Effect of quaternary ammonium salt as a phase transfer catalyst for the microwave depolymerization of polyethylene terephthalate waste bottles

Poly(ethylene terephthalate) (PET) obtained from waste bottle product was depolymerized under microwave irradiation in open vessel equipment. PET bottle was shredded and ground to <0.5 mm particle size and subjected to basic hydrolysis to terephthalic acid (TPA) and ethylene glycol using 10% NaOH under the influence of microwave irradiation (200 W) in the presence of quaternary ammonium salt as a phase transfer catalyst (PTC). The effect of irradiation time, base concentration, particle size, PTC quantity, and microwave irradiation power on the extent of depolymerization was investigated. Results show that the optimum conditions to give ∼99% of TPA were 10% NaOH, 60 min, 200 W power, and 3% wt./wt. PTC/PET. This process is viable economically and interesting, since that PTC could be recovered and the side products after acidification are glycol and sodium chloride.

► Poly(ethylene terephthalate) was hydrolyzed under microwave irradiation. ► Phase transfer catalyst (PTC) increases the rate of depolymerization to ∼99%. ► Increasing microwave power and PTC concentration reduces reaction time. ► The process could be described as an ecofriendly method for the recycling of PET.