PtRu合金及奈米RuO2.H2O之合成鑑定極催化活性研究

Abstract

本研究第一部分為利用涵浸法將PtRu 合金吸附於CeO2 上，製成 5%wt.PtRu/CeO2 催化劑，探討不同莫耳比例之PtRu 合金對於乙醇轉氫 效率的影響。利用X 光光電子能譜儀鑑定PtRu 合金之組成，由掃描電 子顯微鏡觀察氧化鋁擔體上之PtRu 與CeO2，均無特殊形狀。在乙醇轉 氫之測試中，以氣相層析儀偵測催化反應後生成之氣體；經過測試，發 現於PtRu 合金比例1：2 時有最佳轉換效率約為113(2)%，經長時間測 試，效率近似於含5%純釕金屬之催化劑約為107%，顯示有較佳穩定 性。另外，隨著合金中Pt 含量增加，可有效降低起始預熱反應之溫度。 本研究第二部分成功的利用水熱法，以不同氫氧化鈉濃度調控奈米 形狀，合成出了RuO2•xH2O 奈米片及奈米球，並且使其還原成Ru 金 屬，分別研究不同奈米形狀之RuO2•xH2O 及Ru 金屬對於乙醇轉氫效 率之影響。對RuO2•xH2O 及Ru 金屬之定性，利用拉曼光譜、X-ray 粉末繞射及X 光光電子能譜確定為rutile 結構；利用比表面積測定發現 均為高比表面積材料，球狀約為109m2/g，片狀約為274m2/g。定量方 面，利用熱重分析對結晶水做定量，球狀RuO2 結晶水約為0.69H2O、 片狀RuO2 結晶水約為0.60H2O。將片狀、球狀及不規則RuO2•xH2O 製成催化劑(10%wt.RuO2/Al2O3)經乙醇轉氫測試，發現均有催化能力， 其中以片狀之氫氣選擇率最高約115(3)%。對於Ru 金屬，奈米片之氫 氣選擇率最高約為84(1)%。

In the first part, we prepared various 5% wt. PtRu/CeO2 catalysts with different Pt/Ru atomic molar ratios by impregnation methods to study the catalytic performance of each catalyst to the ethanol reforming reaction. PtRu alloy was characterized by X-ray Photoelectron Spectrometer and Scanning Electron Microscope, PtRu/CeO2 on Al2O3 support exhibited irregular particles. According to the GC analyses, the catalyst (Pt/Ru=0.5)/CeO2 revealed H2 selectivity of 113(2)% when the carbon-to-oxygen ratio equaling to 0.5. The selectivity of the catalyst gradually decreases to 107% after 24 hours, which is close the catalyst with pure Ru metal and CeO2, indicating a better stability. Otherwise, the preheating temperature could be reduced effectively by loading Pt metal. In the second part, hydrothermal process was carried out to synthesize RuO2•xH2O with various shapes under different concentrations of NaOH. The quantity of the water of crystallization was measured by TGA, including 0.69H2O for spherical RuO2•xH2O and 0.60 H2O for plate-form RuO2•xH2O. Subsquently, the as-synthesized RuO2•xH2O samples were reduced to Ru metal under H2 flow. Both RuO2•xH2O and Ru materials were tested to study the catalytic activities for the conversion of ethanol to iii hydrogen. The as-synthesized RuO2•xH2O were characterized by Raman spectra, X-ray diffraction and XPS. The RuO2•xH2O of spherical and plate-forms exhibit high specific areas of 109m2/g and 274m2/g, respectively. The H2 selectivity of 10%wt. RuO2•0.6H2O /Al2O3 and 5% -Ru/Al2O3 are 115(3)% and 84(1)%, respectively.