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

Abstract

A method for preparing a sorbent material (3) 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 a sorbent material (3) capable of reversibly binding carbon dioxide and adsorbing said gaseous carbon dioxide in a unit (8), wherein the sorbent material (3) comprises: primary amine moieties as well as at least one of secondary amine, and tertiary amine moieties immobilized on a solid support, and is made using an amination pathway avoiding cross-linking.

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-alkyl 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).

[0017] 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.

[0018] US-A-2017259255 discloses a high exchange-capacity anion exchange resin with dual functional-groups and a method of synthesis thereof. The invention relates to the field of environmental function material synthesis and application. The resin is based on chloromethylated polystyrene-divinylbenzene polymer as matrix, and by primary amination and quaternization, yields an anion exchange resin with dual functional-groups having both a weak base anionic group and a strong base anionic group. The anion exchange resin not only has high adsorption capacity for water-born nitrate ions, but also can effectively squelch natural organic acids such as phytic acid in water, thus simultaneously removing nitrate ions and phytic acid organic matter from water. Therefore, the resin has a broad application potential in the fields of drinking water treatment, groundwater remediation, and advanced urban sewage treatment.

[0019] WO-A-97 / 31864 relates to anion-exchange compositions comprising anion-exchange functional groups comprising at least a first and a second nitrogen group, wherein the first nitrogen group is a positively charged quaternary amine and the second nitrogen group is selected from the group consisting of primary, secondary, tertiary or quaternary amines. Methods of making and using the compositions are also provided.

[0020] SUMMARY OF THE INVENTION

[0021] 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 to perform the cyclic adsorption / desorption of CO2 for hundreds or thousands of cycles over the same sorbent material, where the sorbent shall not undergo any or if at all only insignificant chemical transformations that impedes its reactivity towards 002.

[0022] The co-polymerization of styrene and divinylbenzene is shown in Scheme 1 :

[0023] Scheme 1

[0024] For converting such systems, e.g. in particulate form, into materials suitable for carbon dioxide capture, they can be chloromethylated in a first step under formation of a chloromethylated styrene-divinylbenzene resin and then aminated to form primary benzylamine groups which are then providing the primary amines for carbon dioxide capture. Amination can e.g. be carried out by reacting the chloromethylated styrene- divinylbenzene resin with hexamethylenetetramine followed by hydrolysis typically under acidic conditions.

[0025] While such primary amine systems perform well for carbon dioxide capture purposes, including direct air capture, still higher capture capacity is needed for a more efficient carbon dioxide removal process.

[0026] According to the present invention this object is achieved by a new method of making such materials and methods for separating gaseous carbon dioxide from a gas mixture using a new sorbent material e.g. made according to claim 1.

[0027] It is noted that in the document WO 2022 / 013197 mentioned above, in the experimental section reacting chloromethylated poly(styrene-co-divinylbenzene) based starting material with hexamethylentetramine (HMTA) is disclosed, which leads to a simple amination, so the resulting product is a primary amine poly(styrene-co-divinylbenzene) system, according to the following scheme:

[0028] 1. Chloromethylation 2. Amination 3. Hydrolysis & 4. Acid-base washing

[0029] Furthermore, it is noted that in the document GB 1 296 889 also mentioned above, reacting chloromethylated poly(styrene-co-divinylbenzene) based starting material with diamine systems is disclosed, however only with polyamine systems, such as diethylenetriamine or triethylenetetramine. The focus there is on using polyfunctional amine systems, so obtaining predominantly secondary amine functionality in the resulting system due to the polyamine chains attached to the divinylbenzene backbone structure.

[0030] Surprisingly, as will be detailed and evidenced further below, the claimed systems show superior properties compared with the polyamine systems known in the prior art, in particular if the chain length of the diamine system is chosen to have 3-4 carbon atoms.

[0031] According to a first aspect of the invention, it relates to a method for preparing 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, containing said gaseous carbon dioxide as well as further gases different from gaseous carbon dioxide, by cyclic adsorption / desorption using a sorbent material capable of reversibly binding carbon dioxide and adsorbing said gaseous carbon dioxide in a unit. Said use for separating gaseous carbon dioxide from a gas mixture is correspondingly a use, which entails cyclic adsorption / desorption using this sorbent material capable of reversibly binding carbon dioxide and adsorbing said gaseous carbon dioxide in a unit. The sorbent material is thus one which is capable of reversibly binding carbon dioxide and adsorbing said gaseous carbon dioxide in a unit in such a process.

[0032] According to this first aspect, the method for preparing such a sorbent material includes methods for preparing such sorbent materials ab initio, i.e. using starting solid support precursor material which before has not yet been used in corresponding carbon dioxide capture processes. However, it also includes methods where the solid support precursor starting material has already been used in such a carbon dioxide capture process and where the method is used for regenerating corresponding material, i.e. to regenerate, at least to a certain extent, the initial capture capacity. This regeneration can be carried out with used sorbent material as solid support precursor which previously has never been treated in a method as claimed, but it can also be carried out with material as solid support precursor which previously has been treated in a method as claimed, then has been used in a carbon dioxide capture process until reaching a corresponding level of degradation, and then the method is applied again for regenerating (in this case refunctionalizing) and reestablishing the capture capacity of the corresponding solid support precursor.

