U.S. patent application number 15/573199 was filed with the patent office on 2018-03-29 for improved membranes for separation of alkenes from alkanes.
The applicant listed for this patent is COMPACT MEMBRANE SYSTEMS, INC.. Invention is credited to ANDREW EDWARD FEIRING, SUDIPTO MAJUMDAR, NING SHANGGUAN.
Application Number | 20180085714 15/573199 |
Document ID | / |
Family ID | 57248230 |
Filed Date | 2018-03-29 |
United States Patent
Application |
20180085714 |
Kind Code |
A1 |
SHANGGUAN; NING ; et
al. |
March 29, 2018 |
IMPROVED MEMBRANES FOR SEPARATION OF ALKENES FROM ALKANES
Abstract
Ionomers of Group 11 metals which include repeat units from
vinylidene fluoride, can separate alkenes from alkanes when
comprising a layer of a membrane. These membranes have excellent
permeability and/or selectivity for alkenes in the separation of
alkenes from alkanes.
Inventors: |
SHANGGUAN; NING; (CHERRY
HILL, NJ) ; FEIRING; ANDREW EDWARD; (WILMINGTON,
DE) ; MAJUMDAR; SUDIPTO; (NEWARK, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COMPACT MEMBRANE SYSTEMS, INC. |
NEWPORT |
DE |
US |
|
|
Family ID: |
57248230 |
Appl. No.: |
15/573199 |
Filed: |
May 6, 2016 |
PCT Filed: |
May 6, 2016 |
PCT NO: |
PCT/US16/31117 |
371 Date: |
November 10, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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62159646 |
May 11, 2015 |
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62159668 |
May 11, 2015 |
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62262169 |
Dec 2, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 7/144 20130101;
C08F 216/1466 20130101; B32B 27/322 20130101; B32B 27/08 20130101;
C08F 214/262 20130101; B32B 2307/724 20130101; C08F 4/34 20130101;
B01D 71/82 20130101; B01D 2325/20 20130101; C08F 214/202 20130101;
B01D 53/228 20130101; B01D 71/34 20130101; C08F 216/1408 20130101;
B01D 71/26 20130101; B32B 27/205 20130101; B32B 27/28 20130101;
B32B 27/286 20130101; B01D 71/76 20130101; B01D 71/32 20130101;
B32B 3/26 20130101; B32B 2307/732 20130101; B01D 69/12 20130101;
B01D 69/02 20130101; C08G 61/10 20130101; C08F 216/1416 20130101;
B32B 2307/70 20130101; C08F 216/1475 20200201; C09D 129/10
20130101; C08F 216/1466 20130101; C08F 214/20 20130101; C08F
216/1408 20130101; C08F 216/1408 20130101; C08F 216/1475 20200201;
C09D 129/10 20130101; C08K 3/28 20130101; C08F 216/1408 20130101;
C08F 216/1475 20200201 |
International
Class: |
B01D 71/34 20060101
B01D071/34; B01D 71/82 20060101 B01D071/82; B01D 53/22 20060101
B01D053/22; B01D 69/02 20060101 B01D069/02; B01D 69/12 20060101
B01D069/12; B32B 3/26 20060101 B32B003/26; B32B 27/08 20060101
B32B027/08; C07C 7/144 20060101 C07C007/144 |
Goverment Interests
GOVERNMENT RIGHTS
[0001] Support was provided under Department of Energy awards of
DE-SC0004672 and DE-SC0007510. The U.S. government has rights in
this patent application.
Claims
1. A process for separating one or more alkanes from one or more
alkenes using a membrane, wherein the improvement consists of using
a membrane comprising a nonporous layer of an ionomer of a Group 11
metal, comprising repeat units derived from vinylidene fluoride and
a monomer containing a precursor to a sulfonic acid group or a
sulfonic acid group, provided that carbon-fluorine groups are at
least 30% of the total of said carbon-fluorine groups and
carbon-hydrogen groups present in said ionomer, and wherein said
ionomer does not comprise repeat units derived from a cyclic or
cyclizable perfluorinated monomer.
2. The process as recited in claim wherein id Group 11 metal is
silver.
