Dissolution of lignocellulosic materials and its constituents using ionic liquids—A review

The state of art from the dissolution of cellulose, lignin and wood using ionic liquids is presented in this work. The emphasis is put on the relationship between the properties of ionic liquids and the dissolution capacity. The impact of the following solvation parameters, namely Hildebrand solubility parameter and hydrogen bond basicity are related to the dissolution of lignocellulosic material. Good solvents for cellulose are 1-butyl- and 1-allyl-3-methylimidazolium chlorides as well as 1-ethyl-3-methylimidazolium acetate, whereas for lignocellulosic material the best solvents are 1-ethyl-3-methylimidazolium acetate and 1-allyl-3-methylimidazolium chloride. In allyl group the ethylene functionality facilitates B-interactions with the aromatic lignin structure. Furthermore, small polarizable anions are also powerful when aiming at dissolution of cellulose. The properties of regenerated cellulose and reconstituted lignin are also given and compared with those of the native materials. Furthermore, the results from the regeneration and reuse of ionic liquids are presented here.