[0033] The corresponding carbon dioxide capture process, which the sorbent material has undergone prior to being subjected to such a regeneration process is normally a carbon dioxide capture process involving a heat and / or temperature and / or humidity swing and alternating capture and release steps. So, the starting material of the proposed method for regeneration is sorbent material which has been used before as adsorbent for carbon dioxide separation from a gas mixture, but which has been oxidised due to having been used in this context and typically having lost at least 30% of the initial carbon dioxide capture capacity. Such regeneration of sorbent material thus is preferably carried out if the carbon dioxide capture capacity has dropped by more than 30%, preferably by more than 20%, more preferably by more than 15% compared with the carbon dioxide capture capacity of pristine sorbent material, or regeneration of the sorbent material is carried out after having cycled the sequence of adsorption / desorption steps at least 500 times, preferably at least 1000 times, more preferably at least 10,000 times, but preferably before having cycled the sequence of steps 50,000 times, preferably before having cycled the sequence of steps 25,000 times.

[0034] The sorbent material (being the result of the method) comprises: primary amine moieties as well as at least one of secondary amine, and tertiary amine moieties, immobilized on a solid support, preferably it is sorbent material having primary amine functionality as well as secondary amine moieties immobilized on a solid support.

[0035] According to this method in a first step a solid support precursor (which, as pointed out above, can be a pristine material or can be a material already having been used in such a carbon dioxide capture process and where the method is used for regenerating corresponding material) is provided, having at least one of a primary amine and secondary amine functionality, preferably it is one having primary amine functionality.

[0036] Then in a second step, this solid support precursor is reacted with at least one reactant selected from the following group: wherein PG is a protecting group, with the proviso that PG may also be a cyclic group with one branch of the cycle replacing the hydrogen bound to the protected secondary amine moiety of the reactant, X is a leaving group, i is in the range of 1-6 for the left structure and 0-5 for the right structure, in particular 1-3, and includes moieties of the type -CH2- as well as of the type -CH(CH3)- (preferably only one of the type -CH(CH3)- is present).

[0037] Preferably, degrees of post-functionalization between 10-80% are targeted, preferably between 10-30%. Then, in a third step, resulting material from the second step is converted into said sorbent material by removing said protecting group. Notably, the solid support precursor is one which does not comprise any alkyhalide, in particular alkylchloride as pendant groups, or in particular does not comprise any such methylchloride groups, which are available for reaction with the reactant.

[0038] The typical approach for the manufacturing of corresponding sorbent materials and to generate primary amine groups for the sorbent material / solid support precursor is by way of chloromethylation followed by amination (see scheme above). If this is to be modified with attachment of alkyldiamine moieties, the corresponding pathway is used but the stage following the chloromethylation is replaced by amination with alkyldiamine moieties, as illustrated below (and as detailed in GB 1 296 889 )

[0039] So, this conventional approach leads to cross-linking and corresponding decrease in the total amount of primary amine site, which are known to be the most active for CO2 capture from the air. This ultimately leads to a decrease in carbon capture capacity, thus to a less effective sorbent.

[0040] The proposed approach is a longer synthetic route but avoids cross-linking, with the enormous advantage of providing at least one of a higher carbon dioxide capture capacity, faster kinetics and higher stability.

[0041] The approach can be summarized as follows, wherein the upper branch shows the route with protecting groups of the covalent type, and the lower branch shows the route with protecting group of the salt type. The starting material illustrated on the left carries corresponding surface accessible structures of the primary amine type, and the corresponding solid support precursor can be structured / porous polymers, silica, but also class II or class III MOF or the like.

[0042]

[0043] PG: protecting group; H; HX; X: Cl, Br, I

[0044] According to a preferred embodiment of the proposed method, the protecting group is selected from the group consisting of: hydrogenhalogenide (in particular for precursor material having primary amine functionality), including HCI, HBr, HI, phthalimide (in particular for precursor material having primary amine functionality), tert-butyloxycarbonyl, para-toluenesulfone, benzylidene, acetate / acetamide or trifluoroacetate / trifluoroacetamide. Systems of the type t only -CH2-) include systems of the following type: wherein X' is an anion, preferably selected from the group of tosylate, mesylate, or in particular halogens, in particular Cl, I, Br.

[0045] Possible examples are as follows:

[0046] Also possible are systems of the following type (note: Cl’ can be generally replaced by X’ as defined above, and Cl as substituent can be replaced by X, i.e. a leaving group as defined herein): where PG is hydrogenhalogenide, can be provided for the reaction by starting from a system with the primary amine and wherein X= OH, and reacting this with a reagent such as thionyl chloride.

[0047] So for example such a pathway may look as follows:

[0048] The general structure of the reagents can be as follows: wherein X is halogen, in particular Cl, Br, or I, i is 1-6, in particular 1-3, and again includes moieties of the type -CH2- as well as of the type -CH(CH3)- (preferably only one of the type -CH(CH3)- is present).

[0049] Examples are as follows:

[0050] The advantage of using this approach is that the reagent can be provided from well available alkanolamine starting material and can, without further need of purification, directly be used for treatment of the solid support precursor. For example, it is possible to provide, in a solvent, ethanolamine, react it with thionylchloride and then combine the reaction product with the solid support precursor, for example by adding the solid support precursor to a corresponding solution or suspension.

[0051] According to a preferred embodiment of the proposed method, the conversion into said sorbent material takes place by removing said protecting group using an organic base or an inorganic base or combination thereof, wherein preferably organic bases are selected from the group of pyridine, alkylamines, such as triethylamine, imidazole, tetramethylammonium hydroxide and wherein inorganic bases are preferably selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium carbonate, and a combination thereof.

