Coated nonwoven porous article

Abstract

Described herein is a porous article comprising: a nonwoven comprising oxidized polyacrylonitrile staple fibers; wherein a coating is disposed on at least a portion of a surface of the nonwoven composite, wherein the coating is derived from an azasilane and wherein the porous article. Such porous articles may be used to sorb components of interest such as carbon dioxide.

Description

PA102867W002COATED NONWOVEN POROUS ARTICLETECHNICAL FIELD

[0001] Disclosed herein is a nonwoven comprising oxidized polyacrylonitrile staple fibers, which is5 coated with an azasilane. Such articles may be used to reversibly bind carbon dioxide.SUMMARY

[0002] Concern over environmental effects of greenhouse gasses has resulted in significant effort to reduce overall atmospheric carbon dioxide (CO?). One such effort is using a sorbent to remove carbon0 dioxide from gas streams such as plant exhaust or directly from the air. Ideally, these sorbents are reused, wherein carbon dioxide is sorbed from a gas stream onto the sorbent. Then, the carbon dioxide is released from the sorbent and collected and the sorbent is regenerated for use.

[0003] It is advantageous if the sorbent materials can be used over a range of temperatures. One reason is because this would enable any heat generated from a manufacturing plant, geosystem, or renewable5 energy source to be utilized to extract CO? without requiring additional energy to control or regulate the intake air temperature. Further, actual air streams for removal of CO2 are multi-component, comprising in addition to water and CO2, other components such as bacteria, dust, pollen, and / or soot, which can adsorb into the sorbents, impacting sorbent lifetime. Using high temperatures during regeneration of the sorbents can be used to improve lifetimes. 0

[0004] Thus, there is a desire to identify sorbents for carbon capture that not only provide good initial sorption of CO2 and are scalable, but can be used over a wide temperature range and / or have long service times as indicated by good performance over multiple cycles.

[0005] In one aspect, a porous article is discussed. The article comprises a nonwoven comprising oxidized polyacrylonitrile staple fibers. A coating is disposed on at least a portion of a surface of the5 nonwoven, wherein the coating is derived from an azasilane. In some embodiments, the disclosed porous article has a surface area of at least 0.10 m2 / g.

[0006] In another embodiment, a method for capturing carbon dioxide is disclosed. The method comprises contacting carbon dioxide to a nonwoven, which has a coating derived from an azasilane thereon, wherein the nonwoven comprises oxidized polyacrylonitrile staple fibers. 0

[0007] In yet another embodiment, the use of a coated nonwoven for capturing carbon dioxide and / or a carbonyl-containing compound is disclosed. The nonwoven, which comprises oxidized polyacrylonitrile staple fibers, has a coating derived from an azasilane thereon. The coated nonwoven could be used to capture carbon dioxide and / or a carbonyl-containing compound.

[0008] The above summary is not intended to describe each embodiment. The details of one or more5 embodiments of the invention are also set forth in the description below. Other features, objects, and advantages will be apparent from the description and from the claims.DETAILED DESCRIPTION

[0009] As used herein, the term“a”, “an”, and “the” are used interchangeably and mean one or more; and“and / or” is used to indicate one or both stated cases may occur, for example A and / or B includes, (A and B) and (A or B). Also herein, recitation of ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0010] Also herein, recitation of “at least one” includes all numbers of one and greater (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).

[0011] As used herein, “comprises at least one of’ A, B, and C refers to element A by itself, element B by itself, element C by itself, A and B, A and C, B and C, and all three.

[0012] The present application is directed toward a porous article coated with an aminoalkoxy silane, which can be used to capture a desired analytes, such as CO2, heavy metal, and / or carbonyl compounds such as formaldehyde, acetaldehyde, acrolein, acetone, etc.

[0013] The porous articles disclosed herein comprise a nonwoven with a coating disposed on at least a portion of the surface of the nonwoven and wherein the coating is derived from an azasilane.

[0014] The nonwoven disclosed herein is a substrate that comprises a plurality of oxidized polyacrylonitrile fibers. As used herein, “nonwoven” generally refers to a fibrous web or material characterized by entanglement or point bonding of a plurality of fibers, wherein the fibers are interlaid, but not in an identifiable manner as in a knitted fabric.

