DE1567734A1 - Process for the production of nitrosylsulfuric acid - Google Patents

Description

Dipl.-ing. Dipl. Oec. publ. DIETRICH LEWINSKY

PATE N TA N W ALT

- _r 1965

Agnes-Bernauer-Stra.ee 202-phone 18139 Telearamm-Adrease: EUROPE MÜENCHENPASINa Yours Zalchan> Main Zelohani

3761

zif

"67734

SociStS Organico, 22, ave

Franklin Roosevelt, Paris 8 (France)

"Process for the production of nitrosylsulfuric acid"

French priority dated ^ O. Nov. 1964 from French patent application No. 996 752

The invention relates to a process for the preparation of nitrosylsulfuric acid by reacting sulfurous anhydride with nitric acid.

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Solutions of Nitrosy! Sulfuric Acid (HSO ^ NO) In Sulfuric acid is widely used in organic syntheses, for example in nitrosation / the Diazotization, the production of lactams and the like.

It is known to nitrosylsulfuric acid by exposure from sulfurous anhydride to fuming nitric acid according to equation (1):

(1) SO ₂ + ENT, ■ - »NOHSO ₄

The known processes based on this reaction consist in converting gaseous sulfur dioxide with highly concentrated or fuming nitric acid. The nitrosulfuric acid crystallizes and the reaction mixture quickly thickens, so that it is impossible to completely convert the nitric acid. Various difficult methods have been tried to remove the residual nitric acid. However, it gave only an average yield of Nitrosy1- s chwefeisäure, based on the nitric acid. A significant increase in yield afforded a method of / * which is the reaction mass with an organic Löaunge- _t agents such as carbon tetrachloride diluted. The organic

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Solvent dilutes the reaction mixture without, however, dissolving the nitrosylsulfuric acid. To prepare a solution of nitrosylsulfuric acid in sulfuric acid, the suspension of the nitrosylsulfuric acid in an "organic diluent" can be treated with sulfuric acid. This reaction is carried out at a low temperature, namely from -5 to + 5 ° C. The use
Organic solvents and the need to work at low temperatures * make the process uneconomical.

It is also known to nitrosylsulfuric acid by the action of a mixture of nitrogen monoxide and NO
Produce nitrogen dioxide NOg (or N ₃ O ₄ ) on sulfuric acid according to equation (2):

(2) NO + NO ₂ + HgSO ^ - \ 2 NOHSO ₄

In this procedure it is necessary to use equimolar amounts of the two nitrogen oxides to use.

Technically, the mixture of nitrogen oxides is obtained by burning ammonia, i.e. the reaction that

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forms the basis of nitric acid production. However, it is very difficult to adjust the proportion of the two nitrogen oxides, if the gas contains an excess of NO, this amount is lost. On the other hand, when NO _{2 is} in excess, nitric acid is produced according to equation (3) below. The formation of nitric acid occurs in a great many reactions in which nitrosylsulfuric acid is used. Finally, one known method for producing nitrosylsulfuric acid is based on equation (3):

(?) 2 NO ₂ + H ₃ SO ₄ ^ NOHSO ^ + HNO,

In this reaction, only half of the nitrogen is converted into nitrosylsulfuric acid, which corresponds to a maximum yield of 50 % , based on NOg. The other half of the nitrogen forms nitric acid, so that the nitrosylsulfuric acid is contaminated with a large amount of nitric acid.

The known processes for the production of nitrosylsulfuric acid therefore all have serious disadvantages. The invention provides a remedy here.

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It has set itself the task of developing a process for the production of nitrosysulphuric acid, which leads to a yield of 92 to 100 % , based on the sulphurous anhydride or nitric acid, and in which the nitrosysulphuric acid is in the form of concentrated solutions in Receives sulfuric acid.

The object is achieved according to the invention in that one sulfurous anhydride on a solution of nitric., allows acid to act in sulfuric acid, which contains water and nitrosylsulfuric acid or such substances as initiators, which form nitrosylsulfuric acid in situ.

If you put SOg in an anhydrous mixture of sulfuric acid and introduces nitric acid, there is no reaction at all. The implementation is also not triggered, when adding nitrosylsulfuric acid alone to the mixture.

