The nature of antimony-enriched surface layer of Fe-Sb mixed oxides
The nature of antimony-enriched surface layer of Fe-Sb mixed oxides
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DOI：
10.1016/j.apsusc.2005.09.055
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发表时间：
2006-09
影响因子：
6.7
通讯作者：
Yan Huang;P. Ruiz
中科院分区：
文献类型：
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作者：
Yan Huang;P. Ruiz
锑的偏析是铁锑复合氧化物的一个共同特征，铁锑复合氧化物被广泛应用于选择性氧化和氨氧化反应中。本文试图通过XPS表面分析，阐明这一共同特征的原因和FeSbO_4表面富锑层的性质。研究了不同方法制备的单相FeSbO 4样品，发现其表面层的锑是Sb 5+和Sb 3+的混合物，而不是单一的Sb 5+。它们的表面组成接近于FeSb_2O_6，可以用（FeSbO_4）（Sb_2O_4）δ来描述，δ=0.5，而不是文献中所说的“Fe（II）Sb（V）_2O_6”。Sb/Fe>1（mol/mol）的Fe-Sb复合氧化物是FeSbO 4和Sb 2 O 4的混合物，FeSbO 4颗粒表面形成一层（FeSbO 4）（Sb 2 O 4）δ，δ≥0.5。Sb/Fe<1的Fe-Sb复合氧化物为FeSbO 4和Fe 2 O3的混合物，FeSbO 4颗粒表面形成一层（FeSbO 4）（Sb 2 O 4）δ，δ≤0.5，而剩余的Fe 2 O3被一层FeSbO 4包裹。
Antimony segregation is a common feature in Fe–Sb mixed oxides, which have been widely applied as catalysts in selective oxidation and ammoxidation reactions. This paper attempts to shed a light on the cause of such a common feature and on the nature of the antimony-enriched surface layer over FeSbO4by means of XPS surface analysis. Single-phase FeSbO4samples prepared by different methods were studied, and the antimony in their surface layer is a mixture of both Sb5+and Sb3+rather than single Sb5+. Their surface composition is close to FeSb2O6, which could be described as (FeSbO4)(Sb2O4)δ, δ=0.5, and it is not “Fe(II)Sb(V)2O6” as suggested in literature. Fe–Sb mixed oxides with Sb/Fe>1 (mol/mol) are mixtures of FeSbO4and Sb2O4, and the surface of FeSbO4grains would be a layer of (FeSbO4)(Sb2O4)δ, δ≥0.5. Fe–Sb mixed oxides with Sb/Fe<1 are mixtures of FeSbO4and Fe2O3, and the surface of FeSbO4grains would be a layer of (FeSbO4)(Sb2O4)δ, δ≤0.5, but the remaining Fe2O3would be encapsulated by a layer of FeSbO4.