U.S. patent application number 12/819457 was filed with the patent office on 2010-10-07 for method for producing purified ammonium salt of fluorinated bis-sulfonylimide.
This patent application is currently assigned to ASAHI GLASS COMPANY, LIMITED. Invention is credited to Masao IWAYA.
Application Number | 20100256384 12/819457 |
Document ID | / |
Family ID | 40378151 |
Filed Date | 2010-10-07 |
United States Patent
Application |
20100256384 |
Kind Code |
A1 |
IWAYA; Masao |
October 7, 2010 |
METHOD FOR PRODUCING PURIFIED AMMONIUM SALT OF FLUORINATED
BIS-SULFONYLIMIDE
Abstract
Methods for preparing an ammonium salt and a lithium salt of a
fluorinated bis-sulfonylimide by a practical and efficient method
with a high yield with a small number of steps. Further, a high
purity ammonium salt of a fluorinated bis-sulfonylimide useful for
the method for producing a lithium salt is provided. A method for
producing a purified particulate solid (II) of a salt represented
by the formula (1), which comprises suspending a particulate solid
(I) of a salt represented by the formula (1) in a solvent
comprising an etheric oxygen atom-containing compound, and
separating the solvent by filtration:
[HNR.sub.3].sup.+[Q.sup.1-SO.sub.2--N--SO.sub.2-Q.sup.2].sup.- (1)
wherein each of R' s which may be the same or different, is a
hydrogen atom or a C.sub.1-10 alkyl group, and each of Q.sup.1 and
Q.sup.2 which are independent of each other, is a monovalent
fluoroorganic group, or Q.sup.1 and Q.sup.2 together form a
bivalent fluoroorganic group.
Inventors: |
IWAYA; Masao; (Tokyo,
JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
ASAHI GLASS COMPANY,
LIMITED
Tokyo
JP
|
Family ID: |
40378151 |
Appl. No.: |
12/819457 |
Filed: |
June 21, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12699912 |
Feb 4, 2010 |
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12819457 |
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PCT/JP08/64653 |
Aug 15, 2008 |
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12699912 |
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Current U.S.
Class: |
548/123 |
Current CPC
Class: |
C07D 285/01
20130101 |
Class at
Publication: |
548/123 |
International
Class: |
C07D 285/01 20060101
C07D285/01 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 17, 2007 |
JP |
2007-212920 |
Claims
1. An ammonium salt represented by the following formula (1), which
has a purity as measured by NMR of 99 mol % or higher:
[HNR.sub.3].sup.+[Q.sup.1-SO.sub.2--N--SO.sub.2-Q.sup.2].sup.- (1)
wherein R's which may be the same or different, is a hydrogen atom
or a C.sub.1-10 alkyl group, and each of Q.sup.1 and Q.sup.2, which
may be the same or different, is a monovalent fluoroorganic group,
or Q.sup.1 and Q.sup.2 together form a bivalent fluoroorganic
group.
2. The ammonium salt according to claim 1, wherein R is a methyl
group, an ethyl group, a n-propyl group, an isopropyl group or a
n-butyl group.
3. The ammonium salt according to claim 1, wherein
[HNR.sub.3].sup.+ is ammonium, trimethylammonium, triethylammonium,
tri-n-propylammonium, triisopropylammonium, tri-n-butylammonium,
dimethylethylammonium, methyldiethylammonium,
dimethyl-n-propylammonium, methyl-di-n-propylammonium,
dimethylisopropylammonium, methyldiisopropylammonium,
dimethyl-n-butylammonium, methyl-di-n-butylammonium,
diethyl-n-propylammonium, ethyl-di-n-propylammonium,
diethylisopropylammonium, ethyldiisopropylammonium,
diethyl-n-butylammonium or ethyl-di-n-butylammonium.
4. The ammonium salt according to claim 1, wherein
[HNR.sub.3].sup.+ is ammonium (NH.sub.4.sup.+) or
triethylammonium.
5. The ammonium salt according to claim 1, wherein each of Q.sup.1
and Q.sup.2 is a monovalent fluoroorganic group.
6. The ammonium salt according to claim 5, wherein each of Q.sup.1
and Q.sup.2 is independently selected from a fluorinated alkyl
group, a fluorinated alkenyl group and a fluorinated allyl
group.
7. The ammonium salt according to claim 5, wherein each of Q.sup.1
and Q.sup.2 is independently selected from perfluoroalkyl group, a
perfluoroalkenyl group and a perfluoroallyl group.
8. The ammonium salt according to claim 1, wherein Q.sup.1 and
Q.sup.2 together form a bivalent fluoroorganic group.
9. The ammonium salt according to claim 8, wherein Q.sup.1 and
Q.sup.2 together form a perfluoroalkyl group having 1 or 2 carbon
atoms, or they together form a C.sub.1-3 perfluoroalkylene
group.
10. The ammonium salt according to claim 1, wherein
[Q.sup.1-SO.sub.2--N--SO.sub.2-Q.sup.2] is represented by one of
the following formulae: ##STR00010##
11. The ammonium salt according to claim 1, wherein the NMR is
.sup.19F-NMR.
