JP2000281690A - Production of ethane-1-hydroxy-1,1-diphosphonic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain, at a low cost and in a high yield, the subject compound useful as a metal sequestering agent utilizing its chelating ability to metal ions, a scale inhibitor or corrosion inhibitor or the like each for boilers, etc., by reacting pyrophosphorous acid with acetic anhydride under easy control. SOLUTION: This compound is obtained by reacting (A) pyrophosphorous acid with (B) acetic anhydride pref. at the rate of 0.5 to 1 mol of the component B based on one phosphorus atom of the component A, pref. under reflux using by-product acetic acid after supplying the component B to the component A heated in advance pref. at a temp. of 90 to 100 deg.C. In the above reaction, it is desirable to age the reaction mixture under heating after finishing supply of the component B. After finishing the above reaction, it is desirable to supply water to the reaction liquid to conduct hydrolysis treatment. In the above hydrolysis, it is desirable to supply water at 1.5 times the theoretical amount necessary for breaking the C-O-C bond of the component B used in excess of the P-O-P bond of the component A and the component A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing ethane-1-hydroxy-1,1-diphosphonic acid, and more particularly to a method for producing ethane-1-hydroxy-1,2-diphosphonic acid by reacting pyrophosphoric acid with acetic anhydride. The present invention relates to a method for producing 1,1-diphosphonic acid. The ethane-1-hydroxy-1,1-diphosphonic acid produced according to the present invention can be used as a metal sealant utilizing a chelating ability with metal ions, a scale inhibitor and a corrosion inhibitor such as a boiler, or an alkali. The bleaching agent used can be used as a stabilizer for hydrogen peroxide.

[0002]

2. Description of the Related Art Conventionally, ethane-1-hydroxy-1,1-
Many methods for producing diphosphonic acid have been proposed. These production methods can be roughly classified into three types depending on the raw materials used. That is, the phosphorus trichloride method of reacting acetic acid with phosphorus trichloride (Japanese Patent Publication No. 50-17457, Japanese Patent Publication No.
No. -1180), a phosphorous acid method of reacting acetic anhydride and phosphorous acid (Japanese Patent Publication Nos. 40-13730 and 47-32969), and an anhydride of reacting acetic acid with phosphorous anhydride. The phosphorous acid method (JP-B-43-933, JP-B-43-8250, etc.).

[0003]

However, all of these conventional manufacturing methods have serious drawbacks as described below. In the phosphorus trichloride method, an intermediate acetyl chloride and phosphorous acid are first formed by the reaction of phosphorus trichloride and acetic acid. Next, the phosphorous acid is acetylated by acetyl chloride, and hydrogen chloride is by-produced. Acetyl chloride is an important intermediate for forming ethane-1-hydroxy-1,1-diphosphonic acid, and it is essential that acetyl chloride be present in an equimolar system with respect to phosphorous acid. However, the boiling point of acetyl chloride is 52 ° C., and it is difficult to keep the acetyl chloride in the system in a hydrogen chloride gas fluid with a normal condenser, and acetyl chloride is separated from the hydrogen chloride gas fluid flowing out of the system. Requires special separation equipment. In order to minimize the loss of acetyl chloride in the hydrogen chloride gas, a low reaction temperature may be used, but in this case, the reaction rate of phosphorus trichloride is low, and the reaction requires a long time, This leads to poor yield and quality.

[0004] The phosphorous acid method does not have the drawbacks of hydrogen chloride by-product and acetyl chloride separation, unlike the phosphorus trichloride method, but it has another industrial problem. That is, since phosphorous acid is a solid, conventionally, a method of mixing and dissolving it in acetic anhydride in advance and heating the mixture to start the reaction has been adopted. However, when the temperature of the mixture is raised, a rapid temperature rise may cause a decomposition reaction of the product. Cooling the reaction mixture stopped the reaction and avoided ethane-1-hydroxy-
1,1-Diphosphonic acid may not be obtained. Although a gradual temperature increase is desirable, the product may still be markedly colored, even in this case, with high yields and high quality ethane.
It is difficult to produce 1-hydroxy-1,1-diphosphonic acid. In addition, both the raw material phosphorous acid and acetic anhydride are expensive and disadvantageous in cost.

