Organosolv fractionation and simultaneous conversion of lignocellulosic biomass in aqueous 1,4-butanediol/acidic ionic-liquids solution

Abstract

The development of bioenergy and biorefineries has generated new requirements for the comprehensive utilization of all biomass components in fractionation. Thus, the mass balance and component streams of lignocellulosic biomass during the fractionation process have become important research components. We explored the comprehensive utilization of biomass via fractionation and partial conversion of coir with an aqueous 1,4-butanediol/acidic ionic-liquids organosolv process and analyzed the mass balance and component streams of the process. A delignification selectivity parameter was introduced to evaluate the fractionation efficiency and screen the promising experimental conditions (processing temperature, duration, and solvent ratio). The process exhibited an excellent capability for lignin extraction and hemicellulose conversion. Cellulose-rich materials with a purity of up to 87% were obtained with an elevated relative crystallinity of cellulose materials (up to 65%). The process resulted in a near complete conversion of hemicellulose (up to 93%) and a high delignification rate (up to 88%). The conversion products can be readily extracted from the reaction liquid using ethyl acetate. The experimental conditions, especially temperature, had a significant influence on the component conversion of biomass during the process. Acid, ester, and aldehyde products had a significant, linear relationship with mass removal throughout the process. 4-Methyl-hexanoic acid, γ-lactone D-glucuronic acid, and 2-hydroxy-pentanoic acid ethyl ester were identified as the primary conversion products for carbohydrates (mainly hemicellulose), whereas only a limited number of phenol compounds were recognized as lignin derivatives. Through the efficient fractionation of cellulose and lignin components as well as the conversion of most hemicellulose to chemicals, this process provides a potential strategy for transforming lignocellulosic biomass into materials, chemicals, and energy sources.