JP6725876B2 - Method for producing anhydrous alkali metal sulfide - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing anhydrous alkali metal sulfide, and more particularly, to a method for efficiently producing fine-particled, highly pure anhydrous alkali metal sulfide.

In recent years, as a raw material of engineering plastics and pharmaceuticals, anhydrous alkali metal sulfides of high purity and easy to handle, especially polyarylene sulfide and anhydrous sodium sulfide which is a raw material of pharmaceuticals having a sulfide bond are required. Currently, as the sodium sulfide generally commercially available, sodium sulfide crystals (Na ₂ S · 9H ₂ O having a crystal water to crystallize by cooling or concentrating the aqueous sodium _{sulphide, Na 2 S · 6H 2 O} , Na ₂ S・5.5H ₂ O, Na ₂ S・5H ₂ O, etc.) and hydrous sodium sulfide obtained by solidifying sodium sulfide aqueous solution with a concentration of about 60% into pellets, flakes, chips, etc. .. However, these sodium sulfides have a water content of 30% or more, and have the drawbacks of low purity, strong deliquescent property, and easy oxidation.

In chemical reactions using these alkali metal sulfides as raw materials, there are problems that water present in the product induces undesired side reactions and changes the equilibrium state of the reaction. An operation such as dehydration becomes necessary and the operation becomes complicated. Further, in order to allow the reaction to proceed smoothly, a fine particulate anhydrous alkali metal sulfide that is easily dispersed and easily dissolved in a reaction solvent is desired.

As a method for obtaining anhydrous sodium sulfide, a method in which hydrated or hydrous sodium sulfide is heated to a temperature equal to or higher than the melting point and dehydrated is general. However, when sodium sulfide containing water is melted, it becomes an extremely high-viscosity lump and firmly adheres to the container, making it difficult to stir or take it out. What has been known so far as a method for producing anhydrous sodium sulfide,
(1) Fill a pipe with hydrated sodium sulfide nonahydrate and heat it under a reduced pressure of 1 torr without stirring to heat it up to 800°C gradually while avoiding melting and forcibly dehydrating. Method (see Patent Document 1).
(2) Method for precipitating anhydrous sodium sulfide crystals from an aqueous sodium sulfide solution containing 2 to 15 mass% of sodium hydroxide and having a temperature of 97° C. or higher (see Patent Document 2).
(3) Heating the highly hydrated sodium sulfide crystals at a pressure of 500 Torr or less at a phase transition point ±10° C. from the highly hydrated sodium sulfide crystals to sodium sulfide monohydrate for 4 to 5 hours, and then under atmospheric pressure. Alternatively, a method of obtaining anhydrous sodium sulfide by heating under reduced pressure at 90 to 200° C. for 4 to 5 hours (see Patent Document 3).
(4) In the presence of a hydrocarbon solvent or a polyhaloaromatic compound, at least one selected from sodium sulfide hydrate and organic sulfonic acid metal salt, lithium halide, organic carboxylic acid metal salt, and phosphoric acid alkali metal salt. There is known a method of obtaining a sodium sulfide composition by bringing a metal salt into contact with water for dehydration (see Patent Documents 4 and 5) and the like.

However, the method (1) is not practical because the heating temperature is extremely high, and the anhydrous sodium sulfide obtained is a skeletal crystal that retains the crystal shape of the hydrate, and has a large specific surface area and deliquescent properties. And was very easily oxidized. The methods (2) and (3) improve these drawbacks, but the method (2) strictly controls the sodium hydroxide concentration and the temperature during the precipitation of anhydrous sodium sulfide crystals. It was necessary and not an easy method. Further, the method (3) requires a long time under reduced pressure and requires several steps, and dehydration is performed while maintaining the particle shape without melting Na ₂ S.5 hydrate as a raw material. The particle size of the raw material Na ₂ S.5 hydrate was directly reflected on the particle size of anhydrous sodium sulfide, and the particle size of the obtained anhydrous sodium sulfide was 1 to 1.5 mm, which was a relatively large crystal. .. When such a crystal is present, the specific surface area becomes small and the reactivity decreases when it is used as a raw material for engineering plastics and pharmaceuticals. Therefore, the crystal is separately added into fine particles (for example, 800 μm or less). In some cases, a step of crushing was required. Further, in the method (4), it is necessary to add an organic sulfonic acid metal salt, a lithium halide, an organic carboxylic acid metal salt, an alkali metal phosphate or the like as a dispersant to the dehydrated system, It became almost impossible to take out the anhydrous sodium sulfide alone as a mixture with those metal salts.

