NMR a critical tool to study the production of carbon fiber from lignin |
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| Affiliation: | 1. BioEnergy Science Center, School of Chemistry and Biochemistry, Institute of Paper Science and Technology, Georgia Institute of Technology, 500 10th St., Atlanta, GA 30332, United States;2. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6087, United States;1. Lehrstuhl für Makromolekulare Stoffe und Faserchemie, Institut für Polymerchemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany;2. Institut für Textilchemie und Chemiefasern (ITCF), Körschtalstr. 26, D-73770 Denkendorf, Germany;3. BASF SE, 67056 Ludwigshafen, Germany;1. Composite Materials Research Laboratories, TORAY Industries, Inc., 1515 Tsutsui, Masaki-cho, Iyo-gun, Ehime, 791-3193, Japan;2. School of Materials, University of Manchester, Grosvenor Street, Manchester, M1 7HS, UK;3. Department of Physics, University of Bath, Claverton Down, Bath, BA2 7AY, UK;4. Department of Aerospace Engineering, Tohoku University, 6-6-01, Aoba-yama, Aoba-ku, Sendai, Miyagi, 980-8579, Japan;1. LRGP, CNRS, Université de Lorraine, 1 rue Grandville, 54000 Nancy, France;2. ICS, CNRS, Université de Strasbourg, 1 rue Blaise Pascal BP 296 R8, 67008 Strasbourg Cedex, France;3. IS2M, CNRS, Université de Haute Alsace, 15, rue Jean Starcky BP 2488, 68057 Mulhouse Cedex, France;4. LERMAB, Université de Lorraine, BP239, 54506 Vandoeuvre les Nancy Cedex, France;1. Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, Sweden;2. Materials and Production, RISE IVF Research Institutes of Sweden, Mölndal, Sweden;3. Institute of Bioproducts and Paper Technology, Graz University of Technology, Graz, Austria;4. Wallenberg Wood Science Center, Göteborg, Sweden;1. School of Polymer Science and Engineering & Alan G. MacDiarmid Energy Research Institute, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 500-757, Republic of Korea;2. Institute of Advanced Composite Materials, Korea Institute of Science and Technology, Eunha-ri San 101, Bongdong-eup, Wanju-gun, Jeollabukdo 565-905, Republic of Korea;1. School of Science, Guizhou Minzu University, Guiyang 550025, China;2. Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education of China, Chongqing University, Chongqing 400044, China;3. School of Chemistry and Environmental Science, Guizhou Minzu University, Guiyang 550025, China |
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| Abstract: | The structural changes occurring to hardwood Alcell™ lignin as a result of fiber devolatilization/extrusion, oxidative thermo-stabilization and carbonization are investigated in this study by solid-state and solution nuclear magnetic resonance (NMR) spectroscopy techniques. Solution based 1H–13C correlation NMR of the un-spun Alcell™ lignin powder and extruded lignin fiber detected modest changes occurring due to fiber devolatilization/extrusion in the type and proportion of aliphatic side-chain carbons or monolignol inter-unit linkages. Molecular weight analysis by gel permeation chromatography (GPC), along with an additional 31P NMR method used to indicate changes in terminal hydroxyl functionality, suggest fiber devolatilization/extrusion causes both chain scission and condensation reactions. 1H CRAMPS (combined rotation and multiple-pulse spectroscopy) and 13C cross-polarization/magic angle spinning (CP/MAS) spectra of extruded and stabilized lignin fibers indicate stabilization severely reduces the proportion of methoxy groups present, while also increasing the relative proportion of carbonyl and carboxyl-related structures, typically associated with cross-linking chemistries. 13C direct-polarization/magic angle spinning (DP/MAS) analysis of stabilized and carbonized fibers shows an increased relative amount of carbon–carbon bonds on aryl structures and a relative decrease of aryl ethers. DP/MAS dipolar dephasing experiments suggest that a majority of non-protonated carbons convert from carbonyl to aryl and condensed aryl structures during carbonization. |
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