Synthesis of MnOx catalysts via sucrose reduction deposition technique for efficient low-temperature NH3-SCR

Abstract

Air pollution is significantly affected by nitrogen oxides (NO_x), and among various denitrification technologies, NH₃-SCR is commonly regarded as the most potent one. In this research, a series of MnO_x-1:a (where a = 1,3,5,10) catalysts were synthesized by controlling the molar ratios of KMnO₄ and sucrose using the sucrose reduction deposition method. Notably, the MnO_x-1:5 catalysts demonstrated excellent N₂ selectivity and nearly 100 % NO_x conversion within the extensive temperature range of 80–200 °C. Furthermore, the catalyst exhibited exceptional resistance to sulfur poisoning, maintaining over 90 % NO_x conversion at 140 °C for more than 5 h with a concentration of 100 ppm SO₂ present. Additionally, at a molar ratio of 1:5 between sucrose and KMnO₄, the catalyst prepared exhibited rich pore structures, which could effectively adsorb the reactive gases and facilitate the SCR reaction process. XPS analysis indicated that the MnO_x-1:5 catalyst has more Mn⁴⁺ and chemisorbed oxygen (O_α), contributing to its enhanced reduction capacity. Moreover, the MnO_x-1:5 catalyst has more acid content, which helps to absorb and activate the reactant molecules thereby facilitating the NH₃-SCR reaction process. Therefore, the MnO_x-1:5 catalyst demonstrates a wide operational temperature range, from 40 to 240 °C, and exhibits exceptional resistance to sulfur poisoning during the NH₃-SCR reaction. The above results offer novel insights for the synthesis process of NH₃-SCR low-temperature catalysts.