Efficient Biomass Pretreatment Process Based on the Simple Reuse of a Low-Viscosity Ionic-Liquid Solvent System

Abstract

Ionic liquids (ILs) are expensive, so it is necessary to reuse ILs; however, the reuse process is cumbersome as antisolvents are added and evaporated to regenerate ILs after each biomass pretreatment. Increasing the treatment capacity of biomass before regenerating ILs is desired; however, the high treatment capacity of biomass before IL regeneration and high lignin removal rate are a contradiction in terms. In this paper, a solution was proposed that includes pretreating biomass with a binary system composed of low-viscosity IL 1-ethyl-3-methylimidazole tetrafluoroborate ([Emim][BF4]) and l-arginine (Arg). It was shown that Arg could promote lignin dissolution and inhibit cellulose degradation in [Emim][BF4]. The system could be reused just by vacuum filtration after pretreatment without using antisolvents. After using [Emim][BF4]–Arg five times, the cumulative treatment capacity of corn straw reached 20.55%, while the total removal rate of lignin (84.94%) and the total yield of cellulose (93.23%) remained high. This method is of great significance for the industrial application of biomass pretreatment using ILs.