3. The process as recited in claim 2 wherein the repeat units that
contain said pendant sulfonic acid groups or a monomer containing a
precursor of a sulfonic acid group at least about 10 mole percent
of said repeat units present.
4. The process as recited in claim 2 wherein said carbon-fluorine
groups are at least about 60% of the total of said carbon-fluorine
and said carbon hydrogen groups present in said ionomer.
5. The process as recited in claim 2 wherein said precursor is one
or r ore of CF2.dbd.CFOCF2CF2SO2F, CF2.dbd.CFOCH2CF2CF2SO2F and
CF2.dbd.CFOCF2CF(CF3)OCF2CF2SO2F.
6. The process as recited in claim 2 wherein said ionomer
additionally comprises repeat units derived from one or more of
tetrafluoroethylene, chlorotrifluoroethylene, vinyl fluoride,
trifluororethylene hexafluoropropylene, and ethylene.
7. The process of claim 1 wherein said alkanes and alkenes are
gases.
8. The process of claims 2 herein said alkanes and alkenes are
gases.
9. The process of claims 3 wherein said alkanes and alkenes are
gases.
10. The process of claims 4 wherein said alkanes and alkenes are
gases.
11. The process of claims 5 wherein said alkanes and alkenes are
gases.
12. The process of claims 6 wherein said alkanes and alkenes are
gases.
Description
FIELD OF THE INVENTION
[0002] Membranes containing Group 11 metal ionomers comprising
repeat units derived from vinylidene fluoride have exceptionally
good permanences and/or selectivities for alkenes compared to other
membranes, when used to separate alkenes from alkanes in mixtures
of these types of compounds.
TECHNICAL BACKGROUND
[0003] Nonporous, but permeable, membranes have been used to
separate various types of chemicals for a long time. For instance
certain types of semipermeable membranes are used to separate water
from seawater, or oxygen from nitrogen, or alkenes from
alkanes.
[0004] The separation of alkenes from alkanes is usually
accomplished using a silver ionomer of a fluorinated polymer.
Often, because fluoropolymers are more stable to oxidation than
unfluorinated polymers, the silver ionomers of fluorinated polymers
are often more stable than unfluorinated polymers. Also polymers
which contain fluoro substituents near, for instance sulfonic acid
or carboxyl groups tend to be very strong acids (sometimes called
"super acids), the silver salts may be more stable.
[0005] In oil refineries or olefin polymerization plants sometimes
one has mixtures of alkenes and alkanes and one desires to separate
the alkenes from the alkanes. This may be relatively easy if these
two types of compounds have significant differences in boiling
points, but separation of such compounds with similar boiling
points are more difficult and expensive, especially if the boiling
points are lower in temperature. For instance propane boils at
-44.5.degree. C. and propylene boils at -47.8.degree. C. Separation
of these two compounds by cryogenic distillation is very expensive
because of high equipment and energy costs. Therefore cheaper, less
energy intensive methods of separation are desirable.
[0006] U.S. Pat. No. 5,191,151 to Erikson et al. describes the
separation of lower alkenes (containing 2 to 4 carbon atoms) from
lower alkanes (containing one to six carbon atoms) using a membrane
which is a silver ionomer of a polymer of tetrafluoroethylene (TFE)
and a perfluorovinyl ether containing a terminal precursor group to
a sulfonic acid.
[0007] U.S. Patent Application 2015/0025293 to Feiring et al.
describes the use of a membrane which is a silver ionomer of a
fluorinated polymer. The ionomer includes repeat units derived from
perfluorinated cyclic monomers.
[0008] L. Sauguet, et al., Fluorinated Copolymers and Terpolymers
Based on Vinylidene Fluoride and Bearing Sulfonic Acid Side-Group,
Journal of Polymer Science, Part A:, Polymer Chemistry, Vol. 45,
(2007), p. 1814-1834, reports the synthesis of a wide range of
fluorinated polymers containing repeat units derived from
vinylidene fluoride and an olefinic sulfonyl fluoride. There is no
mention of using such polymers or their ionomers to separate
alkenes from alkanes, and only ionomers of alkali metals such as
potassium are discussed.