Add to the mixture of sulfuric acid and nitric acid with nitrosylsulfuric acid, water is added, the reaction between sulfurous anhydride and nitric acid takes place for the formation of nitrosylsulfuric acid.

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The amount of water required for the reaction is proportional to the amount of sulfuric acid in the reaction mixture.

The minimum amount of water that must be present for the reaction to take place results from the fact that the weight ratio between the amount of sulfuric acid in the mixture and the sum of the amount of sulfuric acid and water must not be more than about 97 % . Thus, assuming that in the reaction mixture only sulfuric acid and water are present, the sulfuric acid concentration is at most about 97 wt -.% Amount, based on the total weight of HgSO ^ + HgO. On the other hand, the minimum concentration of sulfuric acid is 70 % and preferably 75 %. In hydrous sulfuric acid, nitrosylsulfuric acid undergoes partial hydrolysis, which leads to sulfuric acid and nitrous acid. This hydrolysis does not interfere with most reactions in which nitrosylsulfuric acid is used. However, if you want to reduce the hydrolysis and stabilize the nitrosylsulfuric acid solutions, you only need to add sulfuric anhydride (SO,) or oleum after the reaction is complete to increase the sulfuric acid concentration.

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The use of a less highly concentrated sulfuric acid has the advantage that the reaction rate is greater at lower concentrations; the rate of reaction in sulfuric acid of 90% is four times greater than that in sulfuric acid of 97%. On the other hand, the advantage of using more highly concentrated sulfuric acid is that it is possible to produce concentrated solutions of nitrosylsulfuric acid, because the solubility of nitrosylsulfuric acid in sulfuric acid increases with its concentration (see Table 1).

The one used to initiate the reaction between the sulfurous anhydride and the amount of nitrosylsulfuric acid required for nitric acid is greater, the higher the concentration of sulfuric acid and the more nitric acid the reaction mixture contains when the introduction of sulfurous anhydride is started.

Table 1 below gives for a number of look for the values of the weight ratio nitrosy! sulfuric acid: nitric acid used to initiate the reaction in percent for different concentrations of

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Sulfuric acid in the reaction mixture:

Table 1 relationship
NOHSO ₁ ^ / ENT,
in % Induction
period concentration
of sulfuric acid 400 # 97 % 200 % 95 #. IQO # 90 % 30 % 86 % 12 # 4 minutes 82 pounds 25 ji 1 minute 82 % 50 % 10 sec 82 pounds traces 75 %

It can be seen from the table above that the ratio of the nitrous sulfuric acid used as the reaction initiator to the nitric acid can vary greatly as a function of the concentration of the sulfuric acid in the reaction mixture. It is also found that for a given sulfuric acid concentration, for example 82 %, the ratio between the initiator nitrosulfuric acid and nitric acid of

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12 to 50 % , only changing the induction period of the reaction, which is shorter, the larger the ratio.

If one considers the nitrosy to be used at the beginning of the reaction If you want to reduce the amount of sulphurous acid, you can use start with a small amount of the reaction mixture, for example from a previous production and consists of sulfuric acid and nitrosulfuric acid, and then gradually during the introduction of the gaseous Sulfur dioxide the nitric acid and the sulfuric acid or a mixture of nitric acid in Allow sulfuric acid to flow in.

If the concentration of sulfuric acid is about 75 % , traces of nitrosylsulfuric acid are sufficient to initiate the reaction. The required small amount of nitrosylsulfuric acid can also be formed in situ. If a stream of sulfurous anhydride is introduced into a flask containing a solution of nitric acid in 75 pounds of sulfuric acid, no nitrosulfuric acid is formed. If one introduces oxygen or air, the reaction occurs immediately. the

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Formation of nitrosylsulfuric acid in this case is due to the following known reactions:

3 SO ₂ + 2 HNO ^ + 2 H ₂ O >> 3 H ₃ SO ₄ + 2 NO

(5) 2 NO + O ₂ > 2 NO

(6) 2 NO ₂ + H ₂ SO ₄ 1 NOHSO ₄ + HNO ₅

If 70 # sulfuric acid is used as the solvent for the nitric acid, the first nitrosylsulfuric acid is formed according to the equation

(7) SO ₂ + 2 HNO,} 2 NO ₂ + H ₃ SO ₄

The resulting NO ₂ reacts with the sulfuric acid to form nitrosylsulfuric acid according to equation (6).

