Kilpeläinen Ilkka, Xie Haibo, King Alistair, Granstrom Mari, Heikkinen Sami, Argyropoulos Dimitris S
Department of Forest Biomaterials Sciences and Engineering, North Carolina State University, Raleigh, NC 27659-8005, USA.
J Agric Food Chem. 2007 Oct 31;55(22):9142-8. doi: 10.1021/jf071692e. Epub 2007 Oct 2.
The present paper demonstrates that both hardwoods and softwoods are readily soluble in various imidazolium-based ionic liquids (ILs) under gentle conditions. More specifically, a variety of ionic liquids can only partially dissolve wood chips, whereas ionic liquids such as 1-butyl-3-methylimidazolium chloride and 1-allyl-3-methylimidazolium chloride have good solvating power for Norway spruce sawdust and Norway spruce and Southern pine thermomechanical pulp (TMP) fibers. Despite the fact that the obtained solutions were not fully clear, these ionic liquids provided solutions which permitted the complete acetylation of the wood. Alternatively, transparent amber solutions of wood could be obtained when the dissolution of the same lignocellulosic samples was attempted in 1-benzyl-3-methylimidazolium chloride. This realization was based on a designed augmented interaction of the aromatic character of the cation of the ionic liquid with the lignin in the wood. After dissolution, wood can be regenerated as an amorphous mixture of its original components. The cellulose of the regenerated wood can be efficiently digested to glucose by a cellulase enzymatic hydrolysis treatment. Furthermore, completely acetylated wood was found to be readily soluble in chloroform, allowing, for the first time, detailed proton nuclear magnetic resonance (NMR) spectra and NMR diffusion measurements to be made. It was thus demonstrated that the dissolution of wood in ionic liquids now offers a variety of new possibilities for its structural and macromolecular characterization, without the prior isolation of its individual components. Furthermore, considering the relatively wide solubility and compatibility of ionic liquids with many organic or inorganic functional chemicals or polymers, it is envisaged that this research could create a variety of new strategies for converting abundant woody biomass to valuable biofuels, chemicals, and novel functional composite biomaterials.
本文表明，在温和条件下，硬木和软木都能很容易地溶解于各种基于咪唑鎓的离子液体（ILs）中。更具体地说，多种离子液体只能部分溶解木屑，而诸如1-丁基-3-甲基咪唑鎓氯化物和1-烯丙基-3-甲基咪唑鎓氯化物等离子液体对挪威云杉锯末以及挪威云杉和南方松热机械浆（TMP）纤维具有良好的溶解能力。尽管所得到的溶液并非完全澄清，但这些离子液体提供的溶液能使木材完全乙酰化。另外，当尝试在1-苄基-3-甲基咪唑鎓氯化物中溶解相同的木质纤维素样品时，可以得到木材的透明琥珀色溶液。这一认识是基于离子液体阳离子的芳香特性与木材中木质素之间设计增强的相互作用。溶解后，木材可以再生为其原始成分的无定形混合物。再生木材的纤维素可以通过纤维素酶酶解处理有效地消化为葡萄糖。此外，发现完全乙酰化的木材很容易溶解于氯仿中，这首次使得能够进行详细的质子核磁共振（NMR）光谱和NMR扩散测量。因此证明，木材在离子液体中的溶解现在为其结构和大分子表征提供了多种新的可能性，而无需事先分离其各个组分。此外，考虑到离子液体与许多有机或无机功能化学品或聚合物具有相对广泛的溶解性和相容性，可以设想，这项研究能够创造出多种将丰富的木质生物质转化为有价值的生物燃料、化学品和新型功能复合生物材料的新策略。
