JPH07106888B2 - Chlorapatite manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing chlorapatite, and more particularly to a method for producing chlorapatite having high purity and high reactivity with carbon dioxide gas.

The chlorine apatite of the present invention is highly reactive with carbon dioxide gas and can be used as a carbon dioxide gas detection element or a carbon dioxide gas detection element material, and a fire is generated by detecting a rapid increase in carbon dioxide gas in the air. Can be used for detecting the occurrence of incomplete combustion in the combustor by detecting the decrease in the amount of carbon dioxide gas generated during the steady generation of carbon dioxide gas.

[Technical Background and Description of Prior Art]

Apatite (apatite) is a calcium phosphate containing fluorine, chlorine, and a hydroxyl group, and Cl> F, OH is called chlorine apatite (chlorapatite). (Kyoritsu Shuppan Co., Ltd., “Chemical Dictionary”, Volume 9, pages 776-777, “Apatite”) So far, there are dry method, wet method, hydrothermal method and melting method as apatite synthesis methods. For the synthesis of chlorapatite, dry method with tricalcium phosphate and calcium chloride, hydrothermal method with tricalcium phosphate, sodium chloride, diammonium phosphate and ammonium chloride and melting with sodium phosphate and calcium chloride Although there is a method, it is said that the wet method by reaction in a solution state cannot be synthesized under the conditions of normal temperature and normal pressure. (Takafumi Kanazawa, Hideki Kadama "Chemistry of Calcium Phosphate": Area of Chemistry 27-8, pp. 22-32) [Hideki Kadama, Takafumi Kanazawa "Wet Formation Process of Non-stoichiometric Hydroxyapatite from Calcium Phosphate": Ceramic Industry Association magazine Vol. 86, No. 2 (1978)] Hydroxyapatite [Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ ] has a characteristic that its electric resistance fluctuates when it comes into contact with carbon dioxide at high temperature, Due to its characteristics, it has been proposed to use hydroxyapatite as a carbon dioxide gas detection element (Japanese Patent Application No. 59-59).
No. 211287), and a composite material of hydroxyapatite and calcium chloride is proposed as a carbon dioxide sensing element material. (Japanese Patent Application No. 61-85126) The present inventors continued their research, and in that research, a single phase of chlorine apatite [Ca ₁₀ (PO ₄ ) ₆ Cl ₂ ] or chlorine apatite formed a solid solution with hydroxyapatite. It was found that the electrical resistance fluctuates when contacted with carbon dioxide gas without complexing other materials, and further, when hydroxyapatite is reacted with ammonium chloride in an aqueous medium, chlorine The inventors have found that apatite is produced, and arrived at the present invention based on these findings.

[Purpose of Invention and Summary of Invention]

An object of the present invention is to provide chlorine apatite, more specifically to provide chlorine apatite with high purity, and more specifically, chlorine apatite with high purity that can be used for detection of carbon dioxide gas. To provide a manufacturing method of.

The present invention is a method for producing chlorapatite, which comprises reacting hydroxyapatite with ammonium chloride in an aqueous medium under alkaline conditions.

Another aspect of the present invention is to calcinate hydroxyapatite, then mix with calcium chloride in an ethanol medium, and calcine the mixture to prepare calcium-excessive chlorine apatite, and calcium-excessive chlorine apatite. A method for producing chlorapatite characterized by reacting with ammonium chloride.

Hydroxyapatite in the production of chlorapatite of the present invention, it is possible to use those obtained by reacting calcium hydroxide with phosphoric acid, the reaction of hydroxyapatite and ammonium chloride pH: 7 ~ 11 It can be carried out in an aqueous medium under alkaline conditions, and further, the reaction between hydroxyapatite and ammonium chloride is carried out in an aqueous medium under alkaline conditions of pH: 8-9, whereby the purity of chlorine apatite can be improved. Can be improved.

The chlorine apatite according to the present invention has the property of increasing its electrical resistance when it comes into contact with carbon dioxide gas without the addition of an additive (inorganic halide), and due to this property, it is used for detecting carbon dioxide gas. be able to.

