WO2017095527A1

WO2017095527A1 - Aerogel filtration devices and uses thereof

Info

Publication number: WO2017095527A1
Application number: PCT/US2016/055870
Authority: WO
Inventors: Alan SAKAGUCHI; Garrett Poe
Original assignee: Blueshift International Materials, Inc.
Priority date: 2015-12-02
Filing date: 2016-10-07
Publication date: 2017-06-08

Abstract

Apparatuses and/or methods for filtrating fluids are described. The apparatuses can include polymeric aerogels.

Description

AEROGEL FILTRATION DEVICES AND USES THEREOF CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 62/262,059, filed December 2, 2015. The contents of the referenced application are incorporated into the present application by reference.

BACKGROUND OF THE INVENTION

A. Field of the Invention

[0002] The present disclosure relates to the removal of contaminants from fluids. In particular, the invention concerns apparatuses and methods of using polymeric aerogels for filtration of fluids.

B. Description of Related Art

[0003] There are many uses of fluids wherein filtered fluids ("filtrates") are required or preferred. The filtrates needed vary greatly; thus, there is a need for many different filters, filter apparatuses, and filtering methods. As examples, fluid filtrates may be liquids, gases, supercritical feed fluids, or mixtures thereof. Some filtrates need to be provided at flow rates of gallons or liters per minute, while other filtrates are needed from feed fluids of less than 1 ml in volume. Some filtrates and feed fluids can cause undesired solvation or degradation of the available filters and filter systems. Many filters have poor performance (e.g. , clogging or slow rates) due to agglomeration of impurities in the filter. [0004] Several factors can impact the performance of a filter, and these factors can be important in determining the most appropriate filter for the desired application. These factors include the porosity, structure, material, and surface area of a filter. Porosity of a filter can control the flow rate of a fluid through the filter as well as the amount and characteristics of the contaminants that a filter will remove. The structure of a filter can impact the types of practical applications that the filter can be put to use. For example, a powdered filter may make it difficult to bond with an adhesive and may require special handling and/or packaging in a filtering device, while larger size of pores in a filter can make a filter useless for trapping small particle impurities and/or small particle desired substances. The material of a filter can determine the cost and what feed fluids will cause undesired degradation or solvation of the filter. Increased surface area of a filter can be used to increase exposure to a feed fluid to the material of the filter or affixed/imbedded chemicals therein that attract or repel contaminants and/or desired substances contained in the feed fluid. Recent attempts to purify water have included the use of carbon (e.g. , carbon black, charcoal, graphene, carbon nanotubes and the like) or carbon aerogels for removal of ions and/or other impurities. For example, Xu et al., "Treatment of brackish produced water using carbon aerogel-based capacitive deionization technology", Water Research, 2008, 42, 2605-2617, describes the use of carbon-aerogel electrodes to remove iodide, bromide, calcium, magnesium, sodium and chloride ions from brackish water. [0005] An aerogel is a porous solid that is formed from a gel, in which the liquid that fills the pores of the solid has been replaced with a gas. Shrinkage of the gel' s solid network during drying is negligible or all-together prevented. Aerogels are generally characterized as having high porosity (about 94-98%), and high specific surface area. Aerogels also possess relatively low densities and are unique solids with up to 99% porosity. Such large porosities confer a number of useful properties to aerogels, including high surface area, low refractive index, low dielectric constant, low thermal-loss coefficient, and low sound velocity.

[0006] The variation in filtrate needs has driven the development of numerous types of commercially available fluid filtrations systems. However, the available fluid filtration systems do not satisfy all of the demands for filtrates. SUMMARY OF THE INVENTION

[0007] A discovery has been made that solves many problems associated with filtration of fluid. Notably, the discovery is premised on the use of polymeric aerogels in fluid filtration apparatuses and filtration methods.

[0008] In some aspects, disclosed herein are methods for filtering a fluid. The fluid can contain impurities and/or desired substances. The method can include contacting a feed fluid with a polymeric aerogel under conditions sufficient to remove at least a portion of the impurities and/or desired substances from the feed fluid and produce a filtrate. In some instances, the aerogel can be an organic polymer aerogel. The polymer can be a thermoset polymer and/or a thermoplastic polymer. In a particular aspect, the aerogel can be a polyimide aerogel. In some instances, the aerogel is not a carbon nanotube aerogel, a silica aerogel, an inorganic aerogel, or combinations thereof. The aerogel can be a polysiloxane aerogel and/or a modified polysiloxane aerogel. In some instances, the aerogel can be in the form of a film, powder, blanket, or a monolith.

[0009] In some instances, the feed fluid used in the methods disclosed herein can be a liquid, a gas, a supercritical fluid, or a mixture thereof. The feed fluid can contain water (H₂0) and/or be a non-aqueous liquid. Water can be any type of water, water vapor, steam, pressurized water, ice, and/or supercritical water. The non-aqueous fluid can be an oil, a solvent, or any combination thereof. In some instances, the feed fluid can be a solvent (e.g., an organic solvent). The feed fluid can be an emulsion (e.g., a water-oil emulsion, an oil- water emulsion, a water-solvent emulsion, a solvent-water emulsion, an oil-solvent emulsion, or a solvent-oil emulsion). The feed fluid can be a biological fluid (e.g., blood, plasma, or both). The feed fluid can be a gas (e.g., air, nitrogen, oxygen, an inert gas, or mixtures thereof). In some instances, the filtrate can be substantially free of impurities and/or a desired substance.

