Abstract
Waste poly (ethylene terephthalate) (PET) from drink bottles wasdepolymerized using novel zwitterionic imidazolium-2-carboxylate salts ascatalysts (or catalyst-precursors) in the presence of ethylene glycol viaglycolysis to give bis(hydroxyethyl)terephthalate (BHET). The influence ofreaction temperature, glycolysis time, ethylene glycol:PET ratios, and theamount of the zwitterionic imidazolium-2-carboxylate catalysts used on theconversion of PET, isolated yield of BHET, and the selectivity of BHET in theglycolysis of PET were investigated.The results demonstrate that 1,3-dimethylimidazolium-2-carboxylate can bean effective basic catalyst for PET glycolysis, with PET depolymerization of upto 100% observed. BHET was isolated from the reaction mixture with yields ofup to 61.0% under the optimum reaction conditions using 0.15 g catalyst to 1.0g PET in the presence of 10.0 g ethylene glycol (0.15:1:10 mass ratio) at 185oCin 1 h. This is the first time that 1,3-dialkyl-imidazolium-2-carboxylates havebeen reported to be catalysts for glycolysis of PET and, compared to 1,3-dialkylimidazolium acetate ionic liquids, were more effective as catalyst in theglycolysis. The purified monomer was characterized by the nuclear magneticresonance (NMR), mass spectrometry, and high performance liquidchromatography (HPLC).
| Date of Award | 2019 |
|---|---|
| Original language | English |
| Awarding Institution |
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| Supervisor | John Holbrey (Supervisor) & Gosia Swadzba-Kwasny (Supervisor) |
Keywords
- Poly (ethylene terephthalate) (PET)
- bis (hydroxyethyl) terephthalate (BHET)
- glycolysis
- carbene
- zwitterionic catalyst
- imidazolium2-carboxylate (NHC-CO2)