[0009] U.S. Pat. No. 6,025,093 to Doyle, et al., describes ionomers
of univalent metals which contain repeat units derived from
vinylidene fluoride and a perfluorinated sulfonic acid
precursor.
[0010] The present invention results in membranes which have higher
permanences and separation alkene/alkane separation coefficients,
and longer useful lives over previously used alkene/alkane
separation membranes.
SUMMARY OF THE INVENTION
[0011] This invention concerns, an ionomer of a Group 11 metal,
comprising repeat units derived from vinylidene fluoride and a
monomer containing a precursor to a sulfonic acid group or a
sulfonic acid group, and provided that carbon-fluorine groups are
at least 30% of the total of said carbon-fluorine groups and
carbon-hydrogen groups present in said ionomer.
[0012] Also described herein is a partially fluorinated polymer,
comprising repeat units derived from vinylidene fluoride; and a
monomer containing a precursor to a sulfonic acid group or a
sulfonic acid group, provided that carbon-fluorine groups are at
least 30% of the total of said carbon-fluorine groups and
carbon-hydrogen groups present in said ionomer.
[0013] Also described herein is a process for separating one or
more alkanes from one or more alkenes, comprising: [0014] (a)
providing a membrane comprising a layer of an ionomer, said ionomer
comprising repeat units derived from vinylidene fluoride and a
monomer containing a precursor to a sulfonic acid group or a
sulfonic acid group, said membrane having a first side and a second
side, providing that carbon-fluorine groups are at least 30% of the
total of said carbon-fluorine groups and carbon-hydrogen groups
present in said ionomer; [0015] (b) exposing said first side to a
feed composition comprising a mixture of one or more alkanes and
one or more alkenes; [0016] (c) providing a driving force; and
[0017] (d) producing a second mixture, on a second side of said
membrane, having a higher ratio of alkene to alkane than said first
mixture.
DETAILS OF THE INVENTION
[0018] Herein certain terms are used, and some of them are defined
below:
[0019] Of the total of the carbon-hydrogen groups and the carbon
fluorine groups in the ionomer, 30% or more are carbon-fluorine
groups, preferably 60% or more, and more preferably 80% or more are
carbon fluorine groups. By a carbon-hydrogen group is meant a
hydrogen atom bound directly to a carbon atom, while a
carbon-fluorine group is a fluorine atom bound directly to a carbon
atom. Thus --CF.sub.2-- groups contains 2 carbon fluorine groups,
while a --CH.sub.3 group contains 3 carbon-hydrogen groups. In a
homopolymer of vinylidene fluoride, in which the repeat groups are
--CH.sub.2CF.sub.2-the carbon-hydrogen groups and the carbon
fluorine groups are each 50% of the total of carbon-hydrogen plus
carbon-fluorine groups present. In a copolymer of 20 mole percent
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F and
80 mole percent vinylidene fluoride the carbon-hydrogen groups are
27.6% of the total of the carbon-fluorine plus carbon hydrogen
groups present. The relative amount of carbon-fluorine and carbon
hydrogen groups present can be determined by NMR Spectroscopy, for
instance using .sup.14C NMR, or a combination of .sup.19F and
proton spectroscopy.
[0020] By a "monomer containing a precursor to a sulfonic acid
group" is meant a monomer, when part of the polymer after
polymerization, that can be readily converted to a sulfonic acid.
Such groups include sulfonyl halides, especially sulfonyl
fluorides, sulfonyl esters, sulfonamides, etc. It will be
understood by those skilled in the art that the "monomer containing
a precursor to a sulfonic acid group" is converted to the sulfonic
acid group, often by hydrolysis, after chemical treatment of the
polymer formed by the initial polymerization. Also that in the
ionomeric form the "sulfonic acid" group is actually at least
partly the sulfonate salt of a Group 11 metal. For the sake of
simplicity herein, in the hydrolyzed or otherwise reacted original
polymer, and in the ionomer, these are sometimes referred to herein
as sulfonic acid groups.
