(50a) A Tuneable Process for the Conversion of Lignin to Jet Fuel over Molybdenum Carbide Catalysts

The aviation industry has a growing demand for sustainable aviation fuels (SAF) that can reduce greenhouse gas emissions while satisfying strict physical property requirements to meet safety and quality standards of jet fuel. Between 8% and 25% of such SAFs must be aromatic to satisfy requirements related to energy density, lubricity, material compatibility, and elastomeric swelling. One of the most promising feedstocks for the aromatic portion of SAFs is lignin, as it constitutes 15-30 wt% of all lignocellulosic biomass and is currently underutilized waste in the cellulosic-ethanol and pulp-and-paper-industries. The utilization of lignin in jet fuel hinges on effective methods for reducing oxygen content (lignin O/C ~0.3-0.4 vs jet fuel O/C<0.03), while limiting ring hydrogenation and maximizing yields of C9-C20 hydrocarbons. Molybdenum carbide (Mo₂C) has been shown to selectively cleave aryl-oxygen bonds in model compounds such as anisole and m-cresol, removing oxygen and preserving aromaticity. Herein, we test the efficacy of Mo₂C during hydrodeoxygenation of lignin oil produced via reductive catalytic fractionation (RCF), which is a stabilized mixture of oxygenated, lignin-derived monomers, dimers, trimers and tetramers. Flowing pure RCF lignin oil over a packed catalyst bed in a 3-phase trickle bed reactor enables the generation of steady-state partial-conversion data to understand and optimize catalyst performance while deoxygenating complex lignin streams. Through recycling products, we can obtain and characterize fully deoxygenated lignin oil, concluding that both monomer and dimer products are strong jet fuel candidates. Finally, by co-supporting small amounts of late transition metals, we can shift the product selectivity to tune the aromaticity, closing the loop to enable rational catalyst design for desired jet fuel properties.