TECHNICAL FIELD
[0001] The present invention relates to a method for producing a
perfluoroalkanesulfinate, which is useful as an organic synthesis intermediate.
BACKGROUND OF THE INVENTION
[0002] Perfluoroalkanesulfinates are compounds that are useful, for example, as
intermediates of medicine and agricultural chemical raw materials. Patent
Publication 1 describes potassium trifluoromethanesulfmate as an intermediate of
sulfonyl compounds, which are said to be useful for diabetes, etc. Furthermore,
Patent Publication 2 discloses that a perfluoroalkanesulfinate is useful as a
perfluoroalkylation agent.
[0003] As a conventional method for producing perfluoroalkanesulfinic acid
derivatives, there is disclosed in Patent Publication 3 a method for producing a
fluoroalkanesulfinic acid by reacting a perfluoroalkanesulfonyl fluoride with
hydrazine into a hydrazium salt, and then reacting it with an acid.
[0004] Furthermore, Patent Publication 4 discloses a method for producing an
alkali metal salt of perfluoroalkanesulfinic acid by bringing a
perfluoroalkanesulfonyl fluoride into contact with an alkali metal sulfite in the
presence of water. Non-patent Publication 1 discloses a method for obtaining
potassium trifluoromethanesulfmate by reacting trifluoromethanesulfonic chloride
with potassium sulfite. Non-patent Publication 2 discloses a method of reacting
sodium carbonate or potassium carbonate with trifluoromethanesulfinic acid,
thereby obtaining a corresponding sulfinate.
[0005] Furthermore, Non-patent Publication 3 also discloses that a zinc salt of
tifluoromethanesulfinic acid is formed by reacting trifluoromethanesulfonyl
chloride with zinc powder.

[0006] Furthermore, Non-patent Publication 4 discloses a method for obtaining
potassium trifluoromethanesulfinate by reacting benzyl trifluoromethyl sulfone,
potassium carbonate, and ethyl 3-bromopropionate.
[0007] Furthermore, Patent Publication 5 discloses a method in which hydrazine
is reacted on a perfluoroalkanesulfonyl halide to obtain a perfluoroalkanesulfinic
acid hydrazine salt (RfSO2H- N2H4), followed by a conversion into a
perfluoroalkanesulfinate.
PRIOR ART PUBLICATIONS
PATENT PUBLICATIONS
[0008] Patent Publication 1: Japanese Patent Application Publication
2006-513266.
Patent Publication 2: Japanese Patent Application Publication Heisei 9-263548.
Patent Publication 3: Japanese Patent Application Publication Showa 48-56619.
Patent Publication 4: Japanese Patent Application Publication 2001-316353.
Patent Publication 5: International Publication 2010-013687.
NON-PATENT PUBLICATIONS
[0009] Non-patent Publication 1: R. M. Scribner, J. Org. Chem., 31, 3671
(1966).
Non-patent Publication 2: H. W. Roesky and G. Holtschneider, J. Fluorine.
Chemistry, 7, 77(1976).
Non-patent Publication 3: R. N. Haszeldine, J. M. Kidd, J. Chem. Soc, 2901-2910
(1955).
Non-patent Publication 4: B. R. Langlois et al, J. Fluorine. Chemistry, 851, 128
(2007).

SUMMARY OF THE INVENTION
[0010] The methods of Patent Publication 3 and Non-patent Publication 2 can be
named as preferable methods at a glance, since it is possible to obtain the sulfinic
acid and the sulfinic acid metal salt with high yields. It is, however, necessary to
purify the sulfinic acid by distillation. With this, the sulfinic acid may be
decomposed. Furthermore, in a post-treatment procedure, a hazardous substance,
hydrazine sulfate, is formed. Therefore, there were some difficulties in
producing them with safety and easiness in an industrial scale.
[0011] Furthermore, the method of Non-patent Publication 3 is considered to
have a danger of explosion in the production in an industrial scale due to the use of
metal zinc powder and to have a waste treatment cost due to discharge of
zinc-series wastes in large amounts. Therefore, it is difficult to say that the
method is a method that is industrially usable.
[0012] The method of Non-patent Publication 4 necessitates using an expensive
reagent when producing the raw material, benzyl trifluoromethyl sulfone, and is
not efficient due to going through a three-step reaction in order to obtain the target
product from the starting material. Therefore, it has had some difficulty in terms
of production cost.
[0013] It is a task of the present invention to provide a method for producing a
perfluoroalkane sulfinate in an industrial scale, which is superior in production
cost and easiness.
MEANS FOR SOLVING TASK
[0014] After repeating a further study to solve the task, the present inventors
have found, in a method for obtaining an alkali metal perfluoroalkanesulfinate by
reacting a perfluoroalkanesulfonyl halide with a sulfur-containing reducing agent

in water, that the target product, an alkali metal perfluoroalkanesulfinate, is
obtained with high purity and good operability by concentrating a reaction mixture
liquid containing the alkali metal sulfinate obtained following the reaction to have
a specified concentration, thereby precipitating an inorganic salt, which is an
impurity in the solution, then removing it, and then subjecting a filtrate prepared
by removing the inorganic salt to an operation such as concentration, drying, etc.
[0015] That is. the present invention provides a method for producing an alkali
metal perfluoroalkanesulfinate, which is described in the following [Invention 1]
to [Invention 5].
[0016] [Invention 1]
In a method that a perfluoroalkanesulfonyl halide represented by formula
[2]
R1SO2X [2]
(In the formula, Rf represents a C1-4, straight-chain or branched-chain
perfluoroalkyl group, and X represents a fluorine, chlorine, bromine or iodine
atom,) is reacted with a sulfur-containing reducing agent (Herein, the
sulfur-containing reducing agent refers to an alkali metal salt of sulfurous acid,
hydrogen sulfite, thiosulfuric acid, dithionous acid, pyrosulfurous acid, or sulfide.)
in the presence of water, thereby producing an alkali metal
perfluoroalkanesulfinate represented by formula [1]
R1SO2M [1]
(in the formula, Rf is defined as in formula [2], and M represents lithium, sodium,
potassium, rubidium, or cesium.), the method for producing the alkali metal
perfluoroalkanesulfinate represented by formula [1] being characterized by that a
reaction mixture liquid containing the alkali metal perfluoroalkanesulfinate, which

