Synthesis of cerium-doped MCM-48 molecular sieves and its catalytic performance for selective oxidation of cyclohexane
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- 作者：Wangcheng ZHAN ; Guanzhong LU ; Yanglong GUO ; Yun GUO ; Yanqin WANG ; Yunsong WANG ; Zhigang ZHANG ; Xiaohui LIU
- 关键词：Ce-doped MCM-48 ; synthesis ; cyclohexane ; catalytic oxidation ; rare earths
- 刊名：Journal of Rare Earths
- 出版年：2008
- 出版时间：August 2008
- 年：2008
- 卷：26
- 期：4
- 页码：515-522
- 全文大小：891 K
文摘
Cerium-doped MCM-48 molecular sieves were synthesized hydrothermally and characterized by X-ray diffraction, nitrogen adsorption, transmission electron microscope, FT-IR spectroscopy, UV-visible spectroscopy, and Raman spectroscopy. The results showed that all the samples held the structure of MCM-48, and Ce could enter the framework of MCM-48. However, when Ce/Si molar ratio in the samples was high (0.04 or 0.059), there were CeO2 crystallites as secondary phase in the extraframework of MCM-48. Ce-doped MCM-48 was a very efficient catalyst for the oxidation of cyclohexane in a solvent-free system with oxygen as an oxidant. In the conditions of 0.5 MPa O2 and 413 K for 5 h, the conversion of cyclohexane was 8.1 % over Ce-MCM-48-0.02, the total selectivity of cyclohexanol and cyclohaxnone was 98.7 % . With an increase of Ce content, the conversion of cyclohexane and the selectivity to cyclohexanol decreased somewhat, but the selectivity to cyclohexanone increased.