Methane concentration and oxidation system

Abstract

Methods and systems for converting methane to CO2 are disclosed herein. In at least one embodiment, an exemplary method comprises: providing an initial gas stream comprising methane; concentrating methane in the initial gas stream to produce a concentrated gas stream wherein the concentrated gas stream has a methane concentration of at least 0.2 wt%; and feeding the concentrated gas stream to a reactor comprising a methane oxidation catalyst to effect conversion of methane to CO2.

Description

Cross-references to applications related to methane concentration and oxidation systems

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 542,618, filed October 5, 2023, the disclosure of which is hereby incorporated herein by reference in its entirety. Technical Field

[0002] This disclosure relates to methane catalysis, and more particularly to systems for converting methane into carbon dioxide. Background Technology

[0003] While carbon dioxide is a central greenhouse gas in the global climate dialogue, methane is arguably the bigger problem. Methane is more potent and acts faster; however, there is currently no technology to address the majority of the world's methane sources.

[0004] Atmospheric methane concentrations are rising, making novel solutions crucial. While atmospheric methane accounts for approximately 0.4% of carbon dioxide, it has contributed as much as 25% to radiative forcing since pre-industrial times. During this period, atmospheric methane concentrations have increased almost twice as rapidly as CO2. The scientific community agrees that significant reductions in greenhouse gas emissions are needed by 2030 to prevent a temperature rise of 2 degrees Celsius or higher. Therefore, technological innovation is essential to help reduce and curb global methane emissions. Summary of the Invention

[0005] The following is a simplified overview of various aspects of this disclosure in order to provide a basic understanding of such aspects. This overview is not a comprehensive summary of this disclosure. It is neither intended to identify key or essential elements of this disclosure, nor to depict any scope of any particular embodiment of this disclosure or any scope of the claims. Its sole purpose is to present some concepts of this disclosure in a simplified form as a prelude to the more detailed description that follows.

[0006] One aspect of this disclosure relates to a method for converting methane to CO2, the method comprising: providing an initial gas stream containing methane; concentrating the initial gas stream to produce a concentrated gas stream, wherein the concentrated gas stream has a methane concentration of at least 0.2 wt%; and feeding the concentrated gas stream to a reactor comprising a methane oxidation catalyst to achieve the conversion of methane to CO2.

[0007] Another aspect of this disclosure relates to a method for converting methane into CO2, the method comprising: receiving a concentrated gas stream or concentrating an initial gas stream to produce a concentrated gas stream, wherein the concentrated gas stream has a methane concentration of at least 0.2 wt%; and feeding the concentrated gas stream to a reactor comprising a methane oxidation catalyst to achieve the conversion of methane to CO2.

[0008] In at least one embodiment, the method further includes maintaining the O2 concentration in the reactor at about 10 wt% to less than 21 wt%.

[0009] In at least one embodiment, the methane concentration of the concentrated gas stream is from about 0.2 wt% to about 17 wt%.

[0010] In at least one embodiment, the methane concentration of the concentrated gas stream is from about 0.25 wt% to about 5 wt%.

[0011] In at least one embodiment, the methane concentration of the concentrated gas stream is from about 0.3 wt% to about 1.2 wt%.

[0012] In at least one embodiment, the methane concentration of the concentrated gas stream is at least 1.5 times, at least 5.0 times, or at least 10.0 times the methane concentration of the initial gas stream.

[0013] In at least one embodiment, the methane concentration of the initial gas stream is from about 0.01 wt% to about 4.6 wt%.

[0014] In at least one embodiment, the methane concentration of the initial gas stream is from about 0.1 wt% to about 3 wt%.

[0015] In at least one embodiment, the methane concentration of the initial gas stream is from about 0.5 wt% to about 2 wt%.

[0016] In at least one embodiment, the methane conversion rate is at least about 25%.

[0017] In at least one embodiment, the methane conversion rate is at least about 50%.

[0018] In at least one embodiment, the methane conversion rate was maintained at less than about 75%.

[0019] In at least one embodiment, the methane conversion rate was maintained at less than about 85%.

[0020] In at least one embodiment, the reactor comprises two or more containers with intermediate cooling.

[0021] In at least one embodiment, the heat removed from the reaction products of the reactor is used to generate steam.

[0022] In at least one embodiment, the oxidation reactor is in the form of a shell-and-tube heat exchanger having hot oil and / or hot fluid and / or evaporated water as cooling fluids to provide heat removal.

[0023] In at least one embodiment, the oxidation reactor has integrated cooling pipes therein to allow heat removal.

[0024] In at least one embodiment, concentrating methane in the initial gas stream includes feeding the initial gas stream to an adsorption system.

[0025] In at least one embodiment, the adsorption system is a simulated moving bed adsorption system.

[0026] In at least one embodiment, the adsorption system is a temperature-switching adsorption system.

[0027] In at least one embodiment, the adsorption system is a pressure swing adsorption system.

[0028] In at least one embodiment, the adsorption system includes a cage-shaped hydrate adsorbent.

[0029] In at least one embodiment, the adsorption system includes one or more solid adsorbents selected from zeolites, metal-organic frameworks, carbon-based adsorbents, or combinations thereof.

[0030] In at least one embodiment, the adsorption system is adapted to cycle between an adsorption phase, a cooling phase, and a desorption phase. In at least one embodiment, the method further includes: during the desorption phase, achieving desorption by transferring heat from the reaction products of the reactor to the adsorption system.

[0031] In at least one embodiment, methane concentration includes using a liquid absorbent to concentrate the methane.

