An integrated biorefinery process to comprehensively utilize corn stalk in a MIBK/water/Al(NO3)3·9H2O biphasic system: Chemical and morphological changes

Abstract Developing an effective and efficient biorefinery process is crucial for the utilization of biomass. In this work, corn stalk was treated in a methyl isobutyl ketone (MIBK)/water biphasic system to produce furfural and treated-corn stalk residues. The results showed that Al(NO3)3·9H2O owned the best property to convert hemicelluloses into furfural in the MIBK/water system. Under the optimal conditions (0.1 M Al(NO3)3·9H2O, 160 °C and 60 min), the furfural yield could reach 52.0%, while only 2.3% hemicelluloses remained in the treated-corn stalk residues. The cellulose largely remained in the residues, and the glucose yield had an apparent increment by the subsequent enzymatic hydrolysis process (85.5%). Additionally, lignin was the main component of the residues obtained after enzymatic hydrolysis process, which has been degraded to some extent. Moreover, in the morphological aspect, the cell walls swelled evidently and the vascular bundles were broken down. The result of confocal Raman microscopy indicated that there was a severe cleavage of ether and ester linkages between hydroxycinnamic acids and hemicelluloses or lignin, and lignin largely remained during the treatment. In short, the MIBK/water/Al(NO3)3·9H2O treatment process provided an efficient integrated utilization of corn stalk to produce furfural and fermentable glucose for the bioethanol production, and the feasible biorefinery process is beneficial for the environment protection and sustainable development.