Zeolite catalyzed glycolysis of poly(ethylene terephthalate) bottle waste

Abstract

Polyethylene terephthalate (PET) bottle waste was depolymerized using excess of ethylene glycol (EG) in the presence of zeolites, b-zeolite and Y-zeolite as transesterification catalyst. The glycolysis reaction was carried out under reflux in excess of ethylene glycol up to 8 h. The product of glycolysis was mainly the virtual monomer, bis(2-hydroxyethyl) terephthalate (BHET) admixed with dimer as residue. The BHET was obtained in pure crystalline form. Influence of the reaction time, PET : EG ratio, type, and concentration of catalyst on the yield of the glycolysis products was investigated. The characterization of the purified monomer was carried out by elemental analysis, melting point, IR spectroscopy, DSC, and NMR. The yield of BHET monomer was more than 60%, which is comparable with the conventionally used heavy metal catalysts such as zinc acetate and lead acetate. This process of glycolysis of PET is economically viable and the catalysts are environment friendly.

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].…”

“…Depolymerization of PET can be achieved by hydrolysis using water [19] or lysis using alcohol [20] (methanolysis using methanol) [21,22] or amines [23] or acids [24]. The most established or commercialized processes for the depolymerization of PET are glycolysis, hydrolysis, and methanolysis [5]. The depolymerization of PET can also be classified based on the type of catalyst or ionic liquids or supercritical conditions used in the process [25].…”

“…Glycolysis is usually carried out in boiling ethylene glycol [30] in the presence of catalysts like zinc acetate [31] or lead acetate [16]. The use of such catalysts in large scale may cause pollution due to their toxic nature [5]. The properties of PET can be modulated by treating it with suitable reagents or dry processes for use in various applications [32,33].…”

Poly (ethylene terephthalate) recycling for high value added textiles

“…The glycolysis rate and BHET monomer yield are dependent on various reaction parameters such as temperature, PET/ethylene glycol ratio, and type and amount of catalysts. A number of studies are summarized in Table 3, detailing the optimum glycolysis conditions and reaction parameters obtained (Dulio et al 1995;Pingale et al 2010;Xi et al 2005;Troev et al 2003;Shukla and Kulkarni 2002;Shukla et al 2008;Imran et al 2011;Wang et al 2009;Yue et al 2011). …”

Oligoester and Polyester Production via Acido-alcoholysis of PET Waste

“…Thus a wide range of catalysts were studied and introduced, including metal salts, ionic liquids, heterogeneous catalyst like magnetic nanoparticles and MOFs (metal-organic frameworks) to enhance BHET yield. [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] High ratio of ester:alcohol (1:3-1:8) were used in these studies to shift the equilibrium to the BHET production. The reaction product was recrystallized from water or other good solvents of BHET.…”