Synthesis of bio-based terephthalic acid

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Title: Synthesis of bio-based terephthalic acid
Author: Talvitie, Juulia
Contributor: University of Helsinki, Faculty of Science, Department of Chemistry
Publisher: Helsingin yliopisto
Date: 2018
Language: eng
Thesis level: master's thesis
Discipline: Organic chemistry
Orgaaninen kemia
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Abstract: Terephthalic acid (TPA) is a monomer used widely in the production of poly(ethylene terephthalate) (PET) and other polyesters. The other monomer of PET, ethylene glycol, can already be produced from bioethanol. However, TPA is still produced via the traditional route from petrochemical sources, but the global demand for environmental-friendly options has increased throughout the past years making the synthesis of bio-based TPA an attractive research target. Several companies have formed a collaborative to support the development of 100% bio-based PET and thus bio-based TPA. The challenge is not only to develop an ecologically beneficial but also a cost-effective process. In the literature section of this work, the current methods to produce bio-based TPA have been reviewed. A highly attractive option is to use lignocellulosic biomass - cellulose, hemicellulose and lignin - as the starting material due to its high abundance and low cost. Lignocellulosic biomass can be utilized directly via biotechnical pathways by using either catalytic fast pyrolysis or fermentation and reforming strategies. The other option is to convert it into small platform chemicals, for instance HMF, furfural and acrolein, which are then used in Diels–Alder approaches to get TPA or its precursors. Besides lignocellulose, other viable starting materials, like monoterpenes, have been discussed. The experimental of the thesis is focused on N-heterocyclic carbene (NHC)-catalyzed umpolung reactions in order to make TPA-precursors and other value-added chemicals from benzaldehyde. The research hypothesis was that by forming an electron-rich enaminol, called Breslow intermediate, from benzaldehyde and NHC, we could reverse the reactivity of benzaldehyde from ortho,para-deactivating to ortho,para-activating. Two NHC-precursors were synthesized, isolated and characterized. Several pathways utilizing both two-electron and single-electron transfer were attempted, but unfortunately no success in these reactions was achieved.

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