(357i) Extraction of Lignin from Lignocellulosic Biomass By Formic Acid

In order to make full use of the various components of lignocellulosic biomass, fractionation is a required step to separate the main polymers in the feedstock. In this case, formic acid was applied to fractionate both eucalyptus and corn stover bioethanol residue to solubilize and recover lignin. The sugar content and molecular weight changes of lignin separated at different cooking stages were compared, and the structural changes in the lignin were characterized. In the eucalyptus, increasing reaction time resulted in increasing lignin removal, with the dissolution rate initially fast and slowing over the course of the extraction, while the molecular weight of the solubilized lignin increased. With 0-30 min of reaction, 23.70% of the holocellulose was dissolved and after 30 min, the holocellulose dissolution decreased and the yield of pulp dropped slightly. During the reaction, the S-type lignin dissolved earlier, but the degradation process was relatively complete during the process, and the G-type lignin dissolution was stable and the structure was more likely to be destroyed later in the reaction. Corn stover bioethanol residue was refluxed with 90% formic acid for 1 h. Then the mixture was filtered and the solid fraction was washed with formic acid. The black liquors were combined and the mixture was added into water to precipitate lignin. It was found that the total lignin removal rate was over 80% for formic acid fractionation together with alkali extraction (1% NaOH and 1 h). The research provides an easy way to extraction of lignin from lignocellulose and the lignin product is a good feedstock for further applications in polymers and chemicals.