Electrically conductive adsorbent fiber for acid gas removal

Abstract

The invention relates to an electrically conductive adsorbent fiber for acid gas removal, particularly carbon dioxide, from gas streams using electric swing adsorption. The fiber comprises a chrome alloy wire embedded within an adsorbent composite material, which includes a high-loading solid adsorbent and a binder. The invention also relates to methods for preparing the electrically conductive adsorbent fiber and its various uses in carbon capture processes.

Description

[0001] Electrically Conductive Adsorbent Fiber for Acid Gas Removal

[0002] TECHNICAL FIELD

[0003] The present invention relates to electrically conductive adsorbent fibers. More specifically, the invention pertains to composite fibers that integrate a chrome alloy wire for electrical conductivity with high-loading solid adsorbents. The invention also covers methods for preparing these fibers and their applications in carbon capture, utilization, and storage (CCUS) technologies.

[0004] TECHNICAL BACKGROUND

[0005] Carbon capture, utilization and storage (CCUS) technologies are widely recognized as crucial for meeting global energy and climate goals, particularly in limiting global temperature increases to 1.5°C. However, the high cost of CO2 capture remains a significant obstacle to large-scale deployment of CCUS technologies.

[0006] Solid adsorbents have emerged as a promising method for CO2 capture, offering several distinct processes for implementation. Conventional pressure swing adsorption (PSA) processes involve adsorption at high pressure and regeneration at low pressure. Vacuum swing adsorption (VSA) utilizes atmospheric pressure for adsorption and vacuum conditions for desorption. Temperature swing adsorption (TSA) operates with adsorption at ambient temperature and desorption at elevated temperatures. Among these, TSA is often preferred for CO2 capture due to its lower energy requirements compared to the compression and high vacuum processes used in PSA and VSA.

[0007] The economics of TSA processes are heavily influenced by the methods used for adsorbent heating. Externally heated TSA systems often require a large number of columns, resulting in high capital costs due to the extensive thermal resistance of mesoporous adsorbers and the large column dimensions. These factors necessitate long regeneration times, often spanning hours to days. To address these limitations, researchers have explored "in situ" heating methods using the Joule effect, leading to the development of electric swing adsorption (ESA).

[0008] Electric Swing Adsorption offers several advantages over traditional TSA and PSA approaches. ESA allows for direct heating without the need for additional heat to warm ancillary parts. It provides independent control of carrier gas flow rate and column heating rate, enables faster heating, and improves desorption kinetics and dynamics. These benefits make ESA an attractive option for more efficient CO2 capture processes. However, implementing ESA requires the adsorbent bed to be electrically conductive, which presents a challenge as many effective CO2 capture adsorbents, such as zeolites and metal-organic frameworks (MOFs), are not inherently conductive.

[0009] To make the adsorbent bed electric conductive, researchers have explored various methods of incorporating conductive materials into adsorbent beds. This often involves mixing or embedding conductive materials in the form of spherical particles, grains, cloths, fibers, or monoliths within the adsorbents (B. Verougstraete et al., Sep. Purif. Technol., 2025, 353, 128522; and A. A. Moinee, ACS Energy Lett. 2024, 9, 1228).

[0010] Structured adsorbents like monoliths and fibers provide several advantages over traditional packed beds of beads or pellets. For instance, structured adsorbents can enhance mass and heat transfer while minimizing pressure drop, as discussed in a comparative review by DeWitt et al. (S. J. A. DeWitt et al., Annu. Rev. Chem. Biomol. Eng., 2018, 9, 129). Reviews by Rezaei and Webley (Sep. Purif. Techn., 2010, 70, 243) and Akhtar et al. (J. Eur. Ceram. Soc., 2014, 34, 1643) summarize research efforts into optimizing structured adsorbents for gas separation.

[0011] In carbon capture and storage (CCS), structured adsorbents, particularly adsorbent fibers, demonstrate clear advantages over conventional packed beds and monoliths. Adsorbent fibers, for example, achieve pressure drops 10-30 times lower than packed beds at high superficial velocities and exhibit superior mass and heat transfer characteristics (Y. H. Lee et al., Chem. Mater., 2020, 32, 7081 ).

[0012] US Patent No. 9,114,364 discloses a hollow fiber, for adsorption or filtration, the fiber containing a tubular matrix having a first end and a second end, and a winding channel formed through the tubular matrix and extending between the first end and the second end. The disclosed adsorbent fiber has a curved configuration to promote mass transfer. However, the adsorbent fiber does not contain an electric conductive layer.

[0013] Quan et al. also developed adsorbent hollow fibers using polyether sulfone and diamine-appended Mg-MOF for post-combustion CO2capture, though without an electrically conductive layer (W. Quan et al., JACS Au, 2022, 2, 1350).

[0014] US Patent 8,540,810 discloses an adsorption unit comprising an electrically conductive, hollow fiber with layers of adsorbent particles embedded in a polymeric matrix and a conductive polyaniline layer for heat transmission. However, these fibers exhibit low flexibility (bending angle below 30°) and challenging manufacturability. Keller et al. describe polyethylenimine-impregnated silicon carbide fibers (SiC-PEI) and fibers consisting of a carbon nanotube matrix with dispersed zeolite particles (CNT-zeolite) with conductive layers, though both are limited by low adsorbent loading (20 wt%) and complex processing requirements (L. Keller et al., Chem. Eng. J., 2019, 371, 107).

[0015] W. H. Lee et al. describe the preparation of sorbent-coated carbon fibers for ESA carbon removal (W. H. Lee et al., Joule, 2023, 7, 1241 ). However, the roll to roll coating process used suffers from low coating speed and low sorbent loading (below 60 w%), rending the process not commercially scalable.

[0016] EP4,420,772 described the methods to prepare electrically conductive adsorbent fibers, including formation of a conductive layer on the bore surface of a hollow fiber support, on the shell surface of the hollow fiber support, or on the interior of the fiber support. The conductive layer can further be a bulk wire. However, the resulting electrically conductive adsorbent fibers suffer from low adsorbent loading and thus low adsorption capacities.

[0017] Therefore, current electrically conductive adsorbent technologies face several challenges, including low flexibility, manufacturing difficulties, high conductive material content reducing overall adsorbent capacity and scalability issues.

[0018] Within this context, there is a need for developing electrically conductive adsorbents for CO2 capture that combines high adsorption capacity and sufficient electrical conductivity for ESA applications.

