Hydride transfer versus deprotonation kinetics in the isobutane-propene alkylation reaction
| Autor: | Rutger A. van Santen, Chong Liu, Ejm Emiel Hensen, Evgeny A. Pidko, Ali Poursaeidesfahani, Tjh Thijs Vlugt |
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| Přispěvatelé: | Inorganic Materials & Catalysis |
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
Reaction mechanism
010405 organic chemistry Hydride microkinetics General Chemistry Alkylation 010402 general chemistry Photochemistry 01 natural sciences Catalysis 0104 chemical sciences Propene chemistry.chemical_compound Carbenium ion Deprotonation chemistry hydride transfer Isobutane periodic DFT deactivation alkylation faujasite Research Article |
| Zdroj: | ACS Catalysis, 7(12) ACS Catalysis ACS Catalysis, 7(12), 8613-8627. American Chemical Society |
| ISSN: | 2155-5435 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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