成果報告書詳細
管理番号20110000001086
タイトル*平成22年度中間年報 固体高分子形燃料電池実用化推進技術開発 基盤技術開発 定置用燃料電池システムの低コスト化のためのMEA高性能化(高活性・高耐久性・低S/C燃料改質触媒の開発と評価)
公開日2011/11/10
報告書年度2010 - 2010
委託先名国立大学法人山梨大学
プロジェクト番号P10001
部署名新エネルギー部
和文要約和文要約等以下本編抜粋:1.研究開発の内容及び成果等
(1)今年度の研究開発の目標
本研究開発は、定置用燃料電池システムの燃料改質器に搭載される水素製造・精製触媒のうち、特に一酸化炭素(以下CO)選択メタン化触媒を対象としている。CO 選択メタン化触媒は、現行のCO 選択酸化触媒(以下PROX 触媒)と違って反応に空気を必要としないことから、空気ポンプの削減や燃料改質器構造・制御の簡略化によりシステムコストが大幅に低減できると期待されている。
これまで我々は、微量のRu を含むNi 系CO 選択メタン化触媒がPROX 触媒よりも高い入口CO 濃度0.8~1.0%(8000~10000ppm)においても99.0~99.9%の優れたCO 除去性能を示すことを見いだした1、2)。またメタルハニカムにコーティングして使用することで粒状触媒の1/5 程度の触媒量でも同等の性能が期待でき3)、実機サイズのハニカム触媒で200~250℃の温度帯で安定に運転できる事も示した4)。しかし、その後本触媒に対し500 時間の連続運転を実施したところ、運転時間の経過と伴にCO 浄化性能と反応選択性が徐々に低下するという問題が確認された。
今年度は、このCO 選択メタン化触媒に認められる性能低下の原因を明らかにし、劣化機構に基づく触媒改善指針を立案することを目標とした。平成24 年度の最終年度には、反応・劣化機構の知見とナノテクノロジー等の先端材料技術を融合することで、CO 選択メタン化触媒の高性能・高耐久・低コストを同時に実現するための基礎的技術を確立し、定置用燃料電池システムの本格普及に資することを目的とする。
英文要約Title: Development of PEFC Technologies aiming for Practical Application/Base Technology/R&D on PEFC components for reducing cost and improving performance of residential systems
This study is aiming to develop highly active and selective catalysts for selective CO methanation, which is going to be employed for hydrogen purification for residential polymer electrolyte fuel cells. Compared with a conventional preferential CO oxidation method, CO methanation is more cost-effective and space-saving substitute. Recently, our group developed Ni-Al mixed oxides with a small amount of Ru addition through different methods, showing high CO conversion for the reaction. In this fiscal year, the durability was tested over two types of catalyst and the degradation factors and mechanism was clarified. Ru doped Ni-Al oxides prepared by two different methods with the excellent initial catalytic activity were tested for 500-1000 h. The catalyst prepared by a solution-spray plasma technique showed no detectable degradation for 500 h when Steam/CO is 0. However, if steam is fed, the outlet CO (increase rate for outlet CO concentration: 200ppm/500h) and CH4 increased over time, indicating that the selectivity becomes worse. In the case of the mesoporous Ni-Al oxide catalyst prepared by a sol-gel method, the CO increase rate (5ppm/500h) was much lower than that of the monolithic catalysts. There is no significant change of Ni crystallite size, H2 uptake amount and surface area of catalysts before and after durability test. Furthermore, the influence of NH3 produced from nitrogen and carbon deposition was also studied. However, there is no obvious evidence can confirm its effect on degradation. It is interesting to point out that the amount of Cl contained by these two catalysts decreased significantly over durability test time. Based on mentioned above, it can be concluded that the main factor induced the degradation is the concentration of Cl contained in catalysts. The effect of chlorine existed on the Ni-Al oxide catalyst for adsorption state of CO2 was studied by FTIR measurements. For the catalysts without chlorine, formation of adsorbed CO occurred immediately after CO2 introduction, while for the ones with chlorine the adsorbed CO formation suppressed remarkably. These results clearly demonstrate that the chlorine inhibited dissociation of CO2 due to a modification of the electronic properties of Ni metal sites. The improvement of the selectivity for CO methanation should be caused by the suppression of CO2 dissociation. At present more stable and effective additives have been studied. Compared to pellet catalysts, monolithic ones can effectively decrease cost because of low necessary amount of catalysts. For monolithic catalysts, one of the most important works is to prepare high quality monolith with no or very low bad cells. Furthermore, considering of practical application, it is necessary to fabricate a real size monolithic catalysts in the next fiscal year. An apparatus used for this purpose had been set up, which can guarantee the quality of slurries and monoliths to some extent and ensure the repentance of experiment results.
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