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Hydride Transfer versus Deprotonation Kinetics in the Isobutane–Propene Alkylation Reaction: A Computational Study
ACS Catalysis ( IF 11.3 ) Pub Date : 2017-11-21 00:00:00 , DOI: 10.1021/acscatal.7b02877 Chong Liu , Rutger A. van Santen , Ali Poursaeidesfahani 1 , Thijs J. H. Vlugt 1 , Evgeny A. Pidko 2 , Emiel J. M. Hensen
ACS Catalysis ( IF 11.3 ) Pub Date : 2017-11-21 00:00:00 , DOI: 10.1021/acscatal.7b02877 Chong Liu , Rutger A. van Santen , Ali Poursaeidesfahani 1 , Thijs J. H. Vlugt 1 , Evgeny A. Pidko 2 , Emiel J. M. Hensen
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The alkylation of isobutane with light alkenes plays an essential role in modern petrochemical processes for the production of high-octane gasoline. In this study we have employed periodic DFT calculations combined with microkinetic simulations to investigate the complex reaction mechanism of isobutane–propene alkylation catalyzed by zeolitic solid acids. Particular emphasis was given to addressing the selectivity of the alkylate formation versus alkene formation, which requires a high rate of hydride transfer in comparison to the competitive oligomerization and deprotonation reactions resulting in catalyst deactivation. Our calculations reveal that hydride transfer from isobutane to a carbenium ion occurs via a concerted C–C bond formation between a tert-butyl fragment and an additional olefin, or via deprotonation of the tert-butyl fragment to generate isobutene. A combination of high isobutane concentration and low propene concentration at the reaction center favor the selective alkylation. The key reaction step that has to be suppressed to increase the catalyst lifetime is the deprotonation of carbenium intermediates that are part of the hydride transfer reaction cycle.
中文翻译：
异丁烷-丙烯烷基化反应中氢化物转移与去质子动力学的计算研究
异丁烷与轻链烯烃的烷基化在生产高辛烷值汽油的现代石油化学工艺中起着至关重要的作用。在这项研究中，我们结合DFT计算和微观动力学模拟研究了沸石固体酸催化异丁烷-丙烯烷基化的复杂反应机理。特别强调解决烷基化物形成与烯烃形成的选择性，与导致催化剂失活的竞争性低聚和去质子化反应相比，这要求高的氢化物转移速率。我们的计算表明，由异丁烷氢化物转移到一个碳正离子经由之间协调一致C-C键的形成发生叔-丁基片段和另外的烯烃，或通过叔丁基片段的去质子化反应生成异丁烯。反应中心处高异丁烷浓度和低丙烯浓度的组合有利于选择性烷基化。必须抑制以延长催化剂寿命的关键反应步骤是作为氢化物转移反应循环一部分的碳car中间体的去质子化。
更新日期：2017-11-21
中文翻译：
异丁烷-丙烯烷基化反应中氢化物转移与去质子动力学的计算研究
异丁烷与轻链烯烃的烷基化在生产高辛烷值汽油的现代石油化学工艺中起着至关重要的作用。在这项研究中，我们结合DFT计算和微观动力学模拟研究了沸石固体酸催化异丁烷-丙烯烷基化的复杂反应机理。特别强调解决烷基化物形成与烯烃形成的选择性，与导致催化剂失活的竞争性低聚和去质子化反应相比，这要求高的氢化物转移速率。我们的计算表明，由异丁烷氢化物转移到一个碳正离子经由之间协调一致C-C键的形成发生叔-丁基片段和另外的烯烃，或通过叔丁基片段的去质子化反应生成异丁烯。反应中心处高异丁烷浓度和低丙烯浓度的组合有利于选择性烷基化。必须抑制以延长催化剂寿命的关键反应步骤是作为氢化物转移反应循环一部分的碳car中间体的去质子化。
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