Tungstoborate heteropolyacid-catalyzed lignin liquefaction: Product yield and component distribution: Fid-Bau Portal

Tungstoborate heteropolyacid-catalyzed lignin liquefaction: Product yield and component distribution

Chen, Min / Lou, Jing / Zhang, Yang / Li, Lu / Li, Yan / Xie, Xin-an

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 C_α–O bond, the breaking of C_β–C_γ and C_α–C_β 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.