Patent Application
20150114906
This invention relates generally to membranes for fluid molecular separation, and more particularly to silylated mesoporous silica on polymeric hollow fiber membranes.
Separation membranes have various potential industrial applications including organic/water separations in the production of biofuels, bio-based chemicals, pharmaceuticals and biomolecules. Membrane-based gas separations have a growing market share due to low energy requirements and facile scale-up of the separation unit. Currently, fluid separation applications may involve the use of porous polymeric or inorganic membranes. Polymeric membranes used for fluid separation applications may be fabricated in a hollow fiber form. Hollow fiber modules have a high surface area/volume ratio, typically in the range of 5,000-10,000 m2/m3, which is an important design consideration for commercial large-scale processes. While polymeric hollow fibers may be adequate for some separation processes, the fluid separation performance of polymeric materials may be limited by their chemical composition and structure.
Despite concentrated efforts to tailor polymer structure to improve separation properties, current polymeric membrane materials have seemingly reached a limit in the trade-off between productivity and selectivity. Although this trade-off is well-studied in the context of gas separations, it also exists in liquid organic/water separations.
Therefore, it remains highly desirable to provide an alternate cost-effective membrane with improved separation properties compared to the polymer membranes. In particular, a long-standing goal has been to produce a selective inorganic membrane on a highly scalable and economical platform (such as a polymeric hollow fiber).
To make such separation membranes more competitive with other separation processes, such as distillation, adsorption and cryogenic separations, there is a need to develop mesoporous silica membranes grown on polymeric hollow fibers with at least one of the following properties:
Thus, a fabrication method is also needed for such mesoporous silica membranes, and their subsequent silylation for use in organic/water separations.
This invention relates generally to membranes for liquid molecular separation and, more particularly, to silylated mesoporous silica on polymeric hollow fiber membranes. Silylated mesoporous silica membranes grown on polymeric hollow fiber supports have been fabricated for the first time, thereby suggesting a scalable membrane platform for organic recovery applications. The silylated mesoporous membranes were selective for permeation of organic molecules in ethanol (EtOH)/water, methyl ethyl ketone (MEK)/water, ethyl acetate (EA)/water, isobutanol (i-BuOH)/water, and n-butanol (n-BuOH)/water pervaporation experiments, whereas the bare membranes are selective for water.
We have surprisingly been able to develop a processing route for making thin, defect-free, silylated mesoporous silica membranes on polymeric hollow fibers, and furthermore used them as a selective membrane for organic/water separation. Additionally, the silylated mesoporous coated hollow fibers of the invention can be packed together (in the thousands to millions) to make highly compact membrane modules with membrane surface areas of several thousand square meters per cubic meter of module volume.
The method of the invention allows the cost effective synthesis of silylated mesoporous membranes on porous polymeric hollow fibers for use in various organic/water separation technologies.
Generally speaking, the method comprises four steps. First, immersion of porous polymeric hollow fibers in an acidic precursor solution containing dissolved silica and a long-chain quaternary amine surfactant (quat). Second, a vapor-phase treatment is performed with a silica source to complete the formation of a stable mesoporous coating. Third, the quaternary amine is extracted from the mesopores by treatment with an appropriate solvent, thereby opening the mesopores for permeation. Finally, after quat extraction, the mesopores are open for treatment with an appropriate silylation agent (e.g., hexamethyldisilazane (HMDS), heptamethyldisilazane) to impart molecular selectivity to the membrane for organic molecules. In contrast, the bare membranes are selective for water. The porous polymeric hollow fibers can be previously produced by an established spinning process.
In more detail, the method includes preparing a coating solution, wherein the coating solution comprises a mixture of a silica source, a quaternary amine surfactant, and acidic water; immersing polymeric hollow fibers in the coating solution, thereby forming a wet mesoporous silica membrane on the polymeric hollow fibers; rinsing and drying the wet mesoporous silica membrane on the polymeric hollow fibers, thereby forming a dried mesoporous silica membrane on the polymeric hollow fiber; and aging the dried mesoporous silica membrane in a vapor of, for example, saturated alkoxysilane. If desired, the quaternary amine molecules can be extracted from the membrane by treatment with an appropriate solvent, rinsing and drying. The remaining mesoporous hollow fiber can then be silylated as desired for a particular application.
