Reaction mechanism of low temperature NH ₃ SCR over MnOx/sewage sludge char

The reaction mechanism of selective catalytic reduction of N Ox over sewage sludge char impregnated with MnOx using NH ₃ as the reducing agent was investigated. The active Mn phase was shown to be Mn ₃O ₄ from the XRD analysis. Adsorption was the dominant N Ox removal mechanism at low temperatures below 150 °C although reduction reaction also contributed partly to the N Ox removal at 100 ~ 150 °C. The reaction rate constants of N Ox removal over non-impregnated and Mn Ox-impregnated active chars were compared based on experimental results. The Mn Ox-impregnated char was shown to have a higher reaction rate constant and a higher N Ox removal efficiency due to a higher collision coefficient and a lower activation energy. The activation energy for both chars was shown to be relatively low (10~12 kJ/mol) under the experimental conditions of this study.