Synthesis Of Manganese Based Catalyst For Desulfurization And Denitrification From Low-temperature Flue Gas

In this paper,the industrial low-temperature MnOx granular catalyst(?5×30mm)with high activity is successfully prepared with manganese sulfate as precursor by serial operations of precipitation,washing,extrusion and calcination.Its low-temperature denitration application is explored in two different typical flue gas conditions,with high H2O vapor content but little sulfur or a few sulfur but no H2O vapor included.The produced industrial catalyst is firstly applied in the denitration purification of flue gas from Cold,hot&electric triple supply(CCHP)system on the conditions of 850-1000 mg/m3 inlet NOx and 145-175?.The NO conversion can achieve to 87.88-97.47%under the GHSV of 4405 h-1 and 3%decline of denitration efficiency is observed after use for 1080 hours.The laboratory test also confirm the reduced activity for the used sample.Moreover,XRD,BET,SEM and XPS results show the crystal transition,sintered particle,gincreased particle size,decreased surface area and reduced chemisorption oxygen for the used MnOx sample,which account for the observed decline of denitration efficiency after long term use on the industrial conditionsTo deal with the decline of denitration efficiency from the structural degradation,the CeaMnbOx catalyst and samples seperately treated by hydrothermal degradation or high temperature calcination are prepared.And then the characterizations and SCR activities for both the fresh and degradatd catalysts are evaluated.These results indicate that CeO2 doping can to some extent reduce the activity decline for degraded samples,prevent structural degradations,i.e.crystal transformation,decreased specific surface area and reduced chemisorption oxygen,and improve the structural thermal and hydrothermal stability.Therefore,the Mn-based catalyst still has a good prospect in 130-200? low-sulfur flue gas denitration application.Regarding the deactivation of MnOx particles in sulfur-containing flue gas in fixed bed process,although it can be prolonged by lowering space velocity or SO2 concentration of flue gas.Based on the simulated fluidized bed and multi-layer bed,the simultaneous removal of NO and SO2 by MnOx particles is operated in 500 ppm SO2 included flue gas at a four-layer MSFB reactor with a feed of 5g/min,2125 h-1 and 160?.It shows that the NO conversion and SO2 removal of the top layer maintain above 95%within 24 hours after operation to stability,while the NO conversion and SO2 removal both decrease layer by layer as MnOx particles go through the reator from top to bottom.Further,charactions for samples in different layers demonstrate that the active Mn species consumed from top to bottom,meanwhile the toxic sulfur species-MnSO4 increase,the specific surface area and the oxidizability reduce for layers until the catalyst get to the bottom and completely become deactivated.As for the regenaration of deactivated MnOx,the sulfates on surface disappeare and the oxidation ability,valence and NO activity of the newly exposed MnOx recover to the same as fresh catalyst after ammonia washing.We can deduce that the recycling of MnOx catalyst could be realized in a circle of continuous denitrification with desulfurization and ammonia-washing regeneration.