Thermal stability of 12-tungstophosphoric acid supported on zirconia
Thermal stability of 12-tungstophosphoric acid supported on zirconia
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DOI：
10.1016/s0926-860x(99)00431-7
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发表时间：
2000-02
影响因子：
5.5
通讯作者：
E. López-Salinas;J. G. Hernández-Cortez;I. Schifter;E. Torres-García;J. Navarrete;A. Gutiérrez-Carrillo-A.-Gutiérrez-Carr
中科院分区：
文献类型：
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作者：
E. López-Salinas;J. G. Hernández-Cortez;I. Schifter;E. Torres-García;J. Navarrete;A. Gutiérrez-Carrillo-A.-Gutiérrez-Carr
用H3[W12 PO 40]·6 H2O（TPA）的乙醇溶液浸渍新鲜沉淀的氧化锆，以获得0- 25 wt.%的TPA/ZrO 2。用差热分析、X射线衍射、比表面积、红外光谱、拉曼光谱、~（31）P核磁共振等方法对373 ~ 1073 K热处理后的固体进行了分析，并将其用作异丙醇分解的催化剂。在673 K以下，TPA在ZrO_2上以畸变的Keggin物种形式存在，与ZrO_2上的Zr-OH或ZrO_2上的Zr ~+基团相互作用。然而，在773 K，散装一样完整的TPA物种被检测到。在773 K以上，TPA的Keggin结构崩溃并转变为WO 3和磷的氧化物。即使加入20 wt.%的TPA也不能观察到TPA的特征衍射峰。TPA负载，表明TPA的高分散或非常小的晶体尺寸，而20 wt. TPA负载于SiO_2上的结果表明TPA颗粒的存在，热处理温度影响TPA在ZrO_2上的催化活性。在773 K焙烧的TPA/ZrO_2催化剂中，反应速率是473 K焙烧的3.3倍。
A freshly precipitated zirconia was impregnated with an ethanol solution of H3[W12PO40]·6H2O (TPA) in order to obtain 0–25wt.% TPA/ZrO2. The solids, heat-treated from 373 to 1073K, were examined by means of differential thermal analysis, X-ray diffraction, surface area, infrared, Raman,31P nuclear magnetic resonance analyses, and used as catalysts in the decomposition of isopropanol. Below 673K, TPA on ZrO2exist as distorted intact Keggin species interacting with Zr–OH or Zr+groups. However, at 773K, bulk-like intact TPA species were detected. Above 773K, the Keggin structure of TPA collapse and transforms into WO3and phosphorous oxides. The characteristic diffraction peaks of TPA cannot be observed even with 20wt.% TPA loading, indicating a high dispersion or a very small crystal size of TPA, while 20wt.% TPA loaded on SiO2clearly shows the presence of TPA particles.The heat-treatment temperature affects the catalytic activity of TPA on Zirconia. The reaction rate was 3.3 times higher in a TPA/ZrO2calcined at 773 than that at 473K.