[0015] The nonwoven substrates comprise oxidized polyacrylonitrile (OP AN) fibers. OP AN is known for its inherent fire resistance and is used in applications such as safety gloves and blankets for protecting equipment. Unexpectedly, it has been discovered that nonwovens comprising OP AN fibers may also be used to remove components such as CO2, formaldehyde, acetaldehyde, acrolein, and / or acetone from fluid streams.

[0016] The OP AN fibers are oxidized polyacrylonitrile (PAN) processed into a non-woven fibrous web. The OP AN fibers are staple fibers, meaning they are short fibers having a length of at least 10, 20, 30, or even 40 millimeters (mm); and at most 110, 100, 85, or even 65 mm, although shorter and longer fibers (e.g., continuous filaments) may also be useful. In some embodiments, the plurality of OP AN fibers has an average fiber diameter of at least 0.1, 0.5, 1, 5, 10, 25, 50, 100, 200, or even 500 micrometers. In some embodiments, the plurality of OP AN fibers has an average fiber diameter of at most 500, 1000, 2000, 5000, 8000, or even 10000 micrometers. The diameter and length of the fibers can be determined using techniques known in the art such as optical microscopy.

[0017] The OP AN fibers may have a fineness or linear density of at least 1.7, 6, or even 17 decitex (dtex, i.e., grams / 10,000 meters); and at most 560, 280, or even 120 dtex, although fibers having lesser and / or greater linear densities may also be useful.

[0018] The OP AN fibers are either partially or folly oxidized. In some embodiments, the PAN fiber is treated thermally at a high temperatures (e.g., 230°C) to oxidize the polymer forming the OP AN fibers. OP AN fibers are commercially available under the trade designation ZOLTEK OX from Zoltek Corp.,Bridgeton, MO; PANOX Oxidized PAN Fibers from SGL Group, Meitingen, Germany; and PYROMEX from Teijin Carbon America, Inc., Greenwood, SC.

[0019] Typically, to maximize the flame retardancy, commercially available nonwovens comprise over 85, 90. or even 95 vol % of OP AN fibers versus the total volume of fibers present. In some embodiments, at least 50, 60, 70 or even 75% by weight of all of the fibers in the nonwoven are OP AN fibers. In some embodiments, at most 99, 98, 95, 90, 85 or even 80% by weight of all of the fibers in the nonwoven are OP AN fibers. In some embodiments, the nonwoven contains no other fibers other than the OP AN fibers.

[0020] Nonwoven substrates comprising OP AN fibers are known in the art. Such nonwoven substrates can be made via a dry -laid or wet-laid process using OP AN fibers. OP AN fiber-containing nonwovens are commercially available under the trade designation ZOLTEK OX from Zoltek Corp.

[0021] In some embodiments, a silica aerogel is disposed within the nonwoven to form a composite.

[0022] Silica aerogels are solid, amorphous materials composed of silica. Silica aerogels are typically highly porous material (80 to 99.8%). However, due to the porosity, the materials generally have low mechanical strength and can be composited with polyacrylonitrile fibers. Exemplary surface areas of aerogels are 500 to 1200 m2 / g.

[0023] In some embodiments, the nonwoven composite comprises at least 10, 15, 20, 25, or even 30 wt % of silica aerogel. In some embodiments, the nonwoven composite comprises at most 35, 40, 45, 50, 55, 60, or even 70 wt % of silica aerogel.

[0024] In some embodiments, the silica aerogel is physically entangled with the OP AN fibers in a nonwoven composite. Nonwoven OP AN composites comprising silica aerogel are known in the art. In some embodiments, the nonwoven composites comprising silica aerogel can be made by thermally stabilizing OP AN fibers forming the fiber into a nonwoven such as a felt, impregnating the felt with an aerogel sol followed by solvent replacement and supercritical drying to form a nonwoven composite such as disclosed herein. Commercially available nonwoven composites are available under the trade designation OX AEROGEL COMPOSITE from Zoltek Corp., Bridgeton, MO and silica aerogel impregnated OX felt from Shanghai Tanchain New Material Technology Co., Ltd., Shanghai, China.

