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 based on at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof copolymerized and cross-linked with divinyl building blocks, wherein the at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof are non-aromatic monomeric building blocks with 2 - 4 carbon atoms, and wherein the molar proportion of the divinyl building blocks to the sum of the divinyl building blocks and the at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof and, if present, further building blocks, is in the range of 10-20%.

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.

[0012] Several academic publications, such as Alesi et al. in Industrial & Engineering Chemistry Research 2012, 51 , 6907-6915; Veneman et al. in Energy Procedia 2014, 63, 2336; Yu et al. in Industrial & Engineering Chemistry Research 2017, 56, 3259-3269, also investigated in detail the use of cross-linked polystyrene resins functionalised with primary benzylamines as solid sorbents for DAC applications. Polystyrene-divinylbenzene resins have also been used as a support to impregnate amines such as tetraethylenepentamine and diethanolamine (CN 105195113A and Kim et al., Bull Chem. Soc. Jpn. 2015, 88, 1317-1322), 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 as reported by Alesi et al. in Industrial & Engineering Chemistry Research 2012, 51 , 6907-6915. An optimal sorbent ideally should be predominant composed of active phase to be able to intensify the carbon capture process.

[0013] 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.

[0014] Heydari-Gorji et al. (Polyethylenimine-lmpregnated Mesoporous Silica: Effect of Amine Loading and Surface Alkyl Chains on CO2 Adsorption, Langmuir 2011 , 27, 12411-12416) discuss poly(ethyleneimine) (PEI) supported on pore-expanded MCM-41 whose surface is covered with a layer of long-al kyl chains, and which was found to be a more efficient CO2 adsorbent than PEI supported on the corresponding calcined silica and all PEI-impregnated materials reported in the literature. The layer of surface alkyl chains is reported to play an important role in enhancing the dispersion of PEI, thus decreasing the diffusion resistance. It was also found that at low temperature, adsorbents with relatively low PEI contents are more efficient than their highly loaded counterparts because of the increased adsorption rate. Extensive CO2 adsorption-desorption cycling showed that the use of humidified feed and purge gases affords materials with enhanced stability, despite limited loss due to amine evaporation.

[0015] Zhang et al. (Capturing CO2 from ambient air using a polyethyleneimine-silica adsorbent in fluidized beds, Chemical Engineering Science 116 (2014) 305-316) report the performance of a mesoporous silica-supported polyethyleneimine (PEI)— silica adsorbent for CO2 capture from ambient air in a laboratory-scale Bubbling Fluidized Bed (BFB) reactor. The air capture tests lasted for between 4 and 14 days using 1 kg of the PEI-silica adsorbent in the BFB reactor. Despite the low CO2 concentration in ambient air, nearly 100% CO2 capture efficiency has been achieved with a relatively short gas-solid contact time of 7.5 s. The equilibrium CO2 adsorption capacity for air capture was found to be as high as 7.3 wt%. The proposed “PEI-CFB air capture system” mainly comprises a Circulating Fluidized Bed (CFB) adsorber and a BFB desorber with a CO2 capture capacity of 40 t-CO2 / day. A large pressure drop is required to drive the air through the CFB adsorber and also to suspend and circulate the solid adsorbents within the loop, resulting in higher electricity demand than other reported air capture systems. However, the Temperature Swing Adsorption (TSA) technology adopted for the regeneration strategy in the separate BFB desorber has resulted in much smaller thermal energy requirement. The total energy required is 6.6 GJ / t-CO2 which is comparable to other reference air capture systems.

[0016] 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). 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.

[0017] WO-A-2023 / 152659 discloses polymeric amine 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. The polymeric amine 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 sorbents for separation of a component from a multi-component gas stream.

[0018] 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.

[0019] 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. Dogan et al. (ChemSusChem 10.1002 / cssc.201700190) report chemical tuning of nanoporous, solid sorbents for an ideal CO2 binding requiring unhindered amine functional groups on the pore walls. Although common for soluble organics, post-synthetic reduction of nitriles in porous networks often fail due to the insufficient and irreversible metal hydride penetration. They synthesized a nanoporous network with pendant nitrile groups, microsphere morphology and in large scale. The hollow microspheres were easily decorated with primary amines through in situ reduction by widely available boranes. CO2 capture capacity of the modified sorbent was increased up to four times of the starting nanoporous network with a high heat of adsorption (98 kJ / mol). Surface area can be tuned between 1 and 354 m2 / g. Average particle size (~50 pm) is also quite suitable for CO2 capture applications where processes like fluidized bed require spheres of micron sizes. Bachmann (DOE-PARC-FE0031951) reports on a polyvinylamine-divinlybenzene system (PVAm-DVB) and reports CO2 adsorption capacity, CO2 adsorption kinetics, and oxidative stability.

