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

Abstract

Simultaneous nitrogen monoxide (NO) reduction and elemental mercury (Hg0) 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% Hg0 oxidation were concurrently achieved on the CuO/TiO2 catalyst at 250°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 Hg0 oxidation. NH3 itself did not affect Hg0 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 Hg0 oxidation and therefore resulted in a relatively lower Hg0 conversion efficiency. However, compared to flue gas without NO and NH3, the combined presence of NO and NH3 still enhanced Hg0 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 Hg0 conversion.