Abstract
Cellulose acetylation has been reported as a side reaction of cellulose treatment with the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) (Karatzos et al. in Cellulose 19:307–312, 2012) and other 1,3-dialkylimidazolium acetate ionic liquids. 1-Acetylimidazole (AcIm), an [EMIm][OAc] impurity, has been found to be the actual acetylating agent (Zweckmair et al. in Cellulose 22:3583–3596, 2015), and the degree of acetylation was relatively low, below a DS of approx. 0.1%. Higher degrees of cellulose acetylation (DS > 10%) have been observed when the entire wood was mixed with [EMIm][OAc] instead of cellulosic pulp only (Abushammala et al. in Carbohydr Polym 134:609–616, 2015). In this paper, we explore the impact of wood constituents, mainly lignin, on cellulose acetylation using AcIm. The results demonstrate that lignin itself can be readily acetylated upon mixing with AcIm, and—noteworthy—that lignin presence significantly accelerates cellulose acetylation. The initial rate of cellulose acetylation by AcIm increased from 1.8 to 4.7%/h when only 1% of lignin, based on cellulose mass, was added. A mechanistic study employing cellulose and lignin model compounds showed lignin to be more susceptible to acetylation than cellulose and to act as an intermediate acetyl group source for further cellulose acetylation in a catalytic scenario.
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Abushammala H, Krossing I, Laborie M-P (2015) Ionic liquid-mediated technology to produce cellulose nanocrystals directly from wood. Carbohydr Polym 134:609–616
Abushammala H, Goldsztayn R, Leao A, Laborie M-P (2016) Combining steam explosion with 1-ethyl-3-methylimidazlium acetate treatment of wood yields lignin-coated cellulose nanocrystals of high aspect ratio. Cellulose 23:1813–1823
Brandt A, Ray MJ, To TQ, Leak DJ, Murphy RJ, Welton T (2011) Ionic liquid pretreatment of lignocellulosic biomass with ionic liquid–water mixtures. Green Chem 13:2489–2499
Brandt A, Gräsvik J, Hallett JP, Welton T (2013) Deconstruction of lignocellulosic biomass with ionic liquids. Green Chem 15:550–583
Clough MT, Geyer K, Hunt PA, Son S, Vagt U, Welton T (2015) Ionic liquids: not always innocent solvents for cellulose. Green Chem 17:231–243
Cremer T et al (2010) Towards a molecular understanding of cation-anion interactions—probing the electronic structure of imidazolium ionic liquids by NMR spectroscopy, X-ray photoelectron spectroscopy and theoretical calculations. Chem Eur J 16:9018–9033
Ebner G, Schiehser S, Potthast A, Rosenau T (2008) Side reaction of cellulose with common 1-alkyl-3-methylimidazolium-based ionic liquids. Tetrahedron Lett 49:7322–7324
Gazit OM, Katz A (2012) Dialkylimidazolium ionic liquids hydrolyze cellulose under mild conditions. ACS Sustain Chem Eng 5:1542–1548
Hubbell CA, Ragauskas AJ (2010) Effect of acid-chlorite delignification on cellulose degree of polymerization. Biores Technol 101:7410–7415
Jonoobi M, Harun J, Mathew AP, Hussein MZB, Oksman K (2010) Preparation of cellulose nanofibers with hydrophobic surface characteristics. Cellulose 17:299–307
Karatzos SK, Edye LA, Wellard RM (2012) The undesirable acetylation of cellulose by the acetate ion of 1-ethyl-3-methylimidazolium acetate. Cellulose 19:307–312
Kim D-Y, Nishiyama Y, Kuga S (2002) Surface acetylation of bacterial cellulose. Cellulose 9:361–367
Köhler S, Liebert T, Schöbitz M, Schaller J, Meister F, Günther W, Heinze T (2007) Interactions of ionic liquids with polysaccharides 1. unexpected acetylation of cellulose with 1-ethyl-3-methylimidazolium acetate. Macromol Rapid Commun 28:2311–2317
Leskinen T, King AW, Argyropoulos DS (2014) Fractionation of lignocellulosic materials with ionic liquids. In: Zhen F, Richard LSJ, Xinhua Q (eds) Production of biofuels and chemicals with ionic liquids, vol 1. Springer, Netherlands, pp 145–168
Liebert T, Heinze T (2008) Interaction of ionic liquids with polysaccharides. 5. Solvents and reaction media for the modification of cellulose. BioResources 3:576–601
Liebner F, Patel I, Ebner G, Becker E, Horix M, Potthast A, Rosenau T (2010) Thermal aging of 1-alkyl-3-methylimidazolium ionic liquids and its effect on dissolved cellulose. Holzforschung 64:161–166
Rodríguez H, Gurau G, Holbrey JD, Rogers RD (2011) Reaction of elemental chalcogens with imidazolium acetates to yield imidazole-2-chalcogenones: direct evidence for ionic liquids as proto-carbenes. Chem Commun 47:3222–3224
Salmén L (2015) Role of lignin in the structure of wood fibres. In: 8th Plant Biomechanics International, Nagoya, Japan
Steinfeld JI, Francisco JS, Hase WL (1989) Chemical kinetics and dynamics, vol 3, 2nd edn. Prentice Hall Englewood Cliffs, Upper Saddle River, p 07458
Van Oss CJ, Chaudhury MK, Good RJ (1988) Interfacial Lifshitz-van der Waals and polar interactions in macroscopic systems. Chem Rev 88:927–941
Zweckmair T, Becker M, Ahn K, Hettegger H, Kosma P, Rosenau T, Potthast A (2014) A novel method to analyze the degree of acetylation in biopolymers. J Chromatogr A 1372:212–220
Zweckmair T, Hettegger H, Abushammala H, Bacher M, Potthast A, Laborie M-P, Rosenau T (2015) On the mechanism of the unwanted acetylation of polysaccharides by 1, 3-dialkylimidazolium acetate ionic liquids: part 1—analysis, acetylating agent, influence of water, and mechanistic considerations. Cellulose 22:3583–3596
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The authors thank Sona Othman for the surface energy measurements and Marina Hagios for the GPC measurements.
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Abushammala, H., Hettegger, H., Bacher, M. et al. On the mechanism of the unwanted acetylation of polysaccharides by 1,3-dialkylimidazolium acetate ionic liquids: part 2—the impact of lignin on the kinetics of cellulose acetylation. Cellulose 24, 2767–2774 (2017). https://doi.org/10.1007/s10570-017-1322-x
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DOI: https://doi.org/10.1007/s10570-017-1322-x