[0010] In some aspects, the present disclosure provides an apparatus for filtering a fluid in need of filtering. The fluid can be a feed fluid containing impurities and/or a desired substance. The apparatus can include: a separation zone configured to remove impurities and/or desired substance from the feed fluid and produce a filtrate; and an inlet configured to be in fluid communication with the separation zone to receive a feed fluid and/or an outlet configured to be in fluid communication with the separation zone to remove the filtrate from the separation zone. The separation zone can include a polymeric aerogel (e.g., organic polymeric aerogel, a thermoset polymeric aerogel, a thermoplastic polymeric aerogel or any combination thereof). In a particular instance, the aerogel can be a polyimide aerogel. In some instances, the aerogel is not a carbon nanotube aerogel, a silica aerogel, an inorganic aerogel or combinations thereof. In some instances, the aerogel can be in the form of a film, membrane powder, blanket, or a monolithic aerogel.

[0011] In some instances, the apparatus is configured to remove impurities and/or desired substances from a feed fluid that can be a liquid, a gas, a supercritical fluid, or a mixture thereof. The feed fluid can contain water (H₂0), a non-aqueous fluid, an oil, a solvent, or any combination thereof. Water can be any type of water, water vapor, steam, pressurized water, ice, and/or supercritical water. The non-aqueous fluid can be a solvent (e.g., an organic solvent). The feed fluid can be an emulsion (e.g., a water-oil emulsion, an oil-water emulsion, a water-solvent emulsion, a solvent-water emulsion, an oil-solvent emulsion, or a solvent-oil emulsion). In certain instances, the feed fluid can be a biological fluid (e.g., blood, plasma, or both). The feed fluid can be a gas (e.g., air, nitrogen, oxygen, an inert gas, or mixtures thereof). The filtrate can be substantially free of impurities and/or desired substances. [0012] In some aspects, disclosed herein are methods for filtering a fluid using any one of the apparatus disclosed herein. In some instances, the method includes providing a fluid containing impurities and/or desired substances to a polymeric aerogel of the separation zone of the apparatus; and contacting at least a portion of the fluid with the polymeric aerogel to form a filtrate. [0013] The following includes definitions of various terms and phrases used throughout this specification.

[0014] "Aerogel", as used herein, refers to a unique class of low density and primarily open-cell materials. Aerogels typically have low bulk densities (about 0.15 g/cm or less, preferably about 0.03 to 0.3 g/cm ), very high surface areas (generally from about 200 to 1,000 m 2 /g and higher, preferably about 700 to 1000 m 2 /g), high porosity (about 90% and greater, preferably greater than about 97%), and relatively large pore volume (more than about 3.8 mL/g, preferably about 3.9 mL/g and higher).

[0015] The terms "polymer" or "polymeric" aerogel refers to aerogels that include carbon, hydrogen atoms and optionally, heteroatoms, and/or siloxane or modified siloxane compounds. Non-limiting examples of polymer aerogels include aerogels made from thermoset or thermoplastic polymers. Polymer or polymeric aerogels do not include compounds made of allotrope of carbon such as amorphous carbon, graphene, carbon nanotubes, graphite or other carbon allotropes.

[0016] The terms "impurity" or "impurities" refers to unwanted substances in a feed fluid that are different than a desired filtrate and/or are undesirable in a filtrate. In some instances, impurities can be solid, liquid, gas, or supercritical fluid. In some embodiments, an aerogel can remove some or all of an impurity.

[0017] The term "desired substance" or "desired substances" refers to wanted substances in a feed fluid that are different than the desired filtrate. In some instances, the desired substance can be solid, liquid, gas, or supercritical fluid. In some embodiments, an aerogel can remove some or all of a desired substance.

[0018] The term "substantially" and its variations are defined as being largely but not necessarily wholly what is specified as understood by one of ordinary skill in the art, and in one non-limiting embodiment substantially refers to ranges within 10%, within 5%, within 1%, or within 0.5%.

[0019] The use of the word "a" or "an" when used in conjunction with the terms "comprising," "including," "containing," or "having" in the claims and/or the specification may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one."

[0020] The terms "about" or "approximately" are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment, the terms are defined to be within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%. [0021] The use of the term "or" in the claims is used to mean "and/or" unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and "and/or."

[0022] As used in this specification and claim(s), the words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include") or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0023] The methods and apparatus of the present invention can "comprise," "consist essentially of," or "consist of particular ingredients, components, compositions, etc. disclosed throughout the specification. With respect to the transitional phase "consisting essentially of," in one non-limiting aspect, a basic and novel characteristic of the methods and apparatus of the present invention is the ability to use a polymeric aerogel to filter a fluid in need of filtering. [0024] Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings.

[0026] FIG. 1 is a schematic of system of an embodiment for filtering a fluid using an aerogel, the system having a separation zone, an inlet, and an outlet.

[0027] FIG. 2 is a schematic of system of an embodiment for filtering a fluid using an aerogel, the system having a separation zone and an inlet. [0028] FIG. 3 is a schematic of system of an embodiment for filtering a fluid using an aerogel, the system having a separation zone and an outlet.

[0029] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and may herein be described in detail. The drawings may not be to scale. DETAILED DESCRIPTION OF THE INVENTION

[0030] A discovery has been made that provides apparatus and/or methods that include a polymeric aerogel for filtrating a fluid. These and other non-limiting aspects of the present invention are discussed in further detail in the following sections. A. Filtration Apparatuses and Applications

[0031] Systems and methods to filter a fluid using an aerogel are described. The feed fluid can be contacted with an aerogel such that some, all or, substantially all, of the impurities and/or desired substances are removed from the feed fluid to produce a filtrate essentially devoid of the impurities and/or desired substances. The filtrate, impurities, and/or desired substances can be collected, stored, transported, recycled, or further processed. The aerogel can be further processed to release the impurities and/or desired substances from the aerogel.

