Sorbent materials for co2 capture, uses thereof and methods for making same

Abstract

Sorbent material capable of reversibly binding carbon dioxide, for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air (1), flue gas and biogas, preferably for direct air capture, in particular using a temperature, vacuum, or temperature / vacuum swing process, wherein said sorbent material (3) is a particulate copolymeric material, having an average particle size in the range of 200 – 3000 µm, and having primary amine groups capable of reversibly binding carbon dioxide wherein said sorbent material (3) is a terpolymer based on at least one vinyl nitrile building block (at least 12 mole %), selected from the group consisting of acrylonitrile, methacrylonitrile, transcrotonitrile, fumaronitrile, and combinations thereof; at least one vinyl building block (at least 10 mole %); divinyl benzene (in the range of 8-28 mole %); wherein in the sorbent material the vinyl building block is converted to said primary amine groups capable of reversibly binding carbon dioxide.

Description

[0001] TITLE

[0002] SORBENT MATERIALS FOR CO2 CAPTURE, USES THEREOF AND METHODS FOR MAKING SAME

[0003] TECHNICAL FIELD

[0004] The present invention relates to carbon dioxide capture materials with primary and / or secondary amine carbon dioxide capture moieties with good capture and swelling properties, as well as methods for preparing such capture materials, uses of such capture materials and carbon dioxide capture methods involving such materials.

[0005] PRIOR ART

[0006] According to the OECD report of 2017 [Global Energy & CO2 Status Report 2017, OECD / IEA March 2018] the yearly emissions of CO2 to the atmosphere are ca 32.5 Gt (Gigatons, or 32.5x10E9 tons). As of February 2020 all but two of the 196 states that in 2016 have negotiated the Paris Agreement within the United Nations Framework Convention on Climate Change (UFCCC) have ratified it. The meaning of this figure is that a consensus is reached regarding the threat of climate change and regarding the need of a global response to keep the rise of global temperature well below 2 degrees Celsius above pre-industrial levels.

[0007] The technical and scientific community engaged in the challenge of proposing solutions to meet the target of limiting CO2 emissions to the atmosphere and to remove greenhouse gases from the atmosphere through or with a number of technologies. Flue gas capture, or the capture of CO2 from point sources, such as specific industrial processes and specific CO2 emitters, deals with a wide range of relatively high concentrations of CO2 (3-100 vol %) depending on the process that produces the flue gas. High concentrations make the separation of the CO2 from other gases thermodynamically more favorable and consequently economically favorable as compared to the separation of CO2 from sources with lower concentrations, such as ambient air, where the concentration is in the order of 400 ppm. Nonetheless, the very concept of capturing CO2 from point sources has strong limitations: it is specifically suitable to target such point sources, but is inherently linked to specific locations where the point sources are located and can at best limit emissions and support reaching carbon neutrality, while as a technical solution it will not be able to contribute to negative emissions (i.e., permanent removal of carbon dioxide from the atmosphere) and to remove historic emission. In order to achieve negative emissions (i.e., permanent removal carbon dioxide from the atmosphere), the two most notable solutions currently applied, albeit being at an early stage of development, are the capturing of CO2 by means of vegetation (i.e., trees and plants, but not truly permanent removal) using natural photosynthesis, and by means of DAC technologies, which is the only truly permanent removal.

[0008] Forestation has broad resonance with the public opinion. However, the scope and feasibility of re-forestation projects is debated and is likely to be less simple an approach as believed because it requires a large footprint in terms of occupied surface to captured CO2 ratio. On the other hand, DAC has lower land footprint and therefore it does not compete with the production of crops, can permanently remove CO2 from the atmosphere and can be deployed everywhere on the planet.

[0009] The above-described strategies to mitigate climate change all have potential and are considered as a potential part of the overall solution. The most likely future scenario is the deployment of multiple or a variety of different approaches, after undergoing further development.

[0010] Several DAC technologies were described, such as for example, the utilization of alkaline earth oxides to form calcium carbonate as described in US-A-2010034724. Different approaches comprise the utilization of solid CO2 adsorbents, hereafter named sorbents, in the form of packed beds of typically sorbent particles and where CO2 is captured at the gassolid interface. Such sorbents can contain different types of amino functionalisation and polymers, such as immobilized aminosilane-based sorbents as reported in US-B-8834822, and amine-functionalised cellulose as disclosed in WO-A-2012 / 168346.

[0011] WO-A-2011 / 049759 describes the utilization of an ion exchange material comprising an aminoalkylated bead polymer for the removal of carbon dioxide from industrial applications. WO-A-2016 / 037668 describes a sorbent for reversibly adsorbing CO2 from a gas mixture, where the sorbent is composed of a polymeric adsorbent having a primary amino functionality. The materials can be regenerated by applying pressure or humidity swing. Polystyrene-divinylbenzene resins have also been used as a support to impregnate amines such as tetraethylenepentamine and diethanolamine (CN 105195113A), systems that are only compatible with desorption processes that do not involve any condensation of a gas stream such as saturated or supersaturated steam. Also, WO2021136744A1 show the functionalisation of polystyrene-divynylbenzen polymers with a high variaty of amines and their use in carbon capture of gas stream with high conentration of CO2. However, the nitrogen content reported in WO2021136744A1 is between 5-10 mol / kg, which is similar to the amount that can be reached by functionalising PS-DVB with benzylamine. An optimal sorbent ideally should be predominant composed of active phase to be able to intensify the carbon capture process.

[0012] Amines react with CO2 to form a carbamate moiety, which in a successive step can be regenerated to the original amine, for example by increasing the temperature of the sorbent bed to ca 100°C and therefore releasing the CO2. An economically viable process for carbon capture implies the ability of the sorbent to capture as much CO2 as possible in a very short period of time so that the throughput of the system can be increased. To this end, this feature is of course related to the amount of active amine sites able to bind CO2, thus, it is very important to develop new materials with a high CO2 capture capacity. Some materials show limits to the degree of functionalisation that can be achieved, thus new nontrivial sorbent structures are required to be invented to overcome this limitation.

