(134b) Separation of Lignin Streams after Alkali and Ionic Liquid Pretreatment Using Tangential Flow Filtration

Lignin is Nature’s most abundant aromatic polymer, and replacement of petroleum-based chemicals with those derived from lignin represents a virtuous challenge for chemists. After biomass pretreatment under basic condition, most or significant amount of the lignin will be stripped from the feedstock and retained in the aqueous stream. In this work, lignin-rich stream was obtained from alkali and ionic liquid (IL) pretreatment process on corn stover. After pretreatment, the slurry was cooled down and solids removed. Three different technologies are being investigated for solids removal: ultrasonic separation (US), tangential flow filtration (TFF) and centrifugation. Ultrasonic separation is being used to remove fines (i.e., particles < 100 microns) for improved TFF membrane permeability or increase flow rates for centrifugation. Ultrasonic separation of fines can be achieved with low energy due to the high acoustic contrast between the lignocellulosic solids and water medium. TFF was also employed for the fractionation of lignin molecules. Samples were taken from processing streams and analyzed using different techniques. In general, weight-average and polydispersity decreased with the decrease of membrane pore size. Lignin properties from the two different pretreatment processes were compared to understand the pretreatment mechanisms with distinct catalysts.