microporous aerogel

Abstract

This disclosure generally relates to a microporous aerogel, a process for preparing the microporous aerogel, and applications of the microporous aerogel. This disclosure also generally relates to an apparatus for capturing carbon dioxide from a gas stream or atmosphere, said apparatus comprising a microporous aerogel for selectively adsorbing and desorbing carbon dioxide.

Description

Technical Field

[0001] This disclosure generally relates to a microporous aerogel, a process for preparing the microporous aerogel, and applications of the microporous aerogel. This disclosure also generally relates to an apparatus for capturing carbon dioxide from a gas stream or atmosphere, the apparatus comprising a microporous aerogel for selectively adsorbing and desorbing carbon dioxide. Background Technology

[0002] Various methods have been used for CO2 capture, including the use of liquid-based and solid-based adsorbents. The liquids used typically involve alkaline solutions that chemically react with CO2. However, the absorption rate and energy requirements for regenerating the materials are challenging. Furthermore, corrosion and evaporation problems arise due to the highly alkaline nature of the liquids. Solid adsorbents have attracted increasing attention for their application in CO2 capture and sequestration due to their good adsorption capacity. Many emerging solid materials are available, including amine-functionalized silica, oxides, zeolites, carbon, polymers, and metal-organic frameworks (MOFs). While these materials offer lower regeneration energy, their synthesis can be costly, and some require expensive chemicals, toxic solvents, involve multi-step operations (extraction, filtration, washing, and drying), are thermally unstable, and are prone to chemical degradation.

[0003] Therefore, there is a need to provide alternative or improved aerogels and processes for preparing alternative or improved aerogels. Summary of the Invention

[0004] This disclosure provides an alternative microporous aerogel, particularly a silica-based aerogel for carbon dioxide capture, a process for preparing the silica-based aerogel, an adsorption device for the silica-based aerogel, and associated adsorption and desorption methods. The inventors of this invention have researched and developed a process for capturing carbon dioxide (CO2) from a gas stream using a silica-based aerogel. Silica-based aerogel compositions can be tailored to provide control and selectivity over CO2 adsorption efficiency. In particular, silica-based aerogels can capture CO2 from a low-CO2-concentration gas stream by adsorbing CO2 within the aerogel, thereby removing it from the gas stream. The adsorbed CO2 can then be collected from the silica-based aerogel, and the regenerated silica-based aerogel can be reused to adsorb more CO2 (e.g., recycle, continuously recycled). This disclosure can also be extended to industrial applications, and uses can be found particularly in the direct air capture of CO2. The present disclosure using selected silica-based aerogels can combine one or more of the following advantageous properties: microporosity, hydrophobicity, CO2 selectivity, environmental CO2 conditions for effective capture, heat of adsorption of carbon dioxide, and / or regeneration capability.

[0005] In one aspect, a silica-based aerogel for carbon dioxide capture is provided, wherein the microporous aerogel comprises a plurality of pores, and at least 50% of the pores have a diameter of less than about 2 nm. The aerogel can adsorb CO2 from air in an environment with a CO2 concentration of less than about 10 vol%. The aerogel can adsorb CO2 from air in a closed environment or indoor environment (DACi) with a CO2 concentration of less than about 2 vol%. The aerogel can adsorb CO2 from air in an environment with a CO2 concentration of about 0.04 vol%, wherein the environment is a direct air capture (DAC).

[0006] In one embodiment or example, the CO2 adsorption capacity of the aerogel may be at least 0.47 mmol / g.

[0007] In some embodiments or examples, the microporous aerogel may comprise or consist of a reaction product of at least one amino-substituted silane, at least one silicate, and optionally at least one alkyl-substituted silane.

[0008] In one embodiment or example, the density of the aerogel may be about 0.02 g / cm³. 3 Approximately 0.6 g / cm³ 3 In one embodiment or example, the aerogel may have a thickness of approximately 0.1 m. 2 / g and 500m 2 The surface area is between / g. In one embodiment or example, the aerogel may have a pore size of about 0.1 nm to about 2 nm.

[0009] In some embodiments or examples, aerogels can be in the form of particles, powders, beads, granules, sheets / layers, ingots, cylinders, discs, porous membranes, or monolithic materials. Aerogels may include multiple particles, powders, granules, beads, granules, coatings, or sheets / layers.

[0010] In some embodiments or examples, the aerogel may be a self-supporting aerogel. In another embodiment or example, the aerogel may be applied to a substrate as a coating composition or film.

[0011] In one embodiment or example, the reaction product can be prepared via a one-pot synthesis.

[0012] In another embodiment or example, the aerogel may be in the form of a composite material, wherein the composite material may include or consist of the aerogel, one or more additives, optionally a lubricant, and optionally a solvent. One or more additives may be selected from binders, optionally metal-organic frameworks (MOFs), and nanoparticles. Based on the total weight of the aerogel, the amount of additives may be from about 5% to about 35% by weight. In some embodiments or examples, the composite material may be self-supporting in the form of granules, beads, flakes, or particles. In other embodiments, the composite material may be applied to a substrate as a coating composition, paste, or film.

[0013] In another aspect, an aerogel composite material is provided, the aerogel composite material comprising: (i) a microporous aerogel or combination thereof according to any of the embodiments or examples described herein, the microporous aerogel comprising reaction products of amino-substituted silanes, silicates, and optionally alkyl-substituted silanes; (ii) one or more additives, wherein the additives have a loading percentage of about 5% to about 35% by weight; (iii) optionally a lubricant; and optionally a solvent. The one or more additives may be selected from binders, optionally metal-organic frameworks (MOFs), and nanoparticles. The binder may be selected from cellulose-based polymers, silane-based polymers, cellulose-siloxane-based polymers, polyethylene glycol-based polymers, polyvinylpyrrolidone, polyvinyl alcohol, polyethyleneimine, bentonite, graphite, or combinations thereof.

[0014] On the other hand, a process is provided for preparing a silica-based microporous aerogel for carbon dioxide, wherein the microporous aerogel comprises a plurality of pores and at least 50% of the pores have a diameter of less than about 2 nm, the process comprising: (i)(a) mixing an aqueous solution comprising at least one amino-substituted silane, at least one silicate and optionally at least one alkyl-substituted silane, optionally a buffer, optionally one or more additives and a solvent system to form a wet gel matrix; and (ii) drying the wet gel matrix to provide a dry silica-based aerogel, provided that drying the wet gel matrix does not involve supercritical CO2.

[0015] In one embodiment or example, the process may be a sol-gel process, and step (ii) includes: (a1) optionally heating the wet gel matrix to obtain a gel; and (a2) drying the gel by solvent evaporation and / or heat treatment to provide a dry silica-based aerogel.

[0016] In another embodiment or example, step (ii) may further include: (b1) wherein a wet gel matrix may be applied to a substrate to form a wet gel film coated on the substrate; and (b2) drying the wet gel film by solvent evaporation and / or heat treatment to provide a dry silica-based coated substrate.

[0017] In another embodiment or example, the process may further include preparing an aerogel composite material by: (c1) pressing a mixture of an aerogel or combination thereof according to any of the embodiments or examples described herein, one or more additives, and optionally a lubricant into granules, wherein the additives have a loading of about 5% to about 35% by weight; or (c2) liquid extruding a mixture of an aerogel or combination thereof according to any of the embodiments or examples described herein, one or more additives, optionally a lubricant, and optionally a solvent to provide a viscous paste, wherein the additives have a loading of about 5% to about 35% by weight.

[0018] Amino-substituted silanes may have the formula 1R as defined in any of the embodiments or examples described herein. 1 Si(OR2) n -L-NH2.

[0019] Alkyl-substituted silanes may have the formula 2R as defined in any of the embodiments or examples described herein. 5 m Si(OR 6 ) n .

[0020] Silicates may have the chemical formula 3Si(OR) as defined in any of the embodiments or examples described herein. 7 4.

[0021] In some embodiments or examples, the solvent may be water, a non-aqueous solvent, or a combination thereof.

[0022] In one embodiment or example, the process may further include step (iii) activation step.

[0023] On the other hand, a silica-based microporous aerogel for carbon dioxide (CO2) is provided, wherein the microporous aerogel comprises a plurality of pores and at least 50% of the pores have a diameter of less than about 2 nm, and is prepared by a process according to any one or more embodiments or examples described herein.

[0024] On the other hand, a silica-based microporous aerogel for carbon dioxide (CO2) capture is provided, wherein the microporous aerogel comprises a plurality of pores and at least 50% of the pores have a diameter of less than about 2 nm, the microporous aerogel comprising a reaction product according to any one or more embodiments or examples described herein and prepared by a process according to any one or more embodiments or examples described herein.

[0025] On the other hand, a process for capturing carbon dioxide (CO2) from a CO2-containing gas stream or atmosphere is provided, comprising: contacting the gas stream or atmosphere with a silica-based aerogel for capturing at least some CO2 from the gas stream or atmosphere, wherein the silica-based aerogel is a silica-based aerogel according to any of the embodiments or examples described herein, or a silica-based aerogel prepared by a process according to any of the embodiments or examples described herein.

[0026] In one embodiment, the airflow or atmosphere may have a CO2 concentration of less than about 150,000 ppm. The airflow or atmosphere may have a CO2 concentration in the range of about 3,000 ppm to 150,000 ppm, wherein the process can be direct air capture (DACex) at an external power plant. The airflow or atmosphere may have a CO2 concentration of less than about 40,000 ppm. The airflow or atmosphere may have a CO2 concentration of less than about 20,000 ppm. The airflow or atmosphere may have a CO2 concentration of less than about 10,000 ppm. The airflow or atmosphere may have a CO2 concentration of less than about 7,000 ppm. The airflow or atmosphere may have a CO2 concentration of less than about 5,000 ppm. The airflow or atmosphere may have a CO2 concentration in the range of about 4,000 ppm to 5,000 ppm, wherein the process can be direct air capture of exhaled gases in a face mask or personal protective equipment (DACp). The airflow or atmosphere may have a CO2 concentration of less than about 1,000 ppm. The airflow or atmosphere may be ambient air. The airflow or atmosphere may be less than about 500 ppm, and the process described therein may be direct air capture (DAC). This disclosure is applicable to capturing CO2 from the atmosphere, where the CO2 concentration is at atmospheric level (DAC) or where a higher concentration may be present in a closed environment (DACi).

[0027] In some embodiments or instances, contacting an airflow or atmosphere with the aerogel may include passing the airflow or atmosphere through a bed comprising the aerogel.

[0028] In some embodiments or examples, at least about 50% to about 99% of CO2 can be removed from the airflow or atmosphere. Preferably, at least about 90% of CO2 can be removed from the airflow.

[0029] In some embodiments or examples, the process may further include a regeneration process to desorb adsorbed CO2 from the silica-based aerogel. The regeneration process may include heating the silica-based aerogel to a temperature range between about 60°C and about 140°C by depressurization, by a flow of a gas having low CO2, or a combination thereof, to desorb adsorbed CO2 from the silica-based aerogel.

[0030] On the other hand, an adsorption device for capturing carbon dioxide (CO2) from a CO2-containing gas stream or atmosphere is provided, comprising: enclosing a chamber containing at least one silica-based aerogel, the silica aerogel being as defined and / or prepared according to any of the embodiments or examples described herein, the chamber including an inlet and an outlet through which a gas stream can flow to the silica-based aerogel and through which an outflowing gas stream can flow out of the silica-based aerogel.

[0031] In some embodiments or examples, the device may include two or more chambers enclosing at least one silica-based aerogel, the chambers being connected in parallel with the gas flow. The device may also include at least three chambers, each enclosing at least one silica-based aerogel, wherein each chamber may be connected in parallel with the gas flow. The silica-based aerogel enclosed in at least three chambers may operate in different sections of the adsorption and regeneration cycle to produce a continuous flow of outflow gas.

[0032] In some embodiments or instances, the outflowing gas from the outlet can flow to various secondary processes. Attached Figure Description

[0033] Referring to the accompanying drawings, preferred embodiments of this disclosure will be further described and illustrated by way of example only, wherein:

[0034] Figure 1 shows (a) a plot showing the pore size distributions of candidates A, B, C, and D determined using PALS; (b) a plot showing the pore size distributions of J, P, M, and L determined using N2 gas; (c) a plot showing CO2 absorption as a function of density for selected silica-based aerogels at different pressures; and (d) a plot showing CO2 absorption as a function of density for selected silica-based aerogels at different pressures.

[0035] Figure 2 A plot of the complete CO2 adsorption isotherm for silica-based aerogel candidate A at 298 K is shown. An important property of the isotherm is low-pressure absorption (<1 mbar). This is where direct air trapping will occur, and the stepped absorption exhibited in the isotherm is an indication of a microporous material.

[0036] Figure 3 The diagram shows the complete CO2 adsorption isotherms of silica-based aerogel candidate A operating at two temperatures: 313 K and 298 K. Candidate A can capture CO2 at higher temperatures, improving the operating conditions of the material.

[0037] Figure 4 A plot of the complete CO2 adsorption isotherm for silica-based aerogel candidate B at 298 K is shown. An important property of the isotherm is low-pressure absorption (<1 mbar). This is where direct air trapping will occur, and the stepped absorption exhibited in the isotherm is an indicator of a microporous material.

[0038] Figure 5 The diagram shows the complete CO2 adsorption isotherms of silica-based aerogel candidate B operated at two temperatures: 313 K and 298 K. Candidate B can capture CO2 at higher temperatures, increasing the operating conditions of the material.

[0039] Figure 6 A plot of the complete CO2 adsorption isotherm of silica-based aerogel candidate C at 298 K is shown.

[0040] Figure 7 The diagram shows the complete CO2 adsorption isotherms of silica-based aerogel candidate C operating at two temperatures: 313 K and 298 K. Candidate C can capture CO2 at higher temperatures, increasing the operating conditions of the material.

[0041] Figure 8 A plot of the complete CO2 adsorption isotherm of silica-based aerogel candidate D at 298 K is shown.

[0042] Figure 9 A plot of the complete CO2 adsorption isotherm of silica-based aerogel candidate E at 298 K is shown.

[0043] Figure 10 A plot of the complete CO2 adsorption isotherm of silica-based aerogel candidate J at 298 K is shown.

[0044] Figure 11 A plot of the complete CO2 adsorption isotherm of silica-based aerogel candidate K at 298 K is shown.

[0045] Figure 12 A plot of the complete CO2 adsorption isotherm of silica-based aerogel candidate L at 298 K is shown.

[0046] Figure 13A plot of the complete CO2 adsorption isotherm of silica-based aerogel candidate M at 298 K is shown.

[0047] Figure 14 A plot of the complete CO2 adsorption isotherm of silica-based aerogel candidate N at 298 K is shown.

[0048] Figure 15 A plot of the complete CO2 adsorption isotherm of silica-based aerogel candidate O at 298 K is shown.

[0049] Figure 16 A plot of the complete CO2 adsorption isotherm of silica-based aerogel candidate P at 298 K is shown.

[0050] Figure 17 A plot of the complete CO2 adsorption isotherm of silica-based aerogel candidate Q at 298 K is shown.

[0051] Figure 18 A plot of the complete CO2 adsorption isotherm of silica-based aerogel candidate R at 298 K is shown.

[0052] Figure 19 A plot of the H2O adsorption isotherm collected at 298 K is shown, illustrating the decrease in water absorption as the contents of TEMS and APEMS increase. Candidate D, with only 20% TEMS loading and no APEMS, produced a higher H2O absorption compared to other candidates with various loadings of 60-80% APEMS, TEMS, DMDES, and / or TEES.

[0053] Figure 20 The graphs show the CO2 breakthrough curves of candidates A (GM86-01), B (GM92-01), and D (GM108-01) under dry and humid conditions (70-80% RH) at 740 ppm.

[0054] Figure 21 The graph shows the CO2 breakthrough curves of candidate B at 500 ppm and 740 ppm under dry and humid conditions (70-80% RH).

[0055] Figure 22 The graphs show the CO2 breakthrough curves of candidates A (GM86-01), B (GM92-01), D (GM108-01) and zeolite 13X at 740 ppm under dry and wet conditions (70-80% RH).

[0056] Figure 23The plot shows the N2 adsorption isotherm of candidate A at 77 K. Solid circles represent adsorption data points, and hollow circles represent desorption data points.

[0057] Figure 24 The diagram shows the N2 adsorption isotherm of candidate B at 77 K. Solid circles represent adsorption data points, and hollow circles represent desorption data points.

[0058] Figure 25 The diagram shows the N2 adsorption isotherm of candidate C at 77 K. Solid circles represent adsorption data points, and hollow circles represent desorption data points.

[0059] Figure 26 The diagram shows the N2 adsorption isotherm of candidate D at 77 K. Solid circles represent adsorption data points, and hollow circles represent desorption data points.

[0060] Figure 27 The plot shows the N2 adsorption isotherm of candidate E at 77 K. Solid circles represent adsorption data points, and hollow circles represent desorption data points.

[0061] Figure 28 The plot shows the N2 adsorption isotherm of candidate K at 77 K. Solid circles represent adsorption data points, and hollow circles represent desorption data points.

[0062] Figure 29 A plot of the CO2 adsorption isotherm for candidate J at 298 K is shown. This adsorption isotherm depicts the properties of the aerogel after activation between consecutive adsorption runs and each run. The properties of the aerogel remain unchanged at 0.4 mbar, representing a 10% performance loss compared to the initial adsorption.

[0063] Figure 30 A plot of the CO2 adsorption isotherm for candidate K at 298 K is shown. This adsorption isotherm depicts the properties of the aerogel after activation between consecutive adsorption runs and between each run. The properties of the aerogel remain unchanged at 0.4 mbar, with a performance loss of 1% compared to the initial adsorption.

[0064] Figure 31 The CO2 adsorption isotherm of candidate K at 298 K is shown. Less than 1% performance loss was observed at a pressure of 0.4 mbar.

[0065] Figure 32 A graph showing CO2 at 740 ppm in a breakthrough experiment at 298 K under dry conditions is presented. Five cycles were run, with the aerogel activated at 100 °C for 12 h between each run. No loss of CO2 performance was observed for candidate D.

[0066] Figure 33A graph showing CO2 removal at 740 ppm at 298 K under humid conditions is presented. Five cycles (runs 6–10) were performed, with the aerogel activated at 100 °C for 12 h between each run. A 20% performance loss was observed during the cycling experiments. Under the same conditions, this CO2 removal remained superior to that of the commercial zeolite 13X sample.