[0013] WO-A-2022013197 discloses a method for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air, flue gas and biogas, by cyclic adsorption / desorption using a sorbent material, wherein the method comprises at least the following sequential and in this sequence repeating steps (a) - (e): (a) contacting said gas mixture with the sorbent material to allow gaseous carbon dioxide to adsorb; (b) isolating said sorbent material from said flow-through; (c) inducing an increase of the temperature of the sorbent material; (d) extracting at least the desorbed gaseous carbon dioxide from the unit and separating gaseous carbon dioxide from steam in or downstream of the unit; (e) bringing the sorbent material to ambient atmospheric conditions; wherein said sorbent material comprises primary and / or secondary amine moieties immobilized on a solid support, wherein the amine moieties, in the a -carbon position, are substituted by one hydrogen and one non-hydrogen substituent (R). Importantly, the treatment of chloromethylated poly(styrene-co-divinylbenzene) based starting material with hexamethylentetramine (HMTA) disclosed in that document in the experimental section leads to amination and formation of primary amines only. No secondary amines are formed. WO-A-2021239748 discloses a method for separating gaseous carbon dioxide from a gas mixture by cyclic adsorption / desorption, using a unit containing an adsorber structure with said sorbent material, wherein the method comprises the following sequential and in this sequence repeating steps: (a) contacting said gas mixture with the sorbent material to allow said gaseous carbon dioxide to adsorb under ambient atmospheric pressure and temperature conditions in an adsorption step, using a speed of the adsorption gas flow; (bO) isolating said sorbent with adsorbed carbon dioxide in said unit from said flow-through of gas mixture; (b1) injecting a stream of saturated steam essentially at ambient atmospheric pressure conditions and thereby inducing an increase of the temperature of the sorbent to a temperature between 60 and 110°C, (b2,b3) extracting at least the desorbed gaseous carbon dioxide while still injecting and / or circulating saturated steam at ambient atmospheric pressure conditions into said unit; (c) bringing the sorbent material to ambient atmospheric temperature conditions; wherein the speed of steam flow through the unit in step (b1) and / or on average in steps (b1)-(b3) is in the range of 0.5-10 times the speed of the adsorption gas flow in step (a).

[0014] GB-A-1296889 discloses how carbon dioxide is separated from mixtures with non-acid gases such as air by sorption on a weakly basic ion exchange resin followed by desorption with steam under conditions such that the steam condenses at the inlet end of the resin bed and a front of condensing steam then progressively passes through the bed displacing the carbon dioxide. Sorption is suitably conducted at 40-90 F and at a relative humidity of 75- 90%. The preferred ion exchanger is a polystyrene-divinylbenzene copolymer containing polyamino functional groups, each of which comprises at least one secondary amino nitrogen atom. In a figure, an automatically controlled single bed sorption-regeneration system is illustrated.

[0015] WO-A-2023 / 152659 discloses polymeric amine solid sorbents with enhanced stability to moisture and / or oxygen for sorptive gas separation processes. In one example allylamine is reacted with divinylbenzene to form an amine sorbent powder. The polymeric amine solid sorbents can be supported on a porous support or integrated into solid porous polymer networks. Sorptive gas separators can employ contactors with such polymeric amine solid sorbents for separation of a component from a multi-component gas stream.

[0016] US 11 ,059,024 discloses supported amine polymer adsorbents based on polymers containing only or primarily primary amines sites to be used as regenerable adsorbents for CO, capture from ultradilute gas streams, such as ambient air, or from mixtures of gases containing preferably at least 10% oxygen, and can also be useful for use at the moderate gas pressures found in typical post-combustion capture processes, such as flue gas from large point sources such as coal-fired power plants. Preferred supported solid amine adsorbents are based on poly(allylamine) ("PAA") and poly(vinylamine) ("PVAm"), both of which are linear polymers, and their derivatives, containing substantially all primary amine groups, supported on substrates. Preferred such substrates include silica mesocellular foam (MCF) and mesoporous-y-alumina, as well on mesoporous-y-alumina coated throughout the pores of MCF, most preferably of monolithic structure. Preferred derivatives include the guanidinylated and cross-linked poly(allylamine) materials.

[0017] US 9,169,370 discloses an adsorption-desorption material, e.g., crosslinked polyvinylamine material having an Mw from about 500 to about 1x10A6, total pore volume from about 0.2 cc / g to about 2.0 cc / g, and a CO2 adsorption capacity of at least about 0.2 millimoles per gram of crosslinked material, and / or linear polyvinyl-amine material having an Mw from about 160 to about 1 x10A6, total pore volume from about 0.2 cc / g to about 2.0 cc / g, and a CO2 adsorption capacity of at least about 0.2 millimoles per gram of linear material. This disclosure also involves processes for preparing the crosslinked polyvinyl-amine materials and linear polyvinylamine materials, as well as selective removal of CO2 and / or other acid gases from a gaseous stream using the polyvinylamine materials.

[0018] JP-A-2018172477 provides a polyvinyl carboxylic acid amide crosslinked polymer spherical particle having a porous structure, by convenient operation and with high efficiency, and a method for producing the same, wherein, such a polyvinyl carboxylic acid amide crosslinked polymer spherical particle having a porous structure cannot be obtained by conventional methods. In salt water, a mixture of N-vinyl carboxylic acid amide, polyvinyl compound and a specific organic solvent is subjected to suspension polymerization in the presence of cationic polymer dispersant, to obtain a spherical polyvinyl carboxylic acid amide crosslinked polymer spherical particle having a porous structure.

[0019] Bachmann (DOE-PARC-FE0031951) reports on a polyvinylamine-divinlybenzene system (PVAm-DVB) and reports CO2 adsorption capacity, CO2 adsorption kinetics, and oxidative stability.

[0020] US-A-2024024852 discloses a polymer aerogel monolith comprising a polymer aerogel having a nitrogen content of greater than seven weight percent impregnated into a mesh. A method of manufacturing an amine-containing polymer aerogel monolith, includes combining a vinyl-containing cross-linking monomer, a vinyl-containing functional monomer, an organic solvent, and a radical initiator into a liquid mixture, applying the liquid mixture to a mesh fabric to produce a monomer-impregnated mesh, heating the monomer- impregnated mesh to produce a polymer aerogel monolith, washing the polymer aerogel monolith with acid to produce an ammonium-containing polymer aerogel monolith, and applying a base to neutralize the ammonium-containing polymer aerogel monolith to produce an amine-containing polymer aerogel monolith. A direct air capture module has one or more amine-containing polymer aerogel monoliths, one or more air flow channels positioned to pass air through the monolith A monolith comprising a poly(alkylamine-co- divinylbenzene) impregnated mesh.