[0025] In some embodiments, the nonwoven further comprises an organic binder. In one embodiment, the organic binder is a fiber, which can be used to support or stabilize the nonwoven. A variety of fibers may be suitable, including amorphous, meltable fibers, adhesive coated fibers which may be discontinuously coated, and bicomponent fibers that have an adhesive component and a support component arranged in a coextensive side-by-side, concentric sheath-core, or elliptical sheath-core configuration along the length of the fiber with the adhesive component forming at least a portion of the outer surface of the bicomponent fiber. The adhesive component of the bondable fibers may be bonded, for example, thermally, by solvent bonding, solvent vapor bonding, and salt bonding. The adhesive component of thermally bonding fibers must be thermally activatable (i.e., meltable) at a temperature below the melt temperature of the structural staple fibers of the non-woven web.

[0026] One particularly useful fiber for stabilizing the nonwoven is a crimped sheath-core fiber having a core of crystalline polyethylene terephthalate surrounded by a sheath of an adhesive polymer formed from isophthalate and terephthalate esters. The sheath is heat softenable at a temperature lower than the core material. An exemplary binder fiber that is commercially available is a polyester fiber available under the trade designation TREVIRA T-254 from Trevira GmbH, Bobingen, Germany.

[0027] In some embodiments, a multifunctional compound comprising more than one (meth)acrylate, isocyanate, alcohol, and / or aziridine functional groups, can be used to induce crosslinking between the hydroxy -containing OP AN fibers, aiding in structural stability of the nonwoven. In some embodiments, the multifunctional compound comprises at least 2, 3, or even 4 functional groups selected from (meth)acrylate, isocyanate, alcohol, and / or aziridine groups. Exemplary multifunctional isocyantes include, diphenylmethane 4,4'-diisocyanate; 4,4'-methylenebis(cyclohexyl isocyanate) and isomers thereof; isophorone diisocyanate; poly(hexamethylene diisocyanate) and oligomers thereof; 4arm- PEG20K-isocyanate with a number average molecular weight of 20,000 grams / mole; and combinations thereof. Exemplary multifunctional (meth)acrylates include ethoxylated trimethylolpropane triacrylate available under the trade designation “SR454” from Arkema Inc. Blooming Prairie, MN; ethoxylated trimethylolpropane triacrylate available under the trade designation “SR415” or “SR9035” from Arkema; and combinations thereof. An exemplary multifunctional alcohol is a polyvinyl alcohol. An exemplary multifunctional aziridine is 1-aziridinepropanoicacid, 2 -methyl-, l,l'-[2-ethyl-2-[[3-(2-methyl-l- aziridiny 1)- 1 -oxopropoxy]methyl] -1,3 -propanediyl] ester.

[0028] Because the organic binder fibers and or multifunctional compounds can block and / or react with the hydroxy functional groups of the OP AN fibers, it may be advantageous to use minimal amounts of such components to establish good structural stability of the nonwoven, while maximizing the ability of the azasilane coated nonwoven to capture analytes from a fluid stream. For example, in some embodiments, the nonwoven comprises at least 0.1, 0.5, or even 1 wt % of the organic binder fibers and or multifunctional compounds; and at most 1, 2, 5, 8, or even 10 wt % of the organic binder fibers and or multifunctional compounds. In some embodiments, a hydroxy containing multifunctional group can be used to link together adjacent OP AN fibers, leading to improved structural stability, while providing sites for reaction with the azasilane. Such hydroxy containing multifunctional groups include polyvinylalcohols.

[0029] In some embodiments, the nonwoven does not comprise an organic fiber or additional multifunctional compound to aid in structural stability. In these embodiments, the OP AN fibers of the nonwoven may be held together by entanglement that occurs during the fabrication.

[0030] In some embodiments, the nonwoven has an average surface area of at least 0.05, 0.1, 0.15, 0.2, 0.4, 0.5, 1, 5, 10, 20, 25, 50, 100, 200, 300, or even 400 m2 / g; and typically, at most 500 m2 / g as determined by BET (Brunauer Emmet Teller) nitrogen adsorption.

[0031] In the present disclosure, the nonwoven comprising OP AN fibers are treated with an azasilane. An azasilane is a compound comprising an amine and a silane.

[0032] Preferably, the azasilane is a cyclic azasilane, wherein the nitrogen and the silicon atoms are vertices in the ring. In some embodiments, the cyclic azasilane is a 5-membered or a six-membered ring.

