Support promotion effect on the SO2 and K+ co-poisoning resistance of MnO2/TiO2 for NH3-SCR of NO

Mn-based catalysts are expected to be applied for removing NOx due to its excellent low-temperature activity. However, the practical use of these catalysts is extremely restricted with the co-poisoning of alkali metal and SO2 in the flue gas. Here the MnO2/TiO2 catalyst was employed to elucidate the co-poisoning mechanisms of K and SO2 for the low temperature selective catalytic reduction (SCR) of NO. The physicochemical properties of catalysts under different toxicity conditions were studied by experiments. The adsorption of NH3, SO2, NO, and K on active component (MnO2) and support (TiO2) was studied by density functional theory. This work unravels a promotion effect of support on the alkali and sulfur resistance. The SO2&K co-poisoning catalyst had higher SCR activity than the SO2-poisoned and K-poisoned catalyst alone. For a single toxic condition: (1) SO2 was preferentially bonded with the terminated O site of MnO2 inhibiting the dehydrogenation of NH3 and redox cycle. (2) The presence of Lewis base (K atom) on the catalyst decreased the binding energy of a Lewis base (NH3) and hindered the adsorption of NH3. For the synergistic effect of K and SO2, the majority of K adsorbed on the support (TiO2) lead to increase alkalinity, which could promote the adsorption of SO2 on the TiO2 and reduce the toxicity of the active component (MnO2).