At present, there is no excellent treatment method for maleic anhydride production wastewater in the industry. The following is a summary of the treatment experience.

Background of Maleic Anhydride Wastewater Production

Maleic anhydride is an important basic raw material of organic chemical industry, and it is the third largest anhydride in consumption after acetic anhydride and phthalic anhydride. Maleic anhydride is mainly used for the production of unsaturated polyester resin, in addition, maleic anhydride is also used in coatings, inks, lubricating oil additives, agricultural chemicals, paper sizing agent, textile permanent finishing agent, surfactants and so on. A series of important fine chemical products such as 1,4-butanediol, γ-butyrolactone, tetrahydrofuran, fumaric acid and tetrahydrophthalic anhydride can also be produced from maleic anhydride.

The production process route of maleic anhydride in industry can be divided into benzene oxidation method, n-butane oxidation method, C4 olefin method and phthalic anhydride by-product method according to raw materials. Among them, benzene oxidation method is the most widely used method. In addition to maleic anhydride, a series of by-products will be produced in the production process. Therefore, the by-products will block the condenser, which will have a certain impact on the condensation effect. Therefore, it needs to be cleaned once after a certain interval, this is easy to produce some waste water; in the process of azeotropic dehydration and vacuum distillation, there will be some residual maleic anhydride in the tower kettle. Therefore, it is necessary to clean the inside of the tower and the kettle regularly. Therefore, a certain amount of waste water will be produced. The cleaned waste water will be discharged directly as waste liquid, thus wasting water resources and polluting the environment.

Maleic anhydride wastewater treatment process

1) the maleic anhydride wastewater first through the oil separation tank, and remove most of the floating oil;

2) Add strong acid and isomerization agent to maleic anhydride wastewater, and make the mixture react at 58-63 ℃ for 30-40 minutes, cool the mixture to 10-16 ℃ and stand for 15-18 minutes, then put the mixture into a centrifugal device for centrifugation;

3) Place the centrifuged reactant in step 2) into a reaction kettle, add water at 100 ℃ to the mixture, stir the mixture, heat the mixture to 105-116 ℃ for 24-27 minutes, stir the mixture, add the catalyst to the mixture for stirring and filtering, add the catalyst to the mixture again for stirring and filtering, and then centrifuge the filtered material after cooling and crystallization, putting the separated mixture into a drying device for drying;

4) Add coagulant to the centrifugal liquid after centrifugation in step 2), stir the mixture at 30-34°C for 30-40 minutes, and control the pH of the solution to 7-8, put the mixture into a filtration device for filtration, put the filtrate into a centrifugal extractor, and add the extractant to the mixture for reaction;

5) Put the mixture at the lower end of the centrifugal extractor after the reaction in step 4) into the biofilter for aerobic fermentation, and degrade the mixture;

6) After adding lye to the mixture at the upper end of the centrifugal extractor after the reaction in step 4) for mixing, the mixture is concentrated and distilled, and the resulting mixture is recovered.