Rötzer Marian D, Krause Maximilian, Hinke Tobias, Bertrang Kevin, Schweinberger Florian F, Crampton Andrew S, Heiz Ueli
Technical University of Munich, TUM School of Natural Sciences, Chair of Physical Chemistry, Catalysis Research Center, Lichtenbergstrasse 4, Garching bei München, Germany.
Phys Chem Chem Phys. 2024 May 8;26(18):13740-13750. doi: 10.1039/d4cp00719k.
The selective hydrogenation of acetylene catalyzed by Pd nanoparticles is industrially used to increase the purity of ethylene. Despite the implementation of Pd based catalysts on an industrial scale, little is known about metal-support interactions on a fundamental level due to the complexity of these systems. In this study, the influence of metal-support interactions between Pd nanoparticles and two electronically modified a-SiO thin films on acetylene hydrogenation is investigated under ultra-high vacuum (UHV) conditions. The hydrogenation is performed under isothermal reaction conditions using a pulsed molecular beam reactive scattering (pMBRS) technique. Besides the activity and selectivity of clean Pd particles also the impact of dehydrogenated species intentionally introduced is elucidated, whereas the active phase of the catalyst is additionally characterized by CO infrared reflection-absorption spectroscopy (IRRAS) and temperature-programmed reaction (TPR). Metal-support interactions are found to influence the catalytic properties of Pd particles by charge-transfer, where positive charging leads to increased activity for acetylene hydrogenation. However, the increased activity is accompanied by formation of undesired byproducts. The active sites for acetylene and ethylene hydrogenation are shown to be different as previously proposed by the A and E model. The availability of the two different active sites on the Pd nanoparticles is determined by dehydrogenated species, whose nature and stability can be tuned by metal-support interactions. Based on these findings an electronic model is proposed how selectivity for acetylene hydrogenation can be steered solely by metal-support interactions leading to blocking of unselective sites .
钯纳米颗粒催化乙炔选择性加氢在工业上用于提高乙烯纯度。尽管钯基催化剂已在工业规模上得到应用，但由于这些体系的复杂性，在基础层面上对金属-载体相互作用仍知之甚少。在本研究中，在超高真空（UHV）条件下，研究了钯纳米颗粒与两种电子改性的a-SiO薄膜之间的金属-载体相互作用对乙炔加氢的影响。加氢反应在等温反应条件下采用脉冲分子束反应散射（pMBRS）技术进行。除了清洁钯颗粒的活性和选择性外，还阐明了有意引入的脱氢物种的影响，而催化剂的活性相则通过CO红外反射吸收光谱（IRRAS）和程序升温反应（TPR）进行了额外表征。发现金属-载体相互作用通过电荷转移影响钯颗粒的催化性能，正电荷导致乙炔加氢活性增加。然而，活性增加伴随着不需要的副产物的形成。如先前A和E模型所提出的，乙炔和乙烯加氢的活性位点是不同的。钯纳米颗粒上两种不同活性位点的可用性由脱氢物种决定，其性质和稳定性可通过金属-载体相互作用进行调节。基于这些发现，提出了一个电子模型，即如何仅通过金属-载体相互作用来控制乙炔加氢的选择性，从而导致非选择性位点的阻断。
