Multiple Hydrogen Bonds Promote the Nonmetallic Degradation Process of Polyethylene Terephthalate with an Amino Acid Ionic Liquid Catalyst

Abstract

The formation of hydrogen bonds in the polyethylene terephthalate degradation process is beneficial for the break of ester bonds and accelerates the reaction. Therefore, we designed a series of amino acid ionic liquid catalysts, which have several donor and receptor groups and can form multiple hydrogen bonds with the reactants to enhance the nonmetallic degradation process. By comparing with the traditional catalysts, the designed catalysts avoid the introduction of metal elements and have a similar catalytic efficiency to the traditional metal catalysts. Under the optimal conditions with [Bmim]Pro, the conversion reached 100.0% and the yield of bis(2-hydroxyethyl terephthalate) reached 75.3%. The catalyst has good recycling performance under the reaction condition. Through two-dimensional overhauser enhancement spectroscopy, it was found that there are multiple interactions between [Bmim]Pro and the reactants. Multiple hydrogen bonds between reactants and [Bmim]Pro were proved by density functional theory (DFT) calculations. Finally, the reaction kinetics were studied, which are consistent with the shrinking-core model.

In silico COSMO-RS predictive screening of ionic liquids for the dissolution of plastic

“…In our study, amino acid-based ILs are also predicted to be better solvents for PET, and the results agree with Yao et al (2021). 67 The present study predicted excess enthalpy values of PET in ethylene glycol + ILs were also compared with the experimental conversion of PET and found that the COSMO-RS predicted H E and experimental PET conversion are in good agreement (Fig. 2), and thus confirms that our COSMO-RS predicted results agree with experimental data.…”

Insights into the depolymerization of polyethylene terephthalate in methanol

“…It indicates that the solid‐phase PET decreases obviously in the initial reaction stage (0–20 min), but the consumption rate of PET is bigger than that of DMT formation, which indicates that DMT is not the direct product from ester bond breaks of PET. The generation rate of product DMT is significantly increased in the medium stage of reaction (20–40 min), which suggests that DMT is the product of deep depolymerization of PET 41,42 . Moreover, 43,44 according to the evolution of PET structure, two methanol molecules are needed to form DMT and EG in the depolymerization process (Figure 9b).…”

“…The generation rate of product DMT is significantly increased in the medium stage of reaction (20-40 min), which suggests that DMT is the product of deep depolymerization of PET. 41,42 Moreover, 43,44 according to the evolution of PET structure, two methanol molecules are needed to form DMT and EG in the depolymerization process (Figure 9b).…”

Investigating the degradation of PET utilizing NHC‐based catalysts and effective reuse of the degradation product as an additive with polyurethane adhesive material

“…To ensure the high utility of the glycolysis product (BHET) obtained after PET degradation, it should be able to reuse as a potential material in some other applications other than their ability to undergo re-polymerization to produce PET. 16,25 Hence in this work, we have performed benzoylation with the BHET to synthesize its corresponding dibenzoylated derivative, bis (2-([4-butoxybenzolyl]oxy) ethyl) terephthalate (BBET).…”

“…Only a few reports focused on PET degradation and the further reuse of the glycolysis product (BHET) into the synthesis of helpful material. For instance, Yao et al 16 had reported glycolysis of PET into BHET using amino acid ionic liquid catalysts to promote hydrogen bonding in PET which in turn assist in the breakage of ester bonds as a nonmetallic degradation process. In addition to the degradation of PET into BHET, the author also utilized the BHET as one of the monomers with isophorone diisocyanate to synthesize polyurethanes.…”