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Development of metal oxide catalysts for the removal of acetaldehyde from poly(ethylene terephthalate)

Marchant, David 2020. Development of metal oxide catalysts for the removal of acetaldehyde from poly(ethylene terephthalate). PhD Thesis, Cardiff University.
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Acetaldehyde (AA) is a degradation product of poly(ethylene terephthalate) (PET). AA can migrate from the walls of a PET bottle into drinking water and cause an off-taste at very low concentrations. Currently anthranilamide (ATA) is added to PET to scavenge the AA and is able to remove up to 80% of the contaminant. However, ATA is a stoichiometric scavenger so there is scope for a more efficient technology to be developed that utilises catalytic scavengers. ColorMatrix owns a patent for catalytic AA removal technology that uses a hydrous zirconium oxide catalyst. In this study the claims made in that patent were examined and scrutinised, and alternative metal oxide catalysts were prepared and tested to determine if they could be more effective for AA removal. A laboratory testing protocol for testing the AA conversion activity of the metal oxide catalysts was developed that involved a gas-phase reactor equipped with online Gas Chromatography (GC) analysis. This reactor could be used to determine the suitability of samples for testing in PET at ColorMatrix in Knowsley. ColorMatrix have the capability to test the catalysts under application-like conditions because they have the apparatus to dry, extrude, and analyse the PET. The catalyst samples that were prepared in the laboratory were also subjected to a bevy of characterisation techniques in order to gain understanding regarding which physicochemical properties are most important for an effective AA removal catalyst. CeO2 catalysts were found to be the most active of the samples tested in this study. Alternative preparation methods, milling, and doping were among the routes that were explored to attempt to increase the efficiency of the CeO2 catalysts. The catalyst sample that achieved the greatest AA reduction in PET of 32%, was prepared using urea precipitation with a urea to metal nitrate molar ratio of 3:1. This project was half-funded by ColorMatrix/PolyOne and half-funded by the EPSRC through the Centre for Doctoral Training in Catalysis.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Chemistry
Date of First Compliant Deposit: 23 February 2021
Last Modified: 23 Feb 2022 02:30

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