The support polymeric hollow fiber used can be any suitable polymer or copolymer made by any conventional method, e.g., spun from a solution through a spinneret. Such hollow fibers include polymeric hollow fibers including various types of polyamide-imides (e.g. TORLON®), polyetherimides (e.g., ULTEM® 1000), polyimides (e.g., MATRIMID®), PVP, CA, PSF, PAN, EC, AR and the like.
The silica in the dissolved silica (silicon hydroxide, also referred to as silicic acid or [SiOx(OH)4-2x]n) can be from any source. Silicic acids may be formed by acidification of silicate salts (such as sodium silicate) in aqueous solution, and herein we employed a common source of silica, which is tetraethylorthosilicate (TEOS). It is known that use of different alkoxysilanes can control the type of mesoporous silica. The use of TEOS can create a mesoporous silica Mobil Composition Matter 48 (MCM-48) surface, whereas the use of other silicates and surfactants can create other mesoporous silicas.
Quaternary amine surfactants (also known as quats) include the positively charged polyatomic ions of the structure NR4+, R being an alkyl or aryl group, and where each R can be the same or different. In preferred embodiments, the R is an alkyl or aryl of at least 6, for example 8 carbons. Preferred quaternary amine surfactants include benzalkonium chloride, benzethonium chloride, methylbenzethonium chloride, cetalkonium chloride, cetylpyridinium chloride, cetrimonium, cetrimide, dofanium chloride, tetraethylammonium bromide, didecyldimethylammonium chloride and domiphen bromide, and the like. Particularly preferred is cetyltrimethylammonium bromide (CTAB).
One embodiment of a liquid separation device in accordance with the present disclosure includes a porous support structure comprising polymeric hollow fibers and a mesoporous membrane or coating disposed on the porous support structure, wherein the mesoporous membrane comprises an inorganic material such as silica. Moreover, the pore diameter of these materials can be controlled within mesoporous range between about 1.5 nm to about 20 nm by adjusting the synthesis conditions and/or by employing surfactants with different chain lengths in their preparation.
It is possible to scale up the preparation of one foot or longer silica/CTAB membranes in the present disclosure free of any substantial defect, and such long coated hollow fibers can be bundled together to make various separation devices. There appears no limitation to the formation of these coatings on hollow fibers of any desirable length. These devices can then be used in various separation or purification processes.
These and other objects, features, and advantages will become apparent as reference is made to the following detailed description, preferred embodiments, and examples, given for the purpose of disclosure, and taken in conjunction with the accompanying drawings and appended claims.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed disclosure, taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals, and wherein:
The following detailed description of various embodiments of the present invention references the accompanying drawings, which illustrate specific embodiments in which the invention can be practiced. While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those skilled in the art to which the invention pertains. Therefore, the scope of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.
One aspect of the present invention relates to liquid separation devices and methods of making and using such devices. Referring to
The mesoporous membrane 102 may comprise a suitable inorganic material, such as mesoporous MCM. The MCM may be silica-based, such as MCM-48 or MCM-41, and the like.
The mesoporous membrane 102 may comprise a suitable inorganic material, such as a mesoporous silica. For example, the composite inorganic material may include a mesoporous silica-type material and a quaternary amine. In an exemplary embodiment, the mesoporous membrane 102 may comprise mesoporous silica and cetyltrimethylammonium bromide (CTAB). The CTAB may be disposed in the network of pores formed in the mesoporous structure.
The porous support structure 104 may be made from any suitable polymer spun by a conventional method (e.g., spun from a solution through a spinneret). Macroporous hollow fiber supports may be fabricated by a dry-jet/wet-quench method. (See e.g., Brown, A. J., et al., A
An exemplary self-assembly method is provided herein for preparing a mesoporous silica/CTAB composite membrane. Conventional techniques for coating silica/surfactant composite films with 2-dimensional hexagonal, 3-dimensional hexagonal and simple cubic structures on dense flat surfaces are described in Aksay, I. A., et al., S
The present disclosure, however, provides an improved immersion technique for disposing a composite membrane on porous hollow fibers as well as on a flat, dense surface. The presence of the porous, rough surface alters the mechanism of formation of the mesoporous coating in comparison to a flat, dense surface, because the combination of physical and chemical interactions between the reactants and the surface changes. Importantly, the mesoporous coatings must be uniform over large areas and/or fiber lengths, and free of defects (such as pin-holes and cracks) over large areas and/or fiber lengths. Therefore, molecules should only permeate through the pores of the mesoporous material.
