The Efects Of Alkali Earth Metal On The Performances Of Mn-based Low-temperature SCR DeNO_x Catalysts

NOx is one of the main air pollutants where selective catalytic reduction (SCR) is one of the most promising and widely used methods to remove NOx in the flue gas from stationary sources. Recently, low-temperature SCR technology has attracted more and more attentions, but there are still a lot of problems to be solved before industrial applications, such as the poisoning of alkaline earth metals, SO2, and uncertainty of their combined effect mechanisms. To solve these problems, the combined effect of alkaline earth metals and SO2was investigated by using MnOx based catalysts in this dissertation.Firstly, the SO2resistance of Ca doped Mn(0.4)/TiO2catalysts prepared by impregnation method was investigated. It was observed that the doping of Ca could reduce the SCR activity. And Ca doped Mn(0.4)/TiO2catalysts showed better SO2resistance than the undoped one as Ca could react with SO2prior to Mn and Ti and protect the active sites. However, the protection would be out of action under the long-time SO2reaction.Secondly, the effects of Ca modification by sol-gel method were also investigated. It was found that the modification of Ca increase the SO2resistance of catalysts significantly. This is attributed to the fact that Ca could inhibit the formation of surface sulfates. What’s more, the strong interactions between Ca, Mn and Ti could increase the surface area and pores volume, leading to the enhancement of SO2resistance.Finally, Mg(x)Mn(0.4)/TiO2catalysts were prepared by sol-gel method. It was found that the Mg modification could obviously increase the SCR activity of Mn(0.4)/TiO2catalysts, and inhibit the formation of N2O. At the same time, the SO2resistance was also increased. Mg modification leaded to the interaction between Mn with Ti, resulting in good dispersion of MnOx. In addition, the adsorption of NO was enhanced on the catalysts surface, leading to better SCR activity. It was also found part of Lewis acid sites could be preserved on the Mg(0.1)Mn(0.4)/TiO2catalysts surface under the SO2atmosphere, which could be one of the reasons of good SO2 tolerance.