On-Filter Integration of Soot Oxidation and Selective Catalytic Reduction of NOx with NH3 by Selective Two Component Catalysts.

A group of catalysts was developed with the purpose of enhancing the soot oxidation in the selective catalytic reduction on filter system, without negatively effecting the NO_x conversion associated to NH₃ oxidation. The impregnation with alkali metal of a series of supports, characterized by a lack of strong superficial acid sites, improved soot oxidation simultaneously preventing ammonia adsorption, thus its catalytic oxidation. Strong synergy was observed between a ZrO₂–CeO₂ support and potassium, decreasing the T₅₀ of the soot conversion of 170 °C in loose contact. This catalyst was added to a Fe-ZSM5 selective catalytic reduction (SCR) catalyst without negative effect for the SCR activity. The complex interaction between the potassium-based soot oxidation catalyst and the SCR one was investigated. The soot–soot oxidation catalyst-SCR catalyst contact mode was found to be a key factor and the increased contact of the soot–soot oxidation catalyst is preferable. Such dual component catalyst system was demonstrated to be promising for simultaneous removal of NO_x and soot on a single filter. [ABSTRACT FROM AUTHOR]