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Three-Dimensional Kinetic Trends in Zeolites Catalyzed Benzene Ethylation Reaction: A Descriptor-Based DFT Study Coupled with Microkinetic Modeling
ACS Catalysis ( IF 12.9 ) Pub Date : 2020-01-09 , DOI: 10.1021/acscatal.9b04556
Dong Wang 1, 2 , Chuan-Ming Wang 1 , Wei-Min Yang 1
Affiliation  

In zeolite catalysis, both the Brønsted acidity (e.g., acid strength) and reaction conditions (e.g., temperature) have significant influence on catalytic performance. Because of the intimate coupling between acidity-relevant enthalpies and temperature-relevant entropies, it has been challenging to locate the optimal reactivity zone for a given reaction. Here, periodic DFT calculations combined with microkinetic modeling were employed to investigate the effect of both acid strength and reaction temperature simultaneously on benzene ethylation reaction in MFI-structured zeolites involving both the concerted and stepwise pathways. The acid strength using the adsorption energy of ammonia as a descriptor was tailored by two strategies of the isomorphic substitution of heteroatoms and the introduction of extra-framework cations. Good scaling relations were established between the enthalpies of involved transition states and intermediates and the descriptor of acid strength. We pioneered the revelation a three-dimensional activity plot varying with the acid strength and reaction temperature. Three regions with diverse kinetic trends and two boundaries signifying the maximum activity were theoretically demonstrated in benzene ethylation. Subsequent kinetic analyses rationalized these intriguing properties and indicated that the rate-limiting step actually changes with the acid strength. The results hold broad implications for understanding Brønsted acid catalyzed reactions and developing robust catalysts in the future.

中文翻译:

沸石催化的苯乙基化反应的三维动力学趋势:基于描述符的DFT研究与微动力学建模。

在沸石催化中,布朗斯台德酸度(例如酸强度)和反应条件(例如温度)都对催化性能有重要影响。由于与酸度有关的焓和与温度有关的熵之间的紧密耦合,为给定的反应确定最佳的反应区一直是挑战性的。在这里,定期的DFT计算与微观动力学模型相结合,用于研究酸强度和反应温度同时对MFI结构沸石中苯的乙基化反应的影响,涉及协同和逐步的途径。通过杂原子的同构取代和引入骨架外阳离子这两种策略,对使用氨的吸附能作为描述符的酸强度进行了定制。在涉及的过渡态和中间体的焓与酸强度的描述词之间建立了良好的比例关系。我们开创了随酸强度和反应温度变化的三维活性图的揭示。理论上在苯乙基化中证明了三个区域具有不同的动力学趋势和两个边界表示最大活性。随后的动力学分析使这些有趣的特性合理化,并表明限速步骤实际上随酸强度而变化。该结果对理解布朗斯台德酸催化的反应以及将来开发坚固的催化剂具有广泛的意义。我们开创了随酸强度和反应温度变化的三维活性图的揭示。理论上证明了在苯乙基化反应中三个具有不同动力学趋势的区域和两个边界表示最大活性。随后的动力学分析使这些有趣的特性合理化,并表明限速步骤实际上随酸强度而变化。该结果对理解布朗斯台德酸催化的反应以及将来开发坚固的催化剂具有广泛的意义。我们开创了随酸强度和反应温度变化的三维活性图的揭示。理论上在苯乙基化中证明了三个区域具有不同的动力学趋势和两个边界表示最大活性。随后的动力学分析使这些有趣的特性合理化,并表明限速步骤实际上随酸强度而变化。该结果对于理解布朗斯台德酸催化的反应以及将来开发坚固的催化剂具有广泛的意义。随后的动力学分析使这些有趣的特性合理化,并表明限速步骤实际上随酸强度而变化。该结果对于理解布朗斯台德酸催化的反应以及将来开发坚固的催化剂具有广泛的意义。随后的动力学分析使这些有趣的特性合理化,并表明限速步骤实际上随酸强度而变化。该结果对于理解布朗斯台德酸催化的反应以及将来开发坚固的催化剂具有广泛的意义。
更新日期:2020-01-10
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