U.S. patent application number 16/515594 was filed with the patent office on 2019-11-07 for method of purifying dimethyl sulfoxide.
The applicant listed for this patent is Toray Fine Chemicals Co., Ltd.. Invention is credited to Haruo Murano, Katsuhiro Shibayama.
Application Number | 20190337892 16/515594 |
Document ID | / |
Family ID | 59013175 |
Filed Date | 2019-11-07 |
United States Patent
Application |
20190337892 |
Kind Code |
A1 |
Murano; Haruo ; et
al. |
November 7, 2019 |
METHOD OF PURIFYING DIMETHYL SULFOXIDE
Abstract
A method of purifying dimethyl sulfoxide includes distilling a
dimethyl sulfoxide-containing liquid in the presence of sodium
carbonate under a reduced pressure in an inert gas atmosphere to
distill out dimethyl sulfoxide, an amount of the sodium carbonate
with respect to 100 g of pure dimethyl sulfoxide in a residual
liquid after the distillation being 6 times or more the amount of
the sodium carbonate with respect to 100 g of the pure dimethyl
sulfoxide in the dimethyl sulfoxide-containing liquid before the
distillation.
Inventors: |
Murano; Haruo; (Ichihara,
JP) ; Shibayama; Katsuhiro; (Ichihara, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Toray Fine Chemicals Co., Ltd. |
Tokyo |
|
JP |
|
|
Family ID: |
59013175 |
Appl. No.: |
16/515594 |
Filed: |
July 18, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15781874 |
Jun 6, 2018 |
|
|
|
PCT/JP2016/084414 |
Nov 21, 2016 |
|
|
|
16515594 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 317/04 20130101;
C07C 315/06 20130101; C07C 315/06 20130101; C07C 317/04
20130101 |
International
Class: |
C07C 315/06 20060101
C07C315/06; C07C 317/04 20060101 C07C317/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 9, 2015 |
JP |
2015-240081 |
Claims
1. A method of purifying dimethyl sulfoxide comprising distilling a
dimethyl sulfoxide-containing liquid in the presence of sodium
carbonate under reduced pressure in an inert gas atmosphere to
distill out dimethyl sulfoxide, an amount of the sodium carbonate
with respect to 100 g of pure dimethyl sulfoxide in a residual
liquid after the distillation being 6 times or more the amount of
the sodium carbonate with respect to 100 g of the pure dimethyl
sulfoxide in the dimethyl sulfoxide-containing liquid before the
distillation.
2. The method according to claim 1, wherein the distillation is
performed by adding, at a start of the distillation, the sodium
carbonate in an amount of 0.0005 to 1.0 g with respect to 100 g of
the pure dimethyl sulfoxide in the dimethyl sulfoxide-containing
liquid.
3. The method according to claim 1, wherein the amount of the
sodium carbonate with respect to 100 g of the pure dimethyl
sulfoxide in the residual liquid after the distillation is 6 to
1000 times the amount of the sodium carbonate with respect to 100 g
of the pure dimethyl sulfoxide in the dimethyl sulfoxide-containing
liquid before the distillation.
4. The method according to claim 1, wherein the amount of the
sodium carbonate in the residual liquid after the distillation is
0.01 to 100 g with respect to 100 g of the pure dimethyl sulfoxide
in the residual liquid after the distillation.
5. The method according to claim 1, wherein, after water in the
dimethyl sulfoxide-containing liquid is distilled out as an early
distillate, the dimethyl sulfoxide is distilled out as a main
distillate.
6. The method according to claim 1, wherein the purified dimethyl
sulfoxide has a purity of 99.990 area % or more.
7. The method according to claim 1, wherein the sodium carbonate is
used as an inhibitor for dimethyl sulfoxide decomposition.
8. The method according to claim 2, wherein, after water in the
dimethyl sulfoxide-containing liquid is distilled out as an early
distillate, the dimethyl sulfoxide is distilled out as a main
distillate.
9. The method according to claim 3, wherein, after water in the
dimethyl sulfoxide-containing liquid is distilled out as an early
distillate, the dimethyl sulfoxide is distilled out as a main
distillate.
10. The method according to claim 4, wherein, after water in the
dimethyl sulfoxide-containing liquid is distilled out as an early
distillate, the dimethyl sulfoxide is distilled out as a main
distillate.
11. The method according to claim 2, wherein the purified dimethyl
sulfoxide has a purity of 99.990 area % or more.
12. The method according to claim 3, wherein the purified dimethyl
sulfoxide has a purity of 99.990 area % or more.
13. The method according to claim 4, wherein the purified dimethyl
sulfoxide has a purity of 99.990 area % or more.
14. The method according to claim 5, wherein the purified dimethyl
sulfoxide has a purity of 99.990 area % or more.
15. The method according to claim 2, wherein the sodium carbonate
is used as an inhibitor for dimethyl sulfoxide decomposition.
16. The method according to claim 1, wherein the distillation is
performed at a reduced pressure of 10 to 750 Torr.
17. The method according to claim 1, wherein the distillation is
performed at a reduced pressure of 15 to 730 Torr.
18. The method according to claim 1, wherein the distillation is
performed at a temperature of 108.degree. C. to 180.degree. C.
19. The method according to claim 1, wherein the distillation is
performed at a temperature of 120.degree. C. to 170.degree. C.
20. The method according to claim 1, wherein the distillation is
performed at a. temperature of 131.degree. C. to 160.degree. C.
Description
TECHNICAL FIELD
[0001] This disclosure relates to a method of purifying dimethyl
sulfoxide (DMSO).
BACKGROUND
[0002] Dimethyl sulfoxide is widely used in industries as a solvent
for polymerization of polymers and spinning polymer fibers.
Additionally, recovery and reuse of dimethyl sulfoxide used once
are widely performed in industry, and require steps of heating and
distilling to purify.
[0003] It is, however, known that dimethyl sulfoxide is relatively
thermally unstable and slightly decomposed when distilled under
atmospheric pressure. In manufacturing or recovering dimethyl
sulfoxide by distillation, contaminating a partially decomposed
decomposition product in dimethyl sulfoxide reduces efficiency of
dimethyl sulfoxide as a solvent. Thus, distillation of dimethyl
sulfoxide is often performed under reduced pressure at 100.degree.
C. or less.
[0004] If dimethyl sulfoxide can be distilled, for example, at a
high temperature of 110.degree. C. or more, it is unnecessary to
use high vacuum in distillation and, furthermore, no load is
applied to a decompression device. Thus, facility for distillation
can be simplified, which is industrially preferable.
[0005] There are known methods of adding a metal hydroxide such as
sodium hydroxide or potassium hydroxide as an inhibitor for
dimethyl sulfoxide decomposition (see JP-B-S43-3765, JP-B-S38-20721
and JP-A-2015-145359). The amount of addition of sodium hydroxide,
potassium hydroxide or the like is limited to 0.003 to 0.5%, and
adding in an amount of 1% or more promotes dimethyl sulfoxide
decomposition.
[0006] In JP '765, the amount of a decomposition product quantified
as formaldehyde after heating at 150.degree. C. for 10 hours was
0.032% when no metal hydroxide was added, 0.054% when 1% of
potassium hydroxide was added, and 0.052% when 1% of sodium
hydroxide was added.
[0007] When purifying by distilling dimethyl sulfoxide, the
purified dimethyl sulfoxide is distilled out of the system by the
distillation. In addition, water contained in a dimethyl
sulfoxide-containing liquid, a solvent having a lower boiling point
than dimethyl sulfoxide, unreacted monomers in polymerization, and
impurities such as a decomposition product of dimethyl sulfoxide
are distilled out of the system by distillation. As a result, when
a metal hydroxide such as sodium hydroxide or potassium hydroxide
as an inhibitor for dimethyl sulfoxide decomposition is added, the
metal hydroxide such as sodium hydroxide or potassium hydroxide
remains at a bottom of a distillation column during purification as
the distillation and purification of dimethyl sulfoxide proceed.
This increases concentration of the metal hydroxide contained in a
residual liquid after the distillation. In distilling dimethyl
sulfoxide, even if a metal hydroxide is added at low concentration,
dimethyl sulfoxide decomposition is rather promoted when dimethyl
sulfoxide is distilled out and the concentration of the metal
hydroxide reaches 1% or more. Thus, there has been a problem in
that purity is reduced due to contaminating a decomposition product
of dimethyl sulfoxide in distilled dimethyl sulfoxide.
[0008] There has been a desire for a dimethyl sulfoxide-purifying
method that enables high purity dimethyl sulfoxide to be obtained
safely, for example, at a high temperature of 110.degree. C. or
more and even when a decomposition inhibitor is highly concentrated
in distilling and purifying dimethyl sulfoxide.
[0009] It could therefore be helpful to provide a method of
purifying dimethyl sulfoxide to obtain high purity dimethyl
sulfoxide.
SUMMARY
[0010] We provide a method of purifying dimethyl sulfoxide
including distilling a dimethyl sulfoxide-containing liquid in the
presence of sodium carbonate in an inert gas atmosphere to distill
out dimethyl sulfoxide, in which an amount of the sodium carbonate
with respect to 100 g of pure dimethyl sulfoxide in a residual
liquid after the distillation is 6 times or more the amount of the
sodium carbonate with respect to 100 g of pure dimethyl sulfoxide
in the dimethyl sulfoxide-containing liquid before the
distillation.
