1. Kraft Process-Formation of Secoisolariciresinol Structures and Incorporation of Fatty Acids in Kraft Lignin
- Author
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Kirsi S. Mikkonen, Ilkka Kilpeläinen, Joona Mikkilä, Maarit Lahtinen, Department of Food and Nutrition, Food Materials Science Research Group, Department of Chemistry, Department of Microbiology, Helsinki Institute of Sustainability Science (HELSUS), and Synthesis and Analysis
- Subjects
0106 biological sciences ,Chemical structure ,116 Chemical sciences ,RESIDUAL LIGNIN ,Ether ,macromolecular substances ,01 natural sciences ,complex mixtures ,Lignin ,PINE ,Article ,Lignans ,CONDENSATION ,condensation reaction ,chemistry.chemical_compound ,COMPOSITES ,Organic chemistry ,Butylene Glycols ,Secoisolariciresinol ,Kraft and residual lignin ,PYROLYSIS ,Tall oil ,010401 analytical chemistry ,fungi ,Fatty Acids ,technology, industry, and agriculture ,food and beverages ,General Chemistry ,0104 chemical sciences ,Solvent ,416 Food Science ,chemistry ,Kraft process ,mild thermal treatment ,General Agricultural and Biological Sciences ,Pyrolysis ,010606 plant biology & botany - Abstract
Correction to this article has published 4 May 2022: https://doi.org/10.1021/acs.jafc.2c02007 The complex chemical structure and the fact that many areas in pulping and lignin chemistry still remain unresolved are challenges associated with exploiting lignin. In this study, we address questions regarding the formation and chemical nature of the insoluble residual lignin, the presence of fatty acids in kraft lignin, and the origin of secoisolariciresinol structures. A mild thermal treatment of lignin at maximum kraft-cooking temperatures (similar to 170 degrees C) with tall oil fatty acids (TOFA) or in an inert solvent (decane) produced highly insoluble products. However, acetylation of these samples enabled detailed chemical characterization by nuclear magnetic resonance (NMR) spectroscopy. The results show that the secoisolariciresinol (beta-beta) structure in kraft lignin is formed by rearrangement of the beta-aryl ether structure. Furthermore, fatty acids bind covalently to kraft lignin by reacting with the stilbene structures present. It is highly probable that these reactions also occur during kraft pulping, and this phenomenon has an impact on controlling the present kraft pulping process along with the development of new products from kraft lignin.
- Published
- 2021