Recovery of Terephthalic Acid from Densified Post-consumer Plastic Mix by HTL Process

Abstract

In this study, we investigate the hydrothermal liquefaction (HTL) of PET separated from a densified postconsumer plastic mix, with the aim of recovering its monomer. This second raw material is made up of 90% polyolefin, while the remaining 10% is made up of PET, traces of metals, paper, and glass. After preliminary separation by density in water, two batch experiments were performed on the sunken fraction (composed mainly of PET) in a stainless steel autoclave at 345 °C for 30 and 20 min. Both trials resulted in similar yields of the three phases. In particular, the solid yield is around 76% by weight. After a purification step, this phase was analyzed by UV–Vis, 1H-NMR, and FTIR spectroscopy and resulted to be constituted by terephthalic acid (TPA), a product of considerable industrial interest. The study proved that the hydrothermal liquefaction process coupled with density separation in water is effective for obtaining TPA from a densified postconsumer plastic mix, which can be used for new PET synthesis.

Effect of chloride salts and microwaves on polyethylene terephthalate (PET) hydrolysis by iron chloride/acetic acid Lewis/Brønsted acidic deep eutectic solvent

“…2 In particular, polyethylene terephthalate (PET) is one of the preferred polymers for depolymerization studies; this research eld is very active, and original ideas are continuously emerging. [14][15][16][17] Generally, the depolymerization process of PET leads to bis(2-hydroxyethyl)-terephthalate (BHET) if ethylene glycol (EG) is the nucleophile, 18 and to dimethyl terephthalate using methanol and terephthalic acid (TA) with water. In most cases, harsh conditions are necessary (T > 160 °C, many hours, sometimes high pressure) although exceptions can be found in recent studies.…”

Hydrothermal Processing of Multilayer Plastic Film for Cascaded Valorization of Nonrecyclable Waste

“…Polyethylene terephthalate (PET) is converted to its monomers terephthalic acid (TPA) and ethylene-glycol . TPA was recovered after HTP of a mixture of PET and PA-6, following density separation of a postconsumer plastic mixture, and from LLDPE-PET multilayer film . Polycarbonate (PC) was converted into Bisphenol A .…”