Methods for capturing sulfur dioxide

Abstract

The present disclosure relates to manganese metalloxerogels, processes for their preparation, and their use in gas capture applications. The manganese metalloxerogels are reaction products comprising at least one amino substituted silane of Formula 1, at least one substituted silicate of Formula 2, and at least one manganese salt, forming a cross-linked manganese–silicate sol-gel network having mesoporosity. By controlling the ratios of amino substituted silane, substituted silicate, and manganese ion, the pore structure and selectivity of the materials can be tuned. The manganese metalloxerogels are suitable for use in capturing sulfur dioxide (SO₂) from gaseous streams or the atmosphere.

Description

[0001] Methods for capturing sulfur dioxide

[0002] FIELD

[0003] The present disclosure generally relates to a manganese metalloxerogel and a method for capturing sulfur dioxide from a gaseous stream or an atmosphere containing sulfur dioxide with a manganese metalloxerogel.

[0004] BACKGROUND

[0005] Toxic industrial chemical gases (TICs) are harmful substances released during industrial processes and activities, such as chemical manufacturing, petrochemical refining and metal production. These gases can pose a serious threat to human health and the environment. One such TIC is sulfur dioxide, which is produced for example during the burning of fossil fuels. It is found in the atmosphere and is usually present in high concentrations in urban and industrial locations.

[0006] Sulfur dioxide is a respiratory irritant that is highly soluble in the aqueous surfaces of the respiratory airways. Because of this high solubility, most of the sulfur dioxide is absorbed in the nose and upper airways and very little reaches the lungs directly. Exposure to sulfur dioxide can lead to respiratory problems, skin irritation, eye damage, and, in severe cases, even death.

[0007] The efficient capture, storage and controlled release of TICs in general and SO2 in particular is still a challenge in the material science field. While there have been recent developments in the use of porous materials, such as metal-organic frameworks, for capturing sulfur dioxide, most systems known to date are inefficient, expensive and complex.

[0008] Consequently, there is a need to provide a technology that allows efficient, reliable, cheap and safe SO2 capture and storage.

[0009] SUMMARY

[0010] The present disclosure provides a manganese metalloxerogel, processes for preparing a manganese metalloxerogel, and applications for manganese metalloxerogels. The present inventors have undertaken research and development into methods for capturing sulfur dioxide (SO2) from a gaseous stream or atmosphere using the manganese metalloxerogels of the present disclosure.

[0011] In one aspect, there is provided a manganese metalloxerogel comprising a reaction product comprising of at least one amino substituted silane according to Formula 1, at least one substituted silicate according to Formula II and at least one manganese salt, wherein Formula 1 is: R1Si(OR2)2-L-NH2, wherein: R1is a substituted or unsubstituted Ci-ealkyl; R2is a Ci- ealkyl; L is a -Ci-ealkyl- linker group between the silicon and nitrogen atom; Formula II is: Si(OR7)4, wherein: R7may be Ci-ealkyl and wherein: the manganese metalloxerogel is selective for sulfur dioxide (SO2)gas capture. In an embodiment, the at least one amino substituted silane may be 3-aminopropyl (diethoxy) methyl silane (APEMS).

[0012] In a further embodiment, the at least one substituted silicate may be triethyl orthosilicate (TEOS).

[0013] In embodiments the mol ratio of amino substituted silane to silicate to manganese ion is in the range between 0.6-1 :0.2-0.70:0.1-0.5.

[0014] In embodiments, the amino substituted silane may have a % loading of between about 35 mol% to about 70 mol%, the substituted silicate may have a % loading of between about 10 mol% to about 35 mol% and the manganese may have a % loading of between about 15 mol% to about 50 mol%.

[0015] In embodiments, the mol% of the manganese salt is less than or equal to the mol% of the amino substituted silane. In further embodiments, the mol% of silicate is less than the amino substituted silane.

[0016] In embodiments, the manganese in the manganese metalloxerogel may have a % loading less than or equal to 50 mol%. In embodiments, the manganese in the manganese metalloxerogel has a % loading of between about 15 mol% to about 50 mol%.

[0017] In embodiments, the amount of the manganese in the manganese metalloxerogel may be effective for facilitating sulfur dioxide (SO2) capture.

[0018] In embodiments, the silicate in the manganese metalloxerogel may have a % loading of less than or equal to 50 mol%. In embodiments, the silicate in the manganese metalloxerogel has a % loading of between about 15 mol% to about 50 mol%.

[0019] In embodiments, the manganese metalloxerogel may be in the form of a metalloxerogel composite, wherein the composite further comprises one or more additives.

[0020] In embodiments, the one or more additives may be selected from the group comprising or consisting of a metal-organic framework (MOF), a binder, a lubricant, and a buffer, or combinations thereof.

[0021] In embodiments, the binder may be selected from organic or inorganic binders. Organic binders may be selected from the group comprising or consisting of a cellulose-based polymer, a silane-based polymer, cellulose-siloxane-based polymers, polyglycol-based polymers, epoxy-based polymers, colloidal silica, a polyvinyl pyrrolidone, a polyvinyl alcohol, a polyethylene imine, a polyethylene glycol, a polyvinyl butyral, a thermoplastic polyurethane, a thermoplastic fluoropolymer or combinations thereof. Inorganic binders may be selected from clays, alumina or silica based binders.

[0022] In some embodiments or examples, the composite may be self-supporting in the form of a pellet, bead, sheet or granule. In other embodiment, the composite may be applied as a coating composition, paste or film on a substrate.

[0023] In embodiments, the manganese being present in the metalloxerogel as manganese ions or manganese-containing species derived from the manganese salt. The manganese salt may be selected from the group comprising or consisting of manganese chloride, manganese iodide, manganese bromide, manganese acetate, manganese sulfate, manganese nitrate, manganese citrate, manganese triflate, manganese oxide, manganese carbonate and manganese gluconate. In a preferred embodiment, the manganese salt may be manganese chloride.

[0024] In embodiments, the amino substituted silane is provided in excess of the metal ion.

[0025] In an embodiment, the metalloxerogel composite for SO2 capture may comprise: (i) a manganese metalloxerogel consisting of or consisting essentially of a reaction product of an amino substituted silane, preferably 3-aminopropyl (diethoxy) methyl silane (APEMS); a substituted silicate, preferably triethyl orthosilicate (TEOS); and a manganese salt, preferably selected from manganese chloride, manganese iodide, manganese bromide, manganese acetate, manganese sulfate, manganese nitrate, manganese citrate, manganese triflate, manganese oxide, manganese carbonate and manganese gluconate; and (ii) optionally one or more additives; wherein the one or more additives, when present, may be selected from the group consisting of a metal-organic framework (MOF), a binder, a lubricant, and a buffer, or combinations thereof.

[0026] In another aspect, there is provided a process for preparing a metalloxerogel according to any one or more embodiments or examples described herein, the process comprising the steps of: (i) mixing an aqueous solution comprising at least one manganese metal salt together with a solvent system comprising at least one amino substituted silane and at least one substituted silicate, optionally one or more additives, to form a wet-gel matrix comprising the one or more manganese metals bonded within a cross-linked manganese-silicate sol gel network; and (ii) drying the wet-gel matrix to provide a dried manganese metalloxerogel; with the proviso that drying the wet-gel matrix does not involve supercritical CO2.

[0027] In embodiments, the process may be a sol gel process and step (ii) may comprise: (al) 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 dried manganese metalloxerogel. In embodiments, the drying step (ii) may be an ambient pressure drying or a vacuum drying step.

[0028] In another aspect there is provided a method for capturing sulfur dioxide (SO2) from a gaseous stream or atmosphere containing sulfur dioxide (SO2) comprising: contacting the gaseous stream or atmosphere with a manganese metalloxerogel for capturing at least some of the sulfur dioxide (SO2) from the gaseous stream or atmosphere, wherein the manganese metalloxerogel may be a reaction product of at least one amino substituted silane, at least one substituted silicate and at least one manganese salt.

[0029] In embodiments, the gaseous stream or atmosphere may have a sulfur dioxide (SO2) concentration of less than about 10,000 ppm.

[0030] In embodiments, at least about 50% to 99% of the sulfur dioxide (SO2) may be removed from the gaseous stream or atmosphere.