[0019] There is also a need for developing electrically conductive adsorbents with versatile shapes suitable for integration into various devices, along with straightforward and reliable manufacturing methods.

[0020] SUMMARY OF THE INVENTION

[0021] It is a first object of the invention to provide an electrically conductive adsorbent fiber comprising at least one chrome alloy wire and an adsorbent composite material comprising a solid adsorbent and a binder, wherein the solid adsorbent constitutes more than 80% by weight of the total weight of the adsorbent composite material.

[0022] In one embodiment, the chrome alloy wire is selected from nickelchromium or iron-chromium-aluminum alloys.

[0023] Preferably, the nickel-chromium alloy consists essentially of 80% nickel and 20% chromium.

[0024] Preferably, the iron-chromium-aluminum alloy consists essentially of 61 % nickel, 15% chromium, and the balance being iron. In one embodiment, the solid adsorbent constitutes from 85 to 95% by weight of the total weight of the adsorbent composite material.

[0025] In one embodiment, the chrome alloy wire is embedded within the adsorbent composite material.

[0026] In one embodiment, the chrome alloy wire has a diameter corresponding to a gauge between 30 and 50.

[0027] Preferably, the solid adsorbent is selected from the group consisting of zeolites, metal-organic frameworks, covalent organic frameworks, porous aromatic frameworks, microporous organic polymers, activated carbon, and combinations thereof.

[0028] Advantageously, the MOF is selected from zinc-based MOFs, preferably CALF-20 and / or UTSA-16(Zn).

[0029] Preferably, the binder is selected from water-insoluble polymers.

[0030] Preferably, the binder is selected from polyacrylonitrile, copolymers and / or terpolymers thereof.

[0031] In one embodiment, the fiber has an outer diameter ranging from 0.1 mm to 10 mm.

[0032] It is a second object of the invention to provide a method for preparing the electrically conductive adsorbent fiber as described above, the method comprising: forming a dope solution containing a solid adsorbent, a binder, and a solvent; and extruding the dope solution along with a chrome alloy wire.

[0033] Preferably, the solvent is selected from N-methyl-2-pyrrolidone, dimethyl sulfoxide, or combinations thereof.

[0034] In one embodiment, the extrusion is performed through an orifice spinneret, with the chrome alloy wire extruded through an inner orifice and the dope solution extruded through an outer orifice simultaneously.

[0035] In one embodiment, the method further comprises passing the extruded nascent fiber through a coagulation bath to induce phase separation and solidify the composite material.

[0036] Preferably, the coagulation bath comprises water.

[0037] In one embodiment, the method further comprises washing the solidified fiber in a washing medium selected from water or isopropanol.

[0038] It is a third object of the invention to provide a method for removing an acid gas from an acid gas-enriched gas stream, comprising:

[0039] - a step of contacting the acid gas-enriched gas stream with the electrically conductive adsorbent fiber as defined above, wherein at least a portion of the acid gas is adsorbed by the electrically conductive adsorbent fiber; - a step of regenerating the electrically conductive adsorbent fiber by applying a voltage to the chrome alloy wire, generating heat to desorb the acid gas.

[0040] Preferably, the acid gas comprises carbon dioxide, hydrogen sulfide, or a combination thereof.

[0041] Preferably, the regeneration step is performed using electric swing adsorption, and the voltage applied to the chrome alloy wire generates heat through Joule heating.

[0042] In one embodiment, the regeneration step is assisted by a vacuum.

[0043] Preferably, the acid gas-enriched gas is selected from flue gas or atmospheric air.

[0044] It is a fourth object of the invention to provide a system for removing acid gases from an acid gas-enriched gas stream, comprising an adsorption unit containing comprising one or more electrically conductive adsorbent fibers as defined above; and a power supply configured to apply voltage to the chrome alloy wire within each fiber for regeneration via electric swing adsorption.

[0045] The electrically conductive adsorbent fiber described herein offers advantages for gas separation and carbon capture applications, particularly in ESA processes. The integration of a chrome alloy wire within the adsorbent composite material enables efficient in situ heating through Joule heating when a voltage is applied. This allows for rapid and controlled desorption of captured gases, such as CO2, without the need for external heating sources, reducing energy consumption and improving process efficiency.

[0046] Additionally, the high-loading solid adsorbent ensures a high adsorption capacity while maintaining sufficient electrical conductivity for ESA.

[0047] The fiber structure also enhances mass and heat transfer, minimizes pressure drop, and provides flexibility for integration into various system designs.

[0048] BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 illustrates a cross section of an electrically conductive adsorbent fiber according to an embodiment of the invention comprising the chrome alloy wire embedded in the adsorbent composite material.

[0050] Figure 2 illustrates a preparation set up for the electrically conductive adsorbent fiber of the invention via the dry-jet wet-quench process.

[0051] Figure 3 shows the PXRD spectrum of the NiChrome / UTSA-16(Zn) / PAN fiber as prepared in Example 1. The X-axis represents the diffraction angle (20) in degrees and the Y-axis represents the intensity of the diffracted X-rays, usually in arbitrary units (a.u.).

[0052] Figure 4 shows the PXRD spectrum of the NiChrome / CALF-20 / PAN fiber as prepared in Example 2. The X-axis represents the diffraction angle (20) in degrees and the Y-axis represents the intensity of the diffracted X-rays, usually in arbitrary units (a.u.).

[0053] Figure 5 shows the CO2 and N2 adsorption isotherms for the NiChrome / UTSA-16(Zn) / PAN fiber as prepared in Example 1. The X-axis represents the amount of gas adsorbed in mg / g and the Y-axis represents the absolute pressure in bar.

[0054] Figure 6 shows the CO2, N2 adsorption isotherms for the NiChrome / CALF-20 / PAN fiber as prepared in Example 2. The X-axis represents the amount of gas adsorbed in mg / g and the Y-axis represents the absolute pressure in bar.

[0055] Figure 7 shows the temperature profiles of the NiChrome / CALF-20 / PAN fibers enclosed in a 3 / 8-inch stainless steel tubing by applying different direct current voltages. The X-axis represents the temperature in °C and the Y-axis represents the time in seconds.

[0056] Figure 8 shows the cooling temperature profiles of the NiChrome / CALF- 20 / PAN fibers enclosed in a 3 / 8-inch stainless steel tubing by passing ambient temperature nitrogen flows. The X-axis represents the temperature in °C and the Y-axis represents the time in seconds.

