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

Abstract

Method 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) adsorbing said gaseous carbon dioxide in a unit (8), wherein as sorbent material a packed bed or layer is used, which consists of a mixture of 75 – 98 wt.-% of first particles of support material functionalised with primary and / or secondary amines, or a combination thereof, capable of reversibly binding carbon dioxide, and 2 - 25 wt.-% of second particles of activated carbon material, the weight percent of the first and second particles adding up to 100% of the mixture in the packed bed or layer.

Description

[0001] TITLE

[0002] SORBENT MATERIAL 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 optimum carbon dioxide capture capacity 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 3x109 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 has envisioned 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 ppmv. 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 emission from the past. 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 really permanent removal) using natural photosynthesis, and by means of DAC technologies, which is the only really 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 a mix of such 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 functionalization and polymers, such as immobilized aminosilane-based sorbents as reported in US-B-8,834,822, and amine-functionalized 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] The state-of-the-art technology to capture CO2 from point sources typically uses liquid amines, as for example in industrial scrubbers, where the flue gas flows into a solution of an amine (US-B-9, 186,617). Other technologies are based on the use of solid sorbents in either a pack-bed or a flow-through structure configuration, where the sorbent is made of impregnated or covalently bound amines onto a support.

[0013] WO-A-2022013197 discloses a method for separating gaseous carbon dioxide from a gas mixture, e.g. 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 (8); (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).

[0014] SUMMARY OF THE INVENTION

[0015] It is an object of the present invention to provide for an improved sorbent material for carbon dioxide capture, in particular one which is particularly stable and withstands deterioration, and which has a high carbon dioxide capture capacity over time also under conditions and over large variations in process conditions in terms of temperature and relative humidity.

[0016] According to a first aspect of the invention, it is a method 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 adsorbing said gaseous carbon dioxide in a unit.

[0017] The method comprises at least the following sequential and in this sequence repeating steps (a) - (e):

[0018] (a) contacting said gas mixture with the sorbent material to allow at least said gaseous carbon dioxide to adsorb on the sorbent material by flow-through through said unit essentially under ambient atmospheric pressure conditions and ambient atmospheric temperature conditions in an adsorption step;

[0019] (b) isolating said sorbent material with adsorbed carbon dioxide in said unit (8) from said flow-through;

[0020] (c) inducing an increase of the temperature of the sorbent material, preferably to a temperature between 60 and 110°C, starting the desorption of carbon dioxide;

[0021] (d) extracting at least the desorbed gaseous carbon dioxide from the unit and separating gaseous carbon dioxide in or downstream of the unit;

[0022] (e) bringing the sorbent material essentially to ambient atmospheric temperature conditions and ambient atmospheric pressure conditions.

[0023] According to the invention, said sorbent material consists of a packed bed, monolith or layer structure comprising or consisting of a mixture of

[0024] 75 - 98 wt.-% of first particles of support material functionalised with primary and / or secondary amines, or a combination thereof, capable of reversibly binding carbon dioxide, and 2 - 25 wt.-% of second particles of activated carbon material, the weight percent of the first and second particles adding up to 100% of the mixture in the sorbent material.

[0025] It is noted that in case the sorbent material takes the form of a layer or a monolith, there may be, in addition to the primary and secondary particles, additional binder particles or binder material to provide for coherence between the first and second particles. Such additional binder particles or binder material however being present in a proportion of less than 5 parts by weight, or even less than 3 parts by weight, in each case relative to 100 parts of the total of the primary and secondary particles.

[0026] The proposed sorbent material increases the stability of amino sorbent in humidified 02- containing atmosphere, solving the long-standing stability issue with amino sorbent in particular for (direct air capture) DAC applications.

[0027] Unexpectedly, a physical mixture of amino sorbent such as amine-functionalized ion exchange resin (I ER) and activated carbon reduces amine degradation under thermal- oxidative conditions. It is surprising that carbon has such a positive effect solely by physically mixing it with amino sorbent.

[0028] Various types of carbon materials are possible, e.g. graphene, fullerene, carbon nanosheets, nanoparticles, nanotube and other forms, heteroatoms doped carbon materials Various ways to prepare the amine functionalized polymers-carbon composite are possible e.g. impregnation, grafting, in-situ polymerization in the presence of carbon, coating Various types of amine-based sorbents are possible, e.g. different amine-functionalized materials, molecular amines, amino polymers.

