DE2731638C2 - Process for cleaning organically contaminated waste sulfuric acids - Google Patents

Description

Aqueous waste sulfuric acids are produced in various organic chemical processes and their concentration is comparatively low in sulfuric acid and its impurities are essentially more organic Are nature.

The concentration and oxidative purification of such abiaüschweieisaufen by the addition of nitric acid has long been known (German patent 2 99 774). Other known methods, such as. B. in Chemische Apparatur 23 (1936) page 41 ff. And German Offenlegungsschrift 23 30 281, are based on this known Pauling process.
These processes convert the organic contaminants into gaseous volatile oxidation products.

whereby the oxidizing agent, for example nitric acid, is used.

If the reaction is assumed to be ideal, i. h "if from an organically bonded carbon atom by oxidation with nitric acid and / or nitrous gases only carbon dioxide, nitrogen and water arises, the theoretical minimum requirement for nitric acid can be derived from the respective reaction equation determine. The actual need for oxidizing agent may be higher as it is usually not the total amount Nitric acid (oxidation level of nitrogen plus 5) is converted into nitrogen (oxidation level 0).

An object of the present invention is to determine the amount of nitric acid necessary for the oxidation to keep it as low as possible without reducing the quality of the processed sulfuric acid in terms of the content of to reduce organic contamination.

The present invention thus relates to a method for processing organic compounds contaminated sulfuric acid by concentrating the hydrous sulfuric acid a <if about 50 to 100% by weight acid and subsequent treatment with nitric acid, at temperatures between 200 "C and 320 ° C.

According to the invention, it has been found that such a process results in reusable water-clear sulfuric acids with a strength of more than 90% by weight, which are free of organic impurities

genes if the dark to black-colored concentrates obtained are mixed with nitric acid at the same time

and / or nitrous gases and gases containing molecular oxygen. The fe

Oxidizing agent is formed /. B. by the simultaneous addition of nitric acid and air, either after |

prior mixing via a common metering device, or via two separate feeds in the reaction space. Nitrose is understood to mean pure NO, NO2. N2O4 or mixtures of these gases.

In the context of the present invention, gases containing molecular oxygen are understood to mean air, air enriched with oxygen or technical oxygen. The molecular ratio of the nitrogenous Oxidizing agent to oxygen of the molecular oxygen-containing oxidizing agent is preferable less than 2.

Surprisingly, it has been found that it is possible. through the simultaneous use of nitric acid and / or nitrous gases and, for example, air or oxygen with considerably less nitric acid or nitrous gases to get to a sulfuric acid free of organic impurities reach, since under these conditions oxygen obviously also acts as an oxidizing agent.

It has also been found that in the treatment process according to the invention, the resulting exhaust gases are free from or lower in sulfur dioxide than by known processes.

As waste sulfuric acid contaminated with organic compounds come for the inventive All waste sulfuric acids that are inevitably produced in organic chemical reactions are taken into account. In particular, these waste sulfuric acids are process acids. as they do with the usual Sulfonation * -. Chlorosulfonation and denaturation reactions of especially aromatic compounds such as benzene. Naphthalene and the corresponding substituted derivatives arise.

As examples of the waste sulfuric acids used in the process according to the invention may be mentioned: The resulting from the production of benzene sulfonic acid chloride from benzene and chlorosulfonic acid, 20 to 25% of the waste acid contaminated primarily with benzenesulphonic acid; Paranitrotoluene, mainly contaminated with paranitrotoluene sulfonic acid, approx. 40 to 45% dilute acid: those obtained during the nitration of acetanilide in sulfuric acid as a solvent, mainly with Paranitroacetanilide sulfonic acid contaminated about 25% dilute acid and that in the sulforation of naphthalene Approx. 30 to 35% dilute acid contaminated with 1,5-naphthalenedisulphonic acid.

The process according to the invention can also be applied to waste sulfuric acids with a high salt content, such as them for example in the production of naphthalenesulphonic acids, nitronaphthalenesulphonic acids and in the unier

the term letter acids known naphthalene intermediates arise.

The content of organic-chemical impurities in the waste sulfuric acids is usually between 0.1 and 15% by weight. Waste sulfuric acids with are particularly suitable for the process according to the invention an organic impurity content of about 0.2 to 10% by weight.

The nitric acid used in the process according to the invention can be con / entriene and / or <> act as smoking nitric acid or nitric acid vapor.

