Rice Husk-Derived Ni/NaY Zeolites as Effective Catalysts for the Production of Renewable Hydrocarbons from Vegetable Oil

Abstract

Catalytic deoxygenation of crude soybean oil is a strategic route for the production of advanced biofuels, yet achieving precise fuel-range selectivity while maintaining process efficiency remains a challenge. In this study, the behavior of pure NaY synthesized with rice husk as a silica source catalyst and those incorporating nickel at different metal loadings was investigated to modulate deoxygenation pathways at 450 °C, 1 atm, and continuous H2 flow. As revealed by the catalyst characterization results, the Ni functionalization promoted a reduction in the zeolite’s total acidity while increasing its pore size and volume. These changes directly influenced the product distribution obtained from the crude soybean oil conversion reaction to hydrocarbons, increasing the selectivity for C10–C16 from approximately 10% for pure NaY to about 55% with the 5Ni/NaY catalyst and 46% with 10Ni/NaY. The analysis of carbon number distributions showed that, up to 60 min of reaction, the predominance of C17 over C18 and C15 over C16, along with the formation of COx, indicated that the decarbonylation/decarboxylation pathway was the predominant reaction route. Coke formation revealed amorphous and aromatic species, suggesting favorable coke removal behavior under oxidative conditions.