Research On NH₃-SCR Catalysts With Sulfur Resistance

NO_x is one of the major air pollutants,which is the emphasis of air pollution control in China.The control of nitrogen oxides emission have been becoming increasingly stringent these years.Selective catalytic reduction of NO_x by NH₃ is the the most widely used technology for NO_x control.The core of SCR technology are catalysts.However,how to improve the activity and sulfur resistance of the catalyst at low temperatures is the main concern nowadays.This paper was based on Mn-Ni catalysts.Through different synthisize methods and modification of the samples,we chose the best Mn-Ni-Ce?mixed 400°C?catalyst and studied it.Mn-Ni and Mn-Ni-Ce?mixed 400°C?were characterized and analyzed by XRD,TPR,XPS,NH₃-TPD and so on.This paper analyzed the differences before and after the Mn-Ni catalyst's modification through the physical and chemical properties,which also analyzed why catalytic activity and sulfur resistance of Mn-Ni-Ce?mixed 400°C?catalyst were excellent.1)We prepared the Mn-Ni-Ce?mixed 400°C?catalyst and discovered its catalytic activity was excellent at low temperatures.Among them,Ni:Mn had the best SCR effect,whose Mn-Ni atomic ratio was 0.4.The effects of supporting capacity on the catalytic activity and sulfur resistance of Mn-Ni/TiO₂ catalysts were also investigated.It was found that the SCR performance of Mn-Ni/TiO₂ catalysts were similar to Mn-Ni oxide catalysts when the carrying capacity was 10wt%.But the sulfur resistance of Mn-Ni/TiO₂ was much lower than the unsupported Mn-Ni oxide catalyst.2)We selected Mn-Ni oxide catalyst without any supporter as the study object,using co-precipitation method and compounding method,and mixing different metal elements to improve the sulfur resistance of the catalyst.It was found that the Mn-Ni-Ce?mixed 400°C?catalyst prepared by compounding method had the best catalytic activity and sulfur resistance,while the catalyst prepared by co-precipitation method had poor sulfur resistance effect.Long time sulfur resistance of Mn-Ni-Ce?mixed 400°C?was also studied,it was found that the catalytic activity of Mn-Ni-Ce?mixed 400°C?was stable at 250°C and 200 ppm SO₂ for 10h,and the NO removal efficiency was over 90%.3)For Mn-Ni-Ce?mixed 400°C?,Ce existed in the form of CeO₂,the other ingredients were NiMnO₃ and Mn₂O₃,amorphous Mn,Ni and Ce oxides,which were dispersed on the surface of the catalyst.The modified catalyst had no effect on the existing form and valence state of Mn and Ni elements in the catalyst.The redox capacity of the catalyst had slight improvement,and the acid sites and acid amount were increased,which were the main reasons for the excellent catalytic activity and sulfur resistance.