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首页> 外文期刊>Catalysis science & technology >Catalytic properties of copper-manganese mixed oxides prepared by coprecipitation using tetramethylammonium hydroxide
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Catalytic properties of copper-manganese mixed oxides prepared by coprecipitation using tetramethylammonium hydroxide

机译：使用氢氧化四甲基铵制备制备的铜 - 曼加纳混合氧化物的催化特性

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摘要

Copper-manganese (Cu-Mn) mixed oxide catalysts were prepared by a coprecipitation technique from metal nitrates in aqueous solution using tetramethylammonium hydroxide (TMAH) as a pH regulator. The structures and properties of the mixed oxide catalysts were investigated by X-ray diffraction, extended X-ray absorption fine structure. X-ray photoelectron spectroscopy and H2-TPR studies. Spinel-type mixed oxides were mainly formed in the Cu-Mn mixed oxides in which Cu and Mn species occupied both tetra-hedrally and octahedrally coordinated sites. The occupancy of Cu and Mn in these sites depended on the Cu/Mn ratio. The average oxidation state of Cu was evaluated to be 2+ and was almost independent of the Cu/Mn ratio; reduced Cu species were also formed on the surface sites. By incorporation of Cu into Mn oxides, the average oxidation state of Mn increased.both in the bulk sites and on the surface sites. The concentration of Mn on the surface sites was higher than that in the bulk sites. The Cu-Mn mixed catalysts exhibited higher activity than corresponding single-metal oxides at the reaction temperature range of 343-403 K. Formation of Cu-Mn spinel-type oxides gave rise to the increase in the catalyst surface area and the rate for CO oxidation normalized by surface area, and the Cu-Mn mixed oxides with the Cu/Mn molar ratio of 1 exhibited the highest activity for CO oxidation. CO-TPR studies revealed that in the temperature range of 343-403 K, the lattice oxygen at the first layer of the mixed oxides reacted with CO to form CO2.
机译：通过使用氢氧化四甲基铵（TMAH）作为pH调节剂，通过从水溶液中的金属硝酸盐中制备了铜 - 甘油（CU-MN）混合氧化物催化剂。通过X射线衍射，扩展的X射线吸收精细结构研究了混合氧化物催化剂的结构和性能。 X射线光电子光谱和H2-TPR研究。尖晶石型混合氧化物主要形成在Cu-Mn混合氧化物中，其中Cu和Mn物种占据了四方和八面体配位的位点。这些位点中Cu和Mn的占用率取决于CU/MN比率。评估Cu的平均氧化状态为2+，几乎与Cu/Mn比率无关。在表面部位也形成了降低的Cu物种。通过将Cu掺入MN氧化物中，MN的平均氧化态在大体位点和表面位点上都增加。表面位点上MN的浓度高于大容量位点。 Cu-MN混合催化剂比在343-403 K的反应温度范围内表现出比相应的单金属氧化物的活性更高。形成Cu-Mn尖晶石型氧化物的形成导致催化剂表面积的增加和CO的速率增加通过表面积归一化的氧化，Cu-Mn混合氧化物具有1个摩尔比的氧化作用，表现出最高的CO氧化活性。联合研究研究表明，在343-403 K的温度范围内，混合氧化物的第一层的晶格氧与CO形成CO2的混合氧化物。

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