[0067] Figure 34 The graphs of H2O adsorption at 298 K for candidate particles B, E, and K are shown, with a comparison to zeolite 13X particles and TIF-SIX particles. Detailed Implementation

[0068] This disclosure describes various non-limiting embodiments relating to studies aimed at determining a process for capturing carbon dioxide (CO2) from a gas stream (e.g., the atmosphere) using a silica-based aerogel. It has been found that silica-based aerogels can be used to adsorb CO2 from gas streams with low CO2 concentrations. The silica-based aerogel comprises a reaction product of at least one amino-substituted silane and at least one alkyl-substituted silane, which can adsorb and retain CO2. The captured CO2 can be removed from the silica-based aerogel, and the regenerated silica-based aerogel can be reused as an adsorbent material to capture CO2 from low CO2 concentration environments.

[0069] General definitions and terms

[0070] The following description will be made with reference to the accompanying drawings, which form part of the description and illustrate some embodiments by way of illustration. It should be understood that other embodiments and structural changes can be made without departing from the scope of this disclosure.

[0071] Regarding the definitions provided herein, unless otherwise stated or implied from the context, the defined terms and phrases have the meanings provided. Unless otherwise expressly stated or obvious from the context, the terms and phrases below do not exclude the meanings already known to those skilled in the art. The definitions are provided to aid in describing particular embodiments and are not intended to limit the claimed invention, as the scope of the invention is defined only by the claims. Furthermore, unless the context requires otherwise, singular terms shall include plural terms, and plural terms shall include singular terms.

[0072] All publications discussed and / or cited in this article are incorporated herein in their entirety.

[0073] Any discussion of documents, actions, materials, devices, articles of manufacture, etc., already included in this specification is for the purpose of providing context for this disclosure only. It should not be construed as an admission that any or all of these matters constitute part of the prior art or common general knowledge in the field relating to this disclosure, as they existed prior to the priority date of each claim of this application.

[0074] Throughout this disclosure, unless specifically stated otherwise or the context otherwise requires, references to a single step, combination of substances, group of steps, or group of substances should be understood to encompass one or more (i.e., one or more) of such steps, combinations of substances, group of steps, or group of substances. Therefore, as used herein, the singular forms “a,” “an,” and “the” include the plural aspect unless the context clearly indicates otherwise. For example, reference to “a” includes one and two or more; reference to “an” includes one and two or more; reference to “the” includes one and two or more, and so on.

[0075] Those skilled in the art will understand that, apart from the specific description, the disclosure herein is open to variation and modification. It should be understood that this disclosure includes all such variations and modifications. This disclosure also includes all instances, steps, features, methods, compositions, coatings, processes, and coated substrates that are individually or collectively mentioned or indicated in this specification, as well as any and all combinations or any two or more of such steps or features.

[0076] The term “and / or”, such as “X and / or Y”, should be understood to mean “X and Y” or “X or Y”, and should be regarded as providing explicit support for both meanings or either meaning.

[0077] Unless otherwise stated, the terms “first,” “second,” etc., are used merely as identifiers in this document and are not intended to impose any order, position, or hierarchy on the items referred to by these terms. Furthermore, references to a “second” item do not require or exclude the existence of a lower-numbered item (e.g., a “first” item) and / or a higher-numbered item (e.g., a “third” item).

[0078] As used in this article, when used with a list of items, the phrase "at least one" means that different combinations of one or more of the listed items may be used, and it may be necessary to have only one item from the list. The item can be a specific object, thing, or category. In other words, "at least one" means that any combination of items or the number of items from the list may be used, but not all items in the list are required. For example, "at least one of items A, B, and C" could mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, "at least one of items A, B, and C" could mean, for example, but not limited to, two of items A, one of items B, and ten of items C; four of items B and seven of items C; or some other suitable combination.

[0079] As used herein, unless otherwise stated, the term “about” generally refers to + / - 10% of the specified value, such as + / - 5%.

[0080] It should be understood that, for clarity, certain features described herein in the context of individual embodiments may also be provided in combination in a single embodiment. Conversely, for brevity, the various features described in the context of a single embodiment may also be provided individually or in any sub-combination.

[0081] Throughout this specification, various aspects and components of this disclosure may be presented in a range format. The range format is included for convenience and should not be construed as an immutable limitation on the scope of the invention. Therefore, unless specifically indicated, the description of a range should be considered as having specifically disclosed all possible subranges and individual numerical values ​​within that range. For example, a description of a range such as 1 to 5 should be considered as having specifically disclosed subranges such as 1 to 3, 1 to 4, 1 to 5, 2 to 4, 2 to 5, 3 to 5, etc., and individual and partial numbers within the stated range, such as 1, 2, 3, 4, 5, 5.5, and 6, unless integers are required or implied from the context. This applies regardless of how broad the disclosed range may be. Where specific values ​​are required, these will be noted in the specification.

[0082] Throughout this specification, the word “comprise” or variations thereof, such as “comprises” or “comprising”, shall be understood to imply inclusion of the stated elements, integers or steps, or groups of elements, integers or steps, but not to exclude any other elements, integers or steps, or groups of elements, integers or steps.

[0083] Throughout this specification, the term "consistent with substantially all of" is intended to exclude elements that would substantially affect the properties of the claimed composition.

[0084] The terms “comprising,” “comprise,” and “comprises” in this document are intended to be optionally replaced, in each case, by the terms “consisting essentially of,” “consisting essentially of,” “consistsessentially of,” “consisting of,” “consist of,” and “consists of,” respectively.

[0085] In this document, the term “about” covers a 10% tolerance for any one or more values ​​associated with the term.

[0086] The phrase "substantially free of" generally means that the compound or component is absent from the composition except for any trace amounts or impurities that may be present. This could be, for example, an amount less than about 1%, 0.1%, 0.01%, 0.001%, or 0.0001% by weight in the total composition. The compositions described herein may also contain, for example, impurities in an amount less than about 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.01%, 0.001%, or 0.0001% by weight in the total composition. For example, this could be an amount less than about 0.001% or 0.0001% by volume in the total gas flow. For example, the gas flow described herein may also contain impurities, for example, in an amount less than about 0.01%, 0.001%, or 0.0001% by volume in the total gas flow. An example of such impurities is the amount of methane (CH4) that may be present in the air, present in amounts less than 0.0005% by volume.

[0087] In this article, “weight%” can be abbreviated as “wt.%”.

[0088] The term "alkyl" includes straight-chain, branched, and cyclic alkyl groups, and includes unsubstituted and substituted alkyl groups. In one instance, the alkyl group is straight-chain and / or branched, and optionally separated by 1 to 3 cyclic alkyl groups. Unless otherwise specified, alkyl groups typically contain 1 to 20 carbon atoms. Alkyl groups may, for example, contain 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. Examples of "alkyl" as used herein include, but are not limited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl, isobutyl, tert-butyl, isopropyl, n-octyl, n-heptyl, ethylhexyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, and norbornyl. Unless otherwise specified, alkyl groups may be monovalent or polyvalent. Alkyl groups may optionally be substituted by one or more heteroatoms and / or optionally separated by one or more heteroatoms. For use as a divalent or polyvalent linking group, an alkyl group may be referred to as "-alkyl-".

[0089] The term "alkylsilyl" refers to an alkyl group that is linked to the rest of the molecule by a silicon atom and can be replaced by up to three independently chosen alkyl groups, each as defined above.

[0090] silica-based aerogels

[0091] This disclosure relates to a silica-based microporous aerogel that can be provided in a wide range of forms. Illustrative examples of suitable forms may include particles, powders, granules, beads, coatings, sheets / layers, ingots, cylinders, discs, porous membranes, and bulk materials. For example, the silica-based aerogel can be provided as multiple granules. For example, the silica-based aerogel can be provided as a membrane / coating, a gel layer, on which an airflow can flow or through the layer. Such layers can be provided as rolled sheets or 3D substrates. Alternatively, the silica-based aerogel layer can also be provided as a bulk material comprising multiple porous channels in which an airflow flows. Other layer or coating forms and geometries are also applicable.

[0092] In one embodiment or example, the silica-based aerogel may comprise a plurality of particles. The term "particle" (also referred to as "particulate") refers to the form of discrete solid units. These units may take the form of flakes, fibers, clumps, granules, pellets, powders, beads, spheres, pulverized materials, and combinations thereof. Particles may have any desired shape, including but not limited to cubic, rod-shaped, polyhedral, spherical or hemispherical, circular or semi-circular, angular, irregular, etc. The particle morphology may be determined by any suitable means such as optical microscopy.

[0093] In some embodiments or examples, the aerogel can be a plurality of particles, powders, granules, beads, pellets, coatings, or sheets / layers. In some embodiments or examples, the particles, powders, granules, beads, pellets, coatings, or sheets / layers can be compositions further comprising optional additives selected from the group consisting of metal-organic frameworks, nanoparticles, magnetic nanoparticles, other porous materials, binders, buffers, or combinations thereof. For example, silica-based aerogels can be provided as a plurality of particles, powders, or granules. In one example, silica-based aerogels can be provided as a plurality of granules. In one embodiment, a silica-based aerogel can be pressed or extruded together with at least one additive (e.g., a binder) and optionally a lubricant to form a shape / granule, thereby forming a composite material. The inventors have found that the choice of binder can be a decisive factor in whether the aerogel composition can be pressed or extruded, and even further found that the amount of binder added to the composition will depend on the final application or use. The aerogel composite material can be any suitable size and / or shape. In some embodiments or examples, the silica-based aerogel composite material can have an average particle size.

[0094] The metal-organic framework can be selected from the group consisting of TIF-SIX-3-Ni, TIF-SIX-3-Ni, CuBTC, Mg-MOF-74, Mg-MOF-74-ED, Nb-OFFIVE, or combinations thereof. The nanoparticles can be selected from the group consisting of carbon-based nanoparticles (e.g., fullerenes and carbon nanotubes), metal-based nanoparticles (e.g., alkali metals and noble metals), ceramic nanoparticles, polymer nanoparticles, lipid-based nanoparticles, quantum dots, silica nanoparticles, graphene, or combinations thereof. The magnetic nanoparticles can be selected from the group consisting of iron oxides, ferrites, or combinations thereof. The binder can be selected from the group consisting of cellulose-based polymers, silane-based polymers, cellulose-siloxane-based polymers, polyethylene glycol-based polymers, epoxy-based polymers, colloidal silica, polyvinylpyrrolidone, polyvinyl alcohol, polyethyleneimine, or combinations thereof. The binder can be selected from commercial adhesives. It should be understood that other components can form part of a commercial adhesive. In one example, the adhesive may contain other components, such as a lubricant. Lubricants can be used as needed to adjust the viscosity of the aerogel formulation to, for example, an extrudable material. Other components may include dicalcium phosphate, silica, glucose monohydrate, and magnesium stearate. Buffers may be selected from the group consisting of (NH4)2CO3, NH4CH3CO2, NH3, NH4HCO3, and carbon dioxide.

[0095] Aerogel particles can have any suitable size and / or shape and / or morphology. In some embodiments or examples, silica-based aerogel particles can have an average particle size. For spherical silica-based aerogel particles, the particle size is the diameter of the particle. For non-spherical silica-based aerogel particles, the particle size is the longest cross-sectional dimension of the particle. In some embodiments or examples, silica-based aerogel particles can have an average particle size in the range of about 10 nm to about 2000 nm (e.g., about 10 nm to about 1000 nm). Silica-based aerogel particles can have an average particle size of at least about 10, 20, 50, 100, 200, 300, 400, 500, 700, 1000, 1500, or 2000 nm. In other embodiments or examples, silica-based aerogel particles may have an average particle size of less than about 2000, 1500, 1000, 700, 500, 400, 300, 200, 100, 50, 20, or 10 nm. Combinations of these particle size values ​​forming various ranges are also possible; for example, silica-based aerogel particles may have an average particle size of about 30 nm to about 70 nm, about 30 nm to about 80 nm, or, for example, about 20 nm to about 100 nm. The average particle size can be determined by any means known to those skilled in the art, such as scanning electron microscopy, dynamic light scattering, optical microscopy, or size exclusion methods (such as grading sieves). In one example, the method for measuring the average particle size may be scanning electron microscopy. Silica-based aerogel particles can have a controlled average particle size and can maintain their morphology under a range of different environmental and shear conditions, such as when in contact with airflow and / or humid or dry environments.

[0096] In another embodiment, the silica-based aerogel may be self-supporting. As used herein, the term "self-supporting" refers to the ability of a silica-based aerogel to maintain its shape without a supporting material (e.g., a scaffold). For example, a silica-based aerogel may comprise multiple particles, wherein the particles maintain their shape without scaffold support. The self-supporting nature of silica-based aerogels can provide certain advantages, such as allowing the aerogel particles to contact with an airflow in a fluidized bed reactor. Therefore, in one embodiment or example, the silica-based aerogel does not include a separate support structure, such as a separate porous support structure. This does not preclude the aerogel itself from being porous in nature. Therefore, it should be understood that in the case where the silica-based aerogel is "self-supporting," there is no external supporting material (e.g., a scaffold) for the aerogel.

[0097] In yet another embodiment, a silica-based aerogel can be provided as a layer within a column, wherein a gas flow can pass through the column and through the silica-based aerogel layer. This layer is not limited to any particular aerogel morphology. In one example, a suitable column can be filled with multiple silica-based aerogel particles to form a packed bed with sufficient gaps between adjacent particles to allow gas flow. Alternatively, the silica-based aerogel can be provided flowing along with the gas flow (e.g., in a fluidized bed reactor).

[0098] In another embodiment, the silica-based aerogel can be provided as a coating composition on a substrate. In some embodiments or examples, the substrate can be planar, such as a planar sheet. In certain examples, the substrate can be a flexible sheet. The planar substrate provides a double-sided element on which the silica-based aerogel coating composition can be applied. Each substrate can be coated with the silica-based aerogel coating composition on two opposite sides. The planar substrate can have any configuration. In some embodiments or examples, the planar substrate can include a flat solid surface. In other embodiments or examples, the planar substrate can include one or more pores designed to facilitate gas flow through and around the substrate. In certain embodiments or examples, the substrate can include a mesh, such as a microfilament mesh. The use of a mesh provides a large number of pores (e.g., micro-sized pores), thereby providing a high surface area on which the silica-based aerogel coating composition can be coated, while also providing a suitable flow path with a relatively low pressure drop across the substrate (relative to the size and configuration of the mesh) compared to other configurations such as a packed bed.

[0099] This disclosure provides a silica-based aerogel, which is a microporous aerogel. The aerogel preferably has low mesopority while maintaining excellent microporosity (pore diameter < 2 nm). In some embodiments, the microporous aerogel may have multiple pores, and at least 50% of the pores have a diameter less than about 2 nm. Preferably, at least 60% of the pores have a diameter less than about 2 nm. More preferably, at least 70% of the pores have a diameter less than about 2 nm. Even more preferably, at least 80% of the pores have a diameter less than about 2 nm. In some embodiments or examples, the porosity of the silica-based aerogel may be less than about 2 nm. The pore size may be less than about 1.8 nm. It should be understood that microporous aerogels differ from mesoporous and macroporous aerogels. Mesoporous aerogels contain pores with diameters between 2 nm and 50 nm, and macroporous aerogels contain pores with diameters greater than 50 nm. In some embodiments or examples, silica-based aerogels can have pore sizes in the range of about 0.1 nm to about 2 nm (e.g., about 0.2 nm to about 2 nm). Silica-based aerogels can have pore sizes (nm) of at least about 0.1, 0.2, 0.5, 1, 1.2, 1.4, 1.6, 1.8, or 2. In other embodiments or examples, silica-based aerogels can have pore sizes (nm) smaller than about 2, 1.8, 1.6, 1.4, 1.2, 1, 0.5, 0.2, or 0.1. Combinations of these pore size values ​​forming various ranges are also possible; for example, silica-based aerogels can have pore sizes of about 0.1 nm to about 1.8 nm, about 0.5 nm to about 2 nm, or, for example, about 1 nm to about 2 nm. Pore size can be determined by any means known to those skilled in the art, such as gas adsorption experiments, mercury porosimetry, and capillary flow porosity determination methods. In one example, the method for measuring pore size can use positron annihilation lifetime spectroscopy (PALS). It has been found that microporous aerogels with pore sizes of 2 nm or smaller are produced during the one-pot synthesis method described herein. Furthermore, aerogels with pore sizes of 2 nm or smaller have been found to be best suited for capturing carbon dioxide from the atmosphere (DAC) and in closed environments (DACi).

[0100] In some embodiments or examples, silica-based aerogels can have a thickness of approximately 0.1 m. 2 / g to approximately 500m 2 / g (e.g., about 2m) 2 / g to approximately 200m 2 Silica-based aerogels can have a surface area in the range of approximately 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 10, 20, 50, 100, 200, or 500 m². 2 / g). In other embodiments or examples, silica-based aerogels may have a surface area (m²) of less than about 500, 200, 100, 50, 20, 10, 5, 4, 3, 2, 1, 0.5, 0.2, or 0.1. 2 / g). It is also possible for these surface area values ​​to combine to form various ranges; for example, silica-based aerogels can have approximately 0.1 m² / g. 2 / g to approximately 500m 2 / g, approximately 2m 2 / g to approximately 200m 2 / g, for example, about 3m 2 / g to approximately 150m 2 / g of surface area.

[0101] In some embodiments or examples, the density of the aerogel can be approximately 0.02 g / cm³. 3 Approximately 0.6 g / cm³ 3 (For example, approximately 0.05 g / cm³) 3 To approximately 0.5 g / cm 3 Within the range of ), the density of silica-based aerogels can be at least about 0.02, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, or 0.6 g / cm³. 3 In other embodiments or examples, the density of the silica-based aerogel may be less than about 0.6, 0.55, 0.5, 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, 0.15, 0.1, 0.05, or 0.02 g / cm³. 3 These density values ​​can be combined to form various ranges; for example, silica-based aerogels can have a density of approximately 0.02 g / cm³. 3 Approximately 0.6 g / cm³ 3 Approximately 0.05 g / cm³ 3 To approximately 0.5 g / cm 3 Approximately 0.15m 2 / g to approximately 0.4g / cm 3 For example, about 0.2m 2 / g to approximately 0.6m 2 / g or approximately 0.3m 2 / g to approximately 0.6m 2The density is measured in g. Higher-density aerogels are best suited for applications where weight is a consideration. High-density formulations can be used in CO2 adsorption-desorption devices that can be adapted to confined spaces or environments. These types of devices are commonly used in space, aerospace, underwater vehicles, or platforms. For example, in aerospace or space applications, aerogels can be used to capture CO2 from the atmosphere. When space is not an issue, low-density formulations may be appropriate. For example, DAC units intended for placement in greenhouses or power plants involve converting CO2 into methane.

