Wood liquefaction by ionic liquids

The liquefaction of wood (Metasequoia glyptostroboides) has been studied in two imidazole-based ionic liquids: IL1, 3,3′-ethane-1,2-diylbis(1-methyl-1H-imidazol-3-ium) dichloride; and IL2, 3,3′-ethane-1,2-diylbis(1-methyl-1H-imidazol-3-ium) dichloroaluminate. Rapid and complete liquefaction was obtained in IL2 without residue at 120°C for 25 min, in contrast to liquefaction in phenol/H2SO4 (liquid/wood ratio 20:1) with 25.9% residue. Temperature- and time-dependent studies indicate that the performance of the reagents investigated is IL2>IL1> phenol/H2SO4. The liquid/wood ratio and the amount of AlCl3 as catalyst affect the liquefaction rate. In the course of liquefaction with IL2, AlCl3 plays a dual role as a catalyst and a liquefaction reagent. Ionic liquids separated from the liquefied product can be recycled at least five times to maintain a good liquefaction rate.