Therefore, as a method for obtaining fine-grained high-purity anhydrous alkali metal sulfide, dehydration is performed by contacting an aqueous alkali metal sulfide solution with a dispersion medium having a melting point equal to or lower than the boiling point of the aqueous solution. A method for producing a mixture of dispersion media is known (see Patent Document 6). However, this method also has low energy efficiency and cannot produce anhydrous alkali metal sulfide with good productivity.

US Pat. No. 2,533,163 JP-A-64-28207 JP-A-2-51404 JP-A-60-200807 JP, 60-210509, A Japanese Patent Laid-Open No. 9-67108

Therefore, the problem to be solved by the present invention is to produce fine-particled high-purity anhydrous alkali metal sulfide with high productivity.

The present inventors have conducted extensive studies to solve the above problems, and as a result, in the presence of an excess of hydrous alkali metal hydrosulfide, an aqueous solution containing hydrous alkali metal sulfide is maintained at a high temperature of 97° C. or higher. By concentrating, it has been found that finely particulate anhydrous alkali metal sulfide can be efficiently obtained with high purity, and the present invention has been completed.

That is, the present invention comprises a step of crystallizing anhydrous alkali metal sulfide by concentrating an aqueous solution containing a hydrous alkali metal sulfide and an aqueous solution containing a hydrous alkali metal hydrosulfide while maintaining a temperature range of 97° C. or higher. A method for producing an alkali metal sulfide,
Production of anhydrous alkali metal sulfide, wherein the number of moles of hydrous alkali metal hydrosulfide is in the range of 0.01 to 1.00 mol with respect to 1 mol of hydrous alkali metal sulfide in the aqueous solution. Regarding the method.

According to the present invention, a highly pure anhydrous alkali metal sulfide in the form of fine particles can be produced with good productivity.

It is a figure showing the solubility curve of various hydrates of sodium sulfide.

The method for producing an anhydrous alkali metal sulfide of the present invention comprises removing an anhydrous alkali metal sulfide by concentrating an aqueous solution containing a hydrous alkali metal sulfide and an aqueous alkali metal hydrosulfide while maintaining a temperature range of 97° C. or higher. A method for producing an anhydrous alkali metal sulfide having a step of crystallizing,
It is characterized in that the molar number of the hydrous alkali metal hydrosulfide is in the range of 0.01 to 1.00 mol with respect to 1 mol of the hydrous alkali metal sulfide in the aqueous solution.

Examples of the hydrous alkali metal sulfide used in the present invention include liquid or solid hydrates of compounds such as lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide, and the solid content concentration is not particularly limited. Is 10 to 80% by mass, and particularly preferably 35 to 65% by mass. As the hydrated alkali metal sulfide, preferred is hydrated sodium sulfide. The shape of the hydrous sodium sulfide used may be any of crystals, flakes, solids, liquids and aqueous solutions. When the shape of the hydrous sodium sulfide used is crystals, flakes, solid or liquid, water may be added to form an aqueous solution. At that time, the number of moles of the hydrous alkali metal hydrosulfide is 0.01 to 1.00 mol, preferably 0.01 to 0.10 mol, relative to 1 mol of the alkali metal sulfide in the aqueous solution. It is adjusted so that it is contained in a ratio within the range.

