Sorbent structures for co2 capture

Abstract

Method of producing an embossed sorbent sheet (2) for use in 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 said sorbent structure adsorbing said gaseous carbon dioxide, wherein the method comprises the following steps: provision of a thermoplastic sheet (1) of sorbent material comprising at least one of particles, fibers and a coating of a material adsorbing said gaseous carbon dioxide, subjecting said thermoplastic sheet (1) to a temperature in the range of 60-180°C and embossing at least one protrusion (5) into said thermoplastic sheet (1) to form an embossed sorbent sheet (2).

Description

[0001] TITLE

[0002] SORBENT STRUCTURES FOR CO2 CAPTURE

[0003] TECHNICAL FIELD

[0004] The present invention relates to carbon dioxide capture materials, in particular for example those provided with primary and / or secondary and / or tertiary amine carbon dioxide capture moieties, as well as to methods for preparing such capture materials, and to uses of such materials in particular in direct air capture processes.

[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) had ratified it. The meaning of this figure is that a consensus at the time was 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 three most notable solutions currently applied, albeit being at an early stage of development, are the capturing of CO2 by means of vegetation (e.g. trees and plants, but not really permanent removal) using natural photosynthesis, by means of combining bioenergy from combustion of biomass with point source CO2 capture and subsequent permanent storage (BECCS) and by means of DAC and carbon dioxide storage technologies, which also results in permanent removal but a significantly reduced land footprint compared to BECCS.

[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 potentially arable land surface to captured CO2 ratio. BECCS suffers from the same shortcoming. On the other hand, DAC coupled with carbon dioxide storage technologies 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 gas-solid interface. Such sorbents can contain different types of amino functionalization and polymers, such as immobilized aminosilane-based sorbents as reported in US-B-8834822, 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] 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 functionalized with primary benzylamines as solid sorbents for DAC applications.

[0013] 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-9186617). Other technologies are based on the use of solid sorbents in either a packed-bed or a flow-through structure configuration, where the sorbent is made of impregnated or covalently bound amines onto a support.

[0014] 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 using the same sorbent material without or with little loss of sorbent performance and without damaging the mechanical integrity of the adsorption unit.

[0015] More recently, structured adsorbers have also been employed for capturing CO2 from flue gas, such as the structures described by WO-A-2010096916 and WO-A-2018085927, that specify parallel passage contactors for the purpose of flue gas CO2 capture. These adsorber structures in their configuration for flue gas capture are designed for the high concentrations of CO2 present in flue gas and operate with the aim of capturing a high fraction of CO2from the flue gas.

[0016] More specifically, WO-A-2018085927 discloses an adsorptive gas separation apparatus and method. The adsorbent structure may include a first adsorbent layer having at least a first adsorbent material, a second adsorbent layer including at least a second adsorbent material, and a barrier layer, where the barrier layer is interposed between the first adsorbent layer and the second adsorbent layer. A parallel passage contactor including a plurality of adsorbent structures each comprising a barrier layer, and arranged to form first and second fluid passages is also disclosed. An adsorption process for separating at least a first component from a multi-component fluid stream using the adsorbent structure is also provided.

[0017] US-A-2015139862 discloses a structured adsorbent sheet, including a nano-adsorbent powder, and a binder material, wherein the nano-adsorbent powder is combined with the binder material to form an adsorbent material, and a porous electrical heating substrate, wherein the adsorbent material is applied to the porous electrical heating substrate thereby forming a structured adsorbent sheet. A structured adsorbent module is provided, including a plurality of stacked structured adsorbent sheets, configured to produce a plurality of fluid passages, wherein the plurality of fluid passages have a cross-sectional shape in the direction of a fluid stream. The structured adsorbent module may have a cross-sectional shape that is trapezoidal, rectangle, square, triangular or sinusoidal. A structured adsorbent bed is provided, including a plurality of modules, stacking the modules, thereby providing a plurality of process fluid passages, and a process fluid inlet and a process fluid outlet, in fluid communication with the plurality of process fluid.

[0018] US-A-2012076711 discloses a structure containing a sorbent with amine groups that is capable of a reversible adsorption and desorption cycle for capturing CO2 from a gas mixture wherein said structure is composed of fiber filaments wherein the fiber material is carbon and / or polyacrylonitrile.