[0033] In some embodiments, the azasilane is of formula I:where R2and R3are independently selected from substituted or unsubstituted, alkyl or alkenyl groups comprising 1 to 12 carbon atoms; R4is selected from hydrogen, a substituted or unsubstituted, alkyl, alkenyl, or alkynyl group comprising 1 to 12 carbon atoms; R1is selected from hydrogen or an alkyl group comprising 1 to 12 carbon atoms; x is 1, 2, or 3; and y is 1, 2, or 3.

[0034] R1may be linear, branched, and / or cyclic and may be substituted or unsubstituted. Exemplary substitutions include O, N, S, Si, etc. R1can comprise at least 1, 2, 3, 4, or even 5 carbon atoms and at most 6, 8, 10, or even 12 carbon atoms. Exemplary R1groups include -H, -CH3, -CH2CH3, -OCH3, - OCH2CH3, or combinations thereof.

[0035] R2and R3may be substituted or unsubstituted. Exemplary substitutions include O, N, S, Si, etc. R2and R3can comprise at least 1, 2, 3, 4, or even 5 carbon atoms and at most 6, 8, 10, or even 12 carbon atoms. In some embodiments, R2and R3are the same. In some embodiments, R2and R3are different. Exemplary R2and R3groups include -CH3, -CH2CH3, -OCH3, -OCH2CH3, or combinations thereof.

[0036] R4may be linear, branched, and / or cyclic. R4may be substituted or unsubstituted. Saturated or unsaturated. Exemplary substitutions include O, N, S, Si, etc. R4can comprise at least 1, 2, 3, 4, or even 5 carbon atoms and at most 6, 8, 10, or even 12 carbon atoms. Exemplary R4groups include -CH3, - CH2CH3, -CH2CH2CH2CH3, -CH2CH=CH2, -CH2CH=CH, -(CH2)2NH2, -(CH2)3N(CH3)2, or combinations thereof.

[0037] Another cyclic azasilane includes those according to Formula IIWhere R5and R6are independently selected from hydrogen, a substituted or unsubstituted, alkyl, alkenyl, or alkynyl group comprising 1 to 12 carbon atoms; R7and R8are independently selected from a substituted or unsubstituted, alkyl, or alkenyl group comprising 1-8 carbon atoms.

[0038] R5and / or R6may be linear, branched, and / or cyclic and may be substituted or unsubstituted.Exemplary substitutions include O, N, S, Si, etc. R5and / or R6can comprise at least 1, 2, 3, 4, or even 5carbon atoms and at most 6, 8, 10, or even 12 carbon atoms. Exemplary R5and / or R6groups include -H, - CH3, -CH2CH3, -OCH3, -OCH2CH3, or combinations thereof.

[0039] R7and / or R8may be substituted or unsubstituted. Exemplary substitutions include O, N, S, Si, etc. R7and R8can comprise at least 1, 2, 3, 4, or even 5 carbon atoms and at most 6, 8, 10, or even 12 carbon atoms. In some embodiments, R7and R8are the same. In some embodiments, R7and R8are different. Exemplary R7and R8groups include -CH3, -CH2CH3, -OCH3, -OCH2CH3, or combinations thereof.

[0040] Exemplary azasilanes include:-aminethyl)-2,2,4-trimethyl-l-aza-2-silacyclopentane; 2, 2,6,6- tetramethyl-l-oxa-4-aza-2,6-disilacyclohexane-4-ethanamine; N-n-butyl-aza-2,2- dimethoxysilacycopentane; 2,2-dimethoxy-l,6-diaza-2-silacyclooctane; or combinations thereof.

[0041] In some embodiments, the azasilane has a molecular weight of at least 70, 80, or even 90 grams per mole (g / mol). In some embodiments, the azasilane has a molecular weight of at most 500, 450, 400, 350, 300, 250, 200, or even 150 g / mol. Generally, the azasilane should have a sufficiently low molecular weight to enable vapor coating onto the nonwoven.

[0042] Generally, the azasilane should not be sterically bulky to enable higher packing density at the surface of the nonwoven.

[0043] In some embodiments, the azasilane has a boiling point of no more than 100, 120, 150, or even 175°C at ambient atmospheric pressure (e.g., 1 atmosphere). In some embodiments, the azasilane has a boiling point of no more than 40, 50, 70, 80, or even 90°C at reduced atmospheric pressure (e.g., 2 mmHg).

