High-Quality Jet Fuel Blend Production by Oxygen-Containing Terpenoids Hydroprocessing

Biojet fuel production has attracted a lot of research interest due to the double threats of fuel shortage and environmental concerns. This paper works on the high-quality jet fuel blend production by oxygen-containing terpenoids hydroprocessing. Hydroprocessing of three typical oxygen-containing terpenoids (geranyl acetone, nerolidol, and geraniol) over Pt/Al₂O₃ was first studied. The results indicate that the coexistence of branched carbon backbone, carbon–carbon double bond, and oxygen-containing functional group makes the terpenoids highly reactive during the hydroprocessing. The Pt/Al₂O₃ catalyst, which is considered to have a mild acidity, is still too active in terpenoids hydrogenation and results in large heat release and extensive side reactions. Hence, Pt supported on a support with a milder acidity and better diffusion property was proposed to build a suitable terpenoids hydroprocessing catalyst. Pt/Al-MCFs (MCF: mesocellular silica foam) were then successfully prepared, characterized, and tested in this reaction. Acidic sites could be introduced into MCFs by Al grafting of the pure silica MCF. The acidities of MCF supports, and consequently Pt/MCFs, could be fine-tuned by the Si/Al ratio in the resulting supports. Pt/Al-MCF-20 with a milder acidity than Pt/Al₂O₃ shows an excellent performance in geranyl acetone hydroprocessing with complete deoxygenation, limited side reaction, and high stability. Characterization results of Pt/Al-MCFs and Pt/MCF indicate that Al introduction is critical for the stable performance. The products obtained from geranyl acetone hydroprocessing over Pt/Al-MCF-20 are highly promising as jet fuel or jet fuel blend due to their multibranched alkane and alkyl-cycloalkane nature, which meets all the specifications of ASTM 7566 in the desired freezing point (−72 °C), density (0.80 g/mL), flash point (51 °C), heat of combustion (45 MJ/kg), and aromatics content (<1%)