[0019] US-B-8262774 discloses a process for forming a CO2 capture element which comprises providing a mixture of a monomer or monomer blend or a polymer binder, a miscible liquid carrier for the binder and a CO2 sorbent or getter in particle form, forming the mixture into a wet film or membrane, evaporating the liquid carrier to form a film or membrane, and treating the wet film or membrane to form pores in the body of the film or membrane. Also disclosed is a process of forming a CO2 capture element which comprises the steps of applying a mixture including a sorbent material and a polymer to an underlying material; polymerizing the mixture in place on the material; and aminating the polymer-coated material.

[0020] US-A-2007217982 discloses an apparatus for capture of CO2 from the atmosphere comprising an anion exchange material formed in a matrix exposed to a flow of the air.

[0021] US-B-8999279 provides a method for removing carbon dioxide from a gas stream without consuming excess energy, wherein a solid sorbent material is used to capture the carbon dioxide. The solid sorbent material may utilize a water-swing for regeneration. Various geometric configurations are disclosed for advantageous recovery of CO2 and regeneration of the sorbent material.

[0022] US-B-7708806 and US-B-9861933 relate to a method and apparatus for extracting CO2 from air comprising an anion exchange material formed in a matrix exposed to a flow of the air, and for delivering that extracted CO2 to controlled environments. The present invention contemplates the extraction of CO2 from air using conventional extraction methods or by using one of the extraction methods disclosed; e.g., humidity swing or electro dialysis. The present invention also provides delivery of the CO2 to greenhouses where increased levels of CO2 will improve conditions for growth. Alternatively, the CO2 is fed to an algae culture. US-B-8715393 discloses a method for removing carbon dioxide from a gas stream, comprising placing the gas stream in contact with a resin, wetting the resin with water, collecting water vapor and carbon dioxide from the resin, and separating the carbon dioxide from the water vapor. The resin may be placed in a chamber or a plurality of chambers connected in series wherein the first chamber contains resin that was first contacted by the gas, and each successive chamber contains resin which has been wetted and carbon dioxide collected from for a greater period of time than the previous chamber, and so on, until the last chamber. Secondary sorbents may be employed to further separate the carbon dioxide from the water vapor.

[0023] US-B-9527747 provides a method and apparatus for extracting carbon dioxide (CO2) from a fluid stream and for delivering that extracted CO2 to controlled environments for utilization by a secondary process. Various extraction and delivery methods are disclosed specific to certain secondary uses, included the attraction of CO2 sensitive insects, the ripening and preservation of produce, and the neutralization of brine.

[0024] US-B-8088197 and US-B-10010829 are directed to methods for removing CO2 from air, which comprises exposing sorbent covered surfaces to the air. The invention also provides for an apparatus for exposing air to a CO2 sorbent. In another aspect, the invention provides a method and apparatus for separating carbon dioxide (CO2) bound in a sorbent.

[0025] WO-A-2023001810 discloses a method for the production of amine functionalized polyacrylonitrile (PAN) fibres, preferably for direct air capture, wherein pristine polyacrylonitrile fibres are added to a solution of tetraethylenepentamine (TEPA) or pentaethylenehexamine (PEHA) at a concentration of tetraethylenepentamine (TEPA) or pentaethylenehexamine (PEHA) of at least 80 % v / v, and wherein the mixture is kept, preferably stirred, at a temperature in the range of 120- 160°C for a time span of at least 4 hours, as well as uses of corresponding fibres.

[0026] WO-A-2018174848 provides an ion-exchange membrane that includes a supporting substrate impregnated with an ion-exchange material. The supporting substrate includes an imprinted non-woven layer, and the imprinting includes a plurality of deformations at a surface density of at least 16 per cm2. The supporting substrate may lack a reinforcing layer. In some examples, the supporting substrate may include only a single layer of the imprinted non-woven fabric.

[0027] US-B-6273938 discloses how channel flow filtration media possessing high efficiency and low pressure drop are formed from a plurality of filtration layers at least some of which include a multi-dimensional channel pattern having a plurality of continuous, tortuous channels and a multi-dimensional edge at each end of the plurality of channels formed therein. The filtration medium is configured as a stack with the multi-dimensional edge of the channel pattern forming a plurality of inlets open through a first face of the stack, a plurality of outlets open through a second face of the stack, and a corresponding plurality of disruptive fluid pathways passing from the inlets through the stack to the outlets. The filtration layers may be formed from a non-woven material, such as a carbon loaded multilayer BMF web capable of adsorption of undesired vapors and odors from a fluid.

