Novel synthesis of reed flower-like SmMnOx catalyst with enhanced low-temperature activity and SO2 resistance for NH3-SCR

Abstract

In this work, a novel co-precipitation coupled solvothermal procedure is proposed to prepare a SmMnO_x catalyst (SmMnOx-CP + ST) with a reed flower-like structure for the selective catalytic reduction of NO_x by NH₃ (NH₃-SCR). Over 90% NO_x conversion and N₂ selectivity was achieved at a low temperature range (25-200 °C), and 96% NO_x conversion was achieved in the presence of 100 ppm SO₂ at 75 °C. While the NH₃-SCR of the SmMnO_x catalysts prepared by co-precipitation (SmMnO_x-CP) and solvothermal (SmMnO_x-ST) methods performed much poorer than the SmMnO_x-CP + ST catalyst. All catalysts were characterized by XRD, BET, SEM, XPS, H₂-TPR, NH₃-TPD, NO_x-TPD, and FT-IR. The results revealed that the superior performance of the SmMnO_x-CP + ST is due to the unique reed flower-like structure morphology, which endows the SmMnO_x-CP + ST with the largest surface area, the strongest synergistic reaction of Sm and Mn, abundant surface oxygen species and surface active sites, and significantly enhances the redox ability. Furthermore, the amorphous reed flower-like structure showed strong short-range ordered interaction between the active components and weaken the formation of sulfates species. In addition, the highest content of Mn⁴⁺ and Mn³⁺+Mn⁴⁺ greatly promotes the redox cycles of Sm²⁺↔Mn⁴⁺ and Sm²⁺↔Mn³⁺, and suppresses the production of sulfate species in the presence of SO₂.

Keywords: Catalyst; NH(3)-SCR; NO(x); SO(2) resistance; SmMnO(x).