Study of rare Earth tailings modified by Mn for selective catalytic reduction of NO x by NH 3

In this paper, rare earth tailings catalysts with different amounts of Mn modification were prepared by hydrothermal method, and the effects of Mn modification on the physical and chemical properties of rare earth tailings catalysts and the mechanism of surface thermal stability reaction were investigated by means of characterization, such as XRD, BET, NH 3 -TPD, H 2 -TPR, and infrared spectroscopy. The experiments showed that Mn modification of rare earth tailings under hydrothermal conditions allowed the synthesis of low-temperature wide-window (50 °C ~ 300 °C) catalysts. The best catalytic activity was achieved within the Mn-5% catalyst, which was above 85%. The results showed that Mn interacted with Fe/Ce elements in the rare earth tailings under hydrothermal conditions to improve the specific surface area and acid type and quantity of the rare earth tailings. In a mechanistic study of the surface thermal stability reaction during catalysis carried out by the Mn-5% catalyst, it was concluded that a large amount of Brønsted acid existed in the catalyst and acted as a reactive substance in the low-temperature section to mainly adsorb the NH 4+ species, promoting the efficiency of low-temperature catalytic. Meanwhile the unstable nitrite species produced by hydrothermal Mn modification can react with NH 3 adsorbed on the catalyst surface to enhance the low temperature catalytic capacity.