[0011] The method of purifying dimethyl sulfoxide inhibits
decomposition of dimethyl sulfoxide even when the concentration of
sodium carbonate increases from low to high so that high purity
dimethyl sulfoxide can be obtained by distillation.
[0012] The amount of dimethyl sulfoxide decomposition is small not
only in a distillate after the distillation (a main distillate and
an early distillate) but also in a residual liquid after the
distillation. Dimethyl sulfoxide decomposition is small in the
residual liquid after the distillation or even in a liquid during
the distillation so that high purity dimethyl sulfoxide can be
obtained by the distillation.
[0013] The amount of dimethyl sulfoxide decomposition is small,
which is calculated from dimethyl sulfoxide purity in a mixed
liquid of the distillate (the main distillate and the early
distillate) after distillation and the residual liquid after
distillation. Thus, the sodium carbonate used in the dimethyl
sulfoxide-purifying method effectively inhibits dimethyl sulfoxide
decomposition.
[0014] The method of purifying dimethyl sulfoxide enables
distillation to be performed at high temperature so that the method
does not require any high vacuum facility and enables purification
at low cost. Since sodium carbonate is safe, operation can be
performed safer as compared to conventional purification methods
using dangerous substances.
[0015] Dimethyl sulfoxide obtained by the method of purifying
dimethyl sulfoxide can be used as solvents in steps of polymerizing
and spinning polymers such as polyacrylonitrile, cellulose,
polyimide, polysulfone, and polyurethane, stripping liquids for
photoresists that are electronic materials, solvents used in
synthesizing pharmaceuticals and agrochemicals, removing and
cleaning liquids for lens molds and the like, or liquids used in
paint stripping.
DETAILED DESCRIPTION
[0016] We provide a method of purifying dimethyl sulfoxide,
including distilling a dimethyl sulfoxide-containing liquid in the
presence of sodium carbonate in an inert gas atmosphere to distill
out dimethyl sulfoxide, in which an amount of the sodium carbonate
with respect to 100 g of pure dimethyl sulfoxide in a residual
liquid after the distillation is 6 times or more the amount of the
sodium carbonate with respect to 100 g of the pure dimethyl
sulfoxide in the dimethyl sulfoxide-containing liquid before the
distillation.
[0017] The sodium carbonate may be either an anhydride or hydrate,
and the hydrate is preferably a monohydrate or decahydrate that are
easily available.
[0018] The sodium carbonate may be added in powder or solid form as
it is or may be added as an aqueous solution. When added as an
aqueous solution, the sodium carbonate can be automatically and
continuously charged at a uniform concentration in a distillation
apparatus, which is therefore preferable in terms of safety. The
concentration of the sodium carbonate when prepared into an aqueous
solution can be increased up to a concentration saturated at a
temperature used. When adding a sodium carbonate as an aqueous
solution, the amount of the sodium carbonate to be added is
preferably 0.1 to 35 g, more preferably 0.2 to 30 g, still more
preferably 1 to 30 g, and most preferably 10 to 25 g, with respect
to 100 g of water.
[0019] Solubility of sodium carbonate into 100 g of water is 22 g
at 20.degree. C., which is high. Accordingly, when sodium carbonate
concentration is increased by distillation and sodium carbonate
crystals are deposited, the crystals in the column can be easily
removed even in removing by cleaning with water due to its high
water solubility.
[0020] The dimethyl sulfoxide-containing liquid may be an
impurity-free and 100% dimethyl sulfoxide liquid. Additionally, the
dimethyl sulfoxide-containing liquid may be a liquid containing a
very small or small amount of impurity (impurities). Furthermore,
the dimethyl sulfoxide-containing liquid may contain a large amount
of a liquid other than dimethyl sulfoxide.
[0021] Since it is costly to distill and remove an impurity
(impurities), the dimethyl sulfoxide-containing liquid before
distillation preferably contains pure dimethyl sulfoxide in an
amount of 10% by weight or more. The pure dimethyl sulfoxide refers
to dimethyl sulfoxide with a purity of 100%. The dimethyl
sulfoxide-containing liquid before distillation contains the pure
dimethyl sulfoxide in an amount of more preferably 20% by weight or
more, and still more preferably contains the pure dimethyl
sulfoxide in an amount of from 30 to 100% by weight.
[0022] The dimethyl sulfoxide-containing liquid before distillation
may contain water other than dimethyl sulfoxide. The amount of the
water in the dimethyl sulfoxide-containing liquid before
distillation is preferably 0.01 to 900 g, more preferably 0.1 to
400 g, still more preferably 1 to 250 g, and still further more
preferably 5 to 100 g, with respect to 100 g of the pure dimethyl
sulfoxide in the liquid.
[0023] When the dimethyl sulfoxide-containing liquid contains an
impurity and/or the like that hinder(s) distillation such as a
resin component, an insoluble substance, a component that tends to
be gelled when concentrated, an acid or a strong alkali, and/or a
component that reacts with dimethyl sulfoxide, it is preferable to
remove, separate, inactivate, or neutralize the impurity and/or the
like by previously performing filtering, adsorption and separation,
addition of an activated carbon, an ion-exchange resin or a base or
the like.
[0024] When distilling and purifying by adding a decomposition
inhibitor in the dimethyl sulfoxide-containing liquid, purified
dimethyl sulfoxide is distilled out of the system by the
distillation. Additionally, water contained in the dimethyl
sulfoxide-containing liquid, a solvent having a lower boiling point
than dimethyl sulfoxide, unreacted monomers in polymerization, and
impurities such as a decomposition product of dimethyl sulfoxide
are distilled out of the system by the distillation. As a result,
as distillation and purification of dimethyl sulfoxide proceed, the
decomposition inhibitor remains at the bottom of the distillation
column during the purification, increasing the concentration of the
decomposition inhibitor in a residual liquid during the
distillation. When sodium hydroxide or potassium carbonate is used
as the decomposition inhibitor, even if added at low concentration,
dimethyl sulfoxide decomposition is promoted when dimethyl
sulfoxide is distilled out and the concentration of the
decomposition inhibitor increases. Then, a decomposition product of
dimethyl sulfoxide is contaminated in distilled dimethyl sulfoxide,
thereby reducing dimethyl sulfoxide purity.
[0025] On the other hand, sodium carbonate inhibits decomposition
of dimethyl sulfoxide even when highly concentrated by
distilling-out of dimethyl sulfoxide so that high purity dimethyl
sulfoxide can be obtained.
[0026] The amount of the sodium carbonate added at a start of
distillation is preferably 0.0005 to 1.0 g, and more preferably
0.001 to 0.5 g with respect to 100 g of the pure dimethyl sulfoxide
in the liquid.
[0027] The amount of the sodium carbonate with respect to 100 g of
the pure dimethyl sulfoxide in the residual liquid after the
distillation is 6 times or more the amount of the sodium carbonate
with respect to 100 g of the pure dimethyl sulfoxide in the
dimethyl sulfoxide-containing liquid before the distillation.
[0028] The phrase "the residual liquid after the distillation"
refers to a dimethyl sulfoxide-containing liquid left at the bottom
of a distillation column or in a flask at the end of distillation
without being distilled when distilling the dimethyl
sulfoxide-containing liquid in a distillation facility.
[0029] As long as stirring is possible, the concentration of the
sodium carbonate in a residual liquid after distillation can be
increased.
[0030] When the amount of the sodium carbonate with respect to 100
g of the pure dimethyl sulfoxide in the residual liquid after the
distillation is below 6 times the amount of the sodium carbonate
with respect to 100 g of the pure dimethyl sulfoxide in the
dimethyl sulfoxide-containing liquid before the distillation,
dimethyl sulfoxide recovery rate is low, thus increasing cost for
purifying dimethyl sulfoxide.
[0031] The amount of the sodium carbonate with respect to 100 g of
the pure dimethyl sulfoxide in the residual liquid after the
distillation is preferably 6 to 1000 times, more preferably 10 to
500 times, and still more preferably 20 to 200 times as much as the
amount of the sodium carbonate with respect to 100 g of the pure
dimethyl sulfoxide in the dimethyl sulfoxide-containing liquid
before the distillation.
[0032] The amount of the sodium carbonate after the distillation is
preferably concentrated to 0.01 to 100 g, and more preferably to
0.1 to 85 g, with respect to 100 g of the pure dimethyl sulfoxide
in the residual liquid after the distillation. When the amount of
the sodium carbonate after the distillation is 100 g or more,
slurry of the residual liquid may be hardened at the bottom of the
distillation column, which may cause difficulty in stirring.
[0033] Regarding timing of sodium carbonate addition in the
dimethyl sulfoxide-containing liquid, the sodium carbonate may be
added before the distillation or may be added after distilling away
an impurity (impurities) having a lower boiling point than dimethyl
sulfoxide to perform the distillation. Additionally, sodium
carbonate deposited after the distillation may be discarded or
recovered and reused.
