# No-CH4-SCR Over Core-Shell MnH-Zeolite Composites
## 3 Results and Discussion
### The Effects of H\({}_{2}\)O and SO\({}_{2}\) on NO-CH\({}_{4}\)-SCR Activity  
During the combustion of the fuel, the existence of H\({}_{2}\)O and SO\({}_{2}\) in the exhaust is inevitable. Indeed, the existence of H\({}_{2}\)O and SO\({}_{2}\) greatly suppressed CH\({}_{4}\)-SCR catalytic activity of the Co-zeolite catalysts [5]. Mn-ZSM-5 exhibited better H\({}_{2}\)O tolerance than Co-ZSM-5 for CH\({}_{4}\)-SCR [11]. Thus, it is of considerable interest to study H\({}_{2}\)O and SO\({}_{2}\) tolerance of the MnH-ZZs-n for CH\({}_{4}\)-SCR. Figure 4 shows the NO-CH\({}_{4}\)-SCR activity over MnH-ZZs-0.5 and MnH-Beta at 773 K in the presence of H\({}_{2}\)O or/and SO\({}_{2}\). As shown in Figure 4A, addition of 2.5% (_v/v_) water vapor, NO to N\({}_{2}\) conversion over MnH-ZZs-0.5 decreases from 75.2% a stable level 51.2% in about 3 h, while the CH\({}_{4}\) conversion decreases from 73.3% to 48.1%. In the same condition, NO to N\({}_{2}\) conversion over MnH-Beta decreases from 61.1% to 36.0% from 30 min to 200 min, and the conversion of CH\({}_{4}\) decreases from 84.2% to 58.9%. As the water is removed, the CH\({}_{4}\)-SCR activity almost recovers to the original extent, which indicated that the deactivation caused by the water is reversible. The decrease in the activity in the presence of water vapor may be due to the competence of H\({}_{2}\)O with NO for interacting with Mn\({}^{2+}\) ions to form hydrated \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{6}{c}{**NO Conversion to N\({}_{2}\) (CH\({}_{4}\) Conversion to CO\({}_{2}\)) (\%)**} \\ \cline{2-9}  & **573 K** & **623 K** & **673 K** & **723 K** & **773 K** & **823 K** & **873 K** & **923 K** \\ \hline MnNa-ZZs-0.5 & \(2.8\pm 0.12\) & \(4.3\pm 0.20\) & \(21.1\pm 0.76\) & \(49.9\pm 2.12\) & \(60.1\pm 2.90\) & \(55.4\pm 2.61\) & \(41.2\pm 1.98\) & - \\ MnH-ZZs-0.5 & \(2.8\pm 0.13\) & \(5.4\pm 0.26\) & \(21.6\pm 0.50\) & \(54.8\pm 2.61\) & \(75.5\pm 3.11\) & \(73.7\pm 3.66\) & \(78.2\pm 2.90\) & \(68.7\pm 3.00\) \\ MnH-ZZs-0.5 & \((1.6\pm 0.11)\) & \((2.8\pm 0.18)\) & \((41.8\pm 0.74\) & \((42.4\pm 2.10)\) & \((73.2\pm 4.06)\) & \((65.4\pm 5.25)\) & \((99.4\pm 6.01)\) & \((100.0\pm 0.50)\) \\ MnH-ZZs-0.5-1 & \(2.4\pm 0.18\) & \(4.2\pm 1.13\) & \(16.9\pm 1.13\) & \(43.4\pm 2.71\) & \(55.1\pm 3.30\) & \(59.8\pm 3.60\) & \(62.6\pm 3.21\) & \(56.9\pm 3.01\) \\ MnH-ZZs-0.5-1 & \((1.2\pm 0.10)\) & \((3.6\pm 0.80)\) & \((11.6\pm 0.81)\) & \((31.9\pm 2.01)\) & \((63.3\pm 3.50)\) & \((81.4\pm 5.00)\) & \((81.4\pm 5.00)\) & \((89.8\pm 5.25)\) & \((100.0\pm 0.51)\) \\ MnH-ZZs-0.5-2 & \(2.3\pm 0.16\) & \(4.5\pm 0.93\) & \(13.9\pm 0.95\) & \(33.2\pm 2.10\) & \(48.1\pm 2.90\) & \(59.9\pm 3.45\) & \(55.3\pm 2.95\) & \(50.6\pm 2.61\) \\ MnH-ZZs-0.5-2 & \((1.3\pm 0.11)\) & \((3.5\pm 0.75)\) & \((10.7\pm 0.75)\) & \((26.5\pm 1.81)\) & \((47.6\pm 2.81)\) & \((79.7\pm 4.95)\) & \((91.2\pm 5.01)\) & \((100.0\pm 0.46)\) \\ MnH-ZZs-0.5-3 & \(2.5\pm 0.17\) & \(3.9\pm 0.75\) & \(10.9\pm 0.80\) & \(26.6\pm 1.72\) & \(38.1\pm 2.15\) & \((32.4\pm 2.81)\) & \(45.6\pm 2.66\) & \(45.2\pm 2.41\) \\ MnH-ZZs-0.5 & \((1.1\pm 0.09)\) & \((3.3\pm 0.65)\) & \((6.3\pm 0.66)\) & \((24.7\pm 1.71)\) & \((36.2\pm 2.16)\) & \((65.7\pm 4.01)\) & \((058.4\pm 4.80)\) & \((100.0\pm 0.50)\) \\ H-ZZs-0.5 & \(0.9\pm 0.09\) & \(1.5\pm 0.09\) & \(3.7\pm 0.15\) & \(10.8\pm 0.45\) & \(17.3\pm 0.71\) & \(20.5\pm 1.03\) & \(22.1\pm 0.53\) & \(23.9\pm 1.01\) \\ (0.1\pm 0.01) & \((0.2\pm 0.02)\) & \((1.6\pm 0.10)\) & \((6.2\pm 0.70)\) & \((142.0\pm 0.80)\) & \((25.1\pm 1.93)\) & \((30.2\pm 2.51)\) & \((34.8\pm 1.50)\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Effect of the Mn content in the MnH-ZZs-n on the catalytic activity. species. The adsorption of H\({}_{2}\)O on the catalysts is physical and/or weak-chemical, and there are no strong chemical bonds formed between H\({}_{2}\)O and active sites on the surface of the catalysts. In other words, the Mn catalysts have a good resistance to H\({}_{2}\)O [21; 32].