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Polyethylene terephthalate is produced largely from purified terephthalic acid (PTA), as well as to a lesser extent from (mono-)ethylene glycol (MEG) and dimethyl terephthalate (DMT). [41] [5] As of 2022, ethylene glycol is made from ethene found in natural gas, while terephthalic acid comes from p-xylene made from crude oil.
The first enzyme of the PET degradation pathway, PETase, cleaves this plastic into the intermediates MHET (Mono-(2-hydroxyethyl)terephthalic acid) and minor amounts BHET (Bis-(2-hydroxyethyl)terephthalic acid). MHETase hydrolyses the ester bond of MHET forming terephthalic acid and ethylene glycol. Enzymatic PET degradation by PETase and MHETase
Terephthalic acid can also be made from toluene by the Gattermann-Koch reaction, which gives 4-methylbenzaldehyde. Oxidation of the latter gives terephthalic acid. [18] Terephthalic acid can be prepared in the laboratory by oxidizing many para-disubstituted derivatives of benzene, including caraway oil or a mixture of cymene and cuminol with ...
PETase and MHETase reaction pathway. [14] In I. sakaiensis, the resultant MHET is further broken down by the action of MHETase enzyme to terephthalic acid and ethylene glycol. [1] Laboratory experiments showed that chimeric proteins that artificially link a MHETase and a PETase outperform similar mixtures of free enzymes. [15]
Together with 2-hydroxyethyl terephthalic acid, bis ... (ethylene terephthalate). It is the product of the glycolysis reaction of PET with Ethylene glycol.
The reaction yields ethylene glycol and the terephalate salt, in aqueous solution. After separation and filtration, in a second step, the salt is neutralized with strong mineral acid to precipitate the terephthalic acid. [(CO)C 6 H 4 (CO 2 CH 2 CH 2 O)] n + 2n MOH → n C 6 H 4 (CO 2 M) 2 + n HOCH 2 CH 2 OH C 6 H 4 (CO 2 M) 2 + 2HCl → C 6 H 4 ...
Ethylene glycol has relatively high mammalian toxicity when ingested, roughly on par with methanol, with an oral LD Lo = 786 mg/kg for humans. [30] The major danger is due to its sweet taste, which can attract children and animals. Upon ingestion, ethylene glycol is oxidized to glycolic acid, which is, in turn, oxidized to oxalic acid, which is ...
An example of polyester is polyethylene terephthalate (PET), which is made from the monomers terephthalic acid and ethylene glycol. If one of the components in the polymerization is in excess, then that polymers functionality will be at the ends of the polymers (a carboxylic acid or alcohol group respectively).