[0034] Dimethyl sulfoxide is distilled in an inert gas atmosphere.
The term "inert gas atmosphere" means a nitrogen, carbon dioxide,
helium, or argon atmosphere, and may be composed of one kind of gas
or a mixed gas composed of two or more gases. The inert gas
atmosphere is preferably a nitrogen atmosphere. When distilled in
air, dimethyl sulfoxide is easily decomposed.
[0035] Dimethyl sulfoxide is distilled more preferably in an inert
gas atmosphere and under atmospheric to reduced pressure. When
there is a small difference in boiling point between an impurity to
be desirably removed and dimethyl sulfoxide, the degree of pressure
reduction is not very lowered to increase the difference in boiling
point between the impurity and dimethyl sulfoxide, thereby
facilitating removal of the impurity.
[0036] When distilling under atmospheric pressure, temperature
during the distillation is preferably 160.degree. C. to 200.degree.
C., more preferably 170.degree. C. to 195.degree. C., still more
preferably 180.degree. C. to 194.degree. C., and still further more
preferably 189.degree. C. to 193.degree. C., whereby no load is
applied to the apparatus, and also the facility for distillation is
simplified, which is industrially preferable.
[0037] When distilling under reduced pressure, distillation is
performed preferably at 10 to 750 Torr, and more preferably 15 to
730 Torr.
[0038] When distilling under reduced pressure, temperature during
the distillation is preferably 108.degree. C. to 180.degree. C.,
more preferably 120.degree. C. to 170.degree. C., and still more
preferably 131.degree. C. to 160.degree. C.
[0039] The purity of dimethyl sulfoxide is measured by gas
chromatography with a capillary column.
[0040] The purity of dimethyl sulfoxide purified is analyzed by the
gas chromatography using a capillary column and represented by area
%. The purity thereof is preferably 99.990% or more, more
preferably 99.991% or more, and still more preferably 99.992% or
more.
[0041] The amount of decomposition (area %) of dimethyl sulfoxide
will be defined as below. The dimethyl sulfoxide-containing liquid
before distillation is defined as "charged liquid." A liquid
obtained by mixing a distillate after distillation (including a
main distillate and, if any, an early distillate) and a residual
liquid after the distillation is defined as "post-distillation
mixed liquid." The purity (area %) of dimethyl sulfoxide in each of
the charged liquid and the "post-distillation mixed liquid" was
measured by the gas chromatography, and the amount of decomposition
of dimethyl sulfoxide was obtained by the following calculation
equation:
Amount of decomposition of dimethyl sulfoxide (area %)=purity in
charged liquid (area %)-purity in post-distillation mixed liquid
(area %).
[0042] The amount of decomposition of dimethyl sulfoxide is
preferably 0.009 area % or less, more preferably 0.008 area % or
less, and still more preferably 0.007 area % or less.
[0043] In the method of purifying dimethyl sulfoxide, distillation
is applicable to both of batch distillation and continuous
distillation, and the distillation column may be a single column, a
composite column, or a combination of two or more distillation
columns. When performing a continuous distillation, a sodium
carbonate aqueous solution is preferably continuously supplied
before the distillation column(s).
[0044] As for the number of theoretical plates of the distillation
column(s), preferred is/are distillation column(s) with 1 to 50
theoretical plates, and suitably, more preferred is/are
distillation column(s) with 3 to 40 theoretical plates.
[0045] The dimethyl sulfoxide-containing liquid may be a dimethyl
sulfoxide-containing reaction liquid obtained in a step of
synthesizing by oxidation or the like of dimethyl sulfide, a
dimethyl sulfoxide-containing waste liquid used in a step of
polymerization or spinning of a polymer such as polyacrylonitrile,
cellulose, polyimide, polysulfone, or polyurethane, a dimethyl
sulfoxide-containing waste liquid used as a stripping liquid for a
photoresist that is an electronic material, a dimethyl
sulfoxide-containing waste liquid used as a solvent for
synthesizing a pharmaceutical or agrochemical, a dimethyl
sulfoxide-containing waste liquid used as a removing and cleaning
liquid for a lens mold or the like, a dimethyl sulfoxide-containing
waste liquid used as a paint stripping liquid or the like.
EXAMPLES
[0046] Our methods will be specifically described by Examples
hereinafter. Various kinds of measurement values used in the
Examples and the like were measured by the following measurement
methods.
(1) Dimethyl Sulfoxide Purity (Area %)
[0047] Dimethyl Sulfoxide Purity was measured by gas chromatography
under the following conditions:
[0048] Apparatus used: GC-2010 (FID) manufactured by Shimadzu
Corporation
[0049] Column: DB-WAX, 0.25 mm.times.60 m, film thickness: 0.25
.mu.m
[0050] Carrier gas: He: 165.7 kPa
[0051] Column temperature-increasing conditions: 35.degree.
C..fwdarw.7.degree. C./min.fwdarw.140.degree. C..times.10
min.fwdarw.15.degree. C./min.fwdarw.250.degree. C..times.10 min
[0052] Inlet temperature: 200.degree. C.
[0053] Detector temperature: 250.degree. C.
[0054] FID: Air: 400 ml/min, H2: 40 ml/min, Makeup: 30 ml/min
[0055] Split ratio: 14
[0056] Preparation of analysis sample: samples were filtered
through a 0.5 .mu.m PTFE syringe filter
[0057] Amount of injection: 1.0 .mu.l.
(2) Amount of Decomposition of Dimethyl Sulfoxide (Area %)
[0058] Regarding a dimethyl sulfoxide-containing liquid before
distillation (a charged liquid) and a mixed liquid prepared by
mixing a distillate after the distillation (including a main
distillate and, if any, an early distillate) and a residual liquid
after the distillation (a post-distillation mixed liquid), dimethyl
sulfoxide purities (area %) were measured in the same manner as in
(1), and then, an amount of decomposition of dimethyl sulfoxide was
obtained by the following calculation equation:
Amount of decomposition of dimethyl sulfoxide (area %)=purity in
charged liquid (area %)-purity in post-distillation mixed liquid
(area %).
(3) Amount of Additive
[0059] The amount of an additive before distillation is an amount
of the additive with respect to 100 g of pure dimethyl sulfoxide in
the dimethyl sulfoxide-containing liquid. In the gas
chromatographic measurement of dimethyl sulfoxide in (1), neither
water nor additive is detected. The amount of the pure dimethyl
sulfoxide in the charged liquid was obtained by multiplying a value
obtained by subtracting amounts of water and the additive from a
total liquid amount by dimethyl sulfoxide purity in the charged
liquid.
[0060] The amount of the additive after the distillation is an
amount of the additive with respect to 100 g of pure dimethyl
sulfoxide in the residual liquid after the distillation. The amount
of the pure dimethyl sulfoxide in the residual liquid after the
distillation was obtained by multiplying a value obtained by
subtracting amounts of water and the additive from an amount of the
residual liquid in the flask by dimethyl sulfoxide purity in the
residual liquid.
(4) Additive Concentration Rate Between Before and After
Distillation
[0061] Additive concentration rate between before and after the
distillation was obtained by the following calculation
equation:
Additive concentration rate between before and after
distillation=(amount (g) of additive with respect to 100 g of pure
dimethyl sulfoxide in residual liquid after distillation)/(amount
(g) of additive with respect to 100 g of pure dimethyl sulfoxide in
dimethyl sulfoxide-containing liquid before distillation).
EXAMPLE 1
[0062] A 1-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver, a stirrer, and a thermometer necessary for
simple distillation operation was charged with 720 g of dimethyl
sulfoxide (purity: 99.997 area %) (pure &methyl sulfoxide:
719.98 g), 80 g of ion-exchanged water, and, as an additive, 0.0072
g of sodium carbonate (0.001 g with respect to 100 g of the pure
dimethyl sulfoxide). After substituting the inside of the flask
with nitrogen, a rubber balloon filled with nitrogen was mounted at
a top of the Dimroth condenser to seal the flask. The flask was
heated in an oil bath maintained at 200.degree. C. and a point in
time when distillation started was considered to be a startup time.
After collecting 100 ml containing water as an early distillate, a
main distillation operation was performed in which the temperature
of the oil bath was increased to 230.degree. C., and distillate was
collected until the amount of a residual liquid in the flask
reached 8 g (the amount of water in the residual liquid: 0.0 g) and
the amount of the additive after the distillation reached 0.09 g
with respect to 100 g of the pure dimethyl sulfoxide. Heating time
from the startup was 3 hours.
[0063] Dimethyl sulfoxide purity in the main distillate was 99.997
area % as shown in Table 1 so that high purity dimethyl sulfoxide
was obtained.
[0064] Dimethyl sulfoxide purity in the residual liquid was 99.903
area % as shown in Table 1. Dirnethyl sulfoxide was hardly
decomposed even when heated for three hours at 147 to 170.degree.
C. (temperatures in the flask) in the early distillation operation
and at 170 to 191.degree. C. (temperatures in the flask) in the
main distillation operation. Since the amount of the sodium
carbonate in the residual liquid was 0.09 g with respect to 100 g
of the pure dimethyl sulfoxide in the residual liquid, the sodium
carbonate was concentrated to 90 times by the dimethyl sulfoxide
distillation.
