| 摘要 |
<p>Process for recovering glycols from glycol terephthalates prodn. by distillation of the vapour mixt. coming from the esterification zone comprises subjecting the vapour mixt., without any intermediate condensation, to distillation in vacuo, pref. at 50-400 Torr absolute, and then recycling the high-boiling liquid fraction, principally glycol, so produced to the esterification process while still hot. All or part of the glycol may be returned to the zone where glycol and terephthalic acid make-up are mixed, or part is returned directly to the esterification reactor and none removed, or a part of the liquid is removed from the process. Recovery is effected more efficiently with less consumption of energy; at lower temp. (less glycol ether formation); water (which has to be re-evaporated) is not recycled with the glycol but any esters present are material losses are reduced; and by recycling to the mixing zone the glycol-acid suspension is diluted to made easier to transport.</p> |
