| Selective catalytic reduction(SCR)is widely used in the flue gas denitration,and H2-SCR is studied by many researchers due to the advantages of no secondary pollution and environmental friendly.Catalyst is the key of H2-SCR that can influence the efficiency.Due to the good redox properties,thermal stability and structural stability of perovskite,this paper choose perovskite as H2-SCR catalyst.We prepared a series of new type perovskite catalysts with different methods and had a research for the combination of Pd and perovskite in this paper,trying to get higher efficiency at lower temperature.The main way for the combination of Pd and perovskite is doping and loading,meanwhile,we add certain additives to optimize the properties of the catalyst.By testing the activity of catalyst at different temperature,different gas hourly space velocity,different oxygen concentration,different H2/NO ratio and different SO2 concentration,we finally summarizes the optimal combination of Pd and perovskite.At the same time,we combined with a series of physical and chemical characterization to analyze the activity of the catalyst,and explain the reason of good activity essentially.Firstly,due to the easy doping feature of sol-gel method,we doped little Pd in the B-site of perovskite to improve the activity of perovskite catalyst,at the same time,doped little Ce as additive to improve the sulfur resistance of catalyst,prepared a series of new type perovskite catalyst in H2-SCR.For the three different B-site(B = Mn,Co,Fe)new type perovskite,we conclude the active order in denitration test:La0.9Ce0.1Mn0.9Pd0.1O3>La0.9Ce0.1Co0.9Pd0.1O3>La0.9Ce0.1Fe0.9Pd0.1O3,demonstrated that the denitration activity of perovskite is related to B-site ion species.In addition,we have a sulfur resistance test for the three new type perovskite,the results showed that the catalyst only have little influence of SO2,demonstrated that Ce doping can improve the sulfur resistance of catalyst.Due to the good activity of La0.9Ce0.1Mno.9Pd0.1O3 catalyst,we have a further research about its physical and chemical properties and denitration activity.By comparing the physical and chemical characterization results of La0.9Ce0.1Mn0.9Pd0.1O3 and LaMnO3 catalyst,we found the surface morphology,specific surface area and acid sites are obvious change after doping,and these changes are all conducive to the H2-SCR denitration reaction.At the same time,a series of denitration activity experiment of La0.9Ce0.1Mn0.9Pd0.1O3 showed that:under the condition of 2%O2,La0.9Ce0.1Mn0.9Pd0.1O3 always keep the removal efficiency of 90%above;under the condition of 4%02,La0.9Ce0.1Mn0.9Pd0.1O3 can still keep the removal efficiency of 83%;under the condition of 300 ppm SO2,the removal efficiency of La0.9Ce0.1Mn0.9Pd0.1O3 catalyst fall by less than 10%.Those all indicate that the catalyst can keep a good activity and excellent sulfur resistance in relatively poor conditions.In addition,due to the high dispersion feature of hydrothermal method,we select the higher specific surface area of LaCoO3 as the base,and put Pd on the LaCoO3 surface for H2-SCR denitration.We prepare a series of different Pd content x%Pd@LaCoO3(x=0,0.5,1,2,4)catalyst and choose nickel foam as supporter to reduce the dosage of the catalyst.For x%Pd@LaCoO3 catalyst,we do many denitration activity test under different oxygen concentrations,the results showed that under the condition of 4%O2 as O2 promoting effect for the reaction is strong,resulting in catalyst denitration efficiency better than 2%O2 denitration efficiency,which is beneficial to the catalyst used for the flue gas denitration in the factory.In addition,we also study the denitration activity under other conditions,the results prove the catalyst has good denitration activity under different conditions and keep good performance under low SO2 concentration.In general,the combination of Pd and perovskite can affect H2-SCR denitration reaction,at the same time,change B-site,Pd content,adding additives and reaction conditions can also have an effect on the denitration efficiency of catalyst.For the two different Pd combining ways of perovskite catalyst,we need to consider both their optimal reaction conditions and their actual situations to achieve an ideal removal effect. |
