DE2426448B1 - Process for the purification of waste water from the production of esters - Google Patents

Description

preferably with untreated wastewater in countercurrent. The organic phase separates out within a few minutes. Up to 150 kg of organic products are obtained per m ^{3 of wastewater.} Surprisingly, the ester plasticizers dissolved in the wastewater are hardly attacked. In contrast, the alcohols are split off almost quantitatively from the alkyl sulfates and from the half-esters of the dicarboxylic acids and separated out with the organic phase. Small amounts of olefins are obtained as by-products, some of which were already formed during the ester synthesis and are dissolved in the untreated wastewater.

After the organic phase has been separated off, the wastewater still contains, among other things, the salts of the Carboxylic acids, e.g. B. the disodium salt of phthalic acid. By adding mineral acids, e.g. B. sulfuric acid, hydrochloric acid, phosphoric acid, these can be converted into Easily separate off water sparingly soluble dicarboxylic acids. Phthalic acid is largely already separating at a pH of 3.0 to 3.5. You can then by known methods, for. B. by filtration, Centrifugation, decanting and others.

Without taking the dicarboxylic acids into account, 85% of the organic matter removed from wastewater. A separation of more than 98% of the organic substances is achieved when the above-described separation of the carboxylic acids with subsequent filtration performs. The organic substances still remaining in the water can be removed by partial distillation without Difficulties are severed.

The recovered organic materials are almost exclusively starting materials, intermediate products and Finished products of the ester plasticizer production and can be returned to the synthesis. the Ester plasticizer production does not suffer from the recycling of the substances obtained from the wastewater Disadvantages, the quality of the ester is not reduced as a result.

The esters are usually prepared with a greater than stoichiometric amount of alcohol. The separation of the excess alcohol from the ester produced is therefore one for such Processes necessary action. The separated alcohol is either immediately or after work-up, z. B. distillation, returned to the esterification. The alcohol obtained in wastewater treatment can be used without any special measures separated and reused in a known manner.

Also the discharge of the by-products obtained in small quantities during the ester production, such as Olefins, is made by recycling those from wastewater extracted substances are not disturbed.

Thus, the present invention leads besides the improvement the wastewater quality to a noticeable recovery of valuable products and thus to an improvement in the yield, based on the starting materials used in the ester production.

The implementation of the procedure and achievable with it Results can be seen from the following examples.

Examples

The untreated process wastewater had the following average parameters:

Amount of 400 to 500 liters / h

pH value 9.3

Sodium carbonate 37.6 g / l

Sodium hydrogen carbonate 29.0 g / l SCB value 360 to 380 g / l

The experiments described below were carried out with this waste water. The wastewater composition is typical of phthalic acid esters and other esters from aliphatic dicarboxylic acids and aliphatic alcohols.

Attempt 1

Waste quantity (1) 3.3

Temperature ( ⁰ C) 210

Duration (hours) 5

Max. Pressure (atü) 33

Stir no

Addition of 45% NaOH - (g / batch)

Amount of org. Products (g) 355

Composition of the org.

Product

Hydrocarbons 4.7 (propellants)

Olefin 33.7

Alcohol 57.3

Ester 3.9

Otherwise, org. Verb. 0.4

Characteristics of the water phase

pH 7.9

Na ₂ CO ₃ content (g / l) 1.1

NaHCO ₃ content (g / L) 36.5

COD value (g / l) 63

3.3

210

25th

Yes

150

362

4.8

27.8 66.1 1.0 0.3

8.1 4.0 53.2 51 3.3

210

36

Yes.

364

4.3

29.6
60.5
5.4
0.2

7.5
0.4
29.1
52

3.3

200

Yes

204

5.3

25.6 64.5 4.2
0.4

8.5
3.0
39.3 99

3.3

220

41

Yes

360

4.6

31.0 58.8 5.4 0.4

8.1 1.7 34.8 52

5 6

η.; .. · ι α substances was 365g. The organic product had

The following composition: 3.3 liters of waste water of the above composition were placed in a 5 liter stirred autoclave. Hydrogen 4.5 / ₀

The autoclave was then quickly set to the 5 ViiTih 'i ήΐ ο ° /

temperature given in the table above, Alkonol Λί /

and held at this temperature for 2 to 5 hours. With ί? ~ ^Γ · '···· Τ,' Ζά

advancing degree of conversion, the pressure rose byproducts U, _2/0

in the autoclave. By adding 45% sodium bicarbonate.

lye (see column 2 of the table) if the pressure anio b e ι s ρ ι e 1 3

rose diminish. After the reaction time has ended, 500 liters of the waste water of the above composition

the reaction mixture was reduced to room temperature- were continuously in a lm ³ pressure reactor,

cooled, relaxed and drained from the autoclave. which was filled with stainless steel packing, pumped in.

The upper organic phase was separated, gewo- Before was pre water at 230 ⁰ C under pressure

genes and analyzed by gas chromatography. The aqueous 15 heated; no further heat was added to the reactor

Phase was examined for residual impurities. drove.