The formation of nitrosylsulfuric acid in situ can also be effected by adding to the mixture of Sulfur and nitric acid, mineral salts of nitrous acid or organic salts of nitrous acid are added. These react with the sulfuric acid

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with the formation of nitrosylsulfuric acid. Likewise you can Introduce nitrous vapors into the mixture, which with the ! Sulfuric acid form nitrosylsulfuric acid (equation 2 or 3).

The preparation of nitrosylsulfuric acid according to the invention Process can be carried out within a wide temperature range. The reaction can take place at a temperature of -15 ° to 70 ° G ru However, it is not economical, at au low. Temperatures to work «and would also prefer to work high temperatures are avoided so that the "nitrosyl" Sulfuric acid does not decompose «The preferred one peräturberelch is + 15 to + 30 ° C *

The process allows the production of very slow sulfuric acid solutions. This royal concentration is only limited by the solubility of nitrosylsulfuric acid. The solubility again depends on. Q depends on the concentration of the sulfuric acid and on the temperature. For orientation purposes, the solubilities of the nitrosyl sulfuric acid are shown approximately in Table 2 below. The percentages are \ in percent by weight.

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Table 2 20 ° 50 ° 50 ° 20 ° Temperature ° C 97 97 90 76 Concentration of
Sulfuric acid %

Concentration of

Nitrosyl sulphate acid

in the saturated

Solution % 53 76 70 35

Weight ratio

Nitric acid:

Sulfuric acid % 56.3 158 115 27

The Solubility of Nitrosysulfuric Acid in Sulfuric Acid determines the amount of sulfuric acid or nitric acid to be used. The last line of the table gives the weight ratio between the amount of nitric acid and the amount of sulfuric acid for the in the values of concentration and reaction temperature given in the table.

The reaction mixture can also contain a larger amount of nitrosysulphuric acid than corresponds to the solubility ratio, because the presence of a small amount of nitrosysulphuric acid in the solid phase, dispersed in the mixture, is not disadvantageous for the reaction, provided that the Reaction mixture

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remains sufficiently fluid to allow easy diffusion of the sulfur dioxide gas. enable.

Instead of mixing sulfuric acid with nitric acid, this mixture can also be produced by letting nitrogen dioxide act on excess sulfuric acid according to equation (3). It is also possible to introduce sulfuric anhydride SO ₂ and nitrogen dioxide NO ₂ into excess sulfuric acid at the same time. Under these conditions the nitric acid formed according to equation (»is immediately converted into nitrosylsulphuric acid according to equation (1).

Incidentally, in the methods using the reaction (2), and in the case where the mixture of nitrogen oxides has a NO / NO ₂ molar ratio smaller than 1, that is, contains an excess of NO ₂ , resulting in the solution the nitrosylsulfuric acid in sulfuric acid contains nitric acid, this nitric acid can be converted into nitrosylsulfuric acid by the process according to the invention * This means a double advantage, namely the removal of the troublesome nitric acid and the increase in the yield of nitrosylsulfuric acid, based on the nitrogen oxides.

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The method according to the invention can be carried out in the most varied of ways. You can work batchwise and continuously. In the case of discontinuous operation, a stream of gaseous sulfuric anhydride can be passed into the suitable mixture of sulfuric acid, water, nitrosylsulfuric acid and nitric acid. But you can also start with a suitable mixture of the reactants and gradually add either nitric acid or a solution of nitric acid in sulfuric acid while introducing SOg in good time.

In order to bring about the mixing of the liquid phase with the SOg , methods can be used that are customary in reactions between a Qas and a liquid. If the method is continuous, the sulphurous anhydride and the mixture of sulfuric acid and nitric acid can be introduced at the same time. The dissolved reaction product flows off via an overflow.

