Chapter 5: Reduction of Biomass Recalcitrance via Ionic Liquid Pretreatments

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

“…Surprisingly, a sharp vibrational peak at 1741 cm −1 characteristic of C O bonds appears again in WR-2 (90% cellulose), suggesting acetylation. Cellulose (and lignin) acetylation as a side reaction using [EMIM][OAc] has been previously reported (Ç etinkol et al, 2010;Hauru et al, 2013;Karatzos, Edye, & Wellard, 2012;King, Xie, Fiskari, & Kilpelaeinen, 2014;Köhler et al, 2007). This structural change will be revisited in the next section.…”

“…Cellulose acetylation by [EMIM][OAc] is temperature dependent: at low temperature (80 • C) it is only revealed when a catalyst is used (Köhler et al, 2007); at higher temperature (e.g., 185 • C) it occurs also in the absence of a catalyst (Karatzos et al, 2012;Li et al, 2011). In whole wood, transacetylation from xylan to lignin has also been proposed (King et al, 2014). In the proposed pulping process, no acetylation was detected in the first pulping cycle.…”

Combining steam explosion with 1-ethyl-3-methylimidazlium acetate treatment of wood yields lignin-coated cellulose nanocrystals of high aspect ratio

“…To explain the efficacy of this technology and the apparent recovery of nanocrystals in sizes very similar to native cellulose crystallites, we proposed that hydrolysis of lignin-carbohydrate complexes (LCCs) (King et al 2014), and acetylation of wood polymers favored a demixing or phase separation of wood polymers (Zweckmair et al 2015), which together with the hydrolyzing power of the IL (Gazit and Katz 2012) resulted in CNCs separation (Abushammala et al 2015). Also critical to the proposed mechanism, the acetylating power of [EMIM][OAc] allows derivatizing lignin phenolic hydroxyls thus deactivating its propensity for recondensations (Abushammala et al 2015;Ç etinkol et al 2010;Ebner et al 2008;Hauru et al 2013;Karatzos et al 2012;King et al 2014;Köhler et al 2007).…”

Ionic Liquids in Biomass Processing

“…Since the pioneering work in this field by Varanasi et al., a number of research groups have explored this major application of ILs . The vast number of publications in this area for about a decade have been reviewed as well …”