TECHNICAL FIELD
Fluorine-containing carboxylic acid, esters are useful compounds, which
are used for catalysts in various reactions, intermediates of medicines and
agricultural chemicals, or intermediates of functional materials, etc. The
present invention relates to a method for producing a fluorine-containing
carboxylic acid ester.
BACKGROUND TECHNIQUE
As a method for producing a fluorine-containing carboxylic acid ester,
(here are known (1) a method of esterifying a fluorine-containing carboxylic
acid in the presence of an acid catalyst, (2) a method of reacting
1-alkoxy-1,1,2,2-tetrafluoroethane, sulfuric acid, and silica (Non-patent
Publication 1), (3) a method of reacting difluoroacetic acid fluoride, which is
obtained by subjecting 1-alkbxy-1,1,2,2-tetrafluoroethane to a gas-phase
reaction in the presence of a metal oxide catalyst, with an alcohol (Patent
Publication 1), etc.
In the method of (1), there is a problem that difluoroacetic acid as the raw
material is not easily available. As a method for producing difluoroacetic acid,
there have been reported (4) a method in which chlorotrifluoroethylene as a
starting material is reacted with an alkylamme, followed by hydrolysis to
obtain a chlorofluoroacetic amide, moreover fluorination to convert it into
difluoroacetic amide, and then hydrolysis (Non-patent Publication 2). (5) a
method in which ammonia is added to tetrafluoroethylene to prepare
2,4,6-difluoromethyl-1.3.5-triazine, followed by hydrolysis (Patent Publication
2), etc
In the method of (4), however, there are problems that the fluorination of
chlorofluoroacetic amide is a reaction of a long time and a high temperature,
that a post-treatment after the fluorination is complicated, and that yield is
also low. Furthermore, in the method of (5), an industrial execution is

difficult, since the addition of tetrafluoroethylene and ammonia is a
high-pressure reaction of a gauge pressure of 3.4MPa (34kgG/cm2).
Furthermore, in each method of (4) and (5), a hydrolysis step is necessary.
When using a hydrolysis step using sulfuric acid, there is a problem that a
large amount of sulfuric acid waste liquid occurs. Furthermore, in the case of
using a hydrolysis step using an alkali metal hydroxide aqueous solution,
difluoroaeetic acid is obtained as a mixture of water and an inorganic salt.
Since difluoroacetic acid has a boiling point higher than that of water, there is
a problem that separation from the inorganic salt by distillation is difficult,
and recovery is low.
Furthermore, in the method of (2), it is difficult to control the reaction,
and there is a risk that the reactor may corrode. Furthermore, the method of
(3) is composed of a two-step reaction in which difluoroacetic acid fluoride is
once produced from l-alkoxy-l,l,2,2-tetrafluoroethane, and an alcohol is
reacted with it. In more detail, it is composed of complicated steps that the
alkoxy group moiety is eliminated as an alcohol by the first step reaction, and
the alcohol is again added in the second step. In such reaction process, it is
necessary to have a large-scale reaction apparatus and complicated operations.
Furthermore, there is a risk, that resources may be wasted by dumping a part
of the raw material, and an excessive energy may be consumed.
Nonpatent Publication 1: J. Am. Chem. Soc, 72, 1860(1950)
Non-patent Publication 2- Collect. Czech. Chem. Comm., 42(8), 2537(1977),
CS180697
Patent Publication 1-" Japanese Patent Application Publication 8-92162
Patent Publication 2- US Patent No. 2442995 specification

DISCLOSURE OF THE INVENTION
TASK TO BE SOLVED BY THE INVENTION
The present invention provides a production method that the target
tluorine-eontaining carboxylic acid ester can be obtained from a
fluorine-containing ether by a one-step reaction, that a complicated step and a
troublesome operation are not necessary, and that an excessive energy is not
consumed.
MEANS FOR SOLVING THE TASK
The present inventors have repeated eager studies about an
advantageous method replacing the above conventional methods. As a result,
we have found a method for industrially producing a fluorine-containing
carboxylic acid ester with high yield.
That is, the present invention is a method for producing a
fluorine-containing carboxylic acid ester represented by the general formula
R1HCFCOOR2 (R1 and R2 represent the same meanings as below) comprising
reacting a fluorine-containing ether represented by the general formula
R1HCFCF2OR2 (R1 represents either of a fluorine atom and a C1-1
porlluoroalkyl group, and R2 represents a monovalent organic group) with
water in the presence of a solid catalyst.
In the description and the claims of the present invention, the
fluorine-containing ether may be written as "HFE".
ADVANTAGEOUS EFFECT OF THE INVENTION
The method for producing a fluorine-containing carboxylic acid ester of
the present invention comprises a reaction showing extremely high reactivity
and selectivity and makes it possible to obtain a fluorine-containing carboxylic
acid ester of high purity. Furthermore, the method of the present invention is
a method that makes it possible to produce the target fluorine-containing

