NOx-storage property of BaFeO3 and BaCeO3 perovskite-type oxides

作者：Chen JF; Meng M; Lin PY^*; Li XA; Fu YL; Yu SM

来源：Chinese Journal of Catalysis, 2003, 24(6): 419-422.

• nitrogen oxide trap
• nitrogen storage
• barium
• iron
• cerium
• perovskite

Under lean conditions, NOx is oxidized into nitrite or nitrate and adsorbed or absorbed on the alkaline components (Ba, Sr, Ca, Li, K and La) of catalysts, and then NOx is reduced to N-2 and released under rich conditions. The key point of this kind of catalysts is to have high efficiency of storage-release nitrogen and resistance to SO2-poison for practical purpose. The BaSnO3 perovskite-type catalyst possesses high NOx-storage capacity (NSC) and resistance to SO2-poison. The Ba-Fe-O (n(Ba)/n(Fe) = 0.5) and Ba-Ce-O (n(Ba)/n(Ce) = 1) perovskite-type oxides were prepared by improved sol-gel method and the Ba-Sn-O (n(Ba)/n(Sn) = 1) oxide as referential sample was prepared according to literature. The NOx-storage property of Ba-Fe-O and Ba-Ce-O oxides was mainly examined by XRD, BET, FT-IR and NSC measurement. The NSC of Ba-Fe-O sample calcined at 750 degreesC is the highest (114.7 mumol/g) at 400 degreesC, the NSC of Ba-Ce-O sample calcined at 900 degreesC comes second (56.8 mumol/g). However, the NSC of BaSnO3 is only 7.31 mumol/g. The NSC of all the samples is higher at 400 degreesC than that at 200 degreesC when the calcination temperature is the same. The main phases of all the three samples are perovskite-type structure. The defect perovskite BaFeO3-delta of Ba-Fe-O sample calcined at 750 degreesC may be the main active phase for NOx storage, however, the active phase of Ba-Ce-O and Ba-Sn-O samples for NOx storage may be the perfect BaCeO3 and BaSnO3 perovskite phase respectively. The specific surface area of all the samples is smaller than 10 m(2)/g except Ba-Sn-O sample. The adsorbed and absorbed NOx species were characterized Both the nitrite and the nitrate appear after NOx is adsorbed and absorbed at 200 degreesC, whereas the nitrite disappears and the nitrate increases at 400 degreesC. The NOx absorption is beneficial to NOx oxidation to form nitrate with alkaline Ba2+ ions at 400 degreesC, while the nitrite is unstable. The relationship of NSC with absorption temperature, absorbed NOx species or oxide structure is also discussed.

• 出版日期2003-6
• 单位中国科学技术大学