JP2010116333A - Method for producing difluoroacetic acid ester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrial method for obtaining a purified difluoroacetic acid ester by removing hydrogen fluoride from a difluoroacetic acid ester containing hydrogen fluoride entrained as a by-product. <P>SOLUTION: The purifying method of the difluoroacetic acid ester comprises bringing the difluoroacetic acid ester containing hydrogen fluoride, obtained by causing difluoroacetic acid fluoride obtained by thermolysis of a 1-alkoxy-1,1,2,2-tetrafluoroethane represented by the formula: CHF<SB>2</SB>CF<SB>2</SB>OR' (wherein R' is a monovalent organic group) to react with an alcohol, into contact with water in the presence of a hydrocarbon to remove hydrogen fluoride. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing difluoroacetate used as an intermediate for medicines and agricultural chemicals and a reaction reagent, and more particularly to a method for removing hydrogen fluoride mixed in a difluoroacetate 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, this reaction generates equimolar amounts of hydrogen fluoride as a by-product, and thus purification treatment is necessary to remove hydrogen fluoride from the product. In general, hydrogen fluoride is removed from the product. However, there is a problem that difluoroacetic acid ester is hydrolyzed when washing with water, which is the simplest method, and this method cannot be simply applied.

  An object of the present invention is to provide a method in which hydrolysis of a difluoroacetic acid ester does not proceed in water washing.

  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, difluoroacetic acid ester is easily hydrolyzed using a base or acid as a catalyst to produce difluoroacetic acid and alcohol, and the separation operation at the interface between the layer rich in difluoroacetic acid ester and the water tank is not clear. It may be complicated and it is difficult to employ water washing to remove hydrogen fluoride from difluoroacetate containing hydrogen fluoride. Further, in the above-mentioned production method of difluoroacetic acid ester, the product usually contains unreacted alcohol, but the mixture of hydrogen fluoride and alcohol corrodes not only glass but also stainless steel. It is also difficult.

  Therefore, the present inventors examined a method for removing hydrogen fluoride by washing difluoroacetate containing hydrogen fluoride with water. When water washes in the presence of a hydrocarbon solvent, hydrolysis of the difluoroacetate was performed. As a result, the production method of the present invention was completed.

The present invention is as follows.
[1] Difluoroacetic acid ester not containing hydrogen fluoride by bringing a difluoroacetic acid ester represented by CHF ₂ COOR containing hydrogen fluoride (R represents an alkyl group having 1 to 3 carbon atoms) into contact with water A process for producing a hydrocarbon having 5 to 8 carbon atoms when contacting with water.
[2] 1-alkoxy-1,1,2,2-tetra, in which a difluoroacetate containing hydrogen fluoride is represented by CHF ₂ CF ₂ OR ′ (R ′ represents a monovalent organic group) The production method of [1], which is a difluoroacetic acid ester obtained as a reaction product of an alcohol represented by a thermal decomposition product of fluoroethane and ROH (R represents an alkyl group having 1 to 3 carbon atoms).
[3] Production of [2], wherein the pyrolysis product is a pyrolysis product obtained by pyrolyzing 1-alkoxy-1,1,2,2-tetrafluoroethane in the presence of an aluminum phosphate catalyst Method.
[4] Alcohol is dissolved in hydrocarbon when obtaining a reaction product of a thermal decomposition product of 1-alkoxy-1,1,2,2-tetrafluoroethane and an alcohol according to [2] or [3] Production method.
[5] A difluoroacetic acid ester represented by CHF ₂ COOR containing hydrogen fluoride (R represents an alkyl group having 1 to 3 carbon atoms) and water in the presence of a hydrocarbon having 5 to 8 carbon atoms. A process for purifying difluoroacetate comprising contacting to form two layers, of which a layer rich in difluoroacetate is obtained.

  Since difluoroacetate is easily hydrolyzed under acidic conditions, hydrogen fluoride contained in difluoroacetate cannot usually be removed by washing with water. However, in the method of the present invention, hydrolysis is remarkably suppressed. Therefore, hydrogen fluoride can be removed by contact with water.