The content of the organic-chemical sulfur obtained by concentrating the aqueous waste sulfur Compounds contaminated concentrates of sulfuric acid is between 50 and 100 wt .-%. In a, According to the preferred embodiment, concentrates are used which contain between 80 and 95% by weight Contain sulfuric acid.

The temperature, according to the invention, the oxidation of the preconcentrated Abfalisäure in is in the range of about 200 to 320 ⁰ C, preferably 250 to 300 ⁰ C, particularly preferably in the range 260 to 290 ° C When oxidation temperatures above 260 ° C, a pre-concentration of the waste sulfuric acid sulfuric acid contents of at least 80% by weight are particularly preferred.

The preferred sulfuric acid concentration of 80-95% by weight can optionally also be determined by an is Achieve metered addition of sulfur trioxide.

The waste sulfuric acid can be concentrated in a known manner by distilling off water caused by the raw acid (or by heating); will. The acid contains 90% by weight at atmospheric pressure eic- "n boiling point of about 255 ° C, the actual boiling point, however, by the presence of organic impurities is changed by heating the waste sulfuric acid to a a temperature in the range from 250 to 270 ° C and distilling off the water a sufficient pre-concentration

ι causes.

The concentration can also be carried out by vacuum distillation. At a pressure of 15 Torr, a pot temperature of 150 is sufficient to reach sulfuric acid to 18O ⁰ C. to provide the desired concentration of preferably 80 to 95 wt .-%.

In a special embodiment of the method according to the invention, wel & '- it contaminated sulfuric acid, mainly with aromatic sulfonic acids, such as. B. benzenesulfonic acid. Paranitrotoluenesulfonic acid or naphthalenesulfonic acid are contaminated, a hydrolysis is carried out before the concentration Part of the organic compounds separated; this is done according to the reaction equation below

AryS - SOjH + H ₂ O * = * aryl - H + H ₂ SO ₄

in the course of concentration, in the case of aryl = benzene z. B. by azeoirope distillation at a Sump temperature from 180 to 185 ° C and normal pressure. Such hydrolysis of aromatic sulfonic acids generally only proceeds up to a certain state of equilibrium The pre-concentrated waste sulfuric acids therefore contain in the form of organic impurities in spite of the previous separation the corresponding aromatic compounds obtained by hydrolysis still contain organic impurities. The separation of some of the organic constituents leads to hydrolysis and Abdesf'-lation however, to a reduction in the organic components in the concentrated acids and thus to a Saving of oxidizing agents.

The hydrolysis is preferably carried out at from 170 to Tempe shaves 22O ⁰ C at a pressure of about 8 to 10 bar and for a period of about 1 to 5 hours.
jj The amount of oxidizing agent necessary for the oxidation treatment according to the invention depends on the

S | Amount of organic impurities in the waste sulfuric acid. The amount of is characterized

, α organic impurities by the expression% by weight of organic carbon, based on the total

weight of waste sulfuric acid (wt% TOC). The stoichiometric minimum requirement for oxidizing agent can be determine from the reaction equations.

Due to the simultaneous use of nitric acid and / or nitrous and containing molecular oxygen Gases according to the present invention, it is possible to meet the actual demand for sulfuric acid or to reduce nitrous gases below the stoichiometrically calculated. According to the invention you can do this up to / u 30% of the calculated nitric acid or nitrous requirement.

The oxidizing agent mixture according to the invention can be used in various ways from the pre-concentrated waste sulfuric acid be added, for example, it has been found to be useful, the oxidizing agent mixture to be fed into the reaction vessel containing the pre-concentrated acid below the contents of the vessel.

The process according to the invention can be operated batchwise or continuously.

In one embodiment of the continuous process, the crude waste sulfuric acid is one at a Temperature from 200 to 270 ° C. preferably 250 to 270 ° C held first reaction vessel fed into which the concentration takes place continuously. The concentrated crude acid is then used in a second Reaction vessel, which is kept at a temperature of 260 to 290 ° C, transferred. The inventive Oxidizing agent mixture is continuously fed into the second reaction vessel, with water and volatile components escape.

