| 摘要 |
PURPOSE:To efficiently recover valuable substances such as p-toluic acid from the mother solution of purified terephthalic acid and further reduce the amount of p-xylene accompanied in the mother solution, thereby reducing the amounts of organic substances which are discharged together with the mother solution and which cause environmental pollution. CONSTITUTION:An alkyl benzene is oxidized with molecular oxygen in the presence of a transition metal compound and a bromine compound in a lower aliphatic carboxylic acid in a liquid phase, and the produced crude terephthalic acid is dissolved in hot water. The solution is brought into contact with the group VIII metal and the pure terephthalic acid is crystallized and separated to obtain the mother solution of the purified terephthalic acid. The mother solution is brought into contact with p-xylene and subsequently oxidized to recover valuable p-toluic acid capable of being oxidized into terephthalic acid into the xylene in a high ratio. The remained mother solution is bubbled with air or an inert gas to remove the p-xylene accompanied in the mother solution as the gas, thereby permitting to reduce the amounts of organic substances in the mother solution and reduce the load covering the subsequent discharge treatment of the mother solution into water. |
