Liu Huizhen, Jiang Tao, Han Buxing, Liang Shuguang, Zhou Yinxi
Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Science. 2009 Nov 27;326(5957):1250-2. doi: 10.1126/science.1179713.
Cyclohexanone is an industrially important intermediate in the synthesis of materials such as nylon, but preparing it efficiently through direct hydrogenation of phenol is hindered by over-reduction to cyclohexanol. Here we report that a previously unappreciated combination of two common commercial catalysts-nanoparticulate palladium (supported on carbon, alumina, or NaY zeolite) and a Lewis acid such as AlCl3-synergistically promotes this reaction. Conversion exceeding 99.9% was achieved with >99.9% selectivity within 7 hours at 1.0-megapascal hydrogen pressure and 50 degrees C. The reaction was accelerated at higher temperature or in a compressed CO(2) solvent medium. Preliminary kinetic and spectroscopic studies suggest that the Lewis acid sequentially enhances the hydrogenation of phenol to cyclohexanone and then inhibits further hydrogenation of the ketone.
环己酮是合成尼龙等材料过程中一种具有重要工业价值的中间体，但通过苯酚直接加氢高效制备环己酮会因过度还原为环己醇而受阻。在此我们报告，两种常见商业催化剂——纳米颗粒钯（负载于碳、氧化铝或NaY沸石上）和路易斯酸（如AlCl3）——的一种此前未被重视的组合能协同促进该反应。在1.0兆帕氢气压力和50摄氏度下，7小时内转化率超过99.9%，选择性大于99.9%。在更高温度或压缩CO(2)溶剂介质中反应会加速。初步的动力学和光谱研究表明，路易斯酸依次增强苯酚加氢生成环己酮的反应，然后抑制酮的进一步加氢。