[0021] CN-A-116043597 discloses test paper for rapidly detecting low-concentration formaldehyde and a preparation method of the test paper, and belongs to the field of functional materials. It provides the application of the N-vinylformamide-acrylonitrile polymer in formaldehyde detection. The test paper for rapidly detecting the low-concentration formaldehyde is prepared by mixing an N-vinylformamide-acrylonitrile polymer and paper pulp and then removing a solvent, or is prepared by loading the N-vinylformamide-acrylonitrile polymer on the surface of a blank test strip. The lowest detection limit of the test paper can reach 0.02 mg / m < 3 >, the sensitivity is relatively high, the detection conditions are simple, and portable rapid detection of formaldehyde is realized.

[0022] EP-A-3196217 discloses a method for producing polyvinylamine crosslinked polymer particles without using an organic solvent. Transparent polyvinylamine crosslinked polymer particles are produced by performing suspension polymerization in salt water containing N- vinylcarboxylic acid amide and a polyvinyl cross-linkable compound in the presence of a dispersant to obtain particles of a polyvinyl carboxylic acid amide crosslinked polymer and subsequently hydrolyzing the polyvinyl carboxylic acid amide crosslinked polymer. Divinylbenzene is preferred as the polyvinyl compound. N-Vinylcarboxylic acid amide, acrylonitrile, and a polyvinyl compound may be used.

[0023] US-A-2024024852 proposes a polymer aerogel monolith comprising a polymer aerogel having a nitrogen content of greater than seven weight percent impregnated into a mesh. A method of manufacturing an amine-containing polymer aerogel monolith, includes combining a vinyl-containing cross-linking monomer, a vinyl-containing functional monomer, an organic solvent, and a radical initiator into a liquid mixture, applying the liquid mixture to a mesh fabric to produce a monomer-impregnated mesh, heating the monomer- impregnated mesh to produce a polymer aerogel monolith, washing the polymer aerogel monolith with acid to produce an ammonium-containing polymer aerogel monolith, and applying a base to neutralize the ammonium-containing polymer aerogel monolith to produce an amine-containing polymer aerogel monolith. A direct air capture module has one or more amine-containing polymer aerogel monoliths, one or more air flow channels positioned to pass air through the monolith A monolith comprising a poly(alkylamine-co- divinylbenzene) impregnated mesh.

[0024] US-A-2024033682 proposes a carbon dioxide capture composition which includes a hydroxide-ion-exchanged poly(N-vinyl guanidine)-based polymer material as a sorbent. A method of preparing the carbon dioxide capture composition includes contacting a poly(N- vinyl guanidine)-based polymer material with hydroxide ion exchange beads, and exchanging hydroxide ion into the poly(N-vinyl guanidine)-based polymer material to form the sorbent. A carbon dioxide capture method includes contacting the sorbent with a gas stream, and sorbing carbon dioxide in the gas stream with the sorbent. A carbon dioxide capture system includes a sorption bed having a hydroxide-ion-exchanged poly(N-vinyl guanidine)-based polymer material as a sorbent.

[0025] SUMMARY OF THE INVENTION

[0026] According to a first aspect of the present invention, it relates to a sorbent material for use in carbon dioxide capture processes.

[0027] The object is to provide an improved sorbent material having a high CO2 capture capacity and which can be produced efficiently in bead form, preferably as porous beads. Preferably, the material is further stable over a long time, so resists oxidation and further deterioration mechanisms. The material can be used in particulate form either as a loose bed or embedded in a structure or layer, be it a layered structure or a monolithic structure. For such use the material may also be milled after the manufacturing process. The morphological aspects (pore size and surface area) of the powder after milling should preferably be comparable to the beads prior to milling.

[0028] So according to a first aspect, the present invention relates to a sorbent material capable of reversibly binding carbon dioxide, for separating gaseous carbon dioxide from a gas mixture.

[0029] Said sorbent material is a particulate copolymeric material, which has an average particle size in the range of 200 - 3000pm (so takes the form of granules or beads), and which has primary amine groups capable of reversibly binding carbon dioxide.

[0030] When mentioning an "average particle size" this is meant to be determined using the following protocol: The average particle size is determined by measuring the diameters for a random selection of 100 non-overlapping particles of a sample under an optical microscope and the corresponding values were number-averaged.

[0031] The proposed sorbent material is a terpolymer based on at least one vinyl nitrile building block, selected from the group consisting of acrylonitrile, methacrylonitrile, trans-crotonitrile, fumaronitrile, and combinations thereof, so one or a combination of the following: acrylonitrile methacrylonitrile trans-crotonitrile fumaronitrile at least one vinyl building block, convertible to polyalkyl primary amine by hydrolysis; as well as divinyl benzene (acting also as a cross-linker).

[0032] These are the building blocks for the manufacturing, in the final copolymeric sorbent material the vinyl building block is converted to said primary amine groups capable of reversibly binding carbon dioxide. Preferably this conversion of the vinyl building block to said primary amine groups is carried out by hydrolysis.

[0033] According to the invention,

[0034] (A) the molar proportion of the vinyl nitrile building blocks is at least 12 mole %;

[0035] (B) the molar proportion of the vinyl building block is at least 10 mole %;

[0036] (C) the molar proportion of the divinylbenzene is in the range of 8-28 mole %; wherein the sum of (A)-(C) makes up 100 mole % of the total of the building blocks of the terpolymer.

[0037] Typically, the material is provided for the separation of carbon dioxide from at least one of ambient atmospheric air, flue gas and biogas, preferably for direct air capture, in particular using a temperature, vacuum, or temperature / vacuum swing process, copolymeric

[0038] In fact, it was found out, that surprisingly only in a narrow window of the proportions of these three building blocks, the co-polymerization can be carried out to lead to mechanically stable granular structures having the above-mentioned average particle size. In particular the particles are stable also when after the copolymerization the vinyl building blocks are converted by hydrolysis to the primary amine functionalities.

[0039] If the above-mentioned proportions of the building blocks are not complied with, either already in the copolymerization process a gel or a powder with very small and non-porous particles is generated, or, if larger particles are generated, these are not mechanically stable and during hydrolysis they disintegrate into powders of very small and non-porous particles, which are not useable as sorbent materials for reversibly binding carbon dioxide and for separating carbon dioxide from a gas mixture. The vinyl nitrile building block, in particular in the form of acrylonitrile, was identified as a key monomer to facilitate the formation of in particular macroporous stable beads. In the absence of acrylonitrile, in particular macroporous beads were not obtained. An additional advantage associated with the vinyl nitrile building blocks is that these can also be converted into carbon dioxide capture active primary and / or secondary amine functionalities, by simple reduction. This can be used to further increase significantly the capture capacity of the material.