carboxylic acid ester by a one-step reaction from an industrially available raw
material. Furthermore, since the method of the present invention is
essentially denydrofluorination and a transfer reaction in the molecule, it is a
method that all the carbons of the ether compound as the raw material can
effectively be used as the product. Therefore, the method of the present
invention is a method that is industrially extremely superior.
BEST MODE FOR CARRYING OUT THE INVENTION
As the C1-1 perfluoroalkyl group in the fluorine-containing ether
represented by the general formula R1HCFCF2OR2 (R1 represents either of a
fluorine atom and a C1-1 perfluoroalkyl group, and R2 represents a monovalent
organic group), which is the raw material of the present invention, it is possible
to cite trifluoromethyl group, pentafluoroethyl group, n-heptafluoropropyl
group, heptafluoroisopropyl group, n'nonafluorobutyl group, s-nonafluorobutyl
group, and t-nonafluorobutyl group. As R1, a fluorine atom or trifluoromethyl
group is particularly preferable.
As the monovalent organic group, it is possible to cite a C1-8 alkyl group
optionally having a branch, a cycloalkyl group optionally having an alkyl group
as a substituent, a fluorine containing alkyl group, an aryl group, and an
aralkyl group. Of these, an alkyl group or fluorine-containing alkyl group is
preferable, an alkyl group is more preferable, and a lower alkyl group is still
more preferable. The lower alkyl group refers to a C1-8alkyl group.
The C1-8 alkyl group optionally having a branch can be exemplified by
methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group,
sbutyl group, t-butyl group, n-pent.yl group, and isopentyl group.
As the cycloalkyl group optionally having an alkyl group as a substituent,
it is possible to cite cyclobutyl group, cyclopentyl group, 2-methylcyclopentyl
group, 3-methylcyclopentyl group, 2-ethylcyclopentyl group, 3-ethylcyclopentyl
group, cyclohexyl group, 2-methyleyelohexyl group, 3-methylcyclohexyl group,
4-methylcyclohexyl group, 2-ethylcyclohexyl group, 3-ethylcyclohexyl group,

lethylcyelohexyl group, cycloheptyl group, 2-methylcycloheptyl group.
3-methytcycloheptyl group, 3-methylcycloheptyl group, 4-methylcycloheptyl
group, etc.
The aryl group can be exemplified by 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-dimethvlphenyl group, 2-methoxyphenyl group, 3-methoxyphenyl group,
Imethoxyphenyl group, 1-naphthyl group, 2-naphthyl group, etc.
The fluorine-containing alkyl group can be exemplified by fluoromethyl
group, difluoromethyl groupj, trifluoromethyl group, chlorofluoromethyl group,
chlorodifluoromethyl group,bromofluoromethyl group, dibromofluoromethyl
group, 2.2,2-trifluoroethyl group, pentafluoroethyl group,
2,2,3,3,3-pentafluoropropyl group, n-hexafluoropropyl group,
hexafluoroisopropyl group, etc.
The aralkyl group can be exemplified by phenethyl group,
2-methylphenylmethyl group, 3-methylphenylmethyl group,
4-methylphenylmethyl group, 2,3-dimethyrphenylmethyl group,
2,4-dimethylphenylmethyl group, 2,5-dimethylphenylmethyl group,
2,6-dimethylphenylmethyl group, 3.4-dimethylphenylmethyl group.
3,5-dimot hylphenylmethyl group, 3,(rdimethylphenylmethyl group.
4-ethylphenylmethyl group, 4-(n-propyl)mcthylphenylmethyl group,
4-(n-butyl)methylphenylmethyl group, etc.
It is possible by a publicly known production method to obtain the
fluorine-containing ether represented by the general formula R1HCFCF2OR2
(R1 represents either a fluorine atom oraC1-1 perfluoroalkyl group, and R2
represents a monovalent organic group), which is the raw material of the
present invention.

