Degradation of waste poly(ethylene terephthalate) in a steam atmosphere to recover terephthalic acid and to minimize carbonaceous residue

Poly(ethylene terephthalate) (PET) waste was successfully decomposed in a steam atmosphere, yielding an amount of terephthalic acid predicted from the chemical formula of PET. It was found that steam accelerated the hydrolysis of PET, yielding terephthalic acid and oxygen-containing compounds such as aldehyde and ester with less than 1% carbonaceous residue. The amount of carbonaceous residue decreased with an increase in the fraction of steam in the carrier gas and was about 16% in nitrogen steam and below 1% in steam. The amount of terephthalic acid predicted from the chemical formula of PET (about 87%) was recovered at about 723 K in a carrier gas containing 70% steam and 30% nitrogen. Kinetic equations are proposed by considering both the hydrolysis and thermal pyrolysis of PET. (C) 1997 Elsevier Science Limited.