Preparation And Performance Of Mn-Ce-O_x/TiO₂ Catalyst For Low-temperature SCR Of NO_x With NH₃

The emission of nitrogen oxides(NOx)can cause a series of environmental problems,which pose a great threat to human living environment and physical health.Due to being a mature technology,high NOx removal and simple practical operation,selective catalytic reduction with ammonia(NH3-SCR)is a well-known mainstream technology for NOx abatement.V2O5-WO3(MoO3)/TiO2 catalyst widely used in industry has the disadvantages of high operating temperature,strong toxicity,and easy to cause secondary pollution.Therefore,it is highly desirable to develop a novel SCR catalyst with low pollution,low cost,and high de-NOx efficiency at low temperature.Mn-based catalysts,especially Mn-Ce-Ox/TiO2 catalyst,are non-toxic and have a strong low-temperature redox capability.They are the hotspots of current research,but their reaction temperature window is narrow,N2 selectivity and sulfur resistance are poor.Therefore,the purpose of this paper was to optimize its low-temperature SCR activity through improving the preparation methods and preparation conditions of Mn-Ce-Ox/TiO2 catalyst.The main research contents are as follows:(1)Effect of different preparation methods on the low-temperature de-NOx performance of Mn-Ce-Ox/TiO2 catalyst was srudied.The results show that the Mn-Ce-Ox/TiO2(MCT-CP)catalyst prepared by co-precipitation method has better SCR activity and excellent N2 selectivity compared with Sol-gel and citric acid complexation.The characterization results show that the MCT-CP catalyst has the largest specific surface area,strong NH3 and NO adsorption capacity,and high concentraions of Mn4+,Ce3+and adsorbed oxygen on catalyst surface.In addition,the MCT-CP catalyst has good sulfur resistance.(2)Effect of different aging temperatures on the low-temperature de-NOx performance of Mn-Ce-Ox/TiO2 catalyst prepared by the co-precipitation method was explored.The results show that the MCT-30 catalyst prepared at an aging temperature of 30℃ has a higher low-temperature SCR catalytic activity,which mainly be due to the high dispersion of Mn and Ce species on the surface of the MCT-30 catalyst,the high content of Mn4+ and the surface adsorbed oxygen Oα,large reduction peak area and more acid sites.(3)Effect of the type of precipitant on the low-temperature de-NOx performance of Mn-Ce-Ox/TiO2 catalyst prepared by co-precipitation method was investigated.The results show that the precipitant cations(NH4+ and Na+)have a great effect on the SCR activity.The Mn-Ce-Ox/TiO2 catalysts prepared by precipitants with cation of NH4+ has a better NOx conversion rate.It can be attributed to the presence of crystalline phase TiO2 on the catalyst surface,Ce and Mn species are highly dispersed on the catalyst surface,the relative contents of Mn4+,Ce3+,and Oαare high,and there are large number of L acid sites on the surface.