[0044] Although not wanting to be limited by theory, it is believed that the azasilanes react with hydroxyl groups of the OP AN fibers, grafting the azasilane onto the surface of the nonwoven, while amine groups are available for interaction with analytes such as CO2. When using the cyclic azasilanes, it is believed that there is a single ring opening reaction. Surprisingly, it has been discovered that a high level of removal of CO2 was observed for nonwovens without the presence of the high surface area aerogel. It is theorized that perhaps the cyclic azasilanes are forming a branched structure leading to a higher than expected surface area of the coated nonwoven.

[0045] In some embodiments, the nonwoven is contacted with an azasilane vapor. In some embodiments, the azasilane is condensed onto the surface of the nonwoven. Exemplary radiation to condense the azasilane includes electromagnetic or thermal radiation. In some embodiments, the nonwoven is vapor coated with the azasilane. Vapor coating can be conducted by heating the azasilane to vaporize it and placing the nonwoven near the vapor. In some embodiments, the vapor coating can bedone at ambient pressures (e.g., 1 atmosphere). Ideally, the azasilanes are vapor coated at a temperature of at most 25, 30, 40, 50, 60, 70, 80, or even 85°C. Under these types of conditions, the azasilane may deposit onto the nonwoven a mix of partial condensation reactions following anhydrous deposition and partial hydrogen-bonded intermediates. It is postulated that the hydrogen-bonded silane can undergo a condensation reaction and covalently bond firmly with the sample, enabling a strong covalent bond attaching the amino functional group to the nonwoven. Following vapor coating, the sample may be heated, for example, at a temperature of at least 50 to 120°C to covalently bond the azasilane to the nonwoven surface. In some embodiments, the vapor coating can be done under controlled vacuum conditions at reduced pressures, which can enable lower temperatures to vapor coat.

[0046] The amount of azasilane deposited onto the nonwoven can be controlled by (1) the amount of azasilane used, (2) the duration of the vapor coating, and (3) the temperature used. Azasilanes can modify surfaces under anhydrous conditions consistent with monolayer and vapor phase deposition requirements. Extended vapor coating times (4-12 hours) at elevated temperatures (50-120 °C) are typical.

[0047] In some embodiments, the azasilane (or compound derived therefrom) is disposed on both the surface of the oxidized polyacrylonitrile staple fibers, and optionally the surface of the silica aerogel if present.

[0048] The surface of the nonwoven is at least partially coated with a layer derived from azasilane. Typically, the surface of the nonwoven is thinly coated (for example, with a monolayer or bilayer). Generally, the article should not be heavily coated with the azasilane to inhibit the sorption of the desired analytes to be removed (e.g., CO2).

[0049] It has been surprisingly discovered that the nonwoven comprising OP AN has a sufficient amount of hydroxy groups available to generate coated nonwovens having good performance for adsorption of CO2. In some embodiments, the articles of the present disclosure are able to load (as evidenced by weight gain) at least 15, 20, 25, or even 30 % of the azasilane and at most 40, 50, 60, 70, 75, 80, 90, 100, 110, or even 125 % of the azasilane. Generally, more azasilane is advantageous to capture CO2, however if too much is coated, the azasilane may hinder CO2 uptake by limiting the available surface area.

[0050] The coated nonwovens of the present disclosure can have a high surface area. For example, in some embodiments, the porous articles have an average surface area of at least 0.05, 0.1, 0.15, 0.2, 0.4, 0.5, 1, 5, 10, 20, 25, 50, 100, 200, 300, or even 400 m2 / g; and typically, at most 500 m2 / g as determined by BET (Brunauer Emmet Teller) nitrogen adsorption. BET is commonly used to determine surface area and involves adsorbing a monolayer of nitrogen on the surface of the article under cryogenic conditions. The amount of adsorbed nitrogen is proportional to the surface area.

[0051] In some embodiments, the coating on the nonwoven has a thickness of at least 0.5, 0.6, 0.8, 1, 5, 10, or even 20 nanometers (nm). In some embodiments, the coating on the nonwoven has a thickness of at most 1000, 800, 500, 400, 200, 100, 50, 40, 30, or even 20 nm.