has been obtained following the reaction, is concentrated such that a weight ratio
of the alkali metal sulfinate to water becomes 1:2.5 to 1:0.1, and an inorganic salt
precipitated after the concentration is separated and removed.
[0017] [Invention 2]
The method according to Invention 1, wherein the
perfluoroalkanesulfonyl halide represented by formula [2] is a
perfluoroalkanesulfonyl chloride or perfluoroalkanesulfonyl fluoride.
[0018J [Invention 3]
The method according to Invention 1 or Invention 2, wherein the
sulfur-containing reducing agent is sodium sulfite, potassium sulfite, sodium
hydrogensulfite. potassium hydrogensulfite, sodium thiosulfate, potassium
thiosulfate, or sodium dithionite.
[0019] [Invention 4]
The method according to any of Invention 1 to Invention 3, which is
characterized by that, when the perfluoroalkanesulfonyl halide represented by
formula [2] is reacted with the sulfur-containing reducing agent, a basic compound
(herein, the basic compound is a hydroxide, oxide, carbonate or
hydrogencarbonate of an alkali metal, and there is used a basic compound having a
metal that is identical with that of the alkali metal perfluoroalkanesulfinate
represented by formula [1]) is added to the reaction mixture liquid containing the
alkali metal perfluoroalkanesulfinate, which has been obtained following the
reaction, then pH value of the reaction mixture liquid after the addition is adjusted
to 7-9. and then the concentration is conducted.

[0020] [Invention 5]
The method according to Invention 4, wherein the basic compound is a
hydroxide or carbonate of an alkali metal.
[0021] [Invention 6]
The method according to Invention 1 to Invention 5, which is
characterized by that water is added to the inorganic salt, which has been separated
and removed, to extract the alkali metal perfluoroalkanesulfinate contained in the
inorganic salt, and the obtained filtrate containing the alkali metal
perfluoroalkanesulfinate is added again to the solution prior to the concentration.
[0022] By reacting the perfluoroalkanesulfonyl halide with the sulfur-containing
reducing agent in the presence of water, inorganic salts, such as a salt derived from
the sulfur-containing reducing agent and a halogen salt, are formed simultaneously
with the formation of the target alkali metal perfluoroalkanesulfinate.
[0023] It is possible to satisfactorily obtain the target alkali metal sulfmate by
conventional methods, for example, Patent Publication 4 and Non-patent
Publication 1. However, in order to remove the inorganic salt from the alkali
metal sulfonate, it is necessary to remove water from the reaction mixture liquid
after the reaction, then extract the target product with an organic solvent, and
separate insoluble inorganic salts (In the specification, '"separation" refers to an
operation to separate solid and liquid, such as filtration or centrifugalion.).
[0024] Even when the inventors actually conduct a study, the reaction proceeds
satisfactorily. However, when removing water from the reaction mixture liquid
and then extracting and separating the alkali metal sulfmate with an organic
solvent, there has been found a tendency that inorganic salts, such as salt derived
from the alkali metal sulfite and halogen salt, are precipitated from the filtrate and

that the alkali metal sulfinate obtained following the purification is contaminated
with those inorganic salts (see the after-mentioned Comparative Example 1). In
this manner, since a part of the inorganic salts, which has been dissolved in the
organic solvent, is sometimes precipitated from the filtrate in the separation
operation, it has been impossible to efficiently obtain the alkali metal sulfinate
with high purity.
[0025] In particular, in a study assuming an industrial scale production,
inorganic salts have been precipitated from the filtrate during the separation, and
furthermore there has been a difficulty in separation of the inorganic salts.
Therefore, it has been found that there is a necessity to repeatedly conduct the
extraction and separation operations to take a lot of effort and that the amount of
the extraction solvent used is large to cause a problem in operability (see the
after-mentioned Scheme 1. the left drawing and Comparative Example 2).
[0026] Thus, when the present inventors conducted the separation operation after
precipitating inorganic salts by concentrating the concentration of the reaction
mixture liquid after the reaction to be within a specific range, we have found that
there is no salt precipitation from the filtrate after the separation and that
separation is also good. Furthermore, since the filtrate is a homogeneous
aqueous solution in the present invention, it is easy to check the composition by
ion chromatography, etc. In case that inorganic salts have been found in the
filtrate, it is possible to precipitate the inorganic salts by concentrating the solvent
again. Therefore, according to need, it is possible to obtain the alkali metal
perfluoroalkanesulfinate with high purity. Furthermore, there is no need in the
present invention to conduct an extraction by organic solvent. As compared with
prior art. it is possible to omit operations such as extraction and solvent distillation.

Therefore, it has been found to be a useful method that poses fewer burdens on the
environment and that can omit the disposal cost (see the right drawing of Scheme
1).
[00271

[0028] It has been never known that, from a mixed aqueous solution of an
organic acid salt and an inorganic salt, the inorganic salt is precipitated, and the
organic acid salt is taken out as an aqueous solution, by using operations of
concentration and separation as in the present invention.

