JP2010138164A - Method for producing difluoroacetate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrial method for producing a refined difluoroacetate through removing hydrogen fluoride from difluoroacetate containing the hydrogen fluoride accompanying as a byproduct. <P>SOLUTION: The method includes retrieving the objective difluoroacetate by separating, from a crude difluoroacetate, a tertiary amine/hydrogen fluoride salt formed by contacting hydrogen fluoride concomitant with a difluoroacetate represented by CHF<SB>2</SB>COOR (wherein, R is 1-3C alkyl) with a tertiary amine represented by R<SP>1</SP>R<SP>2</SP>R<SP>3</SP>(wherein, R<SP>1</SP>, R<SP>2</SP>and R<SP>3</SP>are each straight-chain, branched or cyclic alkyl, the total number of carbon atoms being 9-15). The tertiary amine may be recovered and reused. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for purifying difluoroacetic acid esters used as intermediates for medicines and agricultural chemicals and reaction samples, and more particularly to a method for removing hydrogen fluoride mixed in a difluoroacetic acid ester production step and the like.

  The difluoroacetic acid ester can be produced by reacting 1-alkoxy-1,1,2,2-tetrafluoroethane with an alcohol and difluoroacetic acid fluoride obtained by gas phase reaction in the presence of a metal oxide catalyst ( Patent Document 1).

CHF ₂ COF + ROH → CHF ₂ COOR + HF

JP-A-8-92162

  As is apparent from the above reaction formula, equimolar amount of hydrogen fluoride is generated as a by-product, and thus a purification treatment for removing hydrogen fluoride from the product is necessary.

  A purification method for removing hydrogen fluoride by bringing hydrogen fluoride accompanying a product obtained by a fluorination reaction or decomposition reaction into contact with water or a basic aqueous solution is generally performed in the field of fluorine chemistry. However, since difluoroacetate is easily hydrolyzed using a base or acid as a catalyst, such a method cannot be simply adopted. Further, in the above-mentioned production method of difluoroacetic acid ester, the product usually contains unreacted alcohol, but this mixture corrodes not only glass but also stainless steel, so that distillation which is a general separation method is difficult.

  Therefore, the present inventors have examined alternatives to these purification methods. When a tertiary amine having three alkyl groups is used as a dehydrofluorinating agent (fixing agent), the tertiary amine is efficiently used. Not only can capture hydrogen fluoride as a hydrogen fluoride salt, but tertiary amines / hydrogen fluoride salts with a total number of carbons of 9 or more are hardly soluble in basic aqueous solutions. It was discovered that by regenerating tri-n-butylamine by decomposing a hydrogen salt and drying it, a tertiary amine that can be reused as a dehydrofluorinating agent can be recovered, and the present invention has been completed.

That is, the present invention is as follows.
[1] Hydrogen fluoride coexisting with a difluoroacetate ester represented by CHF ₂ COOR (R represents an alkyl group having 1 to 3 carbon atoms) is R ¹ R ² R ³ N (R ¹ , R ² , R ³ is a linear, branched or cyclic alkyl group having a total carbon number of 9 to 15). A method for producing a difluoroacetic acid ester, comprising a step of separating and recovering a hydrogen salt from the difluoroacetic acid ester.
[2] The difluoroacetic acid ester according to [1], which includes the step of decomposing the recovered tertiary amine / hydrogen fluoride salt by contacting with a basic aqueous solution and then separating and recovering the released tertiary amine from the aqueous layer. Manufacturing method.
[3] The method for producing difluoroacetic acid ester according to [2], wherein the basic aqueous solution is an aqueous solution of any one of sodium hydroxide, potassium hydroxide, and calcium hydroxide.
[4] The process for producing a difluoroacetic acid ester according to [1] to [3], wherein the tertiary amine is a tertiary amine obtained by decomposing and recovering the tertiary amine / hydrogen fluoride salt with a basic aqueous solution.
[5] The method for producing a difluoroacetic acid ester according to [1] to [4], wherein the tertiary amine is tri-n-butylamine (Bu ₃ N).
[6] The difluoroacetic acid ester is a difluoroacetic acid ester obtained by reacting difluoroacetic acid fluoride with an alcohol represented by ROH (R represents an alkyl group having 1 to 3 carbon atoms) [1] A process for producing a difluoroacetic acid ester of [5].
[7] Difluoroacetic acid fluoride thermally decomposes 1-alkoxy-1,1,2,2-tetrafluoroethane represented by CHF ₂ CF ₂ OR ′ (R ′ represents a monovalent organic group). [6] The method for producing a difluoroacetic acid ester of [6], which is a thermal decomposition product obtained as described above.
[8] The method for producing a difluoroacetic acid ester according to [7], wherein the thermal decomposition is performed in the presence of a solid catalyst. [9] The method for producing a difluoroacetic acid ester according to [8], wherein the solid catalyst is a phosphate catalyst or a metal oxide catalyst.

  In this specification, “alcohol” refers to a compound having a hydroxyl group, and includes diols having two or more hydroxyl groups.

  The method of the present invention minimizes the consumption of tertiary amine because tertiary amine can be easily regenerated and reused from tertiary amine / hydrogen fluoride salt formed by capturing hydrogen fluoride with tertiary amine. It's an economical way to stay.

<Production of difluoroacetic acid fluoride> The difluoroacetic acid fluoride according to the present invention may be produced by any method. For example, 1-alkoxy-1,1,2,2-tetrafluoroethane represented by CHF ₂ CF ₂ OR ′ (R ′ represents a monovalent organic group) is reacted in the presence of a catalyst. Can be manufactured. This reaction is represented by the following formula.