[0028] SUMMARY OF THE INVENTION

[0029] It is an object of the present invention to provide for improved structured carbon dioxide capture elements, preferably for direct air capture (DAC), in particular in the form of layers or sheets or monolithic structures or channel contactors, which preferably are provided as self-supporting structures, in particular for example for the case without the need of an additional solid supporting layer.

[0030] According to a first aspect of the invention, it relates to a method of producing a sorbent sheet with a non-planar deformation such as an emboss, hereafter also referred to as embossed sorbent sheet, for use in 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 said sorbent structure adsorbing said gaseous carbon dioxide.

[0031] The method comprises the steps according to claim 1 , in particular the following steps:

[0032] • provision of a thermoplastic sheet comprising or composed of sorbent material, i.e. preferably a porous material that can adsorb and desorb gases in relevant amounts for the application through physisorption or more preferably chemisorption, and optionally a second material with limited gas adsorption properties for the relevant application, and comprising at least one of particles, fibers, or a fibrous material

[0033] • subjecting said thermoplastic sheet to a temperature in the range of 50-300°C, preferably 60-240°C and embossing at least one protrusion into said thermoplastic sheet to form an embossed sorbent sheet.

[0034] Preferably, the thermoplastic sheet of sorbent material comprising at least one of particles, fibers and a coating of a material adsorbing said gaseous carbon dioxide is a contiguous structure, which is self-supporting and suitable and adapted to withstand the airflow in a carbon dioxide capture process. The thermoplastic sheet of sorbent material can consist of the above-mentioned particles and / or fibers of a material adsorbing said gaseous carbon dioxide, or it may comprise particles, fibers or coating, or a combination thereof, having these adsorbing properties. Typically, there are either carrier fibers which are coated with an adsorbing material or which are surface functionalized to have the adsorbing properties, and / or such carrier fibers which themselves are not adsorbing are mixed with particles and / or fibers having adsorbing properties. Preferably the adsorbing properties in these cases are provided by functionalization with primary or secondary or tertiary amines (or a combination thereof).

[0035] Further preferably, the thermoplastic sheet of sorbent material comprising at least one of particles, fibers and a coating of a material adsorbing said gaseous carbon dioxide is such that the material adsorbing said gaseous carbon dioxide is a material which is functionalized with primary or secondary or tertiary amines (or a combination thereof).

[0036] For example, the thermoplastic sheet of sorbent material can comprise or consist of thermoplastic particles and / or fibers (without or with limited gas adsorption properties for the relevant application, including bi-component and multi-component particles and / or fibers, including such where not all components are thermoplastic or thermoplastic at the temperature used for embossing; bi-component and multi-component particles and / or fibers generally include fibres or particles with a thermoplastic shell and a non-thermoplastic core or a core with a higher Tm and / or Tg than the shell, such that during embossing essentially only the shell is softened or molten) and non-thermoplastic adsorbing particles or powder, that are dry mixed and then sintered (heat treatment).

[0037] Alternatively, the thermoplastic sheet of sorbent material can comprise or consist of thermoplastic fibers or fibrous material (non-adsorbing), including bi-component and multicomponent fibers, including such where not all of the components are thermoplastic, and non-thermoplastic particles or powder sorbent material, produced through (wet or dry) impregnation.

[0038] Also, the thermoplastic sheet of sorbent material can comprise or consist of nonthermoplastic sorbent fibers, and thermoplastic binder fibers (including bi-component and multicomponent fibers, including such where not all of the components is thermoplastic, for example such that have a non-thermoplastic core, and a thermoplastic shell).

[0039] According to a first preferred embodiment, said thermoplastic sheet comprises or consists of at least one heat treated or sintered and / or extruded porous structure from a mixture of first particles and / or fibres (including yarns and fibrous materials such as wovens or non- wovens) of support material functionalized with primary or secondary or tertiary amines, or a combination thereof, capable of reversibly binding carbon dioxide, with thermoplastic second particles and / or fibres or fibrous materials different from the first particles (including bi-component and multi-component elements, that have a non-thermoplastic core, and a thermoplastic shell) and not functionalized with primary or secondary or tertiary amines.

