# No-CH4-SCR Over Core-Shell MnH-Zeolite Composites
## 1 Introduction  
The combustion of coal, gasoline, and natural gas meets mankind's demands for energy. However, the emission of flue gas has caused severe environmental pollution, particularly NOx (among them 90% is NO), which can not only cause acid rain and photochemical smog, but also result in the greenhouse effect. The catalytic removal of NOx is one of the most important ways to decrease the impact of NOx on the environment [1]. Indeed, selective catalytic reduction of NO by NH3 (NH3-SCR) has been put into commercial operation. However, well-known disadvantages such as storage of ammonia, costly equipment, the danger of ammonia leakage, and the possible formation of ammonium sulfates due to the reaction of SO2 (SO3), NH3 and H2O greatly restrict the widely application of this technology [2]. Thus, many researchers have made efforts to find other new reductants to substitute for NH3. It has been found that hydrocarbons such as C3H6 and C3H8 exhibit high activity for NO reduction over many catalysts [3]. In particular, [PERSON]'s group reported that NO can be selectively reduced by CH4 over Co ion-exchange ZSM-5 and ferrierite in the presence of excess oxygen [4]. This is of considerable interest because there are plenty of CH4 and natural gas vehicles increasing worldwide, and CH4 itself is a greenhouse gas with a stronger greenhouse effect than carbon dioxide. A thorough review on the state of research has been reported [5; 6] in which three types of catalysts, i.e., metal oxides, loadedmetal, and zeolite loaded metal, are active for CH\({}_{4}\)-SCR. Among them, metal-zeolite catalysts have received the greatest attention because zeolite not only has a large surface, but also acid function and high hydrothermal stability. Zeolite-based catalysts containing different metals have been reported as active materials for the selective catalytic reduction of NOx with methane (CH\({}_{4}\)-SCR) [4]. CO [5; 7; 8], Mn [6; 9; 10; 11], Pd [12] etc. incorporated into ZSM-5 have been confirmed to be active sites for CH\({}_{4}\)-SCR. On the other hand, the zeolite structure has considerably affected the CH\({}_{4}\)-SCR reactivity. For example, ZSM-5, ferrierite, mordenite [13], and Beta [14] loaded metals exhibited high CH\({}_{4}\)-SCR activity, while zeolite Y loaded metals are poor for the reaction. So far, almost all research has been focused only on the zeolites with single topology. In fact, zeolitic composites with different porous structure have shown the special synergic effects in catalysis [15; 16; 17]. CH\({}_{4}\)-SCR reactivity of the catalysts based on two different zeolite structures (MOR and BEA) containing Pd and Ce was reported [18]. Compared to each individual-zeolite catalyst, the catalytic performance of the zeolite composite was significantly improved because of the synergic effects of the zeolites. In our group, a new type of zeolite composite ZZs-n with FAU and BEA topology was synthesized. CoH-Beta/Y exhibited not only high CH\({}_{4}\)-SCR activity but also better SO\({}_{2}\) and H\({}_{2}\)O tolerance than CoH-Beta. Mn-zeolite is promising for CH\({}_{4}\)-SCR because of relatively higher tolerance to water vapor [19] than Co-zeolite with single topology. Thus, it is of considerable interest to investigate NO-CH\({}_{4}\)-SCR over MnH-ZZs-n. It is clearly evident from the transient studies of the NO and NO + O\({}_{2}\) reaction that the adsorbed NO molecules must be dissociated over the partially reduced manganese sites [20]. The Mn/TiO\({}_{2}\) catalyst showed good phase stability during the NOx decomposition reaction at a different temperature and exhibited a good resistance to 10 vol% H\({}_{2}\)O and 100 ppm of SO\({}_{2}\)[21]. In comparison, Mn/TNT showed an impressive deNOx potential compared to other active components in titania nanotubes [22].  
In this contribution, NO-CH\({}_{4}\)-SCR over MnH-ZZs-n is investigated. Effects of H\({}_{2}\)O and SO\({}_{2}\) on the catalytic performance of MnH-ZZs-n are reported.