[0020] EP-A-0576198 discloses a method for producing carbonaceous resins with superior physical properties that are useful as ion exchange materials, adsorbents, catalysts and catalyst support systems. The carbonaceous resins are produced by heating a polymer obtained by polymerizing a monomer mixture comprising acrylonitrile, crosslinking agent and porogen.

[0021] 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.

[0022] Ratayakorn Khunsupat in a 2011 master thesis at the Georgia Institute of Technology entitled "Poly(allylamine) and derivatives for co2 capture from flue gas or ultra dilute gas streams such as ambient air" proposes polymers rich in primary amine groups to be effective adsorbents for the reversible adsorption of CO2 from moderately dilute gas streams (10% CO2) and ultra-dilute gas streams (e.g. ambient air, 400 ppm CO2), with their performance under ultra-dilute conditions being competitive with or exceeding the state-of- the-art adsorbents based on supported poly(ethyleneimine) (PEI). The CO2 adsorption capacity (mmol CO2 / g sorbent) and amine efficiency (mmol CO2 / mmol amine) of linear poly(allylamine) (PAA), cross-linked poly(allylamine) prepared by post-polymerization crosslinking with epichlorohydrin (PAAEPI), and branched poly(allylamine) prepared by branching of poly(allylamine) with divinylbenzene (PAADVB) are presented and compared with state-of-the-art adsorbents based on supported PEI, specifically branched and linear, low molecular weight PEI. Silica mesocellular foam, MCF, serves as the support material for impregnation of the amine polymers. In general, branched polymers are found to yield more effective adsorbents materials. Overall, the results of show that linear PAA, crosslinked PAAEPI, and branched PAADVB are candidates for solid adsorbents with high capacity for CO2.

[0023] SUMMARY OF THE INVENTION

[0024] According to a first aspect of the present invention, it relates to a sorbent material for use in carbon dioxide capture processes.

[0025] The object is to provide an improved sorbent material having a high CO2 capture capacity and which is stable over a long time, so which resists oxidation and further deterioration mechanisms, and which also allows to 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.

[0026] 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, preferably from at least one of ambient atmospheric air, flue gas and biogas, preferably for direct air capture. This in particular using a temperature, vacuum, or temperature / vacuum swing process.

[0027] Said sorbent material is a particulate copolymeric material based on at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof copolymerized and cross-linked with divinyl building blocks.

[0028] A particulate material according to the present invention is a material which is solid up to a temperature of at least 80°C, so typically in the range of 0-80°C. It can be a powder material or a granular or bead material, and in any case, it is not a liquid or liquid viscous material in that temperature range.

[0029] According to the invention, the at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof are non-aromatic monomeric building blocks with 2 - 4 carbon atoms, and the molar proportion of the divinyl building blocks to the sum of the divinyl building blocks and the at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof and, if present, further building blocks (so to the sum of all monomeric building blocks plus the divinyl building blocks), is in the range of 8-30% preferably 10-20%.

[0030] The molar proportion of the divinyl building blocks to the sum of the divinyl building blocks and the at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof and, if present, further building blocks (so the sum of all monomeric building blocks plus the divinyl building blocks), is preferably more than 10%, 10 - 20% or 10-18% or in the range of 12-17%.

[0031] To make sure that the resulting material indeed is a particulate and thus solid material, the corresponding reaction is preferably carried out in the presence of a low water solubility (radical) initiator, so an initiator that, at room temperature (20°C), normally has a solubility in water of at most 1 g / 100g, preferably less than 1 g / 100g, more preferably less than 0.5 g / 100g.

[0032] It was surprisingly found that using this particular cross-linking proportion and avoiding the usual styrene building blocks - preferably the proposed material is completely free of aromatic building blocks except for divinyl building blocks which can be aromatic (e.g. DVB) - provides for a high capture capacity and a high oxidation resistance, i.e. high stability under continued capture use.

[0033] According to a first preferred embodiment, said amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof are selected from the group consisting of wherein X is hydrogen and R can be selected from the group consisting of methyl and halogen, the latter preferably selected as Cl or Br. R can also be CN except for the case where the above rightmost structure is taken. For solubility reasons, it may be preferable if the monomeric building blocks are selected from the above two leftmost and the rightmost structure.

[0034] Preferably, said amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof are selected from the group consisting of wherein X is hydrogen and R can be selected from the group consisting of methyl, CN and halogen, the latter preferably selected as Cl or Br.

[0035] Said sorbent material can be a particulate copolymeric material based exclusively on at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof copolymerized and cross-linked with divinyl building blocks, wherein preferably it is based exclusively on amino mono allyl or precursors thereof copolymerized and cross-linked with divinylbenzene building blocks, or it is based exclusively on amino mono vinyl monomeric building blocks or precursors thereof copolymerized and cross-linked with divinylbenzene building blocks.

