Study On Preparation And Low Temperature Denitration Mechanism Of MnO_x-CeO₂/low Titanium Blast Furnace Slag Catalyst

With the rapid development of our country's economy,the utilization of solid waste resources and the treatment of environmental pollution have received more and more attention.The standards for the treatment of solid waste slag and the emission of air pollutants from the metallurgical industry are becoming more and more stringent.Titanium-containing blast furnace slag,as a by-product of blast furnace smelting vanadium-titanium magnetite,is a hard-to-use resource;the metallurgical sintering process is the main emission source of nitrogen oxides in iron and steel enterprises,and is also the top priority of environmental governance in metallurgical enterprises.This paper aims at the comprehensive utilization of titanium-containing blast furnace slag and the removal of nitrogen oxides from metallurgical sintering flue gas.The titanium-containing blast furnace slag(low-titanium slag)is used as the carrier,and Mn O_x-Ce O₂ composite oxide is used as the active component to prepare low-temperature denitration catalyst,investigate its effect on low-temperature denitration of sintering flue gas and its anti-sulfur and water resistance,aiming to develop a low-temperature denitration catalyst of titanium-containing blast furnace slag suitable for metallurgical sintering flue gas.First,by acid-treating low-titanium blast furnace slag to optimize its performance as a catalyst carrier,the best process conditions for modified low-titanium blast furnace slag are obtained:the concentration of dilute hydrochloric acid solution is 2 mol/L,the treatment temperature was set at 30 ^oC,the solid-liquid ratio is 1:10.This process can obtain acid-modified slag carriers with a calcium removal rate of over 95%,and a silicon and titanium enrichment rate of 72.66%and 16.78%,respectively.After the treatment,the specific surface area of the slag increased from 2.24 m²/g to 360 m²/g,and the pore size distribution was uniform,which provided a good foundation as a catalyst carrier.Secondly,using the modified slag as the carrier,the effect of different preparation methods and conditions on the low-temperature denitration performance of the catalyst was studied.The results show that the best preparation method of the catalyst is the impregnation method,and the corresponding best process conditions are:Mn/Ce molar ratio is 4:1 and calcination temperature at 400?.The catalyst prepared under this condition has excellent low-temperature denitration activity,the denitration rate at 200?can reach 90%.Mn⁴⁺plays a leading role in the catalytic reaction activity.The higher the Mn⁴⁺,the higher the denitration activity;the addition of Ce can form a solid solution with Mn and promote the oxidation of Mn O_x.The acid sites on the surface of the catalyst play an important role in the denitration activity.The more weak acid sites on the surface,the more favorable for the denitration reaction.The catalyst denitration process is mainly the reaction of adsorbed NH₃ with gas phase NO or weakly adsorbed NO,and the reaction process follows the E-R reaction mechanism.The catalyst prepared by this method exhibits excellent water resistance,the denitrification activity of the catalyst is basically not affected after the steam treatment for 3 hours.However,the presence of water vapor will aggravate the sulfur poisoning of the catalyst,and the sulfur resistance of the catalyst still needs to be improved.The sulfation of the catalyst surface and the decrease of Mn⁴⁺content are the main causes of sulfur poisoning.