SCR denitration performance and mechanism of magnetic separation rare earth tailings activated by Mn combined with NaOH alkaline fusion

Selective catalytic reduction (SCR) is presently the predominant technology for controlling nitrogen oxides (NO x ) emissions from industrial flue gas in China. Central to its operation is the denitration catalyst; however, the conventional systems face constraints such as a limited active temperature range, potential toxicity of certain active components, and high production costs. Bayan Obo rare earth tailings, enriched in catalytically active elements including Fe, Ce, and Nb, present a promising alternative raw material for denitration catalyst development. Currently, catalyst modification to improve denitration performance is a key research focus. In this study, Fe-rich magnetic separation rare earth tailings were obtained via magnetic separation processing of Bayan Obo tailings. We systematically evaluated the denitration performance and mechanism of catalysts prepared from these magnetic separation rare earth tailings through Mn modification in combination with NaOH alkaline fusion activation. Results indicate that when the catalyst is produced under conditions of 3 wt.% Mn loading and an ore-to-alkali ratio of 1:1.5, activated at 200 °C, the denitration efficiency reaches 89.6%. Furthermore, as the reaction temperature increases, the catalyst consistently exhibits high N 2 selectivity, maintaining values above 90% within the 100–300 °C range. The Mn-modified, NaOH alkaline fusion-activated catalyst shows enhanced stable adsorption of ammonia species, suppression of intermediate conversion to N 2 O, and improved N 2 selectivity. This work offers a viable approach for the high-value, sustainable utilization of rare earth tailings in environmentally friendly denitration technologies.