[0031] BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Preferred embodiments of the present disclosure will be further described and illustrated, by way of example only, with reference to the accompanying drawings in which:

[0033] Figure 1 shows the N2 gas adsorption isotherms measured at 77K for Examples 1(a)- 2(c).

[0034] Figure 2 shows the CO2 gas adsorption isotherms measured at 298K for Examples Series 1 and 2. CO2 was used as a model gas for toxic industrial chemical gas (TIC) sorption capacity.

[0035] Figure 3 shows the pore size distribution of the exemplified cases. The plots were determined by a density functional theory fit to the data obtained in Figure 1.

[0036] Figure 4 shows stacked 29 regions from the diffractograms collected of Examples 1(b) to 2(c).

[0037] Figure 5 shows 5-85° 29 regions from the diffractogram for Example 1(a).

[0038] Figure 6 shows Transmission Electron Microscope images of Examples l(a)-(c) and 2(a).

[0039] Figure 7 shows Transmission Electron Microscope images of Examples 2(b) and 2(c).

[0040] DETAILED DESCRIPTION

[0041] The present disclosure describes the following various non-limiting embodiments, which relate to investigations undertaken to identify processes for capturing sulfur dioxide (SO2) from gaseous streams (e.g. atmosphere) containing sulfur dioxide (SO2) using manganese metalloxerogels. It was surprisingly found that manganese metalloxerogels could be used to efficiently absorb sulfur dioxide (SO2) from a gaseous stream and atmosphere.

[0042] General Definitions and Terms

[0043] In the following description, reference is made to the accompanying drawings which form a part hereof, and which is shown, by way of illustration, several embodiments. It is understood that other embodiments may be utilised and structural changes may be made without departing from the scope of the present disclosure.

[0044] With regards to the definitions provided herein, unless stated otherwise, or implicit from context, the defined terms and phrases include the provided meanings. Unless explicitly stated otherwise, or apparent from context, the terms and phrases below do not exclude the meaning that the term or phrase has acquired by a person skilled in the relevant art. The definitions are provided to aid in describing particular embodiments, and are not intended to limit the claimed invention, because the scope of the invention is limited only by the claims. Furthermore, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular.

[0045] All publications discussed and / or referenced herein are incorporated herein in their entirety.

[0046] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present disclosure. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.

[0047] Throughout this disclosure, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality (i.e., one or more) of those steps, compositions of matter, groups of steps or groups of compositions of matter. Thus, as used herein, the singular forms “a”, “an” and “the” include plural aspects unless the context clearly dictates otherwise. For example, reference to “a” includes a single as well as two or more; reference to “an” includes a single as well as two or more; reference to “the” includes a single as well as two or more and so forth.

[0048] Those skilled in the art will appreciate that the disclosure herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the disclosure includes all such variations and modifications. The disclosure also includes all of the examples, steps, features, methods, compositions, coatings, processes, and coated substrates, referred to or indicated in this specification, individually or collectively, and any and all combinations or any two or more of said steps or features.

[0049] The term “and / or”, e.g., “X and / or Y” shall be understood to mean either “X and Y” or “X or Y” and shall be taken to provide explicit support for both meanings or for either meaning.

[0050] Unless otherwise indicated, the terms “first,” “second,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to a “second” item does not require or preclude the existence of lower-numbered item (e.g., a “first” item) and / or a higher-numbered item (e.g., a “third” item).

[0051] As used herein, the phrase “at least one of’, when used with a list of items, means different combinations of one or more of the listed items may be used and only one of the items in the list may be needed. The item may be a particular object, thing, or category. In other words, “at least one of’ means any combination of items or number of items may be used from the list, but not all of the items in the list may be required. For example, “at least one of item A, item B, and item C” may 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 item A, item B, and item C” may mean, for example and without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination.

[0052] As used herein, the term “about”, unless stated to the contrary, typically refers to + / - 10%, for example + / - 5%, of the designated value.

[0053] It is to be appreciated that certain features that are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any sub-combination.

[0054] Throughout the present specification, various aspects and components of the invention can be presented in a range format. The range format is included for convenience and should not be interpreted as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range, unless specifically indicated. For example, description of a range such as from 1 to 5 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 5, from 3 to 5 etc., as well as individual and partial numbers within the recited range, for example, 1, 2, 3, 4, 5, and 6, unless where integers are required or implicit from context. This applies regardless of the breadth of the disclosed range. Where specific values are required, these will be indicated in the specification.

[0055] Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0056] Throughout this specification, the term “consisting essentially of’ is intended to exclude elements which would materially affect the properties of the claimed composition.

[0057] Throughout this specification the word “consisting of’ will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, and the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0058] The terms “comprising”, “comprise” and “comprises” herein are intended to be optionally substitutable with the terms “consisting essentially of’, “consist essentially of’, “consists essentially of’, “consisting of’, “consist of’ and “consists of’, respectively, in every instance.

[0059] Herein the term “about” encompasses a 10% tolerance in any value or values connected to the term.

[0060] The reference to “substantially free” generally refers to the absence of that compound or component in the composition other than any trace amounts or impurities that may be present, for example this may be an amount by weight % in the total composition of less than about 1%, 0.1%, 0.01%, 0.001%, or 0.0001%. The compositions as described herein may also include, for example, impurities in an amount by weight % in the total composition of less than about 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.01%, 0.001%, or 0.0001%. For example, this may be an amount by vol. % in the total gaseous stream of less than about 0.001%, or 0.0001%. For example, the gaseous streams as described herein may also include, for example, impurities in an amount by vol. % in the total gaseous stream of less than about 0.01%, 0.001%, or 0.0001%.

[0061] Herein “weight %” may be abbreviated to as “wt.%”.

[0062] The term “alkyl” includes straight-chained and branched, and includes both unsubstituted and substituted alkyl groups. In one example, the alkyl groups are straight- chained and / or branched alkyl groups. Unless otherwise indicated, the alkyl groups typically contain from 1 to 6 carbon atoms. The alkyl groups may for example contain carbon atoms from 1 to 6, 1 to 5, 1 to 4, 1 to 3 or 1 to 2. Examples of “alkyl” as used herein include, but are not limited to, methyl, ethyl, n-propyl. n-butyl, n-pentyl, isobutyl, t-butyl, isopropyl and the like. Unless otherwise noted, alkyl groups may be mono- or polyvalent. The alkyl groups may be optionally substituted and / or optionally interrupted by one or more heteroatoms. The alkyl groups may be referred to as “-alkyl-“ in relation to use as a bivalent or polyvalent linking group.

[0063] The term "alkylsilyl" represents an alkyl group that is linked to the rest of the molecule through the silicon atom, which may be unsubstituted or substituted with up to three independently selected alkyl groups in which each alkyl group is as defined supra.

[0064] The term “manganese” refers to the chemical element manganese. The metal may be in its ionic form as a positively charged metal cation.

[0065] Unless specified otherwise, the term “salt” refers to a chemical compound comprising an ionic assembly of positively charged cations and negatively charged anions. When the cation is a metal cation, such as a manganese ion, it may be referred to as “metal ion” or “manganese salt”. Typical anions include inorganic and organic anions, including but not limited to chloride, fluoride, bromide, iodide, acetate, citrate, nitrate, gluconate, sulfate, tritiate, carbonate, hydroxide, and oxide.

[0066] The term “selective” in the context of gas absorbance or capture refers to the absorbance or capture of a particular gas in preference to other gases present in a gaseous stream. For example, the term “selective” may mean that more than 50% of a particular gas is preferentially absorbed from a mixture of gases. Preferably, more than 60% or more than 70% or more than 80% or more than 90% of a particular gas is selectively absorbed from a mixture of gases. Alternatively, the selective absorption may be expressed in a range. For example, between about 50% to about 99%, or between about 60% to about 99%, or between about 70% to about 99%, or between about 80% to about 99%, or between about 90% to about 99% of a particular gas may be absorbed from a mixture of gases.

[0067] Manganese metalloxerogels and processes for preparing the same

[0068] The present disclosure relates to manganese metalloxerogels and various applications in the capture of sulfur dioxide (SO2) from a gaseous stream or atmosphere.