[0052] In some embodiments, the porous articles of the present disclosure have an initial CO2 absorbance of at least 0.5, 0.6, 0.8, 1.0, or even 1.2 mmol CO2 / g at 80°C. In some embodiments, theporous articles of the present disclosure have a percentage difference in CO2 absorbance from an initial cycle to a final cycle of less than 10, 8, 5, or even 2% when tested at 80°C.

[0053] Increased heat (for example, 110 °C) may be used to regenerate the porous articles. In some embodiments, the porous articles of the present disclosure have thermal stability up to 110°C, meaning the absorption properties do not deteriorate at temperature below 110°C. Although not wanting to be limited by theory, it is believed that the azasilanes have a strong covalent bond with the nonwoven composite enabling good thermal stability.

[0054] Ideally, the porous articles of the present disclosure can be regenerated and used repeatedly, for example used for at least 10, 20, 50 or even 100 cycles. In some embodiments, the porous articles of the present disclosure after 20 cycles have a CO2 absorbance of at least 0.5, 0.6, 0.8, 1.0, or even 1.2 mmol CO2 / g at 50°C.

[0055] Ideally, the porous articles of the present disclosure can be regenerated and used repeatedly, for example used for at least 10, 20, 50, or even 100 cycles. In some embodiments, the porous articles of the present disclosure after 20 cycles have a CO2 absorbance of at least 0.5, 0.6, 0.8, 1.0, or even 1.2 mmol CO2 / g at 80°C.

[0056] In some embodiments, the porous articles disclosed herein may be used in carbon capture, wherein the porous articles are contacted with fluid (e.g., gas or liquid) streams. CO2 from a fluid stream can be sorbed onto the porous articles of the present disclosure. In some embodiments, the porous articles disclosed herein may be used to remove carbonyl-containing contaminates from the fluid streams (e.g., air or water), such as formaldehyde, acetaldehyde, acrolein, and / or acetone. In some embodiments, the porous articles disclosed herein may be used to remove heavy metals such as mercury, cadmium, copper, etc.

[0057] Contaminates from a fluid stream can be sorbed onto the porous articles of the present disclosure. In some embodiments, the porous articles disclosed herein may be used in flow through operationfiltration type modules.

[0058] Objects and advantages of this disclosure are further illustrated by the following non-limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure.EXAMPLES

[0059] Unless otherwise noted, all parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, and all reagents used in the examples were obtained, or are available, from general chemical suppliers such as, for example, Sigma-Aldrich Company, Saint Louis, Missouri, or may be synthesized by conventional methods.

[0060] These abbreviations are used in the following examples: °C = degree Celsius, cm = centimeter, g = gram, gsm = grams per square meter, h = hour, pm= micrometer, L = liter, m = meter, mg = milligram, min = minute, mL = milliliter, mmol = millimole, MPa = megapascal, rpm = revolutions per minute, psi = pounds per square inch, s = second, and wt = weight.Materials

[0061] Method of Making Nonwoven 2

[0062] OP AN fibers were opened and conveyed into an air laid webber where high velocity air jets lay down fibers into a nonwoven mat. The nonwoven mat had a basis weights of 120 gram / m2.

[0063] Vapor Coating

[0064] The designated nonwoven was cut into 1.5 in (3.8 cm) by 1.5 in (3.8 cm) square samples using a die cutter. A designated amount of azasilane was placed on an aluminum weighing pan. The pan of azasilane was placed on the top of a hot plate, the nonwoven stood upright right next to the pan to maximize the vapor exposure. A glass dish (available under the trade designation PYREX 3140, 70 mm X 50 mm) was used to cover the nonwoven and the pan of azasilane to create a vapor coating apparatus. The glass dish was sealed on top of the hot plate using a Dow Coming High Vacuum Grease. The hot plate was set to 65°C and the nonwoven was vapor coated for a designated time after the hot plate reached the set temperature. After vapor coating, the sample was transferred to an oven pre-set at 80°C, baked overnight (~12 h) under nitrogen atmosphere, and weighed the following day upon cooling. The amount of azasilane used and length of vapor coating for each sample and the corresponding results of weight changes are summarized in Table 2, where CE-1 and CE-2 are control samples.Table 2NA = Not Applicable

[0065] Thermogravimetric analysis (TGA) Test Method 1: CO2 capture performance

[0066] A hole punch was used to cut out samples from the vapor-coated nonwoven samples weighing approximately 5-50 mg. The sample was loaded on a clean and tared platinum TGA pan. The thermogravimetric analyzer (a Q500 model from TA Instruments New Castle, DE) was plumbed with house nitrogen (supplied by Praxair, Danbury, CT) in gas line #1 and a mixed gas canister on gas line #2 regulated to 20 psi (0.138 MPa). The mixed gas canister was a 20 volume % CO2 with a balance of N2obtained from Airgas, Randor, PA.

