## 1 Introduction  
Nitrogen oxides (NO\({}_{\rm x}\)) are global air pollutants, resulting from high-temperature combustion processes and adverse poisons in the atmosphere [1; 2; 3], including nitrogen monoxide (NO), nitrogen dioxide (NO\({}_{2}\)), nitrous oxide (N\({}_{2}\)O), and their derivatives, which have a wide range of health and environmental impacts. Selective catalytic reduction (SCR) of NOx with NH\({}_{3}\) is an advanced, economic, and fuel-efficient technology that allows the removal of NOx from stationary sources [4]. SCR can not only alleviate NOx emissions by more than 90%, but can also concurrently reduce carbon monoxide emissions by 50-90%, and particulate matter emissions by 30-50%. V\({}_{2}\)O\({}_{5}\)-WO\({}_{3}\)/TiO\({}_{2}\) and V\({}_{2}\)O\({}_{5}\)-MoO\({}_{3}\)/TiO\({}_{2}\) have been widely used as commercial SCR catalysts [5; 6]. However, their operating temperature (300-400 \({}^{\circ}\)C) limits the location of the SCR reactor to upstream from the electrostatic precipitator and desulfurizer [7; 8]. This limitation causes some problems, such as the tendency to catalyse the rapid oxidation of SO\({}_{2}\) to SO\({}_{3}\), the corrosion of the downstream devices, and high concentrations of particulates and SO\({}_{2}\) in the flue gases, which shorten the life of the catalyst [9]. Toavoid these adverse effects, it has been suggested that the SCR reactor could be located downstream of the particle control and desulfurizer devices where the flue gas temperature is typically below 150 \({}^{\circ}\)C. In particular, after the wet desulfurization process, the flue gas will be cool, even below 100 \({}^{\circ}\)C [10; 11]. Allow-temperature SCR unit could be located downstream of the particulate control device and desulfurizer without heating, which results in low system energy consumption and ease of retrofitting into the boiler system; this would eliminate the need to reheat the stack gas,thus increasing the operational lifetime of the catalyst. Therefore, it is urgent to develop low-temperature SCR catalysts with high activity, high stability, a broad range of operating temperatures, and good SO\({}_{2}\) resistance. Manganese oxides (MnO\({}_{\rm x}\)) have been extensively studied and proven to be highly active for low-temperature SCR of NO with NH\({}_{3}\) since they contain various types of labile oxygen species, which are essential for completing the catalytic cycle [12; 13; 14; 15; 16]. Researchers have also developed various Mn-based catalysts, such as MnO\({}_{\rm x}\)/Al\({}_{2}\)O\({}_{3}\)[15], MnO\({}_{\rm x}\)/TiO\({}_{2}\)[16; 17] andMn-Ce-SnO\({}_{2}\)[18]. In addition, small concentrations of SO\({}_{2}\) remain in the flue gases after the desulfurizer, thus requiring consideration of the effect of SO\({}_{2}\) on activity. Many researchers [19; 20; 21] have shown that SO\({}_{2}\) has an apparent passivation effect on the catalytic activity of manganese oxide at low temperatures. [PERSON] et al. [20; 21] used the addition of CeO\({}_{2}\) to modified Mn/TiO\({}_{2}\) to significantly enhance the SO\({}_{2}\) poisoning resistance because CeO\({}_{2}\) can generate highly thermally stable Ce\({}_{2}\)(SO\({}_{4}\))\({}_{3}\) and Ce(SO\({}_{4}\))\({}_{2}\), which prevent the formation of Mn(SO\({}_{4}\))\({}_{\rm x}\) and inhibit the deposition of NH\({}_{4}\)HSO\({}_{4}\) and (NH\({}_{4}\))\({}_{2}\)SO\({}_{3}\). However, the majority of catalysts for the preparation are in granular or powder form, which are unable to meet the needs of industrial applications due to the large bed pressure decrease and unequal surface distribution of the reactants in the catalyst. Limited research has focused on studying the mechanism of the effect, at pilot-scale, of allow concentration of SO\({}_{2}\) on honeycomb crodierite-based Mn-Ce/Al\({}_{2}\)O\({}_{3}\) catalysts at 100 \({}^{\circ}\)C [3; 7].