Carbohydrate Free Lignin: A Dissolution−Recovery Cycle of SodiumLignosulfonate in a Switchable Ionic Liquid System
2016 (English)In: ACS - Sustainable Chemistry and EngineeringArticle in journal (Refereed) Published
In this work, carbohydrate free lignin wasobtained by treating a technical lignin such as sodiumlignosulfonate (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 by1H,13C,and1H−13C two-dimensional heteronuclear multiple-bondcorrelation nuclear magnetic resonance (NMR) spectroscopy.The as-synthesized SIL was used as a solvent medium fordissolution of SLS-containing polysaccharide (e.g., glucan andxylan) impurities under various reaction conditions. Parame-ters such as dissolution time and temperature as well as theSLS concentration were varied. In a manner independent of the dissolution time and temperature, 2 g of SIL was able tocompletely 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 the SIL steadily decreased withincreasing amounts of accumulated SLS. The recovered solids were analyzed by1H−13C two-dimensional heteronuclear single-quantum coherence NMR spectroscopy to elucidate the potential structural changes occurring in the SLS structure afterdissolution−recovery treatment in the SIL. It was observed that in all experiments, SIL demonstrated its ability to extract theinterlinked polysaccharide impurities from the SLS while the linkages and aromatic subunits remain unaffected during thedissolution−recovery cycle. Most importantly, here we describe that the SIL can be used as an affordable solvent medium (incomparison to typical commercially available ionic liquids) to obtain carbohydrate free lignin from an impure lignin source.
Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016.
Switchable ionic liquids, Sodium lignosulfonate, Carbohydrate impurity, Lignin pretreatment, 2D NMR analysis
IdentifiersURN: urn:nbn:se:umu:diva-126880DOI: 10.1021/acssuschemeng.6b01927OAI: oai:DiVA.org:umu-126880DiVA: diva2:1038550