[0069] It will be appreciated that the selection of each component of the manganese metalloxerogel, as well as the process conditions, plays an important role in defining the properties of the manganese metalloxerogels of the present disclosure. In some embodiments, the manganese metalloxerogel may be a mesoporous manganese metalloxerogel capable of SO2 gas capture. The present inventors have surprisingly found that the manganese metalloxerogel composition can be tailored to provide improved control and selectivity for increased SO2 absorption efficiency. The manganese metalloxerogels described herein are formed through a sol-gel process involving at least one amino substituted silane, at least one substituted silicate and a manganese salt. The mol ratio of amino substituted silane to manganese ion to substituted silicate, may be precisely controlled to directly influence the porosity, surface area, and SO2 adsorption characteristics of the resulting manganese metalloxerogel. Maintaining an excess of amino substituted silane relative to the manganese ion can facilitate the formation of open, porous networks that promote rapid gas diffusion and high adsorption capacity. The amino groups serve as coordination points for manganese ions, ensuring uniform dispersion within the matrix, minimising aggregation, and providing a high density of active sites accessible for SO2 binding.

[0070] The use of amino substituted silanes bearing two alkoxy groups (i.e., where n = 2) contributes to a reduced crosslinking density in the siloxane backbone, allowing the manganese metalloxerogels to retain structural integrity during drying, with minimal shrinkage or cracking. This results in materials with a consistent mesoporous architecture, mechanical robustness, and reproducible gas uptake performance.

[0071] The substituted silicate, such as tetraethyl orthosilicate (TEOS), acts as a covalent crosslinker to modulate network rigidity, pore size distribution, and bulk density, and is essential to produce the porous, amorphous manganese metalloxerogels of the present disclosure.

[0072] Unlike conventional porous sorbents that rely on rigid, highly crosslinked silica networks, the manganese metalloxerogels of the present disclosure allow for tunable network structures ranging from flexible, lightly crosslinked frameworks to more rigid architectures, without compromising porosity or gas accessibility.

[0073] The present disclosure provides a manganese metalloxerogel comprising a cross-linked manganese silicate sol gel network comprising a plurality of pores in a mesoporous form, thereby providing an ideal porosity for SO2 gas absorption. It will be appreciated by a person of skill in the art that a mesoporous metalloxerogel has pores with a diameter of between about 2 nm and about 50 nm whereas a microporous metalloxerogel contains pores with a diameter of less than 2 nm and a macroporous metalloxerogel contains pores larger than 50 nm. In some embodiments, the mesoporous manganese metalloxerogel may have a plurality of pores and at least 50% of the pore volume may be mesoporous (as measured by N2 gas adsorption isotherms, performed at 77K). Preferably, at least 55%, or 60%, or 65%, or 70%, or 75%, or 80%, or 85%, or 90%, or 92%, or 95%, or 98%, or 99% of the pore volume may be mesoporous (as measured by N2 gas adsorption isotherms, performed at 77K). In embodiments, the mesoporous manganese metalloxerogel may have a plurality of pores and between 50% and 99%, or between 55% and 99%, or 60% and 99%, or 65% and 99%, or 70% and 99%, or 75% and 99%, or 80% and 99%, or 85% and 99%, or 90% and 99% of the pore volume may be mesoporous (as measured by N2 gas adsorption isotherms, performed at 77K).

[0074] In some embodiments, less than 30% of the pore volume may be microporous (as measured by N2 gas adsorption isotherms, performed at 77K or CO2 gas adsorption isotherms, performed at 298K.

[0075] In some embodiments or examples, the manganese metalloxerogel may have a pore size in a range of from about 2 nm to about 50 nm, for example from about 2 nm to about 45 nm, or from about 2 nm to about 40 nm, or from about 2 nm to about 35 nm, or from about 2 nm to about 30 nm, or from about 2 nm to about 25 nm, or from about 2 nm to about 20 nm, or from about 2 nm to about 15 nm, or from about 2 nm to about 10 nm, or from about 2 nm to about 9 nm, or from about 2 nm to about 8 nm, or from about 2 nm to about 7 nm, or from about 2 nm to about 6 nm, or from about 2 nm to about 5 nm, or from about 2 nm to about 4 nm, or from about 2 nm to about 3.5 nm. The manganese metalloxerogel may have a pore size (nm) of at least about 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10. In other embodiments or examples, the manganese metalloxerogel may have a pore size (nm) of less than about 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4.9, 4.8, 4.7, 4.6, 4.5, 4.3, 4.2, 4.1, 4.0, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1 or 3. Combinations of these pore size values to form various ranges are also possible, for example the manganese metalloxerogel may have a pore size of between about 2 nm to about 35 nm, about 2.1 nm to about 15 nm, for example about 2.5 nm to about 8 nm. The pore size can be determined by any means known to the skilled person, such as gas adsorption experiments (i.e. N2 gas adsorption isotherms, performed at 77K, or CO2 gas adsorption isotherms, performed at 298K)), mercury intrusion, and capillary flow porometry. In particular, the pore size may be determined via a density functional theory fit using N2 or CO2 gas adsorption isotherms. It has been found that manganese metalloxerogel s wherein at least 50% of the pore volume may be mesoporous are produced during the simple single step one-pot synthesis described herein. It has also been found that manganese metalloxerogels wherein at least 50% of the pore volume may be mesoporous (as measured by N2 gas adsorption isotherms, performed at 77K) are most suitable for SO2 capture from a gaseous stream or atmosphere containing SO2.

[0076] In some embodiments or examples, the manganese metalloxerogel may have a BET surface area in a range of from about 3 m2 / g to about 1000 m2 / g, for example from about 100 m2 / g to about 900 m2 / g. The manganese metalloxerogel may have a BET surface area (m2 / g) of at least about 3, 4, 5, 10, 20, 50, 100, 200, 300, 400, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950 or 1000. In other embodiments or examples, the manganese metalloxerogel may have a BET surface area (m2 / g) of less than about 1000, 950, 900, 850, 800, 750, 700, 650, 600, 550, 500, 400, 300, 200, 100, 50, 20, 10, 5, 4 or 3. Combinations of these surface area values to form various ranges are also possible, for example the manganese metalloxerogel may have a BET surface area of between about 0.1 m2 / g to about 900 m2 / g, about 50 m2 / g to about 800 m2 / g, for example about 450 m2 / g to about 850 m2 / g. The BET surface area may be measured by N2 gas adsorption isotherms, performed at 77K.

[0077] It may be beneficial to define the metalloxerogels by their density. It will be appreciated that density is defined herein as bulk density of the metalloxerogel powder. The bulk density may be measured in accordance with ASTM C29, or for example, as follows: a 1 mL vile is filled with metalloxerogel powder and the weight of metalloxerogel fitting into the 1 mL vile is measured. It will be understood that 1 g of metalloxerogel in a 1 mL vile corresponds to a metalloxerogel having a density of 1 g / cm3. In some embodiments or examples, the density of the metalloxerogel may be in a range of from about 0.02 g / cm3to about 1.0 g / cm3, for example from about 0.1 g / cm3to about 0.8 g / cm3. The density of the manganese metalloxerogel may 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, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 or 1.0 g / cm3. In other embodiments or examples, the density of the manganese metalloxerogel may be less than about 1.0, 0.95, 0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 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. Combinations of these density values to form various ranges are also possible, for example the manganese metalloxerogel may have a density of between about 0.02 g / cm3to about 0.6 g / cm3, about 0.05 g / cm3to about 0.5 g / cm3, about 0.15 m2 / g to about 0.4 g / cm3, for example, about 0.2 m2 / g to about 0.6 m2 / g, or about 0.3 m2 / g to about 0.6 m2 / g. It will be appreciated that the density of the manganese metalloxerogel can be optimised by variation in the amount of the covalent crosslinker (e.g. the substituted silicate component, TEOS) and / or the amount of manganese / amino substituted silane. Higher density metalloxerogels would be most suited for application where weight is a consideration. Formulations with high density can be used for gas adsorption-desorption devices that may fit into restricted spaces or environments. For example, metalloxerogel formulations with high density can be used to prepare adsorptiondesorption devices such as respirators. These types of devices can be typically used in space, aerospace, underwater vehicles or platforms. For example in aerospace or space applications where metalloxerogels can be used to capture gas from atmospheric air. Formulations with low density may be suitable when space is not an issue. The manganese metalloxerogel can be provided in a range or morphologies. Illustrative examples of suitable morphologies may include particles, powders, pellets, beads, coatings, sheets / layers, cast blocks, cylinders, discs, porous membranes and monoliths. For example, the manganese metalloxerogel may be provided as a plurality of pellets. For example, the manganese metalloxerogel may be provided as a film / coating layer, a gel layer where the gaseous stream may be flowed thereon or through the layer. Such layers may be a provided as a rolled sheet or a 3D substrate. Alternatively, the manganese metalloxerogel layer may also be provided as a monolith comprising a plurality of porous channels, wherein the gaseous stream flows through. Other layer or coating morphologies and geometries are also applicable.

