(43a) Fractionation and Purification of Biorefinery Lignins Using Aqueous Renewable Solvents

Aqueous Lignin Purification using Hot Agents (ALPHA) processing is being investigated for the isolation of high-purity lignins of controlled molecular weight from biorefinery lignins, particular those lignins derived from hybrid poplar and corn stover. Aqueous renewable solvents – including alcohols, ketones, and organic acids in solution with water – are being investigated for their ability to fractionate, clean, and solvate the lignins remaining in both the liquor (after alkaline pretreatment) and the solid cake (after enzymatic hydrolysis). Initial work is focused on finding the ALPHA operating conditions that will create the desired two-phase, liquid–liquid system required to effect lignin fractionation, purification, and, sometimes, even chemical modification. The effect (both positive and negative) of specific lignin impurities on the formation of the desired liquid–liquid equilibria will also be discussed.