奈米金擔載於改質二氧化鈰應用於催化氫氣流中選擇性氧化一氧化碳反應; Gold Nanoparticle Supported on Modified Cerium Oxide in Preferential Oxidation Reaction of CO in H2 stream

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题名:	奈米金擔載於改質二氧化鈰應用於催化氫氣流中選擇性氧化一氧化碳反應;Gold Nanoparticle Supported on Modified Cerium Oxide in Preferential Oxidation Reaction of CO in H2 stream
作者:	周映潔;Ying-Chieh Chou
贡献者:	化學工程與材料工程研究所
关键词:	氫氧化鎂;氧化銅;二氧化鈰;金觸媒;一氧化碳氧化;PROX;燃料電池;fuel cell;CO oxidation;gold;CeO2;CuO;Mg(OH)2;PROX
日期:	2011-06-19
上传时间:	2012-01-05 11:16:01 (UTC+8)
摘要:	本研究將金之奈米顆粒擔載於以銅或鎂改質之二氧化鈰上，並應用於富氫氣流中之一氧化碳選擇性氧化反應。氧化銅-二氧化鈰擔體是以共沉澱法製備；另一方面，鎂則是以含浸法方式與商用二氧化鈰（Nikki）擔體混合。最後，再使用沉積沉澱法將金顆粒擔載於上述改質擔體中。在此研究中，改變不同的促進劑比例和擔體鍛燒溫度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、高解析穿透式電子顯微鏡、X光電子能譜儀和氮氣吸附儀等鑑定分析其觸媒性質。PROX反應以固定床反應器填充0.1克觸媒，並以進料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。結果顯示在特定的銅比例和擔體鍛燒溫度，Au/CuO-CeO2觸媒可在質子交換膜燃料電池(PEM fuel cells)的操作溫度(65℃-100℃)下將一氧化碳完全轉化。將金的承載量由1 wt. %降至0.5 wt. %亦可得到完全轉化的成果。金以約2-5奈米的大小分佈於擔體上。銅離子進入二氧化鈰晶格可提升二氧化鈰的儲/釋氧能力以促進觸媒活性。而升高擔體之鍛燒溫度可提高擔體之結晶性、增加二氧化鈰中氧空缺之數量，因此可提高觸媒活性。反應中一氧化碳之選擇性隨銅的添加量而提高。Au/Mg(OH)2-CeO2觸媒在較高的擔體鍛燒溫度下(550℃或700℃)才有比較明顯的促進作用。將兩種觸媒進行160小時的長時間活性測試，Au/CuO-CeO2觸媒在活性上有較佳的穩定性。 Nanoscaled gold particle supported on CeO2 and modified by CuO or Mg(OH)2 were used for preferential oxidation of carbon monoxide in hydrogen-rich stream (PROX). CuO-CeO2 support was prepared by co-precipitaion method, while magnesium was loaded on commercial CeO2 (Nikki) through impregnantion method. Finally, gold was added to these supports by deposition-precipitation method. Different amounts of promoter and different calcination temperatures of the support were changed to develop the best catalyst for PROX reaction. These catalysts were characterized by XRD, TEM, HR-TEM, XPS, and N2-sorption. 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 Cu content and calcination temperature could reach 100% of CO conversion at the PEM fuel cells operating temperature (65℃-100℃) even as the gold content was reduced from 1 wt. % to 0.5 wt. %. The particle size of gold was around 2-5 nm and Au particles were dispersed well on the support. The incorporation of copper ion into ceria lattice promoted the oxygen storage capacity of ceria support and encouraged the activity of catalysts. The higher calcinations temperature for the support resulted higher crystallinity of CeO2, leading to the higher activity. The CO selectivity increased with increasing copper amount. The promotional effect of magnesium addition was more obvious at higher calcinations temperature (550℃ and 700℃) of support. After deposition-precipitation method, the magnesium presented as phase of Mg(OH)2 rather than MgO as observed by XRD. However, the existed of this hydroxide did not show significant promotion on catalytic activity. These two kinds of catalyst underwent long-term reaction test for 160 hours. The Au/CuO-CeO2 catalyst was more stable than Au/Mg(OH)2-CeO2.
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