JP2018002514A - Method for producing anhydrous alkali metal sulfide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a particulate, high purity anhydrous alkali metal sulfide at high productivity.SOLUTION: Provided is a method for producing an anhydrous alkali metal sulfide containing a process where an aqueous solution including a hydrous alkali metal sulfide and a hydrous alkali metal hydrosulfide is concentrated while maintaining the temperature range of 97°C or higher to crystallize an anhydrous alkali metal sulfide, in which the molar number of the hydrated alkali metal sulfide to 1 mon of the hydrated alkali metal sulfide in the aqueous solution being a ratio in the range of 0.01 to 1.00 mol.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing an anhydrous alkali metal sulfide, and more particularly, to a method for efficiently producing an anhydrous alkali metal sulfide having a fine particle shape and high purity.

In recent years, anhydrous alkali metal sulfides that are highly pure and easy to handle, especially anhydrous sodium sulfide, which is a raw material for pharmaceuticals having polyarylene sulfide and sulfide bonds, are required as raw materials for engineering plastics and pharmaceuticals. Currently, commercially available sodium sulfide includes sodium sulfide crystals (Na ₂ S · 9H ₂ O, Na ₂ S · 6H ₂ O, Na) having crystal water crystallized by cooling or concentrating a sodium sulfide aqueous solution. 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 contain 30% or more of moisture, and have the disadvantage that they are highly pure and easy to oxidize in addition to low purity.

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

As a method for obtaining anhydrous sodium sulfide, a method is generally used in which hydrated or hydrous sodium sulfide is heated to a temperature higher than the melting point and dehydrated. However, when water-containing sodium sulfide is melted, it becomes a very viscous mass and adheres firmly to the container, making stirring and taking out difficult. What has been known as an anhydrous sodium sulfide process so far
(1) Filling the pipe with hydrated sodium sulfide / 9 hydrate, heating it under specific conditions under reduced pressure of 1 torr without stirring and gradually raising the temperature to 800 ° C. while avoiding melting, forced dehydration (See Patent Document 1).
(2) A method of depositing anhydrous sodium sulfide crystals from an aqueous sodium sulfide solution at 97 ° C. or higher containing 2 to 15% by mass of sodium hydroxide (see Patent Document 2)
(3) Highly hydrated sodium sulfide crystals are heated 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 at atmospheric pressure Alternatively, a method of obtaining anhydrous sodium sulfide by heating at 90 to 200 ° C. for 4 to 5 hours under reduced pressure (see Patent Document 3).
(4) In the presence of a hydrocarbon solvent or a polyhaloaromatic compound, at least one selected from sodium sulfide hydrate, organic sulfonic acid metal salt, lithium halide, organic carboxylic acid metal salt, and alkali metal phosphate A method of obtaining a sodium sulfide composition by bringing a metal salt into contact with each other and performing dehydration (see Patent Documents 4 and 5) is known.

However, the method (1) is not practical because the heating temperature is extremely high, and the obtained anhydrous sodium sulfide becomes a body crystal that retains the crystal shape of the hydrate, and has a large specific surface area and deliquescence. It was very easy to oxidize. Although the methods (2) and (3) are methods that improve these drawbacks, the method (2) strictly controls the sodium hydroxide concentration and temperature during the precipitation of anhydrous sodium sulfide crystals. It was necessary and not easy. In the method (3), it takes a long time under reduced pressure and several steps are required, and dehydration is performed while maintaining the particle shape without melting Na ₂ S · pentahydrate as a raw material. The particle diameter of the raw material Na ₂ S · pentahydrate is directly reflected in the particle diameter of anhydrous sodium sulfide, and the particle diameter of the anhydrous sodium sulfide obtained is a relatively large crystal of 1 to 1.5 mm. . When such a crystal is presented, the specific surface area becomes small, and the reactivity decreases when used as a raw material for engineering plastics and pharmaceuticals. Therefore, the crystal is separated into fine particles (for example, 800 μm or less). ) May be required to be crushed. In the method of (4), it is necessary to add organic sulfonic acid metal salt, lithium halide, organic carboxylic acid metal salt, alkali metal phosphate, etc. as a dispersing agent to the system during dehydration. It was nearly impossible to take out anhydrous sodium sulfide alone as a mixture with these metal salts.

