Patent ID: 7951980
Filing Date: 2011-05-31
Classification: C02F,C07C,C08G

Abstract:
1. A process for recovering ethylene glycol from 2-methyl-1,3-dioxolane (MDO), in which ethylene glycol is bonded in the form of an acetal, during production of polyethylene terephthalate from ethylene glycol and terephthalic acid, which comprises the steps of: (a) subjecting ethylene glycol and terephthalic acid to an esterification reaction to form ethylene terephthalate and a process waste water containing contaminants, which include ethylene glycol, separating the ethylene terephthalate from the process waste water and subjecting the ethylene terephthalate to a polycondensation reaction to form polyethylene terephthalate; (b) subjecting the process waste water obtained from step (a), to at least one separation step in a rectification column, in which the contaminants present in the process waste water, including ethylene glycol, are partially separated from the process waste water, to collect in the sump of the rectification column, and to obtain as a head product a partially purified process waste water; and (c) mixing in a collecting tank at least a part of the partially purified process waste water obtained according to step (b) with a fluid containing 2-methyl-1,3-dioxolane (MDO), said fluid obtained from one or more ethylene glycol process flows, upstream of the rectification column, and as a result of an increase in the water content in the fluid, a shift in the reaction equilibrium takes place and consequently a hydrolytic cleavage of the 2-methyl-1,3-dioxolane takes place so that at least a portion of the 2-methyl-1,3-dioxolane (MDO) is hydrolytically cleaved into ethylene glycol and acetaldehyde, before passing the mixture into the rectification column according to step (b).