Revealing the influencing mechanism of CO2 on SCR of NOx with NH3 over FeW mixed oxide catalyst: interactions of carbonate-Fe2O3–FeWO4†
Abstract
The effect of CO2, a major component of the exhaust gas, on the elimination of NOx over FeW oxide catalyst was studied. It reveals that the presence of CO2 inhibits NOx conversion and N2 selectivity, which is due to the triple interactions of carbonate-Fe2O3–FeWO4. CO2 could be adsorbed to form carbonate species. The electron interactions between carbonate species and FeW oxides decrease the electron cloud density of Fe and W, leading to the increment of electrophilicity of metal species and thereby promoting the formation of nitrates. Meanwhile, a new reaction mechanism is proposed in which the NO2 species formed on the catalyst surface can react with the adsorbed NH3 or NH4+ by following the E–R mechanism. Meanwhile, NO3− could combine with NH4+ to form the NH4NO3 intermediate, which disciplines the L–H mechanism.