[0057] Figure 9 shows the CO2 concentration and temperature profiles for a complete adsorption, desorption, and cooling cycle of the NiChrome / CALF- 20 / PAN fibers enclosed in a 3 / 8-inch stainless steel tubing.

[0058] DETAILED DESCRIPTION

[0059] The invention will now be described in more detail without limitation in the following description.

[0060] According to a first aspect, the invention provides an electrically conductive adsorbent fiber comprising at least a chrome alloy wire, an adsorbent composite material, the adsorbent composite material comprising a solid adsorbent and a binder.

[0061] “Electrically conductive," as used in this invention, refers to the ability of a material to carry an electric current. This means that the material allows electricity to flow through it when a voltage is applied. In this invention, the chrome alloy wire in the fiber provides this electrical conductivity, enabling the fiber to generate heat when an electric current passes through it. The chrome alloy wire

[0062] In the present invention, a chrome alloy wire is used as the electric conductive material in the adsorbent fiber, enabling efficient heat generation through electrical resistance.

[0063] Chrome alloy wires are especially suited for this purpose due to their wide availability, cost-effectiveness, and superior corrosion and oxidation resistance in heating applications.

[0064] The electrically conductive adsorbent fiber of the invention may comprise a single chrome alloy wire or multiple chrome alloy wires.

[0065] In one embodiment, the chrome alloy wire is embedded within the adsorbent material.

[0066] Advantageously, the chrome alloy wire is preferably selected from nickelchromium (NiChrome) and iron-chromium-aluminum (AluChrome) alloys.

[0067] NiChrome alloys are typically available in two common compositions: NiCr A, which consists essentially of 80% nickel and 20% chromium, and NiCr C, which consists essentially of 61 % nickel, 15% chromium, with the balance being iron.

[0068] Chrome alloy wires are available in a range of gauges and forms, including round wires and ribbons. Preferably, the cross-section of the chrome alloy wire used in the invention is circular.

[0069] The term "gauge" refers to the chrome alloy wire's diameter; a smaller gauge number indicates a thicker wire, while a larger gauge number corresponds to a thinner wire. For example, NiChrome wires are commercially available from Gage 000 (diameter= 0.41 inch) to Gage 50 (diameter= 0.001 inch).

[0070] In a particularly preferred embodiment, smaller-diameter wires are used, as they contribute to:

[0071] - reduced weight percentage of the conductive wire in the electrically conductive adsorbent fiber,

[0072] - lower overall chrome alloy consumption, leading to cost savings,

[0073] - enhanced heat generation efficiency per unit length.

[0074] In one embodiment, the chrome alloy wire gauge is preferably greater than 20, more preferably greater than 30, most preferably between 30 and 50.

[0075] The adsorbent composite material

[0076] The adsorbent composite material comprises a solid adsorbent and a binder. The solid adsorbent can include a wide range of materials, including amine adsorbents supported on solid supports, zeolites, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), porous aromatic frameworks (PAFs), microporous organic polymers (MOPs), activated carbon, activated alumina, graphene, silica, layered double hydroxide (LDH), and combinations thereof.

[0077] Amine adsorbents supported on solid supports are adsorbents where amine groups (compounds containing -NH2) are chemically attached to a solid material, such as silica or polymer-based supports. The solid support may include polymers, carbon, silica, molecular sieves, MOFs, which can be further modified to enhance hydrophobicity.

[0078] Zeolites are microporous aluminosilicate minerals with a crystalline structure and very high surface area.

[0079] MOFs are materials made of metal ions coordinated to organic ligands, creating a highly porous structure.

[0080] COFs are porous crystalline materials formed by covalent bonds between light elements such as carbon, nitrogen, and boron.

[0081] PAFs are porous materials built from aromatic (benzene-ring-based) units, creating a robust, stable framework. PAFs are inherently hydrophobic due to their aromatic structures.

[0082] MOPs are porous polymers with organic backbones and microporous structures, providing high surface area. Due to their organic nature, MOPs are often hydrophobic.

[0083] Activated carbon is carbon that has been processed to have small, low- volume pores, resulting in a large surface area for adsorption. Activated carbon is inherently hydrophobic.

[0084] Activated alumina is a highly porous form of aluminum oxide with a large surface area.

[0085] Graphene is a single layer of carbon atoms arranged in a two- dimensional honeycomb lattice.

[0086] Silica is a form of silicon dioxide with a porous structure, available in various forms like silica gel.

[0087] LDHs are materials with a layered structure, consisting of metal hydroxides with a positive charge balanced by anions.

[0088] In a preferred embodiment, the adsorbent material is selected from zeolites, MOF, and their combinations.

[0089] The MOFs can be selected from a diverse range, including but not limited to: - general MOFs: such as MOF-2, MOF-3, MOF-4, MOF-5, MOF-70, MOF-73, MOF-74, MOF-75, MOF-76, MOF-177, MOF-303, MOF-505, MOF-80, and MOF-808,

[0090] - UiO-type MOFs: Examples include UiO-66, UiO-67, and UiO-68,

[0091] - ZIF-type MOFs (Zeolitic Imidazolate Frameworks): Examples include ZIF-7, ZIF-8, ZIF-9, ZIF-10, ZIF-12, ZIF-68, ZIF-69, ZIF-70, ZIF-78, ZIF-79, ZIF-81 , ZIF-82, and ZIF-90,

[0092] - MIL-type MOFs (Materials Institute Lavoisier): Examples include MIL- 53, MIL-88, MIL-96, MIL-101 , MIL-140L, and MIL-160,

[0093] - HKUST-1 : A copper-based MOF,

[0094] - PCN-type MOFs (Porous Coordination Networks): Examples include PCN-224 and PCN-250,

[0095] - zinc-based MOF such as CALF-20, CALF-15 and UTSA-16Zn (disclosed for example in US Patent No. 11 ,230,562),

[0096] - MUF Series: such as for example MUF-15 and MUF-16,

[0097] - CAU Series: such as for example CAU-10 and CAU-10-H.

[0098] - frameworks with specific anions or cations: such as for example AI(OH) fumarate, Al-formate, Mg-formate, Zr-fumarate, Fe-BTC, and MIL-120(AI), as well as Mg(H2gal), and

[0099] - IISERP-MOF such as IISERP-MOF-2.

[0100] The MOF may consist of a single type or a mixture of different MOFs.

[0101] In some embodiments, the MOF can be functionalized with suitable functional groups, including in particular amine-containing functional groups such as for example UiO-66-NH2. An amine-functionalized magnesium MOF is also described in US Patent Nos. 9,861 ,953 and 10,137,430.