CHF ₂ CF ₂ OR '→ CHF ₂ COF + R'F
As R ′ of the alkoxy group of 1-alkoxy-1,1,2,2-tetrafluoroethane which is a starting material for this reaction, an alkyl group having 1 to 8 carbon atoms which may have a branch or an alkyl group is substituted. A cycloalkyl group, a fluorine-containing alkyl group, an aryl group, and an aralkyl group that may be present as a group can be mentioned, and among these, an alkyl group or a fluorine-containing alkyl group is preferable, an alkyl group is more preferable, and a lower alkyl group is further preferable. The lower alkyl group refers to an alkyl group having 1 to 4 carbon atoms.

  Examples of the alkyl group having 1 to 8 carbon atoms that may have a branch include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, and n-pentyl group. An example is an isopentyl group.

  Examples of the cycloalkyl group that may have an alkyl group as a substituent include a cyclobutyl group, a cyclopentyl group, a 2-methylcyclopentyl group, a 3-methylcyclopentyl group, a 2-ethylcyclopentyl group, a 3-ethylcyclopentyl group, a cyclohexyl group, and 2 -Methylcyclohexyl group, 3-methylcyclohexyl group, 4-methylcyclohexyl group, 2-ethylcyclohexyl group, 3-ethylcyclohexyl group, 4-ethylcyclohexyl group, cycloheptyl group, 2-methylcyclohexyl group, 3-methylcyclohexane A heptyl group, 4-methylcycloheptyl group, etc. can be mentioned.

  As the aryl group, phenyl group, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 2,3-dimethylphenyl group, 2,4-dimethylphenyl group, 2,5-dimethylphenyl group, 2,6-dimethylphenyl group, 3,4-dimethylphenyl group, 3,5-dimethylphenyl group, 3,6-dimethylphenyl group, 2-methoxyphenyl group, 3-methoxyphenyl group, 4-methoxyphenyl group, Examples include 1-naphthyl group, 2-naphthyl group and the like.

  The fluorine-containing alkyl group includes a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a chlorofluoromethyl group, a chlorodifluoromethyl group, a bromofluoromethyl group, a dibromofluoromethyl group, and a 2,2,2-trifluoroethyl group. And pentafluoroethyl group, 2,2,3,3,3-pentafluoropropyl group, n-hexafluoropropyl group, hexafluoroisopropyl group and the like.

  Examples of the aralkyl group include phenethyl group, 2-methylphenylmethyl group, 3-methylphenylmethyl group, 4-methylphenylmethyl group, 2,3-dimethylphenylmethyl group, 2,4-dimethylphenylmethyl group, 2,5 -Dimethylphenylmethyl group, 2,6-dimethylphenylmethyl group, 3,4-dimethylphenylmethyl group, 3,5-dimethylphenylmethyl group, 3,6-dimethylphenylmethyl group, 4-ethylphenylmethyl group, 4 Examples include-(n-propyl) methylphenylmethyl group and 4- (n-butyl) methylphenylmethyl group.

  1-alkoxy-1,1,2,2-tetrafluoroethane can be obtained by a known production method. For example, it can be synthesized by a method in which alcohol (R′OH) and tetrafluoroethylene are reacted in the presence of a base.

  Specifically, 1-methoxy-1,1,2,2-tetrafluoroethane can be synthesized by a method in which methanol and tetrafluoroethylene are reacted in the presence of potassium hydroxide (J. Am. Chem. Soc. 73, 1329 (1951)).

  Specific examples of the fluorine-containing ether that can be used in the present invention include, but are not limited to, the following. 1-methoxy-1,1,2,2-tetrafluoroethane, 1-ethoxy-1,1,2,2-tetrafluoroethane, 1- (n-propoxy) -1,1,2,2-tetrafluoro Ethane, 1-isopropoxy-1,1,2,2-tetrafluoroethane, 1- (n-butoxy) -1,1,2,2-tetrafluoroethane, 1- (s-butoxy) -1,1 , 2,2-tetrafluoroethane, 1- (t-butoxy) -1,1,2,2-tetrafluoroethane, 1-trifluoromethoxy-1,1,2,2-tetrafluoroethane, 1-difluoro Methoxy-1,1,2,2-tetrafluoroethane, 1- (2,2,2-trifluoroethoxy) -1,1,2,2-tetrafluoroethane, 1-pentafluoroethoxy-1,1, 2,2-tetrafluoro Ethane, 1- (2,2,2,3,3-pentafluoropropoxy) -1,1,2,2-tetrafluoroethane, 1-hexafluoroisopropoxy-1,1,2,2-tetrafluoroethane And so on.

  The catalyst used for the thermal decomposition according to the present invention is a solid catalyst, and metal oxides, metal fluorinated oxides and phosphates described in JP-A-8-92162 can be used as catalysts. The phosphate may be supported on a carrier. As phosphoric acid, any of orthophosphoric acid, polyphosphoric acid, and metaphosphoric acid may be used. Examples of polyphosphoric acid include pyrophosphoric acid. Phosphate is the metal salt of these phosphoric acids. Since it is easy to handle, orthophosphoric acid is preferred. Phosphate refers to a metal salt of these phosphoric acids. In this specification, an acid in which a metal is substituted with a hydrogen atom is also referred to as a metal salt.

  Although it does not specifically limit as a phosphate, It consists of hydrogen, aluminum, boron, alkaline-earth metal, titanium, zirconium, lanthanum, cerium, yttrium, rare earth metal, vanadium, niobium, chromium, manganese, iron, cobalt, nickel And at least one metal phosphate selected from the group. Preferably, the main component is aluminum phosphate, cerium phosphate, boron phosphate, titanium phosphate, zirconium phosphate, chromium phosphate, or the like. It is also preferable that the metal of a subsidiary component is included. As specific subcomponents, cerium, lanthanum, yttrium, chromium, iron, cobalt, nickel and the like are preferable, but cerium, iron and yttrium are more preferable. Of these, aluminum phosphate, cerium phosphate, and phosphates composed of these two types are more preferable.

