JP6809000B2 - Method for producing anhydrous alkali metal sulfide - Google Patents

Description

The present invention relates to a method for producing an anhydrous alkali metal sulfide, and more particularly to a method for efficiently producing a high-purity and uniform anhydrous alkali metal sulfide.

In recent years, as a raw material for engineering plastics and pharmaceuticals, anhydrous alkali metal sulfide which has high purity and is easy to handle, particularly anhydrous sodium sulfide which is a raw material for pharmaceuticals having polyarylene sulfide and a sulfide bond, has been 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 a hot aqueous solution of sodium sulfide with a concentration of about 60% into pellets, flakes, chips, etc. is there. However, these sodium sulfides contain 30% or more of water, and have the disadvantages of low purity and 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 unfavorable side reactions and changes the equilibrium state of the reaction, so before using it in the reaction, Operations such as dehydration are required, which complicates the operations. Further, in order to allow the reaction to proceed smoothly, a fine particle anhydrous alkali metal sulfide that is well dispersed in the reaction solvent and easily dissolved is desired.

As a method for obtaining anhydrous sodium sulfide, a method of heating hydrated or hydrous sodium sulfide to a temperature equal to or higher than the melting point and dehydrating it is common. However, when sodium sulfide containing water is melted, it becomes an extremely viscous mass, which firmly adheres to the container, making it difficult to stir or take it out. What has been known as a method for producing anhydrous sodium sulfide is
(1) Hydrate Sodium sulfide / 9 hydrate) is filled in a pipe and heated under a reduced pressure of 1 toll under specific conditions without stirring to gradually raise the temperature to 800 ° C. while avoiding melting. Method of dehydration (see Patent Document 1).
(2) A method for precipitating anhydrous sodium sulfide crystals from an aqueous sodium sulfide solution containing 2 to 15% by mass of sodium hydroxide at 97 ° C. or higher (see Patent Document 2).
(3) The hyperhydrated sodium sulfide crystal is heated at a pressure of 500 toll or less at the phase transition point ± 10 ° C. from the highly hydrated sodium sulfide crystal to sodium sulfide monohydrate for 4 to 5 hours, and then under atmospheric pressure or A method for obtaining anhydrous sodium sulfide by heating under reduced pressure at 90 to 200 ° C. for 4 to 5 hours (see Patent Document 3).
(4) At least one selected from sodium sulfide hydrate and organic sulfonic acid metal salt, lithium halide, organic carboxylic acid metal salt, and alkali metal phosphate salt in the presence of a hydrocarbon solvent or a polyhalo aromatic compound. A method of contacting a metal salt and performing dehydration to obtain a sodium sulfide composition (see Patent Documents 4 and 5) and the like are known.

However, the method (1) is not practical because the heating temperature is extremely high, and the obtained anhydrous sodium sulfide becomes skeletal crystals that retain the crystal shape of hydrate, and has a large specific surface area and deliquescent property. It was very easy to oxidize. The methods (2) and (3) are methods that improve these drawbacks, but the method (2) strictly controls the sodium hydroxide concentration and temperature during the precipitation of anhydrous sodium sulfide crystals. It was necessary and not an easy method. In the method (3), it is necessary required number of steps for a long time under reduced pressure, and subjected to dehydration while retaining the particulate form without melting the Na ₂ S · 5-hydrate as a raw material The particle size of the raw material Na ₂ S. pentahydrate was directly reflected in the particle size of anhydrous sodium sulfide, and the obtained particle size of anhydrous sodium sulfide was 1 to 1.5 mm, which was a relatively large crystal. .. When such a crystal is exhibited, 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 micro-granular (for example, 800 μm or less). In some cases, a step of crushing up to) was required. Further, in the method (4), it is necessary to add an organic sulfonic acid metal salt, lithium halide, an organic carboxylic acid metal salt, an alkali metal phosphate, etc. as a dispersant to the system at the time of dehydration, so that the inside of the system after dehydration is It was almost impossible to take out anhydrous sodium sulfide alone as a mixture with these metal salts.

Therefore, as a method for obtaining fine-grained high-purity anhydrous alkali metal sulfide, an anhydrous alkali metal sulfide is dehydrated by contacting an aqueous alkali metal sulfide aqueous 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 obtain anhydrous alkali metal sulfide with good productivity.

U.S. Pat. No. 25333163 Japanese Unexamined Patent Publication No. 64-28207 Japanese Unexamined Patent Publication No. 2-51404 Japanese Unexamined Patent Publication No. 60-20807 Japanese Unexamined Patent Publication No. 60-210509 Japanese Unexamined Patent Publication No. 9-67108

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

As a result of intensive research to solve the above problems, the present inventors efficiently dehydrate the water of crystallization contained in the hydrous alkali metal sulfide while eluting it in alcohol, thereby efficiently performing anhydrous alkali metal. They have found that sulfides can be obtained and have completed the present invention.