[0065] As shown in Table 1, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.994 area
%, and the amount of decomposition was 0.003%, extremely small.
EXAMPLE 2
[0066] A 1-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver, a stirrer, and a thermometer necessary for
simple distillation operation was charged with 720 g of dimethyl
sulfoxide (purity: 99.997 area %) (pure dimethyl sulfoxide: 719.98
g), 80 g of ion-exchanged water, and, as an additive, 0.72 g of
sodium carbonate (0.1 g with respect to 100 g of the pure dimethyl
sulfoxide). After substituting the inside of the flask with
nitrogen, a rubber balloon filled with nitrogen was mounted at the
top of the Dimroth condenser to seal the flask. The flask was
heated in an oil bath maintained at 200.degree. C., and a point in
time when distillation started was considered to be a startup time.
After collecting 100 ml containing water as an early distillate, a
main distillation operation was performed in which the temperature
of the oil bath was increased to 230.degree. C., and distillate was
collected until the amount of a residual liquid in the flask
reached 72 g (the amount of water in the residual liquid: 0.0 g)
and the amount of the additive after the distillation reached 1 g
with respect to 100 g of the pure dimethyl sulfoxide. Heating time
from the startup was 2.5 hours.
[0067] Dimethyl sulfoxide purity in the main distillate was 99.995
area % as shown in Table 1 so that high purity dimethyl sulfoxide
was obtained.
[0068] Dimethyl sulfoxide purity in the residual liquid was 99.964
area % as shown in Table 1. Dimethyl sulfoxide was hardly
decomposed even when heated for 2.5 hours at 147 to 170.degree. C.
(temperatures in the flask) in the early distillation operation and
at 171 to 191.degree. C. (temperatures in the flask) in the main
distillation operation. Since the amount of the sodium carbonate in
the residual liquid was 1 g with respect to 100 g of the pure
dimethyl sulfoxide in the residual liquid, the sodium carbonate was
concentrated to 10 times by the dimethyl sulfoxide
distillation.
[0069] As shown in Table 1, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.991 area
%, and the amount of decomposition was 0.006%, extremely small.
EXAMPLE 3
[0070] A 1-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver, a stirrer, and a thermometer necessary for
simple distillation operation was charged with 720 g of dimethyl
sulfoxide (purity: 99.997 area %) (pure dimethyl sulfoxide: 719.98
g), 80 g of ion-exchanged water, and, as an additive, 7.2 g of
sodium carbonate (1 g with respect to 100 g of the pure dimethyl
sulfoxide). After substituting the inside of the flask with
nitrogen, a rubber balloon filled with nitrogen was mounted at the
top of the Dimroth condenser to seal the flask. The flask was
heated in an oil bath maintained at 200.degree. C., and a point in
time when distillation started was considered to be a startup time.
After collecting 100 ml containing water as an early distillate, a
main distillation operation was performed in which the temperature
of the oil bath was increased to 230.degree. C., and distillate was
collected until the amount of a residual liquid in the flask
reached 16 g (the amount of water in the residual liquid: 0.0 g)
and the amount of the additive after the distillation reached 82 g
with respect to 100 g of the pure dimethyl sulfoxide. Heating time
from the startup was 3 hours.
[0071] Dimethyl sulfoxide purity in the main distillation was
99.994 area % as shown in Table 1 so that high purity dimethyl
sulfoxide was obtained.
[0072] Dimethyl sulfoxide purity in the residual liquid was 99.892
area % as shown in Table 1. Dimethyl sulfoxide was hardly
decomposed even when heated for 3 hours at 147 to 170.degree. C.
(temperatures in the flask) in the early distillation operation and
at 170 to 191.degree. C. (temperatures in the flask) in the main
distillation operation. Since the amount of the sodium carbonate in
the residual liquid was 82 g with respect to 100 g of the pure
dimethyl sulfoxide in the residual liquid, the sodium carbonate was
concentrated to 82 times by the dimethyl sulfoxide
distillation.
[0073] As shown in Table 1, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.992 area
%, and the amount of decomposition was 0.005%, extremely small.
Comparative Example 1
[0074] A 1-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver, a stirrer, and a thermometer necessary for
simple distillation operation was charged with 720 g of dimethyl
sulfoxide (purity: 99.997 area %) (pure dimethyl sulfoxide: 719.98
g) and 80 g of ion-exchanged water without adding any additive.
After substituting the inside of the flask with nitrogen, a rubber
balloon filled with nitrogen was mounted at the top of the Dimroth
condenser to seal the flask. The flask was heated in an oil bath
maintained at 200.degree. C., and a point in time when distillation
started was considered to be a startup time. After collecting 100
ml containing water as an early distillate, a main distillation
operation was performed in which the temperature of the oil bath
was increased to 230.degree. C., and distillate was collected until
the amount of a residual liquid in the flask reached 11 g (the
amount of water in the residual liquid: 0.0 g). Heating time from
the startup was 3 hours.
[0075] Dimethyl sulfoxide purity in the main distillate was 99.988
area % as shown in Table 1 which indicated reduced dimethyl
sulfoxide purity.
[0076] Dimethyl sulfoxide purity in the residual liquid was 99.922
area % as shown in Table As shown in Table 1, dimethyl sulfoxide
purity in a mixed liquid of the distillate after the distillation
(the main distillate and the early distillate) and the residual
liquid after the distillation (a post-distillation mixed liquid)
was 99.987 area %, and the amount of decomposition was 0.010% that
was larger than Examples from 1 to 3.
Comparative Example 2
[0077] A 1-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver, a stirrer, and a thermometer necessary for
simple distillation operation was charged with 720 g of dimethyl
sulfoxide (purity: 99.997 area %) (pure dimethyl sulfoxide: 719.98
g), 80 g of ion-exchanged water, and as an additive, 0.144 g of
sodium hydroxide (0.02 g with respect to 100 g of the pure dimethyl
sulfoxide). After substituting the inside of the flask with
nitrogen, a rubber balloon filled with nitrogen was mounted at the
top of the Dimroth condenser to seal the flask. The flask was
heated in an oil bath maintained at 200.degree. C., and a point in
time when distillation started was considered to be a startup time.
After collecting 100 ml containing water as an early distillate, a
main distillation operation was performed in which the temperature
of the oil bath was increased to 230.degree. C., and distillate was
collected until the amount of a residual liquid in the flask
reached 7 g (the amount of water in the residual liquid: 0.0 g) and
the amount of the additive after the distillation reached 2 g with
respect to 100 g of the pure dimethyl sulfoxide. Heating time from
the startup was 3 hours.
[0078] Dimethyl sulfoxide purity in the main distillate was 99.960
area % as shown in Table 1 which indicated reduced dimethyl
sulfoxide purity.
[0079] Dimethyl sulfoxide purity in the residual liquid was 99.568
area % as shown in Table 1. Dimethyl sulfoxide was slightly
decomposed when heated for 3 hours at 147 to 170.degree. C.
(temperatures in the flask) in the early distillation operation and
at 170 to 191.degree. C. (temperatures in the flask) in the main
distillation operation.
[0080] As shown in Table 1, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.956 area
%, and the amount of decomposition was 0.041% that was larger than
Examples from 1 to 3.
Comparative Example 3
[0081] A 1-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver, a stirrer, and a thermometer necessary for
simple distillation operation was charged with 720 g of dimethyl
sulfoxide (purity: 99.997 area %) (pure dimethyl sulfoxide: 719.98
g), 80 g of ion-exchanged water, and as an additive, 7.2 g of
potassium carbonate (1 g with respect to 100 g of the pure dimethyl
sulfoxide). After substituting the inside of the flask with
nitrogen, a rubber balloon filled with nitrogen was mounted at the
top of the Dimroth condenser to seal the flask. The flask was
heated in an oil bath maintained at 200.degree. C., and a point in
time when distillation started was considered to be a startup time.
After collecting 100 ml containing water as an early distillate, a
main distillation operation was performed in which the temperature
of the oil bath was increased to 230.degree. C., and distillate was
collected until the amount of a residual liquid in the flask
reached 18 g (the amount of water in the residual liquid: 0.0 g)
and the amount of the additive after the distillation reached 67 g
with respect to 100 g of the pure dimethyl sulfoxide. Heating time
from the startup was 3 hours.
[0082] Dimethyl sulfoxide purity in the main distillate was 99.984
area % as shown in Table 1 which indicated reduced dimethyl
sulfoxide purity.
[0083] Dimethyl sulfoxide purity in the residual liquid was 99.617
area % as shown in Table 1. Dimethyl sulfoxide was slightly
decomposed when heated for 3 hours at 147 to 170.degree. C.
(temperatures in the flask) in the early distillation operation and
at 170 to 191.degree. C. (temperatures in the flask) in the main
distillation operation.
[0084] As shown in Table 1, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.975 area
%, and the amount of decomposition was 0.022% that was larger than
Examples from 1 to 3.