The hydrated alkali metal sulfide may be, for example, one prepared from a hydrated alkali metal hydrosulfide and an alkali metal hydroxide. Examples of the hydrated alkali metal hydrosulfide include liquid or solid hydrates of compounds such as lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, rubidium hydrosulfide, and cesium hydrosulfide. Although not limited, it is preferably 10 to 80% by mass, and particularly preferably 35 to 65% by mass. As the hydrous alkali metal hydrosulfide, preferred is hydrous sodium hydrosulfide. The shape of the hydrous sodium hydrosulfide used may be any of crystals, flakes, solids, liquids and aqueous solutions. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, and aqueous solutions thereof. When used as the aqueous solution, it is preferably an aqueous solution having a concentration of 20% by mass or more. Among these, lithium hydroxide, sodium hydroxide and potassium hydroxide are particularly preferable, and sodium hydroxide is particularly preferable. The amount of the alkali metal hydroxide used is preferably 0.50 to 0.99 mol, and particularly preferably 0.95 mol, per mol of the alkali metal hydrosulfide, from the viewpoint that the formation of anhydrous alkali metal sulfide is promoted. The range of -0.99 mol is more preferable. The amount of the alkali metal hydroxide used may be adjusted by adding an alkali metal hydroxide or a hydrous alkali metal hydrosulfide even when the amount is out of the range, and the amount in the finally obtained aqueous solution may be adjusted. The proportion of hydrous alkali metal hydrosulfide should be in the range of 0.01 to 1.00 mol, preferably in the range of 0.01 to 1.00 mol, per mol of the alkali metal sulfide. Adjustment is preferable from the viewpoint of productivity.

The aqueous solution containing the hydrous alkali metal sulfide thus prepared may contain an organic solvent which is soluble in water. Examples of the organic solvent soluble in water include ketones such as acetone (solubility: compatible with water in all proportions; boiling point: 56.1° C.); methanol (solubility: compatible with water in all proportions) , Boiling point: 64.7° C.), ethanol (solubility: compatible with water in all proportions, boiling point: 78.3° C.), isopropyl alcohol (solubility: compatible with water in all proportions, boiling point: 82. 26° C.), alcohols such as ethylene glycol (solubility: compatible with water in all proportions, boiling point: 197° C.); esters such as methyl acetate (solubility: 24% by mass, boiling point: 56.9° C.) Are listed. These organic solvents may be used alone or in combination of two or more. Preferred organic solvents are ketones and alcohols, more preferred are ethanol, acetone, isopropyl alcohol and ethylene glycol, and most preferred are ethanol, acetone and ethylene glycol.

The aqueous solution containing the hydrated alkali metal sulfide thus prepared may be allowed to stand to remove impurities before being concentrated as described below while maintaining a temperature range of 97° C. or higher. The standing time is not particularly limited, but 1 to 5 hours is preferable.

The aqueous solution containing the hydrous alkali metal sulfide prepared in this manner is maintained at a temperature range of 97° C. or higher, preferably at a temperature range of 97° C. or higher and 120° C. Anhydrous alkali metal sulfide can be precipitated in an aqueous solution by concentrating along the saturation concentration curve of metal sulfide. Anhydrous alkali metal sulfide can be deposited by concentrating the saturated concentration. An anhydrous alkali metal crystal slurry solution of a saturated aqueous solution of alkali metal sulfide in which crystals are precipitated can be precipitated to a slurry concentration of 1 to 50%, but 1 to 30% by mass is preferable from the viewpoint of maintaining fluidity of the liquid. The concentration is preferably dehydrated under reduced pressure, preferably in the range of 4 to 40 kPa in absolute pressure, and more preferably in the range of 8 to 20 kPa.

When the concentration of the hydrated alkali metal sulfide and the aqueous solution containing the hydrated alkali metal hydrosulfide is performed in a batch, the time required for each concentration is not particularly limited, but it is performed in the range of 10 minutes to 10 hours. Is preferable, and it is more preferable to carry out in the range of 30 minutes to 2 hours. Further, in the case of performing the continuous method, along with the saturation concentration curve of the alkali metal sulfide shown in FIG. 1, after concentrating to a concentration range in which anhydrous alkali metal sulfide is deposited, the hydrated alkali is kept so that the concentration range is maintained. It suffices to add an aqueous solution containing a metal sulfide and a hydrous alkali metal hydrosulfide while adjusting it, and then concentrate the solution to a saturation concentration or higher.