To the oxidation effect of air or oxygen-enriched air or technical oxygen in the To be able to better utilize the oxidizing agent mixture, it is according to a special embodiment of the According to the crfindüngsgemäße method, a partial flow of the amount of gas leaving the reaction chamber in the Circle to lead (10 to 90 vol .-%). Since part of the oxidizing agent mixture according to the invention is a gaseous component, you can in a further embodiment of the present Invention proceed so that the best possible exchange of substances between the gaseous oxidizing agent and the crude concentrated acid contaminated by organic compounds is guaranteed. this

can be carried out, for example, in a column if the oxidizing agent mixture is fed into the bottom and the crude, concentrated acid, at a temperature of ^{about 260 to 290 ° C., is allowed to flow in at the top of the column}

Because in the course of the oxidation process through the formation of water the sulfuric acid concentration decreases, it is advisable to find the optimal concentration range by continuously distilling off Keep the water volume or the addition of sulfur trioxide constant.

Another embodiment of the method according to the invention relates to the cleaning of high salt contents Melt wastewater, as z. B. in the production of letter acids by reaction of amino-naphthalene-sulfonsänren with caustic soda. The resulting salty, little acid-containing organically contaminated waste water is mixed with concentrated sulfuric acid and either in a vacuum

ίο at about 160 to 180 ⁰ C, or under atmospheric pressure to a bottom temperature of 250-270 ⁰ C aufkonzentrie-t (80 to 95% by weight sulfuric acid). The dark to black-colored concentrates are then treated with the oxidizing agent mixture according to the invention. In this way, water-clear or light yellow-colored solutions are obtained which, on cooling, change to sulfuric acid containing crystal slurry, which is free from organic chemical impurities. It is also possible according to the method according to the invention that

Carry out preconcentration of the melt wastewater in such a way that the melt wastewater is allowed to flow into hot, concentrated approximately 96% sulfuric acid, the temperature of ^{which is kept at 270 °} C., with simultaneous discharge of water.

In the following, the present invention will be explained by way of example, taking the prepared examples consciously were designed so that no 100% degradation of the organic chemical impurities was achieved to give numerical comparison possibilities.

example 1

In a 250 ml four-necked flask fitted with a dropping funnel (with an extended inlet tube), thermometer, gas inlet tube. Stirrer and reflux condenser is provided, 150 g of a 0.96% carbon containing, under normal pressure with the aid of azeotropic removal of most of the benzene at 182 ⁰ C by introducing steam and then concentrated up to 295 ° C effluent (complete analysis see table 1) which comes from the Benzolsulfonsäurecfilorid manufacture, after thorough flushing of the apparatus with argon and heated to 270 ⁰ C at this temperature in 30 minutes, 4 ml of 98% igfe nitric acid and oxygen introduced into the solution, wherein the supply of oxygen by means of a rotameter is kept constant and is approx. 11 l / h. The escaping gas mixture is passed through a reflux condenser, which is cooled with ice water, and quantitatively collected in an evacuated storage vessel. A light yellow solution containing 0.12% carbon is obtained, the complete analysis of which and the total gas J

analysis is listed in Table 1. The determined gas volume V ₀ is reduced to 0 ⁰ C and 760 Torr I

I.

Example 2a-2b

A reaction as described in Example 1 is carried out with variation of the oxygen supply in the glexhen Apparatus carried out. The results are shown in Table 1.

Example 3
(Comparative example)

as A, vie circumcision ene in Example 1 reaction is conducted without ^oxygen; carried out in the same apparatus. A pale yellow solution containing 0.23% carbon is obtained, the complete analysis of which and the Gesami gas analysis are listed in Table 1. The determined gas volume V ₀ is reduced to 0 ⁰ C and 760 Torr.

Example 4

250 ml veal neck flasks in buckets. the one with pinem dropping funnel (with extended inlet tube), thermometer. Gas inlet pipe, stirrer and reflux condenser is provided. 150 g of a 5.4% carbon containing, under normal pressure up to 295 ° C aufkonzentriei th process (complete analysis see Table 1). which comes from the production of benzenesulfonyl chloride, after thorough flushing of the apparatus with argon and heating to 270 ° C at this temperature in 75 minutes, 6 ml of 98% nitric acid and oxygen are introduced into the solution, the oxygen supply being kept constant with the help of a rotameter and is approx. 10 l / h. Proceed as described in Example 1 with the escaping gas. A light yellow solution containing 4.14% carbon will be obtained. the full analysis of which and the total gas analysis are listed in Table 1. The determined gas volume V ₀ is reduced to 0 ° C. and 760 Torr.

