Influence factors and mechanism of selective catalytic reduction of NO in the flue gas over activated coke

Abstract

ABSTRACT The aim of this study was to study the influence factors of selective catalytic reduction (SCR) of NO with NH3 in flue gas and to clarify the mechanism of SCR over activated coke (AC). An AC in various simulated flue gases for reduction of NO was examined in a fixed-bed reactor. X-ray photoelectron spectroscopy (XPS) was used to performhigh-resolution scanning of surface N element. The results indicate that the presence of O2 in flue gas facilitates the NO reduction in SCR. Higher polarity of H2O molecule may inhibit NH3 or NO adsorption on the surface of ACs, so that NO reduction has been restrained. A lowest NO conversion was tested at 250°C in the temperature range of 100–350°C, meaning that may presence of different SCR mechanism at low or high temperature. Adsorption of NH3 below 250°C is dominated by physical adsorption and adsorption of NH3 higher than 250°C is dominatedby the chemical reaction between NH3 and AC base on the determination of XPS and adsorption capacities of NH3. There was a good correlation between adsorption capacity of NH3 and NO conversion, which indicated that NH3 adsorption is a key step in SCR regardless of whether NH3 was physically or chemically adsorbed on the AC.