Theoretical investigation of catalytic n-butane isomerization over H-SSZ-13

Frontiers in Catalysis

Catalysis

Lucas Spiske¹  Felix Studt¹  Philipp N. Plessow¹  Kamila Kazmierczak²  Bart D. Vandegehuchte² 

[1] Institute of Catalysis Research and Technology, Karlsruhe Institute of Technology, Karlsruhe, Germany;TotalEnergies OneTech Belgium, Feluy, Belgium;

关键词: zeolites;    isomerization;    chabazite;    H-SSZ-13;    DFT;    ab initio;    hydrocarbons;   

DOI  :  10.3389/fctls.2023.1213803

 received in 2023-04-28, accepted in 2023-05-26,  发布年份 2023

来源: Frontiers

【 摘 要 】

Hybrid density functional theory calculations are used to investigate different mechanisms of the isomerization of n-butane to isobutane via intermediate formation of olefins. The monomolecular mechanism for isomerization of butene and isobutene is found to be prevalent, with a Gibbs free energy barrier of 155 kJ/mol at 400°C, compared to the bimolecular mechanism (190 kJ/mol) due to less favorable entropy for the latter. Hydrogen transfer reactions that convert olefins into alkanes (and vice versa) are also included in the investigations, and show a free energy barrier of 203 kJ/mol for conversion of isobutene to isobutane. Additionally, a methyl transfer mechanism is discussed as a possible pathway for formation of C3 and C5 side products, in comparison to the bimolecular mechanism; the highest barrier of the initial methyl transfer is calculated to be 227 kJ/mol. We discuss the influence of entropy and anharmonicity on all mechanisms, stating that through the uncertainties in computational methods when calculating these systems, the calculated reaction barriers are likely to be overestimated here.

【 授权许可】

Unknown   
Copyright © 2023 Spiske, Plessow, Kazmierczak, Vandegehuchte and Studt.