[0029] According to the invention, the method 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 such a sorbent material adsorbing said gaseous carbon dioxide in a unit, preferably comprises at least the following sequential and in this sequence repeating steps (a) - (e):

[0030] (a) contacting said gas mixture with the sorbent material to allow at least said gaseous carbon dioxide to adsorb on the sorbent material by flow-through through said unit under ambient atmospheric pressure conditions and ambient atmospheric temperature conditions in an adsorption step (if ambient atmospheric air is pushed 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 through the reactor by the ventilator has a pressure slightly above the surrounding ambient atmospheric pressure, and the pressures to is in the ranges as detailed above in the definition of "ambient atmospheric pressures") ; (b) isolating said sorbent material with adsorbed carbon dioxide in said unit from said flow- through, preferably while maintaining the temperature in the sorbent;

[0031] (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 heat exchangers or by injecting a stream of saturated or superheated steam by flow-through through the unit 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);

[0032] (d) extracting at least the desorbed gaseous carbon dioxide from the unit and preferably separating gaseous carbon dioxide from steam, preferably by condensation, in or downstream of the unit;

[0033] (e) bringing the sorbent material to ambient atmospheric temperature 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). According to the invention, the primary particle sorbent material comprises primary and / or secondary amine moieties immobilized on a solid support.

[0034] 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. However, also flue gas can be the source, in this case the input CO2 concentration of the input gas mixture is typically in the range of up to 20% or up to 12% by volume, preferably in the range of 1-20% or 1 - 12% by volume.

[0035] In the above carbon dioxide capture method step sequence (a)-(e), in steps (a) and (e) reference is made to ambient atmospheric pressure conditions and ambient atmospheric temperature conditions. This only applies if the supplied gas mixture is provided under these conditions, for example in case of direct air capture, where the source of the gas mixture is atmospheric air. If, however the source of gas mixture is a different source, it may well be that the supply conditions are not ambient atmospheric pressure and / or are not ambient atmospheric temperature conditions. In particular, in case of flue gas the gas mixture can be and normally will be at an elevated temperature, for example at a temperature above room temperature, it may even be at a temperature above 50°C. The temperature may even go up to 70°C, and in that case normally the setup is adapted such that the temperature to desorb the carbon dioxide in step (c) is at least 10°C, preferably at least 20°C higher than that temperature of the supply gas. So, under these non-atmospheric temperature and pressure conditions in step (a) and in step (e) normally the pressure and temperature conditions are different, specifically contacting in step (a) takes place under temperature and pressure conditions of the supplied gas mixture, and in step (e) the sorbent is brought to the temperature and pressure conditions of the supplied gas mixture.

[0036] Said unit is preferably evacuable to a vacuum pressure of 400 mbar(abs) or less, and step (b) may include isolating said sorbent with adsorbed carbon dioxide in said unit from said flow-through while maintaining the temperature in the sorbent and then evacuating said unit to a pressure in the range of 20-400 mbar(abs), wherein in step (c) injecting a stream of saturated or superheated steam is also inducing an increase in internal pressure of the reactor unit, and wherein step (e) includes bringing the sorbent material to ambient atmospheric pressure conditions and ambient atmospheric temperature conditions. Preferably, after step (d) and before step (e) the following step is carried out:

[0037] (d1) ceasing the injection and, if used, circulation of steam, and evacuation of the unit to pressure values between 20 - 500 mbar(abs), preferably in the range of 50-250 mbar(abs) in the unit, thereby causing evaporation of water from the sorbent and both drying and cooling the sorbent.

[0038] Step (e) is preferably carried out exclusively by contacting said ambient atmospheric air with the sorbent material under ambient atmospheric pressure conditions and ambient atmospheric temperature conditions to evaporate and carry away water in the unit and to bring the sorbent material to ambient atmospheric temperature conditions.

[0039] After step (b) and before step (c) the following step can be carried out:

[0040] (b1) flushing the unit of non-condensable gases by a stream of non-condensable steam while essentially holding the pressure of step (b), preferably holding the pressure of step (b) in a window of ± 50 mbar, preferably in a window of ± 20 mbar and / or holding the temperature below 75°C or 70°C or below 60°C, preferably below 50°C.

[0041] In a further embodiment of the step b1 , the temperature of the adsorber structure rises from the conditions of step (a) to 80-110°C preferably in the range of 95-105°C.