12. An ammonium salt represented by the following formula (1-1),
which has a purity as measured by NMR of 99 mol % or higher:
##STR00011##
13. The ammonium salt according to claim 12, wherein the NMR is
.sup.19F-NMR.
Description
REFERENCE TO PRIOR APPLICATIONS
[0001] This application is a Divisional application of U.S.
application Ser. No. 12/699,912, filed Feb. 4, 2010, now pending;
which is a Continuation application of PCT/JP08/64653, filed Aug.
15, 2008; and claims priority to Japanese patent application
2007-212920, filed Aug. 17, 2007, all incorporated herein by
reference.
TECHNICAL FIELD
[0002] The present invention relates to a method for producing a
purified ammonium salt of a fluorinated bis-sulfonylimide, and a
method for producing a lithium salt of a fluorinated
bis-sulfonylimide.
BACKGROUND ART
[0003] An ammonium salt of a fluorinated bis-sulfonylimide such as
a compound represented by the formula (1-1) is known as a salt
useful as an electrolyte material excellent in electric
conductivity and chemical stability:
##STR00001##
[0004] As a general method for purifying an ammonium salt,
recrystallization is most widely employed. The present inventors
have attempted recrystallization of an ammonium salt represented by
the formula (1), however, it is specifically difficult to
recrystallize an ammonium salt represented by the above formula
(1-1), and they have found that purification by a recrystallization
method is difficult:
[HNR.sub.3].sup.+[Q.sup.1-SO.sub.2--N--SO.sub.2-Q.sup.2].sup.-
(1)
wherein R' s which may be the same or different, is a hydrogen atom
or a C.sub.1-10 alkyl group, and each of Q.sup.1 and Q.sup.2 which
are independent of each other, is a monovalent fluoroorganic group,
or Q.sup.1 and Q.sup.2 together form a bivalent fluoroorganic
group.
[0005] For example, they have attempted a means of suspending the
ammonium salt represented by the formula (1) in a poor solvent, and
gradually adding a good solvent with heating to dissolve the
ammonium salt represented by the formula (1) in the solvent,
followed by cooling for recrystallization. However, the ammonium
salt solution after addition of the good solvent did not become a
uniform solution but was separated into two phases of a good
solvent solution phase of the ammonium salt and a poor solvent
solution phase, and recrystallization could not be carried out.
[0006] Further, the present inventors have attempted, as another
recrystallization method, a method of adding a good solvent to the
ammonium salt represented by the formula (1), followed by cooling
to precipitate crystals. However, although a crystalline substance
was formed, the purity of the crystalline substance was low, and
the yield was very low, and thus this recrystallization method
could not be employed.
[0007] Patent Document 1 discloses a purification method of washing
[NH(C.sub.2H.sub.5OCH.sub.3)(C.sub.2H.sub.5)(CH.sub.3)].sup.+[CF.sub.3--S-
O.sub.2--N--SO.sub.2--CF.sub.3].sup.- with an acidic aqueous
solution or an alkaline aqueous solution. It is Li, Na, I, Br and
the like that can be removed by this method, and even if this
method was employed for purification of the ammonium salt
represented by the formula (1), the purity was not increased.
Further, the decomposition reaction of ammonium represented by the
formula (1) occurred.
[0008] A lithium salt represented by the formula (3) is a compound
which can be used as e.g. an electrolyte for a lithium ion
secondary battery. In a case where the lithium salt represented by
the formula (3) is used as an electrolyte for a lithium ion
secondary battery, high purity of 99 mass % or higher is
essential:
Li.sup.+[Q.sup.1-SO.sub.2--N--SO.sub.2-Q.sup.2].sup.- (3)
wherein Q.sup.1 and Q.sup.2 are as defined for the formula (1).
[0009] As a method for purifying a lithium salt, Patent Document 2
discloses a method of reacting
[NH(C.sub.2H.sub.5).sub.3].sup.+[CF.sub.3--SO.sub.2--N--SO.sub.2--CF.sub.-
3].sup.- with an alkali metal hydroxide such as sodium hydroxide to
convert it to an alkali metal salt, followed by
crystallization.
[0010] However, it is a sodium salt that is formed in a case where
sodium hydroxide is used, and salt exchange is required to obtain a
lithium salt. A method of using lithium hydroxide instead of sodium
hydroxide may be mentioned so as to directly obtain a lithium salt,
but a solvent is coordinated to the precipitated lithium salt, and
a complicated step to remove the solvent is required. Further, if
impurities to be removed are reacted with an alkali metal
hydroxide, an alkali metal salt of impurities will be formed, and
its removal is more difficult.
