Cu-based catalysts have been widely used in dimethyl oxalate (DMO) hydrogenation due to their ability to activate C-O/C=O bonds without breaking C–C bonds. In this work, the electronic structures of Cu/SiO2 and Cu/γ-Al2O3 as well as their catalytic performance have been studied by the machine-learning-based stochastic surface walking-global neural network potential (SSW-NN) method, density functional theory calculation, and microkinetic analysis including a plug flow reactor (PFR) model. Among SiO2- and γ-Al2O3-supported Cun (n = 1–9), the Cu5 and Cu7 clusters are held most tightly on SiO2(111) and γ-Al2O3(110), respectively. The electron transfer from Cu5 to SiO2(111) leads to the formation of Cuδ+ and Cu0, which are responsible for the stabilization of unsaturated C and O atoms in the intermediates, respectively, while on γ-Al2O3(110) an electron-rich Cu0-Al3c site is most active. Both the Cuδ+-Cu0 and the Cu0-Al3c sites synergistically catalyze the dissociation of gas-phase species and hydrogenation of intermediates. Under the typical operating conditions, although the selectivity towards methyl glycolate (MG) is invariably highest at the reactor inlet, Cu5/SiO2(111) and Cu7/γ-Al2O3(110) are actually selective for the production of ethylene glycol (EG) and ethanol (EtOH), respectively, if the overall selectivity is taken into consideration, signifying the importance of including a reactor model to probe the kinetics of series of consecutive reactions. The dissociation of DMO is found to be the rate-determining step, and the high energy barrier for EG dissociation on Cu5/SiO2(111) hinders its deep hydrogenation while the relatively low barrier on Cu7/γ-Al2O3(110) is beneficial to the formation of EtOH.

中文翻译：

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关于Cu/SiO2和Cu/γ-Al2O3对草酸二甲酯加氢的催化行为，包括活塞流反应器模型


Cu 基催化剂因其能够在不破坏 C-C 键的情况下激活 C-O/C=O 键而被广泛用于草酸二甲酯 （DMO） 加氢。在这项工作中，通过基于机器学习的随机表面行走全局神经网络势 （SSW-NN） 方法、密度泛函理论计算和微动力学分析（包括活塞流反应器 （PFR） 模型）研究了 Cu/SiO2 和 Cu/γ-Al2O3 的电子结构及其催化性能。在 SiO2- 和 γ-Al2O3 负载的 Cun （n = 1–9） 中，Cu5 和 Cu7 簇分别最紧密地固定在 SiO2 （111） 和 γ-Al2O3 （110） 上。从 Cu5 到 SiO2（111） 的电子转移导致 Cuδ+ 和 Cu0 的形成，它们分别负责中间体中不饱和 C 和 O 原子的稳定，而在 γ-Al2O3（110） 上，富电子的 Cu0-Al3c 位点最活跃。Cuδ+-Cu0 和 Cu0-Al3c 位点协同催化气相物质的解离和中间体的氢化。在典型的操作条件下，尽管反应器入口处对乙醇酸甲酯 （MG） 的选择性始终最高，但如果考虑到整体选择性，Cu5/SiO2（111） 和 Cu7/γ-Al2O3（110） 实际上分别对乙二醇 （EG） 和乙醇 （EtOH） 的生产具有选择性，这表明包括反应器模型以探测一系列连续反应的动力学的重要性。发现 DMO 的解离是速率决定步骤，EG 在 Cu5/SiO2（111） 上解离的高能垒阻碍了其深层氢化，而 Cu7/γ-Al2O3（110） 上相对较低的势垒有利于 EtOH 的形成。