It can be synthesized, for example, by a method of reacting an alcohol
compound (R2OH) with a fluorine-containing compound having a double bond,

such as tetrafluoroethylene br hexafluoropropene, in the presence of a base.
Specifically, it is possible to synthesize
1-methoxyl,1,2,2-tetrafluoroethane by a method of reacting methanol with
tetrafluoroethylene in the presence of potassium hydroxide (J. Am. Chem. Soc,
73, 1329 (1951)).
Furthermore, it is possible to synthesize 1-hexafluoroisopropyl
1,1,2,3,3,3-hexafluoropropane by a method of reacting hexafluoroisopropanol
with hexafluoropropene in the presence of potassium hydroxide (US Patent No.
3557294).
As specific examples of the fluorine-containing ether usable in the present
invention, it is possible to cite 1-methoxy-1,1,2,2-tetrafluoroethane,
1-ethoxy-1,1,2,2-tetrafluoroetthane, 1-(n-propoxy)-1,1,2,2-tetrafluoroethane,
1-isopropoxyl.l,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-difluoromethoxy-1,1,2,2-tetrafluoroethane,
1-(2,2,2-trifluoroethoxy)-1,1,2,2-tetrafluoroethane,
1-pentafluoroethoxy-1,1,2,2-tetrafluoroethane,
1-(2,2,2,3.3-pentafluoropropoxy)-1,1,2,2-tetrafluoroethane,
1-hexafluoroisopropoxy-1,1,2,2-tetrafluoroethane.
1-methoxy-1,1,2,3,3,3-hexafluoropropane,
1-ethoxyl,l,2,3,3,3hexafluoropropane,
1-(n-propoxy)-1,1,2,3,3,3-hexafluoropropane.
1 - isopropoxy 1,1,2,3,3,3-hexafluoropropane.
1-(n-butoxy)-1,1,2,3,3,3-hexafluoropropane,
1-(s-butoxy)-1,1,2,3,3,3-hexafluoropropane,
1-(t-butoxy)-1,1,2,3,3,3-hexafluoropropane,
1-trifluoromethoxy-1,1,2,3,3,3-hexafluoropropane,

1-difluoromethoxyl,l,2,3,3,3-hexafluoropropane,
1-(2,2,2-trifluoroethoxy)-1,1,2,3,3,3-hexafluoropropane,
1-pentafluoroethoxy-1,1,2,3,3,3-hexafluoropropane,
1-(2,2,2,3,3-pentafluoroproppxy)-1,1,2,3,3,3-hexafluoropropane,
1-hexafluoroisopropoxy-1,1,2.3,3,3-hexafluoropropane, etc. It is, however, not
limited to these.
Water used in the present invention is not particularly limited.
Ordinary tap water (tap water) or distilled water, ion exchanged water, and
other purified waters are acceptable.
In the present invention, a fluorine-containing ether represented by the
general formula R1HCFCF2OR2 (R1 represents a fluorine atom or a C1-1
perfluoroalkyl group, and R2 represents a monovalent organic group) is reacted
with water in the presence of a solid catalyst, thereby producing a
fluorine-containing carboxylic acid ester represented by the general formula
R1HCFCOOR2. This reaction is represented by the following formula.
R2HCFCF2OR2 + H2O → R1HCFCOOR2 + 2HF
The solid catalyst is not particularly limited, as long as it is a catalyst
that makes the above reaction efficiently proceed. As the solid catalyst, it is
possible to use a metal oxide, such as alumina, titania, zirconia, and sulfated
zirconia (ZrO(SO4)), an activated carbon on which an inorganic acid, such as
sulfuric acid or phosphoric acid, is supported, an activated carbon on which a
metal compound is supported, a resin having acid sites, or an inorganic
material such as aluminum phosphate (AlPO4).
Alumina used in the present invention is not particularly limited.
Normally, it is an alumina obtained by shaping and dehydrating a precipitate
produced from an aluminum salt aqueous solution by using ammonia or the
like. It is possible to preferably use an y-alumina on the market for a catalyst
support use or a drying use.