[0036] Preferably the amino mono vinyl building blocks or precursors thereof are selected as vinylamine and / or the amino mono allyl building blocks or precursors thereof are selected as allylamine or acrylic nitrile or methacrylonitrile.

[0037] Typically, the reaction is carried out in the presence of a porogen to make sure the porosity of the resulting particulate sorbent material provides the functionality of reversibly binding carbon dioxide from the gas phase. Preferably, these porogen systems also have an adapted solubility, preferably the respective solubility parameter SP (also designated as 6;) of the porogen is in the range of 9.5 (cal / cm3)1 / 2or less, preferably in the range of 5-9 (cal / cm3)1 / 2(using the Hildebrand solubility parameter SP values as e.g. defined and available from the Polymer Handbook, Brandrup, J. I Immergut, Edmund H. I Grulke, E. A. / Abe, Akihiro I Bloch, Daniel R. (Editor), 4thEdition 2003, John Wiley & Sons, p. 675 -711 ; (cal / cm3)1 / 2= 2.046 MPa1 / 2).

[0038] 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. The nitrogen content is determined and calculated according to the description given further below.

[0039] According to yet another preferred embodiment, the sorbent material takes the form of preferably essentially spherical beads with an average particle size in the range of 0.002 - 4 mm, 0.005 - 2 mm, 0.002 - 1.5 mm, 0.005 - 1.6 mm or 0.01-1.5 mm, preferably in the range of 0.25-0.50 mm. The average particle size is determined and calculated according to the description given further below.

[0040] The sorbent material is preferably in porous form, and has a specific BET surface area, in the range of 0.5-150 m2 / g or 10-200, preferably 30-80 m2 / g, and / or has an average pore diameter in the range of 1-200 nm, preferably in the range of 10-150 nm, preferably in the range of 50-120 nm. BET (Brunauer, Emmett and Teller, also termed SBET) surface area analysis values are determined applying the method ISO 9277, and average pore diameters (average pore sizes) were determined using Mercury porosimetry and following the protocol according to ISO 15901-1 :2016 (Evaluation of pore size distribution and porosity of solid materials by mercury porosimetry and gas adsorption Part 1).

[0041] Said divinyl building blocks are preferably selected from the group consisting of divinylbenzene; 1 ,9-decadiene; 1 ,7-octadiene; 2,4,6-triallyloxy-1 ,3,5-triazine; pentaerythritol triacrylate (PETA); ethylene glycol diacrylate; ethylene glycol dimethacrylate; triethylene glycol diacrylate; tetraethylene glycol dimethacrylate; and mixtures thereof, wherein preferably said divinyl building blocks are selected only as divinylbenzene.

[0042] According to a further aspect of the present invention, it relates to a carbon dioxide capture adsorber structure. More specifically, it relates to an 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 as defined above.

[0043] According to yet another aspect of the present invention, it relates to the use of such a sorbent material. More specifically, it relates to the use of 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, preferably for direct air capture, in particular using a temperature, vacuum, or temperature / vacuum swing process.

[0044] Furthermore, according to another aspect of the present invention, it relates to a method for separating carbon dioxide from other gases using such a sorbent material.

[0045] 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):

[0046] (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");

[0047] (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;

[0048] (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;

[0049] (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;

[0050] (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).

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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, wherein amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof are copolymerized and cross-linked with divinyl building blocks, wherein the at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof are non-aromatic monomeric building blocks with 2-9 or 2 - 4 carbon atoms, and wherein the molar proportion of the divinyl building blocks to the sum of the divinyl building blocks and the at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof and, if present, further building blocks, is in the range of 10-20%.

[0055] The molar proportion of the divinyl building blocks to the sum of the divinyl building blocks and the at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof and, if present, further building blocks, is preferably more than 10%, 10-18% or in the range of 12-17%.

[0056] According to a preferred embodiment of this method, in a first step acrylic nitrile alone or in combination with further amino mono allyl and / or amino mono vinyl monomeric building blocks or precursors thereof is copolymerized and cross-linked with divinyl building blocks, and in a second step the resulting copolymer is subjected to a reduction to convert the pendant nitrile groups into primary amine groups, wherein preferably in said first step exclusively acrylic nitrile is reacted with divinylbenzene building blocks.

[0057] The acrylic nitrile can also take the more general structure: with the definition of R as given above. Preferably in this case R is selected as methyl, so the acrylic nitrile system is preferably methacrylonitrile. Preferably only DVB and methacrylonitrile are reacted in this case as monomers.

[0058] A general scheme of this approach is summarized in Fig. 2.

[0059] Said reduction in the second step is preferably carried out so as to convert at least 80%, preferably at least 90 or 95 % of the nitrile groups into primary amine groups, wherein preferably for the reduction at least two, preferably at least three reduction cycles are carried out.