[0067] First, house nitrogen was flowed over the sample at 80 °C for 90 min at 267 mL / min to drive off CO2 and get a baseline weight %.

[0068] Then, the gas composition supplied at a flow rate of 200 mL / min was adjusted (by splitting gas lines #1 and #2) to supply a 15 vol% CO2 to the sample in the chamber while holding the chamber at 80°C. The 15 vol% CO2 was flowed across the sample for a set time (either 10 or 30 min) and the weight gain of the sample was monitored.

[0069] Then, the CO2gas supply was stopped and the sample was regenerated with house nitrogen flow for 10 min while held at 80°C.

[0070] Then, the gas in the sample chamber was adjusted to 15 vol% CO2 and the chamber was cooled to 65°C. The 15 vol% CO2 was flowed across the sample at a flow rate of 200 mL / min for a set time (either 10 or 30 min) and the weight gain of the sample was monitored.

[0071] The sample was then regenerated by flowing house nitrogen and ramping the chamber up to 80 °C at 10 °C / min for 10 min to remove CO2 from the sorbent.

[0072] Then, the gas in the sample chamber was adjusted to 15 vol% CO2and the chamber was cooled to 50°C. The 15 vol% CO2 was flowed across the sample at a flow rate of 200 mL / min for a set time (either 10 or 30 min) and the weight gain of the sample was monitored.

[0073] The sample was then regenerated by flowing house nitrogen and ramping the chamber up to 80 °C at 10 °C / min for 10 min to remove CO2 from the sorbent.

[0074] Then, the gas in the sample chamber was adjusted to 15 vol% CO2and the chamber was cooled to 35°C. The 15 vol% CO2 was flowed across the sample at a flow rate of 200 mL / min for a set time (either 10 or 30 min) and the weight gain of the sample was monitored.

[0075] The sample was then regenerated by flowing house nitrogen and ramping the chamber up to 80 °C at 10 °C / min for 10 min to remove CO2 from the sorbent.

[0076] While at 80°C, the gas composition was switched and 15 vol% CO2was flowed across the sample at a flow rate of 200 mL / min for a set time (either 10 or 30 min) and the weight gain of the sample was monitored.

[0077] The mmol of CO2 per gram of sample at each temperature isotherm (80°C, 65°C, 50°C, 35°C, and 80°C) was calculated based on the difference between peak wt % and baseline wt% from the TGA and then multiplied by the molecular weight of CO2 to convert into mmoles of sample and divided by the weight of the initial sample. The results are shown in Table 3.Table 3

[0078] TGA Test Method 2: multicycle performance

[0079] A sample of EX-1 and EX-2 were cut out and tested in the thermogravimetric analyzer similar to TGA Test Method 1, except the following cycling was done.

[0080] After determining the initial baseline weight %, the chamber was cooled to 50 °C and 15 vol% CO2 was flowed across the sample for 90 min at 200 mL / min the TGA at 35 °C for CO2 adsorption. Then the CO2 gas supply was stopped and the sample was regenerated with house nitrogen flow for 90 min while held at 80°C.

[0081] The sample was cycled 10 times using the above process (i.e., flowing CO2 followed by regeneration) monitoring the weight change of the sample.

[0082] The mmol of CO2 per gram of sample at each cycle was calculated based on the difference between peak wt % and baseline (initial) wt% from the TGA and then multiplied by the molecular weight of CO2 to convert into mmoles of sample and divided by the weight of the initial sample. The results are reported in Table 4.Table 4

[0083] Foreseeable modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention. This invention should not be restricted to the embodiments that are set forth in this application for illustrative purposes. To the extent that there is any conflict or discrepancy between this specification as written and the disclosure in any document mentioned or incorporated by reference herein, this specification as written will prevail.

