U.S. patent application number 14/497353 was filed with the patent office on 2016-03-31 for high permeability polyimide membranes: gas selectivity enhancement through uv treatment.
The applicant listed for this patent is UOP LLC. Invention is credited to Michael B. Hamoy, Carl W. Liskey, Chunqing Liu.
Application Number | 20160089628 14/497353 |
Document ID | / |
Family ID | 55582249 |
Filed Date | 2016-03-31 |
United States Patent
Application |
20160089628 |
Kind Code |
A1 |
Liskey; Carl W. ; et
al. |
March 31, 2016 |
HIGH PERMEABILITY POLYIMIDE MEMBRANES: GAS SELECTIVITY ENHANCEMENT
THROUGH UV TREATMENT
Abstract
Polyimide membranes are provided that provide extremely high
permeability. The polyimides do not contain carbonyl or sulfonyl
functional groups. These membranes are useful in separating gases
including the separation of gas pairs including carbon
dioxide/methane, hydrogen/methane and propylene/propane as well as
other gas mixtures. The membrane selectivity can be adjusted by
exposure to ultraviolet light.
Inventors: |
Liskey; Carl W.; (Chicago,
IL) ; Liu; Chunqing; (Arlington Heights, IL) ;
Hamoy; Michael B.; (Crystal Lake, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UOP LLC |
Des Plaines |
IL |
US |
|
|
Family ID: |
55582249 |
Appl. No.: |
14/497353 |
Filed: |
September 26, 2014 |
Current U.S.
Class: |
95/45 |
Current CPC
Class: |
B01D 53/228 20130101;
B01D 69/125 20130101; B01D 2323/345 20130101; B01D 67/009 20130101;
B01D 2323/30 20130101; C08G 73/1067 20130101; B01D 71/64 20130101;
B01D 71/56 20130101; Y02C 20/20 20130101; C08G 73/1042
20130101 |
International
Class: |
B01D 53/22 20060101
B01D053/22; B01D 69/12 20060101 B01D069/12; B01D 71/56 20060101
B01D071/56 |
Claims
1. A process for separating at least one gas from a mixture of
gases comprising providing a UV treated polyimide polymer membrane
having a polyimide polymer with a formula ##STR00007## where m and
n are independent integers from 10 to 500 and are in a ratio from
1:10 to 10:1; contacting the mixture of gases to one side of the UV
treated polyimide polymer membrane to cause at least one gas to
permeate said membrane; and removing from an opposite side of said
UV treated polyimide polymer membrane a permeate gas composition
comprising a portion of said at least one gas that permeated said
membrane.
2. The process of claim 1 wherein said mixture of gases comprises a
mixture of carbon dioxide and methane.
3. The process of claim 1 wherein said mixture of gases comprises a
mixture of hydrogen and methane.
4. The process of claim 1 wherein said mixture of gases comprises a
mixture of helium and methane.
5. The process of claim 1 wherein said mixture of gases comprises a
mixture of at least one volatile organic compound and at least one
atmospheric gas.
6. The process of claim 1 wherein said mixture of gases comprises
nitrogen and hydrogen.
7. The process of claim 1 wherein said mixture of gases comprises a
mixture of carbon dioxide, oxygen, nitrogen, water vapor, hydrogen
sulfide, helium and methane.
8. The process of claim 1 wherein said UV treated polyimide polymer
membrane comprises a species that adsorbs strongly to at least one
gas.
9. The process of claim 1 wherein said mixture of gases comprises a
mixture of paraffins and olefins.
Description
BACKGROUND OF THE INVENTION
[0001] The membranes most commonly used in commercial gas
separation applications are asymmetric polymeric membranes and have
a thin nonporous selective skin layer that performs the separation.
Separation is based on a solution-diffusion mechanism. This
mechanism involves molecular-scale interactions of the permeating
gas with the membrane polymer. According to this solution/diffusion
model, the membrane performance in separating a given pair of gases
is determined by two parameters: the permeability coefficient
(P.sub.A) and the selectivity (.alpha..sub.A/B). The P.sub.A is the
product of the gas flux and the selective skin layer thickness of
the membrane, divided by the pressure difference across the
membrane. The .alpha..sub.A/B is the ratio of the permeability
coefficients of the two gases (.alpha..sub.A/B=P.sub.A/P.sub.B)
where P.sub.A is the permeability of the more permeable gas and
P.sub.B is the permeability of the less permeable gas. Gases can
have high permeability coefficients because of a high solubility
coefficient, a high diffusion coefficient, or because both
coefficients are high. In general, the diffusion coefficient
decreases while the solubility coefficient increases with an
increase in the molecular size of the gas. In high performance
polymer membranes, both high permeability and selectivity are
desirable because higher permeability decreases the size of the
membrane area required to treat a given volume of gas, thereby
decreasing capital cost of membrane units, and because higher
selectivity results in a higher purity product gas. These new
membranes have high permeability and the selectivity of some of
these membranes can be tuned via cross-linking in the presence of
UV light.