[0102] In some embodiments or examples, the content of the amino group from the aminoalkylsilane unit can effectively provide free amine groups for promoting carbon dioxide (CO2) capture, wherein the free amine content can be less than about 60 mol%. In some embodiments or examples, the content of the aminoalkylsilane group can range from about 10 mol% to about 60 mol% (e.g., from about 20 mol% to about 40 mol%). The free amine content can be at least about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 mol%. In other embodiments or examples, the free amine content can be less than about 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, or 10 mol%. It is also possible for these free amine content values ​​to form various ranges, for example, the free amine content can have values ​​of about 10 mol% to about 60 mol%, about 15 mol% to about 50 mol%, or, for example, about 20 mol% to about 40 mol%. While the amino group derived from the aminoalkylsilane unit effectively provides the free amine group for facilitating carbon dioxide (CO2) capture, the methyl group derived from the aminoalkylsilane unit provides the desired hydrophobicity. In other words, one of the advantages of this disclosure is that, due to the hydrophobicity, silica-based aerogels can operate in environments with a wide range of relative humidity, which prevents the aerogels from competing for water adsorption when adsorbing CO2 from the air. Unlike zeolite 13X or TIF-SIX, the inventors have surprisingly discovered, as described herein, that microporous aerogels do not provide good water adsorption properties, making them far superior in the selective adsorption of CO2.

[0103] In some embodiments or examples, the reaction products forming at least one amino-substituted silane, at least one silicate, and optionally at least one alkyl-substituted silane comprise a siloxane backbone having a plurality of side groups selected from aminoalkyl and alkyl groups. It should be understood that because hydrophobic aminoalkyl and alkyl groups are present in the siloxane backbone, and each silicon atom has only three available siloxane bonds, silica-based aerogels as described herein can be hydrophobic and can generally have lower crosslinking densities and higher deformability than those derived from conventional tetraalkoxysilanes. These advantageous characteristics offer greater potential for further engineering the fine structure of silica-based aerogels to achieve low volume shrinkage through a drying process without the use of additional solvent exchange and surface modification. In some embodiments or examples, the reaction products forming at least one amino-substituted silane, at least one silicate, and optionally at least one alkyl-substituted silane can undergo hydrolysis and condensation reactions to form a polyalkylsiloxane network structure. These hydrolysis and condensation reactions may be the cause of the microstructure of silica-based aerogels. In one embodiment or example, the reaction product may include a siloxane backbone having a plurality of side groups selected from aminoalkyl and alkyl groups, wherein the molar ratio of side groups to the siloxane backbone may be at least 60% based on molecular weight. Based on molecular weight, the molar ratio of side groups to the siloxane backbone may range from about 60% to about 160% (e.g., from about 80% to about 140%). Based on molecular weight, the molar ratio of side groups to the siloxane backbone may be at least about 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, or 160%. In other embodiments or examples, based on molecular weight, the molar ratio of side groups to the siloxane backbone may be less than about 160, 150, 140, 130, 120, 110, 100, 90, 95, 90, 85, 80, 75, 70, 65, or 60%. It is also possible for these molar ratio values ​​to form various ranges; for example, based on molecular weight, the molar ratio of side groups to the siloxane backbone can have values ​​of about 60% to about 160%, about 65% to about 150%, or, for example, about 70% to about 140%.

[0104] In one embodiment, the amino-substituted silane may conform to formula 1: R 1 Si(OR 2 ) n -L-NH2, where: R 1 Can be selected from C 1-6 Alkyl groups may or may not be present; R 2 It can be C 1-6 Alkyl group; L is the -C between silicon and nitrogen atoms. 1-6Alkyl-linking group; and n can be 2 or 3. Based on the total weight of the aerogel formulation, the amino-substituted silane can have a loading of at least about 40 mol%. Based on the total weight of the aerogel formulation, the amino-substituted silane can have a loading of less than about 60 mol%.

[0105] In one embodiment, an alkyl-substituted silane may conform to formula 2: R 5 m Si(OR 6 ) n , where: R 5 and R 6 Each can be independently selected from C. 1-6 Alkyl; and m can be 1, and n can be 3, or m and n can each be 2. Based on the total weight of the aerogel formulation, the alkyl-substituted silane can have a loading of at least about 10 mol%. Based on the total weight of the aerogel formulation, the alkyl-substituted silane can have a loading of less than about 40 mol%.

[0106] In one embodiment, the silicate can conform to formula 3: Si(OR) 7 )4, where: R 7 It can be C 1-6 Alkyl groups. Based on the total weight of the aerogel formulation, silicates can have a loading of at least about 20 mol%. Based on the total weight of the aerogel formulation, silicates can have a loading of less than about 40 mol%.

[0107] The content of aminosilyl groups can effectively provide free amine groups for promoting carbon dioxide (CO2) capture, wherein the free amine content can be less than about 60 mol% based on the total weight of the aerogel formulation. In one embodiment or example, the amino-substituted silane may be 3-aminopropyl(diethoxy)methylsilane, which has a loading of about 40 mol% to about 60 mol% based on the total aerogel formulation.

[0108] In one embodiment or example, the aerogel may comprise or consist of a reaction product of at least one amino-substituted silane, at least one silicate, and optionally at least one alkyl-substituted silane.

[0109] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 40 mol%, the alkyl-substituted silane is triethoxymethylsilane with a loading of about 40 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0110] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(triethoxy)silane with a loading of about 40 mol%, the alkyl-substituted silane is triethoxymethylsilane with a loading of about 40 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0111] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 40 mol%, the alkyl-substituted silane is triethoxymethylsilane with a loading of about 20 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 40 mol%.

[0112] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(triethoxy)silane with a loading of about 40 mol%, the alkyl-substituted silane is triethoxymethylsilane with a loading of about 20 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 40 mol%.

[0113] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane and an alkyl-substituted silane, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 40 mol%, and the alkyl-substituted silane is triethoxymethylsilane with a loading of about 60 mol%.

[0114] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane and an alkyl-substituted silane, wherein the amino-substituted silane is 3-aminopropyl(triethoxy)silane with a loading of about 40 mol%, and the alkyl-substituted silane is triethoxymethylsilane with a loading of about 60 mol%.

[0115] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(triethoxy)silane with a loading of about 60 mol%, the alkyl-substituted silane is triethoxymethylsilane with a loading of about 20 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0116] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 40 mol%, the alkyl-substituted silane is triethoxy(ethyl)silane with a loading of about 40 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0117] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(triethoxy)silane with a loading of about 40 mol%, the alkyl-substituted silane is triethoxy(ethyl)silane with a loading of about 40 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0118] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 40 mol%, the alkyl-substituted silane is dimethyldiethoxysilane with a loading of about 40 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0119] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 40 mol%, the alkyl-substituted silane is a mixture of triethoxymethylsilane and dimethyldiethoxysilane with a loading of about 20 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0120] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 60 mol%, the alkyl-substituted silane is dimethyldiethoxysilane with a loading of about 10 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 30 mol%.

[0121] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 40 mol%, the alkyl-substituted silane is dimethyldiethoxysilane with a loading of about 30 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 30 mol%.

[0122] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(triethoxy)silane with a loading of about 40 mol%, the alkyl-substituted silane is a mixture of triethoxymethylsilane and dimethyldiethoxysilane with a loading of about 20 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0123] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 40 mol%, the alkyl-substituted silane is a mixture of triethoxymethylsilane and triethoxy(ethyl)silane with a loading of about 20 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0124] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 60 mol%, the alkyl-substituted silane is triethoxymethylsilane with a loading of about 20 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0125] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(triethoxy)silane with a loading of about 60 mol%, the alkyl-substituted silane is triethoxymethylsilane with a loading of about 20 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0126] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 60 mol%, the alkyl-substituted silane is a mixture of triethoxymethylsilane and triethoxy(ethyl)silane with a loading of about 10 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0127] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 50 mol%, the alkyl-substituted silane is a mixture of triethoxymethylsilane and triethoxy(ethyl)silane with a loading of about 15 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0128] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 50 mol%, the alkyl-substituted silane is triethoxymethylsilane with a loading of about 25 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 25 mol%.

[0129] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 60 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 40 mol%.

[0130] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 60 mol%, the alkyl-substituted silane is triethoxy(ethyl)silane with a loading of about 20 mol%, and the silicate is tetraethyl orthosilicate with a loading of about 20 mol%.

[0131] In one embodiment or example, the microporous aerogel may comprise or consist of a reaction product of an amino-substituted silane, an alkyl-substituted silane, and a silicate, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of about 40 mol%, and the alkyl-substituted silane is triethoxymethylsilane with a loading of about 40 mol% and triethoxy(ethyl)silane with a loading of about 20 mol%.

[0132] amino-substituted silanes

[0133] CO2 can be captured from a gas stream by adsorption into a silica-based aerogel. For example, CO2 can be adsorbed into a silica-based aerogel via a chemical or physical process. In some embodiments, the amino-substituted silane may include functional groups capable of binding CO2. For example, due to its porous nature, low CO2 concentrations of gas can pass through the pores within the silica-based aerogel and react with and bind to the functional groups on the amino-substituted silane upon contact with a low CO2 concentration gas stream. In some embodiments or examples, the amino-substituted silane is capable of adsorbing CO2 upon contact with a low CO2 concentration gas stream. Suitable amino-substituted silanes capable of adsorbing CO2 include one or more of the amino-substituted silanes described herein. In some embodiments or examples, the amino-substituted silane can adsorb CO2 via a chemical or physical process. In some embodiments or examples, the amino-substituted silane includes functional groups capable of binding to CO2. For example, the amino-substituted silane may include one or more amine groups, such as primary amines (-NH2). These amine groups are CO2-loving and readily react with and bind to CO2. In some embodiments or examples, amino-substituted silanes include one or more amine groups, such as, for example, 3-aminopropyl(diethoxy)methylsilane.

[0134] In some embodiments or examples, the amino-substituted silane may include about 10 mol% to 50 mol% of a primary amine (-NH2) group (also referred to herein as "free amine content"). The mol% of the primary amine (-NH2) group may be at least about 10, 15, 20, 25, 30, 35, 40, 45, or 50. In other embodiments or examples, the mol% of the primary amine (-NH2) group may be less than about 50, 45, 40, 35, 30, 25, 20, 15, or 10. Combinations of these mol% values ​​to form various ranges are also possible; for example, the mol% of the primary amine (-NH2) group may have values ​​from about 10 mol% to about 50 mol%, from about 15 mol% to about 45 mol%, and for example, from about 20 mol% to about 40 mol%.

[0135] In some embodiments or examples, amino-substituted silanes may include at least one or more aliphatic amine groups (e.g., amines in which no aromatic ring group is directly bonded to the nitrogen atom of the amine).

[0136] In some embodiments or examples, the amino-substituted silane conforms to formula 1:

[0137] R 1 m Si(OR 2 ) n -L-NH2

[0138] Formula 1

[0139] in:

[0140] R 1 It can be C 1-6 Alkyl groups may not be present;

[0141] R 2 It can be C 1-6 alkyl;

[0142] L is the -C between silicon and nitrogen atoms. 1-12 alkyl-linking groups; and

[0143] n can be 2 or 3. It should be understood that when R... 1 When it exists, n is 2, and when R 1 If n does not exist, n is 3.

[0144] In some embodiments or examples, amino-substituted silanes may include C 1-6 Alkyl groups, which may be provided by any alkyl group having a chain of 1 to 6 atoms as described above or herein.

[0145] In some embodiments or examples, amino-substituted silanes may include C 1-4 Alkyl groups, which may be provided by any alkyl group having a chain of 1 to 4 atoms as described above or herein.

[0146] The alkyl group of an amino-substituted silane may include 1 to 4 carbon atoms. The alkyl group may be methyl, ethyl, propyl, n-butyl, tert-butyl, or other higher carbon alkyl groups. In some embodiments or examples, the amino-substituted silane may be selected from the group consisting of 3-aminopropyl(diethoxy)methylsilane, 3-aminopropyl-triethoxysilane, 3-aminopropyl-trimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, or combinations thereof. For example, the amino-substituted silane may be selected from the group consisting of 3-aminopropyl(diethoxy)methylsilane or 3-aminopropyl-triethoxysilane.

[0147] Alkyl-substituted silanes

[0148] Alkylsilane groups are effective for achieving hydrophobicity and microporosity. In other words, one of the advantages of this disclosure is that, due to hydrophobicity, silica-based aerogels can operate in environments with a wide range of relative humidity, which prevents the aerogels from competing for water adsorption when adsorbing CO2 from the air. Furthermore, silica-based aerogels can include alkylsilane groups, which allows the microporosity of silica-based aerogels to effectively generate a more open structure with microsized pores, increasing the accessibility of CO2 to the reactive functional groups on the aforementioned amino-substituted silanes.

[0149] In some embodiments or examples, the alkyl-substituted silane conforms to formula 2:

[0150] R 5 m Si(OR 6 ) n

[0151] Formula 2

[0152] in:

[0153] R 5 and R 6 Each is independently selected from C 1-6 alkyl;

[0154] m can be 1 and n can be 3, or m and n can each be 2.

[0155] In some embodiments or examples, alkyl-substituted silanes may include C 1-6 Alkyl groups, which may be provided by any alkyl group having a chain of 1 to 6 atoms as described above or herein.

[0156] The alkyl group in an alkyl-substituted silane may include 1 to 6 carbon atoms. Alkyl-substituted silanes may also have additional functional groups. The alkyl group may be methyl, ethyl, propyl, n-butyl, tert-butyl, or other higher carbon alkyl groups. The alkyl-substituted silanes of this disclosure may contain monoalkyl, dialkyl, or trialkyl groups, and may be selected from the group consisting of: methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, diethyldimethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, triethylmethoxysilane, triethylethoxysilane, tripropylmethoxysilane, tripropylethoxysilane, tripropylethoxysilane, (3,3,3-trifluoropropyl)trimethoxysilane, (3,3,3-trifluoropropyl)triethoxysilane, and combinations thereof.

[0157] silicates

[0158] Silicates can be incorporated into silica-based aerogel matrices, resulting in complex structures with unique CO2-capturing properties associated with the resulting silica-based aerogels. Silicates conform to Equation 3:

[0159] Si(OR 7 )4

[0160] Formula 3

[0161] in:

[0162] R 7 It is C 1-6 alkyl.

[0163] In some embodiments or examples, silicates may include C 1-6 Alkyl groups, which may be provided by any alkyl group having a chain of 1 to 6 atoms as described above or herein.

[0164] The alkyl group of a silicate may include 1 to 6 carbon atoms. The alkyl group may be methyl, ethyl, propyl, n-butyl, tert-butyl, or other higher carbon alkyl groups. The silicates disclosed herein may be selected from tetraalkoxysilanes. For example, the silicate may be tetramethoxysilane, tetraethoxysilane, or combinations thereof.

[0165] Process for preparing silica-based aerogels

[0166] In some embodiments or examples, a process for preparing microporous aerogels is provided. Specifically, this disclosure provides a novel process for preparing silica-based aerogels as described herein from reaction products consisting of at least one amino-substituted silane, at least one silicate, and optionally at least one alkyl-substituted silane. In some embodiments, the process for preparing silica-based microporous aerogels (wherein the microporous aerogel comprises a plurality of pores and at least 50% of the pores have a diameter of less than about 2 nm) may include or consist of: (i)(a) mixing an aqueous solution comprising at least one amino-substituted silane, at least one silicate, and optionally at least one alkyl-substituted silane, optionally a buffer, optionally one or more additives, and a solvent system to form a wet gel matrix; and (ii) drying the wet gel matrix to provide a dry silica-based aerogel, provided that drying the wet gel matrix does not involve supercritical CO2. In some embodiments or examples, step (i) further includes step (i)(b) rinsing the wet gel matrix. Rinsing the wet gel enables solvent exchange and removal of byproducts from the pores of the material. One or more advantages of the process of the present invention according to at least some of the embodiments or examples described herein are that it is a scalable one-pot synthesis with short reaction times (e.g., about 6 hours for some formulations compared to 48 hours or more) and gelation times (e.g., about 5 to 30 minutes) to prepare microporous aerogels capable of capturing CO2. The synthesis and washing steps require an oven or water bath and basic reaction vessels. No specialized gas or pressure vessels are required for this process, and the typical density of preferred candidates can be in the range of 0.3 g / mL to 0.6 g / mL, allowing for the use of smaller volumes of aerogel in practical carbon capture devices. The economic advantages in terms of synthesis and equipment costs are very advantageous. This differs somewhat from previous processes, such as US 9,931,612 B2 (Aspen), where the synthesis of mesoporous aerogels involves lengthy multi-step processes and supercritical drying. For example, Aspen describes the synthesis of aerogels involving at least two sol-gel processes and solvent removal using supercritical CO2 extraction. For example, (i) two separate sols containing precursors are prepared at different temperatures and times, step (ii) the two separate sols are combined, (iii) gelation is allowed to occur within 2 days, and (iv) supercritical drying is performed using liquid CO2.

[0167] In some embodiments or examples, prior to step (ii), at least one amino-substituted silane and at least one alkyl-substituted silane may be hydrolyzed in an acidic medium (e.g., an organic acid, such as hydrochloric acid or phosphoric acid).

[0168] For example, in step (i), mixing an aqueous solution comprising at least one amino-substituted silane, at least one silicate and optionally at least one alkyl-substituted silane, optionally a buffer, optionally one or more additives and a solvent system to form a wet gel matrix can be carried out at ambient temperature for at least 24 hours, or can be heated to about 60°C to about 80°C for about 6 hours. In steps (i)(b), rinsing the wet gel matrix in sufficient water to exchange the solvent (e.g., ethanol) allows the wet gel matrix to dry (in step (ii)) to form an open, porous gel (e.g., a dried silica-based aerogel). Failure to remove the solvent may result in a “hard” gel with poor performance. The wet gel matrix, rinsed in sufficient water to remove the solvent, can be dried at room temperature and heated between about 80°C and 100°C to remove any residual water.

[0169] In some embodiments or examples, the process may be a sol-gel process, and step (ii) may include or consist of: (a1) optionally heating the wet gel matrix to obtain a gel; and (a2) drying the gel by solvent evaporation and / or heat treatment to provide a dry silica-based aerogel.

[0170] In other embodiments or examples, the process may include an alternative step (ii), which may include: (b1) wherein a wet gel matrix may be applied to a substrate to form a wet gel film coated on the substrate; and (b2) drying the wet gel film by solvent evaporation and / or heat treatment to provide a dry silica-based coated substrate. In one embodiment or example, the drying step (ii) may be vacuum drying or freeze drying. Preferably, the drying step is vacuum drying. It should be understood that the drying step (ii) does not involve supercritical CO2.

[0171] The alcogel in step (i) or the sol-gel (e.g., colloidal solution) in step (a1) can be formed by a process that gradually evolves into a gel-like two-phase system containing both a liquid and a solid phase, the morphology of which can range from discrete particles to a continuous polymer network (aging process). In some embodiments or examples, the particle density may be low, making it possible to initially remove a certain amount of liquid to identify the gel-like properties. In another embodiment or example, centrifugation can be used to accelerate the phase separation and gel formation process to form an aged alcogel or an aged sol-gel. Removal of the remaining liquid (solvent) phase may require a drying step (e.g., steps (ii) and (a2)).