In an embodiment according to the present disclosure, a mesoporous silica/CTAB composite membrane layer is prepared by immersion of the polymeric hollow fibers in a coating solution containing a dissolved silica source, CTAB, and acidic water for between about 10 minutes and about 24 hours at a temperature of between about 10° C. to 80° C. The pH of the coating solution may be between about 0 and about 4, as adjusted by adding an acid (e.g., HCl). The composition of the mixture solution may be expressed in terms of the following molar ratios: 1.0 SiO2:a CTAB:b H2O. In an embodiment, a is between about 0.1 and about 1, and b is between about 20 and about 200. In one embodiment, the source of silica is alkoxysilane, such as TEOS, fumed silica, colloidal silica and the like.
After immersion of at least a portion of the polymeric hollow fibers in the coating solution, a mesoporous silica/CTAB composite membrane layer is grown on the surface of the polymeric hollow fibers. It is believed that during substrate immersion in the coating solution, surfactants are adsorbed on the surface of the substrate and self-assemble to form ordered micelles. At the same time, capillary forces can be used to drive the reactant solution into the pores of the hollow fiber near the surface, thereby further assisting the formation of a continuous membrane. Silica precursors are intercalated into the self-assembled surfactants, and, thereby, the mesoporous silica/CTAB composite is grown at the surface of the porous substrate.
The resultant mesoporous silica/CTAB membranes include a silica structure containing a network of 3-dimensionally ordered pores filled with CTAB molecules. The diameter of the channels is preferably between about 1 nm and about 5 nm. In the mesoporous silica/CTAB membrane, CTAB molecules may be confined within the rigid silica wall, and continuously connected to each other.
The presence of a mesoporous silica/CTAB membrane or coating is confirmed by scanning electron microscopy (SEM) as shown in
The thickness of the mesoporous silica/CTAB membrane layer depends in part on the immersion time and the porous structure of the polymeric hollow fibers. The layer thicknesses can be measured by scanning electron microscopy (SEM). As shown in
The mesoporous silica/CTAB membrane is then aged with saturated TEOS vapor in a closed vessel prior to use. We have discovered that the initial coating of mesoporous silica is silicon-deficient (i.e., there are not enough silicate species to form a mechanically strong network, even though it does form a cubic pore structure). However, when exposed to TEOS vapor, additional silica species were provided and incorporated into the existing network, thus strengthening the mesoporous structure. In one embodiment, an aging temperature is between about 50° C. and about 150° C., and an aging period is between about 1 hour and about 48 hours.
The gas separation performance of hollow fiber membranes can be evaluated by measuring its gas permeance. Permeance is measured in gas permeation units (GPU), which is defined as follows:
GPU=(10−6×cm3(STP))/(cm2×sec×(cm Hg)
In other words, permeance of a membrane may be measured in terms of the amount of gas permeated by the membrane per unit time (cm3(STP)/sec) per unit (cm2) surface area of the membrane, per unit pressure difference (cm Hg) across the membrane. The selectivity of gas separation membranes is defined as the ratio of the rate of passage of the more permeable components (e.g., CO2) to the rate of passage of the less permeable component (e.g., N2).
In an embodiment, the support polyamide-imide (e.g., TORLON®) hollow fiber has CO2 permeance of 50,000 GPU and CO2/N2 selectivity of 0.93 at 35° C. for gases with 10 psig feed pressure. In another embodiment, N2 and CO2 permeances of the mesoporous silica/CTAB membrane coated on polyamide-imide (e.g., TORLON®) hollow fibers were measured at the 50 psig feed pressure. The silica/quat membrane has CO2 permeance of 11 and CO2/N2 selectivity of 1.9. Selective transport of CO2 through silica/quat composite membranes is facilitated by adsorption of CO2 to quaternary amine group of CTAB and by diffusion through continuously connected CTAB channels.
