Preparation Of Halloysite-based Nano Desulfurizer And Its Performance In Dry Desulfurization Process

The production characteristics of the coking industry determine that the quenching process has many types of pollutants,difficult treatment,and high environmental hazards.In order to meet the national emission standards,coke quenching tail gas containing SO₂ must be desulfur-ized before it can be discharged.However,different from the sulfur-containing flue gas of coal chemical enterprises,the temperature of the coke quenching flue gas is only 160-200℃ after countercurrent heat exchange between the inert gas and the hot red coke,while the reaction temperature of the conventional semi-dry desulfurization catalyst is mostly At 200-280℃.Therefore,it is of great significance to develop a low-temperature desulfurization catalyst suitable for coke quenching flue gas.In this paper,halloysite with natural nanotube structure is selected as the catalyst carrier,and halloysite is modified by low-temperature molten salt etching,and the transition metal manganese oxide is supported by hydrothermal method.Stone molding,carried out experimental research on the treatment of sulfur dioxide with a modified combined supported catalyst.Analyzed the generation of inert gas coke quenching pollutants,chitosan microsphere molding ratio,molten salt modification time,molten salt modification ratio,molten salt modification temperature,hydrothermal metal loading temperature,hydrothermal reaction metal loading The influence of factors such as amount,hydrothermal reaction time,molten salt modification and hydrothermal metal loading on the degradation effect of sulfur dioxide,and the mechanism is explained.（1）When the laboratory simulates coke quenching with inert gas nitrogen and argon,the concentration of SO₂ produced by nitrogen quenching is between 200-450ppm,and the concentration of SO₂ produced by argon quenching is 200-450ppm SO₂ and 100-300ppm NO pollutants.Under the guidance of laboratory simulation of coke quenching,430ppm SO₂ was configured as the polluting gas for subsequent catalyst activity evaluation,and a desulfurization catalyst suitable for the actual flue gas conditions of coke quenching was developed.（2）Analyze the influence of chitosan microsphere shaping ratio（chitosan dosage,acetic acid concentration,solid-liquid ratio and NaOH concentration）on the desulfurization effect of the catalyst by orthogonal experiment.The best modification condition is:chitosan Using 1.8g,the solid-to-liquid ratio is 0.03 g/mL,acetic acid 0.175 mol/L and 2 mol/L NaOH solution are jointly prepared.（3）Explore the influence of molten salt etching modification conditions on the catalyst’s low-temperature flue gas desulfurization performance.Choose 350℃,reaction time 2 hours,and molten salt ratio of 10:10 as the best molten salt etching halloysite-based catalyst Under reaction conditions,the cumulative desulfurization amount can reach 65.01 mg,the desulfurization rate remains above 80% for 9.5 minutes,and the average desulfurization rate reaches 70.55%.（4）The catalyst is supported by hydrothermal metal.In the molten salt etching modification,anhydrous sodium carbonate and sodium nitrate form fine droplets to etch the halloysite outer surface and the siloxane at the end of the tube first with the fully ionized molten salt to make the halloysite nanotube surface Roughness and porosity increase.Sodium nitrate has a low melting point in this melting system.As a melting medium,it is closely related to the surface etching effect.Sodium nitrate acts as a flux to make a certain amount of sodium carbonate uniformly collide with halloysite nanotubes in the melting system.The metal manganese oxides are mainly MnO₂,Mn₂O₃,MnO.The optimal preparation conditions for the catalyst are the hydrothermal temperature of 180℃ and the metal loading ratio of 7%.The desulfurization rate of the hydrothermal reaction is 18 hours.The penetration time above 80%is 15.7 minutes,which is 51.20%higher than the average desulfurization rate of untreated halloysite nanotubes.From the perspective of desulfurization effect and economic development,the optimal hydrothermal time of metal-supported halloysite reaction is 18 hours.（5）The halloysite modified by molten salt etching is subjected to hydrothermal metal loading,and the desulfurization rate is always maintained above 80%within 20 minutes of the desulfurization experiment,and the subsequent desulfurization rate decline rate is also very slow,showing excellent performance The ability to oxidize sulfur dioxide gas,the cumulative sulfur dioxide removal rate during the test period was 1.71 times that of the blank catalyst,and the average removal rate was as high as 92.2%.（6）When the Mn loading is 5%,the relative concentration of lattice oxygen（Oβ）on the surface of the catalyst is the highest.An appropriate amount of Mn is helpful to the formation of the desulfurizer Oβ,thereby providing the desulfurizer with more oxygen holes and surface hydroxyl groups.,The metal cations that promote the unsaturated coordination on the surface of the desulfurizer can combine with the oxygen in the background gas to form O2^2-and O^-in the chemisorption state,and promote the progress of the desulfurization reaction.With the increase of metal content,the content of Mn²⁺increases by 1.13 times.Due to the higher oxidation potential of Mn²⁺,it helps the reaction to 2Mn²⁺+SO₂*→Mn₂SO3³⁺+SO₃*.After molten salt etched halloysite-based desulfurizer and then coordinated with hydrothermal metal loading,the O^2- content in manganese oxide increases,and the chemical adsorbed oxygen（O_α）content increases by 47.4%,which can increase the number of oxygen vacancies in the desulfurizer.Reduce the reaction energy in the chemical process,thereby promoting the desulfurization activity,and at the same time promoting the reaction to SO₂*+O*→SO₃*;co-processing the desulfurizer,the Mn²⁺content is significantly increased by 3.69 times,which helps the reaction to Mn²⁺+SO₂*→Mn₂SO₃³⁺+SO₃*is going forward to achieve higher desulfurization efficiency.