| Mercury(Hg)has been highly concerned as a major pollutant in power plants.Mercury in coal-fired flue gas is easily released into the atmosphere due to its susceptibility to oxidation and non-reactive chemistry.The total amount of mercury emitted from power plants accounts for half of all mercury emissions.In this paper,metal-supported catalysts are used to remove mercury,and further studies on the effects of other pollutants in flue gas on mercury removal of catalysts.Two methods were used to prepare the catalyst.A series of different cerium doping Mn-Ce/SAPO-34 catalysts were prepared by impregnation method and Cu/ZSM-5 catalysts were prepared by ion exchange method.BET,XRD,SEM,XPS,TGA,H2-TPR,Hg-TPD and in-situ DRIFT were used to determine the physical and chemical properties of the studied catalysts.And the mechanism is revealed.(1)In this paper,Mn-Ce/SAPO-34 catalysts with different levels of cerium doping were prepared to study the catalytic oxidisation of elemental mercury(Hg0).Sulphur tolerance and SO3 formation over the catalyst were studied further.Mn could incorporate into the cerium oxide lattice to form capping oxygen and well-dispersed high valance manganese ions after the addition of Ce,which was conducive to NO removal and Hg0 oxidisation at low temperatures.The sulphur resistance of the Mn-based catalyst was significantly improved after the addition of cerium due to the high affinity of Ce for SO2,and the relative content of HgSO4 was more than 72%on the 9Mn-9Ce catalyst in the presence of SO2;SO3 formation over the 9Mn-9Ce catalyst decreased by 17%compared with the 9Mn catalyst.H2O not only reduced the available active site,but also decreased the oxidation rate of SO2.The active sites were preferentially occupied by NH3 rather than Hg0 and SO2,generated NH4+occupied cation vacancies.Therefore,both H2O and NH3 have inhibitory effects on Hg0 conversion and SO3 formation.(2)Secondly,the Cu/ZSM-5 catalyst prepared by ion exchange method was used to study the effects of SO3 on mercury removal.The results indicated that SO2 addition decreased Hg0 conversion efficiency,but that increased from 82%to 95%with SO3 at 200℃.The inhibition effect of SO2 was weakened,and the promotion of SO3 was significantly enhanced at 400℃.HgSO4 was the main mercury compounds in the presence of SO3.The in-situ DRIFT results shown that a large number of S-related peaks generated on the surface of the catalyst with SOx(SO2 and SO3),the peak of SO2 weakened compared with only SO2,representing the SO3 inhibited the adsorption of SO2.Moreover,the peak of adsorbed SO3 was the most obvious,and then gradually consumed after the introduction of Hg0,meanwhile,the peak of sulfate appeared on the surface of catalyst,indicating that SO3 firstly adsorbed on the surface of the catalyst to provide a new active site for Hg0 conversion.Compared with 200℃,The adsorption process of SO3 was promoted,which directly contribute to the enhancement of Hg0 conversion at 400℃... |
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