JPH0859205A - Production of hydroiodic acid - Google Patents

Abstract

PURPOSE: To provide a method for producing hydroiodic acid in high conversion ratio of raw material iodine available even in production of highly concentrated hydroiodic acid, capable of extremely suppressing evaporation of raw material iodine during reaction. CONSTITUTION: Iodine is reacted with an aqueous solution of a reducing agent (e.g. phosphorous acid, hypophosphorous acid, pyrophosphoric acid, pyrophosphorous acid or isohypophosphoric acid) by continuously or intermittently adding iodine. After the reaction is over, hydroiodic acid is distilled from the reaction solution.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing hydroiodic acid. Hydroiodic acid is a useful substance used as a raw material for synthesizing various iodides, a pharmaceutical intermediate, or a reducing agent.

[0002]

Hydroiodic acid, which is an aqueous solution of hydrogen iodide, can be produced by adding iodine to a suspension of red phosphorus or by feeding hydrogen sulfide gas into the suspension of iodine. However, since hydrogen sulfide is a poisonous substance, red phosphorus is a dangerous substance, and it is easily affected by impurities contained in it, industrially, it is usually a mixed solution or suspension of iodine and water. In addition, a reducing agent such as hypophosphorous acid is added, or iodine is reduced while heating a mixed solution of these, and then hydroiodic acid is distilled from the reaction solution by distillation. The method is commonly practiced.

However, in the above-mentioned conventional production method, there is a problem that iodine vapor is very likely to be generated from the liquid during the reaction, and iodine in the raw material is likely to be lost. However, special abatement equipment is usually attached to prevent harmful emission of iodine out of the system. Furthermore, during the reduction reaction, the reaction solution often generates abrupt heat, which is very difficult to control, and there is a risk that the reaction will run away.

When the reducing agent is added after the iodine is completely dissolved in water, the above-mentioned risk of iodine vapor generation and reaction runaway is mitigated, but the solubility of iodine in water is reduced. Very small (1.06 g / l,
20 ° C), the volumetric efficiency deteriorates, and a large amount of dilute hydroiodic acid distills out during the distillation after the reaction, which makes it very difficult to obtain a high concentration of hydroiodic acid. Occurs.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing hydroiodic acid which does not have the drawbacks of the conventional methods described above. That is, it is an object to provide a production method in which iodine vapor is not generated during the reaction and a high concentration of hydroiodic acid can be safely obtained with a high yield.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the inventors of the present invention have conducted diligent research and found that a reducing agent is added to a mixed solution or suspension of iodine and water as in the conventional method. Alternatively, it is a very effective method to carry out the reaction by continuously or intermittently adding iodine to an aqueous solution of a reducing agent, rather than heating the mixed solution to react. Heading out, the present invention has been completed.

That is, the present invention provides an aqueous solution of a reducing agent,
A method for producing hydriodic acid is characterized in that iodine is continuously or intermittently added to carry out the reaction, and after the reaction, hydriodic acid is distilled from the reaction solution by distillation.

In general, when iodine is reduced to produce hydroiodic acid, when iodine is added all at once to an aqueous solution of a reducing agent and reacted, heat is generated violently and unreacted iodine is evaporated from the solution. It's easy to do. This phenomenon occurs almost similarly when a reducing agent is added to an aqueous solution or suspension containing a large amount of iodine. However, as in the method of the present invention, when iodine is continuously or intermittently added to an aqueous solution of a reducing agent, heat is not suddenly generated, and iodine added under mild conditions is reduced very quickly, It is possible to significantly suppress the evaporation of iodine. Therefore, the effect of suppressing the loss of iodine is particularly remarkable, and hydriodic acid having a high purity can be obtained in a high yield only by adding a predetermined amount of the raw materials and reacting them.

The reducing agents usable in the method of the present invention include phosphorous acid, hypophosphorous acid, hypodiphosphoric acid, diphosphorous acid,
Sulfurous acid, pyrophosphoric acid, pyrophosphorous acid, isohypophosphoric acid, diphosphoric acid, hypophosphoric acid, oxalic acid, formic acid, malonic acid, lactic acid,
A wide range of reducing compounds such as pyruvic acid and ascorbic acid can be mentioned, and two or more compounds may be used. Among these, phosphorous acid,
When hypophosphorous acid, pyrophosphoric acid, pyrophosphorous acid, or isophosphoric acid is used, it is highly effective to obtain the product in high yield, and further, hypophosphorous acid, phosphorous acid, or pyrophosphoric acid is used. When used, the reaction temperature during the reduction reaction can be controlled more easily, and the effect of suppressing the loss of iodine is particularly remarkable.