That is, the present invention provides a method for producing an anhydrous alkali metal sulfide, which comprises a step of irradiating a hydrous alkali metal sulfide with microwaves in the presence of an alcohol solvent.

According to the present invention, fine particles of high-purity anhydrous alkali metal sulfide can be produced with high productivity.

The method for producing an anhydrous alkali metal sulfide of the present invention is characterized by having a step of irradiating the hydrous alkali metal sulfide with microwaves in the presence of an organic solvent soluble in water.

Examples of the hydrous alkali metal sulfide used in the present invention include liquid or solid hydrous of compounds such as lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide, and the solid content concentration thereof is not particularly limited. Is preferably 10 to 80% by mass, particularly preferably 35 to 65% by mass. As the hydrous alkali metal sulfide, hydrous sodium sulfide is preferable. The shape of the hydrous sodium sulfide used may be crystalline, flake-like, solid, liquid or aqueous solution.

The hydrous alkali metal sulfide may be, for example, one prepared from a hydrous alkali metal hydrosulfide and an alkali metal hydroxide. Examples of the hydrous alkali metal hydrosulfide include liquid or solid hydrous of compounds such as lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, rubidium hydrosulfide, and cesium hydrosulfide, and the solid content concentration thereof is particularly high. Although not limited, it is preferably 10 to 80% by mass, particularly preferably 35 to 65% by mass. As the hydrous alkali metal hydrosulfide, hydrous sodium hydrosulfide is preferable. The shape of the hydrous sodium hydrosulfide used may be crystalline, flake-like, solid, liquid or aqueous solution. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, and an aqueous solution 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 in the range of 0.8 to 1.2 mol, particularly 0.9 mol, per 1 mol of the alkali metal hydrosulfide from the viewpoint of promoting the formation of anhydrous alkali metal sulfide. A range of ~ 1.1 mol is more preferred.

Examples of the organic solvent that dissolves in water include ketones such as acetone (solubility: compatible with water at all ratios; boiling point: 56.1 ° C.); methanol (solubility: compatible with water at all ratios). , Boiling: 64.7 ° C), Ethanol (Solubility: Incompatible with water in all proportions, Boiling: 78.3 ° C), Isopropyl alcohol (Solubility: Incompatible with water in all proportions, Boiling: 82. 26 ° C.), alcohols such as ethylene glycol (solubility: compatible with water at all ratios, boiling point: 197 ° C.); esters such as methyl acetate (solubility: 24% by mass, boiling point: 56.9 ° C.), etc. Can be mentioned. These organic solvents may be used alone, or a mixed solvent in which two or more kinds are mixed may be used. Preferred organic solvents are ketones and alcohols, more preferred are methanol, acetone, isopropyl alcohol and ethylene glycol, and most preferred are methanol, acetone and ethylene glycol.

Further, the ratio of the organic solvent to the total of the organic solvent and water at the time of microwave irradiation is not particularly limited as long as it does not impair the effect of the present invention, but is preferably in the range of 0.1% or more. Yes, more preferably the range is 15% by mass or more, and further preferably the range is 30% by mass or more. On the other hand, the upper limit value is preferably in the range of less than 100% by mass, more preferably in the range of 90% by mass or less, and further preferably in the range of 80% by mass or less. In addition, less than 100% by mass includes water of crystallization existing in the system and free water (so-called free water) in a state where all free water is removed.

The aqueous alkali metal sulfide solution containing the hydrous alkali metal sulfide and the organic solvent are heated by microwave irradiation so as to be at a temperature at which water can be removed, generally 70 ° C. to 200, preferably 100 ° C. to 200 ° C. By doing so, dehydration is performed.

