The simultaneous extraction and depolymerisation of lignin, from vine shoots using one-pot microwave-assisted deep eutectic solvent systems

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dc.contributor.advisorChimphango, Annie Fabian Abelen_ZA
dc.contributor.advisorPfukwa, Helenen_ZA
dc.contributor.authorScholtz, Nicholas Edwarden_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Process Engineering.en_ZA
dc.date.accessioned2024-03-05T08:45:48Zen_ZA
dc.date.accessioned2024-04-26T22:01:17Zen_ZA
dc.date.available2024-03-05T08:45:48Zen_ZA
dc.date.available2024-04-26T22:01:17Zen_ZA
dc.date.issued2024-03en_ZA
dc.descriptionThesis (MEng)--Stellenbosch University, 2024.en_ZA
dc.description.abstractENGLISH ABSTRACT: The growing concern stemming from the use of fossil fuel-based materials has become prominent over -time. The environmental pollution it causes, together with the rapid decline of their reserves has demanded for more sustainable alternatives. One such material is lignin. Its aromaticity makes it unique from other constituents which together with its high carbon content makes it a suitable material for the synthesis of carbonaceous materials, such as phenol, which is mostly derived from fossil fuels. Currently, the largest commercial supplier of lignin is waste effluents from pulp and paper mills, but lignin obtained from these mills has altered chemical structures resulting from the numerous, intense processing conditions and harsh chemicals used and currently has no significant commercial value. Alternative sources of lignin are biomass materials. It is difficult to selectively obtain lignin from biomass because of the complex and irregular structure of lignin. Therefore, severe, and multiple processing steps are required to obtain adequate yields of pure lignin. Large amounts of biomass (organic waste) such as vine shoots that contain lignin, are generated from vineyards for vinification (winemaking), and currently, they have limited uses. Therefore, the aim of this study entailed the development of a one-pot process, using green chemicals and processes, to extract lignin whilst simultaneously depolymerising it from vine shoot powder (VSP). The solvents used were two deep eutectic solvents (DESs) namely, ChCl: LA and AlCl3: ChCl: BDO and to minimise processing times and temperatures the use of microwave-assisted extraction (MAE) was employed as a heating system. A Box-Behnken experimental design (BBD) was used to optimise the molar ratio (between the HBA and HBD), reaction temperature, and reaction time to maximise the lignin yield and purity from VSP. The lignin content of the VSP was estimated to be 26.3%. Under optimised conditions using ChCl: LA, a yield and purity of 92.5% and 99.6% were obtained and using AlCl3: ChCl: BDO a yield and purity of 88.0% and 91.4% were obtained. The degree of depolymerisation was gauged through molecular weight analysis using size-exclusion chromatography (SEC). The two optimised lignin samples measured weight average- (Mw) and number average- (Mn) molecular weights of 12580 and 5090 g/mol, respectively using a microwave-assisted ChCl: LA system and 10490 and 4830 g/mol, respectively using a microwave-assisted AlCl3: ChCl: BDO system. The degree of depolymerisation was compared to a reference lignin sample obtained using organosolv process. The reference sample had Mw and Mn values of 16080 and 9400 g/mol, respectively. Under optimised conditions, DESs were recycled and reused for lignin extraction and obtained lignin yields of 32.1% and 26.8% using ChCl: LA and AlCl3: ChCl: BDO, respectively. The purities were 81.3% and 67.6%, respectively. Hence, high- quality lignin could be obtained using recycled DESs. Furthermore, a one-pot process for the simultaneous extraction and depolymerisation of lignin from vine shoots was successful and has shown that less energy intensive processes can be used to do so, whilst using green chemicals. The findings of this study showed that vine shoots were a suitable source of lignin and could be extracted in high yields and of high quality using green procedures and chemicals in a one-pot process.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.af_ZA
dc.format.extentxiv, 174 pages : illustrationsen_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/130559en_ZA
dc.language.isoen_ZAen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshExtraction (Chemistry)en_ZA
dc.subject.lcshLignin -- Separationen_ZA
dc.subject.lcshFossil fuelsen_ZA
dc.subject.lcshBiomass chemicalsen_ZA
dc.titleThe simultaneous extraction and depolymerisation of lignin, from vine shoots using one-pot microwave-assisted deep eutectic solvent systemsen_ZA
dc.typeThesisen_ZA
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