(216c) Effect of Pretreatment Conditions on the Structure of Celf Lignin

A major challenge in lignocellulosic biorefinery is the economical and effective utilization of co-product lignins. Because the chemical structure of lignin is modified based upon the pretreatment methods, it is vital to understand the structural features of co-product lignins so they can be tailored for specific applications. The newly developed Co-Solvent Enhanced Lignocellulosic Fractionation (CELF) pretreatment deconstructs lignocellulosic biomass in tetrahydrofuran mixed with water and dilute acid as a catalyst to prepare biomass for subsequent conversion to biofuels and commodity organic chemicals. The co-product lignin obtained from the CELF process is highly soluble in organic solvents, and its structural features, molecular weight and polydispersity depend on pretreatment temperature, catalyst loading, and duration. To understand the influence of lignin molecular weight on its chemical structure, a CELF lignin sample prepared at medium-severity was dissolved in tetrahydrofuran-methanol co-solvent and then fractionated by adding hexane as an anti-solvent. A thorough characterization including ³¹P NMR, HSQC, GPC, DSC and TGA, was conducted to provide a detailed understanding of the structure of CELF lignin fractions recovered during precipitation.