  The method for preparing the catalyst is not particularly limited, and a commercially available phosphate may be used as it is, or a general precipitation method may be used. As a specific preparation method of the precipitation method, for example, diluted ammonia water is added dropwise to a mixed aqueous solution of metal nitrate (in the case of a plurality of raw material salts, each raw material salt solution is prepared) and phosphoric acid to adjust the pH. To adjust to precipitate and leave to mature as necessary. Then, it is washed with water and it is confirmed that it has been sufficiently washed with the conductivity of the washing water. In some cases, alkali metal containing a portion of the slurry is measured. It is then filtered and dried. There is no particular limitation on the drying temperature. Preferably 80 to 150 degreeC is good. More preferably, it is 100 degreeC-130 degreeC. The obtained dried product is pulverized to uniform particle size, or further pulverized and molded. Thereafter, firing is performed in an air or nitrogen atmosphere at 200 ° C. to 1500 ° C. The firing is preferably performed at 400 to 1300 ° C, more preferably 500 to 900 ° C.

  Although depending on the temperature, the firing time is about 1 to 50 hours, preferably about 2 to 24 hours. Since the calcination treatment is a treatment necessary for stabilizing the phosphate, if the treatment is performed at a temperature lower than the above temperature range or the treatment time is short, the catalyst activity may not be sufficiently exhibited at the initial stage of the reaction. . In addition, it is not preferable to perform the calcination treatment at a temperature higher than the above temperature range or for a long time because not only excessive heating energy is required but also crystallization of the catalyst may occur.

The operation of adding a metal component other than the main component is preferably performed with a metal salt, and nitrates, chlorides, oxides, phosphates, and the like of the metal are preferable. Among them, nitrate is preferable because it is easy to prepare. Although there is no restriction | limiting in particular in addition amount, Generally it is 1 gram atom or less with respect to 1 gram atom of phosphorus, Preferably it is 0.5 gram atom or less. More preferably, it is 0.3 gram atom or less. The addition of these metal components may be performed at the time of catalyst preparation, or may be performed on the phosphate after the catalyst is calcined. The obtained catalyst has different physical properties depending on the type of metal salt and the preparation method and conditions. The catalyst may be used as it is, but it can also be used in a state of being supported on a carrier. Examples of the carrier include metal oxides such as alumina, titania, zirconia, zirconia sulfate (ZrO (SO ₄ )), silicon carbide, silicon nitride, activated carbon, and the like. preferable.

  Activated carbon carrying phosphoric acid or phosphate can be prepared by immersing it in a phosphoric acid aqueous solution and impregnating it, or drying and coating or adsorbing it by spraying. In the case of loading a compound, it can be prepared by impregnating a solution of the compound to be loaded, or drying a coating or adsorbed by spraying. In addition, a second compound is allowed to act on activated carbon impregnated with a solution of the compound, or coated or adsorbed by spraying to cause a precipitation reaction or the like on the activated carbon surface, thereby supporting a compound different from the first compound. You can also. Further, the phosphate-carrying catalyst can also be prepared by carrying out the above-described phosphate preparation method in the presence of a support such as activated carbon. As an example, activated carbon supporting aluminum phosphate is shown in the examples.

  Activated carbon is made from plant-based, peat, lignite, lignite, bituminous, and anthracite-based coal, petroleum residue, oil carbon, etc. Any of petroleum type or synthetic resin type such as carbonized polyvinylidene chloride may be used. These activated carbons can be selected and used. For example, activated carbon produced from bituminous coal (BPL granular activated carbon manufactured by Toyo Calgon), coconut shell charcoal (granular white birch GX, SX, CX, XRC manufactured by Nippon Enviro Chemicals), Toyo Calgon PCB) and the like, but is not limited thereto. The shape and size are usually used in a granular form, but can be used within a normal knowledge range as long as it is suitable for a reactor such as a sphere, fiber, powder, or honeycomb.

The activated carbon used in the present invention is preferably activated carbon having a large specific surface area. The specific surface area of the activated carbon is sufficient in a range of commercially available standards, are each 400m ² / g~3000m ² / g, preferably 800m ² / g~2000m ² / g. Furthermore, when using activated carbon as a support, it is usually immersed in a basic aqueous solution such as ammonium hydroxide, sodium hydroxide, potassium hydroxide or the like for about 10 hours or longer at room temperature or when activated carbon is used as a catalyst support. It is desirable to perform pretreatment with acid such as nitric acid, hydrochloric acid, hydrofluoric acid, etc. to activate the carrier surface and remove ash in advance.

  Further, the carrier such as an oxide of the present invention may contain a metal component and an atom other than oxygen, and the other atom is preferably a fluorine atom or a chlorine atom. For example, partially fluorinated alumina, partially chlorinated alumina, partially fluorinated chlorinated alumina, partially fluorinated zirconia, partially fluorinated titania and the like may be used. The ratio of chlorine atoms and fluorine atoms in the oxide catalyst is not particularly limited.

  In the present specification and claims, unless otherwise limited, oxides such as “alumina” and “zirconia” that are partially fluorinated and chlorinated alumina and zirconia as described above are used. Display by name.

These supports include at least one metal oxide selected from the group consisting of alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), titania (TiO ₂ ), zirconia sulfate, and partially fluorinated oxides thereof. Catalysts are preferred, and alumina and partially fluorinated alumina are more preferred in terms of reactivity and catalyst life.

