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 SO 2 in the flue gas. Here the MnO 2 /TiO 2 catalyst was employed to elucidate the co-poisoning mechanisms of K and SO 2 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 3 , SO 2 , NO, and K on active component (MnO 2) and support (TiO 2) was studied by density functional theory. This work unravels a promotion effect of support on the alkali and sulfur resistance. The SO 2 &K co-poisoning catalyst had higher SCR activity than the SO 2 -poisoned and K-poisoned catalyst alone. For a single toxic condition: (1) SO 2 was preferentially bonded with the terminated O site of MnO 2 inhibiting the dehydrogenation of NH 3 and redox cycle. (2) The presence of Lewis base (K atom) on the catalyst decreased the binding energy of a Lewis base (NH 3) and hindered the adsorption of NH 3. For the synergistic effect of K and SO 2 , the majority of K adsorbed on the support (TiO 2) lead to increase alkalinity, which could promote the adsorption of SO 2 on the TiO 2 and reduce the toxicity of the active component (MnO 2). [Display omitted] • The SO 2 &K co-poisoning MnO 2/ TiO 2 catalyst has higher SCR activity. • The synergistic poisoning mechanism of SO 2 and K+ over MnO 2/ TiO 2 is revealed. • The support promotion effect on the resistance to the co-poisoning is illustrated. [ABSTRACT FROM AUTHOR]