[0060] Preferably the reduction is carried out by using at least one of borohydride, lithium aluminium hydride, sodium cyanoborohydride, sodium bis(2-methoxyethoxy)aluminium hydride in an organic solvent, preferably selected from the group consisting of tetrahydrofuran, dioxane, dimethylsulfide, dimethoxymethane, or a mixture thereof, for a time span of at least 14h, preferably at least 18 hours per cycle.

[0061] In an alternative approach, the following method is proposed in a first step amino mono vinyl or a precursor thereof alone or in combination with further amino mono allyl and / or amino mono vinyl monomeric building blocks or precursors thereof is copolymerized and cross-linked with divinyl building blocks, wherein said amino mono vinyl or precursor thereof is selected from the group consisting of

[0062] V Rwherein X is selected from the group consisting of tert-butyloxycarbonyl (Boc), phthalimide and R can be selected from the group consisting of methyl and halogen, the latter preferably selected as Cl or Br, in a second step the resulting copolymer is subjected to a deprotection to convert the pendant secondary amine groups into primary amine groups, wherein preferably in said first step exclusively said amino mono vinyl is reacted with divinylbenzene building blocks.

[0063] A general scheme of this approach is summarized in Fig. 3.

[0064] The selection of the specific protecting group on the amine can influence the synthesis significantly. If particle formation is intended, for example formyl protecting groups are not suitable due to the water solubility of the monomer.

[0065] The copolymerization normally 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- methyl butyronitrile, 2-2'-azobis(2,4-dimethyl)valeronitrile or 2,2-dimethoxy-2-phenyl-acetophenone of combinations thereof. As mentioned above, preferably such an initiator, at room temperature (20°C), normally has a solubility in water of at most 1 g / 100g, preferably less than 1 g / 100g, more preferably less than 0.5 g / 100g. Further embodiments of the invention are laid down in the dependent claims.

[0066] BRIEF DESCRIPTION OF THE DRAWINGS

[0067] 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;

[0068] Fig. 2 shows a reaction scheme for PAA-co-DVB; Fig. 3 shows a reaction scheme for PVA-co-DVB;

[0069] Fig. 4 shows the carbon dioxide capture capacity as a function of the reduction cycles for the PAA-co-DVB systems in comparison with standard PS-DVB systems;

[0070] Fig. 5 shows the quantification of conversion of nitriles to amines as a function of the reduction cycles for the PAA-co-DVB systems;

[0071] Fig. 6 shows the carbon dioxide capture capacity as a function of DVB proportion for the PAA-co-DVB systems;

[0072] Fig. 7 shows the influence of aging (convection oven; after 72 h of exposure at 90°C) for the proposed systems as opposed to conventional PS-DVD systems.

[0073] DESCRIPTION OF PREFERRED EMBODIMENTS

[0074] Synthesis procedure of acrylonitrile-divinylbenzene resin:

[0075] In a 1 L reactor, 300 g of ion-exchanged water, 0.2 g of hydroxyethylcellulose (dispersant, average Mv -90,000 g / mol), and 15 g of sodium chloride were added, and stirred at 300rpm at 50°C for 1 hour to completely dissolve the contents (Solution A).

[0076] Separately, 70 g of acrylonitrile (AN, Mw= 53.06 g / mol, 1.319 mol), 30 g of divinylbenzene (content 80%, DVB, Mw = 130.19 g / mol, 0.1843 mol), 100 g of toluene, and 1 g of azobisisobutyronitrile (AIBN, Mw = 164.21 g / mol, 6.09 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).

[0077] 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.

[0078] 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 one more time.

[0079] 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.

[0080] The desired polymer particles were then dried under reduced pressure at 75°C and 200 torr for 1 hour.

[0081] The average particle diameter was 330 micrometers (number average), the pore size determined by mercury injection method was 75 nanometers, and the specific surface area determined by the BET method was 62 m2 / g.

[0082] The beads are dried in rotavapor. The proposed synthetic approach allows for control of the morphology (pore size and surface area and cross-linking) as well as of the particle size and the nitrogen content (through the acrylonitrile monomer).

[0083] The following Table 1 shows how the properties of the PAN-co-DVB and also of the PAA- co-DVB after the reduction can be tuned as a function of the DVB to monomer ratio, wherein the DVB percentage and the AN percentage in the ratios are given as percentages relative to the total of the acrylonitrile (AN). and DVB.

[0084] Table 1 : properties of different PAN-co-DVB systems

[0085] Preferred pore size: 50-200nm; preferred surface area: <50m2 / g.

[0086] The acrylonitrile-divinylbenzene (PAN-co-DVB) beads are then reacted with a reducing agent to obtain the allylamine-divinylbenzene (PAA-co-DVB) beads.