[0005] In the phosphorous anhydride process, the reaction between phosphorous anhydride and acetic acid is a highly exothermic reaction, sometimes even explosive. For this reason, ethane-1-hydroxy-1,1 is required without a reaction solvent for absorbing the reaction heat.
It is not possible to produce diphosphonic acids. At this time, the reaction solvent needs to be inert to the starting materials and reaction products and to be able to dissolve the starting materials and reaction products to some extent. However, since phosphorous anhydride is highly reactive and the reaction product has extremely high polarity, general solvents such as hydrocarbons, alcohols, ethers, esters, and ketones are not suitable for the phosphorous anhydride method. However, there is a drawback that only special solvents such as di-n-propyl sulfone or sulfolane can be used.

That is, an object of the present invention is to overcome the above-mentioned disadvantages of the prior art and to provide ethane-1-hydroxy-1,1.
-To provide an industrial process for the production of diphosphonic acids, in particular to provide a process which is inexpensive, whose reaction can be easily controlled and which has a high yield.

[0007]

Means for Solving the Problems The present inventors have proposed ethane-
As a result of intensive studies on the method of producing 1-hydroxy-1,1-diphosphonic acid, formation of pyrophosphorous acid with water and phosphorus trichloride in advance avoids the production of acetyl chloride, which is difficult to separate from hydrogen chloride. Further, the present inventors have found a production method capable of greatly reducing the molar ratio of acetic anhydride to phosphorus atoms by reacting the pyrophosphorous acid with acetic anhydride as compared with the phosphorous acid method.

The inventors of the present invention have been able to elucidate the reaction mechanism of the phosphorous acid method in the course of the intensive research. That is, in the phosphorous acid method, when acetic anhydride and phosphorous acid are reacted, first, as shown in the following formula, a diacetylated product of phosphorous acid is generated,

[0009]

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Next, by applying heat, a rearrangement reaction represented by the following formula occurs to convert to a compound containing a carbon atom directly bonded to a phosphorus atom.

[0011]

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Further, as shown in the following formula, the rearranged product reacts with the remaining phosphorous acid without being acetylated to form an intermediate [A], and undergoes the rearrangement again to form the intermediate [B] ] Is formed.

[0013]

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Since the intermediate [B] has an ester bond and a hydroxyl group in the molecule, it is easily subjected to intermolecular deacetic acid condensation as shown in the following formula to give ethane-1-hydroxy-1,1-
A cyclic condensate of diphosphonic acid [C] is formed.

[0015]

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Further, as shown in the following formula, the desired ethane-1-hydroxy-1,1-diphosphonic acid is obtained by hydrolyzing this cyclic condensate [C]. These series of reaction processes were first revealed by the present inventors.

[0017]

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When producing ethane-1-hydroxy-1,1-diphosphonic acid by the phosphorous acid method, the reaction molar ratio (acetic anhydride / phosphorous acid) must be 1 or more.
Further, since phosphorous acid is diacetylated when acetylated with acetic anhydride, it is necessary to react 1 mol or more of acetic anhydride with one phosphorous atom of the charged phosphorous acid.
When the amount is less than the mole, phosphorous acid remains as an unreacted substance in the reaction solution.

The inventors of the present invention have made the reaction of pyrophosphorous acid with acetic anhydride instead of phosphorous acid, using the results of the analysis of the reaction mechanism of the above-mentioned phosphorous acid method as a hint. It has been found that an amount of acetic anhydride of 0.5 mole per phosphorus atom is sufficient. That is, phosphorous acid has two hydroxyl groups for one phosphorus atom, whereas pyrophosphorous acid has two hydroxyl groups for two phosphorus atoms, so that the amount of acetic anhydride required is only half. It will be. The advantage of using pyrophosphorous acid is apparent. Incidentally, the reaction after acetylation, as described in detail later, similarly to the phosphorous acid method, rearrangement, the reaction with non-acetylated pyrophosphorous acid,
It proceeds with rearrangement and, as in the phosphorous acid method, ethane-1-
Cyclic condensate of hydroxy-1,1-diphosphonic acid [C]
Generate Therefore, even when phosphorous acid or pyrophosphorous acid is used as a starting material, ethane-1-hydroxy-1,1-diphosphonic acid can be easily obtained by hydrolysis of the cyclic condensate [C].