[0172] It should be understood that pore size is primarily determined by the concentrations of amino-substituted and alkyl-substituted silanes, as well as the gelation conditions. Higher concentrations of amino-substituted and alkyl-substituted silanes result in a denser alcogel or sol-gel, and thus smaller pore sizes. At the same concentrations of amino-substituted and alkyl-substituted silanes, faster gelation at higher temperatures may involve accelerated chemical reactions and cluster aggregation, leading to relatively larger voids (or pores) in silica-based aerogels, while slower gelation at lower temperatures may result in smaller voids (or pores). On the other hand, the siloxane network structure formed during gelation may require further development and reinforcement to maintain network integrity during the drying process. This reinforcement and hardening effect can be achieved through an aging process, where many unreacted -OR and -OH groups can continue to condense and form Si-O-Si bonds.

[0173] The addition of silicates can form covalent bonds with the other four silicon atoms, thereby increasing the rigidity of the siloxane network structure. Amino-substituted and alkyl-substituted silanes can form only two or three covalent bonds in the siloxane network structure, thus allowing for flexibility.

[0174] Prior to steps (a1) and (b1), the wet gel matrix may be heated to a suitable temperature and maintained at that temperature (aging process). In some embodiments or examples, the wet gel matrix may be heated in a range between about 20°C and about 100°C. The temperature of the wet gel matrix may be at least about 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100°C. The temperature of the wet gel matrix may be less than about 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, or 20°C. Combinations of these heating temperatures are also possible, for example, between about 20°C and about 30°C, between about 25°C and about 80°C, or between about 75°C and about 85°C.

[0175] According to at least some of the embodiments or examples described herein, the wet gel matrix can be heated to the desired temperature by immersing the reaction vessel in an oven at the desired temperature, and the solution can be allowed to reach the desired temperature.

[0176] According to at least some embodiments or examples as described herein, the wet gel matrix can be maintained at the temperatures in steps (a1) and (b1) for about 3 hours to about 24 hours. The wet gel matrix can be maintained at the temperatures in steps (a1) and (b1) for at least about 3, 6, 9, 12, 15, 18, 21, or 24 hours. The wet gel matrix can be maintained at the temperatures in steps (a1) and (b1) for less than 24, 21, 18, 15, 12, 9, 6, or 3 hours. Combinations of these times are also possible, for example, between about 6 hours and about 12 hours.

[0177] In some embodiments or examples, for steps (a1) and (b1), the wet gel matrix can then be cooled to ambient temperature. In one embodiment or example, the wet gel matrix can be cooled to ambient temperature.

[0178] In one instance, after the formation of the wet gel, residual solvent and organic reaction products can be removed to prevent the wet gel matrix from plasticizing. This is achieved by disrupting the matrix and immersing it in at least 10 times the excess of water for at least one hour, which exchanges water. Water exchange protects the wet gel matrix from collapse and also allows any unreacted silanes to form Si-O-Si bonds. Insufficient water exchange can result in a gel that is dissimilar to a typical aerogel dried using conventional methods. When using freeze-drying methods or other reduced-pressure drying processes, solvent exchange (e.g., ethanol) becomes less important. The incorporation of amino-substituted silanes such as those of Formula 1 (e.g., 3-aminopropyl(diethoxy)methylsilane) means that the solvated matrix retains plastic properties, unlike conventional aerogels in which all silicon atoms are covalently bonded to at least three other oxygen atoms.

[0179] When solvents in the air are evaporated during the drying process of a wet gel matrix, the wet gel matrix may experience shrinkage and breakage due to differences in capillary forces and solvent extraction rates at the air / liquid interface during the drying process, and supercritical drying processes are typically used to suppress this. However, supercritical drying is carried out under high pressure and increases manufacturing costs, thus hindering the commercialization of aerogels. For example, US 9,931,612 B2 (Aspen) discloses a two-step process for forming mesoporous aerogels by first forming two different sols, then mixing the sols to form a gel, and then using supercritical CO2 drying. Supercritical CO2 drying is typically used to remove any solvent from the pores of mesoporous aerogels, where the gel is subjected to liquid CO2, followed by heating the CO2-filled gel under pressure until the liquid becomes a supercritical fluid. It should be understood that this is a major drawback of the Aspen process, as introducing CO2 into the pores instead of a solvent is not an environmentally friendly solution when the purpose of the aerogel is to capture CO2 from the air. Another key difference is that the two-step process results in the formation of mesoporous gels with much larger pore sizes. It has been found that the selective adsorption of CO2 by mesoporous gels is less efficient and more suitable for situations with higher CO2 concentrations, such as capturing CO2 in flue gas where the CO2 level is about 12-14%.

[0180] One or more advantages of the process of the present invention according to at least some embodiments or examples described herein are that a dry silica-based aerogel can be obtained by drying a wet gel matrix by minimizing the effects previously observed with other drying processes. The drying process described in this disclosure can be carried out in a variety of advantageous manners, including reduced pressure drying, ambient pressure or vacuum drying, freeze drying, or various combinations thereof. Vacuum drying or freeze drying is preferred.

[0181] For step (ii), the wet gel matrix can be dried at a temperature suitable for producing a dry silica-based aerogel. In one example, when using reduced pressure drying to dry the wet gel matrix, the drying equipment can be controlled at about 40°C to about 60°C or about 55°C, the initial drying pressure can be ambient atmospheric pressure, and a vacuum pump can be turned on to initiate vacuum drying (-80 kPa) for at least about 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, or 24 hours to produce a dry silica-based aerogel. In another example, when using a freeze-drying process to dry the wet gel matrix, the wet gel matrix is ​​held under typical freeze-drying conditions for at least about 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, or 24 hours to produce a dry silica-based aerogel. In yet another instance, when using ambient pressure or drying the wet gel matrix in an oven, the temperature can be controlled at about 40°C to about 60°C or about 50°C, and the wet gel matrix is ​​held under ambient pressure or in a vacuum for at least about 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours to produce a dried silica-based aerogel.

[0182] In some embodiments or examples, amino-substituted silanes may have Formula 1 as described herein. In some embodiments or examples, alkyl-substituted silanes may have Formula 2 as described herein. In some embodiments or examples, silicates may have Formula 3 as described herein.

[0183] In some embodiments or examples, the solvent may be water, a non-aqueous solvent, or a combination thereof. Various non-aqueous solvents, including alcohols containing between 1 and 6 carbon atoms, may be used in steps (i)(a) and (i)(b) of the process. In one embodiment or example, the solvent may be selected from methanol, ethanol, propanol, butanol, isobutanol, tert-butanol, pentanol, hexanol, and combinations thereof. In one embodiment or example, ethanol may be used as the solvent. For example, in this process, ethanol may be used in combination with water. Various ratios of water may also be involved to complete the sol-gel reaction. Water may also be a product of some of these reactions. The ratios and solvents can be adjusted to avoid precipitation or phase separation.

[0184] In some embodiments or examples, the process may further include step (iii) an activation step. The silica-based aerogel prepared by this process can be activated at a temperature in the range of about 80°C to about 160°C. The activation temperature can be at least about 80, 90, 100, 110, 120, 130, 140, 150, or 160°C. The activation temperature can be lower than about 160, 150, 140, 130, 120, 110, 100, 90, or 80°C. Combinations of these activation temperatures are possible; for example, the activation temperature can be between about 80°C and about 160°C, between about 90°C and about 150°C, or between about 100°C and about 140°C.

[0185] In some embodiments or examples, one or more additives may be selected from buffers, binders, optionally metal-organic frameworks (MOFs), and nanoparticles. The total amount of additives (when present) may be less than 50% of the aerogel formulation. MOFs, when present as additives, will be less than 10% of the aerogel formulation, preferably less than 5%. In some embodiments or examples, the silica-based aerogel prepared by this process may be multiple particles, powders, granules, beads, pellets, coatings, or sheets / layers. In some embodiments or examples, particles, powders, granules, beads, pellets, coatings, or sheets / layers may be compositions and further include optional additives selected from the group consisting of metal-organic frameworks, nanoparticles, magnetic nanoparticles, binders, buffers, or combinations thereof. In one embodiment, MOFs (when present) are used as surface modifiers after aerogel formation to modify the surface of the aerogel for the purpose of manufacturing beads or granules. In another embodiment or example, the silica-based aerogel prepared by this process may be provided as multiple granules. The granules may further include optional additives selected from the group consisting of metal-organic frameworks, nanoparticles, magnetic nanoparticles, binders, buffers, or combinations thereof. In one example, the granules may comprise or consist of a silica-based aerogel prepared by the process combined with a binder and optional lubricant. The binder may be selected from the group consisting of cellulose-based polymers, silane-based polymers, cellulose-siloxane-based polymers, polyethylene glycol-based polymers, epoxy-based polymers, colloidal silica, polyvinylpyrrolidone, polyvinyl alcohol, polyethyleneimine, or combinations thereof. The binder may be selected from commercial binders. It should be understood that other components may form part of a commercial binder. In one example, the binder may contain other components, such as a lubricant. Lubricants may be used as needed to adjust the viscosity of the aerogel formulation to, for example, an extrudable material. For example, other components may include dicalcium phosphate, silica, glucose monohydrate, and magnesium stearate.

[0186] In some embodiments or examples, the amount of additives, based on the total aerogel composition, can range from about 1% by weight to about 50% by weight. The amount of additives can be at least about 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50% by weight. The amount of silicate can be less than about 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, or 1% by weight. Combinations of these amounts are possible; for example, the amount of additives can be between about 10% by weight and about 50% by weight, between about 15% by weight and about 45% by weight, or between about 20% by weight and about 40% by weight. For example, based on the total aerogel composition, the amount of binder can be between about 10% by weight and about 50% by weight, between about 15% by weight and about 45% by weight, or between about 20% by weight and about 40% by weight.

[0187] In another embodiment or example, the silica-based aerogel may be in the form of a composite material, wherein the composite material can be prepared by pressing a mixture of dried silica-based aerogel, a binder, and optionally a lubricant into granules. In another embodiment or example, the aerogel composite material may include or consist of: (i) an aerogel or combination thereof according to any of the embodiments or examples described herein, the aerogel comprising a reaction product of amino-substituted silanes, alkyl-substituted silanes, and silicates; (ii) one or more additives, wherein the additives have a loading of about 5% to about 35% by weight; (iii) optionally a lubricant; and (iii) optionally a solvent. In yet another embodiment or example, the aerogel composite material may include or consist of: (i) an aerogel or combination thereof according to any of the embodiments or examples described herein, the aerogel comprising a reaction product of amino-substituted silanes, alkyl-substituted silanes, and silicates; (ii) one or more additives, wherein the additives have a loading of about 5% to about 35% by weight; and (iii) optionally a lubricant.

[0188] In some embodiments, the composite material can be prepared by (c1) pressing a mixture of an aerogel, optionally a lubricant, and one or more additives described in any or more of the embodiments or examples described herein into granules, wherein the one or more additives have a loading percentage of about 5% to about 35% by weight; or (c2) liquid extrusion of a mixture of an aerogel, one or more additives, optionally a lubricant, and a solvent described in any or more of the embodiments or examples described herein to provide a viscous paste, wherein the one or more additives have a loading percentage of about 5% to about 35% by weight. One or more additives may be selected from binders, optionally metal-organic frameworks (MOFs), and nanoparticles. In certain embodiments, one or more additives may be binders. Binders may be selected from the group consisting of cellulose-based polymers, silane-based polymers, cellulose-siloxane-based polymers, polyethylene glycol-based polymers, polyvinylpyrrolidone, polyvinyl alcohol, polyethyleneimine, bentonite, graphite, or combinations thereof. It should be understood that when any combination of two or more aerogels described in any one or more of the embodiments or examples described herein is used in the process of preparing a composite material, the composite material may be referred to as a hybrid aerogel composite material.

[0189] In another example, the silica-based aerogel can be in the form of a composite material, wherein the composite material can be prepared by liquid extrusion of a mixture consisting of a dried silica-based aerogel, an adhesive, and optionally a lubricant, to provide a viscous paste. In yet another example, the silica-based aerogel can be in the form of a composite material, wherein the composite material can be prepared by liquid extrusion of a mixture consisting of a dried silica-based aerogel, an adhesive, optionally a lubricant, and a solvent, to provide a viscous paste that can be used as a coating, for example, on a substrate.

[0190] In some embodiments or examples, one or more additives may be selected from binders, optionally metal-organic frameworks (MOFs), surfactants, and nanoparticles. The additives (when present) may be less than 35% of the aerogel formulation, preferably less than 10%. In some embodiments or examples, the silica-based aerogel prepared by this process may be a plurality of particles, powders, granules, beads, pellets, coatings, or sheets / layers. In some embodiments or examples, the particles, powders, granules, beads, pellets, coatings, or sheets / layers may be compositions and further include optional additives selected from the group consisting of metal-organic frameworks, nanoparticles, magnetic nanoparticles, binders, or combinations thereof. In one embodiment, the MOF (when present) is used as a surface modifier after aerogel formation to modify the surface of the aerogel for the purpose of manufacturing beads or granules.

[0191] In some embodiments, composite granules can be prepared by mixing a dried aerogel as described herein with about 5% to about 35% by weight of an additive (e.g., a binder) and optionally a lubricant. In another embodiment, a composite paste can be prepared by mixing a dried aerogel as described herein with about 5% to about 35% by weight of an additive (e.g., a binder), optionally a lubricant, and a solvent (e.g., an aqueous solution of ethanol and water). The resulting viscous paste can be used to form composite granules by liquid extrusion or, if necessary, further diluted for use as a coating on a substrate.

[0192] The loading percentage of the additive (e.g., adhesive) can be at least about 5, 10, 15, 20, 25, 30, or 35% by weight. In other embodiments or examples, the loading percentage of the additive (e.g., adhesive) can be less than about 35, 30, 25, 20, 15, 10, or 5% by weight. Combinations of these values ​​to form various ranges are also possible, for example, the loading percentage of the additive (e.g., adhesive) can be about 5% by weight to about 30% by weight, about 8% by weight to about 25% by weight, or, for example, about 10% by weight to about 20% by weight.

[0193] In one embodiment or example, the silica-based aerogel prepared by this process can be self-supporting. As described above, the term "self-supporting" as used herein refers to the ability of a silica-based aerogel to maintain its shape without a supporting material (e.g., a scaffold). For example, a silica-based aerogel prepared by this process may comprise multiple particles, wherein the particles maintain their shape without scaffold support. The self-supporting nature of silica-based aerogels can provide certain advantages, such as allowing the aerogel particles to be contacted with an airflow using a fluidized bed reactor. Therefore, in one embodiment or example, the silica-based aerogel does not include a separate support structure, such as a separate porous support structure. Thus, it should be understood that when a silica-based aerogel is "self-supporting," there is no external supporting material (e.g., a scaffold) for the aerogel.

[0194] In other embodiments or examples, the silica-based aerogel prepared by this process can be provided as a layer within a column, wherein a gas flow passes through the column and through the silica-based aerogel layer. This layer is not limited to any particular silica-based aerogel morphology. In one example, a suitable column can be filled with multiple silica-based aerogel particles to form a packed bed with sufficient gaps between adjacent particles to allow gas flow. Alternatively, the silica-based aerogel can be provided flowing with the gas flow (e.g., in a fluidized bed reactor).

[0195] In another embodiment or example, the silica-based aerogel prepared by this process can be provided as a coating composition on a substrate. In some embodiments or examples, the substrate can be planar, such as a planar sheet. In certain examples, the substrate can be a flexible sheet. The planar substrate provides a double-sided element on which the silica-based aerogel coating composition can be applied. Each substrate can be coated with the silica-based aerogel coating composition on two opposite sides. The planar substrate can have any configuration. In some embodiments or examples, the planar substrate can include a flat solid surface. In other embodiments or examples, the planar substrate can include one or more pores designed to facilitate gas flow through and around the substrate. In certain embodiments or examples, the substrate can include a mesh, such as a microfilament mesh. The use of a mesh provides a large number of pores (e.g., micro-sized pores), thereby providing a high surface area on which the silica-based aerogel coating composition can be coated, while also providing a suitable flow path with a relatively low pressure drop across the substrate compared to other configurations such as a packed bed (relative to the size and configuration of the mesh, of course).

[0196] In some embodiments or examples, the amount of amino-substituted silanes, based on the total aerogel, can range from about 10% by weight to about 80% by weight. The amount of amino-substituted silanes can be at least about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80% by weight. The amount of amino-substituted silanes can be less than about 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, or 10% by weight. Combinations of these amounts are possible; for example, the amount of amino-substituted silanes can be between about 10% by weight and about 60% by weight, between about 20% by weight and about 50% by weight, between about 35% by weight and about 45% by weight, or between about 40% by weight and about 60% by weight.

[0197] In some embodiments or examples, the amount of alkyl-substituted silanes, based on the total aerogel, can range from about 10% by weight to about 80% by weight. The amount of alkyl-substituted silanes can be at least about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80% by weight. The amount of alkyl-substituted silanes can be less than about 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, or 10% by weight. Combinations of these amounts are possible; for example, the amount of alkyl-substituted silanes can be between about 10% by weight and about 60% by weight, between about 15% by weight and about 65% by weight, or between about 20% by weight and about 40% by weight.

[0198] In some embodiments or examples, the amount of silicate, based on the total aerogel, can range from about 10% by weight to about 50% by weight. The amount of silicate can be at least about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80% by weight. The amount of silicate can be less than about 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, or 10% by weight. Combinations of these amounts are possible; for example, the amount of silicate can be between about 10% by weight and about 50% by weight, between about 15% by weight and about 45% by weight, or between about 20% by weight and about 40% by weight.

[0199] airflow with low CO2 concentration

[0200] The process disclosed herein can capture CO2 from a gas stream with a CO2 concentration. For example, the process can capture CO2 from the atmosphere with a low CO2 concentration. Examples of low-concentration gas streams include the atmosphere (e.g., ambient air), ventilation air (e.g., air conditioning units and building ventilation), greenhouse environments (where CO2 is adsorbed at a specific time and used at different times), and partially closed systems that recirculate breathing air (e.g., submarines, spacecraft, aircraft, or ventilators).

[0201] As described herein, microporous aerogels are best suited for adsorbing CO2 from air containing low levels of CO2. Preferably, microporous aerogels can be used for direct CO2 capture applications. Microporous aerogels are suitable for adsorbing less than 10,000 ppm (10% CO2), preferably less than 7,000 ppm (7% CO2), more preferably less than 5,000 ppm (5% CO2), and even more preferably less than 500 ppm (0.5% CO2) of CO2 from air. Microporous aerogels are also suitable for adsorbing CO2 from air containing less than 50 ppm (0.05% CO2). For example, microporous aerogels are suitable for directly capturing CO2 from an atmosphere having about 0.04% CO2, or where CO2 levels are between about 360 ppm and about 412 ppm. Microporous aerogels can also be used to adsorb CO2 and purify air in enclosed environments with CO2 levels below about 2.5% or in enclosed environments with higher CO2 levels of up to about 7% or lower.