[0040] According to a further preferred embodiment, said thermoplastic sheet comprises or consists of at least one layered and / or woven and / or non-woven support material coated and / or impregnated and / or functionalized with primary or secondary or tertiary amines (which can also be in powder or particulate form), or a combination thereof, capable of reversibly binding carbon dioxide.

[0041] According to another preferred embodiment, said thermoplastic sheet comprises or consists of fibers or fibrous materials not functionalized with primary or secondary or tertiary amines impregnated with first particles (including powders) and / or fibers of support material functionalized with primary or secondary or tertiary amines. Fibrous material herein refers to fibers and / or yarns and / or yarn-based woven and / or non-woven materials and includes materials manufactured using typical yarn and woven and non-woven manufacturing processes including but not limited to plain weaves and / or twill weaves and / or wet-laid and / or dry-laid and / or spunlace and / or meltblown and / or acupuncture and / or stitch and / or spunbond and / or thermobonded fibrous materials

[0042] According to yet another preferred embodiment, said thermoplastic sheet comprises or consists of first particles and / or fibres (including yarns and fibrous materials such as wovens or non-wovens) of support material functionalized with primary or secondary or tertiary amines combined with fibers into a sheet, for example in a wet-laying or (E-)spinning process or other typical yarn-making and / or woven and / or non-woven manufacturing process as mentioned above.

[0043] Embossing can take place batch-wise in a mold comprising an interior cavity structure with mold / die indentations / corresponding mold / die protrusions embossing the protrusions, and / or embossing can take place in a continuous process between at least two transporting and / or embossing elements such as belts or rolls, preferably heated belts / rolls, with belt / roll indentations / corresponding belt / roll protrusions embossing the protrusions.

[0044] The dies’ or rollers’ design enables one-sided and double-sided embossing in one or more process-steps by alternating the initial position of the thermoplastic sheet. By alternating the relative position between the form-giving element (e.g. die or roller) the embossing pattern can be altered.

[0045] The thermoplastic sheet during embossing can be subjected to a temperature in the range of 60-240°C, preferably in the range of 60-180°C or 100-180°C and more preferably to a temperature between 120-160°C.

[0046] Preferably, a multitude of more than two, or more than 5, or more than 10, or more than 20, or more than 100, or more than 500, or more than 1000 protrusions per sheet are formed in the embossing step, wherein the protrusions are preferably arranged regularly and / or wherein further preferably the protrusions are pointing all in one direction or are pointing, preferably alternatingly, in opposite directions, and wherein further preferably the protrusions take the form of point wise protrusions or local pleating, with sharp or rounded edges, and wherein further preferably essentially the full surface of the sheet is provided with a pattern of protrusions.

[0047] Preferably there is provided a multitude of more than two, or more than 5, or more than 10, or more than 20 protrusions or more than 100, and wherein the protrusions take the form of point wise protrusions or of protrusions the lengths of which in any direction are smaller than a maximum extension of said sheet, preferably the lengths of which are at most one third or at most one quarter or at most 5% or 10% of said maximum extension of said sheet in any direction.

[0048] Typically the embossing density is in the range of 20 - 40000 embossings (protrusions) per m2, preferably in the range of 50-5000 embossings per m2, more preferably in the range of 100-3000 or 300-2000 embossings per m2 or 500-1000 embossings per m2.

[0049] According to another aspect of the present invention, it relates to the production of an adsorber structure. According to this aspect, it relates to a method, wherein at least two embossed sheets with the protrusions all pointing in the same direction are obtained using the method batch wise or in a continuous process, combined with cutting as needed, and wherein they are assembled in an adsorber structure in an essentially parallel arrangement of said embossed sheets, in which the protrusions of said embossed sheets are not overlapping, seen in a direction perpendicular to the planes of the sheets, such that the protrusions of said embossed sheets are contacting the flat portions of the other contacting sheet, and the distance between said embossed sheets is defined by the height of the protrusions.

[0050] According to another aspect of the present invention, it relates to a method for making an adsorber structure wherein at least one sheet with the protrusions pointing, preferably alternatingly, in opposite directions, is obtained using the batchwise method or a continuous process, and wherein this sheet is assembled together with at least one sheet without protrusions in an essentially parallel arrangement of alternating sheets without embossing and sheets with bidirectional embossings.

