Abstract
Supercritical ethanolysis (scEtOH) is a method that allows the production of monomers, e.g., diethyl terephthalate (DET), from Polyethylene terephthalate PET chemical recycling. The use of the ionic liquids (ILs) such as 1-n-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) as a catalyst has advantages in such processes by enhancing the yield at reduced times, as shown in previous work from our lab. However, the effects of water and dyes (from the coloured PET-bottles) regarding those advantages have not been investigated. Here, a study of the effects of water and dyes on IL-catalysis is provided. Results showed that the yield related to DET formation was 98% when anhydrous ethanol was employed, but decreased to 30% (or less) when water was present in the reaction even in low amounts. Furthermore, the DET-formation yield also decreased to 66% or to 21% if 2-aminoanthraquinone or zinc phthalocyanine were present, respectively, even in anhydrous conditions. Poisoning effect on the IL-catalysis was observed in both cases. Thus, these data are relevant for expanding the study of ILs as catalysts in this and other reaction systems.
Highlights
Polyethylene terephthalate (PET), a synthetic thermoplastic polyester, is considered one of the most versatile polymers in use today [1]
Taking into account all these considerations and the evident lack of information regarding the role played by ionic liquids (ILs) in different types of reaction media, the main objective of this work was to investigate the effects of water and two different dyes (2-aminoanthraquinone or zinc phthalocyanine) on the PET depolymerization reaction catalyzed by [Bmim][BF4] under supercritical ethanol
The depolymerization reactions were conducted in the presence of requested amounts of water and coloured or colourless PET flakes from waste bottles
Summary
Polyethylene terephthalate (PET), a synthetic thermoplastic polyester, is considered one of the most versatile polymers in use today [1]. This is due to the combination of desirable properties such as excellent tensile and impact strength, chemical resistance, processability, transparency, and appropriate thermal stability [2]. The production of PET-based materials has increased and, as a direct consequence, a major problem faced by the plastics industry is that of the waste disposal that increases year after year[4,5]. Growing environmental concerns have promoted searches to find reasonable methods for mitigating or avoiding plastic-waste pollution and to rethink the consumption of plastic-based products. The most promising method to control plastic-waste pollution is the chemical recycling, which has become increasingly important [6]
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