Mechanism unraveling for efficient hydrodeoxygenation of fatty acids/esters over highly stable Ni/Nb2O5-SiO2 catalyst

Abstract

The conventional hydrodeoxygenation process for sustainable aviation fuel production using Al₂O₃-supported Ni-Mo sulfide catalyst faces dual challenges: sulfur contamination and catalyst hydrothermal instability. This work develops a hydrothermally stable 5% Ni/Nb₂O₅-SiO₂ catalyst, where strong metal-support interaction drives Nb to Ni electron transfer to form oxygen vacancies activating oxygen-rich groups. The addition of SiO₂ increases the specific surface area of the catalyst, while niobium oxide enhances its water resistance. The catalyst exhibits highly catalytic activity in the hydrodeoxygenation of methyl palmitate with >99% conversion and 96% liquid alkane yield, maintaining activity over a 1000-h on a fixed-bed continuous-flow reactor. Furthermore, the catalyst demonstrated stable and reliable performance over a cumulative period of 500 h, comprising 240 h during the hydrodeoxygenation of palm oil and an additional 260 h of continuous operation with waste cooking oil. This work provides a green, non-sulfur, and stable approach for the production of renewable fuels.