Characterization of biomass fractionation by sequential hydrolysis in a flow-through reactor

Abstract

This study offers an integrated approach for sequential hydrolysis of biomass using flow-through hot-compressed water (HCW) and HCW with oxidative alkaline (HCW-OA), which effectively enhances the selective hemicellulose removal, lignin recovery and preserving the cellulose structure. Kinetics of both hemicellulose and lignin degradation by the flow-through HCW and HCW-OA treatments were found to obey the first-order reaction with low activation energies. Accounting 77.9 % of hemicellulose in biomass can be significantly removed by HCW treatment at a mild temperature of 180 ºC for 90 min, alongside regeneration of reducing sugars with xylose as the dominated. Subsequently about 82.8 % of total lignin was removed by HCW-OA at 140 ºC for 90 min with 3 wt% H₂O₂ and 1.0 mol/L Na₂CO₃ solutions using the residue pretreated by HCW at 180 ºC for 30 min as feedstock, accompanying with recovery of 64.5 % acid-soluble lignin and 30.8 % acid-insoluble lignin, which have a potential for lignin-derived chemicals. Post-treatment analysis revealed the residues after sequential HCW and HCW-OA treatments were enriched in cellulose up to 77.4 %, with no hemicellulose and less lignin. The significant decrease of cellulose thermal stability after flow-through HCW and HCW-OA treatments further highlights its potential in high-value products. This study provides an efficient separation and potential cascade utilization of three biomass components in biomass valorization.