Method of recovering acetic acid and water in production of aromatic carboxylic acid

Abstract

A method of recovering acetic acid and water in the production of aromatic carboxylic acid adopts a separation technology of combined four towers which comprise an extracting tower, an azeotropic rectifying tower, a solvent extraction pro-tower and a solvent extraction tower connected orderly. The separation technology comprises the following steps: carrying out extraction, azeotropic distillation and solvent separation on the materials to obtain the water and the acetic acid, wherein the material with high water content is extracted first, then is combined with other materials for azeotropic distillation, the extraction and the azeotropic distillation adopt the same acetic ester separating agent, and the solvent recovery tower system adopts the compositive energy conservation combined technology. By adopting the method in the invention to separate and recover the acetic acid and water in the production of aromatic carboxylic acid, the organic matter in the water is less than or equal to 100ppm, the water and the acetic acid recovered can be used in the production system of aromatic carboxylic acid, thereby reducing the acid consumption and waste water discharge in the productive process. The method has low-cost separating agent, reasonable technology, is energy-saving and efficient in the separation process, and can save energy consumption by 20-30%, and reduce operating cost by 10-20%.

Description

technical field [0001] The invention relates to a method for recovering solvent in the production of aromatic carboxylic acid, in particular to a method for recovering acetic acid and water by adopting an integrated energy-saving separation process in the production process of aromatic carboxylic acid. Background technique [0002] The traditional production process of aromatic hydrocarbon carboxylic acid is usually obtained by liquid-phase air oxidation of alkyl aromatic hydrocarbon 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-contai...

AI Technical Summary

Problems solved by technology

However, in general, there are disadvantages such as low acetic acid recovery rate, excessive steam consumption, high wastewater volume and high wastewater treatment costs due to high concentrations of acetic acid and methyl acetate in wastewater.

Also, unreacted aromatics in the feed stream enter the dehydration unit, resulting in low yields of aromatic carboxylic acids

In the aqueous solution at the top of the azeotropic distillation tower, the content of acetic acid can only be controlled at 500-800ppm, which cannot meet the goal of water recycling

[0016] At present, in the industrial production of aromatic hydrocarbon carboxylic acids, low water content solvents tend to be used in the oxidation reaction, which requires more water produced by the reaction to be removed from the reactor, which means that the water entering the stream of acetic acid and water rectification tower The water content will increase, which also increases the cost of the separation operation

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