Low-Temperature NH₃-SCR over Hierarchical MnO Supported on Montmorillonite Prepared by Different Methods

Hierarchical MnO pillared or supported on montmorillonite were prepared by three methods, i.e., impregnation (IM), chemical precipitation (CP), and in situ deposition (SP). The catalysts were characterized by low-temperature N₂ adsorption (BET), XRD, XPS, SEM, TEM, H₂-TPR, NH₃-TPD, NO-TPD, TPSR, in situ DRIFTS, and evaluation of catalytic performance for NH₃-SCR. The best catalytic performance was obtained for catalysts prepared by SP in terms of activity and selectivity, obtaining >90% NO conversion with >95% selectivity to N₂ in 100-300 °C and GHSV of 70,000 h^-1. Compared to IM and CP, SP greatly simplified catalyst preparation, resulting in higher BET surface areas; a spongy pore structure; more highly dispersed, pillared MnO species; and higher density of acid sites distributed on catalysts surface, which all contributed to its superior performance for NH₃-SCR. The activity for low-temperature NH₃-SCR of manganese catalysts could be widely tailored by preparation methods.