Xia Yunsheng, Dai Hongxing, Jiang Haiyan, Deng Jiguang, He Hong, Au Chak Tong
Laboratory of Catalysis Chemistry and Nanoscience, Department of Chemistry and Chemical Engineering, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, China.
Environ Sci Technol. 2009 Nov 1;43(21):8355-60. doi: 10.1021/es901908k.
Mesoporous chromia with ordered three-dimensional (3D) hexagonal polycrystalline structures were fabricated at 130, 180, 240, 280, and 350 degrees C in an autoclave through a novel solvent-free route using KIT-6 as the hard template. The as-obtained materials were characterized (by means of X-ray diffraction, transmission electron microscopy, N(2) adsorption-desorption, temperature-programmed reduction, and X-ray photoelectron spectroscopy techniques) and tested as a catalyst for the complete oxidation of toluene and ethyl acetate. We found that with a high surface area of 106 m(2)/g and being multivalent (Cr(3+), Cr(5+), and Cr(6+)), the chromia (meso-Cr-240) fabricated at 240 degrees C is the best among the five in catalytic performance. According to the results of the temperature-programmed reduction and X-ray photoelectron spectroscopy investigations, it is apparent that the coexistence of multiple chromium species promotes the low-temperature reducibility of chromia. The excellent performance of meso-Cr-240 is because of good 3D mesoporosity and low-temperature reducibility as well as the high surface area of the chromia. The combustion follows a first-order reaction with respect to toluene or ethyl acetate in the presence of excess oxygen, and the corresponding average activation energy is 79.8 and 51.9 kJ/mol, respectively, over the best-performing catalyst.
以KIT-6为硬模板，通过一种新型无溶剂路线，在高压釜中于130、180、240、280和350摄氏度制备了具有有序三维（3D）六方多晶结构的介孔氧化铬。对所得材料进行了表征（采用X射线衍射、透射电子显微镜、N₂吸附-脱附、程序升温还原和X射线光电子能谱技术），并测试了其作为甲苯和乙酸乙酯完全氧化催化剂的性能。我们发现，在240摄氏度制备的氧化铬（介孔Cr-240）具有106 m²/g的高比表面积且为多价态（Cr³⁺、Cr⁵⁺和Cr⁶⁺），在这五种材料中催化性能最佳。根据程序升温还原和X射线光电子能谱研究结果，显然多种铬物种的共存促进了氧化铬的低温还原性。介孔Cr-240的优异性能归因于良好的3D介孔结构、低温还原性以及氧化铬的高比表面积。在过量氧气存在下，燃烧反应对甲苯或乙酸乙酯遵循一级反应，在性能最佳的催化剂上，相应的平均活化能分别为79.8和51.9 kJ/mol。
