Effect of solvent and acid catalyst selection on lignin recovery and purity in autoclave-assisted organosolv extraction

This study leverages the autoclave-assisted method to explore a range of acid catalysts (H₂SO₄, HCl, HNO₃, H₃PO₄) and solvents (methanol, ethanol, acetone, 2-butanol, 2-propanol) for lignin extraction, with a focus on identifying optimal efficiency-enhancing combinations. By contrasting the performance of various acid catalysts and solvents, this work transcends previous efforts in this field. Notably, H₂SO₄ yields the highest lignin recovery (44.7 %) but with lower purity (78.4 %) compared to HCl (85.7 %) in the same solvent. Methanol yields the highest recovery (45.1 %), yet lower purity (79.2 %) than ethanol (85.7 %) with a similar catalyst. A pivotal improvement lies in the elucidation of structural purity, substantiated by IR and NMR resulting signals, supported by microscale morphology and chemical composition (SEM-EDX). This study extends current understanding, providing profound insights into optimizing extraction procedures for producing lignin with desired attributes.