[0040] Macropores are pores with diameters exceeding 50 nm, and macroporous beads have a high proportion of such pores, and preferably a low proportion or are essentially free from mesopores i.e. pores with diameters between 2 and 50 nm, and / or preferably also have a low proportion or are essentially free from micropores i.e. pores with diameters not exceeding or below 2 nm, leading inter alia to a reduction of accumulation of condensed water in the porosity and for the carbon dioxide capture process in the presence of water and / or steam to a much higher capacity in cyclic operation.

[0041] Preferably, the sorbent material has a pore diameter distribution, measured by Mercury intrusion, such that 90%, preferably 95% of the pore volume is in the range of 50-300 nm, preferably in the range of 50-250 nm, and / or the sorbent material has a pore volume distribution, measured by Mercury intrusion, such that the maximum pore volume is at a pore diameter in the range of 80-150 nm, preferably in the range of 100-150 nm, wherein preferably 90%, more preferably 95% of the total pore volume of the distribution is in a window of -50 nm and +150 nm, preferably of - 40 and + 100 nm around the diameter of said maximum of the pore volume distribution.

[0042] Mercury porosimetry measurements are used to analyze the pore diameter distribution, pore volume distribution, pore sizes, average pore size, and pore volumes of particles as described in the experimental section.

[0043] By eliminating the conventional aromatic (styrene) backbone of such material, the CO2 capacity (equilibrium and time dependent) and the stability against oxidative degradation is increased.

[0044] Preferably, the vinyl nitrile building block is selected exclusively as acrylonitrile.

[0045] Further preferably, the vinyl building block is selected as vinyl formamide.

[0046] Particularly preferably, the vinyl nitrile building block is selected exclusively as acrylonitrile, and the vinyl building block is selected exclusively as vinyl formamide. The material resulting from the copolymerization in this case is polyvinylformamide(VFAmide)- acrylonitrile(AN)-divinylbenzene (DVB): which is then converted by hydrolysis to the actual sorbent material having primary amine groups, polyvinylamine(VFAm)-AN-DVB:

[0047] Systems without the vinyl nitrile building blocks such as:

[0048] lead to the formation of gels in the polymerization step.

[0049] Systems where the proportions of the building blocks are not in the claimed ranges, in particular systems of the following type (the numerical values next to the angular brackets indicating molar proportions): lead, at the latest upon hydrolysis, to the formation of powders, which cannot be used for carbon dioxide capture processes.

[0050] Only if for example the proportions are chosen as follows: proper beads can be obtained, which are also stable in the following hydrolysis step.

[0051] As pointed out above, the resulting systems can also be reduced to lead to systems where the nitrile groups are converted into primary amine groups, further increasing the capture capacity:

[0052] So the sorbent material can also be one where said vinyl nitrile building blocks are converted to primary amine groups by reduction.

[0053] Preferably, (A) the molar proportion of the vinyl nitrile building blocks is in the range of 12 - 50 mole %, preferably in the range of 13-30 mole %.

[0054] Preferably, (B) the molar proportion of the vinyl building block is in the range of 12 - 79 mole %, preferably in the range of 50-75 mole %.

[0055] Preferably, (C) the molar proportion of the divinylbenzene is in the range of 9-25 mole %, preferably in the range of 9.5-20 mole % or 10-20 mole % or 10-15 mole %.

[0056] In each for these cases, the sum of (A)-(C) makes up 100 mole % of the total of the building blocks of the terpolymer.

[0057] The particulate copolymeric material preferably has an average particle size in the range of 300 - 2000pm, preferably in the range of 300 - 1000pm.

[0058] Preferably the particulate copolymeric material takes the form of essentially spherical beads.

[0059] The particulate copolymeric material normally has an average pore size in the range of 30- 200 nm, preferably in the range of 50-100 nm.

[0060] Preferably, the particulate copolymeric material has a BET surface area in the range of 5- 50 m2 / g, preferably in the range of 10-30 m2 / g. BET (Brunauer, Emmett und Teller) surface area analysis is used for the determination of the specific BET surface area applying the method as described in ISO 9277.

[0061] Said sorbent material can have a nitrogen content of at least 10% by weight, preferably of at least 14% by weight, preferably in the range of 14-25% by weight.

[0062] The present invention also in a further aspect relates to an adsorber structure being based on such a sorbent material.

[0063] So according to a preferred embodiment of the invention, it relates to an adsorber structure, preferably in the form of monolith, the form of a layer or a plurality of layers, the form of hollow or solid fibres, including in woven or nonwoven (layer) structures, or the form of hollow or solid particles (e.g. a packed particle bed), comprising or consisting of such a sorbent material.

[0064] According to yet another aspect of the present invention, it relates to the use of such a sorbent material for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air, flue gas and biogas, preferably for direct air capture, in particular using a temperature, vacuum, or temperature / vacuum swing process.

[0065] According to a further aspect, the present invention relates to a method for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air, flue gas and biogas, preferably for direct air capture.

[0066] The method for separating gaseous carbon dioxide from the gas mixture is preferably a method, which comprises at least the following sequential and in this sequence repeating steps (a) - (e):

[0067] (a) contacting said gas mixture with the sorbent material to allow at least said gaseous carbon dioxide (parts thereof or essentially all of the CO2) to adsorb on the sorbent material by flow-through through said unit (and thus through and / or over the sorbent material adsorbing at least part of said gaseous carbon dioxide) under ambient atmospheric pressure conditions and ambient atmospheric temperature conditions in an adsorption step (if ambient atmospheric air is pushed / pulled through the device using a ventilator or the like, this is still considered ambient atmospheric pressure conditions in line with this application, even if the air which is pushed / pulled through the reactor by the ventilator has a pressure slightly above or below the surrounding ambient atmospheric pressure, and the pressure is in the ranges as detailed below in the definition of "ambient atmospheric pressures");

[0068] (b) isolating said sorbent material with adsorbed carbon dioxide in said unit from said flow- through, preferably while essentially maintaining the temperature in the sorbent;

[0069] (c) inducing an increase of the temperature of the sorbent material, preferably to a temperature between 60 and 110°C, starting the desorption of CO2. This is e.g. possible by injecting a stream of partially of fully saturated or superheated steam, preferably by flow- through through the unit and over / through the sorbent, and thereby inducing an increase of the temperature of the sorbent material to a temperature between 60 and 110°C, starting the desorption of CO2;

[0070] (d) extracting at least the desorbed gaseous carbon dioxide from the unit (preferably most or all of the desorbed gaseous carbon dioxide) and separating gaseous carbon dioxide, preferably by condensation, in or downstream of the unit;

[0071] (e) bringing the sorbent material to ambient atmospheric temperature conditions and ambient atmospheric pressure conditions (if the sorbent material is not cooled in this step down to exactly the surrounding ambient atmospheric temperature conditions, this is still considered to be according to this step, preferably the ambient atmospheric temperature established in this step (e) is in the range of the surrounding ambient atmospheric temperature +25°C, preferably +10°C or +5°C).