[0078] In one embodiment or example, the manganese metalloxerogel may comprise a plurality of particles. The term “particle” (also referred to as “particulate”) refers to the form of discrete solid units. The units may take the form of flakes, fibres, agglomerates, granules, pellets, powders, beads, spheres, pulverized materials or the like, as well as combinations thereof. The particles may have any desired shape including, but not limited to, cubic, rod like, polyhedral, spherical or semi -spherical, rounded or semi-rounded, angular, irregular, and so forth. The particle morphology can be determined by any suitable means such as optical microscopy.

[0079] In some embodiments or examples, the metalloxerogel may be a plurality of particles, powders, pellets, beads, granules, coatings, or sheets / layers. For example, the manganese metalloxerogel may be provided as a plurality of particles, powders, pellets. In one example, the manganese metalloxerogel may be provided as a plurality of pellets.

[0080] In embodiments, the manganese metalloxerogel may be a reaction product of at least one amino substituted silane, at least one substituted silicate and at least one manganese salt. Without wishing to be bound by theory, it is hypothesised that the pore size of the manganese metalloxerogel can be tailored by varying the amount of the at least one amino substituted silane and the amount of the manganese ion. For example, the greater the amount of amino substituted silane and manganese ion the denser the metalloxerogel may be forming relatively smaller pore sizes. On the other hand, when the amount of amino substituted silane and manganese ion is reduced the metalloxerogel formed may be less dense with relatively larger pore sizes. It has been found that manganese-silicate based metalloxerogels containing low amounts of manganese demonstrate mesoporosity and good SO2 sorption properties.

[0081] In some embodiments or examples, the manganese metalloxerogel comprises a reaction product of at least one amino substituted silane and at least one substituted silicate. As demonstrated by the Examples, the addition of a substituted silicate, such as TEOS, is essential for the formation of a mesoporous gel capable of SO2 absorption. The backbone may comprise a siloxane backbone with a plurality of pendant groups selected from amino alkyl groups and alkyl groups. It will be appreciated that due to the hydrophobic amino alkyl groups and the alkyl groups present in the siloxane backbone, and only two siloxane bonds available per silicon atom, the manganese metalloxerogels, as described herein, may be hydrophobic and may generally have a lower cross-linking density and higher deformability than those derived from the conventional tetraalkoxysilanes. These advantageous characteristics may provide greater potential for further engineering the fine structures of the manganese metalloxerogels for achieving low volume shrinkage by the drying process without the use of further solvent exchange and surface modification. In some embodiments or examples, the reaction product of the at least one amino substituted silane and the at least one substituted silicate to form the silica based metalloxerogel backbone may undergo hydrolysis and condensation reactions to form polyalkylsiloxane network structures. These hydrolysis and condensation reactions may be responsible for the microstructures of the silica based metalloxerogel.

[0082] In an embodiment, the amino substituted silane may be according to Formula 1 : R1Si(OR2)2-L-NH2, wherein: R1may be a substituted or unsubstituted Ci-ealkyl; R2may be a Ci-ealkyl; L is a -Ci-ealkyl- linker group between the silicon and nitrogen atoms.

[0083] In an embodiment, the substituted silicate may be according to Formula 2: Si(OR7)4, wherein: R7may be Ci-ealkyl.

[0084] In an embodiment or example, the manganese metalloxerogel may comprise, consist essentially of or consist of a reaction product of at least one amino substituted silane, at least one substituted silicate, and at least one manganese salt. It has been surprisingly found that manganese metalloxerogels produced using a manganese salt, such as manganese chloride, and a combination of APEMS and TEOS are shown to have mesoporosity, with gels containing no or very low TEOS having a very low BET surface area, and almost no SO2 absorption, whereas metalloxerogels with TEOS show higher surface areas and good SO2 sorption. Manganese metalloxerogels containing lower manganese concentration were also found to have mesoporosity and good SO2 sorption properties, furthermore at most concentrations, the manganese ions are found to bind in a form such that the counterions (such as chloride) are almost entirely removed during purification.

[0085] In an embodiment or example, the manganese metalloxerogel may comprise or consist of a reaction product of an amino substituted silane according to Formula 1, a substituted silicate according to Formula 2 and a manganese salt. In an embodiment, the amino substituted silane is according to Formula 1 and has a % loading of between about 35 mol% to about 70 mol%, preferably between about 40 mol% to about 60 mol%, the substituted silicate is according to Formula 2 and has a % loading of between about 10 mol% to about 35 mol% and the manganese has a % loading of between about 15 mol% to about 50 mol%, preferably between about 20 mol% to about 50 mol%, even more preferably between about 30 mol% to about 50 mol%.

[0086] In an embodiment or example, the manganese metalloxerogel may comprise or consist of a reaction product of an amino substituted silane, a substituted silicate and a manganese salt, wherein the amino substituted silane is 3 -aminopropyl (di ethoxy) methyl silane (APEMS) with a % loading of between about 35 mol% to about 70 mol% and the substituted silicate is tetraethyl orthosilicate (TEOS) with a % loading of between about 10 mol% to about 35 mol% and the manganese has a % loading of between about 15 mol% and about 50 mol%.

[0087] In some embodiments or examples, there is provided a process for preparing a manganese metalloxerogel. In particular, the present disclosure provides a process for preparing a manganese metalloxerogel s, as described herein, from the reaction product of at least one amino substituted silane, at least one substituted silicate, and at least one manganese salt. In some embodiments, the process for preparing a manganese metalloxerogel, wherein the metalloxerogel comprises a plurality of pores and at least 50% of the pore volume is mesoporous, may comprise or consist of: (i)(a) mixing an aqueous solution comprising at least one manganese salt together with a solvent system comprising at least one amino substituted silane, preferably according to Formula 1, and at least one substituted silicate, preferably according to Formula 2, optionally a buffer, optionally one or more additives, to form a wetgel matrix; and (ii) drying the wet-gel matrix to provide a dried manganese metalloxerogel, with the proviso that drying the wet-gel matrix does not involve supercritical CO2. In some embodiments or examples, step (i) further comprises step (i)(b) rinsing the wet-gel matrix. Rinsing the wet-gel enables solvent exchange and the removal of by-products, such as the counter ions (manganese ions) of the manganese salt, within the pores of the materials. One or more advantages of the present process according to at least some embodiments or examples as described herein is that the process is a scalable one pot synthesis with short reaction times (e.g. approximately 6 hours for some formulations compared to 48 hours or more) and gelation times (e.g. approximately 5 to 30 minutes) to prepare mesoporous manganese metalloxerogels capable of SO2 capture. The synthesis and washing steps require an oven or water bath and rudimentary reaction vessels. No specialised gasses or pressure vessels are necessary for the described process, and the typical density of the preferred candidates may be in the range of 0.3 to 0.8g / mL, allowing smaller volume of metalloxerogel to be used in practical manifestations of a gas capture apparatus. Furthermore, the drying does not require supercritical drying using CO2, freeze drying or any other harsh drying conditions. Hence, the financial advantages in both synthesis cost and equipment costs are greatly advantageous.

[0088] For example, in step (i) mixing an aqueous solution comprising at least one manganese salt with a solvent system comprising at least one amino substituted silane and at least one substituted silicate, and, optionally a buffer, optionally one or more additives, to form a wetgel matrix, may proceed at ambient temperature for at least 24 hours or may be heated to between about 60°C and about 80°C for about 6 hours. In step (i)(b), rinsing the wet-gel matrix in a sufficient amount of water to exchange solvent (e.g. ethanol) with water allows the wetgel matrix to dry (in step (ii)) to form an open porous gel (e.g. a dried manganese metalloxerogel). Failure to remove the solvent may result in a “hard” gel with poor performance. The wet-gel matrix rinsed in sufficient amounts of 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.