[0202] Preferably, the selectivity for CO2 from a gas stream including water is greater than 50%. For example, microporous aerogels can be used to adsorb CO2 from air containing less than 500 ppm CO2 and at least 1000 ppm H2O, wherein the selectivity for CO2 is 50% higher than that for H2O.

[0203] In some embodiments or examples, the low CO2 concentration gas stream may have a CO2 concentration of less than about 200,000 parts per million (ppm). In one embodiment or example, the low CO2 concentration gas stream may have a CO2 concentration of less than 150,000, 100,000, 75,000, 50,000, 25,000, 20,000, 10,000, 7,000, 5,000, 4,000, 1,000, 900, 800, 700, 600, 500, 400, 300, 200, or 100 ppm. In another embodiment or example, the low CO2 concentration airflow may have a CO2 concentration of about 100 ppm to about 100,000 ppm, about 400 ppm to about 20,000 ppm, about 3,000 ppm to about 150,000 ppm, about 4,000 ppm to about 5,000 ppm, about 100 ppm to about 10,000 ppm, about 100 ppm to about 1,000 ppm, or about 100 ppm to about 500 ppm. In one embodiment, the low CO2 concentration airflow may have a CO2 concentration of about 200 ppm to about 500 ppm, or about 400 ppm to about 500 ppm, or about 400 ppm to about 450 ppm.

[0204] It should be understood that 1 ppm is equivalent to 0.0001 vol%. For example, an airflow with a CO2 concentration of less than about 100,000 ppm is equivalent to 10.0 vol% CO2 in the airflow. Therefore, in some embodiments or examples, the airflow with low CO2 concentration may have a CO2 concentration of less than about 20, 15, 10, 7.5, 5, 2.5, 1, 0.5, 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01 vol%. In another embodiment or example, the airflow with low CO2 concentration may have a CO2 concentration of about 0.01 vol% to about 15 vol%, about 3 vol% to about 15 vol%, about 4 vol% to about 5 vol%, 0.1 vol% to about 2 vol%, about 0.01 vol% to about 1 vol%, about 0.01 vol% to about 0.1 vol%, or 0.01 vol% to about 0.05 vol%. In one embodiment or example, the low CO2 concentration gas stream may have a CO2 concentration of about 0.02 vol% to about 0.05 vol% (e.g., about 0.04 vol%).

[0205] In one embodiment or example, the low CO2 concentration airflow can have the same CO2 concentration as ambient air (e.g., the atmosphere). Therefore, in one embodiment, the low CO2 concentration airflow can have a CO2 concentration of about 400 ppm to about 450 ppm CO2, for example, about 400 ppm to 415 ppm, as is the case in ambient air in most parts of the world. Therefore, in one embodiment, the process is used for direct air capture (DAC).

[0206] In one embodiment or example, this process is used for direct air capture in a sealed indoor environment (DACi). Therefore, the CO2 concentration in the airflow can be as high as 2,000 ppm.

[0207] In one embodiment or example, the process is used to directly capture exhaled gases in a face mask or personal protective equipment (DACp). Therefore, the CO2 concentration of the airflow can be from about 4,000 ppm to about 5,000 ppm.

[0208] In one embodiment or example, the process is used for direct air capture (DACex) in an external power plant. Therefore, the CO2 concentration in the gas stream can be from about 3,000 ppm to about 150,000 ppm.

[0209] In one embodiment or example, the gas stream may include less than 100 ppm (i.e., 0.01 vol%) of hydrocarbon gas. For example, the gas stream may include less than about 100, 75, 50, 25, 20, 15, 10, 5, 4, 3, or 2 ppm of hydrocarbon gas. The term "hydrocarbon gas" will be understood to refer to a gaseous mixture of hydrocarbon compounds, including but not limited to methane, ethane, ethylene, propane, and other C3+ hydrocarbons. For example, those skilled in the art will understand that ambient air includes methane as a minor impurity (e.g., 2 ppm / 0.0002 vol%), and therefore ambient air may include less than 3 ppm of hydrocarbon gas. The low CO2 concentration gas stream may consist primarily of nitrogen, which constitutes the majority vol% of the gas stream. For example, the low CO2 concentration gas stream may include at least about 50 vol% nitrogen, such as at least about 70 vol% nitrogen. In one embodiment, the low CO2 concentration gas stream includes about 78 vol% nitrogen (e.g., ambient air).

[0210] A low CO2 concentration gas stream may include a certain amount of water (e.g., the gas stream is humid / wet, such as a moist gas stream). For example, a low CO2 concentration gas stream may include about 1% to about 10% by volume of water. Alternatively, a low CO2 concentration gas stream may be a dry gas stream.

[0211] In an alternative embodiment, the process can capture CO2 from a high-CO2-concentration gas stream or atmosphere. For example, the high-CO2-concentration gas stream or atmosphere may have a CO2 concentration of 925 mbar (100 vol%).

[0212] In some embodiments or instances, the airflow originates from a ventilation system, such as building ventilation or air conditioning. In other embodiments or instances, the airflow originates from a closed system, or at least a partially closed system, designed to recirculate breathing gases, such as in submarines, spacecraft, or aircraft. It should be understood that the silica-based aerogels of this disclosure can also adsorb CO2 from airflows with high CO2 concentrations, highlighting the versatility of silica-based aerogels in a wide range of air capture applications. In one instance, the inventors have found that the effectiveness of silica-based aerogels in capturing high concentrations of CO2 at 100 vol% CO2 concentrations (e.g., 925 mbar) is surprising. In another instance, the inventors of the present invention have also found that the effectiveness of silica-based aerogels in capturing CO2 at concentrations equivalent to 15 vol% CO2 concentrations (e.g., 150 mbar) in flue gas conditions (e.g., external power plants) is surprising. In another instance, the inventors also found that the effectiveness of silica-based aerogels in capturing CO2 in enclosed indoor environments with CO2 concentrations up to 2% by volume (e.g., 2,000 ppm) is surprising. It should be understood that CO2 concentrations of less than 2% by volume in enclosed indoor environments can include, for example, rooms, submarines, spacecraft, aircraft, or any other enclosed environment. In yet another instance, the inventors also found that the effectiveness of silica-based aerogels in capturing CO2 from exhaled gases from face masks / personal protective equipment is surprising at CO2 concentrations of about 4 to 5% by volume (e.g., about 4,000 ppm to about 5,000 ppm). For example, the inventors found the effectiveness of silica-based aerogels in capturing CO2 at relatively low concentrations of 0.04% by volume (e.g., 400 ppm) to be particularly surprising. It should be understood that CO2 concentrations of 0.04% by volume or less than 500 ppm refer to direct air capture from the atmosphere (DAC).

[0213] An airflow or atmosphere with low CO2 concentration comes into contact with the silica-based aerogel. The airflow can have a suitable velocity to contact (e.g., pass through) the silica-based aerogel. Alternatively, the airflow can contact the silica-based aerogel without applying any back pressure or velocity (e.g., the airflow can organically diffuse into the silica-based aerogel upon contact). In some embodiments or instances, the airflow can be the atmosphere surrounding the silica-based aerogel, such as an atmosphere with low CO2 concentration, for example, when the silica-based aerogel is configured as a greenhouse. In some embodiments, the airflow passes through the silica-based aerogel (e.g., enters from a first side or face of the silica-based aerogel and exits from a different side or face), or it can simply diffuse into the silica-based aerogel, for example, when the silica-based aerogel is placed in the atmosphere (e.g., ambient air). Therefore, it should be understood that in some embodiments, it is not necessary to apply back pressure to the airflow to substantially force the airflow "through" the silica-based aerogel, although this may be desirable in some embodiments, such as when the silica-based aerogel is configured, for example, as a building ventilation system. In one embodiment, the airflow (e.g., the atmosphere) diffuses into the silica-based aerogel upon contact with it.

[0214] In some embodiments or instances, the airflow has no velocity, for example, 0 m / s. 3 / hour. In some embodiments or instances, the airflow has a range of approximately 0.01m. 3 / hour to approximately 1500m 3 The airflow velocity is between [value missing] and [value missing] per hour. 3 The airflow velocity (m³ / h) can be at least approximately 0.01, 0.05, 0.1, 0.5, 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or 1500. 3 The velocity (per hour) can be less than approximately 1500, 1000, 900, 800, 700, 600, 500, 400, 300, 200, 100, 90, 80, 70, 60, 50, 40, 30, 20, 10, 5, 1, 0.5, 0.1, 0.05, or 0.01. Combinations of these velocities are possible; for example, the airflow velocity could be approximately 0.01 m / s. 3 / hour to approximately 1500m 3 / hour, approximately 5m 3 / hour to approximately 1000m 3 / hour, approximately 10m 3 / hour to approximately 500m 3 / hour, approximately 20m 3 / hour to approximately 200m3 / hour, or approximately 60m 3 / hour to approximately 1000m 3 / hour. In some embodiments or examples, increasing the airflow velocity when the airflow contacts the silica-based aerogel can lead to a faster CO2 adsorption and capture rate in the silica-based aerogel. For industrial-scale applications, airflow velocities can reach up to 1000 m / s. 3 / hour. In some embodiments or instances, the airflow has no velocity (e.g., ambient atmosphere).

[0215] Before contact with the silica-based aerogel, the airflow with a low CO2 concentration can be at least partially dried to remove at least some of the moisture (H2O) present in the airflow. For example, the airflow can be dried to a humidity of less than 10%, 8%, 6%, 4%, 2%, or 1%, or to a humidity between any two of these values, such as about 1% to about 10%, about 1% to about 6%, or about 1% to about 4%. The airflow can be dried by any conventional means (e.g., through a hygroscopic material or in contact with a heat source), and its humidity can be measured via a method as described herein.

[0216] In some embodiments or examples, the low CO2 concentration airflow has an initial CO2 concentration before contacting the silica-based aerogel and a final CO2 concentration after contacting the silica-based aerogel (also referred to herein as the effluent airflow and / or effluent CO2 concentration). It should be understood that as CO2 is adsorbed from the airflow into the silica-based aerogel, the CO2 concentration in the effluent airflow will be lower than the initial CO2 concentration of the airflow before contacting (e.g., passing through) the silica-based aerogel.

[0217] The concentration of CO2 in the gas stream can be measured by any suitable means, such as gas chromatography-mass spectrometry, isotope analysis (e.g., using a G2201-i isotope analyzer (PICARRO), and / or infrared spectroscopy (e.g., an online-calibrated cavity ring-down IR spectrometer). The concentration of CO2 in the gas stream can be monitored by any suitable means, such as those covering a range of 0-100%. -6S and K30 environmental sensor with a range of 0-1% CO2.

[0218] Adsorption equipment

[0219] In some embodiments or examples, an adsorption device for capturing carbon dioxide from an airflow or atmosphere is provided, comprising: a chamber enclosing at least one silica-based aerogel as described herein, the chamber including an inlet and an outlet through which an airflow can flow to the silica-based aerogel and through which an outflowing airflow can exit from the silica-based aerogel. At least one silica-based aerogel may be located between the inlet and outlet of the chamber.

[0220] Fluid flow is typically required to move the airflow from the inlet of the chamber, through at least one enclosed silica-based aerogel, and out of the chamber through the outlet. The fluid flow can be driven by at least one fluid flow device that directs the fluid from the inlet to the outlet of the adsorption device. Various different fluid flow devices can be used. In some embodiments or examples, the fluid flow device includes at least one fan or pump. In some embodiments or examples, the flow velocity of the airflow entering through the inlet and passing through at least one silica-based aerogel can be approximately 0.01 m³ / s. 3 / hour and 1500m 3 Between / hour. Airflow velocity (m 3 The airflow velocity (m³ / h) can be at least approximately 0.01, 0.05, 0.1, 0.5, 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or 1500. 3 The velocity (per hour) can be less than approximately 1500, 1000, 900, 800, 700, 600, 500, 400, 300, 200, 100, 90, 80, 70, 60, 50, 40, 30, 20, 10, 5, 1, 0.5, 0.1, 0.05, or 0.01. Combinations of these velocities are possible; for example, the airflow velocity can be as low as approximately 0.01 m / s. 3 / hour to approximately 1500m 3 Between / hour, at approximately 5m 3 / hour to approximately 500m 3 Between / hour, within approximately 10m 3 / hour to approximately 200m 3 Between / hour, at approximately 20m 3 / hour to approximately 600m 3 Between / hour, or around 60m 3 / hour to approximately 1000m 3Between [amount] m / s. Flow rates through the chamber and through at least one silane-based aerogel can be achieved with virtually no measurable back pressure passing through or across the silica-based aerogel. In an alternative embodiment or example, pressure variation or suction can be used to drive the fluid flow of the airflow through the device. For industrial-scale applications, airflow velocities can reach up to 1000 m / s. 3 / Hour.

[0221] The chamber can have any suitable construction. In some embodiments or examples, the chamber includes an entrance at one end and an exit at the opposite end. In one embodiment or example, as described herein, the substrate can be positioned compactly or otherwise filled within the chamber to increase the surface area within the volume.

[0222] As described herein, the device may include one or more chambers enclosed by a silica-based aerogel. In some embodiments or examples, the device may include two or more chambers enclosed by at least one silica-based aerogel, the chambers being connected in parallel with a gas flow. In another embodiment or example, the device may include at least three chambers, each enclosed by at least one silica-based aerogel, wherein each chamber may be connected in parallel with a gas flow. In some embodiments or examples, the silica-based aerogel enclosed in at least three chambers may operate in different sections of an adsorption and regeneration cycle to produce a continuous flow of outflow gas.

[0223] In some embodiments or examples, the process may be a cyclic method, wherein an effluent gas stream is continuously generated by a step of adsorbing CO2 in a chamber-enclosed silica-based aerogel and a step of releasing CO2 by operating at least one desorption device in repeated cycles. The cycle time may depend on the configuration of the adsorption device, the configuration of the chamber, the type of desorption device, the composition of the silica-based aerogel, the specific breakthrough point, saturation point and characteristics of the silica-based aerogel, temperature, pressure, and other process conditions. In some embodiments or examples, the cycle time may be about 10 minutes, 15 minutes, 20 minutes, 30 minutes, 45 minutes, 60 minutes (1 hour), 2 hours, 5 hours, 10 hours, 24 hours, 48 ​​hours, or 36 hours.

[0224] In some embodiments or examples, the desorption apparatus can take any number of forms, depending on whether heating and / or depressurization are used. In some embodiments or examples, the device is designed for pressure swing adsorption, where desorption is achieved by reducing pressure, for example, by using a vacuum pump to evacuate air from the chamber enclosed by the silica-based aerogel. In other embodiments or examples, temperature swing adsorption is performed to collect CO2 from the silica-based aerogel. This can be achieved using direct heating methods, or in some cases using magnetically inductive oscillating adsorption.

[0225] In some embodiments or examples, the desorption device may include a temperature-switching adsorption device in which the silica-based aerogel is heated. For example, operating at least one desorption device heats the silica-based aerogel to a temperature of about 60°C to 140°C. The temperature used for desorption can be at least about 60, 70, 80, 90, 100, 110, 120, 130, or 140°C. The temperature used for desorption can be lower than about 140, 130, 120, 110, 100, 90, 80, 70, or 60°C. Combinations of these temperatures are possible; for example, the temperature used for desorption can be between about 60°C and about 140°C, between about 70°C and about 130°C, or between about 80°C and about 120°C.

[0226] This disclosure provides a process in which an airflow containing a certain concentration of CO2 is fed into adsorption contact with a silica-based aerogel as described herein. After the silica-based aerogel is charged with a certain amount of CO2, a desorption device is activated, forcing at least a portion of the CO2 to be released from the silica-based aerogel. The desorbed silica-based aerogel can be collected using a secondary process.

[0227] In other words, the outflow gas from the outlet can be directed to various secondary processes. For example, for carbon dioxide capture, the adsorption device of this disclosure can be integrated with a liquefier and / or a dry ice granulator to provide dry ice on demand. In another example, the adsorption device of this disclosure can be integrated with a hydrogenation device to convert carbon dioxide (CO2) into methane. In yet another example, the adsorption device of this disclosure can be used to adsorb carbon dioxide (CO2) and store it for use at different times. This would be suitable for greenhouse-type environments where CO2 is adsorbed at specific times and used at different times. In yet another example, the adsorption device of this disclosure can be particularly suitable for CO2 in confined spaces. For example, in submarines, spacecraft, aircraft, or other enclosed spaces (such as rooms where the adsorption device will be used to remove CO2), and the device is capable of adsorbing and desorbing CO2 in a continuous cycle. In another example, the adsorption device of this disclosure can be used to convert CO2 into liquid fuel. In yet another example, the adsorption device of this disclosure can be included in a swimming pool to adjust the pH or injected into concrete (capture and storage). In yet another example, the adsorption device of this disclosure can be used to carbonate beverages such as carbonated drinks and soda water, and finds applications in the brewing and / or bottling industries. In yet another example, the adsorption device of this disclosure can be used to control the ripening of fruits and vegetables.

[0228] It should be understood that the density of the aerogel can be used to select a silica-based aerogel formulation for any given application. High-density silica-based aerogel formulations are suitable for any device, preferably smaller ones. For example, high-density aerogel formulations can be used to prepare CO2 adsorption-desorption devices suitable for confined spaces or environments. These types of devices are typically used in space, aerospace, underwater vehicles, or platforms. When space is not an issue, low-density aerogel formulations may be more suitable. For example, DAC units placed in greenhouses or power plants involve converting CO2 into methane.

[0229] The adsorption device disclosed herein is advantageously compact and can be positioned closer to the end user, thereby allowing for disruptive supply opportunities and better customer value.

[0230] CO2 capture / release and regeneration process based on silica aerogel

[0231] CO2 can be captured from a gas stream by being adsorbed into a silica-based aerogel. In some embodiments or examples, the silica-based aerogel is capable of adsorbing from about 10 mg CO2 / g silica-based aerogel (mg / g) to about 300 mg / g CO2. In some embodiments or examples, the silica-based aerogel is capable of adsorbing at least about 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 150, 200, 250, or 300 mg / g CO2. In other embodiments or examples, the silica-based aerogel is capable of adsorbing less than about 300, 250, 200, 150, 120, 100, 90, 80, 70, 60, 50, 40, 30, 20, or 10 mg / g CO2. Combinations of these adsorption values ​​are possible; for example, silica-based aerogels can adsorb CO2 from about 10 mg / g to about 80 mg / g, from about 20 mg / g to about 70 mg / g, or from about 100 mg / g to about 300 mg / g, or from about 200 mg / g to about 300 mg / g. For instance, silica-based aerogels can adsorb CO2 from about 2 mg / g at 0.02 mbar to about 100 mg / g at 1110 mbar (at 298 K).

