Production of Jet Fuel‐Range Hydrocarbons from Hydrodeoxygenation of Lignin over Super Lewis Acid Combined with Metal Catalysts

• Published in: ChemSusChem Vol. 11; no. 1; pp. 285 - 291
• Main Authors: Wang, Hongliang, Wang, Huamin, Kuhn, Eric, Tucker, Melvin P., Yang, Bin
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 10.01.2018
• Subjects: Acids; Aluminum oxide; Aromatic compounds; biomass conversion; Catalysis; Catalysts; Chemical industry; Chemical reactions; Cyclohexane; Deoxygenation; fuels; Gas Chromatography-Mass Spectrometry; Hafnium; Hydrocarbons; Hydrocarbons - chemical synthesis; hydrodeoxygenation; Hydrogenation; Hydroxyl groups; Jet engine fuels; Lewis acid; Lewis Acids - chemistry; Lignin; Lignin - chemistry; Mesylates - chemistry; metal triflates; Metals - chemistry; Noble metals; Platinum; Ruthenium; Ruthenium - chemistry; Substrates; metal triflates; biomass conversion; hydrodeoxygenation; fuels; hydrocarbons
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201701567

Super Lewis acids containing the triflate anion [e.g., Hf(OTf)4, Ln(OTf)3, In(OTf)3, Al(OTf)3] and noble metal catalysts (e.g., Ru/C, Ru/Al2O3) formed efficient catalytic systems to generate saturated hydrocarbons from lignin in high yields. In such catalytic systems, the metal triflates mediated rapid ether bond cleavage through selective bonding to etheric oxygens while the noble metal catalyzed subsequent hydrodeoxygenation (HDO) reactions. Near theoretical yields of hydrocarbons were produced from lignin model compounds by the combined catalysis of Hf(OTf)4 and ruthenium‐based catalysts. When a technical lignin derived from a pilot‐scale biorefinery was used, more than 30 wt % of the hydrocarbons produced with this catalytic system were cyclohexane and alkylcyclohexanes in the jet fuel range. Super Lewis acids are postulated to strongly interact with lignin substrates by protonating hydroxyl groups and ether linkages, forming intermediate species that enhance hydrogenation catalysis by supported noble metal catalysts. Meanwhile, the hydrogenation of aromatic rings by the noble metal catalysts can promote deoxygenation reactions catalyzed by super Lewis acids. The biggest Lewiser: Super Lewis acids and noble metals form an efficient catalytic system that can overcome the energy barrier for conversion of lignin into high yield jet‐fuel range hydrocarbons. Metal triflates mediate rapid ether bond cleavage through selective bonding to the etheric oxygen, whereas the noble metal catalyzes the subsequent hydrogenation reaction, eliminating functional groups.