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Preparation of pyrophosphorous acid
pt. , Rend. , 136, 814 (1903). In this method, pyrophosphorous acid can be synthesized quantitatively by reacting 0.2 mol of phosphorus trichloride with 1 mol of phosphorous acid. Further, in advance, phosphorous acid is synthesized by a reaction of water and phosphorus trichloride, and then excess water is removed by topping under reduced pressure, and further reacted with phosphorus trichloride to form pyrophosphorous acid. Can also. Thus, despite the fact that phosphorus trichloride is used as a raw material, acetyl chloride is not by-produced, so that there is an advantage that hydrogen chloride can be easily recovered.

(Synthesis of phosphorous acid) The reaction for synthesizing phosphorous acid from water and phosphorus trichloride is represented by the following formula:

[0022]

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The theoretical amount of water required for 1 mole of phosphorus trichloride is 3 moles, but the actual amount of water used must be in excess of the theoretical amount in order to complete the reaction quickly. It is. Usually, 4 to 15 per mol of phosphorus trichloride.
Moles, preferably 6 to 10 moles of water are used. Since this hydrolysis reaction produces hydrogen chloride as a by-product, it is necessary to guide the reaction to an appropriate absorption facility charged with an aqueous sodium hydroxide solution or the like.

On the other hand, in order to synthesize pyrophosphorous acid, the phosphorous acid to be reacted with phosphorus trichloride must be substantially anhydrous. That is, the presence of water is not preferable because it causes a decrease in the purity of pyrophosphorous acid.
The following moisture can be tolerated. Therefore, excess water remaining in the phosphorus trichloride hydrolysis reaction solution must be dehydrated under reduced pressure. Similarly, commercially available phosphorous acid can be used as a raw material for pyrophosphorous acid synthesis, provided that the water content is 0.05% or less.

(Synthesis of pyrophosphorous acid) The reaction for synthesizing pyrophosphorous acid from phosphorous acid and phosphorus trichloride is represented by the following formula:

[0026]

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The theoretical amount of phosphorus trichloride required for 1 mol of phosphorous acid is 0.2 mol, but the actual amount of phosphorus trichloride used is in the range of 0.2 to 0.3 mol. Preferably 0.
It is selected from the range of 2 to 0.25 mol. That is,
The use of too little or too much phosphorus trichloride is undesirable in any case because it causes undesirable side reactions, lowers the purity of pyrophosphorous acid, and hinders the progress of the reaction with acetic anhydride described below. As in the synthesis of phosphorous acid, it is necessary to introduce by-produced hydrogen chloride into an appropriate absorption facility.

The reaction temperature is preferably from 30 to 80 ° C.,
C. or higher is not preferable because the amount of phosphorus trichloride that escapes out of the system together with by-product hydrogen chloride increases. The time required for dropping a predetermined amount of phosphorus trichloride is 1 hour or more, preferably 2 to 5 hours. That is, when the dropwise addition is completed in a short period of time, the reaction rapidly occurs, and the loss of phosphorus trichloride increases with the rapid increase in the amount of generated hydrogen chloride, which is not preferable. After the completion of the addition of phosphorus trichloride, the reaction is completed by, for example, 1 to 3 at the same temperature as the reaction.
Aging for about an hour. Further, since the pyrophosphorous acid obtained by aging contains a small amount of hydrogen chloride, an appropriate amount of an inert gas such as a nitrogen gas is blown, and hydrogen chloride is removed by accompanying the inert gas. By selecting appropriate production conditions in this way, the anhydrous point is easily at least 6.50 (theoretical value 6.
85), high-purity pyrophosphorous acid is obtained. This anhydrous point is defined as the number of millimoles of water consumed in the hydrolysis of 1 g of pyrophosphorous acid when hydrolyzed by adding water to pyrophosphorous acid.

Ethane-1-hydroxy-1,1-diphos
Production of ethane-1-hydroxy-1,1-diphosphonic acid in the manufacture invention of acid is a raw material and pyrophosphorous acid and acetic anhydride, cyclic ethane-1-hydroxy-1,1-diphosphonic acid It comprises a step of synthesizing a condensate and a step of synthesizing ethane-1-hydroxy-1,1-diphosphonic acid by hydrolysis of the cyclic condensate.

(Reaction between pyrophosphorous acid and acetic anhydride)
It is considered that the synthesis of the cyclic condensate [C] of 1-hydroxy-1,1-diphosphonic acid consists of an elementary reaction represented by the following four formulas.

