ABSORPTION BEHAVIOR OF NO WITH Y-SR-CO-O TYPE COMPOUNDS

Absorption of nitrogen oxides (NO(x)) is one of the NO(x) removing processes. The absorption behavior of nitrogen monoxide (NO) with some oxide compounds was studied. NO(x) removal of employed four samples which were Y-Sr-Co-O, Y-Sr-Mn-O, Y-Sr-V-O, Y-Ba-Co-O compounds, were investigated. The NO(x) removal meant (a reduced values of NO(x) after reaction/a reactant NO(x) values) x 100 at the point after 30 min reaction, when the N2 gas including NO 300 ppm, O2 3% pass thorugh 3 cm3 sample oxides at flow rate 1000 ml/min. Then Y-Sr-Co-O oxide compounds indicated highest activity, ca, 100% for NO removal at 300-degrees-C among the employed samples shown in Fig. 1. When Y-Sr-Co-O was saturated by NO at 300-degrees-C reaction, the amount of NO absorbed was 1.55 mol per 1 mol sample, and it clearly absorbed in the bulk. The absorption of NO by Y-Sr-Co-O occurred only in oxidizing atmosphere, and it was found that NO was oxidized to NO3- and absorbed by the oxide compounds because NO3- signals could be seen in FT-IR spectra (Fig. 6). Y-Sr-Co-O included Co3O4 and Y2O3 crystals and ABO, type perovskite consisting of Y, Sr, Co and O. Since Co3O4 and Y2O3 crystals didn't absorb NO and the ABO3 type perovskite disappeared after NO absorption, the ABO3 type perovskite in Y-Sr-Co-O might be absorbing NO. It was found that Y-Sr-Co-O had active oxygen in compounds which was desorbed from sample at about 500-degrees-C in TPD spectra. It implied that these active oxygen help NO oxidation and absorption. We suggested the schematic diagrams in Fig. 8 for NO absorption of Y-Sr-Co-O.