Hydrothermal conversion of linoleic acid and ethanol for biofuel production

• Pt/C catalyzes linoleic acid conversion into heptadecane in a water/ethanol mixture.
• Ethanol serves as H-donor solvent.
• Reaction pathway follows consecutive reactions: hydrogenation, esterification, hydro-decarboxylation.
• Kinetic modelling shows that ethyl stearate is converted into heptadecane, not stearic acid.

The catalytic conversion of linoleic acid in ethanol/water mixtures (1:1 vol. ratio) was explored in a batch reactor using a Pt/C catalyst. Linoleic acid was converted into heptadecane with high yields (>80%) after 6 h at 350 °C under autogenous pressure. The reaction proceeded through consecutive steps: linoleic acid → stearic acid → ethyl stearate → heptadecane. Hydrogen was generated in-situ by oxidation of ethanol into acetaldehyde. A moderate sintering of platinum was evidenced after hydrothermal reaction.A reaction network based on products distribution and kinetic studies was proposed. It was found that the hydrogenation route proceeds via the free acids whereas the hydrogenation of the ethyl esters was negligible. The formation of heptadecane, on the other hand, proceeded via ethyl stearate and not via stearic acid.

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