Treating birch wood with a switchable 1,8-diazabicyclo-[5.4.0]-undec-7-ene- glycerol carbonate ionic liquid

The suitability of a new switchable ionic liquid (SIL) has been investigated as a solvent for fractionation of lignocellulosic materials. SIL was prepared from inexpensive chemicals, e.g., glycerol, CO₂, and 1,8-diazabicyclo-[5.4.0]- undec-7-ene (DBU). Fresh Nordic birch wood (B. pendula) was treated with the SIL for a time period of 1 - 5 days at 100 °C and under atmospheric pressure. Upon SIL treatment, at best, 57% of the hemicelluloses were dissolved and 50% of lignins were dissolved from the native birch. The slightly fibrillated SIL treated chips contained about 55% cellulose. Up to 76% of the recovered species removed from the spent SIL liquor was originating from hemicelluloses, mainly from xylan. The spent SILs were reused for fresh wood dissolution in four consecutive cycles and each time the wood dissolution efficiency was similar. SILs could offer affordable (easyto- synthesize) solvent systems for partial elimination of hemicelluloses and lignin from wood. SILs can also be prepared in-situ and on-site.