[0087] To afford the allylamine-divinylbenzene beads:

[0088] The acrylonitrile-divinylbenzene beads (7g) are added to a three-necked flask, flushed with nitrogen and the three-necked flask was cooled with an ice bath. The borane-THF-solution (1M, 80 mL) was added dropwise under stirring. After complete addition, the reaction temperature is increased to 65°C (reflux) and the mixture is stirred for 24h. The steps can be repeated up to 4 times, and after complete addition, the reaction temperature is increased to 65°C (reflux) and the mixture is stirred for 24h.

[0089] Subsequently, the mixture is cooled to 0°C, 100 mL of 2M HCI (aqueous) in methanol is added and the mixture is stirred at 40°C for 3h. After that, the beads are filtered off and washed with water. At this stage the amine is protonated and to free the base, the beads are treated with 50 mL of an NaOH solution 2 M and stirred for 1 h at 40°C. The aminated beads are filter off and washed to neutral pH with demineralized water.

[0090] As one can see from the representation in Fig. 4, summarizing the carbon dioxide capture capacities of the resulting PAA-co-DVB systems as a function of the reduction cycles (Red_1x - Red_4x) and compared with standard PS-DVB based systems, the proposed systems can be tuned for optimum capture capacity by us completely reducing the systems as possible.

[0091] As one can see from the representation in Fig. 5, the nitrogen content essentially corresponds to the capture capacity properties as illustrated in Fig. 4.

[0092] The very particular advantages in particular as concerns the DVB proportion and the influence thereof are illustrated in Fig. 6, showing the carbon dioxide uptake capacity as a function of the DVB proportion, indicating a clear sweet spot in the range between more than 10 and 18%, with an optimum in the range of 15%. N elemental analysis gives the total nitrogen content (nitriles+primary amines), the N exchange capacity gives exchangeable amine content (primary amines), and the gives the quantitative amount of -CN groups left in the sorbent and hence, the conversion.

[0093] The further unexpected particular advantages in particular as concerns the DVB proportion and the influence thereof are illustrated in Fig. 7, showing the reduction in capture capacity after aging of the proposed systems as opposed to conventional PS-DVB based systems (Benzylamine-co-DVB). The deterioration in capture capacity can be reduced very significantly. PAA-co-DVB has a different optimum as compared to Benzylamine-co-DVB.

[0094] Synthesis procedure of tert-butyl protected vinylamine-divinylbenzene resin:

[0095] In a 1 L reactor, 280 g of ion-exchanged water and 0.1 g of hydroxyethylcellulose were added and stirred at 300rpm at 35°C for 1 hour to completely dissolve the contents (Solution A).

[0096] Separately, 35 g of tert-butyl vinyl carbamate (Mw = 143.18 g / mol, 0.244 mol), 8.74 g of divinylbenzene (content 80%, DVB, Mw = 130.19 g / mol, 0.05368 mol), 20 g of n-heptane and 0.5 g of azobisisobutyronitrile (AIBN, Mw = 164.21 g / mol, 3.05 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). Solution B was added to Solution A all at once while the stirring, and the temperature of the reaction solution was set at 80°C. After the reaction solution reached 80°C, the reaction was continued for 8 hours.

[0097] The average particle diameter was 310 micrometers (number average), the number average pore size determined by mercury porosimetry was 140 nanometers, and the specific surface area determined by the BET method was 49 m2 / g.

[0098] Deprotection of the tert-butyl protected vinylamine-divinylbenzene resin to obtain the vinylamine-divinylbenzene resin:

[0099] The 10 g beads are placed in a 3-neck flask containing 100mL of ethanol and cooled to OdegC, and stirred at 100rpm for 1 h. Then 80g of 37% HCI was added to the flask, and the temperature of the reaction solution was set at 55degC. After the reaction solution reached 55°C, the reaction was continued for 18 hours.

[0100] After that, the beads are filtered off and washed with water. At this stage the amine is protonated and to free the base, the beads are treated with 50 mL of an NaOH solution 2 M and stirred for 24h at 20degC. The aminated beads are filter off and washed to neutral pH with demineralized water.

[0101] Synthesis procedure of primary amine-functionalized styrene-divinylbenzene resin (for comparison):

[0102] In a 1 L reactor, 1% (mass ratio) of gelatin and 2% (mass ratio) of sodium chloride are 30 dissolved in 300 mL of water at 45°C for 1h. In another flask, 1 g of benzoyl peroxide is dissolved in a mixture of 54 g of styrene (Mw = 104.15 g / mol, 0.518 mol), 5.06 g of divinylbenzene (content 80%, Mw = 130.19 g / mol, 0.03108 mol), 68 g of heptane and 22 g of toluene. The resulting mixture is then added to the reactor. After that the reaction mixture is stirred and heated up to 70°C maintaining the temperature for 2 h, then the temperature is raised to 80°C and kept it for 16 h. The temperature is then raised 35 to 100°C for 3 h to distill out the porogen. The reaction mixture is cooled down to room temperature and the beads are filtered off using a funnel glass filter and vacuum suction.

