National Changhua University of Education Institutional Repository : Item 987654321/16837
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题名: 新型含鈮之抗水性固體酸觸媒的酸點結構鑑定及其在水溶液中催化活性的測試
Characterization and Testing of a New Type of Water-Tolerant Solid Acid Catalyst Containing Niobium
作者: 林秋薰
贡献者: 化學系
关键词: Niobic acid;Hexaniobate;Nanotubes;Solid acid catalyst;Phosphric;Sulfuric
六鈮酸氫鈉奈米管;硫酸;磷酸;氧化鈮
日期: 2005
上传时间: 2013-06-05T09:36:28Z
出版者: 行政院國家科學委員會
摘要: A sodium hexaniobate nanotube of high purity can be prepared in gram quantities by treating Nb2O5 powder with 1.0 M NaOH solution at 150℃ without utilizing template molecule. SEM revealed that these nanotubes formed a bundle. TEM indicated that a signal sodium hexaniobate nanotube had an outer diameter of 15-20 nm and an inner pore diameter of 3-4 nm. The molecular composition of these nanotubes was Na8-xHxNb6O19‧nH2O. After being rinsed with diluted sulfuric solution or phosphoric solution, they became niobic acid nanotubes 3Nb2O5‧(n+4) H2O. TPD/NH3 indicated that nanotubes rinsed with 0.3M H3PO4 catalyst was more acidic than that rinsed with 0.1M H2SO4. However, the activity in catalyzing the formation of cyclic acetals from cyclohexanone and diols indicated the opposite. These results implied that acid sites in these acid-rinsed nanotubes had severe steric effect.
利用水熱法及Nb2O5 粉末吾人可以在150C 和1.0M NaOH 水溶液中,製備高純度的六鈮酸氫鈉的奈米管。SEM 顯示這种奈米管幾根聚在一起,形成一奈米管束。TEM 顯示單根奈米管外徑為15-20nm,內部中空管徑為3-4nm,長度為幾微米到數十微米。此奈米管組成為Na8-xHxNb6O19‧nH2O。這些六鈮酸氫鈉的奈米管經過稀硫酸或稀磷酸水溶液潤洗之後,轉變成組成為H8Nb6O19‧nH2O 的鈮酸奈米管。利用TPD/NH3 所量測到鈮酸奈米管所含強酸點結果顯示,經0.3MH3PO4 潤洗過的所含強酸點的數目和強度,比0.10M H2SO4 潤洗過的高。但利用環已酮和分子大小不同的双醇經酸催化轉變成環狀縮酮的催化活性結果,顯示剛好相反。我們認為經磷酸潤洗過的鈮酸奈米管上的酸點密度很高,對分子較大的縮酮有擴散限制的障礙,故催化活性變小。而两种酸洗過的觸媒,其酸點都有空間立體障礙效應,故形成較大分子的縮酮時,其催化活性亦變小。
關聯: 國科會計畫, 計畫編號: NSC94-2113-M018-005; 研究期間: 9408-9507
显示于类别:[化學系] 國科會計畫

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