Example 5
(Comparative example)

A reaction as described in Example 4 is carried out in the same apparatus without the addition of oxygen. A pale yellow solution containing 4. θ% carbon is obtained, the full analysis of which and the total gas analysis are listed in Table 1. The determined gas volume K ₀ is reduced to 0 ⁰ C and 760 Torr

Example 6

In a 250 ml four-necked flask fitted with a dropping funnel (with an extended inlet tube), thermometer, Gas inlet pipe, stirrer and distillation bridge are provided, 200 g of a 5.4% carbon containing, under normal pressure up to 295 "C on concentrated discharge (complete analysis see table 1 and 2), which comes from the Benzolsulfonsäurechloriri production, after heating to 270 ° C in this Temperature in 90 minutes 20 ml of 98% nitric acid and oxygen passed into the solution, the Oxygen supply is kept constant with the help of a rotameter and is approx. 10 l / h. It will be a 1.76% Obtained carbon-containing solution, the full analysis of which is given in Table 2. At this Procedure contains the exhaust gas SO *

Example 7
(Comparative example)

A reaction as described in Example 6 is carried out in the same apparatus without the addition of oxygen. A solution containing 2.78% carbon is obtained, the complete analysis of which is given in Table 2 is listed.

Example 8

It is a reaction as described in Example 6, but in which the distillation bridge by a The reflux condenser, which is cooled with ice water, is replaced. It becomes a 2.06% carbon containing solution, the full analysis of which is shown in Table 2 below. At this In practice, the exhaust gas practically no longer contains any SO2.

Table 1 ENT addition ENT O / o HNO _3,. Cj H ₂ SO., sulfate
precipitation anorg. example g ml Savings ¹ ) % TOC LtrVStd. acidf-
metric chlorine

2b ⁴ )

6.04
6.04
6.04
6.04

9.06
9.06

4.0 4.0 4.0 4.0

6.0 6.0

4.15
4.08
4.70
5.22

4.21
5.22

11 7 3

10

923
93.7

93.2
93.7
92.7

84.0
84.0

82.9

91.5 923

93.1 92.6 923

76.5 79.9

77.1

- ¹ y 15th 4th 0.2 0.96 0.04 8.92 - 0.6 20.6 60.3 16.7 1.5 - 0.1 1 4 ¹ ) 0.2 0.12 - 1.5 51.9 - 42.1 3.8 _ 0.3 ι ⁴ ) 5 0.09 7.27 - 0.9 25.6 50.9 20.4 1.9 - 0.2 10 2a 0.2 0.17 _ 1.8 52.1 - 41.5 3.9 - 0.4 2a <) 0.02 5.34 - 1.1 34.3 28.7 33.3 2.4 - 0.2 2 B 0.2 0.20 - 1.5 48.1 - 46.7 3.4 - 0.3 2b ⁴ ) 0.06 4.20 8.3 1.8 48.9 - 38.8 0.3 1.9 - 3 0.2 0.23 0.2 5.40 0.01 17.95 _ 0.6 16.9 67.9 12.8 1.5 - 0.1 03 4.14 - i.S. 52.6 - 4.7 - 0.3 7.40 16.8 1.6 43.6 28.3 0.2 4.35

20th

45

9.6

Explanations for Table 1

') HNOj savings compared to the theoretical value of the comparative experiment without oxygen supply.

The theoretical value is, provided that the entire HNOj is completely reduced to nitrogen, no SO _{2 is} formed and no oxygen or air supply is used, 5.25. The ratio found was formed from the actual HNOj consumption (amount of HNOj used minus nitrous in the exhaust gas minus nitrogen content in the oxidized acid) and the carbon oxidized by HNOj (total oxidized carbon minus carbon that was oxidized by H ₂ SO *).

^J ) Not oxidized, ie starting materials for the corresponding examples given in the table.

■ *) The total gas analysis is converted to Vo! .-% with the elimination of oxygen.

Example 9
(Comparative example)

A reaction as described in Example 6 is carried out with 26 ml of 98% strength nitric acid without supply of oxygen in carried out the same apparatus. A solution containing 2.02% carbon dioxide is obtained full analysis is listed in Table 2.

