Li Bing-Bing, Ma Hong-Yan, Wang Gui-Chang
Tianjin RenAi College, Tianjin 301636, China.
Frontiers Science Center for New Organic Matter, Tianjin Key Lab and Molecule-Based Material Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China.
Langmuir. 2024 Sep 10;40(36):19043-19050. doi: 10.1021/acs.langmuir.4c02092. Epub 2024 Aug 28.
Acetylene semihydrogenation is an important process both theoretically and experimentally. Pure Pd catalysts usually suffer from limited selectivity for ethylene products and poor stability. Pd-Bi bimetallic compounds are synthesized and show not only excellent catalytic performance but also remarkable long-term stability. However, the detailed mechanism is still unclear. In this paper, the acetylene semihydrogenation mechanism on Pd(100), PdBi(100), and PdBi(100) is studied by density functional theory (DFT) calculation and microkinetic modeling. Adding Bi causes the surface d-band center (ε) to move to a lower energy, and the adsorption strength of the intermediate becomes weaker. Besides, ethylidyne (CCH) formation becomes more difficult on the Pd-Bi alloy due to the lack of continuous surface Pd atoms. As a spectator, CCH deactivates the Pd and Pd-Bi alloys by a steric effect. However, the selectivity for ethylene on the Pd-Bi alloy is still high because of the weakly bonded ethylene. We found the relationship between ε and the catalysts' activity and selectivity. This study may supply some clues for the design of selective hydrogenation catalysts.
乙炔半加氢在理论和实验方面都是一个重要的过程。纯钯催化剂通常对乙烯产物的选择性有限且稳定性较差。合成的钯 - 铋双金属化合物不仅表现出优异的催化性能，而且具有显著的长期稳定性。然而，其详细机理仍不清楚。本文通过密度泛函理论（DFT）计算和微观动力学建模研究了乙炔在Pd(100)、PdBi(100)和PdBi(100)上的半加氢机理。添加铋会使表面d带中心（ε）向较低能量移动，中间体的吸附强度变弱。此外，由于缺乏连续的表面钯原子，在钯 - 铋合金上亚乙基（CCH）的形成变得更加困难。作为旁观者，CCH通过空间效应使钯和钯 - 铋合金失活。然而，由于乙烯的弱键合，钯 - 铋合金对乙烯的选择性仍然很高。我们发现了ε与催化剂活性和选择性之间的关系。该研究可能为选择性加氢催化剂的设计提供一些线索。