[0021] By a "driving force" in the separation of the alkene and
alkane by the membrane is generally meant that the effective
concentration of the alkene on the first ("feed") side of the
membrane is higher than on the second ("product") side of the
membrane. This may be accomplished by, if the separation is on a
gaseous feed, having higher partial pressure of the alkene on the
feed side of the membrane. Thus the gaseous feed may be at a higher
pressure than the product side, and/or the alkene may be swept away
from the product side of the membrane by an "inert" gas such as
nitrogen to lower the partial pressure of the alkene on the product
side. If a liquid feed is being separated, the feed side may be at
a higher pressure, and/or the alkene may be swept away by an inert
liquid on the product side. These and other known methods in the
art of applying a driving force may be used.
[0022] This may be quantified for a separation of gases to some
extent by a mathematical relationship:
Q.sub.a.alpha.F.sub.a(P1.sub.a-P2.sub.a))
[0023] wherein Q.sub.a is the flow rate of component "a" through
the membrane, F.sub.a is the permeance of component a through the
membrane, P1.sub.a is the partial pressure of a on the first (feed)
side, and P2.sub.a is the partial pressure of a on the second
(product) side.
[0024] By a membrane comprising the silver ionomer is meant a
membrane comprising a thin nonporous layer of the silver ionomer
and one or more other polymeric layers which physically support or
reinforce the silver ionomer layer. Preferably the silver ionomer
layer is about 0.1 .mu.m to about 1.0 .mu.m thick, more preferably
about 0.2 .mu.m to about 0.5 .mu.m thick. These other layer(s)
should preferably be relatively permeable to the alkenes and
alkanes to be separated, and not themselves have much if any
tendency to separate alkenes and alkanes.
[0025] In one preferred embodiment of the invention the Group 11
metal is copper or silver, more preferably silver.
[0026] In the ionomer, and its precursor acidic form, the repeat
units that contain the pendant sulfonic acid groups are preferably
at least about 5 mole percent of the total repeat units present,
more preferably at least about 10 mole percent, very preferably at
least about 20 mole percent, and especially preferably at least
about 25 mole percent. It is preferred that the repeat units that
contain the pendant acid groups are no more than 45 mole percent of
the repeat units present in the silver ionomer or its precursor
acid form. It is to be understood that any minimum amount of such
repeat units and any maximum amount of such repeat units may be
combined to form a preferred range of the amount of these repeat
units.
[0027] Useful monomers containing a sulfonic acid group or a
precursor to a sulfonic acid group include one or more of
CF.sub.2.dbd.CFOCF.sub.2CF.sub.2SO.sub.2F,
CF.sub.2.dbd.CFOCH.sub.2CF.sub.2CF.sub.2SO.sub.2F and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F, and
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.2F is
preferred. In another type of preferred monomer containing a
sulfonic acid or its precursor the carbon atom bound to the
sulfonic acid group has at least one fluorine bound to that carbon
atom.
[0028] Preferably the various forms of the VF2 copolymer described
herein (referring to what exactly "Y" is, especially when Y is a
Group 11 metal cation) are so-called "glassy" copolymers. By that
is meant the copolymer has no melting point above about 30.degree.
C. with a heat of fusion of 3 J/g or more when measured by
Differential Scanning calorimetry using ASTM Test D3418-12e1 using
a heating and cooling rate of 10.degree. C./min, and measured on
the second heat. Also a glassy copolymer has a Glass Transition
Temperature (Tg) above about 40.degree. C., more preferably about
40.degree. C. The Tg is measured according to ASTM Test D3418-12e1
at a heating and cooling rate of 10.degree. C./min, and the Tg is
taken as the midpoint (inflection point) of the transition on the
second heat. Preferably the Tg is less than about 220.degree. C.,
because for instance if the Tg is too high it may be difficult to
dissolve the polymer to form a coating or layer.
[0029] Preferably the Group 11 metal ionomer is produced by
contacting, in a liquid medium, a fluorinated polymer containing
pendant sulfonic acid groups (not metal sulfonate salts) with a
Group 11 metal salt whose anion's conjugate Bronsted acid has a pKa
in water at 25.degree. C. of less than 1.0.
[0030] The polymeric portion of the ionomers may contain repeat
units derived from other monomers, as long as other compositional
limits of the polymer, such as the minimum fraction of
carbon-fluorine groups present. Useful monomers include one or more
of tetrafluoroethylene, chlorotrifluoroethylene, vinyl fluoride,
trifluororethylene hexafluoropropylene, and ethylene.
