Method for recycling water from separation system for acetic acid and water

Abstract

The present invention relates to a method for recycling water from a separation system for acetic acid and water. Materials with high water content are added to an azeotropic rectifying column; all light component oil flows back to the azeotropic rectifying column; water phase penetrates into a penetration evaporator; water phase with organic matter content less than 100ppm is obtained at the bottom of the penetration evaporator; an acetic acid solvent basically free of an azeotropic agent can be generated at the bottom of the azeotropic rectifying column, wherein water content of the solvent is controlled at 4-10% (mass percentage); and water with total organic matter content less than 100ppm can be produced at the top of the azeotropic rectifying column. The method provided by the invention can further improve separating efficiency of the separation system for acetic acid and water.

Description

technical field [0001] The invention relates to a method for recycling water in an acetic acid and water separation system, in particular to a method for recycling water separated by azeotropic rectification in the production process of aromatic dibasic acids. technical background [0002] The traditional production process of aromatic carboxylic acids is usually obtained by liquid-phase air oxidation of alkylaromatics under high pressure. Liquid-phase oxidation of alkylaromatics is the gradual oxidation of alkyl groups on aromatics to aldehydes and carboxylic acids in the presence of an aqueous medium containing lower aliphatic carboxylic acids and a metal catalyst system, and finally to aromatic carboxylic acids. [0003] The oxidation process of alkylaromatics will generate a lot of heat. In order to keep the temperature stable in the reaction process, the heat is usually removed by evaporating water-containing lower aliphatic carboxylic acids (such as acetic acid). The ...

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Problems solved by technology

Among them, the patent prefers p-xylene as the entrainer for acetic acid and water separation, but since the azeotrope and compounds such as methyl acetate produced in the production process of aromatic hydrocarbon carboxylic acid are also more likely to form azeotrope, therefore, the separation requires a higher The reflux ratio consumes a lot of energy. At the same time, the content of organic matter in the top water of the rectification tower is high, and the content of acetic acid will be greater than 0.5%.

[0013] In the above-mentioned azeotropic distillation patent technology, in order to recycle the top water, the water phase material is usually put into the solvent recovery tower system for separation and purification, because the water phase Contains three components of water, acetic acid and entrainer. Therefore, in order to achieve the purpose of separation, the solvent recovery tower system also needs to adopt a two-tower rectification process, which has low recovery rate of acetic acid, excessive steam consumption and due to the High concentration of organic matter (such as entrainer), resulting in high wastewater treatment costs, and the use of these waters is subject to various restrictions due to water quality problems

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