[0031]

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In the present invention, as shown in the above formula, 2 mol of pyrophosphorous acid and 2 mol of acetic anhydride are used to synthesize 1 mol of the cyclic condensate [C]. That is, the theoretical ratio of both raw materials is equivalent to 0.5 mol of acetic anhydride per phosphorus atom in pyrophosphorous acid. However, the starting pyrophosphorous acid usually has an anhydride point slightly lower than the theoretical value. Therefore, in practice, the amount is preferably in the range of 0.5 mol or more to less than 1 mol, preferably 0.5 mol to 1 phosphorus atom in pyrophosphorous acid.
It is desirable to select an amount of acetic anhydride in the range of 5 to 0.60 mol. That is, use of less than 0.5 mole of acetic anhydride results in ethane-1-hydroxy-1,1
-Not only the residual amount of phosphorous acid contained in the diphosphonic acid increases, but also a large amount of crystals precipitate in the reaction solution, and the fluidity decreases, which may hinder the stirring and mixing of the reaction solution. Also, the use of an amount of acetic anhydride exceeding 0.65 mol
It only increases the amount of acetic acid by-product, and has no economic significance.

In the present invention, when synthesizing the cyclic condensate [C] of ethane-1-hydroxy-1,1-diphosphonic acid, it is important to control the reaction temperature. That is, when acetic anhydride is supplied at an appropriate rate to pyrophosphorous acid that has been heated to an appropriate temperature in advance, the above four elementary reactions: (1) acetylation reaction of pyrophosphorous acid with acetic anhydride,
(2) acetyl group rearrangement reaction accompanied by PC bond formation,
(3) Reaction of acetyl group with pyrophosphorous acid and (4) P-
The rearrangement reaction of the pyrophosphorous acid residue accompanied by the formation of C bond occurs promptly, and the reaction heat eventually raises the reactor temperature to the boiling point of acetic acid (about 120 ° C. at normal pressure). Reflux is observed. Also, if the acetic anhydride feed rate is appropriately adjusted, the reaction temperature can be controlled by absorbing the heat of reaction by evaporation of the by-product acetic acid,
There is an advantage that no extra cooling equipment is required.

That is, when the reaction is started at an excessively low temperature, the acetylation reaction of (1) proceeds, but the subsequent rearrangement reaction of the acetyl group of (2) is very slow, and the desired ethane-1 Does not lead to the production of -hydroxy-1,1-diphosphonic acid. Further, in the method in which acetylation is once performed at a low temperature and then the temperature is raised to cause a rearrangement reaction, a rapid rearrangement reaction may occur, and it may be impossible to control the reaction. On the other hand, it is possible to start the reaction at a high temperature, but this only increases the load of heat removal and does not bring any practical benefit. Accordingly, a suitable preheating temperature for pyrophosphorous acid is generally selected from the range of 70 to 150 ° C, preferably 90 to 100 ° C.

Another important point in the synthesis of the cyclic condensate [C] is that after the supply of a predetermined amount of acetic anhydride is completed, aging is performed under heating to complete the reaction. In particular,
This aging is usually performed at a temperature equal to or higher than the boiling point of acetic acid, for a sufficient period of time, depending on the remaining amount of pyrophosphorous acid.
It is carried out for 5 hours, preferably for 2 to 3 hours. That is, unreacted pyrophosphorous acid may remain during aging for a short time, and crystals may be precipitated and the reaction solution may be solidified during aging for a long time.

(Hydrolysis) A reaction solution from the step of synthesizing a cyclic condensate of ethane-1-hydroxy-1,1-diphosphonic acid using the above-mentioned pyrophosphorous acid and acetic anhydride as starting materials is a cyclic condensate [ C] is a viscous liquid containing by-product acetic acid and unreacted acetic anhydride, and possibly a small amount of unreacted pyrophosphorous acid. Therefore, in the step of synthesizing ethane-1-hydroxy-1,1-diphosphonic acid by this hydrolysis, the cyclic condensate and acetic anhydride present in the reaction solution are converted into ethane-1-hydroxy-1,1-acetic acid, respectively.
Converted to 1-diphosphonic acid and acetic acid. The hydrolysis reaction is represented by the following two equations.

