奈米金觸媒於富氫氣流中選擇性一氧化碳氧化反應之應用

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Title:	奈米金觸媒於富氫氣流中選擇性一氧化碳氧化反應之應用
Authors:	查昱伶;Cha,Yu-lin
Contributors:	化學工程與材料工程學系
Keywords:	一氧化碳氧化;金觸媒;二氧化鋯;四氧化三鈷;二氧化鈰;燃料電池;CO oxidation;gold;CeO2;PROX;fuel cell
Date:	2013-06-27
Issue Date:	2013-07-10 11:51:23 (UTC+8)
Publisher:	國立中央大學
Abstract:	燃料電池除了能高效率的把化學能轉化成電能，更是一種方便攜帶的能源。在燃料電池產氫能的過程中會產出副產物一氧化碳，一氧化碳會毒化白金電極，而選擇性氧化一氧化碳反應(PROX)將一氧化碳減至< 5 ppm，是目前最能有效移除一氧化碳方法之一。本研究將金之奈米顆粒擔載於二氧化鈰-四氧化三鈷及二氧化鈰-二氧化鋯上，並應用於富氫氣流中之一氧化碳選擇性氧化反應中。四氧化三鈷和二氧化鋯則是以含浸法和共沉澱法這兩種方式與二氧化鈰擔體混合，之後再使用沉積沉澱法將金顆粒擔載於上述擔體。在此研究中，改變不同的促進劑比例和製備方法找出最佳的條件以製備出最適合PROX反應之金觸媒。製備完成的觸媒經過X光繞射分析儀、穿透式電子顯微鏡和X光電子能譜儀等鑑定分析其觸媒性質。PROX反應是在固定床反應器中填充0.1克觸媒，並以進料氣體CO/O2/H2/He 體積比為1.33/1.33/65.33/32.01，總流量控制在50 ml/min下進行反應。結果顯示在某些比例下金/二氧化鋯-二氧化鈰及金/四氧化三鈷-二氧化鈰觸媒在80-100℃對一氧化碳的轉化率及轉化率比金/二氧化鈰觸媒更好。其中金/四氧化三鈷-二氧化鈰(5:95)觸媒在80℃下更可將一氧化碳完全轉化。金以1-3奈米的大小分佈於擔體上。加入二氧化鋯之後，不論是使用含浸法或是共沉澱法製備，觸媒在低溫下的轉化率相較於金擔載於二氧化鈰都有明顯的提升。在金/四氧化三鈷-二氧化鈰觸媒方面，一氧化碳氧化的選擇率隨著四氧化三鈷加入的比例增加而上升。兩種觸媒在燃料電池操作溫度(65-100℃)下進行反應，金/四氧化三鈷-二氧化鈰(5:95)使用共沉澱法製備的觸媒可在80℃將一氧化碳完全轉化。 Nanoscaled gold particles supported on CeO2-ZrO2 and CeO2-Co3O4 was used for preferential oxidation of carbon monoxide in hydrogen-rich stream (PROX). They were loaded on CeO2-ZrO2 and CeO2-Co3O4 through deposition-precipitation method. The catalysts with different ratio of Ce/Zr andCe/Co and different preparation method were tested to develop the best catalyst for PROX reaction. These catalysts were characterized by XRD, TEM, and XPS. The PROX reaction was carried out in a fixed bed continuous flow reactor with a feed of CO: O2: H2: He = 1.33: 1.33: 65.33: 32.01 in volume ratios. The results showed that the catalyst with specific Ag content and calcinations temperature could reach 100% of CO conversion at the PEM fuel cells operating temperature (65℃-100℃) even as the gold content was 1 wt. %. The particle size of gold was around 1-3 nm and Au particles were dispersed well on the support. In Au/Co3O4-CeO2 catalysts, only Co/Ce=2/98and5/95 show better activity than Au/Ceo2 and the CO selectivity increase because of adding Cobalt. In Au/ZrO2-CeO2 catalyst, only Zr/Ce=2/98and5/95 show better activity than Au/Ceo2 and the CO selectivity decrease as the reaction temperature increase. These two kinds of catalyst underwent reaction with operating temperature 80℃, the Au/ Co3O4-CeO2 (5:95)catalysts prepared by co-precipitation can converted CO to CO2completely.
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