Removal of Elemental Mercury by MnOx Catalysts Supported on TiO2 or Al2O3

The performance of two Mn-based catalysts/sorbents developed for simultaneous low-temperature selective catalytic reduction (SCR) of NOx with NH3 and Hg capture was studied in the temperature range 50-250 °C. In particular, the effect of the type of support (TiO2 vs Al2O3) on both NOx conversion and Hg capture efficiency was investigated. The two catalysts displayed significant and quite similar NH3-SCR activity at low temperatures, showing an optimal performance in the range 80-140 °C. On the contrary, the Mn-based sorbent over TiO2 showed a much better Hg capture performance than that supported over Al2O3. The most likely reason was the higher proportion of Mn4+ sites, as revealed by H2-temperature-programmed reduction and X-ray diffraction analysis. The presence of NO in the simulated flue gas slightly decreased the Hg capture performance of the sorbents, while NH3 had a limited impact. Overall, MnOx-based catalysts appear to be well suited for the simultaneous SCR and Hg capture, with the TiO2-supported one showing the most promising results.