[0032] Aerogels can be used in or with filtration apparatuses known in the art. Non- limiting examples of filtration apparatuses and applications include gas filters such as, but not limited to, building air filters, automotive cabin air filters, combustion engine air filters, aircraft air filters, satellite air filters, face mask filters, diesel particulate filters, in-line gas filters, cylinder gas filters, soot filters, pressure swing absorption apparatus, etc. Additional non-limiting examples of filtration apparatuses and applications include solvent filtration systems, column filtration, chromatography filtration, vacuum flask filtration, microfiltration, reverse osmosis filtration, nanofiltration, ultrafiltration, centrifugal filtration, gravity filtration, cross flow filtration, dialysis, hemofiltration, hydraulic oil filtration, automotive oil filtration, etc. Further, non-limiting examples of the purpose of filtration includes sterilization, separation, purification, isolation, etc. [0033] FIGS. 1, 2, and 3 are non-limiting schematics of a system 100 used to carry out a filtration of a fluid using an aerogel. System 100 can include a separation zone 101. The materials, size, and shape of the separation zone 101 can be determined using standard engineering practice to achieve the desired flow rates and contact time. The separation zone

101 is capable of holding or may be made of one or more aerogels and includes a feed fluid inlet 102 (inlet) and/or a filtrate outlet 103 (outlet). In some instances, the separation zone is made entirely of one or more aerogels or one or more aerogels in or around a supporting structure. The feed fluid 104 can be introduced to the separation zone 101 through the inlet

102 (See, FIGS. 1 and 2) or through direct contact with the separation zone 101 (FIG. 3). In some embodiments, the feed fluid 104 can be received under greater or reduced pressure than ambient pressure. Introduction of the feed fluid 104 into separation zone 101 can be at a rate sufficient to allow optimum contact of the feed fluid with the one or more aerogels. Contact of the feed fluid 104 with the aerogel can allow the feed fluid to be filtered by the aerogel, which results in the filtrate 105. The filtrate 105 can have less impurity and/or desired substance when compared with the feed fluid 104. In certain aspects, the filtrate 105 can be essentially free of the impurity and/or the desired substance. The filtrate 105 can exit the separation zone 101 via the outlet 103 (See, FIGS. 1 and 3) or through directly exiting the separation zone 101 (See, FIG. 2). In some instances, the filtrate can be recycled back to a separation zone, collected, stored in a storage unit, etc. In some instances, one or more aerogels can be removed and/or replaced from the separation zone. In some instances, the filtrate 105 can be collected and/or removed from the separation zone 101 without the filtrate 105 flowing through an outlet 103. In some instances, the impurities and/or desired substance can be removed from the separation zone 101. As one non-limiting example, the impurities and/or desired substances can be removed from the separation zone by flowing a fluid through the separation zone in the reverse direction from the flow of the feed fluid through the separation zone.

[0034] The filtration conditions in the separation zone 101 can be varied to achieve a desired result (e.g., removal of substantially all of the impurities and/or desired substance from the feed fluid). The filtration conditions include temperature, pressure, fluid feed flow, filtrate flow, or any combination thereof. Filtration conditions are controlled, in some instances, to produce streams with specific properties. The separation zone 101 can also include valves, thermocouples, controllers (automated or manual controllers), computers or any other equipment deemed necessary to control or operate the separation zone. The flow of the feed fluid 104 can be adjusted and controlled to maintain optimum contact of the feed fluid with the one or more aerogel. In some embodiments, computer simulations can be used to determine flow rates for separation zones of various dimensions and various aerogels.

[0035] The compatibility of an aerogel with a fluid and/or filtration application can be determined by methods known in the art. Some properties of an aerogel that may be determined to assess the compatibility of the aerogel may include, but is not limited to: the temperature and/or pressures that the aerogel melts, dissolves, oxidizes, reacts, degrades, or breaks; the solubility of the aerogel in the material that will contact the aerogel; the flow rate of the fluid through the aerogel; the retention rate of the impurity and/or desired product form the feed fluid; etc. B. Aerogels

[0036] A gel can be a spongelike, three-dimensional solid network whose pores are filled with another non-gaseous substance, such as a liquid. Drying of the gel that exhibits unhindered shrinkage and internal pore collapse during drying provides materials commonly referred to as xerogels.

[0037] By contrast, a gel that dries that exhibits little or no shrinkage and internal pore collapse during drying can yield an aerogel. An aerogel is a porous solid that is formed from a gel, in which the liquid that fills the pores of the solid has been replaced with a gas. Shrinkage of the gel's solid network during drying is negligible or all-together prevented due to the minimization of or resistance to the capillary forces acting on the network as the liquid is expended. Aerogels are generally characterized as having high porosity (about 94-98%), and high specific surface area. Aerogels also possess relatively low densities and are unique solids with up to 99% porosity. Such large porosities confer a number of useful properties to aerogels, including high surface area, low refractive index, low dielectric constant, low thermal-loss coefficient, and low sound velocity.

1. Methods of Making Polymeric Aerogels

[0038] Polymeric aerogels may be made by methods known in the art. The polymeric aerogels or wet gels used to prepare the aerogels may be prepared by any known gel-forming techniques: examples include adjusting the pH and/or temperature of a dilute polymer sol to a point where gelation occurs. The gel may be dried in a manner known in the art that prevents or reduces gel contraction during drying. Non-limiting examples of methods of drying include using a supercritical drying technique to remove the solvent from the gel. Supercritical C0₂ is one example of a supercritical fluid that can be used during the supercritical drying technique. Non-limiting examples of supercritical drying techniques include the Hunt process and can be found in U.S. Patent Number 9,109,088 to Meador et al. Other examples of methods for making aerogels include those disclosed in the following U.S. Patent Publication Number: 2014/0350134 by Rodman et al. a. Synthesis of Polymeric Gels