[0037]

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As is apparent from this reaction formula, in the cyclic condensate [C], a PO—P bond derived from pyrophosphorous acid, and in acetic anhydride, a C—O—C bond is formed. ,
Converted to the free acid by hydrolysis. Therefore, the amount of water required for the hydrolysis depends on the P-O-P bond or C-O-
One mole is the theoretical amount for one C bond. However, in practice, the amount of water added in the hydrolysis is not sufficient with the above stoichiometric amount, and is 1.5 times or more the stoichiometric amount, preferably 2 to 2, including the amount necessary for dissolving the product. Three times is selected. By the way, when the amount of water is as small as the theoretical amount, ethane-1-hydroxy-1,1 produced by hydrolysis is used.
-The fact that diphosphonic acid is essentially insoluble in acetic acid is insufficient to dissolve it, not only precipitates crystals from the reaction solution, but also solidifies the entire reaction solution, making it unhandleable. May lead to. That is, the addition of excess water dissolves ethane-1-hydroxy-1,1-diphosphonic acid in the presence of acetic acid, and enables suppression of crystallization. But too much,
For example, the addition of more than three times the stoichiometric amount of water only increases the energy cost of the subsequent acetic acid removal step and is not suitable. That is, since the vapor pressure of water is higher than the vapor pressure of acetic acid, if the concentration of water in the reaction solution increases, the concentration of water in the distillate also increases, resulting in poor acetic acid removal efficiency. For this reason, it is important to appropriately select the amount of water to be added in the hydrolysis step.

Incidentally, the addition of water in the hydrolysis step
The reaction is exothermic and requires careful control of the reaction temperature. For example, when the required amount of water is added to the viscous reaction solution at a time, the acetic acid evaporates rapidly due to a rise in temperature, and the entire reaction solution may be solidified. Therefore, once the reaction solution, the temperature of 90 ℃ or less,
For example, after cooling to 60 to 90 ° C, it is desirable to keep the reaction temperature at 90 to 120 ° C by gradually adding water. After the addition is completed, 90
Aging is performed at -120 ° C for 0.5 hours or more, preferably 0.5-1 hour.

(Purification) The liquid reaction product containing about 30% of acetic acid is subjected to 100 ° C. or higher, preferably 1 ° C., at atmospheric pressure.
Heat to 00-120 ° C to remove acetic acid. When the distillation of acetic acid stops, acetic acid is recovered while gradually lowering the pressure in the system. Then, when the pressure reaches 300 mmHg or less and the liquid temperature reaches 100 ° C. or less, preferably 80 to 100 ° C., under the same conditions, After steaming, the remaining acetic acid is evaporated off. The reaction solution thus treated is in a highly concentrated state, and ethane-1-hydroxy-1,1-diphosphone is adjusted to a desired concentration (50 to 60 wt%) by adding water thereto. Obtain the acid.

According to the present invention, if necessary, an alkaline substance such as an alkali metal hydroxide or aqueous ammonia may be present in the hydrolysis step, or an alkaline substance may be added after the hydrolysis and the removal of acetic acid. Neutralization with a substance can also provide an alkali metal or ammonium salt of ethane-1-hydroxy-1,1-diphosphonic acid.

The following examples illustrate the specific procedures of the present invention, but do not limit the appropriate scope of the present invention.

Example 1 Preparation of phosphorous acid In a 500 ml four-necked flask, 108.0 g of water (6.0 g) was added.
mol)) and phosphorus trichloride 13 placed in a dropping funnel.
7.3 g (1.0 mol) is slowly added dropwise over about 2 hours while cooling to keep the reaction temperature at 20 to 30 ° C. The by-produced hydrogen chloride is absorbed in a 15% aqueous sodium hydroxide solution. After all the phosphorus trichloride in the dropping funnel is added, the mixture is aged at 30 ° C. for 1 hour. Then 5
At a pressure of 0 mmHg, the temperature is gradually increased,
Remove water and hydrogen chloride. When it reaches 130 ° C., it is left at this temperature for 1 hour. Here, the phosphorous acid solution obtained in the flask was sampled, and the phosphorous acid content and the water content were measured.
8.7% and 0.03%.

Preparation of pyrophosphorous acid The phosphorous acid solution in the flask is cooled to 75 ° C. 7
Care must be taken because lowering the temperature to 0 ° C. may lead to crystallization and solidification. To the cooled phosphorous acid solution, 32.9 g (0.24 mol) of phosphorus trichloride is added dropwise from a dropping funnel while maintaining the reaction temperature at 60 to 70 ° C. Hydrogen chloride by-produced is absorbed in an aqueous sodium hydroxide solution as described above. After completion of the dropping of phosphorus trichloride, the mixture is aged at 60 to 70 ° C for 1 hour. Further, at the same temperature, 50 ml of nitrogen is added.
Blow at a rate of / min for 30 minutes. The thus obtained pyrophosphorous acid had an anhydrous point of 6.78 (theoretical value: 6.85).