[0089] In some embodiments or examples, the process may be a sol gel process and step (ii) may comprise or consists of: (al) 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 dried manganese metalloxerogel.

[0090] In other embodiments or examples, the process may comprise an alternate step (ii) which may comprise: (bl) wherein the wet gel matrix may be applied to a substrate to form a wet-gel film coating the substrate; and (b2) drying the wet-gel film by solvent evaporation and / or heat treatment to provide a dried silica-based coated substrate. In an embodiment or example, the drying step (ii) may be vacuum drying or ambient pressure drying at below 80 °C. It will be appreciated that the drying step (ii) does not involve supercritical CO2.

[0091] In step (i) an alcogel or step (al) a sol gel (e.g. a colloidal solution) may be formed from the process that gradually evolves towards the formation of a gel-like diphasic system containing both the liquid phase and the solid phase whose morphologies may range from discrete particles to continuous polymer networks (ageing process). In some embodiments or examples, the particle density may be low such that an amount of liquid may need to be removed initially for the gel-like properties to be recognized. In another embodiment or example, centrifugation may be used to accelerate the process of phase separation and gel formation to form the aged alcogel or aged sol gel. Removal of the remaining liquid (solvent) phase may require a drying step (for example, step (ii) and step (a2)).

[0092] As demonstrated by the Examples, the manganese-silicate based metalloxerogels produced using manganese chloride and a combination of APEMS and TEOS are shown to have mesoporosity. Without wishing to be bound by theory, it is hypothesised that the addition of the substituted silicate increases the rigidity of the manganese-silicate network structure as it forms covalent bonds to four other silicon atoms. The amino substituted silane may form only two covalent bonds in the siloxane network structure allowing flexibility.

[0093] Prior to step (al) and (bl) the wet-gel matrix may be heated to a suitable temperature and maintained at the temperature (ageing 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 to about 30°C, about 25 °C to about 80°C, or about 75°C to about 85°C.

[0094] At least according to some embodiments or examples as described herein, the wet-gel matrix may be heated to the desired temperature by immersing the reaction vessel in an oven at the required temperature and the solution allowed to reach the required temperature.

[0095] At least according to some embodiments or examples as described herein, the wet-gel matrix may be maintained at the temperature in step (al) and (bl) for about 3 hours to about 24 hours. The wet-gel matrix may be maintained at the temperature of step (al) and (bl) for at least about 3, 6, 9, 12, 15, 18, 21 or 24 hours. The wet-gel matrix may be maintained at the temperature of step (al) and (bl) 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.

[0096] In some embodiments or examples, the wet-gel matrix may then be cooled to ambient temperature for step (al) and (bl). In an embodiment or example, the wet-gel matrix may be cooled to ambient temperature.

[0097] In an example, after formation of the wet-gel may, residual solvent and organic reaction products may be removed to avoid plasticizing the wet-gel matrix. These are interchanged with water by breaking up the matrix and soaking in at least 10 times excess of water, for no less than 1 hour. The water interchange may protect the wet-gel matrix from collapsing and also may allow any unreacted silanes to form Si-O-Si bonds. Insufficient interchange of water may result in gels that do not resemble typical metalloxerogels dried using traditional methods. The incorporation of amino substituted silanes such as those of Formula 1 (e.g. 3 -aminopropyl (diethoxy) methyl silane) means that the solvated matrix still has plastic properties, unlike the traditional silica-containing gels where all the silicon atoms are covalently bound to no fewer than three other oxygen atoms. When evaporating the solvent in air during drying of the wet-gel matrix, the wet-gel matrix is likely to undergo contraction and cracking caused by differences in capillary force and solvent extraction rate at an air / liquid interface during the drying process, and a supercritical drying process is conventionally used to suppress this. However, supercritical drying is performed at high pressure and increases manufacturing costs, thereby providing an obstacle in commercialization of silica-based gels.

[0098] One or more advantages of the present process according to at least some embodiments or examples as described herein is that the wet-gel matrix may be dried to obtain a dried manganese metalloxerogel by minimising the effects previously observed with other drying processes. The drying process described by the present disclosure may be performed in various advantageous ways, including reduced pressure drying, ambient pressure or in a vacuum drying, or various combinations thereof. Preferably, vacuum drying or ambient pressure drying in an oven at below about 80°C .

[0099] For step (ii) the wet-gel matrix may be dried at a temperature suitable to produce a dried manganese metalloxerogel. In an example, when the wet-gel matrix is dried using reduced pressure drying, the drying equipment may be controlled at about 40 to about 60°C, or about 55°C, the initial drying pressure may be ambient atmospheric pressure, and the vacuum pump may be turned on to start vacuum drying (-80kPa) for at least about 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hour, 18 hours, 20 hours, 22 hours or 24 hours, to produce the dry manganese metalloxerogel. In another example, when the wet-gel matrix is dried using ambient pressure or in an oven, the temperature may be controlled between about 40°C to about 80°C, or between about 40°C to about 60°C, or about 50°C and the wet-gel matrix is maintained under ambient pressure or in a vacuum for at least about 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hour, 18 hours, 20 hours, 22 hours or 24 hours, to produce the dry manganese metalloxerogel.

[0100] In some embodiments or examples, the amino substituted silane may be of Formula 1, as described herein. In some embodiments or examples, the substituted silicate may be of Formula 2, as described herein. In some embodiments or examples, the manganese salt may be as described herein.

[0101] In some embodiments or examples, the solvent may be water, a non-aqueous solvent, or a combination thereof. A variety of non-aqueous solvents may be used in step (i)(a) and step (i)(b) of the process, including alcohols containing between 1 and 6 carbon atoms. In an embodiment or example, the solvent may be selected from methanol, ethanol, propanol, butanol, isobutyl alcohol, t-butyl alcohol, pentanol, hexanol, and combinations thereof. In one embodiment or example, ethanol may be used as the solvent. For example, ethanol may be used in combination with water in the process. Water in various mol ratios may also be involved to accomplish the sol-gel reactions. Water may also be a product of some of these reactions. The mol ratios and solvents may be adjusted so that precipitation or phase separation can be avoided.

[0102] In some embodiments or examples, the process may further comprise step (iii) an activation step. The manganese metalloxerogels prepared by the process may be activated at temperature in a range or about 80°C to about 160°C. The activation temperature may be at least about 80, 90, 100, 110, 120, 130, 140, 150 or 160°C. The activation temperature may be less 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 may be between about 80°C to about 160°C, between about 90°C to about 150°C, or between about 100°C to about 140°C.

[0103] The metalloxerogel may be in form of a composite, wherein the composite optionally comprises one or more additives selected from the group comprising or consisting of metalorganic frameworks, nanoparticles and other porous materials, binders, lubricants, and buffers, or combinations thereof. The additive may be in an amount of about 5 to about 35 wt. % based on the total weight of the manganese metalloxerogel. In some embodiments or examples, the composite may be self-supporting in the form of a pellet, bead, sheet or granule. In other embodiment, the composite may be applied as a coating composition, paste or film on a substrate.

[0104] The nanoparticles may be selected from the group comprising carbon-based nanoparticles (e.g. fullerenes and carbon nanotubes), metal based nanoparticles (e.g. alkali and noble metals), ceramic nanoparticles, polymeric nanoparticles, lipid-based nanoparticles, quantum dots, silica nanoparticles, graphene, or combinations thereof. The nano-magnetic particles may be selected from the group comprising iron oxides, ferrite, or combinations thereof.

[0105] The binders may be selected from organic or inorganic binders. Organic binders may be selected from the group comprising cellulose-based polymers, silane-based polymers, cellulose-siloxane-based polymers, polygly col -based polymers, epoxy-based polymers, colloidal silica, polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene imine, polyethylene glycol, polyvinyl butyral, thermoplastic polyurethane, thermoplastic fluoropolymer or combinations thereof. Inorganic binders may be selected from clays, alumina or silica based binders. It will be appreciated that the binders as described herein may be selected from commercial binders and that other components may form part of the commercial binder. In an example, the binders may include other components such as a lubricant and / or a buffer.

