| Summary: | A novel Mn/TiO<sub>2</sub> catalyst, prepared through modification with the rare-earth metal Dy, has been employed for low-temperature selective catalytic reduction (SCR) denitrification. Anatase TiO<sub>2</sub>, with its large specific surface area, serves as the carrier. The active component MnO<sub>x</sub> on the TiO<sub>2</sub> carrier is modified using Dy. Dy<sub>x</sub>Mn/TiO<sub>2</sub>, prepared via the impregnation method, exhibited remarkable catalytic performance in the SCR of NO with NH<sub>3</sub> as the reducing agent at low temperatures. Experiments and characterization revealed that the introduction of a suitable amount of the rare-earth metal Dy can effectively enhance the catalyst’s specific surface area and the gas–solid contact area in catalytic reactions. It also significantly increases the concentration of Mn<sup>4+</sup>, chemisorbed oxygen, and weak acid sites on the catalyst surface. This leads to a notable improvement in the reduction performance of the DyMn/TiO<sub>2</sub> catalyst, ultimately contributing to the improvement of the NH<sub>3</sub>-SCR denitrification performance at low temperatures. At 100 °C and a space velocity of 24,000 h<sup>−1</sup>, the Dy<sub>0.1</sub>Mn/TiO<sub>2</sub> catalyst can achieve a 98% conversion rate of NO<sub>x</sub>. Furthermore, its active temperature point decreases by 60 °C after the modification, highlighting exceptional catalytic efficacy at low temperatures. By doubling the space velocity, the NO<sub>x</sub> conversion rate of the catalyst can still reach 96% at 130 °C, indicating significant operational flexibility. The selectivity of N<sub>2</sub> remained stable at over 95% before reaching 240 °C.
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