Enhancement of NH3-SCR performance of LDH-based MMnAl (M = Cu, Ni, Co) oxide catalyst: influence of dopant M

Abstract

Transition metal (Cu, Ni, Co) doped MnAl mixed oxide catalysts were prepared through a novel method involving the calcination of hydrotalcite precursors for the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR). The effects of transition metal modification were confirmed by means of XRD, BET, TEM, XPS, NH₃-TPD, and H₂-TPR measurements. Experimental results evidenced that CoMnAl-LDO presented the highest NO_x removal efficiency of over 80% and a relatively high N₂ selectivity of over 88% in a broad working temperature range (150–300 °C) among all the samples studied. Moreover, the CoMnAl-LDO sample possessed better stability and excellent resistance to H₂O and SO₂. The reasons for such results could be associated with the good dispersion of Co₃O₄ and MnO_x, which could consequently provide optimum redox behavior, plentiful acid sites, and strong NO_x adsorption ability. Furthermore, dynamics calculations verified the meaningful reduction in apparent activation energy (E_a) for the CoMnAl-LDO sample, which is in agreement with the DeNO_x activity.