Title
Pretreatment of cellulosic substrates with acetate- and chloride-based ionic liquids and their mixtures
Authors
IAKOV A. MASIUTIN ALEXANDER V. GOLYSHKIN ARTEM A. LITVIN ANDREI A. NOVIKOV MIKHAIL S. KOTELEV EVGENII V. IVANOV and VLADIMIR A. VINOKUROV

Received December 21, 2016
Published Volume 52 Issue 1-2 January-February
Keywords lignocellulose, cellulose, pretreatment, ionic liquids, biofuel

Abstract
Cellulose has a complex structure that seriously hinders its processing. Ionic liquids (ILs) have the ability to dissolve cellulose, thus modifying its structure. A series of acetate- and formate-based ILs was synthesized from their chloride analogues and tested for dissolution of microcrystalline cellulose. Cellulose solubility in 1-butyl-3-methylimidazolium acetate [BMIm]Ac, 1-ethyl-3-methylimidazolium acetate [EMIM]Ac, 1-butyl-3-methylimidazolium chloride [BMIm]Cl, 1-ethyl-3-methylimidazolium chloride [EMIM]Cl and their mixtures was investigated. The optimal weight ratio of a chloride-based IL to an acetate-based IL was found to be 3:2. The solubilizing power of that mixture was maximal, while that of butyl-substituted ILs exceeds the solubilizing power of individual compounds. Despite having better solvent power, acetate-based ILs provide a lower decrease in cellulose crystallinity, as revealed by powder X-ray diffraction studies, in comparison with their chloride-based counterparts. The initial and pretreated cellulose substrates were also analyzed by scanning electron microscopy; the micrographs confirmed that substrate morphology changed profoundly after the pretreatment with ILs.