Study of the valence state and coordination of antimony in MoVSbO catalysts determined by XANES and EXAFS
Study of the valence state and coordination of antimony in MoVSbO catalysts determined by XANES and EXAFS
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DOI：
10.1016/s0926-860x(02)00614-2
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发表时间：
2003-05
影响因子：
5.5
通讯作者：
J. Millet;M. Baca;A. Pigamo;D. Vitry;W. Ueda;J. Dubois
中科院分区：
文献类型：
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作者：
J. Millet;M. Baca;A. Pigamo;D. Vitry;W. Ueda;J. Dubois
用EXAFS和XANES分别研究了MoVSbO复合氧化物催化剂中Sb在正交相和六方相两相中的配位情况。虽然XANES揭示了这两个相都含有SbIII和SbV，但它也表明相M1主要含有SbV，而相M2主要含有SbIII。从这两种技术获得的数据，可以提出，在这两个阶段，SbIII和SbV主要位于窗口的六边形通道的结构。SbIII以六方窗口的两个氧和通道中的一个氧形成类似于Sb 2 Mo 10 O31的SbO 3E三角锥，而SbV以六方窗口的两个氧和通道中的两个氧形成类似于TeMo 5 O 16的SbO 4三角双锥（正交晶型）。因此，在通道中，锑和氧主要形成六方相的二聚体[Sb-O-Sb]和正交相的无限链[Sb-O]∞。得到的结果允许确定的正式化学计量的两个阶段，分别是，（Sb 2 O）M6 O 18和（SbO）2 M20 O 56（M = Mo，V），并讨论了阴离子和阳离子的亚化学计量遇到。与碲环境中的类似阶段的比较进行了讨论。
The coordination of antimony in the two phases, orthorhombic and hexagonal, of the MoVSbO mixed oxides catalysts has been investigated by EXAFS at the Sb K-edge at 77K and its valence state by XANES at the Sb L1-edge. While XANES revealed that both phases contained SbIIIand SbV, it also demonstrated that the phase M1 contained mainly SbVwhile the phase M2 contained mainly SbIII. From data obtained with the two techniques, it can be proposed that in both phases, SbIIIand SbVare mostly located in the windows of hexagonal channels of the structures. SbIIIforms, with two oxygens of the hexagonal window and one oxygen in the channel, SbO3E trigonal pyramids similar to that in Sb2Mo10O31whereas SbVforms, with two oxygens of the hexagonal window and two oxygens in the channel, SbO4trigonal bipyramids like in TeMo5O16(orthorhombic form). In the channels antimony and oxygens are thus forming mainly dimers [Sb–O–Sb] in the hexagonal phase and infinite chains [Sb–O]∞in the orthorhombic one. The results obtained allowed determining the formal stoichiometries of the two phases which are, respectively, (Sb2O)M6O18and (SbO)2M20O56with (M = Mo, V) and to discuss the anionic and cationic sub-stoichiometries encountered. The comparison with the tellurium environment in the similar phases is discussed.