Flow-through strategy to fractionate lignin from eucalyptus with formic acid/hydrochloric solution under mild conditions.

Formic acid is an attractive solvent for the fractionation of lignocellulose for the production of biomaterials and chemicals, while the operation conducted in a batch manner is not conducive to mass transfer in separation process. In this research, eucalyptus was fractionated with formic acid/hydrochloric solution in a flow-through reactor at 95 °C, and the structural characteristics and the composition of fractionated lignin in different stages were investigated. Results showed that the fractionation efficiency was notably improved with a flow-through reactor, as evidenced by the low solid residue yield of 49.5% and the lignin removal rate of 79.4% as compared to the batch manner. During the fractionation process, the dissolution rate of lignin decreased gradually, and the obtained lignin samples showed low molecular weight (<3000), good uniformity (<2), and high thermal stability. The structure analysis showed that ß-O-4, ß-ß, and ß-5 linkages in lignin were degraded to varying degrees with increased time, and the degradation of G units was more severe than S ones.

Hydrothermal liquefaction of lignocellulose for value-added products: Mechanism, parameter and production application.

Abundant, environmentally friendly, and sustainable lignocellulose is a promising feedstock for replacing fossil fuels, and hydrothermal liquefaction is an effective technology to convert it into liquid fuels and high-value chemicals. This review summarizes and discusses the reaction mechanism, main influence factor and the production application of hydrothermal liquefaction. Particular attention has been paid to the reaction mechanism of the structural components of lignocellulose, i.e., cellulose, hemicellulose, and lignin. In addition, the influence factors including types of lignocellulose, temperature, heating rate, retention time, pressure, solid-to-liquid ratio, and catalyst are discussed in detail. The limitations in the hydrothermal liquefaction of lignocellulose and the prospects are proposed. This provides deep knowledge for understanding the process as well as the development of advanced products from lignocellulose.

Tetrahydro-2-furanmethanol pretreatment of eucalyptus to enhance cellulose enzymatic hydrolysis and to produce high-quality lignin.

In this study, an organosolv process based on tetrahydro-2-furanmethanol/acid aqueous solution was developed to release lignin and hemicelluloses from eucalyptus for the enhancement of enzymatic hydrolysis. The pretreatment with 80% THFA aqueous solution containing 1% HCl at a solid to liquid ratio of 1:10 was conducted at 120-180 °C for 30 min. Under the serious conditions, the cellulose-rich residue had a high proportion of cellulose up to 87.31%. The enzymatic hydrolysis rate of the cellulose-rich fraction was 94.18%, which was enhanced by 7.3-fold as compared to that of the raw material without pretreatment. The fractionation process resulted in a high delignification rate of 93.95%. The lignin produced with medium molecular weight (2190 g/mol) and high purity (contaminated sugar content 0.6%) was a good substrate for further application as chemicals.