In another embodiment, the quaternary amine molecules confined within the ordered silica wall can be removed by the solvent extraction. The extraction method used in the present disclosure allows the production of mesoporous silica membranes with continuous open pore channels formed on support polymeric hollow fibers. In this embodiment, the quaternary amine molecules are extracted using a solvent such as water, alcohols or a mixture thereof, for a period between about 1 hour and about 72 hours at a temperature between about 20° C. and about 100° C. The pH of the extraction solvent may be between about 0 to about 7, as adjusted by adding an acid (e.g., HCl). Examples of alcohols include, but are not limited to, methanol (MeOH), ethanol (EtOH), propanol (PrOH), isopranol (i-PrOH), n-butanol (n-BuOH), isobutnaol (i-BuOH), sec-butanol (sec-BuOH), and tert-butnaol (tert-BuOH).
After the solvent extraction, the mesoporous silica membrane coated on polyamide-imide (e.g., TORLON®) hollow fiber has a CO2 permeance of 4,400 GPU and N2 permeance of 3,300 GPU at 35° C. for gases with 50 psig feed pressure. The support polyamide-imide (e.g., TORLON®) hollow fiber has a CO2 permeance of 50,000 GPU and N2 permeance of 54,000 GPU at 35° C. for gases with 10 psig feed pressure. These permeances show that CTAB has been extracted and the mesoporous silica membrane has continuous open pore channels.
After quat extraction, the mesoporous channels are open for treatment with an appropriate silylation agent (e.g., hexamethyldisilazane (HMDS), heptamethyldisilazane) in order to impart molecular selectivity to the membrane for organic molecules. In contrast, the bare membranes are selective for water. With the selective use of silylation agents, the separation devices can be used in organic/water separation applications.
These embodiments provide an organic selective membrane with a hollow fiber support and its economically feasible manufacture method. The silylated mesoporous silica membranes of the present invention can be prepared by simile immersion, vapor deposition, extraction and silylation techniques.
As a support polymeric fiber, polyamide-imide (e.g., TORLON®) hollow fibers were used. Macroporous polyamide-imide (e.g., TORLON®) hollow fiber supports were fabricated by a dry-jet/wet-quench method. (See e.g., Brown, A. J., et al., A
The mesoporous silica membrane was fabricated by simple immersion, vapor deposition and extraction techniques. (See Jang, K. S., et al., C
After the immersion process, the prepared hollow fiber membranes were aged with saturated TEOS vapor prior to use. A 22 cm-long fiber membrane was placed with 25 μL of TEOS in a closed vessel at 373° K for 24 hours. After the aging process, the fiber membranes were washed with 0.05 N HCl/ethanol under stirring for about 24 hours to extract the surfactant.
After the extraction process, the extracted mesoporous silica membranes were evacuated in a vacuum oven at 423° K under 0.07 atm, to remove physically adsorbed moisture and residual surfactant prior to silylation.
After the evacuation process, the evacuated membranes were exposed to HMDS vapor in a closed vessel at 373° K for about 24 hours. After the silylation process, the silylated membranes were washed with deionized water for about 30 minutes in a separate container under stirring. After the water extraction process, the coated membranes were dried at 363° K before preparing the pervaporation measurement module.
The gas permeation of the mesoporous silica membranes was measured using an in-house constructed hollow fiber permeation testing system. (See e.g., Al-Jualed, M.; Koros, W. J., J. M
The gas permeances of the silylated mesoporous membranes were also measured. Permeances of N2 and CO2 decrease substantially after silylation, consistent with a reduction in porosity and decreased adsorption due to pore functionalization with trimethylsilyl groups. However, CO2 shows less reduction, possibly due to its stronger adsorption on the silylated surface. As in the case of other mesoporous membranes (templated-extracted and evacuated membranes), the silylated mesoporous membranes have a constant permeance regardless of feed pressure, consistent with gas molecule transport being governed by a Knudsen-like mechanism. Surprisingly, a significant reduction of gas permeance may also be attributed to silylation of the polyamide-imide (e.g., TORLON®) support. As shown in
Pervaporation measurements were carried out using an aqueous mixture of a specific organic (5 wt % organic) at 303° K and 323° K using an in-house constructed hollow fiber pervaporation testing system. (See Al-Jualed, M.; Koros, W. J., J. M
The pore structure of the mesoporous silica membrane was investigated in further detail by XRD and TEM imaging. The X-ray diffraction (XRD) patterns of the membranes were obtained by a PANalytical X'pert diffractometer using a Cu-K-alpha X-ray source, diffracted beam collimator, and a proportional detector. For XRD, the samples were aligned on the center of an aluminum mount and attached to the surface with double-sided tape.