[0051] According to yet another aspect of the present invention, at least one embossed sheet with protrusions pointing in the same direction can rolled or at least one embossed sheet with protrusions pointing in alternating direction can be arranged together with at least one flat sheet and the arrangement is then rolled.

[0052] The sheets can be oriented in a vertical direction and the embossings can have a length in an airflow direction which is less than 20 cm, or less than 5 cm or less than 3 cm or less than 1 cm, or less than 0.5 cm and have a length perpendicular to the airflow direction which is less than 5 cm or less than 3 cm or less than 1 cm, or less than 0.5 cm.

[0053] Typically, embossings have a height, perpendicular to the plane of the sheet, in the range of 0.1-10 mm or more preferably in the range of 0.2-5 mm.

[0054] The embossings in each of the sheets can have the same shape, and are preferably bellshaped or dome-shaped, or tear-shaped or wing-shaped, or a drop-shaped freeform geometrical element. The embossings can be asymmetric with respect to the airflow, so they can be shaped such that the cross-section perpendicular to the airflow direction is as small as possible, while it is longer / larger parallel to the airflow direction in order to minimize pressure drop without jeopardizing stability. So preferably the extension in a direction perpendicular to the airflow direction is smaller than the extension parallel to the airflow direction, preferably by a factor of at least 1.2 or 2. The shape can be optimized for high stability and low pressure drop. Moreover, the protrusions can be designed to induce turbulence.

[0055] The proposed method can be carried out using particularly suitable and adapted embossing tools. It is noted that the embossing tools that are described above and in the following can be used in the context of the above mentioned process, however the invention also relates to these embossing tools independently of this method and as embossing tools as such, or as embossing tools for use in such a method.

[0056] The embossing tools may comprise, on one side, an element provided with at least one protrusion, for forming an indentation in the sheet from one side, and a corresponding opening or indentation in a counter element to be applied to the sheet from the other side. The elements can be heated and / or materials with different thermal conductivity (e.g. metals vs insulators) can be chosen for the embossing elements to either accelerate or slow down heating.

[0057] The protrusion and the counter opening or indentation are arranged in an overlapping or congruent manner.

[0058] Typically, the protrusion is a convex, rounded, for example dome-shaped protrusion. In the counter element there can be provided a correspondingly shaped rounded concave indentation, or there can be a through-opening. The opening can have a cross-section that is widening in the direction of the plate with the protrusion, for example the openings can be circular and can be trumpet shapes. The diameter of the opening at the surface side facing the other plate with the protrusion is typically as large as the maximum diameter of the protrusion or is larger than maximum diameter of the protrusion. It is also possible to have small protrusions with a diameter only one third or one half of the maximum diameter of the opening at the surface side facing the other plate. Different support materials may require different processing parameters from dry-impregnated sheets and different shapes (dome-shaped) for the embosses as they break more easily. The specific shape of the embossing tool used is thus adapted in addition to the temperatures / times for embossing, and one of the special features is that such an embossing tool may only have the convex part build into the embossing tool, whereas the concave part is a (through) hole which may help to prevent micro-cracks and / or the formation of significant plastic deformation in the emboss, i.e. improve stability.

[0059] The protrusions can be part of and one piece with an embossing tool in the form of a plate or a roll. Also, it is possible to have an embossing plate which carries embossing elements which provide for the protrusions. These embossing elements are then separate elements mounted in the embossing plate. Such a structure allows for mounting different types of embossing elements in a plate or roll, allowing for adapting the protrusions for different materials and / or thicknesses or for having different types of protrusions in one material according to a pattern.

[0060] In line with the above the present invention not only relates to a method for making such structures / sheets, but also to using such tools for making such sheets and such embossing tools as such. The corresponding structures of protrusions and indentations / openings can be provided in flat large-scale embossing plates but also can be provided on or in rolls.

[0061] An arrangement of at least 4 or at least 8 or at least 12 or at least 20 sheets or at least 50 sheets or at least 100 sheets or at least 500 sheets or > 1000 sheets can be arranged in one adsorber structure which comprises a cage or frame, e.g. a cage with walls parallel to the airflow direction which are air permeable or air impermeable (or also e.g. air permeable in case of horizontal walls parallel to the airflow direction and air impermeable in case of vertical walls parallel to the airflow direction) and walls perpendicular to the airflow direction which are air permeable or these faces are of the cage are free of wall elements.

[0062] According to yet another aspect of the present invention, it relates to one or a plurality of embossed sorbent sheets obtained using a method as described above.

