Collaborative Research: Towards a Generalized Microkinetic Description of Lignin Liquefaction

Lignin is an abundant, natural, polydisperse, and random copolymer with varying proportions of monomers and interunit linkages, forming a hyper-branched topology. Although it is structurally more complex than cellulose and hemicellulose, its higher carbon content makes it very attractive for the production of fuels and chemicals. Lignin liquefaction is necessary to convert this underutilized resource into monomeric phenols that can be easily upgraded to fuels and chemicals. Liquefaction can be conducted in aqueous environments (hydrothermal liquefaction), in organic solvents (solvolysis), in ionic liquids or in solvent free conditions (pyrolysis). Assigning a realistic chemical formula to lignin and its oligomeric intermediates is one of the major challenges to rationally describe and control lignin liquefaction reactions. The mechanisms by which solvents and additives impact liquefaction reactions are also poorly known. Because of this, lignin liquefaction remains an art rather than a science. Thus, there is a critical need to develop a rational understanding on how the chemical composition of lignin and its oligomeric intermediaries in the presence of solvents, acid base catalysts and capping agents affects .depolymerization and repolymerization reactions.