[0042] In step (b1) the unit can preferably be flushed with saturated steam or steam overheated by at most 20°C in a ratio of 1 kg / h to 10 kg / h of steam per liter volume of the adsorber structure, while remaining at the pressure of step (b1), to purge the reactor of remaining gas mixture / ambient air. The purpose of removing this portion of ambient air is to improve the purity of the captured CO2.

[0043] In step (c), steam can be injected in the form of steam introduced by way of a corresponding inlet of said unit, and steam can be (partly or completely) recirculated from an outlet of said unit to said inlet, preferably involving reheating of recirculated steam, or by the re-use of steam from a different reactor.

[0044] It should be noted that heating for desorption according to this process in step (c) is preferably only affected by this steam injection and there is no additional external or internal heating e.g. by way of tubing with a heat fluid.

[0045] In step (c) furthermore preferably the sorbent can be heated to a temperature in the range of 80-110°C or 80-100°C, preferably to a temperature in the range of 85-98°C.

[0046] According to yet another preferred embodiment, in step (c) the pressure in the unit is in the range of 700-950 mbar(abs), preferably in the range of 750-900 mbar(abs).

[0047] According to a first preferred embodiment of this first aspect of the invention, the sorbent material consists of a mixture of 85-96 wt.-%, preferably 88-95 wt.-% of first particles, and 4-14 wt.-%, preferably 5-12 wt.-% of second particles, the weight percent of the first and second particles adding up to 100% of the mixture in the sorbent material.

[0048] The support material of the first particles can be an organic cross linked polymeric polystyrene based support material, in case of the first particles functionalised on the surface and / or in the bulk with primary or secondary amines, or a combination thereof, wherein preferably the support material is based on polymeric polystyrene cross-linked by divinylbenzene, wherein further preferably the polystyrene based support material is a styrene divinylbenzene copolymer, preferably in case of said first particles to form the sorbent material surface and / or in the bulk functionalised with primary amine, preferably methyl amine, most preferably benzylamine moieties, wherein the solid polymeric support material is preferably obtained in a suspension polymerisation process.

[0049] The material of the first particles can comprise primary amine moieties as well as in addition at least one of secondary amine moieties and tertiary amine moieties immobilized on a solid styrene-divinylbenzene support, wherein said solid styrene-divinylbenzene support is functionalised by at least one of secondary benzylamine groups, tertiary benzylamine groups, secondary a-methylbenzylamine groups, and tertiary a-methylbenzylamine groups, wherein in each case the secondary or tertiary amine groups are substituted with at least one of ethyleneamine, branched or linear polyethyleneimine, branched or linear propyleneamine, branched or linear polypropyleneimine, branched or linear polyethylenepropyleneimine, branched or linear butyleneamine, branched or linear pentanamine, branched or linear hexyleneamine.

[0050] The material of the first particles can comprise primary amine moieties as well as at least one of secondary amine, and / or ether, amide, and amidine moieties, immobilized on a solid support, wherein they are obtained in that a solid support precursor is provided, having at least one of a primary amine, secondary amine, and alcohol 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 0-5, and wherein the resulting material is converted into said sorbent material by removing said protecting group.

[0051] The first particles can be 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%.

[0052] According to yet another preferred embodiment, the second particles have a particle size (D50) in the range of 0.2-4 mm, preferably in the range of 0.5-3 mm.

[0053] Preferably, the second particles are based on organic renewable starting material, including wood, shell material preferably wood bark, coconut shells or on styrene-divinylbenzene copolymer based beads.

[0054] Preferably, the second particles have a bulk density in the range of 400-600 g / l and / or an ash content of 2-5%.

[0055] Preferably, the second particles have an iodine number above 0.5 mg / g, preferably in the range of 0.7-1.5 mg / g.

[0056] Step c) may involve injecting a stream of partially of fully saturated or superheated steam (4), preferably by flow-through through said unit for heating the sorbent.

[0057] The contacting of the sorbent with said gas mixture in step (a) may take place by flow over and / or by flow through. The mean particle size (D50) of the first and / or second particles is preferably in the range of 0.002 - 4 mm, preferably 0.01-1.5 mm, most preferably in the range of 0.30-1.25 mm.

[0058] The first particles of support material functionalised on the surface and / or in the bulk with primary or secondary amines, or a combination thereof, capable of reversibly binding carbon dioxide typically have a nitrogen content in the range 4-50 wt.%, preferably in the range of 5 - 25 wt.% or 5 - 15 wt.% or 6 - 12 wt.%, in each case for dry sorbent material. The gas mixture is preferably ambient atmospheric air, so it is a DAC process.