[0039] The first stage in the synthesis of a polymeric aerogel can be the synthesis of a gel. A gel may be prepared by any means known in the art. The following is a non-limiting example of the synthesis of a polyimide aerogel. For a polyimide aerogel, at least one acid monomer can be reacted with at least one diamino monomer in a reaction solvent to form a poly(amic acid). As discussed below, numerous acid monomers and diamino monomers may be used to synthesize the poly(amic acid). In one aspect, the poly(amic acid) is contacted with an imidization catalyst in the presence of a chemical dehydrating agent to form a polymerized polyimide gel via an imidization reaction. Any imidization catalyst suitable for driving the conversion of polyimide precursor to the polyimide state is suitable. Preferred chemical imidization catalysts can include at least one compound selected from the group consisting of pyridine, methylpyridines, quinoline, isoquinoline, l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), triethylenediamine, lutidine, N-methylmorpholine, triethylamine, tripropylamine, tributylamine, and other trialkylamines. Any dehydrating agent suitable for use in formation of an imide ring from an amic acid precursor is suitable for use in the methods of the present invention. In some instances, dehydrating agents can include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic, anhydride, trifluoro acetic anhydride, phosphorus trichloride, and dicyclohexylcarbodiimide.

[0040] In some instances, the reaction solvent may be selected from the group consisting of dimethylsulfoxide, diethylsulfoxide, Ν,Ν-dimethylformamide, N,N-diethylformamide, Ν,Ν-dimethylacetamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, l-methyl-2- pyrrolidinone, N-cyclohexyl-2-pyrrolidone, 1 , 13 -dimethyl-2-imidazolidinone, diethyleneglycoldimethoxyether, o-dichlorobenzene, phenols, cresols, xylenol, catechol, butyrolactones, hexamethylphosphoramide, and mixtures thereof.

[0041] The polyimide solution may optionally be cast onto a casting sheet for a period of time. In one embodiment, the casting sheet can be a polyethylene terephthalate (PET) casting sheet. After a passage of time, the polymerized gel can be removed from the casting sheet and prepared for the solvent exchange process. b. Solvent Exchange

[0042] After the gel is synthesized, it can be desirable to conduct a solvent exchange wherein the reaction solvent is exchanged for a more desirable second solvent. Accordingly, in one embodiment, a solvent exchange can be conducted wherein the polymerized gel is placed inside of a pressure vessel and submerged in a mixture comprising the reaction solvent and the second solvent. Then, a high pressure atmosphere is created inside of the pressure vessel thereby forcing the second solvent into the polymerized gel and displacing a portion of the reaction solvent. Alternatively, the solvent exchange step may be conducted without the use of a high pressure environment. It may be necessary to conduct a plurality of rounds of solvent exchange.

[0043] The time necessary to conduct the solvent exchange will vary depending upon the type of polymer undergoing the exchange as well as the reaction solvent and second solvent being used. In one embodiment, each solvent exchange can range from 1 to 168 hours or any period time there between including 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, or 23, 24, 25, 50, 75, 100, 125, 150, 155, 160, 165, 166, 167, or 168 hours. In another embodiment, each solvent exchange can take approximately 12 hours to 36 hours, or about 24 hours, or 15 minutes to 60 minutes, or about 30 minutes.

[0044] Exemplary second solvents include methanol, ethanol, 1-propanol, 2-propanol, 1- butanol, 2-butanol, isobutanol, tert-butanol, 3-methyl-2-butanol, 3,3-dimethyl-2-butanol, 2- pentanol, 3-pentanol, 2,2-dimethylpropan-l-ol, cyclohexanol, diethylene glycol, cyclohexanone, acetone, acetyl acetone, 1,4-dioxane, diethyl ether, dichloromethane, trichloroethylene, chloroform, carbon tetrachloride, water, and mixtures thereof. Each second solvent has a freezing point. For example tert-butyl alcohol has a freezing point of 25.5 °C and water has a freezing point of 0 °C under one atmosphere of pressure.

[0045] The temperature and pressure used in the solvent exchange process may be varied. The duration of the solvent exchange process can be adjusted by performing the solvent exchange at a varying temperatures or atmospheric pressures, or both, provided that the pressure and temperature inside the pressure vessel does not cause either the first solvent or the second solvent to leave the liquid phase and become gaseous phase, vapor phase, solid phase, or supercritical fluid. Generally, higher pressures and/or temperatures decrease the amount of time required to perform the solvent exchange, and lower temperatures and/or pressures increase the amount of time required to perform the solvent exchange. c. Cooling and Drying

[0046] In one embodiment after solvent exchange, the polymerized gel can be exposed to supercritical drying. In this instance the solvent in the gel can be removed by supercritical CO₂ extraction. [0047] In another embodiment after solvent exchange, the polymerized gel can be exposed to subcritical drying. In this instance the gel is cooled below the freezing point of the second solvent and subjected to a freeze drying or lyophilization process to produce the aerogel. For example, if the second solvent is water, then the polymerized gel can be cooled to below 0 °C. After cooling, the polymerized gel can be subjected to a vacuum for a period of time wherein the second solvent sublimes.

[0048] In still another embodiment after solvent exchange, the polymerized gel can be exposed to subcritical drying with optional heating after the majority of the second solvent has been removed through sublimation. In this instance the partially dried gel material can be heated to a temperature near or above the boiling point of the second solvent for a period of time. The period of time can range from a few hours to several days, although a typical period of time is approximately 4 hours. During the sublimation process, a portion of the second solvent present in the polymerized gel has been removed, leaving the mesoporous and microporous gel. After the sublimation process is complete, or nearly complete, the aerogel has been formed.

[0049] In yet another embodiment after solvent exchange, the polymerized gel can be dried under ambient conditions, for example by removing the solvent under a stream of air or anhydrous gas.