[0232] In some embodiments, at least about 50% of CO2 can be removed from the gas stream (e.g., at least about 50% of the CO2 is adsorbed into a silica-based aerogel from the gas stream). In some embodiments or examples, at least about 50%, 85%, 90%, 95%, 99%, or 99.9% of CO2 is removed from the gas stream. In some embodiments, about 50% to about 99% of CO2 is removed from the gas stream.

[0233] An airflow contacts a silica-based aerogel (e.g., through a bed comprising a silica-based aerogel), generating an outflow airflow upon contact with the silica-based aerogel. As described above, the airflow has an initial CO2 concentration before contact with the silica-based aerogel. After contact with the silica-based aerogel, the outflow airflow has an outflow CO2 concentration. The concentration of CO2 in the outflow airflow after contact with the silica-based aerogel can be measured to determine the concentration of residual CO2 in the airflow.

[0234] In some embodiments or instances, the concentration of CO2 in the effluent gas stream may increase over time after contact with the silica-based aerogel, indicating that CO2 adsorption decreased or ceased during contact with the silica-based aerogel (e.g., indicating that the silica-based aerogel is "depleted" and CO2 adsorption is little or no longer occurring). This can serve as an indicator of replacing and / or regenerating the silica-based aerogel to continue CO2 capture. The concentration of CO2 in the effluent gas stream can be measured by any suitable means, such as using an online-calibrated cavity ring-down IR spectrometer.

[0235] In some embodiments or examples, the silica-based aerogel can be enclosed in a suitable chamber, wherein the chamber includes one or more inlets and one or more outlets through which airflow can flow to contact the silica-based aerogel enclosed therein, and through which outflow airflow can exit from the chamber through the outlets. Alternatively, the silica-based aerogel can be enclosed in a suitable chamber including one or more openings through which airflow can diffuse (e.g., without back pressure / flow rate) to contact the silica-based aerogel enclosed therein. It should be understood that the chamber can take many forms, as long as airflow can access the silica-based aerogel. In one embodiment or example, the chamber can be a packed bed column as described herein.

[0236] In some embodiments, the silica-based aerogel can be provided as a bed, wherein contacting the gas flow with the silica-based aerogel includes passing the gas flow through the bed comprising the silica-based aerogel. In one embodiment or example, the silica-based aerogel is provided as a packed bed reactor. In other embodiments, contacting the gas flow with the silica-based aerogel includes introducing a flow of silica-based aerogel into the gas flow, for example, using a fluidized bed reactor.

[0237] Silica-based aerogels can be in contact with the gas flow for any suitable period of time, such as until the silica-based aerogel is depleted and CO2 adsorption ceases. In one embodiment or example, the silica-based aerogel is in contact with the gas flow until the concentration of CO2 in the outflowing gas flow is the same as the initial concentration of CO2 in the gas flow. In some embodiments or examples, the silica-based aerogel is in contact with the gas flow for at least about 5 seconds, 10 seconds, 30 seconds, 60 seconds (1 minute), 10 minutes, 15 minutes, 20 minutes, 30 minutes, 45 minutes, 60 minutes (1 hour), 2 hours, 5 hours, 10 hours, 24 hours, 48 ​​hours, or 36 hours.

[0238] In some embodiments or examples, the silica-based aerogel provides different rates of CO2 adsorption. In one embodiment or example, the rate of CO2 adsorption can be measured by monitoring the CO2 concentration in the outflow gas stream over time. For example, after approximately 2 hours of contact with the silica-based aerogel, the CO2 concentration in the outflow gas stream can be less than approximately 50% of the initial CO2 concentration. In some embodiments or examples, after approximately 4 hours of contact with the silica-based aerogel, the CO2 concentration in the outflow gas stream can be less than approximately 5% of the initial CO2 concentration (in other words, after 4 hours, at least approximately 95% of the CO2 is removed from the gas stream). Other rates of CO2 adsorption are also possible.

[0239] In some embodiments or examples, the stability of the silica-based aerogel can be measured by monitoring the performance of the original composition over time. For example, after three capture-regeneration cycles, at high humidity and a CO2 concentration of 740 ppm, the silica-based aerogel is able to retain at least 80% of its original composition. In another example, after three capture-regeneration cycles, at low humidity and a low CO2 concentration of 400 ppm, the silica-based aerogel is able to retain at least 99% of its original composition. In yet another example, after three capture-regeneration cycles, at low humidity and a high CO2 concentration of 925 mbar, the silica-based aerogel is able to retain at least 99% of its original composition. In some embodiments or examples, at low CO2 concentrations, at low humidity, or at high humidity, the silica-based aerogel is able to retain at least 80%, 85%, 90%, 95%, 97%, or 99% of its original composition. Silica-based aerogels can be stably maintained for at least approximately 2, 3, 5, 10, 15, 20, 50, 100, 150, 200, 250, 500, 1000, or 2000 capture-regeneration cycles. Silica-based aerogels can be stably maintained for more than 50 capture-regeneration cycles.

[0240] The inventors unexpectedly demonstrated that, at a CO2 concentration of approximately 400 ppm, the CO2 selectivity of the silica-based aerogel prepared herein is higher than that of zeolites (e.g., zeolite 13X) and MOFs (e.g., TIF-SIX as described in WO2020113281). At a CO2 concentration of approximately 400 ppm, the CO2 selectivity of the silica-based aerogel is at least 2 times higher than that of zeolite 13X and TIF-SIX. At a CO2 concentration of approximately 400 ppm, the CO2 selectivity of the silica-based aerogel is at least 3 times higher than that of zeolite 13X and TIF-SIX. At a CO2 concentration of approximately 400 ppm, the CO2 selectivity of the silica-based aerogel is at least 4 times higher than that of zeolite 13X and TIF-SIX.

[0241] CO2 adsorbed in a silica-based aerogel can be released by breaking the bonds between CO2 and amine groups. This can be achieved using temperature (by heating) or pressure (by vacuum). This may involve heating the column containing the silica-based aerogel or passing it through a hot gas stream (e.g., steam) or hot air. This desorption can be provided by any suitable environment capable of providing heating (e.g., temperature) or pressurization (e.g., by vacuum) or a combination thereof, which contacts or surrounds the silica-based aerogel, allowing it to desorb at least some of the CO2 adsorbed within the silica-based aerogel. This desorption environment can be operated in an “on” or “off” state. For example, once the CO2 concentration in the effluent gas stream after contact with the silica-based aerogel has increased to a level indicating reduced or no longer occurring CO2 adsorption, the desorption environment can be “turned on” to desorb CO2 from the silica-based aerogel.

[0242] The adsorption process disclosed herein can be carried out at ambient temperatures, for example, in the range of about 10°C to 40°C. For example, the ambient temperature can be between 15°C and 30°C, or between 20°C and 25°C. The process can typically be carried out at approximately atmospheric pressure (e.g., about 20 kPa to 100 kPa) or at low pressure (e.g., about 0.01 kPa to 0.05 kPa).

[0243] The desorption process disclosed herein can be carried out in a temperature range, for example, from about 80°C to 180°C. For example, the temperature can be from 90°C to 160°C, or from 100°C to 140°C.

[0244] The process using silica-based aerogels as described herein is also applicable to environments with low or high humidity. In this case, low humidity means a water vapor partial pressure less than about 5 mB. At about 21°C, this corresponds to a relative humidity of about 20% or lower. In this case, high humidity means a water vapor partial pressure greater than about 5 mB. At about 21°C, this corresponds to a relative humidity greater than about 20%. Relative humidity is defined as follows.

[0245]

[0246] The saturated vapor pressure of water is well known and varies with temperature (Donald Ahrens, 1994, *Meteorology Today—An Introduction to Weather, Climate and the Environment*, 5th Edition, West Publishing Co.). Therefore, for a given relative humidity, the water vapor pressure will vary with temperature. An explanation of this is provided below (http: / / ww2010.atmos.uiuc.edu / %28Gh%29 / guides / mtr / cld / dvlp / rh.rxml, available for download December 2014).

[0247]

[0248] While this process is effective in low-humidity environments, it is also effective at higher humidity levels where other processes may be ineffective. In other words, one of the advantages of this process and silica-based aerogels is that they can be used in a relatively wide range of applications (e.g., a wide combination of parameters of temperature, pressure, and humidity), and particularly in a wide humidity range, although another particular advantage is their use at even higher humidity levels.

[0249] The process can be carried out, for example, at relative humidity levels less than about 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 18%, 16%, 14%, 12%, 10%, 8%, 6%, 4%, or 2%. The process can also be carried out at relative humidity levels greater than about 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 30%, 40%, 50%, 60%, or 70%. The process can also be carried out at relative humidity levels between any two of these values, for example, between about 1% and about 90%, between about 2% and about 50%, between about 70% and about 80%, between about 1% and about 30%, or between about 2% and about 5%. It should be understood that for a given partial pressure of water vapor, relative humidity depends on temperature. Water vapor partial pressure and temperature are independent variables, and relative humidity (RH) is the dependent variable, but there is a limitation that the relative humidity cannot exceed 100% at any given temperature. For example, any one or more of the above-mentioned relative humidity values ​​can be provided when the temperature is between approximately 10°C and 45°C, between approximately 15°C and 40°C, or between approximately 20°C and 35°C. The above-mentioned relative humidity values ​​can be, for example, values ​​where the temperature is approximately 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C, or 45°C. The application window for the currently disclosed process can be any combination of the above-mentioned RH and temperature ranges or values. For example, the application window could be where the RH is between about 1% and about 80%, and the temperature is between about 15°C and about 40°C.

[0250] Humidity can be provided by a water vapor partial pressure (in MB) less than about 60, 50, 40, 30, 20, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, or 2. Humidity can be provided by a water vapor partial pressure (in MB) greater than about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 30, 40, 50, or 60. Humidity can be provided by a water vapor partial pressure (in MB) between any two of these values, such as between about 1 and about 50, between about 2 and about 25, between about 3 and about 15, or between about 4 and about 10. Humidity can be provided by a given temperature according to the temperature values ​​or ranges described above, although it is understood that the temperature values ​​result in a humidity not exceeding 100% relative humidity or a partial vapor pressure not exceeding its saturated vapor pressure. At a given temperature, for any of these water vapor partial pressure values, the relative humidity can be, for example, less than about 90%, 80%, 70%, 60%, 50%, 40%, 30%, or 20%.

[0251] Those skilled in the art will understand that various changes and / or modifications can be made to the above embodiments without departing from the broad scope of this disclosure. Therefore, the embodiments of the present invention are to be considered illustrative rather than restrictive in all respects.

[0252] Example

[0253] To better understand this disclosure, specific embodiments of the invention will be described in more detail below with reference to the following non-limiting experimental materials, methods, and examples.

[0254] Example 1 is mainly an overview of silica aerogels and their gelling properties.

[0255] The inventors have developed induced microporous aerogels (Table 1) based on various silanes (SiO2) and their various combinations thereof for the purpose of direct air capture (DAC) of CO2, and their performance for CO2 concentrations of 0.5%, 1%, and 100%. The induced microporous aerogels exhibit selective CO2 adsorption under ambient conditions (298 K and 0.4 mbar). The microporous aerogels are designed to possess the following advantageous properties: microporosity, hydrophobicity, CO2 selectivity, ambient CO2 conditions for capture, and regeneration capability.

[0256] Table 1. Various silane (SiO2) groups used for preparing silica-based aerogels.

[0257]

[0258]

[0259] Table 2: List of silica-based aerogels and their CO2 absorption performance at 298 K for 0.04% (0.4 mbar direct air capture), 0.5%, 1%, and 100% CO2 concentrations.

[0260]

[0261] *TIF-SIX(MOF) is only included for comparison purposes.

[0262] Table 3 shows the gelation properties of the selected silica-based aerogels.

[0263] Candidates level of gelation A high B high C Low / None — Water needs to be added to initiate gelation. D Medium—requires freeze-drying to initiate gelation. E high K high L Medium / Low M medium N medium O medium P medium Q medium R Low / None S Very low / None T Very low / None

[0264] Example 2: General process for preparing silica-based aerogels

[0265] All reagents were received and used as is without any purification. Remaining reagents were stored in an inert environment (N2-filled glove bags) to prevent any hydrolysis of silanes.

[0266] Any combination of two or more amino-substituted silanes, alkyl-substituted silanes, and silicates can be added to an aqueous solution of ethanol and water. The aqueous solution including the silane can be mixed to form a wet gel matrix. A buffer (e.g., NH3, NH4HCO3) or an acid (e.g., an HCl acid solution) can optionally be added to the wet gel matrix, and optionally followed by an alkaline solution (e.g., NaOH solution). The wet gel matrix can then be rinsed / soaked with water and optionally heated at a slightly elevated temperature. Drying methods can be used to dry the aqueous solution including the wet gel matrix to provide a dried silica-based aerogel.

[0267] Example 2a - Candidate A

[0268] (i) Add the following substances to 3.6 mL of AR grade ethanol: 8 mmol (1.672 mL, 1.531 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS), 8 mmol (1.594 mL, 1.426 g) of triethoxymethylsilane (TEMS), and 4 mmol (0.892 mL, 0.833 g) of triethyl orthosilicate (TEOS). Vortex the solution manually for 1 second to combine each addition. Add 0.600 mL of water to the combined solution, vortex to mix, and heat the sealed container in an oven at 80 °C for 6 hours to form a gel. Allow the sample to cool to room temperature overnight. The gel is then dissolved in 10 mL of water and filtered through a porous glass frit. The gel is further soaked for 2 hours during multiple water rinses. The gel is then dried overnight in a vacuum oven at approximately 50 °C.

[0269] (ii) Add the following substances to 3.6 mL of AR grade ethanol: 8 mmol (1.672, 1.531 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS), 8 mmol (1.594 mL, 1.426 g) of triethoxymethylsilane (TEMS), and 4 mmol (0.892 mL, 0.833 g) of triethyl orthosilicate (TEOS). Vortex the solution manually for 1 second to combine with each addition. Add 1.00 mL of 2M HCl to the combined solution, vortex to mix, and heat the sealed container overnight at 60°C. Allow the liquid to cool to room temperature, add 1.00 mL of 2M NaOH, vortex to mix, and heat the sealed container overnight at 60°C to form a gel. The gel is then dissolved in 10 mL of water and filtered through a porous glass frit. The gel is further soaked for 2 hours during multiple water rinses. The gel was then dried overnight in a vacuum oven at approximately 50°C.

[0270] (iii) Add the following substances to 3.6 mL of AR grade ethanol: 8 mmol (1.672, 1.531 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS), 8 mmol (1.594 mL, 1.426 g) of triethoxymethylsilane (TEMS), and 4 mmol (0.892 mL, 0.833 g) of triethyl orthosilicate (TEOS). Vortex the solution manually for 1 second to combine each addition. Add 0.600 mL of 2M NH3 (aqueous solution) to the combined solution, vortex to mix, and heat the sealed container in an oven at 80 °C for 6 hours to form a gel. Allow the sample to cool to room temperature overnight. The gel is then dissolved in 10 mL of water and filtered through a porous glass frit. The gel is further soaked for 2 hours during multiple water rinses. The gel is then dried overnight in a vacuum oven at approximately 50 °C.

[0271] Example 2b - Candidate B

[0272] Add the following substances to 3.6 mL of AR grade ethanol: 8 mmol (1.672 mL, 1.531 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS), 4 mmol (0.797 mL, 0.713 g) of triethoxymethylsilane (TEMS), and 8 mmol (1.784 mL, 1.667 g) of triethyl orthosilicate (TEOS). Vortex the solution manually for 1 second to combine each addition. Add 0.600 mL of water to the combined solution, vortex to mix, and heat the sealed container in an oven at 80 °C for 6 hours to form a gel. Allow the sample to cool to room temperature overnight. The gel is then dissolved in 10 mL of water and filtered through a porous glass frit. The gel is further soaked for 2 hours during multiple water rinses. The gel is then dried overnight in a vacuum oven at approximately 50 °C.

[0273] Example 2c - Candidate C

[0274] (i) Add the following substances to 4.0 mL of AR grade ethanol: 8 mmol (1.672 mL, 1.531 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS) and 12 mmol (2.297 mL, 2.139 g) of triethoxymethylsilane (TEMS). Add 1.5 mL of water and 0.80 mL (approximately 8 mmol) of 32% hydrochloric acid. Vortex the solution manually for 1 second to combine each addition. Keep the combined solution at room temperature overnight. Add solid NaOH (0.425 g, 10.6 mmol), and the solution becomes cloudy the next day. Add 1.0 mL of water to produce a clear solution. After 5 days, collect the precipitate by centrifugation (5000 rpm) and wash with 10 mL of water, repeating five times. Then dry the gel in a vacuum oven at approximately 50 °C overnight.

[0275] (ii) Add the following substances to 3.6 mL of AR grade ethanol: 8 mmol (1.672 mL, 1.531 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS) and 12 mmol (2.403 mL, 2.139 g) of triethoxymethylsilane (TEMS). Vortex the solution manually for 1 second to combine each addition. Add 0.600 mL of water to the combined solution, vortex to mix, and age the sealed container in an oven at 80 °C for 6 hours. Allow the aged solution to cool to room temperature. Then add 20 mL of water to allow gel formation. Filter the product through a porous glass frit. The gel is further soaked for 2 hours during multiple water rinses. The gel is then dried overnight in a vacuum oven at approximately 50 °C.

[0276] (iii) Add the following substances to 4.5 mL of AR grade ethanol: 20 mmol (4.178 mL, 3.827 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS), 30 mmol (5.977 mL, 5.349 g) of triethoxymethylsilane (TEMS), and 1.5 mL of water. Vortex the solution manually for 1 second to combine each addition. Heat the combined solution at 60 °C overnight. The solution remains clear, and 20 mL of water is added to make the solution cloudy, and the solution is heated again at 60 °C overnight. The formed gel is then washed with at least 10 times its volume in excess water, repeated three times. The gel is then dried overnight in a vacuum oven at approximately 50 °C.

[0277] Example 2d - Candidate D

[0278] Add the following substances to 3.6 mL of AR grade ethanol: 12 mmol (2.808 mL, 2.656 g) of 3-aminopropyl(triethoxy)silane (APTES), 4 mmol (0.797 mL, 0.713 g) of triethoxymethylsilane (TEMS), and 4 mmol (0.892 mL, 0.833 g) of triethyl orthosilicate (TEOS). Vortex the solution manually for 1 second to combine with each addition. Add 0.600 mL of water, vortex the solution to mix, and heat the sealed container in an oven at 80 °C for 6 hours. Allow the sample to cool to room temperature overnight. The gel is then dissolved in 10 mL of water and filtered through a porous glass frit. The gel is further soaked for 2 hours during multiple water rinses. The gel is then freeze-dried overnight.

