JP3425612B2 - Manufacturing method of caustic soda - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing caustic soda which uses sodium chloride as a raw material but does not co-produce chlorine.

[0002]

BACKGROUND OF THE INVENTION Caustic soda has a wide range of uses such as synthetic fiber and synthetic resin production, dyes and intermediates, soap production, petroleum refining and pulp production, and has a large demand.

Most of the present methods for producing caustic soda are methods in which caustic soda and chlorine are co-produced by electrolyzing sodium chloride. Therefore, the balance between supply and demand of caustic soda and chlorine is important.

However, in recent years, due to the destruction of the ozone layer by chlorofluorocarbons, the importance of chlorine can be seen to be more important due to environmental problems, and it is expected that it will become increasingly difficult to maintain the balance between supply and demand of caustic soda and chlorine. It If the supply and demand of chlorine decreases and the supply and demand balance of caustic soda and chlorine cannot be maintained, it will be necessary to safely treat surplus chlorine, and chlorination will cost a considerable amount. The manufacturing method of causes a problem in economic efficiency. Therefore, if the supply and demand balance of caustic soda and chlorine cannot be maintained, a method for producing caustic soda that does not co-produce chlorine is required.

However, it is extremely difficult if the conventional caustic soda manufacturing technology can cope with the situation when the demand for chlorine is drastically reduced. This is because, as described above, chlorine is inevitably co-produced in the conventional technique of producing sodium hydroxide by electrolyzing sodium chloride. Moreover, the amount is enormous, equivalent to the caustic soda produced. It is also extremely difficult to control the amount of chlorine produced by conventional techniques. Therefore, in conclusion, it is almost impossible to produce caustic soda without co-producing chlorine with the conventional caustic soda production technology.

[0006]

The problem to be solved by the present invention is that sodium hydroxide is used as a raw material, but caustic soda is produced without co-producing chlorine.

[0007]

The present invention uses sodium chloride as a raw material and produces caustic soda without co-producing chlorine. Soluble nitrate which forms an insoluble chloride is reacted with sodium chloride in an aqueous solution. To generate sodium nitrate and insoluble chloride, and to cause sodium nitrate to chemically react with metallic copper to generate sodium oxide, while to cause insoluble chloride to react with hydrogen thermochemically to generate hydrogen chloride. In addition to this, copper oxide, nitric oxide, oxygen, and the reduced metal by-produced in each reaction are subjected to thermochemical treatment to regenerate metallic copper and nitrate. The most important feature is the cyclic use.

[0008]

The soluble nitrate forming an insoluble chloride disclosed in the present invention means a metal salt in which a chloride is insoluble but a nitrate is soluble in a metal salt. Examples of such metal salts include silver and lead compounds. Hereinafter, the present invention will be described in detail with respect to a silver compound.

In the present invention, sodium nitrate and silver chloride are produced by mixing a saturated aqueous solution of sodium chloride and a saturated aqueous solution of silver nitrate or by adding solid sodium chloride to the saturated aqueous solution of silver nitrate. Although sodium nitrate exists as an aqueous solution, silver chloride precipitates and precipitates, so that the separation of both can be carried out by the most general method such as filtration.

NaCl + AgNO ₃ → NaNO ₃ + AgCl (1) The temperature when carrying out the reaction (1) according to the present invention is 0 to 100 ° C., preferably 50 to 100 ° C. In order to obtain solid sodium nitrate from the produced sodium nitrate aqueous solution, water is evaporated and removed, or a saturated sodium nitrate aqueous solution at a higher temperature is cooled, and solid sodium nitrate is deposited by utilizing the difference in solubility depending on the temperature. To separate.

The solid sodium nitrate thus obtained is then subjected to thermochemical reaction with metallic copper to produce sodium oxide. At that time, the produced sodium oxide can be made into a product as a solid. It is also possible to add water to the solid sodium oxide to produce solid caustic soda or an aqueous solution of caustic soda. When solid sodium oxide is sold as a commercial product, the volume required is significantly reduced compared to the caustic soda aqueous solution currently distributed in large quantities as a commercial product, and the cost required for its transportation is greatly reduced.

In order to produce sodium oxide using sodium nitrate as a raw material, metallic copper is used as a decomposer of sodium nitrate.

NaNO ₃ + Cu → 1 / 2Na ₂ O + CuO + NO + 1 / 4O ₂ (2) This reaction (2) is 700 to 1400 ° C., preferably 80
It is carried out in the temperature range of 0 to 1200 ° C. Since a part of the sodium oxide produced by this reaction exists as a gas at the above-mentioned reaction temperature, it can be easily separated from the solid copper oxide by-produced by suctioning under reduced pressure. Further, if a gas such as gaseous nitrogen or argon that does not react with sodium oxide is passed through the reaction system, it is possible to more advantageously separate the produced sodium oxide and copper oxide. In either case, the sodium oxide separated outside the reaction system can be collected as solid sodium oxide in the temperature range of the reaction temperature or lower and 320 ° C. or higher.

