Glycolysis of postconsumer polyethylene terephthalate waste

Abstract

Glycolytic depolymerization of polyethylene terephthalate (PET) bottle waste was attempted using ethylene glycol (EG) in the presence of chlorides of zinc, lithium, didymium, magnesium, and iron as catalysts. Virtual monomer bis (2-hydroxyethyl terephthalate) (BHET) was obtained in all cases with nearly 74% yield, the highest yield being achieved with zinc chloride catalyst 0.5% w/w, PET : EG ratio 1 : 14 and 8 h under reflux conditions. The results were comparable to other catalysts like common alkalis, acids, and salts of some earth metals and zeolites used earlier although parameters of glycolysis were observed to vary depending on the catalyst.

The Glycolysis of Poly(ethylene terephthalate) Waste: Lewis Acidic Ionic Liquids as High Efficient Catalysts

“…When the reaction time was shorted to 2 h, the conversion of PET in the glycolysis arrived at 100% in the presence of 5 wt % [Bmim]ZnCl 3 , and the BHET yield rose to 82.6% (Table 1, entry 5), respectively. In the literature, ZnCl 2 showed better catalytic activity [20], but when using ZnCl 2 as a catalyst, the PET was glycolized completely, and the yield of BHET was decreased to 78.6% ( entry 12). These results indicated that the catalytic activity of metal-containing ionic liquids was higher than that of [Bmim]Cl.…”

Recent Developments in the Chemical Recycling of PET

“…Fig. 4 shows the reaction mechanisms of uncatalyzed glycolysis and that of glycolysis with metal-based catalyst (Shukla & Harad, 2005;Pingale et al, 2010). A free electron pair on the EG oxygen initiates the reaction by attacking the carbonyl carbon of the ester group of the polyester.…”

“…López-Fonseca et al also used these eco-friendly catalysts in their study of catalyzed glycolysis kinetics (López-Fonseca et al, 2010, 2011. The latest catalysts that Shukla's group developed are inexpensive and readily available metal chlorides, wherein zinc chloride reportedly gave the highest BHET yield equal to 73.24% (Pingale et al, 2010).…”

Recycling of poly(ethylene terephthalate) – A review focusing on chemical methods

“…They found that de-polymerization increased in the order Pb These results were confirmed by Ghaemy and Moassaddegh as well as Goje and Mishra [184,192,211]. Pingale et al [191] also studied the influence of different cations, namely zinc, lithium, didymium, magnesium and iron, on the catalytic effect of respective chlorides in the glycolysis of PET. They found zinc chloride to be the most effective catalyst yielding 73% BHET, followed by didymium chloride, magnesium chloride, lithium chloride and ferric chloride.…”