Dissolving lignocellulosic biomass in a 1-butyl-3-methylimidazolium chloride-water mixture

An ionic liquid (IL)-water mixture employed to treat lignocellulosic biomass is promising. The addition of water decreases viscosity and process cost so as to improve the IL practical application. In this work, effects of temperature (50-170 degrees C), water content (0-80 wt%), treating duration (0.5-4 h) and pressure (0.1-3.2 MPa) on treating legume straw process using a 1-butyl-3-methylimidazolium chloride [C(4)mim]Cl-water mixture were experimentally investigated. Legume straw was found to be partially dissolved, and the dissolved substances can be flocculated by adding the coagulating agent water (equal to volume of the solution). For this process at 0.1 MPa, the maximum 29.1 wt% legume straw is dissolved in the [C(4)mim]Cl-water mixture with water content of 20 wt% at 150 degrees C during 2 h, which is much higher than 9.8 wt% using pure [C(4)mim]Cl. A hemicellulose-free lignin-rich material (64.0 wt% lignin and 35.3 wt% cellulose) is obtained by adding the water. Even for 0.5 h, 22.3 wt% of legume straw is dissolved in the case of water content of 20 wt%, 150 C and 0.1 MPa. High pressure favors the dissolution of legume straw but lignin content in the residue has no obvious change. The addition of proper amount of water facilitates the dissolution of legume straw and a relative rapid dissolving rate can be achieved in a [C(4)mim]Cl-water mixture. There are great differences in chemical and physical properties between legume straw and the obtained samples (residue and floc) due to the dissolution and reconstitution. C) 2011 Elsevier B.V. All rights reserved.