| abstract |
Spent ethylene glycol recovered from polyester manufacture contains dissolved antimony catalyst residues and other impurities. Prior to distillation of the spent glycol to recover purified ethylene glycol, the antimony compounds are removed by adjusting the pH of the spent glycol to about 2 to 7, preferably 5 to 7, preferably by adding an organic acid (e.g., acetic acid) adding an alkali metal borohydride (e.g., sodium borohydride) in the absence of oxygen and with intimate mixing to form a metallic antimony precipitate, and recovering the precipitate. The process is further improved by adding a catalytic amount of a strong inorganic base, e.g., sodium hydroxide, prior to the pH adjustment step, to convert any terephthalyl values to dihydroxyethyl terephthalate which can be recovered. |