[0106] The lubricating agent may be used as required to adjust the viscosity of the metalloxerogel formulation to, for example, an extrudable material. For example, the other components may include dicalcium phosphate, silicon dioxide, dextrose monohydrate and magnesium stearate.

[0107] The buffers may be selected from the group comprising (NF ^CCh, NH4CH3CO2, NH3, NH4HCO3, carbon dioxide.

[0108] Amino substituted silane

[0109] In some embodiments or examples, the amino substituted silane may comprise at least one or more aliphatic amine groups (e.g. an amine wherein no aromatic ring groups are directly bound to the nitrogen atom of the amine).

[0110] In some embodiments or examples, the amino substituted silane as described herein may be according to Formula 1 :

[0111] R1Si(OR2)2-L-NH2

[0112] Formula 1 wherein:

[0113] R1may be substituted or unsubstituted Ci-ealkyl;

[0114] R2may be Ci^alkyl;

[0115] L is a -Ci-i2alkyl- linker group between the silicon and nitrogen atoms.

[0116] In some embodiments or examples, the amino substituted silane may comprise a Ci- ealkyl which may be provided by any alkyl as described above or herein having a 1 to 6 atom chain.

[0117] In some embodiments or examples, the amino substituted silane may comprise a Ci- 4alkyl which may be provided by any alkyl as described above or herein having a 1 to 4 atom chain.

[0118] The alkyl groups of the amino substituted silane may comprise between 1 and 4 carbon atoms. The alkyl groups may be methyl, ethyl, propyl, n-butyl, t-butyl or other higher carbon alkyl groups. In some embodiments or examples, the amino substituted silane may be selected from the group comprising or consisting of 3 -aminopropyl (di ethoxy) methyl silane (APEMS).

[0119] In embodiments, the amount of the amino substituted silane present in the metalloxerogel may be in a range of from about 35 mol% to about 70 mol%, for example from about 35 mol% to about 70 mol%, or from about 40 mol% to about 60 mol%. The amount of the amino substituted silane may be at least about 35, 40, 45, 50, 55, 60, 65 or 70 mol%. In other embodiments or examples, the amount of the amino substituted silane may be less than or equal to about 70, 65, 60, 55, 50, 45, 40 or 35 mol%. Combinations of these values to form various ranges are also possible, for example the amount of the amino substituted silane may have a mol% value of between about 35 mol% to about 70 mol%.

[0120] Substituted silicate

[0121] A substituted silicate may be included in the manganese metalloxerogel matrix and may produce complex structures with unique properties relevant to the resulting manganese metalloxerogel. The substituted silicate may be according to Formula 2:

[0122] Si(OR7)4

[0123] Formula 2 wherein:

[0124] R7is Ci-ealkyl.

[0125] In some embodiments or examples, the substituted silicate may comprise a Ci-ealkyl which may be provided by any alkyl as described above or herein having a 1 to 6 atom chain.

[0126] The alkyl groups of the substituted silicate may comprise between 1 and 6 carbon atoms. The alkyl groups may be methyl, ethyl, propyl, n-butyl, t-butyl or other higher carbon alkyl groups. The substituted silicate of the present disclosure may be selected from a tetraalkoxy silane. For example, the substituted silicate may be tetramethyl orthosilicate, tetraethyl orthosilicate (TEOS), or combinations thereof.

[0127] In some embodiments or examples, the amount of substituted silicate may be in a range between about 10 mol% to about 35 mol% based on the total metalloxerogel. The amount of substituted silicate may be less than about 35, 30, 25, 20 or 15 mol%. Combinations of these amounts are possible, for example the amount of substituted silicate may be between about 10 mol% to about 35 mol%, between about 15 mol% to about 25 mol%, or between about 20 mol% to about 35 mol%.

[0128] Manganese Salts and Manganese Ions

[0129] Unless otherwise specified, the positively charged cation from a manganese salt is a manganese ion. A person of skill in the art would be able to determine suitable counter anions for the manganese cations, including inorganic and organic counterions. The negatively charged anions may include but are not limited to acetate, chloride, fluoride, bromide, iodide, carbonate, citrate, triflate, nitrate, gluconate, sulfate, hydroxide, and oxide.

[0130] In some embodiments or examples, the manganese salt may be selected from the group comprising or consisting of manganese chloride, manganese iodide, manganese bromide, manganese acetate, manganese sulfate, manganese nitrate, manganese citrate, manganese oxide, manganese carbonate, manganese triflate and manganese gluconate. In some embodiments, the manganese salt may be manganese chloride.

[0131] In embodiments, the manganese ion may have a % loading of at least 15, 20, 25, 30, 35, 40, 45 or 50 mol%. In embodiments, the manganese ion may have a % loading of in between about 15 mol% to about 50 mol%, or between about 20 mol% to about 50 mol%, or between about 25 mol% to about 50 mol%, or between about 30 mol% to about 50 mol%, or between about 35 mol% to about 50 mol%, or between about 40 mol% to about 50 mol%, or between about 45 mol% to about 50 mol%. In embodiments, the manganese ion may have a % loading of between about 15 mol% to about 45 mol%, or between about 20 mol% to about 45 mol%, or between about 25 mol% to about 45 mol%, or between about 30 mol% to about 45 mol%, or between about 35 mol% to about 45 mol%, or between about 40 mol% to about 45 mol%. In embodiments, the manganese ion may have a % loading of between about 10 mol% to about 40 mol%, or between about 15 mol% to about 40 mol%, or between about 20 mol% to about 40 mol%, or between about 25 mol% to about 40 mol%, or between about 30 mol% to about 40 mol%, or between about 35 mol% to about 40 mol. In embodiments, the manganese ion may have a % loading of less than 50, 47, 45, 42, 40, 37, 35, 32, 30, 27, 25, 22, 20, 17, or 15 mol%.

[0132] Without wishing to be bound by theory, it is hypothesised that the amino groups of the amino substituted silane unit coordinate to the manganese ions. It may be therefore beneficial to express the manganese ion loading as mol ratio between amino substituted silane and manganese ions wherein the amine groups are in excess of the metal ions.

[0133] In embodiments, the mol ratio of amino substituted silane to metal ion may be selected from 1 :0.1, 1 :0.2, 1 :0.25, 1 :0.3, 1 :0.4, 1 :0.5. Combinations of these values to form various ranges are also possible, for example, the mol ratio of amino substituted silane to metal ion may be in a range between 1 :0.1 and 1 :0.5, or expressed as a range selected from any two of the listed values. The number of mols of the metal ion is either equal or less than the number of mols of the amino substituted silane. In embodiments, the mol ratio of amino substituted silane to substituted silicate may be selected from 1 :0.7, 1 :0.6, 1 :0.5, 1 :0.4, 1 :0.2. Combinations of these values to form various ranges are also possible, for example, the mol ratio of amino substituted silane to substituted silicate may be in a range between 0.75-1 :0.2-0.7, or expressed as a range selected from any two of the listed values.

[0134] In embodiments, the mol ratio of amino substituted silane to manganese ion to substituted silicate may be selected from 0.75-1 :0.2-0.7:0.1-0.5. Combinations of these values to form various ranges are also possible.

[0135] In embodiments, the amount of manganese ion may be effective for facilitating sulfur dioxide (SO2) capture.

[0136] It will be appreciated that the amino substituted silane, substituted silicate and manganese ion as described above may be as described for any aspect, embodiment, or combination of embodiments.

[0137] Gas capture from gaseous streams or the atmosphere

[0138] The manganese metalloxerogels of the present disclosure can be used to capture sulfur dioxide (SO2) from a gaseous stream or atmosphere containing sulfur dioxide (SO2). It has been surprisingly found that the incorporation of manganese ions into the silica based metalloxerogel allows efficient capture of SO2 from a gaseous stream or atmosphere containing sulfur dioxide SO2.

[0139] In embodiments, the method for capturing sulfur dioxide SO2 from a gaseous stream or atmosphere containing sulfur dioxide (SO2) comprises: contacting the gaseous stream or atmosphere with a manganese metalloxerogel for capturing at least some of the sulfur dioxide (SO2) from the gaseous stream or atmosphere, wherein the manganese metalloxerogel may be as described herein. In an embodiment, the manganese metalloxerogel may be a reaction product of at least one amino substituted silane, at least one substituted silicate and at least one manganese ion.

