JPS5858337B2 - Ester Kasozai no Seizou Deshiyoujiru High Suinoseiji Youkahou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Aromatic or aliphatic polycarboxylic acids such as phthalic acid, trimellitic acid, adipic acid, sebacic acid, azelaic acid and aliphatic alcohols such as 2-ethylhexanol,
Esters with isooctatool, isononanol or decanol are used in large quantities for plasticizing plastics, especially polyvinyl chloride.

Especially the ester of phthalic acid and 2-ethylhexanol (
dioctyl phthalate (DOP), its ester with isononyl alcohol (diisononyl phthalate) – DINP
), esters with isodecyl alcohol (diisodecyl phthalate-DIDP) and esters with butyl alcohol (dibutyl phthalate-DBP) are important.

The reaction of starting compound, alcohol and acid or acid anhydride is very strongly promoted by the addition of a catalyst, in particular a proton-active compound such as sulfuric acid, so that it is possible to operate under mild temperature conditions.

In addition to the addition of catalysts, it is also often the case that the water produced in the reaction is removed from the equilibrium mixture by means of propellants.

When using sulfuric acid as a proton-active catalyst, alkyl sulfuric acids and, to a very minor extent, dialkyl sulfates are formed as a rule from the alcohol used in side reactions.

The crude ester thus contains, in addition to unreacted residual amounts of carboxylic acid and alcohol and sulfuric acid, also alkyl sulfuric acid.

Generally, the crude ester is first neutralized with an alkaline solution, such as a sodium hydroxide solution or potassium hydroxide solution, or an alkali metal carbonate, such as an aqueous sodium carbonate solution.

The resulting alkali metal salts of organic acids, including alkali metal salts of alkyl sulfates, are soluble in water and are separated with the aqueous phase.

Alkyl sulfates, partially esterified polycarboxylic acids and sodium salts of carboxylic acids are known to be surface-active if the organic groups have a corresponding molecular weight.

Examples for this are half esters of phthalic acid and monoalcohols having 4 and more carbon atoms and alkyl sulfates of octyl alcohol or polymeric alcohols.

Due to the surface activity of the compounds, in addition to them, large amounts of other sparingly soluble organic compounds are dissolved in the wastewater of ester plasticizer production, namely the esters themselves and the starting compounds.

The content of organic substances in the wastewater is conventionally determined by the oxygen required for reaction to CO□ and water.

The error value is the BOD value [chemical oxygen demand (biochemi
It is known as cal oxygen demand).

For wastewater from plasticizer ester production, BOD values of 350-400 grams of oxygen per 11 ml of wastewater are not uncommon.

This type of wastewater cannot be directly processed using biological purification equipment.

The waste water should generally be cleaned beforehand by certain means, but should be diluted with at least a large amount of unloaded water.

The wastewater produced in ester synthesis has other undesirable properties that make it difficult to separate the oil from the other wastewater when it is passed through a precipitation vessel for the oil.

In addition to the economic disadvantage due to the loss of useful products dissolved in the waste water, further environmental protection problems therefore arise.

Therefore, it is possible to clean the process wastewater produced when sulfuric acid is used as a catalyst in the production of ester plasticizers and to recover the organic substances dissolved in the wastewater and return it to the process without expensive purification and separation treatments. Challenges arise.

Surprisingly, the problem arises when producing ester plasticizers by esterifying polybasic aliphatic or aromatic carboxylic acids with aliphatic alcohols in the presence of sulfuric acid as catalyst. The problem is solved by a process for cleaning the waste water which, in addition to the substances, also contains alkyl sulfates and dialkyl sulfates and recovering the starting and final substances, in which case the waste water is heated at temperatures above 200° C. under a pressure adjusted in each case. After heating to a temperature and, if necessary, acidifying the reaction mixture beforehand, it is separated by mechanical or thermal methods.

The reaction is preferably carried out at a temperature of 210-250°C.

Depending on the temperature used, the treatment time is between 15 minutes and 5 hours.

At 220° C., the reaction is completed, for example, after about 2 hours.

Completion of the reaction is confirmed by the fact that, despite a significant prolongation of the reaction time within the abovementioned temperature range, the content of organic substances in the aqueous phase can no longer be reduced.

The wastewater from the neutralization process using aqueous sodium carbonate solutions generally contains large amounts of sodium bicarbonate as well as small residual amounts of carbonic acid.