A very sensitive indicator enables the end of the reaction between the SOg and the nitric acid to be determined when the nitric acid is completely converted

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the excess SO ₂ causes a purple color. As soon as this phenomenon occurs, it is important to interrupt the supply of _{SO 2 , because excess SO 2} destroys the nitrosyl sulfuric acid formed. In the discontinuous embodiments of the process in which the addition of the Reactionteil-

* ■ ■ -

If it takes place gradually, the color change to blue indicates a lack of nitric acid. When carried out continuously, the reaction mixture should be kept constant immediately before the changeover _{by adjusting the supply of SO 2 and nitric acid.}

The invention is explained in more detail below on the basis of exemplary embodiments.

example 1

The following are placed in a 500 ml gas washing bottle with a frit plate and thermometer: 250 g of 90% sulfuric acid, 100 g of nitrosylsulfuric acid and 50 g of 95% nitric acid (47.5 g of 100% HNO ₃ ). A stream of sulfurous anhydride is then passed in, the temperature being raised by means of external cooling

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keeps between 20 and 25 ° C and completely prevents the escape of gases at the outlet of the device. The end . the reaction is indicated by a change in the color of the reaction mass, which turns slightly blue-violet. At this moment the supply of sulfur dioxide is interrupted. 448 g of a 43.2 # nitrosyl sulfuric acid solution, corresponding to 193 * 7 g of nitrosyl sulfuric acid, are obtained. 93.7 g of nitrosysulfuric acid have thus been formed. The yield is 97 * 0 %, based on the nitric acid used.

. Example 2

In a / flask equipped with a powerful stirrer, a thermometer, a dropping funnel for introducing the reagents, a gas inlet at the bottom of the device and an outlet pipe for the unreacted gases as well as a downstream gas washing bottle filled with sulfuric acid, place 20 g of a 41.6 # nitrosylsulfuric acid solution in 93 # sulfuric acid. ■ While stirring, sulfur dioxide gas is introduced into the liquid and at the same time a solution of 1,248 g 95 # HNO ^ (l 185 g 100 # HNO,) and 3 366 g 93 # H ₂ SO is gradually added ^ add.

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The temperature is kept at 20 to 25 ° C. by external cooling. The S0 ₂ supply is regulated in such a way that no gas escapes and that the reaction mixture does not turn blue until the sulfuric acid-nitric acid solution has been completely added. When the entire sulfuric acid-nitric acid mixture has been introduced, which takes about 4 hours, and so that the nitro sylsulfuric acid solution contains practically no nitric acid, the introduction of sulfur dioxide is continued until a light blue-violet color appears, which can be achieved by adding a few Drops of nitric acid can disappear.

5836 g of a 4.0.4 # strength nitric / sulfuric acid solution are obtained, corresponding to 2360 g of nitrosylsulphuric acid. If one takes into account that 8 g of nitrosylsulfuric acid were used at the beginning, the result is a nitrosylsulfuric acid yield of 98.5 %.

Example ^

In a 3 liter flask equipped with a powerful stirrer, a thermometer, a dropping funnel, a gas inlet at the bottom of the device and an external step tube,

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filled

which is connected to a sulfuric acid / wash bottle one puts 450 g of 95 # nitric acid and 1,750 g of 97 # sulfuric acid.

The temperature is kept at 25 to 50 ° C by external cooling and the reactants are added in such a way that that the sulfur oxide gas is completely absorbed and the reaction mixture shows no blue color.

The introduction takes about 4 hours. Finally, 2,662 g of a 32.7 # nitrosysulphuric acid solution, corresponding to 872.5 g of NOHSOh, are obtained. 849 g of nitrosyl sulfuric acid were thus formed during the reaction, which corresponds to a yield of 98.5 % based on the nitric acid.

Example 4

In this example , the initiator nitrosulfuric acid and nitric acid are formed in situ.

In a 250 ml flask with a good stirrer, a thermometer, a dropper for introduction

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of the liquid nitrogen dioxide NO ₂ or N ₂ O ^, a gas inlet pipe and a gas outlet tube, 100 g of 90 # sulfuric acid are introduced and 25 g of liquid nitrogen dioxide are gradually added with stirring so that none at the outlet of the device Gas evolution occurs. The temperature is kept at 20 ° C. by external cooling. One obtains

g of a solution containing 33.6 g or 27 % nitrosylsulfuric acid and 16.7 g or 13.4 # HNO. The yield of nitrosylsulfuric acid and nitric acid, based on the nitrogen dioxide, is 97.5 %

The mixture is passed into the same device and into the reaction mixture obtained with thorough stirring and while keeping constant the temperature by means of external cooling to 20 to 25 ° C, the sulfurous anhydride in such a way, that no gas escapes at the outlet of the device. Sulfur dioxide is introduced until a faint purple color appears, which indicates the end of the reaction *,

The amount of the reaction mixture obtained is 14 l g. S ^ e contains 47.4 % or 67 g of nitrosylsulphuric acid. The yield, based on the nitrogen dioxide, is 97.2

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Example 5

In this example again a certain amount of nitrosy isulfuric acid is presented and one of the modes of representation of nitric acid in situ is illustrated.

