HAADF-STEM研究Mo-V-Te-Ta-O M1相中Mo/V的分布及其与表面反应性的关系
HAADF-STEM Study of Mo/V Distributions in Mo-V-Te-Ta-O M1 Phases and Their Correlations with Surface Reactivity
摘要：
采用两种不同的Ta前体，乙醇Ta和定制的Ta草酸盐络合物，通过常规水热（HT）和微波辅助HT合成方法（MW）制备MoVTeTaO M1相。从HAADF-STEM图像的表面到本体区域沿[hk 0]方向取向的M1相的HAADF-STEM图像的轮廓强度分析表明，表面ab平面的化学组成与它们在本体中的组成非常相似。HAADF-STEM图像分析表明，合成方法对MoVTeTaO M1相的Mo/V分布及其在丙烷氨氧化反应中的反应活性有显著影响。增强的丙烯腈（ACN）产率和丙烷消耗的一阶不可逆反应速率常数（归一化为估计的表面ab平面面积）与提议的催化中心（S2-S4-S4-S7-S7）中增加的V含量相关。这些观察结果进一步支持的想法，即多个VOx网站存在于表面ab平面可能是负责丙烷氨氧化的M1相的活性和选择性。
英文摘要：
The MoVTeTaO M1 phases were prepared by conventional hydrothermal (HT) and microwave-assisted HT synthesis methods (MW) employing two different Ta precursors, Ta ethoxide and a custom-made Ta oxalate complex. The profile intensity analysis of the HAADF-STEM image of M1 phases oriented along [hk0] directions from the surface to bulk region of HAADF-STEM images indicated that the chemical composition of surface ab planes is very similar to their composition in the bulk. The HAADF-STEM image analysis showed that synthesis methods have a significant impact on the Mo/V distribution in the MoVTeTaO M1 phases and their reactivity in propane ammoxidation. Enhanced acrylonitrile (ACN) yield and 1st order irreversible reaction rate constants for propane consumption, normalized to the estimated surface ab plane areas, correlated with increased V content in the proposed catalytic center (S2-S4-S4-S7-S7). These observations lend further support to the idea that multiple VOx sites present in the surface ab planes may be responsible for the activity and selectivity of the M1 phase in propane ammoxidation.
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