[0011] Patent Document 3 discloses as a method for purifying
Li.sup.+[CF.sub.3--SO.sub.2--N--SO.sub.2--CF.sub.3].sup.-, a method
of recrystallizing it from 1,4-dioxane, dissolving it in a polar
solvent having a boiling point of at most 100.degree. C., followed
by filtration, and removing the solvent. The present inventors have
practically conducted this method, and they have found problems in
this method such that the yield was so low as 60%, removal of the
solvent was very difficult, and removal of the solvent took a long
period of time.
[0012] Patent Document 1: JP-A-2005-298375
[0013] Patent Document 2: JP-A-2000-302748
[0014] Patent Document 3: JP-A-9-255685
DISCLOSURE OF THE INVENTION
Object to be Accomplished by the Invention
[0015] The object of the present invention is to provide a method
for producing a high purity ammonium salt of a fluorinated
bis-sulfonylimide simply and efficiently, and a method for
producing a high purity lithium salt of a fluorinated
bis-sulfonylimide using the purified ammonium salt as a starting
material.
[0016] That is, methods for producing an ammonium salt and a
lithium salt of a fluorinated bis-sulfonylimide using a practical
and efficient method with a high yield with a small number of
steps, are provided. Further, the present invention provides a high
purity ammonium salt of a fluorinated bis-sulfonylimide useful for
the above method for producing a lithium salt.
Means to Accomplish the Object
[0017] The present invention provides the following.
[0018] [1] A method for producing a purified particulate solid (II)
of a salt represented by the following formula (1), which comprises
suspending a particulate solid (I) of a salt represented by the
following formula (1) in a solvent comprising an etheric oxygen
atom-containing compound, and separating the solvent by
filtration:
[HNR.sub.3].sup.+[Q.sup.1-SO.sub.2--N--SO.sub.2-Q.sup.2].sup.-
(1)
wherein each of R' s which may be the same or different, is a
hydrogen atom or a C.sub.1-10 alkyl group, and each of Q' and
Q.sup.2 which are independent of each other, is a monovalent
fluoroorganic group, or Q.sup.1 and Q.sup.2 together form a
bivalent fluoroorganic group.
[0019] [2] The method according to the above [1], wherein the
purity of the particulate solid (I) as measured by NMR is 80 mol %
or higher and less than 99 mol %, and the purity of the particulate
solid (II) as measured by NMR is 99 mol % or higher.
[0020] [3] The method according to the above [1] or [2], wherein
the particulate solid (I) of a salt represented by the formula (1)
is suspended in the solvent comprising an etheric oxygen
atom-containing compound by heating with stirring and swelled, and
then filtration is carried out.
[0021] [4] The method according to any one of the above [1] to [3],
wherein the solvent comprising an etheric oxygen atom-containing
compound is used in an amount of from 0.5 to 20 times the mass of
the particulate solid (I).
[0022] [5] The method according to any one of the above [1] to [4],
wherein the solvent comprising an etheric oxygen atom-containing
compound is a cyclic ether compound.
[0023] [6] The method according to any one of the above [1] to [5],
wherein the solvent comprising an etheric oxygen atom-containing
compound is 1,4-dioxane.
[0024] [7] The method according to any one of the above [1] to [6],
wherein the salt represented by the formula (1) is a salt
represented by the following formula (1-1):
##STR00002##
[0025] [8] An ammonium salt represented by the following formula
(1), which has a purity as measured by NMR of 99 mol % or
higher:
[HNR.sub.3].sup.+[Q.sup.1-SO.sub.2--N--SO.sub.2-Q.sup.2].sup.-
(1)
wherein each of R' s which may be the same or different, is a
hydrogen atom or a C.sub.1-10 alkyl group, and each of Q.sup.1 and
Q.sup.2 which are independent of each other, is a monovalent
fluoroorganic group, or Q.sup.1 and Q.sup.2 together form a
bivalent fluoroorganic group.
[0026] [9] An ammonium salt represented by the following formula
(1-1), which has a purity as measured by NMR of 99 mol % or
higher:
##STR00003##
[0027] [10] A method for producing a lithium salt represented by
the following formula (3), which comprises obtaining a particulate
solid (II) of a salt represented by the formula (1) by the method
as defined in any one of the above [1] to [7], reacting the
particulate solid (II) with concentrated sulfuric acid to obtain an
imidic acid represented by the following formula (2), and reacting
the imidic acid with a compound containing a lithium ion to obtain
a lithium salt represented by the following formula (3):
Q.sup.1-SO.sub.2--NH--SO.sub.2-Q.sup.2 (2)
Li.sup.+[Q.sup.1-SO.sub.2--N--SO.sub.2-Q.sup.2].sup.- (3)
wherein each of R' s which may be the same or different, is a
hydrogen atom or a C.sub.1-10 alkyl group, and each of Q.sup.1 and
Q.sup.2 which are independent of each other, is a monovalent
fluoroorganic group, or Q.sup.1 and Q.sup.2 together form a
bivalent fluoroorganic group.
