Integrated process for recovering acetic acid and methyl acetate in production process of aromatic carboxylic acid

Abstract

The invention relates to an integrated process for recovering acetic acid and methyl acetate in a production process of aromatic carboxylic acid. The integrated process is as follows: water solution of acetic acid from an oxidation unit enters the upper part of a dehydrating tower, steam at the top of the dehydrating tower enters a condenser at the tower top for cooling, and concentrated acetic acid extracted from a tower kettle directly returns to an oxidation reactor; condensed fluid at the top of the dehydrating tower enters a phase splitter and is automatically splitted into an oil phase and a water phase, the oil phase enters an entrainer refining tower, methyl acetate is extracted from the tower top and is recovered, and the entrainer in the tower kettle returns to the top of the dehydrating tower; the water phase enters a methyl acetate recovering tower, methyl acetate extracted from the tower top and methyl acetate at the top of the entrainer refining tower are recovered together, water part in the tower kettle flows back to the top of the dehydrating tower, and part of water is extracted and treated. When the entrainer in the acetic acid of the tower kettle of the dehydrating tower is higher than 5 percent, the tower kettle material firstly enters an entrainer separating tower, the condensed acetic acid extracted from the tower top returns to the oxidation reactor, and excess entrainer is separated from the tower kettle. By utilizing the process, the quantity of the entrainer flowing back can be greatly reduced, and the oxidation reaction can be stably performed.

Description

technical field [0001] The invention relates to a method for recovering the reaction solvent acetic acid and the reaction by-product methyl acetate in the production process of aromatic carboxylic acids. The separation method mainly involved in the present invention is azeotropic rectification. Background technique [0002] Aromatic carboxylic acid is an important class of chemical intermediates, and is the basic raw material for the production of industrial products such as polyester, fiber, film, and bottles. Aromatic carboxylic acids such as terephthalic acid and isophthalic acid are generally prepared by catalytic oxidation of their corresponding alkyl-substituted aromatic hydrocarbons such as p-xylene and m-xylene. The oxidation reaction uses acetic acid as a solvent, cobalt acetate, manganese acetate, hydrogen bromide or tetrabromoethane as a catalyst, and is carried out at a certain temperature and pressure, and the process is accompanied by the formation of water. ...

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Problems solved by technology

However, the reflux rate of the process entrainer mentioned in the above-mentioned patent is relatively large, resulting in high energy consumption in the recovery process of acetic acid; in addition, the excess entrainer in the dehydration tower kettle mentioned in the above-mentioned patent is directly returned to the oxidation reactor with acetic acid The treatment method will inevitably increase the difficulty of controlling the oxidation feed and affect the stability of the oxidation reaction.

Still contain a certain amount of methyl acetate in the entrainer that refluxes in the dehydration tower, if the methyl acetate wherein can be separated, not only can improve the separation effect of dehydration tower, also can improve the economy of separating device, for above-mentioned co- Separation and recovery process of methyl acetate in boiling agent, there is no literature report at present

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