[0102] The MOF (UTSA-16) with the general formula of K2(M1xM2i-x)s(Cit)2 where Cit is fully dehydrogenated citrate anion and M1 and M2 are metal cations of Zn, Co, Cu, Mg, Ni, Ca, Mn, Cr, Zr, and Fe and x is from 0 to 1 , is preferred to be manufactured by the methods disclosed in the US patent application No. 63 / 593,627. The methods utilize water as the solvent and the reactions are carried out at atmospheric pressure with temperature below 100 °C. The methods may comprise:

[0103] (a) reacting 1 molar equivalent of citric acid with / molar equivalent of a metal carbonate component and with j molar equivalent of a basic potassium compound;

[0104] (b) reacting the product of (a) with k molar equivalent of a metal salt component, wherein the method is conducted in a solvent consisting of water at ambient pressure and at a temperature no greater than 100 °C, and wherein / is from 0 to 1 .0, J is from 3.0 to 1 .0, and k is from 1 .0 to 1 .5.

[0105] In a one embodiment, the MOF is selected from a zinc-based MOF, such as for example CALF-20 and UTSA-16(Zn), a cobalt-based MOF, such as for example UTSA-16(Co), a zeolitic imidazolate framework, such as ZIF-94, and / or an amine-functionalized magnesium MOF such as epn-grafted Mg2(dobpdc) (epn = 1-ethylpropane-1 ,3-diamine), disclosed for example in US Patent Nos. 9,861 ,953 and 10,137,430.

[0106] In one preferred embodiment, the MOF is UTSA-16(Zn).

[0107] In another embodiment, the MOF is UTSA-16(Co).

[0108] In another embodiment, the MOF is CLAF-20.

[0109] The zeolite may be selected from a diverse range, including but not limited to:

[0110] - classical aluminosilicate zeolites, like 13X, 5A, and 4A, SSZ-13,

[0111] - high-silica zeolites, such as ZSM-5 and Sil ical ite-1 ,

[0112] - aluminum phosphate-based zeolites, including SAPO-34 and SAPO- 56,

[0113] - high surface area zeolites like Y and AIPO-18,

[0114] - Zeolites with a chabazite (CHA) framework, such as SSZ-13,

[0115] - ion-exchanged zeolites, such as M-Y, M-X, M-MOR, M-MAZ, M-CHA, M-MER, and M-SSZ, where M is a metal cation selected from the group consisting of Li+, Cs+, Na+, K+, Ca2+, Mg2+, Zn2+, and Ba2+,

[0116] - natural zeolites, such as Mordenite, Merlinoite, Erionite, and Clinoptilolite.

[0117] The zeolite may consist of a single type or a mixture of different zeolites.

[0118] Advantageously, the amount of solid adsorbent in the adsorbent material may vary from 80 to 98 % by weight, preferably from 85 to 98 % by weight, more preferably from 85 to 95% by weight.

[0119] In the present application, the expression 'more than 80' is intended to mean values strictly greater than 80, thereby excluding the value 80 itself.

[0120] The adsorbent material also comprises a binder, which plays a role in maintaining the cohesion and structure of the adsorbent material, in particular for powdered adsorbents like MOFs and zeolites.

[0121] The presence of a binder typically stabilizes the adsorbent structure and enhances its mechanical strength without blocking the pores, making it easier to incorporate into practical devices for the adsorption of gases.

[0122] Advantageously, the binder is selected from water-insoluble polymers. As used herein, the term "water-insoluble polymer" refers to a polymer that is incapable of dissolving in water or aqueous solutions under standard conditions. Specifically, it is defined as a polymer that exhibits a solubility of less than 5 g, preferably less than 2 g, and more preferably less than 1 g per 100 g of water at 25°C. Preferably, for accurate assessment of solubility, the polymer must be thoroughly dried at 105°C for 2 hours to eliminate any residual moisture. Solubility testing may be conducted once the polymer has reached a constant dry weight.

[0123] The water-insoluble polymer can be a natural or a synthetic polymer.

[0124] Natural polymers may include but are not limited to cellulose and its derivatives (e.g., cellulose acetate, cellulose nitrate), lignin, chitosan, starch and modified starch, alginate and its dérivâtes and combinations thereof.

[0125] Synthetic polymers may include but are not limited to polyacrylonitrile, poly(methyl methacrylate), polystyrene, polyethylene terephthalate), aromatic polyamides, aliphatic polyamides, polyimides, polyesters, polyetherketones, polyethersulfones, polyetheresters, polysulfones, polyvinyl fluoride, polyvinyl difluoride, polyvinylchloride, polybenzimidazoles, polybenzoxazoles, polyazoaraomatics, poly(2,6-dimethylphenylene oxide), polyphenylene oxides, polyureas, polyurethanes, polyhydrazides, polyazomethines, polyacetals, polyquinoxaline, polyamideesters, polyacetylenes, polymer with intrinsic porosities (PIMs), any combinations thereof (blends) and / or copolymers or terpolymers thereof.

[0126] Preferably, the water-insoluble polymer is polyacrylonitrile (PAN), a copolymer and / or a terpolymer thereof. PAN copolymers include for example poly(acrylonitrile-co-itaconic acid), poly(acrylonitrile-co-acrylic acid), poly(acrylonitrile-co-methacrylic acid), poly(acrylonitrile-co-methyl methyl acrylate), and poly(acrylonitrile-co-methyl acrylate). PAN terpolymers include for example poly(acrylonitrile-methyl acrylate-itaconic acid), poly(acrylonitrile-methyl methacrylate-itaconic acid) and poly(acrylonitrile-methyl acrylate-acrylic acid).

[0127] Advantageously, the water-insoluble polymer has a weight-average molecular weight (Mw) ranging from 10,000 to 2,000,000 Dalton, preferably from 60,000 to 500,000 Dalton.

[0128] Advantageously, the amount of binder in the adsorbent composite material ranges from 2 to 20 % by weight, preferably from 2 to 15 % by weight, more preferably from 5 to 15% by weight.

[0129] Advantageously, the weight ratio between the solid adsorbent and the binder in the adsorbent composite material is greater than 4, preferably between 5 and 50, preferably between 5 and 20. Advantageously, the water-insoluble polymer forms a porous matrix in which the solid adsorbent is dispersed, preferably homogeneously dispersed. This arrangement facilitates the creation of a high-surface-area material with enhanced porosity.

