Glycolysis of Poly(ethylene terephthalate) Catalyzed by the Lewis Base Ionic Liquid [Bmim][OAc]

Abstract

The glycolysis of poly­(ethylene terephthalate) (PET) was studied using 1-butyl-3-methylimidazolium acetate ([Bmim]­[OAc]) as a catalyst. The effects of temperature, time, ethylene glycol dosage, PET amount, and [Bmim]­[OAc] dosage on the glycolysis reaction were examined. The results revealed that [Bmim]­[OAc] has a PET conversion of 100% and a bis­(2-hydroxyethyl)­terephthalate (BHET) yield of 58.2% under the optimum conditions of 1.0 g of [Bmim]­[OAc] with 20 g of ethylene glycol in the presence of 3.0 g of PET at 190 °C after 3 h of glycolysis. The ionic liquid could be reused up to six times with no apparent decrease in the conversion of PET or yield of BHET. The pH plays a major role in explaining the proposed mechanism of glycolysis using the Lewis base ionic liquid [Bmim]­[OAc]. The kinetics of the reaction was first-order with an activation energy of 58.53 kJ/mol.

PET glycolysis optimization using ionic liquid [Bmin]ZnCl3 as catalyst and kinetic evaluation

“…The apparent activation energy for the process of glycolysis with the catalyst [Bmin]ZnCl 3 , calculated on the straight line slope in Arrhenius plot (Figure 8) was 36.49 kJ/mol. The calculated result of the apparent activation energy is well lower compared to the data reported in the literature (Table 4), the energy values 53.8 kJ/mol and 56.4 kJ/mol for 1-butyl-3-methylimidazole acetate combined with zinc and copper acetates respectively [9] , 58.53 kJ/mol with 1-butyl-3-methylimidazole acetate [23] , 79.3 kJ/mol with zinc and aluminum oxides mixture [24] , 85 kJ/mol with zinc acetate [25] , 92 kJ/mol with zinc (acetate and stereate) salts [26] and 108 kJ/mol without catalyst [25] .…”

“…PET depolymerization studies usually assume the process as having first-order kinetics [9,23] . The depolymerization reaction rate constant is proportional to the PET concentration (per repeating unit) and ethylene glycol (EG).…”

Reactive Extrusion of Polyethylene Terephthalate Waste and Investigation of Its Thermal and Mechanical Properties after Treatment

“…The nonbiodegradability of synthetic polymers has triggered a major unease for environmentalists in terms of polymer waste management [2]. In recent years, recycling of synthetic polymers has caught the attention of many research groups, for two major motives: to minimize the ever growing volume of polymer waste and to create value-added items from low cost resources by transforming synthetic polymeric waste into beneficial and useful items having similar properties to virgin materials [3][4][5][6].…”

Chemical recycling of unsaturated polyester resin and its composites via selective cleavage of the ester bond

“…26,27 In addition to solvolysis, the degradation of UPR was reported by using strong oxidants such as hydrogen peroxide [28][29][30] and ionic liquid. [31][32][33] However, high temperature, long reaction times, strong corrosive solvent (e.g., nitric acid), or rigorous conditions (e.g., supercritical fluid) are usually required to cleave the chemical bonds of UPR. More importantly, such cleavage of chemical bonds is non-selective, which inevitably produces small toxic molecules, introduces a complex distribution of products and causes a serious damage in the strength of GF.…”