Variations in structure and properties of lignin during pulping processes
Lignin is a phenolic polymeric material, which is likely to be suitable for several uses, based mostly on the aromatic structure and on its reactive sites. Nowadays it is typically burned for energy generation, but the environmental consciousness and the fact that non-renewable sources should be rep...
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| Hlavní autor: | |
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| Médium: | masterThesis |
| Jazyk: | angličtina |
| Vydáno: |
2011
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| Témata: | |
| On-line přístup: | https://hdl.handle.net/20.500.12008/53017 |
| Tagy: |
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| Shrnutí: | Lignin is a phenolic polymeric material, which is likely to be suitable for several uses, based mostly on the aromatic structure and on its reactive sites. Nowadays it is typically burned for energy generation, but the environmental consciousness and the fact that non-renewable sources should be replaced, makes it necessary to search for new profitable market opportunities and novel and/or cost-effective applications and processes. Sulphur free lignin is almost a must for the major part of the lignin uses in materials. Therefore the study of the changes of the main properties occurring to the lignin during different NaOH and NaOH/AQ cookings, regarding to its potential reactivity for being used in high added value products, was performed. The literature review includes lignin basic concepts, cooking chemistry and procedures, analytical techniques, lignin uses and market perspectives. Lignin was extracted from wood during sulphur free cookings and then isolated from the spent pulping liquors through acid precipitation. Lignin originated in modern softwood and hardwood kraft pulp mills were also isolated with the same procedure and under the same conditions and analysed and used as reference values. Efficiency of lignin extraction, phenolic hydroxyl and methoxyl content, lignin share and carbohydrate content as well as MWD and Tg were determined. Considering the results obtained in the whole isolation method applied, which includes the cooking and precipitation conditions used, it is possible to claim that AQ addition, higher H-factors and longer cooking times result not only in higher amounts of lignin in the sample but also in higher phenolic hydroxyl content. The fact that methoxyl content also increases with cooking time and temperature must also be considered and a compromise between phenolic hydroxyl and methoxyl content must be achieved in order to get the most reactive material. |
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