Selective separation of poplar hemicellulose and simultaneous enrichment of soluble xylose in the hydrolysate by itaconic acid pretreatment.

Organic-acid pretreatments designed to efficiently separate hemicellulose and preserve high-value soluble monosaccharides in hydrolysates have become a significant research focus. In this study, the efficiency of the catalytic degradation of a lignocellulosic model using itaconic acid (IA) was evaluated. The exceptional selectivity of IA for xylan degradation was confirmed. The separation yield of poplar fractions was assessed after IA pretreatment. The yield of xylose was 81.91 % under the optimal conditions (IA concentration: 5.0 wt%, 160 °C, 60 min). The hydrolysate contained up to 12.10 g/L xylose, exceeding that obtained with formic acid and levulinic acid pretreatments. The simultaneous separation of hemicellulose and protection of soluble sugars was achieved. The high crystallinity index (66.69 %) of the residual solid (RS) confirmed the effective protection of cellulose by IA pretreatment. Additionally, the lignin in the RS contained 53.45 % β-O-4 and 1.21 mmol/g phenolic hydroxyl. This suggests that the IA-pretreated lignin retains more active functional groups, which are advantageous for subsequent conversion and utilization. These findings offer a novel approach for efficient hemicellulose separation and the effective protection of soluble xylose during organic-acid pretreatment.