Effect of Sodium in Ferrierite on Selective Catalytic Reduction of NO by Acetylene

Influence of sodium in ferrierite (HFER) zeolite on selective catalytic reduction of NO by acetylene (C₂H₂-SCR) was investigated. NO _x -TPD and FT-IR indicated that small amount of sodium exchanged into the proton-form zeolite with an exchange level of about 11.8% is beneficial for the title reaction by accelerating active nitrate species formation on catalyst surface from NO₂ and by suppressing the reductant combustion. Nevertheless, no further improved catalytic performance in C₂H₂-SCR could be observed by a larger amount of sodium exchanged into HFER due to some inactive nitrate species formed on the zeolite. Instead, activity of the zeolite for C₂H₂-SCR was drastically reduced, since the capacity of the zeolite for catalyzing NO oxidation and accelerating active NO⁺ species formation was remarkably depressed.