PdZn intermetallic compounds (IMCs) have been extensively reported for acetylene semi‐hydrogenation due to unique geometric and electronic structure of isolated Pd sites. However, to achieve high ethylene selectivity at high conversion remains challenging. Here we show the promotional role of ceria in modifying the geometric and electronic structure of PdZn IMCs towards enhanced catalytic performance for acetylene semi‐hydrogenation. The Ce (0.1wt%) promoted Pd‐Zn‐Al catalyst shows by far the best catalytic performance among other Pd based catalysts in literature, maintaining high selectivity (>95%) and excellent stability (~130 h) at high acetylene conversion (~ 90%). Using in situ spectroscopic techniques, the geometric and electronic effects of CeOx promotor were clearly elucidated. At low Ce content, the presence of highly dispersed Ce3+ species in the periphery of PdZn alloys enhanced electronic metal‐oxide interaction, resulting in electron‐rich Pd sites that promote hydrogen dissociation and ethylene desorption, and account for the outstanding catalytic performance. At high Ce content, the formation of bulk‐phase CeO2 suppressed the PdHx formation during PdZn alloying and led to phase separation yielding highly dispersed Pd ensembles, consequently lowering ethylene selectivity. Our results provide a new route for the design of PdZn catalyst by applying rare earth promoters towards high‐performance acetylene semi‐hydrogenation.

中文翻译：

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二氧化铈对 PdZn 催化剂增强乙炔半加氢反应的几何和电子效应

由于孤立的 Pd 位点独特的几何和电子结构，PdZn 金属间化合物（IMC）已被广泛报道用于乙炔半氢化。然而，在高转化率下实现高乙烯选择性仍然具有挑战性。在这里，我们展示了二氧化铈在改变 PdZn IMC 的几何和电子结构以增强乙炔半加氢催化性能方面的促进作用。 Ce (0.1wt%) 促进的 Pd-Zn-Al 催化剂显示出迄今为止文献中其他 Pd 基催化剂中最好的催化性能，在高乙炔转化率下保持高选择性 (>95%) 和优异的稳定性 (~130 h) ( 〜90%）。利用原位光谱技术，CeOx 促进剂的几何和电子效应得到了清晰的阐明。在低 Ce 含量下，PdZn 合金外围存在高度分散的 Ce3+ 物质，增强了电子金属氧化物相互作用，产生富电子的 Pd 位点，促进氢离解和乙烯解吸，并具有出色的催化性能。在高 Ce 含量下，体相 CeO2 的形成抑制了 PdZn 合金化过程中 PdHx 的形成，并导致相分离，产生高度分散的 Pd 集合体，从而降低了乙烯选择性。我们的研究结果为应用稀土助剂实现高性能乙炔半加氢的 PdZn 催化剂设计提供了一条新途径。