| Selective catalytic reduction of Nitrogen oxides?NOx?by NH3?NH3-SCR?is well established and widely used for NOx removal.Ce-based catalysts have attention for the NH3-SCR of NOx.So in our research,we have studied Ce-Sb oxide and Ni-Ce-Ti oxide catalysts for the reduction of NOx.It was found that the both catalysts showed high NH3-SCR activity in a wide operation temperature window.N2-adsorption,BET,XRD,H2-TPR,NH3-TPD,XPS were conducted to investigate the catalyst structure of Ce-Sb and Ni-Ce-Ti catalysts.The reaction mechanism was also investigated by in situ DRIFTS experiments.A series of Ce-Sb catalysts prepared by the citric acid method possessed high NH3-SCR activity,high N2 selectivity and a high tolerance to H20 and S02.Nearly 80%NOx conversion was achieved in the temperature range of 250-450 ?.Characterization results suggested the strong interaction between Sb and Ce species not only improves the redox property of the Ce-Sb catalyst but also enhances the surface acidity,which promotes the adsorption and activation of NH3 species,thus promoting NH3-SCR performance.Ni-Ce-Ti catalysts prepared by the hydrothermal method aiso exhibited high NH3-SCR performance with nearly 90%NOx conversion and 100%N2 selectivity achieved in the temperature range of 250-450 ?,Moreover,it showed strong resistance against H20 and SO2.Based on the characterization,it was found that Ni-Ce-Ti catalyst is of amorphous structure.The doping of Ni improved the BET surface area and enhancing the redox property of the catalyst.The strong surface acidity over Ni-Ce-Ti catalysts promotes the adsorption and activation of NH3 species on the Lewis acid sites,thus producing more reactive intermediates,which contributes to improving the NH3-SCR performance. |
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