[0072] In the context of this disclosure, the expressions “ambient atmospheric pressure” and “ambient atmospheric temperature” refer to the pressure and temperature conditions to that a plant that is operated outdoors is exposed to, i.e. typically ambient atmospheric pressure stands for pressures in the range of 0.8 to 1.1 barabs and typically ambient atmospheric temperature refers to temperatures in the range of -40 to 60° C, more typically -30 to 45°C. The gas mixture used as input for the process is preferably ambient atmospheric air, i.e. air at ambient atmospheric pressure and at ambient atmospheric temperature, which normally implies a CO2 concentration in the range of 0.03-0.06% by volume, and a relative humidity in the range of 3-100%. However, also air with lower relative humidity, i.e. < 3%, or with lower or higher CO2 concentration can be used as input for the process, e.g. with a concentration of 0.1-0.5% CO2 by volume, so generally speaking, preferably the input CO2 concentration of the input gas mixture is in the range of 0.01-0.5% by volume.

[0073] According to a preferred embodiment, in step (c) the pressure in the unit (preferably at the end of this step) is in the range of 500-1000 mbarabs, preferably in the range of 550-1000 mbarabs or 600-950 mbarabs. Preferred ranges of 650-700 mbarabs or 700-950 mbarabs, preferably in the range of 750-850 mbarabs.

[0074] Preferably step (d) may include reduction of the pressure in the unit to values between 20- 500 mbarabs, preferably 50-250 mbarabs by means of evacuation, which causes evaporation of water from the sorbent subsequently both drying and cooling the sorbent. Finally, the present invention relates to methods for preparing such a sorbent material.

[0075] Correspondingly, a method for preparing a sorbent material is given, preferably a sorbent material as described above, for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air, flue gas and biogas, containing said gaseous carbon dioxide as well as further gases different from gaseous carbon dioxide, by cyclic adsorption / desorption using said sorbent material capable of reversibly binding carbon dioxide and adsorbing said gaseous carbon dioxide in a unit,

[0076] According to yet another aspect of the present invention, it relates to a method for preparing a sorbent material which is a particulate copolymeric material, having an average particle size in the range of 200 - 3000pm, and having primary amine groups capable of reversibly binding carbon dioxide, preferably a sorbent material as detailed above, in particular for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air, flue gas and biogas, containing said gaseous carbon dioxide as well as further gases different from gaseous carbon dioxide, by cyclic adsorption / desorption using said sorbent material capable of reversibly binding carbon dioxide and adsorbing said gaseous carbon dioxide in a unit.

[0077] According to this method, in a first step at least one vinyl nitrile building block, selected from the group consisting of acrylonitrile, methacrylonitrile, trans-crotonitrile, fumaronitrile, and combinations thereof; at least one vinyl building block, convertible to polyalkyl primary amine by hydrolysis; and divinyl benzene; wherein

[0078] (A) the molar proportion of the vinyl nitrile building blocks is at least 12 mole %;

[0079] (B) the molar proportion of the vinyl building block is at least 10 mole %;

[0080] (C) the molar proportion of the divinylbenzene is in the range of 9-28 mole %; wherein the sum of (A)-(C) makes up 100 mole % of the total of the building blocks of the terpolymer, are copolymerized and cross-linked by said divinyl benzene.

[0081] In a second step the vinyl building block is converted to said primary amine groups capable of reversibly binding carbon dioxide by hydrolysis.

[0082] In said first step the vinyl nitrile building block is preferably selected exclusively as acrylonitrile, and the vinyl building block is selected exclusively as vinyl formamide.

[0083] In a further step the vinyl nitrile building blocks can be converted to amine, preferably primary amine, groups by reduction, wherein preferably this further step takes place after the second step.

[0084] The copolymerization in the first step preferably takes place in the presence of a radical initiator, wherein preferably the radical initiator is selected from the group consisting of azobisisobutyronitrile, benzoyl peroxide, 2,2 -azobis-2- methylbutyronitrile, 2-2'-azobis(2,4- dimethyl)valeronitrile or 2,2-dimethoxy-2-phenyl-acetophenone of combinations thereof. The copolymerization in the first step preferably takes place in the presence of a dispersant. This dispersant is preferably a cationic dispersant in particular to accommodate the large amount of ammonium sulfate salt required for the bead formation. Further preferably the dispersant is not a poly-2-acrylamide-2-methylpropanesulfonate sodium dispersant.

[0085] The copolymerization in the first step preferably takes place in water in the presence of a porogen which can be selected as an organic solvent immiscible with the ammonium chloride / dispersant solution. The porogen can e.g. be selected as an acetate, e.g. ethyl acetate. The weight proportion of the porogen to the water is the preferably smaller than 20%, preferably smaller than 15%.

[0086] Further embodiments of the invention are laid down in the dependent claims.

[0087] BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings, Fig. 1 shows a schematic representation of a direct air capture unit;

[0088] Fig. 2 shows carbon dioxide capture capacities of the resulting PVAm-co-AN-co-DVB beads systems;

[0089] Fig. 3 spherical beads obtained from the synthesis.

[0090] DESCRIPTION OF PREFERRED EMBODIMENTS

[0091] Synthesis procedure of vinylformamide-acrylonitrile-divinylbenzene resin synthesis additive: dispersant A:

[0092] In a 1 L reactor, 300 g of ion exchanged water, 200g of [2-(methacroyloyloxy)ethyl] trimethylammonium chloride solution (75wt% in water), 0.05 g of 2,2-Azobis(2- methylpropionamide) dihydrochloride were added, and stirred at 300rpm, the temperature of the reaction solution was set at 50°C. After the reaction solution reached 50°C, the reaction was continued for 12 hours. Then, the temperature of the reaction solution was set at 80°C. After the reaction solution reached 80°C, the reaction was continued for 2 hours. After that, the reaction solution was then allowed to cool down to room temperature. The solids concentration was 29 wt%.

