JPS5842122B2 - Thermochemical production method of caustic alkali and halogen - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for thermochemically producing alkali and halogen from an alkali metal halide, the purpose of which is to use an energy source completely different from conventional methods. The aim is to manufacture these products efficiently.

Recently, from the perspective of energy conservation or effective use of energy, there has been a great deal of interest in chemical industrial processes that use thermal energy directly without converting it into electrical energy, and the development of industrial methods for this is an important technology. It has become a challenge.

Up until now, electrolysis and ion-exchange membrane methods have been the main methods for producing chlorine and alkali such as sodium chloride and potassium chloride from alkali metal halides such as sodium chloride and potassium chloride. However, all of these methods require the use of electrical energy, and there is no practical method that uses only thermal energy.

The present invention provides a novel chemical process that uses only thermal energy as an energy source in producing the corresponding hard alkalis such as sodium hydroxide and potassium hydroxide from alkali metal halides such as sodium chloride and potassium chloride. The purpose is to

That is, according to the present invention, an alkali metal halide is reacted with nitrogen dioxide to produce a halogen and an alkali nitrite, and then the produced alkali nitrite is reacted with water and oxygen to produce a strong alkali. Provided is a method for producing a strong alkali and a halogen, which is characterized by:

The method of the present invention essentially consists of two reactions. In addition to the alkali metal halide, the method of the present invention only requires heat, water, which exists infinitely, and oxygen in the air, to be used as raw materials. can be produced and all other materials produced in the process can be recycled.

In the present invention, nitrogen dioxide is used as a decomposing agent for alkali metal halides.

This nitrogen dioxide reacts with alkali metal halides,
It generates halogen and is itself converted to alkali nitrite.

MX+NO2→ MNO2+'/2X2 (
1) (In the formula, M represents an alkali metal such as sodium or potassium, and X represents a halogen atom such as chlorine, bromine, iodine, or fluorine.) This reaction is efficient at temperatures above room temperature, preferably from 150 to 350°C. progresses well.

According to the present invention, the alkali nitrite IJ (MNO,) obtained in the above reaction (1) is reacted with water and oxygen,
Generates alkali.

In this case, nitrogen dioxide is produced as a by-product.

MN02+1/2H20-1-1/40. ．． 40H+N
O2 (2) This reaction is carried out under heating, and the heating temperature varies depending on the type of nitrite IJ (MNO,), but usually a temperature of 350°C or higher is adopted.
In particular, in the case of sodium nitrite, a temperature range of about 400 DEG C. or higher, preferably from 500 to 900 DEG C., and in the case of potassium nitrite, a temperature range of about 350 DEG C. or higher, preferably from 45-0 DEG C. to 900 DEG C., is employed.

The alkali produced in this reaction (2) is recovered as a commercial product, but the nitrogen dioxide produced at the same time is recycled and used again as a reaction raw material in the reaction (1).

In the present invention, reaction (1) involves reacting gaseous NO2 with solid MX, and reaction (2) reacting gaseous water vapor and oxygen with liquid MNo2. Since the reaction proceeds in this reaction system, it is extremely easy to separate and recover the products.

In the present invention, nitrogen dioxide can also be used in combination with oxygen in the presence of water as a decomposing agent for alkali metal halides.

The reaction in this case is shown by the following formula.

MX+NO2+ 1/202→MNO3+ 1/2CA
'2 (3) This reaction is carried out at a temperature of 100°C or less, preferably in the temperature range of room temperature to 50'C.

This reaction is advantageously carried out by simultaneously acting nitrogen dioxide and oxygen on a saturated aqueous solution Q of an alkali metal halide.

According to the present invention, the alkali nitrate produced in the reaction (3) is reacted with water to produce a hydroalkali.

MN03+1/2H20-)MOH+NO2+1/40
2 (4) Reaction (4) is carried out under heating, and the heating temperature varies depending on the type of alkali nitrate, but is generally about 350'C or higher, especially in the case of sodium nitrate.
A temperature range of about 400°C or higher, preferably 500-900°C, and in the case of potassium nitrate, a temperature range of about 350°C or higher, preferably 450-900°C, is employed.

As is clear from the foregoing, the process of the present invention is carried out essentially by only two reactions, and the raw materials consumed are essentially only the alkali metal halide, water and oxygen, with no other reaction raw materials being used. All of them are recycled and used in the reaction system in an appropriate form.

Therefore, only the alkali and halogen produced by the decomposition of the alkali metal halide are extracted from the reaction system, and no other by-products are discharged from the reaction system, causing no chemical waste pollution problem. .

Furthermore, since the present invention directly uses thermal energy to decompose alkali metal halides, the production of alkalis and halogens is more efficient than conventional methods in which thermal energy is converted into electrical energy and then carried out. It can significantly reduce costs and has great industrial significance.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Eleven common salt solids were placed in a platinum boat and placed in a quartz tube installed in a circular electric furnace, and nitrogen dioxide gas was passed through the boat while heating it to about 240°C.