[0052] According to another preferred embodiment of the proposed method, the reaction with the reactant and / or the step of removal of said protecting group is carried out in an organic or an inorganic solvent or a combination thereof, wherein preferably the solvent is selected from the group consisting of water, methanol, ethanol, di-methoxy methane, tetrahydrofurane, dimethylformamide, or a combination thereof, wherein preferably the solvent is water.

[0053] According to a further preferred embodiment of the proposed method, the reactant is added to the solid support precursor in an equivalent ratio of 0.1-10, preferably 0.1 -1.0, relative to the primary / secondary amine of the solid support precursor.

[0054] According to yet another preferred embodiment of the proposed method, the solid support precursor is polystyrene based, preferably a polystyrene based benzyl amine, polystyrene based allylamine, preferably it is an amine functionalized styrene-divinylbenzene support, preferably functionalised by primary benzylamine or primary a-methylbenzylamine, or a styrene allylamine support and / or the solid support precursor is a solid styrene-divinylbenzene support functionalised by primary benzylamine or primary a-methylbenzylamine groups as the result of a reaction of halogenmethylated styrene-divinylbenzene, preferably chloromethylated styrene- divinylbenzene, with hexamethylentetramine or through amidomethylation of styrene- divinylbenzene and subsequent hydrolysis.

[0055] As for styrene allylamine supports, the disclosure of EP 23 212 181.4 is expressly included into this specification as for the manufacturing thereof and the structural characterization and properties.

[0056] According to another preferred embodiment of the proposed method, the reactant has i=1- 4, preferably i=1 -3.

[0057] Preferably, the solid support precursor material, preferably in the form of a primary benzylamine based support material or a styrene allylamine support, is in the form of at least one of monolith, layer or sheet, hollow or solid fibres, preferably in woven or nonwoven structures, hollow or solid particles, or extrudates, wherein preferably it takes the form of preferably essentially spherical beads.

[0058] Preferably, the solid support material, based on primary benzylamine styrene- divinylbenzene support material or a styrene allylamine support, is in the form of at least one of monolith, layer or sheet, hollow or solid fibres, preferably in woven or nonwoven structures, hollow or solid particles, or extrudates, wherein preferably it takes the form of preferably essentially spherical beads.

[0059] The solid support material, preferably in the form of a styrene-divinylbenzene based support material or a styrene allylamine support, can be in the form of solid particles embedded in a porous or non-porous matrix.

[0060] The sorbent material may take the form of preferably essentially spherical beads with a particle size (D50) 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 0.30-1.25 mm.

[0061] According to a preferred embodiment of the proposed method, X of the reactant is selected from the group consisting of halogen, tosylate, mesylate, ester, imide, carbodiimide, pyrazole. According to another aspect of the present invention, it 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, in particular using a temperature, vacuum, or temperature / vacuum swing process, wherein said sorbent material is obtainable or obtained using a method as defined above. The sorbent material is one which comprises: primary amine moieties as well as at least one of secondary amine, and tertiary amine moieties, immobilized on a solid support, preferably it is sorbent material having primary amine functionality as well as secondary amine moieties immobilized on a solid support.

[0062] 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, or, alternatively speaking, to a method of carbon dioxide separation from a gas mixture using such a sorbent material, preferably for separating CO2 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, wherein said sorbent material, wherein the sorbent material comprises: primary amine moieties as well as secondary amine and / or ether moieties immobilized on a solid support.

[0063] Preferably such a method for separating gaseous carbon dioxide is a method or a method is used, which comprises at least the following sequential and in this sequence repeating steps (a) - (e):

[0064] (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 for 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");

[0065] (b) isolating said sorbent material with adsorbed carbon dioxide in said unit from said flow- through, preferably while essentially maintaining the temperature in the sorbenl(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 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;

[0066] (d) extracting at least the desorbed gaseous carbon dioxide from the unit and separating gaseous carbon dioxide, preferably by condensation, in or downstream of the uni

[0067] (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 tl step (e) is in the range of the surrounding ambient atmospheric temperature +25°C, preferably +10°C or +5°C).

[0068] 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. However, also air with lower or higher CO2 concentration can be used as input for the process, e.g. with a concentration of 0.1 -0.5% 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.

[0069] According to a further aspect of the present invention, it relates to a unit for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air, flue gas and biogas, preferably direct air capture unit, comprising at least one reactor unit containing sorbent material suitable and adapted for flow-through of said gas mixture, wherein the reactor unit comprises an inlet for said gas mixture, preferably for ambient air, and an outlet for said gas mixture, preferably for ambient air during adsorption, wherein the reactor unit is heatable to a temperature of at least 60°C for the desorption of at least said gaseous carbon dioxide and the reactor unit being openable to flow-through of the gas mixture, preferably of the ambient atmospheric air, and for contacting it with the sorbent material for an adsorption step, wherein preferably the reactor unit is further evacuable to a vacuum pressure of 400 mbar(abs) or less, wherein the sorbent material preferably takes the form of at least part of an adsorber structure comprising an array of individual adsorber elements, each adsorber element preferably comprising at least one support layer and at least one sorbent material layer comprising or consisting of at least one sorbent material, wherein preferably the adsorber elements in the array are arranged essentially parallel to each other and spaced apart from each other forming parallel fluid passages for flow- through of said gas mixture, preferably of ambient atmospheric air and / or steam, at least one device, preferably a condenser, for separating carbon dioxide from water, wherein preferably at the gas outlet side of said device for separating carbon dioxide from water, preferably said condenser, there is at least one of, preferably both of a carbon dioxide concentration sensor and a gas flow sensor for controlling the desorption process.

