Hydrodecarboxylation of fatty acids into liquid hydrocarbons over a commercial Ru/C catalyst under mild conditions

Abstract

Deoxygenation of fatty acids into liquid hydrocarbons is an efficient method of producing second-generation biofuels from biomass. Herein, we report efficient upgrading of stearic acid into a long-chain hydrocarbon at relatively low reaction temperature (140–220 °C) over a commercial Ru/C catalyst. The conversion process is predominantly through the hydrodecarboxylation pathway and not hydrodeoxygenation since heptadecane and not octadecane is found as the main product with the detection of CO₂ in the gaseous products. The effects of process parameters including the solvent type (hexane, dodecane, isopropanol, water, and solvent-free), solvent volume, hydrogen pressure, catalyst loading, mass of feedstock, reaction temperature and reaction time on the conversion of stearic acid were systematically studied and optimized and the reusability of the catalyst was also studied. Hexane is found to be the most suitable solvent for the catalytic system. Under the optimized reaction conditions, 100% stearic acid conversion can be achieved at even 160 °C alongside a 90.1% yield of heptadecane. The apparent activation energy of the hydrodecarboxylation process over the commercial Ru/C catalyst was calculated to be 58.6 kJ mol⁻¹. Notably, the reusability potential of the Ru/C catalyst is slightly limited by the accumulation of carbon deposits across multiple usage cycles.