[0093] Synthesis procedure of vinylformamide-acrylonitrile-divinylbenzene resin:

[0094] Polymer A: In a 1 L reactor, 216 g of ion-exchanged water, 4 g of the dispersant A, and 144 g of ammonium sulfate were added, and stirred at 300rpm at 50°C for 1 hour to completely dissolve the contents (Solution A).

[0095] Separately, 33g of N-vinylformamide (VFA, Mw= 71.08 g / mol, 0.464 mol), 15 g of divinylbenzene (highest commercially available purity: content 80%, DVB, Mw = 130.19 g / mol, 0.0921 mol), 12 g of acrylonitrile (AN, Mw=53, 0.226 mol), 30 g of ethyl acetate, and 0.6 g of azobisisobutyronitrile (AIBN, Mw = 164.21 g / mol, 3.7 mM) were placed in a 200 mL beaker and stirred at 300 rpm for 1 hour at room temperature to completely dissolve them (Solution B).

[0096] Solution B was added to Solution A all at once while maintaining the stirring, and the temperature of the reaction solution was set at 65°C. After the reaction solution reached 65°C, the reaction was continued for 18 hours.

[0097] The reaction solution was then allowed to cool down to room temperature and filtered. The solids were then transferred to a 1 L beaker, 1 L of ion-exchanged water was added, stirred with a magnetic stirrer for 30 minutes, and filtered. This was repeated two more time. The solids were then transferred to a 1 L beaker, 1 L of methanol was added, stirred with a magnetic stirrer for 30 minutes, and filtered.

[0098] The desired polymer particles were then dried under reduced pressure at 75°C and 200 torr for 1 hour, yielding cross linked poly vinylformamide-acrylonitrile-divinylbenzene (PVFA-co- AN-co-DVB) as Polymer A.

[0099] The average particle diameter was 318 micrometers (number average particle diameter, calculated by adding up the diameters of 200 arbitrary particles and dividing by 200), the specific surface area determined by the BET method was 29 m2 / g, and average pore size are determined by Mercury porosimetry measurements was 77 nm.

[0100] Polymers B-E: The proposed synthetic approach allows for control of the morphology (pore size and surface area) as well as of the particle size and the nitrogen. Different variants were synthesized using the same approach as for Polymer A, but different proportions of the starting materials VFA, AN and DVB, the Polymers C-E serving as comparative examples.

[0101] Polymer F (comparative example, not capable of reversibly binding carbon dioxide): The same procedure and amounts were used as for Polymer A, but the porogen in the form of ethyl acetate was omitted.

[0102] Polymer F: In a 1 L reactor, 216 g of ion-exchanged water, 4 g of the dispersant A, and 144 g of ammonium sulfate were added, and stirred at 300rpm at 50°C for 1 hour to completely dissolve the contents (Solution A).

[0103] Separately, 33g of N-vinylformamide (VFA, Mw= 71.08 g / mol, 0.464 mol), 15 g of divinylbenzene (highest commercially available purity: content 80%, DVB, Mw = 130.19 g / mol, 0.0921 mol), 12 g of acrylonitrile (AN, Mw=53, 0.226 mol), and 0.6 g of azobisisobutyronitrile (AIBN, Mw = 164.21 g / mol, 3.7 mM) were placed in a 200 mL beaker and stirred at 300 rpm for 1 hour at room temperature to completely dissolve them (Solution B).

[0104] Solution B was added to Solution A all at once while maintaining the stirring, and the temperature of the reaction solution was set at 65°C. After the reaction solution reached 65°C, the reaction was continued for 18 hours.

[0105] The reaction solution was then allowed to cool down to room temperature and filtered. The solids were then transferred to a 1 L beaker, 1 L of ion-exchanged water was added, stirred with a magnetic stirrer for 30 minutes, and filtered. This was repeated two more time.

[0106] The solids were then transferred to a 1 L beaker, 1 L of methanol was added, stirred with a magnetic stirrer for 30 minutes, and filtered.

[0107] The desired polymer particles were then dried under reduced pressure at 75°C and 200 torr for 1 hour, yielding cross linked poly vinylformamide-acrylonitrile-divinylbenzene (PVFA-co- AN-co-DVB) as Polymer A.

[0108] The beads were translucent or transparent and showed no CO2 capture capacity and negligible BET surface area (< 1 m2 / g).

[0109] The following Table 1 shows how the properties of the PVFA-AN-co-DVB and PVFA- coDVB (Polymer D).

[0110] Table 1 : properties of different PVFA-co-AN-co-DVB systems values after deprotection to afford the vinylamine-acrylonitrile-divinylbenzene beads;

[0111] ** incomplete deprotection of the formyl protecting group;

[0112] Exchange and CO2 capacity of powders cannot be measured.

[0113] To afford the vinylamine-acrylonitrile-divinylbenzene beads:

[0114] The poly vinylformamide-acrylonitrile-divinylbenzene (PVFA-co-AN-co-DVB) beads are then reacted with a deprotecting agent to obtain the vinylamine-acrylonitrile-divinylbenzene (PVAm-co-AN-co-DVB) beads.

[0115] Example 01 : The vinylformamide-acrylonitrile-divinylbenzene beads (Polymer A, 6.5g) and 110mL of methanol are added to a three-necked flask, and are cooled to 0°C and stirred for 1 h. Hydrochloric acid (37%, 65 mL) is added dropwise under stirring. After complete addition, the reaction temperature is increased to 55°C and the mixture is stirred for 12 h. Subsequently, the mixture is cooled to 25 °C, 110 mL of 2M sodium hydroxide (aqueous solution) is added and the mixture is stirred at 25 °C for 1h. The beads are filtered off and washed to neutral pH with demineralized water. The exchange capacity as measured was 3.8 mmol / g and the CO2 capture capacity as measured was 1.1 mmol / g.

[0116] Example 02:

[0117] The vinylformamide-acrylonitrile-divinylbenzene beads (Polymer A, 6.5g) and 110mL of ethanol are added to a three-necked flask, and are cooled to 0°C and stirred for 1 h. Hydrochloric acid (37%, 65 mL) is added dropwise under stirring. After complete addition, the reaction temperature is increased to 70°C and the mixture is stirred for 12 h.

[0118] Subsequently, the mixture is cooled to 25 °C, 110 mL of 2M sodium hydroxide (aqueous solution) is added and the mixture is stirred at 25 °C for 1h. The beads are filtered off and washed to neutral pH with demineralized water. The exchange capacity as measured was 4.3 mmol / g and the CO2 capture capacity as measured was 1.3 mmol / g.

