JPS5930706A - Manufacture of iodine - Google Patents

Abstract

PURPOSE:To manufacture iodine industrially in a high yield without forming by- products such as nitrogen iodide and producing industrial waste by oxidizing ammonium iodide in an aqueous medium contg. a specified transition metallic compound and a specified weak acid and recovering and reutilizing the weak acid. CONSTITUTION:Ammonium iodide is oxidized with oxygen or air in an aqueous medium contg. a transition metallic compound other than vanadium compounds and a weak acid such as phosphoric acid or ammonium dihydrogenphosphate to manufacture molecular iodine. The transition metallic compound includes a copper compound. The preferred amount of the ammonium iodide is 10-20g per 100g water. The preferred oxidation temp. is room temp. -100 deg.C. It is preferable that the formed ammonium salt of the weak acid is thermally decomposed at 100-210 deg.C to recover the weak acid and to reutilize it in the generation of iodine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for oxidizing ammonium iodide to obtain iodine.

Iodine is widely used as an intermediate in organic synthesis, catalysts, medicines, health drugs, disinfectants, livestock feed additives, organic compound stabilizers, dyes, photoengraving, agricultural chemicals, rare metal scouring, and analytical reagents. It is a useful compound. It is generally obtained from saltpeter, a brine that comes with natural gas. Industrially, a method of oxidizing iodine anions contained in salt water with an aqueous solution of copper sulfate (■) and iron sulfate (nJ) is often used.

Since this method is usually carried out under strong acidic conditions, salts of strong acids and strong alkalis such as sodium sulfate are produced as by-products, which poses problems in their treatment.

Methods for obtaining iodine from ammonium iodide include an electrolytic method (described in German Patent No. 2,436,111 (Japanese Unexamined Patent Publication No. 53-50122)), an oxygen oxidation method ( Japanese Patent Publication No. 53-73489
(No. Publication), etc.

In the method using electrolysis (German Patent No. 2,436,111), the reaction is carried out in a dilute solution and a diaphragm is required, resulting in a large-scale apparatus and consuming a large amount of electricity. Therefore, it cannot be said that it is an industrially advantageous method. In the method using a cupric compound (Patent Publication No. 53-50122), since the reaction is stoichiometric, the cupric compound does not act as a catalyst and is disadvantageous for producing a large amount of iodine. In the method using oxygen oxidation (JP-A-53-73489), ammonium iodide is oxidized with oxygen in an ammonia aqueous solution using a copper compound as a catalyst to obtain iodine. In this method, the iodine production reaction is carried out under ammoniacal alkaline conditions, so the rate of iodine production is extremely slow, and as ammonia is produced along with the production of iodine, it is expected that the reaction will become even slower. . In addition, under ammoniacal alkaline conditions, the Chemistry Encyclopedia (Kyoritsu Shuppan,
Vol. 9, p. 447), it is clear that it is easy to produce explosive nitrogen iodide (and cannot be said to be industrially advantageous).

The present inventors had been considering a method to obtain hydrogen atoms by oxidizing ammonium iodide, but by combining a transition metal and a weak acid, it was possible to oxidize ammonium iodide in the presence of a molecular radical. The inventors have discovered that iodine can be obtained in high yield without producing by-products such as nitrogen iodide, and have arrived at the present invention.

That is, the present invention is based on the above findings, and when attempting to obtain molecular iodine by oxidizing ammonium iodide with oxygen or air, the oxidation reaction is carried out in a narcissus medium containing a transition metal compound and a weak acid. This is a method for producing iodine. %
In the present invention, a sufficient iodine production rate is obtained by using a weak acid, and after the generated iodine is extracted from the system or consumed by an appropriate reaction, the iodine is removed from the system. This method provides an extremely efficient method for obtaining iodine by thermally decomposing the generated ammonium salt of a weak acid, recovering the weak acid, and reusing it in the iodine production reaction.

The transition metal compound used in the present invention is preferably one selected from the group consisting of copper compounds.The reaction of the present invention is exemplified using a copper compound and anthonium dihydrogen phosphate. It is estimated that iodine is produced by the following reaction mechanism.

Cu? 10NI (4I ”: CuI 1NH4”Cu
"+ 2NH4I": Cu5 + 2NH4"
2CuI + TO, -1-2NH4I -1-Hρ→
2CuI, + 2NH40H2Cu5 →2CuI
10 If 2NH, OH+ 2NH4H, PO4 → 2 (boar,) 2H
PO, + 2H20 Therefore, the copper compound used as a catalyst is considered to be simply a source of copper ions, and the type of anion side of the fine compound is not related to the essence of the reaction (although there are no special restrictions). The fine compound is not particularly limited and most copper compounds can be used, including cuprous iodide, cuprous chloride, cuprous oxide, cuprous bromide, cuprous cyanide, Copper sulfate, cupric chloride, cupric hydroxide, cupric oxide, cupric bromide, cupric phosphate, copper nitrate, copper carbonate, copper acetate, and the like are preferred.

