Acetone fractionation of heterogeneous tetrahydrofurfuryl alcohol lignin to improve its homogeneity and functionality

Abstract

Lignin, a carbon-rich biopolymer, has great application potentials in the field of biomaterial manufacture. However, lignin produced from separation process is a heterogeneous polymer with low functionality, which largely limits its application. In this case, a simple and green approach was proposed to fractionate tetrahydrofurfuryl alcohol lignin with different acetone concentrations to produce homogeneous lignin having high antioxidant capacity. Lignin dissolved in 60% acetone solution was stirred for 1 h at room temperature and water was gradually added to precipitate and to obtain fractions with a high purity. The molecular weight distribution, structural characteristics and thermal stability of lignin before and after fractionation were extensively studied by using various methods (nuclear magnetic resonance techniques, thermogravimetric analysis, etc.). At the lowest acetone concentration, the molecular weight of lignin was 1490 g/mol, the polydispersity index was as low as 1.16, and the total phenolic hydroxyl content reached 3.3 mmol/g. Results showed that lignin samples had strong antioxidant activity as compared to commercial antioxidant butylated hydroxytoluene. This study indicated that separation with acetone/water system is meaningful approach to prepare homogeneous lignin with excellent functionality.

Keywords

• Tetrahydrofurfuryl alcohol lignin
• Acetone
• Lignin fractionation
• Molecular weight
• Antioxidant capacity