[0032] In at least one embodiment, methane concentration includes using a membrane system to concentrate methane.

[0033] In at least one embodiment, the methane oxidation catalyst comprises a copper zeolite catalyst.

[0034] In at least one embodiment, the methane oxidation catalyst comprises a zeolite catalyst having more than one transition metal for exchange.

[0035] In at least one embodiment, the methane oxidation catalyst comprises a zeolite catalyst having one or more transition metals, including nickel, iron, cobalt, copper, manganese, vanadium, cerium, zinc, tungsten, molybdenum, platinum, palladium, silver, gold, or combinations thereof.

[0036] In at least one embodiment, the methane oxidation catalyst comprises a zeolite catalyst mixed with a supported oxide catalyst. In at least one embodiment, the supported oxide catalyst comprises one or more of the following: zirconium oxide, titanium dioxide, silica, alumina, or combinations thereof.

[0037] In at least one embodiment, the methane oxidation catalyst is a shaped catalyst. In at least one embodiment, the shaped catalyst is in the form of tablets, granules, extrusions, or combinations thereof.

[0038] In at least one embodiment, a methane oxidation catalyst is coated onto a substrate.

[0039] In at least one embodiment, the methane oxidation catalyst is a combination of a coated substrate and a molded catalyst.

[0040] Another aspect of this disclosure relates to a system for converting methane into CO2, the system comprising: a methane concentration system adapted to concentrate methane in a methane-containing gas stream; and a reactor fluidly coupled to the methane concentration system, the reactor comprising a methane oxidation catalyst adapted to support a methane oxidation reaction.

[0041] In at least one embodiment, the methane concentration system includes a plurality of adsorption towers configured for moving bed adsorption.

[0042] In at least one embodiment, at least one of the plurality of adsorption towers comprises one or more of a solid adsorbent, a liquid absorbent, or a cage-like hydrate adsorbent. In at least one embodiment, the system is configured to use heat from the methane oxidation reaction products from the reactor to achieve desorption of at least one of these adsorption towers during a desorption phase. In at least one embodiment, the system is configured to cool at least one of these adsorption towers during a cooling phase.

[0043] In at least one embodiment, the system is configured to feed an O2-containing gas stream to the reactor to support the methane oxidation reaction.

[0044] In at least one embodiment, the methane oxidation catalyst comprises a copper zeolite catalyst.

[0045] In at least one embodiment, the methane oxidation catalyst comprises a zeolite catalyst having more than one transition metal for exchange.

[0046] In at least one embodiment, the methane oxidation catalyst comprises a zeolite catalyst mixed with a supported oxide catalyst.

[0047] In at least one embodiment, the methane oxidation catalyst is a molding catalyst.

[0048] In at least one embodiment, the molding catalyst is in the form of tablets, granules, extrusions, or combinations thereof.

[0049] In at least one embodiment, a catalyst is added to the substrate.

[0050] In at least one embodiment, the catalyst is a combination of a coated substrate and a molded catalyst.

[0051] In at least one embodiment, the methane conversion rate is at least about 25%.

[0052] In at least one embodiment, the methane conversion rate is at least about 50%.

[0053] In at least one embodiment, the methane conversion rate was maintained at less than about 75%.

[0054] In at least one embodiment, the methane conversion rate was maintained at less than about 85%.

[0055] In at least one embodiment, the bed size of the reactor system is about 5% to 35% of the bed size of a similar system capable of achieving about 99% methane conversion.

[0056] In at least one embodiment, the bed size of the reactor system is approximately 1 m. 3 to less than about 10 m 3 Less than approximately 8 m 3 Less than approximately 6 m 3 Less than approximately 4 m 3 or less than about 3 m 3 .

[0057] In at least one embodiment, the reactor comprises two or more containers with intermediate cooling.

[0058] In at least one embodiment, the system is adapted to use the heat removed from the reaction products of the reactor to generate steam.

[0059] Another aspect of this disclosure relates to a system for converting methane into CO2, the system comprising: a methane adsorbent or absorbent adapted to concentrate methane in a methane-containing gas stream; and a methane oxidation catalyst adapted to support a methane oxidation reaction, wherein the methane adsorbent or absorbent and the methane oxide catalyst are contained together in a single container.

[0060] In at least one embodiment, the methane adsorbent or absorbent comprises one or more solid adsorbents, which include zeolites, metal-organic frameworks, carbon-based adsorbents, or combinations thereof.

[0061] In at least one embodiment, the container includes a membrane system to facilitate the concentration and oxidation of methane within the container.

[0062] In at least one embodiment, the system is configured to feed an O2-containing gas stream to a methane oxide catalyst to support the methane oxidation reaction.

[0063] In at least one embodiment, the methane oxidation catalyst comprises a copper zeolite catalyst.

[0064] In at least one embodiment, the methane oxidation catalyst comprises a zeolite catalyst having more than one transition metal for exchange.

[0065] In at least one embodiment, the methane oxidation catalyst comprises a zeolite catalyst mixed with a supported oxide catalyst.

[0066] In at least one embodiment, the methane oxidation catalyst is a molding catalyst.

[0067] In at least one embodiment, the molding catalyst is in the form of tablets, granules, extrusions, or combinations thereof.

[0068] In at least one embodiment, a catalyst is added to the substrate.

[0069] In at least one embodiment, the catalyst is a combination of a coated substrate and a molded catalyst.

[0070] In at least one embodiment, the methane conversion rate is at least about 25%.