Metal oxides, such as titania, zirconia and sulfated zirconia, can also be
prepared by similar methods or publicly known methods, and commercial
products can also be used. Furthermore, these metal oxides can also be used
as complex oxides prepared by a coprecipitation method, etc. Furthermore, it
is also possible to support a metal compound by using alumina, titania,
zirconia or the like as a support. The type and the amount of the metal to be
i
supported, the supporting method, and the like can be conducted, based on
knowledge in the technical field of catalyst, according to the explanation about
the after-mentioned activated carbon.
It is possible to prepare an activated carbon, on which sulfuric acid,
phosphoric acid or a metal compound is supported, by immersion in sulfuric
acid or phosphoric acid or immersion in a solution, in which the metal
compound is dissolved, for impregnation, or by spraying to prepare a covered or
adsorbed one. and then by drying. In the case of supporting a compound, it
can be prepared by impregnation with a solution of the compound or by
spraying to prepare a covered or adsorbed one. and then by drying.
Furthermore, it is also possible to support a compound that is different from
the first compound by making the second compound act on an activated carbon
covered or adsorbed by impregnation with a solution of the compound or
spraying to generate a precipitation reaction or the like on the activated carbon
surface. As a specific example, an activated carbon on which aluminum
phosphate is supported is shown in Examples.
The activated carbon can be any of vegetable series using raw materials
such as wood, charcoal, coconut husk coal, palm core coal, and raw ash' coal
series using raw materials such as peat, lignite, brown coal, bituminous coal,
and anthracite; petroleum series using raw materials such as petroleum
residue and oil carbon; synthetic resin series using raw materials such as
carbonated polyvinylidene chloride. It is possible to use one by selecting from
these commercial activated carbons. For example, it is possible to cite an
activated carbon produced from bituminous coal (BPL GRANULAR
ACTIVATED CARBON made by TOYO CALGON CO.), a coconut husk coal

(GRANULAR SHIRO SAGI GX, SX, CX and XRC made by Takeda Chemical
Industries, Ltd. And PCB made by TOYO CALGON CO.), etc., but it is not
limited to these. It is used generally in the form of granules in terms of shape
and size, too. It is possible to use one in the form of sphere, fiber, powder,
honeycomb, or the like in an ordinary knowledge scope as long as it fits into the
reactor.
The activated carbon used in the present invention is preferably an
Motivated carbon that, is large in specific surface area. It is acceptable that the
specific surface area and the micropore volume of the activated carbon are in
ranges of the standard of commercial products. It is desirable that they are
respectively greater than 400m2/g and greater than 0.1cnvVg. Furthermore, it
is satisfactory that they are respectively 8003000m2/g and 0.2-1.0cmVg.
Furthermore, in the case of using the activated carbon as a support, it is
desirable to previously conduct an activation of the support surface and
removal of ash by immersing it in a basic aqueous solution, such as ammonium
hydroxide, sodium hydroxide, potassium hydroxide, etc., at around ordinary
temperature for a period of time of about 10 hours or longer or by conducting a
pretreatment by an acid, such as nitric acid, hydrochloric acid, hydrofluoric
acid, etc., which is generally conducted upon using activated carbon as a
catalyst support.
As a metal compound to be supported, compounds of Al, Ti, Zr, Ce, Cr, Mn,
Fe, Co, Ni, Zn, Nb, Sn, Sb, Pb and Bi are preferable. It is preferable that they
are water-soluble compounds such as chlorides, bromides, nitrates, etc.
Furthermore, these may be alone, or may be supported in a combination of at
least two kinds.
Furthermore, as a solid acid catalyst, it is possible to use resins having
acid sites, such as perfluorosulfonic acid resins such as Nafion (Nafion, a
product of DuPont Co.), cation exchange resins such as Amberlite. Amberjet,
Amberlyst, Amberlite XAD and Amberlite CG50 (each is a registered
trademark of Rohm and Haas Co.). etc.

Furthermore, a solid catalyst of the present invention may contain other
atoms besides a metal component and oxygen. As other atoms, fluorine atom,
chlorine atom, etc. are preferable. It may be, for example, a partially
fluorinated alumina, a partially chlorinated alumina, a partially
fluorochlorinated alumina, a partially fluorinated zirconia, a partially
fluorinated titania, etc. The proportion of chlorine atom or fluorine atom in
the solid catalyst is not particularly limited.
In the present description and the claims, unless particularly limited,
oxides, such as alumina and zirconia, subjected to the above-mentioned partial
fluorination, chlorination, etc. are denoted by oxide names such as 'alumina"
and "zirconia".
As these solid catalysts, at least one metal oxide catalyst selected from
the group consisting of alumina (Al2O3), zirconia (ZrO2) and titania (TiO2) and
sulfated zirconia and partially fluorinated oxides of these is preferable.
Alumina and a partially fluorinated alumina are more preferable in terms of
reactivity and catalyst lifetime.
The solid catalyst is used normally in the form of particles or granulated
matter. Diameter of the particles or granulated matter (each may be referred
to as "particle size") is not particularly limited. It is normally around
20µm-10mm. Furthermore, in case that the solid catalyst contains chlorine
atom or fluorine atom, the chlorine atom or fluorine atom may exist only on the
surface of the metal oxide catalyst.
It is effective for any solid catalyst to prevent compositional change,
lifetime shortening, abnormal reaction, etc. of the catalyst in the reaction by
previously bringing it into contact, prior to use, with a fluorine-containing
compound such as hydrogen fluoride, a fluorinated hydrocarbon or a
fluorochlorinated hydrocarbon or the like to achieve a partial fluorination or
partial chlorination.

