氧化鋅-氧化鐵複合擔載金-銀雙金屬觸媒應用於甲醇部分氧化產製氫氣之研究; Hydrogen production by partial oxidation of methanol over Au-Ag/ZnO-Fe2O3 catalyst

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Title:	氧化鋅-氧化鐵複合擔載金-銀雙金屬觸媒應用於甲醇部分氧化產製氫氣之研究;Hydrogen production by partial oxidation of methanol over Au-Ag/ZnO-Fe2O3 catalyst
Authors:	吳曉旻;Hsiao-min Wu
Contributors:	化學工程與材料工程研究所
Keywords:	甲醇部分氧化;雙金屬觸媒;產氫;partial oxidation of reaction;produce hydrogen;bimetallic catalysts
Date:	2008-06-15
Issue Date:	2009-09-21 12:31:05 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本研究以共沈澱法製備Au-Ag/ZnO-Fe2O3雙金屬觸媒，應用於甲醇部分氧化反應產製氫氣 (CH3OH+0.5O2→2H2+CO2, POM)。利用熱重分析儀 (TGA) 了解觸媒前趨物在煅燒過程中，擔體中的金屬鹽類和擔體本身的熱解特性，發現在540 K左右重量損失最大，是由hydrozincite (Zn5(CO3)2(OH)6) 遇熱分解為ZnO所造成的重量損失。由X-ray繞射儀 (XRD) 鑑定觸媒樣品的成分的晶相，發現煅燒前後皆無法看見金與銀的繞射波峰，僅觀察到擔體中hydrozincite形成結晶良好的ZnO。由程式升溫還原 (TPR) 結果可知，觸媒中的過渡金屬弱化了位於金屬原子附近的Fe-O鍵結力而有利於氧化鐵的還原。穿透式電子顯微鏡 (TEM) 觀察的結果顯示，煅燒程序對於金屬顆粒大小並無顯著影響，因此排除觸媒因為粒徑大小影響催化活性的可能。O2/CH3OH進料比例在0.3，相較於理論值0.5更有利於POM反應的進行，有較少的MD (CH3OH→2H2+CO) 反應發生，一氧化碳選擇率較低。反應溫度低時雖然一氧化碳選擇率低，但是反應以MC (CH3OH+1.5O2→CO2+2H2O) 反應為主，生成太多的水降低了氫氣選擇率。當溫度提升至523 K時，POM反應伴隨WGS (H2O+CO→CO2+H2) 反應發生，於是可得最低的一氧化碳選擇率。 Au-Ag/ZnO-Fe2O3 bimetallic catalysts prepared by co-precipitation method were studied to produce hydrogen from partial oxidation of methanol reaction (CH3OH+0.5O2→2H2+CO2, POM) for fuel cell application. TGA analysis was used to investigate the thermal decomposition of catalyst precursors. During calcination, the main weight loss of catalyst precursor was about 540 K. It was due to the hydrozincite (Zn5(CO3)2(OH)6) decomposed to ZnO. XRD results revealed that no diffraction peak of Au and Ag could be seen before and after calcination; only hydrozincite could be found in the patterns which transformed into the well crystalline ZnO structure. The TPR results showed that the transition-metal of catalyst weakened the Fe-O bond leading to the better reducibility of iron. TEM results revealed that calcination process did not have obvious influence on metal particle size. Thus, the effect of particle size to catalytic activity could be ignored. O2/CH3OH molar ratio of 0.3 exhibited better activity than the ratio of 0.5, theoretical value of POM reaction. Less MD (CH3OH→2H2+CO) reaction occurred resulted in lower CO selectivity. At lower reaction temperature, even it showed lower CO selectivity, the MC reaction predominated which lead to the decrease of H2 selectivity. When the reaction temperature increase to 523 K, POM reaction occurred with WGS (H2O+CO→CO2+H2) reaction, and had the lowest CO selectivity.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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