Comparative Example 4
[0085] A 1-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver, a stirrer, and a thermometer necessary for
simple distillation operation was charged with 720 g of dimethyl
sulfoxide (purity: 99.997 area %) (pure dimethyl sulfoxide: 719.98
g), 80 g of ion-exchanged water, and as an additive, 0.216 g of
sodium carbonate (0.03 g with respect to 100 g of the pure dimethyl
sulfoxide). Without performing nitrogen substitution, a rubber
balloon filled with air was mounted at the top of the Dimroth
condenser to seal the inside of the flask in the air. The flask was
heated in an oil bath maintained at 200.degree. C., in which a
point in time when distillation started was considered to be a
startup time. After collecting 100 ml containing water as an early
distillate, a main distillation operation was performed in which
the temperature of the oil bath was increased to 230.degree. C.,
and distillate was collected until the amount of a residual liquid
in the flask reached 22 g (the amount of water in the residual
liquid: 0.0 g) and the amount of the additive after the
distillation reached 0.99 g with respect to 100 g of the pure
dimethyl sulfoxide. Heating time from the startup was 3 hours.
[0086] Dimethyl sulfoxide purity in the main distillate was 99.982
area % as shown in Table 1 which indicated reduced dimethyl
sulfoxide purity.
[0087] Dimethyl sulfoxide purity in the residual liquid was 99.844
area % as shown in Table 1. Dimethyl sulfoxide was slightly
decomposed when heated for 3 hours at 147 to 170.degree. C.
(temperatures in the flask) in the early distillation operation and
at 171 to 193.degree. C. (temperatures in the flask) in the main
distillation operation.
[0088] As shown in Table 1, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.978 area
%, and the amount of decomposition was 0.019% that was larger than
Examples from 1 to 3.
TABLE-US-00001 TABLE 1 Purity Addi- in post- Charged liquid Main
distillate Residual liquid tive distilla- Amount Atmo- Dimethyl
Amount Amount Temper- Dimethyl Dimethyl Amount con- tion of sphere
sulfoxide of of atures sulfoxide sulfoxide of centra- mixed
decompo- Addi- in purity additive water in flask purity purity
additive tion liquid sition tive system (area %) (g) (g) Pressure
(.degree. C.) (area %) (area %) (g) rate (area %) (area %) Ex 1
Sodium Nitrogen 99.997 0.001 11 Atmo- 170-191 99.997 99.903 0.09 90
99.994 0.003 carbonate spheric Pressure Ex 2 Sodium Nitrogen 99.997
0.1 11 Atmo- 171-191 99.995 99.964 1 10 99.991 0.006 carbonate
spheric Pressure Ex 3 Sodium Nitrogen 99.997 1 11 Atmo- 170-191
99.994 99.892 82 82 99.992 0.005 carbonate spheric Pressure Com
None Nitrogen 99.997 -- 11 Atmo- 171-192 99.988 99.922 -- -- 99.987
0.010 Ex 1 spheric Pressure Com Sodium Nitrogen 99.997 0.02 11
Atmo- 170-191 99.960 99.568 2 100 99.956 0.041 Ex 2 hydroxide
spheric Pressure Com Potassium Nitrogen 99.997 1 11 Atmo- 170-191
99.984 99.617 67 67 99.975 0.022 Ex 3 carbonate spheric Pressure
Com Sodium Air 99.997 0.03 11 Atmo- 171-193 99.982 99.844 0.99 33
99.978 0.019 Ex 4 carbonate spheric Pressure Amount of additive is
the amount of an additive with respect to 100 g of the pure
dimethyl sulfoxide in the liquid. Amount of water in charged liquid
is the amount of water with respect to 100 g of the pure dimethyl
sulfoxide in the liquid.
[0089] In Examples from 1 to 3, high purity dimethyl sulfoxide was
obtained as the main distillates. On the other hand, the dimethyl
sulfoxide purities in the main distillates obtained in Comparative
Examples from 1 to 4 were lower than those in Examples from 1 to
3.
EXAMPLE 4
[0090] A 10-L four-necked flask equipped with a distillation column
filled with a structured packing, a distillate receiver, a stirrer,
a thermometer, and a Dimroth condenser provided at the top of the
distillation column was charged with 4830 g of dimethyl sulfoxide
(purity: 99.998 area %) (pure dimethyl sulfoxide: 4829.9 g), 1998 g
of ion-exchanged water, and, as an additive, 1.4 g of sodium
carbonate (0.03 g with respect to 100 g of the pure dimethyl
sulfoxide). After substituting the inside of the flask with
nitrogen, a rubber balloon filled with nitrogen was mounted at the
top of the Dimroth condenser to seal the flask. The flask was
heated in an oil bath maintained at from 145 to 191.degree. C.
under a pressure of from 20 to 720 Torr, and a point in time when
distillation started was considered to be a startup time. After
collecting 2289 g containing water as an early distillate, a main
distillation operation was performed in which the flask was heated
in an oil bath at from 153 to 192.degree. C. under a pressure of 20
Torr, and main distillate during a time when the temperature in the
flask ranged from 110 to 112.degree. C. was collected until the
amount of a residual liquid in the flask reached 688 g (the amount
of water in the residual liquid: 0.0 g) and the amount of the
additive after the distillation reached 0.2 g with respect to 100 g
of the pure dimethyl sulfoxide. Heating time from the startup was
12 hours.
[0091] Dimethyl sulfoxide purity in the main distillate was 99.999
area % as shown in Table 2 so that high purity dimethyl sulfoxide
was obtained.
[0092] Dimethyl sulfoxide purity in the residual liquid was 99.975
area % as shown in Table 2. Even when heated, dimethyl sulfoxide
was hardly decomposed. Since the amount of the sodium carbonate in
the residual liquid was 0.2 g with respect to 100 g of the pure
dimethyl sulfoxide in the residual liquid, the sodium carbonate was
concentrated to 7 times by the dimethyl sulfoxide distillation.
[0093] As shown in Table 2, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate) and the residual liquid after the distillation (a
post-distillation mixed liquid) was 99.992 area % and the amount of
decomposition was 0.006%, extremely small. In Example 4, high
purity dimethyl sulfoxide was obtained as the main distillate.
TABLE-US-00002 TABLE 2 Purity Charged liquid Main distillate
Residual liquid in post- Amount Dimethyl Amount Amount Temper-
Dimethyl Dimethyl Amount distilla- of sulfoxide of of atures
sulfoxide sulfoxide of Additive tion mixed decompo- purity additive
water in flask purity purity additive concentra- liquid sition
Additive (area %) (g) (g) Pressure (.degree. C.) (area %) (area %)
(g) tion rate (area %) (area %) Ex 4 Sodium 99.998 0.03 41 Reduced
110-112 99.999 99.975 0.2 7 99.992 0.006 carbonate pressure Amount
of additive is the amount of an additive with respect to 100 g of
the pure dimethyl sulfoxide in the liquid. Amount of water in
charged liquid is the amount of water with respect to 100 g of the
pure dimethyl sulfoxide in the liquid.
EXAMPLE 5
[0094] A 1-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver, a stirrer, and a thermometer necessary for
simple distillation operation was charged with 400 g of dimethyl
sulfoxide (purity: 99.995 area %) (pure dimethyl sulfoxide: 399.98
g), 400 g of ion-exchanged water, and as an additive, 0.004 g of
sodium carbonate (0.001 g with respect to 100 g of the pure
dimethyl sulfoxide). After substituting the inside of the flask
with nitrogen, a rubber balloon filled with nitrogen was mounted at
the top of the Dimroth condenser to seal the flask. The flask was
heated in an oil bath maintained at 220.degree. C., and a point in
time when distillation started was considered to be a startup time.
After collecting 500 ml containing water as an early distillate, a
main distillation operation was performed in which the temperature
of the oil bath was increased to 230.degree. C., and distillate was
collected until the amount of a residual liquid in the flask
reached 9 g (the amount of water in the residual liquid: 0.0 g) and
the amount of the additive after the distillation reached 0.044 g
with respect to 100 g of the pure dimethyl sulfoxide. Heating time
from the startup was 3 hours.
[0095] Dimethyl sulfoxide purity in the main distillate was 99.994
area % as shown in Table 3 so that high purity dimethyl sulfoxide
was obtained.
[0096] Dimethyl sulfoxide purity in the residual liquid was 99.932
area % as shown in Table 3. Dimethyl sulfoxide was hardly
decomposed even when heated for 3 hours at 108 to 192.degree. C.
(temperatures in the flask) in the early distillation operation and
at 192 to 193.degree. C. (temperatures in the flask) in the main
distillation operation. Since the amount of the sodium carbonate in
the residual liquid was 0.044 g with respect to 100 g of the pure
dimethyl sulfoxide in the residual liquid, the sodium carbonate was
concentrated to 44 times by the dimethyl sulfoxide
distillation.
[0097] As shown in Table 3, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.992 area
%, and the amount of decomposition was 0.003%, extremely small.
EXAMPLE 6
[0098] Example 6 was performed in the same manner as Example 5
except that the amount of sodium carbonate added was changed to
0.024 g (0.006 g with respect to 100 g of the pure dimethyl
sulfoxide), and distillate was collected until the amount of a
residual liquid in the flask reached 32 g (the amount of water in
the residual liquid: 0.0 g) and the amount of the additive after
the distillation reached 0.075 g with respect to 100 g of the pure
dimethyl sulfoxide. Heating time from the startup was 2.5
hours.