Furthermore, prior to the reaction, it is preferable to conduct an
activation treatment. As the activation treatment, there is applied a normal
method that is applied when using a metal oxide catalyst for a fluorination
reaction, and it is not particularly limited. As a preferable activation
treatment, it is preferable to conduct a sufficient dehydration in a nitrogen
stream of about 250°C-300°C and an activation with an organic fluorine
compound, such as dichlorodifluoromethane and chlorodifluoromethane, or a
gas such as hydrogen fluoride or chlorine trifluoride, or an inorganic fluorine
compound showing a sufficient vapor pressure under the catalyst treatment
condition. This activation treatment is considered to generate an active metal
component containing an atom besides the metal component and oxygen, on
the surface or entirety of the solid catalyst, Furthermore, it is effective for the
prolongation of catalyst lifetime and the improvement of reactivity and
reaction yield to supply chlorine, a fluorochlorinated hydrocarbon or
chlorinated hydrocarbon, etc. to the reactor during the reaction.
The reaction of the fluorine-containing ether with water in the presence of
a solid catalyst uses 0.5-20 mols of water, preferably 1/10 mols of water,
relative to lmol of the fluorine-containing ether. 1 mol of water is equivalent
in the reaction. Less than 0.5 mols of water is not preferable due to low
reactivity. It is, however, not limited to this in a production process assuming
recovery and reuse. The use exceeding 20 mols is not preferable in terms of
both consumption energy and recovery of the product in the production.
The reaction of the fluorine-containing ether (R1HCFCF2OR2) with water
in the presence of a solid catalyst may either a liquid phase reaction or a gas
phase reaction. It is preferably conducted in a gas phase reaction in an
industrial production. In the following, conditions and the like regarding the
gas phase reaction are explained. It corresponds to design change and is easy
for a person skilled in the art to adjust this to conditions and the like of the
liquid phase reaction.

In this reaction, it is optional to make an inert gas present. As the inert
gas, it is possible to cite nitrogen or rare gas. In terms of handling easiness
and availability, nitrogen or helium is preferable. The amount in the ease of
making an inert gas present is not particularly limited. In case that it is too
much, there is a fear of lowering of recovery. Therefore, in normal cases, it is
preferable to make an inert gas present to be about 90 volume % or lower in the
total amount with a vaporized matter of the fluorine-containing ether of the
raw material.
As a reactor for conducting a reaction between the fluorine-containing
ether and water in the presence of a solid catalyst, a fixed bed type or fluidized
bed type is preferable. The size and shape of the reactor can suitably be
changed depending on the type, the amount, and the like of the reactant.
The temperature of the reaction between the fluorine containing ether
and water in the presence of a solid catalyst varies, depending on the type of
the catalyst and the raw material. Normally, it is 80-350°C, preferably
around 100-300°C, particularly preferably 150-250°C. Low reaction
temperature tends to lower conversion. If the reaction temperature exceeds
350°C, by-products of the organic matter may be produced. The reaction time
(contact time) is normally 0.1-300 seconds, preferably 1-200 seconds, more
preferably 2-(50 seconds. In case that the reaction time is overly short too.
there is a fear of lowering of conversion. On the other hand, if it is overly long,
there is a fear that the production of byproducts increases. The reaction
pressure is not particularly limited. Any of normal pressure, reduced
pressure or pressurization is acceptable. In normal cases, around
0.05-0.5Mpa (0.5-5 atmospheres) is preferable.
In the reaction between the fluorine-containing ether and water in the
presence of a solid catalyst of the present invention, hydrogen fluoride is
produced as a by-product besides the target fluorine-containing carboxylic acid
ester, and it may be accompanied with the unreacted water. Therefore, it is