The silica layers of the same set of membranes were examined by high-resolution transmission electron microscopy (TEM).
Attenuated total reflectance (FT-ATR) was used to investigate the modification of the silica layer.
Pervaporation data for five different organic/water mixtures is summarized in
J
i=(Pm,i)(γixipisat−yipp)Ji=(Pm,i)(γixipisat−yipp)
where Ji is the molar flux of component i, Pm,i the permeance, γi the activity coefficient, xi the feed mole fraction, pisat the saturated vapor pressure, yi the permeate mole fraction, and pp the permeate pressure.
Interestingly, the permeances of the organic species do not change much with increasing temperature, whereas the permeance of water increases significantly at 323° K. This result indicates that the permeance of the organic species is more highly dependent on adsorption of the components into the mesopores rather than diffusivity in the mesopores. Even though the silylated mesoporous membrane has high organic fluxes and high organic separation factors (see
As a result of the pervaporation properties discussed above, the inventors found that the silylated mesoporous silica on polyamide-imide (e.g., TORLON®) hollow fiber membranes according to an embodiment of the present invention are able to upgrade 5 wt % organic/water feed mixtures to 19% EtOH, 53% MEK, 83% EA, 45% i-BuOH, and 40% n-BuOH permeate streams in a single pass at 303° K (see
Similarly, these template-extracted membranes, evacuated membranes, and silylated membranes may also be used to upgrade other organic/mixtures. In various embodiments of the present invention, other alcohol/water feed mixtures may be used to upgrade the organic component to a significantly higher concentration. For example, the organic/water feed mixtures may be (about 2/98 w/w to about 20/80 w/w) EtOH/water, MEK/water, EA/water, i-BuOH/water, and n-BuOH/water. The alcohol/water pervaporation separations may be performed at about 300 to 325° K, as discussed above.
In other embodiments, other organic/water feed mixtures may be used to upgrade the organic component as summarized below in Table 3. The organic/water feed mixtures may contain one or more compounds. Each organic compound in water may have a concentration range of about 2/98 w/w to 20/80 w/w for acids/water, alcohols/water, aldehydes/water, ethers/water and ketones/water, and a concentration range of about 20/80 w/w to 40/60 w/w for sorbitol/water and sugars/water.
In an embodiment, the oxygenates may be selected from the group consisting of acids, alcohols, aldehydes, cyclic ethers, cyclic ketones, ethers, and ketones. In an embodiment, the oxygenates may be selected from C1 to C6 oxygenates.
In an embodiment, the acids may be selected from the group consisting of C2 to C6 acids. In an embodiment, the acids may be selected from the group consisting of acetic acid (HAc) and propanoic acid (HPr).
In an embodiment, the alcohols may be selected from the group consisting of C1 to C6 alcohols. In an embodiment, the alcohols may be selected from the group consisting of MeOH, EtOH, PrOH, i-BuOH and n-BuOH.
In an embodiment, the aldehydes may be selected from the group consisting of C2 to C6 aldehydes. In an embodiment, the aldehydes may be selected from the group consisting of acetaldehyde (AA) and propanal.
In an embodiment, the ethers may be selected from the group consisting of C2 to C6 ethers. In an embodiment, the cyclic ethers may be selected from the group consisting of C4 to C6 cyclic ethers. In an embodiment, the cyclic ethers may be selected from a group consisting of tetrahydrofuran (THF) and dioxane (Di). In an embodiment, the ether is EA.
In an embodiment, the ketones may be selected from the group consisting of C3 to C6 ketones. In an embodiment, the ketones may be selected from the group consisting of acetone, butanone and hexanone. In an embodiment, the ketone is MEK.
In an embodiment, the cyclic ketones may be selected from the group consisting of C5 to C6 cyclic ketones. In an embodiment, the cyclic ketones may be selected from the group consisting of cyclopentanone and cyclohexanone.