[0130] The term "porous matrix" refers to a solid material characterized by a network of interconnected pores or voids permeating its structure. These pores, which can vary in size, shape, and distribution, contribute to the material's high surface area and allow for the passage of gases.

[0131] Advantageously, the adsorbent composite material exhibits an open-cell or interconnected structure, where the polymer matrix encapsulates the solid adsorbent without obstructing them, promoting efficient mass transport.

[0132] The porosity of the adsorbent composite material can range from 20% to 80%, preferably from 30% to 70% by volume relative to the entire volume of the adsorbent composite material.

[0133] Porosity can be measured by comparing the weight difference when the material is dry and when saturated with a liquid such as water or isopropanol.

[0134] The pore size of the adsorbent composite material can vary and can include macroporosity, mesoporosity and / or microporosity.

[0135] As used herein, macroporosity is defined by pores having a diameter larger than about 50 nm; mesoporosity is defined by pores having a diameter within a range of from about 2 nm to about 50 nm; and microporosity is defined by pores having diameter less than about 2 nm. The type of porosity most relevant with respect to the removal of an acid gas such as carbon dioxide from a stream is macroporosity and / or mesoporosity.

[0136] The density of the adsorbent composite material (excluding the chrome alloy wire) can range from 0.2 g / cm3to 1 g / cm3, preferably from 0.3 g / cm3to 0.8 g / cm3.

[0137] The electrically conductive adsorbent fiber of the invention can be manufactured in any desired diameter. In one embodiment, the electrically conductive adsorbent fiber may have an outer diameter within a range of from 0.1 mm to 10 mm, preferably from 0.5 to 6 mm.

[0138] Method of preparation of the electrically conductive adsorbent fiber

[0139] In a second aspect, the invention provides a method for preparing the electrically conductive adsorbent fiber described above.

[0140] In one embodiment, the electrically conductive adsorbent fiber is prepared by: a) forming a dope solution containing the solid adsorbent, the binder and a solvent and b) extruding the dope solution along with the chrome alloy wire.

[0141] Step a)

[0142] As used herein, a “dope solution” refers to a mixture, solution, or suspension of the solid adsorbent and the binder in a solvent, which can subsequently be processed into a fiber.

[0143] The solid adsorbent is preferably in powder form, with particles having a size of less than or equal to 1000 pm, typically less than or equal to 500 pm, and sometimes even less than or equal to 10 pm. Particle sizes may range from 0.01 pm to 500 pm, depending on the desired properties of the final composite material.

[0144] As used herein, the term "particle size" refers to the average dimensions of a particle, as measured by methods such as scanning electron microscopy (SEM) and sieving.

[0145] The amount of solid adsorbent in the dope solution preferably ranges from 5% to 65% by weight, preferably from 15% to 55%, and more preferably from 25% to 45% by weight based on the total weight of the dope solution. For example, the solid adsorbent content may vary in specific increments, such as from 5% to 15%, from 15% to 25%, and so on, up to 65%.

[0146] The amount of the binder in the dope solution may range from 0.5 to 25%, preferably from 1 % to 20% by weight, preferably from 2% to 15%, and more preferably from 2% to 10%, most preferably from 2% to 8%.

[0147] The solvent used in the dope solution can be a polar protic solvent and / or a polar aprotic solvent. A single solvent or mixtures of solvents may be used.

[0148] Polar protic solvents are typically solvents that have a hydrogen atom attached to an electronegative atom, typically oxygen or nitrogen, which allows them to form hydrogen bonds.

[0149] Polar aprotic solvents are typically solvents that are polar but do not have acidic hydrogen, meaning they lack O-H, N-H, S-H or P-H bonds. They cannot donate protons for hydrogen bonding but can accept them.

[0150] The use of polar solvents is preferred, since the polar solvent can be conveniently removed by using water, in particular during the shaping step.

[0151] In one embodiment, the solvent used in the dope solution is selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethylsufoxide (DMSO), tetrahydrofurane (THF) and combinations thereof. In one preferred embodiment, the solvent used in the dope solution is NMP and / or DMSO.

[0152] The amount of solvent in the dope solution may vary from 20 to 80% by weight, preferably from 30% to 70%, more preferably from 40% to 60% by weight based on the total weight of the dope solution.

[0153] The dope solution may also comprise one or more additives, which can be either liquid or solid. These additives can be selected to serve various functions, including modifying viscosity, imparting porosity, and enhancing other properties of the composite material.

[0154] Examples of additives that can be employed in the dope solution include but are not limited to: water, aliphatic alcohols, particularly polyhydric alcohols such as ethylene glycol, glycerin, polyethylene oxides and polypropylene oxides, polyvinylalcohol, polyvinylpyrrolidone, surfactants such as alkylaryl polyether alcohols, alkyl sulfates, alkylarylsulfates, triethylphosphate, formamide, and salts such as lithium chloride or calcium chloride, or combinations thereof.

[0155] In one embodiment, the additive is a pore-forming compound. A poreforming compound is a compound that promotes the formation of open, interconnected pores in the final product. This can be achieved through the complete or partial removal of the pore former additive during the material's processing, leaving behind a network of voids. Examples of pore-forming compounds may include polyethylene oxide), volatile solvents or 1 ,3,5- trimethylbenzene.

[0156] The amount of additive in the dope solution may vary within a range of from about 0% to about 30% by weight based on the total weight of the dope solution. The amount of additives in the dope solution may vary for example from 5 to 25% by weight, from 10 to 20% by weight, or from 10 to 15% by weight.

[0157] It is to be understood that the nature and amount of the additives can be selected depending on desired material properties, process and / or equipment parameters or other factors.

[0158] In one embodiment, the dope solution comprises:

[0159] - from 20 to 40% by weight of solid adsorbent; preferably a MOF,

[0160] - from 2 to 10% by weight of binder, preferably a polyacrylonitrile polymer;

[0161] - from 30 to 70% by weight of solvent;

[0162] - from 0 to 10% by weight of additives.

[0163] In one embodiment, the dope solution is prepared by first dissolving the water-insoluble polymer in the solvent to create a polymer solution. The solid adsorbent, preferably in powder form, is then added to the polymer solution. Optional additives, such as CaCl2, LiCI, or polyethylene oxide, can be introduced either alongside the polymer or the solid adsorbent or at different stages during the preparation of the dope solution.

[0164] Step b)

[0165] Prior to extrusion, the dope solution may be degassed under heat and / or vacuum to remove any trapped air or gases.

