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論文

Spontaneous activation behavior of Ni$$_{3}$$Sn, an intermetallic catalyst, for hydrogen production via methanol decomposition

Fan, M.*; Xu, Y.*; 櫻井 惇也*; 出村 雅彦*; 平野 敏幸*; 寺岡 有殿; 吉越 章隆

International Journal of Hydrogen Energy, 40(37), p.12663 - 12673, 2015/10

 被引用回数:8 パーセンタイル:25.28(Chemistry, Physical)

Ni$$_{3}$$Sn単相粉末試料のメタノール分解反応に対する触媒特性を調べた。触媒反応は713K, 793K, 873Kの各温度で等温実験であった。793K以上の温度では触媒活性は時間の増加に伴い高くなることを見出した。また、Ni$$_{3}$$SnはH$$_{2}$$とCOに高い選択性を示すことが分かった。表面キャラクタリゼーションの結果、触媒反応中触媒表面にNi$$_{3}$$Sn微粒子が生成されることが分かった。これらの微粒子は自発活性化の原因と考えられる。

論文

Effect of water vapor and hydrogen treatments on the surface structure of Ni$$_{3}$$Al foil

Xu, Y.*; Ma, Y.*; 櫻井 惇也*; 寺岡 有殿; 吉越 章隆; 出村 雅彦*; 平野 敏幸*

Applied Surface Science, 315, p.475 - 480, 2014/10

 被引用回数:7 パーセンタイル:36.72(Chemistry, Physical)

The Ni$$_{3}$$Al foils were heat treated in water vapor at 873 K for 1 h followed by H$$_{2}$$ reduction at 873 K for 1 h. The effects of the water vapor treatment and the H$$_{2}$$ reduction on the surface structure of the Ni$$_{3}$$Al foils were investigated by means of scanning electron microscopy and synchrotron radiation X-ray photoemission spectroscopy. Both Ni and Al were oxidized during the water vapor treatment; fine NiO particles were formed on the surface, accompanied by the formation of Al(OH)$$_{3}$$ and NiAl$$_{2}$$O$$_{4}$$/Al$$_{2}$$O$$_{3}$$. The NiO particles were reduced to metallic Ni and the Al(OH)$$_{3}$$ was decomposed to Al$$_{2}$$O$$_{3}$$, whereas the NiAl$$_{2}$$O$$_{4}$$ and Al$$_{2}$$O$$_{3}$$ remained unchanged during the H$$_{2}$$ reduction, forming a Ni-enriched porous structure on the surface layer of NiAl$$_{2}$$O$$_{4}$$/ Al$$_{2}$$O$$_{3}$$.

論文

Catalytic performance of Ni$$_{3}$$Sn and Ni$$_{3}$$Sn$$_{2}$$ for hydrogen production from methanol decomposition

Fan, M.*; Xu, Y.*; 櫻井 惇也*; 出村 雅彦*; 平野 敏幸*; 寺岡 有殿; 吉越 章隆

Catalysis Letters, 144(5), p.843 - 849, 2014/05

 被引用回数:12 パーセンタイル:35.92(Chemistry, Physical)

In this study, the catalytic properties of Ni$$_{3}$$Sn and Ni$$_{3}$$Sn$$_{2}$$ powders were investigated for producing hydrogen from decomposing methanol in the temperatures from 593 to 953 K. The catalytic activities of Ni$$_{3}$$Sn and Ni$$_{3}$$Sn$$_{2}$$ both increased with increasing temperature, but Ni$$_{3}$$Sn showed much higher catalytic activity than Ni$$_{3}$$Sn$$_{2}$$. The results of an isothermal test performed at 873 K revealed that the catalytic activity of Ni$$_{3}$$Sn significantly increased with methanol decomposition time, indicating that Ni$$_{3}$$Sn was spontaneously activated. Ni$$_{3}$$Sn and Ni$$_{3}$$Sn$$_{2}$$ both showed a high degree of selectivity and both suppressed side reactions such as methanation and water-gas shift reaction. Surface analysis revealed that fine Ni-Sn particles were formed together with carbon deposited onto the catalyst surface. These Ni-Sn particles were supposed to serve as active sites for methanol decomposition.

口頭

Catalytic performance of Ni$$_{3}$$Sn alloy for hydrogen production from methanol decomposition

Fan, M.*; Xu, Y.*; 櫻井 惇也*; 出村 雅彦*; 平野 敏幸*; 寺岡 有殿; 吉越 章隆

no journal, , 

We have examined the catalytic performance of Ni$$_{3}$$Sn for hydrogen production from methanol decomposition. The single-phase Ni$$_{3}$$Sn alloy ingot was prepared using a high-frequency furnace. The ingot was mechanically crushed to powders. The powders were sieved to get the samples less than 75 micrometer in size for reaction test. Methanol decomposition was performed in a conventional fixed-bed flow reactor. The characterization of Ni$$_{3}$$Sn was carried out by XRD, SEM, BET, and synchrotron XPS in SPring-8. The methanol conversion increased with time indicating that Ni$$_{3}$$Sn spontaneously activated during the reaction. It was also found that Ni$$_{3}$$Sn shows a high selectivity. The characterization of the samples before and after reaction shows that Ni$$_{3}$$Sn phase remained unchanged, and no obvious oxidation of Ni and Sn occurred during reaction, suggesting that Ni$$_{3}$$Sn itself might serve as the active species.

