Microwave-assisted extraction of Xianfeng lignite in 1-butyl-3-methyl-imidazolium chloride

The extraction of Xianfeng lignite (XL) with ionic liquid-1-butyl-3-methyl-imidazolium chloride ([Bmim]Cl) was carried out at mild conditions under microwave irradiation in this work. The effects of the temperature, XL to [Bmim]Cl ratio and acid pretreatment on extract yield of lignite and product compositions were investigated. The extraction results of XL indicated that [Bmim]Cl has high performance on the extraction of the XL. With the increases of extraction temperature and mass ratio of [Bmim]Cl to lignite the extract yield of XL in [Bmim]Cl significantly increases. FT-IR measurements for XL, its extracts and residues at different mass ratio of XL/[Bmim]Cl indicated that [Bmim]Cl can break the non-covalent interactions such as hydrogen bonds and extracts the aromatics fractions from lignite. (C) 2011 Elsevier Ltd. All rights reserved.