Promotional effect of metal cations doping on OMS-2 catalysts for NH3-SCR reaction.

• The NH 3 -SCR activity of metal doped OMS-2 is higher than that of undoped K-OMS-2. • The NH 3 -SCR activity over M-OMS-2 increased with the Brønsted acid sites. • Na-OMS-2 showed optimal NO conversion due to the presence of more Brønsted acid sites. • The Brønsted acid sites and lattice oxygen play important role in NH 3 -SCR reaction. Different metal cations (Li+, Na+, Mg2+, Ca2+, Al3+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, and Ag+) were doped into the OMS-2 material via "one-pot" refluxing approach to investigate the influence of metal cations doping on the structure of OMS-2 and on the activity of selective catalytic reduction (SCR) of NO x with NH 3. The catalytic performance over the doped M-OMS-2 catalysts increased with the Brønsted acid sites. Na-OMS-2 displayed the best deNO x performance, which is primarily due to the higher surface area, reducibility and Brønsted acid sites. Kinetic results demonstrate that the activation energy (E a) of Na-OMS-2 catalyzed NH 3 -SCR reaction is evidently lower than that of the undoped K-OMS-2 catalyst owing to a larger number of NH 3 adsorbed on Brønsted acid sites and more facile activation of NH 3. Meanwhile, the Na+ loading of Na-OMS-2 is further optimized for the NH 3 -SCR reaction, the results indicate that the Na-OMS-2 with Na/(Na + Mn) ratio of 0.03 exhibits the best activity because of the higher reducibility and more acid sites. A feasible NH 3 -SCR mechanism is proposed to highlight the importance of the Brønsted acid sites and the lattice oxygen. [ABSTRACT FROM AUTHOR]