DETAILED EXPLANATION
[0029] It is possible to efficiently produce an alkali metal
perfluoroalkanesulfinate with high purity, which is useful as an intermediate of
medicines, agricultural chemicals, and functional materials. Furthermore,
according to the present invention, an organic solvent for the extraction becomes
unnecessary, and it is possible to greatly reduce wastes.
[0030] In the following, the present invention is explained in detail. The
present invention is a method that a perfluoroalkanesulfonyl halide represented by
formula [2] is reacted with a sulfur-containing reducing agent in the presence of
water, thereby producing an alkali metal perfluoroalkanesulfinate represented by
formula [1]. the method for producing the alkali metal perfluoroalkanesulfinate
represented by formula [1] being characterized by that a reaction mixture liquid
containing the alkali metal perfluoroalkanesulfinate, which has been obtained
following the reaction, is concentrated such that a weight ratio of the metal salt to
water becomes 1:2.5 to 1:0.1. and an inorganic salt precipitated after the
concentration is separated and removed.
[0031] The perfluoroalkanesulfonyl halide used in the present invention is
represented by formula [2]. Rf is a C1-4, straight-chain or branched-chain
perfluoroalkyl group, and X is a fluorine, chlorine, bromine or iodine atom.
Specifically, it is possible to mention trifluoromethanesulfonyl fluoride,
trifluoromelhanesulfonyl chloride, trifluoromethanesulfonyl bromide,
trifluoromethanesulfonyl iodide, pentafluoroethanesulfonyl fluoride,
pentafluoroethanesulfonyl chloride, pentafluoroethanesulfonyl bromide,
pentafluoroethanesulfonyl iodide, heptafluoropropanesulfonyl fluoride,
heptafluoropropanesulfonyl chloride, heptafluoropropanesulfonyl bromide,

heptafluoropropanesulfonyl iodide, nonafluorobulanesulfonyl fluoride,
nonafluorobutanesulfonyl chloride, nonafluorobutanesulfonyl bromide,
nonafluorobutanesulfonyl iodide, heptafluoropropane-2-sulfony! fluoride,
heptafluoropropane-2-sulfonyl chloride, heptafluoropropane-2-sulfonyl bromide,
heptafluoropropane-2-sulfonyl iodide, nonafluorobutane-2-sulfonyl fluoride,
nonafluorobutane-2-sulfonyl chloride, nonafluorobutane-2-sulfonyl bromide,
nonafluorobutane-2-sulfonyl iodide,
hexafluoro-2-trifluoromethyl-propane-1-sulfonyl fluoride.
hexafluoro-2-trifluoromethyl-propane-1-sulfonyl chloride,
hexafluoro-2-trifluoromethyl-propane-1-sulfonyl bromide,
hexafluoro-2-trifluoromethyl-propane-1-sulfonyl iodide,
hexafluoro-2-trifluoromethyl-propane-2-sulfonyl fluoride,
hexafluoro-2-trifluoromethyl-propane-2-sulfonyl chloride,
hexafluoro-2-trifluoromethyl-propane-2-sulfonyl bromide,
hexaf1uoro-2-trifluoromethyl-propane-2-sulfonyl iodide, etc. Preferably, they are
trifluoromethanesulfonyl fluoride, trifluoromethanesulfonyl chloride,
pentafluoroethanesulfonyl fluoride, pentafluoroethanesulfonyl chloride,
heptafluoropropanesulfonyl fluoride, heptafluoropropanesulfonyl chloride,
nonafluorobutanesulfonyl fluoride, and nonafluorobutanesulfonyl chloride.
Particularly preferably, they are trifluoromethanesulfonyl fluoride and
trifluoromethanesulfonyl chloride.
[0032] The sulfur-containing reducing agent of the present invention refers to an
alkali metal salt of sulfurous acid, hydrogen sulfite, thiosulfuric acid, dithionous
acid, pyrosulfurous acid, or sulfide. Specifically, it is possible to mention lithium
sulfite, sodium sulfite, potassium sulfite, rubidium sulfite, cesium sulfite, lithium

hydrogensulfite, sodium hydrogensulfile. potassium hydrogensulfite, rubidium
hydrogensulfite, cesium hydrogensulfile, lithium thiosulfate, sodium thiosulfate,
potassium thiosulfate. rubidium thiosulfate, cesium thiosulfate, lithium dithionite,
sodium dithionite, potassium dithionite, rubidium dithionite, cesium dithionite,
lithium pyrosulfite. sodium pyrosulfite, potassium pyrosulfite. rubidium
pyrosulfite. cesium pyrosulflte, lithium sulfide, sodium sulfide, potassium sulfide,
rubidium sulfide, cesium sulfide, etc. Above all, sodium sulfite, potassium
sulfite, sodium hydrogensulfite, potassium hydrogensulfite, sodium thiosulfate,
potassium thiosulfate, and sodium dithionite are particularly preferable.
[0033] The usage of the sulfur-containing reducing agent is preferably 1-10 mols,
more preferably 1-4 mols, relative to 1 mol of the perfluoroalkanesulfonyl halide.
[0034] Normally, the amount of water in the present reaction is preferably 3g to
100g, more preferably 3 to 30 g, relative to lg of the perfluoroalkanesulfonyl
halide used. In case that the amount of water is less than 3g, the slurry
concentration of the reaction liquid is high. Therefore, it is not preferable in
terms of operability.
[0035] The reaction temperature condition is not particularly limited. It
suffices to conduct that in a range of-10°C to 100°C. Normally. -10°C to 60°C
is preferable. In particular, 0°C to 40°C is more preferable. If the reaction
temperature is higher than 100°C, the perfluoroalkanesulfonyl halide is hydrolyzed
into an alkali metal perfluoroalkanesulfonate. At a temperature lower than
-10°C, the reaction becomes slow. Therefore, it is not preferable.
[0036] The perfluoroalkanesulfonyl halide used in the present invention exists,
depending on its kind, as liquid or gas under ordinary temperature and ordinary
pressure. The condition of the halide upon the feeding is not particularly limited,