[0279] The gel was dissolved in 10 mL of water and soaked for one hour, then allowed to settle and the water was poured off. This process was repeated five times. The solid was finally collected by adding approximately 50 mL of water, and the total volume was freeze-dried.

[0280] Example 2e - Candidate E

[0281] Add the following substances to 3.6 mL of AR grade ethanol: 8 mmol (1.672 mL, 1.5321 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS), 8 mmol (1.720 mL) of triethoxy(ethyl)silane (TEES), and 4 mmol (0.892 mL, 0.833 g) of triethyl orthosilicate (TEOS). Vortex the solution manually for 1 second each time to form a homogeneous solution. Add 0.6 mL of water to the solution and incubate at 80 °C for 6 hours. Break up the formed gel, wash with excess water, and collect by filtration. Dry the gel in an oven at 55 °C under reduced pressure.

[0282] Example 2f - Candidate J

[0283] Add the following substances to 3.6 mL of AR grade ethanol: 8 mmol (1.39 mL, 1.43 g) of 3-aminopropyl(triethoxy)silane (APTES), 4 mmol (0.797 mL, 0.713 g) of triethoxymethylsilane (TEMS), 4 mmol (0.892 mL, 0.833 g) of triethyl orthosilicate (TEOS), and 4 mmol (0.593 g, 0.685 mL) of dimethyldiethoxysilane. Vortex the solution manually for 1 second to combine with each addition. Add 0.600 mL of water, vortex the solution to mix, and heat the sealed container in an oven at 80 °C for 6 hours. Allow the sample to cool to room temperature overnight. The gel is then dissolved in 10 mL of water and filtered through a porous glass frit. The gel is further soaked for 2 hours during multiple water rinses. The gel is then freeze-dried overnight.

[0284] Example 2g - Candidate K

[0285] Add the following substances to 3.6 mL of AR grade ethanol: 8 mmol (1.672 mL, 1.5321 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS), 4 mmol (0.797 mL, 0.713 g) of triethoxymethylsilane (TEMS), 4 mmol (0.860 mL) of TEES, and 4 mmol (0.892 mL, 0.833 g) of triethyl orthosilicate (TEOS). Vortex the solution manually for 1 second each time it is added to form a homogeneous solution. Add 0.6 mL of water and incubate at 80 °C for 6 hours. Break up the formed gel, rinse with excess water, and collect by filtration. Dry the gel in an oven at 55 °C under reduced pressure (-80 kPa).

[0286] Example 2h - Candidate L

[0287] Add the following substances to 3.6 mL of AR grade ethanol: 12 mmol (2.507 mL, 2.296 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS), 4 mmol (0.801 mL, 0.713 g) of triethoxymethylsilane (TEMS), and 4 mmol (0.887 mL, 0.833 g) of triethyl orthosilicate (TEOS). Vortex manually for 1 second to combine the solutions upon each addition. Add 0.600 mL of water to the combined solutions, vortex to mix, and heat the sealed container in an oven at 80 °C for 6 hours to form a gel. Allow the sample to cool to room temperature overnight. The gel is then broken up with 10 mL of water and shaken at 80 rpm for approximately 2 hours. It is then filtered through a porous glass frit filter. The gel is further washed with water and shaken at 60 ppm for approximately 2 hours, and then filtered through a glass frit filter. Repeat these washing procedures three times. The gel is then dried overnight in a vacuum oven at approximately 50°C, or at room temperature in a fume hood until completely dry.

[0288] Example 2i - Candidate M

[0289] Add the following substances to 3.6 mL of AR grade ethanol: 12 mmol (2.507 mL, 2.296 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS), 2 mmol (0.401 mL, 0.356 g) of triethoxymethylsilane (TEMS), 2 mmol (0.430 mL, 0.385 g) of triethoxy(ethyl)silane (TEES), and 4 mmol (0.887 mL, 0.833 g) of triethyl orthosilicate (TEOS). Vortex the solution manually for 1 second to combine each addition. Add 0.600 mL of water to the combined solution, vortex to mix, and heat the sealed container in an oven at 80 °C for 6 hours to form a gel. Allow the sample to cool to room temperature. The gel is then broken up with 10 mL of water and shaken at 80 rpm for approximately 2 hours. The gel is then filtered through a porous glass frit. The gel was further washed with water and agitated at 60 ppm for approximately 2 hours, and then filtered through a glass frit filter. These washing procedures were repeated three times. The gel was then dried overnight in a vacuum oven at approximately 50°C, or at room temperature in a fume hood, until completely dry.

[0290] Example 2j - Candidate N

[0291] Add the following substances to 3.6 mL of AR grade ethanol: 10 mmol (2.089 mL, 1.913 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS), 3 mmol (0.601 mL, 0.535 g) of triethoxymethylsilane (TEMS), 3 mmol (0.645 mL, 0.577 g) of triethoxy(ethyl)silane (TEES), and 4 mmol (0.887 mL, 0.833 g) of triethyl orthosilicate (TEOS). Vortex the solution manually for 1 second to combine each addition. Add 0.600 mL of water to the combined solution, vortex to mix, and heat the sealed container in an oven at 80 °C for 6 hours to form a gel. Allow the sample to cool to room temperature. Break up the gel and wash three times with excess water, collecting the gel by filtration. Then dry the gel overnight in a vacuum oven at approximately 50 °C.

[0292] Example 2k - Candidate O

[0293] Add the following substances to 3.6 mL of AR grade ethanol: 10 mmol (2.089 mL, 1.913 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS), 5 mmol (1.001 mL, 0.891 g) of triethoxymethylsilane (TEMS), and 5 mmol (1.108 mL, 1.042 g) of triethyl orthosilicate (TEOS). Vortex the solution manually for 1 second to combine each addition. Add 0.600 mL of water to the combined solution, vortex to mix, and heat the sealed container in an oven at 80 °C for 6 hours to form a gel. Allow the sample to cool to room temperature. Break up the gel and wash three times with excess water, collecting the gel by filtration. Then dry the gel overnight in a vacuum oven at approximately 50 °C.

[0294] Example 2l - Candidate P

[0295] Add the following to 3.6 mL of AR grade ethanol: 12 mmol (2.507 mL, 2.296 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS) and 8 mmol (1.773 mL, 1.667 g) of triethyl orthosilicate (TEOS). Vortex the solution manually for 1 second to combine each addition. Add 0.600 mL of water to the combined solution, vortex to mix, and heat the sealed container in an oven at 80 °C for 6 hours to form a gel. Allow the sample to cool to room temperature overnight. Then break up the gel with 10 mL of water and agitate at 80 rpm for approximately 2 hours. Filter through a porous glass frit. Wash the gel further with water, agitated at 60 ppm for approximately 2 hours, and filter through a glass frit. Repeat these washing procedures three times. Then dry the gel in a vacuum oven at approximately 50 °C overnight, or in a fume hood at room temperature, until completely dry.

[0296] Example 2m - Candidate Q

[0297] Add the following substances to 3.6 mL of AR grade ethanol: 12 mmol (2.507 mL, 2.296 g) of 3-aminopropyl(diethoxy)methylsilane (APEMS), 4 mmol (0.860 mL, 0.769 g) of triethoxy(ethyl)silane (TEES), and 4 mmol (0.887 mL, 0.833 g) of triethyl orthosilicate (TEOS). Vortex manually for 1 second to combine the solutions upon each addition. Add 0.600 mL of water to the combined solutions, vortex to mix, and heat the sealed container in an oven at 80 °C for 6 hours to form a gel. Allow the sample to cool to room temperature. Then break up the gel with 10 mL of water and agitate at 80 rpm for approximately 2 hours. Filter through a porous glass frit. The gel is further washed with water and agitated at 60 ppm for approximately 2 hours, and then filtered through a glass frit. Repeat these washing procedures three times. The gel is then dried overnight in a vacuum oven at approximately 50°C, or at room temperature in a fume hood until completely dry.

[0298] Example 3 Performance and Feature Data

[0299] As defined in Example 2, the following performance measurements were performed on silica-based aerogels to determine their direct air capacity:

[0300] I. CO2 gas adsorption

[0301] II. H2O vapor adsorption

[0302] III. CO2 Penetration Test

[0303] IV. N2 gas adsorption method for determining surface area

[0304] V. Adsorption and Desorption Cycles

[0305] The following characterization methods have been used to understand material structure:

[0306] i. PALS (Positron Annihilation Lifetime Spectroscopy) – The aperture distribution determined for candidates A, B, C, and D using PALS. Figure 1a The aperture distributions of J, P, M, and L are shown in the figure. Figure 1b As shown in the figure, and determined using N2 gas.

[0307] ii. Density - in Figure 1c (particle density) and Figure 1d The (bulk density) figure shows the relationship between the density of candidates A, B, D, E, and K and the amount of CO2 absorbed under different pressures.

[0308] iii. Thermal stability and activation overview

[0309] Example 3a - Performance Data

[0310] I) CO2 gas adsorption

[0311] The information presented in this section highlights the performance of silica-based aerogels as adsorbents for direct air capture of CO2. Table 6 summarizes the properties of the best candidate aerogels, including BET surface area, density of the solid material, and various CO2 capture performances. As previously mentioned, for direct air capture, the aerogel needs to adsorb 0.4 mbar of CO2, which is equivalent to 400 ppm of CO2 in the atmosphere. Aerogels were formed at an ambient temperature of 298 K, and CO2 performance is provided in mmol / g, mg / g, and CO2 wt%. It should be understood that surface area BET (m² / g) provides information on the physical adsorption of gases (e.g., N2 gas on the solid surface of the candidate aerogel). Using the surface area BET of N2 gas requires the gas molecules to be able to enter the accessible pores to determine the inherent surface area and porosity. Surface area BET is not a performance indicator of the CO2 capacity of these aerogels and can in fact be a general indicator of the level of microporosity of the candidate aerogel. For example, the inventors were surprised to find that surface area is not a measure of the extent to which the aerogel adsorbs CO2. Surprisingly, aerogels with low surface area provided excellent CO2 adsorption.

[0312] As a performance guideline, TIF-SIX is the benchmark and known for performing direct air capture of CO2. As described in this paper, these novel silica-based aerogels surprisingly improve the direct air capture performance of TIF-SIX (see Table 2).

[0313] Table 4 provides details on the CO2 adsorption performance of selected silica-based aerogels. Figures 2 to 18 The CO2 isotherm for all candidate materials at 298 K is provided.

[0314] Table 4 selects properties based on silica aerogels, including BET surface area, density, and the weight percentage of CO2 absorbed from CO2 gas adsorption isotherms at different pressures.

[0315]

[0316] *0.4 mbar pressure is equivalent to 400 ppm atmospheric CO2 in the air, 150 mbar is equivalent to flue gas conditions with a CO2 concentration of 15%, and 925 mbar is equivalent to 100% CO2.

[0317] Instance 3b performance data

[0318] II) H2O vapor adsorption

[0319] For direct air capture, it is desirable for aerogels to include hydrophobic elements. This ensures that the material does not compete with water adsorption when adsorbing CO2 from the air. This is a necessary characteristic for aerogels to operate in various relative humidity environments. The introduction of APEMS, TEMS, TEES, and / or DMDES enables two main improvements: 1) increased hydrophobicity and 2) induced microporosity to form pores with a diameter less than 2 nm, thereby enabling CO2 selectivity relative to H2O. Table 5 presents the SiO2 units used in each silica-based aerogel. The H2O adsorption performance isotherm is shown in... Figure 19 Provided by China.

[0320] Table 5. Composition of SiO2 units in silica-based aerogels

[0321]

[0322] Example 3c performance data

[0323] III) CO2 Penetration Test

[0324] For dynamic performance testing, CO2 penetration experiments were conducted under both dry and humid conditions. Figure 20 Breakthrough curves of candidates A, B, and D at a CO2 concentration of 740 ppm are shown under dry and humid (70-80% RH) conditions. Figure 21Breakthrough curves for candidate B at 500 ppm and 740 ppm under dry and wet (70-80% RH) conditions at a flow rate of 20 sccm are presented. At 740 ppm, increasing CO2 concentration showed a faster breakthrough time, but also a higher CO2 capacity. Table 6 provides CO2 wt% capacity at 400 ppm (DAC), 740 ppm, and 10,000 ppm under dry and wet conditions. Figure 22 The transmittance curves for the standard DAC material zeolite 13X are presented. Figure 22 Table 6 unexpectedly shows that the microporous candidate is superior to zeolite 13X, and more importantly, it can continuously capture CO2 in the presence of humidity.

[0325] Table 6. Permeability of CO2 (wt%) in silica-based aerogels

[0326]

[0327] Example 3D performance data

[0328] IV) N2 gas adsorption

[0329] The N2 adsorption capacity was measured at 77 K, and the BET surface area could be determined from this data. Figure 23-28 The N2 adsorption isotherm is provided, and Table 7 provides the BET surface areas of the candidate aerogels. According to Table 7, there is a range of low BET surface areas, which may be due to N2's inability to penetrate the pores, as it is related to the N2 adsorption isotherm. Compared to CO2 gas, N2 gas has a larger diameter. The large dynamic diameter.

[0330] Table 7 shows the BET surface area range of candidate materials, calculated from N2 at the 77K adsorption isotherm.

[0331]

[0332]

[0333] Instance 3e performance data

[0334] v) CO2 adsorption cycle

[0335] Figures 29 to 31 The surprisingly excellent performance of the candidate aerogels under various conditions after continuous adsorption / desorption cycles, with activation occurring between each cycle, is demonstrated.

[0336] Figure 32 and 33Information from penetration tests is provided, in which the candidate aerogel exhibits superior cycling performance compared to zeolite 13X. These tests were conducted under both dry and wet conditions at a CO2 concentration level of 740 ppm.

[0337] Example 4: General process for the formation of silica-based aerogel granules

[0338] (i) Preparation of compressed granules: The binder and graphite are mixed with the dried silica-based aerogel, ensuring all components are uniformly mixed. The compression pressure and filling depth are adjusted to form solid granules of the desired thickness. Lower pressure (i.e., setting 3) is generally associated with a smaller filling depth to produce robust granules. Higher pressure (i.e., setting 5) requires a greater filling depth. Both combinations produce granules within the desired thickness range.

[0339] (ii) Preparation of slurry-based extrudates of granules: A cellulose / siloxane-based binder is prepared by combining 50 mL of each of the following ethanol and water solutions into 3 g of a siloxane solution in a screw-capped bottle. 3 g of cellulose is added to the mixture, in 100 mg portions. After each addition, the slurry is continuously stirred until the cellulose dissolves. After adding all remaining cellulose, the slurry is mixed until a viscous solution consistency is obtained. The silica-based aerogel is sieved to obtain particles <200 mm in size. Optionally, a lubricant (e.g., magnesium stearate) may be used as needed to adjust the viscosity of the extrudable material.

[0340] A common method for liquid extrusion involves using a 10mL plastic syringe with a 2.0mm internally threaded Luer-lock barb attachment. This allows for the extrusion of formulated pastes in quantities of 0.5–2g.

[0341] A silica-based aerogel and binder were combined and processed into a paste using a scraper. The solvent was slowly evaporated using a gentle nitrogen stream, which provided a pellet-like paste after approximately 2–3 minutes of exposure. The pellet was pushed through a 5 mL / 10 mL syringe fitted with a 2.0 barb. This formed a noodle-like extrusion, and the pellets were individually cut into lengths of approximately 3–4 mm. The pellets were dried at room temperature and then further dried under vacuum (0.1 mbar) at 80 °C for 12 hours.

[0342] Example 4a - Candidate B

[0343] According to the method described in (i) above, granules are formed by mixing 11 g of binder and 1.58 g of graphite with 66 g of candidate B until all components are homogeneously mixed. The pressing pressure and filling depth are adjusted to form solid granules of the desired thickness of candidate B.

[0344] Example 4b - Candidate E

[0345] Granules were formed according to the method described in (ii) above, by preparing an adhesive solution according to (ii) and a silica-based aerogel formulation using 0.62 g of candidate E (sieved at <200 mm), 2.92 g of cellulose / siloxane adhesive, and 0.06 mg of magnesium stearate (lubricant). The adhesive solution and silica-based aerogel formulation were combined and processed into a paste using a scraper. The volume was slowly evaporated with a gentle stream of nitrogen, which provided a clump-like paste after exposure for 2–3 minutes. The clump was pushed through a 5 mL / 10 mL syringe fitted with a 2.0 barb. A noodle-like extrudate was formed, and the granules were individually cut into 3–4 mm lengths. The granules were dried at room temperature and then further dried under vacuum (0.1 mbar) at 80 °C for 12 hours.

[0346] Example 4c - Candidate K

[0347] According to the method described in (i) above, granules are formed by mixing 15.38 g of binder and 1.54 g of graphite with 60 g of candidate K until all components are homogeneously mixed. The pressing pressure and filling depth are adjusted to form solid granules of the desired thickness of candidate K.

[0348] Example 5: Granulation properties of silica-based aerogels

[0349] The properties of silica-based aerogel granules are determined by selecting the type and amount of binder. The inventors unexpectedly discovered that the type and amount of binder will determine whether the granules can be compressed or extruded, and will depend on the specific application (e.g., granules for DAC devices relative to where the granules form an unrelated coating), and alternatively, the viscosity of the formulation becomes important.

[0350] Depending on the specific application, aerogel products are preferably in granular form (e.g., DAC devices). Therefore, the type of binder, candidate types, and binder content were investigated to obtain robust strength and excellent CO2 absorption performance.

[0351] Table 8 summarizes the findings of various adhesives and their impact on the strength of the granules of the same candidate. The results show that, in terms of the final granule strength, NH2 siloxane adhesives perform better than other adhesives.

[0352] Table 8. Adhesive type of candidate A relative to the strength of silica-based aerogel particles

[0353] adhesives Amount of adhesive (by weight %) Shape forming Compressibility / Cutability Silica / hydroxypropyl cellulose 29 no No / No <![CDATA[NH2 siloxane]]> 35 yes Yes / Yes Poly(vinyl alcohol) 35 yes whether Low molecular weight polyethylene glycol 25 yes Yes / Yes Methylcellulose / poly(propylene glycol) 25 yes Yes / Yes Poly(vinyl alcohol) 36 yes whether polymethylsiloxane 36 yes whether polydimethylsiloxane 30 yes whether Polyvinylpyrrolidone 30 yes whether

[0354] Table 9 summarizes the granulation properties of different aerogel candidates prepared in granular form with NH2 siloxane binders. The results show that candidate L provides the strongest granule combination and excellent performance among the tested candidates.

