Preparation And Characterization Of Co And Sn Modified Honeyco Mb Ceramic Supported Iron Catalysts And Their Catalytic Properties For Selective Reduction Of NO By C₃H₆

Nitrogen oxides?NO_x?are mainly composed of NO?>90%?and NO₂,which can cause many kinds of harsh environmental problems such as photochemical smog,atmospheric acid deposition,and seriously endanger human health and ecological environment.NO_x control technology has become a key topic for research in various countries in recent years.The HC-SCR flue gas denitrifi-cation technology has been a key topic for academic research in recent years.In contrast,metal oxide catalysts have many advantages such as low cost,good hydrothermal stability,high HC-SCR activity and selectivity in the mid-high temperature range,and so on,which are the recent researches on the HC-SCR flue gasdenitration technology.The research group conducted a series of studies on the characteristics of low-carbon hydrocarbons on iron and supported iron-based catalysts to reduce NO in the early stage,and achieved certain results.Among them,the monolithic iron-based catalyst?Fe/Al₂O₃/cordierite,which can be abbreviated as Fe/Al₂O₃/CM?developed by the laboratory showed good denitrification performance,and about 97%NO conversion was achieved at 600?,but SO₂ and water vapor inhibited the activity of the catalyst.Effect,and the catalyst under aerobic conditions,the reaction temperature is lower than 400? when the denitration efficiency is low.In order to further improve the selective catalytic activity of Fe/Al₂O₃/CM catalysts and improve their anti-SO₂ and H₂O properties,this study used Co to modify the Fe/Al₂O₃/CM catalyst to make a Co/Fe/Al₂O₃/CM catalyst;To improve the catalytic activity of Fe/Al₂O₃/CM catalysts under oxygen-enriched conditions,Sn was used to modify Fe/Al₂O₃/CM catalysts to form Sn/Fe/Al₂O₃/CM catalysts;C₃H₆ was used as reducing agent in the flow reaction.The denitrification efficiency of the catalyst was experimentally studied in the device,and the catalyst was characterized by XRD,SEM,H2-TPR and other means to further study its reaction mechanism.This research mainly achieved the following research results:1.A series of Co/Fe/Al₂O₃/CM catalysts supported on honeycomb ceramics were prepared by sol-gel method and impregnation method.A series of tests were performed on the catalytic performance of catalysts for selective reduction of NO by C₃H₆.The test results show that the efficiency of NO reduction by propene in the presence of 1.5Co/6.2Fe/Al₂O₃/CM at a reaction temperature of 550? can reach 97%,showing the best denitrification performance over the entire reaction temperature range?200-700??.Its denitrification efficiency is significantly higher than that of Fe/Al₂O₃/CM.The characterization results show that the surface of1.5Co/Fe/Al₂O₃/CM modified by a suitable amount of Co becomes looser,and spherical crystal grains composed of cobalt iron and cobalt aluminum double metal oxides are formed.The introduction of Co can significantly increase the Lewis acid on the surface of the catalyst and produce Br?nsted acid.In addition,Co can increase the specific surface area of the catalyst.2.The performance of anti-H₂O and SO₂ properties of Co/Fe/Al₂O₃/CM catalyst was tested under simulated flue gas conditions.The test results show that the introduction of Co can significantly enhance the ability of Fe/Al₂O₃/CM catalysts to resist SO₂ and H₂O.After the simultaneous introduction of 0.02%SO₂ and 3%H₂O in the simulated flue gas,the de-NO_x performance of 1.5Co/Fe/Al₂O₃/CM is affected little.When the reaction temperature is greater than 500?,1.5Co/Fe/Al₂O₃/CM catalyzes the reduction of C₃H₆.The efficiency of NO can reach more than 90%.In comparison,the performance of Fe/Al₂O₃/CM without CO modification is severely inhibited.In the entire reaction temperature range?200-700??,it catalyzes C₃H₆.The NO reduction efficiency is less than 50%.The abundant acid sites on the surface of Co/Fe/Al₂O₃/CM catalysts and the spherical grains with uniform distribution of cobalt-iron and cobalt-aluminum double-metal oxides may be important reasons for their good resistance to H₂O and SO₂.3.By changing the calcination temperature in the catalyst preparation process,Co/Fe/Al₂O₃/CM-T?T=400,500,600,800?series catalysts were prepared,and the denitrification performance of the catalyst was tested.The test results show that the roasting temperature will affect the catalytic reduction of NO by C₃H₆.Among them,Co/Fe/Al₂O₃/CM-600 samples with a calcination temperature of 500 and 600? exhibited good denitration performance.The characterization results show that the calcining temperature is too low,the surface active material of the chemical agent is not likely to form more granular grain structure,and the catalyst surface is difficult to form a microporous structure.However,when the calcination temperature is too high,the active materials will be a great deal of aggregation together The formation of large irregular bulk crystals can also lead to the collapse of pores,which is not conducive to the full contact of the active material with the reaction gas.4.The Sn/Fe/Al₂O₃/CM?Sn/Fe/Al₂O₃/CM?series catalysts supported on honeycomb ceramics were prepared by sol-gel method and impregnation method.A series of tests were performed on the catalytic performance of catalysts for selective reduction of NO by C₃H₆.The test results show that the introduction of Sn into Fe/Al₂O₃/CM catalyst can significantly improve the denitration performance of the catalyst under oxygen enrichment conditions.The increase in oxygen concentration in the simulated flue gas atmosphere increased the denitrification performance of7.2Sn/Fe/Al₂O₃/CM to some extent.When the oxygen concentration in the simulated flue gas increases to 4.5%,the catalyst can achieve a denitrification efficiency of about 55%at 500?.H2O in the flue gas promotes the catalytic activity of the catalyst,while SO2 slightly inhibits the catalytic activity of the catalyst.The results of catalyst characterization show that the introduction of Sn leads to the formation of nanometer small particles on the surface of the catalyst.The main components of the particulate active material are Sn-Fe and SnO₂.A synergistic effect exists between iron and tin,which effectively promotes the redox performance of the catalyst.