銀-二氧化矽核殼結構奈米粒子觸媒應用｜國立清華大學博碩士論文庫

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研究生：	許誌麟 Hsu, Chi-Lin
論文名稱：	銀-二氧化矽核殼結構奈米粒子觸媒應用 Catalytic applications of Ag@SiO2 core-shell nanoparticles
指導教授：	周更生 Chou, Kan-Sen
口試委員:
學位類別：	碩士 Master
系所名稱：	工學院 - 化學工程學系 Department of Chemical Engineering
論文出版年：	2009
畢業學年度：	97
語文別：	中文
論文頁數：	70
中文關鍵詞：	奈米銀、二氧化矽、核殼結構、甲醇直接脫氫反應
外文關鍵詞：	Ag nanoparticles, silica, core-shell structure, methanol dehydrogenation
相關次數：	點閱：2 下載：0
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本研究在奈米銀外披覆一層多孔二氧化矽，使之能夠做為屏障，避免奈米銀彼此燒結失去活性。而氣相反應物可經由二氧化矽孔洞進入與奈米銀反應。
本研究調整PVP的濃度，可製備得平均粒徑為10 nm的奈米銀懸浮液。在空殼二氧化矽研究方面，藉由UV-Vis吸收光譜測量奈米銀表面電漿共振的吸收強度能夠證明氨水會與奈米銀以及銀-二氧化矽核殼粒子貣錯離子反應，進而形成空殼二氧化矽。在溶膠-凝膠法合成核殼粒子實驗中，實驗證明以二甲胺取代氨水做為催化劑，可以避免奈米銀被溶出的問題，維持核殼結構的完整性。TEOS的添加量為控制殼層厚度的重要參數。我們能製備出不同厚度的二氧化矽殼層，從15 nm到42 nm。熱處理溫度對核殼結構之熱穩定性影響方面，當熱處理溫度在600 ℃以下，二氧化矽殼層能有效阻擋奈米銀燒結成長；當熱處理溫度700 ℃以上，奈米銀會熔化離開多孔二氧化矽殼層而燒結聚集。
使用Ag@SiO2觸媒進行甲醇直接脫氫成甲醛實驗中。當反應溫度為500℃，甲醇轉化率可達48 mole %且甲醛選擇率達95 mole %以上，副產物一氧化碳和二氧化碳總合低於5 mole %以下。此實驗結果顯示，Ag@SiO2觸媒能提供大量的Oγ活性點與甲醇貣直接脫氫反應。然而，由於積碳的影響，觸媒活性會隨時間緩慢下降。在相同的反應條件下，使用電解銀觸媒無法催化甲醇直接脫氫成甲醛。

摘要.....................................................I
Abstract 謝............................................ III
圖目錄 ................................................. V
表目錄 ............................................... VIII
前言 ................................................. 1
文獻回顧 ............................................. 2
1 甲醇轉化為甲醛反應機構之介紹 ....................... 2
1.1 甲醇部分氧化為甲醛................................ 2
1.2 甲醇直接脫氫為甲醛................................ 4
1.3 甲醇直接脫氫為熱力學計算 ......................... 7
1.4 甲醇競爭反應熱力學計算 .......................... 10
2 甲醇轉化為甲醛觸媒 媒 ............................. 13
2.2 甲醇直接脫氫觸媒 ................................ 13
2.2.1 銀與銅觸媒 .................................... 13
2.2.2 鋅金屬觸媒 .................................... 14
2.2.3 碳酸鈉觸媒 .................................... 14
2.3 電解銀表面原子吸附氧介紹 ........................ 17
3 核殼結構之觸媒應用 ................................ 24
3.1 文獻回顧 ........................................ 24
3.2 研究目標 ........................................ 27
觸媒製備方法與實驗設備 .............................. 28
1 藥品與儀器 ........................................ 28
2 整體實驗規畫與架構 ................................ 29
3 銀-二氧化矽核殼粒子之製備.......................... 30
3.1 奈米銀的製備 .................................... 30
3.2 二氧化矽包覆奈米銀............................... 32
4 銀-二氧化矽核殼粒子的特性分析 ..................... 33
4.1 TEM觀測 ......................................... 33
4.2 UV-vis光譜分析 .................................. 33
4.3 XRD粒徑分析 ..................................... 33
4.4 BET以及等溫物理吸附量測 ......................... 35
5 觸媒活性3.5.1 反應系統 ............................ 35
5.2 數據分析 ........................................ 37
5.3 名詞解釋與定義 .................................. 38
結果與討論 .......................................... 39
1 銀-二氧化矽核殼粒子製程之改良 ..................... 39
1.1 氨水催化劑對核殼結構的影響 ...................... 40
1.2 使用二甲胺做為催化劑製備核殼粒子 .................44
1.2.1 奈米銀濃度對核殼結構的影響 .................... 44
1.2.2 二甲胺濃度對核殼結構的影響 .................... 46
1.2.3 改變TEOS添加量控制殼層厚度 .................... 48
2 觸媒結構分析 ...................................... 52
2.1 XRD分析 ......................................... 52
2.2 TEM分析 ......................................... 54
2.3 BET分析 ......................................... 58
3 甲醇直接脫氫成甲醛實驗 ............................ 60
3.1 結構對觸媒活性的影響 ............................ 60
3.2 二氧化矽殼層厚度對活性的影響 .................... 62
3.3 滯留時間(WHSV)與產率的關係........................64
3.4 銀-二氧化矽核殼粒子長時間之活性測試 ............. 66
結論 ................................................ 68
參考文獻 ............................................ 69

                                

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