Since both nitric oxide and oxygen produced as a by-product according to the reaction (2) are gases, they can be easily separated from the solid copper oxide produced at the same time. On the other hand, even if the produced sodium oxide is led out of the reaction system together with by-produced nitric oxide and oxygen as gases, at 320 ° C. or higher, preferably at 500 ° C. or higher, the nitric oxide and oxygen and the mixed gas thereof are It solidifies without reacting. Therefore,
Generated sodium oxide and by-produced nitric oxide and oxygen,
And their separation from the mixed gas can be easily carried out.

The copper oxide by-produced in the reaction (2) can be reduced by causing gaseous hydrogen to act thereon to regenerate metallic copper. The regenerated metallic copper can be recycled to the reaction (2).

CuO + H ₂ → Cu + H ₂ O (3) This reaction (3) is 50 ° C. or higher, preferably 80 ° C. or higher,
Particularly, it is advantageously carried out at a temperature of 100 to 250 ° C. Hydrogen used as a reducing agent in the reaction (3) is easily produced in a large amount by the decomposition of naphtha and the decomposition of coal. Therefore, even if the demand for hydrogen is greatly expanded due to the practical application of the present invention, it is possible to obtain hydrogen at a relatively low cost.

Nitric oxide and oxygen produced as a by-product in the reaction (2) are further added with water and oxygen in the air to generate nitric acid. The produced nitric acid is used to regenerate the silver nitrate used in the reaction (1) as described later.

NO + 3 / 4O ₂ + 1 / 2H ₂ O → HNO ₃ (4) This reaction (4) can be carried out at room temperature according to the nitrogen oxide suction process in the nitric acid production which is currently being industrially carried out.

According to the present invention, gaseous hydrogen is reacted with the solid silver chloride which is formed together with sodium nitrate in the reaction (1) and is precipitated and separated. Hydrogen chloride is generated by this reaction, and silver is by-produced along with it. The produced hydrogen chloride can be used as a product as it is, or can be dissolved in water to be manufactured as hydrochloric acid.

AgCl + 1 / 2H ₂ → Ag + HCl (5) This reaction (5) is carried out at 300 to 500 ° C., preferably 35
It is carried out at 0 to 450 ° C. The silver by-produced according to the reaction (5) reacts with the nitric acid produced according to the above reaction (4) to produce silver nitrate. This silver nitrate can be reused in the reaction (1).

Ag + HNO ₃ → AgNO ₃ ½ H ₂ (6) This reaction (6) is normal temperature to 150 ° C., preferably 80 to 1
It can be carried out at 40 ° C. The concentration of nitric acid used to carry out the reaction (6) is 60 wt% or more, preferably 80 wt% or more. Hydrogen produced as a byproduct of silver nitrate can be circulated in the reaction (3) or the reaction (5).

[0022]

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

Example 1 At 80 ° C., an aqueous solution substantially saturated with 2.93 g of sodium chloride was mixed with an aqueous solution saturated with 8.5 g of silver nitrate at 80 ° C. while stirring. Immediately after mixing, silver chloride was deposited. After stirring this mixed solution for about 5 minutes, while maintaining the temperature at 80 ° C., precipitated and precipitated silver chloride was filtered off using a commercially available filter paper. When the filtrate was allowed to cool to room temperature, part of the sodium nitrate in the solution precipitated,
Precipitated. This was filtered off by the same operation as in the case of silver chloride.

Further, regarding the filtrate, water in the solution was evaporated in a platinum boat to obtain solid sodium nitrate. The total amount of solid sodium nitrate obtained was 4.23 g.
This means that about 99.5% of the sodium component in the initially used sodium chloride was present in the sodium nitrate obtained. On the other hand, the weight of the solid silver chloride produced with sodium nitrate and filtered off was 7.1 g after drying. This means that about 99.7% of the silver component in the initially used silver nitrate was present in the resulting silver chloride.

Next, to 4.23 g of the obtained sodium nitrate, 3.8 g of metallic copper was added and put into a platinum boat. In that case, the metallic copper was merely placed on the solid sodium nitrate and the both were not mixed. The platinum boat containing these samples was then placed in a quartz protective tube and heated in an annular electric furnace. In order to solidify and collect the generated gaseous sodium oxide, a wire mesh made of nickel was bent into a protective tube at 450 to 550 ° C outside the end of the electric furnace, and packed so as to cover the entire cross section of the tube. It is.

