CS242250B1 - A method for treating waste aqueous solution of formic acid and acetic acid - Google Patents

Abstract

Method for processing a solution of so-called acidic wastewater from cyclohexanone production, which contains 2 to 10% by weight of formic acid and 0.25 to 5% by weight of acetic acid. They are processed in the process of pentaerythritol production into calcium formate at the stage of its separation from neutralized reaction solutions, into which acidic water and calcium hydroxide suspensions were dosed in a weight ratio of 0.674 to 4.29:1, while maintaining the pH of the resulting solution before its processing at 5.5 to 6.5. The obtained calcium formate is used for the production of formic acid or as a preservative for green plant matter. Calcium acetate is released as a by-product of pentaerythritol production in so-called syrups.

Description

242250

The present invention provides a process for the treatment of a solution of formic acid and acetic acid resulting from the production of cyclohexanone by benzene in a cyclohexane air oxidation process.

This aqueous solution containing 2 to 10% w / w. formic acid and 0.25 to 5% by weight acetic acid] is an undesirable waste in the production of cyclohexanone, which after its previous neutralization is alkali, for example a soda solution obtained in the process of dispersing the so-called alkaline wastewater of cyclohexanone processed into methanol - Biological wastewater treatment plant.

It is more economically advantageous, but this acid solution is used in the reaction stage of the production of pentaerythritol to quench the reaction of formaldehyde with acetaldehyde and calcium hydroxide to pentaerythritol. The result is characterized by their use in which a portion of the acid solution is used to terminate the reaction in the pentaerythritol production step, the second part is converted to a calcium formate in the reaction step or the pentaerythritol reaction solutions prior to treatment. From this solution, the calcium formate is obtained by fractional crystallization, and the octanediate is removed from the production of pentaerythritol in an aqueous solution of the so-called pentasirups.

It is also known to propose the use of an aqueous acid solution as a preservative for vegetable vegetable matter, or as a component thereof, or after concentrating it, or to use this acid mixture to produce calcium formate, preferably using calcium hydroxide in the production of ethine of calcium carbide.

However, when the acid solution of the pentaerythritol preparation reaction is applied, there is a possibility of admixture reactions occurring in the acid / formaldehyde solution or the reaction intermediates in the process of rectification separation in the reaction of unreacted formaldehyde at temperatures of 120 to 140 degrees Celsius at a pressure of 0.2 to. 0.5 MPa. However, in this case, it is possible to process the entire amount of the acid mixture into formic calcium if the process according to the invention is used.

It is an object of the present invention to provide a process for treating a waste aqueous solution containing 2 to 10 wt. formic acid and 0.2 to 5 wt. acetic acid formed by the process of oxidation of cyclohexane by air, characterized in that at the same time a slurry of calcium hydroxide hydroxide and a waste acid solution is added to the solution from the reaction stage of the production of pentaerythritol after the separation reaction in the reaction of the preparation of the unreacted formaldehyde formaldehyde; one part by weight. 0.674 to 4.29 parts by weight of calcium hydroxide slurry is added. waste solution of formic acid and acetic acid. Due to the increased likelihood of undesirable reactions occurring in the by-products of the reaction of formaldehyde itself, acetaldehyde alone and their undesirable cross-linking products, as well as monopen-taerythritol itself and its derivatives, it is preferable to prepare a solution having a pH of 5.5 to 6.

Said formate and calcium acetate enriched solution of the pentaerythritol reaction step comprises pentaethrititol, formate and calcium acetate, reaction products of acetaldehyde alone and their undesirable products, so-called syrups, concentrated to a solution saturated with pentaerythritol at temperatures of 75-95 ° C. During the saturation of the solution to pentaerythritol, it forms a crystalline calcium formate which is separated by hot filtration, most often by filtration centrifugation. The calcium formate is washed with water and dried to obtain a technical product containing at least 97% calcium formate, which is used to form formic acid, but preferably as a preservative for green vegetable matter.

Calcium acetate is in solution due to its solubility and the amount of acidic acid formed during the separation process of calcium formate and pentaerythritol, and in the production of these products, it leaves in the undesired product, so-called pentasirups.

The main advantage of treating the solution of the above-mentioned acids according to the invention in the production of pentaerythritol is the use of the process of this technology for the production of calcium formate from a solution of these acids. An important advantage of the process is also the reduction in the cost of neutralizing the so-called acidic wastewater from the cyclohexane production, reducing the salinity of these Vedas and reducing the cost of subsequent biological purification-neutralized wastewater from the cyclohexanone. The following examples illustrate the advantage of using the process of the invention: Example 1 (comparative) To 4,500 kg / h of a solution of so-called acid wastewater containing 4.2% by weight of formic acid and 0.9% by weight of acetic acid, In addition to the production of cyclohexanone, 1120 kg / h of a 22% by weight solution of carbonate containing 4% by weight of sodium bicarbonate are added to give a solution of pH 6.1 which is discharged into a biological wastewater treatment plant. from bio-purification, they contain about 110 kg / h of sodium cation more than in the case of purification of the waters of the so-called acidic wastewater from cyclohexanone production, and about 200 kilograms of solid soda can be produced from the amount of sodium carbonate solution used.

Claims (1)

SUBJECT A process for treating a waste aqueous solution of formic acid and acetic acid containing 2 to 10 wt. % formic acid and 0.25 to 5 wt. of acetic acid and formed in the process of oxidation of cyclohexane by air, characterized in that the waste aqueous acid solution and the suspension of the calcium xYL-INVENTION are fed to the solution from the reaction stage of pentaerythritol production after rectification separation in the unreacted reaction. % of formaldehyde, preferably maintaining the pH of the resulting solution 5.5-5