[0355] Table 9 shows the strength of candidates relative to silica-based aerogel particles for NH2 siloxanes.

[0356] Candidates adhesives Amount of adhesive (by weight %) Shape forming Compressibility / Cutability A <![CDATA[NH2 siloxane]]> 35 yes whether B <![CDATA[NH2 siloxane]]> 13 yes whether B <![CDATA[NH2 siloxane]]> 24 yes Yes / Yes L <![CDATA[NH2 siloxane]]> 23 yes Yes / Yes

[0357] Table 10 summarizes the effect of binder amount on the strength and properties of aerogel particles. The results show that when the binder amount is less than about 10% by weight, the strength of the aerogel particles of candidate L combined with the NH2 siloxane binder deteriorates.

[0358] Table 10 shows the amount of binder relative to the strength of silica-based aerogel particles for candidate L containing NH2 siloxane.

[0359] Candidates adhesives Amount of adhesive (by weight %) Shape forming Compressibility / Cutability L <![CDATA[NH2 siloxane]]> 10 yes whether L <![CDATA[NH2 siloxane]]> 20 yes Yes / Yes L <![CDATA[NH2 siloxane]]> 30 yes Yes / Yes L <![CDATA[NH2 siloxane]]> 43 yes Yes / Yes

[0360] Example 6: Water Adsorption Properties of Silica-Based Aerogel Granules

[0361] Figure 34 Information on water adsorption of the candidate aerogel particles compared to TIF-SIX particles and 13X zeolite particles is provided. This was conducted under dry and wet conditions operated at 298 K. The results show that, unlike zeolite 13X or TIF-SIX particles, the candidate aerogel particles do not provide good water adsorption properties, surprisingly making the silica-based aerogel particles of the present invention far superior in selective CO2 adsorption.

Claims

1. A silica-based microporous aerogel for carbon dioxide capture, wherein the microporous aerogel comprises a plurality of pores, wherein at least 50% of the pores have a diameter of less than 2 nm, wherein the diameter of the pores is measured using positron annihilation lifetime spectroscopy. in, The microporous aerogel comprises the reaction product of the following reagents, wherein the reagents include at least one amino-substituted silane, at least one alkyl-substituted silane, and at least one tetraalkoxysilane; Wherein, the at least one tetraalkoxysilane has Formula 3: Si(OR 7 )4 Formula 3 in: R 7 It is C 1-6 alkyl, The tetraalkoxysilane wherein the tetraalkoxysilane has a loading of at least 20 mol%.

2. The microporous aerogel according to claim 1, wherein the aerogel adsorbs CO2 from the air in an environment with a CO2 concentration of less than 10% by volume.

3. The microporous aerogel according to claim 1, wherein the aerogel adsorbs CO2 from the air in a closed environment with a CO2 concentration of less than 2% by volume.

4. The microporous aerogel according to claim 1, wherein the aerogel adsorbs CO2 from the air in an environment with a CO2 concentration of 0.04% by volume.

5. The microporous aerogel according to claim 4, wherein the CO2 adsorption of the aerogel is at least 0.47 mmol / g.

6. The microporous aerogel according to claim 1, wherein the amino-substituted silane conforms to formula 1: R 1 Si(OR 2 ) n -L-NH2 Formula 1 in: R 1 It is C 1-6 Alkyl groups may not be present; R 2 It is C 1-6 alkyl; L is the -C between silicon and nitrogen atoms. 1-6 alkyl-linking groups; and n is 2 or 3.

7. The microporous aerogel according to claim 1 or claim 6, wherein the amino-substituted silane has a loading of at least 40 mol%.

8. The microporous aerogel according to claim 1 or claim 6, wherein the amino-substituted silane has a loading of less than 60 mol%.

9. The microporous aerogel according to claim 1, wherein the alkyl-substituted silane conforms to formula 2: R 5 m Si(OR 6 ) n Formula 2 in: R 5 and R 6 Each is independently selected from C 1-6 Alkyl; and m is 1 and n is 3, or m and n are both 2.

10. The microporous aerogel according to claim 1 or claim 9, wherein the alkyl-substituted silane has a loading of at least 10 mol%.

11. The microporous aerogel according to claim 1 or claim 9, wherein the alkyl-substituted silane has a loading of less than 40 mol%.

12. The microporous aerogel according to claim 1, wherein the tetraalkoxysilane has a loading of less than 40 mol%.

13. The microporous aerogel according to claim 1, wherein the amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane having a loading of between 40 mol% and 60 mol%.

14. The microporous aerogel according to claim 1, wherein the amino-substituted silane is 3-aminopropyl (triethoxy)silane having a loading of between 40 mol% and 60 mol%.

15. The microporous aerogel according to claim 1, wherein the density of the aerogel is 0.02 g / cm³. 3 Up to 0.6 g / cm 3 Within the range between.

16. The microporous aerogel according to claim 1, wherein the density of the aerogel is 0.2 g / cm³. 3 Up to 0.6 g / cm 3 Within the range between.

17. The microporous aerogel according to claim 1, wherein the aerogel is in the form of particles, powder, beads, sheets / layers, ingots, cylinders, discs, porous membranes or monolithic materials.

18. The microporous aerogel according to claim 1, wherein the aerogel is a plurality of granules.

19. The microporous aerogel according to claim 1, wherein the aerogel is a coating or a membrane.

20. The microporous aerogel according to claim 1, wherein the aerogel is a self-supporting aerogel.

21. The microporous aerogel of claim 1, wherein the aerogel is applied to a substrate as a coating composition or a film.

22. The microporous aerogel of claim 1, wherein the aerogel has a porous structure at 0.1 m... 2 / g and 500 m 2 Surface area within the range of / g.

23. The microporous aerogel according to claim 1, wherein the aerogel has a porous structure at 2 m... 2 / g and 200 m 2 Surface area within the range of / g.

24. The microporous aerogel of claim 1, wherein the aerogel has a pore size in the range of 0.1 nm to 2 nm.

25. The microporous aerogel of claim 1, wherein the aerogel comprises one or more additives selected from buffers, binders, optionally present metal-organic frameworks, and nanoparticles.

26. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of 40 mol%, the at least one alkyl-substituted silane is triethoxymethylsilane with a loading of 40 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 20 mol%.

27. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl (triethoxy)silane with a loading of 40 mol%, the at least one alkyl-substituted silane is triethoxymethylsilane with a loading of 40 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 20 mol%.

28. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of 40 mol%, the at least one alkyl-substituted silane is triethoxymethylsilane with a loading of 20 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 40 mol%.

29. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl (triethoxy)silane with a loading of 40 mol%, the at least one alkyl-substituted silane is triethoxymethylsilane with a loading of 20 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 40 mol%.

30. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl (triethoxy)silane with a loading of 60 mol%, the at least one alkyl-substituted silane is triethoxymethylsilane with a loading of 20 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 20 mol%.

31. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of 40 mol%, the at least one alkyl-substituted silane is triethoxy(ethyl)silane with a loading of 40 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 20 mol%.

32. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl (triethoxy)silane with a loading of 40 mol%, the at least one alkyl-substituted silane is triethoxy (ethyl)silane with a loading of 40 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 20 mol%.

33. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of 40 mol%, the at least one alkyl-substituted silane is dimethyldiethoxysilane with a loading of 40 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 20 mol%.

34. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 40 mol% of 3-aminopropyl(diethoxy)methylsilane, the at least one alkyl-substituted silane is a mixture of 20 mol% of triethoxymethylsilane and 20 mol% of dimethyldiethoxysilane, and the at least one tetraalkoxysilane is 20 mol% of tetraethyl orthosilicate.

35. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of 60 mol%, the at least one alkyl-substituted silane is dimethyldiethoxysilane with a loading of 10 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 30 mol%.

36. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of 40 mol%, the at least one alkyl-substituted silane is dimethyldiethoxysilane with a loading of 30 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 30 mol%.

37. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 40 mol% of 3-aminopropyl (triethoxy)silane, the at least one alkyl-substituted silane is a mixture of 20 mol% of triethoxymethylsilane and 20 mol% of dimethyldiethoxysilane, and the at least one tetraalkoxysilane is 20 mol% of tetraethyl orthosilicate.

38. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 40 mol% of 3-aminopropyl(diethoxy)methylsilane, the at least one alkyl-substituted silane is a mixture of 20 mol% of triethoxymethylsilane and 20 mol% of triethoxy(ethyl)silane, and the at least one tetraalkoxysilane is 20 mol% of tetraethyl orthosilicate.

39. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of 60 mol%, the at least one alkyl-substituted silane is triethoxymethylsilane with a loading of 20 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 20 mol%.

40. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 60 mol% of 3-aminopropyl(diethoxy)methylsilane, the at least one alkyl-substituted silane is a mixture of 10 mol% of triethoxymethylsilane and 10 mol% of triethoxy(ethyl)silane, and the at least one tetraalkoxysilane is 20 mol% of tetraethyl orthosilicate.

41. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of 50 mol%, the at least one alkyl-substituted silane is a mixture of triethoxymethylsilane and triethoxy(ethyl)silane with a loading of 15 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 20 mol%.

42. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of 50 mol%, the at least one alkyl-substituted silane is triethoxymethylsilane with a loading of 25 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 25 mol%.

43. The microporous aerogel according to claim 1, wherein, The at least one amino-substituted silane is 3-aminopropyl(diethoxy)methylsilane with a loading of 60 mol%, the at least one alkyl-substituted silane is triethoxy(ethyl)silane with a loading of 20 mol%, and the at least one tetraalkoxysilane is tetraethyl orthosilicate with a loading of 20 mol%.

44. The microporous aerogel according to any one of claims 1 and 26-43, wherein the reaction product is prepared by a one-pot synthesis.

45. The microporous aerogel according to any one of claims 1 and 26-43, wherein the microporous aerogel is in the form of a composite material, wherein the composite material further comprises one or more additives and optionally a lubricant.

46. ​​The microporous aerogel of claim 45, wherein one or more additives are selected from buffers, binders, optionally present metal-organic frameworks, and nanoparticles.

47. The microporous aerogel of claim 45, wherein the amount of the additive is from 5% to 35% by weight, based on the total weight of the aerogel.

48. The microporous aerogel of claim 45, wherein the composite material is self-supporting in the form of granules, beads, or sheets.

49. The microporous aerogel of claim 45, wherein the composite material is applied to a substrate as a coating composition, paste, or film.

50. An aerogel composite material, comprising the following components: (i) the microporous aerogel or combination thereof according to any one of claims 1 to 43; (ii) One or more additives, wherein the additives have a loading of 5% to 35% by weight; (iii) Any available lubricant; and (iv) Any solvent that is available.

51. The aerogel composite material of claim 50, wherein one or more additives are selected from buffers, binders, optionally present metal-organic frameworks, and nanoparticles.

52. The aerogel composite material according to claim 51, wherein the binder is selected from cellulose-based polymers, silane-based polymers, cellulose-siloxane-based polymers, polyethylene glycol-based polymers, polyvinylpyrrolidone, polyvinyl alcohol, polyethyleneimine, bentonite, graphite, or combinations thereof.

53. The aerogel composite material according to claim 50, wherein the solvent is water, a non-aqueous solvent, or a combination thereof.

54. A process for preparing a silica-based microporous aerogel for carbon dioxide capture, wherein the microporous aerogel comprises a plurality of pores, wherein at least 50% of the pores have a diameter of less than 2 nm, wherein the diameter of the pores is measured using positron annihilation lifetime spectroscopy, the process comprising: (i)(a) Mixing an aqueous solution comprising at least one amino-substituted silane, at least one alkyl-substituted silane, and at least one tetraalkoxysilane, optionally a buffer, optionally one or more additives, and a solvent system to form a wet gel matrix; and (ii) Drying the wet gel matrix to provide a dry silica-based microporous aerogel. The condition is that drying the wet gel matrix does not involve supercritical CO2. The aerogel comprises the reaction product of the following reagents, wherein the reagents include at least one amino-substituted silane, at least one alkyl-substituted silane, and at least one tetraalkoxysilane; Wherein, the at least one tetraalkoxysilane has Formula 3: Si(OR 7 )4 Formula 3 in: R 7 It is C 1-6 alkyl, The tetraalkoxysilane wherein the tetraalkoxysilane has a loading of at least 20 mol%.

55. The process according to claim 54, wherein step (i) further comprises step (i)(b) rinsing the wet gel matrix.

56. The process of claim 54, wherein the process is a sol-gel process, and step (ii) comprises: (a1) Optionally, the wet gel matrix is ​​heated to obtain a gel; and (a2) The gel is dried by solvent evaporation and / or heat treatment to provide a dried silica-based microporous aerogel.

57. The process according to claim 54, wherein step (ii) further comprises: (b1) Apply the wet gel matrix to a substrate to form a wet gel film coated on the substrate; and (b2) The wet gel film is dried by solvent evaporation and / or heat treatment to provide a dry silica-based coated substrate.

58. The process according to claim 54, wherein the drying step (ii) is vacuum drying or freeze drying.

59. The process of claim 54, wherein the amino-substituted silane has Formula 1 as defined in claim 6.

60. The process of claim 54, wherein the alkyl-substituted silane is as defined in formula 2 of claim 9.

61. The process of claim 54, wherein the process further comprises preparing the aerogel composite material by: (c1) Compressing a mixture of the dried silica-based microporous aerogel, one or more additives, and optionally a lubricant into granules, wherein the additives have a loading of 5% to 35% by weight; or (c2) Liquid extrusion of a mixture consisting of the dried silica-based microporous aerogel, one or more additives and optionally a lubricant to provide a viscous paste, wherein the additives have a loading of 5% to 35% by weight.

62. The process of claim 54, wherein one or more additives are selected from binders, optionally present metal-organic frameworks, and nanoparticles.

63. The process of claim 54, wherein the aerogel is provided as a plurality of particles, powders, granules, coatings, or films.

64. The process of claim 54, wherein the aerogel is provided as a sheet / layer.

65. The process according to claim 54, wherein the aerogel is a self-supporting silica-based microporous aerogel.

66. The process according to claim 54, wherein the solvent is water, a non-aqueous solvent, or a combination thereof.

67. The process according to claim 54, wherein the process further comprises step (iii) activation step.

68. The process of claim 54, wherein the amount of amino-substituted silane is in the range of 10% to 80% based on the total microporous aerogel.

69. The process of claim 54, wherein the amount of alkyl-substituted silane is in the range of 10% to 80% based on the total microporous aerogel.

70. A silica-based microporous aerogel for carbon dioxide capture, wherein the microporous aerogel comprises a plurality of pores, wherein at least 50% of the pores have a diameter of less than 2 nm, and is prepared by the process according to claim 54.

71. A silica-based microporous aerogel for carbon dioxide capture, wherein the microporous aerogel comprises a plurality of pores, wherein at least 50% of the pores have a diameter of less than 2 nm, the microporous aerogel comprising the microporous aerogel according to any one of claims 26 to 43, and prepared by the process according to claim 54.

72. A process for capturing carbon dioxide from a CO2-containing gas stream or atmosphere, comprising: The airflow or atmosphere is brought into contact with the aerogel to capture at least some CO2 from the airflow or atmosphere. The aerogel thereon is a silica-based microporous aerogel according to any one of claims 1 and 26 to 43, or a silica-based microporous aerogel prepared by the process described in claim 54.

73. The process of claim 72, wherein the gas stream or atmosphere has a CO2 concentration of less than 150,000 ppm.

74. The process of claim 72, wherein the airflow or atmosphere has a CO2 concentration in the range of 3,000 ppm and 150,000 ppm, wherein the process is a direct air capture at an external power plant.

75. The process of claim 72, wherein the gas stream or atmosphere has a CO2 concentration of less than 7,000 ppm.

76. The process of claim 72, wherein the gas stream or atmosphere has a CO2 concentration of less than 5,000 ppm.

77. The process of claim 72, wherein the airflow or atmosphere has a CO2 concentration in the range of 4,000 ppm and 5,000 ppm, wherein the process is a direct air capture of exhaled gas in a mask.

78. The process of claim 72, wherein the airflow or atmosphere has a CO2 concentration in the range of 4,000 ppm and 5,000 ppm, wherein the process is a direct air capture of exhaled gases in a personal protective device.

79. The process of claim 72, wherein the airflow or atmosphere has a CO2 concentration of less than 2,000 ppm, wherein the process is a direct air capture in a sealed indoor environment.

80. The process according to claim 72, wherein the airflow or atmosphere is ambient air.

81. The process of claim 72, wherein the airflow or atmosphere has a carbon dioxide concentration of less than 500 ppm, wherein the process is direct air capture.

82. The process of claim 72, wherein contacting the airflow or atmosphere with the aerogel comprises passing the airflow or atmosphere through a bed comprising the aerogel.

83. The process of claim 72, wherein at least 50% to 99% of CO2 is removed from the gas stream or atmosphere.

84. The process of claim 72, wherein the process further comprises a regeneration and recovery process to desorb the adsorbed CO2 from the aerogel.

85. The process of claim 84, wherein the regeneration and recycling process comprises heating the aerogel to a temperature range between 60°C and 140°C by depressurization, by a gas stream having low CO2, or a combination thereof, to desorb the adsorbed CO2 from the aerogel.

86. The process of claim 85, wherein the aerogel is heated by contacting the aerogel with steam.

87. An adsorption device for capturing carbon dioxide from a CO2-containing gas stream or atmosphere, comprising: A chamber is formed by sealing at least one silica-based microporous aerogel as described in any one of claims 1 and 26 to 43 and / or a silica-based microporous aerogel prepared by the process according to claim 54, the chamber comprising an inlet and an outlet, wherein an airflow may flow through the inlet to the silica-based microporous aerogel and an outflow airflow may flow out from the silica-based microporous aerogel through the outlet.

88. The device of claim 87, wherein the at least one silica-based microporous aerogel is located between the inlet and outlet of the chamber, and wherein the inlet and outlet are located at opposite ends of the chamber.

89. The device of claim 87 or claim 88, wherein the chamber comprises a silica-based microporous aerogel in granular form.

90. The device of claim 89, wherein the chamber comprises a substrate coated with the silica-based microporous aerogel located in or filling the chamber.

91. The device according to claim 87 or claim 88, wherein the device comprises two or more chambers enclosing at least one silica-based microporous aerogel, the chambers being connected in parallel with the gas flow.

92. The device according to claim 87 or claim 88, wherein the device comprises at least three chambers, each chamber being sealed with at least one silica-based microporous aerogel, wherein each chamber is connected in parallel with the gas flow.

93. The device according to claim 92, wherein, The silica-based microporous aerogel, enclosed in the at least three chambers, operates in different sections of the adsorption and regeneration cycle to generate a continuous flow of the outflow gas.

94. The apparatus of claim 93, wherein the outflowing gas from the outlet flows to various secondary processes.

Images