To clarify the K modified effects over activated carbon (AC) supported Mn–Ce oxide catalysts, several Mn–Ce/AC and xK–Mn–Ce/AC mixed oxide catalysts prepared via an impregnation method supported on AC were investigated for low-temperature selective catalytic reduction (SCR) of NO with NH₃ in the simulated sintering flue gas. The Mn–Ce/AC catalyst with a K loading of 8% showed the highest catalytic activity, corresponding to 92.1% NO conversion and 92.5% N₂ selectivity at 225 °C with a space velocity of 12,000 h^–1. Furthermore, the 0.08K–Mn–Ce/AC catalyst exhibited better resistance to SO₂ and H₂O than Mn–Ce/AC, which could convert 72.3% and 74.1% of NO at the presence of 5% SO₂ and H₂O, respectively. After K modification, the relative ratios of Mn⁴⁺/Mnⁿ⁺ as well as Ce³⁺/Ceⁿ⁺ and surface adsorbed oxygen increased. Additionally, the reduction performance of the catalyst was improved obviously, and both acid strength and quantity of acid sites increased significantly after the K species were introduced in Mn–Ce/AC. Especially, the NO adsorption capacity of the catalyst was enhanced, which remarkably promoted the denitration efficiency and SO₂ resistance. The SCR of NO with NH₃ on K–Mn–Ce/AC catalysts followed the L-H mechanism.

The viscosity, melting proprieties, and molten structure of the high-Al silicon–manganese slag of SiO₂–CaO–25 mass% Al₂O₃–MgO–MnO–K₂O system with a varying MgO and K₂O content were studied. The results show that with the increase in MgO content from 4 to 10 mass%, the measured viscosity and flow activation energy decreases, but K₂O has an effect on increasing those of slags. However, the melting temperature increases due to the formation of high-melting-point phase spinel. Meanwhile, Fourier transform infrared (FTIR) and X-ray photoelectron spectra (XPS) were conducted to understand the variation of slag structure. The O²⁻ dissociates from MgO can interact with the O⁰ within Si–O or Al–O network structures, corresponding to the decrease in the trough depth of [SiO₄] tetrahedral and [AlO₄] tetrahedral. However, when K₂O is added into the molten slag, the K⁺ can accelerate the formation of [AlO₄] tetrahedra, resulting in the increase in O⁰ and O⁻ and the polymerization of the structure.

Low-temperature NH₃-SCR is an efficient technology for NO_x removal from flue gas. The carbon-based catalyst designed by using porous carbon material with great specific surface area and interconnected pores as the support to load the active components shows excellent NH₃-SCR performance and has a broad application prospect. However, overcoming the poor resistance of H₂O and SO₂ poisoning for carbon-based catalysts remains a great challenge. Notably, reviews on the sulfur and water resistance of carbon-based low-temperature NH₃-SCR catalysts have not been previously reported to the best of our knowledge. This review introduces the reaction mechanism of the NH₃-SCR process and the poisoning mechanism of SO₂ and H₂O to carbon-based catalysts. Strategies to improve the SO₂ and H₂O resistance of carbon-based catalysts in recent years are summarized through the effect of support, modification, structure control, preparation methods and reaction conditions. Perspective for the further development of carbon-based catalysts in NO_x low-temperature SCR is proposed. This study provides a new insight and guidance into the design of low-temperature SCR catalysts resistant to SO₂ and H₂O in the future.