Regioselectivity and Reaction Mechanism of Ru-Catalyzed Hydrogenolysis of Squalane and Model Alkanes.

ChemSusChem

Department of Applied Chemistry, School of Engineering, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai, 980-8579, Japan.

Published: January 2017


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Article Abstract

The dependence of the C-C hydrogenolysis activity on reaction parameters and the structure of the substrate alkanes was investigated for Ru/CeO catalyst with very small (dispersion: H/Ru=0.89) Ru particles. The substrate concentration and reaction temperature did not have a significant effect on the selectivity pattern, except that methane production was promoted at high temperatures. However, the hydrogen pressure had a marked effect on the selectivity pattern. C -C bond dissociation, terminal C -C bond dissociation, and fragmentation to form excess methane had negative reaction order with respect to hydrogen partial pressure, whereas C -C bond dissociation had an approximately zero reaction order. Therefore, a high hydrogen pressure is essential for the regioselective hydrogenolysis of C -C bonds in squalane. Ru/SiO catalyst with larger Ru particles showed similar changes in the product distribution during the change in hydrogen pressure. The reaction mechanism for each type of C-C bond dissociation is proposed based on reactivity trends and DFT calculations. The proposed intermediate species for the internal C -C dissociation, terminal C -C dissociation, and C -C dissociation is alkyls, alkylidynes, and alkenes, respectively.

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http://dx.doi.org/10.1002/cssc.201601204DOI Listing

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