不同晶相结构二氧化锰催化完全氧化乙醇

采用水热合成法制备了α-MnO₂、β-MnO₂、γ-MnO₂和δ-MnO₂催化剂, 运用N₂吸脱附实验、X射线衍射(XRD)、X射线光电子能谱(XPS)和H₂程序升温还原(H₂-TPR)等方法对催化剂进行了表征, 并将催化剂用于催化完全氧化乙醇反应中, 考察了不同晶型MnO₂催化剂催化氧化乙醇活性的差异, 探讨了催化剂晶型结构与催化氧化活性的关联. 结果表明, 不同晶型的MnO₂催化剂催化氧化乙醇活性差异显著, 活性顺序为α-MnO₂>δ-MnO₂>γ-MnO₂>β-MnO₂. 系列表征结果显示, 晶体结晶度和比表面积不是影响不同晶型MnO₂催化剂活性的主要原因, α-MnO₂催化剂具有的较高晶格氧浓度和较高的可还原性是其具有良好催化氧化乙醇活性的关键因素.

Complete Catalytic Oxidation of Ethanol over MnO2 with Different Crystal Phase Structures

α-MnO₂, β-MnO₂, γ-MnO₂, and δ-MnO₂ catalysts were synthesized by hydrothermal methods, and their catalytic performances towards the oxidation of ethanol were evaluated in detail. The as-synthesized MnO₂ catalysts were characterized by N₂ adsorption- desorption measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and H₂ temperature-programmed reduction (H₂-TPR). The α-MnO₂ catalyst showed the best activity of the catalysts tested for the combustion of ethanol and the trend in the activity of different MnO₂ catalysts towards the oxidation of ethanol was of the order α-MnO₂>δ-MnO₂>γ-MnO₂>β-MnO₂. The effect of the crystal phase structure on the activity of the MnO₂ catalysts was investigated. The XRD results showed that there were differences in the crystallinities of the α-, β-, γ-, δ-MnO₂ catalysts, but these differences did not have a significant effect on their catalytic performances towards the oxidation of ethanol. The BET surface areas of the α-, β-, γ-, δ-MnO₂ catalysts exhibited similar tendencies to their ethanol oxidation activities, although the results of standardization calculations showed that the surface area was not the main factor affecting their catalytical activities. The XPS results showed that the lattice oxygen concentration played an important role in defining the catalytic performance of the MnO₂. The α-MnO₂ catalyst showed the best reducibility of all of the MnO₂ catalysts tested, as determined by H₂-TPR. The excellent performance of α-MnO₂ was attributed to its higher lattice oxygen concentration and reducibility, which were identified as the main factors affecting the activity of the MnO₂ towards the complete oxidation of ethanol.