[0031] It is preferred that repeat units derived from cyclic or
cyclizable perfluorinated monomers not be present in the ionomer.
By a cyclic perfluorinated monomer is meant a perfluorinated olefin
wherein a double bond of the olefin is in the ring or the double
bond is an exo double bond wherein one end of the double bond is at
a ring carbon atom. By a cyclizable perfluorinated monomer is meant
a noncyclic perfluorinated compound containing two olefinic bonds,
and that on polymerization forms a cyclic structure in the main
chain of the polymer (see for instance N. Sugiyama,
Perfluoropolymers Obtained by Cyclopolymereization and Their
Applications, in J. Schiers, Ed., Modern Fluoropolymers. John Wiley
& Sons, New York, 1997, p. 541-555, which is hereby included by
reference). Such perfluorinated cyclic and cyclizable compounds
include perfluoro(2,2-dimethyl-1,3-dioxole),
perfluoro(2-methylene-4-methyl-1,3-dioxolane), a perfluoroalkenyl
perfluorovinyl ether, and
2,2,4-trifluoro-5-trifluoroimethoxy-1,3-dioxole.
[0032] Preferably the Group 11 metal ionomer has no melting point
above about 0.degree. C. with a heat of fusion of 3 J/g or more
when measured by Differential Scanning calorimetry using ASTM Test
D3418-12e1 using a heating rate of 10.degree. C./min, and measured
on the second heat. Also preferably the ionomer has no Glass
Transition Temperature (Tg) above 50.degree. C. The Tg is measured
according to ASTM Test D3418-12e1 at a heating rate of 10.degree.
C./min, and the Tg is taken as the midpoint of the transition.
Preferably there is no Tg above 30.degree. C., and more preferably
above 10.degree. C. Alternatively when actually doing a separation
of one or more alkanes from one or more alkenes, the Tg of the
ionomer (if present) is below the temperature at which the process
is run.
[0033] The ionomers may be produced by methods described in this
application, US Patent Application 2015/0025293 to Feiring et al.,
U.S. Pat. No. 5,191,151 to Erikson et al. and L. Sauguet, et al.,
Fluorinated Copolymers and Terpolymers Based on Vinylidene Fluoride
and Bearing Sulfonic Acid Side-Group, Journal of Polymer Science,
Part A:, Polymer Chemistry, Vol. 45, (2007), p. 1814-1834, all of
which are hereby included by reference. Some compositions of
polymers useful in this invention are also described in Feiring et
al., and such polymers described therein containing pendant acidic
groups may also be treated as described herein to form silver
ionomers.
[0034] Determination of Permeance and Selectivity for Olefin/Alkane
Separations
[0035] For determinations of permeance (GPU, reported in units of
sec/cm.sup.2.s.cm Hg) and selectivity the following procedure was
used. A 47 mm flat disc membrane was punched from a larger flat
sheet 3 inch composite membrane. The 47 mm disc is then placed in a
stainless steel cross flow testing cell comprised of a feed port,
retentate port, a sweep inlet port, and a permeate port. Four hex
bolts were used to tightly secure the membrane in the testing cell
with a total active area of 13.85 cm.sup.2.
[0036] The cell was placed in a testing apparatus comprising of a
feed line, a retentate line, a sweep line, and a permeate line. The
feed consisted of a mixture of an olefin (propylene) gas and a
paraffin (propane) gas. Each gas was supplied from a separate
cylinder. For olefin, polymer grade propylene (99.5 vol % purity)
was used and for paraffin, 99.9 vol % purity propane was used. The
two gases were then fed to their respective mass flow controllers
where a mixture of any composition can be made. The standard mixing
composition was 20 vol % olefin and 80 mol % paraffin at a total
gas flow rate of 200 mL/min. The mixed gas was fed through a water
bubbler to humidify the gas mixture bringing the relative humidity
to greater than 90%. A back pressure regulator is used in the
retentate line to control the feed pressure to the membrane. The
feed pressure was normally kept at 60 psig (0.41 MPa) after the
back pressure regulator the gas is vented.
