Ionic liquid-aided fractionation of wood has evoked much interest recently, but unsolved problems remain, from high viscosity to low chemical selectivity in the regeneration step. First, this study elucidates the effect of autohydrolysis on the fractionation of birchwood, in order to reduce the amount of undissolved material, and second, how the solution viscosity and fractionation selectivity is modified by addition of cosolvents. Kneading 25 g of autohydrolyzed birchwood with [emim]OAc (1-ethyl-3-methylimidazolium acetate) at 5�10% concentration under vacuum at elevated temperature (100 �C) followed by direct filtration, using different cosolvents to aid the process, gives wood solutions for further processing. Due to the high viscosities and temperatures, a vertical kneader system and a heated filtration unit powered by a 10-ton bench press are used. Precipitation into antisolvent gives fractions that are analyzed for molecular weight and chemical composition. A mass balance is provided for a selective fractionation.

Effect of pretreatment and cosolvent on the fractionation of birch with 1-ethyl-3-methylimidazolium acetate

243rd National Meeting (2012)

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