The amount of copper compound used is not particularly limited, but in practice it is 3 x 10-4 to 0.3 mql per 10,054 ml of water.
is preferred. Furthermore, the transition metal compound may or may not be dissolved in the aqueous medium.

The amount of ammonium iodide used is not particularly limited, but
The higher the concentration in the aqueous medium, the faster the production rate of iodine (
There is a tendency to Practically preferred is 10 to 200 Li- per 100 LiP of water.

As for the oxygen used, not only oxygen gas but also air can be used to achieve the purpose of this method.

The oxygen pressure or partial pressure is not particularly limited, but the higher the pressure, the faster the iodine production rate tends to be.

Practically preferred range is 02 to 10 atm.

The oxidation reaction is fast at high temperatures, but if the temperature is too high, the ammonia salt of a weak acid will decompose and the ammonia concentration in the system will increase, so the oxidation will be slow.
00°C.

Weak acid is used to react with ammonia produced by the iodine production reaction, reduce noise in the system, accelerate the oxidation reaction rate, and prevent the production of nitrogen iodide. It is preferable to thermally decompose the ammonium salt of a weak acid, recover the weak acid, and reuse it in the iodine generation reaction.The weak acid used may be one that releases ammonia when the ammonium salt is heated.
Inorganic acids such as phosphoric acid, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, boric acid, arsenic acid, chromic acid, telluric acid, silicic acid, organic acids such as acetic acid and globionic acid,
Preferred are phosphoric acid, ammonium dihydrogen phosphate, and organic acids. Furthermore, in the case of ammonium dihydrogen phosphate, heating the ammonium salt, ammonium phosphate-hydrogen, releases ammonia quantitatively in a short period of time, and returns to ammonium dihydrogen phosphate, which is particularly preferred.

In order to recover the weak acid in the present invention, the generated iodine is removed from the system by extraction with ether or a suitable iodine consumption reaction, and then the aqueous medium containing the generated ammonium salt of the weak acid is heated. good. The weak acid recovered here can be used again as a raw material for the iodine production reaction, and there is no particular need to add new acid. The higher the decomposition temperature of the ammonium salt of a weak acid, the better the decomposition rate and decomposition rate, and is preferably 100 to 210°C.

The aqueous medium used in the present invention is mainly water alone, but substances that substantially react with iodine in this system, such as benzene and chlorobenzene, can be used in combination with water. The hydrogen ion concentration of the aqueous medium is not limited as it varies depending on the acid used and conditions, but the iodine production rate tends to be faster when the hydrogen ion concentration is higher.

The method of the present invention has a fast production rate of iodine (high yield,
The weak acid can be recovered and reused, and there are no by-products such as nitrogen iodide (this can be said to be an extremely advantageous industrial method for producing iodine as it does not generate industrial waste). In addition, in the method of the present invention, if the iodination reaction is performed at the same time as iodine is generated, iodine can be purified and isolated (
, it can also be applied to methods for obtaining useful iodides. Furthermore, since ammonia is generated when the weak acid is recovered, it is possible to recover this ammonia and use it for other purposes if necessary.

The present invention will be explained in more detail with reference to Examples below.

In the following examples, it is assumed that the oxidation reaction follows the formula (1) in 1 when ammonium dihydrogen phosphate is used as an example of a weak acid, and the yield of iodine was determined from the formula (2).

-402+2NLI+2NILH! PO4. u+also(
MacJ+I2+2(NH,)J(P o, 10HtO(1
) (2) Furthermore, assuming that the thermal decomposition of a weak acid follows equation (3) when ammonium dihydrogen phosphate is used as the weak acid, the recovery rate of the weak acid was determined from equation (4).

(NH4) 2I (P04→N) M H, PO, 10■, (3
) Calculations were also performed using equation (21, ('1)) when other weak acids were used.

Example 1 (1) Generation of iodine In a 50 Q ml pressure-resistant glass autoclave, ammonium iodide 300 y-(2.07 mol) and iodide steel 5
t (0,0263 molJ), ammonium dihydrogen phosphate 100iiL (0,870 mol), pure water 20027
2A! The reaction was carried out under conditions of an oxygen pressure of 2 to 5 Φ (gauge pressure) and a temperature of 50° C. under slow stirring. Oxygen has a pressure of 5
k117′cT? At the time when it was reduced from 2 kv/al,
The amount was again supplied up to 5 kg/d. After 7 hours, the amount of iodine generated was determined using a 0.1N aqueous sodium thiosulfate solution and found to be 77.37 (0,305 mol). The yield of iodine was 70%.