[0037] The sweep line consisted of a pure humidified nitrogen
stream. Nitrogen from a cylinder was connected to a mass flow
controller. The mass flow controller was set to a flow of 300
mL/min. The nitrogen was fed to a water bubbler to bring the
relative humidity to greater than 90%. After the bubbler the
nitrogen was fed to the sweep port of the membrane to carry any
permeating gas through to the permeate port.
[0038] The permeate line consisted of the permeated gas through the
membrane and the sweep gas as well as water vapor. The permeate was
connected to a three way valve so flow measurements could be taken.
A Varian.RTM. 450 GC gas chromatograph (GC) with a GS-GasPro
capillary column (0.32 mm, 30 m) was used to analyze the ratio of
the olefin and paraffin in the permeate stream. The pressure in the
permeate side was typically between 1.20 and 1.70 psig (8.3 to 11.7
kPa). Experiments were carried out at room temperature.
[0039] During experiment the following were recorded: feed
pressure, permeate pressure, temperature, sweep-in flow rate
(nitrogen+water vapor) and total permeate flow rate
(permeate+nitrogen+water vapor).
[0040] From the results recorded the following were determined: all
individual feed partial pressures based on feed flows and feed
pressure; all individual permeate flows based on measured permeate
flow, sweep flows, and composition from the GC; all individual
permeate partial pressures based on permeate flows and permeate
pressures. From these the transmembrane partial pressure difference
of individual component were calculated. From the equation for
permeance
Q.sub.i=F.sub.i/(A..DELTA.p.sub.i )
wherein, Q.sub.i=permeance of species `i`, F.sub.i=Permeate flow
rate of species `i` .DELTA.p.sub.i=transmembrane partial pressure
difference of species `i`, and A is the area of the membrane (13.85
cm.sup.2), the permeance(Q.sub.i) was calculated.
[0041] In the Examples certain abbreviations are used, and they
are:
[0042] HFPO--hexafluoropropylene oxide (For preparation of HFPO
dimer peroxide see U.S. Pat. No. 7,112,314, which is hereby
included by reference. HFPO dimer [2062-98-8] is available from
Synquest Laboratories, Alachua, Fl., USA)
[0043] PDD--perfluoro(2,2-dimethyl-1,3-dioxole)
[0044]
SEFVE--CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)OCF.sub.2CF.sub.2SO.sub.-
2F
[0045] VF2--vinylidene fluoride (H.sub.2C.dbd.CF.sub.2)
Comparative Example A
[0046] Synthesis of PDD/SEFVE (Feed ratio; 100/200 total) Copolymer
and Hydrolysis
[0047] Into a 100 mL pear shape glass reaction flask, after argon
purging for 5 minutes at 0.degree. C., were placed a magnetic
stirring bar, 4.0 g of PDD, 29.3 g SEFVE, 10 mL of
2,3-dihydrodecafluoropentane (Vertrel.RTM. XF specialty fluid, E.I.
DuPont de Nemours & Co., Inc., Wilmington, Del. 19898, USA),
and 0.8 mL of an initiator solution in Vertrel.RTM. XF of
hexafluoropropylene oxide (HFPO) dimer peroxide (0.12 M) (see U.S.
Pat. No. 7,112,314, which is hereby included by reference, for
synthesis of this peroxide) made from the reaction of
CF3CF3CF3OCF(CF3)CFO with basic hydrogen peroxide. The reaction
mixture was sealed with a rubber septum, protected with an argon
balloon, stirred, and allowed warm to room temperature in a water
bath. After stirring overnight, 4.0 g of PDD and 0.8 mL of the HFPO
dimer peroxide solution (0.12 M) was added into the reaction
mixture by a syringe. After stirring for one more day, the flask
was opened to ambient air and 40 mL of acetone was added into the
mixture. The liquid was decanted after stirring for 15 min and 40
mL of fresh acetone was added. After stirring for 15 min, the
liquid was again decanted and the solid residue was transferred to
a watch glass. Drying in an oven at 100.degree. C., overnight
yielded 10.0 g of a white solid, PDD/SEFVE copolymer.
