Aqueous phase hydrodeoxygenation of dilute alkali extracted corn stover lignin to jet fuel range hydrocarbons (C7-C18)

The utilization of waste lignin as a feedstock  for conversion to hydrocarbons offers a promising opportunity for enhancing the overall operational efficiency, carbon conversion, economic viability, and sustainability of biofuels production. Lignin consists of phenylpropanoid units linked via C-O-C bonds and C-C bonds, among which C-O-C linkages account for 67-75%. Selective cleavage of C-O-C bonds in lignin without disrupting C-C linkages can result in releasing aromatic monomers and dimers that can subsequently and facilely be converted into chemicals and fuels. Our results show that the existence of characteristic structural features of biomass-derived lignin dictates the feasibility for conversion to C7–C18 jet fuel range hydrocarbons. The catalytic approach applying ruthenium catalysts combined with H-Y type of acidic zeolite in water achieved 70% lignin conversions with good selectivity on C12-C18 (more than 30%) of hydrodeoxygenation (HDO) hydrocarbon products. An advantage of this approach is that the ring structure of lignin can be largely retained. H-Y type of zeolites which possess large-pore structure and contain high concentrations of active acid sites that could effetely disrupt the lignin polymer into oligomers via selectively cleaving C-O-C bonds. Notably, 4-of- the 6 hydrocarbon classes inherent to jet fuels were directly generated within the process. Thus, it may be possible to develop the complete suite of molecules that are required for jet fuel using only biomass feedstocks. The ability to do so would impact the necessity of blending and would add value to the product of the biomass-to-fuels pathways.