Hydrodeoxygenation of levulinic acid dimers on a zirconia-supported ruthenium catalyst

The hydrodeoxygenation (HDO) of levulinic acid (LA) aldol condensation product dimers was studied between 250 and 300 °C and 50 bar H2 in a batch reactor with Ru catalyst supported on mesoporous zirconia. During the reaction, the unsaturated dimers, which contained ketone groups and double bonds, were hydrogenated to saturated dimers. A greater degree of deoxygenation was achieved at higher temperatures, and oxygen was removed as water and CO2. Oxygen removal was evidenced by elemental analysis and infrared spectroscopy, in which the C=O peak decreased with increasing temperature. A drawback of high reaction temperature (300 °C) was a minor degree of oligomerization. The formation of aromatics was also observed at the higher temperatures. Aside from the saturated dimers, volatile products were obtained at all temperatures, including ketones, acids, and esters. This study demonstrates for the first time the potential of LA dimers as a sustainable route from lignocellulosic biomass to biofuels and biocomponents.