Lignin Valorization for Added-Value Chemicals: Kraft Lignin versus Lignin Fractions
Lignin is a raw material that can potentially be converted into valuable compounds through depolymerization reactions in addition to its use as a polymer or material. However, the chemical recalcitrance and the heterogeneous composition and structure of lignin make it challenging to establish proces...
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MDPI AG
2023-05-01
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| Series: | ChemEngineering |
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| Online Access: | https://www.mdpi.com/2305-7084/7/3/42 |
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| author | Carina A. E. Costa Filipa M. Casimiro Carlos Vega-Aguilar Alírio E. Rodrigues |
| author_facet | Carina A. E. Costa Filipa M. Casimiro Carlos Vega-Aguilar Alírio E. Rodrigues |
| author_sort | Carina A. E. Costa |
| collection | DOAJ |
| description | Lignin is a raw material that can potentially be converted into valuable compounds through depolymerization reactions in addition to its use as a polymer or material. However, the chemical recalcitrance and the heterogeneous composition and structure of lignin make it challenging to establish processes that add value to this complex aromatic biopolymer. In this work, solvent fractionation was applied to obtain lignin fractions with a narrowed molecular weight and specific structural characteristics, improving its homogeneity and purity. A kraft lignin was submitted to fractionation using different ratios of acetone, ranging from 60 to 15% <i>v</i>/<i>v</i>, in aqueous mixtures. The composition, structure, and molecular weight of each fraction were studied and their potential applications were evaluated. The most water-soluble fraction has more phenolic OH, less aliphatic OH groups, and shows the lowest content of aryl-ether linkages, which is in accordance with its highest degree of condensation. On the other hand, the insoluble fraction from the mixture with 60% of acetone has the lowest molecular weight and the highest content of inorganic material. Radar plots were applied for lignin fractions evaluation and the fraction with the highest potential (IF 30:70) was submitted to alkaline oxidation with O<sub>2</sub>. The results were compared with the products yielded from kraft lignin. An increase of about 13 and 19% was found for vanillin and syringaldehyde, respectively, when the fraction IF 30:70 was submitted to oxidation. In conclusion, the proposed fractionation process showed to be an effective method to obtain lignin fractions with specific composition and structural characteristics that could improve its potential as a source of high added-value monomeric phenolic compounds. |
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| last_indexed | 2024-03-11T02:39:08Z |
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| series | ChemEngineering |
| spelling | doaj.art-bcf7f0d81afe405e92331615eca652582023-11-18T09:44:59ZengMDPI AGChemEngineering2305-70842023-05-01734210.3390/chemengineering7030042Lignin Valorization for Added-Value Chemicals: Kraft Lignin versus Lignin FractionsCarina A. E. Costa0Filipa M. Casimiro1Carlos Vega-Aguilar2Alírio E. Rodrigues3LSRE-LCM—Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, PortugalLSRE-LCM—Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, PortugalLSRE-LCM—Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, PortugalLSRE-LCM—Laboratory of Separation and Reaction Engineering-Laboratory of Catalysis and Materials, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, PortugalLignin is a raw material that can potentially be converted into valuable compounds through depolymerization reactions in addition to its use as a polymer or material. However, the chemical recalcitrance and the heterogeneous composition and structure of lignin make it challenging to establish processes that add value to this complex aromatic biopolymer. In this work, solvent fractionation was applied to obtain lignin fractions with a narrowed molecular weight and specific structural characteristics, improving its homogeneity and purity. A kraft lignin was submitted to fractionation using different ratios of acetone, ranging from 60 to 15% <i>v</i>/<i>v</i>, in aqueous mixtures. The composition, structure, and molecular weight of each fraction were studied and their potential applications were evaluated. The most water-soluble fraction has more phenolic OH, less aliphatic OH groups, and shows the lowest content of aryl-ether linkages, which is in accordance with its highest degree of condensation. On the other hand, the insoluble fraction from the mixture with 60% of acetone has the lowest molecular weight and the highest content of inorganic material. Radar plots were applied for lignin fractions evaluation and the fraction with the highest potential (IF 30:70) was submitted to alkaline oxidation with O<sub>2</sub>. The results were compared with the products yielded from kraft lignin. An increase of about 13 and 19% was found for vanillin and syringaldehyde, respectively, when the fraction IF 30:70 was submitted to oxidation. In conclusion, the proposed fractionation process showed to be an effective method to obtain lignin fractions with specific composition and structural characteristics that could improve its potential as a source of high added-value monomeric phenolic compounds.https://www.mdpi.com/2305-7084/7/3/42kraft ligninsolvent fractionationhomogeneous fractionsstructural characterizationoxidative depolymerization |
| spellingShingle | Carina A. E. Costa Filipa M. Casimiro Carlos Vega-Aguilar Alírio E. Rodrigues Lignin Valorization for Added-Value Chemicals: Kraft Lignin versus Lignin Fractions ChemEngineering kraft lignin solvent fractionation homogeneous fractions structural characterization oxidative depolymerization |
| title | Lignin Valorization for Added-Value Chemicals: Kraft Lignin versus Lignin Fractions |
| title_full | Lignin Valorization for Added-Value Chemicals: Kraft Lignin versus Lignin Fractions |
| title_fullStr | Lignin Valorization for Added-Value Chemicals: Kraft Lignin versus Lignin Fractions |
| title_full_unstemmed | Lignin Valorization for Added-Value Chemicals: Kraft Lignin versus Lignin Fractions |
| title_short | Lignin Valorization for Added-Value Chemicals: Kraft Lignin versus Lignin Fractions |
| title_sort | lignin valorization for added value chemicals kraft lignin versus lignin fractions |
| topic | kraft lignin solvent fractionation homogeneous fractions structural characterization oxidative depolymerization |
| url | https://www.mdpi.com/2305-7084/7/3/42 |
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