[0028] [11] A method for producing a lithium salt represented by
the following formula (3), which comprises obtaining a particulate
solid (II) of a salt represented by the formula (1) by the method
as defined in the above [1], and reacting the particulate solid
(II) with a compound containing a lithium ion to obtain a lithium
salt represented by the following formula (3):
Q.sup.1-SO.sub.2--NH--SO.sub.2-Q.sup.2 (2)
Li.sup.+[Q.sup.1-SO.sub.2--N--SO.sub.2-Q.sup.2].sup.- (3)
wherein each of R' s which may be the same or different, is a
hydrogen atom or a C.sub.1-10 alkyl group, and each of Q.sup.1 and
Q.sup.2 which are independent of each other, is a monovalent
fluoroorganic group, or Q.sup.1 and Q.sup.2 together form a
bivalent fluoroorganic group.
[0029] [12] The method according to the above [10] or [11], wherein
the purity of the lithium salt represented by the formula (3) as
measured by NMR is 99 mol % or higher.
[0030] [13] The method according to any one of the above [10] to
[12], wherein the compound containing a lithium ion is lithium
hydroxide, lithium carbonate or lithium hydrogencarbonate.
[0031] [14] The method according to any one of the above [10] to
[13], wherein the lithium salt represented by the formula (3) is a
lithium salt to be used as an electrolyte for a lithium ion
secondary battery.
EFFECTS OF THE INVENTION
[0032] According to the present invention, a high purity ammonium
salt of a fluorinated bis-sulfonylimide can be obtained by a
practical and efficient method with a high yield with a small
number of steps. Further, according to the present invention, a
high purity lithium salt of a fluorinated bis-sulfonylimide can be
obtained simply and efficiently. Further, according to the present
invention, a high purity lithium salt of a fluorinated
bis-sulfonylimide useful for the method for producing the lithium
salt can be provided.
BEST MODE FOR CARRYING OUT THE INVENTION
[0033] In the present specification, groups are as defined above
unless otherwise specified. In the present specification, a salt
represented by the formula (1) will be referred to as a salt (1),
and an anion represented by the formula (A) will be referred to as
an anion (A). The same applies to salts, anions, cations, compounds
and the like represented by other formulae.
[0034] The salt (1) in the present invention is a salt made of the
following cation (C) and anion (A):
[HNR.sub.3].sup.+ (C)
[Q.sup.1-SO.sub.2--N--SO.sub.2-Q.sup.2].sup.- (A)
[HNR.sub.3].sup.+[Q.sup.1-SO.sub.2--N--SO.sub.2-Q.sup.2].sup.-
(1)
[0035] In the cation (C), in a case where R is a C.sub.1-10 alkyl
group, R is preferably a methyl group, an ethyl group, a n-propyl
group, an isopropyl group or a n-butyl group.
[0036] The cation (C) may, for example, be ammonium,
trimethylammonium, triethylammonium, tri-n-propylammonium,
triisopropylammonium, tri-n-butylammonium, dimethylethylammonium,
methyldiethylammonium, dimethyl-n-propylammonium,
methyl-di-n-propylammonium, dimethylisopropylammonium,
methyldiisopropylammonium, dimethyl-n-butylammonium,
methyl-di-n-butylammonium, diethyl-n-propylammonium,
ethyl-di-n-propylammonium, diethylisopropylammonium,
ethyldiisopropylammonium, diethyl-n-butylammonium or
ethyl-di-n-butylammonium.
[0037] In a case where the cation (C) is ammonium (NH.sub.4.sup.+)
or triethylammonium, preparation of an ammonium salt is easy, such
being preferred.
[0038] In the anion (A), in a case where each of Q.sup.1 and
Q.sup.2 is a monovalent fluoroorganic group, it is preferably a
monovalent fluorinated hydrocarbon group, more preferably a
fluorinated alkyl group, a fluorinated alkenyl group or a
fluorinated allyl group, particularly preferably a perfluoroalkyl
group, a perfluoroalkenyl group or a perfluoroallyl group. Each of
the fluorinated alkyl group and the fluorinated alkenyl group may
have a linear structure or a branched structure.
[0039] In a case where Q.sup.1 and Q.sup.2 together form a bivalent
fluoroorganic group, it is preferably a fluorinated alkylene group,
particularly preferably a perfluoroalkylene group.
[0040] It is preferred that Q.sup.1 and Q.sup.2 are a
perfluoroalkyl group having 1 or 2 carbon atoms, or they together
form a C.sub.1-3 perfluoroalkylene group.
[0041] Specifically, the anion (A) is preferably any one of anions
represented by the following formulae:
##STR00004##
[0042] In the present invention, the salt (1) is particularly
preferably the following ammonium salt (1-1):
##STR00005##
[0043] As a means of obtaining the salt (1), for example, a method
disclosed in WO 2006/106960 (Example 4), a method disclosed in
JP-A-08-081436, or a method disclosed in WO97/23448 may be
mentioned.
[0044] The particulate solid (I) of the salt (1) in the present
invention is obtained by concentrating a reaction solvent solution
containing a salt (I) formed by the production method as disclosed
in such a document. In a case where a solid is contained in the
reaction solvent solution before the concentration, it is preferred
to preliminarily remove the solid by a method such as filtration,
whereby the purification method will efficiently be carried
out.
