## 3 Results and Discussion
### Effects of SO\({}_{2}\) and H\({}_{2}\)O on NO Removal Activity
#### 3.3.1 BET, SEM-EDS Mapping  
The surface area data of the fresh and sulfated samples are illustrated in Figure 3. Compared with that of the fresh Mn-Ce/Al\({}_{2}\)O\({}_{3}\) catalyst, the BET surface area of the sulphated Mn-Ce/Al\({}_{2}\)O\({}_{3}\) catalyst is decreased by 53.1%. Compared to those of S-Mn-Ce/Al\({}_{2}\)O\({}_{3}\), the pore size and pore volume of F-Mn-Ce/Al\({}_{2}\)O\({}_{3}\) are decreased by 27.6% and 37.1%, respectively. These results indicate that NO removal in the presence of SO\({}_{2}\) leads to a decrease in the BET surface area, pore size, and pore volume, which can be correlated with the formation of some species on the surface of the catalyst, which leads to the clogging of some of the catalyst pores. SEM studies were conducted to investigate the change in morphology of the catalysts after the SCR reaction. The SEM images in Figure 4 demonstrate that the surface of the F-Mn-Ce/Al\({}_{2}\)O\({}_{3}\) was smoother and more compact than those of R-Mn-Ce/Al\({}_{2}\)O\({}_{3}\) and S-Mn-Ce/Al\({}_{2}\)O\({}_{3}\). As shown in Figure 4, the surface of the F-Mn-Ce/Al\({}_{2}\)O\({}_{3}\) catalyst is almost flat. However, after SO\({}_{2}\) (50 ppm) poisoning, a high degree of aggregation on the surface was observed (Figure 4a,c). Additionally, compared with F-Mn-Ce/Al\({}_{2}\)O\({}_{3}\) (Figure 4a), there was no apparent change on the surface of the R-Mn-Ce/Al\({}_{2}\)O\({}_{3}\) catalyst (Figure 4b), but a few depositions could be seen on S-Mn-Ce/Al\({}_{2}\)O\({}_{3}\) (Figure 4c). This finding can be interpreted as a cause for the decrease in the surface area and pore volume (Figure 3). In addition, EDS displayed the Mn, Ce, Al, C, and O signals, further proving  
Figure 2: Effect of SO\({}_{2}\) and/or H\({}_{2}\)O on NO removal activities of the honeycomb cordierite-based Mn–Ce/Al\({}_{2}\)O\({}_{3}\) catalyst at 100 °C. (**a**) 50 ppm SO\({}_{2}\) resistance tests; (**b**) 5 vol % H\({}_{2}\)O resistance tests; (**c**) 50 ppm SO\({}_{2}\) and 5 vol % H\({}_{2}\)O resistance tests. that mixed metal oxide catalysts have been fabricated and supported on the honeycomb cordierite (Figure 4d). To further investigate the dispersion degree of the catalyst powder on the surface of the carrier, the SEM-EDS mapping of the F-Mn-Ce/Al2O3 is displayed in Figure 4e-h. The existence of Mn, Ce, Al, and O elements is clear, and high dispersion is shown (Figure 4e-g), indicating a well-mixed state of the catalyst. The above characteristics are also consistent with the analysis results of EDS. Figure 5 shows the N2 adsorption-desorption isotherms and pore size distribution of the fresh and poisoned catalysts, in which the isotherms are classical type IV [24]. The H2-type hysteresis loop was observed, which is typical for a wormhole-like mesostructure [18]. In addition, the beginning and end of the adsorption volume shifted in the direction of a large p/p0, which shows that there was some smaller pore clogging of the catalyst after poisoning by SO2. Figure 4: **(a–c)** Scanning electron microscopy (SEM) images of fresh and SO2 poisoned catalysts and **(d–h)** SEM-Energy dispersive spectroscopy (EDS) element mapping of fresh catalyst. **(a)** F-Mn–Ce/Al2O3; **(b)** R-Mn–Ce/Al2O3; **(c)** S-Mn–Ce/Al2O3; and **(d)** EDS spectra of the Mn–Ce/Al2O3 particles in yellow panel **(a)**; **(e)** Mn; **(f)** Ce; **(g)** Al, **(h)** O.  
Figure 3: Brunauer–Emmet–Teller (BET) Surface Area, pore size, and pore volume of the fresh (F) and sulfated (S) honeycomb cordierite-based Mn–Ce/Al2O3 catalysts (AA = (A\({}_{\text{F}}-\) A\({}_{\text{S}}\)/A\({}_{\text{F}}\)) \(\times\) 100%). To further understand the microstructure of the poisoned Mn-Ce/Al2O3, XRD analysis was performed. The XRD patterns of the honeycomb cordierite-based Mn-Ce/Al2O3 catalysts before and after the reaction are depicted in Figure 6. Several diffraction peaks observed at 28.95\({}^{\circ}\), 33.29\({}^{\circ}\), 47.49\({}^{\circ}\), 57.16\({}^{\circ}\), and 76.71\({}^{\circ}\) could be assigned to a cubic CeO2 crystallite (PDF#34-0394).