Method for producing glycolide, which is provided with rectification step by means of gas-liquid countercurrent contact, and method for purifying crude glycolide

Abstract

A method for producing glycolide provided with: step (1) wherein a GAO composition, which preferably contains a high-boiling-point organic solvent or a solubilizing agent, is supplied into a reactor and heated to a temperature at which a depolymerization reaction of the GAO occurs; step (2) wherein the heating is continued to subject the GAO to the depolymerization reaction, thereby producing glycolide; step (3) wherein glycolide is distilled out of the reactor; step (4) wherein the distillate is introduced into a rectifier and is rectified by means of gas-liquid countercurrent contact; and step (5) wherein glycolide is recovered. A method for purifying crude glycolide provided with: step (i) wherein a crude glycolide composition, which preferably contains a high-boiling-point organic solvent or a solubilizing agent, is supplied into a reactor and heated so that glycolide is distilled; step (ii) wherein the distillate is introduced into a rectifier and is rectified by means of gas-liquid countercurrent contact; and step (iii) wherein glycolide is recovered. A glycolide producing apparatus and a crude glycolide purifying apparatus, each of which is provided with a reactor and a rectifier.

1 . A method for purifying crude glycolide comprising the following steps (i) to (iii):
 step (i): a step in which a crude glycolide composition is supplied into a reactor and heated at normal pressure or reduced pressure so that glycolide is distilled;   step (ii): a step in which the distillate is introduced into a rectifier and is rectified by means of gas-liquid countercurrent contact; and   step (iii): a step in which glycolide is recovered.   
     
     
         2 . The method for purifying crude glycolide according to  claim 1 , wherein the crude glycolide composition is a crude glycolide composition containing crude glycolide and a high-boiling-point organic solvent having a boiling point within a range of 220 to 500° C. at normal pressure, and
 the step (i) is a step in which glycolide is distilled out together with the high-boiling-point organic solvent. 
 
     
     
         3 . The method for purifying crude glycolide according to  claim 1 , wherein the crude glycolide composition is a crude glycolide composition containing a solubilizing agent. 
     
     
         4 . The method for purifying crude glycolide according to  claim 1 , wherein at least one of the high-boiling-point organic solvent and a solubilizing agent which is separated in at least one of the step (ii) and the step (iii) and has a boiling point within a range of 220 to 500° C. at normal pressure is refluxed to the reactor.