These partially fluorinated oxides can be used as a support for a difluoroacetic acid fluoride synthesis catalyst, and can also be used as a catalyst. Preparation, pretreatment, use, etc. as a catalyst can be applied as described in the present specification for preparation, pretreatment, use, etc. as a carrier as it is or according to technical common sense. That is, when a metal oxide such as alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), titania (TiO ₂ ) or the like is used as a catalyst, it can be handled in the same manner as a supported catalyst on which a metal compound or the like is supported. Good.

  Catalysts comprising or carrying phosphates are usually used in the form of particles or granules. The diameter of the particles or the granulated body (all may be referred to as “particle diameter”) is not particularly limited, and is usually about 20 μm to 10 mm. When the catalyst contains a chlorine atom or a fluorine atom, the chlorine atom or the fluorine atom may exist only on the surface of the metal oxide.

  The catalyst comprising the phosphate of the present invention or carrying the phosphate is also partially fluorinated by contacting with a fluorine-containing compound such as hydrogen fluoride, fluorinated hydrocarbon or fluorinated chlorinated hydrocarbon before use. In addition, it is effective to prevent changes in the composition of the catalyst during the reaction, shortening of the service life, abnormal reactions, and the like.

  In particular, treatment with hydrogen fluoride can significantly increase the activity of the reaction. The fluorination treatment with hydrogen fluoride is preferably performed by contacting with hydrogen fluoride at least at a temperature higher than the reaction temperature of the reaction according to the present invention. Specifically, in the case of a phosphate simple substance, it is about 200 to 700 ° C, preferably about 250 to 600 ° C, and more preferably 300 to 550 ° C. On the other hand, in the case of a phosphate-carrying catalyst, the temperature is about 200 to 600 ° C, preferably about 250 to 500 ° C, and more preferably 300 to 400 ° C. In any case, if the temperature is lower than 200 ° C., it takes time for the treatment, and it is not preferable to perform the treatment beyond the maximum temperature range because excessive heating energy is required. The treatment time is also related to the treatment temperature and cannot be limited, but it is about 1 hour to 10 days, preferably about 3 hours to 3 days.

  In the case of activated carbon that does not carry phosphoric acid, even if it is treated with hydrogen fluoride, it shows almost no activity. However, when activated carbon treated with phosphoric acid is treated with hydrogen fluoride, the conversion rate is 96 under the same reaction conditions. The catalyst activity was 0.1% and selectivity: 98.0%. Also from this, the effect of the hydrogen fluoride treatment can be easily seen.

  Furthermore, it is preferable to perform an activation treatment prior to the reaction. As the activation treatment, it is sufficiently dehydrated in a nitrogen stream of about 250 ° C. to 300 ° C., and an organic fluorine compound such as dichlorodifluoromethane or chlorodifluoromethane, or a gas or catalyst treatment such as hydrogen fluoride or chlorine trifluoride. It is preferable to activate with an inorganic fluorine compound showing a sufficient vapor pressure in the state. Of these, hydrogen fluoride is particularly preferred. By this activation treatment, it is considered that an active catalyst composed of a phosphate containing a fluorine atom is generated on the entire surface of the catalyst.

When R ′ of 1-alkoxy-1,1,2,2-tetrafluoroethane (CHF ₂ CF ₂ OR ′), which is a reaction raw material, is a group having 2 or more carbon atoms, the generated R′F is reacted. It is estimated that hydrogen fluoride is generated by decomposition in the region, and this may have an effect of increasing the activity of the catalyst.

  In the method of the present invention, the gas-phase continuous flow method is recommended as the most preferable format, but is not limited thereto. The type of the reactor is preferably a fixed bed type or a fluidized bed type, and the dimensions and shape of the reactor can be appropriately changed according to the amount of the reactants.

  In the reaction according to the present invention, an inert gas inert under the reaction conditions may be present. Examples of the inert gas include nitrogen or rare gases, and nitrogen or helium is preferable from the viewpoint of ease of handling and availability. The amount in the presence of the inert gas is not particularly limited, but if it is too much, there is a possibility that the recovery rate is lowered. Therefore, in the usual case, the raw material 1-alkoxy-1,1,2,2-tetrafluoro An amount less than the ethane feed rate is preferred.

  The reaction temperature in the method of the present invention varies depending on the type of catalyst and the raw material. Usually, it is 100-400 degreeC, about 150-350 degreeC is preferable and 180-280 degreeC is more preferable. If the reaction temperature is less than 100 ° C., the conversion tends to be low, which is not preferable. When the reaction temperature exceeds 400 ° C., severe heat resistance is required for the reaction apparatus, and excessive heating energy is required, which is not economically preferable.

  The reaction time (contact time) is usually 0.1 to 300 seconds, preferably 0.5 to 200 seconds, and more preferably 1 to 60 seconds. If the reaction time is too short, the conversion rate may be lowered. On the other hand, if the reaction time is too long, productivity is lowered, which is not preferable. The reaction pressure is not particularly limited and may be normal pressure, reduced pressure, or increased pressure. A pressure of about 0.05 to 0.5 MPa (0.5 to 5 atmospheres) is preferable, and usually a pressure in the vicinity of atmospheric pressure that facilitates operation is preferable.

  In the catalyst according to the present invention, coking may occur over time, and the activity of the catalyst may decrease. The catalyst having reduced activity can be easily regenerated by contacting with oxygen at 200 ° C. to 1200 ° C., preferably 400 ° C. to 800 ° C. It is convenient to perform the oxygen treatment while it is loaded in the reaction tube or in an external device. This is done by circulating oxygen there. Other gases may coexist as a method for circulating oxygen, and oxygen, air, nitrogen-diluted oxygen and the like can be used, but air or air diluted with nitrogen is economically preferable. Further, a gas having oxidizing power such as chlorine and fluorine can be used.

