Highly efficient MnOx/biochar catalysts obtained by air oxidation for low-temperature NH3-SCR of NO

In this study, a novel air oxidation treatment strategy was proposed to modify Mn-doped biochar catalysts for enhanced removal of NO at low temperature. The pre-oxidation at 400 °C and post-oxidation at 250 °C under air atmosphere was applied respectively before and after impregnating biochar with Mn-containing solution (BC-OMO). The results showed that, after pre-oxidation the specific surface area and total pore volume of the sample increased to 734 m2/g and 0.440 cm3/g respectively in comparison with those without pre-oxidation (557 m2/g and 0.353 cm3/g). After further post-oxidation, the contents of Mn4+ and chemisorbed oxygen (Oα) in BC-OMO increased to 36.2% and 49.8% respectively from those without air oxidation (25.4% and 38.7%), which could enhance the surface acidity and redox capabilities of the catalysts. The denitration results showed that the conversion efficiency of NO for BC-OMO catalyst reached as high as 97.0% at 150 °C, which was significantly higher than that without air oxidation (61.8%). The mechanisms for improving denitration efficiency of MnOx/biochar catalysts by pre- and post-air oxidation were also discussed.