[0059] Said mixture of the sorbent material can be in the form of at least one, normally essentially continuous coherent, layer in a monolith or in (layered) containers having air permeable side walls in the form of grids, having a mesh width which is smaller than the average particle size or smaller than the particle size of the 10% smallest particles in the mixture (D10) so that the particles of the mixture are retained in the corresponding containers.

[0060] According to a second aspect of the present invention, it relates to a sorbent material. That sorbent material preferably takes the form of a layer, monolith or packed bed, 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, preferably for use in a method according to any of the preceding claims. The sorbent material consists of a mixture of 75 - 98 wt.-% of first particles of support material functionalised with primary and / or secondary amines, or a combination thereof, capable of reversibly binding carbon dioxide, and 2 - 25 wt.-% of second particles of activated carbon material, the weight percent of the first and second particles adding up to 100% of the mixture in the sorbent material.

[0061] According to yet another aspect, the present invention relates to the use of such a sorbent material for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air, flue gas and biogas, containing said gaseous carbon dioxide as well as further gases different from gaseous carbon dioxide, by cyclic adsorption / desorption.

[0062] According to further aspect of the present invention, it relates to a method for making such a sorbent material. According to this method, first particles and second particles are provided, and the first and second particles are mixed and packed to form the monolith or layer, preferably by generating a coherent layer or monolith structure, or to form a packed bed by inserting the mixture into a container having air permeable side walls, preferably in the form of grids having a mesh width suitable and adapted to retain the mixture in the container.

[0063] Further embodiments of the invention are laid down in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] 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,

[0065] Fig. 1 shows a schematic representation of a direct air capture unit;

[0066] Fig. 2 shows the CO2 capacity normalized to the initial capacity before degradation for different mixtures;

[0067] Fig. 3 shows the relationship between the retained capacities at normalized time = 0.5 and the loading of activated carbon.

[0068] DESCRIPTION OF PREFERRED EMBODIMENTS

[0069] In the following working examples, cross-linked polystyrene beads (essentially spherical beads with a particle size (D50) in the range of 0.30-1.2 mm) functionalized with benzylamine units were used.

[0070] Synthesis procedure of styrene-divinylbenzene resin particles functionalized with benzylamine units (Sorbent A)

[0071] 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.

[0072] 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.

[0073] To afford the benzylamine: the chloromethyl-functionalized polystyrene-divinylbenzene beads are aminated using the benzylamine-amination reaction:

[0074] 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.

[0075] The resultant particles had an average particle size of 500 urn and an average pore diameter in the range of 50-300nm. Surface area is 19 m2 / g, pore volume is 0.55 cm3 / g, N content is 9.0 wt.%.

[0076] The resulting is sorbent called Sorbent A.

[0077] Sample preparation

[0078] For the activated carbon particles, granular or pelletized systems having a particle size (D50) in the range of 0.2-4 mm, preferably in the range of 0.5-3 mm can be used.

[0079] Possible are systems which are based on organic renewable starting material, for example wood, shell material for example wood bark, coconut shells etc.

[0080] The activated carbon material typically has a bulk density in the range of 400-600 g / l and an ash content of 2-5%. The iodine number is typically above 0.5 mg / g, preferably in the range of 0.7-1.5 mg / g.

[0081] Possible are for example the following commercially available systems:

[0082] Granular activated carbon, mesh size 20 - 40 (0.841 - 0.420 mm) CAS no.: 7440-44-0, Sigma Aldrich, DARCO®;

[0083] Granular activated carbon mesh size 4 - 12 (4.76 - 1.68 mm), CAS no.: 7440-44-0, Sigma Aldrich, DARCO®;

[0084] Extruded activated carbon 3 mm, CAS no.: 7440-44-0, Cabotcorp, Norit®.

[0085] Microporous activated carbon adsorbers in the form of essentially spherical beads based on styrene-divinylbenzene copolymers, size: 0.4-0.8 mm (>90 vol%).

[0086] Example 1: 5 g of the activated carbon material (AC; with a particle size 0.5 - 1.5 mm, D50) was added to 50 g (dried weight) of Sorbent A in a beaker. The materials were mixed with a spatula for 30 seconds.

[0087] Example 2: 12.5 g of activated carbon material (AC; with a particle size 0.5 - 1.5 mm, D50) was added to 50 g (dried weight) of Sorbent A in a beaker. The materials were mixed with a spatula for 30 seconds.

