Recent History of Organosolv Pulping, 1992 Solvent Pulping Symposium Proceedings

Research and development on the use of organic solvents to facilitate delignification of woody materials has been greatly expanded during the past half decade. The rationale for this work, progress in developing viable commercial processes, differentiating types of processes, and deduction of chemical mechanisms involved are briefly summarized in this review. A bibliography of all pertinent work since 1987 has been prepared and should be of use to all those interested in or actively involved in organosolv pulping. Processes have been differentiated on the basis of whether they involve (a) water hydrolysis at elevated temperature followed by solvent extraction or cotreatment with solvent and water only, (b) acid- catalyzed solvent treatment, (c) reaction with phenolic solvents, (d) alkali and organic solvents, (e) sulfites or sulfides and organic solvents, and (f) oxidation in the presence of solvents. Philosophically, two major commercial approaches have emerged. One centers on isolation of lignin and chemical byproducts in addition to pulp, while the other focuses on pulp only concurrent with process simplification. Both will likely have their place in the future.