  In the reaction according to the method of the present invention, in addition to the desired difluoroacetic acid fluoride, a compound obtained by further decomposing alkyl fluoride (R′F) or R′F is produced as a by-product. For example, when ethyl fluoride is generated as R′F, ethylene and hydrogen fluoride may be formed. However, the crude product obtained by the reaction can also be used as a raw material for other reactions without purification.

  <Production of difluoroacetic acid ester> Difluoroacetic acid ester can be produced by reacting difluoroacetic acid fluoride with alcohol (ROH).

CHF ₂ COF + ROH → CHF ₂ COOR + HF
Although it does not specifically limit as alcohol, R is a C1-C8 alkyl group which may have a branch, or a fluorine-containing alkyl group, the cycloalkyl group which may have an alkyl group as a substituent, an aryl group, aralkyl Among them, an alkyl group having 1 to 8 carbon atoms or a fluorine-containing alkyl group having 2 to 8 carbon atoms is preferable. Furthermore, a C1-C4 alkyl group or a C2-C4 fluorinated alkyl group is more preferable. Examples of the alkyl group having 1 to 8 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, n-pentyl group, and isopentyl group. Can be mentioned. Examples of the fluorine-containing alkyl group having 2 to 8 carbon atoms include 2,2,2-trifluoroethyl group, pentafluoroethyl group, 2,2,3,3,3-pentafluoropropyl group, and n-hexafluoropropyl group. Examples thereof include a hexafluoroisopropyl group.

  There is no problem in the reaction even if an excessive amount of alcohol is used with respect to difluoroacetic acid fluoride, but the excessive amount remains unreacted, so that post-treatment is difficult and wasteful. Therefore, the usage-amount of alcohol may be 0.5-10 equivalent with respect to difluoroacetic acid fluoride, 0.7-2 equivalent is preferable and 0.8-1.5 equivalent is more preferable.

  The temperature of this esterification reaction is not particularly limited, and may be in a state where heating and cooling are not performed separately, and usually about 0 to 50 ° C. The reaction pressure does not particularly affect the reaction, so it may be carried out under pressure or reduced pressure, but it may be carried out in the vicinity of normal pressure where no pressure is applied or reduced.

  In the present invention, a tertiary amine is added to a mixture of difluoroacetic acid ester and hydrogen fluoride produced by the esterification reaction, or the tertiary amine is mixed and dissolved in alcohol in advance during the esterification reaction. Thus, hydrogen fluoride is captured (fixed) with a tertiary amine as a tertiary amine / hydrogen fluoride salt.

The tertiary amine is not particularly limited, general ^{formula, R 1 R 2 R 3 N} (R 1, R 2, R 3 represents a linear, a branched or cyclic alkyl group, the total carbon number 9 to 15) is preferred. Even tertiary amines with a total carbon number of 8 or less can capture hydrogen fluoride as tertiary amines / hydrogen fluoride salts, but such tertiary amines are produced because of their high water solubility. This is not preferable because the recovery rate is reduced when the amine is decomposed with water or an aqueous solution and the tertiary amine is separated and recovered from the aqueous layer. Tertiary amines having a total carbon number of 16 or more are suitable for decomposition and recovery with water because of their low water solubility, but it is preferable to avoid them practically because of the small amount of hydrogen fluoride trapped per weight.

  Examples of the tertiary amine having 9 to 15 carbon atoms represented by the general formula include tri-n-propylamine, tri-isopropylamine, tri-n-butylamine, tri-isobutylamine, tri-sec-butylamine, Symmetrical tertiary amines such as tri-tert-butylamine, tri-n-amylamine, tri-isoamylamine, tri-sec-amylamine, tri-tert-amylamine, N-methyldi-n-butylamine, N-methyldiisobutylamine, N-methyldi-tert-butylamine, N, N-diisopropylbutylamine, N, N-dimethyl-n-octylamine, N, N-dimethylnonylamine, N, N-dimethyldecylamine, N, N-dimethylundecylamine N, N-dimethyldodecylamine, N-methyldihexylamine, etc. Amine and the like. Of these, symmetric amines are preferred because they are readily available, and tri-n-propylamine, tri-isopropylamine, tri-n-butylamine, tri-isobutylamine, tri-n-amylamine, tri-isoamylamine and the like are more preferred. Tri-n-butylamine is preferred and particularly preferred. These tertiary amines can also be used as a mixture.

  A method of capturing hydrogen fluoride generated together with the difluoroacetate ester by introducing difluoroacetic acid fluoride into the tertiary amine alcohol solution immediately after the production is preferred. A predetermined amount of alcohol and tertiary amine are mixed in advance to prepare a solution, and difluoroacetic acid fluoride is introduced therein. The introduction of difluoroacetic acid fluoride is preferably a method in which a thermal decomposition product obtained by thermal decomposition of 1-alkoxy-1,1,2,2-tetrafluoroethane is brought into contact by means such as bubbling. Moreover, it is also preferable to use this thermal decomposition product, without isolate | separating the difluoroacetic-acid fluoride obtained by thermal decomposition, and the fluoride (R'F) byproduced.

  In the esterification reaction system, 0.5 to 10 mol of tertiary amine is added to 1 mol of monohydric alcohol (hydroxyl group), preferably 0.8 to 5 mol, more preferably 1 to 3 mol. preferable. In order to fix the hydrogen fluoride generated in the esterification reaction, 1 mol of tertiary amine is required for about 2 mol of hydrogen fluoride, so the tertiary amine is based on the alcohol (hydroxyl group) involved in the reaction. 0.5 mol or more is added to the reaction system. Tertiary amine can be recovered and reused, so even if it is used in a large amount, there is no technical problem, but it is unnecessary because hydrogen fluoride is captured sufficiently quickly. In addition, the reaction product solution generated by the esterification reaction includes a difluoroacetate and tertiary amine / hydrogen fluoride layer and a free tertiary amine layer. Difluoroacetate is collected by distillation. Since the tertiary amine / hydrogen fluoride salt decomposes to generate hydrogen fluoride and the solid tertiary amine / 1HF precipitates, the tertiary amine is 0.5 mol or more per 1 mol of alcohol. It is preferable that

  The composition containing the difluoroacetic acid ester obtained by the esterification reaction contains unreacted alcohol and tertiary amine / hydrogen fluoride salt. If the composition is separated into two layers, it is separated by decantation or the like. Although, the difluoroacetic acid ester fraction can be recovered by distilling the composition. At this time, it is efficient to perform flash distillation (simple distillation), particularly flash distillation under reduced pressure.