[0071] In at least one embodiment, the methane conversion rate is at least about 50%. Attached Figure Description

[0072] This disclosure is illustrated by way of example, not limitation, in the accompanying drawings, in which:

[0073] Figure 1 illustrates exemplary reaction systems according to various embodiments for performing one or more of the methods described herein; and

[0074] Figure 2 illustrates another exemplary reaction system according to various embodiments for performing one or more of the methods described herein.

[0075] definition

[0076] As used herein, the singular forms “a / an” and “the” include plural indicators unless explicitly stated otherwise in the context. Thus, for example, references to “microsphere” include single microspheres as well as mixtures of two or more microspheres.

[0077] Furthermore, as used herein, the term "about" in conjunction with the quantity being measured refers to a standard variation of the quantity being measured, as would be expected by a person skilled in the art when performing the measurement and implementing a level of caution commensurate with the accuracy of the measurement target and the measuring equipment. In some embodiments, the term "about" includes the listed number ± 10%, such that "about 10" would include 9 to 11.

[0078] As used herein, the terms “catalyst” or “catalyst composition” or “catalyst material” or “catalyst component” refer to materials that promote a reaction.

[0079] As used herein, the term "zeolite" refers to a crystalline aluminosilicate having a framework based on a broad three-dimensional network of silicon, aluminum, and oxygen ions and a substantially uniform pore distribution.

[0080] Unless otherwise indicated herein, the descriptions of ranges of values ​​herein are intended only as a shorthand for individually referring to each individual value falling within that range, and each individual value is incorporated into this specification as if it were described separately herein. Unless otherwise indicated herein or expressly contradicted by the context, all methods described herein may be performed in any suitable order. The use of any and all instances or exemplary language (e.g., “such”) provided herein is intended only to illustrate certain materials and methods and does not limit the scope. No language in this specification should be construed as indicating that any non-claimed element is essential to the practice of the disclosed materials and methods. Detailed Implementation

[0081] In some embodiments, this disclosure relates to the conversion of methane to CO2. More specifically, some embodiments relate to providing an initial gas stream containing methane and concentrating the methane in the initial gas stream to produce a concentrated gas stream. This concentrated gas stream comprises at least about 0.2 wt% methane concentration. The concentrated gas stream can be fed into a reactor including a methane oxidation catalyst to achieve the conversion of methane to CO2. It has been found that concentrating methane increases the rate of methane to CO2 conversion. It has also been found that the use of a copper zeolite catalyst in the methane oxidation catalyst can efficiently convert methane to CO2. Further, the concentrated stream should not exceed 5 wt%, which is just below the flammability level of the stream. By maintaining the concentrated methane stream at this amount, it has been found that such concentration can be combined with the methane oxidation catalyst described herein to increase the methane to CO2 conversion rate.

[0082] Figure 1 illustrates exemplary reaction systems for performing one or more of the methods described herein, according to various embodiments. For example, the system includes a methane concentration system adapted to concentrate methane within a methane-containing gas stream. As shown, the concentration system includes multiple towers configured in a simulated moving bed adsorption arrangement. For example, at any given time during the adsorption process, one tower may be in adsorption mode to actively adsorb methane, one tower may be in cooling mode, and another tower may be in desorption mode to purge the adsorbed methane. During adsorption mode, the effluent gas stream may contain a low methane concentration (e.g., less than about 5 wt% methane). In some embodiments, the towers may be cooled in cooling mode using ambient air, after which the towers may be ready for adsorption mode. The reaction system further includes a reactor (also referred to as a methane reduction reactor) containing a methane oxidation catalyst adapted to support the methane oxidation reaction. The concentrated methane gas stream may be fed to the reactor for methane conversion, while an air stream is provided to the reactor, which may be used to maintain a target O2 concentration within the reactor (e.g., less than about 20 wt% during the reaction). In some embodiments, during cooling mode operation, the heated gas stream generated by the methane oxidation reaction can be used to heat one or more towers.

[0083] Figure 2 illustrates another exemplary reaction system according to various embodiments for performing one or more of the methods described herein. In at least one embodiment, the reactor can be configured using a shell and tube to generate steam without using an external steam generation system. In at least one embodiment, multiple reactor stages can be used in conjunction with an intercooler-steam generator, depending on the concentration of CH4 present in the desorbed gas.

[0084] Further aspects of the illustrative reaction systems of Figures 1 and 2, as well as their variations, are described in more detail below.

[0085] In some embodiments, the methane concentration of the concentrated gas stream can be from about 0.2 wt% to about 7 wt%. In other embodiments, the methane concentration of the concentrated gas stream can be from about 0.25 wt% to about 5 wt%. In another embodiment, the methane concentration of the concentrated gas stream can be from about 0.3 wt% to about 1.2 wt%. In yet another embodiment, the methane concentration of the concentrated gas stream can be from about 0.35 wt% to about 1 wt%, or from about 0.4 wt% to about 0.8 wt%.

[0086] In some embodiments, the methane concentration of the concentrated gas stream may be at least 1.5 times, at least 5.0 times, or at least 10.0 times the methane concentration of the initial gas stream.

[0087] In some embodiments, the methane concentration of the initial gas stream can be from about 0.01 wt% to about 4.6 wt%. In other embodiments, the methane concentration of the initial gas stream can be from about 0.1 wt% to about 3 wt%. In yet another embodiment, the methane concentration of the initial gas stream can be from about 0.5 wt% to about 2 wt%. In still another embodiment, the methane concentration of the initial gas stream can be from about 0.8 wt% to about 1.7 wt%, or from about 1 wt% to about 1.5 wt%.

