Wolfson Catalysis Centre, Department of Chemistry, University of Oxford, Oxford, UK OX1 3QR.
Phys Chem Chem Phys. 2011 Feb 21;13(7):2590-602. doi: 10.1039/c0cp01832e. Epub 2011 Jan 7.
It is reported that catalytic hydrogenation of cinnamaldehyde to cinnamyl alcohol is a structural sensitive reaction dependent on size and type of metal doper of unsupported platinum nanocrystals used. Smaller sizes of platinum nanocrystals are found to give lower selectivity to cinnamyl alcohol, which suggests the high index Pt sites are undesirable for the terminal aldehyde hydrogenation. A plot of reaction selectivity across the first row of transition metals as dopers gives a typical volcano shape curve, the apex of which depicts that a small level of cobalt on platinum nanocrystals can greatly promote the reaction selectivity. The selectivity towards cinnamyl alcohol over the cobalt doped Pt nanocrystals can reach over 99.7%, following the optimization in reaction conditions such as temperature, pressure and substrate concentration. Detailed studies of XRD, CO chemisorption (for FTIR), TEM, SEM, AES and XPS of the nanostructure catalyst clearly reveal that the decorated cobalt atoms not only block the high index sites of Pt nanocrystals (sites for Co deposition) but also exert a strong electronic influence on reaction pathways. The d-band centre theory is invoked to explain the volcano plot of selectivity versus metal doper.
据报道，肉桂醛催化加氢制备肉桂醇是一个结构敏感反应，取决于所使用的未负载的铂纳米晶中金属掺杂剂的尺寸和类型。较小尺寸的铂纳米晶表现出较低的肉桂醇选择性，这表明高指数 Pt 位对于末端醛加氢是不利的。通过对过渡金属作为掺杂剂的第一行进行反应选择性作图，可以得到一个典型的火山形曲线，曲线的顶点表明，铂纳米晶上少量的钴可以极大地促进反应选择性。在优化反应条件（如温度、压力和底物浓度）后，钴掺杂铂纳米晶对肉桂醇的选择性可达到 99.7%以上。对纳米结构催化剂的 XRD、CO 化学吸附（用于 FTIR）、TEM、SEM、AES 和 XPS 的详细研究清楚地表明，修饰的钴原子不仅可以阻止铂纳米晶的高指数位（Co 沉积位），而且对反应途径施加强烈的电子影响。d 带中心理论被用来解释选择性与金属掺杂剂的火山形图。