[0070] Further embodiments of the invention are laid down in the dependent claims.

[0071] BRIEF DESCRIPTION OF THE DRAWINGS

[0072] 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,

[0073] Fig. 1 shows a schematic representation of a direct air capture unit;

[0074] Fig. 2 shows the increase in carbon dioxide capture capacity through post modification for two different starting benzylamine beads;

[0075] Fig. 3 shows the increase in carbon dioxide capture capacity by way of chloro methylation and amination for different systems;

[0076] Fig.4 compares the increase in carbon dioxide capture capacity by way of chloro methylation and amination to post-functionalization;

[0077] Fig. 5 shows the improvement in kinetics for the materials obtained through post modification for two different solid supports

[0078] Fig. 6 shows the increase in carbon dioxide capture capacity through post modification for benzylamine beads using 2-methylchloropropylamine HCI and 1- methylchloropropylamine HCI;

[0079] Fig. 7 shows the increase in carbon dioxide capture capacity through post modification for allylamine systems;

[0080] Fig. 8 shows the increase in carbon dioxide capture capacity through post modification of a structured sorbent (beads or amine sorbent embedded in a structure);

[0081] Fig. 9 shows the carbon dioxide capture capacity through post modification for regeneration or re-functionalization of beads post degradation.

[0082] DESCRIPTION OF PREFERRED EMBODIMENTS

[0083] Synthesis procedure of primary amine-functionalized styrene-divinylbenzene resin:

[0084] 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 1 h. In another flask, 1 g of benzoyl peroxide is dissolved in a mixture of 54 g of styrene, 10 g of divinylbenzene (content 80%), 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. 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.

[0085] To afford the benzylamine: the chloromethyl-functionalized polystyrene-divinylbenzene beads are aminated using the benzylamine-amination reaction:

[0086] 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.

[0087] Synthesis procedure of diamine-functionalized styrene-divinylbenzene resin, comparative examples:

[0088] To afford the diamine (with cross-linking as side reaction, not according to this invention): the chloromethyl-functionalized polystyrene-divinylbenzene beads are aminated using the direct amination reaction:

[0089] 6 g of chloromethylated beads are added to a three-neck flask with 23 g of methylal and the mixture is stirred for 1 h at 40°C. To this mixture, depending on the final functional group of the amino-based sorbent either of the following amounts of amines are added:

[0090] 12 g of 1 ,2-ethylenediamine; 15 g of 1 ,3-propylenediamine;

[0091] 18 g of 1 ,4-butanediamine;

[0092] 21 g of 1 ,5-pentanediamine;

[0093] 23 g of 1 ,6-hexanediamine.

[0094] The mixture containing chloromethylated beads, methylal and one of the above amine are kept under stirring at 50°C for 12 h. The beads are filtered off and washed with methanol and water. The aminated beads are then dried in the vacuum oven at 60°C for 12h.

[0095] Synthesis procedure of diamine-functionalized styrene-divinylbenzene resin, examples according to the invention:

[0096] Generally, the framework can be defined as follows:

[0097] Examples of amines on sorbent carrier material: polystyrene-based benzylamines; aliphatic amines (e.g. polyallylamines), other functionalities that react favorably with named reagents.

[0098] Examples of solvents that can be used for the synthesis procedure of diamine- functionalized systems: H2O, methanol, ethanol, dimethoxymethane, dimethylformamide, preferably H2O.

[0099] Examples of bases: organic bases such as alkylamines, e.g. triethylamine, pyridine, imidazole, tetramethylammonium hydroxide, ; inorganic bases such as sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium carbonate, and a combination thereof. Equivalents of amine reagent: 0.1 -1.0 compared to e.g. benzylamine styrene- divinylbenzene.

[0100] Example with a phthalimide protected amine-reagent:

[0101] 6 g of benzylamine beads are added to a three-necked flask with 38 g of dimethylformamide (DMF) and the mixture is stirred for 1h at 25°C (room temperature). To this mixture, depending on the final functional group of the amino-based sorbent, are added:

[0102] 10 g of N-(3-Brompropyl)-phthalimide;

[0103] 11g of N-(3-Brombutyl)-phthalimide

[0104] 12g of N-(3-Brompentyl)-phthalimide.

[0105] The mixture containing the benzylamine beads, DMF and of the above phthalimide- protected amines is kept under stirring at 60°C for 18h. The mixture is then cooled to room temperature, the beads are filtered off and washed with methanol and water.

[0106] The beads are then added to an autoclave and 10M aqueous NaOH (20g) is added. The autoclave is heated to 180 °C for 10h. The beads are washed with water, methanol and dried in the vacuum oven at 60°C for 12h. Example with a salt protected amine-reagent (such as bromo- or chloropropyl ammonium bromide / chloride):

[0107] 5 g of benzylamine beads are added to a three-necked flask with 30 g of dimethylformamide (DMF) and the mixture is stirred for 1h at 25°C (room temperature). To this mixture, depending on the final functional group of the amino-based sorbent, are added:

[0108] 8 g 3-Bromopropylamine hydrobromide;

[0109] 5 g 3-Chloropropylamine hydrochloride.

