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

Abstract

Abstract 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.