Hydrogenolysis of CO bond over Re-modified Ir catalyst in alkane solvent

• IrReOx/SiO2 catalyzes hydrogenolysis of alcohols in n-heptane as well as in water.
• Alkane solvent is advantageous to the hydrogenolysis of secondary alcohols.
• Alkane solvent is good at the dehydration–hydrogenation mechanism.
• Water solvent is good at the hydride-driven direct hydrogenolysis mechanism.

Hydrogenolysis of alcohols was carried out using n-heptane solvent and IrReOx/SiO2 catalyst, which has been known to be active in water solvent. Hydrogenolysis of trans-1,2-cyclohexanediol proceeded more smoothly in n-heptane than in water. The maximum yield of cyclohexanol was 74%, and at longer reaction time cyclohexane was selectively formed (>80% yield). Stronger adsorption of substrate on catalyst surface in n-heptane than in water is one of factors in obtaining the good yields. Alkane solvent was also advantageous to water solvent in hydrogenolysis of mono-alcohols. The reaction route via acid-catalyzed dehydration and subsequent hydrogenation is enhanced in alkane solvent. On the other hand, the “direct” hydrogenolysis driven by the hydride-like species is suppressed in alkane solvent, leading lower activity in n-heptane for hydrogenolysis of tetrahydrofurfuryl alcohol or 1,2-hexanediol, which smoothly react over IrReOx/SiO2 catalyst in water.

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