either gas condition or liquid condition. A person skilled in the art can suitably
select the condition of the halide upon the feeding.
[0037] The feeding method upon reacting the perfluoroalkanesulfonyl halide
with the sulfur-containing reducing agent is not particularly limited. Normally, it
can be conducted by adding the perfluoroalkanesulfonyl halide after feeding the
sulfur-containing reducing agent into the reactor. For example, as shown in the
after-mentioned Examples, in the case of using trifluoromethanesulfonyl fluoride
as the perfluoroalkanesulfonyl halide. it is one of particularly preferable modes to
previously feed the sulfur-containing reducing agent into the reaction vessel and
then add the fluoride at one time, one after another, or continuously, while
conducting stirring or pump circulation.
[0038] As to a reactor used upon conducting the reaction under pressurized
condition, it can be conducted by using a metal container, such as stainless steel,
Hastelloy. Monel, etc. Furthermore, in the case of conducting the reaction under
ordinary pressure, a person skilled in the art can make a suitable selection in terms
of reactor, too.
[0039] The pressure during the reaction is normally -0.1 to 10 MPa, preferably
-0.1 to 5 MPa, more preferably -0.1 to 2 MPa, in terms of gauge pressure of a
pressure gauge attached to the reactor.
[0040] The reactor used in the present step is not particularly limited in material,
as long as it is pressure-proof upon conducting the reaction under ordinary
pressure or increased pressure. it is possible to use a reactor lined with
tetrafluoroethylene resin, chlorotrifluoroelhylene resin, vinylidene fluoride resin,
PFA resin, polypropylene resin, polyethylene resin, glass or the like, or a glass
container.

[0041] In case that the perfluoroalkanesulfonyl halide exists as gas, it is
preferable to conduct that by maintaining the reactor at a low temperature or by
using a low-temperature condenser in order that it may not be discharged from the
reaction region when introducing it into the reaction system. Furthermore, upon
using a normal reactor, it is effective to suitably use a method by a common means
for increasing the contact efficiency, such as gas introducing rate adjustment, a
stirring device, a gas blowing device, a sparger (a porous sparging tube), etc.
Furthermore, it is one of preferable modes to use a scrubber-type reactor using a
pump circulation device in order to improve the contact efficiency.
[0042J The reaction time is not particularly limited. Normally, it can be
conducted in a range of 24 hours or shorter. It is preferable to follow the
condition of progress of the reaction by an analysis means, such as ion
chromatography, NMR, etc., and judge the time when the raw material substrate
has almost disappeared as being the end point.
[0043] In the present invention, water is used as solvent. It is possible to use an
organic solvent together with water, but it is not particularly preferable since an
organic waste liquid is discharged and its disposal requires effort. Normally, it is
preferable to conduct the reaction with only water.
[0044] Depending on the reagents and conditions used in the reaction, salt may
be precipitated upon completion of the reaction. In that case, it is preferable to
conduct the next operation after removing the precipitated salt by a normal
separation operation.
[0045] In the present invention, when the perfluoroalkanesulfonyl halide is
reacted with the sulfur-containing reducing agent, the pH value lowers along with
the progress of the reaction. By leaving it as it is, the concentration can be

conducted, too. It is,however, a preferable method to add a basic compound to
the reaction mixture liquid to adjust the pH value and then conduct the
concentration operation. As a method of adding the basic compound, it is
possible to select either 1) a method of adding after termination of the reaction or
2) a method of adding one after another along with progress of the reaction. In
the case of 1), it suffices to adjust the pH value to 7-9 by adding the basic
compound in a suitable amount, depending on the pH value after termination of
the reaction. In the case of 2), it suffices to conduct an adjustment, in order that
the pH value after termination of the reaction may become 7-9. by adding the basic
compound while checking the pH value during the reaction. In the case of the
method of 2). it is a particularly preferable method, since it is possible to reduce
the amount of the sulfur-containing reducing agent, which is necessary for the
reaction (see Example 2 and Table 5: It is understood that the sulfur-containing
reducing agent used relative to the alkali metal sulfinate obtained in Example 2 has
lowered to half of Example 1. However, since the rate of the lowering is not
limited to this, but changes depending on the reagents used, it is preferable to
examine the condition when it is necessary).
[0046] The basic compound of the present invention is a hydroxide, oxide,
carbonate or hydrogencarbonate of an alkali metal. Specifically, it is possible to
mention lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium
hydroxide, cesium hydroxide, lithium oxide, sodium oxide, potassium oxide.
rubidium oxide, cesium oxide (these alkali metal oxides are hydroxides in the
presence of water), lithium carbonate, sodium carbonate, potassium carbonate,
rubidium carbonate, cesium carbonate, lithium hydrogencarbonate, sodium
hydrogencarbonate, potassium hydrogencarbonate. rubidium hydrogencarbonate,

cesium hydrogencarbonate, etc.. and there is used a metal that is identical with that
of the sulfur-containing reducing agent. For example, in the case of using
potassium sulfite as the sulfur-containing reducing agent, it is necessary to provide
a compound having potassium as a counter cation of the basic compound.
Specifically, potassium hydroxide, potassium oxide, potassium carbonate, etc. are
preferable, and potassium hydroxide and potassium carbonate are particularly
preferable.
[0047] By conducting the pH adjustment with the basic compound, a salt may be
precipitated depending on the reagent. In that case, it is preferable to conduct the
next operation after removing the precipitated salt by a normal separation
operation.
[0048] Then, a post-treatment after the reaction, which is a characteristic of the
present invention, is explained in detail.
[0049] It suffices to conduct the concentration of the reaction liquid by a normal
distillation operation, such as distillation under reduced pressure. It suffices to
conduct the concentration such that the weight of water becomes 0.1 to 2.5 parts,
preferably 0.1 to 1.5 parts, particularly preferably 0.1 to 1.0 part, provided that the
weight of the alkali metal perfluoroalkanesulfinate in the solution is 1 part. In
case that the proportion of water is higher than 2.5, the precipitation of inorganic
salts, particularly halides. in the reaction liquid is insufficient. In contrast, if the
proportion of water is smaller than 0.1, the target alkali metal
perfluoroalkanesulfinate is also precipitated together with inorganic salts to lower
yield. Therefore, it is not preferable (see Comparative Example 2). The
concentration of water may be conducted several times in parts until the target