[0088] In some embodiments, the methane conversion rate in the method can be at least about 25%. In other embodiments, the methane conversion rate in the method can be at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, or at least about 60%. In yet another embodiment, the methane conversion rate in the method is about 25% to about 80%, about 30% to about 75%, about 35% to about 70%, about 40% to about 65%, about 45% to about 60%, or about 50% to about 55%.

[0089] In some embodiments, such as in Figure 2, the reactor assembly may include one or more steps for intercooling. In some embodiments of the method, heat can be removed from the reaction products of the reactor, which can then be used to generate steam.

[0090] In some embodiments of the method, the reactor is an oxidation reactor. The oxidation reactor may be in the form of a shell-and-tube heat exchanger having hot oil and / or hot fluid and / or evaporated water as cooling fluids to provide heat removal. In some embodiments, the oxidation reactor may have cooling pipes integrated therein to allow heat removal.

[0091] In some embodiments, the method may further include maintaining the O2 concentration in the reactor at about 10 wt% to less than 21 wt%. In other embodiments, the O2 concentration in the reactor may be maintained at about 10 wt%, about 12 wt%, about 14 wt%, about 16 wt%, about 18 wt%, or about 20 wt%. In still other embodiments, the O2 concentration in the reactor may be maintained at 10 wt% to less than 21 wt%, 11 wt% to 20 wt%, 12 wt% to 19 wt%, 13 wt% to 18 wt%, or 14 wt% to 17 wt%.

[0092] In some embodiments of the method, concentrating methane in the initial gas stream may include feeding the initial gas stream to an adsorption system. In some embodiments, the adsorption system may be a simulated moving bed adsorption system. In other embodiments, the adsorption system may be a temperature swing adsorption system. In another embodiment, the adsorption system may be a pressure swing adsorption system. In yet another embodiment, the adsorption system may include a cage-like hydrate adsorbent. In yet another embodiment, the adsorption system may include one or more solid adsorbents selected from zeolites, metal-organic frameworks, carbon-based adsorbents, or combinations thereof.

[0093] In some embodiments, the adsorption system may be adapted to cycle between an adsorption phase, a cooling phase, and a desorption phase. In such systems, the method may further include, during the desorption phase, achieving desorption by transferring heat from the reaction products of the reactor to the adsorption system.

[0094] In some embodiments of the method, methane concentration may include using a liquid adsorbent to concentrate the methane. In some embodiments of the method, methane concentration may include using a membrane system to concentrate the methane.

[0095] In some embodiments of the method, the methane oxidation catalyst may comprise a copper zeolite catalyst. In some embodiments, the methane oxidation catalyst may comprise a zeolite catalyst having more than one transition metal for exchange. In embodiments, the methane oxidation catalyst may comprise a zeolite catalyst having one or more transition metals, including nickel, iron, cobalt, copper, manganese, vanadium, cerium, zinc, tungsten, molybdenum, platinum, palladium, silver, gold, or combinations thereof.

[0096] In another embodiment, the methane oxidation catalyst may comprise a zeolite catalyst mixed with a supported oxide catalyst. The supported oxide catalyst may comprise one or more of the following: zirconium oxide, titanium dioxide, silica, alumina, or combinations thereof.

[0097] In some embodiments of this method, the methane oxidation catalyst may be a molded catalyst. The molded catalyst may be in the form of tablets, granules, extrusions, or combinations thereof.

[0098] In some embodiments of the method, the methane oxidation catalyst can be coated onto a substrate. In another embodiment, the methane oxidation catalyst can be a combination of a coated substrate and a molded catalyst.

[0099] Exemplary catalysts for methane conversion compatible with the embodiments described herein include the following. International Application Publication No. WO 2008 / 106519 describes a multi-step synthesis of CuSSZ-13 by two 1 M copper sulfate exchanges of SSZ-13 in the form of NH4, the disclosure of which is hereby incorporated herein by reference in its entirety. The synthesis of copper chalcogenide is also described in Tables 1 and 2 of U.S. Patent No. 8,293,198, the disclosure of which is hereby incorporated herein by reference in its entirety. Base metal catalysts comprising, for example, manganese and copper can be produced as described in U.S. Patent Publication No. 2014 / 0255284, the disclosure of which is hereby incorporated herein by reference in its entirety. Sodium-type Y zeolite catalysts can be produced as described, for example, in British Patent Publication No. GB1376250, the disclosure of which is hereby incorporated herein by reference in its entirety.

[0100] Another embodiment of this disclosure includes a system for converting methane to CO2. The system includes a methane concentration system adapted to concentrate methane within a methane-containing gas stream; and a reactor fluidly coupled to the methane concentration system. The reactor may include a methane oxidation catalyst suitable for supporting the methane oxidation reaction.

[0101] In some embodiments, the methane concentration system may include a plurality of adsorption towers configured for moving bed adsorption. In some embodiments, at least one of the plurality of adsorption towers may include one or more of a solid adsorbent, a liquid adsorbent, or a cage hydrate.