140 g of a 12 # nitrosylsulfuric acid solution in 90 # is placed in a 250 ml flask equipped with a powerful stirrer, a thermometer, an inlet tube for sulfur dioxide, a dropping funnel for the addition of liquid nitrogen dioxide and a gas outlet tube Sulfuric acid (16.8 g NOHSO ^) a. Sulfur dioxide gas and liquid nitrogen dioxide NO ₂ or NgOh are then allowed to enter the reaction mass at the same time. The introduction of the reactants is regulated in such a way that no gas escapes and the reaction mixture does not turn blue. The temperature is kept at 20 to 25 ° C. with the aid of external cooling. After 25 g of nitrogen dioxide and the stoechiometrically corresponding amount of sulfur dioxide have been introduced, the reaction is terminated. 209 g of a 40.2 # nitrosylsulfuric acid solution, corresponding to 84.3 g of nitrosylsulfuric acid, are obtained. So 84.5 - 16.8 «67.5 g have formed. The yield is 97.8 %.

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Claims (1)

Claims 1. A process for the preparation of nitrosylsulfuric acid by reacting sulfuric anhydride with nitric acid, characterized in that the sulfuric anhydride is allowed to act on a solution of nitric acid in sulfuric acid which, as initiators, is nitrosylsulfuric acid or substances which form nitrosylsulfuric acid in situ, as well as water in in an amount such that the concentration of sulfuric acid based on the total amount of sulfuric acid and water is 70 to 97 % . 2. The method according to claim 1, characterized in that the weight ratio between the amount of nitric acid and the sum of the amount of sulfuric acid and water selects such that the nitrosylsulfuric acid, which by reaction of the sulfurous anhydride with the Nitric acid has been formed, in which sulfuric acid can dissolve « 2. The method according to claim 1 or 2, characterized marked j net that the concentration of sulfuric acid, related [ - - ■ ί based on the total amount of sulfuric acid and water, from 70 to 97 %, preferably from 75 to 97 % . ■■■ '' "2g- 009838/1659 4. The method according to claim 1, 2 or 3, characterized in that that the nitrososulphuric acid serving as initiator in trace amounts up to four times the amount of nitric acid present at the start of the reaction begins. 5. The method according to claim 1, 2 or J5, characterized in that inorganic or organic nitrites, nitrogen dioxide, nitrous oasis or molecular oxygen are used to form the nitrosylsulfuric acid in situ . 6. The method according to any one of the preceding claims, characterized in that for the preparation of the sulfuric acid-nitric acid solution containing the initiator nitrosylsulfuric acid, nitrogen dioxide is allowed to act on excess sulfuric acid and the conversion of nitric acid into nitrosylsulfuric acid is effected by introducing sulfurous anhydride. 7 · Method according to one of claims 1 to 5, daduroh characterized that one for the production of the Sohwefel- -23- 009838/1659 acid-nitric acid solution that acts as the initiator Serving nitr.osylsulfuric acid contains, progressively nitrogen dioxide to excess sulfuric acid can act and the conversion of nitric acid into nitrosylsulfuric acid according to its formation caused by the introduction of sulfurous anhydride. 8. The method according to any one of claims 1 to 5, characterized characterized in that one for the preparation of the sulfuric acid -nitric acid solution containing the nitrosylsulfuric acid contains a mixture of nitric oxide NO and excess nitrogen dioxide on sulfuric acid lets act in excess » 9 · Method according to one of the preceding claims, characterized in that one is at a temperature between - 15 and + 70 ° C, preferably between + and + 30 ° G, works. 10. The method according to any one of the preceding claims, characterized in that one works under normal or increased pressure, .Verfahreη according to one of the preceding claims, characterized in that the reaction is continuous is carried out. 009838/1659