  Therefore, as a method for obtaining fine particulate high purity anhydrous alkali metal sulfide, an anhydrous alkali metal sulfide that performs dehydration by contacting an aqueous alkali metal sulfide solution with a dispersion medium having a melting point lower than the boiling point of the aqueous solution, A method for producing a dispersion medium mixture is known (see Patent Document 6). However, this method is also low in energy efficiency, and an anhydrous alkali metal sulfide cannot be obtained with good productivity.

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

  Accordingly, the problem to be solved by the present invention is to produce fine, high purity anhydrous alkali metal sulfides with high productivity.

  As a result of intensive studies to solve the above problems, the present inventors have maintained an aqueous solution containing a hydrous alkali metal sulfide in an excess of the hydrous alkali metal hydrosulfide while maintaining a high temperature of 97 ° C. or higher. As a result of the concentration, it was found that fine anhydrous alkali metal sulfides can be obtained with high purity and efficiency, and the present invention has been completed.

That is, the present invention includes an anhydrous alkali metal sulfide crystallization step by concentrating an aqueous solution containing a hydrous alkali metal sulfide and a hydrous alkali metal hydrosulfide while maintaining a temperature range of 97 ° C. or higher. A method for producing an alkali metal sulfide comprising:
Production of anhydrous alkali metal sulfide, characterized in that the number of moles of hydrated alkali metal hydrosulfide is in the range of 0.01 to 1.00 mole per mole of hydrated alkali metal sulfide in the aqueous solution Regarding the method.

  ADVANTAGE OF THE INVENTION According to this invention, a particulate high purity anhydrous alkali metal sulfide can be manufactured with sufficient productivity.

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

In the method for producing an anhydrous alkali metal sulfide of the present invention, an anhydrous alkali metal sulfide is obtained by concentrating an aqueous solution containing a hydrous alkali metal sulfide and a hydrous alkali metal hydrosulfide while maintaining a temperature range of 97 ° C. or higher. A method for producing anhydrous alkali metal sulfide having a step of crystallizing,
It is characterized in that the number of moles of hydrated alkali metal hydrosulfide is in the range of 0.01 to 1.00 mole per mole of hydrated 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, cesium sulfide, and the solid content concentration is not particularly limited. Is preferably 10 to 80% by mass, more preferably 35 to 65% by mass. Preferred as the hydrated alkali metal sulfide is hydrated sodium sulfide. The shape of the hydrous sodium sulfide to be used may be any of crystal, flake, solid, liquid and aqueous solution. When the hydrous sodium sulfide used is in the form of crystals, flakes, solids or liquids, water may be added to form an aqueous solution. At that time, the number of moles of the hydrated alkali metal hydrosulfide is 0.01 to 1.00 mole, preferably 0.01 to 0.10 mole, with respect to 1 mole of the alkali metal sulfide in the aqueous solution. It adjusts so that it may contain in the ratio of the range of.

