Enhancing DeNOx performance of CoMnAl mixed metal oxides in low-temperature NH3-SCR by optimizing layered double hydroxides (LDHs) precursor template

LDHs templates (marked as CoAl-MnO₂-LDH and CoMnAl-CO₃-LDH) were fabricated via ion-exchange/redox reaction and hexamethylenetetramine (HMT) hydrolysis methods respectively. CoMnAl mixed metal oxides (marked as MnO₂/CoAl-LDO and CoMnAl-LDO) from the as-prepared LDHs templates were novelly prepared and tested as low-temperature NH₃-SCR catalysts. Catalytic evaluation pronouncedly affirmed that the catalytic performances of the as-acquired catalysts were vulnerable to the preparation method of precursor template, where MnO₂/CoAl-LDO presented preferable DeNOx activity (over 90% NOx conversion), N₂ selectivity and SO₂ resistance in much broader working temperature window (90–300 °C) than CoMnAl-LDO. Multiple characterizations revealed that the excellent catalytic performance of the MnO₂/CoAl-LDO could be attributed to its higher specific surface area which could promote dispersion of abundant Mn⁴⁺ and Co³⁺ species, and resultantly afforded stronger redox ability and more acid sites. Moreover, dynamic calculation confirmed that the relatively lower activation energy on MnO₂/CoAl-LDO for low-temperature NH₃-SCR reaction should be closely related to the occurrence of a more rapid redox cycle and in agreement with the excellent DeNOx performance.