Lignin extraction and purification with ionic liquids

BACKGROUND In new biorefineries the use of new green solvents is essential in order to minimize the employment of volatile organic solvents.Lignin is the most abundant residue in paper industries, however, it is necessary to purify it in order to obtain revalorized products. RESULTS In this study, soda and organosolv lignins obtained from apple tree prunings (Malus domestica) were purified using [Bmim][MeSO4], and the lignin extracted from raw material was tested comparing different conditions. [Bmim][MeSO4], EtmimAc(1-Ethyl-3-methylimidazolium acetate) and BmimCl, were the ionic liquids chosen for the experimentation. The lignins obtained were characterized by FTIR, TGA, RMN and HPLC, in order to determinate the influence of the different treatments on their structures. Lignin of 91.2% purity was obtained directly from raw material using ionic liquids, whereas organosolv lignin purity ranges from 85.7% to 90.9%, and soda lignin from 12.9% to 89.6% after treatment with [Bmim][MeSO4]. CONCLUSION Results showed that the use of [Bmim][MeSO4] is the best option to purify and extract lignin from raw material. In addition, microwave radiation enhanced the energy consumption of the process.(c) 2012 Society of Chemical Industry