  The hydrous alkali metal sulfide may be prepared from, for example, a hydrous alkali metal hydrosulfide and an alkali metal hydroxide. Examples of hydrous alkali metal hydrosulfides include liquid or solid hydrates of compounds such as lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide, and the solid content concentration is particularly high. Although it is not limited, it is preferable that it is 10-80 mass%, especially 35-65 mass%. A preferred hydrous alkali metal hydrosulfide is hydrous sodium hydrosulfide. The shape of the hydrous sodium hydrosulfide to be used may be a crystal, flake, solid, liquid or aqueous solution. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, and aqueous solutions thereof. In addition, when using as this aqueous solution, it is preferable that it is an aqueous solution with a density | concentration of 20 mass% or more. Among these, lithium hydroxide, sodium hydroxide, and potassium hydroxide are particularly preferable, and sodium hydroxide is particularly preferable. The amount of alkali metal hydroxide used is preferably in the range of 0.50 to 0.99 mole per mole of alkali metal hydrosulfide, particularly 0.95, from the point of promoting the formation of anhydrous alkali metal sulfide. A 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 hydrated alkali metal hydrosulfide, even if it is out of the range. The ratio of the hydrated alkali metal hydrosulfide is such that the ratio is in the range of 0.01 to 1.00 mol, preferably in the range of 0.01 to 1.00 mol, with respect to 1 mol of the alkali metal sulfide. It is preferable to adjust from the viewpoint of productivity.

  The aqueous solution containing the hydrated alkali metal sulfide thus prepared may contain an organic solvent that dissolves in water. Examples of organic solvents that are 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 mass%, boiling point: 56.9 ° C), etc. Is mentioned. These organic solvents may be used alone or a mixed solvent in which two or more kinds are mixed. 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 prepared in this way may be left standing to remove impurities before maintaining the temperature range of 97 ° C. or higher before concentration described below. The standing time is not particularly limited, but is preferably 1 to 5 hours.

  The aqueous solution containing the hydrous alkali metal sulfide thus prepared maintains the temperature range of 97 ° C. or higher, and preferably maintains the temperature range of 97 ° C. or higher and 120 ° C. while maintaining the alkali range shown in FIG. Anhydrous alkali metal sulfide can be precipitated in the aqueous solution by concentration along the saturation concentration curve of the metal sulfide. When the saturated concentration is concentrated, anhydrous alkali metal sulfide can be precipitated. The anhydrous alkali metal crystal slurry solution of the alkali metal sulfide saturated aqueous solution in which crystals are precipitated can be precipitated up to a slurry concentration of 1 to 50%, but is preferably 1 to 30% by mass from the viewpoint of maintaining the fluidity of the liquid. 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 aqueous solution containing the hydrated alkali metal sulfide and the hydrated alkali metal hydrosulfide is concentrated in a batch, the time required for the concentration per time is not particularly limited, but it should be 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 in a continuous manner, when the concentration is concentrated to the concentration range where the anhydrous alkali metal sulfide precipitates along the saturation concentration curve of the alkali metal sulfide shown in FIG. An aqueous solution containing a metal sulfide and a hydrated alkali metal hydrosulfide may be added while adjusting and concentrated to a saturation concentration or higher.

  In the production method of the present invention, a fine particulate anhydrous alkali metal sulfide having a desired secondary particle size range in the range of 30 to 600 μm, and further in the range of 300 to 500 μm can be obtained.

  The anhydrous alkali metal sulfide obtained through the step (1) is then solid-liquid separated using an appropriate filter, and then cooled and dried to prepare a powdery or granular anhydrous alkali metal sulfide. be able to. Anhydrous alkali metal sulfides have deliquescence and react with carbon dioxide in the air, so it is desirable to store them sealed and cut off from the air.

  The production method of the present invention can produce anhydrous alkali metal sulfides while suppressing the corrosiveness. Therefore, although it is extremely excellent in corrosion resistance, it is necessary to use expensive and difficult metal materials such as zirconium and titanium. However, it is possible to use a manufacturing apparatus using SUS or a nickel alloy. The nickel alloy that can be used in the present invention is an alloy composed of 43 to 47% by mass of chromium, 0.1 to 2% by mass of molybdenum, and the balance of nickel and inevitable impurities. is there. Tungsten, iron, cobalt and copper are preferably those having a content below the detection limit. In the present invention, the term “inevitable impurities” means a very small amount of impurities that are technically difficult to remove. In the present invention, for example, carbon atoms contained in the alloy at a ratio of 1% by mass or less, preferably the detection limit or less can be mentioned. The nickel alloy is commercially available, for example, as MC alloy (Hitachi Metals MMC Superalloy).