[0099] Dimethyl sulfoxide purity in the main distillate was 99.992
area % as shown in Table 3 so that high purity dimethyl sulfoxide
was obtained.
[0100] Dimethyl sulfoxide purity in the residual liquid was 99.964
area % as shown in Table 3. Dimethyl sulfoxide was hardly
decomposed even when heated for 2.5 hours at 108 to 192.degree. C.
(temperatures in the flask) in the early distillation operation and
at 192 to 193.degree. C. (temperatures in the flask) in the main
distillation operation. Since the amount of the sodium carbonate in
the residual liquid was 0.075 g with respect to 100 g of the pure
dimethyl sulfoxide in the residual liquid, the sodium carbonate was
concentrated to 13 times by the dimethyl sulfoxide
distillation.
[0101] As shown in Table 3, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.988 area
%, and the amount of decomposition was 0.007%, extremely small.
EXAMPLE 7
[0102] Example 7 was performed in the same manner as Example 5
except that the amount of sodium carbonate added was changed to
0.08 g (0.02 g with respect to 100 g of pure dimethyl sulfoxide),
and distillate was collected until the amount of a residual liquid
in the flask reached 34 g (the amount of water in the residual
liquid: 0.0 g) and the amount of the additive after the
distillation reached 0.24 g with respect to 100 g of the pure
dimethyl sulfoxide. Heating time from the startup was 2.5
hours.
[0103] Dimethyl sulfoxide purity in the main distillate was 99.991
area % as shown in Table 3 so that high purity dimethyl sulfoxide
was obtained.
[0104] Dimethyl sulfoxide purity in the residual liquid was 99.965
area % as shown in Table 3. Dimethyl sulfoxide was hardly
decomposed even when heated for 2.5 hours at 108 to 192.degree. C.
(temperatures in the flask) in the early distillation operation and
at 192 to 193.degree. C. (temperatures in the flask) in the main
distillation operation. Since the amount of the sodium carbonate in
the residual liquid was 0.24 g with respect to 100 g of the pure
dimethyl sulfoxide in the residual liquid, the sodium carbonate was
concentrated to 12 times by the dimethyl sulfoxide
distillation.
[0105] As shown in Table 3, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.988 area
%, and the amount of decomposition was 0.007%, extremely small.
EXAMPLE 8
[0106] Example 8 was performed in the same manner as Example 5
except that the amount of sodium carbonate added was changed to 0.
4 g (0.1 g with respect to 100 g of pure dimethyl sulfoxide), and
distillate was collected until the amount of a residual liquid in
the flask reached 28 g (the amount of water in the residual liquid:
0.0 g) and the amount of the additive after the distillation
reached 1.4 g with respect to 100 g of the pure dimethyl sulfoxide.
Heating time from the startup was 2.5 hours.
[0107] Dimethyl sulfoxide purity in the main distillate was 99.991
area % as shown in Table 3 so that high purity dimethyl sulfoxide
was obtained.
[0108] Dimethyl sulfoxide purity in the residual liquid was 99.956
area % as shown in Table 3. Dimethyl sulfoxide was hardly
decomposed even when heated for 2.5 hours at 108 to 192.degree. C.
(temperatures in the flask) in the early distillation operation and
at 192 to 193.degree. C. (temperatures in the flask) in the main
distillation operation. Since the amount of the sodium carbonate in
the residual liquid was 1.4 g with respect to 100 g of the pure
dimethyl sulfoxide in the residual liquid, the sodium carbonate was
concentrated to 14 times by the dimethyl sulfoxide
distillation.
[0109] As shown in Table 3, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.987 area
%, and the amount of decomposition was 0.008%, extremely small.
EXAMPLE 9
[0110] Example 9 was performed in the same manner as Example 5
except that the amount of sodium carbonate added was changed to 4 g
(1 g with respect to 100 g of pure dimethyl sulfoxide), and
distillate was collected until the amount of a residual liquid in
the flask reached 42 g (the amount of water in the residual liquid:
0.0 g) and the amount of the additive after the distillation
reached 11 g with respect to 100 g of the pure dimethyl sulfoxide.
Heating time from the startup was 2.5 hours.
[0111] Dimethyl sulfoxide purity in the main distillate was 99.995
area % as shown in Table 3 so that high purity dimethyl sulfoxide
was obtained.
[0112] Dimethyl sulfoxide purity in the residual liquid was 99.985
area % as shown in Table 3. Dimethyl sulfoxide was hardly
decomposed even when heated for 2.5 hours at 108 to 192.degree. C.
(temperatures in the flask) in the early distillation operation and
at 192 to 193.degree. C. (temperatures in the flask) in the main
distillation operation. Since the amount of the sodium carbonate in
the residual liquid was 11 g with respect to 100 g of the pure
dimethyl sulfoxide in the residual liquid, the sodium carbonate was
concentrated to 11 times by the dimethyl sulfoxide
distillation.
[0113] As shown in Table 3, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.992 area
%, and the amount of decomposition was 0.003%, extremely small.
EXAMPLE 10
[0114] Example 10 was performed in the same manner as Example 5
except that the amount of sodium carbonate added was changed to 4 g
(1 g with respect to 100 g of pure dimethyl sulfoxide), and
distillate was collected until the amount of a residual liquid in
the flask reached 17 g (the amount of water in the residual liquid:
0.0 g) and the amount of the additive after the distillation
reached 31 g with respect to 100 g of the pure dimethyl sulfoxide.
Heating time from the startup was 3 hours.
[0115] Dimethyl sulfoxide purity in the main distillate was 99.994
area % as shown in Table 3 so that high purity dimethyl sulfoxide
was obtained.
[0116] Dimethyl sulfoxide purity in the residual liquid was 99.968
area % as shown in Table 3. Dimethyl sulfoxide was hardly
decomposed even when heated for 3 hours at 108 to 192.degree. C.
(temperatures in the flask) in the early distillation operation and
at 192 to 193.degree. C. (temperatures in the flask) in the main
distillation operation. Since the amount of the sodium carbonate in
the residual liquid was 31 g with respect to 100 g of the pure
dimethyl sulfoxide in the residual liquid, the sodium carbonate was
concentrated to 31 times by the dimethyl sulfoxide
distillation.
[0117] As shown in Table 3, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.992 area
%, and the amount of decomposition was 0.003%, extremely small.
Comparative Example 5
[0118] Comparative Example 5 was performed in the same manner as
Example 5 except for not adding sodium carbonate, and distillate
was collected until the amount of a residual liquid in the flask
reached 23 g (the amount of water in the residual liquid: 0.0 g).
Heating time from the startup was 3 hours.
[0119] Dimethyl sulfoxide purity in the main distillate was 99.978
area % as shown in Table 3 which indicated reduced dimethyl
sulfoxide purity.
[0120] Dimethyl sulfoxide purity in the residual liquid was 99.961
area % as shown in Table 3. Dimethyl sulfoxide was slightly
decomposed when heated for 3 hours at 108 to 192.degree. C.
(temperatures in the flask) in the early distillation operation and
at 192 to 193.degree. C. (temperatures in the flask) in the main
distillation operation. As shown in Table 3, dimethyl sulfoxide
purity in a mixed liquid of the distillate after the distillation
(the main distillate and the early distillate) and the residual
liquid after the distillation (a post-distillation mixed liquid)
was 99.979 area %, and the amount of decomposition was 0.016% that
was larger than Examples 5 to 10. Additionally, as a decomposition
product of the dimethyl sulfoxide, a small amount of polymer, which
seemed to be polyacetal, was deposited on the tool after the
distillation.
Comparative Example 6
[0121] Comparative Example 6 was performed in the same manner as
Example 5 except that the kind of the additive was changed to
sodium hydroxide and the amount of the additive added was changed
to 0.08 g (0.02 g with respect to 100 g of pure dimethyl
sulfoxide), and distillate was collected until the amount of a
residual liquid in the flask reached 35 g (the amount of water in
the residual liquid: 0.0 g) and the amount of the additive after
the distillation reached 0.23 g with respect to 100 g of the pure
dimethyl sulfoxide. Heating time from the startup was 2.5
hours.
[0122] Dimethyl sulfoxide purity in the main distillate was 99.980
area % as shown in Table 3 which indicated reduced dimethyl
sulfoxide purity.
[0123] Dimethyl sulfoxide purity in the residual liquid was 99.926
area % as shown in Table 3. Dimethyl sulfoxide was slightly
decomposed when heated for 2.5 hours at 108 to 192.degree. C.
(temperatures in the flask) in the early distillation operation and
at 192 to 193.degree. C. (temperatures in the flask) in the main
distillation operation. As shown in Table 3, dimethyl sulfoxide
purity in a mixed liquid of the distillate after the distillation
(the main distillate and the early distillate) and the residual
liquid after the distillation (a post-distillation mixed liquid)
was 99.971 area %, and the amount of decomposition was 0.024% that
was larger than Examples from 5 to 10.