weight ratio. It is preferable to separate and remove the precipitated inorganic
salts each time in terms of operabilily.
[0050] Normally, a solid is precipitated from the reaction liquid after the
concentration by concentrating water, irrespective of temperature. The
temperature and the time necessary for the precipitation are different depending on
the types of inorganic salts contained in the reaction liquid and on the degree of
the concentration. Therefore, it is preferable to suitably change the conditions.
[0051] It suffices to conduct a normal separation operation on the precipitated
inorganic salts. The operation temperature at that time is normally around -10 to
100°C. preferably -10 to 70°C, particularly preferably 0 to 50°C.
[0052] The salt separated and removed may contain the target alkali metal
perfluoroalkanesulfinate. In that case, it is possible to extract the target alkali
metal suliinate by adding water to this inorganic salt and then stirring for about 1
hour. It is possible to recover the target alkali metal sulfinate by adding the
filtrate obtained by the extraction to the mixed liquid prior to the repetitive
concentration or to the mixed liquid, prior to the concentration, of another batch
reaction, thereby improving the productivity and making waste reduction possible.
Therefore, it is one of preferable modes (see Scheme 2).

[0053]
[Scheme 2]

[0054] By conducting the measurement, such as ion chromatography, on the
filtrate obtained by the separation, its composition can be checked. In case that
unnecessary inorganic salts remain, it is possible to remove the inorganic salts by
conducting again the concentration in the same range as above. By subjecting
the filtrate, from which inorganic salts have sufficiently been removed, to the
water removal and drying by a normal operation, such as distillation under reduced
pressure, it is possible to obtain the target alkali metal perfluoroalkanesulfinate
with a high purity. Alternatively, water may be removed by adding an organic
solvent, such as toluene, to the filtrate and then an azeotropic water removal. The
conditions upon the water removal and the drying are not particularly limited. It

may be conducted at an operation temperature normally in a range of 20 to 120°C,
preferably 20 to 100°C, particularly preferably 40 to 80°C.
[0055J Furthermore, it is also possible to extract the alkali metal
perfluoroalkanesulfinate by adding an organic solvent, such as acetone,
acetonitrile. ethyl acetate, methanol, ethanol. etc.. to the solid after the drying. It
is. however, not particularly preferable, since it takes a lot of trouble with dumping
by using an organic solvent.
[0056] [Examples]
In the following, the present invention is explained in detail by examples.
The present invention is not limited to these examples. Herein, "%" of the
composition analysis value represents "wt%" of a composition obtained by
directly measuring the reaction liquid with ion chromatography.
Example 1
[0057] [A reaction using trifluoromethanesulfonyl chloride and potassium sulfite
(concentration until the alkali metal sulfinate : water = 1 : 0.37 by weight ratio)]
A 500ml, four-necked flask was charged with 250g of water and 150g
(0.945mol) of potassium sulfite, followed by cooling the solution. When it
became 5°C or lower, 53.Og (0.315mol) of trifluoromethanesulfonyl chloride was
slowly added by using a dropping funnel, while maintaining an inside temperature
of 5 to 10°C. After the dropping of the trifluoromethanesulfonyl chloride
terminated, it was continued to stir the reaction liquid as it was. 32 hours later,
the reaction liquid was filtered under 0°C to remove inorganic salts undissolved.
Then, pH of the reaction liquid was checked, and pH was adjusted to about 9 by
adding 47g of 48% KOH aqueous solution. At this time an inorganic salt, such
as potassium sulfate, was precipitated, and therefore this was removed by filtration

under 0°C. Water was distilled out of the obtained filtrate under reduced
pressure to remove 194g of water. This solution was cooled down until 0°C to
precipitate solid. The solid was removed by filtration. Water was distilled out
of the obtained filtrate under reduced pressure to remove 40g of water. This
solution was cooled down until 0°C to precipitate solid. The solid was removed
by filtration. In 56g of the obtained filtrate, 40g of potassium
trifluoromethanesulfinate and 15g of water were contained, and the ratio was 1 :
0.37. The obtained filtrate was concentrated and dried under reduced pressure.
thereby obtaining 41.8g of potassium trifluoromethanesulfinate (yield: 77%) with
a purity of 96.7% (the analysis result of ion chromatography) (the composition is
shown in Table 1). Of waste materials generated at this time, solid matter
(inorganic salts and organic acid salts) weighed 201 g, and waste water weighed
249.1 g. There was no organic waste liquid.
[0058] [Recovery process]
As a result of analyzing 201g of the solid waste material generated by
ion chromatography, potassium trifluoromethanesulfinate was contained by 4.1g
in this inorganic salt. 200g of water was added to this, followed by stirring for 1
hour and then filtration. With this, the obtained filtrate contained 3.5g of
potassium trifluoromethanesulfinate. Therefore, it was possible to recover 86%
of potassium trifluoromethanesulfinate from the inorganic salt.
[0059] [Table 1]