(See table for results.) After the reaction had ended, the reac-die The water phase of the test was carried out with an ion mixture in countercurrent with untreated sulfuric acid watered up to a pH value of 3.0 and · then cooled with cooling water and acidifies. The phthalic acid immediately separated out in crystalline form. 20 relaxed to normal pressure. In a follow-up night Filtration showed the water had a COD value of the phase separator, the organic phase was from the 6.0 g / l. In further experiments, the partially aqueous phase was separated and the organic phase in even COD values of 2.5 to 3.0 g / l were found. returned the esterification process. There were

56.1 kg / h organic product of the following composition

. Example 2 ² 5 Settlement recovered:

3.3 liters of the wastewater were concentrated with 60 g of hydrocarbon (propellant) 4.3%

added sulfuric acid, d. H. with the amount that the olefin 29.5%

Sodium carbonate present in the wastewater to Na alcohol 60.6%

trium hydrogen carbonate converts. The solution was 30 esters 5.5%

then as in Example 1 for three hours Unspecified side problems

treated at 220 ° C. The yield of organic products 0.1%

Claims (2)

1 2 poorly soluble, organic compounds, namely the claims: Esters themselves and their starting compounds, solved. The content of organic substances in wastewater is 1. Process for purifying the oxygen required for the esterification, usually by the polybasic, aliphatic or aromatic 5 and water required _{for the conversion to CO 2.} The carboxylic acids with aliphatic alcohols in this value is known under the name COD value (chemical presence of sulfuric acid as a catalyst for oxygen demand). For the wastewater from the falling wastewater, which in addition to the initial and plasticizer ester production, the COD values of the end materials, alkylsulfuric acids and di- 350 to 400 g oxygen / liter wastewater does not contain any rare alkyl sulfates, are thus identified. Such wastewater can ei ch η et, in biological sewage treatment; that the sewage under the layers cannot be processed easily. They are each adjusting. Pressure, heated to a temperature generally by certain measures vorzutur above 200 ⁰ C and, if necessary, clean, or at least to dilute with large amounts unbelastenach previous acidification in a known per se th water. Way. . - 15 The wastewater from the ester synthesis 2. The method according to claim 1, characterized also have the undesirable peculiarity that Abscheizeichnet, that one is at a temperature between the dung of oils from other wastewater when they ge-210 heated to 250 ° C. · Together with these by separating basins for Oils are directed to complicate ao In addition to economic disadvantages due to losses of valuable products that are dissolved in the wastewater, therefore, environmental protection problems arise to an increased extent. Esters of aromatic or aliphatic polycarbonate There was therefore the object of using acids, such as phthalic acid, trimellitic acid, adipic acid, 25 sulfuric acid as a catalyst in the ester softening Sebacic acid, azelaic acid with aliphatic alcohol-maker production to resulting process wastewater len, such as 2-ethylhexanol, isooctanol, isononanol or clean and, in addition, the dissolved in them, Decanol, are used in large quantities for plasticizing organic substances to be recovered without of plastics, especially polyvinyl chloride, a. agile cleaning and separating operations in the set. 30 process. The phthalic esters are of particular importance. Surprisingly, the task is carried out by a acid with 2-ethylhexanol (dioctyl phthalate-DOP), iso-process for cleaning the poly-nonyl alcohol during esterification (Diisononyl phthalate-DINP), isodecyl-basic, aliphatic or aromatic carbon alcohol (Diisodecylphthalate-DIDP) and butyl alcohol acids with aliphatic alcohols in the presence of (Dibutyl phthalate-DBP). 35 sulfuric acid as a catalyst for waste water, The conversion of the starting compounds, alcohol which, in addition to the starting and end materials, and acid or acid anhydride, can be dissolved by adding alkylsulfuric acids and dialkylsulfates. accelerated so strongly advertising autogenous pressure to a temperature above the that it is possible, heated for 40 200 ⁰ C under mild temperature and to operate if appropriate after prior conditions. In addition to the addition of acidifiers, separates in a manner known per se. Catalysts, it is often common for the preferred when the reaction is carried out at a Tempe reaction water formed by a entrainer temperature 210-250 ⁰ C,
to remove from balance. Depending on the temperature used, the When using sulfuric acid as the proton-45 treatment time 15 min. To 5 hours. At 220 ⁰ C is the active catalyst formed from the reaction Einsatzalkoho- z. B. finished after about 2 hours,
In secondary reactions, alkylsulfur wastewater from neutralization with aqueous soda acid and a very minor amount of dialkylsulfide solution generally contain small residual amounts of fate. The crude esters contain not only residual amounts of sodium carbonate but also larger proportions of sodium acids and alcohols which have not been converted, 50 hydrogen carbonate. In the case of the verse and sulfuric acid according to the invention, therefore, also alkylsulfuric acid. Not only will the sodium carbonate drive, but In general, the crude esters are initially mixed with some of the sodium hydrogen carbonate Alkali hydroxide, such as sodium hydroxide solution or potassium hydroxide solution, or CO ₂ elimination implemented. The reaction proceeds Alkali carbonates, e.g. B. aqueous soda solution, neutral even in the absence of an alkaline reaction lized. The resulting alkali salts of the organic chemicals, e.g. B. in the presence of the neutral reactive Acids including those of sodium hydrogen carbonate which rend alkylsulfuric acid, and differentiates are soluble in water and are thus separated from the saponification of esters with the aqueous solution. Phase separated. Sodium salts of alkylsulphurous strong bases. acids, partially esterified polycarboxylic acids and As is known, carboxylic acids are responsible for the CO ₂ evolution during cleaning when the corresponding amount is used Molecular weight of the organic residue surface wastewater containing sodium carbonate to prevent active. Examples are half esters of phthalic acid, z. B. to prevent the formation of exhaust gases with monoalcohols that contain four or more carbon or an excessive pressure increase in the reaction contain atoms, and avoid alkyl sulfates of octyl alcohol. In such cases this can arise or higher molecular weight alcohols. 65 current CO ₂ by adding a stoichiometric Due to the surface activity of this compound amount of alkali, such as caustic soda or potassium hydroxide, fertilizers are next to them in the sewage of the ester to alkali hydrogen carbonate are bound. Plasticizer production, also larger quantities, otherwise the reaction mixture is then cooled,