Comparative Example 7
[0124] Comparative Example 7 was performed in the same manner as
Example 5 except that the kind of the additive was changed to
sodium hydroxide and the amount of the additive added was changed
to 0.4 g (0.1 g with respect to 100 g of pure dimethyl sulfoxide),
and distillate was collected until the amount of a residual liquid
in the flask reached 32 g (the amount of water in the residual
liquid: 0.0 g) and the amount of the additive after the
distillation reached 1.3 g with respect to 100 g of the pure
dimethyl sulfoxide. Heating time from the startup was 2.5
hours.
[0125] Dimethyl sulfoxide purity in the main distillate was 99.972
area % as shown in Table 3 which indicated reduced dimethyl
sulfoxide purity.
[0126] Dimethyl sulfoxide purity in the residual liquid was 99.910
area % as shown in Table 3. Dimethyl sulfoxide was slightly
decomposed when heated for 2.5 hours at 108 to 192.degree. C.
(temperatures in the flask) in the early distillation operation and
at 192 to 193.degree. C. (temperatures in the flask) in the main
distillation operation. As shown in Table 3, dimethyl sulfoxide
purity in a mixed liquid of the distillate after the distillation
(the main distillate and the early distillate) and the residual
liquid after the distillation (a post-distillation mixed liquid)
was 99.963 area %, and the amount of decomposition was 0.032% that
was larger than Examples from 5 to 10.
TABLE-US-00003 TABLE 3 Purity Charged liquid Main distillate
Residual liquid in post- Amount Dimethyl Amount Amount Temper-
Dimethyl Dimethyl Amount distilla- of sulfoxide of of atures
sulfoxide sulfoxide of Additive tion mixed decompo- purity additive
water in flask purity purity additive concentra- liquid sition
Additive (area %) (g) (g) Pressure (.degree. C.) (area %) (area %)
(g) tion rate (area %) (area %) Ex 5 Sodium 99.995 0.001 100
Atmospheric 192-193 99.994 99.932 0.044 44 99.992 0.003 carbonate
pressure Ex 6 Sodium 99.995 0.006 100 Atmospheric 192-193 99.992
99.964 0.075 13 99.988 0.007 carbonate pressure Ex 7 Sodium 99.995
0.02 100 Atmospheric 192-193 99.991 99.965 0.24 12 99.988 0.007
carbonate pressure Ex 8 Sodium 99.995 0.1 100 Atmospheric 192-193
99.991 99.956 1.4 14 99.987 0.008 carbonate pressure Ex 9 Sodium
99.995 1 100 Atmospheric 192-193 99.995 99.985 11 11 99.992 0.003
carbonate pressure Ex 10 Sodium 99.995 1 100 Atmospheric 192-193
99.994 99.968 31 31 99.992 0.003 carbonate pressure Com None 99.995
-- 100 Atmospheric 192-193 99.978 99.961 -- -- 99.979 0.016 Ex 5
pressure Com Sodium 99.995 0.02 100 Atmospheric 192-193 99.980
99.926 0.23 12 99.971 0.024 Ex 6 hydroxide pressure Com Sodium
99.995 0.1 100 Atmospheric 192-193 99.972 99.910 1.3 13 99.963
0.032 Ex 7 hydroxide pressure Amount of additive is the amount of
an additive with respect to 100 g of the pure dimethyl sulfoxide in
the liquid. Amount of water in charged liquid is the amount of
water with respect to 100 g of the pure dimethyl sulfoxide in the
liquid.
[0127] In Examples 5 to 10, high purity dimethyl sulfoxide was
obtained as the main distillates. On the other hand, the dimethyl
sulfoxide purities in the main distillates obtained in Comparative
Examples 5 to 7 were lower than those in Examples 5 to 10.
EXAMPLE 11
[0128] A 1-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver, a stirrer, and a thermometer necessary for
simple distillation operation was charged with 720 g of dimethyl
sulfoxide (purity: 99.995 area %) (pure dimethyl sulfoxide: 719.96
g) and, as an additive, 7.2 g of sodium carbonate (1 g with respect
to 100 g of the pure dimethyl sulfoxide). After substituting the
inside of the flask with nitrogen, a rubber balloon filled with
nitrogen was mounted at the top of the Dimroth condenser to seal
the flask. The flask was heated in an oil bath maintained at
220.degree. C., and a point in time when distillation started was
considered to be a startup time. Distillate was collected until the
amount of a residual liquid in the flask reached 56 g (the amount
of water in the residual liquid: 0.0 g) and the amount of the
additive after the distillation reached 15 g with respect to 100 g
of the pure dimethyl sulfoxide. Heating time from the startup was
2.5 hours.
[0129] Dimethyl sulfoxide purity in the main distillate was 99.990
area % as shown in Table 4 so that high purity dimethyl sulfoxide
was obtained.
[0130] Dimethyl sulfoxide purity in the residual liquid was 99.930
area % as shown in Table 4. Dimethyl sulfoxide was hardly
decomposed even when heated for 2.5 hours at 192 to 193.degree. C.
(temperatures in the flask). Since the amount of the sodium
carbonate in the residual liquid was 15 g with respect to 100 g of
the pure dimethyl sulfoxide in the residual liquid, the sodium
carbonate was concentrated to 15 times by the dimethyl sulfoxide
distillation.
[0131] As shown in Table 4, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate) and the residual liquid after the distillation (a
post-distillation mixed liquid) was 99.986 area %, and the amount
of decomposition was 0.009%, extremely small.
EXAMPLE 12
[0132] A 1-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver. a stirrer, and a thermometer necessary for
simple distillation operation was charged with 720 g of dimethyl
sulfoxide (purity: 99.995 area %) (pure dimethyl sulfoxide: 719.96
g). Next, as an additive, 7.2 g of sodium carbonate monohydrate
(0.86 g of the sodium carbonate with respect to 100 g of the pure
dimethyl sulfoxide) was charged therein. After substituting the
inside of the flask with nitrogen, a rubber balloon filled with
nitrogen was mounted at the top of the Dimroth condenser to seal
the flask. The flask was heated in an oil bath maintained at
220.degree. C., and a point in time when distillation started was
considered to be a startup time. After collecting 12 ml containing
water as an early distillate, a main distillation operation was
performed in which the temperature of the oil bath was increased to
230.degree. C., and distillate was collected until the amount of a
residual liquid in the flask reached 61 g (the amount of water in
the residual liquid: 0.0 g) and the amount of the sodium carbonate
after the distillation reached 11.4 g with respect to 100 g of the
pure dimethyl sulfoxide. Heating time from the startup was 2.5
hours.
[0133] Dimethyl sulfoxide purity in the main distillate was 99.990
area % as shown in Table 4 so that high purity dimethyl sulfoxide
was obtained.
[0134] Dimethyl sulfoxide purity in the residual liquid was 99.936
area % as shown in Table 4. Dimethyl sulfoxide was hardly
decomposed even when heated for 2.5 hours at 191 to 192.degree. C.
(temperatures in the flask) in the early distillation operation and
at 192 to 193.degree. C. (temperatures in the flask) in the main
distillation operation. Since the amount of the sodium carbonate in
the residual liquid was 11.4 g with respect to 100 g of the pure
dimethyl sulfoxide in the residual liquid, the sodium carbonate was
concentrated to 13 times by the dimethyl sulfoxide
distillation.
[0135] As shown in Table 4, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.986 area
%, and the amount of decomposition was 0.009%, extremely small.
EXAMPLE 13
[0136] A 1-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver, a stirrer, and a thermometer necessary for
simple distillation operation was charged with 720 g of dimethyl
sulfoxide (purity: 99.995 area %) (pure dimethyl sulfoxide: 719.96
g). Next, as an additive, 7.2 g of sodium carbonate decahydrate
(0.37 g of the sodium carbonate with respect to 100 g of the pure
dimethyl sulfoxide) was charged therein. After substituting the
inside of the flask with nitrogen, a rubber balloon filled with
nitrogen was mounted at the top of the Dimroth condenser to seal
the flask. The flask was heated in an oil bath maintained at
220.degree. C., and a point in time when distillation started was
considered to be a startup time. After collecting 16 ml containing
water as an early distillate, a main distillation operation was
performed in which the temperature of the oil bath was increased to
230.degree. C., and distillate was collected until the amount of a
residual liquid in the flask reached 82 g (the amount of water in
the residual liquid: 0.0 g) and the amount of the sodium carbonate
after the distillation reached 3.4 g with respect to 100 g of the
pure dimethyl sulfoxide. Heating time from the startup was 2.8
hours.
[0137] Dimethyl sulfoxide purity in the main distillate was 99.990
area % as shown in Table 4 so that high purity dimethyl sulfoxide
was obtained.
[0138] Dimethyl sulfoxide purity in the residual liquid was 99.951
area % as shown in Table 4. Dimethyl sulfoxide was hardly
decomposed even when heated for 2.8 hours at 187 to 190.degree. C.
(temperatures in the flask) in the early distillation operation and
at 191 to 193.degree. C. (temperatures in the flask) in the main
distillation operation. Since the amount of the sodium carbonate in
the residual liquid was 3.4 g with respect to 100 g of the pure
dimethyl sulfoxide in the residual liquid, the sodium carbonate was
concentrated to 9 times by the dimethyl sulfoxide distillation.
