title: Extraction of lignins from aqueous-ionic liquid mixtures by organic solvents.
abstract: The commercial development of ionic liquids (ILs) to pretreat lignocellulose by dissolution of whole biomass and cellulose precipitation by addition of water is hindered by the absence of an effective technique to recover the lignin content of the biomass from the IL. Three organic solvents [ethyl acetate, 1,4-dioxane, and tetrahydrofuran (THF)] were studied for their ability to form a two-liquid-phase system with water and 1-ethyl-3-methylimidazolium acetate ([C(2)mim][OAc]), and for partitioning model lignins and lignin monomers between the two liquid phases. Ternary diagrams were obtained for three [C(2)mim][OAc]/organic solvent/water systems at 22°C. Partition coefficients were measured for several types of lignin in these three systems. Partition coefficients increase with rising water content in the IL phase, and depend strongly on the type of lignin and on the organic solvent. Partition coefficients rise as the pH of the ionic-liquid-rich phase falls. Small molecule model lignin monomer compounds (guaiacol, syringaldehyde) are also readily extracted from the IL/water system by THF.
authors.affiliation: State Key Laboratory of Chemical Engineering, Department of Chemistry, East China University of Science and Technology, Shanghai, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Xin
authors.forename: Katie
authors.initials: K
authors.lastname: Pfeiffer
authors.forename: John M
authors.initials: JM
authors.lastname: Prausnitz
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Clark
authors.forename: Harvey W
authors.initials: HW
authors.lastname: Blanch
mesh_terms: D000085:Acetates / Q000737:chemistry; D056804:Biofuels; D018533:Biomass; D006863:Hydrogen-Ion Concentration; D052578:Ionic Liquids / Q000737:chemistry*; D008031:Lignin / Q000302:isolation & purification*; D006109:Poaceae; D012997:Solvents / Q000737:chemistry*; D014867:Water
chemical_list: D000085:Acetates; D056804:Biofuels; D052578:Ionic Liquids; D012997:Solvents; D014867:Water; C007650:ethyl acetate; D008031:Lignin