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Study on Liquid Phase Depolymerization of Lignin Catalyzed by Zinc-based Compounds |
Received:December 17, 2022 |
DOI:10.11980/j.issn.0254-508X.2023.04.012 |
Key Words:lignin depolymerization liquefaction rate homogeneous catalyst catalytic |
Fund Project:广西自然科学基金面上项目(2020GXNSFAA159114);广西科学研究与技术开发计划项目(桂科AB21196001);国家自然科学基金面上项目(22175045)。 |
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Abstract:Bagasse lignin (BL) was extracted from bagasse soda pulping black liquor by acid precipitation. Aiming at the shortcomings of BL such as low reactivity and solubility in uti1ization, four kinds of catalysts, such as Zn, ZnO, Zn(NO3)2, and ZnAc, were used to catalyze BL liquefaction reaction in NaOH/H2O2 solution at high lignin concentration (mass fraction of 10%). The results indicated that BL was oligomers with rich phenolic hydroxyl group content (approximately 2.81 mmol/g) and broad molecular weights (Mn =11270). The BL could be depolymerized into soluble compounds effectively by zinc and its compounds, and ZnAc had the best catalytic effect, with a BL liquefaction yield of 40.9%, which was 2.68 times that of the blank. The catalytic active center was converted into the corresponding zinc-ammonia complex by adding NH3·H2O, and the repolymerization of lignin quinoid intermediates in the NaOH/H2O2 solution system could be reduced by adding phenol. The liquefaction yield of BL could be further improved to 84.2% under the optimized conditions. SEM-EDS and GPC showed that the insoluble material produced by depolymerization was mainly coke, and the liquefied products included small molecular aromatic compounds and lignin chain fragments with number average molecular weight and molecular weight distribution of 3058 and 1.570, respectively. |
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