Dehydration of crystalline water by microwave irradiation is performed by (1) irradiating the hydrous alkali metal sulfide with a microwave in the presence of the organic solvent, (2) when the hydrous alkali metal sulfide is in an aqueous state, and the organic solvent. When a solvent having a boiling point higher than that of water is used, (2a) the alkali metal sulfide-containing aqueous solution is externally heated with a heater or the like to dehydrate the free water, and the hydrous alkali metal sulfide is added while adding the organic solvent. After the dissolution or precipitation, the organic solvent or the dispersion medium described later is added to the dissolved or precipitated hydrous alkali metal sulfide as necessary, and then microwave irradiation is performed. (2b) Alkali metal sulfide. After adding the organic solvent to the substance-containing aqueous solution, externally heat it with a heater or the like to dissolve or precipitate a hydrous alkali metal sulfide while dehydrating free water, and then dissolve or precipitate a hydrous alkali metal. Microwave irradiation is performed while adding the organic solvent or the dispersion medium described later to the sulfide as necessary. (3) When the hydrous alkali metal sulfide is in an aqueous state, and the organic solvent has a boiling point higher than that of water. When using a low-grade solvent, (3a) the alkali metal sulfide-containing aqueous solution is externally heated with a heater or the like to dehydrate the free water, and the hydrous alkali metal sulfide is precipitated while adding a dispersion medium described later. Next, the above-mentioned organic solvent is added to the precipitated hydrous alkali metal sulfide and then irradiated with microwaves. (3b) The dispersion medium described later is added to the alkali metal sulfide-containing aqueous solution, and then the outside is used with a heater or the like. After heating to precipitate hydrous alkali metal sulfide while dehydrating free water, the organic solvent is added to the precipitated hydrous alkali metal sulfide, and then microwave irradiation is performed. Can be mentioned. In either case, it is important to precipitate the hydrous alkali metal sulfide in a state of being dissolved in the organic solvent or in a state of being dispersed in a dispersion medium, and to maintain the dissolved or dispersed state before irradiating with microwaves.

Examples of the dispersion medium include aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, mesitylene, tetraline and diphenyl, aliphatic hydrocarbons such as n-hexane, n-heptane, n-octane and isooctane, cyclohexane and decalin. Examples thereof include hydrocarbon compounds of alicyclic hydrocarbons, polyhaloaromatic compounds such as bromobenzene, iodobenzene, chlorobenzene, dichlorobenzene, trichlorobenzene, tetrachlorobenzene, dichlorodiphenyl sulfone, and dichlorodiphenyl ether, and mixtures thereof. Of these, xylene and p-dichlorobenzene are particularly suitable. Especially when p-dichlorobenzene is used as the dispersion medium, it is more preferable because it can be used as it is for the production of polyarylene sulfide. When a dispersion medium is used, the amount thereof is not particularly limited as long as the above-mentioned dispersed state can be maintained, but is preferably in the range of 0.1 to 10 mol with respect to 1 mol of sulfur atom of the alkali metal sulfide. It is preferably in the range of 1 to 5 mol, more preferably.

Microwave irradiation is performed using a microwave oscillator, and the frequency is not particularly limited as long as it can heat water molecules, but 0.915 GHz or 2.450 GHz is preferable, and any of these is preferable. You may.

The anhydrous alkali metal sulfide obtained by the above method can be dried and prepared as a powdery or granular anhydrous alkali metal sulfide. It is preferable that the inside of the system at the time when dehydration is completed is in a state in which fine-grained anhydrous alkali metal sulfide is dispersed in the organic solvent or the dispersion medium. Anhydrous alkali metal sulfide can be solid-liquid separated from the organic solvent or dispersion medium by means such as filtration, but since it has deliquescent property, it is finely granular in the organic solvent or the dispersion medium. It is preferable to store or use the anhydrous alkali metal sulfide in a dispersed state.

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 of its high purity and uniformity.

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

(Measurement method) Using a coulometric Karl Fischer titer (manufactured by Kyoto Denshi Kogyo Co., Ltd.) equipped with a moisture vaporizer, the obtained anhydrous sodium sulfide is heated at 280 ° C. for 20 minutes, and the evaporated moisture is nitrogen gas. It was sent to the Karl Fischer solution and the water content was measured by the Karl Fischer method.

(Measurement method) Measurement of purity of anhydrous sodium sulfide The purity of anhydrous sodium sulfide was measured 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 in accordance with JIS Z8815-1994.

[Example 1]
116.1 g (1.000 mol of sodium hydrosulfide) containing hydrous sodium hydrosulfide (48.30% sodium hydrosulfide aqueous solution) and 82.22 g (sodium hydroxide) of 48.64% sodium hydroxide aqueous solution in a flask equipped with a stirrer and a decanter. (1,000 mol) and 62.00 g of ethylene glycol (1.00 mol, density 1.113 (room temperature, normal pressure)) were added and the temperature rise was started. The internal temperature was maintained at 170 ° C. for 2 hours, and water was distilled off. Some time after the start of distillation, the particles began to disperse in the system. After 2 hours, 118.0 g of water was distilled off, so dehydration was completed. In the system at the end of dehydration, fine particles containing hydrous sodium sulfide were dispersed in ethylene glycol.

Next, while maintaining the internal temperature of 140 ° C., microwaves having a frequency of 2.450 GHz were irradiated in nitrogen gas for 2 minutes using a microwave oscillator. In the system after microwave irradiation, anhydrous sodium sulfide fine particles were dispersed in ethylene glycol.

After cooling, the particles were filtered and dried under reduced pressure at 100 ° C. for 2 hours to obtain 77.20 g (yield 99.50%) of granular products. The product contained 99.99% anhydrous sodium sulfide and 0.001% water. The particle size of the obtained anhydrous sodium sulfide is shown in Table 1 below.