Example 2

[0060] [A reaction using trifluoromethanesulfonyl chloride and potassium sulfite
while conducting pH adjustment as occasion arises (concentration until the alkali
metal sulfinate : water = 1 : 0.42 by weight ratio)]
A 300ml, four-necked flask was charged with 100g of water and 71.2g
(0.450mol) of potassium sulfite, followed by cooling the solution. When it
became 5°C or lower, 50.6g (0.300mol) of trifluoromethanesulfonyl chloride was
slowly added by using a dropping funnel, while maintaining an inside temperature
of 5 to 10°C. At this time, pH of the reaction solution was timely checked.
When pH was acidic, the pH value was adjusted to about 7 by adding 48% KOH
aqueous solution (the total amount of 48% KOH aqueous solution added: 62.9g).
After the dropping of the trifluoromethanesulfonyl chloride terminated, it was
continued to stir the reaction liquid as it was. 12 hours later, an inorganic salt,
such as potassium sulfate, was precipitated by cooling the reaction liquid till 0°C.
Therefore, this was removed by filtration. Water was distilled out of the obtained
filtrate under reduced pressure to remove 98.6g of water. This solution was
cooled down until 0°C to precipitate solid. The solid was removed by filtration.
Water was again distilled out of the obtained filtrate under reduced pressure to
remove 12.8g of water. This solution was cooled down until 0°C to precipitate
solid. The solid was removed by fdtration. In 57g of the obtained filtrate. 39g
of potassium trifluoromethanesulfinate and 16.4g of water were contained, and the
ratio was 1:0.42. The obtained filtrate was concentrated and dried under reduced
pressure, thereby obtaining 40.6g of potassium trifluoromethanesulfinate (yield:
78.6%) with a purity of 96.1% (the analysis result of ion chromatography) (the
composition is shown in Table 2). Of waste materials generated at this time.

solid matter weighed 102g, and waste water weighed 122g. There was no
organic waste liquid.
[0061] [Recovery process]
As a result of analyzing 102g of the solid waste material generated by
ion chromatography, potassium trifluoromethanesulfinate was contained by 3.0g
in this inorganic salt. 100g of water was added to this, followed by stirring for 1
hour and then filtration. With this, the obtained filtrate contained 2.7g of
potassium trifluoromethanesulfinate. Therefore, it was possible to recover 90%
of potassium trifluoromethanesulfinate from the inorganic salt.
[0062] [Table 2]
Example 2

[0063] [Comparative Example 1]
[A reaction using trifluoromethanesulfonyl chloride and potassium sulfite (water is
removed from the reaction liquid, followed by extraction with methanol and then
separation and drying)]
A 500ml. four-necked flask was charged with 250g of water and 150g
(0.945mol) of potassium sulfite, followed by cooling the solution. When it
became 5°C or lower. 53.0g (0.315mol) of trifluoromethanesulfonyl chloride was
slowly added by using a dropping funnel, while maintaining an inside temperature
of 5 to 10°C. When the dropping of the trifluoromethanesulfonyl chloride
terminated, it was continued to stir the reaction liquid as it was. 12 hours later.
the reaction liquid was cooled till 0°C. followed by filtration to remove

undissolved inorganic salts. Then, pH of the reaction liquid was checked, and pH
was adjusted to about 9 by adding 42g of 48% KOH aqueous solution. Water
was removed from the obtained solution under reduced pressure. To the obtained
solid matter, 140g of methanol was added to extract potassium
trifluoromethanesulfmate, and inorganic salts undissolved in the solvent were
removed by filtration. Although inorganic salts were precipitated from the
obtained filtrate, separation was difficult. Therefore, the filtrate was concentrated
and dried as it was under reduced pressure, thereby obtaining 40.5g of potassium
trifluoromethanesulfmate (yield: 75%) with a purity of 95.6% (the analysis result
of ion chromatography) (composition is shown in Table 3). Of waste materials
generated at this time, solid matter weighed 186g, waste water weighed 260.3g,
and organic waste liquid weighed 135g.
[0064J [Table 3]
Comparative Example 1

[0065] [Comparative Example 2]
j A large-scale reaction using trifluoromethanesulfonyl chloride and potassium
sulfite (water is removed from the reaction liquid, followed by extraction with
methanol and then separation and drying)]
A 1000L SUS reactor was charged with 450kg of water and 288kg
(1.82kmol) of potassium sulfite, followed by cooling the solution. When the
inside temperature became 5°C or lower, 100kg (0.593kmol) of
trifluoromethanesulfonyl chloride was slowly added to maintain an inside

temperature of 5 to 10°C. When the dropping of the trifluoromethanesulfonyl
chloride terminated, it was continued to stir the reaction liquid as it was. 12
hours later, the reaction liquid was cooled till 3°C to remove undissolved inorganic
salts by filtration. Then, pH of the reaction liquid was checked, and pH was
adjusted to about 9 by adding 100kg of 40% KOH aqueous solution. From the
obtained solution, 500kg of water was removed under reduced pressure. Then,
500kg of toluene was added, and the solution was distilled again under reduced
pressure to remove 35kg of water. After the concentration, solid matter
precipitated in the solution was taken by a centrifugal separator. To the obtained
solid matter, 198kg of methanol was added to extract potassium
trifluoromethanesulfinate, and inorganic salts undissolved in solvent were
removed by filtration. In the inorganic salts, however, potassium
trifluoromethanesulfinate still existed. Therefore, an extraction operation was
further conducted two times with 132kg of methanol. However, when the
obtained solution was allowed to stand still, an inorganic salt was precipitated. It
was difficult to separate this inorganic salt by a filtration operation. Therefore,
only the supernatant of the methanol solution was taken, and solid matter was
removed. The obtained supernatant was concentrated. Finally. 106kg of
toluene was added, followed by azeotropic dehydration drying to obtain 62.3kg
(yield 64%) of potassium trifluoromethanesulfinate with a purity of 95% (the
analysis result of ion chromatography) (composition is shown in Table 4). Of
waste materials generated at this time, solid matter weighed 369kg, waste water
weighed 535kg. organic waste liquid necessary for the extraction weighed 485kg,
and the total of the waste organic liquid weighed 1012kg.