[0102] In some embodiments, the solid adsorbent may be zeolite, metal-organic framework, carbon material, or a combination thereof. In some embodiments, the metal-organic framework may include [Co3(HCOO)6], [Mg3(HCOO)6], [Mn3(HCOO)6], [Ni3(HCOO)6], [Cu(Me-4py-trz-ia)], MIL-53(Al), MIL-101, UTA-30a, [Cu(INA)2], [Cu(hfipbb)(H2hfipbb)] 0.5 ], ROD-8, Ni-L, MOF-5, MOF-177, Cu-BTC, MOF-5, ZIF-8, Mg-MOF-74, Ni-MOF-74, Co-MOF-74, MIL-100(Cr), Zn2 (5-aip)2(bpy), ATC-Cu, [Co3(C4O4)2(OH)2], Uio-66-Br2, Uio-6, CAU-21-BPDC, CAU-8-BPDC, [Co(ma)(bpy) 0.5 [Ni(ma)(bpy)] 0.5SBMOF-1 or Al-CDC. In some embodiments, the zeolite may include K-chamite, SSZ-13, SAPO-34, Linde 4A, H + Mordenite, Na-X, Ca-X, Sr-X, Ba-X, β-zeolite, SAPO-18, SAPO-34, NaETS-4, ZSM-5, MEA(40)-β, silicate-1, DD3R, Beta, 5A, 13X, or clinoptilolite. In some embodiments, the carbon material may include Takeda CMS 3k, MAC, Norit RB 3, ACM, CAC, activated carbon beads, PRC, GAC, Ac, SAC-ben, SAC-ben-P-N2, SAC, N-doped porous carbon, OTSS-1-550, or PS-2-450.

[0103] In some embodiments, the system may be configured to use heat from the methane oxidation reaction products from the reactor to achieve desorption of at least one of these adsorption towers during the desorption phase. In other embodiments, the system may be configured to cool at least one of these adsorption towers during a cooling phase.

[0104] In some embodiments, the system can be configured to feed an O2-containing gas stream to the reactor to support the methane oxidation reaction.

[0105] In some embodiments, the methane oxidation catalyst may comprise a copper zeolite catalyst. In other embodiments, the methane oxidation catalyst may comprise a zeolite catalyst having more than one transition metal for exchange. In another embodiment, the methane oxidation catalyst may comprise a zeolite catalyst mixed with a supported oxide catalyst. The supported oxide catalyst may comprise one or more of the following: zirconium oxide, titanium dioxide, silica, alumina, or combinations thereof. In yet another embodiment, the methane oxidation catalyst may be a molded catalyst. The molded catalyst may be in the form of tablets, granules, extrusions, or combinations thereof.

[0106] In some embodiments, a catalyst may be added to the substrate. In another embodiment, the catalyst may be a combination of a coated substrate and a molded catalyst.

[0107] In some embodiments, the methane conversion rate in the system is at least about 25%. In other embodiments, the methane conversion rate in the system can be at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, or at least about 60%. In another embodiment, the methane conversion rate in the system is about 25% to about 80%, about 30% to about 75%, about 35% to about 70%, about 40% to about 65%, about 45% to about 60%, or about 50% to about 55%.

[0108] In some embodiments of the system, the reactor may include two or more containers with intercooling.

[0109] In some embodiments of the system, the system may be adapted to use the heat removed from the reaction products of the reactor to generate steam.

[0110] Some embodiments of this disclosure relate to an additional system for converting methane to CO2. This additional system may include a methane adsorbent or absorbent suitable for concentrating methane within a methane-containing gas stream; and a methane oxidation catalyst suitable for supporting the methane oxidation reaction. The methane adsorbent or absorbent and the methane oxidation catalyst may be contained together in a single container.

[0111] In some embodiments, the methane adsorbent or absorbent may comprise one or more solid adsorbents, which may include zeolites, metal-organic frameworks, carbon-based adsorbents, or combinations thereof.

[0112] In some embodiments, the container may include a membrane system to facilitate the concentration and oxidation of methane within the container.

[0113] In some embodiments, the system can be configured to feed an O2-containing gas stream to the methane oxide catalyst to support the methane oxidation reaction.

[0114] In some embodiments of the additional system, the methane oxidation catalyst may comprise a copper zeolite catalyst. In some embodiments, the methane oxidation catalyst may comprise a zeolite catalyst having more than one transition metal. In some embodiments, the methane oxidation catalyst may comprise a zeolite catalyst having one or more transition metals, including nickel, iron, cobalt, copper, manganese, vanadium, cerium, zinc, tungsten, molybdenum, platinum, palladium, silver, gold, or combinations thereof.

[0115] In some embodiments, the methane oxidation catalyst may comprise a zeolite catalyst mixed with a supported oxide catalyst. The supported oxide catalyst may comprise one or more of the following: zirconium oxide, titanium dioxide, silica, alumina, or combinations thereof. In some embodiments, the methane oxidation catalyst may be a molded catalyst. The molded catalyst may be in the form of tablets, granules, extrusions, or combinations thereof.

[0116] In some embodiments of the additional system, the catalyst may be added to the substrate. In another embodiment, the catalyst may be a combination of a coated substrate and a molded catalyst.

[0117] In some embodiments, the methane conversion rate in the system is at least about 25%. In other embodiments, the methane conversion rate in the system can be at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, or at least about 60%. In another embodiment, the methane conversion rate in the system is about 25% to about 80%, about 30% to about 75%, about 35% to about 70%, about 40% to about 65%, about 45% to about 60%, or about 50% to about 55%.