In such a state, the reaction was carried out at a reaction temperature of about 830 ° C. for about 30 minutes while flowing gaseous nitrogen over the sample in the platinum boat. As a result, the amount of sodium oxide obtained was 1.43 g. This means that about 93% of the sodium nitrate used in the reaction was decomposed and was recovered as sodium oxide.

Next, gaseous hydrogen was circulated for about 20 minutes while keeping the produced and remaining solid copper oxide at about 100 ° C. in a platinum boat left in the electric furnace. After allowing to cool to room temperature, the weight of metallic copper produced in the platinum boat was 3.7 g. This means that almost 100% of the metallic copper that was originally used as a decomposer of sodium nitrate was recovered.

Further, with respect to nitric oxide and oxygen produced as a byproduct of the decomposition reaction of sodium nitrate, oxygen was further added to this mixed gas and absorbed in water to be collected as nitric acid. When this nitric acid was quantified, it was 3.0 g in terms of 100 wt% nitric acid. This is about 9 of the theoretical amount of nitric oxide and oxygen generated by the decomposition reaction of sodium nitrate.
6% has been recovered.

Next, silver chloride was reacted with hydrogen to generate hydrogen chloride. That is, 7.1 g of silver chloride produced together with sodium nitrate by the reaction of sodium chloride and silver nitrate was put into a porcelain boat in a quartz protective tube, and gaseous hydrogen was maintained at about 430 ° C. in an annular electric furnace. It was made to flow for about 1 hour (about 100 ml / min).
Hydrogen chloride generated by this reaction is 0.1N-NaO.
After the reaction was completed, the amount of hydrogen chloride generated was absorbed and quantified. As a result, the amount of hydrogen chloride generated was 1.7.
It was 3 g. This means that about 95% of the chlorine component in the silver chloride used in the reaction was converted to hydrogen chloride. On the other hand, when the amount of silver remaining in the porcelain boat was weighed,
It was 5.3 g. This means that almost 100% of the silver component in the silver chloride used in the reaction was recovered.

Finally, in order to regenerate the silver nitrate consumed in the reaction of the sodium chloride and silver nitrate, 5.3 g of silver remaining in the porcelain boat was put into a platinum boat. To this, add 9.0 g of 80 wt% nitric acid aqueous solution and add 1
The heating was continued at 00 to 110 ° C until all the silver had reacted. Then, raise the temperature to about 180 ° C,
Water and excess nitric acid were all evaporated and removed to obtain solid silver nitrate. After cooling, the obtained silver nitrate was weighed and found to be 8.0.
It was g. This is about 94% of the first used silver nitrate
Will be collected.

[0031]

As described above, in the method for producing caustic soda of the present invention, the consumption raw materials are substantially only sodium chloride, hydrogen and oxygen (or air), and all other reaction raw materials are in the reaction system. Are recycled in an appropriate form. Therefore, only sodium oxide (caustic soda) and hydrogen chloride (hydrochloric acid) produced by the decomposition of sodium chloride are taken out from the reaction system, and other by-products are not discharged from the reaction system. Therefore, when the demand for chlorine is reduced due to environmental problems and the like, the production method is economically advantageous as compared with the conventional production method of producing caustic soda, which has great industrial significance.

Claims (2)

(57) [Claims] 1. A sodium nitrate is formed by reacting a soluble nitrate that forms an insoluble chloride in an aqueous solution with sodium chloride to form sodium nitrate and an insoluble chloride, and reacting the sodium nitrate with metallic copper. On the other hand, a method for producing caustic soda, characterized in that hydrogen chloride is produced by reacting insoluble chloride with hydrogen. 2. A method for producing caustic soda according to claim 1.
Furthermore, in the reaction between sodium nitrate and metallic copper,
The by-produced copper oxide is reduced by applying gaseous hydrogen to reduce gold
The regenerated metallic copper is regenerated from the genus copper, and the regenerated metallic copper according to claim 1.
It can be recycled and used in the reaction of sodium nitrate and metallic copper.
In addition, as a by-product in the reaction between the above sodium nitrate and metallic copper
Oxygen is added to the mixed gas consisting of nitric oxide and oxygen.
Then, it is absorbed in water to produce nitric acid, and the resulting nitric acid is obtained.
Is a metal by-produced in the reaction of insoluble chloride with hydrogen.
Regenerate nitrate by reacting with the above-mentioned regenerated nitrate
Is sodium chloride as the soluble nitrate according to claim 1.
Caustic, characterized by recycling for reaction with
Manufacturing method of soda.