[Example 2]
Add 240.2 g (1.00 mol of sodium sulfide), 79.20 g of water and 62.00 g (1.00 mol) of ethylene glycol of hydrous sodium sulfide / 9 hydrate (Wako Pure Chemical Industries, Ltd. "Wako 1st grade"). The temperature rise was started. The internal temperature was maintained at 140 ° C. for 2 hours, and water was distilled off. Some time after the start of distillation, the particles began to disperse in the system. After 2 hours, 79.20 g of water was distilled off, so dehydration was completed. In the system at the end of dehydration, fine particles containing hydrous sodium sulfide were dispersed in ethylene glycol.

Next, while maintaining the internal temperature of 140 ° C., microwaves having a frequency of 2.450 GHz were irradiated in nitrogen gas for 2 minutes using a microwave oscillator. In the system after microwave irradiation, anhydrous sodium sulfide fine particles were dispersed in ethylene glycol.

After cooling, the particles were filtered and dried under reduced pressure at 100 ° C. for 2 hours to obtain 77.2 g (yield 99.5%) of granular products. The product contained 99.999% anhydrous sodium sulfide and 0.001% water. The particle size of the obtained anhydrous sodium sulfide is shown in Table 1 below.

[Example 3]
240.2 g of hydrous sodium sulfide / nine hydrate (1.00 mol of sodium sulfide), 79.2 g of water and 62 g of ethylene glycol (1.0 mol) were added to start the temperature rise. The internal temperature was maintained at 140 ° C. for 2 hours, and water was distilled off. Some time after the start of distillation, the particles began to disperse in the system. After 2 hours, 79.2 g of water was distilled off, so dehydration was completed. In the system at the end of dehydration, fine particles containing hydrous sodium sulfide were dispersed in ethylene glycol.

Next, while maintaining the internal temperature of 140 ° C., the pressure was reduced to 13.3 kPa, and then microwaves having a frequency of 2.450 GHz were irradiated for 2 minutes using a microwave oscillator. In the system after microwave irradiation, anhydrous sodium sulfide fine particles were dispersed in ethylene glycol.

After cooling, the particles were filtered and dried under reduced pressure at 100 ° C. for 2 hours to obtain 77.2 g (yield 99.5%) of granular products. The product contained 99.999% anhydrous sodium sulfide and 0.001% water. The particle size of the obtained anhydrous sodium sulfide is shown in Table 1 below.

[Comparative Example 1]
116.1 g (1.000 mol of sodium hydrosulfide) containing hydrous sodium hydrosulfide (48.30% sodium hydrosulfide aqueous solution) and 82.22 g (sodium hydroxide) of 48.64% sodium hydroxide aqueous solution in a flask equipped with a stirrer and a decanter. 1.000 mol) and 147.0 g (1.000 mol) of p-dichlorobenzene were added as a dispersion medium, and the temperature was started. Distillation of water and p-dichlorobenzene began when the internal temperature reached 140 ° C. The p-dichlorobenzene was separated by a decanter and continuously returned to the system. Some time after the start of distillation, the particles began to disperse in the system. After 2 hours, 90.0 g of water was distilled off and the internal temperature rose to 174 ° C., which is the boiling point of p-dichlorobenzene, so dehydration was completed. In the system at the end of 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 granular products. The product contained 98% sodium sulfide and 0.001% water. The particle size of the obtained anhydrous sodium sulfide is shown in Table 1 below.

Claims (6)

An anhydrous alkali metal sulfide, which comprises a step of irradiating a hydrous alkali metal sulfide with a microwave in the presence of an organic solvent soluble in water, and the organic solvent dissolved in water is an alcohol. Production method. The production of the anhydrous alkali metal sulfide according to claim 1, wherein the hydrous alkali metal sulfide is contained in the alkali metal sulfide-containing aqueous solution prepared from the hydrous alkali metal hydrosulfide and the alkali metal hydroxide. Method. The method for producing an anhydrous alkali metal sulfide according to claim 2, wherein an aqueous solution containing an alkali metal sulfide is externally heated to precipitate a hydrous alkali metal sulfide, and then microwave irradiation is performed . The method for producing an anhydrous alkali metal sulfide according to any one of claims 1-3, wherein the ratio of the organic solvent to the total of the organic solvent and water is in the range of 0.1 wt% or more and less than 100 wt% . The method for producing an anhydrous alkali metal sulfide according to any one of claims 1-4, wherein the organic solvent is methanol, isopropyl alcohol or ethylene glycol. The method for producing an anhydrous alkali metal sulfide according to any one of claims 1 to 5, wherein microwave irradiation is performed under reduced pressure.