Characterization and Catalytic Properties of Ni 3 Al for Hydrogen Production from Methanol
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Characterization and Catalytic Properties of Ni3Al for Hydrogen Production from Methanol Ya Xu1, Satoshi Kameoka2, Kyosuke Kishida1, Masahiko Demura1, An-pang Tsai1,2 and Toshiyuki Hirano1 1 Materials Engineering Laboratory, National Institute for Materials Science, 1-2-1 Segen, Tsukuba, Ibaraki 305-0047, Japan 2 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan ABSTRACT The stability of catalytic activity and selectivity of Ni3Al for methanol decomposition were studied by life test at 633 K on the alkali-leached powder samples. The characterization of the samples was carried out by X-ray diffraction, inductively coupled plasma (ICP) analysis, SEM observation, and surface area measurement. The life test showed that the alkali-leached Ni3Al exhibits a very stable activity and a high selectivity for methanol decomposition. The surface characterization after reaction suggests that the high selectivity and stable activity may be attributed to the formation of tiny particles and porous structure which increased the surface area significantly during reaction. These results indicate a possibility of Ni3Al as a catalyst for hydrogen production reaction. INTRODUCTION Some intermetallic compounds are known to have a good catalytic selectivity and activity. For example, Ni3Sn increases the selectivity for hydrogen production [1], and PtGe and CoGe do for hydrogenation[2,3]. In Ni-Al system there are four stable intemetallic compounds, NiAl3, Ni2Al3, NiAl and Ni3Al. Among them a mixture of NiAl3 and Ni2Al3 (Ni-50 wt% Al) is used as a precursor alloy for Raney nickel catalysts: the Raney nickel catalysts are produced from the precursor alloy by leaching aluminum in alkali hydroxide solution. For NiAl and Ni3Al, very limited studies have been carried out on the catalytic properties. Probably it has been thought difficult to effectively leach aluminum from them because of their low aluminum concentration [4], and thus high catalytic activity has not been expected, particularly for Ni3Al. Until now, Ni3Al was known as promising high-temperature structural materials because of its excellent high temperature strength and corrosion/oxidation resistance and thus many studies have been focused on the mechanical properties and the microstructures [5-7]. Recently we examined the
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catalytic activity of Ni3Al powder for hydrogen production from methanol which includes
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methanol decomposition (CH3OH 2H2+CO) and steam reforming of methanol (CH3OH + H2O 3H2+CO2) [8-10]. It was found that alkali-leached Ni3Al shows a high activity and selectivity for methanol decomposition at 633 K. However, the stability of the catalytic activity is not studied yet. In the present study, we carried out a life test of methanol decomposition on the alkali-leached Ni3Al catalyst in order to examine the stability.
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EXPERIMENTAL DETAILS Ni3Al (Ni-24 at% Al) alloy ingot was prepared by conventional induction heating and homogenized at 1573 K for 36 ks in high vacuum. Then the ingot was sc
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