Towards jet fuel from technical lignins: Feedstock-catalyst-product interactions revealed during catalytic hydrogenolysis

One-pot conversion of technical lignins to jet fuel is limited by recondensation of unstable intermediates. A two -stage process that first generates stabilized fragments by reductive depolymerization, then upgrades oligomers to hydrocarbons may increase yield. Insights into factors affecting initial depolymerization of industrially relevant lignins were revealed, whereas many studies have focused on upgrading bio-oil or model compounds. Feed-stocks, catalysts, and process conditions were varied to identify effects on product composition. Hydrogen and temperature synergistically suppressed coking during pine kraft depolymerization to increase monomer pro-duction. Ruthenium was more effective than cobalt at limiting solid residue and improving liquid product yield by promoting hydrogenation and hydrogenolysis. Besides ruthenium, a strong acid-base catalyst effectively deconstructed hardwood biorefinery lignin, targeting alkyl-aryl ether bonds. Ruthenium and zinc converted hardwood kraft lignin to oligomers most suitable for upgrading to jet fuel-range hydrocarbons based on yield (79 % on dry lignin), weight-average molecular weight (1290 g/mol), and chemical structure.