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 NO_x 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).