SUMMARY OF THE INVENTION
[0002] The invention provides a polyimide polymer and a polyimide
membrane having a formula
##STR00001##
where m and n are independent integers from 10 to 500 and are in a
ratio from 1:10 to 10:1
[0003] In some embodiments of the invention, this polyimide
membrane is UV treated.
[0004] The invention further provides a process for separating at
least one gas from a mixture of gases comprising providing a UV
treated polyimide polymer membrane having a formula
##STR00002##
where m and n are independent integers from 10 to 500 and are in a
ratio from 1:10 to 10:1; contacting the mixture of gases to one
side of the UV treated aromatic polyimide membrane to cause at
least one gas to permeate said membrane; and removing from an
opposite side of the polyimide membrane a permeate gas composition
comprising a portion of said at least one gas that permeated said
membrane.
DETAILED DESCRIPTION OF THE INVENTION
[0005] This invention relates to polyimide gas separation membranes
and more particularly to a new class of polyimide membranes with
high permeability. Specifically, an improved polyimide membrane
with more than 430 Barrer CO.sub.2 and H.sub.2 permeabilities
greatly exceeding the intrinsic permeability of commercial
polyimide membranes is disclosed. The permeability is similar to
heat-treated polyimides disclosed in U.S. Pat. No. 8,613,362 B2.
However, in this case heat treatment, which can be problematic in
the preparation of membranes, is not required to achieve such high
permeabilities.
[0006] Although the selectivity for gas separations is low with
these highly permeable polyimides described in the present
invention, it can be increased significantly with UV treatment. In
fact, both high permeability and selectivity can be achieved for
CO.sub.2/CH.sub.4 separation with UV treatment, as demonstrated by
pure gas tests for membrane dense films of these polyimides. This
sensitivity to UV light is also present in thin-film composite
membranes where the disclosed polyimide is the selective layer.
U.S. Pat. No. 4,717,393 by Hayes and U.S. Pat. NO. 7,485,173 by
Liu, et. al., disclosed photochemically cross-linked aromatic
polyimides. In these cases, a functional group that is
cross-linkable to UV light is required, such as a carbonyl or
sulfonyl group. However, the high permeability polyimides described
in the present invention do not comprise functional groups that are
cross-linkable to UV light.
[0007] The polyimides disclosed in the present invention do not
contain these carbonyl or sulfonyl functional groups. U.S. Pat. No.
5,409,524 reported a method for the improvement in selectivity of
polymeric membranes, such as polysulfone, polycarbonate and
polystyrene membranes, without carbonyl or sulfonyl groups through
UV treatment, but heating the membranes to a temperature in the
range of 60-300.degree. C. is required. Furthermore, the UV and
heat treatment of polyimides were not disclosed in this patent.
However, heating is not required during the UV treatment to achieve
high selectivity for the polyimides described in the present
invention. US 2006/0177740 Al disclosed a polymer derived from
pyromellitic dianhydride (PMDA) and
3,3',5,5'-tetramethyl-4,4'-methylene dianiline (TMMDA) monomers.
This disclosure did not include polymers containing
2,4,6-trimethyl-mphenylenediamine (TMPDA). Also, this polymer was
used for polyimide matrix electrolytes for battery applications and
was not considered for use as a polymeric membrane.
[0008] The membranes made in accordance with the present invention
have the formula shown below.
##STR00003##
where m and n are independent integers from 10 to 500 and are in a
ratio from 1:10 to 10:1.
[0009] The invention involves the condensation reaction of
pyrometallic dianhydride (PMDA) with a mixture of
2,4,6-trimethyl-1,3-phenylenediamine (TMPDA) and 4,4'-methylene
bis(2,6-dimethylaniline) (TMMDA) in a polar solvent such as
dimethylacetamide (DMAc) or (NMP) solvent to form the polyimide
described in the present invention. The condensation reaction
described in the current invention is a two-step process involving
the formation of the poly(amic acid) followed by a solution
chemical imidization process. Acetic anhydride is used as the
dehydrating agent and pyridine is used as the imidization catalyst
for the solution chemical imidization reaction. Typical reaction
times are about 20 hours at about 22.degree. C. In a second step,
acetic anhydride is added, followed by pyridine and the mixture is
heated to about 95.degree. C. for 2 hours and then allowed to cool
to room temperature. The resulting mixture is then used to make a
polyimide membrane which is then treated with UV radiation to
produce a polyimide membrane with improved properties.
