Unveiling the SO₂ Resistance Mechanism of a Nanostructured SiO₂(x)@Mn Catalyst for Low-Temperature NH₃-SCR of NO

A novel SiO2@Mn catalyst witha core-shellstructure was constructed by using manganese carbonate tailings, limitingSO(2) adsorption and enhancing the SO2 resistance. Low N-2 selectivity and SO2 resistanceofMn-based catalysts for removal of NO x atlow temperatures by NH3-SCR (selective catalytic reduction)technology are the two main intractable problems. Herein, a novelcore-shell-structured SiO2@Mn catalyst with greatlyimproved N-2 selectivity and SO2 resistance wassynthesized by using manganese carbonate tailings as raw materials.The specific surface area of the SiO2@Mn catalyst increasedfrom 30.7 to 428.2 m(2)/g, resulting in a significant enhancementin NH3 adsorption capacity due to the interaction betweenMn and Si. Moreover, the N2O formation mechanism, the anti-SO2 poisoning mechanism, and the SCR reaction mechanism wereproposed. N2O originated from the reaction of NH3 with O-2 and the SCR reaction, as well as from the reactionof NH3 with the chemical oxygen of the catalyst. Regardingimproving the SO2 resistance, DFT calculations showed thatSO(2) was observed to preferentially adsorb onto the surfaceof SiO2, thus preventing the erosion of active sites. Addingamorphous SiO2 can transform the reaction mechanism fromLangmuir-Hinshelwood (L-H) to Eley-Rideal (E-R)by adjusting the formation of nitrate species to produce gaseous NO2. This strategy is expected to assist in designing an effectiveMn-based catalyst for low-temperature NH3-SCR of NO.