[0045] A compound contained in the particulate solid (I) and to be
removed by the purification method of the present invention may,
for example, be a neutral organic substance which is not charged
and which is a solid at room temperature. For example, impurities
in a case of production by the production method disclosed in the
above document may, for example, be
HN.sub.2SO.sub.2CF.sub.2CF.sub.2SO.sub.2NH.sub.2 and
FO.sub.2SCF.sub.2CF.sub.2SO.sub.2NH.sub.2.
[0046] The purity of the particulate solid (I) used for the
production method of the present invention is preferably 80 mol %
or higher, particularly preferably from 85 to 99 mol %, especially
preferably from 95 to 99 mol %.
[0047] The value of the purity in the present invention is a value
quantified by an NMR (nuclear magnetic resonance) method unless
otherwise specified. A nuclear species in the NMR method may, for
example, be .sup.1H, .sup.19F or .sup.13C, and is preferably
.sup.19F.
[0048] The particle size of the particulate solid (I) is preferably
at most a particle size to such an extent that the particles are
suspended and at least a particle size to such an extent that when
the particles are suspended in a solvent, not all the particles are
dissolved. Usually, the maximum particle size of the particles is
preferably from 0.1 mm to 3.0 mm, more preferably from 0.1 mm to
1.0 mm. The particle size may be measured by a method such as
classification. Further, the particulate solid (I) may be in a
crystalline state, in an amorphous state or in a mixed state
thereof.
[0049] In the production method of the present invention, first,
the particulate solid (I) of the salt (1) is suspended in a solvent
comprising an etheric oxygen atom-containing compound.
[0050] The solvent comprising an etheric oxygen atom-containing
compound (hereinafter referred to as an ether solvent) may be a
cyclic ether compound such as 1,4-dioxane, 1,3-dioxane,
1,3-dioxolane, tetrahydrofuran or tetrahydropyran; or an acyclic
ether compound such as diethyl ether, methyl-t-butyl ether,
diethylene glycol dimethyl ether, diethylene glycol diethyl ether,
diethylene glycol dibutyl ether, tetraethylene glycol dimethyl
ether, tetraethylene glycol diethyl ether or tetraethylene glycol
dibutyl ether, and it is preferably a cyclic ether compound,
particularly preferably 1,4-dioxane, whereby the solubility of the
salt (1) is low, the solubility of impurities is high, and
accordingly efficient purification is possible.
[0051] In the present specification, "being suspended" means a
state where in a solution having a part of the salt (1) dissolved
in a solvent, the rest of the particulate solid (1) is dispersed.
Under normal conditions, a solution having the salt (1) dissolved
can be a saturated solution of the salt (1). The amount of the
ether solvent is preferably from 0.5 to 20 times, particularly
preferably from 1 to 5 times the mass of the particulate solid (I)
to be purified. When the amount of the solvent is within such a
range, the particulate solid (I) will be sufficiently suspended,
and the yield will be high.
[0052] The temperature at the suspending operation may be the
boiling point of the solvent or lower, and is preferably within a
range of from 10 to 80.degree. C. in view of easy operation and
simple apparatus structure, particularly preferably from 20 to
60.degree. C. Further, after the suspending operation, the
suspension is preferably stirred.
[0053] The time for the suspending operation is preferably at least
10 minutes, particularly preferably from 10 minutes to 4 hours,
especially preferably from 30 minutes to 2 hours, after the
particulate solid (I) is suspended in the ether solvent and
swelling of the particulate solid (I) is confirmed.
[0054] In the present invention, the particulate solid (I) is
suspended, and then the ether solvent is separated by filtration to
obtain a purified particulate solid (II). As the filtration method,
any method such as centrifugal separation, pressurized filtration,
vacuum filtration or normal pressure filtration may be selected.
The particulate solid (II) obtained by filtration may be in a
crystalline state, in an amorphous state or in a mixed state
thereof.
[0055] The obtained particulate solid (II) is preferably washed
with a washing solvent from the viewpoint of improvement in the
purity. The washing solvent is preferably an ether solvent which is
the same as or different from the ether solvent used for the
suspending operation, or a solvent other than an ether solvent may
be used. The washing solvent is preferably a nonpolar solvent from
the viewpoint of the recovery rate of the particulate solid (II).
The washing solvent may, for example, be a cyclic ether compound
such as 1,4-dioxane, 1,3-dioxane, 1,3-dioxolane, tetrahydrofuran or
tetrahydropyran; an acyclic ether compound such as diethyl ether,
methyl-t-butyl ether, diethylene glycol dimethyl ether, diethylene
glycol diethyl ether, diethylene glycol dibutyl ether,
tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl
ether or tetraethylene glycol dibutyl ether; n-hexane, n-pentane,
n-heptane, n-octane, benzene, toluene, xylene, cyclohexane,
dichloromethane, chloroform, pentafluorodichloropropane or
1H-perfluorohexane.
