Understanding hydrodeoxygenation of oils and fats

Production of diesel fuels from renewable feedstock is increasing. One auspicious route could be by hydrodeoxygenating waste fats and oils to result long-chain alkanes, a process well suited for existing fuel infrastructure. This was studied over metal oxide-supported platinum-group metals in a batch reactor.

Oleic acid and tripalmitin in n-tetradecane as a solvent and n-dodecane as internal standard was added to an autoclave and mixed with catalyst and charged with 0-50 bar hydrogen at 250-375°C. This model feed closely resembles waste fats and allows relating the products directly to reactants and reaction routes.

Supported Pt and Pd almost exclusively yielded long-chain alkanes via decarboxylation, while complete hydrogenation was suppressed despite high pressures of H2. Deoxygenation without hydrogen was possible as well, although catalysts are prone to faster deactivation. Supported Ni was less active and also consumed more H2 for complete hydrogenation.

CH4 was found to be the major component in the gas phase resulting from methanation of H2 and CO or CO2 from decarboxylation. This protocol may be advantageous for studying production of renewable diesel.