Selective oxidation of benzene to phenol is done in the liquid phase over copper-substituted LaFeO3 perovskite oxides as catalyst using H2O2 as oxidant under mild reaction conditions. Among the different copper-substituted perovskite catalysts synthesized by a novel solution combustion method, the LaFe0.90Cu0.10O3 catalyst showed highest activity (∼56 % with 100 % selectivity of phenol) and also gives better activity than the corresponding catalyst made via incipient wetness impregnation of 10 at % Cu over combustion-synthesized LaFeO3. XRD analysis revealed formation of the perovskite phase as the predominant one. The greater activity of the combustion-made catalyst has been attributed to the occurrence of a peculiar poorly-defined structure having substitutional copper ion sites on top of the LaFeO3 particle as observed in HRTEM analysis. Much less occurrence of this phase in the impregnated catalyst, where copper is primarily present as dispersed CuO crystallites, explains its comparatively lower activity in the oxidation reaction. The effect of catalyst recycling shows negligible change of activity for the combustion-made catalyst whereas the analogous impregnated catalyst shows considerable decrease in activity in recycling. This explained to be due to the essentially intact poorly-defined structure in the former and leaching of the finely dispersed CuO crystallites from the latter catalyst during cycling.

中文翻译：

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以铜取代的 LaFeO3 钙钛矿氧化物为催化剂液相选择性氧化苯生成苯酚

通过铜取代的 LaFeO 在液相中将苯选择性氧化为苯酚3使用 H 的钙钛矿氧化物作为催化剂2氧2在温和的反应条件下作为氧化剂。在通过新型溶液燃烧方法合成的不同铜取代钙钛矿催化剂中，LaFe0.90铜0.10氧3催化剂表现出最高的活性（~56%，苯酚选择性为 100%），并且比通过燃烧合成的 LaFeO 上初湿浸渍 10 at% Cu 制备的相应催化剂具有更好的活性3。XRD 分析表明钙钛矿相的形成是主要的。燃烧制成的催化剂的较高活性归因于在 LaFeO 顶部出现了一种特殊的、定义不明确的结构，该结构具有取代的铜离子位点3HRTEM 分析中观察到的颗粒。在浸渍催化剂中，该相的出现要少得多，其中铜主要以分散的 CuO 微晶形式存在，这解释了其在氧化反应中的活性相对较低。催化剂回收的影响表明，燃烧制成的催化剂的活性变化可以忽略不计，而类似的浸渍催化剂在回收中的活性显着降低。这解释为由于前者基本完整的模糊结构以及循环过程中细分散的 CuO 微晶从后者催化剂中浸出。