[0066] [Table 4]
Comparative Example 2
Component CF3S02K. Inorganic salts in total
Content (wt%) 95.1 4.50
[0067] Thus, there becomes necessary an organic waste liquid treatment when
water is removed from the reaction liquid, followed by conducting an extraction
and separation operation with an organic solvent. In a large-scale as in
Comparative Example 2, there is discharged an organic waste liquid derived from
the extraction, which is 7.8 times the target potassium trifluoromethanesulfinate.
Therefore, the disposal cost increases. As compared with those, in the present
invention, an organic solvent for the extraction is unnecessary. Therefore, it is
considered to be advantageous in terms of cost. Furthermore, when pH value
after the termination of the reaction is adjusted to 7-9 by conducting a pH
adjustment at a suitable timing while checking pH value during the reaction like
Example 2. the reduction of waste water and waste inorganic salts becomes
possible along with the reduction of potassium sulfite to be used (see Table 5).


Example 3
[0069] [A reaction using trifluoromethanesulfonyl fluoride and potassium sulfite
(concentration until the alkali metal sulfinate : water = 1 : 0.39 by weight ratio)]
A 500mL, autoclave reactor was charged with 250g of water and 150g
(0.945mol) of potassium sulfite, followed by cooling the solution. When it
became 5°C or lower, the inside of the reactor was deaerated. After the
deaeration. 48.Og (0.316mol) of trifluoromethanesulfonyl fluoride gasified was
slowly introduced, while maintaining an inside temperature of 5 to 10°C. After
the introduction of the trifluoromethanesulfonyl fluoride terminated, stirring was
continued for 13 hours as it was. 13 hours later, the inside of the reactor was
replaced with nitrogen, followed by taking the reaction liquid out. The reaction
liquid was cooled till 0°C, and the precipitated inorganic salts such as potassium
sulfate were removed by filtration. After checking pH of the reaction liquid, 52g
of 48% KOH aqueous solution was added such that pH became about 9. Since
an inorganic salt was then precipitated, this was removed by filtration under 0°.
Water was distilled out of the obtained filtrate under reduced pressure to remove
177g of water. This solution was cooled down until 0°C to precipitate solid.
The solid was removed by filtration. Water was distilled out of the obtained
filtrate under reduced pressure to remove 36g of water. This solution was cooled
down until 0°C to precipitate solid. The solid was removed by filtration. In 59g
of the obtained filtrate. 41.5g of potassium trifluoromethanesulfinate and 16.6g of
water were contained, and the ratio was 1 : 0.39. The obtained filtrate was
concentrated and dried under reduced pressure, thereby obtaining 42.8g of
potassium trifluoromethanesulfinate (yield: 79%) with a purity of 96.9% (the
analysis result of ion chromatography) (composition is shown in Table 6). Of

waste materials generated al this time, solid matter weighed 201.4g, and waste
water weighed 229.4g. There was no organic waste liquid.
[0070] [Table 6]
Example 3

Example 4
[00711 [A reaction using trifluoromethanesulfonyl chloride and sodium
thiosulfatc (concentration until the alkali metal sulfinate : water = 1 : 0.43 by
weight ratio)]
A 500ml, four-necked flask was charged with 250g of water and 149.4g
(0.945mol) of sodium thiosulfate, followed by cooling the solution. When it
became 5°C or lower, 53g (0.315mol) of trifluoromethanesulfonyl chloride was
slowly added by using a dropping funnel, while maintaining an inside temperature
of 5 to 10°C. After the dropping of the trifluoromethanesulfonyl chloride
terminated, it was continued to stir the reaction liquid as it was. 15 hours later,
the reaction liquid was filtered under 0°C to remove inorganic salts undissolved.
Then, pH of the reaction liquid was checked, and 73.7g of 30% NaOH aqueous
solution was added such that pH became about 9. At this time an inorganic salt
was precipitated, and therefore this was removed by cooling till 0°C and filtration.
The obtained filtrate was distilled under reduced pressure to remove I65g of water.
This solution was cooled down until 0°C to precipitate solid. The solid was
removed by filtration. The obtained filtrate was distilled under reduced pressure
to remove 30g of water. This solution was cooled down until 0°C to precipitate

solid. The solid was removed by filtration. In 54g of the obtained filtrate, 36.8g
of sodium trifluoromethanesulfinate and 16g of water were contained, and the
ratio was 1 : 0.43. The obtained filtrate was concentrated and dried under
reduced pressure, thereby obtaining 38.3g of sodium trifluoromethanesulfmate
(yield: 78%) with a purity of 96.5% (the analysis result of ion chromatography)
(composition is shown in Table 7). Of waste materials generated at this time,
solid matter weighed 158g, and waste water weighed 21 Ig. There was no
organic waste liquid.
[0072] [Table 7]
Example 4

Example 5
[0073J [A reaction using trifluoromethanesulfonyl chloride and sodium sulfite
(concentration until the alkali metal sulfinate : water = 1 : 0.2 by weight ratio)]
A 500ml, four-necked flask was charged with 250g of water and 119g
(0.945mol) of sodium sulfite, followed by cooling the solution. When it became
5°C or lower. 53.Og (0.315mol) of trifluoromethanesulfonyl chloride was slowly
added by using a dropping funnel, while maintaining an inside temperature of 5 to
10°C. After the dropping of the trifluoromethanesulfonyl chloride terminated, it
was continued to stir the reaction liquid as it was. 12 hours later, the reaction
liquid was filtered to remove inorganic salts undissolved. Then, pH of the
reaction liquid was checked, and 73.7g of 30% NaOH aqueous solution was added
such that pH became about 9. An inorganic salt was precipitated, and therefore