[0110] The mixture containing the benzylamine beads, DMF and of the above amines is kept under stirring at 60°C for 18h. The mixture is then cooled to room temperature, the beads are filtered off and washed with water. The beads are then stirred in a 2M aqueous solution of NaOH for 1 h, washed to neutral with water and methanol and dried in the vacuum oven at 60°C for 12h.

[0111] The calculated conversion from the nitrogen content as measured in the elemental analysis amounts to 13-15% (N content in wit%: 9.8 with Sorbent B as starting materials and 12.4 with Sorbent A as starting material).

[0112] Example of re-functionalization of degraded benzylamine beads with chloropropylamine hydrochloride

[0113] Reaction procedure:

[0114] 28 g of beads and 195g of Water (183 + 11 from the beads) are added to the reactor, the beads are stirred for 20 min.

[0115] 50 g of 30% NaOH are then added to the reactor.

[0116] 107.5 g Chloropropyl ammonium chloride are dissolved in a beaker with 250 g of water for 20 min then they are added to the reactor. Rinse the beaker with 50 g of water.

[0117] Let it react while stirring at 65 °C for 7 h.

[0118] Turn off the heating and syphon reaction mixture (420 g, approx 400 mL), add 400 mL of deionized water, stir for 15 mins, syphon water, repeat wash one more time (400 mL, 15 min stirring).

[0119] Remove the water and then add 400 ml 2M NaOH and stir at room temperature for 1 h, syphon NaOH and wash the beads to neutral pH with DI water (3.5 L).

[0120] Results are given in Fig. 9, showing how the spent material can be recovered in terms of capture capacity.

[0121] Example of the generation of a salt protected amine reagent for subsequent reaction with a benzylamine sorbent (2-chloropropylamine hydrochloride and 1- chloropropylamine hydrochloride):

[0122] 2-chloropropane-1 -amine hydrochloride

[0123] A 1 L round bottom flask is charged with 32 g of amino-2-propanol and 150 mL of dioxane. 150 mL of a solution of 4N HCI in dioxane is added and the mixture is stirred at room temperature for 10 min. 34.5 mL of thionyl chloride is added slowly over 2 min. The reaction is stirred at 80 °C for 18h. The mixture is cooled to room temperature and diluted with 200 mL of Et20. The resulting precipitate is filtered off, washed with 200 mL Et20 and dried under vacuum to give 50 g of 2-chloropropane-1 -amine hydrochloride.

[0124] 1 -chloropropane-2-amine hydrochloride

[0125] A 1 L round bottom flask is charged with 10 g of 2-amino-1 -propanol and 75 mL of dioxane. 75 mL of a solution of 4N HCI in dioxane is added and the mixture is stirred at room temperature for 10 min. 17 mL of thionyl chloride is added slowly over 2 min. The reaction is stirred at 80 °C for 18h. The mixture is cooled to room temperature and diluted with 150 mL of Et20. The resulting precipitate is filtered off, washed with 150 mL Et20 to give 25 g of hygroscopic 1-chloropropane-2-amine hydrochloride, which was used immediately for the next step.

[0126] To afford the divinylbenzene beads:

[0127] Sorbent B was functionalized using the above reagents 2-chloropropane-1 -amine hydrochloride and 1-chloropropane-2-amine hydrochloride to yield post-functionalized material.

[0128] For the 2-chloropropane-1 -amine hydrochloride the reaction pathway is as follows:

[0129] The calculated conversion from the nitrogen content as measured in the elemental analysis amounts to 13-15% (N content in wt%: 10.7).

[0130] For the 1-chloropropane-2-amine hydrochloride the reaction pathway is as follows:

[0131] This is leading to capture capacities as shown in Fig. 6.

[0132] The calculated conversion from the nitrogen content as measured in the elemental analysis amounts to 13-15% (N content in wt%: 10.4).

[0133] Example of the functionalization of a non-benzylamine sorbent, e.g. polyallylamine- Divinylbenzene, with 3-chloropropylamine hydrochloride:

[0134] Synthesis procedure of acrylonitrile-divinylbenzene resin:

[0135] In a 1 L reactor, 300 g of ion-exchanged water, 0.2 g of hydroxyethylcellulose, 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). Separately, 70 g of acrylonitrile, 30 g of divinylbenzene, 100 g of toluene, and 1 g of azobisisobutyronitrile 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 65°C. After the reaction solution reached 65°C, the reaction was continued for 18 hours.

[0136] 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. 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. The desired polymer particles were then dried under reduced pressure at 75°C and 200 torr for 1 hour. The average particle diameter was 330 micrometers, the pore size determined by the mercury injection method was 75 nanometers, and the specific surface area determined by the BET method was 62 m2 / g.

[0137] The beads are dried in rotavapor. The acrylonitrile-divinylbenzene beads are then reacted with a reducing agent to obtain the allylamine-divinylbenzene beads.

[0138] To afford the allylamine-divinylbenzene beads:

[0139] 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 (1 M, 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.

[0140] 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.

[0141] Post-functionalization of polyallylamine-divinylbenzene beads:

[0142] The reaction scheme here is as follows:

[0143] Sodium hydroxide in water (14g, 30wt% aqueous NaOH) is added to a three-necked flask. Subsequently, polyallylamine-divinylbenzene beads are added (5.5g), followed by 3- chloropropylamine hydrochloride (10g, 1.1 eq) pre-dissolved in 10mL of water. Upon complete dissolution, the internal temperature of the flask is adjusted to 65°C for 6h.