Ethane-1-hydroxy-1,1-diphos
The pyrophosphorous acid in the flask for producing folic acid is heated to 100 ° C., and 68.6 g (0.67 mol, molar ratio to phosphorus: 0.56) of acetic anhydride is dropped from the dropping funnel. Adjust the rate of addition of acetic anhydride so that the by-product acetic acid slowly refluxes in the condenser. After the total amount of acetic anhydride in the dropping funnel was added in about 30 minutes, the mixture was aged at 120 ° C. for 2 hours, and the unreacted pyrophosphorous acid in the reaction solution was 0.77% (expressed as phosphorous acid content). )Met.

After cooling the reaction solution to 70 ° C., 31.5 g of water is added thereto while maintaining the reaction solution temperature at 90 to 100 ° C. After completion of addition, ripen for 30 minutes. Then
The temperature of the liquid is gradually raised to recover the evaporating acetic acid.
When the temperature reaches 115 ° C., the pressure in the system is gradually reduced, and acetic acid is recovered. When the pressure reaches 300 mmHg and the temperature reaches 85 ° C., steam is blown into the reaction solution for 2 hours to remove the residual acetic acid together with the steam. The pressure was returned to atmospheric pressure, and water was added to obtain 206 g of a 60.1 wt% ethane-1-hydroxy-1,1-diphosphonic acid aqueous solution of APHA10. The phosphorous acid content in the aqueous solution was 0.63%, and the chlorine content was 1 ppm.

Example 2 In place of the phosphorous acid solution in Example 1, 82 g (1.0 mol) of commercially available phosphorous acid containing 0.1% of water was charged into a 500 ml container. After heating at 130 ° C. for 1 hour under a pressure of 300 mmHg to reduce the water content to 0.02%, a solution cooled to 75 ° C. was used.
Pyrophosphorous acid was prepared in exactly the same manner as in Example 1 except that the amount was changed to 0.22 g (0.22 mol) to obtain pyrophosphorous acid having an anhydrous point of 6.83. Using this pyrophosphorous acid, EHDP was produced in the same manner as in Example 1, and AP
60.3% ethane-1-hydroxy-1,1 of HA15
208 g of an aqueous diphosphonic acid solution were obtained. The phosphorous acid content in the aqueous solution was 0.58%, and the chlorine content was 1 ppm.

Example 3 The same procedure as in Example 1 was carried out except that the amount of phosphorus trichloride added was changed to 28.8 g (0.21 mol). 5
4 were obtained. Using this pyrophosphorous acid,
Example 1 except that the amount of acetic anhydride added was changed to 71.5 g (0.70 mol, molar ratio to phosphorus 0.58).
The production of EHDP was performed in exactly the same manner as described above, but after passing 0.93% of unreacted pyrophosphorous acid (expressed in terms of phosphorous acid content) in the reaction solution after aging, 59.8% by weight of APHA10
203.9 g of an aqueous solution of ethane-1-hydroxy-1,1-diphosphonic acid was obtained. Phosphorous acid content in aqueous solution 0.7
7% and a chlorine content of 1 ppm.

[Comparative Example 1] 82.0 g (1.0 mol) of phosphorous acid was charged into a 500 ml four-necked flask.
Heat to 0 ° C. 56.1 g of acetic anhydride (0.55 mol
l) is dropped from the dropping funnel while maintaining the temperature at 110 to 120 ° C and adjusting the addition amount of acetic anhydride so that the by-product acetic acid is slowly refluxed in the condenser. After the addition in about 30 minutes, the mixture was aged at 120 ° C. for 2 hours, and the content of unreacted phosphorous acid in the reaction mixture was 22.7%. After cooling to 70 ° C., 32.3 g of water was added at a reaction liquid temperature of 9
Add while maintaining 0-100 ° C. After heating for 30 minutes, the acetic acid evaporating is recovered by gradually raising the liquid temperature. When the temperature reaches 115 ° C., the pressure in the system is gradually reduced, and acetic acid is further recovered. Pressure 300mmHg, temperature 85 ℃
Is reached, water vapor is blown into the reaction solution for 2 hours,
The residual acetic acid is removed with steam. The pressure was returned to atmospheric pressure, and water was added to obtain 117.8 g of an aqueous solution of APHA200 at 60.5 wt% ethane-1-hydroxy-1,1-diphosphonic acid. The phosphorous acid content in the aqueous solution was 25.9%, and the chlorine content was 1 ppm.

