Optimization of reaction parameters in the conversion of PET to produce BHET

Abstract

The conversion of poly(ethylene terephthalate) (PET) was analyzed in order to define the optimal conditions for the Bis(2‐Hydroxyethyl) terephthalate (BHET) yield as regards catalyst use (zinc acetate), glycol (ethylene glycol), reaction time and temperature. These conditions were optimized so as to decrease the consumption of catalyst and glycolytic agents aiming to extend the analysis to achieve continuous recycling at a greater scale. At the same time, an analysis of the activity of different catalysts (zeolites, acid, and basic resins) was performed; no BHET yields of commercial interest were obtained. The results indicate that a very small catalyst/PET mass ratio and a low glycol/PET ratio are necessary. The reactions were carried out at a temperature of 195°C and a reaction time of 1 h: under these conditions, BHET yield is 30% (starting from pure PET) and up to 88.2% (recycling oligomers plus pure PET). POLYM. ENG. SCI., 58:1500–1507, 2018. © 2017 Society of Plastics Engineers

A focused review on recycling and hydrolysis techniques of polyethylene terephthalate

“…As shown in Figure 3, the final product is BHET. 106,107 PET glycolysis without a catalyst is a sluggish process where PET cannot completely be depolymerized to BHET. To resolve this challenge, various catalysts have been proposed including metal derivatives, zeolites, and ionic liquids where zinc acetate and magnesium acetate are the most significant ones.…”

“…The reaction medium can be EG, diethylene glycol, propylene glycol, or di‐propylene glycol with EG as the most widely used compound. As shown in Figure 3, the final product is BHET 106,107 . PET glycolysis without a catalyst is a sluggish process where PET cannot completely be depolymerized to BHET.…”

Recycling of Polyesters by Organocatalyzed Methanolysis Depolymerization: Environmental Sustainability Evaluated by Life Cycle Assessment

“…However, a 5:1 base to substrate ratio was used, and recovery of EG was not reported. The most employed PET recycling methodology is glycolysis to yield the ester of EG and TA: Bis -2-hydroxyethyl terephthalate (BHET) (Scheme b). − The depolymerizations are usually employed using a metal catalyst at 250 °C. Alcoholysis uses an alcohol such as MeOH to produce dimethyl terephthalate (DMT) and EG. − (Scheme c) The reactions are usually performed at 250 °C and require the use of a metal catalyst, which in turn entails an additional step for separating the solid catalyst from the solid DMT.…”

Optimization of Poly(ethylene terephthalate) Fiber Degradation by Response Surface Methodology Using an Amino Acid Ionic Liquid Catalyst

“…López-Fonseca chose Na 2 CO 3 as the catalyst, which also showed excellent catalytic performance. Zinc acetate , is becoming more and more popular for its excellent catalytic performance. , Stoski et al investigated the efficient degradation of PET when zinc acetate was used as a catalyst and explored the effect of reaction temperature on the degree of depolymerization. In addition, metal–organic framework catalysts such as ZIF-8 and MAF-6 have also been widely used in PET glycolysis in recent years.…”