8. Organosolv Lignin: Extraction

Lignin is the second most abundant biopolymer on earth after cellulose and has a huge potential for developing biobased products. The lignin is conventionally isolated from the lignocelluloses by alkali. Recently, interest has grown in different organic solvents to delignify lignocelluloses. This chapter discusses the removal of lignin from lignocellulosic biomass using organosolv processes. Most of the organosolv process involves alcohol with the mineral acid catalyst. The primary drawback associated with employing alcohol for high-pressure development in the digester is its low boiling point. Therefore, a special equipment for high pressure is required, which increases capital expenditure. Alternatively, organic acids such as formic acid, acetic acid, and a combination of these two acids could resolve the issue related to alcohol, which requires atmospheric pressure. The lignin can be easily separated from the spent liquor by adding water. The lignin is characterized by high phenolic hydroxyl content, low molecular weight, and high reactivity. The organosolv delignification occurs through the cleavage of β-O-4 bonds.