  The separated component or the extracted difluoroacetic acid ester fraction can be directly subjected to precision distillation, or can be washed with water before distillation if desired. In this fraction, since hydrogen fluoride is removed by the tertiary amine, the difluoroacetic acid ester is not substantially decomposed even by the water washing treatment. When the water washing treatment is carried out, it is preferably subjected to precision distillation after drying with a desiccant such as zeolite, anhydrous magnesium sulfate, anhydrous sodium sulfate, or anhydrous calcium chloride.

<Recovery of tertiary amine>
The residual liquid after extracting the difluoroacetic acid ester fraction by flash distillation contains a tertiary amine / hydrogen fluoride salt. The residual liquid can be recovered as a tertiary amine by mixing and stirring with a basic aqueous solution and contacting. The basic aqueous solution is not particularly limited, but aqueous solutions such as potassium hydroxide, sodium hydroxide, calcium hydroxide, magnesium hydroxide can be used, and potassium hydroxide, sodium hydroxide, calcium hydroxide are handled and economical. From the aspect, it is preferable. After mixing and stirring the residual liquid with the basic aqueous solution, the tertiary amine layer of the two layers formed in the container is recovered. The recovered tertiary amine can be reused for capturing hydrogen fluoride according to the present invention as it is or after drying. For drying, zeolite, anhydrous magnesium sulfate, anhydrous sodium sulfate, anhydrous calcium chloride and the like can be used. In the case of zeolite, it can be regenerated by heat treatment after breakthrough.

<Multistage process>
An example to which the present invention is applied is shown without limitation. A tertiary amine-alcohol (cooled in an ice bath without separating and purifying the product gas flowing out of 1-alkoxy-1,1,2,2-tetrafluoroethane flowing over the catalyst at an elevated temperature (without separation and purification) When bubbling into a container (absorption tank) charged with (ROH) solution, difluoroacetic acid ester (CHF ₂ COOR) and tertiary amine / hydrogen fluoride salt are produced almost quantitatively. This solution was flash distilled under reduced pressure to recover the difluoroacetic acid ester fraction, and the organic layer thus recovered was dehydrated with a dehydrating agent such as zeolite, anhydrous magnesium sulfate, anhydrous calcium chloride, and then in the field of organic chemistry. A high-purity difluoroacetic acid ester can be obtained by separating by a known distillation means. At the same time, the residual liquid after extracting the difluoroacetic acid ester fraction by vacuum flash distillation is cooled to room temperature, then added with basic aqueous solution, mixed with stirring, separated into two layers, and further purified such as dehydration as necessary. It returns to an absorption tank again through operation, and can be used again for implementation of this invention.

Preferable specific examples in the application examples of the present invention described above include using an aluminum phosphate catalyst as a catalyst and 1-methoxy-1,1 as 1-alkoxy-1,1,2,2-tetrafluoroethane. , 2,2-tetrafluoroethane (HFE-254pc, CHF ₂ CF ₂ OCH ₃ ) and tri-n-butylamine as the tertiary amine. Here, it is also preferable to use a metal oxide as the catalyst. As alcohol, isopropanol is easy to handle, but the alcohol described above may be used.

The present invention relates to a thermal decomposition product of 1-alkoxy-1,1,2,2-tetrafluoroethane represented by CHF ₂ CF ₂ OR ′ (R ′ represents a monovalent organic group) and an alcohol. It is effective for removing or separating hydrogen fluoride in the reaction product difluoroacetate ester, but it does not matter how the hydrogen fluoride is mixed in. It is generally contained in difluoroacetate ester. Applicable to the case. For example, the present invention can be applied to removal of hydrogen fluoride generated when a purified difluoroacetic acid ester is stored for a long time. Also, the application mode is not particularly limited. For example, difluoroacetic acid ester can be purified without corroding an apparatus such as a distillation tower by adding tertiary amine to difluoroacetic acid ester containing hydrogen fluoride and performing distillation. It can also be applied to.

  The present invention will be described below with reference to examples, but the present invention is not limited to these examples. [Preparation Example 1] Aldrich aluminum phosphate was tableted into 5 mmφ × 5 mmL pellets and calcined at 700 ° C. for 5 hours in a nitrogen stream to prepare an aluminum phosphate catalyst.

[Synthesis Example 1 of difluoroacetic acid fluoride (CHF ₂ COF)]
The aluminum phosphate catalyst prepared in Preparation Example 1 (200 cc) was charged into a stainless steel pyrolysis reaction tube having a JIS nominal diameter of 32 A (inside diameter of 37.1 mm) and a length of 500 mm equipped with an electric furnace outside, and nitrogen was supplied at 50 cc / min. And then heated in an electric furnace. When the temperature of the catalyst reached 50 ° C., hydrogen fluoride (HF) was gradually fed through the vaporizer and increased to 1.2 g / min. With HF flowing at 1.2 g / min as it was, the temperature was slowly raised to 350 ° C. and held for 24 hours. After stopping the flow of HF, increasing the nitrogen flow rate to 200 cc / min and holding for 2 hours, 1 g of 1-methoxy-1,1,2,2-tetrafluoroethane (CHF ₂ CF ₂ OCH ₃ , HFE-254pc) was 4 g / Introduced through the vaporizer at a rate of minutes and the nitrogen supply was stopped. When the reaction temperature reached a steady state at 210 ° C., the product gas was analyzed by gas chromatography (FID detector). As a result, the conversion rate was 99.6%, difluoroacetic acid fluoride selectivity: 99.8% (alkoxy) Area% obtained by excluding by-products such as CH ₃ F based on the group.

