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首页> 外文期刊>Chemistry: A European journal >Surface Chemistry on Small Ruthenium Nanoparticles: Evidence for Site Selective Reactions and Influence of Ligands
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Surface Chemistry on Small Ruthenium Nanoparticles: Evidence for Site Selective Reactions and Influence of Ligands

机译：小型钌纳米粒子的表面化学：位置选择反应和配体影响的证据

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摘要

The reactivity of two classes of ruthenium nanoparticles (Ru NPs) of small size, either sterically stabilized by a polymer (polyvinylpyrrolidone, PVP) or electronically stabilized by a ligand (bisdiphenylphosphinobutane, dppb) was tested towards standard reactions, namely CO oxidation, CO_2 reduction and styrene hydrogenation. The aim of the work was to identify the sites of reactivity on the nanoparticles and to study how the presence of ancillary ligands can influence the course of these catalytic reactions by using NMR and IR spectroscopies. It was found that CO oxidation proceeds at room temperature (RT) on Ru NPs but that the system deactivates rapidly in the absence of ligands because of the formation of RuO2. In the presence of ligands, the reaction involves exclusively the bridging CO groups and no bulk oxidation is observed at RT under catalytic conditions. The reverse reaction, CO_2 reduction, is achieved at 120 8C in the presence of H2 and leads to CO, which coordinates exclusively in a bridging mode, hence evidencing the competition between hydrides and CO for coordination on Ru NPs. The effect of ligands localized on the surface is also evidenced in catalytic reactions. Thus, styrene is slowly hydrogenated at RT by the two systems Ru/PVP and Ru/dppb, first into ethylbenzene and then into ethylcyclohexane. Selectively poisoning the nanoparticles with bridging CO groups leads to catalysts that are only able to reduce the vinyl group of styrene whereas a full poisoning with both terminal and bridging CO groups leads to inactive catalysts. These results are interpreted in terms of location of the ligands on the particles surface, and evidence site selectivity for both CO oxidation and arene hydrogenation.
机译：测试了两类小尺寸的钌纳米粒子（Ru NPs）的反应性，该反应通过聚合物（聚乙烯吡咯烷酮，PVP）空间稳定或通过配体（双二苯基膦基丁烷，dppb）电子稳定，以进行标准反应，即CO氧化，CO_2还原和苯乙烯加氢。这项工作的目的是通过NMR和IR光谱法确定纳米颗粒上的反应位点，并研究辅助配体的存在如何影响这些催化反应的过程。发现在室温下，Ru NPs上会发生CO氧化，但是由于RuO2的形成，该体系在不存在配体的情况下会迅速失活。在配体存在下，该反应仅涉及桥连的CO基团，并且在RT在催化条件下未观察到本体氧化。在H 2存在下于120 8 C达到逆反应，即CO_2还原，生成的CO仅以桥联模式进行配位，因此证明了氢化物和CO之间在Ru NPs配位上的竞争。催化反应中也证实了位于表面上的配体的作用。因此，苯乙烯在室温下通过两种体系Ru / PVP和Ru / dppb缓慢氢化，首先变成乙苯，然后变成乙基环己烷。用桥连的CO基团选择性中毒纳米颗粒导致催化剂只能还原苯乙烯的乙烯基，而同时用末端和桥连的CO基团完全中毒导致催化剂失活。这些结果是根据配体在颗粒表面上的位置以及对CO氧化和芳烃氢化的选择性位点进行解释的。

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