According to the production method of the present invention, it is possible to obtain a particulate anhydrous alkali metal sulfide having a desired secondary particle size range of 30 to 600 μm, more preferably 300 to 500 μm.

The anhydrous alkali metal sulfide obtained through the above step (1) is subsequently solid-liquid separated using an appropriate filter, and then cooled and dried to prepare powdery or granular anhydrous alkali metal sulfide. be able to. Anhydrous alkali metal sulfide has a deliquescent property and reacts with carbon dioxide in the air. Therefore, it is desirable to store it in an airtight manner and shield it from the air.

The production method of the present invention is capable of producing anhydrous alkali metal sulfides with suppressed corrosiveness, and therefore has extremely excellent corrosion resistance, but it is not always necessary to use expensive and difficult-to-process metal materials such as zirconium and titanium. However, a manufacturing apparatus using SUS or nickel alloy can be used. The nickel alloy that can be used in the present invention is an alloy in which the content ratio of chromium is 43 to 47 mass %, the content ratio of molybdenum is 0.1 to 2 mass %, and the balance is nickel and inevitable impurities. is there. Tungsten, iron, cobalt and copper are preferably contained in amounts below the detection limit. In the present invention, the term “unavoidable impurities” means minute amounts of impurities that are technically difficult to remove. In the present invention, for example, carbon atoms contained in the alloy in an amount of 1% by mass or less, preferably a detection limit or less may be mentioned. The nickel alloy is commercially available, for example, as MC alloy (Hitachi Metals MMC Super Alloy).

The anhydrous alkali metal sulfide of the present invention obtained by the above method can be used as a raw material for engineering plastics and pharmaceuticals because it is in the form of fine particles and has high purity.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto. Unless otherwise specified,% means% by mass.

(Measurement Method) Moisture Content Using a coulometric Karl Fischer moisture meter (manufactured by Kyoto Electronics Manufacturing Co., Ltd.) equipped with a moisture vaporizer, the obtained anhydrous sodium sulfide was heated at 280° C. for 20 minutes to evaporate the moisture into nitrogen gas. Was sent to the Karl Fischer liquid and the water content was measured by the Karl Fischer method.

(Measurement method) Component analysis of product The product component measurement was determined by measurement according to JIS K1435-1986.

(Measurement Method) Secondary Particle Size of Anhydrous Sodium Sulfide The secondary particle size of anhydrous sodium sulfide was determined by measurement according to JIS Z8815-1994.

[Calculation method of erosion degree]
The dimensional change and weight change of the test piece were measured, and the erosion degree was calculated from the following calculation formula.

単位は、バッフル２枚の試験前重量（ｇ）、バッフル２枚の試験後重量（ｇ）、密度（ｇ／ｃｍ^３）、バッフル２枚の表面積（ｃｍ²）、試験時間（ｈ）、１０ｍｍ＝１ｃｍで換算、とする。

The unit is the weight of two baffles before the test (g), the weight of the two baffles after the test (g), the density (g/cm ³ ), the surface area of the two baffles (cm ² ), the test time (h), 10 mm. = 1 cm.

[How to create test pieces]
Using "MC alloy" (45% by mass of chromium, 1% by mass of molybdenum and the balance of nickel), make two sheets of size: length 25 (mm) x width 25 (mm) x thickness 2 (mm), and center each other. Welding was performed in the section to prepare a test piece having dimensions: length 50 (mm) x width 25 (mm) x thickness 2 (mm).

[Example 1]
Two pieces of the above-mentioned test piece were attached to a reaction container made of "MC alloy" equipped with a stirrer and a decanter at a position where the whole test piece was immersed in an aqueous solution described later. Next, a 48.64% NaOH aqueous solution (1287 g) (15.68 mol) and a 48.30% NaSH aqueous solution (1857 g) were added to the reaction vessel so that the molar ratio was NaOH:NaSH=0.98:1.00. (16.00 mol) was charged and the internal temperature was raised to 120° C. with stirring to prepare a 38% Na ₂ S aqueous solution. Then, it was left to stand for 5 hours while maintaining 120°C.

