Patent KR-20110043550-A (KR)
Title: Method and device for the recovery of ethylene glycol for the production of polyethylene terephthalate
Inventor: REIMANN RANDOLF
IPC: C02F1/44
Filed: 2009-06-05
Abstract: Recovering ethylene glycol from 2-methyl-1,3-dioxolane (MDO), comprises: (a) subjecting ethylene glycol and terephthalic acid to an esterification reaction to form ethylene terephthalate and a process waste water containing contaminants; (b) subjecting the process waste water, to at least one separation step in a rectification column; and (c) mixing in a collecting tank (1) at least a part of the partially purified process waste water with a fluid containing 2-methyl-1,3-dioxolane, resulting in hydrolytic cleavage of MDO into ethylene glycol and acetaldehyde. 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, comprises: (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 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 (1) at least a part of the partially purified process waste water with a fluid containing 2-methyl-1,3-dioxolane, the 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 at least a portion of the MDO is hydrolytically cleaved into ethylene glycol and acetaldehyde, before passing the mixture into the rectification column according to the step (b). An independent claim is included for an apparatus for the production of polyethylene terephthalate, comprising at least one esterification or transesterification reactor (18), at least one rectification column downstream of the esterification or transesterification reactor, a collecting tank arranged upstream of the rectification column, the collecting tank including at least one feed line for introducing a partially purified process waste-water into the collecting tank, at least one feed line for introducing an ethylene glycol process flow containing MDO into the collecting tank and/or at least one feed line for introducing a mixture of partially purified process wastewater and a fluid containing MDO into the collecting tank and at least one line for channeling a mixture comprising partially purified process wastewater and ethylene glycol recovered from MDO through hydrolytic cleavage from the collecting tank to the rectification column.