## 3 Binary Mn-Based Metal Oxide Catalysts
### Other Binary Mn-Based Metal Oxide Catalysts
They observed that incorporating inert silica into pure MnO\({}_{\text{x}}\) effectively improves lead resistance. By preferentially combining with Pb ions to generate more active intermediates, SiO\({}_{2}\) plays a crucial role in maintaining the activity of Mn sites on MnO\({}_{\text{x}}\)-SiO\({}_{2}\) catalysts. The introduction of Al significantly reduces the thermal stability of NH\({}_{4}\)HSO\({}_{4}\) in the MnO\({}_{\text{x}}\) catalyst, and the adsorption of Al\({}_{2}\)O\({}_{3}\) on the material formed after SO\({}_{2}\) adsorption is weak, thus improving its sulfur resistance. Fan et al. [8] carried out thermogravimetric (TG) and temperature-programmed desorption of SO\({}_{2}\) (SO\({}_{2}\)-TPD) analysis on up to 21 single metal oxides to identify potential practical chemical components as MnO\({}_{\text{x}}\) catalyst additives. The thermogravimetric analysis indicated that Al\({}_{2}\)O\({}_{3}\) notably reduces the thermal stability of NH\({}_{4}\)HSO\({}_{4}\). Furthermore, the SO\({}_{2}\)-TPD analysis revealed that the adsorption of Al\({}_{2}\)O\({}_{3}\) by the substances formed after SO\({}_{2}\) adsorption is weak. Consequently, Al\({}_{2}\)O\({}_{3}\) was selected to mix with MnO\({}_{\text{x}}\) to optimize its SO\({}_{2}\) resistance. Subsequent experimental results demonstrated that the appropriate addition of Al\({}_{2}\)O\({}_{3}\) can effectively improve both the low-temperature SCR denitration activity and the SO\({}_{2}\) resistance of MnO\({}_{\text{x}}\). The results illustrated that introducing Al\({}_{2}\)O\({}_{3}\) into MnO\({}_{\text{x}}\) is beneficial to the decomposition of NH\({}_{4}\)HSO\({}_{4}\) and reduces the thermal stability of adsorbed SO\({}_{2}\) to a certain extent. Compared with the original MnO\({}_{\text{x}}\), the addition of a small amount of Al\({}_{2}\)O\({}_{3}\) as an additive benefits the low-temperature SCR denitration activity and SO\({}_{2}\) resistance of MnO\({}_{\text{x}}\). Co-doping can effectively inhibit the formation of MnO\({}_{4}\) in the MnO\({}_{\text{x}}\) catalyst when SO\({}_{2}\) is present, significantly improving its SO\({}_{2}\) resistance. Chen et al. [47] developed a novel MnCoO\({}_{\text{x}}\) spherical catalyst with high low-temperature activity for the NH\({}_{3}\)-SCR of NOx, substantially improving its SO\({}_{2}\) resistance. XPS analysis and in situ drift indicated that the presence of SO\({}_{2}\) results in the formation of abundant MnSO\({}_{4}\), causing irreversible poisoning of the pure MnO\({}_{\text{x}}\) catalyst and transforming the NH\({}_{3}\)-SCR reaction mechanism from Langmuir-Hinshelwood (L-H) to Eley-Rideal (E-R), which inhibits low-temperature activity. On the MnCoO\({}_{\text{x}}\) spherical catalyst, the formation of MnSO\({}_{4}\) is significantly sup  
Figure 10: The possible anti-poisoning mechanism of the MnO\({}_{\text{x}}\)-SiO\({}_{2}\) catalyst. (Reproduced with permission from Ref. [65]. Copyright 2024, Elsevier). pressed in the presence of SO2, allowing the reaction on the SO2-poisoned Mn5 Co5 Ox catalyst to proceed via the L-H mechanism, maintaining a high catalytic performance. Qiao et al. [67] prepared porous MnCoOx catalysts for low-temperature deoxygenation using a one-step combustion (CB) method. The catalyst exhibits excellent NH3-SCR activity, achieving 100% NOx conversion at 150-300 \({}^{\circ}\)C. Additionally, the catalyst features high N2 selectivity, a wide operating temperature window, good stability, and a strong resistance to H2O and SO2. The crystalline phase, porous structure, and large specific surface area of CoMn2O4 contribute to its deoxidation activity. The catalyst contains abundant Mn4+, Co3+, and surface-adsorbed oxygen, improving its redox performance. The strong interaction between manganese and cobalt oxide produces many acidic sites, which enhances the catalyst's performance. Research has shown that doping certain organic compounds in MnOx catalysts can improve their denitrification activity and H2O resistance.