The Reactivities of Polyaromatic Hydrocarbons in Catalytic Hydrogenation over Supported Noble Metals
作者:Kinya Sakanishi、Masato Ohira、Isao Mochida、Hiroshi Okazaki、Mahito Soeda
DOI:10.1246/bcsj.62.3994
日期:1989.12
The reactivities of several polyaromatic hydrocarbons (pyrene: P, fluoranthene: FL, anthracene: An, fluorene: F, acridine: Ac, and carbazole: C) in the catalytic hydrogenation were studied and compared over supported noble metals (Pt, Pd, Rh, and Ru on a carbon or alumina support). The specific reactivity and selectivity were found to be strongly dependent upon the combination of the catalyst species and the substrate. The catalysts exhibited the activity order of Rh > Pd >> Pt > Ru for tricyclic aromatics of An, F, Ac, and C, although the catalysts provided very variable selectivities of the partially hydrogenated products which were produced via both consecutive and competitive routes, apparently according to the type of ring-skeleton and the presence of a nitrogen atom. The reactivity of the starting substrates and intermediates are compared to the quantum chemical reactivity indices, calculated based on MNDO (modified neglect of diatomic overlap). The values of the LUMO electron density, the π-bond order, and the stability of the product appear to govern the reactivity and selectivity of the hydrogenation, depending upon the combination of the catalyst species and the substrate. No hydrogenation of a substrate proceeds when its reactivity indices are less than the threshold value, which is subject to the activity of the catalyst and the reaction conditions defining product selectivity via both competitive and consecutive schemes.
几种多芳烃(芘:P、氟蒽:FL、蒽:H)的反应活性P、荧蒽:FL、蒽:An、芴:Fluorene)的反应活性:An、芴F、吖啶Ac 和咔唑:在催化氢化过程中,研究并比较了支撑贵金属(碳或氧化铝支撑的铂、钯、铑和钌)的催化氢化作用。)研究发现,特定反应活性和选择性与催化剂种类和底物的组合密切相关。催化剂对 An、F、Ac 和 C 三环芳烃的活性顺序为 Rh > Pd >> Pt > Ru,但催化剂对通过连续和竞争路线产生的部分氢化产物的选择性差异很大,这显然与环骨架类型和氮原子的存在有关。起始底物和中间产物的反应性与量子化学反应性指数进行了比较,量子化学反应性指数是根据 MNDO(修正的二原子重叠忽略)计算得出的。LUMO 电子密度值、π 键顺序和产物的稳定性似乎决定了氢化反应的反应性和选择性,这取决于催化剂种类和底物的组合。当底物的反应性指数小于阈值时,底物不会发生氢化反应,而阈值则取决于催化剂的活性以及通过竞争和连续方案确定产物选择性的反应条件。