[0166] To shape the electrically conductive adsorbent according to the invention into a fiber, the dope solution is extruded simultaneously with the chrome alloy wire.

[0167] The extrusion is preferably carried out through an orifice in an orifice spinneret. The chrome alloy wire is extruded through the inner orifice of the spinneret and the dope solution is extruded through the outer orifice of the spinneret simultaneously.

[0168] Advantageously, upon extrusion, the nascent fiber enters a coagulation bath 3 preferably containing water or an alternative non-solvent. The water bath acts as a medium for phase separation and solidification. The solvent within the dope solution diffuses out while water or another non-solvent diffuses in, inducing phase separation that solidifies the material. This coagulation bath is preferably deionized water but may also include aqueous solutions or alternative non-solvents such as methanol, ethanol, or isopropanol. In one embodiment, the coagulation bath is water.

[0169] In one embodiment, the nascent fiber can be allowed to pass through an air gap before entering the water bath. This air gap serves as a cooling medium, enhancing the phase separation process.

[0170] Once solidified, the fiber can be pulled from the coagulation bath onto a rotating barrel, followed by immersion in a washing medium 4, for example water or isopropanol, to remove any residual solvent or non-solvent.

[0171] The water in the water bath may be for example deionized water or an aqueous solution.

[0172] For additional washing and purification, pulling and piddling techniques (as disclosed in US Patent No. 8,753,741 ) may be applied. These steps involve directing the composite around a rotating barrel within the washing medium, ensuring comprehensive removal of residual chemicals and enhancing the structural stability of the fiber.

[0173] After extrusion, the composite may remain soaked in the water bath for 1 to 72 hours, preferably from 12 hours to 48 hours, more preferably 24 hours, to allow for thorough solvent removal. Obtaining electrically conductive adsorbent fiber of desired morphologies or properties may depend on factors such as spinneret design, dope flow rates and / or physical properties, air gap dimensions, bath conditions, shear forces within the spinneret, draw ratios and so forth.

[0174] In some embodiments, heat treatment in a suitable oven or a in suitable fluid, such as a water bath or a steam chamber, can be carried out. Stepwise heating, followed by plateau temperature maintenance, optionally interspersed with one or more cooling and reheating periods, can be employed in some embodiments. Temperatures can be above room temperature (20 °C) and are often at least 10 °C below the glass transition temperature of the water-insoluble polymer. In some variations, the heat treatment may be carried out by directly extruding the dope solution and the chrome alloy fiber into a heated water bath.

[0175] Alternatively, water bath is exchanged with an alcohol prior to drying. This may involve withdrawing the fiber from the water bath and immersing it into an alcohol bath - or alternatively, gradually modifying the composition of the water bath to turn it into an alcohol bath.

[0176] In some variations, the heat treatment mentioned in the previous paragraph may be carried out after this solvent exchange.

[0177] The alcohol bath may comprise one or more alcohol compounds and optionally water, for example in a total amount of 1 to 50% by weight. When water is present in the alcohol bath, the exchange may simply consist in the addition of one or more alcohol compounds to the water bath. The alcohol compounds preferably comprise or consist of C1 to C6 alcohol compounds, more preferably C1 to C4 alcohol compounds. Preferably, the alcohol compound is selected from the group consisting of methanol, ethanol, isopropanol and mixtures thereof.

[0178] Advantageously, the obtained fiber is dried. Drying can be conducted for example, under ambient conditions or by supplying heat, e.g., in an oven or any drying means known by the skilled person, at temperatures such as from 50 °C to 150 °C.

[0179] Advantageously, the method described herein can produce a chrome alloy wire-based adsorbent fiber that is self-supporting (also referred to as “freestanding”), a property describing a material or an article that does not require an external supporting structure to prevent it from collapsing or crumbling. Applications

[0180] Chrome alloy wire-based adsorbent fiber described herein can be packaged into modular adsorption devices with terminals that can be connected with an electricity supply.

[0181] An illustrative adsorption device (also referred to herein as a “cartridge”) can include a plurality, i.e., two or more fibers that are laid parallel to or wound, e.g., helically, around a center tube.

[0182] One or more cartridges can be assembled into a module. In one embodiment, a module includes at least two modular adsorption devices that are installed in a vessel in series or in parallel. Operations can be conducted in an axial or cross flow arrangement. Either shell side or bore side feeding can be employed. Various cartridge and / or module configurations that can be employed are described, for example, in US patent application No 2023 / 0008877.

[0183] A power supply is preferably configured to apply voltage to the chrome alloy wire.

[0184] According to another aspect of the invention, the electrically conductive adsorbent fiber of the invention, preferably assembled into a cartridge and / or module, is used to remove an acid gas from a gaseous stream.

[0185] It is thus another object of the invention to provide a method for removing an acid gas from an acid gas-enriched gas stream, comprising:

[0186] - a step of contacting the acid gas-enriched gas stream with the electrically conductive adsorbent fiber, wherein at least a portion of the acid gas is adsorbed by the electrically conductive adsorbent fiber;

[0187] - a step of regenerating the electrically conductive adsorbent fiber by applying a voltage to the chrome alloy wire, generating heat to desorb the acid gas.

[0188] The gaseous stream is preferably a flue gas stream or ambient atmosphere.

[0189] The acid gas may be selected from CO2, SO2 and or H2S. In one embodiment, the acid gas is CO2.

[0190] As at least a portion of the acid gas becomes adsorbed by the electrically conductive adsorbent fiber, the gaseous stream is depleted in the acid gas, generating a stream that is purified relative to the acid gas.

[0191] The acid gas laden can be regenerated by applying a predetermined voltage. When a voltage is applied across the electrically conductive adsorbent fiber, an electric current flows through the chrome alloy wire. This current flow generates heat via the Joule effect (also known as resistive heating), where the electric energy is converted into thermal energy within the fiber. The greater the resistance to electron flow, the greater the heat energy created.

[0192] According to Ohm’s Law, resistance R (in ohms) is defined by the equation:

[0193] R=V / I where V is the voltage (in volts) and I is the current (in amps).

[0194] The heat energy or power P (in watts) released is proportional to the square of the voltage divided by resistance, represented as:

[0195] P=V2 / R

[0196] As the temperature of the fiber increases, the heat energy disrupts the interactions between the adsorbent fiber surface and the adsorbed gas molecules. Once enough thermal energy is supplied, the gas molecules detach from the surface and are released back into the gaseous phase.