In an embodiment, the sugars may be selected from the group consisting of monosaccarides, disaccharides, fructose (Fru), sucrose (Suc) and glucose (Glu).
The embodiments and examples set forth herein are presented to best explain the present invention and its practical application and to thereby enable those skilled in the art to make and utilize the invention. However, those skilled in the art will recognize that the foregoing description and examples have been presented for the purpose of illustration and example only. The description as set forth is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching without departing from the spirit and scope of the following claims. Thus, the breadth and scope of the invention(s) should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the claims and their equivalents issuing from this disclosure. Furthermore, the above advantages and features are provided in described embodiments, but shall not limit the application of such issued claims to processes and structures accomplishing any or all of the above advantages.
Additionally, the section headings herein are provided for consistency with the suggestions under 37 C.F.R. §1.77 or otherwise to provide organizational cues. These headings shall not limit or characterize the invention(s) set out in any claims that may issue from this disclosure. Specifically and by way of example, although the headings refer to a “Technical Field,” such claims should not be limited by the language chosen under this heading to describe the so-called technical field. Further, a description of a technology in the “Background” is not to be construed as an admission that technology is prior art to any invention(s) in this disclosure. Neither is the “Summary” to be considered as a characterization of the invention(s) set forth in issued claims. Furthermore, any reference in this disclosure to “invention” in the singular should not be used to argue that there is only a single point of novelty in this disclosure. Multiple inventions may be set forth according to the limitations of the multiple claims issuing from this disclosure, and such claims accordingly define the invention(s), and their equivalents, that are protected thereby. In all instances, the scope of such claims shall be considered on their own merits in light of this disclosure, but should not be constrained by the headings herein.
As used herein, the terms “a,” “an,” “the,” and “said” means one or more.
As used herein, the term “about” means the stated value plus or minus a margin of error or plus or minus 10% if no method of measurement is indicated.
As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.
As used herein, the terms “comprising,” “comprises,” and “comprise” are open-ended transition terms used to transition from a subject recited before the term to one or more elements recited after the term, where the element or elements listed after the transition term are not necessarily the only elements that make up the subject.
As used herein, the terms “containing,” “contains,” and “contain” have the same open-ended meaning as “comprising,” “comprises,” and “comprise,” provided above.
As used herein, the terms “having,” “has,” and “have” have the same open-ended meaning as “comprising,” “comprises,” and “comprise,” provided above.
As used herein, the terms “including,” “includes,” and “include” have the same open-ended meaning as “comprising,” “comprises,” and “comprise,” provided above.
As used herein, the phrase “consisting essentially of” occupies a middle ground, allowing the addition of non-material elements that do not substantially change the nature of the invention, such as various buffers, differing salts, extra wash or precipitation steps, pH modifiers, and the like.
As used herein, the phrase “consisting of” is a closed transition term used to transition from a subject recited before the term to one or more material elements recited after the term, where the material element or elements listed after the transition term are the only material elements that make up the subject.
As used herein, the phrase “free of defects” means that the mesoporous coating is at least 95% free of defects, and preferably at least 97, 98, 99 or 100% free of defects, and that any existing defects are less than 10 nm in diameter, preferably not more than the pore width, such that the coating is essentially continuous and does not allow the gas or liquid to be treated to escape through, e.g., a large crack in the coating.
As used herein, the term “mesoporous” means a three-dimensional (3D) structure of interconnected pores ranging in diameter from 0.1-10 nm. Preferably, the pore sizes range between 1-5 nm or 2-4 nm in diameter, but the sizes can be varied depending on which gases or liquids are to be separated.
As used herein, the term “polymer” includes polymer made from one or more monomeric units, and, thus, includes polymers, copolymers, block polymers, terpolymers and the like unless indicated otherwise.
As used herein, the term “simultaneously” means occurring at the same time or about the same time, including concurrently.
The following abbreviations are used herein:
All patents and patent applications, articles, reports, and other documents cited herein are fully incorporated by reference to the extent they are not inconsistent with this invention, as follows:
The present application claims priority to U.S. Provisional Patent Application No. 61/895,145, filed on Oct. 24, 2013, for “Silylated Mesoporous Silica Membranes on Polymeric Hollow Fiber Supports.”
| Number | Date | Country | |
|---|---|---|---|
| 61895145 | Oct 2013 | US |
