Catalytic deoxygenation of C18 fatty acids over mesoporous Pd/C catalyst for synthesis of biofuels

Deoxygenation was systematically investigated using either stearic, oleic or linoleic acids as a feedstock at 300 °C under 1 vol% hydrogen in argon over a mesoporous Pd/C (Sibunit) catalyst producing one less carbon containing, diesel-like hydrocarbons. The results revealed that catalyst activity and selectivity increased with less unsaturated feedstock. The main products in the case of stearic acid were desired C17 hydrocarbons, whereas the amounts of C17 aromatic compounds increased in case of oleic and linoleic acids. Catalyst deactivation was relatively prominent in linoleic acid deoxygenation giving only 3% conversion of fatty acids in 330 min. The deactivation originated from the formation of C17 aromatic compounds and fatty acid dimers, which was confirmed by size exclusion chromatographic analysis. The latter compounds were formed via Diels-Alder reaction.