[Specific Description of the Invention]

In the production of chlorapatite of the present invention, calcium hydroxide is suspended in water to form lime milk, and phosphoric acid is added to this to form a precipitate of hydroxyapatite at around pH: 9. The addition of phosphoric acid preferably uses a concentrated phosphoric acid solution at its initial stage and a low concentrated phosphoric acid solution at its final stage, thereby facilitating the adjustment of the pH of the reaction mixture.

An aqueous solution of ammonium chloride is added to the reaction mixture having a pH of around 9 to form a precipitate of hydroxyapatite, and a precipitation of chlorine apatite is produced. When the aqueous solution of ammonium chloride is added, ammonia water is added. , The pH of the reaction mixture is 7
However, the purity of chlorapatite can be improved by maintaining the pH of the reaction mixture at 8-9. The amount of ammonium chloride added is preferably about 2 mol of ammonium chloride based on the initial 7 mol of calcium hydroxide.

After the addition of ammonium chloride, the reaction mixture is stirred to complete the reaction, and then the reaction mixture is filtered to obtain a precipitate of chlorapatite. The precipitate of chlorapatite is dried and then calcined at a temperature of 600 ° C. or higher to obtain chlorapatite powder.

In the alternative method of producing the chlorine apatite of the present invention, in the preparation of the hydroxyapatite, the reaction mixture that produced the precipitation of hydroxyapatite around pH: 9 is filtered to obtain the precipitation of hydroxyapatite. This is dried and then calcined at a temperature of 600 ° C. or higher to obtain a hydroxyapatite powder.

This powder of hydroxyapatite was mixed with 1 mol of calcium chloride in 2 mol of hydroxyapatite in ethanol, and the resulting mixture was calcined at a temperature of 600 ° C. or higher to give calcium-excessive chlorine apatite. To get This calcium-excessive chlorapatite is added to an ammonium chloride aqueous solution, stirred well to elute the excess amount of calcium, and then the reaction mixture is filtered to obtain a precipitate of chlorapatite, which is dried to remove chlorine. Obtain apatite powder.

According to the results of the experiment, in the former method (wet method) of the present invention in which hydroxyapatite is reacted with calcium chloride in an aqueous medium under alkaline conditions, chlorine content is less than the theoretical amount, and Although chlorine apatite mixed with apatite can be obtained, when the pH of the hydroxyapatite reacted with ammonium chloride in an aqueous medium is adjusted to 8 to 9, the chlorine content of the generated chlorine apatite becomes high. Is expected to increase.

On the other hand, in the above, after calcination of hydroxyapatite, it is mixed with calcium chloride in ethanol to prepare chlorinated apatite in excess of calcium, and the latter of the present invention in which excess calcium is eluted with ammonium chloride. Since the chlorine content in the method (dry method) is almost equal to the theoretical amount, it is considered that chlorine apatite with high purity can be obtained by the latter method of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 500 g of calcium hydroxide was added to distilled water 5 and stirred by a stirrer (Tokyo Rika Kikai: EYELA MINI DCSTIRRER) to suspend, and the 18N phosphoric acid solution was diluted 3 times with stirring. The pH of the reaction mixture was adjusted to 11 with a microtube pump (Tokyo Rika Kikai: MIP-3).
It was dripped until. When the pH of the reaction mixture reached 11, the phosphoric acid solution diluted 3 times was switched to the phosphoric acid solution diluted 10 times, and thereafter, the phosphoric acid solution diluted 10 times was replaced with the microtube pump described above. The pH of the reaction mixture is 9
It was dripped until. When the pH of the reaction mixture reached 9, the phosphoric acid solution diluted 10 times was replaced with an ammonium chloride aqueous solution obtained by dissolving 100 g of ammonium chloride (special grade reagent, Showa Kagaku) in distilled water 1. , After that, 3N
Add ammonia water dropwise with a syringe to adjust the pH of the reaction mixture.
While maintaining at 10, the ammonium chloride aqueous solution was added dropwise to the reaction mixture.