[0056] The particulate solid (II) obtained by filtration is then
preferably dried. The drying method is not particularly limited,
and a depressurizing method with heating, or a method of making a
dry inert gas flow with heating, is usually employed. In the case
of heating, the temperature is not particularly limited, and it is
preferably the boiling point of the solvent or higher, and is
preferably at most a temperature which is higher by 50.degree. C.
than the boiling point of the solvent, with a view to suppressing
decomposition of an aimed product e.g. by local overheating.
Further, the inert gas may, for example, be a rare gas, nitrogen
gas or carbon dioxide gas, and is preferably nitrogen gas from the
viewpoint of availability and handling efficiency.
[0057] According to the production method of the present invention,
a purified salt (1) can be obtained as the particulate solid (II).
The purity of the purified salt (1) is preferably 90 mol % or
higher, particularly preferably from 98 to 100 mol %, especially
preferably from 99 to 100 mol %. Such a high purity salt (1) is a
novel salt which could not be obtained before.
[0058] The application of the high purity salt (1) obtained by the
production method of the present invention is not particularly
limited, and it may be used, for example, as a material of a
lithium salt (3) as an electrolyte for a lithium ion secondary
battery.
[0059] A method for producing a lithium salt (3) using the salt (1)
obtained by the production method of the present invention is shown
below.
##STR00006##
[0060] For example, (method 1): a method for producing a lithium
salt (3) by reacting a purified salt (1) with concentrated sulfuric
acid to obtain an imidic acid (2), and reacting the imidic acid
with a compound having a lithium ion, or (method 2): a method of
reacting the purified salt (1) with a compound having a lithium ion
to produce a lithium salt (3).
[0061] As a method of obtaining the imidic acid (2) in the method
(1), for example, a method disclosed in "Synthesis, properties, and
reactions of bis((trifluoromethyl)sulfonyl)imide,
(CF.sub.3SO.sub.2).sub.2NH" by Jerry Foropoulos Jr., Darryl D.
DesMarteau, Inorganic Chemistry, Vol. 23, No. 23, 1984, p. 3720,
and a method disclosed in JP-A-57-146776 (Example 1) may be
mentioned.
[0062] Specifically, a method of mixing the compound (1) with
concentrated sulfuric acid, followed by heating under reduced
pressure conditions so that the compound (2) distills by
distillation, or a method of making an aqueous solution of the
compound (1) pass through an acid type cation exchange resin such
as sulfonated polystyrene to obtain a compound (2) may, for
example, be mentioned. The former method is particularly preferred,
since metal impurities, etc. can be removed in the distillation
step.
[0063] As a method of obtaining the lithium salt (3) from the
imidic acid (2), a method disclosed in JP-A-2003-192661 (Examples 8
to 14) may be mentioned. The compound containing a lithium ion to
be reacted with the imidic acid (2) is preferably lithium
hydroxide, lithium carbonate or lithium hydrogencarbonate, more
preferably lithium hydroxide. Such a lithium compound is preferably
used since it is readily available and has high reactivity, and the
by-product is carbon dioxide gas or water and can easily be
separated.
[0064] In the above method of obtaining the lithium salt (3) from
the imidic acid (2), a solvent may be used. As the solvent, a
non-aqueous solvent may be used, or water may be used. The
non-aqueous solvent is preferably a solvent which is not decomposed
by an acid since the compound (2) is very strongly acidic, and a
non-aqueous solvent such as methanol or ethanol is particularly
preferred.
[0065] As the method of obtaining the lithium salt (3) in the
method 2, for example, a method of adding lithium hydroxide
monohydrate to the salt (1) dissolved in tetrahydrofuran, followed
by boiling until generation of ammonia gas is no more observed for
reaction, as disclosed in JP-A-2000-506132 (Example 2) may be
mentioned. As the solvent, an optional solvent may be used, but it
is required to select a solvent which is not decomposed by ammonia.
Further, in a case where the end point of the reaction is to be
detected by ammonia gas generation, a solvent other than a solvent
in which ammonia is well dissolved, such as water, is preferably
used.
[0066] In the method 1 and the method 2, in a case where a high
purity reaction reagent is used, a high purity lithium salt (3) is
obtained. A lithium salt (3) having a purity of 99 mol % or higher
is obtained, and usually a lithium salt (3) having a purity of 99.5
mol % or higher is obtained, for example, by using sulfuric acid
having a purity of at least 98 vol % as concentrated sulfuric acid,
using a compound containing a lithium ion having a purity of at
least 99 mass %, using a solvent having a purity of at least 99
mass %, and using other reaction reagent having a purity of at
least 99 mass % if used.
[0067] In a case where a high purity lithium salt (3) is obtained
by the method 1 or the method 2, usually no purification step is
required, and a lithium salt (3) having an aimed purity can be
obtained only by post-treatment such as removal of the solvent. The
lithium salt (3) may be in a crystalline state, in an amorphous
state or in a mixed state thereof.