Table 2 ENT, - Wt .-% HNOj ₂ O ₂ H ₂ SO ₄ Sulfate-
precipitation anorg. Suirate TOC N At- ENT Savings
nis ¹ ) % TOC 'aeidi-
metric
LtrVh.% chlorine Ashc « (You
mas) game encore
g ml

- ³ ) 3020 20.0 28 4.07 10 84.0 76.5 < 0.1 02 5.40 0.07 6th 3020 20.0 5.65 - 86.0 85.5 < 0.1 0.3 1.76 0.07 7th 30.20 20.0 22 ") 4.43 10 85.5 83.4 < 0.1 0.1 2.78 0.07 S. 3926 26.0 863 85.0 < 0.1 02 2.06 0.06 50 9 87.5 84.6 < 0.1 03 2.02

'i

55

65

Explanations for Table 2

') H NOj savings compared to the corresponding comparative experiment without oxygen supply.

² J Since no gas analyzes were carried out due to the large amount of gas, the ratio found here is formed from the amount of HNOj used and the total oxidized carbon. Theoretical value see footnote 2 in

Table 1.

³ ) See footnote 3 in Table 1.
"*) The HNOj savings are somewhat low because this experiment was compared with Example 7, which, however, was carried out under slightly different reaction conditions.

Example 10

In a bubble column with a dropping funnel (with an inlet tube reaching almost to the beden). Thermometer. Gas inlet pipe and reflux cooler provided and with a diameter of 3.5 cm, 25 cm high, 150 g of a 22% carbon containing, in a vacuum at 15 Torr up to 180 ^° C., are concentrated under magnetic stirring (complete analysis see Table 3 ), which comes from Armstrong's acid production, after thorough flushing of the apparatus with argon and heating to 270 ° C at this temperature in 50 minutes, 5.5 ml of 98% nitric acid and oxygen are introduced into the solution.

let, whereby the oxygen supply is kept constant with the help of a rotameter and amounts to approx. 6 l / h. The escaping gas mixture is passed through a reflux condenser, which is cooled with ice water, and quantitatively collected in an evacuated storage vessel. A yellow suspension is obtained which, after suction, gives a yellow solution containing 1.18% carbon, the full analysis of which and the total gas analysis are listed in Table 3. The determined gas volume Vo is reduced to 0 ^° C. and 760 Torr.

Example 11

A reaction as described in Example 10 is in the same apparatus with 200 g of a 1 53% of carbon-containing, up to 295 ⁰ C concentrated under normal pressure outlet (full analysis see Table 3), which comes from Armstrong production, at 27O ⁰ C treated in 65 minutes with 8 ml of 98% nitric acid and oxygen (7 l / h). A yellow, cloudy solution is obtained which, after suction, gives a yellow solution containing 0.58% carbon, the full analysis of which and the total gas analysis are listed in Table 3. The determined gas volume V ₀ is reduced to 0 ° C. and 760 Torr.

Example 12

A reaction as described in Example 11 is carried out without the supply of oxygen. A yellow, cloudy solution is obtained which, after suction, gives a yellow solution containing 0.58% carbon, the full analysis of which and the total gas analysis are listed in Table 3. The determined gas volume Vo is reduced to 0 ^° C. and 760 Torr.

Example 13

In a bubble column with a dropping funnel (with a tube that almost reaches the bottom). Thermometer, gas inlet tube and reflux condenser and with a diameter of 3.5 cm, 25 cm high, 200 g of a 0.63% carbon-containing effluent concentrated in vacuo at 15 Torr up to 180 ° C (for complete analysis see Table 4), which comes from the p-NitrotoluoIsulfonsäure production, heated ^{to 270 0 C after thorough flushing of the apparatus with argon} . The at 0 ° C and 760 Torr reduced V ₀ - values are shown in Table 4 ⁰ C are introduced at this temperature in 15 minutes 2 ^ ml of 98% nitric acid and oxygen in the solution After reaching 27O, wherein the supply of oxygen by means of of a rotameter is kept constant and amounts to approx. 5 l / h. The gas mixture that escapes is quantitatively collected in a further evacuated storage vessel. A pale yellow solution containing 0.05% carbon is obtained, the complete analysis of which and the total gas analysis are listed in Table 4. The determined gas volume V ₀ is reduced to 0 ° C. and 760 Torr.

Table 3 HNOj addition ENT) - Wt .-% HNOj ,. Oj HjSO ₄ sulfate
precipitation
% anorg. example g ml Savings ¹ )
% % TOC '
LtryStd. acidic
inetric
Vo chlorine
%

- ^J ) 90.9 89.4 <0.1

10 8.30 5.5 12 4.43 6 93.0 93.1 <0.1

10 ").

