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Regioselectivity and Reaction Mechanism of Ru‐Catalyzed Hydrogenolysis of Squalane and Model Alkanes
Author(s) -
Nakagawa Yoshinao,
Oya Shinichi,
Kanno Daisuke,
Nakaji Yosuke,
Tamura Masazumi,
Tomishige Keiichi
Publication year - 2017
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201601204
Subject(s) - chemistry , hydrogenolysis , catalysis , dissociation (chemistry) , bond cleavage , squalane , photochemistry , regioselectivity , reaction mechanism , selectivity , medicinal chemistry , organic chemistry
The dependence of the C−C hydrogenolysis activity on reaction parameters and the structure of the substrate alkanes was investigated for Ru/CeO 2 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 tertiary −C bond dissociation, terminal C secondary −C primary bond dissociation, and fragmentation to form excess methane had negative reaction order with respect to hydrogen partial pressure, whereas C secondary −C secondary bond dissociation had an approximately zero reaction order. Therefore, a high hydrogen pressure is essential for the regioselective hydrogenolysis of C secondary −C secondary bonds in squalane. Ru/SiO 2 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 secondary −C secondary dissociation, terminal C secondary −C primary dissociation, and C tertiary −C dissociation is alkyls, alkylidynes, and alkenes, respectively.