Rational Design of Alkali-Resistant NO Reduction Catalysts using a Stable Hexagonal V-Doped MoO3 Support for Alkali Trapping

To avoid alkali poisoning in the selective catalytic reduction (SCR) of NOx with NH3, it is desirable to design SCR catalysts with abundant alkali-trapping sites spatially separated from catalytically active sites. Here we develop such a catalyst with strong resistance against alkali poisoning by using hexagonal vanadium-doped MoO3 (V-HMoO) with alkali-trapping tunnels as a catalyst support. Although pure HMoO also possesses strong alkali resistance due to size-suitable tunnels, active Mo5+ ions on the framework make HMoO thermally unstable, and hence pure HMoO is not able to be used as a suitable support for SCR in a normal operating temperature window of 280-420 degrees C. We substitute the active Mo5+ by stable V5+ due to its fully unoccupied electron configuration to achieve a thermally stable V-HMoO support, as confirmed by various characterization results. After loading active V2O5 onto the V-HMoO support, the catalyst shows high SCR activity with excellent alkali resistance due to the alkali trapping function of V-HMoO. This work may give a strategy to design stable alkali-trapping SCR catalysts in general.