[0048] Into a round bottom 250 mL glass flask, were added 10.0 g of
PDD/SEFVE copolymer synthesized in the above procedure, 60 mL of
deionized water, 60 mL ethanol, 3.0 g potassium hydroxide and a
magnetic stirring bar. The reaction mixture was heated to reflux
and stirred overnight. Ethanol in the mixture was evaporated and
100 mL of 2.0 M hydrochloric acid was added to the mixture. The
solid was filtered from the mixture and then immersed in 100 mL of
2.0 M hydrochloric acid twice. The resulting solid was washed three
times with 100 mL of deionized water and filtered after each
washing. Finally it was dried in oven at 100.degree. C. for 3 hours
to yield 9.4 g of a brownish solid, the hydrolyzed copolymer
PDD/SEFVE containing sulfonic acid groups. This copolymer had a Tg
of 39.degree. C.
[0049] Into a glass bottle were added 1 g of the polymer made in
the immediately preceding paragraph Fluorinet.RTM. FC770 (available
from 3M Corp., 3M Center, St. Paul, Minn., USA) and 30 mL of 30%
hydrogen peroxide. The reaction mixture was stirred overnight at
ambient temperature and then the polymer filtered off and dried
under vacuum. Dried polymer (0.1 g) was added to a bottle
containing 3.5 g of isopropyl alcohol and 1.5 g of Novec.RTM. 7300
and then 47 mg of AgNO.sub.3 was added and the initial mixture
stirred for 1-2 hours until the polymer was completely dissolved,
and the solid AgNO.sub.3 was not visible. The solution was then
filtered through a glass fiber filter having a 1.2 .mu.m nominal
pore size.
[0050] A 0.3% solution of Teflon.RTM. AF2400 (available from the
DuPont Co, Wilmington, Del. 19898, USA) (for further information
about Teflon.RTM. AF, see P. R. Resnick, et al., Teflon AF
Amorphous Fluoropolymers, J. Schiers, Ed., Modern Fluoropolymers,
John Wiley & Sons, New York, 1997, p. 397-420, which is hereby
included by reference) in Fluorinert.RTM. 770 (available from 3M
Corp., 3M Center, Sty. Paul, Minn., USA) was coated onto a PAN350
membrane made by Nanostone Water, 10250 Valley View Rd., Eden
Prairie, Minn. 53344, USA) (It is believed that the PAN350 membrane
is made from polyacrylonitrile and that it is a microporous
membrane) to form a bilayer membrane, and then dried at 100.degree.
C. for 1 h. Preferably the thickness of the Teflon AF2400 layer is
about 0.1 to about 0.2 .mu.m. At a relative humidity of <30% the
solution of silver ionomer prepared in the previous paragraph was
then coated onto the Teflon AF2400 layer of bilayer membrane, and
then dried at 100.degree. c for 1 h.
Example 1
[0051] Synthesis of VF2/SEFVE (Feed ratio; 200/100) Copolymer and
Hydrolysis, and Membrane of Silver Ionomer
[0052] Into a 150 mL stainless steel pressure vessel , after argon
purging for 5 minutes, were added a magnetic stirring bar, 6.69 g
of SEFVE, 20 mL of Vertrel.RTM. XF, 0.7 mL HFPO dimer peroxide
solution (0.12 M) and 1.92 g of vinylidene fluoride gas all at
0.degree. C. The reaction mixture was sealed in the pressure vessel
and stirred at room temperature in a water bath. After overnight
reaction, the reaction vessel was opened to ambient air and 30 mL
of Novec.RTM.7100 fluorinated solvent (methyl perfluoropropyl
ether, available from the 3M Company, Electronic Materials
Solutions Div., St. Paul, Minn. 55144, USA) was added to the
reaction mixture. The whole solution was transferred to a glass
dish and dried in a fume hood at room temperature for 3 h and then
in oven at 100.degree. C. overnight to yield 7.0 g of VF2/SEFVE
copolymer as a colorless sticky foam. This polymer had a Tg of
39.degree. C.