[0140] In an embodiment, the process can capture SO2 from a low concentration SO2 gaseous stream or atmosphere.

[0141] The manganese metalloxerogels, as described herein, can be used for direct gas capture applications. The manganese metalloxerogels are suitable for adsorption of SO2 from a gaseous stream or atmosphere containing less than 10,000 ppm (10%), preferably less than 7,000 ppm (7%), more preferably less than 5000 ppm (5%) of SO2. In some embodiments or examples, the low concentration SO2 gaseous stream may have a SO2 concentration of less than about 200,000 parts per million (ppm). In one embodiment or example, the low concentration SO2 gaseous stream may have a SO2 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 concentration SO2 gaseous stream may have a SO2 concentration of between 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 5,000 ppm.

[0142] It will be understood that 1 ppm equates to 0.0001 vol. %. For example, a gaseous stream or atmosphere having a concentration of less than about 100,000 ppm equates to 10.0 vol.% of gas in the gaseous stream or atmosphere Thus, in some embodiments or examples, the low concentration SO2 gaseous stream may have a SO2 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 low concentration SO2 gaseous stream may have a SO2 concentration of between 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. %.

[0143] In an alternate embodiment, the process can capture a gas from a high concentration SO2 gaseous stream or atmosphere. For example, the high concentration SO2 gaseous stream or atmosphere may have a SO2 concentration of 925 mbar (100 vol. %).

[0144] The low concentration SO2 gaseous stream or atmosphere is contacted with the manganese metalloxerogel. The gaseous stream may have a suitable flow rate to contact (e.g. pass through) the manganese metalloxerogel. Alternatively, the gaseous stream may come into contact with the manganese metalloxerogel without any back pressure or flow rate being applied (e.g. the gaseous stream may organically diffuse into the manganese metalloxerogels upon contact). In some embodiments or examples, the gaseous stream may be an atmosphere surrounding the manganese metalloxerogels. In some embodiments, the gaseous stream passes through the manganese metalloxerogel (e.g. enters from a first side or face on the manganese metalloxerogel and exits from different side or face). In one embodiment, the gaseous stream (e.g. atmosphere) diffuses into the manganese metalloxerogel upon contact with the manganese metalloxerogel.

[0145] In some embodiments or examples, the low concentration gaseous stream has an initial SO2 concentration prior to contacting the manganese metalloxerogel, and has a final SO2 concentration after contacting the manganese metalloxerogel (also referred to herein as an effluent gaseous stream and / or effluent gas concentration). It will be appreciated that as the SO2 is absorbed into the manganese metalloxerogel from the gaseous stream, the concentration of the SO2 in the effluent stream will be lower than the initial gas concentration of the gaseous stream prior to contact (e.g. passing through) with the manganese metalloxerogel.

[0146] The concentration of the SO2 in the gaseous stream can be measured by any suitable means, for example an gas chromatography-mass spectroscopy, isotopic analyser (e.g. using a G2201-i Isotopic Analyzer (PICARRO) and / or infrared spectrometer (e.g. an in-line calibrated cavity ring-down IR spectrometer).

[0147] Adsorption apparatus

[0148] In some embodiments or examples, there is provided an adsorption apparatus for capturing sulfur dioxide (SO2) from a gaseous stream or atmosphere comprising: a chamber enclosing at least one manganese metalloxerogel, as described herein, the chamber comprising an inlet through which a gaseous stream can flow to the manganese metalloxerogel and an outlet through which the effluent gaseous stream can flow out from the manganese metalloxerogel. The at least one manganese metalloxerogel may be located between the inlet and outlet of the chamber. The manganese metalloxerogel may be in form of a composite, as described herein.

[0149] It will be appreciated that the manganese metalloxerogel formulation for any given application may be chosen based on density of the metalloxerogel. The manganese metalloxerogel formulations with high densities may be suitable for any device. For example, metalloxerogel formulations with high density can be used to prepare adsorption devices that fit into restricted spaces or environments. Whereas metalloxerogel formulations with low density may be more suitable when space is not an issue.

[0150] The adsorption apparatus of the present disclosure is advantageously compact and can be located much closer to end users, thereby allowing disruptive supply opportunities and better customer value.

[0151] Processes for SO2 capture

[0152] The SO2 may be captured from the gaseous stream by being absorbed into a manganese metalloxerogel. In some embodiments or examples, the manganese metalloxerogel is capable of absorbing between about 10 mg of the gas per g of manganese metalloxerogel (mg / g) to about 400 mg / g. In some embodiments or examples, the manganese metalloxerogel is capable of absorbing at least about 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 150, 200, 250,300, 350 or 400 mg / g of SO2. In other embodiments or examples, the manganese metalloxerogel is capable of absorbing less than about 400, 350, 300, 250, 200, 150, 120, 100, 90, 80, 70, 60, 50, 40, 30, 20 or 10 mg / g of SO2. Combinations of these absorption values are possible, for example the manganese metalloxerogel is capable of absorbing between about 10 mg / g to about 80 mg / g, between about 20 mg / g to about 70 mg / g, or between about 100 mg / g to about 400 mg / g, or between about 200 mg / g to about 400 mg / g of SO2. For example, the manganese metalloxerogel is capable of absorbing about 2 mg / g at 0.02 mbar to about 100 mg / g at 1110 mbar (at 298K).

[0153] In some embodiments, at least about 50% of SO2 may be removed from the gaseous stream (e.g. at least about 50% of SO2 is absorbed into the manganese metalloxerogel from the gaseous stream). In some embodiments or examples, at least about 50%, 85%, 90%, 95%, 99% or 99.9% of SO2 is removed from the gaseous stream. In some embodiments, between about 50% to about 99% of SO2 is removed from the gaseous stream.

[0154] As described above, before contact with the manganese metalloxerogel, the gaseous stream has an initial SO2 concentration. After contact with the manganese metalloxerogel, the effluent gaseous stream has an effluent SO2 concentration. The concentration of SO2 in the effluent gaseous stream following contact with the manganese metalloxerogel may be measured to determine the concentration of SO2 remaining in the gaseous stream.

[0155] The concentration of SO2 in the effluent gaseous stream may be measured by any suitable means, for example using an in-line calibrated cavity ring-down IR spectrometer.

[0156] The absorption processes as disclosed herein may be conducted at ambient temperatures, for example ranging from about 10 to 40°C. For example, ambient temperature may be between 15 and 30°C, or 20 to 25°C. The processes may be conducted generally around typical atmospheric pressures (e.g. between about 20 and 100 kPa) or at low pressures (e.g. between about 0.01 and 0.05 kPa).

[0157] It will be appreciated by persons skilled in the art that numerous variations and / or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. EXAMPLES

[0158] In order that the disclosure may be more clearly understood, particular embodiments of the invention are described in further detail below by reference to the following non-limiting experimental materials, methodologies and examples.

[0159] Example 1: Manganese metalloxerogels

[0160] The manganese metalloxerogels were produced in a single step synthesis. In the single- step method the amino substituted silane, such as APEMS, and the substituted silicate, such as TEOS, were dissolved in a non-aqueous solvent, such as ethanol, and the manganese salt, such as manganese chloride, was dissolved in water. The two solutions were then combined to simultaneously form a crosslinked polysiloxane network incorporating the manganese ions . Preferably, the method was performed at moderate pHs.

[0161] Example l(a-c). The following describes the exemplary preparation of a manganese metalloxerogel. A person of skill in the art would know how to make manganese metalloxerogels with other amino substituted silanes and substituted silicates based on this method:

[0162] Two solutions were prepared as set out in Table 1 and Table 2. Solution A was prepared as a solution of 3-aminopropyl(diethoxy)methylsilane (APEMS) and tetraethylorthosilicate (TEOS) in ethanol (Table 1), and Solution B was prepared as an aqueous solution containing the dissolved metal salt (Table 2). Then, solution A was added to Solution B with agitation. After overnight stirring, the solution was filtered and the residue was washed with an excess of water. The residue was dried on the bench overnight and then in an oven at 80 °C overnight. The manganese were obtained in a yield of 6-8g.

