Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions
Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions
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DOI：
10.1007/s11244-007-0293-9
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发表时间：
2007-06-01
影响因子：
3.6
通讯作者：
Flytzani-Stephanopoulos, Maria
中科院分区：
文献类型：
--
作者：
Deng, Weiling;Carpenter, Colin;Flytzani-Stephanopoulos, Maria
我们比较了纳米结构金-氧化铈和金-氧化铁催化剂在CO氧化反应中的活性和相应的金物种。良好分散的金纳米粒子在还原形式提供的CO氧化反应的两个氧化物载体上的活性位点。另一方面，氧化的金物种，强烈地结合在载体上催化水煤气变换反应。与氧化铈（掺杂氧化镧）或氧化铁弱结合的金物种可以在PH >= 12时用氰化钠除去。研究了母体和浸出的催化剂。浸出后的金-铁氧化物催化剂的CO氧化活性比母体材料低两个数量级左右。然而，在暴露于H-2高达400摄氏度后，金扩散出来并在表面上以还原形式存在，这一过程伴随着CO氧化活性的显著增强。用金-二氧化铈催化剂发现了类似的结果。另一方面，预还原的焙烧浸出催化剂样品没有促进其水煤气变换活性。采用UV-Vis、XANES和XPS等手段对不同处理后的催化剂的氧化态进行了表征。
We compare the activity and relevant gold species of nanostructured gold-cerium oxide and gold-iron oxide catalysts for the CO oxidation by dioxygen and water. Well dispersed gold nanoparticles in reduced form provide the active sites for the CO oxidation reaction on both oxide supports. On the other hand, oxidized gold species, strongly bound on the support catalyze the water-gas shift reaction. Gold species weakly bound to ceria (doped with lanthana) or iron oxide can be removed by sodium cyanide at PH >= 12. Both parent and leached catalysts were investigated. The activity of the leached gold-iron oxide catalyst in CO oxidation is approximately two orders of magnitude lower than that of the parent material. However, after exposure to H-2 UP to 400 degrees C gold diffuses out and is in reduced form on the surface, a process accompanied by a dramatic enhancement of the CO oxidation activity. Similar results were found with the gold-ceria catalysts. On the other hand, pre-reduction of the calcined leached catalyst samples did not promote their water-gas shift activity. UV-Vis, XANES and XPS were used to probe the oxidation state of the catalysts after various treatments.