  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 fine and highly pure.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to this. Unless otherwise specified, “%” represents “% by mass”.

(Measurement method) Moisture content Using a coulometric Karl Fischer moisture meter (manufactured by Kyoto Electronics Industry Co., Ltd.) equipped with a moisture vaporizer, the obtained anhydrous sodium sulfide was heated at 280 ° C for 20 minutes, and the evaporated moisture was 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 diameter of anhydrous sodium sulfide The secondary particle diameter of anhydrous sodium sulfide was determined by measurement in accordance with JIS Z8815-1994.

[Calculation method of erosion degree]
The dimensional change and weight change of the test piece were measured, and the degree of erosion was calculated from the following 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 before the test of 2 baffles (g), the weight after the test of 2 baffles (g), the density (g / cm ³ ), the surface area of 2 baffles (cm ² ), the test time (h), 10 mm. = Conversion with 1 cm.

[How to create a test piece]
Using “MC alloy” (45% by mass of chromium, 1% by mass of molybdenum and the remainder of nickel), two dimensions: 25 (mm) x 25 (mm) x 2 (mm) in thickness were created and centered on each other. The test piece of size: length 50 (mm) x width 25 (mm) x thickness 2 (mm) was produced.

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

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

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

  After completion of crystallization, crystals were separated using a centrifugal filter in a nitrogen atmosphere. The obtained crystal (520 g) was filled and stored in a sealed container so as not to be exposed to 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. 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), 48.30% sodium hydrosulfide aqueous solution (1727 g) (14.4) so that the molar ratio of NaOH: NaSH = 1.00: 0.93. 88 mol), and the same procedure as in Example 1 was conducted except that the concentration and dehydration rate was 20 g / Hr. The obtained crystal (528 g) was filled in a sealed container and stored so as not to be exposed to 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. The erosion degree of the test piece is shown in Table 3.

[Comparative Example 2]
Using the same reaction vessel as in Example 1, 48.64% aqueous sodium hydroxide solution (1316 g) (16.00 mol), 48.64% so that the molar ratio NaOH: NaSH = 1.00: 0.93. A 30% aqueous sodium hydrosulfide solution (1727 g) (14.88 mol) and 147.0 g (1.000 mol) of p-dichlorobenzene as a dispersion medium were added to start the temperature rise. When the internal temperature reached 140 ° C, distillation of water and p-dichlorobenzene began. p-Dichlorobenzene was separated in a decanter and continuously returned to the system. The concentration rate was 20 g / Hr. Some time after the start of distillation, the particles began to disperse in the system. Two hours later, 90.0 g of water was distilled, and the internal temperature rose to 174 ° C., which is the boiling point of p-dichlorobenzene. The system at the end of the dehydration was in a state where 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. The erosion degree of the test piece is shown in Table 3.

Claims (4)

Production of anhydrous alkali metal sulfide having a step of crystallizing anhydrous alkali metal sulfide by concentrating an aqueous solution containing hydrous alkali metal sulfide and hydrous alkali metal hydrosulfide while maintaining a temperature range of 97 ° C. or higher A method,
Production of anhydrous alkali metal sulfide, characterized in that the number of moles of hydrated alkali metal hydrosulfide is in the range of 0.01 to 1.00 mole per mole of hydrated alkali metal sulfide in the aqueous solution Method. The method for producing an anhydrous alkali metal sulfide according to claim 1, which is an aqueous solution containing a hydrated alkali metal sulfide prepared from a hydrated 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 with respect to 1 mol of hydrous alkali metal hydrosulfide. The method for producing an anhydrous alkali metal sulfide according to any one of claims 1 to 3, wherein the obtained anhydrous alkali metal sulfide has a secondary particle diameter in the range of 50 to 600 µm.

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