[0163] Table 1: Solution A for synthesis ofMn metalloxerogels Table 2: Solution B for synthesis ofMn metalloxerogels

[0164] Surprisingly, the manganese metalloxerogels produced using manganese chloride with a combination of APEMS and TEOS exhibited mesoporosity. Metalloxerogels prepared with low TEOS content had very low BET surface area and negligible SO2 absorption, whereas those prepared with higher TEOS content showed increased surface areas and good SO2 sorption. Manganese metalloxerogels with lower manganese concentrations were also found to have mesoporosity and to exhibit good SO2 sorption. In most cases, the manganese ions were bound in a form such that the counterions (typically chloride) were almost entirely removed during purification.

[0165] Example 2: Properties of the manganese metalloxerogels

[0166] The physical properties of the prepared manganese metalloxerogels were assessed.

[0167] Density

[0168] The density of the prepared manganese metalloxerogels is shown in Table 3.

[0169] Table 3: Density ofMn metalloxerogels In examples 1(a) to 1(c), the covalent crosslinker concentration (TEOS) was increased. At the lowest TEOS concentration, where linear siloxane chains are held primarily by aminemanganese chelation, the bulk density was highest (0.76 g / cm3). Increasing TEOS concentration progressively reduced density to 0.52 g / cm3.

[0170] In Examples 2(a) to 2(c), TEOS and amino substituted silane concentration was held constant while the manganese ion concentration was reduced, also decreasing density (0.32- 0.28 g / cm3) due to reduced chain-metal-chain crosslinking.

[0171] Porosity

[0172] The BET surface area (as measured by N2 gas adsorption isotherms, performed at 77K) was obtained for all the examples described above. Example 1(a), containing no TEOS, had a BET surface area of 26.4 m2 / g (see Table 4 and Figure 1). Incorporation of 20% TEOS increased the surface area tol95.2 m2 / g, and 40% TEOS produced the highest measured surface area of 322.2 m2 / g (Table 4, Figure 1). Reducing the manganese concentration at constant TEOS content lowered the surface area, indicating that the optimal composition for surface area was Example 1(c).

[0173] Table 4: Composition and Surface Areas ofMn metalloxerogel powders

[0174] The N2 gas adsorption isotherms shown in Figure 1 adopt a type II configuration, consistent with mesoporous materials. The presence of a hysteresis loop in the desorption branch further indicates significant mesoporosity. This observation is consistent with the pore size distribution data (Table 5, Figure 3), which shows a predominance of mesopores with a smaller fraction of micropores.

[0175] The gas adsorption performance of the manganese metalloxerogels was further evaluated using CO2 as a model toxic industrial chemical (TIC) gas, with the adsorption isotherms shown in Figure 2 for Example 1 (a)-(c) and 2 (a)-(c). Pore Size Distribution

[0176] The total pore volume and pore size distribution is shown in Table 5 and Figure 3. The pore volume and pore size distributions has been measured by N2 gas adsorption isotherms, performed at 77K (calculated from the data collected in Figure 1). All manganese metalloxerogels contained <30% micropores (<2 nm) and >70% mesopores (2-50 nm).

[0177] Table 5: Pore size distribution ofMn metalloxerogels

[0178] X-ray Powder Diffraction (XRD)

[0179] The XRD patterns indicated amorphous structures for Examples 1(b) through 2(c) (see Figure 4). In contrast, Example 1(a) was identified as manganese oxide (Figure 5), indicating that a substituted silicate precursor, such as TEOS, is required to obtain a porous amorphous manganese metalloxerogel.

[0180] Inductively coupled plasma mass spectrometry (ICP)

[0181] The elemental composition within the manganese metalloxerogels was determined (see Table 6).

[0182] Table 6: ICP Results The ICP indicate that the manganese metalloxerogels contain high levels of manganese, predominantly in a bound form rather than as MnCh, with counterions (typically chloride) greatly reduced or absent. The data also show that inclusion of the covalent crosslinker TEOS is necessary to produce a metalloxerogel with the desired structure and properties.

[0183] These results demonstrate a high manganese-loading capacity in the metalloxerogels, with significant bound manganese content. In the absence of TEOS, as in Example 1(a), a porous metalloxerogel did not form, resulting in negligible microporosity and poor SO2 dynamic adsorption capacity

[0184] Electron microscopy comparison

[0185] Figure 6 and Figure 7 shows Transition Electron Microscopy (TEM) results of Examples l(a-c) and Examples 2(a-c), at two different magnifications. The images of Examples 1(b), 1(c), and 2(a)-2(c) show amorphous structures without large-scale crystallinity, consistent with XRD data. . Example 1(a), lacking TEOS, did not form a mesoporous structure and exhibited no observable crystals. Example l(c) / 2(a) appeared to form interconnected amorphous particles, with no crystalline features visible at higher magnification.

Claims

CLAIMS:

1. A manganese metalloxerogel comprising: a reaction product comprising of at least one amino substituted silane according to Formula 1, at least one substituted silicate according to Formula II, and at least one manganese salt, wherein Formula 1 is:R1Si(OR2)2-L-NH2Formula 1 wherein:R1is substituted or unsubstituted Ci-ealkyl;R2is Ci-ealkyl;L is a -Ci-ealkyl- linker group between the silicon and nitrogen atoms; wherein Formula 2 is:Si(OR7)4Formula 2 wherein: R7is Ci-ealkyl, and wherein the metalloxerogel is selective for sulfur dioxide (SO2) gas capture.

2. The manganese metalloxerogel according to claim 1, wherein the at least one amino silane is 3-aminopropyl (diethoxy) methyl silane (APEMS).

3. The manganese metalloxerogel according to claim 1 or claim 2, wherein the mol ratio of amino substituted silane to silicate to manganese ion is in the range between 0.75-1 :0.2- 0.70:0.1-0.5.

4. The manganese metalloxerogel according to any one of the preceding claims, wherein the at least one substituted silicate is triethyl orthosilicate (TEOS).

5. The manganese metalloxerogel according to any one of the preceding claims, wherein the amino substituted silane has a % loading of between about 35 mol% to about 70 mol%, the substituted silicate has a % loading of between about 10 mol% to about 35 mol% and the manganese has a % loading of between about 15 mol% to about 50 mol%.

6. The manganese metalloxerogel according to any one of the preceding claims, wherein the manganese metalloxerogel is in the form of a metalloxerogel composite, and wherein the composite further comprises one or more additives.

7. The manganese metalloxerogel according to any one of the preceding claims, wherein the one or more additives is selected from the group consisting of a metal-organic framework (MOF), a binder, a lubricant, and a buffer, or combinations thereof.

8. The manganese metalloxerogel according to any one of the preceding claims, wherein the manganese salt is selected from the group consisting of manganese chloride, manganese iodide, manganese bromide, manganese acetate, manganese sulfate, manganese nitrate, manganese citrate, manganese tritiate, manganese oxide, manganese carbonate and manganese gluconate.

9. A process for preparing a manganese metalloxerogel according to any one of the preceding claims, the process comprising the steps of:(i) mixing an aqueous solution comprising the at least one manganese salt together with a solvent system comprising that at least one amino substituted silane and the at least one substituted silicate, optionally one or more additives, to form a wet-gel matrix comprising manganese bonded within a cross-linked manganese-silicate sol gel network; and(ii) drying the wet-gel matrix to provide a dried manganese metalloxerogel; with the proviso that drying the wet-gel matrix does not involve supercritical CO2.

10. The process according to claim 9, wherein the process is a sol gel process and step (ii) comprises:(al) 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 dried metalloxerogel.

11. The process according to claim 9 or claim 10, wherein the drying step (ii) is an ambient pressure drying step.

12. A method for capturing sulfur dioxide (SO2) from a gaseous stream or atmosphere containing sulfur dioxide (SO2) comprising:contacting the gaseous stream or atmosphere with the manganese metalloxerogel according to any one of claims 1 to 8 for capturing at least some of the sulfur dioxide (SO2) from the gaseous stream or atmosphere.

13. The method according to claim 12, wherein the gaseous stream or atmosphere has a sulfur dioxide (SO2) concentration of less than about 10,000 ppm.

14. The method according to claim 12 or claim 13, wherein at least about 50% to 99% of the sulfur dioxide (SO2) is removed from the gaseous stream or atmosphere.

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