2. Polymeric Aerogel Materials [0050] Non-limiting examples of polymeric aerogel materials can include any material that can form a polymeric or polymer precursor gel, such as organic silanes, organic materials, and mixtures thereof. In some instances, aerogels can be doped with another material and/or crosslinked. Some compounds can be incorporated into the aerogel without being covalently connected to the aerogel. In some instances, the aerogel can be surface modified by methods known in the art. In some instances, the polymeric aerogel is not a graphene or is not a carbon nanotube aerogel, silica material, metal oxide aerogels (e.g., titania, zirconia), mixed metal oxide aerogels, or any combination thereof.

[0051] A polymeric aerogel is an aerogel comprising, consisting essentially of, or consisting of at least one polymer. Polymers can include organic polymers, silicone (polysiloxane) polymers, or mixtures thereof. Polymeric aerogels can include organic polymers, thermoset and/or thermoplastic polymers. Organic polymers may include, but are not limited to agar, agarose, epoxies, cresol formaldehyde, melamine formaldehyde, phenol formaldehyde, resorcinol formaldehyde, phenol furfuryl alcohol, polyacrylamides, polyacrylates, polyacrylonitriles, polycyanurates, polyfurfural alcohol, polyimides, polystyrenes, polyurethanes, polyvinyl alcohol dialdehyde, and mixtures thereof. In some instances, polymeric aerogels can be doped with another material and/or crosslinked. In some instances, the polymeric aerogel can be modified to contain another material on the aerogel surface.

[0052] Non-limiting examples of thermoplastic polymers include polyethylene terephthalate (PET), a polycarbonate (PC) family of polymers, polybutylene terephthalate (PBT), poly(l,4-cyclohexylidene cyclohexane-l,4-dicarboxylate) (PCCD), glycol modified polycyclohexyl terephthalate (PCTG), poly(phenylene oxide) (PPO), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polymethyl methacrylate (PMMA), polyethyleneimine or polyetherimide (PEI) and their derivatives, thermoplastic elastomer (TPE), terephthalic acid (TPA) elastomers, poly(cyclohexanedimethylene terephthalate) (PCT), polyethylene naphthalate (PEN), polyamide (PA), polysulfone sulfonate (PSS), sulfonates of polysulphones, polyether ether ketone (PEEK), polyether ketone ketone (PEKK), acrylonitrile butyldiene styrene (ABS), polyphenylene sulfide (PPS), co-polymers thereof, or blends thereof.

[0053] Non-limiting examples of thermoset polymers include unsaturated polyester resins, polyurethanes, polyoxybenzylmethylenglycolanhydride (e.g., bakelite), urea-formaldehyde, diallyl-phthalate, epoxy resin, epoxy vinylesters, polyimides, cyanate esters of polycyanurates, dicyclopentadiene, phenolics, benzoxazines, co-polymers thereof, or blends thereof. a. Polyimide Aerogel

[0054] In some instances, the polymeric aerogel is a polyimide aerogel. Polyimides are a type of polymer with many desirable properties. In general, polyimide polymers include a nitrogen atom in the polymer backbone, where the nitrogen atom is connected to two carbonyl carbons, such that the nitrogen atom is somewhat stabilized by the adjacent carbonyl groups. A carbonyl group includes a carbon, referred to as a carbonyl carbon, which is double bonded to an oxygen atom. Polyimides are usually considered an AA-BB type polymer because usually two different classes of monomers are used to produce the polyimide polymer. Polyimides can also be prepared from AB type monomers. For example, an aminodicarboxylic acid monomer can be polymerized to form an AB type polyimide. Monoamines and/or mono anhydrides can be used as end capping agents if desired.

[0055] One class of polyimide monomer is usually a diamine, or a diamine monomer. The diamine monomer can also be a diisocyanate, and it is to be understood that an isocyanate could be substituted for an amine in this description, as appropriate. There are other types of monomers that can be used in place of the diamine monomer, as known to those skilled in the art. The other type of monomer is called an acid monomer, and is usually in the form of a dianhydride. In this description, the term "di-acid monomer" is defined to include a dianhydride, a tetraester, a diester acid, a tetracarboxylic acid, or a trimethylsilyl ester, all of which can react with a diamine to produce a polyimide polymer. Dianhydrides are to be understood as tetraesters, diester acids, tetracarboxylic acids, or trimethylsilyl esters that can be substituted, as appropriate. There are also other types of monomers that can be used in place of the di-acid monomer, as known to those skilled in the art. [0056] Because one di-acid monomer has two anhydride groups, different diamino monomers can react with each anhydride group so the di-acid monomer may become located between two different diamino monomers. The diamine monomer contains two amine functional groups; therefore, after the first amine functional group attaches to one di-acid monomer, the second amine functional group is still available to attach to another di-acid monomer, which then attaches to another diamine monomer, and so on. In this manner, the polymer backbone is formed. The resulting polycondensation reaction forms a poly(amic acid).

[0057] The polyimide polymer is usually formed from two different types of monomers, and it is possible to mix different varieties of each type of monomer. Therefore, one, two, or more di-acid monomers can be included in the reaction vessel, as well as one, two or more diamino monomers. The total molar quantity of di-acid monomers is kept about the same as the total molar quantity of diamino monomers if a long polymer chain is desired. Because more than one type of diamine or di-acid can be used, the various monomer constituents of each polymer chain can be varied to produce polyimides with different properties. [0058] For example, a single diamine monomer AA can be reacted with two di-acid co monomers, BiBi and B2B2, to form a polymer chain of the general form of B₂B2)_y in which x and y are determined by the relative incorporations of B₁B₁ and B₂B₂ into the polymer backbone. Alternatively, diamine co-monomers A₁A₁ and A₂A₂ can be reacted with a single di-acid monomer BB to form a polymer chain of the general form of (AiAi-BB)_x-(A₂A₂- BB)_y. Additionally, two diamine co-monomers A₁A₁ and A₂A₂ can be reacted with two di- acid co-monomers B₁B₁ and B₂B₂ to form a polymer chain of the general form (AiAi-BiBi)_w- (AiAi-B2B2)_x-(A2A2-BiBi)y-(A2A2-B2B2)z, where w, x, y, and z are determined by the relative incorporation of A₁A₁-B₁B₁, A₁A₁-B₂B₂, A₂A₂-B₁B₁, and A₂A₂-B₂B₂ into the polymer backbone. More than two di-acid co-monomers and/or more than two diamine co- monomers can also be used. Therefore, one or more diamine monomers can be polymerized with one or more di-acids, and the general form of the polymer is determined by varying the amount and types of monomers used.

