The acetylene hydration method to produce acetaldehyde has been widely used for over 130 years; however, a detailed molecular-level understanding of the reaction mechanism is still lacking. In the present work, we systematically investigated the mechanisms of such reactions on ZnCl₂, Zn(OH) Cl, and Zn(OH)₂ catalysts through density functional theory (DFT) methods. The Fukui function, condensed Fukui function, and Hirshfeld charges enabled us to predict the active sites of the catalysts and acquire electron transfer information. From these data, we found that catalysts bearing hydroxyl groups exhibited relatively low adsorption performances compared with catalysts without this functionality. The calculations demonstrated that the three studied catalysts had three distinct reaction paths. For the Zn(OH)Cl and Zn(OH)₂ catalysts, the reaction took place through a one-shift H₂O molecule transfer route, avoiding higher energy barrier pathways. Interestingly, we found that the energy required for breaking the O–H bond in water determined the activation energy of the studied catalytic reactions. The activation barrier increased in the order Zn(OH)Cl ≈ Zn(OH)₂ < ZnCl₂. This trend suggests that Zn(OH)Cl and Zn(OH)₂ are promising catalysts for the hydration of acetylene.

Graphical abstract

中文翻译：

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乙炔水合锌催化剂的密度泛函理论研究。

乙炔水合生产乙醛的方法已被广泛使用130多年。但是，仍然缺乏对反应机理的分子水平的详细了解。在本工作中，我们系统地研究了此类反应对ZnCl ₂，Zn（OH）Cl和Zn（OH）_2的反应机理。催化剂通过密度泛函理论（DFT）方法。Fukui函数，凝聚Fukui函数和Hirshfeld电荷使我们能够预测催化剂的活性位并获得电子转移信息。从这些数据中，我们发现带有羟基的催化剂与没有这种功能的催化剂相比表现出相对较低的吸附性能。计算表明，所研究的三种催化剂具有三种不同的反应路径。对于Zn（OH）Cl和Zn（OH）₂催化剂，反应通过一班制H _2进行O分子转移途径，避免了更高的能量屏障途径。有趣的是，我们发现打破水中O–H键所需的能量决定了所研究催化反应的活化能。激活势垒按Zn（OH）Cl≈Zn（OH）₂  <ZnCl ₂的顺序增加。该趋势表明，Zn（OH）Cl和Zn（OH）₂是乙炔水合的有前途的催化剂。

图形概要