Organosolvent

An organosolvent is an organic solvent used in organosolv processes, a family of methods for processing lignocellulosic biomass. In these processes, the solvent system is designed to dissolve lignin and, to varying extents, hemicelluloses, while leaving cellulose relatively intact as a solid pulp. Organosolv methods are explored as alternatives or complements to conventional pulping technologies.

Common organosolvents include alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone; esters such as ethyl acetate; and ethers such as tetrahydrofuran. Often the solvent is used with a small amount of water and a catalyst (acid or alkali) to enhance lignin solubility and hemicellulose solubilization. Temperature and pressure conditions vary by system but are typically elevated, enabling efficient separation of biomass into a cellulose-rich solid and a lignin/hemicellulose-containing liquid phase.

Applications of organosolv processes include pulping for paper production and pretreatment for biorefineries aiming to valorize all biomass fractions. The approach can yield high-purity lignin suitable for value-added applications and produce cellulose with relatively high degree of polymerization and accessibility for downstream processing.

Advantages of organosolv solvents include milder degradation of carbohydrates, easier recovery and recycling of solvents, and the potential for producing high-quality lignin. Disadvantages include the need for effective solvent recovery to minimize emissions, energy requirements, solvent flammability and toxicity, and higher capital costs compared with some conventional methods. Ongoing research focuses on developing efficient, safer, and cost-competitive organosolv systems.