CS242250B1 - Formic acid and acetic acid waste aqueous solution treatment method - Google Patents

Abstract

The method of processing the solution called. acidic effluent from cyclohexanone production, which they contain! 2 to 10 wt. of % formic acid and 0.25 to 5 wt. acetic acid. They are processed in the process of producing pentaerythritol on calcium formate in its grade separation from neutralized reaction solutions, into which were acidic water and suspensions calcium hydroxide dosed in weight 0.674 to 4.29: 1 ratio The pH of the resulting solution prior to processing 5.5 to 6.5. Calcium Formate Obtained is used for the production of formic acid or as a preservative for green vegetable matter. Calcium acetate leaves in the by-product of pentaerythritol production v tzv. syrups.

Description

The method of processing the so-called solution. acid waste water from cyclohexanone production, which contain! 2 to 10 wt. % formic acid and 0.25 to 5 wt. of acetic acid. They are processed in the process of producing pentaerythritol into calcium formate in the step of separating it from neutralized reaction solutions into which acidic water and calcium hydroxide suspensions are dosed in a weight ratio of 0.674 to 4.29: 1, maintaining the pH of the resulting solution prior to treatment of 5.5 to 5.5 6.5. The obtained calcium formate is used for the production of formic acid or as a preservative for green plant matter. Calcium acetate leaves in the by-product of pentaerythritol production in the so-called pentaerythritol production. syrups.

SUMMARY OF THE INVENTION The present invention provides a process for the treatment of a mixture of formic acid and acetic acid resulting from the production of cyclohexanone from benzene in the process of air oxidation of cyclohexane.

This aqueous solution containing 2 to 10 wt. % formic acid and 0.25 to 5 wt. acetic acid is an undesirable waste in the production of cyclohexanone, which, after its neutralization by alkali, for example the gypsum solution obtained in the combustion stage, is so-called " Alkaline waste water production of cyclohexanone processed at the mechanical-biological waste water treatment plant.

More economically, however, this acid solution is used in the reaction stage of pentaerythritol production to terminate the reaction of formaldehyde with acetaldehyde and calcium hydroxide to pentaerythritol. A higher effect is characterized by their use in which part of the acid solution is used to terminate the reaction in the pentaerythritol production step, the other part being converted to calcium formate in the reaction step or in the treatment step of the pentaerythritol reaction solutions prior to treatment. Calcium formate is obtained from the solution thus prepared by fractional crystallization. Calcium acetate is withdrawn from the production of pentaerythritol in an aqueous solution of the waste product of the production in the so-called. pentasirupoch.

It is also known to use an aqueous acid solution as a preservative for green plant matter or as a component thereof without or after treatment, or to use this mixture of acids for the production of calcium formate, preferably the use of calcium hydroxide which is lost in the production of carbide ethine calcium.

However, with the application of the acid solution at the pentaerythritol reaction completion step, undesired admixture reactions present in the acid / formaldehyde solution or reaction intermediates in the process of rectification separation in unreacted formaldehyde reactions at temperatures of 120 to 140 degrees Celsius with a pressure of 0.2 to 0 5 MPa. However, even in this case, the entire amount of the acid mixture solution can be processed into calcium formate using the process of the invention.

The present invention is based on a process for treating a waste aqueous solution containing 2 to 10 wt. % formic acid and 0.2 to 5 wt. acetic acid formed in the air oxidation process of cyclohexane, characterized in that a calcium hydroxide slurry and acid waste solution are added simultaneously to the solution from the pentaerythritol production reaction step after rectification separation in the unreacted formaldehyde pentaerythritol preparation reaction, with one part by weight of the acid. 0.674 to 4.29 parts by weight of calcium hydroxide slurry are added. waste solution of formic acid and acetic acid. In view of the increased likelihood of adverse reactions by-products of reaction of formaldehyde alone, acetaldehyde alone and their undesirable mutual reaction intermediates, as well as monopentaerythritol itself and its derivatives, it is preferable to prepare a solution of pH 5.5 to 6.

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

Calcium acetate is, due to its solubility and the amount that is produced during the separation of the acid form during the separation process of calcium formate and pentaerythritol, in the solution and from the production of these products in a by-product undesirable product, so-called. pentasirupoch.

The main advantage of treating the solution of the mixture of the above acids according to the invention in the process of producing pentaerythritol is the use of the separation process of this technology for the production of calcium formate from the solution of these acids. A significant advantage of the process is also the reduction of the costs of acid waste streams from cyclohexanone production, reducing the waste of these leads and reducing the costs of subsequent biological treatment of the neutralized waste streams from cyclohexanone production.

The following examples illustrate the advantages of using the process of the invention: Example 1 (comparative)

K 4,500 kg / h of solution acid wastewater containing 4.2 wt. % formic acid and 0.9 wt. of acetic acid resulting from cyclohexanone production is added 1120 kg / h of 22 wt. % sodium carbonate solution containing 4 wt. sodium bicarbonate. A solution of pH 6.1 is formed, which is sent to a biological waste treatment plant. The water discharged from the biological treatment contains 110 kg / h of sodium cation more than in the case of the purification of the leaders without so-called. acid waste leaders from cyclohexanone production. About 200 kilograms of solid soda can be produced from the amount of sodium carbonate solution used.

Example 2 (comparative)

In the process of producing pentaerythritol at a molar ratio of formaldehyde to acetaldehyde of 6: 1 in the presence of calcium hydroxide, an alkaline solution is produced in an amount of 15,000 kg / h with a concentration of 0.1 mol / kg of free calcium hydroxide solution. This was adjusted with 162 kg / h of 85% formic acid to a pH of 6.1. After rectification separation of unreacted formaldehyde, 599 kg / h of calcium formate is recovered from the solution in the separation stages of the pentaerythritol production process.

Example 3

To 15,000 kg / h of the pentaerythritol production step solution prepared in the same manner as in Example 2 after rectification separation of unreacted formaldehyde, at the same time 4,500 kg / h of so-called " % of acid waste water from cyclohexanone production containing 4.2% by weight % formic acid and 0.9 wt. acetic acid and 2,200 kg / 8% calcium hydroxide slurry. A solution of pH = 6.5 is obtained from which, by fractional crystallization, 850 kg / h of calcium formate is obtained with a purity of 97% by weight.

Treatment of the acid mixture solution from cyclohexanone production increases the calcium formate production by 251 kg / h.

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