SK33494A3 - Method of treatment of acid waters - Google Patents

Abstract

The purpose of the invention is to isolate formic acid from the dilute aqueous solutions in the form of esters thereof. stated the purpose is achieved by esterification of formic acid with alcohol at 25 to 95 ° C in the presence of acidic catalyst.

Description

Technical field: Chemistry

Description of the state of the art

The invention relates to a process for the treatment of acidic waters resulting from the process of producing cyclohexanol and cyclohexanone by oxidation of cyclohexane with air in the presence of oxidation catalysts, organic syntheses where a mixture of organic substances is formed including formic acid or other industrial areas where a mixture of organic and inorganic substances is produced. Cyclohexanone is an industrially important ketone which is produced by the hydrogenation of phenol or by oxidation of cyclohexane in the presence of oxidation catalysts at a temperature of 140 to 170 ° C and a pressure of 0.5 to 2 MPa. The entire cyclohexane oxidation process can be conducted to produce adipic acid (U.S. Pat. No. 3,390,174) or to produce cyclohexanol and cyclohexanone (U.S. Pat. No. 3,350,444, U.S. Pat. No. 3,530,185, U.S. Pat. No. 3,365,491).

In these technologies, the conversion value of cyclohexane is 5 to 8%, the respective yields of cyclohexanol and cyclohexanone being 70 to 75%. If the conversion increases above 8% of the cyclohexane feed rate, the yield of cyclohexanol and cyclohexanone decreases rapidly and substantially more undesirable by-products and cleavage products are formed.

In order to reduce the amount of by-products and fission products, various technological processes have been carried out: oxidation in the presence of alkali metal hydroxides (Nem. Pat. 878 350), repeated washing of the reaction mixture with water (Nem. Pat.

046 610, Nem. pat. 1 175 121), washing the cyclohexane feed before oxidation with acidic water (Nem. Pat. 1 047 778), changing the size of the oxidizing gas bubbles through cyclohexane, reducing the oxygen partial pressure in the oxidizing gas (Nem. Pat.

097,569, Nem. pat. 1 100 020).

The use of boric acid in the process of producing cyclohexanol and cyclohexanone makes it possible to further increase the conversion and selectivity to cyclohexanone and cyclohexanol, but the problems associated with recovering boric acid are very complex.

A disadvantage of the above processes for the oxidation of cyclohexane to cyclohexanone and cyclohexanol is the low conversion and hence the high energy consumption and at the same time the low selectivity, which decreases sharply by increasing the conversion.

The most effective measure to increase the economic efficiency of the production of cycohexanone and cyclohexanol is to reduce cyclohexane consumption by using by-products and fission products that arise in the cyclohexane oxidation process.

One of the secondary streams in the production of cyclohexanone and cyclohexanol is an aqueous solution of mono- and dibasic organic acids C1 to C6, which are not currently used and disposed of in a chemical waste water treatment plant or incinerated.

One possible way to improve the economy of the cyclohexanone production plant and to reduce the amount of waste products is to process or refuse. utilizing the acidic waters resulting from the process of producing cyclohexanol and cyclohexanone containing a mixture of mono- and dibasic organic acids C1 to C6 to neutralize the alkaline reaction solutions.

A disadvantage of this process is that the solution is a mixture of organic acids and other substances, the acid concentration being about 5 to 15% by weight.

SUMMARY OF THE INVENTION

The disadvantages of the hitherto known processes are overcome by the process according to the invention. It relates to a process for the treatment of acidic waters containing formic acid and monohydric organic acids C2 to C6 resulting from a process for the production of cyclohexanol and cyclohexanone or other processing areas, characterized in that formic acid is obtained from esterified aqueous alcohols and other impurities esters at a temperature of 25 to 200 ° C, a pressure of 0.05 to 1.6 MPa in the presence of an acid catalyst. The crude ester obtained is treated in a known manner, e.g. by hydrolysis to formic acid and alcohol, or by refining the crude ester to the desired quality.

Examples:

Example 1 (comparative)

K 1 kg of acidic water containing 10% by weight of formic acid, 2% of acetic acid, 0,2% of propionic acid,

0.05% butyric acid traces of acids C5 to C6 and other organic substances are added 0.1 ml of concentrated hydrochloric acid and 100 g of methanol. The temperature is maintained at the boiling point of the reaction mixture. The resulting methyl esters are condensed and trapped in the template. The reaction is terminated at about 90 ° C. The reaction yielded 160 g of condensate. Rectification of the reaction product yielded 125 g of 98% methyl formate.

Example 2

To the acidic waters of Example 1 are added 0.1 ml of concentrated sulfuric acid and 110 g of ethyl alcohol. The reaction is terminated at 95 ° C. Rectification of the reaction product gave 180 g of 98% formic acid ethyl ester.

Example 3

To the acidic waters of Example 1 are added 20 g of acidic zeolite and 120 g of propyl alcohol. The reaction is terminated at 95 ° C. Rectification of the reaction product gave 185 g of 98% propyl formate.

Claims (4)

Process for the treatment of acidic water containing 2 to 85% by weight of formic acid, cbà 20% of acetic acid, tfa 10% of propionic acid, djr of 10% butyric acid, 1 to 15% of other organic and / or inorganic substances, the rest up to 100% is formed by water, characterized in that formic acid is isolated from its aqueous solution of organic acids and / or organic and / or inorganic substances in the form of its esters with alcohols at a temperature of 25 to 200 ° C, a pressure of 0.05 to 1.6 MPa which are processed in a known manner. 2. A process according to claim 1, wherein the alcohol component is methanol and / or ethyl alcohol and / or propyl alcohol. 3. A process for the treatment of acidic waters according to claim 1, characterized in that an acid catalyst is used in the esterification process. 4. A process according to claim 3, characterized in that the catalyst used is a mineral acid and / or cation exchanger and / or an acidic zeolite and / or acidic molecular sieves.