Molybdenum oxide as an efficient promoter to enhance the NH3-SCR performance of CeO2-SiO2 catalyst for NOx removal

Selective catalytic reduction (SCR) of NOx with NH3 has been widely used for the removal of NOx. Because of the inevitable disadvantages of conventional V2O5-WO3(MoO3)/TiO2 catalysts such as poor low-temperature SCR activity and toxicity of vanadium, as well as the high-cost and over-strong NH3 adsorption of zeolite catalysts, the development of efficient and non-toxic metal oxide SCR catalysts is highly demanded. Previously, we have developed an environmentally-benign CeO2-SiO2 mixed-oxide SCR catalyst (CeSi2), which exhibited superior SO2 resistance ability. However, the low-temperature SCR activity on CeSi2 was not that satisfactory. In this work, we proposed a new strategy of Mo doping to improve the low-temperature SCR activity on CeSi2, which was very crucial for its practical application. By a simple co-precipitation method, a homogenous Mo-Ce-Si mixed-oxide catalyst was prepared. The Mo doping could significantly enhance the NH3-SCR activity on CeSi2 below 250 ?, and the optimal catalyst was Mo(0.1)CeSi2, which could achieve 80% NOx conversion at 200 C. Mo0.1CeSi2 also exhibited superior N2 selectivity and resistance to SO2/H2O poisoning. Via a series of characterizations, it was found that the redox properties and surface acidity on CeSi2 by Mo doping, which accounted for the enhanced low-temperature NH3-SCR activity on Mo(0.1)CeSi2. The reaction mechanism on Mo0.1CeSi2 was also fully revealed by in situ DRIFTS experiments. This work provided a new insight for the development of efficient low temperature SCR catalysts with superior SO2 resistance ability.