Preparation And Characterization Of Modified Scr Catalyst With High Oxidation Efficiency Of Elemental Mercury

The emission of elemental mercury and its compounds into the air will cause serious environmental pollution,Mercury emission from coal fired flue gas is widely concerned around the world.Mercury in coal fired flue gas has three forms:elemental mercury(Hg0),oxidized mercury(Hg2+)and particulate mercury(Hgp),The Hg0 is difficult to be removed by the existing air pollution control device,which can be directly discharged into the atmosphere through the chimney.The study found that the SCR catalyst used to remove NOx from coal-fired power plants can catalyze the oxidation of Hg0 to a certain extent,and then combined with the desulfurization unit,can be used to remove elemental mercury in flue gas.In order to improve the efficiency of mercury oxidation without affecting the performance of SCR catalyst,the traditional SCR catalyst can be modified.This paper prepared Cu Cl2 modified SCR catalyst by wet mixing,and tested its oxidation efficiency of elemental mercury in simulated flue gas at different temperatures.Based on the results of performance evaluation,XRD,BET,XRF,XPS and other characterization methods,combined with chemical adsorption and temperature programmed reduction technology,we discussed redox ability,acid site,specific surface area and component content of modified SCR catalyst,and analyzed the elemental mercury oxidation mechanism of modified catalyst in order to provide theoretical support of optimizing the modified catalyst performance.The results showed that in simulated flue gas under the condition of fixed ratio,with the increase of temperature,the mercury oxidation efficiency increased and then decreased,and was both highest at 350? for traditional SCR catalyst and modified SCR catalyst.The study found that doping Cu Cl2 could effectively increase the acid sites of catalyst and enhance the redox ability to a certain extent,which was related to its catalytic activity for elemental mercury oxidation.The results of elemental analysis showed that the Cu element in the modified SCR catalyst was mainly in the form of Cu2+,After the performance test,the content of Cu2+ decreased and the corresponding low state of Cu element ratio increased,the lattice oxygen in catalyst was consumed after reaction and the corresponding chemical adsorption oxygen ratio increases,which mean Cu and O were all involved in electron transfer,this might be the main reason to improve the oxidation performance of elemental mercury.According to the research results,this paper inferred that the elemental mercury oxidation mechanism of Cu Cl2 modified SCRcatalyst belongs to Mars-Maessen mechanism.