Abstract
In this work, carbohydrate free lignin was obtained by treating a technical lignin such as sodium lignosulfonate (SLS) with a switchable ionic liquid (SIL). The SIL was synthesized from molecular moieties such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), monoethanol amine (MEA), and carbon dioxide gas and characterized by 1H, 13C, and 1H–13C two-dimensional heteronuclear multiple-bond correlation nuclear magnetic resonance (NMR) spectroscopy. The as-synthesized SIL was used as a solvent medium for dissolution of SLS-containing polysaccharide (e.g., glucan and xylan) impurities under various reaction conditions. Parameters such as dissolution time and temperature as well as the SLS concentration were varied. In a manner independent of the dissolution time and temperature, 2 g of SIL was able to completely dissolve 0.3 g of SLS and ≈60% SLS was recovered upon precipitation with an ethanol/hexane antisolvent system. The nonrecovered SLS remained in the viscous SIL phase. However, the dissolution ability of t...
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