<Production of difluoroacetic acid fluoride>
The difluoroacetic acid fluoride according to the present invention may be produced by any method. For example, it can be produced by reacting 1-alkoxy-1,1,2,2-tetrafluoroethane in the presence of a catalyst. This reaction is represented by the following formula.
CHF ₂ CF ₂ OR '→ CHF ₂ COF + R'F
R of the alkoxy group of 1-alkoxy-1,1,2,2-tetrafluoroethane which is a starting material for this reaction is a monovalent organic group. Specific examples include an alkyl group having 1 to 8 carbon atoms that may have a branch, a cycloalkyl group that may have an alkyl group as a substituent, a fluorine-containing alkyl group, an aryl group, and an aralkyl group. Of these, an alkyl group or a fluorine-containing alkyl group is preferable, an alkyl group is more preferable, and a lower alkyl group is more 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 which may have a substituent as an alkyl group include a cyclobutyl group, a cyclopentyl group, a 2-methylcyclopentyl group, a 3-methylcyclopentyl group, a 2-ethylcyclopentyl group, a 3-ethylcyclopentyl group, and a cyclohexyl group. 2-methylcyclohexyl group, 3-methylcyclohexyl group, 4-methylcyclohexyl group, 2-ethylcyclohexyl group, 3-ethylcyclohexyl group, 4-ethylcyclohexyl group, cycloheptyl group, 2-methylcycloheptyl group, 3- Examples thereof include a methylcycloheptyl group, a 3-methylcycloheptyl group, and a 4-methylcycloheptyl group.

  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.

  The phosphate is not particularly limited, but is composed 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 phosphate as the main component is aluminum phosphate, cerium phosphate, boron phosphate, titanium phosphate, zirconium phosphate, chromium phosphate, or the like. These also preferably contain other metals. Specifically, 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 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 phosphoric acid 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 presumed that hydrogen fluoride is generated by decomposition in the region, which may show 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 target difluoroacetic acid fluoride, a compound in which alkyl fluoride (RF) or RF is further decomposed is generated as a by-product. For example, when ethyl fluoride is generated as RF, it may be ethylene and hydrogen fluoride. 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>
The 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 An aralkyl group can be exemplified, and among these, 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 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.

<Washing>
Since the difluoroacetic acid ester obtained by reacting difluoroacetic acid fluoride and alcohol (ROH) contains an equivalent amount of hydrogen fluoride, this hydrogen fluoride is generally removed. In the method according to the present invention, hydrogen fluoride is removed by washing the difluoroacetic acid ester in contact with water. In this case, the present invention is characterized in that it is carried out in the presence of a hydrocarbon.

  The hydrocarbon is a hydrocarbon having 5 to 8 carbon atoms. The hydrocarbon may be linear, branched or cyclic, and may be saturated or unsaturated. Non-limiting examples of such saturated hydrocarbons include n-pentane, n-hexane, n-heptane, n-octane, iso-pentane, iso-hexane, 3-methylpentane, neohexane, 2,3-dimethyl. Butane, iso-heptane, 3-methylhexane, 3-ethylpentane, 2,3-dimethylpentane, 2,2-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, 2,2,3- Trimethylbutane, iso-octane, 3-methylheptane, 2,2-dimethylhexane, 2,3-dimethylhexane, 2,5-dimethylhexane, 3,4-dimethylhexane, 2,2,3-trimethylpentane, 2, 2,4-trimethylpentane, 2,3,3-trimethylpentane, 2,3,4-trimethylpentane, cyclopentane, cyclohexane Sun, cycloheptane, cyclooctane, methylcyclohexane, methylcyclopentane, methyl cycloheptane, dimethylcyclopentane acids, trimethyl cyclopentane compounds, and dimethyl cyclohexanes. Examples of unsaturated hydrocarbons include 1-pentene, 2-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, 1-hexene, and 2,3-dimethyl-2. -Butene, cyclopentene, cyclohexene, cycloheptene, cyclooctene and the like. Of these hydrocarbons, saturated hydrocarbons are preferred because they are easy to handle. Of the saturated hydrocarbons, n-hexane, methylcyclohexane, methylcyclopentane, and the like are particularly preferable. These hydrocarbons can be used alone or in combination of two or more.

