Heterogeneous catalysts are of considerable interest for their ability to produce gases with highly polarized nuclear spins by using parahydrogen. Rh catalysts are known for producing pronounced parahydrogen-induced polarization (PHIP) effects. This study illustrates that modification of Rh with In promotes the electronic/chemical state of Rh offering the new Rh–In bimetallic catalyst, which is more efficient in such processes compared to monometallic Rh. Both catalysts were tested in hydrogenations of propyne and propylene. We associate the 50-fold higher activity of Rh–In/SiO₂ in pairwise hydrogen addition compared to monometallic Rh/SiO₂ with the formation of the intermetallic Rh–In compound, which was confirmed by X-ray photoelectron spectroscopy and X-ray diffraction analysis. Intermetallic Rh–In/SiO₂ provided an ∼1400-fold NMR signal enhancement for propylene in propyne hydrogenation. It was also demonstrated that the activity of Rh–In/SiO₂ can be tuned by controlling the reductive/oxidative pretreatment.

中文翻译：

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用于仲氢诱导极化的铑基金属间化合物 Rh-In/SiO2 催化剂

非均相催化剂因其能够利用仲氢产生具有高度极化核自旋的气体而引起人们极大的兴趣。 Rh 催化剂因产生显着的仲氢诱导极化 (PHIP) 效应而闻名。这项研究表明，用 In 修饰 Rh 可以促进 Rh 的电子/化学态，从而提供新型 Rh-In 双金属催化剂，与单金属 Rh 相比，该催化剂在此类过程中效率更高。两种催化剂均在丙炔和丙烯的加氢中进行了测试。我们将Rh-In/SiO ₂成对氢加成活性比单金属Rh/SiO ₂高50倍与金属间化合物Rh-In化合物的形成联系起来，这通过X射线光电子能谱和X射线证实衍射分析。金属间化合物Rh-In/SiO ₂在丙炔加氢中使丙烯的NMR信号增强了约1400倍。还证明了Rh-In/SiO ₂的活性可以通过控制还原/氧化预处理来调节。