Ru nanoparticles supported on hydrophilic mesoporous carbon catalyzed low-temperature hydrodeoxygenation of microalgae oil to alkanes at aqueous-phase

Abstract

The processing of an energy carrier such as microalgae oil into valuable fuels and chemicals is quite promising. Aqueous-phase processing is suitable for this purpose because the separation of intrinsic water from the algae cell is difficult. In this study, we synthesized ruthenium (Ru) nanoparticles supported on highly hydrophilic mesoporous carbon to catalyze the quantitative hydrodeoxygenation (HDO) of microalgae oil to alkanes in a one-pot process at a low temperature (140 °C) in the aqueous phase. The mesoporous carbon was obtained by single-step calcination of starch and zinc chloride in nitrogen. The as-obtained carbon showed high surface areas and pore volumes, allowing high dispersion of Ru nanoparticles. The surface of the carbon material was rich in hydroxyl groups, as evidenced by X-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, and thermogravimetric analysis (TGA) measurements. As a result, the carbon material contacted preferably with the water phase versus the organic phase, improving the accessibility of substrates. On the other hand, the contact angle test results speculated the superior hydrophilic nature of mesoporous Ru/C (ZnCl2, starch) than commercial Ru/C. Both kinetics modeling and in situ IR monitoring in water revealed the superior performance of the hydrophilic mesoporous and hydrophilic Ru/C compared to a commercial Ru/C for the tandem hydrogenation of stearic acid and decarbonylation of stearyl alcohol. The herein designed hydrothermal carbon material was highly active, environmentally benign, sustainable, and recyclable material, and could be potentially used for other hydrogenation reactions in the aqueous phase.