  Although the usage-amount of hydrocarbon is arbitrary, 1-4 mol is preferable with respect to 1 mol of difluoroacetic acid esters, and 1.5-3 mol is more preferable. If the amount is less than 1 mol, separation of the aqueous layer and the organic layer may be insufficient. If the amount exceeds 4 mol, the ester formation reaction and the difluoroacetate ester / hydrocarbon separation treatment apparatus increase in size, which is not preferable. .

  In the method according to the present invention, the method for adding the hydrocarbon is not limited, and the hydrocarbon can be added to the difluoroacetic acid ester before or at the same time when the difluoroacetic acid ester and water are substantially brought into contact with each other. For example, difluoroacetic acid difluoride is blown into alcohol to form difluoroacetic acid ester, and then hydrocarbon can be added. Hydrocarbon is dissolved in alcohol, and difluoroacetic acid fluoride is blown into it to form difluoroacetic acid ester. Afterwards, hydrocarbons can be added and then contacted with water. In addition, after difluoroacetic acid fluoride is blown into alcohol to form difluoroacetic acid ester, water and hydrocarbon can be added substantially simultaneously, but it is better to dissolve the hydrocarbon before contact with water. preferable.

  For the contact with water, a known method which is carried out by washing the organic substance with water can be employed. For example, contact efficiency can be improved by a stirrer, a line mixer, pump circulation, a sparger, and the like.

  After contact with water, the liquid in the vessel is allowed to settle to form two layers, and a layer rich in difluoroacetate is separated from the aqueous layer and collected.

  Although the treatment temperature is not particularly limited, it is preferably carried out at a temperature of −10 ° C. or more and below the boiling point of the hydrocarbon, but it is usually convenient to carry out at room temperature (particularly, a temperature at which cooling or heating is not performed). When the boiling point of the hydrocarbon approaches the liquid temperature, it is preferably cooled to a temperature that is about 20 ° C. lower than the boiling point of the hydrocarbon. Although it does not solidify even at about −10 ° C., the separation of the two layers is not clear and the operation may be difficult, and there is no merit of lowering the temperature especially at −10 ° C.

  The separated organic liquid in the layer rich in difluoroacetic acid ester can be repeatedly washed with water, and further washed with a basic aqueous solution. As the basic aqueous solution, an aqueous solution of potassium hydroxide, sodium hydroxide, calcium hydroxide, magnesium hydroxide or the like can be used, and potassium hydroxide, sodium hydroxide, or calcium hydroxide is preferable from the viewpoint of economical efficiency. The organic liquid from which the water-soluble acidic component has been removed in this manner is preferably dried with a desiccant such as zeolite, anhydrous magnesium sulfate, anhydrous sodium sulfate, or anhydrous calcium chloride. Then, difluoroacetic acid ester substantially free of impurities is obtained by subjecting to precision distillation.

  The separated aqueous layer mainly contains hydrogen fluoride, but may contain difluoroacetic acid. This aqueous solution can be used as hydrofluoric acid with or without difluoroacetic acid.

<Multistage process>
An example to which the present invention is applied is shown without limitation. Hydrocarbon-alcohol (ROH) 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 When the solution is bubbled into the container, difluoroacetic acid ester (CHF ₂ COOR) and hydrogen fluoride (HF) are produced almost quantitatively. When water is added and shaken, the two-layer interface between the aqueous layer and the organic layer is quickly formed. While recovering the organic layer, the aqueous layer can be further extracted with the same or different hydrocarbon as the hydrocarbon to recover difluoroacetic acid ester dissolved in water. The organic layer thus recovered is dehydrated with a dehydrating agent such as zeolite, anhydrous magnesium sulfate, anhydrous calcium chloride, and then separated by a distillation means known in the field of organic chemistry to obtain a high-purity difluoroacetate ester. Can do. The hydrocarbons recovered by distillation can be used again in the practice of the present invention through further purification operations such as dehydration and the like, if necessary.

Preferable specific examples in the application examples of the present invention described above include using an aluminum phosphate catalyst as the catalyst and 1-methyl-1,1 as 1-alkoxy-1,1,2,2-tetrafluoroethane. , 2,2-tetrafluoroethane (HFE-254pc, CHF ₂ CF ₂ OMe) and n-hexane as the hydrocarbon. Here, it is also preferable to use a metal oxide as a 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, adding hydrocarbon and water to difluoroacetate containing hydrogen fluoride, mixing, shaking, standing, separating into two layers, further distillation and drying as necessary By doing so, a highly pure difluoroacetic acid ester can be obtained.

