Catalytic performance of Co–Fe mixed oxide for NH3-SCR reaction and the promotional role of cobalt

Abstract

Co-modified iron oxide (Co-FeO_x) catalysts were prepared by a citric acid method for the low temperature NH₃-SCR of NO in the presence of O₂. The results show that the amount of Co obviously influences the activity and stability of the Co-FeO_x catalyst for the NH₃-SCR reaction, and when the molar ratio of Co/Fe is 0.2 (Co–Fe-0.2), NO is completely converted at 170 °C and the operation temperature window reaches 210 °C. After eight reaction cycles, the NO conversion and operation temperature window are hardly changed, and the presence of Co can markedly increase both its SO₂ and H₂O resistance ability. It was found that doping Co into α-Fe₂O₃ results in the formation of CoFe₂O₄ crystals, and increases the relative content of Fe³⁺, surface oxygen amount and oxygen activity. The Co–Fe-0.2 catalyst has the smallest particle size and the largest surface area, and possesses higher reducibility and catalytic activity for NO oxidation to NO₂ than α-Fe₂O₃, resulting in an improvement of the “fast-SCR reaction”.