The amount of reducing agent used in the method of the present invention is
It may be equivalent or more, preferably 1.0 to 1.5 equivalents, with respect to iodine used in the reaction. This amount
If it is less than 1.0 equivalent, unreacted iodine remains in the reaction solution, resulting in a poor yield. Further, although there is no particular problem even if it is used in excess of 1.5 equivalents, it is uneconomical because it has no further effect.

The amount of the reaction solution used in the production method of the present invention is appropriately such that the concentration of iodine used in the reaction is 1 to 57% by weight, preferably 40 to 57% by weight. If the amount is such that the concentration becomes 57% by weight or more, it is not preferable because it does not azeotrope during distillation and the proportion of hydrogen iodide lost as a gas increases.

In the production method of the present invention, the reaction is carried out while adding iodine to the aqueous solution of the reducing agent, but the reaction temperature is usually 40-100 ° C. under normal pressure, and more preferably 50-100 ° C. 70 ° C. If the reaction temperature is lower than 40 ° C, the reaction progresses extremely slowly, and if the reaction temperature is higher than 100 ° C, iodine vapor is likely to be generated from the reaction solution, which is not preferable.

In the method of the present invention, iodine may be added to the reducing agent aqueous solution continuously or intermittently. In addition, the rate of addition varies depending on the production amount, reaction temperature, reaction vessel, etc., so it cannot be stated unconditionally, but usually it should be added at such a rate that the reaction solution does not show a dark brown color even at best. It is generally preferable to add it for at least 1 hour or more.

After the addition of iodine is completed, the reaction solution is preferably aged to complete the reaction. The time required for this aging depends on the temperature and is not constant, but it is usually 10 minutes or longer, preferably 30 minutes or longer. When phosphorous acid, hypophosphorous acid, pyrophosphoric acid, pyrophosphorous acid, or isophosphorous acid is used as the reducing agent, it is more preferable to age the reaction solution at a temperature of 70 to 100 ° C. .
This is because the reducing action associated with these self-decompositions is particularly remarkable at temperatures in this range.

When unreacted iodine is present after the reaction, that is, when the reaction solution is colored, the unreacted iodine can be easily converted into hydrogen iodide by adding a reducing agent. Can be

After the reaction solution is aged, the solution is distilled to distill the desired product, whereby hydroiodic acid free from impurities or impurities can be obtained in good yield. Distillation of the reaction solution is possible under a wide range of conditions from reduced pressure to increased pressure.
Generally, it is performed at about 20 to 760 mmHg.

[0017]

EXAMPLES Hereinafter, the production method of the present invention will be described in more detail with reference to examples. In the following, all "%" are based on weight.

Example 1 101.9 g (0.52 mol) of 34% aqueous solution of hypophosphorous acid and water 144.2
g in a 500 ml flask and heated to 50 ° C with stirring,
Add 253.8% iodine to this while maintaining the temperature of the solution at 50-60 ° C.
g (1 mol) was added continuously over 1.5 hours. After the addition was complete, the solution was left at 80 ° C. for 2 hours. At this time, since the solution was colored yellow, 1 g of hypophosphorous acid was added to make it transparent. Next, the solution was distilled under a pressure of 50 mmHg to obtain a fraction between 60 and 63 ° C, which was used as a product. The product obtained has a concentration of 57%
Of hydroiodic acid of 424.3 g, and the yield was 92.8% with respect to the added iodine.

Example 2 In Example 1, 253.8 g of iodine was divided into 5 portions and added in equal amounts at 15-minute intervals. That is, 50.76 g each for 15
All were operated in the same manner except that they were charged at minute intervals. as a result,
The obtained product was 420.6 g of hydroiodic acid having a concentration of 57%, and the yield was 92.0%.

Example 3 93.0 g (1.13 mol) of phosphorous acid and 195.0 g of water were placed in a 500 ml flask and heated to 50 ° C. with stirring, and then the temperature of the solution was adjusted to 50.
While maintaining the temperature at -60 ℃, add 253.8g (1 mol) of iodine to it.
Added continuously over 1.5 hours. After the addition is complete,
It was left at 80 ° C for 2 hours. At this time, since the solution was colored yellow, 1 g of phosphorous acid was added to make it transparent. Next, the solution was distilled under a pressure of 50 mmHg to obtain a fraction between 60 and 63 ° C, which was used as a product. The product obtained had a hydroiodic acid concentration of 57%.
It was 12.0 g, and the yield was 91.8% with respect to the added iodine.

