Study On The Anti-sulfur Poisoning Mechanism Of Fe-Mn/TiO₂ Catalyst

NOx is one of the main air pollutants,and it causes serious harm to human health and the ecological environment.In recent years,selective catalytic reduction technology has become the most mainstream technology for processing NOx in the industry,and the core of selective catalytic reduction technology（SCR）is the catalyst.Among the NH₃-SCR denitration catalysts,Mn catalysts have been widely studied due to their variable valence,strong redox ability and excellent low-temperature denitration activity,but Mn-based catalysts are easily deactivated after being poisoned by SO₂.There are still many controversies as to which factors are affected by Mn-based catalysts and the mechanism of poisoning and deactivation.In view of the above problems,Mn/Ti O₂ and Fe-Mn/Ti O₂ catalysts were prepared by sol-gel method in this paper to study the effect of Fe doping on the activity and poisoning of Mn-based catalysts,and further explore the poisoning of SO₂ on Mn-based catalysts.Inactivation mechanism.Firstly,the influence of Fe doping on the activity of Mn/Ti O₂ catalyst was explored.The results show that the doping of Fe improves the SCR activity of the catalyst,and the T80 activity temperature window can reach 100℃～325℃.Furthermore,in-situ infrared characterization of Mn/Ti O₂ and Fe-Mn/Ti O₂ was carried out to study the promoting effect of Fe doping on the SCR performance of the catalyst.The results show that the Mn/Ti O₂ and Fe-Mn/Ti O₂ catalysts follow the L-H reaction mechanism at low temperature（100°C）.The doping of Fe enhances the adsorption of NOx on the surface and generates nitrate-like active species,which promotes the progress of the denitration reaction.Secondly,the influence of different temperatures on the sulfur resistance of Mn/Ti O₂ and Fe-Mn/Ti O₂ catalysts was explored.The results show that Fe doping at 150°C aggravates the poisoning and deactivation of the catalyst,while Fe doping at 250°C inhibits the poisoning and deactivation of the catalyst to a certain extent.The poisoned catalyst was characterized by TG/DSC,and the influence factors of Fe doping on the poisoning and deactivation of the catalyst were analyzed.The results showed that the sulfation of active sites and the formation of ammonium sulfate on the catalyst surface were the reasons for the deactivation.The NOx-TPD,TG/DSC and dynamic experiments were carried out on the catalyst impregnated with NH₄HSO₄ to explore the formation and decomposition of the surface material on the catalyst.The results showed that the NH₄HSO₄ supported on the Fe-Mn/Ti O₂ catalyst in the low temperature section would inhibit the adsorption capacity of NOx.Weaken the SCR response path.Finally,in-situ DRIFTS experiments were conducted to deeply analyze the poisoning mechanism of Mn/Ti O₂ and Fe-Mn/Ti O₂ catalysts.The results o showed that SO₂ inhibited the formation of corresponding active species on the surface of the catalyst by NOx.For Mn/Ti O₂,SO₂ inhibits the formation of nitrite on its surface at low temperature（100℃）,and inhibits the formation of bidentate nitrate on its surface at high temperature（200℃）;for Fe-Mn/Ti O₂,it inhibits SO₂ at low temperature（100℃）The formation of bidentate nitrate on the surface can inhibit the formation of nitrite on the surface at high temperature（200℃）.