[0118] The system according to this disclosure is now described, which may correspond to the system shown in Figures 1 and 2, or variations thereof, as will be understood by those skilled in the art. It should be understood that this is an exemplary system of this disclosure and is not limited to Figures 1 and 2 as described herein. In at least one embodiment, the system includes a methane concentration system and a reactor. In at least one embodiment, the methane concentration system includes a simulated moving bed adsorption system comprising multiple adsorption towers. The simulated moving bed adsorption may include an adsorption mode tower, a cooling mode tower, and a desorption mode tower. As shown in Figures 1 and 2, the effluent is fed to the methane concentration system. In at least one embodiment, the effluent comprises methane at a concentration of less than 5%. The effluent is then fed to an adsorption tower in the methane concentration system in adsorption mode. In this portion, the adsorption tower of the methane concentration system comprises one or more of a solid adsorbent, a liquid absorbent, or a cage-like hydrate adsorbent. When the adsorption tower has reached its capacity, the feed may be released and fed to a tower in desorption mode. In at least one embodiment, heat from the methane oxidation reaction products from the reactor in the system is used to apply heat to the tower in desorption mode. Once desorption is complete, the feed is then cooled in the cooling mode tower by applying ambient air.

[0119] After cooling, the concentrated methane stream is then fed into the reactor. In at least one embodiment, a single-stage reactor is used (Figure 1). In at least one embodiment, a two-stage reactor is used (Figure 2). Each reactor includes a methane oxidation catalyst as described herein. The concentrated methane stream is received by the reactor and, in some embodiments, can be concentrated to a maximum of 5 wt%. In at least one embodiment, the reactor is maintained at a temperature of about 50°C to about 200°C. In at least one embodiment, an O2-containing gas stream is fed into the reactor to support the reaction therein, and this gas stream may contain up to about 20 wt% O2. Illustrative Examples

[0120] The following examples are provided to aid in understanding this disclosure, and these examples should not be construed as specifically limiting the invention described and claimed herein. Such variations of the invention, including those replacing all equivalents now known or developed hereafter, as well as minor changes in formulation or experimental design, that would be within the scope of the invention incorporated herein by reference, will be considered to fall within the scope of the invention.

[0121] The synthesized catalyst was tested under different operating conditions in a laboratory testing unit. Experimental data, including methane conversion, reactor temperature, and residence time, were collected and analyzed. The exemplary experimental setup primarily includes: a feed system comprising multiple gas or fluid lines fed into a main pipeline; a preheater fluidly connected to the main pipeline; a 1” tubular reactor downstream of the preheater with a packed catalyst bed; a cooling water condenser; and a gas / liquid separator downstream of the packed catalyst bed. The feed system provides both gas and liquid streams. The preheater raises the temperature of the feed stream to the desired temperature before it enters the preheated reactor bed. The reactor bed temperature is controlled via an oil jacket. The composition of both the feed and product streams was analyzed by online GC.

[0122] Feed gas containing less than about 0.2% to less than 1% CH4 can be concentrated on an adsorbent, such that about 4% of the total adsorbed gas is in the form of CH4. Adsorbents such as ZIF-8 and HayeSep can be used to perform this adsorption step. The adsorbed methane, along with N2 / O2, can then be desorbed using hot gas from the methane oxidation reactor. After this desorption of methane, this may result in up to 2.0%–2.6% CH4 in the gas effluent from the adsorption bed. This gas can be compressed and passed through a heat exchanger to raise its temperature to about 300°C–350°C before being fed to a second-stage methane oxidation reactor (e.g., as shown in Figure 2). The amount of catalyst in each reactor can be adjusted so that the temperature of the effluent from the first reactor does not exceed 550°C–650°C. The methane conversion rate in this case corresponds to about 27%–45%. An intercooler between the reactors can be used to cool the temperature back to about 350°C, and the available heat can be used to generate steam. The methane can then be almost completely converted using a subsequent reactor. If recycled, approximately 30-35% of the effluent is sufficient for CH4 desorption from the adsorbent bed. Similarly, to ensure almost complete CH4 conversion, the O2 content in the recycle gas can be controlled at approximately 10-12%. This lower O2 content ensures the CH4-air mixture never reaches its explosive limits. Approximately 65-70% of the reactor effluent can be vented; however, heat can be recovered from this stream before venting for steam generation.

[0123] In the aforementioned experimental setup, feed gas containing 0.5% CH4 was tested at different gas hourly space velocities (GHSV) and a reactor temperature of 425°C. When using a 3.5% Cu-mordenite catalyst, higher conversion was observed at lower GHSVs, while the conversion decreased with increasing GHSV. For example, at 480 h... -1 Under GHSV conditions, the methane conversion rate is greater than 99%, and at 5000 h -1 At GHSV, the conversion decreased to approximately 88%. To investigate the effect of zeolite structure, a Na-ZSM-5 catalyst with 3.3% Cu was also tested. For this catalyst, the conversion was achieved at a reaction temperature of 425°C and a reaction time of 5000 h. -1 At GHSV, the methane conversion rate reached 81%, while at the same temperature and 480 h... -1 Under GHSV, a conversion rate > 99% was observed. Without being bound by theory, the slightly lower conversion rate when using Na-ZSM-5 was attributed to a reduction of approximately 5.7% in Cu content. However, the strong dependence of CH4 conversion on Cu content and the relatively low dependence on framework structure were unexpected.

[0124] The methane conversion of the 3.3% Cu-exchanged Na-ZSM-5 catalyst was also determined at 425°C, and a 7500 h⁻¹ test was conducted simultaneously. -1 At high GHSV, a methane conversion rate of 71% was observed, a surprising result. At relatively low methane concentrations, a relatively linear correlation between methane conversion and residence time is expected; however, the higher conversion rate at high GHSV may offer unexpected benefits. For example, based on this data, for a gas stream with greenhouse gas (GHG) emissions of 3 million tonnes of CO2 equivalent per year, converting >99% of the methane in the stream would require 20 m³ / h. 3 The reactor bed, while for the same gas flow, is relatively small at 2.5 m. 3 The reactor can achieve a moderate GHG emission reduction of 2.1 million tons of CO2 equivalent per year.