Example 4 500 ml of 210.4 g (1.18 mol) of pyrophosphoric acid and 195.0 g of water
The mixture was placed in a flask and heated to 50 ° C. with stirring, and then 253.8 g (1 mol) of iodine was continuously added to this while keeping the temperature of the solution at 50 to 60 ° C. over 1.5 hours. After the addition is complete
The solution was left at 80 ° C. for 2 hours. Since the solution was colored yellow at this time, 1 g of pyrophosphoric acid was added to make it transparent. Next, the solution was distilled under a pressure of 50 mmHg to obtain a fraction between 60 and 63 ° C, which was used as a product. The obtained product was 413.3 g of hydroiodic acid with a concentration of 57%, and the yield was 9 based on the added iodine.
It was 2.1%.

Example 5 101.9 g (0.52 mol) of 34% aqueous solution of hypophosphorous acid and 144.2 of water
g into a 500 ml flask and heating to 40 ° C with stirring,
Add iodine 253.8 to this while maintaining the temperature of the solution at 40-50 ° C.
g (1 mol) was added continuously over 1.5 hours. After the addition was complete, the solution was left at 70 ° C. for 2 hours. Since the reaction solution was colored yellow at this time, 1 g of hypophosphorous acid was added to make it transparent. Next, the solution is distilled under a pressure of 50 mmHg and 60-63 ° C.
The fraction between the two was obtained and used as the product. The product obtained has a concentration of 57
% Hydroiodic acid was 424.3 g, and the yield was 90.8% based on the added iodine.

Example 6 In Example 1, 24.2 g of 144.2 g of water charged in a flask was added.
The same operation was performed except that the amount was 44.2 g. As a result, the obtained product was 530.2% hydroiodic acid with a concentration of 44.9%.
The yield was 93.8% with respect to the added iodine.

Example 7 200.0 g (1.03 mol) of 34% aqueous solution of hypophosphorous acid and 100.1 of water
g in a 500 ml flask and heated to 50 ° C with stirring,
Add 253.8% iodine to this while maintaining the temperature of the solution at 50-60 ° C.
g (1 mol) was added continuously over 1.5 hours. After the addition was complete, the solution was left at 80 ° C. for 2 hours. Next, the solution was distilled as in Example 1 to obtain a product. The resulting product has a concentration
It was 419.7 g of 57% hydroiodic acid, and the yield was 91.8%.

Comparative Example 1 In Example 1, iodine was also added to the flask from the beginning without continuously adding iodine, and the iodine was directly added to the flask.
The temperature was raised to 0 ° C., and the reaction was performed for 2 hours while maintaining the temperature. During this period, a large amount of iodine vapor that was evaporated from the solution was observed. Next, the solution was distilled as in Example 1 to obtain a product. The product obtained has a hydroiodic acid content of 424.3
The yield was 79.7%.

Comparative Example 2 253.8 g (1 mol) of iodine and 144.2 g of water were placed in a 500 ml flask and 101.9 g (0.52 mol) of 34% aqueous solution of hypophosphorous acid was added thereto while maintaining the temperature at 50 to 60 ° C. for 1.5 hours. And added continuously (that is, the mode of addition of hypophosphorous acid and iodine in Example 1 was reversed). Even during this addition, a large amount of iodine vapor evaporated from the solution was observed as in Comparative Example 1. Next, the solution was distilled as in Example 1 to obtain a product. The obtained product was 181.1 g of hydroiodic acid having a concentration of 57%, and the yield was 70.8%.

[0027]

As described in detail above, according to the method for producing hydroiodic acid of the present invention, iodine is continuously or intermittently added to an aqueous solution of a reducing agent to cause a reaction, and then the reaction solution is distilled. Even when obtaining a high-concentration target product, there is almost no loss of iodine used, and a product can be obtained with a high conversion rate. Further, since it is possible to prevent the release of iodine out of the system, it is possible to greatly reduce the equipment for removing the harm. Therefore, when industrially producing hydroiodic acid, the production method of the present invention is preferably used.

Claims (3)

[Claims] 1. A hydroiodic acid characterized in that iodine is continuously or intermittently added to an aqueous solution of a reducing agent to carry out a reaction, and hydroiodic acid is distilled from the reaction solution by distillation after the reaction. Manufacturing method. 2. The production of hydriodic acid according to claim 1, wherein the reducing agent is one or more selected from phosphorous acid, hypophosphorous acid, pyrophosphoric acid, pyrophosphorous acid and isohypophosphoric acid. Method. 3. The method for producing hydroiodic acid according to claim 1, wherein the reaction is carried out at a temperature of 40 to 100 ° C.