[0144] Afterwards, 2x 400mL of water is added and filtered off each time. 400 mL 2M sodium hydroxide solution is added to the flask and the mixture is stirred for 1 h at room temperature. The reaction solution is syphoned out and the wash procedure with deionized water is repeated until the wash water has a pH below 8.

[0145] Results are given in Fig. 7, showing how the allylamine sorbent material can be boosted in terms of capture capacity.

[0146] Procedure of benzylamine sorbents embedded in a structure / sheet:

[0147] The sheets can be produced from a mixture of 50 wt% (wet, -85% solid content) ion exchange resin (I ER) powder at a mean particle size of 75 microns (D50, volume based) and 50 wt% ultra-high-molecular-weight polyethylene (UHMWPE, molecular weight 4.2 million g / mol) at a mean particle size of 30 microns (D50). The two powders are mixed using a 3D rotational mixer for 15 minutes. Approximately 8 g of powder mixture are filled in an aluminum mold with a cross section of 10x20 mm. The mold is closed and placed in an oven previously pre-heated to 220°C. No pressure is applied. The mold is positioned on small metallic supports to facilitate heating on both sides and kept in the oven at temperature for 40 min. Afterwards, the mold is removed from the oven and left to cool in ambient air to reach room temperature before being opened. Upon opening, a sheet matching the mold inner dimensions is obtained. The sheet density is typically 450-500 kg / m3.

[0148] Example of the functionalization of a benzylamine sorbent embedded in a structure / sheet:

[0149] 165 ml of Water are added to the reactor followed by 35.8 g chloropropyl ammonium chloride and stirred for 20 min until dissolution.

[0150] 50 g of 30% NaOH are then added to the reactor. Afterwards sheets are added to the reactor and the reaction is heated up to 65 °C while stirring. Let it react at this temperature for 7 h. Remove the sheets, wash them in 1.5 L of deionized water and let them stir for 30 mins.

[0151] After this suspend the sheet in 100 ml of 2M NaOH for 1 hour and then wash until neutral by adding them to a 2 L beaker with deionized water.

[0152] Air dry for 16 hours.

[0153] Results are given in Fig. 8, showing how the structured sorbent material can be boosted in terms of capture capacity and also how it can be regenerated using the method.

[0154] Generation of haloalkylamine hydrohalide (e.g. 3-chloropropylamine hydrochloride) from alcoholamines:

[0155] To a solution of thionyl chloride (17.36 g) in chloroform (60 mL) 3-aminopropan-1-ol (8.98 g) is added dropwise, while keeping the temperature between 0-10 °C. The mixture is then allowed to warm to room temperature and then slowly heated to 45 °C. Stir at 45 °C for 3 h.

[0156] Allow to cool down to room temperature, the intermediate is then taken up in H2O (60 ml), the Chloroform discharged, and the aqueous solution is then again washed with chloroform (60ml).

[0157] 10g beads and 6g of NaOH pellets are added to the extract from the step before. The reaction mixture is then heated to 65°C and let react while stirring for 7 h.

[0158] Turn off the heating and syphon reaction mixture (42 g, approx 40 mL), add 40 mL of deionized water, stir for 15 mins, syphon water, repeat wash one more time (40 mL, 15 min stirring).

[0159] Remove the water and then add 40 ml of a 2M NaOH solution. Stir at room temperature for 1 h, syphon NaOH.

[0160] NaOH and wash the beads to neutral pH with DI water (2.5 L). Carbon dioxide capture capacity properties:

[0161] 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.

[0162] Exchange capacity determination:

[0163] To measure exchange capacity around 2g of wet material is added to a beaker with 50mL of 1M NaOH solution and stirred at room temperature for 40min. The solution is then filtered on a Buchner funnel with a filter mesh size of 40pm, 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 100mL of 0.1 M HCI solution is added to the flask. The flask is closed and left in the oven at 70°C for 1 h. The solid content of the remaining half is determined following the method below.

[0164] The flask is then removed from the oven and let cool down to room temperature. 25mL of the supernatant are titrated with 0.1M NaOH solution (to inflection point, with an SI Analytics Titrator TitroLine 5000). The exchange capacity is calculated through the following equation:

[0165] (25mL — mL NaOHused) * 0.4

[0166] Exchange capacity[meq / g}=Wet Mass*Solid Content

[0167] Solid Content:

[0168] 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 (0.002g / 15s).

[0169] Nitrogen content measurements:

[0170] 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.

[0171] Method for the specific surface area measurements:

[0172] 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 at40°C for 24 hours. After that, the sample was degassed at 70 °C under vacuum for twelve hours before measurement.

[0173] BET (Brunauer, Emmett und Teller) surface area analysis was used applying the method ISO 9277.

[0174] Mercury Porosimetry Measurements:

[0175] 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:

[0176] • Mercury surface tension: 0.48 N / m

[0177] • Mercury contact angle: 150°

[0178] • Max. pressure: 400 MPa

[0179] • Increase speed: 6-19 MPa / min

[0180] Prior to Hg porosimetry, the samples were degassed under vacuum at 70°C for 12 h.

[0181] Calculation of the degree of post-functionalization (conversion):

[0182] The degree of post-functionalization is calculated as the relative number of e.g propylamine monomers per benzylamine or allylamine monomers.

