Chemical Characterization of Kraft Lignin Prepared from Mixed Hardwoods
Chemical characterization of kraft lignin (KL) from mixed hardwoods (<i>Acacia</i> spp. from Vietnam and mixed hardwoods (mainly <i>Quercus</i> spp.) from Korea) was conducted for its future applications. To compare the structural changes that occurred in KL, two milled wood...
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MDPI AG
2021-08-01
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| Series: | Molecules |
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| Online Access: | https://www.mdpi.com/1420-3049/26/16/4861 |
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| author | Ji-Sun Mun Justin Alfred Pe Sung-Phil Mun |
| author_facet | Ji-Sun Mun Justin Alfred Pe Sung-Phil Mun |
| author_sort | Ji-Sun Mun |
| collection | DOAJ |
| description | Chemical characterization of kraft lignin (KL) from mixed hardwoods (<i>Acacia</i> spp. from Vietnam and mixed hardwoods (mainly <i>Quercus</i> spp.) from Korea) was conducted for its future applications. To compare the structural changes that occurred in KL, two milled wood lignins (MWLs) were prepared from the same hardwood samples used in the production of KL. Elemental analysis showed that the MWL from acacia (MWL-aca) and mixed hardwood (MWL-mhw) had almost similar carbon content, methoxyl content, and C<sub>9</sub> formula. KL had high carbon content but low oxygen and methoxyl contents compared to MWLs. The C<sub>9</sub> formula of KL was determined to be C<sub>9</sub>H<sub>7.29</sub>O<sub>2.26</sub>N<sub>0.07</sub>S<sub>0.12</sub>(OCH<sub>3</sub>)<sub>1.24</sub>. The M<sub>w</sub> of KL and MWLs was about 3000 Da and 12,000–13,000 Da, respectively. The structural features of KL and MWLs were investigated by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectrometry (<sup>1</sup>H, <sup>13</sup>C NMR). The analyses indicated that KL underwent severe structural modifications, such as γ-carbon cleavage, demethylation, and polycondensation reactions during kraft pulping, which resulted in increased aromatic content and decreased aliphatic content. The main linkages in lignin, β-O-4 moieties, were hardly detected in the analysis as these linkages were extensively cleaved by nucleophilic attack of SH<sup>-</sup> and OH<sup>-</sup> during pulping. |
| first_indexed | 2024-03-10T08:33:18Z |
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| id | doaj.art-886a4759691041a6971ceb552e7b69b2 |
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| language | English |
| last_indexed | 2024-03-10T08:33:18Z |
| publishDate | 2021-08-01 |
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| series | Molecules |
| spelling | doaj.art-886a4759691041a6971ceb552e7b69b22023-11-22T08:53:05ZengMDPI AGMolecules1420-30492021-08-012616486110.3390/molecules26164861Chemical Characterization of Kraft Lignin Prepared from Mixed HardwoodsJi-Sun Mun0Justin Alfred Pe1Sung-Phil Mun2Department of Carbon Materials and Fiber Engineering, Jeonbuk National University, Jeonju 54896, KoreaDepartment of Wood Science and Technology, Jeonbuk National University, Jeonju 54896, KoreaDepartment of Wood Science and Technology, Jeonbuk National University, Jeonju 54896, KoreaChemical characterization of kraft lignin (KL) from mixed hardwoods (<i>Acacia</i> spp. from Vietnam and mixed hardwoods (mainly <i>Quercus</i> spp.) from Korea) was conducted for its future applications. To compare the structural changes that occurred in KL, two milled wood lignins (MWLs) were prepared from the same hardwood samples used in the production of KL. Elemental analysis showed that the MWL from acacia (MWL-aca) and mixed hardwood (MWL-mhw) had almost similar carbon content, methoxyl content, and C<sub>9</sub> formula. KL had high carbon content but low oxygen and methoxyl contents compared to MWLs. The C<sub>9</sub> formula of KL was determined to be C<sub>9</sub>H<sub>7.29</sub>O<sub>2.26</sub>N<sub>0.07</sub>S<sub>0.12</sub>(OCH<sub>3</sub>)<sub>1.24</sub>. The M<sub>w</sub> of KL and MWLs was about 3000 Da and 12,000–13,000 Da, respectively. The structural features of KL and MWLs were investigated by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectrometry (<sup>1</sup>H, <sup>13</sup>C NMR). The analyses indicated that KL underwent severe structural modifications, such as γ-carbon cleavage, demethylation, and polycondensation reactions during kraft pulping, which resulted in increased aromatic content and decreased aliphatic content. The main linkages in lignin, β-O-4 moieties, were hardly detected in the analysis as these linkages were extensively cleaved by nucleophilic attack of SH<sup>-</sup> and OH<sup>-</sup> during pulping.https://www.mdpi.com/1420-3049/26/16/4861kraft ligninacaciamixed hardwoodmilled wood ligninstructural analysis |
| spellingShingle | Ji-Sun Mun Justin Alfred Pe Sung-Phil Mun Chemical Characterization of Kraft Lignin Prepared from Mixed Hardwoods Molecules kraft lignin acacia mixed hardwood milled wood lignin structural analysis |
| title | Chemical Characterization of Kraft Lignin Prepared from Mixed Hardwoods |
| title_full | Chemical Characterization of Kraft Lignin Prepared from Mixed Hardwoods |
| title_fullStr | Chemical Characterization of Kraft Lignin Prepared from Mixed Hardwoods |
| title_full_unstemmed | Chemical Characterization of Kraft Lignin Prepared from Mixed Hardwoods |
| title_short | Chemical Characterization of Kraft Lignin Prepared from Mixed Hardwoods |
| title_sort | chemical characterization of kraft lignin prepared from mixed hardwoods |
| topic | kraft lignin acacia mixed hardwood milled wood lignin structural analysis |
| url | https://www.mdpi.com/1420-3049/26/16/4861 |
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