- ^J ) 92.2 91.6 <0.1

11 12.08 8.0 16 4.22 7 93.7 92.0 11 ")

12 12.08 8.0 5.02 - 93.8 91.9

Table 3 (continued)

Example sulfate TOC NV ₀

Ashes (dumas)

SO ₂ N ₂ O

CO ₂

o / o

o / o

N ₂

NO ₂

O / o

NO

o / o

N ₂ O ₄ NO ₂ MO%%

10 10 ")

10 - ³ ) 11 11 «) 12

0.2 0.1

0.1 0.1

2.20 1.18

1.53 0.58

0.07

0.30

0.58 0.04

9.19

1331 8.07

0.8
1.5

1.0
2.2
1.4

24.6 48.1

47.4 -

26.5 54.7
58.5 -

44.7 -

22.2
42.8

14.6
32.2
22.1

2.4
53

0.3 0.7

'), ³ ) and ⁴ ) see the corresponding footnotes in Table I.

² ) The theoretical value is 5.04, assuming that all of the HNOj is completely reduced to nitrogen, no SO _{2 is} formed and no oxygen or air supply is used. For the ratio found see

Footnote 2 in Table 1.

Example 14
(Comparative example)

A reaction as described in Example 13 is carried out in the same apparatus without the addition of oxygen. A yellow solution containing 0.09% carbon is obtained, the complete analysis of which and the total gas analyzes of the gas mixture formed during the reaction and when the solution is heated to 270 ° C. are listed in Table 4. The determined gas volumes Vo are reduced to ⁰ ° C. and 760 Torr.

Table 4 ENT add ENT ₃ - Wt .-% HNO ₃ j j O ₂ H ₂ SO ₄ sulfate
precipitation anorg. example g ml Savings ¹ ) % TOC LtryStd. acidic
metric
o / o chlorine
o / o

_3 \

13 ")

53 3.47 2.3

13 ⁶ )

14 ⁵ )

14 3.47 23

Table 4 (continued)

3.70

4.70

93.8 93.7 <0.1

94.1 94.2 <CU

93.9 94.0 <0.1 l

at fpiel Sulfate- TOC N V ₀ SO ₂ N ₂ O CO ₂ O ₂ N ₂ NO ₂ NO N ₂ O ₄ NO ₂ - 4b ash (Dumas) MO o / o % o / o Ltr. o / o % o / o o / o o / o o / o % o / o o / o

0.1 0.63 0.10

135) 0.1 0.05 13th 13 ⁶ ) 14 ") 14 ⁵ ) <0.05 0.09 Ί4

2.01 3.91 2.02 2.69

23.1 - 14.8 1.0 16.0 41.9 263 1.8 29.1 11.6 1.0 29.3 31.2 26.8 - 16.9 1.5 42.6 - 39.0 - 24.7 - 15.1 1.3 14.5 443 - 27.1 23 26.0 30.2 21.1 36.0 32.4

443 0.1
02 443 0.1 Z 03

Explanations for Table 4

HNO ₃ savings compared to the theoretical value of the comparative experiment without oxygen supply. The theoretical value applies under the prerequisite that all of the HNO _{3 is} completely converted to nitrogen, no SO _{2 is} formed and the work is carried out without the addition of oxygen or air, 4.65. The ratio found was formed from the actual HNOi consumption (amount of HNO _{3 used} minus nitrous in the exhaust gas) and the carbon oxidized by HNOj (total oxidized carbon minus carbon that was oxidized by H ₂ SO * during the reaction or during heating .

Not oxidized, d. Il starting material for the examples given in the table. Amount of gas evolved and its composition when heated to 270 ° C. The total gas analysis is converted to vol.% With elimination of argon. The total gas analysis is converted to% by volume with the elimination of oxygen.

Example 15
(qualitative attempt)

A 1-1 four-stroke flask with a gas inlet tube and a drip funnel. Thermometer, distillation bridge and contact thermometer is provided, 434 ecm of 96% sulfuric acid are introduced and heated to 270 ° C heated Within 3.5 hours, a mixture of 50% salt-containing I-acid mother liquor is poured into the hot sulfuric acid (TOC content: 3.700 mg / 1) and 8.3 ecm of 98% strength nitric acid were added dropwise. At the same time there is air introduced into the solution, the air supply being kept constant with the help of a Rotameteirs and 5 l / h After distilling off 530 ecm of water, a pale yellowish solution is obtained a TOC content of 520 mg / 1.

