One-pot selective synthesis of high-density fuels from lignocellulose derivatives over protonated titanate nanotubes

Efficient synthesis of aviation fuels from biomass-derived compounds is highly desirable. Herein, the selective one-pot production of high-density fuel from lignocellulose-derived methyl benzaldehyde and cyclopentanone was developed by combining the aldol condensation and subsequent hydrodeoxygenation (HDO) over the co-catalyst of efficient titanate nanotubes and Ru/Al2O3. The PTNT-10M-0.5 nanotubes with one-dimensional multilayered walls and large surface areas were fabricated by controlling the NaOH concentration and HNO3 post-treatment. The nanotube surface was enriched with Brønsted acid sites and exposed to stronger acidic active sites in the inner layer. The medium-strong Brønsted acid sites were the active sites and very crucial for activating the C=O/C-O bonds, making the PTNT-10M-0.5 catalyst highly active in the aldol condensation and HDO process. The possible reaction mechanisms were also proposed that the medium-strong Brønsted acid sites localized on the inner surface of PTNT-10M-0.5 actively mediate the catalytic activation of the aldol condensation between methyl benzaldehyde and cyclopentanone. The synergistic effect of PTNT-10M-0.5 and Ru/Al2O3 co-catalyst promoted the selective preparation of high-density tricyclic alkanes (≥80.6 %) in one pot under mild conditions. This work provides a simple and effective route for synthesizing high-density aviation fuels from lignocellulose platform compounds.