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

Hierarchical MnO x 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 x 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.