  The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[Example 1]
Isopropyl difluoroacetate (CHF ₂ COOCHMe ₂ ) (5 g), each cooled beforehand in an ice bath, 10 g of n-hexane and 10 g of a 7.8% aqueous solution of hydrogen fluoride (HF) were mixed and stirred for 5 minutes while cooling in an ice bath. did. 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 0.4 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 1.2%.

[Preparation Example 1]
Aluminum phosphate manufactured by Aldrich was tableted into 5 mmφ × 5 mmL pellets and calcined in a nitrogen stream at 700 ° C. for 5 hours to prepare an aluminum phosphate catalyst.

[Synthesis Example 1 of difluoroacetic acid fluoride (CHF ₂ COF)]
The aluminum phosphate catalyst (200 cc) prepared in Preparation Example 1 was charged into a stainless steel reaction tube having a JIS nominal diameter of 32 A (inner diameter: 37.1 mm) and a length of 500 mm equipped with an external electric furnace, and nitrogen was flowed at 50 cc / min. While heating in an electric furnace. When the catalyst temperature reached 50 ° C., the HF feed was gradually started 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% and the difluoroacetic acid fluoride selectivity: 99.8% (CH _The area% was determined by excluding by-products based on alkoxy groups such as ₃ F. The same applies hereinafter.

[Example 2]
A PFA gas washing bottle (500 cc) was charged with isopropanol (IPA) (61.4 g) and n-hexane (173.3 g) and cooled in an ice bath. The product gas of Synthesis Example 1 was bubbled into this IPA-hexane solution without purification. After supplying 180 g of HFE-254pc to the reactor of Synthesis Example 1, the entire contents of the washing bottle were transferred to a separatory funnel, and ice water (262 g) was added and shaken. After standing, 1 mL was separated from the aqueous phase separated into two layers, diluted to 100 mL, neutralized with 2 mol / L-NaOH aqueous solution, and further 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 0.6 ppm. The amount of CHF ₂ COO ⁻ ion was converted to isopropyl difluoroacetate weight, and the hydrolysis rate of isopropyl difluoroacetate was determined from 188 g of isopropyl difluoroacetate, and found to be 0.9%. Moreover, as a result of analyzing the organic phase by gas chromatography (FID detector), IPA: 0.01 area%, n-hexane: 78.28 area%, isopropyl difluoroacetate: 21.4 area%, others: 0.31 Area%. This was dehydrated with anhydrous magnesium sulfate and distilled to obtain 99.9 area% isopropyl difluoroacetate. Although a glass distillation column was used for distillation, no devitrification was observed in the glass portion.

[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 (5)

A difluoroacetate containing no hydrogen fluoride is produced by contacting a difluoroacetate represented by CHF ₂ COOR containing hydrogen fluoride (R represents an alkyl group having 1 to 3 carbon atoms) with water. A method for producing a hydrocarbon having 5 to 8 carbon atoms when contacting with water. 1-alkoxy-1,1,2,2-tetrafluoroethane in which difluoroacetate containing hydrogen fluoride is represented by CHF ₂ CF ₂ OR ′ (R ′ represents a monovalent organic group) The production method according to claim 1, which is a difluoroacetic acid ester obtained as a reaction product of an alcohol represented by a thermal decomposition product and ROH (R represents an alkyl group having 1 to 3 carbon atoms). The production method according to claim 2, wherein the thermal decomposition product is a thermal decomposition product obtained by thermally decomposing 1-alkoxy-1,1,2,2-tetrafluoroethane in the presence of an aluminum phosphate catalyst. . The production method according to claim 2 or 3, wherein the alcohol is dissolved in the hydrocarbon when the reaction product of the thermal decomposition product of 1-alkoxy-1,1,2,2-tetrafluoroethane and the alcohol is obtained. A difluoroacetic acid ester represented by CHF ₂ COOR containing hydrogen fluoride (R represents an alkyl group having 1 to 3 carbon atoms) is brought into contact with water in the presence of a hydrocarbon having 5 to 8 carbon atoms. A method for purifying difluoroacetate, comprising forming two layers, of which a layer rich in difluoroacetate is obtained.