In the process according to the invention, not only the carbonic acid but also some sodium hydrogen carbonate is reacted with CO2 elimination.

The reaction therefore proceeds in the absence of alkaline-reacting chemicals, ie, for example in the presence of neutrally reacting sodium bicarbonate, and thereby differs from the saponification of esters in the presence of strong bases.

For technical reasons of the process, it is advantageous to prevent the formation of 002 waste water resulting from the purification of sodium carbonate, for example in order to prevent the formation of waste gases or to avoid excessive pressure build-up in the reaction.

The CO2 produced in this type of case can be combined with the alkali metal bicarbonate by adding a stoichiometric amount of an alkaline solution, such as a sodium hydroxide solution or a potassium hydroxide solution.

The reaction mixture is then preferably cooled countercurrently with the untreated waste gas.

The organic phase separates within a few minutes.

Up to 150 kg of organic products are obtained per rn' of wastewater.

Surprisingly, the ester plasticizer dissolved in the wastewater remains virtually undamaged.

In contrast, the alcohol is eliminated almost quantitatively from the alkyl sulfate and half ester of dicarboxylic acid and is separated together with the organic phase.

As by-products, small amounts of olefins are obtained, which are partly already produced in the ester synthesis and are dissolved in the untreated wastewater.

After separation of the organic phase, the waste water contains, inter alia, salts of carboxylic acids, such as the disodium salt of phthalic acid.

By adding a mineral acid, such as sulfuric acid, hydrochloric acid, or phosphoric acid, this slightly water-soluble dicarboxylic acid can be easily separated.

Phthalic acid completely precipitates out already at pH values of 3.0 to 3.5.

The chain acid is then removed by known methods such as filtration, centrifugation,
It can be separated by decantation or the like.

According to the method of operation according to the invention, 85% of organic substances are removed from wastewater without taking into account dicarboxylic acids.

If the carboxylic acid is precipitated and subsequently filtered, more than 98% of the organic substances can be removed.

It should be noted that organic substances remaining in the water can be separated without difficulty by partial distillation.

The recovered organic materials are almost exclusively the starting products, intermediate products and final products of ester plasticizer production and can be returned to the synthesis.

Ester plasticizer production does not suffer any disadvantages by recovering the material obtained from wastewater, and the quality of the ester is not compromised by this.

Usually, the preparation of esters is carried out using superstoichiometric amounts of alcohol.

Separation of excess alcohol from the resulting ester is therefore a necessary step in this type of process.

The separated alcohol is returned to the esterification step either directly or after a post-treatment such as distillation.

The alcohol obtained in the waste water treatment can be separated off without special measures and subsequently used in known manner.

The discharge of small amounts of by-products produced in the ester production, such as olefins, is not disturbed by returning the material obtained from the waste water.

The present invention thus results in an improved quality of the waste water and a significant recovery of useful products, thereby causing an improved yield relative to the starting materials used in the ester production.

The implementation of the method of the invention and the results achieved using the method will now be detailed by way of example.

Example Untreated process wastewater has the following average characteristic value: Volume: 4
00-5ooJ/h pH value; 9.3 Sodium carbonate; 37.6 g/l sodium bicarbonate; 29°O? /1 COD value: 360-380 g/l The wastewater contains the following substances: Nidiclohexane 16.1' di-2-ethylhexyl sulfur 8.2 Z 2-ethylhexyl sulfur di) Na salt 241 di-2 -Ethylhexyl sulfate 2-ethylhexanol isooctyl sulfate Na salt isooctyl butyl ether dioctyl phthalate (DOP) 4-heptyl sulfate Na salt mono-2-ethylhexyl phthalate) Na salt 10.1f 34.49 10g 12.3P 14.2P ■ 3.21 Mono-isooctyl phthalate Na salt, -4-1Puchit, Tat 103fNa salt and 3 others were used in the following experiments using the wastewater.

The composition of the wastewater is typical with respect to phthalate esters and other esters from aliphatic dicarboxylic acids and aliphatic alcohols.

Example 1 Wastewater 3,3 with the above composition was placed in a stirring autoclave with content 51.
I put 1.

The autoclave was then rapidly heated to the temperature specified in the following table and kept at this temperature for 2 to 5 hours.

As the degree of reaction progressed, the pressure in the autoclave increased.

The pressure rise was reduced by adding 45% sodium hydroxide solution (see column 2 of the table).