[0197] The length of the time for the electricity supply depends on the length of the fiber, the diameter of the chrome wire, and the voltage. For example, with careful design, an acid gas, preferably a CO2 laden cartridge can be regenerated in a time span of 5 to 60 seconds, preferably of 10 to 20 second.

[0198] A low vacuum can also be applied at the same time to assist the regeneration of the electrically conductive cartridge.

[0199] Advantageously, the method further comprises a step of cooling the electrically conductive adsorbent fiber, in particular before applying another adsorption / desorption cycle.

[0200] After the voltage is removed, the fiber can be cooled down, and the fiber is ready to start the adsorption process again. Preferably, the cooling step is performed using ambient air.

[0201] The electrically conductive adsorbent fiber of the invention also can find applications in the direct removal of an acid gas from an ambient atmosphere. Some approaches that can be employed to capture carbon dioxide from the atmosphere typically rely on a blower to circulate the air through the adsorbent, included in an adsorbent device. As carbon dioxide is adsorbed, clean air is released. Once the adsorbent is saturated with carbon dioxide, the air circulation is directed to another adsorbent device, and the current adsorbent device is regenerated by supplying an electric voltage. The source of the electricity can be from renewable energy sources, such as solar or wind.

[0202] The acid gas, preferably carbon dioxide, released from the electrically conductive adsorbent fiber(s) of the invention be utilized for enhanced oil recovery, to prepare synthetic fuels, such as methanol, methane, jet fuels, etc. In some embodiments, the carbon dioxide is injected for storage. EXAMPLES

[0203] The invention is further illustrated in the following non-limiting examples. Materials:

[0204] • CALF-20: Zinc-based Calgary Framework 20, [Zn2(1 ,2,4- triazolate)2(oxalate)], synthesized in house from Oxalic acid, 1 ,2,4-triazole, and basic zinc carbonate in 50 / 50 ethanol water solution.

[0205] • UTSA-16Zn: Zinc-based MOF synthesized from citric acid, potassium hydroxide and zinc oxide.

[0206] • NMP: N-Methyl-2-pyrrolidone, anhydrous, 99.5%, purchased from Advanced ChemTech.

[0207] • PAN: acrylonitrile methyl methacrylate (MMA) copolymer, molecular weight (MW) approximately 80,000 Dalton, powder form, purchased from Dolan Gmbh.

[0208] Example 1 : Preparation of NiChrome based UTSA-16Zn fiber

[0209] The preparation process for the NiChrome-based UTSA-16Zn fiber is illustrated in Fig 2. A dope solution 20 was prepared by mixing 43.6 g of UTSA- 16Zn powder, 3.73 g of PAN and 40.0 g of NMP. The solid adsorbent / binder ratio is of 11.7. After degassing, the dope solution was transferred into a homemade fiber spinning apparatus 18 equipped with a tube in an orifice spinneret. The dope solution was extruded from the orifice of the spinneret and a NiChrome wire 14 was extruded through the tube of the spinneret to form a nascent fiber. The NiChrome wire contains 80%of Nickel and 20% of Chromium and has a gage equal to 36. The nascent fiber was delivered into deionized water bath 30. The fiber was further soaked in IPA for 24 hours to remove the NMP solvent, after which it was air dried to obtain an CALF-20 / PAN coated Nichrome wire 38.

[0210] The fiber comprises 92% by weight of CALF-20 and 8% by weight of PAN based on the total weight of CALF-20 and PAN, i.e., excluding the NiChrome wire. The CALF-20 / PAN ratio is 11 .5.

[0211] A section of the fiber was tested with a TGA instrument for its CO2 adsorption properties. The fiber was first heated to 110 °C and held at 110 °C for 30 min to activate the fiber under nitrogen. This was followed by cooling the activated fiber to 30 °C under nitrogen. The fiber was then exposed to a dry CO2 gas stream for 30 min. The weight gain of the fiber after the CO2 exposure was 10.8% by weight.

[0212] Sections of the fiber were then cut into pieces to perform PXRD, CO2 and N2 adsorption isotherm tests at 0, 20, 30 and 50°C. The results are shown in FIG. 3 and FIG. 5, respectively. Example 2: Preparation of NiChrome based CALF-20 fiber

[0213] A dope solution was prepared by mixing 27.0 g of CALF-20 powder, 3.73 g of PAN and 40.0 g of NMP. After degassing, the dope solution was transferred into a homemade fiber spinning apparatus equipped with a tube in an orifice spinneret. The dope solution was extruded from the orifice of the spinneret and a NiChrome wire was extruded through the tube of the spinneret to form a nascent fiber. The NiChrome wire contains 80% of Nickel and 20% Chromium. The gage for the wire is 36. The nascent fiber was delivered into deionized water. The fiber was further soaked in IPA for 24 hours (to remove the NMP solvent), after which it was air dried.

[0214] The fiber comprises 87.8% by weight of CALF-20 and 12.2% by weight of PAN based on the total weight of CALF-20 and PAN, i.e., excluding the NiChrome wire. The CALF-20 / PAN ratio is 7.24.

[0215] A section of the fiber was tested with a TGA instrument for its CO2 adsorption properties. The fiber was first heated to 110 °C and held at 110 °C for 30 min to activate the fiber under nitrogen. This was followed by cooling the activated fiber to 30 °C under nitrogen. The fiber was then exposed to a dry CO2 gas stream for 30 min. The weight gain of the fiber after the CO2 exposure was 9.8% by weight.

[0216] Sections of the sample were then cut into pieces to perform PXRD, CO2 and N2 adsorption isotherm tests at 0, 20, 30 and 50°C. The results are shown in FIG. 4 and FIG. 6, respectively.

[0217] Example 3: Electrically conductive adsorption / desorption test for NiChrome based CALF-20 fiber

[0218] An electrically conductive adsorption desorption testing device was constructed utilizing the NiChrome-based CALF-20 / PAN fiber prepared in Example 2. A total number of 35 of the said fibers are packed into a 3 / 8 stainless tubing equipped with thermos couples and gas inlet and outlet. Both ends of the tube were sealed with high temperature epoxy. The active length of the fibers inside the enclosed tube is 7.0 inch. The extra length of the fibers was utilized to connect to the electricity supply. A DC electricity supply with variable voltages is utilized to perform the tests. The N2 and CO2 gas supplies were controlled by two mass flow controllers, and the voltage supply was controlled by a computer-controlled relay board. The temperature of the adsorbent fiber was recorded by a temperature data logger and CO2 concentration of the outlet gas is measured by a Sensirion CO2 sensor.

