Extraction of phenols from lignin microwave-pyrolysis oil using a switchable hydrophilicity solvent

[Display omitted] •Switchable-hydrophilicity solvents were used to extract phenols from lignin bio-oil.•Phenols were successfully extracted and the SHS (91%) was recovered.•NMR analysis showed the three fractions’ differences in chemical structure.•T1 relaxation time was measured to ensure reliable quantitative 13C NMR analysis. Microwave pyrolysis of lignin, an aromatic polymer byproduct from paper-pulping industry, produces char, gases, and lignin pyrolysis oil. Within the oil are valuable phenolic compounds such as phenol, guaiacol and catechol. In this work, we describe a method using switchable hydrophilicity solvents (SHS) to extract phenols as a mixture from lignin microwave-pyrolysis oil at the scale of 10g of bio-oil. Even at this small scale, losses are small; 96% of the bio-oil was recovered in its three fractions, 72% of guaiacol and 70% of 4-methylguaiacol, the most abundant phenols in the bio-oil, were extracted and 91% of the solvent SHS was recovered after extraction. The starting material (lignin microwave-pyrolysis oil) and the three fractions resulted from SHS extraction were characterized by GC–MS and quantitative 13C{1H} and 31P{1H} NMR spectroscopy.