Catalytic Depolymerization of Lignin in Supercritical Ethanol
Catalytic Depolymerization of Lignin in Supercritical Ethanol
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DOI：
10.1002/cssc.201402094
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发表时间：
2014-08-01
期刊：
影响因子：
8.4
通讯作者：
Hensen, Emiel J. M.
中科院分区：
文献类型：
--
作者：
Huang, Xiaoming;Koranyi, Tamas I.;Hensen, Emiel J. M.
在超临界乙醇中使用CuMgAlOx催化剂一步还原碱木质素导致高单体产率（23重量%）而不形成炭。芳烃是主要产品。该催化剂兼具优异的脱氧活性和低的环加氢活性。几乎一半的单体部分不含氧。反应8小时后THF可溶性木质素残余物的元素分析显示，与起始Protobind P1000木质素相比，O/C降低68%，H/C原子比增加24%。延长反应时间可提高木质素解聚率，降低再聚合产物的生成量。酚羟基被认为是在再聚合和焦炭形成的主要演员。2D HSQC NMR分析证明乙醇通过烷基化和酯化与木质素片段反应。发现烷基化在抑制再聚合中起重要作用。乙醇作为封端剂，通过羟基的O-烷基化和芳环的C-烷基化来稳定高活性酚类中间体。使用乙醇在生产单体和避免炭方面比使用甲醇明显更有效。讨论了乙醇与木质素碎片反应的可能反应网络。
One-step valorization of soda lignin in supercritical ethanol using a CuMgAlOx catalyst results in high monomer yield (23 wt%) without char formation. Aromatics are the main products. The catalyst combines excellent deoxygenation with low ring-hydrogenation activity. Almost half of the monomer fraction is free from oxygen. Elemental analysis of the THF-soluble lignin residue after 8 h reaction showed a 68% reduction in O/C and 24% increase in H/C atomic ratios as compared to the starting Protobind P1000 lignin. Prolonged reaction times enhanced lignin depolymerization and reduced the amount of repolymerized products. Phenolic hydroxyl groups were found to be the main actors in repolymerization and char formation. 2D HSQC NMR analysis evidenced that ethanol reacts by alkylation and esterification with lignin fragments. Alkylation was found to play an important role in suppressing repolymerization. Ethanol acts as a capping agent, stabilizing the highly reactive phenolic intermediates by O-alkylating the hydroxyl groups and by C-alkylating the aromatic rings. The use of ethanol is significantly more effective in producing monomers and avoiding char than the use of methanol. A possible reaction network of the reactions between the ethanol and lignin fragments is discussed.