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Ce1−xCrxO2−δ Nanocrystals as Efficient Catalysts for the Selective Oxidation of Cyclohexane to KA Oil at Low Temperature under Ambient Pressure
ChemCatChem ( IF 4.5 ) Pub Date : 2018-02-19 , DOI: 10.1002/cctc.201701762
Xiubing Huang 1 , Guixia Zhao 2 , Peng Wang 1 , Haiyan Zheng 1 , Wenjun Dong 1 , Ge Wang 1
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The selective oxidation of C−H bonds in saturated hydrocarbons at low temperature with noble‐metal‐free heterogeneous catalysts is a profound challenge for the catalysis community. Here we report the facile synthesis of Ce1−xCrxO2−δ (x=0, 0.1, 0.2, 0.3, and 0.4) nanocrystals through a low‐temperature hydrothermal method. The catalytic activity of the as‐prepared catalysts was evaluated in the selective oxidation of cyclohexane to cyclohexanone/cyclohexanol using H2O2 as an oxidant at room temperature and 45 °C. The activity results were correlated with their phase structure, composition, surface areas, and surface element states with the help of X‐ray diffraction, N2 adsorption, transmission electron microscopy, X‐ray photoelectron spectroscopy, and UV/Vis spectroscopy. It was found that these Ce0.7Cr0.3O2−δ nanocrystals are highly active for the selective oxidation of cyclohexane to cyclohexanone/cyclohexanol using H2O2 as an oxidant at low temperature. In the presence of H2O2 at 45 °C for 5 h using Ce0.7Cr0.3O2−δ as a catalyst, the conversion of cyclohexane reaches 50.3 % and the total selectivity of cyclohexanol/cyclohexanone is 94.4 % with relative good reversibility for at least four cycles. Mechanistic investigation results show that the high activity can be attributed to the high Cr6+ content in the Ce1−xCrxO2−δ solid solutions and the formation of highly oxidative intermediates with H2O2.

中文翻译:

Ce1-xCrxO2-δ纳米晶体作为环境温度下低温下环己烷选择性氧化为KA油的高效催化剂

在低温下,使用不含贵金属的非均相催化剂在饱和烃中对CH键的选择性氧化是催化领域的一项严峻挑战。这里,我们报告Ce的简便合成1- X的Cr X ø 2- δX = 0,0.1,0.2,0.3和0.4)通过低温水热法的纳米晶体。在使用H 2 O 2将环己烷选择性氧化为环己酮/环己醇的过程中,评估了所制备催化剂的催化活性。在室温和45°C下用作氧化剂。借助X射线衍射,N 2吸附,透射电子显微镜,X射线光电子能谱和UV / Vis能谱,将活性结果与其相结构,组成,表面积和表面元素状态相关联。已发现这些Ce 0.7 Cr 0.3 O 2- δ纳米晶体对于在低温下以H 2 O 2为氧化剂将环己烷选择性氧化为环己酮/环己醇具有很高的活性。在H 2 O 2的存在下,在45°C下使用Ce 0.7 Cr 0.3 O 2−进行5 h以δ作为催化剂,环己烷的转化率达到50.3%,环己醇/环己酮的总选择性为94.4%,并且至少四个循环具有相对良好的可逆性。机理研究结果表明,高活性归因于Ce 1− x Cr x O 2− δ固溶体中的高Cr 6+含量以及与H 2 O 2形成的高氧化性中间体。
更新日期:2018-02-19
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