preferable in normal cases to conduct a purification treatment on a crude
product obtained by the reaction.
As the treatment of the crude product, there are a method of separation
by a direct distillation without conducting other treatments, a method of
distilling an organic phase separated by bringing the product into contact with
water, and the like. Since the fluorine-containing carboxylic acid ester of the
target product has a solubility in water, it is preferable to add an extraction
operation in the method of contacting with water.
The reaction between the fluorine-containing ether and water in the
presence of a solid catalyst of the present invention shows an extremely high
reactivity and is superior in reproducibility of reaction yield, too.
Furthermore, it is a reaction in a gas-phase flow continuous system.
Therefore, it is efficient and is a reaction superior in terms of productivity, too.
Furthermore, the fluorine-containing carboxylic acid ester
(R1HCFCOOR2) produced by the reaction may contain the corresponding
alcohol (R2OH) besides hydrogen fluoride, but it can be removed by contact
with water. Furthermore, it is possible to remove R2OH by bringing a
fluorine-containing carboxylic acid fluoride (R1HCFCOF) into contact with the
fluorine-containing carboxylic acid ester containing the alcohol (R-OH) in the
same reaction apparatus and conditions as those of the method of the present
invention to conduct a reaction with the alcohol (R2OH).
The method of bringing the fluorine-containing carboxylic add fluoride
into contact is preferable, particularly in the case of continuously conducting
the react 1021 in an industrial large volume.
The fluorine-containing carboxylic acid ester obtained by the present
invention is an extremely useful compound used for various catalysts,
intermediates of medicines and agricultural chemicals, and intermediates of
functional materials, etc.

In the following, the present invention is specifically explainediby citing
examples, but the present inivention is not limited by these.
(EXAMPLE 1]
[PREPARATION OF CATALYST]
A stainless steel reaction tube with a fluorine resin lining, covered with a
Nichrome wire heater and a lagging material at its exterior and having an
inner diameter of 26mm and a length of 1000mm, was charged with 400cc of
γ-alumina (particle size: 3'4mm). While maintaining the outside temperature
at 220°C, hydrogen fluoride made to accompany nitrogen gas was allowed to
flow for 6 hours, thereby preparing a partially fluorinated alumina catalyst.
[REACTION]
Then, the reaction tube was made to have a temperature of 180°C.
l'methoxy-1,1,2,2-tetrafluoroethane. together with nitrogen, was introduced at
a flow rate of 10.6gr/Hr into the reaction tube by bubbling nitrogen of about 20
ee/minute through a glass container containing
1-methoxy-1,1,2,2-tetrafluoroethane. Furthermore, at the same time, ion
exchanged water was fed at a flow rate of 7.2 gr/Hr with a tube pump into a
vaporizing heater maintained at 200°C for vaporization, and it was introduced
into the reaction tube. An effluent, from the reaction tube was collected for a
period of time of 5 hours after the start of the reaction by a trap containing iced
water and a trap cooled with acetone-dry ice. The organic matter and the
aqueous layer recovered from both traps were extracted with dibutyl ether,
thereby recovering an organic layer. The obtained recovery organic matter
was quantitated with a gas chromatograph (FID detector). With this,
1-methoxy-1,1,2,2-tetrafluoroethane of the raw material was not detected, and
selectivity of methyl difluoroacetate was 99.2%.

Furthermore, the obtained recovery organic matter was subjected to
rectification, thereby obtaining 8.8g (yield 94,5%) of methyl difluoroacetate of a
purity of 99,8% or higher. The results are shown in Table 1.
[Table 1]
i

[EXAMPLE 2]

The same reaction was conducted by the same procedure as in Example 1,
in a manner that the raw material 1-methoxy 1,1,2,2tetrafluoroethane was
made to have a flow rate of 5.3gr/Hr by adjusting flow rate of nitrogen gas to
about 10cc/min and that water was made to have a flow rate of 3.6gr/Hr. The
results obtained by running the reaction for 5 hours are shown in Table 1.
[EXAMPLE 3]
After continuing the reaction under the same conditions as those of
Example 1 for 245 hours, the product was recovered for 5 hours. Reactivity of
the raw material 1-methoxy 1,1.2,2-tetrafluoroet.hane and selectivity of methyl
difluoroacetate were determined. The results are shown in Table 1. Activity
lowering of the catalyst was almost not found.

