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Regioselectivity and Reaction Mechanism of Ru‐Catalyzed Hydrogenolysis of Squalane and Model Alkanes

Abstract

The dependence of the C−C hydrogenolysis activity on reaction parameters and the structure of the substrate alkanes was investigated for Ru/CeO2 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. Ctertiary−C bond dissociation, terminal Csecondary−Cprimary bond dissociation, and fragmentation to form excess methane had negative reaction order with respect to hydrogen partial pressure, whereas Csecondary−Csecondary bond dissociation had an approximately zero reaction order. Therefore, a high hydrogen pressure is essential for the regioselective hydrogenolysis of Csecondary−Csecondary bonds in squalane. Ru/SiO2 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 Csecondary−Csecondary dissociation, terminal Csecondary−Cprimary dissociation, and Ctertiary−C dissociation is alkyls, alkylidynes, and alkenes, respectively.

Many routes, simple guide! Ru‐catalyzed C−C hydrogenolysis involves four types of reactions. Only the Csecondary−Csecondary bond dissociation has a positive reaction order with respect to H2. High hydrogen pressure increases the regioselectivity. The reaction mechanism for each type of C−C bond dissociation is proposed based on reactivity trends and DFT calculations

Authors:   Yoshinao Nakagawa, Shin‐ichi Oya, Daisuke Kanno, Yosuke Nakaji, Masazumi Tamura, Keiichi Tomishige
Journal:   ChemSusChem
Year:   2016
Pages:   n/a
DOI:   10.1002/cssc.201601204
Publication date:   16-Nov-2016
Facts, background information, dossiers
  • alkanes
  • temperature
  • selectivity
  • dependence
  • concentration
  • alkenes
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