[0088] Example 3: 1.5 g of activated carbon material (AC; with a particle size 0.5 - 1.5 mm, D50) was added to 50 g (dried weight) of Sorbent A in a beaker. The materials were mixed with a spatula for 30 seconds.

[0089] Analytical Methods and Test Methods

[0090] Specific surface area measurements: 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.

[0091] BET (Brunauer, Emmett und Teller) surface area analysis was used applying the method ISO 9277.

[0092] 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:

[0093] • Mercury surface tension: 0.48 N / m

[0094] • Mercury contact angle: 150°

[0095] • Max. pressure: 400 MPa

[0096] • Increase speed: 6-19 MPa / min

[0097] 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.

[0098] 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).

[0099] Nitrogen content measurements: 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.

[0100] Cyclic adsorption performance. The packed beds according to the examples below were tested in an experimental rig. The rig is schematically illustrated in Fig. 1. There is an ambient air inflow structure 1. The actual reactor unit 8 comprises a container or wall 7 within which the packed bed forming the sorbent material 3 described above is located. There is an inflow structure 4 for desorption, where steam and / or heat are used for desorption, and there is a reactor outlet 5 for extraction. Further, there is a vacuum unit 6 for optional evacuating the reactor. Such experimental rig was used for characterising the cyclic adsorption performance.

[0101] CO2 capacity measurement: 6 g of dry sample was filled into a cylinder with an inner diameter of 40 mm and a height of 40 mm and placed into a CO2 adsorption / desorption device, where it was exposed to a flow of 2.0 NL / min of air at 30°C containing 450 ppmv CO2, having a relative humidity of 60% corresponding to a temperature of 30°C for a duration of 600 min. Prior to adsorption, the sorbent bed was desorbed by heating the sorbent to 94°C under an N2 flow of 2.0 NL / min. The amount of CO2 adsorbed on the sorbent was determined by integrating the signal of an infrared sensor which measures the CO2 content of the air stream leaving the reactor.

[0102] 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).

[0103] Degradation test: The degradation tests are conducted in flow through reactors. The gas flow rate is controlled by a flow meter. The gas stream is saturated with water at 90 °C (100% RH). The water saturated 02 containing gas mixture is then fed to the reactors at 90 °C. Samples are taken out at regular intervals and their CO2 capture capacity values are measured using a breakthrough analyzer.

[0104] Results

[0105] The results of the measurements on the mixtures and on the sorbent material without activated carbon particles are summarized in Table 1.

[0106] Table 1: Percentages of retained equilibrium CO2 capacity. Initial CO2 capacity corresponds to 100 %.

[0107] Fig. 2 illustrates the carbon dioxide capture capacity normalized to the initial capacity before degradation as a function of degradation time for the different systems.

[0108] Fig. 3 shows the relationship between the retained capacities at normalized time = 0.5 and the loading of activated carbon.

[0109] As one can see, the presence of 3 - 20 wt% of AC improves the stability of Sorbent A in oxidative-thermo degradation described above, with a sweet spot in the range of 4-15 wt% of AC. More than 85 % of the initial CO2 capacity was retained at normalized time = 0.5. The total CO2 capacity will be decreased according to the loading of carbon.

[0110] LIST OF REFERENCE SIGNS

[0111] 1 Ambient air, ambient air inflow structure

[0112] 2 Outflow of ambient air behind adsorption unit in adsorption flow-through mode

[0113] 3 Sorbent material

[0114] 4 Heat and / or steam, heat and / or steam inflow structure for heat / steam desorption

[0115] 5 Reactor outlet for extraction

[0116] 6 Vacuum unit / separator

[0117] 7 Wall

[0118] 8 Reactor unit

Claims

CLAIMS1. A method 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) adsorbing said gaseous carbon dioxide in a unit (8), 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 (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), preferably to a temperature between 60 and 110°C, 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; wherein said sorbent material (3) consists of a packed bed, monolith or layer structure comprising or consisting of a mixture of75 - 98 wt.-% of first particles of support material functionalised with primary and / or secondary amines, or a combination thereof, capable of reversibly binding carbon dioxide, and2 - 25 wt.-% of second particles of activated carbon material, the weight percent of the first and second particles adding up to 100% of the mixture in the sorbent material.

2. The method according to claim 1 , wherein the sorbent material consists of a mixture of85-96 wt.-%, preferably 88-95 wt.-%, of first particles, and4-14 wt.-%, preferably 5-12 wt.-%, of second particles, the weight percent of the first and second particles adding up to 100% of themixture in the sorbent material.