Example 16
(Comparative example to 15, qualitative)

A reaction as described in Example 15 is carried out in the same apparatus without supply of air. Although 9 ecm 98% nitric acid is now used instead of 83 ecm, the TOC content decreases distilling off 500 ecm of water only to 700 mg / l.

20 Example 17

(qualitative attempt)

A waste sulfuric acid which originates manufacturing Diphenylsulfondisulfochlorid of which is, in a distillation apparatus consisting of a three necked flask, equipped Rait stirrer, internal thermometer and distillation under vacuum (15 Torr) and up concentrated to a sump temperature of 150 ⁰ C.

Di ·; crude concentrated acid is colored black, has a content of 84.3 wt .-% sulfuric acid, a Density of 1.796 and is contaminated with 2.515 wt% organic carbon (TOC) The stoichiometric Oxidizing agent requirement is according to the reaction equation for the conversion of Diphenylsulfondisulfonsaufe with nitric acid 5.25 g HNOj per g carbon. It serves for the following experiments 18 to 21 as Starting goods.

Example 18

35 (comparative example)

In a 1 I-Vicrhalskolben which is provided with a dropping funnel (with extended inlet tube), thermometer, gas inlet tube, stirrer and reflux condenser, 582 cc of concentrated in EXAMPLE 17 crude acid at a temperature of 265 ⁰ C within 2 hours under stirring with 127 g nitric acid ao 100 % & 96% of the stoichiometrically required amount of 132 g HNO3 added. A yellow solution containing 0.825% carbon is obtained, the analysis of which is shown in Table 5.

Example 19

45 (comparative example)

A reaction as described in Example 18 is carried out in the same apparatus, only the use of nitric acid was varied, in that only 100.5 g of HNOj (100%) & 76% of the stoichiometrically required amount of nitric acid are used. A brown solution containing 1.255% carbon is obtained, the analysis of which is shown in Table 5.

Example 20

A reaction as described in Example 18 is carried out in the same apparatus. In addition to the Addition of 100.5 g HNOj (100%) - 76% of the stoichiometrically required amount of nitric acid is added to the Solution Air introduced, the air supply being kept constant with the help of a rotameter and approx. 10 l / h afflicted. A honey-yellow solution containing 0.89% carbon is obtained, the analysis of which is given in Table 5 is listed.

ao example 21

A reaction as described in Example 18 is carried out in the same apparatus. In addition to the addition of 100.5 g HNO ₃ (100%) 76% of the stoichiometrically required amount of nitric acid, oxygen is introduced into the solution, the oxygen supply being kept constant with the help of a rotameter and being approx. 8 l / h. A pale yellow solution containing 0.46% carbon is obtained, the analysis of which is shown in Table 5.

Table 5

582 ecm of crude sulfuric acid (d ^M ' ^c : 1.796) with 84.9% by weight of H ₂ SO ₄ and 2.515% organic C are used in each case

At- Oxidation- I air / 1O ₂ / oxidized acid C-Ameil ⁰ AN

game condition hrs hrs. amount d ²⁰ " ^c acidim.% H ₂ SO ₄ Vo Cl% ⁰ AC gC

7 "(° C) gHN0 ₃ (ecm) (g / cem) precipitation inorganic sulphate wet total

ash

18th 255 127 - 19th 265 1003 - 20th 265 100.5 10 21 265 1003

575 1.790 93.8 833

575 1.790 853 87.1

487 1.81 84.6 88.6

570 1,792 87.8 89.1

0.1 0.825 8.48 0.44

0.1 1.255 12.90 0.19

0.1 0.89 7.35 0.12

0.1 0.46 4.69 0.10

Claims (1)

Patent claims: 1. A method for treating contaminated with organic compounds sulfuric acid by concentration of the aqueous sulfuric acid to about 50- 100 wt ° / o acid and subsequent treatment with nitric acid, at temperatures between 200 ⁰ C and 320 ⁰ C, characterized in that the concentrated, contaminated sulfuric acid is treated simultaneously with nitric acid and / or nilrose gases and gases containing molecular oxygen. Z The method according to claim i, characterized in that the molecular oxygen-containing Oxidizing agent technical oxygen is used. ίο 3. The method according to any one of claims 1 to 2, characterized in that the molecular ratio of the nitrogen-containing oxidizing agent to the oxygen of the molecular oxygen-containing oxidizing agent is less than 2.