Yuunosuke Nakahara

Synthesis and crystal structure of (Sr1-xCax)2FeMnOy (x=0-1.0)

Abstract (Sr 1− x Ca x ) 2 FeMnO y ( x = 0–1.0) were synthesized in air at 1150–1200 °C and their crystal structures and electric properties investigated. The perovskite-type and the brownmillerite-type compounds were formed in the compositional range x = 0–0.7 and x = 0.8–1.0, respectively. Ca 2 FeMnO y ( x = 1.0) was the brownmillerite-type compound with lattice parameters a = 0.5338 nm, b = 1.4834 nm and c = −0.5515 nm. The angle of Fe-O-Mn was 151 ° calculated from the refined structure data of Ca 2 FeMnO y . It is indicated that the FeO 4 tetrahedra and the MnO 6 octahedra are alternately arranged zigzag along the b -axis. All samples exhibited p-type semiconducting behavior.

Preparation of apatite-type-silicate-supported precious metal catalysts for selective catalytic reduction of NOx

Apatite-type silicate supported precious metal catalysts were prepared and investigated for their catalytic activity in selective catalytic NO reduction. Single-phase La9.33Si6O26 and La8.33ASi6O25.5 (A=Ca, Sr, Ba) were obtained by a sol-gel method. Pd/La9.33Si6O26 catalyst exhibited high activity for oxidation of C3H6, comparable to Pd/Al2O3 catalyst, although the specific surface area of La9.33Si6O26 was lower than that of Al2O3. In addition, Pt/La9.33Si6O26 catalyst exhibited higher activity for selective catalytic reduction of NO than Pt/Al2O3 catalyst. Substitution of Ba2+ for La3+ of La9.33Si6O26 led to increased catalytic activity at low temperature.

Effect of Aging Atmosphere on Catalytic Activity for NO–CO–C3H6–O2 Reaction of CeO2-Containing Oxide Supported Pd Catalysts

The catalytic activity for CO, hydrocarbon and NO removal on Al2O3 and CeO2 based oxides supported Pd catalysts were studied under switching of aging condition between air and N2 atmosphere. For CeO2-containing Pd catalysts, the deterioration of catalytic activities by aging in N2 was improved by oxidative treatment. Based on results of XPS and FT-IR measurements, it was presumed that the catalytic activity of Pd catalysts was strongly affected by the adsorbed form of CO on Pd, which occurs owing to a change of the chemical state of Pd.Graphical Abstract