Investigation of low-temperature NO2 reduction by NH3 over activated carbon: Effect of pore structure and flue gas conditions

Abstract

NO2–NH3 selective catalytic reduction (SCR) over activated carbon (AC) is a potential deNOx method at low temperatures. In this study, a series of AC samples with developed pore structures were prepared through CO2 activation. DeNOx activity tests indicated that the increase in specific surface area enhanced NOx conversion and decreased the temperature corresponding to the highest NOx conversion. FGAC900, which had the highest specific surface area, showed the highest NOx conversion of 97.80% at 150 °C. The influence of various flue gas conditions was also investigated. O2 concentrations in the range of 0–20 vol% had little effect on NOx conversion. The appropriate gas hourly space velocity and NH3 concentration are important for achieving superior deNOx performance. When 8 vol% H2O was added into dry simulated flue gas at 150 °C, NOx conversion decreased from 97.80% to 90.71%. Transient response experiments and density functional theoretical calculation results showed that the inhibition of H2O is reversible and results from competitive physisorption between NO2 and H2O molecules. The in situ DRIFT results indicated that NH4NO3 is an important intermediate. An efficient deNOx AC catalyst with a developed pore structure was prepared, and the effects of flue gas conditions were systematically investigated.