[0068] The purity of the lithium salt (3) is preferably 99 mol % or
higher, particularly preferably 99.5 mol % or higher, especially
preferably 99.9 mol % or higher. Particularly when the lithium salt
(3) is obtained by the method 1, since the distillation step is a
step capable of removing metal impurities, a lithium salt (3)
having an extremely low metal content can be obtained.
[0069] The obtained high purity lithium salt (3) can be a useful
lithium salt capable of having a potential window broader than from
0 to 4.2 V as an electric potential versus lithium.
[0070] The high purity ammonium salt of a fluorinated
bis-sulfonylimide obtained by the present invention may be used as
e.g. an intermediate for preparation of an ionic liquid, an
electric conductivity-imparting agent, a flame retardancy-imparting
agent. Further, the high purity lithium salt (3) of the imide is
useful as e.g. an electrolyte, an intermediate for preparation of
an ionic liquid, an electric conductivity-imparting agent or a
flame retardancy-imparting agent.
EXAMPLES
[0071] Now, the present invention will be described in further
detail with reference to Examples, but the present invention is by
no means restricted thereto.
[0072] In measurement of the purity by .sup.19F-NMR, a peak of
CF.sub.2 in the SO.sub.2--CF.sub.2--CF.sub.2--SO.sub.2 structure
and peaks other than the peak of CF.sub.2 were measured, and the
structure of impurities based on the peaks other than CF.sub.2 was
identified for quantitative determination. In the following
description, the purity and the yield are based on mol % unless
otherwise specified.
Example 1
Example of the Present Invention
[0073] Example for preparation of compound (1-1)
[0074] A particulate solid of the following ammonium salt (1-1) was
prepared in the same manner as in the method disclosed in Example 4
of WO2006/106960. The purity of the ammonium salt (1-1) before
purification as measured by .sup.19F-NMR was 98.5%.
##STR00007##
Example for Preparation of Ammonium Salt (1-1):
[0075] The particulate solid (380.0 g) of the ammonium salt (1-1)
having an NMR purity of 98.5% was suspended in 1,4-dioxane (760.0
g) and stirred at 40.degree. C. for 4 hours while it was swelled. 4
Hours later, dioxane was separated by filtration, and the obtained
particulate solid was washed with 1,4-dioxane (380.0 g) twice, and
then the solvent was removed by vacuum drying. 374.2 g of a
particulate solid of ammonium salt (1-1) was obtained, and the
yield was 99.9%. The purity was measured by 19F-NMR, whereupon it
was improved to 99.9%.
Example 2
Example of the Present Invention
Example for Preparation of Imidic Acid (2-1)
[0076] The ammonium salt (1-1) (300 g) before purification obtained
in Example 1 and concentrated sulfuric acid (600 g) having a purity
of 98 vol % or higher were charged into a 2 L three-necked flask.
This three-necked flask and a 2 L receiver were connected by a
glass tube. The glass tube was kept at 60.degree. C. or higher by a
ribbon heater to prevent coagulation of the imidic acid (2-1). The
2 L receiver was cooled with ice and connected with a vacuum pump
so that the whole system was a recovery system for the imidic acid.
The pressure in the system was reduced to 266 Pa (absolute
pressure), and the three-necked flask was heated in an oil bath.
Distillation started when the internal temperature of the
three-necked flask exceeded 80.degree. C., and the following imidic
acid (2-1) was solidified and recovered in the receiver cooled with
ice. The reaction was completed after the temperature raising was
continued until the internal temperature reached 100.degree. C. and
as a result, 272.2 g of the imidic acid (2-1) in the form of a
white solid was obtained in the receiver. The yield was 97.1%. The
purity was measured by .sup.19F-NMR, whereupon it was 99.9%.
##STR00008##
Example for Preparation of Lithium Salt (3-1):
[0077] To the obtained imidic acid (2-1) (272.2 g), deionized water
(500 mL) was charged to obtain an aqueous solution. A lithium
hydroxide aqueous solution (concentration: 10 mass %) was dropwise
added with stirring while the pH of the aqueous solution was
monitored, and dropwise addition was continued until the pH
exceeded 7. After completion of dropwise addition of the lithium
hydroxide aqueous solution, stirring was continued for one hour.
Then, water was distilled off, followed by vacuum drying at
100.degree. C. 276.0 g of lithium salt (3-1) in the form of a white
solid was obtained, and the yield was 99.0%. The purity was
measured by .sup.19F-NMR, whereupon it was 99.9%.
##STR00009##
Example 3
Reference Example
[0078] The ammonium salt (1-1) (100 g) before purification obtained
in Example 1 was used without purification by 1,4-dioxane to
prepare the imidic acid (2-1) in the same manner as in Example 2.
90.6 g of imidic acid (2-1) was obtained, but the imidic acid (2-1)
was slightly brown. The yield was 96.4%.