[Example 1]
Tri-n-butylamine (Bu ₃ N, 1108 g) and isopropanol (IPA, 120 g) were charged into a glass four-necked flask (2000 cc) equipped with a blowing tube, a bubbler, and a Dimroth condenser tube, cooled in an ice bath, and stirred. And stirred slowly. A refrigerant at −20 ° C. was passed through the Dimroth cooling pipe, and the product gas of Synthesis Example 1 was bubbled through the blowing pipe as it was without separation and purification. Low-boiling components such as CH ₃ F produced as a by-product with the formation of difluoroacetic acid fluoride were discharged out of the system through a bubbler. When 290 g of HFE-254pc (CHF ₂ CF ₂ OCH ₃ ) was supplied to the thermal decomposition reaction tube, the flask was taken out and flash distillation was performed under reduced pressure (3 kPa). The top temperature at that time was 24-27 degreeC. The fraction (275.4 g) obtained by this operation was washed with 200 g of tap water and separated to obtain 265.9 g of an organic substance, which was dried over anhydrous magnesium sulfate to obtain 261.7 g of a crude product. . As a result of analysis by gas chromatography (FID detector), isopropyl difluoroacetate (CHF ₂ COOCH (CH ₃ ) ₂ ): 96.83%, tri-n-butylamine (Bu ₃ N): 0.21%, others: 2.96%.

[Example 2]
The crude product obtained in Example 1 was distilled in a concentric cylindrical distillation column having 10 theoretical plates. 261.7 g was charged and vacuum distillation at 13 kPa was performed. As a result of analyzing a fraction (237.8 g) having a column top temperature of 55 to 57 ° C., isopropyl difluoroacetate (CHF ₂ COOCH (CH ₃ ) ₂ ) was obtained with a purity of 99.75%. At this time, no corrosion of the device such as devitrification of the glass was observed.

[Example 3]
The flash distillation residue of Example 1 forms two layers, the upper layer being pale yellow tri-n-butylamine (Bu ₃ N) and the lower layer being brown tri-n-butylamine / hydrogen fluoride (Bu ₃ N · nHF salt, n = 2.13). The flash distillation residue (1159 g) was cooled in an ice bath, and 300 g of 48% potassium hydroxide (KOH) aqueous solution was added dropwise with stirring. Stirring was continued for 1 hour after completion of dropping. After standing, the organic phase was separated from the aqueous phase and dried over anhydrous magnesium sulfate to obtain 1056 g of tri-n-butylamine. As a result of analysis by gas chromatography (FID detector), it was found to be tri-n-butylamine (Bu ₃ N): 99.24%.

[Example 4]
1056 g of tri-n-butylamine recovered in Example 3 in a four-necked flask (2000 cc) equipped with a blowing tube, a bubbler and a Dimroth condenser, 52 g of unused tri-n-butylamine (total of 1108 g of tri-n-butylamine), IPA (120 g) was added. The mixture was cooled in an ice bath and slowly stirred with a stirrer. A refrigerant at −20 ° C. was passed through the Dimroth cooling pipe, and the product gas of Synthesis Example 1 was bubbled through the blowing pipe as it was without separation and purification. Low-boiling components such as CH ₃ F produced as a by-product with the formation of difluoroacetic acid fluoride were discharged out of the system through a bubbler. When 290 g of HFE-254pc (CHF ₂ CF ₂ OCH ₃ ) was supplied to the thermal decomposition reaction tube, the four-necked flask was disconnected and flash distillation was performed under reduced pressure (3 kPa). The top temperature at that time was 24-27 degreeC. The fraction (276.8 g) obtained by this operation was washed with 200 g of tap water and separated to obtain 262.4 g of an organic substance, which was dried over anhydrous magnesium sulfate to obtain 259.1 g of a crude product. . As a result of analysis by gas chromatography (FID detector), isopropyl difluoroacetate (CHF ₂ COOCHMe ₂ ): 96.94%, tri-n-butylamine (Bu ₃ N): 0.19%, others: 2.87% Met. The type of impurities was the same as that in Example 1, and it was confirmed that tri-n-butylamine could be recycled.

[Example 5]
The same operation as in Example 1 was performed except that ethanol (EtOH, 92 g) was used instead of isopropanol (IPA, 120 g). After supplying 290 g of HFE-254pc (CHF ₂ CF ₂ OCH ₃ ) to the pyrolysis reaction tube, the contents were taken out and flash distilled under reduced pressure (3 kPa). The fraction obtained by this operation was washed with tap water, separated, and dried over anhydrous magnesium sulfate to obtain 238.1 g of crude ethyl difluoroacetate. As a result of analysis by gas chromatography (FID detector), ethyl difluoroacetate (CHF ₂ COOCHC ₂ H ₅ ): 97.14%, tri-n-butylamine (Bu ₃ N): 0.17%, others: 2. It was 69%.

