Production of Jet Fuel Precursors from Waste Kraft Lignin with a Complex Copper Acid Catalyst

Production of jet fuel precursors from waste kraft lignin through a depolymerization and hydrodeoxygenation (DHDO) method with a complex copper acid catalyst is reported. The kraft lignin undergoes a high degree of depolymerization, deoxygenation, hydrogenation, and C–C coupling. Monomers and dimers with molecular weights in the ranges of <200 Da and 354–452 Da are obtained with optimized yields reaching 93.29 and 39.30 C% at 360 °C for 8 h, while trimers and oligomers with higher molecular weights are also generated with lower contents. The high carbon yields of monomers and dimers are given by the incorporation of methanol solvent. The double bond equivalent (DBE) and polydispersity index (PDI) decrease from 14.77 and 2.77 in kraft lignin to 9.05 and 1.35 in the products, while the high heating value (HHV) increases from 24.53 to 36.47 MJ/kg after reaction. Furthermore, over 45% of the optimized products have boiling points in the range of that of commercial jet fuel (60–280 °C). All these results demonstrate the appropriate properties of the products from kraft lignin DHDO as potential jet fuel precursors.