[0079] To the imidic acid (2-1) (90.6 g), deionized water (300 mL)
was charged to prepare lithium salt (3-1) in the same manner as in
Example 2. 91.8 g of particles of lithium salt (3-1) in the form of
a solid were obtained, but the particles were slightly yellow. The
yield was 98.9%. The purity was measured by .sup.19F-NMR, whereupon
it was 98.0%.
Example 4
Reference Example
[0080] The lithium salt (3-1) (91.8 g) obtained in Example 3 was
suspended in 1,4-dioxane (100 mL), and acetonitrile was gradually
added while the internal temperature was kept at 60.degree. C. to
obtain a uniform solution. This solution was cooled overnight in a
refrigerator kept at 3.degree. C., whereupon a white crystalline
substance was precipitated. Then, the substance was recovered by
filtration. The recovered substance was vacuum dried at from 80 to
120.degree. C. for 100 hours. 57.8 g of a white crystalline
substance was obtained, and it was confirmed that 5 mass % of
1,4-dioxane remained. The purity of the compound other than the
solvent was measured, whereupon it was 99.9%.
[0081] The amount of remaining 1,4-dioxane and the amount of the
lithium salt were quantitatively determined by measuring
.sup.19F-NMR and .sup.1H-NMR using CF.sub.3CH.sub.2OH as an
internal standard substance.
[0082] Then, to remove remaining 1,4-dioxane, a step of dissolving
the substance in n-butylonitrile (100 mL) and distilling off the
solvent was repeatedly carried out 4 times. The substance was
vacuum dried at 100.degree. C. for 12 hours to recover 57.5 g of
lithium salt (3-1). The yield was 63.8%. By .sup.1H-NMR, no
1,4-dioxane remained, and the purity as measured by .sup.19F-NMR
was 99.9%. It is considered that removal of the solvent from the
lithium salt is difficult since coordination properties of
1,4-dioxane to lithium ions is strong.
Example 5
Reference Example
[0083] The ammonium salt (1-1) (5.0 g) before purification obtained
in Example 1 was dispersed in methyl-t-butyl ether (5 mL) and
gradually heated, whereupon a uniform solution was obtained at
50.degree. C. The solution was cooled to -78.degree. C., whereupon
a small amount of a precipitate was obtained. The precipitate was
subjected to filtration and dried, and the purity was measured by
.sup.19F-NMR and as a result, the purity was 98.0%, and high purity
could not be achieved.
Example 6
Reference Example
[0084] The ammonium salt (1-1) (5.0 g) before purification obtained
in Example 1 was dispersed in chloroform (5 mL), 25 drops of
acetonitrile were added, and the dispersion was gradually heated,
whereupon a uniform solution was obtained at 50.degree. C. The
solution was gradually cooled to room temperature, whereupon it was
separated into two phases of an acetonitrile phase in which the
ammonium salt (1-1) was dissolved and a chloroform phase. The
acetonitrile phase containing the ammonium salt (1-1) as an upper
phase was analyzed by .sup.19F-NMR and as a result, the purity
excluding the solvent was 98.0%, and no high purity could be
achieved.
Example 7
Reference Example
[0085] Purification was attempted with reference to a method
disclosed in JP-A-2005-298375. That is, the ammonium salt (1-1)
(5.0 g) before purification obtained in Example 1 was dissolved in
methyl-t-butyl ether (10 mL), stirred in an aqueous solution having
lithium hydroxide (1.42 g) dissolved in deionized water (10 mL),
and reacted at 50.degree. C. for 3 hours. Then, the aqueous phase
as a lower phase was separated, concentrated and vacuum dried with
heating at 100.degree. C. to obtain lithium salt (3-1) having a
.sup.19F-NMR purity of 99.0%. The lithium salt (3-1) was dissolved
in a solvent mixture of ethylene carbonate and ethyl methyl
carbonate in a volume ratio of 1:1 at a concentration of 1 mol/L to
prepare a solution, and the oxidation potential was measured by a
cell using platinum for a counter electrode and a working electrode
and lithium metal for a difference electrode. As a result,
oxidation peak which was not derived from the compound (3-1) was
observed at about 3.5 V. That is, the obtained lithium salt (3-1)
has insufficient oxidation resistance for an application such as a
lithium battery material.
INDUSTRIAL APPLICABILITY
[0086] According to the production method of the present invention,
a high purity ammonium salt of a fluorinated bis-sulfonylimide can
be prepared simply and efficiently without use of a special
apparatus nor reagent, and accordingly it is an industrially useful
method.
[0087] Further, an ammonium salt of a fluorinated bis-sulfonylimide
obtained by the production method of the present invention is
useful as e.g. an intermediate for preparation of an ionic liquid,
an electric conductivity-imparting agent or a flame
retardancy-imparting agent, and further, the lithium salt of the
imide is useful as e.g. an electrolyte, an intermediate for
preparation of an ionic liquid, an electric conductivity-imparting
agent or a flame retardancy-imparting agent.
[0088] The entire disclosure of Japanese Patent Application No.
2007-212920 filed on Aug. 17, 2007 including specification, claims
and summary is incorporated herein by reference in its
entirety.
* * * * *