The low solubility of lignin in most common solvents remains a significant challenge to be solved for its use and recovery. In this work, 18 novel protic ionic liquids (ILs) containing aromatic-substituted imidazolium cations and methanesulfonate and p-toluenesulfonate anions were synthesized and evaluated for lignin dissolution under microwave irradiation. ILs containing methanesulfonate demonstrated good lignin dissolving capacities, which can facilitate its separation and structural modifications to carry out their recovery under relatively mild and environmentally friendly conditions (few minutes, 90 °C). DFT theoretical calculations provided additional insights into the high lignin dissolution observed for the best performing ILs.

A new mechanistic proposal based in theoretical and experimental evidence invoking the participation of water is presented.

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