Green solvents-based fractionation process for kraft lignin with controlled dispersity and molecular weight.

• Lignin solubilisation mechanism in pure solvents and mixtures elucidated. • Novel cost-effective and sustainable process developed for fractionating lignin. • Challenges of design and scale-up for integration into value chains identified. • Techno-economic and environment, health and safety metrics developed for benchmarking. The aim of this work is to develop a novel green solvent based sustainable process to refine lignin into low molecular weight (LMW) and high molecular weight (HMW) fractions. Lignin dispersity reduction were experimentally determined using four solvent mixtures, and benchmarked against eight pure solvents. Data outputs were used for modelling the integrated fractionation process. Dispersity reduction of up to 73% was achieved for the high value LMW fraction. Also, a 90% reduction of energy requirement was achieved with an optimized process incorporating a mechanical vapor compression system. This study showed that solvent mixtures involving water can significantly reduce the cost, environment, health and safety impacts of lignin fractionation. Techno-economic evaluation confirmed the economic viability of a large-scale process processing 50 tonne/day of lignin. [ABSTRACT FROM AUTHOR]