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Towards Quantitative Catalytic Lignin Depolymerization

Authors

  • Dr. Virginia. M. Roberts,

    1. Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85747 Garching (Germany), Fax: (+49) 89 289 13544
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  • Valentin Stein,

    1. Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85747 Garching (Germany), Fax: (+49) 89 289 13544
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  • Thomas Reiner,

    1. Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85747 Garching (Germany), Fax: (+49) 89 289 13544
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  • Prof. Angeliki Lemonidou ,

    1. Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85747 Garching (Germany), Fax: (+49) 89 289 13544
    2. Department of Chemical Engineering, Aristotle University of Thessaloniki, P.O. Box 1517, University Campus 54124, Thessaloniki (Greece)
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  • Dr. Xuebing Li,

    1. Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85747 Garching (Germany), Fax: (+49) 89 289 13544
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  • Prof. Johannes A. Lercher

    Corresponding author
    1. Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85747 Garching (Germany), Fax: (+49) 89 289 13544
    • Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85747 Garching (Germany), Fax: (+49) 89 289 13544
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Abstract

The products of base-catalyzed liquid-phase hydrolysis of lignin depend markedly on the operating conditions. By varying temperature, pressure, catalyst concentration, and residence time, the yield of monomers and oligomers from depolymerized lignin can be adjusted. It is shown that monomers of phenolic derivatives are the only primary products of base-catalyzed hydrolysis and that oligomers form as secondary products. Oligomerization and polymerization of these highly reactive products, however, limit the amount of obtainable product oil containing low-molecular-weight phenolic products. Therefore, inhibition of concurrent oligomerization and polymerization reactions during hydrothermal lignin depolymerization is important to enhance product yields. Applying boric acid as a capping agent to suppress addition and condensation reactions of initially formed products is presented as a successful approach in this direction. Combination of base-catalyzed lignin hydrolysis with addition of boric acid protecting agent shifts the product distribution to lower molecular weight compounds and increases product yields beyond 85 %.

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