After the entire amount of the ammonium chloride aqueous solution was added dropwise, the reaction mixture was stirred for another 24 hours, and the reaction mixture was filtered to obtain a precipitate of chlorapatite produced. After this chlorine apatite was dried at 120 ° C. for 24 hours, it was calcined at 800 ° C. for 3 hours to obtain about 800 g of chlorine apatite powder.

The crystal structure of the chlorapatite powder was analyzed by powder X-ray diffraction, and the chlorapatite powder was analyzed by ion chromatography (IC 500 P, Yokogawa Electric Co., Ltd.) for calcium ion (Ca ²⁺ ) and phosphoric acid. AEON (▲ PO ^3-
₄ ▼) was quantified and the Ca / P molar ratio was measured. Furthermore the chlorine content of the chlorine apatite, similarly to the above, chloride ion ^- was measured by quantifying (Cl).

The X-ray diffraction pattern obtained by powder X-ray diffraction is the first
As shown in the figure, the Ca / P molar ratio by ion chromatography was 1.66, but the chlorine content was 40%.

According to the result of the X-ray diffraction pattern in the powder X-ray diffraction and the result of measurement of the chlorine content, Example 1 and chlorine apatite were found to be hydroxyapatite [Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ ].
It is a solid solution of chlorapatite [Ca ₁₀ (PO ₄ ) ₆ (Cl) ₂ ] and its content of chlorine apatite is 38
It turns out that it is% (weight).

Example 2 (Preparation of Hydroxyapatite) 500 g of calcium hydroxide was added to 5 of distilled water, and the mixture was stirred with a stirrer (Tokyo Rika Kikai: EYELA MINI DCSTIRRER), suspended, and further stirred with 18N phosphoric acid. The pH of the reaction mixture was adjusted to 11 with a microtube pump (Tokyo Rika Kikai: MIP-3).
It was dripped until. When the pH of the reaction mixture reached 11, the phosphoric acid solution diluted 3 times was switched to the phosphoric acid solution diluted 10 times, and then the phosphoric acid solution diluted 10 times was replaced with the microtube pump described above. The pH of the reaction mixture is 9
It dripped gradually until it became.

When the pH of the reaction mixture reached 9, stop adding the 10 times diluted phosphoric acid solution, stir the reaction mixture for another 24 hours, and then filter the reaction mixture to precipitate the hydroxyapatite. The obtained hydroxyapatite was dried at 120 ° C. for 24 hours and then calcined at 800 ° C. for 3 hours to obtain about 800 g of hydroxyapatite powder.

(Preparation of chlorine apatite) 60 g of hydroxyapatite powder was placed in a raider machine, 100 ml of pharmacopoeia ethanol was added thereto, 10 g of calcium chloride (reagent special grade, Showa Chemical Co., Ltd.) was further added, and the mixture was stirred for 8 hours. , Mixed. The resulting mixture was stored at 800 ° C for 24 hours.
Burned for hours. The fired product obtained here was chlorapatite with excess calcium.

After dissolving 100 g of ammonium chloride (special grade reagent, manufactured by Showa Kagaku Co., Ltd.) in distilled water 1, the total amount of the calcium-excessive chlorine apatite obtained above was added and stirred for 1 hour to elute the excess calcium. , After decanting the supernatant,
The chlorapatite precipitate was washed with 2 distilled water. In the final stage of this washing, chlorine apatite suspended in distilled water was filtered to obtain a precipitate of chlorine apatite, which was dried at 120 ° C for 12 hours to obtain about 60 g of chlorine apatite powder. .

(Analysis of Chlorapatite Powder) As in Example 1, the chlorine apatite powder was analyzed for its crystal structure by powder X-ray diffraction, and its Ca / P molar ratio was measured by ion chromatography. Further, the chlorine content was measured.

The X-ray diffraction pattern obtained in the powder X-ray diffraction is the second
As shown in the figure, the Ca / P molar ratio by ion chromatography was 1.67, and 100% of the —OH groups of hydroxyapatite was replaced by —Cl.

