Abstract: A separation system has a distillation column, an overhead vapor supply pipe connected to the top of the distillation column, first and second branch pipes branching from the overhead vapor supply pipe and a superheater connected to the first branch pipe. A separator downstream of the superheater has a separation membrane for separating overhead vapor from the top of the distillation column into permeable vapor and nonpermeable vapor by allowing only a selected portion of the overhead vapor to permeate the separation membrane. A reflux unit has a condenser connected to the second branch pipe for cooling a portion of the overhead vapor into a liquid and a gas-liquid separator for separating gas from the liquid produced by cooling and returning the separated liquid into the top of the distillation column.

Abstract: In a process for producing an aromatic carboxylic acid, it is a dehydrating process which can achieve compactification of a step for removing water from a mixture of acetic acid and water produced in the production process, and which can reduce the consumed energy. In a production process of an aromatic carboxylic acid having an oxidation reaction step for producing a slurry of an aromatic carboxylic acid by carrying out liquid-phase oxidation reaction of an alkyl aromatic compound with an oxygen-containing gas in a solvent containing acetic acid in the presence of an oxidation catalyst, at least a portion of a mixture containing acetic acid and water produced in the production steps is separated into a permeable gas mainly comprising water and nonpermeable substances mainly comprising acetic acid, using a separation membrane having water selectivity.

Abstract: In a process for producing an aromatic carboxylic acid, it is a dehydrating process which can achieve compactification of a step for removing water from a mixture of acetic acid and water produced in the production process, and which can reduce the consumed energy. In a production process of an aromatic carboxylic acid having an oxidation reaction step for producing a slurry of an aromatic carboxylic acid by carrying out liquid-phase oxidation reaction of an alkyl aromatic compound with an oxygen-containing gas in a solvent containing acetic acid in the presence of an oxidation catalyst, at least a portion of a mixture containing acetic acid and water produced in the production steps is separated into a permeable gas mainly comprising water and nonpermeable substances mainly comprising acetic acid, using a separation membrane having water selectivity.