| NOx is a major air pollutant,which can destroy the ozone layer,create acid rain and chemical smog.Among them,N2O becomes the third stronger greenhouse gas after CO2 and CH4 in the atmosphere whose greenhouse potential is 310 times higher than that of CO2 and the lifetime is 120 years.Thus,it has realistic significant to control N2O emission effectively.The catalytic decomposition of N2O into N2 and O2 is considered as a major method.A series of Ru-base catalysts whose supports are Al2O3,Co3O4 and La1.6Sr?Ba?0.4NiO4 were prepared to investigate the model reaction of N2O decomposition and NO+CO.The catalysts were characterized by XRD?TEM?XPS?H2-TPR?O2-TPD and in situ DRIFTS to study the structure,reduction ability,oxygen desorption capacity,surface Ru active species and oxygen vacancy.And it was also investigated that the influence of interaction between Ru and support for the Ru particle size,dispersity,valence state;the change of catalyst surface property and the influence factor of catalyst activity,stability and the resistance of H2O and O2.The main research contents are as following:?1?Ru/Al2O3?Ru/Al2O3-H2,Ru/Al2O3-NaBH4,Ru/Al2O3-air?catalysts with different ratios of metallic Ru on the surface were prepared.The order of N2O decomposition activities of fresh catalyst was followed as:Ru/Al2O3-H2>Ru/Al2O3-NaBH4>Ru/Al2O3-air.However,the deactivation of catalyst was found obviously after using,which are due to the agglomeration of Ru particles.In the decomposition of N2O,the oxygen species can not desorb from metallic Ru,leading to the formation of high valence state of Ru species(Ru4+).The metallic Ru is the active site in N2O decomposition.A weak interaction between Ru and Al2O3 was found which can't stabilize the Ru species on the surface of catalyst.?2?A serial of Rux-Co3O4?x=0.1-0.3?catalysts were prepared by the coprecipitation method and applied to the decomposition of N2O.Compared with Co3O4catalyst,the Rux-Co3O4 catalyst exhibited much higher activity.Ru0.2-Co3O4 showed much highest activity and the N2O conversion maintained unchanged for 30h.The Ru0.2-Co3O4 catalyst also displayed excellent activity and stability in the presence of1.5%O2 and 2.1%H2O.Compare with Co3O4 catalyst,Rux-Co3O4 shows better structural stability,desorption of oxygen and more surface Co2+and oxygen vacancy,resulting from the strong interaction between Ru and Co3O4.The interaction can control the agglomeration,dispersion and valence state of Ru particles.?3?Ru supported on La1.6Sr0.4NiO4?LSN?perovskite-like catalysts were prepared by different methods,incipient wetness procedures with the addition of ethylene glycol?Ru/LSN-EG?and without ethylene glycol?Ru/LSN?,and investigated for the decomposition N2O.The Ru/LSN catalyst presented deactivation with reaction time,which is due to the O species derived from the decomposition of N2O absorbs on the active sites,and it is difficult to desorb.Thus,the regeneration of the active sites is difficult.All metallic Ru and Ru3+species are oxidized to high oxidation state Ru species(Ru4+).Ru/LSN-EG showed the excellent catalytic activity and stability for N2O decomposition in the presence of 3%O2 and 4.2%H2O.The interaction between Ru and LSN can strongly improve the dispersion and valence state of Ru3+particles.?4?Ru/La1.6Ba0.4NiO4?Ru/LBN?perovskite-like catalyst was prepared by EG method and investigated for NO+CO reaction.Ru/LBN exhibits much higher activity and stability than LBN.The interaction between Ru and LBN can led to the reconstruction and enhanced the reducibility,mobility of oxygen species,the amount of oxygen vacancy,CO adsorption,NO adsorption and Ru3+species. |
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