New Insights Toward Quantitative Relationships between Lignin Reactivity to Monomers and Their Structural Characteristics

The heterogeneous and complex structural characteristics of lignin present a significant challenge to predict its processability (e.g., depolymerization, modifications etc.) to valuable products. This study provides a detailed characterization and comparison of structural properties of seven representative biorefinery lignin samples derived from forest and agricultural residues, which were subjected to representative pretreatment methods. A range of wet chemistry and spectroscopy methods were applied to determine specific lignin structural characteristics such as functional groups, inter-unit linkages, and peak molecular weight. In parallel, oxidative depolymerization of these lignin samples to either monomeric phenolic compounds or dicarboxylic acids were conducted, and the product yields were quantified. Based on these results (lignin structural characteristics and monomer yields), we applied for the first time the multivariable linear estimation (MVLE) approach using R Statistics (an open-source programming language and software environment for statistical computing and graphics) to gain insight toward a quantitative correlation between lignin structural properties and their conversion reactivity toward oxidative depolymerization to monomers.