After removing the impurities, depressurization was started and depressurization dehydration was started while maintaining the internal temperature of 120°C. The degree of pressure reduction was gradually increased at an internal temperature of 120±10° C. while paying attention to foaming, and vacuum dehydration was continued until the Na ₂ S concentration reached 60%. The concentration/dehydration rate was 210 g/Hr.

When the Na ₂ S concentration reached 60%, it became a saturated aqueous solution, and anhydrous Na ₂ S crystals were precipitated. The dehydration under reduced pressure was further continued until the crystal slurry concentration reached 30%. Again, the concentration/dehydration rate was 210 g/Hr.

After completion of the crystallization, the crystals were separated using a centrifugal filter in a nitrogen atmosphere. The obtained crystals (520 g) were filled and stored in a sealed container so as not to come into contact with air.

The components of the obtained product are shown in Table 1 below. The particle size of the obtained anhydrous sodium sulfide is shown in Table 2 below. Further, the erosion degree of the test piece is shown in Table 3.

[Comparative Example 1]
48.64% sodium hydroxide aqueous solution (1316 g) (16.00 mol) and 48.30% sodium hydrosulfide aqueous solution (1727 g) (14.14) so that the molar ratio would be NaOH:NaSH=1.00:0.93. 88 mol), and the concentration and dehydration rate was 20 g/Hr. The obtained crystals (528 g) were filled and stored in a sealed container so as not to come into contact with air. The components of the product are shown in Table 1 below. The particle size of the obtained anhydrous sodium sulfide is shown in Table 2 below. Further, the erosion degree of the test piece is shown in Table 3.

[Comparative Example 2]
Using a reaction vessel similar to that in Example 1, a 48.64% aqueous sodium hydroxide solution (1316 g) (16.00 mol), 48.64% was prepared so that the molar ratio was NaOH:NaSH=1.00:0.93. A 30% aqueous sodium hydrogen sulfide solution (1727 g) (14.88 mol) and 147.0 g (1.000 mol) of p-dichlorobenzene as a dispersion medium were put in to start heating. When the internal temperature reached 140°C, distillation of water and p-dichlorobenzene started. The p-dichlorobenzene was separated by a decanter and continuously returned to the system. The concentration rate was 20 g/Hr. Particles began to disperse in the system a while after the start of distillation. After 2 hours, 90.0 g of water was distilled out and the internal temperature rose to 174° C., which is the boiling point of p-dichlorobenzene, so that the dehydration was completed. At the end of the dehydration, fine particles of anhydrous sodium sulfide were dispersed in p-dichlorobenzene. After cooling, the particles were collected by filtration and dried under reduced pressure at 100° C. for 2 hours to obtain 77.2 g (yield 99.0%) of a granular product. The components of the product are shown in Table 1 below. The particle size of the obtained anhydrous sodium sulfide is shown in Table 2 below. Further, the erosion degree of the test piece is shown in Table 3.

Claims (4)

Anhydrous alkali metal sulfide having a step of crystallizing anhydrous alkali metal sulfide, which starts dehydration under reduced pressure while maintaining a temperature range of 97° C. or higher with an aqueous alkali metal sulfide and an aqueous solution containing an aqueous alkali metal sulfide. A manufacturing method,
Production of anhydrous alkali metal sulfide, wherein the number of moles of hydrous alkali metal hydrosulfide is in the range of 0.01 to 1.00 mol with respect to 1 mol of hydrous alkali metal sulfide in the aqueous solution. Method. The method for producing anhydrous alkali metal sulfide according to claim 1, which is an aqueous solution containing a hydrous alkali metal sulfide prepared from a hydrous alkali metal hydrosulfide and an alkali metal hydroxide. The method for producing an anhydrous alkali metal sulfide according to claim 2, which is prepared at a ratio of 0.50 to 0.99 mol of alkali metal hydroxide to 1 mol of hydrous alkali metal hydrosulfide. The method for producing anhydrous alkali metal sulfide according to any one of claims 1 to 3, wherein the secondary particle size of the obtained anhydrous alkali metal sulfide is in the range of 30 to 600 µm.

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