In the last two centuries, humans have relied heavily on the utilization of fossil resources for energy and raw materials, leading to increases in atmospheric CO2 and other greenhouse gases. Analysis has shown that rapid transition away from GHG emitting processes to environmentally benign processes is necessary to avoid climate disaster. Plant biomass is a promising feedstock for difficult to decarbonize industries such as aviation. The goal of this thesis was to improve the economic outlook in the biorefinery by understanding lignin reactivity and molecular structures. First, the dependence of monomer yield and selectivity on catalyst identity is studied during reductive catalytic fractionation (RCF) without the addition of exogenous hydrogen gas (H2-free). Evidence is provided for coniferyl/sinapyl alcohol being the reactive intermediate, and the stabilization pathways to various RCF monomers is investigated through the use of model compounds. Next, a new method for the quantification and classification of phenolic hydroxyl groups in lignin and its derivatives, such as RCF oil, is described. Pentafluoropyridine is shown to react fully with phenols in the presence of base, allowing for cheap, safe, and accurate phenolic measurement. Next, a high throughput method for performing RCF is developed and validated, greatly expanding the capabilities of the RCF practitioner while reducing the time and material footprint. Finally, this methodology is then utilized to study the role of substrate, specifically poplar genotype, during RCF through reactions of approximately 600 genotypes. Variance in the extractability of different poplars was discovered with practical implications for the potential poplar RCF biorefinery. </p
