Novel synthesis of MnOx catalyst with enhanced ultra-low-temperature activity and SO2 resistance for NH3-SCR

Ultra-low-temperature denitrification catalysts (below 150 °C) for low-temperature NH₃-SCR are today's research hotspot. In this study, an efficient ultra-low temperature denitrification manganese oxide catalyst was prepared by ultrasonic-assisted potassium permanganate redox precipitation method using lactic acid as a reducing agent. By controlling the amount of sodium carbonate added to the solution and the different order of addition of sodium carbonate and lactic acid, the catalysts showed different properties. The best First-1.5 catalyst obtained an extremely 210.00 m²/g high specific surface area, an increased content of chemisorbed oxygen (O_α), and exhibited excellent redox performance, which achieved complete conversion of nitrogen oxides within the temperature range of 60–180 °C. In the presence of 200 ppm high concentration sulfur dioxide gas, the catalyst still maintained an outstanding conversion rate higher than 90 % for 157 min, demonstrating excellent sulfur resistance. This is attributed to the fact that adjusting the reaction system to different alkaline states by modulating the amount of pre-added sodium carbonate solution leads to a change in the reaction rate. The change in reaction rate leads to different nucleation rate, which affects the catalyst structure, specific surface area, and the amount of chemisorbed oxygen, thus modulating the performance of the catalyst.