At the end of the reaction time, the reaction mixture is cooled to room temperature, depressurized and discharged from the autoclave.

The upper organic phase was separated, weighed and analyzed by gas chromatography.

The aqueous phase was examined for residual contaminants (see table for results).

The organic phase quantitatively and qualitatively has the following composition: dichlorohexane 2-ethylhexene-(1) 3-methylhebutene Hexanorva 4) 2-ethylhexanol isoocta tool 16.7g 10.3g 109°3g 8.2g 189.21 6.0g isooctyl butyl ether 1.11 Dioctyl phthalate 13.81 Other (not specified) 0.42 It didn't change.

When the same treatment was carried out at 210° C. and otherwise under the same conditions, an almost quantitative clarification of the wastewater occurred, which at 220° C. was already complete after 2 hours.

The aqueous phase of experiment 3 was acidified with sulfuric acid to a pH value of 3.

Immediately, phthalic acid precipitated in the form of crystals. The filtered water had a COD value of 6.0 P/l.

In other experiments, C8B values were partially between 2.5 and 3.0.
It was even P/l.

Comparative Example (1) The waste water from Example 1 was boiled under reflux for 72 hours (ie heated to about 100° C.) and subsequently cooled.

The wastewater remained unchanged in appearance and remained transparent.

The organic products did not separate even after standing for several days.

Furthermore, the wastewater was extracted and adsorbed, and its appearance, composition, and properties remained unchanged compared to untreated wastewater.

(11) The same wastewater was heated to 180° C. with vigorous stirring for 5 hours in an autoclave.

In this case too, no organic phase separated from the waste water after cooling to room temperature.

Therefore, it is readily apparent that waste water is used and that a simple description of the reaction progress is not possible due to the type of complex substance mixtures that result as reaction products, but also that a detailed study of the reaction diversity is not necessary. be.

Example 2 60 grams of concentrated sulfuric acid was added to 3.3 liters of wastewater, ie, an amount that would convert the sodium carbonate present in the wastewater into sodium bicarbonate.

The solution was then treated according to Example 1 for 3 hours at 220.degree.

The yield of organic material was 365 grams.

The organic product had the following composition: Hydrocarbons: 4.5% Olefins: 28.6% Alcohols: 61.9% Esters: 4.8% By-products: 0.2% Example 3 Said composition The waste water of 5001 was continuously pumped into a pressure reactor with a content of 177+'' filled with a precious metal filling.The water was preheated to 230°C under pressure beforehand, and no other heat supply was carried out in the reaction vessel. I didn't do it.

After the reaction was complete, the reaction mixture was cooled countercurrently with untreated waste water and subsequently cooled with cooling water and depressurized to normal pressure.

The organic phase was then separated from the aqueous phase in a phase separator and the organic phase was returned to the esterification stage.

56.1 kg/hour of organic product was recovered with the following composition: 4.3% hydrocarbon diolefins: 29.5% alcohol:
60.6% ester:
55% Undefined by-products:
0.1% Next, embodiments of the present invention will be listed.

A method as claimed in the claims, characterized in that: (1) heating to a temperature between 210 and 250<0>C.

(2) A stoichiometric amount of alkali metal hydroxide is added when the content of alkali metal hydrogen carbonate in the wastewater is high, and the claim described in the above item (1) Method.

(3) After thermal treatment of the wastewater, the aqueous phase is acidified with mineral acids in order to separate the dicarboxylic acids dissolved in the water in the form of alkali metal salts, either before or after separation of the precipitated organic substances. The method according to claims and items (1) to (2) above, characterized in that the pH value is adjusted to 3 to 3.5.

(4) Claims and the above-mentioned items (1) to (3) characterized in that the recovered organic substance is returned to the ester production process.
The method described in section.

Claims (1)

[Claims] 1. In addition to the starting materials and the final materials, there are also alkyl esters which result when producing ester plasticizers by esterifying polybasic aliphatic or aromatic carboxylic acids with aliphatic alcohols in the presence of sulfuric acid as a catalyst. In cleaning the wastewater containing sulfuric acid and dialkyl sulfates and recovering the starting and final substances, the wastewater is heated to a temperature above 200° C. under the respectively adjusted pressure and the reaction mixture is optionally preheated. 1. A method for cleaning wastewater produced in the production of ester plasticizers, characterized in that it is removed and made acidic and then separated by mechanical or thermal methods.