(548o) Towards Lignin Valorization: Pyrolytic Depolymerization and Electrochemical Upgrading of Lignins Extracted from Pretreated Biomass to Valuable Intermediates

Garedew, M., Michigan State University
Saffron, C. M., Michigan State University
Jackson, J. E., Michigan State University
Conventional biomass to ethanol conversion strategies require the use of chemical pretreatments such as extractive ammonia pretreatment (EA) and alkaline hydrogen peroxide pretreatment (AHP) to improve sugar hydrolysis and enable lignin recovery. Though direct combustion of lignin is an option, deriving higher value fuels and chemicals is desired as lignin accounts for 10-30 wt% of biomass and 40% of its energy. The production of lignin at centralized biorefineries provides an opportunity for thermal and electrocatalytic approaches to produce valuable intermediates. Fast pyrolysis is one such thermochemical approach that can be used to depolymerized lignin’s complex structure in the absence of oxygen to form pyrolysis vapor and biochar. Most of the pyrolysis vapor can be condensed to liquid bio-oil with a bulk density greater than that of the feedstock. However, bio-oil corrosiveness and reactive instability pose significant barriers to the adoption of pyrolysis systems. Electrocatalytic hydrogenation (ECH) is proposed to stabilize bio-oil under mild conditions (25-80°C and 1 atm). As lignin is converted to phenolic monomers, dimers, and oligomers upon pyrolysis, the transformation of model compounds exhibiting similar bonding arrangements indicates the potential for the ECH of biomass lignin. In this study, conversion, yield, and electrochemical efficiency of ECH of various lignin-derived monomers and dimers are examined using an activated carbon cloth supported ruthenium cathode. Having uncovered surprisingly easy aryl ether cleavages, the outcome of this research will be an advanced understanding of integrated pyrolysis-ECH systems for bio-oil stabilization and lignin valorization.