[0103] The beads are dried in rotavapor. The polystyrene-divinylbenzene beads are functionalised using the chloromethylation reaction. 5 g of so obtained beads are added to a 3-neck flask containing 30 mL of chloromethyl methyl ether. 3.5 g of zinc chloride is added to the mixture over 2 h and heated for an additional 4 h to 60°C. After that, the mixture is cooled to room temperature and 25% HCI in water is added to quench chloromethyl methyl ether. The chloromethylated beads are washed until neutral with water, filtered off, and dried.

[0104] To afford the benzylamine: the chloromethyl-functionalized polystyrene-divinylbenzene beads are aminated using the benzylamine-amination reaction:

[0105] The chloromethylated beads are added to a three-necked flask with 27 g of methylal and the mixture is stirred for 1 h at 25°C (room temperature). To this mixture, 9 g of hexamethylenetetramine and 12 g of water are added and kept under gentle reflux for 6 h. The beads are filtered off and washed with water. To obtain a primary amine, a hydrolysis step followed by a treatment with a base are required. The beads are placed in a 3-neck flask containing 140 mL of a solution of hydrochloric acid (30%) - ethanol (95%) (volume ratio of 1 :3), the reaction mixture is heated to 80°C and kept at this temperature for 20 h. After that, the beads are filtered off and washed with water. At this stage the amine is protonated and to free the base, the beads are treated with 50 mL of an NaOH solution 2 M, and stirred for 1 h at 50°C. The aminated beads are filter off and washed to neutral pH with demineralized water.

[0106] Synthesis procedure of methacrylonitrile (MAN)-divinylbenzene resin:

[0107] In a 1 L reactor, 300 g of ion-exchanged water, 0.2 g of hydroxyethylcellulose (dispersant, average Mv -90,000 g / mol), and 15 g of sodium chloride were added, and stirred at 300rpm at 50°C for 1 hour to completely dissolve the contents (Solution A).

[0108] Separately, 74 g of methacrylonitrile (MAN, Mw= 67.09 g / mol, 1.103 mol), 26 g of divinylbenzene (content 80%, DVB, Mw = 130.19 g / mol, 0.1598 mol), 100 g of toluene, and 1 g of azobisisobutyronitrile (AIBN, Mw = 164.21 g / mol, 6.09 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).

[0109] Solution B was added to Solution A all at once while maintaining the stirring, and the temperature of the reaction solution was set at 80°C. After the reaction solution reached 80°C, the reaction was continued for 18 hours.

[0110] 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 one more time.

[0111] 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.

[0112] The desired polymer particles were then dried under reduced pressure at 75°C and 200 torr for 1 hour.

[0113] The average particle diameter was 640 micrometers (number average), the pore size determined by mercury injection method was 60 nanometers, and the specific surface area determined by the BET method was 33 m2 / g. Table 2: properties of different PMAN-co-DVB systems

[0114] To afford the methylallylamine-divinylbenzene beads:

[0115] The methacrylonitrile-divinylbenzene beads (7g) are added to a three-necked flask, flushed with nitrogen and the three-necked flask was cooled with an ice bath. The borane-THF- solution (1M, 80 mL) was added dropwise under stirring. After complete addition, the reaction temperature is increased to 65°C (reflux) and the mixture is stirred for 24h. The steps can be repeated up to 4 times, and after complete addition, the reaction temperature is increased to 65°C (reflux) and the mixture is stirred for 24h.

[0116] Subsequently, the mixture is cooled to 0°C, 100 mL of 2M HCI (aqueous) in methanol is added and the mixture is stirred at 40°C for 3h. After that, the beads are filtered off and washed with water. At this stage the amine is protonated and to free the base, the beads are treated with 50 mL of an NaOH solution 2 M and stirred for 1 h at 40°C. The aminated beads are filter off and washed to neutral pH with demineralized water. The eq. CO2 adsorption capacity was 0.98 mmol / g.

[0117] Exchange capacity properties:

[0118] 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:

[0119] (25mL — mL Na.0Hused) * 0.4 Exchange capacity[meq / g]=Wet Mass*Solid Content

[0120] Solid Content: 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).

[0121] CO2 capture capacity properties:

[0122] 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.

[0123] Nitrogen content measurements:

[0124] 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.

[0125] Specific surface area measurements:

[0126] 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.

[0127] BET (Brunauer, Emmett und Teller) surface area analysis was used applying the method ISO 9277.

[0128] Average particle diameter Measurements:

[0129] The average particle size was determined by measuring samples under an optical microscope; a random selection of 100 non-overlapping particles was made.

