Tungstoborate heteropolyacid catalysts have good catalytic degradation performance, especially for selective cleavage of C–C bonds in biomass. In this paper, the product yield and component distribution of tungstoborate heteropolyacid (BW12)-catalyzed lignin liquefaction were investigated at different parameters, including temperatures (120, 140, 160, 180, and 200 °C), catalyst amount (0, 2.5, 5, 10, and 20 wt. %), and reaction time (0, 30, 60, 90, and 120 min). It was found that a higher conversion (72.16 wt. %) and bio-oil yield (68.41 wt. %) could be obtained under suitable reaction conditions (180 °C, 60 min, 5 wt. %). Bio-oil analysis showed that the BW12 catalyst had a significant effect on the distribution of bio-oil fractions, in which mono-aromatic components increased from 32.96% to 47.56% compared to those without the catalyst. In particular, carbonyl substances in the mono-aromatic components increased from 18.66% to 26.97%. Spectroscopic analysis (FT-IR) found that the absorption peaks of C–O and C–C bonds in the liquefied residue catalyzed by BW12 decreased compared to the raw lignin. Moreover, the mechanism of BW12-catalyzed lignin depolymerization was investigated by DFT simulations. The simulation results demonstrated that the shortening of Cα–O bond, the breaking of Cβ–Cγ and Cα–Cβ bonds in lignin promoted the formation of vanillin and benzaldehyde, 3-hydroxy-4-methoxy. Finally, based on the experimental data and simulation results, a possible reaction pathway for the BW12-catalyzed liquefaction of lignin into mono-aromatic substances was proposed.

中文翻译：

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钨硼酸杂多酸催化木质素液化：产品收率和成分分布

钨硼酸盐杂多酸催化剂具有良好的催化降解性能，特别是对于生物质中C-C键的选择性断裂。本文研究了不同参数下钨硼酸杂多酸（BW12）催化木质素液化的产物收率和组分分布，包括温度（120、140、160、180和200℃）、催化剂用量（0、2.5、 5、10 和 20 wt.%），以及反应时间（0、30、60、90 和 120 分钟）。结果发现，在合适的反应条件（180℃，60分钟，5重量％）下可以获得较高的转化率（72.16重量％）和生物油收率（68.41重量％）。生物油分析表明，BW12催化剂对生物油馏分的分布有显着影响，其中单芳烃组分较无催化剂时从32.96%增加到47.56%。特别是单芳香族成分中的羰基物质从18.66%增加到26.97%。光谱分析（FT-IR）发现，与原始木质素相比，BW12催化的液化残渣中C-O和C-C键的吸收峰有所减少。此外，通过DFT模拟研究了BW12催化木质素解聚的机理。模拟结果表明，木质素中Cα-O键的缩短、Cβ-Cγ和Cα-Cβ键的断裂促进了香草醛和苯甲醛、3-羟基-4-甲氧基的形成。最后，基于实验数据和模拟结果，提出了BW12催化木质素液化成单芳香族物质的可能反应路径。