奈米氧化鈰固溶體構形控制與多孔性氧化鈰材料對乙醇轉氫效率的研究

Ce1-xMxO2 (M=Ti, Zr and Hf) solid solution with controlled morphologies and porous structure of ceria applied on ethanol steam reforming

陳韋達(Wei-Ta Chen)

指導教授 ： 李積琛

國立交通大學/理學院/應用化學系所/碩士(2009年)

https://doi.org/10.6842/NCTU.2009.00446

摘要

I. 兩步驟合成之奈米氧化鈰固溶體的構形控制研究

本實驗藉由簡單的兩步驟合成方式，成功地製作出具有奈米方塊
、奈米柱和奈米管構形的Ce1-xMxO2 (M=鈦,鋯與鉿) 固溶體，研究指出此固溶體的組成比例和形貌會受到反應時間、反應溫度及前驅物莫耳比例的影響。其中，我們使用粉末繞射儀、掃瞄式電子顯微鏡和穿透式電子顯微鏡對其結構與形貌進行分析，並由能量分散式光譜儀和感應耦合電漿質譜分析儀的結果確認了此固溶體化學組成的一致性，映射圖譜結果更顯示摻雜元素均勻地分布在固溶體中。除此之外，比表面積分析結果顯示奈米柱具有最大的表面積，且氫氣程溫還原結果發現，摻雜鈦之奈米柱會有最高的氧化活性，利用上述所合成之固溶體，再添加重量百分比5% 的釕金屬來做乙醇轉氫效率之實驗，實驗結果發現這些具有奈米方塊、奈米柱和奈米管構形的Ce1-xMxO2固溶體之氫氣選擇率會比氧化鈰奈米粒子的表現來得高，對於乙醇轉氫實驗而言，為相當具有潛力的材料。

II. 多孔性結構之氧化鈰與氧化鋯對乙醇轉氫效率研究

相對於甲醇，乙醇具有高氫氣含量、便利性、無毒性和易儲存等優點，而藉由乙醇蒸氣重組的反應，我們可以藉此產生出理想產率為166%的氫氣。利用多孔洞性材料具有高表面積的特性，可能因此而製作出高催化活性的觸媒。因此，在我們的研究中，我們利用聚苯乙烯球自組裝反應、多孔洞性氧化鋁載體 (BET= 288 m2/g) 和改良式溶膠凝膠的使用，分別合成出氧化鈰與氧化鋯的三維孔洞結構及改良式膠體催化劑。其中，我們利用粉末繞射儀和掃瞄式電子顯微鏡對其結構與形貌進行分析，並在不同碳氧比值下，對5% 釕/ 三維孔洞結構 MO2，5% 釕/ SixCe1-xO2 /Al2O3 和 3-9% 釕-SixM1-xO2 /Al2O3 (M=鈰,鋯) 催化劑作乙醇轉氫實驗的測試，實驗結果顯示9% 釕-Si0.33 Ce0.67 /Al2O3在碳氧比值為0.6時有最高的氫氣選擇率113.1%，並發現此觸媒的催化表現穩定，在長時間測試50小時後，氫氣選擇率僅下降4%。

關鍵字

氧化鈰 ； 固溶體 ； 乙醇轉氫

並列摘要

I. Two Steps Synthesis of Ce1-xMxO2 (M=Ti, Zr and Hf) Solid-
Solution with Controlled Morphologies

Nanoscale Ce1-xMxO2 solid solution (M=Ti, Zr and Hf) with cube, rod and tube shapes are prepared via a simple two-step synthesis method. It is found that the effect of composition and morphology is related to reaction time, temperature and molar ratio of M/Ce. The structural and morphological analyses are investigated by Powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). Further, homogeneity in composition is confirmed by SEM/EDS, TEM/EDS and ICP-MS. STEM-EDX mapping images reveal uniform distribution of dopant element within the ceria matrix. Moreover, Surface area measurement indicates nanorods have the highest surface area. And TPR results demonstrate Ti-doped CeO2 nanorods have the highest oxidative power. For 5%Ru/Ce1-xMxO2 /Al2O3 as catalyst, the GC test shows the prepared Ce1-xMxO2 solid solution (M=Ti, Zr and Hf) with cube, rod and tube shapes exhibit a higher hydrogen selectivity for ethanol reforming compared to CeO2 nanoparticles.

II. Porous Structure of CeO2 and ZrO2 sol-gel Applied on Ethanol Steam Reforming

Ethanol is more attractive than methanol because of its relatively high hydrogen content, availability, non-toxicity and facile storage and handling safety. By utilizing the catalytic steam reforming reaction, it is possible to produce H2 from ethanol with the ideal hydrogen selectivity of 166%.
For the purpose of manufacturing highly active catalysts, porous materials were used to enhance surface area that may affect the catalytic activity. In this research, two methods were introduced: (1)3-DOM CeO2 and ZrO2 were prepared through the interstitial spaces between polystyrene spheres assembled on glass substrates. (2)The porous Al2O3 supports (BET= 288 m2/g) immersed with CeO2 and ZrO2 sol-gel were used as catalysts. The characterization was investigated by scanning electron microscope (SEM) and Powder X-ray diffraction (PXRD). Steam reforming of ethanol were studied by catalysts of 5% Ru/ 3-DOM MO2, 5% Ru/ SixCe1-xO2 gel/Al2O3 and 3-9% Ru-SixM1-xO2 gel/Al2O3 (M=Ce,Zr) under different carbon-to-oxygen ratio (C/O). The best results indicate that the catalyst 9% Ru-Si0.33 Ce0.67 /Al2O3 exhibits optimized hydrogen selectivity (SH2 = 113.1%) at C/O = 0.6, and the catalyst is stable for at least 50 hrs with decay less than 4%.

並列關鍵字

Ceria ； Solid solution ； Ethanol steam reforming

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