Green bio-based aprotic solvents for efficient fractionation of hemicellulose and targeted value addition of lignin

It is of great significance to inhibit the repolymerization of lignin when removing hemicellulose by acid pretreatment . Adding a lignin fragment scavenger is an effective method to inhibit its repolymerization. Here, the effect of a bio-based polar aprotic solvent, levulinic acid (Lev), and γ-valerolactone (GVL) coupled pretreatment system on the separation yield of poplar biomass components was investigated. The optimum pretreatment conditions were a Lev concentration was 7.0%, reaction temperature was 170 °C, pretreatment time was 60 min, and GVL concentration was 9.0%. The separation yield of hemicellulose was 84.54%, which was a 4.53% increase over that with Lev pretreatment. The retention yield of cellulose was 89.68%. In addition, the separation efficiency was significantly improved when the pretreatment time was reduced by 40 min. The reaggregation of lignin was suppressed under the condition of maximum hemicellulose separation. In the lignin samples the content of β-O-4 was as high as 47.81%. Simultaneously, the content of phenolic and aliphatic hydroxyl increased. The results revealed that Lev/GVL pretreatment had good hemicellulose separation selectivity and excellent lignin fragment removal efficiency. This provides a new strategy for suppressing adverse effects on the lignin structure in the efficient separation of hemicellulose in pretreatment.