(614d) Phase Behavior of Kraft Liqnins with a Tunable, Renewable Solvent System

Authors: 
Klett, A. S., Clemson University
Thies, M. C., Clemson University

Lignin is unique among biopolymers in having significant aromatic character, which makes it potentially attractive for a wide range of uses, including polymeric applications and carbon fibers. Unfortunately, most of the commercial-grade lignins available today (i.e., the Kraft lignins) are severely limited in their applications because of their high metals (primarily sodium) content. 

However, recently Clemson researchers have discovered a powerful, versatile, and renewable solvent system that creates a phase behavior when contacted with lignin such that the sodium content can be reduced 10-fold with each phase split; furthermore, this phase separation also separates the lignin into fractions with significantly different molecular weights and chemical properties. Thermodynamic variables such as temperature, solvent composition and amount, and lignin type (i.e., hardwood vs. softwood) have been studied to determine their effect on the location of phase boundaries, the metals selectivities between phases, and the molecular weight distribution of the lignin within each phase.  

Pseudo-ternary phase diagrams will be presented for different types of feed lignins with the solvent system at several different temperatures, and the global phase-behavior characteristics of this lignin­­­­­­­­­­-solvent system will be discussed, along with the implications of the observed phase equilibria for the development of a viable purification and fractionation process for lignin.