[0125] In the foregoing description, numerous specific details, such as specific materials, dimensions, and process parameters, have been set forth to provide a comprehensive understanding of the invention. Specific features, structures, materials, or properties may be combined in any suitable manner in one or more embodiments. The terms “example” or “exemplary” are used herein to mean that something is used as an instance, example, or illustration. Any aspect or design described herein as an “example” or “exemplary” is not necessarily to be construed as superior to or better than other aspects or designs. In fact, the use of the terms “example” or “exemplary” is intended to present concepts in a specific manner. As used in this application, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless otherwise stated or apparent from the context, “X includes A or B” is intended to mean any natural inclusion arrangement. That is, “X includes A or B” is satisfied in any of the above cases if X includes A; X includes B; or X includes both A and B. Throughout this specification, references to “embodiment,” “some embodiments,” or “one embodiment” mean that a specific feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Therefore, the phrases "embodiment", "some embodiments" or "one embodiment" appearing in different places throughout this specification do not necessarily refer to the same embodiment.

[0126] This disclosure has been described with reference to specific exemplary embodiments thereof. Therefore, this specification and drawings should be considered illustrative rather than restrictive. Various modifications to this disclosure, other than those shown and described herein, will become apparent to those skilled in the art and are intended to fall within the scope of the appended claims.

Claims

1. A method for converting methane into CO2, the method comprising: The method involves receiving a concentrated gas stream or concentrating an initial gas stream to produce a concentrated gas stream, wherein the concentrated gas stream has a methane concentration of at least 0.2 wt%; and feeding the concentrated gas stream into a reactor comprising a methane oxidation catalyst to achieve the conversion of methane to CO2.

2. The method of claim 1, further comprising: The O2 concentration in the reactor was maintained at approximately 10 wt% to less than 21 wt%.

3. The method as described in any of the preceding claims, wherein, The methane concentration in the concentrated gas stream is from about 0.2 wt% to about 17 wt%.

4. The method as described in any of the preceding claims, wherein, The methane concentration in the concentrated gas stream is from about 0.25 wt% to about 5 wt%.

5. The method as described in any one of the preceding claims, wherein, The methane concentration in the concentrated gas stream is from about 0.3 wt% to about 1.2 wt%.

6. The method as described in any of the preceding claims, wherein, The methane concentration of the concentrated gas stream is at least 1.5 times, at least 5.0 times, and at least 10.0 times that of the initial gas stream.

7. The method as described in any of the preceding claims, wherein, The methane concentration of the initial gas stream is from about 0.01 wt% to about 4.6 wt%.

8. The method as described in any of the preceding claims, wherein, The methane concentration of the initial gas stream is from about 0.1 wt% to about 3 wt%.

9. The method as described in any of the preceding claims, wherein, The methane concentration of the initial gas stream is approximately 0.5 wt% to approximately 2 wt%.

10. The method as described in any of the preceding claims, wherein, The conversion rate of methane is at least about 25%.

11. The method as described in any of the preceding claims, wherein, The conversion rate of methane is at least about 50%, maintained at less than about 75%, and / or maintained at less than about 85%.

12. The method as described in any of the preceding claims, wherein, The reactor comprises two or more containers with intercooling.

13. The method as described in any of the preceding claims, wherein, The heat removed from the reaction products of the reactor is used to generate steam.

14. The method as described in any of the preceding claims, wherein, The oxidation reactor is in the form of a shell-and-tube heat exchanger, which has hot oil and / or hot fluid and / or evaporated water as cooling fluid to provide heat removal.

15. The method as described in any of the preceding claims, wherein, The oxidation reactor has integrated cooling pipes to allow heat removal.

16. The method as described in any of the preceding claims, wherein, Concentrating methane in the initial gas stream involves feeding the initial gas stream to an adsorption system.

17. The method of claim 16, wherein, This adsorption system is a simulated moving bed adsorption system.

18. The method of claim 16, wherein, This adsorption system is a temperature-switching adsorption system.

19. The method of claim 16, wherein, This adsorption system is a pressure swing adsorption system.

20. The method of claim 16, wherein, The adsorption system includes cage-shaped hydrate adsorbents.

21. The method of claim 16, wherein, The adsorption system includes one or more solid adsorbents selected from zeolites, metal-organic frameworks, carbon-based adsorbents, or combinations thereof.

22. The method of claim 16, wherein, This adsorption system is suitable for cycling between adsorption, cooling and desorption phases.

23. The method of claim 22, further comprising: During this desorption phase, desorption is achieved by transferring the heat from the reaction products of the reactor to the adsorption system.

24. The method as described in any of the preceding claims, wherein, Concentrating the methane involves using a liquid absorbent to concentrate the methane.

25. The method as described in any of the preceding claims, wherein, Concentrating the methane includes using a membrane system to concentrate the methane.

26. The method as described in any of the preceding claims, wherein, The methane oxidation catalyst contains a copper zeolite catalyst.

27. The method as described in any of the preceding claims, wherein, The methane oxidation catalyst comprises a zeolite catalyst having more than one transition metal for exchange.

28. The method of claim 27, wherein, The methane oxidation catalyst comprises a zeolite catalyst having one or more transition metals, including nickel, iron, cobalt, copper, manganese, vanadium, cerium, zinc, tungsten, molybdenum, platinum, palladium, silver, gold, or combinations thereof.

