Study On NO_x Conversion And Resistance To SO₂ Of Ce-Mn/TiO₂ Low-temperature Catalysts

In recent years,NOx has become the most acid gas pollutants in our country and does harm to the environment and human.selective catalytic reduction?SCR?is one of the most useful methods for denitration and its core technology is the SCR catalys.But SCR technology is still faced with the problems:low activity at low temperature,poor resistance to SO₂ and so on,so it is important to study the high activity at low temperature and strong resistance to SO₂ of catalysts.In this paper,manganese oxide and cerium oxide were used as the active components supported on titanium dioxide and Ce-Mn/TiO₂ were prepared,then studied the NOx conversion and resistance to SO₂ of Ce-Mn/TiO₂ low-temperature catalysts.At last the catalyst was modified by doping metal lelements and the doped catalysts were studied the NOx conversion and resistance to SO₂.Firstly,the preparation conditions of Ce-Mn/TiO₂ were optimized.Results showed that catalyst prepared by impregnation method,and the active components loading:Ce/TiO₂ is 20%?mass ratio?,Mn/TiO₂ is 5.2%?mass ratio?,with synthetic air,calcine 2h at 500?,catalyst which prepared on the above conditions had optimal low temperature denitration activity.At 180?,the NOx conversion were 99.7%,in the presence of 100 ppm SO₂,the NOx conversion of Ce?20?-Mn/TiO₂ can still moer than94%.Secondly,on the basis of Ce-Mn/TiO₂,catalyst was modified by doping metal element X?Fe,Sm?,Fe-doped catalyst showed the better denitration activity at low temperature than Ce-Mn/TiO₂,but Sm of doping weakend the advantage of the high activity at low temperature.But after doping metal element Fe or Sm,the resistance to SO₂ of catalysts were improved,at 180?,the order of the resistance to SO₂ of catalysts:Ce?20?-Mn/TiO₂>Fe?10?-Ce-Mn/TiO₂>Sm?10?-Ce-Mn/TiO₂.Finally,catalysts were characterized by BET,XRD,SEM,XPS,the results showed that the higher ratio of Ce³⁺/Ce⁴⁺,Mn³⁺/Mn⁴⁺,O^?/?O^?+O^??were bad for the catalytic reaction;large specific surface area was beneficial to the denitration activity;the active components had high dispersion and distributed equally on the surface.