(560f) Characterization of Products from Base Catalyzed Depolymerization of Lignins to Determine Changes in Chemical Structure

Authors: 
Johnson, D. K., National Renewable Energy Laboratory

It has long been recognized that lignin is a potential renewable source of chemicals, however, there has been only limited success in the commercialization of processes for converting lignin into chemicals [1,2].  Alkaline hydrolysis of lignin has received considerable attention because the reagents are relatively inexpensive and the phenolic products obtained are of potential value [1,3,4].  Base-catalyzed depolymerization (BCD) of lignin leads to a mixture of oligomeric and monomeric oxyaromatics. The monomeric component contains valuable chemicals [5,6] and the oligomeric component is a desirable feedstock for conversion to high octane gasoline blending components [7]. Lignin depolymerization is a critical step in the valorization of the lignin component in biomass.  Characterization of changes in the molecular weight and functionality of lignins subjected to BCD is important for understanding the chemistry of the reactions involved and for the further utilization of the products obtained.  Characterization of products from the BCD of lignins at different severities, by gel permeation chromatography (GPC), 13C Nuclear Magnetic Resonance (NMR) spectrometry, and elemental analysis (CHO), have been used to determine changes in the chemical structure and molecular weight of the products.  In addition, the characterization of lignin-derived monomers by gas chromatography/mass spectrometry (GC/MS) and high pressure liquid chromatography (HPLC) analyses has also been performed.  In addition, lignin model compounds (vanillin, guaiacol, vanillic acid, etc.) have been reacted under BCD conditions to further elucidate the reactions that occur during lignin depolymerization under alkaline conditions.

References
[1] Goheen, D.W. 1971 “Low Molecular Weight Chemicals” Chapter 19 in Lignins: Occurrence, Formation, Structure and Reactions, Sarkanen, K.V., Ludwig, C.H., Eds., Wiley Interscience, New York, p. 797 – 831.

[2] Goheen, D.W. 1981 “Chemicals from Lignin” Chapter 8 in Organic Chemicals from Biomass, Goldstein, I.S., Ed, CRC Press, Boca Raton, FL, p. 143 – 162.

[3] Thring, R.W., Chornet, E., Overend, R.P., Heitz, M.  1989.  “Production and Hydrolytic Depolymerization of Ethylene Glycol Lignin” Chapter 17 in Lignin: Properties and Materials, Glasser, W.G., Sarkanen, S., Eds.  ACS Symposium Series 397, Washington, DC, p. 228 – 244.

[4] Thring, R.W.  1994. “Alkaline Degradation of ALCELL Lignin” Biomass and Bioenergy, 7 (1-6), p. 125 – 130.

[5] Vigneault, A., Johnson, D. K., Chornet, E. 2007 “Base‐Catalyzed Depolymerization of Lignin: Separation of Monomers” Canadian Journal of Chemical Engineering, 85 (6), 906-916.

[6] Vigneault, A., Johnson, D. K., Chornet, E. 2006 “Advance in the thermal depolymerization of lignin via base-catalysis” Science in thermal and chemical biomass conversion, 1401-1419.

[7] Shabtai, J.S., Zmierczak, W. W., Chornet, E., Johnson, D. K. 2003 “Process for converting lignins into a high octane blending component” US Patent 0115792.

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