472760 Fine Fractionation of Lignin By Molecular Weight Using Supercritical Fluids

Monday, November 14, 2016: 9:40 AM
Lombard (Hilton San Francisco Union Square)
Adam S. Klett and Mark C. Thies, Chemical and Biomolecular Engineering, Clemson University, Clemson, SC

As lignin is the only major constituent of biomass with aromaticity, it has been proposed as a renewable biopolymer replacement for petroleum-derived applications such as the polyols in polyurethane foams, the phenols in phenol–formaldehyde resins, and the polyacrylonitrile in carbon fibers. However, increasing evidence indicates that the molecular weight of the lignin should best be “tuned” for a given product application. In this study, concentrated acetic acid–water mixtures were used to dissolve most of a low-ash (1-2%) lignin recovered from a kraft black liquor via the SLRP process. Supercritical carbon dioxide (CO2) was then added as an anti-solvent to the acetic acid–water–lignin mixture in increments of increasing pressure. Both the molecular weight and metals impurities of the lignin fractions that precipitated from solution were found to be a strong function of the pressure of the supercritical CO2 being added to the acetic acid–water mixtures. The precipitated lignin fractions were characterized by GPC, 1H, 13C, and HSQC-NMR, and unexpected relationships between molecular weight and functional-group composition were obtained. Based on these limited results, we conclude that supercritical CO2 can be an energy-efficient, alternative method for fractionating lignin in terms of molecular weight, while holding other molecular properties constant.

Extended Abstract: File Not Uploaded
See more of this Session: Lignin-Based Materials
See more of this Group/Topical: Forest and Plant Bioproducts Division - See also ICE