##STR00004##
EXAMPLE 1
Synthesis of Polyimide 1: Poly(PMDA-TMPDA-TMMDA) (m=2, n=1)
[0010] An aromatic poly(pyrometallic
dianhydride-2,4,6-trimethyl-1,3-phenylenediamine-4,4'-methylene
bis(2,6-dimethylaniline)) polyimide (poly(PMDA-TMPDA-TMMDA)) was
synthesized from pyrometallic dianhydride (PMDA, 3 equiv),
2,4,6-trimethyl-1,3-phenylenediamine (TMPDA, 2 equiv), and
4,4'-methylene bis(2,6-dimethylaniline) (TMMDA, 1 equiv) in
N,N-dimethylacetamide (DMAc) polar solvent by a two-step process
involving the formation of a polyamic acid followed by a solution
chemical imidization process. Acetic acid was used as the
dehydrating reagent and pyridine was used as the imidization
catalyst for the solution chemical imidization reaction.
[0011] For example, a dry 2 L three-necked round-bottom flask
attached to a mechanical stirrer and a reflux condenser with a
nitrogen inlet was charged with TMPDA (17.0 g, 2.00 equiv),
TMMDA(20.0 g, 1.00 equiv), and anhydrous DMAc (380 g) and the
solution was vigorously stirred. The dianhydride, PMDA (44.9 g,
3.00 equiv), was added. Additional DMAc (130 g) was added slowly.
The reaction vessel was sealed with a septum and stirred at
22.degree. C. for 20 hours. Acetic anhydride (43.2 g) was added to
the viscous reaction mixture slowly over 5 minutes, followed by
pyridine (66.5 g) all at once. The reaction is heated to 95.degree.
C. for 2.5 hours and then allowed to cool to room temperature. The
reaction mixture precipitated into a solution of
isopropanol:acetone (1:1) to form white thin fibers. The white
solid was heated in the vacuum oven for two days at 100.degree. C.
The polymer was isolated in nearly quantitative yield.
EXAMPLE 2
Synthesis of Polyimide 2: Poly(PMDA-TMPDA-TMMDA) (m=1, n=1)
[0012] An aromatic poly(pyrometallic
dianhydride-2,4,6-trimethyl-1,3-phenylenediamine-4,4'-methylene
bis(2,6-dimethylaniline)) polyimide (poly(PMDA-TMPDA-TMMDA)) was
synthesized from PMDA (2 equiv), TMPDA (1 equiv), and TMMDA (1
equiv) in DMAc polar solvent by a two-step process involving the
formation of the polyamic acid followed by a solution chemical
imidization process. Acetic acid was used as the dehydrating
reagent and pyridine was used as the imidization catalyst for the
solution chemical imidization reaction.
[0013] For example, a dry 2 L three-necked round-bottom flask
attached to a mechanical stirrer and a reflux condenser with a
nitrogen inlet was charged with TMPDA (30.0 g,1.00 equiv), TMMDA
(50.8 g, 1.00 equiv), and anhydrous DMAc (775 g) and the solution
was vigorously stirred. The dianhydridePMDA (89.8 g, 2.00 equiv)
was added. Additional DMAc (130 g) was added slowly. The reaction
was sealed with a septum and stirred at 22.degree. C. for 20 hours.
Acetic anhydride (86.4 g) was added to the viscous reaction mixture
slowly over 5 minutes, followed by pyridine (133 g) all at once.
The reaction is heated to 95.degree. C. for 2.5 hours and then
allowed to cool to room temperature. The reaction mixture
precipitated into a solution of isopropanol:acetone (1:1) to form
white thin fibers. The white solid was heated in the vacuum oven
for two days at 100.degree. C. The polymer was isolated in nearly
quantitative yield.
