PET (polyethylene terephthalete) wastes chemical hydrolysis at 200-300 oC yield terephthalic acid (TPA) and etheleneglycol (EG). Reaction rate is improved in alkaline or acid media obtaining complete hydrolysis in ca. 6 h. This is an environmental desirable treatment (sustainable PET recycling) as compare to mechanical treatment where separation and sorting are required; also, the quality of the final plastic flakes or granulates are limited to reused or to be introduced in quite low percentage in the recycling process.
Plastics mix of PET waste with polypropylene and/or biomass waste are commonly found. Recently, a synergy effect has been reported1 in the hydrolysis of PET waste when it is mixed with other plastic waste (PP: polypropylene) or biomass (cellulose). This is quite interesting results since previous separation of PET waste may be avoided. Up to 94 % yield and 76% of TPA is reported at 350°C using PET (pellet) mix with PP and cellulose, respectively. 20 % of g feedstock (1:1)/g water was used. Under conditions (250°C) in which hydrolysis of pure PET bottle waste is minimum, mix 1:1 with PP and cellulose yield 48 and 62 % of TPA, respectively. In all cases, byproducts are formed, although the addition of PP or cellulose does not increase the percentage of byproducts formed. In any case, TPA produced in the hydrolysis requires separation and purification in order to be recycled in the polymerization process as shown in the figure.
1.- S.M. Subramanya, Y. Mu,P.E. Savage ACS Eng. Au (2022) https://doi.org/10.1021/ acsengineeringau.2c00024
