A series of nanocrystalline copper–manganese oxides (denoted as Cu_3−xMn_x, x = 0, 1, 1.5, 2, 2.5, 3, where x means the molar ratio of Cu and Mn) were successfully prepared by a facile citric acid sol–gel method. The combination of Cu²⁺ and Mn³⁺ is intensified and enhanced interface effects generated, which is beneficial for the catalytic oxidation of benzene. A series of analyses, such as X-Ray Diffraction (XRD), N₂ adsorption–desorption, X-ray photoelectron spectroscopy (XPS), and hydrogen temperature programmed reduction (H₂-TPR), were employed to further investigate the structural properties of the catalysts. An optimal Mn/Cu ratio of 2 forms CuMn₂O₄ spinels. CuMn₂ with CuMn₂O₄ spinel structure presents a larger specific surface area, smaller pore diameter as well as more lattice oxygen species, exhibiting remarkable activity and stability for the catalytic oxidation of benzene. On account of these factors, CuMn₂ possesses better low temperature reducibility and shows the best catalytic performance with 90% benzene conversion at 186 °C. The enhanced catalytic activity of CuMn₂ is attributed to the stabilization of CuMn₂O₄ active phases and the intensive synergistic effect between Cu–Mn oxides. To prove the effect of CuMn₂O₄ spinel structure on catalytic performance, a CuO/Mn₂O₃ mixed catalyst (molar ratio 1 : 1) was prepared and applied to benzene oxidation (T_90% = 198 °C), which indicates that the spinel structure has an encouraging effect on benzene catalysis. The catalytic properties of single copper oxide and manganese trioxide were also tested, the results show that CuMn₂O₄ has a crucial role in facilitating electronic transmission and mobility of the lattice oxygen.

中文翻译：

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溶胶-凝胶法合成纳米晶Cu-Mn复合氧化物上苯的低温催化氧化

通过简便的柠檬酸法成功制备了一系列纳米晶态的铜-锰氧化物（表示为Cu _{3- x} Mn _x，x = 0、1、1.5、2、2.5、3，其中x表示Cu和Mn的摩尔比）酸溶胶凝胶法。Cu ²⁺和Mn ^3+的结合被增强并产生增强的界面效应，这对于苯的催化氧化是有利的。一系列分析，例如X射线衍射（XRD），N ₂吸附-解吸，X射线光电子能谱（XPS）和氢程序升温还原（H ₂-TPR）被用于进一步研究催化剂的结构性质。Mn / Cu的最佳比例为2会形成CuMn ₂ O ₄尖晶石。的CuMn ₂与的CuMn ₂ ö ₄尖晶石结构呈现出较大的比表面积，更小的孔径以及多个晶格氧，表现出显着的活性和稳定性为苯的催化氧化。由于这些因素，CuMn ₂具有更好的低温还原性，并在186°C时具有90％的苯转化率表现出最佳的催化性能。CuMn _2的催化活性增强归因于CuMn ₂ O ₄的稳定活性相和Cu-Mn氧化物之间强烈的协同作用。为了证明CuMn ₂ O ₄尖晶石结构对催化性能的影响，制备了CuO / Mn ₂ O ₃混合催化剂（摩尔比为1：1），并用于苯氧化（T _90％ = 198°C），表明尖晶石结构对苯催化具有令人鼓舞的作用。还测试了单一氧化铜和三氧化锰的催化性能，结果表明CuMn ₂ O ₄在促进电子传输和晶格氧的迁移方面具有关键作用。