苯炔与对氢的异质加氢：超极化，反应选择性和动力学。,Physical Chemistry Chemical Physics

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苯炔与对氢的异质加氢：超极化，反应选择性和动力学。
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2019-11-20 , DOI: 10.1039/c9cp02913c
Ekaterina V Pokochueva ₁ , Kirill V Kovtunov , Oleg G Salnikov , Max E Gemeinhardt , Larisa M Kovtunova , Valerii I Bukhtiyarov , Eduard Y Chekmenev , Boyd M Goodson , Igor V Koptyug

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对氢诱导极化（PHIP）是研究气相和液相氢化反应的一项强大技术。将对氢成对添加至氢化底物可赋予反应产物核自旋顺序，表现为来自新生质子位点的增强的¹ H NMR信号。固定在载体上的纳米级金属催化剂包括产生PHIP效果的一类有前途的催化剂。然而，在这种催化剂上，经历成对加成路线的底物百分数（观察PHIP的必要条件）通常很低。在本文中，我们对负载在TiO ₂上的几种金属催化剂（Rh，Pt，Pd和Ir）进行了系统的研究。在不同的原型苯基炔烃（苯乙炔，1-苯基-1-丙炔和3-苯基-1-丙炔）与对氢的液相加氢反应中发现催化剂活性和选择性受活性金属的性质和金属负载百分比的影响。已证明，用于生产超极化产物的最佳催化剂是具有4 wt％金属负载的Rh / TiO ₂，而Pd / TiO ₂为苯基炔烃的半氢化提供了最大的选择性。在液相加氢反应动力学研究中，研究表明，成对的和非成对的H ₂相对于氢的反应顺序几乎相同另外-与这些反应途径的催化活性位点的相似性质一致。

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Heterogeneous hydrogenation of phenylalkynes with parahydrogen: hyperpolarization, reaction selectivity, and kinetics.

Parahydrogen-induced polarization (PHIP) is a powerful technique for studying hydrogenation reactions in gas and liquid phases. Pairwise addition of parahydrogen to the hydrogenation substrate imparts nuclear spin order to reaction products, manifested as enhanced ¹H NMR signals from the nascent proton sites. Nanoscale metal catalysts immobilized on supports comprise a promising class of catalysts for producing PHIP effects; however, on such catalysts the percentage of substrates undergoing the pairwise addition route—a necessary condition for observing PHIP—is usually low. In this paper, we present a systematic study of several metal catalysts (Rh, Pt, Pd, and Ir) supported on TiO₂ in liquid-phase hydrogenation of different prototypical phenylalkynes (phenylacetylene, 1-phenyl-1-propyne, and 3-phenyl-1-propyne) with parahydrogen. Catalyst activity and selectivity were found to be affected by both the nature of the active metal and the percentage of metal loading. It was demonstrated that the optimal catalyst for production of hyperpolarized products is Rh/TiO₂ with 4 wt% metal loading, whereas Pd/TiO₂ provided the greatest selectivity for semihydrogenation of phenylalkynes. In a study of liquid-phase hydrogenation reaction kinetics, it was shown that reaction order with respect to hydrogen is nearly the same for pairwise and non-pairwise H₂ addition—consistent with a similar nature of the catalytically active sites for these reaction pathways.

更新日期：2019-11-20

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