[EXAMPLE 4]
After terminating the reaction of Example 3, the catalyst having a thin
coking was taken out of the reaction tube used in the reaction. It was
transferred to a reaction tube that was equipped with an electric furnace at
exterior, had an inner diameter of 4.2cm and a length of 60cm, and was made
of SUS304. While the air was allowed to flow, the temperature of the electric
furnace was increased to 600°C, and it was maintained at that temperature.
After cooling to room temperature, the catalyst was again returned to the
reaction tube with a fluorine resin lining, used in Example 1. The
temperature of the reaction tube was changed to 220°C, and, while
maintaining that temperature, a pretreatment of the catalyst was conducted
by allowing hydrogen fluoride, made to accompany nitrogen gas, to flow at a
flow rate of 20g/Hr for 2 hours. Then, the reaction was conducted under the
same conditions as those of Example 1. With this, almost the same results as
I hose of Example 1 were obtained. The results are shown in Table 1.
[EXAMPLE 5]
The same reaction was conducted by the same procedure as in Example 1,
in a manner that the raw material 1-methoxy-1,1,2,2-tetrafluoroethane was
made to have a flow rate of 7.7gr/Hr by adjusting flow rate of nitrogen gas to
about 14.5cc/min and that water was made to have a flow rate of 3.1gr/Hr.
The results obtained by running the reaction for 5 hours are shown in Table 1.
[EXAMPLE 6]
The same reaction was conducted under the same procedure as in
Example 1 by adjusting the flow rate of the raw material
1-mnethoxy-1,1,2,2-tetrafluoroethane to 10.6gr/Hr and the flow rate of the water
to 3.6gr/Hr. The results obtained by running the reaction for 5 hours are
shown in Table 1. Lowering of reactivity is found in Example 6, in which the
molar ratio of water/1-methoxy-1,1,2,2-tetrafluoroethane was lowered (the

molar ratio: 2.5), as compared with Example 1 (the molar ratio: 5). but a high
yield of 79.5% was obtained.
[EXAMPLE 7]
The same reaction was conducted under the conditions of Example 1.
except in that the reaction temperature was adjusted to 220°C. The results
i
are shown in Table 1. Selectivity of methyl difluoroacetate was somewhat
low.
[EXAMPLE 8] (Synthesis of ethyl difluoroacetate)
The reaction was conducted by the same procedure as that of Example 1
under the conditions shown in Table 2, in which
1-ethoxy 1,1,2,2-tetrafluoroethane (11.7gr/Hr) was used as the raw material in
place of 1-methoxy 1,1,2,2-tetrafluoroethane and in which the flow rate of the
water was adjusted to 7.2gr/Hr. The results are shown in Table 2.
[Table 2l
The reactivity is a reactivity of HFE (1-ethoxy-1,1,2,2-tetrafluoroethane).
The selectivity is a selectivity of ethyl difluoroacetate.
[EXAMPLE 9]
The same reaction was conducted under the conditions of Example 8,
except in that the reaction temperature was adjusted to 160°C. The results
are shown in Table 2.
[EXAMPLE 10]
The reaction was conducted by the same procedure as that of Example 1
under the conditions shown in Table 3, in which

1-methoxy 1,1,2,3,3,3-hexafluoropropane (14.6gr/Hr) was used as the raw
material in place of 1-methoxy-1,1,2,2-tetrafluoroethane and in which the flow
rate of the water was adjusted to 7.2gr/Hr. The results are shown in Table 3.
[Table 3]

[EXAMPLE 11]
The same reaction was conducted under the conditions of Example 11,
except in that the reaction temperature was adjusted to 220°C. The results
are shown in Table 3.
[ EXAMPLE 12]
A pretreatment was conducted by the same procedure as that of Example
1. except in that 400cc of zirconia was used in place of 400cc of γ-alumina.
Then, the reaction was condjucted at 200°C by the same procedure as that of
Example 1 under conditions shown in Table 4. With this, the formation of
methyl difluoroacetate was found. The results are shown in Table 4.
[Table 4]


[EXAMPLE 13]
The same reaction was conducted under conditions of Example 12, except
in that the reaction temperature was adjusted to 220°C. The results are
shown in Table 4.
[EXAMPLES 14 & 15]
Experiments were conducted under the same reaction conditions as those
of Example 1, except in that, there was used as the catalyst 400cc of aluminum
phosphate tablets having a diameter of about 3mm and shaped from a powder
obtained by a method described in a publication (Applied Catalyst A: General
283(2005) 47-52), in place of γ-alumina. They were conducted at reaction
temperatures of 180°C and 200°C. The results are shown in Table 5.
[Table 5]

[EXAMPLES 16 & 17]
400cc of SHIRO SAGI G2C (4-8 mesh, a product of Takeda Chemical
Industries, Ltd.) was immersed under room temperature for one night in a 10
mass weight percent aluminum nitrate aqueous solution for impregnation.
Then, an equivalent of 85% phosphoric acid was added, and 10% aqueous
ammonia was added dropwise with stirring. The dropping was terminated at
a pH of 5. An aluminum phosphate-supported activated carbon was obtained
by separating the activated carbon from the solution, in which aluminum
phosphate was precipitated, with a resin-made net. Most of water was
removed from this by a drier of 120°C. Then, it was baked for 2 hours in a
baking furnace of nitrogen atmosphere set at 400°C, thereby preparing an

aluminum phosphate-supported activated carbon supporting aluminum
phosphate in 15 weight %.
Experiments were conducted under the same reaction conditions as those
of Example 1, except in that 400cc of this aluminum phosphate-supported
activated carbon was used in place of y-alumina. They were conducted at
reaction temperatures of 180°C and 200°C. The results are shown in Table 6.
[Table 6]

