(636a) Extending the ALPHA Process to Hybrid Poplar and Corn Stover: Producing Lignin Fractions of Controlled Molecular Weight and Purity

Aqueous mixtures of renewable organic solvents such as acetic acid or ethanol have demonstrated the ability to simultaneously fractionate and purify Kraft lignins. Under specific conditions, these solvents cause Kraft lignins to partition into two phases, a lignin-rich phase with a higher molecular weight, and a solvent-rich phase with a lower molecular weight. The developing field of cellulosic ethanol refineries is poised to introduce a new industrially significant stream of lignin, and adequate utilization of this resource is key to the economic feasibility of these refineries. In this research, lignins have been isolated from Hybrid Poplar wood chips and corn stover via alkaline pulping. Using the ALPHA process, these lignins were contacted with aqueous, renewable organic solvents to produce lignin fractions of varying molecular weight and increased purity with the intent of improving the performance of lignin-consuming applications such as carbon fiber spinning or polyurethane synthesis. The molecular weight, metals content, sugars content, and hydroxyl content of each phase were measured as a result of fractionation. These results are also compared against the behavior of Kraft lignins, showing that different solvents or lignin sources produces similar regions of liquid-liquid equilibrium where the ALPHA process can be conducted.