Ligand-Coordination Effects on the Selective Hydrogenation of Acetylene in Single-site Pd-Ligand Supported Catalysts
Ligand-Coordination Effects on the Selective Hydrogenation of Acetylene in Single-site Pd-Ligand Supported Catalysts
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DOI：
10.1016/j.jcat.2022.06.010
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发表时间：
2022-06
影响因子：
7.3
通讯作者：
Eman Wasim;Naseem Ud Din;Duy Le;Xuemei Zhou;G. Sterbinsky;Michael S. Pape;T. Rahman;S. Tait
中科院分区：
文献类型：
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作者：
Eman Wasim;Naseem Ud Din;Duy Le;Xuemei Zhou;G. Sterbinsky;Michael S. Pape;T. Rahman;S. Tait
乙炔选择加氢制乙烯是合成聚乙烯的关键步骤。实现乙烯的高转化率而不过度氢化为乙烷是一项挑战，需要控制过渡金属位点，我们通过配体配位的负载型催化剂（LCSC）策略实现这一目标。采用CeO 2载体上的1，10-菲咯啉-5，6-二酮（PDO）配体配位的Pd催化剂，我们发现反应的选择性强烈依赖于配体与金属的比例，当催化剂中存在更多的配体时，选择性更高。通过扩展X射线吸收精细结构谱、透射电子显微镜和CO吸附研究了催化剂结构，表明Pd具有单原子特征。通过X射线光电子能谱测量确定配体：金属比，并在稳态流动条件下与氢化反应相关，以检查氢化活性和选择性的趋势。这些趋势可以通过密度泛函理论计算更好地理解，该计算表明配体上的氢结合以引导反应选择性朝向所需的乙烯氢化产物。这些结果表明，考虑LCSC的动态特性的重要性，并通知未来的单中心多相催化剂的设计。
The selective hydrogenation of acetylene to ethylene is a critical step in the synthesis of polyethylenes. Achieving high conversion to ethylene without over-hydrogenation to ethane is a challenge that requires control of the transition metal site, which we achieve through a ligand-coordinated supported catalyst (LCSC) strategy. Using Pd catalysts coordinated to 1,10-phenanthroline-5,6-dione (PDO) ligands on CeO2supports, we have discovered that the reaction selectivity depends strongly on the ligand:metal ratio with higher selectivity when more ligand is present in the catalyst. Catalyst structure was examined by extended X-ray absorption fine structure spectroscopy, transmission electron microscopy, and CO adsorption, which indicate single-atom character of the Pd. The ligand:metal ratio is determined by X-ray photoelectron spectroscopy measurements and correlated with hydrogenation reactions under steady-state flow conditions to examine trends in hydrogenation activity and selectivity. Those trends can be better understood by density functional theory calculations that indicate hydrogen binding on the ligand to guide reaction selectivity toward the desired ethylene hydrogenation product. These results demonstrate the importance of considering the dynamic character of LCSCs and inform the design of future single-site heterogeneous catalysts.