(544f) Degradation of Poly(ethylene terephthalate) Wastes Catalyzed by Mn-Containing Ionic Liquid

With the increasing of poly(ethylene terephthalate)(PET) consumption in recent years, the effective recycling of PET wastes becomes an urgent affair focused on by many governments and scientific researchers. Ionic liquids (ILs) have been reported as catalysts to degrade PET and most of them have showed some advantages of mild reaction condition and being easily separated from the main product. But the conversion of PET and the selectivity of the monomer bis(2-hydroxyethyl terephthalate)(BHET) are low. Therefore, the exploitation of novel ionic liquids that can efficiently degrade PET is significant.

In this study, Mn-containing ionic liquid was synthesised, characterized by Raman spectroscopy and Electrospray Ionization-Mass Spectrum and used to the catalytic degradation of PET in ethylene glycol. The results shows that the IL  exhibits higher catalytic activity, compared with conventional ionic liquids,such as [bmim]Cl, [bmim]H₂PO₄, [bmim]HSO₄. The conversion of PET and the selectivity of the BHET reach up to 100% and 78.9% respectively under the conditions of reaction pressure 1atm, reaction temperature 170°C and reaction time 2.5h. They are both higher than 88.6% and 62.8% catalyzed by 1-butyl-3-methylimidazolium tetrachloroferrate ([bmim]FeCl₄) and the reaction time were shortened greatly from 4h to 2.5h(Wang et al, 2010). In addition, the method has advantages that the main product is easily separated from catalyst and has good quality. Finally, the mechanism is proposed and shows that the higher catalytic activity of the IL is owing to the synergistic effect of its cation and anion.

 Reference

Wang, H., Yan, R.Y., Li, Z.X., Zhang, X. P., Zhang, S.J.(2010). Fe-containing magnetic ionic liquid as an effective catalyst for the glycolysis of poly(ethylene terephthalate). Catal. Commun., 11, 763-767.