Research On The Preparation Of LaMnO₃/Iron Ore Catalyst And Its Properties For Low-Temperature NH₃-SCR DE-NO_x

Along with the deteriorating of the atmospheric environment and the increasingly strictness of the standards of NOx emissions, it has become an important research subject to control NOx emissions effectively in the field of energy and environmental protection. Selective catalytic reduction ?SCR? with NH3 as a reductant has been widely applied to reduce NOx emissions and the technology of SCR de-NOx has fully developed. However, the commercial catalysts for detrification are mainly imported and expensive and ineffective at medium-low temperatures nowadays, limiting the widespread utilization of the technology. Therefore, to develop new de-NOx SCR catalysts with the properties of high efficiency at medium-low temperatures, and own intellectual property are of great significance.Supported perovskite catalysts Lai-xCexMnO3/iron ore were prepared by the citric acid complexing method and used for selective catalytic reduction of NO by NH3?NH3-SCR? in the thesis. A series of lanthanum manganite perovskite catalysts were prepared by different loadings of LaMnO₃, different preheating temperature of the iron ore, different adjusting amount of Ce/Co, and different calcination temperature and so on. With the help of the static physical and chemical adsorption of nitrogen?BET?, X-ray diffraction ?XRD?, X-ray fluorescence ?XRF?, temperature progrom desorption ?TPD?, thermogravimetric analysis?TG? and other characterization methods, the phase morphology, surface topography and the active component of Lai-xCexMnO3/ iron ore catalyst are obtained and characterized. The effects of the preparation parameters of catalysts and operation parameters in experiment to examine the activity of the catalyst, such as reaction temperature, gas hourly space velocity ?GHSV?, O2 concentration and NH3 concentration were studied in the intergral experiment system. The main achievements are as follows:The active ingredient and the loading of the supported perovskite catalysts are main factors to affect the SCR denitration efficiency of the catalysts. The main phase of hematite and limonite is ?-Fe2O3, which has a relatively good catalytic activity. The active ingredient, crystal morphology, surface structure of the catalysts are related with the preparation parameters of catalysts, such as loading of the active material, preheating temperature and calcination temperature, and so on. The results show that the optimal preparation conditions of the catalyst are, the hematite carrier as support, preheated at 320?, calcined at 600?, and the loading 40% of the active materials, adding rare earth elements Ce in the denitration experiment. The NO conversion of the catalyst 40% La0.8Ceo.2MnO3/hematite prepared at those conditions yields above 90% at following conditions,which are the reaction temperature window of 150?250?, 9000h-1GHSV,3% O2 concentration,500 ppm NH3 concentration and 500 ppm NO concentration, and the activation temperature of the catalyst is wide.The catalysts doped with Ce suitably, have a stronger ability to redox, NH3 adsorption capacity, and a better phase morphology, surface topography. It also makes sure that the active component is more uniformly supported on the support surface. Due to the reactants ?NH3, O2 and NO? more easily adsorbed on the catalyst surface to react, the de-NOx efficiency has been improved. The performance of de-NOx efficiency is best at the condition of the doping amount of Ce x= 0.2. When the doping amount was further increased to x= 0.3, the de-NOx efficiency of catalysts decreased.The resistance of catalysts, LaMnO₃,LaMnO₃/hematiteand La0.8Ce0.2MnO3/hematite, to SO2 has been researched at the temperature of 180? and 270?. The results show that the anti-posion performance of the supported perovskite catalysts making hematite as carriers is significantly better than that of LaMnO₃ catalyst at the same temperature. However, doping Ce into catalysts does not improve the anti-posion performance. The anti-posion performance of LaMnO₃/hematite at 270? is significantly better than that at 180?.The SO2 ppoisoning of the catalysts is due to the ammonia sulfate and metal sulfates species produced in SCR reaction deposit on the catalyst surface. The relatively high temperature can promote the decomposition of the ammonia sulfate species from the TG results.