Catalytic deNOx activity for this reaction can be maximized when combining copper with the MFI structure zeolites, representatively ZSM-5, depending mainly on the nature of reductant and physicochemical properties of the zeolite employed. These Cu-based zeolites reveal the peak NOx reduction activity at higher tern- 

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