[0130] Mercury Porosimetry Measurements: 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:

[0131] Mercury surface tension: 0.48 N / m

[0132] Mercury contact angle: 150°

[0133] Max. pressure: 400 MPa

[0134] Increase speed: 6-19 MPa / min

[0135] 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. The derivative of this curve provides a pore size distribution of the pores accessible via the exterior of the material.

[0136] Degradation measurements:

[0137] The resulting materials were further subjected to a screening oxidation resistance test, using the following conditions: the sorbent was placed in a petri dish and then placed in a convection oven, after 72 h of exposure at 90°C, the petri dish was taken out and the CO2 adsorption capacity of the sample was tested.

[0138] Reference benzylamine-type sorbents:

[0139] Data is given for two different basic primary aminated benzylamine DVB systems (primary amine-functionalized styrene-divinylbenzene resin as synthesized above) designated as Sorbent A and B:

[0140] Acrylonitrile-co-DVB materials:

[0141] Data is given for four different acrylonitrile-co-DVB systems designated as Sorbents C-F:

[0142] Tert-butyl (tBoc) vinyl carbamate-co-DVB materials:

[0143] Data is given for one tBocVC -co-DVB system:

[0144] Attempt to reproduce Example 6B of WO-A-2023152659:

[0145] The flask was immersed in ice water. The flask was flushed with nitrogen, and then 16.5 g of 36-37% hydrochloric acid and 0.165 g of sodium chloride were added. When the temperature of the contents reached 15 °C, 11 g of allylamine was gradually added (although it generates heat, the rate of allylamine addition was adjusted so that the temperature did not exceed 30 °C). When the temperature dropped to 15°C, 1.75 g of citric acid was slowly added, pH measured was 5.5. After that, 1.8 g of V50 initiator [2,2'-azobis(2- methylpropionamidine) dihydrochloride] and 0.6 g of DVB (80%) were added and the internal temperature raised to 65 °C. Separately, 4.4 g of DVB (80%) was prepared, and the DVB solution was dropped in over a period of 4.3 hours (the reaction temperature was adjusted to be in the range of 65-70°C). After the DVB dropping was complete, the temperature was increased to 82°C and left for 2.5 hours. A low viscosity liquid compound resulted. The low viscosity liquid compound was dried at room temperature for 24 hours, and then dried at 100°C, but it did not solidify. Only a low-viscosity liquid compound was obtained, and no beads or solid material could be obtained. Subsequently, 2g of methanol was added to the product, but this low-viscosity liquid compound only dissolved in the methanol and did not solidify at all. The example 6B of WO-A-2023152659 is thus not providing an enabling disclosure.

[0146] The same results were obtained if the amount of DVB added were adapted assuming that the figures of example 6B of WO-A-2023152659 would refer to 100% DVB content. Also then only a low viscosity liquid compound was obtained and it was impossible to convert the liquid material into a solid particulate material. Also example 6A of WO-A-2023152659 was reproduced and also here only a low viscosity liquid compound could be obtained under the conditions described in the prior art document. Measurement of the materials of Example 1 of EP-A-0 576 198 to determine whether these materials are capable of reversibly binding carbon dioxide, for separating gaseous carbon dioxide from a gas mixture:

[0147] The materials of example 1 of EP-A-0 576 198 use 4-methyl-2-pentanol as porogen leading to materials having BET values above 200 m2 / g (clear beads). Neither before nor after pyrolysis according to this example the materials of that example show any carbon dioxide binding in the gas phase. The equilibrium CO2 capacity was measured. The capacity was found to be 0 mmol / g. So these materials are not capable of reversibly binding carbon dioxide, for separating gaseous carbon dioxide from a gas mixture.

[0148] LIST OF REFERENCE SIGNS

[0149] 1 ambient air, ambient air inflow structure

[0150] 2 outflow of ambient air behind adsorption unit in adsorption flow-through mode

[0151] 3 sorbent material

[0152] 4 steam, steam inflow structure for desorption

[0153] 5 reactor outlet for extraction

[0154] 6 vacuum unit / separator

[0155] 7 wall

[0156] 8 reactor unit

[0157] Al BN azobisisobutyronitrile

[0158] AN acrylonitrile

[0159] DVB divinylbenzene

[0160] PAA polyallylamine

[0161] PS polystyrene

[0162] PVA polyvinylamine tBocVC tert-butyl (tBoc) vinyl carbamate

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 based on at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof copolymerized and cross-linked with divinyl building blocks, wherein the at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof are non-aromatic monomeric building blocks with 2 - 4 carbon atoms, and wherein the molar proportion of the divinyl building blocks to the sum of the divinyl building blocks and the at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof and, if present, further building blocks, is in the range of 8-30%.