this was removed by filtration. Water was distilled out of the obtained filtrate
under reduced pressure to remove 179g of water. This solution was cooled down
until 0°C to precipitate solid. The solid was removed by filtration. Water was
distilled out of the obtained filtrate under reduced pressure to remove 40g of water.
This solution was cooled down until 0°C to precipitate solid. The solid was
removed by filtration. In 37g of the obtained filtrate, 32g of sodium
trifluoromethanesulfinate and 5.2g of water were contained, and the ratio was 1 :
0.2. The obtained filtrate was concentrated and dried under reduced pressure,
thereby obtaining 32.3g of sodium trifluoromethanesulfinate (yield: 65.1%) with a
purity of 99.1% (the analysis result of ion chromatography) (composition is shown
in Table 8).
Example 6
[0074] | A reaction using trifluoromethanesulfonyl chloride and sodium sulfite
(concentration until the alkali metal sulfinate : water = 1 : 0.9 by weight ratio)]
Using 250g of water, 150g of sodium sulfite and 53g of
trifluoromethanesulfonyl chloride, the reaction and the pH adjustment were
conducted by the same operation as that of Example 1, following by concentration
until the weight ratio of the alkali metal sulfinate to water became 1 : 0.9. In the
same manner as that of Example 1, filtration and drying were conducted, thereby
obtaining 39.3g of sodium trifluoromethanesulfinate (yield: 71.5%) with a purity
of 89.5% (composition is shown in Table 8).
Example 7
[0075] [A reaction using trifluoromethanesulfonyl chloride and sodium sulfite
(concentration until the alkali metal sulfinate : water = 1 : 1.2 by weight ratio)]

Using 250g of water, 150g of sodium sulfite and 53g of
trifluoromethanesulfonyl chloride, the reaction and the pH adjustment were
conducted by the same operation as that of Example 1, following by concentration
until the weight ratio of the alkali metal sulfinate to water became 1 : 1.2. In the
same manner as that of Example 1, filtration and drying were conducted, thereby
obtaining 44.6g of sodium trifluoromethanesulfinate (yield: 76.8%) with a purity
of 84.6% (composition is shown in Table 8).
[0076J [Comparative Example 3]
[A reaction using trifluoromethanesulfonyl chloride and sodium sulfite
(concentration until the alkali metal sulfinate : water = 1 : 3.0 by weight ratio)]
Using 250g of water, 150g of sodium sulfite and 53g of
trifluoromethanesulfonyl chloride, the reaction and the pH adjustment were
conducted by the same operation as that of Example 1, following by concentration
until the weight ratio of the alkali metal sulfinate to water became 1 : 3.0. In the
same manner as that of Example 1, filtration and drying were conducted, thereby
obtaining 67.8g of sodium trifluoromethanesulfinate (yield: 83.6%) with a purity
of 60.6% (composition is shown in Table 8).
[0077] Thus, in case that the degree of concentration is insufficient and thereby
the weight ratio of the alkali metal sulfinate : water is lower than the range of the
present invention, the removal of inorganic salts (mainly halogen salts) is
insufficient and thereby purity of the target alkali metal trifluoromethanesulfinate
becomes low. (see Table 8)

WE CLAIM:
1. In a method that a perfluoroalkanesulfonyl halide represented by formula
[2]
RfSO2X [2]
wherein Rf represents a C1-4, straight-chain or branched-chain perfluoroalkyl
group, and X represents a fluorine, chlorine, bromine or iodine atom, is reacted
with a sulfur-containing reducing agent that is an alkali metal salt of sulfurous acid,
hydrogen sulfite, thiosulfuric acid, dithionous acid, pyrosulfurous acid, or sulfide,
in the presence of water, thereby producing an alkali metal
perfluoroalkanesulfinate represented by formula [1]
RfSO2M [1]
wherein Rf is defined as in formula [2], and M represents lithium, sodium,
potassium, rubidium, or cesium, the method for producing the alkali metal
perfluoroalkanesulfinate represented by formula [1] being characterized by that a
reaction mixture liquid containing the alkali metal perfluoroalkanesulfinate, which
has been obtained following the reaction, is concentrated such that a weight ratio
of the alkali metal perfluoroalkanesulfinate to water becomes 1:2.5 to 1:0.1, and an
inorganic salt precipitated after the concentration is separated and removed.
2. The method as claimed in claim 1, wherein the perfluoroalkanesulfonyl
halide represented by formula [2] is a perfluoroalkanesulfonyl chloride or
perfluoroalkanesulfonyl fluoride.
3. The method according to claim 1 or claim 2, wherein the
sulfur-containing reducing agent is sodium sulfite, potassium sulfite, sodium
hvdrogensulfile, potassium hydrogensulfite. sodium thiosulfale, potassium
thiosulfate. or sodium dithionite.
4. The method as claimed in any of claim 1 to claim 3, which is
characterized by that, when the perfluoroalkanesulfonyl halide represented by

formula [2] is reacted with the sulfur-containing reducing agent, a basic compound
that is a hydroxide, oxide, carbonate or hydro gencarbonate of an alkali metal, and
contains a metal that is identical with that of the alkali metal
perfluoroalkanesulfinate represented by formula [1] is added to the reaction
mixture liquid containing the alkali metal perfluoroalkanesulfinate, which has
been obtained following the reaction, then pH value of the reaction mixture liquid
after the addition is adjusted to 7-9. and then the concentration is conducted.
5. The method as claimed in claim 4, wherein the basic compound is a
hydroxide or carbonate of an alkali metal.
6. The method as claimed in any of claim 1 to claim 5, which is
characterized by that water is added to the inorganic salt, which has been separated
and removed, to extract the alkali metal perfluoroalkanesulfinate contained in the
inorganic salt, and the obtained filtrate containing the alkali metal
perlluoroalkanesulfinate is added again to the solution prior to the concentration.