[0139] As shown in Table 4, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.986 area
%, and the amount of decomposition was 0.009%, extremely small.
EXAMPLE 14
[0140] A 1-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver, a stirrer, and a thermometer necessary for
simple distillation operation was charged with 720 g of dimethyl
sulfoxide (purity: 99.996 area %) (pure dimethyl sulfoxide: 759.97
g). Next, as an additive, there was charged a sodium carbonate
aqueous solution prepared by dissolving 7.2 g of sodium carbonate
(1 g with respect to 100 g of the pure dimethyl sulfoxide) in 40 g
of ion-exchanged water. After substituting the inside of the flask
with nitrogen, a rubber balloon filled with nitrogen was mounted at
the top of the Dimroth condenser to seal the flask. The flask was
heated in an oil bath maintained at 220.degree. C., and a point in
time when distillation started was considered to be a startup time.
After collecting 140 ml containing water as an early distillate, a
main distillation operation was performed in which the temperature
of the oil bath was increased to 230.degree. C., and distillate was
collected until the amount of a residual liquid in the flask
reached 56 g (the amount of water in the residual liquid: 0.0 g)
and the amount of the sodium carbonate after the distillation
reached 15 g with respect to 100 g of the pure dimethyl sulfoxide.
Heating time from the startup was 2 hours.
[0141] Dimethyl sulfoxide purity in the main distillate was 99.995
area % as shown in Table 4 so that high purity dimethyl sulfoxide
was obtained.
[0142] Dimethyl sulfoxide purity in the residual liquid was 99.956
area % as shown in Table 4. Dimethyl sulfoxide was hardly
decomposed even when heated for 2 hours at 162 to 191.degree. C.
(temperatures in the flask) in the early distillation operation and
at 192 to 193.degree. C. (temperatures in the flask) in the main
distillation operation. Since the amount of the sodium carbonate in
the residual liquid was 15 g with respect to 100 g of the pure
dimethyl sulfoxide in the residual liquid, the sodium carbonate was
concentrated to 15 times by the dimethyl sulfoxide
distillation.
[0143] As shown in Table 4, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.992 area
%, and the amount of decomposition was 0.004%, extremely small.
EXAMPLE 15
[0144] A 1-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver, a stirrer, and a thermometer necessary for
simple distillation operation was charged with 400 g of dimethyl
sulfoxide (purity: 99.996 area %) (pure dimethyl sulfoxide: 399.98
g). Next, as an additive, there was charged a sodium carbonate
aqueous solution prepared by dissolving 0.4 g of sodium carbonate
(0.1 g with respect to 100 g of the pure dimethyl sulfoxide) in 400
g of ion-exchanged water. After substituting the inside of the
flask with nitrogen, a rubber balloon filled with nitrogen was
mounted at the top of the Dimroth condenser to seal the flask.
Under atmospheric pressure, the flask was heated in an oil bath
maintained at 220.degree. C. and a point in time when distillation
started was considered to be a startup time. An amount of 500 ml
containing water as an early distillate was collected. Next, as a
main distillation operation, the temperature of the oil bath was
decreased to 170.degree. C., and under a pressure of from 150 to
170 Torr, distillate was collected until the amount of a residual
liquid in the flask reached 22 g (the amount of water in the
residual liquid: 0.0 g) and the amount of the sodium carbonate
after the distillation reached 1.9 g with respect to 100 g of the
pure dimethyl sulfoxide. Heating time from the startup was 3
hours,
[0145] Dimethyl sulfoxide purity in the main distillate was 99.997
area % as shown in Table 4 so that high purity dimethyl sulfoxide
was obtained.
[0146] Dimethyl sulfoxide purity in the residual liquid was 99.938
area % as shown in Table 4. Dimethyl sulfoxide was hardly
decomposed even when heated for 3 hours at 108 to 193.degree. C.
(temperatures in the flask) in the early distillation operation and
at 138 to 140.degree. C. (temperatures in the flask) in the main
distillation operation. Since the amount of the sodium carbonate in
the residual liquid was 1.9 g with respect to 100 g of the pure
dimethyl sulfoxide in the residual liquid, the sodium carbonate was
concentrated to 19 times by distillation of dimethyl sulfoxide.
[0147] As shown in Table 4, dimethyl sulfoxide purity in a mixed
liquid of the distillate after the distillation (the main
distillate and the early distillate) and the residual liquid after
the distillation (a post-distillation mixed liquid) was 99.989 area
%, and the amount of decomposition was 0.007%, extremely small.
Comparative Example 8
[0148] Al-L four-necked flask equipped with a Dimroth condenser, a
distillate receiver, a stirrer, and a thermometer necessary for
simple distillation operation was charged with 201 g of dimethyl
sulfoxide (purity: 99.996 area %) (pure dimethyl sulfoxide: 200.99
g), without charging any additive. After substituting the inside of
the flask with nitrogen, a rubber balloon filled with nitrogen was
mounted at the top of the Dimroth condenser to seal the flask. The
flask was heated in an oil bath maintained at 220.degree. C., and a
point in time when distillation started was considered to be a
startup time. When distillate was collected until the amount of a
residual liquid in the flask reached 50 g (the amount of water in
the residual liquid: 0.0 g), dimethyl sulfoxide purity in the main
distillate was 99.972 area % as shown in Table 4. Due to the
reduction of the dimethyl sulfoxide purity, the distillation was
stopped. Heating time from the startup was 2 hours. Dimethyl
sulfoxide purity in the residual liquid was 99.986 area % as shown
in Table 4. As shown in Table 4, dimethyl sulfoxide purity in a
mixed liquid of the distillate after the distillation (the main
distillate) and the residual liquid after the distillation (a
post-distillation mixed liquid) was 99.975 area %, and the amount
of decomposition was 0.021% that was larger than Example 11.
TABLE-US-00004 TABLE 4 Purity Charged liquid Main distillate
Residual liquid in post- Amount Dimethyl Amount Amount Temper-
Dimethyl Dimethyl Amount distilla- of sulfoxide of of atures
sulfoxide sulfoxide of Additive tion mixed decompo- purity additive
water in flask purity purity additive concentra- liquid sition
Additive (area %) (g) (g) Pressure (.degree. C.) (area %) (area %)
(g) tion rate (area %) (area %) Ex 11 Sodium 99.995 1 0 Atmospheric
192-193 99.990 99.930 15 15 99.986 0.009 carbonate pressure Ex 12
Sodium 99.995 0.86 0.14 Atmospheric 192-193 99.990 99.936 11.4 13
99.986 0.009 carbonate pressure Ex 13 Sodium 99.995 0.37 0.63
Atmospheric 191-193 99.990 99.951 3.4 9 99.986 0.009 carbonate
pressure Ex 14 Sodium 99.996 1 5.3 Atmospheric 192-193 99.995
99.956 15 15 99.992 0.004 carbonate pressure Ex 15 Sodium 99.996
0.1 100 Reduced 138-140 99.997 99.938 1.9 19 99.989 0.007 carbonate
pressure Com None 99.996 -- 0 Atmospheric 192-193 99.972 99.986 --
-- 99.975 0.021 Ex 8 pressure Amount of additive is the amount of
an additive with respect to 100 g of the pure dimethyl sulfoxide in
the liquid. Amount of water in charged liquid is the amount of
water with respect to 100 g of the pure dimethyl sulfoxide in the
liquid.
[0149] In Examples 11 to 15, high purity dimethyl sulfoxide was
obtained as the main distillates. The dimethyl sulfoxide purity
obtained in Comparative Example 8 was lower than Example 11.
[0150] The above results showed that our method of purifying
dimethyl sulfoxide provided the high purity dimethyl sulfoxide as
the main distillates.
[0151] Additionally, as purification proceeded by distilling the
dimethyl sulfoxide-containing liquid, the decomposition inhibitor
remained at a bottom of the distillation column during the
purification, thereby increasing concentration of the decomposition
inhibitor included in the residual liquid during distillation. In
the use of sodium carbonate as the decomposition inhibitor, even
when dimethyl sulfoxide was distilled out and the sodium carbonate
concentration increased, decomposition of dimethyl sulfoxide was
not promoted, and dimethyl sulfoxide purity was high. On the other
hand, in the use of sodium hydroxide or potassium carbonate as the
decomposition inhibitor, even when added at low concentration,
decomposition of dimethyl sulfoxide was promoted when dimethyl
sulfoxide was distilled out and the decomposition inhibitor
concentration increased. Then, a decomposition product of the
dimethyl sulfoxide was contaminated into the distilled dimethyl
sulfoxide, thereby reducing dimethyl sulfoxide purity.
INDUSTRIAL APPLICABILITY
[0152] Dimethyl sulfoxide obtained by our method of purifying
dimethyl sulfoxide has high purity and can be used as solvents in
steps of polymerizing and spinning polymers such as
polyacrylonitrile, cellulose, polyimide, polysulfone, and
polyurethane, stripping liquids for photoresists that are
electronic materials, solvents for synthesizing pharmaceuticals and
agrochemicals, removing and cleaning liquids for lens molds and the
like, or paint stripping liquids.
* * * * *