Catalytic Performance Of Co-based Perovskite And Fe/Zeolites Catalysts For NO Reduction By CO

As one of the main pollutants in the atmosphere,the excessive emission of nitrogen oxides will seriously endanger human health and ecological environment.In this research,from the point of view of“treatment of wastes with another wastes”,according to the characteristics of regenerated flue gas of FCC,NO and CO are used as oxidant and reductant,respectively,and are converted into CO₂ and N₂for reducing NO emissions under catalysts.The Co-based perovskite-type complex oxide catalysts and the Fe/zeolites catalysts were prepared by citric acid-ligated combustion method and impregnation method,respectively.The physicochemical properties were characterized by XRD,FT-IR,BET,SEM,H₂-TPR,NO-TPD,NH₃-TPD and Pyridine-IR.The catalytic performance of NO reduction by CO was evaluated in a fixed-bed micro-reactor.The main conclusions are summarized as followings:1.The LaBO₃ catalysts（B=Cr,Mn,Fe,Co）which were prepared under experimental conditions had single perovskite structure.Among which,the LaCoO₃ catalyst had good particle dispersibility,smaller particle size,better redox properties and better catalytic activity.When the NO conversion reached to the maximum,the corresponding reaction temperature(T_NO^max)was 560°C,and the maximum conversion of NO(X_NO ^max)is 74.1%.When the CO conversion reached to 95%,the corresponding reaction temperature(T_CO⁹⁵)was 351°C.2.The La³⁺（A site）of LaCoO₃ catalysts were partially substituted by different alkaline earth metals（Mg,Ca,Sr,Ba）.Both of the alkaline earth metals and the substitution amount affected the catalytic performance of the perovskite composite oxide catalysts.Compared with LaCoO₃catalyst,when La³⁺was partially substituted by Sr²⁺with the substitution amount of 0.15,the La_0.85Sr_0.15CoO₃ catalyst had good redox properties and NO adsorption and desorption ability,thus improved the catalytic activity.Although the NO conversion over La_0.85Sr_0.15CoO₃ catalyst did not significantly improve,T_CO⁹⁵ was 330°C,which decreased 21°C.3.The Co³⁺（B site）of LaCoO₃ catalysts were partially substituted by different transition metals（V,Cr,Mn,Fe,Ni,Cu）.Both of the transition metals and substitution amount affected the catalytic performance of the perovskite composite oxide catalysts.When Co³⁺was partially substituted by Mn with the substitution amount of 0.30,the La Co_0.70Mn_0.30O₃ catalyst had good particle dispersibility,good redox properties,improved NO adsorption and desorption ability and thus better catalytic activity.T_NO^max,X_NO^max and T_CO⁹⁵ of the La Co_0.70Mn_0.30O₃ catalyst were 430°C,82.0%and 353°C,respectively.Compared to LaCoO₃catalyst,T_NO^max decreased 130°C,X_NO^max increased 7.9%,andT_CO⁹⁵basically remains unchanged.4.The zeolite carrier types,silicon-aluminum ratio and the Fe loading amount affected the catalytic performance of Fe/zeolites catalysts.The results showed that the Fe（9）/ZSM-5（70）catalyst,which the zeolite carrier was ZSM-5,the ratio of silicon to aluminum was 70 and the Fe loading was 9 wt%,had better catalytic activity.The Fe species existed in the form ofα-Fe₂O₃ crystal phase with much Fe³⁺species,The redox property of the catalysts was good and the amount of acid was moderate,thus the catalytic activity was better.T_NO^max,X_NO^max and T_CO⁹⁵ of the Fe（9）/ZSM-5（70）catalyst was 510°C,82.3%and 436°C,respectively..5.Both of the metal additives types and the additive amount affected the catalytic performance of Fe/zeolites catalysts.When the additive metal was Cu,different reducing species were formed on the catalysts with hydrogen consumption increased and thus the redox property was improved.When the addition amount of Cu was 2.5 wt%,the catalytic activity of the Cu（2.5）Fe（9）/ZSM-5（70）catalyst was better.T_NO^max,X_NO^maxand T_CO⁹⁵ was 460°C,84.2%and 410°C,respectively.Compared with the Fe（9）/ZSM-5（70）catalyst,T_NO^maxandT_CO ⁹⁵ decreased 50°C and 26°C,respectively,X_NO^max increased 1.9%.