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Oxidative depolymerization of technical lignins into value added chemicals
Thesis (MSc)--Stellenbosch University, 2019.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2019
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| _version_ | 1867614064362913792 |
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| access_status_str | Open Access |
| author | Sibanda, Ndumiso |
| author2 | Pasch, Harald |
| author_browse | Pasch, Harald Sibanda, Ndumiso |
| author_facet | Pasch, Harald Sibanda, Ndumiso |
| author_sort | Sibanda, Ndumiso |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2019. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/105601 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:46:06.004Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2019 |
| publishDateRange | 2019 |
| publishDateSort | 2019 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/105601 Oxidative depolymerization of technical lignins into value added chemicals Sibanda, Ndumiso Pasch, Harald Pfukwa, Helen Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. Monomers Lignin Biomass chemicals Polymers and polymerization Liquid chromatography Thesis (MSc)--Stellenbosch University, 2019. ENGLISH ABSTRACT: Most functional polymeric materials are being derived from non-renewable feedstocks e.g. petroleum and coal. The growing concerns regarding the depletion of non-renewable feedstocks have challenged researchers to investigate renewable and comparably cleaner alternatives to liquid fuels and chemicals. There has been a staggering interest in recent years in the use of lignin as a source of high value chemicals. Lignin has been used mainly as an energy source in combustion processes with only a small fraction (<5%) being used for other purposes. However, due to lignin’s notably high functionalization and aromatic nature, it has great potential for the direct production of aromatic speciality and fine chemicals, and subsequent functionalization to desired platform chemicals. A novel DMSO/HBr oxidative depolymerization approach was developed in order to depolymerize technical lignins, Kraft lignin and SAPPI lignosulfonate, into low molar mass compounds. A mechanism for this depolymerization process which is in agreement with the structure of the compounds formed is proposed. Since there is not much information in published literature focusing on the oxidative depolymerization of lignin using DMSO as the oxidant, other well established oxidative depolymerization methods were carried out in this work for comparison. The methods investigated included oxidative depolymerization using nitrobenzene and oxidative depolymerization in ionic liquid (1-ethyl-3-methylimidazolium trifluoromethanesulfonate) and water using oxygen as an oxidant. Lignin depolymerization products were analyzed by a molar mass determination technique (SEC). LC-MS and GC-MS were used to deconvulate the monomeric and oligomeric compounds according to chemical functionality. Structural elucidation was carried out using ESI-MS, NMR spectroscopy and FTIR spectroscopy. Results obtained using the aforementioned techniques confirmed the successful depolymerization of lignin by DMSO/HBr, as a plethora of carbonyl functionalized compounds were identified. Vanillin (29.5%) and syringaldehyde (28.8%) had the highest amounts of the total quantifiable monomeric compounds. Phloroglucinol, not widely reported as a product of oxidative depolymerization of lignin, was also identified and quantified at approximately 5.4%. Finally, a novel fully bio-based monomer for radical polymerization was successfully synthesized by the reaction of itaconic anhydride and guaiacol (one of the lignin monomeric compounds of lignin depolymerization) via an esterification reaction. AFRIKAANSE OPSOMMING: Die meeste funksionele polimeriese materiale word afgelei van nie-herwinbare toevoerstowwe (bv. petroleum en steenkool). Die toenemende kommer oor die uitputting van nie-herwinbare voedingsbronne daag navorsers egter uit om herwinbare en relatief skoner alternatiewe te ondersoek. Daar is 'n groot belangstelling in lignien as ‘n bron van hoë toegevoegde waarde chemikalieë. Lignien word hoofsaaklik as energiebron in verbrandingsprosesse gebruik, met slegs klein hoeveelhede (<5%) wat vir ander doeleindes gebruik word. As gevolg van lignin se hoë funksionaliteit en aromatiese aard, het dit groot potensiaal vir gebruik in die direkte produksie van aromatiese spesialiteit chemikalieë en die daaropvolgende funksionalisering na gewenste chemikalieë. n Nuwe DMSO / HBr oksidatiewe-depolymerisasie benadering word gebruik om tegniese ligniene – Kraft lignin en SAPPI lignosulfonate – in lae molêre massa verbindings te depolymeriseer. Die meganisme van hierdie benadering word voorgestel. Aangesien daar nie veel inligting in gepubliseerde literatuur is wat fokus op hierdie oksidatiewe depolymerisasie van lignien met DMSO as die oksidant nie, is ander goed gevestigde oksidatiewe depolymerisasiemetodes in hierdie werk vir vergelyking uitgevoer. Die metodes wat ondersoek is sluit in oksidatiewe-depolymerisasie met behulp van nitrobenzeen en oksidatiewe- depolymerisasie in ioniese vloeistof (1-etiel-3-methylimidazolium trifluormetansulfonaat) en water, deur suurstof as oksidant te gebruik. Lignien depolymerisasie produkte was geanaliseer met behulp van 'n molekulêremassa bepalingstegniek (SEC). LC-MS en GC-MS word as skeidingstegnieke gebruik om die monomeer- en oligomere volgens chemiese funksionaliteit te dekonvulueer. Strukturele verduideliking is met behulp van ESI-MS, NMR spektroskopie, en FTIR-spektroskopie uitgevoer. Die resultate dui die suksesvolle depolymerisasie van lignien deur DMSO / HBr aan, deur 'n groot hoeveelheid karboniel verbindings te identifiseer. Vanillien (29%) en syringaldehied (28.8%) het die hoogste hoeveelhede van die totale kwantifiseerbare monomere. Floroglucinol, wat nie wyd gerapporteer word as 'n produk van die oksidatiewe depolymerisasie van lignien nie, is ook geïdentifiseer en gekwantifiseer teen ongeveer 5.4%. Tenslotte word 'n nuwe volledig bio-gebaseerde monomeer vir radikale polimerisasie gesintetiseer deur die veresteringsreaksie van itakonanhidried en guaiacol (een van die lignienmonomeriese verbindings van lignien-depolymerisasie). Masters 2019-02-11T08:20:23Z 2019-04-17T08:04:16Z 2021-02-01T03:00:15Z 2019-03 Thesis http://hdl.handle.net/10019.1/105601 en_ZA Stellenbosch University 168 pages application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Monomers Lignin Biomass chemicals Polymers and polymerization Liquid chromatography Sibanda, Ndumiso Oxidative depolymerization of technical lignins into value added chemicals |
| title | Oxidative depolymerization of technical lignins into value added chemicals |
| title_full | Oxidative depolymerization of technical lignins into value added chemicals |
| title_fullStr | Oxidative depolymerization of technical lignins into value added chemicals |
| title_full_unstemmed | Oxidative depolymerization of technical lignins into value added chemicals |
| title_short | Oxidative depolymerization of technical lignins into value added chemicals |
| title_sort | oxidative depolymerization of technical lignins into value added chemicals |
| topic | Monomers Lignin Biomass chemicals Polymers and polymerization Liquid chromatography |
| url | http://hdl.handle.net/10019.1/105601 |
| work_keys_str_mv | AT sibandandumiso oxidativedepolymerizationoftechnicalligninsintovalueaddedchemicals |