Abstract
Ionic liquids are able to dissolve polysaccharides and lignin, but there is only scarce knowledge about the dissolution of native wood. In the present paper, wood was dissolved by the ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIMAc). A quantitative balance of the dissolved compounds is presented and the investigations are complemented by in situ microscopy of native wood in EMIMAc. The resulting dissolution kinetics in EMIMAc reveals distinct differences between spruce and beech. While particles of 0.1–0.5 mm of spruce dissolve slowly (up to 40% after 24 h), beech is dissolved more efficiently (75% after 24 h and 90% after 72 h). Wood chips of 10 mm length show similar dissolution kinetics and lignin yields of up to 10%. Microscopic studies reveal a disintegration of wood in EMIMAc into cells with large specific surface area, and differences in dissolution between spruce and beech were observed. These findings explain the size-independent dissolution of wood in EMIMAc and may open up new opportunities for the pretreatment of wood in ionic liquids.
Dissolution kinetics of cellulose in ionic liquids: Raman spectral mapping