Claims

What is claimed is:

1. An article comprising:(i) a nonwoven comprising a plurality of oxidized polyacrylonitrile staple fibers; and(ii) a coating disposed on at least a portion of a surface of the nonwoven, wherein the coating is derived from an azasilane.

2. The article of claim 1, wherein the azasilane is a cyclic azasilane.

3. The article of any one of the previous claims, wherein the azasilane has a molecular weight of at least 70 g / mol and most 400 g / mol.

4. The article of any one of the previous claims, wherein the azasilane is according to the formulawhere R2 and R3 are independently selected from substituted or unsubstituted, alkyl or alkenyl groups comprising 1 to 12 carbon atoms; R4 is selected from hydrogen, a substituted or unsubstituted, alkyl, alkenyl, or alkynyl group comprising 1 to 12 carbon atoms; R1 is selected from hydrogen or an alkyl group comprising 1 to 12 carbon atoms; x is 1, 2, or 3; and y is 1, 2, or 3.

5. The article of any one of the previous claims, wherein the azasilane is N-(2-aminethyl)-2,2,4- trimethyl-l-aza-2-silacyclopentane; 2,2,6,6-tetramethyl-l-oxa-4-aza-2,6-disilacyclohexane-4-ethanamine; or combinations thereof.

6. The article of any one of the previous claims, wherein the article has a surface area of at least 0.1 m2 / g and at most 500 m2 / g.

7. The article of any one of the previous claims, wherein the plurality of oxidized polyacrylonitrile staple fibers have a diameter of at least 10 micrometers and at most 10000 micrometers.

8. The article of any one of the previous claims, wherein the plurality of oxidized polyacrylonitrile staple fibers range from 20 to 100 millimeters in length, inclusive.

9. The article of any one of the previous claims, wherein the nonwoven further comprises silica aerogel.

10. The article of claim 9, wherein the nonwoven comprises 10 to 60 wt % of the silica aerogel.

11. The article of any one of the previous claims, wherein the nonwoven further comprises an organic binder.

12. The article of claim 11, wherein the organic binder is derived from a multifunctional (meth)acrylate, multifunctional isocyanate, multifunctional alcohol, multifunctional aziridine, or combinations thereof.

13. The article of any one of the previous claims, wherein the coating has a thickness of at least 0.6 nm and at most 1000 nm.

14. The porous article of any one of the previous claims, wherein the porous article has heat stability of up to at least 110 °C.

15. The porous article of any one of the previous claims, wherein the porous article has an initial CO2 absorbance of at least 0.5 mmol CCT / g at 80°C.

16. The porous article of any one of the previous claims, wherein the porous article after 20 cycles has a CO2 absorbance of at least 0.5 mmol CCT / g at 50°C.

17. A method of carbon capture, the method comprising contacting carbon dioxide to the porous article according to any one of the previous claims.

18. A method of making a coated article, the method comprising:(i) providing a nonwoven comprising a plurality of oxidized polyacrylonitrile staple fibers; and(ii) vapor coating an azasilane on at least a portion of a surface of the nonwoven.

19. The method of claim 18, wherein the vapor coating is conducted at temperature of at most 85°C.

20. The method of any one of claims 18 to 19, wherein the vapor coating is conducted at ambient pressure.

21. The method of any one of claims 18 to 19, wherein the nonwoven has a surface area of at least 0.1 m2 / g.

22. Use of an azasilane-coated nonwoven to capture carbon dioxide, wherein the azasilane-coated nonwoven comprises a nonwoven comprising oxidized polyacrylonitrile staple fibers with a surface coating derived from an azasilane.

23. Use of an azasilane-coated nonwoven composite to capture a carbonyl-containing compound, wherein the azasilane-coated nonwoven comprises a nonwoven comprising oxidized polyacrylonitrile staple fibers with a surface coating derived from an azasilane.

24. The use according to claim 23, wherein the carbonyl-containing compound comprises, formaldehyde, acetaldehyde, acrolein, acetone, or mixtures thereof.

25. Use of an azasilane-coated nonwoven to capture heavy metals, wherein the azasilane-coated nonwoven comprises a nonwoven comprising oxidized polyacrylonitrile staple fibers with a surface coating derived from an azasilane.

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