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

Abstract

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.