Furukawa Shinya, Yi Pingping, Kunisada Yuji, Shimizu Ken-Ichi
Institute for Catalysis, Hokkaido University, Sapporo, Japan.
Elementary Strategy Initiative for Catalysis and Battery, Kyoto University, Kyoto, Japan.
Sci Technol Adv Mater. 2019 Jul 11;20(1):805-812. doi: 10.1080/14686996.2019.1642139. eCollection 2019.
A series of Rh-based intermetallic compounds supported on silica was prepared and tested in alkene hydrogenation at room temperature. H and D were used as the hydrogen sources and the kinetic isotope effect (KIE) in hydrogenation was studied. In styrene hydrogenation, the KIE values differed strongly depending on the intermetallic phase, and some intermetallic compounds with Sb and Pb exhibited remarkably high KIE values (>28). An extraordinarily high KIE value of 91, which has never been reported in catalytic reactions at room temperature, was observed particularly for RhPb/SiO. RhPb/SiO also showed high KIE values in the hydrogenation of other unsaturated hydrocarbons such as phenylacetylene and cyclohexene. The density functional theory calculation focused on the surface diffusion of hydrogen suggested no contribution of the quantum tunneling effect to the high KIE values observed. A kinetic study revealed that the dissociative adsorption of H (D) was the rate-determining step in the styrene hydrogenation over RhPb/SiO. We propose that the large KIE originates from the quantum tunneling occurring at the hydrogen adsorption process with the aid of the specific surface structure of the intermetallic compound and adsorbate alkene.
制备了一系列负载在二氧化硅上的铑基金属间化合物，并在室温下的烯烃加氢反应中进行了测试。使用氢气（H）和氘气（D）作为氢源，研究了加氢反应中的动力学同位素效应（KIE）。在苯乙烯加氢反应中，KIE值因金属间相的不同而有很大差异，一些含锑（Sb）和铅（Pb）的金属间化合物表现出非常高的KIE值（>28）。特别对于RhPb/SiO₂，观察到了高达91的异常高的KIE值，这在室温催化反应中从未有过报道。RhPb/SiO₂在其他不饱和烃如苯乙炔和环己烯的加氢反应中也显示出高KIE值。基于氢表面扩散的密度泛函理论计算表明，量子隧穿效应并非导致所观察到的高KIE值的原因。动力学研究表明，H（D）的解离吸附是RhPb/SiO₂上苯乙烯加氢反应的速率决定步骤。我们认为，大的KIE值源于在金属间化合物和吸附烯烃的特定表面结构的辅助下，氢吸附过程中发生的量子隧穿。
