Mechanism of n-butane hydrogenolysis promoted by Ta-hydrides supported on silica

Type
Article

Authors
Pasha, Farhan Ahmad
Cavallo, Luigi
Basset, Jean-Marie

KAUST Department
Chemical Science Program
KAUST Catalysis Center (KCC)
Physical Science and Engineering (PSE) Division

Online Publication Date
2014-05-09

Print Publication Date
2014-06-06

Date
2014-05-09

Abstract
The mechanism of hydrogenolysis of alkanes, promoted by Ta-hydrides supported on silica via 2 ≡ Si-O- bonds, has been studied with a density functional theory (DFT) approach. Our study suggests that the initial monohydride (≡ Si-O-)2Ta(III)H is rapidly trapped by molecular hydrogen to form the more stable tris-hydride (≡ Si-O-) 2Ta(V)H3. Loading of n-butane to the Ta-center occurs through C-H activation concerted with elimination of molecular hydrogen (σ-bond metathesis). Once the Ta-alkyl species is formed, the C-C activation step corresponds to a β-alkyl transfer to the metal with elimination of an olefin. According to these calculations, an α-alkyl transfer to the metal to form a Ta-carbene species is of higher energy. The olefins formed during the C-C activation step can be rapidly hydrogenated by both mono- and tris-Ta-hydride species, making the overall process of alkane cracking thermodynamically favored. © 2014 American Chemical Society.

Citation
Pasha, F. A., Cavallo, L., & Basset, J. M. (2014). Mechanism of n-Butane Hydrogenolysis Promoted by Ta-Hydrides Supported on Silica. ACS Catalysis, 4(6), 1868–1874. doi:10.1021/cs5001703

Acknowledgements
This work was supported by King Abdullah University of Science and Technology (KAUST) Saudi Arabia.

Publisher
American Chemical Society (ACS)

Journal
ACS Catalysis

DOI
10.1021/cs5001703

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