[0053] Into a 250 mL round bottom glass flask, were added 5.4 g
VF2/SEFVE copolymer synthesized in the above procedure, 20 mL of
deionized water, 40 mL of methanol, 2.7 g of ammonium carbonate and
a magnetic stirring bar. The reaction mixture was stirred and
maintained at 50-60.degree. C. overnight. Then methanol in the
mixture was evaporated and 50 mL of 2.0 M hydrochloric acid was
added to the mixture. The liquid was decanted after stirring for 15
min and 50 mL of 2.0 M hydrochloric acid was added. After stirring
for 15 min, the liquid was again decanted and 50 mL of deionized
water was added. The water washing was repeated twice and the solid
residue was dried in oven at 100.degree. C. overnight. The 5.0 g of
brownish solid obtained was the VF2/SEFVE copolymer having free
sulfonic acid groups. This polymer has a Tg of 39.degree. C.
[0054] A membrane containing having a layer of the silver ionomer
of the sulfonic acid containing polymer made in the previous
paragraph was made by the same method described in Comparative
Example A.
Example 2
[0055] Synthesis of VF2/SEFVE (Feed ratio; 100/100) Copolymer and
Hydrolysis, and Membrane of Silver Ionomer.
[0056] Into a 150 mL stainless steel pressure vessel, after argon
purging for 5 minutes, were added a magnetic stirring bar, 8.92 g
of SEFVE, 15 mL of Vertrel.RTM. XF, 0.5 mL of HFPO dimer peroxide
solution (0.12 M), and then charged 1.28 g of vinylidene fluoride
gas at 0.degree. C. The reaction mixture was sealed in the pressure
vessel and stirred at room temperature in a water bath. After
overnight reaction, the reaction vessel was opened to ambient air
and 30 mL of Novec.RTM. 7100 fluorinated solvent was added to the
reaction mixture. The whole solution is transferred to a glass dish
and dried in a fume hood at room temperature for 3 hours and then
in oven at 100.degree. C. overnight to yield 7.0 g VF2/SEFVE
copolymer as a colorless sticky foam.
[0057] Into a 250 mL round bottom glass flask, were added 7.0 g of
the copolymer synthesized in the previous paragraph, 30 mL of
deionized water, 60 mL of methanol, 3.5 g of ammonium carbonate and
a magnetic stirring bar. The reaction mixture was stirred and
maintained at 50-60.degree. C. After overnight reaction, methanol
in the mixture was evaporated and 50 mL of 2.0 M hydrochloric acid
was added to the mixture. The liquid was decanted after stirring
for 15 minutes and 50 mL of 2.0 M hydrochloric acid was added.
After stirring for 15 minutes, the liquid was again decanted and 50
mL of deionized water was added. The water washing was repeated
twice and the solid residue was dried in oven at 100.degree. C.
overnight. A brownish solid copolymer (5.5 g) containing free
sulfonic acid groups was obtained. The copolymer had a Tg of
52.degree. C.
[0058] A membrane containing a layer of a silver ionomer was made
by the same method described in Example 1, except only 31 mg of
AgNO.sub.3was used.
Example 3
[0059] Table 1 lists the initial permeances of the membranes from
Examples A, 1 and 2. The membrane cell for the permeance
measurements used a 47 mm diameter flat membrane sheet. The feed
gas composition was humidified, by passing through an aqueous
bubbler, and was 20 mole % propylene (polymer synthesis grade), and
80% propane at room temperature. The total flow rate of both gases
was 200 mL/min. The feed gas (mixture of propylene and propane)
pressure was 60 psig, and the sweep gas on the second side of the
membrane was humidified nitrogen at a pressure of 0.0 to 0.3 psig.
The permeate from the second side of the membrane was analyzed by
FTIR to determine the total permeate amounts of propane and
propylene. Permeances (GPU) are given in cm.sup.3/cm.sup.2/sec/cm
Hg.times.10.sup.6.
TABLE-US-00001 TABLE 1 Permeance Selectivity Example C.sub.3H.sub.8
C.sub.3H.sub.6 C.sub.3H.sub.6/C.sub.3H.sub.8 A 0.84 161.3 193 1
0.37 235.2 634 2 0.44 221.7 509
[0060] Table 1 shows that ionomers of the present composition
surprisingly have superior permeances and/or selectivities for
alkenes than prior art membranes.
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