口頭

Catalytic properties of Ni$$_{3}$$Al foils for methane steam reforming

Xu, Y.*; Ma, Y.*; 櫻井 惇也*; 出村 雅彦*; 平野 敏幸*; 寺岡 有殿; 吉越 章隆

no journal, , 

Ni$$_{3}$$Al intermetallic compound is known as a promising high-temperature structural material because of its excellent high temperature strength and corrosion/oxidation resistance. The brittleness at room temperature used to be a big problem which restricted its practical application. We have overcome this problem and successfully developed thin Ni$$_{3}$$Al foils using directional solidification and cold rolling. We investigated the catalytic activities of the cold-rolled Ni$$_{3}$$Al foils for methane steam reforming. The effect of steam pre-treatment on the catalytic activities of the foil was also investigated. It was found that the activity of as-rolled foils increased with temperature above 873 K, while no obvious activity was detected below 873 K. The steam pre-treatment at 873 K significantly enhanced the activity in the temperature range from 873 to 1173 K. The enhanced catalytic activity was attributed to the fine pure Ni particles on the foil formed by the steam pre-treatment.

口頭

Effect of steam treatments on surface morphology of Ni$$_{3}$$Al foil catalysts

Xu, Y.*; Ma, Y.*; 櫻井 惇也*; 寺岡 有殿; 吉越 章隆; 出村 雅彦*; 平野 敏幸*

no journal, , 

We found that Ni$$_{3}$$Al shows high catalytic activity for methanol decomposition and methane steam reforming as catalysts of hydrogen production. It is possible to enhance catalytic activity by modifying the Ni$$_{3}$$Al foil by a pre-steam treatment followed by a reduction with H$$_{2}$$ gas flow. We investigated the effect of the steam treatment and H$$_{2}$$ reduction on the surface morphology of Ni$$_{3}$$Al foil using synchrotron radiation X-ray photoemission spectroscopy. Although the metallic Ni2p$$_{3/2}$$ and 2p$$_{1/2}$$ peaks were detected before the steam treatment, the metallic Ni was significantly decreased and NiO appeared after the steam treatment, suggesting that most of the metallic Ni was oxidized. After the hydrogen reduction, the metallic Ni increased again, indicating that the NiO was reduced. These fine metallic Ni particles formed on the foil surface contribute to the enhanced catalytic activity.

口頭

Oxidation of Ni$$_{3}$$Al(210) surface at room temperature using supersonic oxygen molecular beam; Real-time photoemission spectroscopic study with synchrotron radiation

Syu, Y.*; 櫻井 惇也*; 寺岡 有殿; 吉越 章隆; 出村 雅彦*; 平野 敏幸*

no journal, , 

Intermetallic compounds (IMCs) usually have ordered crystal structure which differs from that of their constitute metals. Some of them have been reported to show good catalytic properties for some reactions, such as Pt$$_{3}$$Ti, Ni$$_{3}$$Sn, and Ni$$_{3}$$Al, demonstrating that IMCs have potential as catalysts and/or catalyst precursors for chemical reactions. In this work, we investigate the initial oxidation process on a Ni$$_{3}$$Al(210) surface at 298 K using a supersonic oxygen molecular beam and a real-time photoemission spectroscopy with synchrotron radiation. The time evolutions of O 1s, Ni 2p, Al 2p, and Ni 3p spectra indicate that both Al and Ni are oxidized, and AlO$$_{x}$$ and NiO are formed during the irradiation of oxygen molecules. The oxidation rate of Al is much higher than that of Ni at the beginning of oxidation, and then quickly saturates. In contrast, the oxidation of Ni progresses gradually for the whole measured period.

口頭

Initial oxidation behavior of Ni$$_{3}$$Al(210) surface induced by supersonic oxygen molecular beam at room temperature

Xu, Y.*; 出村 雅彦*; 寺岡 有殿; 吉越 章隆; 櫻井 惇也*; 平野 敏幸*

no journal, , 

Ni$$_{3}$$Al(210)表面の超音速O$$_{2}$$分子ビーム(2.3eV)による室温酸化を高輝度放射光を利用したリアルタイム光電子分光によって調べた。O 1s, Ni 2p, Al 2p, and Ni 3pスペクトルの分子ビーム照射中の時間発展を調べた。スペクトル分析から、表面のAlとNI原子の両方が酸化され、Alの酸化の方がNiより速いことがわかった。

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