[0183] Formula: degree of postfunctionalization wherein [%N] is the nitrogen content in percent weight as determined by elemental analysis, x is the fraction of monomer B in the polymer (e.g. 10% DVB content, x = 0.1), MWmonomer A is the molecular weight in g / mol of the unfunctionalized monomer A (e.g. styrene, MWstyrene = 104.15 g / mol), MWmonomer B is the molecular weight in g / mol of the crosslinking monomer (e.g. divinyl benzene (DVB), MWDVB = 130.19 g / mol), MWN is the molecular weight in g / mol of nitrogen (MWN = 14.01 g / mol) and M ™efunctionalization is the molecular weight in g / mol of the post-functionalization element carrying the amine (e.g. methylamine, MWmethyiamine = 29.04 g / mol).

[0184] Fig. 2 shows the increase in carbon dioxide capture capacity through post modification for two different starting benzylamine beads, given relative to 100% benzyl amine as a reference. Data is given for two different basic primary aminated DVB systems designated as Sorbent A, and B, one chloromethylated DVB system designated as Sorbent C in the following table:

[0185] As one can see from that Fig. 2, there is an unexpected and significant increase of the equilibrium carbon dioxide capture capacity associated with single alkylamine substitution using the post-modification approach by 25-50%. In fact, the equilibrium carbon dioxide capture capacity increases as a function of the number of carbon atoms in the alkyl chain, reaching a maximum for 4 or 5 carbon atoms, and then decreases again. Surprisingly there is a maximum for propylenediamine and butylenediamine form most systems, where the increase is almost 50% compared with unsubstituted benzylamine.

[0186] Fig. 3 shows the corresponding carbon dioxide capture capacity situation for the case where the material is produced not using post-modification according to this invention but using the conventional approach of chloromethylation and subsequent amination. In this case the relative increase is only in the range of 5-30%, so it is significantly lower than when using the proposed post-modification approach.

[0187] Without being bound to any theoretical explanation, but this is expected to be due to the fact that the post-modification approach using protecting groups avoids cross-linking situations and therefore makes available the amine capture moieties in an optimum way.

[0188] Fig. 4 gives a direct comparison of the carbon dioxide capture capacity situation of Sorbent C, obtained through chloromethylation and amination, with the Sorbent A and B obtained through post-functionalization. Clearly, Sorbent A and B show superior carbon dioxide capture capacity compared to Sorbent C, which - without being bound to any theoretical explanation - is expected to be due to the higher availability of primary amines.

[0189] Fig. 5 shows the improvement in kinetics for the post modified systems, the capacity increase is 45-50%. Also, it was found that the corresponding material is able to go through a larger number of capture cycles without deterioration than the benzyl amine systems.

[0190] Also, it was found that the exchange capacity in water only increases by 15% maximum, which corresponds well to the calculated conversion of the post-functionalization.

[0191] LIST OF REFERENCE SIGNS

[0192] 1 ambient air, ambient air 4 steam, steam inflow structure inflow structure for desorption

[0193] 2 outflow of ambient air behind 5 reactor outlet for extraction adsorption unit in adsorption 6 vacuum unit / separator flow-through mode 7 wall

[0194] 3 sorbent material 8 reactor unit

Claims

CLAIMS1. A method for preparing a sorbent material (3) 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 a sorbent material (3) capable of reversibly binding carbon dioxide and adsorbing said gaseous carbon dioxide in a unit (8), wherein the sorbent material (3) comprises: primary amine moieties as well as at least one of secondary amine, and tertiary amine moieties, immobilized on a solid support, wherein a solid support precursor is provided, having at least one of a primary amine, and secondary amine functionality, and wherein this solid support precursor is reacted with at least one reactant selected from the following group:wherein PG is a protecting group, with the proviso that PG may also be a cyclic group with one branch of the cycle replacing the hydrogen bound to the protected secondary amine moiety of the reactant,X is a leaving group, i is in the range of 1-6 for structure (I) and in the range of 0-5 for structure (II), and in both cases includes substituted or unsubstituted moieties selected from the group consisting of: -CH2- , -CH(CH3)-, and wherein the resulting material is converted into said sorbent material (3) by removing said protecting group.

2. Method according to claim 1 , wherein the protecting group is selected from the group consisting of: hydrogenhalogenide, including HCI, HBr, HI, phthalimide, pyrazole, including pyrazole hydrochloride, tert-butyloxycarbonyl, para-toluenesulfone, benzylidene, acetate / acetamide or trifluoroacetate / trifluoroacetamide, wherein preferably for systems of the type (I), in which the protecting group is selected as hydrogenhalogenide, including HCI, HBr, HI, the reactant is provided for the reaction by starting from a respective alkanolamine and reacting this with a organohalogenating reagent, including thionylchloride, and subsequently contacting this with said solid support precursor.

3. Method according to any of the preceding claims, wherein the conversion into said sorbent material (3) takes place by removing said protecting group using an organic base or an inorganic base or combination thereof, wherein preferably organic bases are selected from the group of alkylamines, including triethylamine, pyridine, imidazole, tetramethylammonium hydroxide and wherein inorganic bases are preferably selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium carbonate, and a combination thereof.

4. Method according to any of the preceding claims, wherein the reaction with the reactant and / or the step of removal of said protecting group is carried out in an organic or an inorganic solvent or a combination thereof, wherein preferably the solvent is selected from the group consisting of water, methanol, tetrahydrofurane, ethanol, di-methoxy methane, dimethylformamide, or a combination thereof, wherein preferably the solvent is water.

