472773 CO2 As an Expanded Solvent for the Fractionation of Lignin

Tuesday, November 15, 2016: 10:10 AM
Yosemite C (Hilton San Francisco Union Square)
Adam S. Klett and Mark C. Thies, Chemical and Biomolecular Engineering, Clemson University, Clemson, SC

Lignin is an abundant byproduct in both the nascent biofuel and pulp-and-paper industries. Because it is the only abundant, renewable biopolymer with aromaticity, it has been proposed as an alternative for petroleum-derived products for applications ranging from coatings to carbon fibers. However, preliminary work indicates that such applications will require the fractionation of lignin by molecular weight. In this work, CO2 was added to acetic acid–water mixtures into which the lignin had been dissolved a priori to create expanded solvents. These systems proved to be highly effective in separating the lignin polymer into fractions with well-defined molecular weights. Precipitation of lignin fractions began at COpressures as low as 7 bar and continued up to the maximum pressure of 55 bar, where the system volume had approximately doubled. The resultant fractions were characterized by GPC, 1H, 13C, and HSQC-NMR, and interesting trends in functionality were obtained, different from those currently being observed by more conventional separation techniques. Finally, the use of CO2 as an expanded solvent facilitates the separation of the solvent system (acetic acid–water) from the anti-solvent (CO2) by pressure reduction, eliminating the need for an energy-intensive separation step such as distillation.

Extended Abstract: File Not Uploaded