Abstract
Poly(ethyleneterephthalate) waste was efficiently depolymerized through glycolysis and aminolysis reactions in the presence of functionalized 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD) catalyst. The new catalyst of monoamide-ester type, was synthesized through reaction of dimethylterephthalate (DMT) with TBD in refluxing benzene. It was developed as a consequence of the mechanistic investigations of the transesterification reaction of isosorbide with DMT. To test the stability of functionalized TBD compound towards possible amide bond breakage, reactions with primary and secondary glycols as well as primary amines were performed when only the carboxymethyl group reacted. Moreover, it was found that the depolymerization of poly(ethyleneterephthalate) wastes proceeds faster in the presence of this novel organocatalyst by comparison with the hygroscopic TBD precursor.
Highlights
Poly(ethyleneterephthalate) waste was efficiently depolymerized through glycolysis and aminolysis reactions in the presence of functionalized 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD) catalyst
The feasibility of the chemolytic depolymerization of PET waste is quite low at the moment due to the harsh reaction conditions required for the polymer scission as well as due the contamination of the products with metal salts from the used catalysts [7-9]
We have previously reported on the use of isosorbide as glycolysis reagent of PET waste using organic catalysis [20,21]
Summary
The catlytic reactions were carried out under inert atmosphere. PET waste was obtained from post-consumer bottles, cut into small flakes and cleaned thoroughly by washing with water containing detergent and with distilled water. The reactivity of the covalently bonded TBD adduct was carbonyl)benzoate, 1H-NMR: 5.39 (m, 1H, exo-ester); 4.65 investigated following two reactions type: i) the possible (m, 1H, CH4-IS) ppm and at endo hydroxyl group, acyl-transfer in the reaction with different diols and/or repectively, 4b, (3S, 3aR, 6R, 6aR)- 6-hydroxy- amine based on the easy formation of amide-ester, 1 hexahydrofuro[3,2-b]furan-3-yl-4-(2,3,4,6,7,8-hexahydro- (scheme 1) and ii) reactions of DMT with various diols in. The structural assignment was established by comparison with 1H-NMR spectra of products formed by PET glycolysis (BHET and/or other ISglycolizate) Based on these data we can affirm that instead of the amide breakage, a transesterification reaction involving the carbomethoxy group occurred. No amide breakage in the intermediate 1 occurred, an aminolysis reaction between the carboxymethyl and primary amine took place (compound 5, scheme 1) This was assigned based on the 1H-NMR spectrum where, the NH proton resonates at 8.06 ppm. Depolymerization of PET waste with diols and primary amine catalyzed by 10 mol % of compound 1
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