Extraction of lignin from lignocellulose at atmospheric pressure using alkylbenzenesulfonate ionic liquid

Lignocellulosic materials are a potentially valuable source of both aromatic compounds via the lignin component and sugars from the cellulose and hemicellulose components. However, efficient means of separating and depolymerising the components are required. An ionic liquid mixture containing the 1-ethyl-3-methylimidazolium cation and a mixture of alkylbenzenesulfonates with xylenesulfonate as the main anion was used to extract lignin from sugarcane plant waste at atmospheric pressure and elevated temperatures (170–190 °C). The lignin was recovered from the ionic liquid by precipitation, allowing the ionic liquid to be recycled. An extraction yield exceeding 93% was attained. The lignin produced had a molecular weight of 2220 g/mol after acetylation. The regenerated ionic liquid showed good retention of structure and properties. The other product of the extraction was a cellulose pulp, which can be used in further processing.