[Comparative Example 1]
Experiments were performed in the same procedure as in Example 1 using triethylamine (Et3N, 605 g (6.0 mol)) instead of tri-n-butylamine (Bu3N, 1108 g (6.0 mol)). After supplying 290 g of HFE-254pc (CHF ₂ CF ₂ OCH ₃ ) to the pyrolysis reaction tube, the contents were taken out and flash distilled under reduced pressure (3 kPa). The fraction (245.7 g) obtained by this operation was washed with 200 g of tap water and separated to obtain 237.8 g of an organic substance, which was dried over anhydrous magnesium sulfate to obtain 237.8 g of a crude product. . As a result of analysis by gas chromatography (FID detector), isopropyl difluoroacetate (CHF ₂ COOCH (CH ₃ ) ₂ ): 97.12%, triethylamine (Et ₃ N): 0.56%, others: 2.83% Met.

  Next, 300 g of a 48% aqueous potassium hydroxide (KOH) solution was added dropwise to the flash distillation residue while stirring, and stirring was continued for 1 hour after completion of the addition. Thereafter, the mixture was allowed to stand for 1 hour, but the aqueous layer and the organic layer were not separated, and triethylamine could not be recovered.

[Reference Example 1]
Methyl difluoroacetate (CHF ₂ COOCH ₃ ) (10 g) and ion-exchanged water (20 g) each previously cooled in an ice bath were mixed and stirred for 5 minutes while cooling in an ice bath. 1 mL of the obtained aqueous phase was collected in a 100 mL volumetric flask, neutralized with a 2 mol / L-NaOH aqueous solution, diluted with ion-exchanged water to obtain a 10,000-fold diluted solution. As a result of quantifying this diluted solution by ion chromatography, the CHF ₂ COO ⁻ ion concentration was 2.2 ppm. The amount of CHF ₂ COO ^- ion was converted to the weight of methyl difluoroacetate and divided by 10 g of isopropyl difluoroacetate before the test to determine the hydrolysis rate. As a result, the decomposition rate was 5.0%.

[Reference Example 2]
Methyl difluoroacetate (CHF ₂ COOCH ₃ ) (10 g) and a 38% HF aqueous solution (20 g), each cooled in an ice bath, were mixed and stirred for 5 minutes while cooling in an ice bath. 1 mL of the obtained aqueous phase was collected in a 100 mL volumetric flask, neutralized with a 2 mol / L-NaOH aqueous solution, diluted to 100 mL with ion-exchanged water, diluted with ion-exchanged water to obtain a 10,000-fold diluted solution. As a result of quantifying this diluted solution by ion chromatography, the CHF ₂ COO ⁻ ion concentration was 18.57 ppm. The amount of CHF ₂ COO ^- ion was converted to the weight of isopropyl difluoroacetate and divided by 10 g of methyl difluoroacetate before the test to determine the hydrolysis rate. As a result, the decomposition rate was 43.0%.

[Reference Example 3]
Isopropyl difluoroacetate (CHF ₂ COO (CH ₃ ) ₂ ) (5 g) and a 38% HF aqueous solution (10 g), each cooled in an ice bath, were mixed and stirred for 5 minutes while cooling in an ice bath. 1 mL of the obtained aqueous phase was collected in a 100 mL volumetric flask, neutralized with a 2 mol / L-NaOH aqueous solution, diluted to 100 mL with ion-exchanged water, diluted with ion-exchanged water to obtain a 10,000-fold diluted solution. As a result of quantifying this diluted solution by ion chromatography, the CHF ₂ COO ⁻ ion concentration was 2.7 ppm. CHF ₂ COO ^- ion amount, in terms of difluoro acetic acid isopropyl weight was determined hydrolysis rate by dividing difluoro isopropyl acetate weight 5g before the test. As a result, the decomposition rate was 8.0%.

  Hydrogen fluoride can be removed from the difluoroacetic acid ester containing hydrogen fluoride in the process or operation such as production, storage, transportation, and recovery of difluoroacetic acid ester for purification.

Claims (9)

Hydrogen fluoride coexisting with the difluoroacetate ester represented by CHF ₂ COOR (R represents an alkyl group having 1 to 3 carbon atoms) R ¹ R ² R ³ N (R ¹ , R ² , R ³ is A tertiary amine / hydrogen fluoride salt formed by contact with a tertiary amine represented by the following formula: a linear, branched or cyclic alkyl group having a total carbon number of 9 to 15. A method for producing a difluoroacetic acid ester comprising a step of separating and recovering from the difluoroacetic acid ester. The recovered tertiary amine / hydrogen fluoride salt is contacted with a basic aqueous solution to decompose, and then the liberated tertiary amine is separated from the aqueous layer and recovered. Production method. The method for producing a difluoroacetic acid ester according to claim 2, wherein the basic aqueous solution is any one of sodium hydroxide, potassium hydroxide, and calcium hydroxide. The method for producing a difluoroacetic acid ester according to any one of claims 1 to 3, wherein the tertiary amine is a tertiary amine obtained by decomposing and recovering the tertiary amine / hydrogen fluoride salt with a basic aqueous solution. The method for producing a difluoroacetic acid ester according to any one of claims 1 to 4, wherein the tertiary amine is tri-n-butylamine (Bu ₃ N). The difluoroacetic acid ester is a difluoroacetic acid ester obtained by reacting difluoroacetic acid fluoride with an alcohol represented by ROH (R represents an alkyl group having 1 to 3 carbon atoms). The manufacturing method of the difluoroacetic acid ester of any one. Difluoroacetic acid fluoride is obtained by thermally decomposing 1-alkoxy-1,1,2,2-tetrafluoroethane represented by CHF ₂ CF ₂ OR ′ (R ′ represents a monovalent organic group). The method for producing a difluoroacetic acid ester according to claim 6, which is a thermal decomposition product obtained. The method for producing a difluoroacetic acid ester according to claim 7, wherein the thermal decomposition is performed in the presence of a solid catalyst. The method for producing a difluoroacetic acid ester according to claim 8, wherein the solid catalyst is a phosphate catalyst or a metal oxide catalyst.