Ni nanoparticle coupled surface oxygen vacancies for efficient synergistic conversion of palmitic acid into alkanes

The catalytic transformation of renewable biomass oil (mainly comprising fatty acids and triglycerides) into high-value alkanes is a versatile technique, and Ni-based catalysts are considered to be the most suitable substitutes for precious metals. Ni nanoparticles supported on CeO2 carriers, prepared by hydrothermal synthesis (Ni/H-CeO2) with abundant oxygen vacancies, exhibited superior catalytic activity compared to precious metal catalysts. For the hydrodeoxygenation of palmitic acid, the Ni/H-CeO2 catalyst converted palmitic acid into pentadecane with a 94.8% selectivity under mild reaction conditions. The outstanding catalytic performance of Ni/H-CeO2 can be attributed to the synergistic effect between the Ni nanoparticles for activating hydrogen and the abundant oxygen vacancies for adsorbing oxygen from palmitic acid. The abundant oxygen vacancies of Ni/H-CeO2 improved the interaction between the Ni metal and CeO2 support, as confirmed by density functional theory calculations. Therefore, the abundant oxygen vacancies were more conducive to the dispersion of Ni, resulting in the formation of Ni nanoparticles, which enhanced the potential for hydrogen activation due to the increased number of exposed Ni and electronic effects. The high pentadecane selectivity was governed by small Ni nanoparticles. This study provides a novel strategy to obtain an efficient hydrodeoxygenation catalyst for converting biomass oil into biofuel.