Deoxygenation of dodecanoic acid under inert atmosphere

A laboratory-scale fixed bed reactor (down-flow) was developed for the deoxygenation of dodecanoic (lauric) acid under inert atmosphere. This reaction can be utilized to produce renewable diesel components. The main products were undecane (decarboxylation) and undecene (decarbonylation). The catalysts were a palladium catalyst supported on mesoporous carbon, Sibunit (egg-shell type with spherical granules of 1.6-2.0 mm in diameter), and a commercial Pd/C catalyst. The challenge was to obtain a high activity and selectivity to undecane, as pure dodecanoic acid without any solvents was used. Moreover, the complete reactor system consisting of a reactant feed vessel, a pump, lines, a sampling valve, and a collector of the residue had to be heated, since saturated fatty acids with more than nine carbon atoms have a melting point exceeding 20 °C. The influence of reaction conditions, such as reaction temperature (300-360 °C), pressure (5-20 bar), gas flow rate, reactant concentrations, was studied. The reactant conversion increased when an inert gas (argon) flow was applied co-currently with the reactant flow. The argon pressure did not have any significant impact on the performance. The reason for the catalyst deactivation was determined to be coking.