期刊
ACS CATALYSIS
卷 7, 期 12, 页码 8613-8627出版社
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.7b02877
关键词
hydride transfer; alkylation; deactivation; faujasite; periodic DFT; rnicrokinetics
资金
- China Scholarship Council (CSC)
- NWO-CW
- Ministry of Education and Science of Russian Federation [11.1706.2017/4.6]
- Netherlands Center for Multiscale Catalytic Energy Conversion (MCEC)
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.
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