Highly selective production of bio-jet fuel grade alkanes over an Fe/SiO2–Al2O3 solid acid catalyst under solvent-free conditions

Abstract

Fatty acid-based biomass is one of the most abundant organic carbon sources and has acquired significant attention as a renewable feedstock for producing renewable bio-jet fuel via hydrocatalytic processes. The hydrocatalytic process usually occurs at high hydrogen pressure, temperature, and noble metal catalyst loading. This work focuses on solvent-free bio-jet fuel generation (C8 to C15) from the model substrate methyl oleate as well as various oils feedstocks (linseed, rapeseed, neem, and tung oils) using Fe-loaded SiO₂–Al₂O₃ as a solid acid catalyst. The acidic sites provided by the Fe metal and SiO₂–Al₂O₃ support reveal that the catalyst is suitable for low-pressure hydrocracking of methyl oleate into bio-jet fuel with excellent selectivity (>74%) and complete conversion at 380 °C, 5 bar H₂ pressure with 10% iron loading in five hours. As determined by NMR, GC, and HRMS techniques, the hydrocatalytic reaction proceeded through three simultaneous plausible pathways: hydrodeoxygenation, decarboxylation, and decarbonylation. The present study has great significance for developing aviation fuel under relatively mild reaction conditions, i.e., low H₂ pressure and high reusability (up to 10 test cycles), using the earth-abundant Fe/SiO₂–Al₂O₃ catalyst.