Promotional effect of metal cations doping on OMS-2 catalysts for NH3-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 NOx with NH3. The catalytic performance over the doped M-OMS-2 catalysts increased with the Bronsted acid sites. Na-OMS-2 displayed the best deNO(x) performance, which is primarily due to the higher surface area, reducibility and Bronsted acid sites. Kinetic results demonstrate that the activation energy (Ea) of Na-OMS-2 catalyzed NH3-SCR reaction is evidently lower than that of the undoped K-OMS-2 catalyst owing to a larger number of NH3 adsorbed on Bronsted acid sites and more facile activation of NH3. Meanwhile, the Na+ loading of Na-OMS-2 is further optimized for the NH3-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 NH3-SCR mechanism is proposed to highlight the importance of the Bronsted acid sites and the lattice oxygen.