Support promotion effect on the SO and K co-poisoning resistance of MnO/TiO for NH-SCR of NO.

Mn-based catalysts are expected to be applied for removing NO 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 SO in the flue gas. Here the MnO/TiO catalyst was employed to elucidate the co-poisoning mechanisms of K and SO 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 NH, SO, NO, and K on active component (MnO) and support (TiO) was studied by density functional theory. This work unravels a promotion effect of support on the alkali and sulfur resistance. The SO&K co-poisoning catalyst had higher SCR activity than the SO-poisoned and K-poisoned catalyst alone. For a single toxic condition: (1) SO was preferentially bonded with the terminated O site of MnO inhibiting the dehydrogenation of NH and redox cycle. (2) The presence of Lewis base (K atom) on the catalyst decreased the binding energy of a Lewis base (NH) and hindered the adsorption of NH. For the synergistic effect of K and SO, the majority of K adsorbed on the support (TiO) lead to increase alkalinity, which could promote the adsorption of SO on the TiO and reduce the toxicity of the active component (MnO).