[0059] There are many examples of monomers that can be used to make polyimide polymers. A non-limiting list of possible diamine monomers comprises 4,4'-oxydianiline, 3,4'-oxydianiline, 3,3'-oxydianiline, p-phenylenediamine, m-phenylenediamine, o- phenylenediamine, diaminobenzanilide, 3,5-diaminobenzoic acid, 3,3'- diaminodiphenylsulfone, 4,4'-diaminodiphenyl sulfones, l,3-bis-(4-aminophenoxy)benzene, l,3-bis-(3-aminophenoxy)benzene, l,4-bis-(4-aminophenoxy)benzene, l,4-bis-(3- aminophenoxy)benzene, 2,2-Bis[4-(4-aminophenoxy)phenyl]-hexafluoropropane, 2,2-bis(3- aminophenyl)- 1,1,1,3,3,3 -hexafluoropropane, 4,4 '-isopropylidenedianiline, 1 -(4- aminophenoxy)-3-(3-aminophenoxy)benzene, l-(4-aminophenoxy)-4-(3- aminophenoxy)benzene, bis-[4-(4-aminophenoxy)phenyl] sulfones, 2,2-bis[4-(3- aminophenoxy)phenyl] sulfones, bis(4-[4-aminophenoxy]phenyl)ether, 2,2'-bis-(4- aminophenyl)-hexafluoropropane, (6F-diamine), 2,2'-bis-(4-phenoxyaniline)isopropylidene, meta-phenylenediamine, para-phenylenediamine, 1,2-diaminobenzene, 4,4'- diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 4,4'diaminodiphenyl propane, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylsulfone, 3,4'diaminodiphenyl ether, 4,4'- diaminodiphenyl ether, 2,6-diaminopyridine, bis(3-aminophenyl)diethyl silane, 4,4'- diaminodiphenyl diethyl silane, benzidine, dichlorobenzidine, 3,3'-dimethoxybenzidine, 4,4'- diaminobenzophenone, N,N-bis(4-aminophenyl)-n-butylamine, N,N-bis(4- aminophenyl)methylamine, 1,5-diaminonaphthalene, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4- aminophenyl-3-aminobenzoate, N,N-bis(4-aminophenyl)aniline, bis(p-beta-amino-t- butylphenyl)ether, p-bis-2-(2-methyl-4-aminopentyl)benzene, p-bis(l,l-dimethyl-5- aminopentyl)benzene, l,3-bis(4-aminophenoxy)benzene, m-xylenediamine, p-xylenediamine, 4,4'-diaminodiphenyl ether phosphine oxide, 4,4'-diaminodiphenyl N-methyl amine, 4,4'- diaminodiphenyl N-phenyl amine, amino-terminal polydimethylsiloxanes, amino-terminal polypropyleneoxides, amino-terminal polybutyleneoxides, 4,4'-Methylenebis(2- methylcyclohexylamine), 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5- diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9- diaminononane, 1,10-diaminodecane, and 4,4'-methylenebisbenzeneamine.

[0060] A non-limiting list of possible diacid monomers comprises hydroquinone dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'- diphenylsulfone tetracarboxylic dianhydride, 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride), 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 4,4'-

(hexafluoroisopropylidene)diphthalic anhydride, bis(3,4-dicarboxyphenyl) sulfoxide dianhydride, polysiloxane-containing dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,2',3'-benzophenonetetraearboxylic dianhydride, 3,3 ',4,4'- benzophenonetetraearboxylic dianhydride, naphthalene-2,3,6,7-tetracarboxylic dianhydride, naphthalene- 1, 4,5, 8-tetracarboxylie dianhydride, 4,4'-oxydiphthalic dianhydride, 3,3',4,4'- biphenylsulfone tetracarboxylic dianhydride, 3,4,9, 10-perylene tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl) sulfide dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4- dicarboxyphenyl)hexafluoropropane, 2,6-dichloronaphthalene- 1 ,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronapthalene-l,4,5,8-tetracarboxylic dianhydride, 2,3,6,7- tetrachloronaphthalene-l,4,5,8-tetracarboxylic dianhydride, phenanthrene-, 8,9,10- tetracarboxylie dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, benzene- 1,2,3, 4- tetracarboxylic dianhydride, and thiophene-2,3,4,5-tetracarboxylic dianhydride. [0061] A poly(amic acid) can be soluble in the reaction solvent and, thus, the solution may be cast into a film such as by spin casting, gravure coating, three roll coating, knife over roll coating, slot die extrusion, dip coating, Meyer rod coating, or other techniques. The cast film can then be heated in stages to elevated temperatures to remove solvent and convert the amic acid functional groups in the poly(amic acid) to imides with a cyclodehydration reaction, also called imidization. "Imidization" is defined as the conversion of a polyimide precursor into an imide. Alternatively, some poly(amic acid)s may be converted in solution to polyimides by using a chemical dehydrating agent, catalyst, and/or heat. [0062] Many polyimide polymers are produced by preparing a poly(amic acid) polymer in the reaction vessel. The poly(amic acid) can be formed into a sheet or a film and subsequently processed with heat (often temperatures higher than 250 °C) or both heat and catalysts to convert the poly(amic acid) to a polyimide. [0063] The characteristics or properties of the final polymer are significantly impacted by the choice of monomers which are used to produce the polymer. Factors to be considered when selecting monomers include the properties of the final polymer, such as the flexibility, thermal stability, coefficient of thermal expansion (CTE), coefficient of hydroscopic expansion (CHE) and any other properties specifically desired, as well as cost. Often, certain important properties of a polymer for a particular use can be identified. Other properties of the polymer may be less significant, or may have a wide range of acceptable values; so many different monomer combinations could be used.