The purity of the nitrogen dioxide gas in the cylinder was 99 or higher.

Chlorine gas generated by the reaction was dissolved in water and collected.

The reaction was carried out for 1 hour. During this time, the chlorine trapped in the water was decomposed with sodium thiosulfate to form chlorine ions, which were quantified.

As a result, the amount of chlorine gas generated by the reaction was 4.919.

This is approximately 8% of the salt used in the reaction as the first raw material.
This means that 1% was decomposed and recovered as chlorine.

Next, the solid in the platinum board was placed as it was in an electric furnace, the flow of nitrogen dioxide was stopped, the temperature was raised to 600°C, and water vapor and air were passed through to cause a reaction.

After reacting for 1 hour, the platinum board was allowed to cool, and the amount of sodium hydroxide produced in the platinum board was determined to be 5.00 g.

This means that 73% of the common salt that was used as the initial raw material for the reaction decomposed to produce hydric soda.

Example 2 A reaction was carried out by blowing nitrogen dioxide and air into a saturated aqueous solution in which 11 common salts were dissolved.

The reaction temperature was about 40°C for 1 hour.

The chlorine gas generated by the reaction is absorbed into water, and after the reaction,
It was decomposed with sodium thiosulfate to form chloride ions and quantified.

As a result, the amount of chlorine gas generated by the reaction was 4.6 g.

This means that approximately 75 parts of the common salt that was used as the initial raw material for the reaction was decomposed and recovered as chlorine.

Next, the aqueous solution after expelling the chlorine gas was transferred into a platinum furnace, placed in an alumina tube installed in a circular electric furnace, and the temperature was gradually raised.

When the temperature reached 600°C, it was kept constant and water vapor was allowed to flow at the same time.

The reaction started at about 400°C, but in this example it started at 600°C.
The mixture was reacted for 1 hour.

Thereafter, the amount of sodium hydroxide produced in the platinum boat after cooling was determined to be 4.3 g.

This is approximately 6% of the salt used in the reaction as the first raw material.
This means that part 3 decomposed and produced hydric soda.

Example 3 11 potassium chloride solids were placed in a platinum boat and placed in a quartz tube installed in a circular electric furnace, and nitrogen dioxide gas was passed through the boat while heating it to about 240°C.

The nitrogen dioxide gas had a purity of 99% or more when packed in the cylinder.

Chlorine gas generated by the reaction was dissolved in water and collected.

The reaction was carried out for 1 hour. During this time, the chlorine collected in the water is decomposed with thiosulfuric acid and turned into chlorine ions.
This was quantified.

As a result, the chlorine gas generated by the reaction was 4.05,9
Met.

This is approximately 8% of the salt used in the reaction as the first raw material.
This means that Section 5 was decomposed and recovered as chlorine.

Next, the solid in the platinum boat was placed as it was in an electric furnace, the flow of nitrogen dioxide was stopped, the temperature was raised to 600°C, and water vapor and air were passed through to cause a reaction.

After reacting for 1 hour, the solution was allowed to cool and the amount of potassium produced in the platinum boat was quantified and found to be 5.64.9.

This means that 75% of the common salt used as the initial raw material for the reaction decomposed to produce potassium potassium.

Example 4 A reaction was carried out by blowing nitrogen dioxide and air into a saturated aqueous solution in which 10 g of potassium chloride was dissolved.

The reaction temperature was about 40°C for 1 hour. The chlorine gas produced by the reaction was absorbed into water, and after the reaction, it was decomposed with sodium thiosulfate to form chlorine ions, which were quantified.

As a result, the amount of chlorine gas generated by the reaction was 3.2i.

This means that approximately 68 parts of the common salt that was used as the initial raw material for the reaction was decomposed and recovered as chlorine.

Next, the aqueous solution after releasing the chlorine gas is transferred into a platinum boat and placed in an alumina tube installed in an annular electric furnace.
The temperature was gradually increased.

When the temperature reached 600°C, it was kept constant and water vapor was allowed to flow at the same time.

The reaction started at about 350°C, but in this example it started at 600°C.
The mixture was reacted for 1 hour.

Thereafter, the amount of potassium produced in the platinum boat after cooling was determined to be 4.43 g.

This means that about 59o;b of potassium chloride, which was used as the initial raw material for the reaction, decomposed to produce active potassium.

Claims (1)

[Claims] 1. In thermochemically decomposing an alkali metal halide, the alkali metal halide is reacted with nitrogen dioxide to produce a halogen and an alkali nitrite, and the resulting alkali nitrite is mixed with water. A method for thermochemically producing a hydroalkali and a halogen, which is characterized by reacting with oxygen to produce a hydroalkali. 2. When decomposing an alkali metal halide thermochemically, an aqueous solution of the alkali metal halide is reacted with nitrogen dioxide and oxygen to generate a halogen and an alkali nitrate, and the resulting alkali nitrate is reacted with water to decompose the alkali metal halide. 1. A method for thermochemically producing a hydroalkali and a halogen, which is characterized by producing a hydroalkali.