3. The method according to any of the preceding claims, wherein the support material of the first particles is an organic cross linked polymeric polystyrene based support material, in case of the first particles functionalised on the surface and / or in the bulk with primary or secondary amines, or a combination thereof, wherein preferably the support material is based on polymeric polystyrene crosslinked by divinylbenzene, wherein further preferably the polystyrene based support material is a styrene divinylbenzene copolymer, preferably in case of said first particles to form the sorbent material surface and / or in the bulk functionalised with primary amine, preferably methyl amine, most preferably benzylamine moieties, wherein the solid polymeric support material is preferably obtained in a suspension polymerisation process.

4. The method according to any of the preceding claims, wherein the first particles comprise primary amine moieties as well as in addition at least one of secondary amine moieties and tertiary amine moieties immobilized on a solid styrene-divinylbenzene support, wherein said solid styrene-divinylbenzene support is functionalised by at least one of secondary benzylamine groups, tertiary benzylamine groups, secondary a-methylbenzylamine groups, and tertiary a-methylbenzylamine groups, wherein in each case the secondary or tertiary amine groups are substituted with at least one of ethyleneamine, branched or linear polyethyleneimine, branched or linear propyleneamine, branched or linear polypropyleneimine, branched or linear polyethylenepropyleneimine, branched or linear butyleneamine, branched or linear pentanamine, branched or linear hexyleneamine, and / or wherein the first particles comprise primary amine moieties as well as at least one of secondary amine, and / or ether, amide, and amidine moieties, immobilized on a solid support, wherein they are obtained in that a solid support precursor is provided, having at least one of a primary amine, secondary amine, and alcohol 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 secondaryamine moiety of the reactant, X is a leaving group, i is in the range of 0-5, and wherein the resulting material is converted into said sorbent material by removing said protecting group, and / or wherein the first particles are 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%.

5. The method according to any of the preceding claims, wherein the second particles have a particle size (D50) in the range of 0.2-4 mm, preferably in the range of 0.5- 3 mm.

6. The method according to any of the preceding claims, wherein the second particles are based on organic renewable starting material, including wood, shell material preferably wood bark, coconut shells, or on styrene-divinylbenzene copolymer based beads.

7. The method according to any of the preceding claims, wherein step c) involves injecting a stream of partially of fully saturated or superheated steam (4), preferably by flow-through through said unit (8) for heating the sorbent.

8. The method according to any of the preceding claims, wherein the contacting of the sorbent with said gas mixture in step (a) takes place by flow over and / or by flow through.

9. The method according to any of the preceding claims, wherein the mean particle size (D50) of the first and / or second particles is in the range of 0.002 - 4 mm, preferably 0.01-1.5 mm, most preferably in the range of 0.30-1.25 mm.

10. The method according to any of the preceding claims, wherein the first particles of support material functionalised on the surface and / or in the bulk with primary or secondary amines, or a combination thereof, capable of reversibly binding carbon dioxidehave a nitrogen content in the range 4-50 wt.%, preferably in the range of 5 - 25 wt.% or 5 - 15 wt.% or 6 - 12 wt.%, in each case for dry sorbent material.

11. The method according to any of the preceding claims, wherein the gas mixture is ambient atmospheric air.

12. The method according to any of the preceding claims, wherein said mixture is contained in at least one essentially continuous coherent layer or in layered containers having air permeable side walls in the form of grids, having a mesh width which is smaller than the average particle size or smaller than the particle size of the 10% smallest particles in the mixture (D10) so that the particles of the mixture are retained in the corresponding containers.

13. A sorbent material (3), preferably in the form of a layer, monolith or packed bed, 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, preferably for use in a method according to any of the preceding claims, wherein the sorbent material consists of a mixture of75 - 98 wt.-% of first particles of support material functionalised with primary and / or secondary amines, or a combination thereof, capable of reversibly binding carbon dioxide, and2 - 25 wt.-% of second particles of activated carbon material, the weight percent of the first and second particles adding up to 100% of the mixture in the sorbent material.

14. Use of a sorbent material according to the preceding claim 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.

15. Method of making a sorbent material according to claim 13, wherein first particles and second particles are provided, and the first and second particles are mixed and packed to form the monolith or layer, preferably by generating a coherent layer or monolith structure, or to form a packed bed by inserting the mixture into a container havingair permeable side walls, preferably in the form of grids having a mesh width suitable and adapted to retain the mixture in the container.

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