[0064] In some instances, the backbone of the polymer can include substituents. The substituents (e.g., oligomers, functional groups, etc.) can be directly bonded to the backbone or linked to the backbone through a linking group (e.g., a tether or a flexible tether). In other embodiments, a compound or particles can be incorporated (e.g., blended and/or encapsulated) into the polyimide structure without being covalently bound to the polyimide structure. In some instances, the incorporation of the compound or particles can be performed during the reaction polyamic reaction process. In some instances, particles can aggregate, thereby producing polyimides having domains with different concentrations of the non-covalently bound compounds or particles.

3. Polymeric Aerogel Structure

[0065] Polymeric aerogels can structurally be thin films, coatings, powders, blankets, and/or monoliths. An aerogel powder can include fine aerogel particles. An aerogel blanket can include a flexible non-woven solid, or a flexible woven solid, etc. A monolith or monolithic aerogel can include a single continuous aerogel. An aerogel can include open cells or can include interconnected pores.

[0066] The polymeric aerogel can have a thickness of greater than 30 cm. For example, the polymeric aerogel can have a thickness of less than 30 cm, less than 20 cm, 10 cm, 5 cm, 1 cm, 5 mm, or 1 mm. The porosity of the polymeric aerogel can be less than 75%. In some instances, the polymeric aerogel can have a porosity of more than 75%, more than 80%, 85%, 90%, 95%, 98%, or 99%. A specific surface area of the polymeric aerogel can be less than

100 m 2 g -^"1 , or, in some instances, the polymeric aerogel can have a specific surface area of more than 100 m² g^"1, more than 500 m² g^"1, 1000 m² g^"1, 1500 m² g^"1, 2000 m² g^"1, or 3000

4. Polymeric Aerogel Articles of Manufacture

[0067] Polymeric aerogels that may be useful for filtering fluids can also be useful and/or can be found in articles of manufacture. Non-limiting example of articles of manufacture include a thin film, a monolith, a wafer, a blanket, a core composite material, a substrate for a radiofrequency antenna, a radome, a sunshield or sunscreen for an antenna, an insulating material for oil and/or gas pipeline, an insulating material for liquefied natural gas pipeline, an insulating material for cryogenic fluid transfer pipeline, an insulating material for apparel, an insulating material for aerospace applications, an insulating material for buildings, cars, and other human habitats, an insulating material for automotive applications, an insulation for radiators, an insulation for ducting and ventilation, an insulation for air conditioning, an insulation for heating and refrigeration and mobile air conditioning units, insulation for coolers, an insulation for packaging, an insulation for consumer goods, a vibration dampening device, a wire and cable insulation, an insulation for medical devices, a support for catalysts, a support for drugs, pharmaceuticals, and/or drug delivery systems, an aqueous filtration applications, an oil-based filtration applications, and a solvent-based filtration applications.

C. Fluids

[0068] A fluid for filtration ("feed") and a filtrate can be any fluid. The fluid can be a liquid, gas, supercritical fluid, or mixture thereof. In some instances, the fluid can be aqueous, organic, non-organic, biological in origin, or a mixture thereof. In some instances, the fluid can contain solids and/or other fluids. As non-limiting examples, the fluid can be or can be partially water, blood, an oil, a solvent, air, or mixtures thereof.

[0069] In some instances, the fluid can contain impurities. Non-limiting examples of impurities include solids, liquids, gases, supercritical fluids, objects, compounds, and/or chemicals, etc. What is defined as an impurity may be different for the same feed fluid depending on the filtrate desired. In some embodiments, one or more aerogels can be used to remove impurities. Non-limiting examples of impurities in water can include ionic substances such as sodium, potassium, magnesium, calcium, fluoride, chloride, bromide, sulfate, sulfite, nitrate, nitrites, cationic surfactants, and anionic surfactants, metals, heavy metals, suspended, partially dissolved, or dissolved oils, organic solvents, nonionic surfactants, chelating agents, microorganisms, particulate matter, defoamants etc. Non- limiting examples of impurities in blood can include red blood cells, white blood cells, antibodies, microorganisms, water, urea, potassium, phosphorus, gases, particulate matter, etc. Non-limiting examples of impurities in oil can include water, particulate matter, heavy and/or light weight hydrocarbons, metals, sulfur, defoamants, etc. Non-limiting examples of impurities in solvents can include water, particulate matter, metals, heavy metals, gases, etc. Non-limiting impurities in air can include water, particulate matter, microorganisms, liquids, carbon monoxide, sulfur dioxide, etc.

[0070] In some instances, the feed fluid can contain desired substances. Desired substances can be, but are not limited to, solids, liquids, gases, supercritical fluids, objects, compounds, and/or chemicals, etc. In some embodiments, one or more aerogels can be used to concentrate or capture a desired substance, or remove a fluid from a desired substance. Non-limiting examples of desired substances in water can include ionic substances such as sodium, potassium, magnesium, calcium, fluoride, chloride, bromide, sulfate, sulfite, nitrate, nitrites, cationic surfactants, and anionic surfactants, metals, heavy metals, suspended, partially dissolved, or dissolved oils, organic solvents, nonionic surfactants, defoamants, chelating agents, microorganisms, particulate matter, etc. Non-limiting examples of desired substances in blood can include red blood cells, white blood cells, antibodies, lipids, proteins, etc. Non-limiting examples of desired substances in oil can include hydrocarbons of a range of molecular weights, gases, metals, etc. Non-limiting examples of desired substances in solvents can include particulate matter, fluids, gases, proteins, lipids, etc. Non-limiting examples of desired substances in air can include water, fluids, gases, particulate matter, etc.

