Lignin recovery from Norway spruce using steam pretreatment and hydrotropic extraction

Abstract Lignin, often considered the most undervalued part of lignocellulose, holds significant potential as a renewable source of valuable chemicals and materials. This study explores new insights into lignin recovery from Norway spruce using two fractionation strategies: (1) hydrotropic extraction (HEX), and (2) steam pretreatment (SE) followed by HEX. The effects of varying sodium xylenesulfonate (SXS) concentrations and catalyst addition on lignin recovery were investigated. The one- and two-step processes achieved lignin recovery rates of 37 % and 29 %, respectively, which are among the highest reported for Norway spruce. The lignin samples were analyzed and compared by FTIR, SEC, and 2D HSQC NMR. The lignin samples showed differences in molecular weights, polydispersity, and interunit linkage abundance.