[0219] The effect of voltage on the fiber temperature rise is shown in Figure 7 and the effect of cooling gas flow on the fiber temperature cooling is shown in Figure 8. Both figures show that the electrically conductive device can be heated and cooled extremely fast, such as in less than 30 seconds.

[0220] Figure 9 shows a complete CO2 adsorption / desorption cycle utilizing 5 v% CO2 as a feed gas comprising CO2 and N2. With the feed flow rate of 1 SLM for the CO2 / N2 mixture, the column breakthrough time is about 160 s. Once the feed gas was switched off, and simultaneously a 1 SLM of N2 and a 10 V of electricity were supplied, the CO2 was completely desorbed in 40 s.

[0221] Example 4: Preparation of NiChrome based UTSA-16Zn fiber outside the scope of the invention

[0222] A dope solution was prepared by mixing 5.2 g of UTSA-16Zn powder, 5.2 g of PAN and 40.0 g of NMP. After degassing, the dope solution was transferred into a homemade fiber spinning apparatus equipped with a tube in an orifice spinneret. The dope solution was extruded from the orifice of the spinneret and a NiChrome wire was extruded through the tube of the spinneret to form a nascent fiber. The NiChrome wire contains 80% of Nickel and 20% Chromium. The gage for the wire is 36. The nascent fiber was delivered into deionized water. The fiber was further soaked in IPA for 24 hours to remove the NMP solvent, after which it was air dried.

[0223] The fiber comprises 50% by weight of CALF-20 and 50% by weight of PAN based on the total weight of CALF-20 and PAN, i.e., excluding the NiChrome wire. The CALF-20 / PAN ratio is 1 .

[0224] A section of the fiber was tested with a TGA instrument for its CO2 adsorption properties. The fiber was first heated to 110 °C and held at 110 °C for 30 min to activate the fiber under nitrogen. This was followed by cooling the activated fiber to 30 °C under nitrogen. The fiber was then exposed to a dry CO2 gas stream for 30 min. The weight gain of the fiber after the CO2 exposure was 3.7 % by weight. This fiber does not have an adsorption capacity as high as that of the fibers in Examples 1 and 2 of the invention, and therefore does not allow efficient CO2capture.

Claims

CLAIMS1. An electrically conductive adsorbent fiber comprising at least one chrome alloy wire and an adsorbent composite material comprising a solid adsorbent and a binder, wherein the solid adsorbent constitutes more than 80% by weight of the total weight of the adsorbent composite material.

2. The electrically conductive adsorbent fiber of claim 1 , wherein the chrome alloy wire is selected from nickel-chromium or iron- chromium-aluminum alloys.

3. The electrically conductive adsorbent fiber of claim 2, wherein the nickel-chromium alloy consists essentially of 80% nickel and 20% chromium.

4. The electrically conductive adsorbent fiber of claim 2, wherein the iron-chromium-aluminum alloy consists essentially of 61 % nickel, 15% chromium, and the balance being iron.

5. The electrically conductive adsorbent fiber of any one of the preceding claims, wherein the solid adsorbent constitutes from 85 to 98% by weight, preferably from 85 to 95% by weight of the total weight of the adsorbent composite material.

6. The electrically conductive adsorbent fiber of any one of the preceding claims, wherein the chrome alloy wire is embedded within the adsorbent composite material.

7. The electrically conductive adsorbent fiber of any one of the preceding claims, wherein the chrome alloy wire has a diameter corresponding to a gauge between 30 and 50.

8. The electrically conductive adsorbent fiber of any one of the preceding claims, wherein the solid adsorbent is selected from the group consisting of zeolites, metal-organic frameworks, covalent organic frameworks, porous aromatic frameworks, microporous organic polymers, activated carbon, and combinations thereof.

9. The electrically conductive adsorbent fiber of claim 8, wherein the MOF is selected from zinc-based MOFs, preferably CALF-20 and / or UTSA-16(Zn).

10. The electrically conductive adsorbent fiber of any one of the preceding claims, wherein the binder is selected from waterinsoluble polymers.

11. The electrically conductive adsorbent fiber of claim 10, wherein the binder is selected from polyacrylonitrile, copolymers and / or terpolymers thereof.

12. The electrically conductive adsorbent fiber of any one of the preceding claims, wherein the fiber has an outer diameter ranging from 0.1 mm to 10 mm.

13. A method for preparing the electrically conductive adsorbent fiber as claimed in any one of claims 1 to 12, the method comprising: forming a dope solution containing a solid adsorbent, a binder, and a solvent; and extruding the dope solution along with a chrome alloy wire.

14. The method of claim 13, wherein the solvent is selected from N- methyl-2-pyrrolidone, dimethyl sulfoxide, or combinations thereof.

15. The method of claim 13 or claim 14, wherein the extrusion is performed through an orifice spinneret, with the chrome alloy wire extruded through an inner orifice and the dope solution extruded through an outer orifice simultaneously.

16. The method of any one of claims 13 to 15, further comprising passing the extruded nascent fiber through a coagulation bath to induce phase separation and solidify the composite material.

17. The method of claim 16, wherein the coagulation bath comprises water.

18. The method of any one of claims 13 to 17, further comprising washing the solidified fiber in a washing medium selected from water or isopropanol.

19. A method for removing an acid gas from an acid gas-enriched gas stream, comprising: a step of contacting the acid gas-enriched gas stream with the electrically conductive adsorbent fiber as defined in any one of claims 1 to 12, wherein at least a portion of the acid gas is adsorbed by the electrically conductive adsorbent fiber; a step of regenerating the electrically conductive adsorbent fiber by applying a voltage to the chrome alloy wire, generating heat to desorb the acid gas.

20. The method of claim 19, wherein the acid gas comprises carbon dioxide, hydrogen sulfide, or a combination thereof.

21. The method of claim 19 or 20, wherein the regeneration step is performed using electric swing adsorption, and the voltage applied to the chrome alloy wire generates heat through Joule heating.

22. The method of claim 21 , wherein the regeneration step is assisted by a vacuum.

23. The method of any one of claims 19 to 22, wherein the acid gas- enriched gas is selected from flue gas or atmospheric air.

24. A system for removing acid gases from an acid gas-enriched gas stream, comprising an adsorption unit containing comprising one or more electrically conductive adsorbent fibers as defined in any one of claims 1 to 12; and a power supply configured to apply voltage to the chrome alloy wire within each fiber for regeneration via electric swing adsorption.

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