From the results of the X-ray diffraction pattern in the powder X-ray diffraction and the results of measuring the chlorine content, it can be seen that the chlorine apatite of Example 2 is 100% chlorine apatite.

Example 3 500 g of calcium carbonate (for alkali analysis, manufactured by Wako Pure Chemical Industries, Ltd.)
Was placed in an electric furnace, calcined at 1000 ° C. for 3 hours to decarboxylate, and when it reached 200 ° C., it was taken out of the electric furnace and steam hydrated. After aging this steam hydrate for 1 day, add this to distilled water 5 and stir with a stirrer (Tokyo Rika Kikai: EYELA MINI DCSTIRRER) to suspend and further add 18N phosphoric acid solution to it while stirring. A 3-fold diluted phosphoric acid solution was added dropwise by a microtube pump (Tokyo Rika Kikai: MIP-3) until the pH of the reaction mixture became 9. When the pH of the reaction mixture reaches 9, add phosphoric acid solution to ammonium chloride (special grade reagent, Showa Kagaku) 10
Switch to 0% ammonium chloride aqueous solution obtained by dissolving 0 g in distilled water 1, and then add 3N ammonia water dropwise to the reaction mixture with a syringe to maintain the pH of the reaction mixture at 8.5 while maintaining ammonium chloride. The aqueous solution was added dropwise to the reaction mixture to dope the hydroxyapatite with chlorine ions.

After the entire amount of the ammonium chloride aqueous solution was added dropwise, the reaction mixture was stirred for another 24 hours, and the reaction mixture was filtered to obtain a precipitate of chlorapatite produced. The precipitate of chlorapatite was dried at 80 ° C and then calcined at 800 ° C to obtain about 600 g of chlorapatite powder.

For this chlorine apatite powder, calcium ion, phosphate ion and chlorine ion were quantified in the same manner as in Example 1 to obtain a measured value of a Ca / P molar ratio of 1.80 and a chlorine content of 84%.

According to this result, the chlorine apatite of Example 3 (the one doped with chlorine with ammonium chloride at pH: 8.5) was the chlorine apatite of Example 1 (the one doped with chlorine with ammonium chloride at pH: 10). ) And chlorine apatite of Example 2 (by the dry method), it is found to be rich in calcium, which is expected to improve the performance as a carbon dioxide detecting element.

X obtained by powder X-ray diffraction of this chlorine apatite
The line diffraction pattern was as shown in FIG.

〔The invention's effect〕

It is possible to obtain chlorine apatite containing a small amount of hydroxyapatite.

Almost pure chlorine apatite close to the theoretical formula of Ca ₁₀ (PO ₄ ) ₆ (Cl) ₂ can be obtained.

Chlorapatite capable of detecting carbon dioxide can be obtained without adding (compositing) an additive (inorganic halide).

[Brief description of drawings]

FIG. 1 is a table showing an X-ray diffraction pattern in powder X-ray diffraction of chlorine apatite obtained in Example 1.
FIG. 3 is a table showing an X-ray diffraction pattern in powder X-ray diffraction of chlorine apatite obtained in Example 2, and FIG. 3 is an X-ray diffraction pattern in powder X-ray diffraction of chlorine apatite obtained in Example 3. FIG.

Claims (4)

[Claims] 1. A process for producing chlorapatite, which comprises reacting hydroxyapatite with ammonium chloride in an aqueous medium under alkaline conditions. 2. The method for producing chlorapatite according to claim 1, wherein the aqueous medium for reacting hydroxyapatite with ammonium chloride is maintained at pH: 7 to 11. 3. The method for producing chlorapatite according to claim 2, wherein the aqueous medium for reacting hydroxyapatite with ammonium chloride is maintained at pH: 8-9. 4. Calcining hydroxyapatite, mixing it with calcium chloride in an ethanol medium, and calcining the mixture to prepare chlorinated apatite in excess of calcium, and chlorinated apatite in excess of calcium with ammonium chloride. A method for producing chlorapatite, which comprises reacting with chlorapatite.