Mo Loading Effects over Mo/Si : Ti Catalysts in the Oxidative Dehydrogenation of Ethane
Mo Loading Effects over Mo/Si : Ti Catalysts in the Oxidative Dehydrogenation of Ethane
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DOI：
10.1006/jcat.2002.3548
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发表时间：
2002-05
影响因子：
7.3
通讯作者：
Rick Watson;U. Ozkan
中科院分区：
文献类型：
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作者：
Rick Watson;U. Ozkan
研究了一系列负载量为0- 20wt%的Al_2O_3/Al_2O_3催化剂的乙烷氧化脱氢活性。还考察了具有二氧化硅和二氧化钛的单一氧化物载体的催化剂。X-射线衍射、拉曼光谱（环境和脱水条件）和X-射线光电子能谱用于确定负载在混合氧化物载体上的水相的性质。最初，MoOx优先负载在二氧化钛上。然而，即使在最低wt%负载下也存在与二氧化硅的相互作用。随着wt%负载量的增加，MoOx与载体的二氧化硅相的相互作用增加，因为二氧化钛越来越多地分离成更大的氧化物畴。由于MoOx物质可以共享具有不同电负性的几种类型的载体配体，因此不能将MoOx物质充分描述为仅负载在SiO2或TiO 2域上，而是如拉曼结果所示，负载在两种物质的混合物上。结构差异反映在ODH反应性能上。乙烯产率随着Mo负载量超过Si：Ti 1：1而增加至在10%Mo/Si：Ti 1：1时的最大值，其中可能存在MoOx的最佳覆盖率，其共享来自载体的二氧化硅和二氧化钛域两者的几种类型的载体配体。采用程序升温脱附法研究了钼负载量对乙烷吸附后产物脱附行为的影响。
A series of molybdena catalysts (0–20 wt% loadings) were studied with regard to their activity for the oxidative dehydrogenation (ODH) of ethane. Catalysts with single oxide supports of silica and titania were also examined. X-ray diffraction, Raman spectroscopy (ambient and dehydrated conditions), and X-ray photoelectron spectroscopy were used to determine the nature of the molybdena phases supported over the mixed oxide support. Initially, MoOx preferentially supports on titania. However, interaction with silica is present even at the lowest wt% loading. With increased wt% loading, MoOx increasingly interacts with the silica phase of the support as titania increasingly segregates into larger anatase domains. Since MoOx species may share several types of support ligands with differing electronegativity, one cannot adequately describe MoOx species as being supported exclusively on SiO2 or TiO2 domains but rather, as indicated by the Raman results, as being supported on a mix of both species. The structural differences are reflected in ODH reaction performance. The ethylene yield increases with Mo loading over Si : Ti 1 : 1 to a maximum at 10% Mo/Si : Ti 1 : 1, where there may exist an optimum coverage of MoOx that shares several types of support ligands from both silica and titania domains of the support. The desorption behavior of products formed following ethane adsorption was studied with Mo wt% loading using temperature-programmed desorption.