Insights into enhancement of NH3-SCR activity and N2 selectivity of LDHs-derived NiMnAlOx catalysts: Combination of experiments and DFT calculations

Abstract

The LDHs-derived NiMnAlOx catalysts was proposed for NH3-SCR denitration technology, which improved the overall catalytic performance. At 100–250 oC, the preferred Ni1Mn0.5Al0.5Ox had NOx conversion of exceeded 95%, and N2 selectivity of more than 89%, which was higher than the control catalysts. Additionally, Ni1Mn0.5Al0.5Ox also performed better resistance to SO2 with less sulfate species deposited on the surface. Transient reaction was conducted to illustrate that Ni1Mn0.5Al0.5Ox reduced the N2O formation by suppressing the occurrence of non-selective catalytic pathway. Physicochemical characterization analyses confirmed that Ni1Mn0.5Al0.5Ox catalyst had more active species, abundant surface oxygen, moderate acidic sites and redox properties, which promoted the adsorption and activation of NOx and NH3, and further accelerated the SCR reaction. Finally, DFT calculations provided insights into the mechanism and influence of the degradation of the Jahn-Teller effect and the reversal of the magnetic moment at the Mn site on the surface adsorption process.