Efficient Pretreatment of Corn Straw with Ionic Liquid Composite System

Proton-type ionic liquids have been proved to be promising for the pretreatment of lignocellulosic biomass, because they can provide high yield cellulase hydrolysis and high lignin removal rate. In this work, three proton-type ionic liquids, ethyl methanesulfonamide (EAM), ethyl amine nitrate (EAN) and ethyl amine acetate (EAN[OAc]), were successfully synthesized to pretreat corn straw, and five sugar platform organic solvents were selected as co-solvents for biomass pretreatment. The experimental results showed that under the optimal pretreatment conditions (10 wt% EAM, 130 degrees C, 2 h, 7 wt% straw loading in PDO solvent), the delignification rate of corn straw could reach 96 wt%, the sugar yield of cellulose-rich substrate could reach 95 wt% in 96 h, the regeneration rate of lignin dissolved in the solvent was 86 wt%, and the remainder of the solvent was small molecular compound, the hemicellulose dissolved in the solvent is degraded to monomolecular sugars (xylose and arabinose). The XRD, SEM characterization data and spectrograms of cellulosic substrate also fully proved that the lignin was successfully dissolved and separated from corn straw by pretreatment of composite system, and in the remaining straw the content and crystallinity of cellulose was improved. In this paper, density functional theory (DFT) is used to explore the pretreatment principle. From the optimized structure, it can be seen that the interaction energy between the ionic liquid cosolvent system and lignin is higher than that in the pure ionic liquid system. The simulation results, experimental analysis and characterization can effectively explain the essence of the system for efficient straw pretreatment, and the system can provide new ideas for the development of biomass pretreatment.