Extraction of cellulose from corn stover using designed ionic liquids with improved reusing capabilities

Abstract

In recent years, the dissolution of lignocellulosic biomass using ionic liquids has attracted a lot of attention. Generally, the processes of valorisation of residual biomass do not extract cellulose. Among the lignocellulosic biomass, corn stover has a great interest because its high content in cellulose. For this reason, five ionic liquids have been designed and produced to dissolve the cellulose contained in corn stover, three tetra-alkyl-phosphonium based ILs and two imidazolium based ILs: tetra-butyl-phosphonium acetate [P4444][OAc]; tri-butyl-methyl-phosphonium acetate [P4441][OAc]; tetra-butyl-phosphonium 2-ethyl-hexanoate [P4444][EH]; 1-dodecyl-3-methyl-imidazolium bis (2,4,4-tri-methyl-pentyl) phosphinate [C12mim][(iC8)2PO2]; 1-decyl-3-methyl-imidazolium bis (2,4,4-tri-methyl-pentyl) phosphinate [C10mim][(iC8)2PO2]. The dissolution of cellulose was carried out under mild conditions (3 h and 80℃). Among the synthesised ionic liquids [P4444][EH] turned out to dissolve the greatest amount of cellulose (84 %), while imidazolium ionic liquids [C12mim][(iC8)2PO2] and [C10mim][(iC8)2PO2] dissolved 61.1 % and 44.0 %, respectively. On the other hand, these designed ILs have the ability to be easily recovered. As they are microemulsion-forming ionic liquids, the recycling of these ionic liquids was more straightforward (without the need of solvent evaporation). Furthermore, imidazolium ionic liquids were found to eliminate more ashes from the corn stover than tetra-alkyl-phosphonium ionic liquids.