成果報告書詳細
管理番号20120000000796
タイトル*平成23年度中間年報 希少金属代替材料開発プロジェクト 排ガス浄化向け白金族使用量低減技術開発及び代替材料開発/ディーゼル排ガス浄化触媒の白金族使用量低減化技術の開発
公開日2012/7/5
報告書年度2011 - 2011
委託先名独立行政法人産業技術総合研究所 三井金属鉱業株式会社 水澤化学工業株式会社 国立大学法人名古屋工業大学 国立大学法人九州大学
プロジェクト番号P08023
部署名電子・材料・ナノテクノロジー部
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
研究開発項目1「白金族使用量を低減したディーゼル酸化触媒の開発」
1-4 要素技術統合による実用候補触媒の抽出
1-4-1 活性種・複合化・担体高度化技術の抽出(産業技術総合研究所)
○活性種高度化技術
触媒活性種については、昨年度までにNO や炭化水素の酸化活性向上にはアルミナ担体の酸性酸化物修飾が有効、耐久性向上にはPt とPd との複合化が有効であることを明らかにした。本年度は酸性酸化物による修飾およびPd 複合法の最適化を試みた。アルミナ担体の酸性酸化物による修飾に関しては、修飾量によって酸量の大きな変化は認められないが、塩基量が減少することがわかった。
英文要約(1) Development of diesel oxidation catalyst (DOC): 1) Advanced techniques for preparation of active species and support materials: The addition of Pd and acidic additives improved the catalytic activity of Pt/Al2O3 for NO and HC oxidation. The increase of metal dispersion by Pd and decrease of basicity by the additives seem to contribute to the highly active species. A new preparation method using precursor solution containing Pt-Pd nanoparticles has been developed. The oxidation activity of the catalysts after a durability test reached a maximum at a small content of Pd, while metal dispersion increased with the Pd content. Alumina-based supports containing secondary elements were investigated. The addition of element (A) increased oxidation activities even after aging treatment. Additionally, hierarchical-structured wash-coat layer with meso- and macro-pores was proved to have high reactivity by a computational fluid dynamic technique. 2) Practical realization of support designing: Methods to produce high purity alumina and alumina with highly dispersed secondary elements have been developed. In addition, a newly assembled pilot-scale plant has been constructed to manufacture these supports. 3) Advanced catalyst design:The total oxidation of HC over Pt/Al2O3 was proposed to proceed via the formation of an acrylate species. The alumina support was considered to play an important role as an adsorption site for acrylate species formed on Pt by interacting with the Lewis acidic centers. 4) Development of catalyst preparation methods: The catalyst preparation method for Pt/CeOx composite nanoparticles was applied to conventional impregnation method, in which a linker molecule was adsorbed on the catalyst support, followed by impregnation of catalyst precursors. The Pt-Pd catalysts supported on a superacid support prepared by the method exhibited superior oxidation activity. 5) Selection of candidate catalysts: Test-manufactured DOC with 40% less PGMs prepared by using the advanced techniques showed almost equivalent catalytic activity to commercial catalysts under model gas conditions. Honeycomb-coated catalysts using alumina supplied from Mizusawa Chemicals also showed good HC oxidation performance. (2) Development of catalyzed diesel particulate filter: The thermal resistance of Ag-Pd alloy catalysts was found to increase with Pd content by reducing volatilization of Ag. The use of Al2O3 as a support for Ag-Pd alloy improved the catalytic oxidation performance after aging treatment. Active species on Ag-Pd/Al2O3 for carbon black oxidation was characterized. XRD results and TEM images revealed the presence of Ag-Pd alloy. Temperature-programmed oxidation measurements suggest that Ag-Pd alloy in a metallic state is an active species. (3) Development of catalyst manufacturing technologies and system development: The PGM content of DOC could be reduced by 40% by arrangement of high concentrations Pt-Pd catalyst at the inlet side in a honeycomb as well as by the control of macropores of the alumina support layer. The PGM content of DPF could also be reduced by 50% by placing Pt-Pd catalyst after the Ag-Pd alloy catalyst. Actual scale test-manufactured catalysts with 43% less usage of PGM than a present commercial catalyst was evaluated by using an real diesel engine. The catalysts exhibited equivalent performance for HC and CO oxidation, although the soot combustion activity was less.
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