29. The method as described in any of the preceding claims, wherein, The methane oxidation catalyst comprises a zeolite catalyst mixed with a supported oxide catalyst.

30. The method of claim 29, wherein, The supported oxide catalyst comprises one or more of the following: zirconium oxide, titanium dioxide, silicon dioxide, aluminum oxide, or a combination thereof.

31. The method as described in any of the preceding claims, wherein, This methane oxidation catalyst is a shaped catalyst.

32. The method of claim 31, wherein, The shaped catalyst is in the form of tablets, granules, extrusions, or combinations thereof.

33. The method as described in any of the preceding claims, wherein, The methane oxidation catalyst was coated onto the substrate.

34. The method as described in any of the preceding claims, wherein, The methane oxidation catalyst is a combination of a coated substrate and a molded catalyst.

35. A system for converting methane into CO2, the system comprising: A methane concentration system adapted to concentrate methane in a methane-containing gas stream; And a reactor fluidly connected to the methane concentration system, the reactor comprising a methane oxidation catalyst suitable for supporting the methane oxidation reaction.

36. The system of claim 35, wherein, The methane concentration system includes multiple adsorption towers configured for moving bed adsorption.

37. The system as claimed in any one of claims 35 to 36, wherein, At least one of the plurality of adsorption towers includes one or more of solid adsorbents, liquid absorbents, or cage-shaped hydrate adsorbents.

38. The system of claim 36, wherein, The system is configured to use the heat from the methane oxidation reaction products from the reactor to achieve desorption of at least one of these adsorption towers during the desorption phase.

39. The system of claim 36, wherein, The system is configured to cool at least one of these adsorption towers during the cooling phase.

40. The system as claimed in any one of claims 35 to 39, wherein, The system is configured to feed an O2-containing gas stream to the reactor to support the methane oxidation reaction.

41. The system of claim 35, wherein, The methane oxidation catalyst contains a copper zeolite catalyst.

42. The system as claimed in any one of claims 35 to 41, wherein, The methane oxidation catalyst comprises a zeolite catalyst having more than one transition metal for exchange.

43. The system as claimed in any one of claims 35 to 42, wherein, The methane oxidation catalyst comprises a zeolite catalyst mixed with a supported oxide catalyst.

44. The system as claimed in any one of claims 35 to 43, wherein, This methane oxidation catalyst is a shaped catalyst.

45. The system of claim 44, wherein, The shaped catalyst is in the form of tablets, granules, extrusions, or combinations thereof.

46. ​​The system as claimed in any one of claims 35 to 45, wherein, The catalyst is added to the substrate.

47. The system as claimed in any one of claims 35 to 46, wherein, The catalyst is a combination of a coated substrate and a molded catalyst.

48. The system as claimed in any one of claims 35 to 47, wherein, The conversion rate of methane is at least about 25%.

49. The system as claimed in any one of claims 35 to 47, wherein, The methane conversion rate is at least about 50%, wherein the methane conversion rate is maintained at less than 75%, and / or the methane conversion rate is maintained at less than 85%.

50. The system of claim 49, wherein, The bed size of this reactor system is about 5%-35% of that of similar systems that can achieve approximately 99% methane conversion.

51. The system of claim 49, wherein, The reactor system has a bed size of approximately 1 m. 3 to less than about 10 m 3 Less than approximately 8 m 3 Less than approximately 6 m 3 Less than approximately 4 m 3 or less than about 3 m 3 .

52. The system as claimed in any one of claims 35 to 51, wherein, The reactor comprises two or more containers with intercooling.

53. The system as claimed in any one of claims 35 to 52, wherein, This system is adapted to use the heat removed from the reaction products of the reactor to generate steam.

54. A system for converting methane into CO2, the system comprising: A methane adsorbent or absorbent suitable for concentrating methane in a methane-containing gas stream; And a methane oxidation catalyst adapted to support a methane oxidation reaction, wherein the methane adsorbent or absorbent and the methane oxidation catalyst are contained together in a single container.

55. The system of claim 54, wherein, The methane adsorbent or absorbent comprises one or more solid adsorbents, which include zeolites, metal-organic frameworks, carbon-based adsorbents, or combinations thereof.

56. The system as claimed in any one of claims 54 to 55, wherein, The container includes a membrane system to facilitate the concentration and oxidation of methane within the container.

57. The system as claimed in any one of claims 54 to 56, wherein, The system is configured to feed an O2-containing gas stream to the methane oxide catalyst to support the methane oxidation reaction.

58. The system as claimed in any one of claims 54 to 57, wherein, The methane oxidation catalyst contains a copper zeolite catalyst.

59. The system as claimed in any one of claims 54 to 58, wherein, The methane oxidation catalyst comprises a zeolite catalyst having more than one transition metal for exchange.

60. The system as claimed in any one of claims 54 to 59, wherein, The methane oxidation catalyst comprises a zeolite catalyst mixed with a supported oxide catalyst.

61. The system as claimed in any one of claims 54 to 60, wherein, This methane oxidation catalyst is a shaped catalyst.

62. The system of claim 61, wherein, The shaped catalyst is in the form of tablets, granules, extrusions, or combinations thereof.

63. The system as claimed in any one of claims 54 to 62, wherein, The catalyst is added to the substrate.

64. The system as claimed in any one of claims 54 to 63, wherein, The catalyst is a combination of a coated substrate and a molded catalyst.

65. The system as claimed in any one of claims 54 to 64, wherein, The conversion rate of methane is at least about 25%.

66. The system as claimed in any one of claims 54 to 65, wherein, The conversion rate of methane is at least about 50%.

Images