Depolymerization of Poly(ethylene terephthalate) Wastes through Glycolysis using Lewis Acidic Bentonite Catalysts

Abstract

In the present investigation, the authors explored the depolymerization of waste poly(ethylene terephthalate) (PET) beverage bottles using glycolysis (transesterification) catalyzed by Al3+, Fe3+ and Zn2+ impregnated bentonite catalysts. Heterogeneous catalysts such as clay, zeolite, alumina etc. preferred over homogeneous catalysts, thus we focused on the development of solid acid catalysts based on economically viable clay catalysts. The desired Lewis acidic nature was introduced by wet impregnation method at variable metal ion to clay ratio such as 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 wt. %. The effect of metal-ion loading on the surface area, pore volume and crystalline nature of the bentonite has been evaluated by nitrogen adsorption and desorption studies and XRD. The PET wastes collected from post-consumer beverage bottles were depolymerized using ethylene glycol as a glycolyting agent afforded bis(2-hydroxy ethyl)terephthalate (BHET) in 85-90 % yield under optimized conditions. The yield of BHET was observed to be increasing with increase in Lewis acidic metal ions loading from 0.5 to 4.0 wt. % as well as increase in catalysts to PET ratio. Among the catalysts, Al3+ and Zn2+-bentonite catalysts showed higher yield of BHET up to 90 % at 4 and 5 wt. % loading of metal-ion.

Recyclable Clay-Supported Heteropolyacid Catalysts for Complete Glycolysis and Aminolysis of Post-consumer PET Beverage Bottles

“…The peaks were found at 19.90° and 24.96° at all samples, revealing the presence of a narrow amount of quartz with bentonite catalysts. The decreased in the (d001 and d020) interval indicates an increased in interlayer space owing to the impregnation of metal ions respectively (Jeya et al, 2019;Bouraie et al, 2017). Moreover, XRD pattern of pure and catalyst supported with bentonite catalysts showed similar crystalline pattern representing that the impregnation is not affected the bentonite framework.…”

“…In our previous study, the effect of aluminium, zinc and iron containing kaolin and bentonite catalysts have been evaluated for the depolymerization of PET polymer using glycolysis was reported (Jeya et al, 2017;Jeya et al, 2019). Among them, Zn 2+ loaded bentonite showed better results than kaolin analogue as well as other metals.…”

Aminolytic Depolymerisation of Polyethylene Terephthalate Wastes using Sn doped ZnO Nanoparticles

“…Chemical recycling process of PET divided: (i) glycolysis, (ii) methanolysis, (iii) hydrolysis, (iv) aminolysis, and (v) ammonolysis. Among the chemical recycling techniques, glycolysis and aminolysis depolymerization of the PET wastes produced bis (2-hydroxy ethyl) terephthalate (BHET) and bis (2-hydroxymethyl) terephthalamide catalysed by Lewis acidic heterogeneous catalysts [15,16]. Aminolysis is any chemical reaction in which post-consumer PET waste completely depolymerized into monomers by reacting with a molecule of an amine.…”

Depolymerization of PET wastes catalysed by Sn and Ag doped ZnO nanoparticles and evaluation of Embryonic Toxicity using Zebrafish

“…PET is belonging polyester type of polymer, in which the polyester linkages can be cleaved by a suitable acid and base through hydrolysis to generate terephthalic acid. Alternatively, the PET can be depolymerized through transesteri cation reaction namely glycolysis and aminolysis catalysed by Lewis acid catalysts (Jeya et al 2017(Jeya et al , 2020(Jeya et al , 2022a(Jeya et al and 2022b.…”