Highly efficient removal of NO with ordered mesoporous manganese oxide at low temperature

Abstract

Highly ordered mesoporous MnO₂ was prepared using KIT-6 as a hard template, for selective catalytic reduction (SCR) of NO with NH₃ at low temperature, which was characterized using TEM, XRD, BET, XPS, H₂-TPR, NH₃-TPD and in situ DRIFT. Based on the results of HRTEM, the ordered mesoporous channels of MnO₂ can be observed clearly. The SCR activity of NO with NH₃ at low temperature was evaluated using these ordered mesoporous MnO₂ as catalysts, and it was found that 100% NO conversion efficiency could be achieved at temperatures from 150 to 250 °C. For comparison, mesoporous Mn₂O₃ and bulk MnO₂ were synthesized and their NO conversions were tested using the same parameters. The mechanism of improved SCR performance was investigated using XPS, H₂-TPR, NH₃-TPD and in situ DRIFT, and it was indicated that specific surface area, surface chemisorbed oxygen, reducibility and acid sites have great effect on the SCR reaction. In addition, the effects of H₂O and GHSV on NO conversion were investigated.