Claims

1. A method of filtering a fluid comprising impurities and/or desired substances, the method comprising contacting a feed fluid with a polymeric aerogel under conditions sufficient to remove at least a portion of the impurities and/or desired substances from the feed fluid and produce a filtrate.

2. The method of claim 1, wherein the aerogel is an organic polymer aerogel.

3. The method of claim 2, wherein the polymer is a thermoset polymer.

4. The method of claim 2, wherein the polymer is a thermoplastic polymer.

5. The method of claim 2, wherein the aerogel is a polyimide aerogel.

6. The method of any of one claims 1 to 5, wherein the polymeric aerogel does not include a carbon nanotube aerogel, a silica aerogel, and an inorganic aerogel.

7. The method of claim 1, wherein the aerogel is a polysiloxane aerogel.

8. The method of claim 7, wherein the aerogel is a modified polysiloxane aerogel.

9. The method of any one of claims 1 to 8, wherein the aerogel is in the form of a film.

10. The method of any one of claims 1 to 8, wherein the aerogel is in the form of a powder.

11. The method of any one of claims 1 to 8, wherein the aerogel is in the form of a blanket.

12. The method of any one of claims 1 to 8, wherein the aerogel is a monolithic aerogel.

13. The method of any one of claims 1 to 12, wherein the feed fluid is a liquid, a gas, a supercritical fluid, or a mixture thereof.

14. The method of claim 13, wherein the feed fluid comprises water.

15. The method of claim 13, wherein the feed fluid is a non-aqueous liquid.

16. The method of claim 15, wherein the non-aqueous fluid is an oil, a solvent, or combinations thereof.

17. The method of claim 16, wherein the feed fluid is a solvent.

18. The method of claim 17, wherein the feed fluid is an organic solvent.

19. The method of any one of claims 1 to 13, wherein the feed fluid is an emulsion.

20. The method of claim 19, wherein the emulsion is a water-oil emulsion, an oil-water emulsion, a water-solvent emulsion, a solvent-water emulsion, an oil-solvent emulsion, or a solvent-oil emulsion.

21. The method of claim 13, wherein the feed fluid is a biological fluid.

22. The method of claim 21, wherein the biological fluid is blood, plasma, or both.

23. The method of claim 13, wherein the feed fluid is a gas.

24. The method of claim 23, wherein the gas comprises air, nitrogen, oxygen, an inert gas, or mixtures thereof.

25. The method of any one of claims 1 to 24, wherein the filtrate is substantially free of impurities and/or a desired substance.

26. An apparatus for filtering a feed fluid comprising impurities and/or a desired substance, the apparatus comprising: a separation zone comprising a polymeric aerogel, the separation zone configured to remove impurities and/or desired substances from the feed fluid and produce a filtrate; and an inlet configured to be in fluid communication with the separation zone to receive a feed fluid and/or an outlet configured to be in fluid communication with the separation zone to remove the filtrate from the separation zone.

27. The apparatus of claim 26, wherein the aerogel is an organic polymer aerogel.

28. The apparatus of claim 27, wherein the polymer is a thermoset polymer.

29. The apparatus of claim 27, wherein the polymer is a thermoplastic polymer.

30. The apparatus of claim 27, wherein the aerogel is a polyimide aerogel.

31. The apparatus of any one of claims 26 to 30, wherein the polymeric aerogel does not include a carbon nanotube aerogel, a silica aerogel, an inorganic aerogel or combinations thereof.

32. The apparatus of claim 26, wherein the aerogel is a polysiloxane aerogel.

33. The apparatus of claim 32, wherein the aerogel is a modified polysiloxane aerogel.

34. The apparatus of any of claims 26 to 33, wherein the aerogel is in the form of a film.

35. The apparatus of any of claims 26 to 33, wherein the aerogel is in the form of a powder.

36. The apparatus of any of claims 26 to 33, wherein the aerogel is in the form of a blanket.

37. The apparatus of any of claims 26 to 33, wherein the aerogel is a monolithic aerogel.

38. The apparatus of any of claims 26 to 37, wherein the feed fluid is a liquid, a gas, a supercritical fluid, or a mixture thereof.

39. The apparatus of claim 38, wherein the feed fluid comprises water.

40. The apparatus of claim 38, wherein the feed fluid is a non-aqueous fluid.

41. The apparatus of claim 40, wherein the non-aqueous fluid is an oil, a solvent, or combinations thereof.

42. The apparatus of claim 41, wherein the non-aqueous fluid is a solvent.

43. The apparatus of any claim 42, wherein the non-aqueous fluid is an organic solvent.

44. The apparatus of any one of claims 26 to 38, wherein the feed fluid is an emulsion.

45. The apparatus of claim 44, wherein the emulsion is a water-oil emulsion, an oil-water emulsion, a water-solvent emulsion, a solvent-water emulsion, an oil-solvent emulsion, or a solvent-oil emulsion.

46. The apparatus of claim 38, wherein the feed fluid is a biological fluid.

47. The apparatus of claim 46 wherein the biological fluid is blood, plasma, or both.

48. The apparatus of claim 38, wherein the feed fluid is a gas.

49. The apparatus of claim 48, wherein the gas comprises air, nitrogen, oxygen, an inert gas, or mixtures thereof.

50. The apparatus of any one of claims 26 to 49, wherein the filtrate is substantially free of impurities and/or desired substances.

51. A method of filtering a fluid using any one of the apparatus of claims 26 to 50, the method comprising: providing a fluid comprising impurities and/or desired substances to a polymeric aerogel of the separation zone of the apparatus; and contacting at least a portion of the fluid with the polymeric aerogel to form a filtrate.