氧化鋅擔載金-鉑雙金屬觸媒應用於甲醇部份氧化產製氫氣之研究; Hydrogen production by partial oxidation of methanol over Au-Pt/ZnO catalyst

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Title:	氧化鋅擔載金-鉑雙金屬觸媒應用於甲醇部份氧化產製氫氣之研究;Hydrogen production by partial oxidation of methanol over Au-Pt/ZnO catalyst
Authors:	陳宏杰;Hung-chieh Chen
Contributors:	化學工程與材料工程研究所
Keywords:	甲醇部份氧化;partial oxidation of methanol
Date:	2007-06-28
Issue Date:	2009-09-21 12:28:15 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本研究以氧化鋅為擔體，以共沉澱法製備擔體奈米金鉑雙金屬觸媒，應用於甲醇部分氧化反應產製氫氣 (CH3OH + 1/2O2 → 2H2 + CO2)，評估此反應生成高純度氫氣應用於燃料電池的可行性。先利用熱重分析儀( TGA )分析觸媒前趨物熱分解情形，發現在573 K左右重量損失趨於穩定，因此以573 K為起始煅燒溫度。由X-ray繞射儀( XRD )結果顯示，煅燒前後觸媒並未有明顯的金及鉑的繞射峰，僅可在煅燒前後發現擔體結構的變化。氮氣吸附( BET )分析結果發現以順向共沉澱法製備的觸媒比表面積較逆向共沉澱法高，顯示製備程序對觸媒的特性有影響，而煅燒過後比表面積有逐漸減小的趨勢。穿透式電子顯微鏡( TEM )觀察的結果發現，不同製備程序的觸媒在未煅燒時表面的金鉑晶粒徑並無太大差異，但隨著煅燒溫度增加由5.7 nm增加到17.2 nm。由程式升溫還原( TPR )分析觸媒的還原特性，發現觸媒煅燒後的還原溫度向低溫偏移，原因在於未煅燒之觸媒前趨物含有大量Cl?離子，其成分與煅燒過後不同，而煅燒後波峰面積減少，可見氧化態金屬減少，觸媒表面主要為零價金屬。觸媒在經過活性測試後，計算其甲醇轉化率、氫氣選擇率與一氧化碳選擇率，發現以順向共沉澱法製備的觸媒雖轉化率較低，但有較高的氫氣選擇率及較低的一氧化碳選擇率;未煅燒的觸媒則有較佳的活性;在反應本身的變因方面，進料氧/甲醇的莫耳比在0.3時有較高的氫氣選擇率及較低的一氧化碳選擇率；隨著反應溫度升高，甲醇轉化率及氫氣選擇率均會增加，但一氧化碳選擇率亦隨之提高。未來在有關金觸媒研究上期望能製備出反應活性佳且能產製高純度氫氣的觸媒，以提供燃料電池的氫氣來源。 ZnO-supported gold and platinum catalysts were prepared by coprecipitation method and were tested by partial oxidation of methanol reaction (CH3OH + 1/2O2 → 2H2 + CO2) to produce hydrogen for fuel cell application. Results of TGA analysis show that minimum temperature required for decomposition of catalyst precursor is about 573 K. From XRD analysis, it was not observed apparent peaks for both gold and platinum probably due to small loading. Only supports could be observed the variation of structure after calcination. BET specific area analysis indicates that catalysts prepared by coprecipitation have higher specific surface area than reverse coprecipitation. With increasing calcination temperature, specific area of catalyst decreases. TEM images show that different preparation procedure does not affect particle size, but it increases from 5.7 nm to 17.2 nm when calcination temperature is up to 773 K. TPR analysis illustrates that reduction temperature of catalyst shifts to lower value due to large amount of chloride ion involving in the components of catalyst precursor before calcination. The peak area of catalyst decreases since oxidized species diminish and mainly contains metallic ones. From catalytic activity tests, copecipitation method shows lower methanol conversion but higher hydrogen selectivity and lower carbon monoxide selectivity than reverse coprecipitation method. It shows better catalytic activity because of the state of metals. The mole ratio O2/CH3OH = 0.3 results in higher hydrogen selectivity and lower carbon monoxide selectivity. With increasing reaction temperature, both hydrogen selectivity and methanol conversion increase but also carbon monoxide selectivity. In the future, we expect to prepare catalyst which could effectively catalyze POM reaction and produce high purity hydrogen supplying sources of energy.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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