5. Method according to any of the preceding claims, wherein the reactant is added to the solid support precursor in an equivalent ratio of 0.1-10, preferably 0.1 -1.0, relative to the primary / secondary amine content of the solid support precursor.

6. Method according to any of the preceding claims, wherein the solid support precursor is at least one of a structured and / or porous polymer, silica, class II or class III MOF, in particular the solid support precursor is polystyrene based, preferably a polystyrene based benzyl amine, preferably it is an amine functionalized styrene-divinylbenzene support, preferably functionalised by primary benzylamine or primary a-methylbenzylamine, or a styrene allylamine solid support precursor and / or wherein the solid support precursor is a solid styrene-divinylbenzenesupport functionalised by primary benzylamine or primary a-methylbenzylamine groups, preferably as the result of a reaction of halogenmethylated styrene-divinylbenzene, preferably chloromethylated styrene-divinylbenzene, with hexamethylenetetramine or, alternatively or through amidomethylation of styrene-divinylbenzene and subsequent hydrolysis, or a styrene allylamine solid support precursor and / or wherein the method is a method of regeneration and wherein the solid support precursor is a solid support capable of reversibly binding carbon dioxide and adsorbing said gaseous carbon dioxide in a unit, which has been used 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, wherein preferably such regeneration is carried out if the carbon dioxide capture capacity has dropped by more than 30%, preferably by more than 20%, more preferably by more than 15% compared with the carbon dioxide capture capacity of pristine sorbent material, or regeneration of the sorbent material is carried out after having cycled the sequence of adsorption / desorption steps at least 500 times, preferably at least 1000 times, more preferably at least 10,000 times, but preferably before having cycled the sequence of steps 50,000 times, preferably before having cycled the sequence of steps 25,000 times.

7. Method according to any of the preceding claims, wherein the reactant has i= 1 -5, preferably i= 1 -4 or i= 1 -3 for structure (I) and i= 1 -4, preferably i= 1 -3 for structure (II).

8. Method according to any of the preceding claims, wherein the solid support material, preferably in the form of a styrene-divinylbenzene based support material or a styrene allylamine support material, is in the form of at least one of monolith, layer or sheet, hollow or solid fibres, preferably in woven or nonwoven structures, hollow or solid particles, or extrudates, wherein preferably it takes the form of preferably essentially spherical beads,9. Method according to any of the preceding claims, wherein the solid support material, preferably in the form of a styrene-divinylbenzene based support material or a styrene allylamine support material, is in the form of solid particles embedded in a porous or non-porous matrix.

10. Method according to any of the preceding claims, wherein the sorbent material takes the form of preferably essentially spherical beads with a particle size (D50) 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 .5mm, preferably in the range of 0.30-1.25 mm.

11. Method according to any of the preceding claims, wherein X of the reactant is selected from the group consisting of halogen, tosylate, mesylate, ester, imide, carbodiimide, pyrazole.

12. 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 obtainable or obtained using a method according to any of the preceding claims.

13. Use of a sorbent material (3) according to claim 12 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), wherein the sorbent material (3) comprises: primary amine moieties as well as at least one of secondary amine, and tertiary amine moieties immobilized on a solid support.

14. Use according to claim 13, wherein for separating gaseous carbon dioxide a method is used, which comprises at least the following sequential and in this sequence repeating steps (a) - (e):(a) contacting said gas mixture (1) with the sorbent material (3) to allow at least said gaseous carbon dioxide to adsorb on the sorbent material (3) by flow-through through said unit (8) essentially under ambient atmospheric pressure conditions and ambient atmospheric temperature conditions in an adsorption step;(b) isolating said sorbent material (3) with adsorbed carbon dioxide in said unit (8) from said flow-through;(c) inducing an increase of the temperature of the sorbent material (3) to a temperature starting the desorption of carbon dioxide;(d) extracting at least the desorbed gaseous carbon dioxide from the unit (8) and separating gaseous carbon dioxide in or downstream of the unit (8);(e) bringing the sorbent material (3) essentially to ambient atmospheric temperature conditions and ambient atmospheric pressure conditions.

15. Unit for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air (1), flue gas and biogas, preferably direct air capture unit, comprising at least one reactor unit (8) containing sorbent material (3) according to claim 12 in a form suitable and adapted for flow-through of said gas mixture (1), wherein the reactor unit comprises an inlet for said gas mixture, preferably for ambient air (1), and an outlet (2) for said gas mixture, preferably for ambient air during adsorption, wherein the reactor unit is heatable to a temperature of at least 60°C for the desorption of at least said gaseous carbon dioxide and the reactor unit being openable to flow-through of the gas mixture, preferably of the ambient atmospheric air, and for contacting it with the sorbent material for an adsorption step, wherein preferably the reactor unit is further evacuable to a vacuum pressure of 400 mbar(abs) or less, wherein the sorbent material (3) preferably takes the form of at least part of an adsorber structure comprising an array of individual adsorber elements, each adsorber element preferably comprising at least one support layer and at least one sorbent material layer comprising or consisting of at least one sorbent material, wherein preferably the adsorber elements in the array are arranged essentially parallel to each other and spaced apart from each other forming parallel fluid passages for flow-through of said gas mixture, preferably of ambient atmospheric air and / or steam, at least one device, preferably a condenser, for separating carbon dioxide from water, wherein preferably at the gas outlet side of said device for separating carbon dioxide from water, preferably said condenser, there is at least one of, preferably both of a carbon dioxide concentration sensor and a gas flow sensor for controlling the desorption process.

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