(2) Recovery of weak acid After adding 600 ryIl of pure water to the iodine aqueous solution obtained in (1), extract the iodine with diethyl ether in Step 11 for 3 minutes.
After repeated tests, almost all of the generated iodine could be recovered.

Furthermore, a trace amount of iodine remaining in the aqueous solution was reduced with sodium thiosulfate to obtain an aqueous solution containing no molecular iodine.

This aqueous solution was charged into a 5US316 autoclave, heated and stirred at 170 to 210°C under a nitrogen atmosphere, and ammonia was released along with water vapor from a nozzle installed at the top of the autoclave. Approximately 600cc was obtained. The ammonia generated is I
When quantified with N sulfuric acid aqueous solution, it was 10.4 ji'(0,
612 mol). Ammonia recovery rate is 100
%Met.

(3) Ammonium iodide 8B7 (0,6
07 mol) was added, and using a pressure-resistant Galanu autoclave, pressurized with oxygen at 2 to 100 g (gauge pressure).
When the oxidation reaction was carried out again at a temperature of 50° C., iodine was obtained in a yield of 50% in 4 hours.

Examples 2 to 4 Reactions were carried out in the same manner as in Example 1 using the compositions shown in Table 1. The obtained results are shown in Figure 1.

Comparative Examples 1-2 With the composition shown in Table 1 without using a weak acid during the oxidation reaction,
When the reaction was carried out in the same manner as in Example 1 (1),
The amount of iodine produced was less than or equal to the amount of catalyst used. At the start of the reaction, the system was neutral, but as iodine was produced, it became alkaline. In Comparative Example 2, nitrogen iodide was produced, and when dried, it exploded upon a slight impact.

(Hereinafter referred to as residual colors) Examples 5 to 8 A reaction was carried out in the same manner as in Example 1 using the compositions shown in Table 2. The results obtained are shown in Table 2.

Examples 9 to 13 Using the composition shown in Section 2, reactions were carried out using the method I in the same manner as in Example 1 (1). The obtained results are shown in Table 2.0 (The following is a blank space) Procedural amendment (voluntary) Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office, dated July 1982. Indication of the case: Patent application No. 13785, filed in 1982.
00,000 Z Title of the invention Process for producing iodine a Relationship to the case of the person making the amendment Patent applicant 1-2-6-4 Dojimahama, Kita-ku, Osaka-shi, Osaka Prefecture, “Scope of Claims” in Statement of Subject of Amendment A and “detailed description of the invention”
Column 5, Contents of amendment (1) Change the "Claims" on pages 1 to 2 of the application specification to
Please make corrections as shown in the attached sheet.

(2) Correct "transition metal" in line 5 of No. 4 of the same statement to "transition metal compound."

(3) On page 4, line 14, "In an aqueous medium containing a transfer metal compound and a weak acid" was changed to "In an aqueous medium containing a transfer metal compound (excluding vanadium compounds) and a weak acid". correct.

(4) "Ammonium salt" on page 6, line 17 is corrected to "ammonium salt."

(5) "Table 1" on page 13 of the same page is corrected in the attached [Table IJK.

Claims 1. Method 2 for producing iodine, characterized in that when ammonium iodide is oxidized with oxygen or air to obtain molecular iodine, the oxidation reaction is carried out in an aqueous medium containing a transition metal acid, the transition metal compound is a copper compound Patent 3, characterized in that the weak acid is at least one selected from the group consisting of phosphoric acid, ifI! selected from the group consisting of phosphoric acid, ammonium dihydrate, and organic acids; A manufacturing method 4 according to claim 1, characterized in that the oxidation reaction is carried out at a temperature of 100° C. or lower, a manufacturing method 5 according to claim 1, characterized in that the weak acid is , at least in part, is a weak acid obtained by thermally decomposing an ammonium salt of a weak acid generated in an oxidation reaction. 100
The manufacturing method according to claim 5, characterized in that the manufacturing method is carried out at a temperature of ~210°C.

Claims (1)

[Claims] 1. Production of iodine, characterized in that when ammonium iodide is oxidized with oxygen or air to obtain molecular iodine, the oxidation reaction is carried out in an aqueous medium containing a transition metal compound and a weak acid. Method 2: The transition metal compound is at least one selected from the group consisting of copper compounds.The manufacturing method 3 according to claim 1, wherein the weak acid is phosphoric acid, ammonium dihydrogen phosphate and A manufacturing method according to claim 1, characterized in that the oxidation reaction is carried out at a temperature of 100° C. or lower. A manufacturing method 5 according to claim 1, wherein the weak acid is at least partially a weak acid obtained by thermally decomposing an ammonium salt of a weak acid generated in an oxidation reaction. Thermal decomposition of ammonium salts of weak acids is carried out at temperatures of 100~
The manufacturing method according to claim 5, characterized in that the manufacturing method is carried out at 210°C.