氧化鋯擔載奈米金觸媒之製備與應用研究; Preparation and application of ZrO2 supported nanosized Au catalyst

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Title:	氧化鋯擔載奈米金觸媒之製備與應用研究;Preparation and application of ZrO2 supported nanosized Au catalyst
Authors:	謝文祥;Wen-Hsiang Hsieh
Contributors:	化學工程與材料工程研究所
Keywords:	金觸媒;甲醇部分氧化反應;燃料電池;氧化鋯;Au catalyst;partial oxidation of methanol reaction;fuel cell;zirconium oxide
Date:	2004-06-30
Issue Date:	2009-09-21 12:24:07 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本研究以氧化鋯為擔體，利用共沈澱法以及沈澱固著法製備成奈米氧化鋯擔體金觸媒(簡稱為Au/ZrO2觸媒)，同時利用感應耦合電漿原子放射光譜儀(ICP-AES)、氮吸附法、X射線繞射儀(XRD)、熱重分析儀(TGA)、掃描式電子顯微鏡(SEM)、穿透式電子顯微鏡(TEM)、光電子光譜儀(XPS)等各項儀器與分析技術，分別對擔體及觸媒進行鑑定，並利用甲醇部分氧化反應做為催化活性的測試，藉以評估Au/ZrO2觸媒產生氫氣並應用於質子交換膜燃料電池的可行性。實驗結果得知，以共沈澱法製備的Au/ZrO2觸媒，其觸媒前趨物至少在698 K下鍛燒才會完全分解形成氧化鋯。由氮吸附結果指出，沈澱固著法所製備的Au/ZrO2觸媒，BET比表面積的幾乎不變；共沈澱法製備的金觸媒，隨著載量的增加使BET比表面積下降。從XRD圖譜結果，發現沈澱固著法所製備的金觸媒，不論鍛燒溫度的高低都可以觀察到金的繞射峰出現；共沈澱法製備的金觸媒只有在高載量才能出現金的繞射峰。從TEM分析結果，發現不論以共沈澱法或是沈澱固著法製備的Au/ZrO2觸媒，都可以在照片中找到圓球形的金晶粒。而XPS分析的結果指出，共沈澱法製備的Au/ZrO2觸媒表面皆為金屬態的金；但是沈澱析出法製備的Au/ZrO2表面都會有金屬態的金和氧化態的金存在，而隨著鍛燒溫度的增加金屬態對氧化態的金比例會逐漸上升。經過活性測試，我們認為氧化態的金為觸媒反應的活性位置，沈澱固著法為較佳的製備方法。而鍛燒的條件會影響觸媒活性，最佳的鍛燒溫度為573 K。以沈澱固著法製備的2 wt% Au/ZrO2觸媒在563 K下進行甲醇部分氧化反應，能發揮最佳的活性和氫氣選擇率。最後和文獻上的銅觸媒、鈀觸媒的催化結果做比較，Au/ZrO2觸媒不僅擁有不錯的催化活性，且沒有CO的產生(小於500 ppm)。顯然地，Au/ZrO2觸媒在甲醇部分氧化反應中能夠選擇性氧化CO，使得氫氣產物中幾乎沒有CO的污染。 In this work, zirconium oxide (ZrO2) was used as a catalyst support. ZrO2 supported nanosized Au catalysts (Au/ZrO2) were prepared by the deposition-precipitation (DP) and co-precipitation method (CP). The supported Au catalysts were characterized by inductively coupled plasma-atomic emission spectrometer (ICP-AES), X-ray diffraction (XRD), thermogravimetric analyzer (TGA), nitrogen adsorption method, scanning electron microcopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The thermal decomposition of the Au catalyst precursor starts above 698K. The specific surface area of the calcined catalysts prepared by CP method decreases with increasing the Au loading but catalysts prepared by DP method do not show any difference. From the image of TEM, we can see the black spherical Au crystallites clearly and good dispersion in both two preparation methods. Furthermore, the mean size of Au crystallites increases with an increase in calcination temperature only occurring in Au/ZrO2 prepared by CP method. In XPS analysis, Au catalysts prepared by DP method shows that not only have metallic Au but also oxidative Au in catalysts surface. As calcination temperature is getting higher, the ratio of metallic Au to ionic Au becomes larger. Zirconium oxide supported Au catalysts was tested by the partial oxidation of methanol (POM) at 503-563K. The results indicate that the optimal preparation method and operating conditions are DP method, 2 wt% in Au loading, 573 K in calcination temperature, and 563 K in reaction temperature. Compare to copper and palladium catalysts in POM reaction, Au/ZrO2 catalysts display good activity and hydrogen selectivity. Furthermore, Au/ZrO2 catalysts show no CO present. Nanosized Au/ZrO2 may have an opportunity to apply in proton exchange membrane fuel cell.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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