[0119] Example 03:

[0120] The vinylformamide-acrylonitrile-divinylbenzene beads (Polymer A, 6.5g) and 110mL of ethanol are added to a three-necked flask, and are cooled to 0°C and stirred for 1 h. Hydrochloric acid (37%, 65 mL) is added dropwise under stirring. After complete addition, the reaction temperature is increased to 70°C and the mixture is stirred for 24 h. The exchange capacity as measured was 5.3 mmol / g and the CO2 capture capacity as measured was 1.6 mmol / g.

[0121] Subsequently, the mixture is cooled to 25 °C, 110 mL of 2M sodium hydroxide (aqueous solution) is added and the mixture is stirred at 25 °C for 1h. The beads are filtered off and washed to neutral pH with demineralized water.

[0122] Note: with further increase of temperature (50-100°C) and hydrolysis time (12-72h) a higher degree of formyl deprotection was observed.

[0123] In addition, deprotection can generally also be achieved under basic conditions with general conditions use 4-10M sodium hydroxide (aqueous solution) at temperatures between 60- 180°C.

[0124] In addition to formyldeprotection, the nitrile groups can generally also be reduced to afford the allylamine-containing sorbents. Typical reduction conditions include lithium aluminum hydride, sodium cyanoborohydride, borane in tetrahydrufurane, borane in dimethylsulide, Sodium bis(2-methoxyethoxy)aluminium hydride.

[0125] As one can see from the representation in Fig. 2, summarizing the carbon dioxide capture capacities of the resulting PVAm-co-AN-co-DVB beads systems according to the examples 1-3 above (the Polymer A with different deprotection conditions). The proposed systems can be tuned for optimum capture capacity.

[0126] As one can see from Fig. 3, the synthesis leads to stable spherical beads.

[0127] Measurements:

[0128] Exchange capacity properties:

[0129] Exchange capacity determination: To measure the exchange capacity, around 2 g of wet material is added to a beaker with 50 mL of 1 M NaOH solution and stirred at room temperature for 40 min. The solution is then filtered on a Buchner funnel with a filter mesh size of 40 pm, the beads are washed to neutral with deionized water and collected. Around half of the beads are transferred to a graduated flask, the weight is noted down and 100 mL of 0.1 M HCI solution is added to the flask. The flask is closed and left in the oven at 70°C for 1h. The solid content of the remaining half is determined following the method below. The flask is then removed from the oven and let cool down to room temperature. 25mL of the supernatant are titrated with 0.1 M NaOH solution (to inflection point, with an SI Analytics Titrator TitroLine 5000). The exchange capacity is calculated through the following equation:

[0130] (25mL — mL Na.0Hused) * 0.4 Exchange capacity[meq / g]=Wet Mass*Solid Content

[0131] Solid Content:

[0132] Solid content is measured with a Halogen Moisture Analyzer (Adam Equipment PMB Moisture Analyzer); measurement temperature is 110°C, the measurement stops automatically at constant weight (0.002 g / 15 s).

[0133] CO2 capture capacity properties:

[0134] The beads according to the above examples were tested in an experimental rig in which the beads were contained in a packed-bed reactor or in air permeable layers. The rig is schematically illustrated in Fig. 1. There is an ambient air inflow structure 1 and the actual reactor unit 8 comprises a container or wall 7 within which the layers of sorbent material 3 are located. There is an inflow structure 4 for desorption, if for example steam is used for desorption, and there is a reactor outlet 5 for extraction. Further, there is a vacuum unit 6 for evacuating the reactor.

[0135] Nitrogen content measurements:

[0136] Elemental analysis of the materials was carried out using a LECO CHN-900 combustion furnace. Prior to the measurement, the samples were treated under N2 flow (2 L / min) at 90°C for 2 h. Alternatively, the sample were treated in a vacuum oven at 60°C for 6 h.

[0137] Specific surface area measurements:

[0138] Nitrogen adsorption measurements were performed at 77 K on a Quantachrome ASiQ. The mass of the sample used was between 0.2-1.0 g. Since the samples contain a significant amount of water, it is important to use a treatment that does not alter their intrinsic porosity and pore structure. Therefore, prior to degassing, the samples were treated using the elutropic row method, which comprises removing water and replacing it with organic solvents with lower boiling point in the following order: methanol, acetone, and n-heptane. 2 g of samples was place in a chromatography column with a frit and flushed with 20 cm3 of each solvent in decreasing polarity order. The sample was then spread out on a petri dish and placed in a vacuum oven at 40°C for 24 hours. After that, the sample was degassed at 70 °C under vacuum for twelve hours before measurement.

[0139] Specific surface area, BET method (m2 / g) was determined as follows:. BET (Brunauer, Emmett und Teller) surface area analysis was used applying the method ISO 9277.

[0140] Average particle diameter measurements:

[0141] The average particle size was determined by measuring samples under an optical microscope; a random selection of 100 non-overlapping particles was made.

[0142] Mercury Porosimetry Measurements:

[0143] Mercury porosimetry measurements were performed to analyze the pore sizes and pore volumes not accessible through N2 adsorption measurements. In order to perform mercury porosimetry measurements the following parameters were used:

[0144] • Mercury surface tension: 0.48 N / m

[0145] • Mercury contact angle: 150°

[0146] • Max. pressure: 400 MPa

[0147] • Increase speed: 6-19 MPa / min

[0148] Prior to Hg porosimetry, the samples were degassed under vacuum at 70°C for 12 h. A sample is placed into a measuring assembly with an empty glass sample cell. Using the Washburn equation, the data set is converted into a cumulative curve of the amount intruded as a function of pore size, expressed as the diameter of the pore in nm. The derivative of this curve provides a pore size distribution n nm of the pores accessible via the exterior of the material.

[0149] Mercury porosimetry is measured with these parameters according to the standard ISO 15901-1 : 2005.

