形状可控的Pd纳米粒子上的乙炔低聚：对氢诱导的极化研究,The Journal of Physical Chemistry C

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形状可控的Pd纳米粒子上的乙炔低聚：对氢诱导的极化研究
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2016-02-26 00:00:00 , DOI: 10.1021/acs.jpcc.5b12391
Vladimir V. Zhivonitko _{1,

2} , Ivan V. Skovpin _{1,

2} , Micaela Crespo-Quesada ₃ , Lioubov Kiwi-Minsker _{3,

4} , Igor V. Koptyug _{1,

2}

Affiliation

通过在催化氢化中使用对氢实现的大量信号增强，是涉及分子H ₂的化学反应机理研究的有力工具。潜在地，该技术可以扩展到其他反应类别，从而提供有关反应机理的新信息。此外，这可能导致新物质具有高度极化的自旋。在本文中，我们报告了乙炔在SiO ₂上负载的不同形状和尺寸的Pd纳米颗粒上进行乙炔的选择性加氢过程中观察到的低聚反应产物的强烈信号增强。C4低聚产物（1,3-丁二烯，1-丁烯，2-丁烯）表现出高度的核自旋极化，其中观察到的最高程度为1-丁烯[大于1.7％，相对于（2.4×10 ^–3）％（在热平衡时），它比三键C-C键的加氢产物大一个数量级。没有观察到极化对金属表面统计的依赖性，或者通常对纳米颗粒形态（立方，八面体，立方八面体）的依赖性。相反，颗粒大小的影响使得较大的颗粒提供了更高的信号增强。该观察结果与在相同催化剂上乙炔加氢过程中观察到的较大的Pd纳米颗粒的活性增加相符。

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Acetylene Oligomerization over Pd Nanoparticles with Controlled Shape: A Parahydrogen-Induced Polarization Study

Substantial signal enhancements achieved by using parahydrogen in catalytic hydrogenations are powerful tools for mechanistic studies of chemical reactions involving molecular H₂. Potentially, this technique can be extended to other reaction classes, providing new information about reaction mechanisms. Moreover, this can lead to new substances with highly polarized spins. Herein, we report strong signal enhancements of oligomerization reaction products observed during the selective hydrogenation of acetylene over Pd nanoparticles of different shapes and sizes supported on SiO₂. C4 oligomeric products (1,3-butadiene, 1-butene, 2-butene) demonstrated a high degree of nuclear spin polarization, with the highest degree observed for 1-butene [more than 1.7% vs (2.4 × 10^–3)% at thermal equilibrium], which was an order of magnitude larger than that of the triple C—C bond hydrogenation products. No dependence of polarization on the metal surface statistics or, generally, on the nanoparticle morphology (cubic, octahedral, cuboctahedral) could be observed. In contrast, the particle size effect was such that larger particles provided higher signal enhancements. This observation is in line with the increased activity over larger Pd nanoparticles observed during acetylene hydrogenation over the same catalysts.

更新日期：2016-02-26

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