Study On The Monolithic Shape And Denitration Performance Of NH₃-SCR With Rare Earth Tailings Catalyst Activated By Sulfuric Acid

In January 2022,the State Council issued the"14th Five-Year Plan"Comprehensive Work Plan for Energy Conservation and Emission Reduction.Since the large amount of pollutant emissions in our country is still the root cause of various environmental problems,the plan proposes specific requirements for substantial emission reduction of pollutants.It mainly includes the control problems of nitrogen oxides and sulfur oxides.At present,the more mature and widely used denitration technology is NH₃-SCR technology.The core of this technology lies in the catalyst,but the widely used V₂O₅-WO₃/Ti O₂catalyst has the disadvantages of high cost and high toxicity,the development of low-cost,high-performance,and environmentally friendly SCR catalysts is increasingly required.Bayan Obo tailings have attracted much attention in recent years because they are rich in active components required for denitration catalysts such as iron and cerium.The catalyst powder needs to be prepared and shaped before it can be used in selective catalytic reduction and denitration.In this thesis,based on the rare earth tailings catalyst powder activated by sulfuric acid in the early stage of the research group,the effects of the types of additives（pore formers,binders,lubricants,strength agents）and calcination temperature on the forming and denitration performance of the catalysts were studied.The rod-shaped catalyst is prepared by the method of integral extrusion.After determining the type and amount of the optimal additives,the catalyst is integrally formed into a honeycomb catalyst under the optimal conditions.Characterization analysis,the experimental results are as follows:The extrusion molding process of catalyst powder will destroy its original macroscopic and microscopic morphology,resulting in a decrease in specific surface area,collapse of micropores,and a decrease in porosity.The performance of the catalyst prepared by molding is inferior to that of powder catalyst.After adding different types and contents of pore-forming agents,polyethylene glycol is preferred as the pore-forming agent,because polyethylene glycol is more conducive to the composition dispersion of the catalyst,and the pore-forming effect is good.When the addition amount is 5%,the specific surface area of the catalyst increases to 3.7m²/g,and the denitration efficiency is still high in the temperature range of 300-450℃,with a wide temperature window,and the denitration efficiency can reach 74%at 350℃.However,the addition of pore-forming agent will cause problems such as difficulty in extrusion,difficulty in bonding powder,and decrease in mechanical strength.Among the binders added,sapura powder has the best binding effect,followed by guar gum,but sapura powder is easy to cover the surface of the catalyst and cover the active components of the catalyst surface.Adding 2.5%guar gum as a binder,the prepared catalyst has a denitration efficiency of over 80%at 300-450℃,and the highest can reach92%.It has a certain viscosity,is easy to form,and can be well maintained.The redox capacity of the catalyst.Adding 10%glycerol as a lubricant improves the fluidity of the catalyst powder,reduces the difficulty of extruding the catalyst,and the extruded catalyst has a smooth surface and less cracks.After adding the binder,pore-forming agent and lubricant,the mechanical strength of the catalyst decreases.Continue to add glass fiber as a strength agent.When the addition amount is 2.5%,the mechanical strength is significantly improved,from the original 0.61MPa to 2.36MPa,the specific surface area and redox capacity are less lower than other additions.In order to facilitate mixing and improve the smoothness of the catalyst surface,an appropriate amount of water is added,and the optimum ratio of mineral water is 4:1,at which time the catalyst still maintains a high mechanical strength.The catalyst calcined at 350℃showed the best denitration efficiency and the largest specific surface area,and the iron ions shifted to the direction of high binding energy.The denitration efficiency of the catalyst remained above 90%at 350-450℃,and the N₂selectivity was 80%.above.The formula for preparing the overall molding of sulfuric acid-activated rare earth tailings catalyst was determined as follows:polyethylene glycol as pore-forming agent,guar gum as binder as lubricant,glycerin as strength agent,glass fiber as strength agent,and the addition amounts were 5%,5%and 5%respectively.2.5%,10%,2.5%,and the ratio of mineral water is 4:1.After fully mixing,the catalyst embryo body is extruded,and after natural air drying and oven drying,it is calcined at 350℃for2h.