[0150] LIST OF REFERENCE SIGNS

[0151] 1 ambient air, ambient air inflow structure

[0152] 2 outflow of ambient air behind adsorption unit in adsorption flow-through mode

[0153] 3 sorbent material

[0154] 4 steam, steam inflow structure for desorption

[0155] 5 reactor outlet for extraction

[0156] 6 vacuum unit / separator

[0157] 7 wall

[0158] 8 reactor unit

[0159] Al BN azobisisobutyronitrile

[0160] AN acrylonitrile

[0161] DVB divinylbenzene

[0162] VFA N-vinylformamide

[0163] VAm Vinylamine

Claims

CLAIMS1. Sorbent material capable of reversibly binding carbon dioxide, for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air (1), flue gas and biogas, preferably for direct air capture, in particular using a temperature, vacuum, or temperature / vacuum swing process, wherein said sorbent material (3) is a particulate copolymeric material, having an average particle size in the range of 200 - 3000pm, and having primary amine groups capable of reversibly binding carbon dioxide wherein said sorbent material (3) is a terpolymer based on at least one vinyl nitrile building block, selected from the group consisting of acrylonitrile, methacrylonitrile, trans-crotonitrile, fumaronitrile, and combinations thereof; at least one vinyl building block, convertible to polyalkyl primary amine by hydrolysis; divinyl benzene; wherein in the sorbent material the vinyl building block is converted to said primary amine groups capable of reversibly binding carbon dioxide, and wherein(A) the molar proportion of the vinyl nitrile building blocks is at least 12 mole %;(B) the molar proportion of the vinyl building block is at least 10 mole %;(C) the molar proportion of the divinylbenzene is in the range of 8-28 mole %; wherein the sum of (A)-(C) makes up 100 mole % of the total of the building blocks of the terpolymer.

2. Sorbent material according to claim 1 , wherein the vinyl nitrile building block is selected exclusively as acrylonitrile.

3. Sorbent material according to any of the preceding claims, wherein the vinyl building block is selected as vinyl formamide and / or wherein in the sorbent material the vinyl building block is converted by hydrolysis to said primary amine groups capable of reversibly binding carbon dioxide.

4. Sorbent material according to any of the preceding claims, wherein the vinyl nitrile building block is selected exclusively as acrylonitrile, and the vinyl building block isselected exclusively as vinyl formamide.

5. Sorbent material according to any of the preceding claims, wherein(A) the molar proportion of the vinyl nitrile building blocks is in the range of 12 - 50 mole %, preferably in the range of 13-30 mole %;(B) the molar proportion of the vinyl building block is in the range of 12 - 79 mole %, preferably in the range of 50-75 mole %;(C) the molar proportion of the divinylbenzene is in the range of 9-25 mole %, preferably in the range of 10-20 mole % or 10-15 mole %; wherein the sum of (A)-(C) makes up 100 mole % of the total of the building blocks of the terpolymer.

6. Sorbent material according to any of the preceding claims, wherein the particulate copolymeric material has an average particle size in the range of 300 - 2000pm, preferably in the range of 300 - 1000pm, wherein preferably the particulate copolymeric material takes the form of essentially spherical beads.

7. Sorbent material according to any of the preceding claims, wherein the particulate copolymeric material has an average pore size in the range of 30-200 nm, preferably in the range of 50-100 nm, and / or wherein the particulate copolymeric material has a BET surface area in the range of 5-50 m2 / g, preferably in the range of 10-30 m2 / g.

8. Sorbent material according to any of the preceding claims, wherein said sorbent material (3) has a nitrogen content of at least 10% by weight, preferably of at least 14% by weight, preferably in the range of 14-25% by weight.

9. Sorbent material according to any of the preceding claims, wherein said vinyl nitrile building blocks are converted to primary amine groups by reduction.

10. Adsorber structure, preferably in the form of a monolith, the form of a layer or a plurality of layers, the form of hollow or solid fibres, including in woven or nonwoven (layer) structures, or the form of hollow or solid particles, comprising a sorbent material according to any of the preceding claims.11 . Use of a sorbent material (3) according to any of the preceding claims for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air (1), flue gas and biogas, preferably for direct air capture, in particular using a temperature, vacuum, or temperature / vacuum swing process.

12. Method for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air (1), flue gas and biogas, preferably for direct air capture, which comprises at least the following sequential and in this sequence repeating steps (a) - (e):(a) contacting said gas mixture with a sorbent material according to any of the preceding claims to allow at least said gaseous carbon dioxide to adsorb on said sorbent material by flow-through through said unit essentially under ambient atmospheric pressure conditions and ambient atmospheric temperature conditions in an adsorption step;(b) isolating said sorbent material with adsorbed carbon dioxide in said unit from said flow-through;(c) inducing an increase of the temperature of said sorbent material, preferably to a temperature between 60 and 110°C, starting the desorption of CO2;(d) extracting at least the desorbed gaseous carbon dioxide from the unit and separating gaseous carbon dioxide in or downstream of the unit;(e) bringing said sorbent material essentially to ambient atmospheric temperature conditions and ambient atmospheric pressure conditions.

13. A method for preparing a sorbent material (3) which is a particulate copolymeric material, having an average particle size in the range of 200 - 3000pm, and having primary amine groups capable of reversibly binding carbon dioxide, preferably a sorbent material according to any of the preceding claims, for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air (1), flue gas and biogas, containing said gaseous carbon dioxide as well as further gases different from gaseous carbon dioxide, by cyclic adsorption / desorption using said sorbent material (3) capable of reversibly binding carbon dioxide and adsorbing said gaseous carbon dioxide in a unit (8), wherein in a first step at least one vinyl nitrile building block, selected from the group consisting of acrylonitrile, methacrylonitrile, trans-crotonitrile, fumaronitrile, and combinations thereof; at least one vinyl building block, convertible to polyalkyl primary amine by hydrolysis;and divinyl benzene; wherein(A) the molar proportion of the vinyl nitrile building blocks is at least 12 mole %;(B) the molar proportion of the vinyl building block is at least 10 mole %;(C) the molar proportion of the divinylbenzene is in the range of 9-28 mole %; wherein the sum of (A)-(C) makes up 100 mole % of the total of the building blocks of the terpolymer, are copolymerized and cross-linked by said divinyl benzene, wherein in a second step the vinyl building block is converted to said primary amine groups capable of reversibly binding carbon dioxide by hydrolysis.

14. Method according to the preceding claim, wherein in said first step the vinyl nitrile building block is selected exclusively as acrylonitrile, and the vinyl building block is selected exclusively as vinyl formamide.

15. Method according to any of the preceding claims, wherein in a further step the vinyl nitrile building blocks are converted to amine, preferably primary amine, groups by reduction, wherein preferably this further step takes place after the second step.

16. Method according to any of the preceding claims, wherein the copolymerization takes place in the presence of radical initiator, wherein preferably the radical initiator is selected from the group consisting of azobisisobutyronitrile, benzoyl peroxide, 2,2-azobis-2-methylbutyronitrile, 2-2'-azobis(2,4-dimethyl)valeronitrile or 2,2- dimethoxy-2-phenyl-acetophenone of combinations thereof.

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