Patent ID: 7893122
Filing Date: 2011-02-22
Classification: C07C,C08J,Y02P,Y02W

Abstract:
1. A chemical process for recycling PET wastes, the process comprising the stages of: a) a saponification reaction stage, wherein PET waste particles are reacted with stoichiometric or excessive amounts of a strong base metal in an alcoholic reaction media that forms a single phase with ethylene glycol, which single phase is not miscible with an aqueous solution of a terephthalic acid salt, where the reaction is brought to the boiling temperature of the alcoholic reaction media and at atmospheric pressure, thereby obtaining as reaction products a salt of terephthalic acid with base metal and ethylene glycol, the latter being incorporated to the alcoholic reaction media; b) a separation stage of such terephthalic acid salt from the alcoholic reaction media comprising the steps of: i) cooling the reaction mixture to a temperature below 90° C.; ii) adding sufficient water to the reaction media in order to dissolve the terephthalic acid salt, thereby obtaining two phases, namely an aqueous phase where the terephthalic acid salt is dissolved, and an organic phase that consists of the alcoholic reaction media in which ethylene glycol is incorporated; and iii) a liquid-liquid separation phase, wherein the aqueous phase containing the terephthalic acid is separated from the organic phase; c) a terephthalic acid formation stage, wherein from terephthalic acid salt of stage (b) terephthalic acid is obtained, reacting said salt with a stronger acid than terephthalic acid to form and precipitate the latter as crystals; d) a solid-liquid separation stage, wherein precipitated terephthalic acid in stage (c) is separated from the media where it was crystallized; and e) an ethylene glycol recovery stage, wherein ethylene glycol and the alcoholic reaction media are separated and recovered from the reaction media separated in stage (b).