EXAMPLE 3
Preparation of poly(PMDA-TMPDA-TMMDA) Polyimide Polymer
Membranes
[0014] The polyimide membrane dense films were prepared as follows:
The aromatic poly(PMDA-TMPDA-TMMDA) polyimide, was dissolved in
N-methyl pyrrolidone (NMP, 18% polymer). The polyimide dope was
filtered, allowed to degas overnight and cast onto a clean glass
plate with a doctor knife with a 20-mil knife gap. The film on the
glass plate was heated to 60.degree. C. for 6 hours and dried in
the vacuum oven at 180.degree. C. for 48 hours. The film was tested
for CO.sub.2/CH.sub.4 and H.sub.2/CH.sub.4 separations at
50.degree. C. under 689 kPa (100 psig) pure gas feed pressure. The
films were also submitted to UV treatment at 254 nm at 2 cm for 10
minutes at 50.degree. C. and subsequently tested again under pure
gas pressures. The results are shown in Table 1.
TABLE-US-00001 TABLE 1 Pure gas permeation test results of
poly(PMDA-TMPDA-TMMDA) membranes for CO.sub.2/CH.sub.4 and
H.sub.2/CH.sub.4 separations.sup.a Membrane.sup.b P.sub.CO2
(Barrer) P.sub.H2 (Barrer) .alpha..sub.CO2/CH4 .alpha..sub.H2/CH4
Polyimide-1 434.6 434.7 11.8 11.8 Polyimide-1-UV 114.6 342.8 33.7
100.8 10 min Polyimide-2 436.3 483.0 10.4 11.5 Polyimide-2-UV 117.7
365.0 45.3 140.4 10 min .sup.aP.sub.CO2, P.sub.CH4, and P.sub.H2
were tested at 50.degree. C. and 690 kPa (100 psig); 1 Barrer =
10.sup.-10 cm.sup.3(STP) cm/cm.sup.2 sec cmHg .sup.bPolyimide 1:
PMDA:TMPDA:TMMDA (3:2:1); Polyimide 2: PMDA-TMPDA:TMMDA
(2:1:1).
EXAMPLE 4
Preparation of poly(PMDA-TMPDA-TMMDA) Polyimide Thin-Film Composite
(TFC) Membrane
[0015] A 2 wt % Polyimide 1 polymer solution was prepared by
dissolving 0.8 g of Polyimide 1 polymer synthesized in Example 1 in
a solvent mixture consisting of 19.6 g of 1,2,3-trichloro-propane
and 19.6 g of dichloromethane. The solution was filtered using a 1
micron-sized filter to remove any insoluble impurities and allowed
to degas overnight. One drop of Polyimide 1 polymer solution was
introduced to the surface of a pure water bath. The Polyimide 1
solution spread on the surface of water with simultaneous solvent
evaporation to form a thin polymer film on the surface of water.
The thin polymer film on the surface of water was then laminated
onto the surface of a low selectivity, high permeance porous
poly(ether sulfone) support membrane. The resulting TFC membrane
was dried at 70.degree. C. for 1 hour in a conventional oven.
EXAMPLE 5
UV Treatment of Polyimide 1 TFC Membrane
[0016] The UV-treated TFC Polyimide 1 polymer membranes were
prepared by submitting the membrane to a UV lamp from a certain
distance and for a period of time selected based upon the
separation properties sought. For example, one UV treated TFC
Polyimide 1 membrane was prepared from TFC Polyimide 1 membrane
obtained in Example 3 by exposure to UV radiation using 254 nm
wavelength UV light generated from a UV lamp with 10 cm (3.94
inches) distance from the membrane surface to the UV lamp and an
radiation time of 10 minutes. The surface of the Polyimide 1 layer
of the TFC Polyimide 1 membrane was dip coated with a RTV615A/615B
silicone rubber solution. The coated membrane was dried inside a
hood at room temperature for 30 minutes and then dried at
70.degree. C. for 1 hour in a conventional oven.
TABLE-US-00002 TABLE 2 Mixed gas permeation test results of
Polyimide 1 TFC membranes for CO.sub.2/CH.sub.4 Membrane
P.sub.CO2/L (GPU) .alpha..sub.CO2/CH4 Polyimide 1-TFC 178 7.0
Polyimide 1-TFC-UV10 min-2% RTV 13.4 15.8 Conditions: Tested at
50.degree. C., 6895 kPa (1000 psig), 10% CO.sub.2/90% CH.sub.4; 1
GPU = 1 .times. 10 - 6 cm 3 ( STP ) cm 2 s cm Hg ##EQU00001##
Specific Embodiments
[0017] While the following is described in conjunction with
specific embodiments, it will be understood that this description
is intended to illustrate and not limit the scope of the preceding
description and the appended claims.