2. Sorbent material according to claim 1 , wherein said amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof are selected from the group consisting ofwherein X is hydrogen and R can be selected from the group consisting of methyl and halogen, the latter preferably selected as Cl or Br.

3. Sorbent material according to any of the preceding claims, wherein said sorbent material (3) is a particulate copolymeric material based exclusively on at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof copolymerized and cross-linked with divinyl building blocks, wherein preferably it is based exclusively on amino mono allyl or precursors thereof copolymerized and cross-linked with divinylbenzene building blocks, or it is based exclusively on amino mono vinyl monomeric building blocks or precursors thereof copolymerized and cross-linked with divinylbenzene building blocks, wherein further preferably the amino mono vinyl building blocks or precursorsthereof are selected as vinylamine and / or the amino mono allyl building blocks or precursors thereof are selected as allylamine or acrylic nitrile.

4. 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.

5. Sorbent material according to any of the preceding claims, wherein the sorbent material takes the form of preferably essentially spherical beads with an average particle size in the range of 0.002 - 4 mm, 0.005 - 2 mm, 0.002 - 1.5 mm, 0.005 - 1.6 mm or 0.01-1.5 mm, preferably in the range of 0.25-0.50 mm.

6. Sorbent material according to any of the preceding claims, wherein the sorbent material, preferably in porous form, and having specific BET surface area, in the range of 0.5-150 m2 / g or 10-200, preferably 30-80 m2 / g, and / or having an average pore diameter in the range of 1-200 nm, preferably in the range of 10-150 nm, preferably in the range of 50-120 nm.

7. Sorbent material according to any of the preceding claims, wherein said divinyl building blocks are selected from the group consisting of divinylbenzene; 1 ,9- decadiene; 1 ,7-octadiene; 2,4,6-triallyloxy-1 ,3,5-triazine; pentaerythritol triacrylate (PETA); ethylene glycol diacrylate; ethylene glycol dimethacrylate; triethylene glycol diacrylate; tetraethylene glycol dimethacrylate; and mixtures thereof, wherein preferably said divinyl building blocks are selected only as divinylbenzene and / or wherein the molar proportion of the divinyl building blocks to the sum of the divinyl building blocks and the at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof and, if present, further building blocks, is in the range of 10-20%, preferably in the range of 12-17%.

8. 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.

9. Use of a sorbent material (3) according to any of the preceding claims forseparating 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.

10. 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.

11. A method for preparing a sorbent material (3), 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 amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof are copolymerized and cross-linked with divinyl building blocks, wherein the at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof are non-aromatic monomeric building blocks with 2 - 9 or 2 - 4 carbon atoms, and wherein the molar proportion of the divinyl building blocks to the sum of the divinyl building blocks and the at least one of amino mono allyl and amino mono vinyl monomeric building blocks or precursors thereof and, if present, further building blocks, is in the range of 8-30% or preferably in the range of 10-20%.

12. Method according to the preceding claim, wherein in a first step acrylic nitrile alone or in combination with further amino mono allyl and / or amino mono vinyl monomeric building blocks or precursors thereof is copolymerized and cross-linked with divinyl building blocks, and in a second step the resulting copolymer is subjected to a reduction to convert the pendant nitrile groups into primary amine groups, wherein preferably in said first step exclusively acrylic nitrile is reacted with divinylbenzene building blocks.

13. Method according to the preceding claim, wherein said reduction in the second step is carried said reduction in the second step converting at least at least 80%, preferably at least 90 or 95 % of the nitrile groups into primary amine groups, wherein preferably for the reduction at least two, preferably at least three reduction cycles are carried out, and / or wherein preferably the reduction is carried out by using at least one of borohydride, lithium aluminium hydride, sodium cyanoborohydride, sodium bis(2- methoxyethoxy)aluminium hydride in an organic solvent, preferably selected from the group consisting of tetrahydrofuran, dioxane, dimethylsulfide, dimethoxymethane, or a mixture thereof, for a time span of at least 14h, preferably at least 18 hours per cycle.

14. Method according to the preceding claim 11 , wherein in a first step amino mono vinyl or a precursor thereof alone or in combination with further amino mono allyl and / or amino mono vinyl monomeric building blocks or precursors thereof is copolymerized and cross-linked with divinyl building blocks, wherein said amino mono vinyl or precursor thereof is selected from the group consisting ofwherein X is selected from the group consisting of tert-butyloxycarbonyl (Boc), phthalimide and R can be selected from the group consisting of methyl and halogen, the latter preferably selected as Cl or Br, in a second step the resulting copolymer is subjected to a deprotection to convert the pendant secondary amine groups into primary amine groups,wherein preferably in said first step exclusively said amino mono vinyl is reacted with divinylbenzene building blocks.

15. Method according to any of the preceding claims 11-14, 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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