Hydrodeoxygenation of fatty acids and triglycerides by Pt-loaded Nb 2 O 5 catalysts

Platinum nanoparticles loaded onto various supports have been studied for the selective hydrogenation of lauric acid to n -dodecane. The activity depends on the support material and pre-reduction temperature. Pt/Nb 2 O 5 reduced at 300 °C gives the highest activity. Pt/Nb 2 O 5 shows higher activity than various Nb 2 O 5 -supported transition metals (Ir, Re, Ru, Pd, Cu, Ni). Under solvent-free conditions Pt/Nb 2 O 5 is effective for the hydrodeoxygenation of lauric, capric, palmitic, myristic, oleic, and stearic acids under 8 bar H 2 at 180–250 °C, which gives high yields (88–100%) of linear alkanes with the same chain length as the starting compound. Tristearin is also converted to give 93% yield of n -octadecane. Pt/Nb 2 O 5 shows more than 60 times higher turnover number (TON) than the previously reported catalysts for the hydrogenation of stearic acid to n -octadecane. Mechanistic study shows a consecutive reaction pathway in which lauric acid is hydrogenated to 1-dodecanol, which undergoes esterification with lauric acid as well as hydrogenation to n -dodecane. The ester undergoes hydrogenolysis to give the alcohol, which is hydrogenated to the alkane. Infrared (IR) study of acetic acid adsorption on Nb 2 O 5 indicates that Lewis acid–base interaction of Nb cation and carbonyl oxygen, which suggests a possible role of Nb 2 O 5 as an activation site of carbonyl groups during hydrodeoxygenation.