Comparative Example 2 In Comparative Example 1, the amount of acetic anhydride dropped from 56.1 g (0.55 mol) to 10
Was changed to 7.2 g (1.05 mol) and the amount of water added was 3
When EHDP was produced in the same manner as in Comparative Example 1 except that the amount was changed from 2.3 g to 47.3 g, the unreacted phosphorous acid content in the reaction solution after aging was 3.49%, AP
60.5 wt% ethane-1-hydroxy- of HA200
175.4 g of an aqueous solution of 1,1-diphosphonic acid was obtained. The chlorine content in the aqueous solution was 1 ppm, and the phosphorous acid content was 3.30% even when the molar ratio was increased.

Comparative Example 3 In a 500 ml four-necked flask, 239.0 g (3.98 mol) of acetic acid and 45.3 g of water were added.
g (2.52 mol), and while cooling so as to keep the temperature at 30 to 40 ° C., 219.3 g (1.6 mol) of phosphorus trichloride.
1) is added from the dropping funnel over 3 hours. By-product hydrogen chloride is absorbed in an aqueous solution of sodium hydroxide as in Example-1. After adding phosphorus trichloride, the temperature is slowly raised to 120 ° C. over 4 hours. Since acetyl chloride is by-produced together with hydrogen chloride, the acetyl chloride is returned to the reactor by passing ice water through the condenser. After reaching 120 ° C., stirring is continued for 1 hour. At this time, when the sodium hydroxide aqueous solution was analyzed, acetic acid hydrolyzed by acetyl chloride was 15.
5 g (6.5% of raw acetic acid) was contained. After cooling to 70 ° C, 35.3 g of water is added while maintaining the reaction solution temperature at 90 to 100 ° C. After aging for 30 minutes, the acetic acid evaporating is recovered by gradually raising the liquid temperature. When the temperature reaches 115 ° C., the pressure in the system is gradually reduced, and acetic acid is recovered. When the pressure reaches 300 mmHg and the temperature reaches 85 ° C., steam is blown into the reaction solution for 2 hours to remove the residual acetic acid together with the steam. Return to atmospheric pressure, add water and APHA
150 of 60.0 wt% ethane-1-hydroxy-1,
254.9 g of 1-diphosphonic acid aqueous solution was obtained. The phosphorous acid content in the aqueous solution was 3.30%, and the chlorine content was 1 ppm.

[0052]

According to the method of the present invention, by reacting pyrophosphorous acid with acetic anhydride, ethane-1-hydroxy-1-hydroxy is easily prepared with a half amount of acetic anhydride as compared with the phosphorous acid method.
The production of 1-diphosphonic acid becomes possible. In addition, by using a material preformed with water and phosphorus trichloride as the raw material pyrophosphorous acid, an advanced facility for separating hydrogen chloride and acetyl chloride is not required as compared with the phosphorus trichloride method. The benefits are added. Further, unlike the phosphoric anhydride method, the use of a special solvent is not required.

Claims (7)

[Claims] 1. A process for producing ethane-1-hydroxy-1,1-diphosphonic acid, which comprises reacting pyrophosphorous acid with acetic anhydride. 2. The method according to claim 1, wherein acetic anhydride is supplied at a rate of 0.5 mol or more and less than 1 mol per phosphorus atom in the pyrophosphorous acid. . 3. The method according to claim 1, wherein the reaction is carried out by supplying acetic anhydride to pyrophosphorous acid which has been heated in advance and refluxing acetic acid as a by-product. 4. The process according to claim 1, wherein after the supply of acetic anhydride is completed, the reaction is aged under heating.
The method according to any of the above. 5. The method according to claim 1, wherein after the completion of the reaction, water is supplied to the reaction solution to carry out hydrolysis. 6. In order to decompose the P—O—P bond of the supplied pyrophosphorous acid and the C—O—C bond of acetic anhydride used in excess with respect to the pyrophosphorous acid during the hydrolysis. 6. The method according to claim 5, wherein the water is supplied at least 1.5 times the required stoichiometric amount. 7. The method according to claim 5, wherein after the completion of the hydrolysis, by-product acetic acid is removed by steam treatment.