Abstract: The ternary liquid-liquid equilibrium system composed of ionic liquid [Hmim] [CF₃SO₃] which dissolved lignin with enzyme solution and the organic acid was investigated in present study. The enzymatic reactions in the system were also studied. The transformation from water-ionic two phase system to homogeneous system should be attributed to the function of carboxylic acid groups in small molecule organic acids. [Hmim] [CF₃SO₃] with dissolved lignin could also compose the ternary system with water and organic acid. In the degradation reaction, formic acid played two roles in balancing the hydrophobic phase ([Hmim] [CF₃SO₃] with dissolved lignin), and aqueous phase (enzyme solution), and acting as radical stabilizer for lignin degrading enzymatic reaction. The degradation rates of alkali lignin and dehydrogenation polymers of lignin (DHPs) were 56.5% and 66.5%, and the content of methoxyl group decreased by 46.7% and 45.3%, respectively. The generated phenolic compounds were 204.7 and 207.0 mg/L, and the formic acid consumption were 0.57 and 0.76 g, respectively. In the DHPs degradation process, the ternary equilibrium was disintegrated due to the excessive consumption of formic acid.

Key words: ternary liquid-liquid system, ionic liquid, lignin degradation, phenols