Fractionation of lignin from rice straw using an acidified biphasic solvent system

To obtain lignin from lignocellulosic biomass, phenoxyethanol (EPH) was employed to construct a biphasic solvent system. The concentration of EPH in this biphasic solvent system was first studied to determine a pre-treatment condition for fractionation of lignin. Then, the fractionation of lignin from rice straw was performed under the conditions of temperature 130 degrees C, cooking time 60 min and sulfuric acid concentration 0.1 M, in 70 % aqueous EPH solvent system. The results showed that 50.97 %, 49.52 % or 82.02 % of the removed lignin with the purity of 89.04 %, 91.30 % or 84.76 % was regenerated from EPH liquor using dimethyl carbonate (DMC), dimethoxymethane (DMM) or diethyl ether (DE) as precipitant, respectively. Additionally, the weight-average molecular weight (Mw) and dispersity index (D) of the regenerated lignin decreased to 4247-4809 g/mol and 1.26-1.60 compared with that of the original lignin (5654 g/mol and 4.78). Finally, the compositional and structural characteristics of lignin, e.g., molecular weight and molecular structure, were also investigated by DSC, HSQC and elemental analysis.

Automated summary

Phenoxyethanol (EPH) was used to create a biphasic solvent system for lignin extraction from lignocellulosic biomass. The concentration of EPH was studied to determine the pre-treatment condition for lignin fractionation. The lignin from rice straw was then fractionated using a 70% aqueous EPH solvent system, resulting in the regeneration of lignin with varying purities using different precipitants. The compositional and structural characteristics of the regenerated lignin were also analyzed.