Coexistence of enhanced Hg0 oxidation and induced Hg2+ reduction on CuO/TiO2 catalyst in the presence of NO and NH3

Simultaneous nitrogen monoxide (NO) reduction and elemental mercury (Hg-0) oxidation in the presence of ammonia (NH3) was for the first time studied on a copper oxide/titanium dioxide (CuO/TiO2) catalyst at low flue gas temperatures. More than 80% NO reduction and 90% Hg-0 oxidation were concurrently achieved on the CuO/TiO2 catalyst at 250 degrees C under a simulated NH3 selective catalytic reduction (SCR) atmosphere. NO was likely oxidized on the CuO/TiO2 catalyst to form active nitrogenous species, particularly with the aid of oxygen. The active nitrogenous species then significantly promoted Hg-0 oxidation. NH3 itself did not affect Hg-0 conversion on the CuO/TiO2 catalyst. The co-occurrences of NO and NH3 led to a reduction in oxidized mercury (HgO in this work), which partially offset the Hg-0 oxidation and therefore resulted in a relatively lower Hg-0 conversion efficiency. However, compared to flue gas without NO and NH3, the combined presence of NO and NH3 still enhanced Hg-0 oxidation over the CuO/TiO2 catalyst, primarily because of the overwhelming benefit from NO. This is superior to many other SCR catalysts, including commercial vanadia-based SCR catalysts, on which an SCR atmosphere generally inhibits Hg-0 conversion.