Process for recovering terephthalic acid from waste polyethylene terephthalate

Terephthalic acid (TPA) is recovered from used polyethylene terephthalate beverage containers by reacting comminuted containers in a reaction zone with an aqueous medium containing ammonium hydroxide at elevated temperatures and pressures to form a water soluble diammonium salt of TP A, separating any undissolved solids from the reaction product, acidifying the remaining reaction product to liberate TP A, and separating the precipitated TPA. A portion of the liquid remaining after separation of TPA can be mixed with lime or slaked lime, the resulting mixture treated in an ammonia stripper to remove ammonia therefrom and the ammonia overheads from the stripper blended with another portion of the liquid remaining after separation of TPA to form a stream containing ammonium hydroxide which is recycled to the reaction zone. Ethylene glycol can be recovered from the bottoms from the ammonia stripper by distillation.https://digitalcommons.mtu.edu/patents/1102/thumbnail.jp