[EXAMPLES 18 & 19]
Experiments were conducted under the same reaction conditions as those
of Example 1, except in that 400cc of 7-9 mesh Nafion NR50 (a product of
DuPont Co.) was used in place of γ-alumina. They were conducted at reaction
temperatures of 160°C and 180°C. The results are shown in Table 7.
[Table 7]


[EXAMPLES 20 & 21]
A 2000ml glass beaker was charged with 700ml of distilled water and
302g of ammonium sulfate, followed by stirring at room temperature, thereby
obtaining a colorless transparent solution. To this, 1367.6g of zirconium
hydroxide was added with stirring, and stirring was further conducted for 1
hour. Then, the reaction mixture was subjected to evaporation to dryness by
a hot plate. The obtained cake was dried in the air at room temperature for
20 hours, thereby obtaining a white-color solid. The obtained white-color solid
was baked at 550°C for 3 hours in the air. This baked material was ground
and sieved to prepare a 48 mesh sulfated zirconia.
Except in that. 400cc of this sulfated zirconia was used in place of 400cc of
γ-alumina, experiments were conducted under the same reaction conditions as
those of Example 1. The results are shown in Table 8.
[Table 8]

[EXAMPLE 22]
800cc of an activated carbon (SHIRO SAGI G2C, 4-8 mesh) was immersed
in a glass beaker containing 400cc of 98% concentrated sulfuric acid, and it was
left for one night as it was. Then, it was taken out, and an excessive sulfuric
acid was drained. After that, it was put into a reaction tube used in Example
1. While nitrogen gas was allowed to flow, the temperature of the reaction
tube was increased to 200°C and maintained for 3 hours as it was. thereby
preparing a sulfuric acid-supported activated carbon.

The temperature of the reaction tube was adjusted to 180°C; and a
reaction was conducted under the same conditions as those of Example 1. The
results are shown in Table 9.
[Table 9]

INDUSTRIAL APPLICABILITY
The reaction of the present invention is a superior reaction that shows
extremely high reactivity arid selectivity and that, is also high in
reproducibility of the reaction results. Furthermore, the reaction is an
appropriate method as an industrial production method too, since it can be
conducted continuously and quantitatively. Furthermore, the reaction of the
present invention is a highly practical method, since it can be conducted under
safe conditions.

We Claim :-
1. A method for producing a fluorine-containing carboxylic acid ester
represented by the general formula R1HCFCOOR2, where R1 represents
either of a fluorine atom and a C1-4 perfluoroalkyl group, and R2 represents a
monovalent organic group, the method comprising reacting a
fluorine containing ether represented by the general formula R1HCFCF2OR2,
where R1 and R2 are defined as above, with water in the presence of a solid
catalyst.
2. The method according to claim 1, wherein the solid catalyst is at least
one selected from the group consisting of a metal oxide, an inorganic
acid -supported activated carbon, a metal compound-supported activated
carbon, a resin having acid sites, and aluminum phosphate.
3. The method according to claim 1, wherein the solid catalyst is at least
one selected from the group consisting of alumina, titania, zirconia, sulfated
zirconia, a sulfuric acid-supported activated carbon, a resin having acid sites,
and aluminum phosphate.
4. The method according to claim 1, wherein the solid catalyst is
alumina.
5. The method according to any one of claims 1-4, wherein the solid
catalyst is a metal oxide in which at least a part of oxygen bonded to a metal
oxide has been replaced with fluorine prior to the reaction or in the reaction.
6. The method according to any one of claims 1-5, which is conducted in
a gas phase.

7. The method according to any one of claims 1-6, wherein R1 is either of
a fluorine atom and a trifluoromethyl group.

It is to provide a production method that the target fluorine-containing
carboxylic acid ester can be obtained from a fluorine-containing ether by a
one-step reaction, that a complicated step and a troublesome operation are not
necessary, and that an excessive energy is not consumed.
A fluorine-containirig carboxylic acid ester represented by the general
formula R'HCFCOOR- is produced by reacting a fluorine-containing ether
represented by the general formula R'HCFCF-jOR2 (R1 represents either of a
fluorine atom and a Ci i perfluoroalkyl group, and R2 represents a monovalent
organic group) with water in the presence of a solid catalyst.