Catalytic Properties of Chemically Pretreated Ni 3 Al/Ni Two-phase Alloy Foils for Methane Steam Reforming
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1128-U05-34
Catalytic Properties of Chemically Pretreated Ni3Al/Ni Two-phase Alloy Foils for Methane Steam Reforming Daisuke Kamikihara1, Ya Xu2, Masahiko Demura2, Toshiyuki Hirano1, 2 1 Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan 2 National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan
ABSTRACT We carried out methane steam reforming on the chemically pretreated Ni3Al/Ni two-phase alloy foils. The chemical pretreatment included two steps: acid leaching followed by alkali leaching. The chemically pretreated foils showed much higher activity than non-treated foils. The catalytic activity of the pretreated foils rapidly increased during the first several hours, and then reached a high-level steady state during the subsequent reaction. The surface morphology analysis revealed that many fine Ni particles were formed during the reaction. We considered that these Ni particles contributed to the increase of catalytic activity during the initial stage of the reaction. INTRODUCTION Ni3Al intermetallic is known as a high-temperature structural material, because of its excellent high-temperature strength and good oxidation/corrosion resistance [1-3]. The brittleness at room temperature has been a big problem which restricted its practical application. Recently we have overcome this problem and successfully developed thin foils of Ni3Al intermetallics by cold rolling of the single crystals without boron addition [4]. Up to now, the catalytic properties of Ni3Al intermetallics have attracted no attention. However, we have recently found a high catalytic activity in the single-phase Ni3Al foils for hydrogen production via methanol decomposition and methane steam reforming in spite of their low surface area [5-9]. The activity is attributed to the fine Ni particles formed on the foil surface during the reaction or by chemical pretreatment. Considering the excellent high-temperature structural properties, the foil catalysts can be used as both catalysts and structural materials of the micro reactor for hydrogen production. In addition to the single-phase Ni3Al, we recently found the catalytic property in the Ni3Al/Ni two-phase alloy foils for methane steam reforming. Since the activity is not so high compared to that in the single-phase Ni3Al foils, we have made an attempt to improve it in this study. In our previous study, it was found that a two-step chemical pretreatment of acid leaching and subsequent alkali leaching significantly enhanced the catalytic activity of atomized Ni3Al powder with a NiAl/Ni3Al two-phase structure [10]. These results show a possibility of the two-step chemical treatment for improving the catalytic activity of Ni3Al/Ni two-phase alloy foils. In this study we carried out this chemical pretreatment on the surface of Ni3Al/Ni two-phase alloy foils and studied the catalytic properties for methane steam reforming.
EXPERIMENTAL PROCEDURES Sample preparation Ni3Al/Ni two-phase alloy foils of 30 µm in
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