Effect of Water on Cumene Dealkylation over H-ZSM-5 Zeolites
Effect of Water on Cumene Dealkylation over H-ZSM-5 Zeolites
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水对 H-ZSM-5 沸石上异丙苯脱烷基的影响
DOI：
10.1021/acscatal.2c05759
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发表时间：
2023
期刊：
影响因子：
12.9
通讯作者：
Crossley, Steven P.
中科院分区：
文献类型：
--
作者：
Chau, Han K.;Mai, Hien D.;Gumidyala, Abhishek;Pham, Tram N.;Bui, Dai-Phat;D’Amico, Andrew D.;Alalq, Ismaeel;Glatzhofer, Daniel T.;White, Jeffery L.;Crossley, Steven P.
最近，人们广泛研究了水对布朗斯台德酸化学的影响，以了解含氧反应物的转化。人们对水对碳氢化合物转化的影响的探索和了解要少得多。在这里，我们发现 H-ZSM-5 沸石上的异丙苯脱烷基化受到布朗斯台德酸位点的位置和沸石孔内水分子的存在的强烈影响。虽然增加酸位点密度会导致吸附态和过渡态的焓稳定，因为在更受限的空隙内酸位点的比例更大，但水的存在通过过渡态的熵稳定来提高速率，但代价是增加了内在活化焓。讨论了水和酸位点位置对提高反应速率的影响。水的直接参与与水引起的催化剂表面修饰形成对比，例如晶格外物质的产生和迁移。这些晶格外物质已被证明可以影响要求更高的化学转化（例如烷烃裂解）的反应速率，但在促进本文研究的简易脱烷基化化学方面效果较差。我们进一步揭示了水分的添加如何通过限制随后形成的产品的低聚反应而对催化剂稳定性产生积极影响。
The influence of water on Brønsted acid chemistry has been studied extensively recently for the conversion of oxygen-containing reactants. The effect of water on hydrocarbon transformations is far less explored and understood. Here, we show that cumene dealkylation over H-ZSM-5 zeolites is strongly influenced by the location of Brønsted acid sites and the presence of water molecules inside zeolite pores. While increasing acid site density leads to enthalpic stabilization of both adsorbed states and transition states due to a greater fraction of acid sites within more confined voids, the presence of water enhances rates via entropic stabilization of transition states at the expense of an increased intrinsic activation enthalpy. Both effects of water and the acid site location on the improving reaction rate are discussed. This direct participation of water is contrasted with water-induced modifications to the catalyst surface, such as the generation and mobility of extra-lattice species. These extra-lattice species have been shown to influence reaction rates for more demanding chemical transformations such as alkane cracking but are less effective at promoting the facile dealkylation chemistry studied here. We further reveal how the addition of moisture also induces positive consequences on catalyst stability by limiting subsequent oligomerization reactions with formed products.
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