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Lignin-based epoxides
Thesis (M. Sc. (Wood Science)) -- University of Stellenbosch, 1990.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2012
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| _version_ | 1867613842190630912 |
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| access_status_str | Open Access |
| author | Conradie, Denise |
| author2 | Vermaas, H. F. |
| author_browse | Conradie, Denise Vermaas, H. F. |
| author_facet | Vermaas, H. F. Conradie, Denise |
| author_sort | Conradie, Denise |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (M. Sc. (Wood Science)) -- University of Stellenbosch, 1990. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/68865 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:42:33.557Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/68865 Lignin-based epoxides Conradie, Denise Vermaas, H. F. Pizzi, A Stellenbosch University. Faculty of AgriSciences. Dept. of Forest & Wood Science. Lignin Epoxy compounds Gums and resins Dissertations -- Forestry Thesis (M. Sc. (Wood Science)) -- University of Stellenbosch, 1990. From an extensive literature survey it became evident that technical lignin has the potential to be used for the commercial preparation of epoxy resins. The procedures given in literature, usually comprised the epoxidation of alkali lignin with epichlorohydrin under basic conditions. These lignin-based epoxides were usually prepared from incompletely described lignins and reaction mechanisms were well known. In this investigation epoxy resins were first prepared from soft- and hardwood lignin model compound reactions at the aromatic hydroxyl group on the para-position, by using the standard method reported by Tai et al 49 for industrial bisphenol-A-based epoxy resins. The two fully characterized local alkali lignins (pine kraft and soda/AQ eucalyptus) were then also epoxidized by using the same reaction with epichlorohydrin under alkaline conditions. The lignin model compounds contained a higher percentage of reactive (and thus available) 2- and 6-positions (metapositions) than para-positions (4-positions). It was, therefore, decided to activate these meta-positions of the lignin model compounds and the two alkali lignins, through the bonding of reactive hydroxyl groups to these positions. Epoxidation at the meta-positions would favour higher yields of epoxide than the epoxidation at the para-positions. The hydroxyl group on the para-position of the two model compounds was methylated to protect it. The two model compounds were then hydroxymethylated at the 2- and 6-positions and reacted with epichlorohydrin under alkaline conditions. Results however, showed that only starting material was obtained. No epoxide formation occurred. The same reaction was repeated with the two alkali lignins under similar conditions, but again no epoxide could be obtained. An alternative approach was, therefore, taken. The hydroxyl group on the 2- or 6-position of the lignin model compounds was reacted with allyl alcohol under acidic conditions to form an allyl ether. In the presence of perbenzoic acid, the softwood model compound ether was successfully epoxidized, however no success was obtained with the hardwood model compound ether. NMR-studies of the two alkali lignins showed possible formation of epoxides, although ether-bonds appeared to be present. An alternative modification route (at the meta-position) was then attempted to prepare lignin-based epoxides from a,Sunsaturated ketones or aldehydes. It was impossible to prepare the hardwood model aldehyde, but the softwood model compound was successfully oxidized to the aldehyde. The latter was reacted with N,N-diethyl-a- chloroacetamide and potassium-t-butoxide under N2 to form the epoxy amide. The epoxy amide was then again transferred to the epoxy ketone in the presence of methyllithium in THF (tetrahydrofuran). The whole reaction was done in the absence of water, but because such reaction conditions would not have any practical or commercial potential for the preparation of lignin-based epoxides, it was not applied to the two alkali lignins. Masters 2012-08-27T12:26:48Z 2012-08-27T12:26:48Z 1990 Thesis http://hdl.handle.net/10019.1/68865 en_ZA Stellenbosch University 235 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Lignin Epoxy compounds Gums and resins Dissertations -- Forestry Conradie, Denise Lignin-based epoxides |
| title | Lignin-based epoxides |
| title_full | Lignin-based epoxides |
| title_fullStr | Lignin-based epoxides |
| title_full_unstemmed | Lignin-based epoxides |
| title_short | Lignin-based epoxides |
| title_sort | lignin based epoxides |
| topic | Lignin Epoxy compounds Gums and resins Dissertations -- Forestry |
| url | http://hdl.handle.net/10019.1/68865 |
| work_keys_str_mv | AT conradiedenise ligninbasedepoxides |