Enhancement of ionic liquid-aided fractionation of birchwood. Part 1: autohydrolysis pretreatment

Abstract

Ionic liquid-cosolvent systems have been proposed as selective solvent media for lignocellulosic materials.We present the ionic liquid-aided fractionation of silver birch (Betula pendula) combined with an autohydrolysis pretreatment. Contrary to untreated birchwood meal, autohydrolyzed birchwood meal reveals quantitative dissolution in 1-ethyl-3-methylimidazolium acetate and distinct separation into the individual wood polymers upon regeneration in acetone/water. The process yields two main fractions, a cellulose-rich precipitate with a residual lignin content of 13-15% and another virtually pure lignin fraction. No cellulose yield loss is observed during the ionic liquid processing step. A comprehensive mass balance of the process, including insoluble material, wash waters, and soluble residues, is provided. The product fractions are characterised for their chemical compositions, molar mass distributions and structural characteristics by Klason lignin and sugar analysis, 13 C NMR, GPC and WAXS. The study investigates the effects of wood particle size and autohydrolysis intensity on fractionation efficiency and selectivity.

Ionic Liquids for the Production of Man-Made Cellulosic Fibers: Opportunities and Challenges

“…In some cases, cellulose enrichment was observed during the spinning process, indicating that some of the lignin and hemicelluloses were not regenerated along with the cellulose matrix but remained in solution. By choosing the right coagulation bath composition, it was possible to amplify the delignification of the lignocellulosic substrate in the spinning process and produce cellulose-enriched strong fibers [102,103]. Fink and coworkers also reported the production of lignocellulosic fibers from hemp and wheat straw using [bmim]cyclohexylcarboxylate, spinning fibers with a tenacity of 22 and 36 cN/tex, respectively [104].…”

“…The sticky pulp-IL mixture was then transferred to a vertical kneader system, which was described in detail in an earlier publication [103,123]. The mixture was stirred at 80 C and 10 rpm under reduced pressure (50 mbar).…”

Ionic liquid-mediated technology to produce cellulose nanocrystals directly from wood

“…It has been utilized for ionic liquid-assisted fractionation (ILAF) of wood under homogeneous conditions thereby producing a cellulose II pulp (Sun et al, 2009). Its potential for heterogeneous ILAF to recover a native cellulose I pulp has also been proposed (Hauru et al, 2013). Moreover, [EMIM] [OAc] has been shown to hydrolyze cellulose under mild conditions (Gazit & Katz, 2012).…”

“…Accordingly, ILs have been successfully used for multiple purposes including notably complete dissolution of wood and sugar recovery (Fadeev & Meagher, 2001;Mäki-Arvela, Anugwom, Virtanen, Sjöholm, & Mikkola, 2010;Vancov, Alston, Brown, & McIntosh, 2012), delignification and recovery of cellulose (Anugwom et al, 2011;Brandt et al, 2011;Hou, Smith, Li, & Zong, 2012;Leskinen, King, Kilpeläinen, & Argyropoulos, 2013;Pinkert et al, 2011;Shamsuri & Abdullah, 2010;Tan et al, 2009). Among ILs commonly used with lignocellulose, 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]) is known to display specificity for lignin dissolution (Brandt et al, 2010;Hauru et al, 2013;Hossain & Aldous, 2012;Lee, Doherty, Linhardt, & Dordick, 2009). It has been utilized for ionic liquid-assisted fractionation (ILAF) of wood under homogeneous conditions thereby producing a cellulose II pulp (Sun et al, 2009).…”

Effect of Ionic Liquids on Oil Palm Biomass Fiber Dissolution

“…For example, the difference and complexity of lignin-carbohydrate bonding make softwoods inaccessible, non-extractable and more recalcitrant to delignification (Tadesse and Luque 2011). In advance studies, pretreatment of the biomass, such as by steam explosion of rice straw (Jiang et al 2011) and autohydrolysis pretreatment of silver birch (Betula pendula) (Hauru et al 2013), improves lignin solubility and thus allows lignin extraction with ILs. The high solubilization of lignin in ILs may have important practical applications for wood delignification, for example in the pulp and paper industry (Li et al 2009;King et al 2014).…”