Abstract

Platinum catalysts prepared by incipient wetness impregnation of different supports (TiO₂, WO₃/TiO₂, CeO₂, Al₂O₃, zeolite ZSM-5) are tested in the ammonia oxidation reaction (TPR–NН₃+О₂) and characterized by a combination of physicochemical (powder XRD, TEM, XPS) and kinetic (TPR–H₂, TPD–NH₃) techniques. On the surface of all catalysts, platinum is present in the highly dispersed form (average particle size <1.5 nm), providing the activity for ammonia oxidation above 150 °C. In the temperature range 150-250 °C, the main oxidation products are nitrous oxide and molecular nitrogen whereas NO_x oxides start to form at T > 250 °C. The highest catalytic activity is observed when platinum is supported on TiO₂ promoted with tungsten. The introduction of tungsten modifies the acidity of the surface and affects the redox properties of platinum catalysts. The role of the support is found to be the stabilization of oxidized or reduced platinum forms on the surface, thus determining the total activity in the ammonia oxidation reaction.

中文翻译：

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负载性质对氨氧化铂催化剂理化性质的影响

摘要

通过不同载体（TiO ₂、WO ₃ /TiO ₂、CeO ₂、Al ₂ O ₃、沸石ZSM-5）的初湿浸渍制备的铂催化剂在氨氧化反应（TPR-NН ₃ +О ₂）和通过物理化学（粉末 XRD、TEM、XPS）和动力学（TPR–H ₂、TPD–NH ₃) 技术。在所有催化剂的表面，铂以高度分散的形式存在（平均粒径 <1.5 nm），在 150 °C 以上提供氨氧化活性。在 150-250 °C 的温度范围内，主要氧化产物是一氧化二氮和分子氮，而 NO _x氧化物在T  > 250 °C 时开始形成。当铂负载在用钨促进的TiO ₂上时，观察到最高的催化活性。钨的引入会改变表面的酸性并影响铂催化剂的氧化还原性能。发现载体的作用是稳定表面上氧化或还原的铂形式，从而确定氨氧化反应的总活性。