Preparation Of Mn-Based Catalyst And Its Application In Low Temperature Denitration

Nitrogen oxides?NO,NO₂ and N₂O?have been the main pollutants in the atmosphere,which harm the health of organisms and destroy the ecological environment system.In order to effectively eliminate NO_x,researchers have conducted a systematic study on NO_x elimination technology,and NH₃ selective catalytic reduction?NH₃-SCR?is considered to be the most practical method.Currently,the NH₃-SCR catalysts widely used in industry are mainly V₂O₅-WO₃/TiO₂ based catalysts and Mn based catalysts.V₂O₅-WO₃/TiO₂ based catalyst temperature window is relatively narrow?300-400^oC?,and vanadium toxic easy to cause re-pollution.However,as a low temperature SCR catalyst,there are still shortcomings such as narrow operating temperature window,high cost,and easy to produce hazardous waste.Mn-based low temperature NH₃-SCR catalyst is the focus of current research.Compared with other metal elements,the d orbital electrons of Mn?3d54s2?are in a semi-filled state,and the easy electron migration enables Mn to have a variety of valence states.The mutual transformation of Mn with different valence states enables it to have oxidation reducibility,which can promote the NH₃-SCR reaction.However,it still faces such problems as poor low temperature activity and serious ammonia zero escape.In this paper,different mn-based catalysts were prepared by the regulation of molecular structure,and the low temperature activity,zero escape of ammonia and catalyst molding of Mn based catalysts were studied.The details are as follows:?1?Study on preparation of mn-ce-fe-al catalyst and its denitration by high shear assisted coprecipitation?HSM-CP?.Mn-Ce-Fe-Al composite metal oxides were prepared by coprecipitation?CP?and HSM-CP.Compared with Mn-Ce-Fe-Al?CP?prepared by traditional precipitation method,Mn-Ce-Fe-Al?HSM-CP?catalyst has good physical structure,BET surface area can reach 224.3 m²/g,pore volume is 0.49 cm³/g on average,and the average pore diameter is 8.89 nm.Mn-Ce-Fe-Al?HSM-CP?has more oxygen vacancy and surface acid sites,and shows excellent catalytic activity at low temperature and"zero escape"performance of ammonia gas.At 150°C and 15300 h^-1 airspeed,the conversion rate of NO was up to 100%and the selectivity of N₂ was 96.5%.Even at room temperature,the catalyst still has a 50%NO conversion rate.At the whole reaction temperature,the utilization rate of ammonia gas reached more than 90%,and even at room temperature,the conversion rate of NO was still 50%.At the same time,the catalyst also showed excellent resistance to water and sulfur.At 200?,when 5%H₂O was introduced into the catalytic reaction system,it decreased slightly from 99.8%to about 94.3%,and returned to the initial value after water supply was stopped.When 100 ppm SO₂+5%H₂O was added,the conversion rate of NO decreased slightly from 98.3%to 83.2%.Study on supported two-dimensional layered Mn/MgAl-LDO catalyst and its denitration performance assisted by rapid casting coprecipitation?FP-CP?.The 2D lamellar MgAl-LDO hydrotalcite derivatives were prepared by slow drop assisted coprecipitates?SD-CP?and?FP-CP?,respectively,and the Mn/MgAl-LDO catalyst was obtained by equivolumetric impregnation.Compared with Mn/MgAl-LDO?CP?,Mn/MgAl-LDO?FP-CP?has excellent specific surface area and acid active site,showing excellent low temperature activity and zero ammonia escape performance.Under the conditions of 150?and 60000 h^-1 airspeed,the conversion rate of NO was up to 100%and the selectivity of N₂ was 90%.At 100?,the catalyst still has 97%NO conversion and 97.3%N₂ selectivity.At the temperature of the whole working condition,the outlet concentration of NH₃ after the reaction was lower than 100 ppm,indicating that the catalyst had an excellent ammonia escape rate.?3?3D printing Mn-Ce-Fe/Attapulgite molding catalyst and its denitrification performance.Using Mn-Ce-Fe/Attapulgite?ATP?as the precursor and using 3D printing technology,the monolithic catalyst was successfully prepared.Through the investigation of different catalyst components and printing conditions,it was found that the molding catalyst Mn-Ce-Fe/Attapulgite with a diameter of 3.3 mm×3.3 mm,a wall thickness of 2 mm and an aperture of 1mm had excellent catalytic activity.At 100?and 2000 h^-1 airspeed,the removal rate of NO reached more than 50%and reached 70%at 400?.The results of this study provide a new method for the synthesis of NH₃-SCR catalyst based on active metal.