[0018] A first embodiment of the invention is a polyimide polymer
having a formula
##STR00005##
where m and n are independent integers from 10 to 500 and are in a
ratio from 1:10 to 10:1. An embodiment of the invention is one, any
or all of prior embodiments in this paragraph up through the first
embodiment in this paragraph wherein the ratio of m to n is in a
range from 1:5 to 5:1. An embodiment of the invention is one, any
or all of prior embodiments in this paragraph up through the first
embodiment in this paragraph wherein a polyimide membrane comprises
a polyimide polymer having the above formula. An embodiment of the
invention is one, any or all of prior embodiments in this paragraph
up through the first embodiment in this paragraph wherein the
polyimide polymer is UV treated.
[0019] A second embodiment of the invention is a process for
separating at least one gas from a mixture of gases comprising
providing a UV treated polyimide polymer membrane having a
polyimide polymer with a formula
##STR00006##
where m and n are independent integers from 10 to 500 and are in a
ratio from 1:10 to 10:1; contacting the mixture of gases to one
side of the UV treated polyimide polymer membrane to cause at least
one gas to permeate the membrane; and removing from an opposite
side of the UV treated polyimide polymer membrane a permeate gas
composition comprising a portion of the at least one gas that
permeated the membrane. An embodiment of the invention is one, any
or all of prior embodiments in this paragraph up through the second
embodiment in this paragraph wherein the mixture of gases comprises
a mixture of carbon dioxide and methane. An embodiment of the
invention is one, any or all of prior embodiments in this paragraph
up through the second embodiment in this paragraph wherein the
mixture of gases comprises a mixture of hydrogen and methane. An
embodiment of the invention is one, any or all of prior embodiments
in this paragraph up through the second embodiment in this
paragraph wherein the mixture of gases comprises a mixture of
helium and methane. An embodiment of the invention is one, any or
all of prior embodiments in this paragraph up through the second
embodiment in this paragraph wherein the mixture of gases comprises
a mixture of at least one volatile organic compound and at least
one atmospheric gas. An embodiment of the invention is one, any or
all of prior embodiments in this paragraph up through the second
embodiment in this paragraph wherein the mixture of gases comprises
nitrogen and hydrogen. An embodiment of the invention is one, any
or all of prior embodiments in this paragraph up through the second
embodiment in this paragraph wherein the mixture of gases comprises
a mixture of carbon dioxide, oxygen, nitrogen, water vapor,
hydrogen sulfide, helium and methane. An embodiment of the
invention is one, any or all of prior embodiments in this paragraph
up through the second embodiment in this paragraph wherein the UV
treated polyimide polymer membrane comprises a species that adsorbs
strongly to at least one gas. An embodiment of the invention is
one, any or all of prior embodiments in this paragraph up through
the second embodiment in this paragraph wherein the mixture of
gases comprises a mixture of paraffins and olefins.
[0020] A third embodiment of the invention is a method of preparing
a polyimide polymer membrane comprising a condensation reaction of
pyrometallic dianhydride (PMDA) with a mixture of
2,4,6-trimethyl-1,3-phenylenediamine (TMPDA) and 4,4'-methylene
bis(2,6-dimethylaniline) (TMMDA) in a polar solvent to produce a
polyimide polymer; then making a polyimide polymer membrane from
the polyimide polymer and treating the polyimide polymer membrane
with UV radiation. An embodiment of the invention is one, any or
all of prior embodiments in this paragraph up through the third
embodiment in this paragraph wherein the polar solvent comprises
dimethylacetamide (DMAc) or N-methylpyrrolidone (NMP) solvent. An
embodiment of the invention is one, any or all of prior embodiments
in this paragraph up through the third embodiment in this paragraph
wherein the condensation reaction is a two-step process involving a
formation of a poly(amic acid) followed by a solution chemical
imidization reaction. An embodiment of the invention is one, any or
all of prior embodiments in this paragraph up through the third
embodiment in this paragraph wherein acetic anhydride is used as a
dehydrating agent and pyridine is used as an imidization catalyst
for the solution chemical imidization reaction.
[0021] Without further elaboration, it is believed that using the
preceding description that one skilled in the art can utilize the
present invention to its fullest extent and easily ascertain the
essential characteristics of this invention, without departing from
the spirit and scope thereof, to make various changes and
modifications of the invention and to adapt it to various usages
and conditions. The preceding preferred specific embodiments are,
therefore, to be construed as merely illustrative, and not limiting
the remainder of the disclosure in any way whatsoever, and that it
is intended to cover various modifications and equivalent
arrangements included within the scope of the appended claims.
[0022] In the foregoing, all temperatures are set forth in degrees
Celsius and, all parts and percentages are by weight, unless
otherwise indicated.
* * * * *