【作者】 曾尚红；

【导师】 刘源；

【作者基本信息】 天津大学 ， 工业催化， 2007， 博士

【摘要】 供给燃料电池的氢气要求CO含量在10ppm以下,一氧化碳优先氧化(CO-PROX)是净化氢气中一氧化碳的重要途径,实用中的CO-PROX催化剂需要制备为规整形状的整体式结构。金属整体式载体上负载氧化物催化剂需要解决的核心问题是使金属和氧化物以高强度粘结;负载以后将可能带来的重要问题则是载体与氧化物之间的相互作用可能影响催化剂的结构,因此影响催化性能。本文就是针对这两个问题展开研究,针对第一个问题探索新的负载方法;在改进粘附性能研究取得好的或较好的效果的基础上,研究载体效应-即载体与氧化物催化剂的相互作用、此相互作用导致的结构变化及其对催化性能的影响。CuO-CeO2催化剂对CO-PROX具有优良的催化性能。催化剂中铜以一价和二价两种价态存在,其中的一价铜包含进入氧化铈晶格通过氧与铈相连的铜和纳米氧化铜与氧化铈相接触的界面处的铜。该一价铜可能是关键活性组分。使用溶胶-高温热解法可以制备出高活性和高粘附稳定性的金属整体催化剂。热解过程中产生的高表面能晶核导致活性组分与金属载体之间容易形成相互作用,因而具有高的粘附稳定性。以微乳液法负载的铜铈金属整体催化剂,特殊的制备原理致使催化剂每次的涂覆量少,反复的涂覆焙烧过程加强了金属载体和活性组分的相互作用,这就确保整体催化剂表现了较好的粘附稳定性。另外,这种特殊的制备方法促进了铜铈之间的协同作用,也产生了更多的氧空位,因此提高了催化性能。原位溶液燃烧法负载的铜铈金属整体催化剂中,掺杂元素的加入不仅改变了活性组分之间、活性组分和金属载体之间的相互作用,而且改变了氧化铜、氧化铈和表面吸附氧的还原行为,从而对催化性能以及整体催化剂的粘附稳定性都产生了影响。其中掺杂Zr或Nd显著提高了CO被完全净化的温度窗口。金属载体的存在改变了氧化物的分布和相互作用。氧化铈在金属载体上的均匀分散使它的颗粒变小,同时氧化铈和金属载体表面氧化铝之间的相互作用削弱了氧化铜和氧化铈之间的相互作用,致使少量的氧化铜在载体表面发生了聚集。和颗粒催化剂相比,整体催化剂在优先氧化一氧化碳反应中同样表现了高的催化性能。优良的传热特性避免了过热点,抑制了逆水煤气反应的发生。更多还原

【Abstract】 Fuel cells are extremely sensitive to even trace amounts (10ppm) of CO. Preferential oxidation of carbon monoxide is regarded as the favorable method for the purification of the hydrogen-rich streams. Catalysts for preferential CO oxidation need to be prepared as monolithic shape for use. The key problem is how to ensure high adherence between oxides and metallic supports. Then, the interaction between oxides and metallic supports could influence the structure of the catalysts and further influence the catalytic performance. The paper intends to resolve these two problems. New preparation methods are developed to prepare the monolithic catalysts with good adhesion stability. Based on this work, the interaction between oxides and supports is studied, and such interaction may lead to the change of the structure and the catalytic performance.CuO-CeO2 catalyst exhibits high activity for PROX. Cu1+ may be the key active component in the CuO-CeO2 catalyst, which either enters into the CeO2 lattice or exists in the interface between copper oxide and CeO2.The monolithic catalysts prepared by the sol-pyrolysis method present high adherence and catalytic performance. High surface energy of the crystal nucleus and interaction between the catalyst and the support promote the adhesion stability. The monolithic catalysts prepared by the microemulsion method also present good adherence. It must use many times to coat active components due to its special property of microemulsion. In addition, the special property of the microemulsion facilitates the interaction between copper oxide and creia. These are favorable for adhesion stability and the catalytic performance.For the monolithic catalyst prepared by in situ combustion synthesis method, the additives not only change the interaction between the active component and the support, but also change the redox properties of copper oxide, creia and the surface adsorbed oxygen, hence influence the adhesion stability and catalytic activity of the catalysts. The additives of Zr and Nd increase the selectivity of the monolithic catalysts.The presence of the support influences distribution and the interaction of the active components. Ceria is highly dispersed on the surface of the support,so CeO2 crystallite sizes become smaller. The interaction between ceria and alumina weakens the interaction between copper oxide and ceria, so partial CuO aggregates in the monolithic catalyst.Compared with the particle catalyst, the monolithic catalysts also present high catalytic performance for PROX. Good ability of heat transfer weakens the unfavorable effect of the reverse water gas shift reaction on CO preferential oxidation.更多还原