Preparation of ordered mesoporous alumina and its catalytic application in metathesis of butene
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摘要: 采用有机铝源及阴离子模板剂制备了高比表面积、大孔容、窄孔径分布的有序介孔氧化铝(Al2O3)载体, 研究了铝源水解速率、模板剂碳链长度以及洗涤介质等因素对有序介孔氧化铝载体合成的影响。实验结果表明,提高铝源水解速率和用乙醇溶剂洗涤Al2O3前躯体都有利于Al2O3载体形成有序介孔结构,所得Al2O3载体的孔径和孔体积随着模板剂碳链长度的增加而增大。分别用有序介孔Al2O3和普通介孔Al2O3为载体,采用浸渍法负载氧化铼(Re2O7)制备了铼基催化剂,并用于评价丁烯歧化合成丙烯的反应性能。实验结果表明,铼基有序介孔催化剂(Re/OMA)的丁烯歧化性能显著优于普通铼基介孔催化剂(Re/MA),丁烯转化率高于50%,丙烯选择性约60%,丙烯收率达30%,催化剂寿命明显延长。Abstract: Ordered mesoporous alumina (OMA) with high surface area, large pore volume, and narrow pore-size distribution was synthesized from organic aluminum precursors and anionic templates; the influence of various preparation parameters such as hydrolysis speed of the aluminum precursor, chain length of the carboxylic templates and washing medium on the properties of as-synthesized OMA was investigated. With OMA as support, rhenium-based catalyst was prepared by incipient-wetness impregnation method and used in the metathesis of butene to propene. The results showed that increasing hydrolysis speed of the aluminum precursor as well as using ethanol as the washing medium are beneficial to the formation of the organized pore structure; the pore volume and pore diameter of as-synthesized OMA increase with an increase of the chain length of the carboxylic templates used here. Compared with the rhenium catalyst supported on conventional mesoporous alumina, the rhenium-based catalyst prepared with OMA as the support exhibits better performance in the metathesis of butane, i.e. higher selectivity to propene and longer catalytic life; the conversion of butane and selectivity to propene reach 50% and 60%, respectively.
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Key words:
- ordered mesoporous alumina /
- rhenium catalyst /
- butene metathesis /
- propene
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