[0063] According to yet another aspect of the present invention, it relates to an adsorber structure with at least such one embossed sorbent sheet, preferably obtained using such a method. Such an adsorber structure may comprise an arrangement of at least 4 or at least 8 or at least 12 or at least 20 or at least 50 or at least 100 or at least 500 or at least 1000 sheets in a cage, preferably with the sheets being arranged parallel to the airflow, further preferably a cage with walls parallel to the airflow direction which are air impermeable and walls perpendicular to the airflow direction which are air permeable or free of wall elements.

[0064] The embossed sheet may be attached to at least one further embossed or non-embossed sheet by way of the protrusions of the embossed sheet being attached to the further embossed or non-embossed sheet, wherein the attachment can be by way of force fit, by way of form fit, by way of adhesive bonding, or a combination thereof.

[0065] The embossing / forming features in each mold / roller / die / belt may have a protruded surrounding platform to only allow punctual heating and hence to avoid unwanted heating of material that is not to be deformed.

[0066] Typically, such surrounding platforms take the form of steps provided around the protrusions in the convex embossing mold and in that indentations in the concave embossing mold are provided in local protruding portions of the concave mold. The surrounding platform in this case is given by the edge portion of the respective protruding portion surrounding the indentation. The surfaces of the surrounding platforms are normally parallel to each other for the facing indentations / protrusions and are typically parallel to the remaining surface of the mold.

[0067] In the molding process these surrounding platforms do contact the sorbent sheet in the closed mold. The remaining surface portions between the indentations / protrusions of the of the two molds do not contact the sorbent material in the closed mold but are well distanced from the sorbent material.

[0068] Also, cooling air circulation or an isolating material or around the forming feature surrounding platforms can be placed to furthermore avoid unwanted heating of material that is not to be deformed.

[0069] Last but not least the present invention relates to a method for separating gaseous carbon dioxide from a gas mixture, preferably from at least one of ambient atmospheric air, flue gas and biogas, containing said gaseous carbon dioxide as well as further gases different from gaseous carbon dioxide, by cyclic adsorption / desorption using such an adsorber structure adsorbing said gaseous carbon dioxide in a unit, wherein the method comprises at least the following sequential and in this sequence repeating steps (a) - (e):

[0070] (a) contacting said gas mixture with the adsorber structure to allow at least said gaseous carbon dioxide (parts thereof or essentially all of the CO2) to adsorb on the adsorber structure by flow-through through said unit (and thus through and / or over the adsorber structure 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");

[0071] (b) isolating said adsorber structure or at least part of said adsorber structure with adsorbed carbon dioxide in said unit from said flow-through, preferably while essentially maintaining the temperature in the adsorber structure;

[0072] (c) inducing an increase of the temperature of the adsorber structure or at least part of said adsorber structure, preferably to a temperature between 60 and 110°C, starting the desorption of CO2. This is e.g. possible by injecting a stream of partially of fully saturated or superheated steam, preferably by flow-through through the unit and over / through the adsorber structure, and thereby inducing an increase of the temperature of the adsorber structure to a temperature between 60 and 110°C, starting the desorption of CO2;

[0073] (d) extracting at least the desorbed gaseous carbon dioxide from the unit (preferably most or all of the desorbed gaseous carbon dioxide) and separating gaseous carbon dioxide, preferably by condensation, in or downstream of the unit; (e) optionally bringing the adsorber structure to ambient atmospheric temperature conditions and ambient atmospheric pressure conditions (if the adsorber structure 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).

[0074] In the context of this disclosure, the expressions “ambient atmospheric pressure” and “ambient atmospheric temperature” refer to the pressure and temperature conditions to that a plant that is operated outdoors is exposed to, i.e. typically ambient atmospheric pressure stands for pressures in the range of 0.8 to 1.1 barabs and typically ambient atmospheric temperature refers to temperatures in the range of -40 to 60° C, more typically -30 to 45°C. The gas mixture used as input for the process is preferably ambient atmospheric air, i.e. air at ambient atmospheric pressure and at ambient atmospheric temperature, which normally implies a CO2 concentration in the range of 0.03-0.06% by volume, and a relative humidity in the range of 3-100%. However, also air with lower relative humidity, i.e. < 3%, or with lower or higher CO2 concentration can be used as input for the process, e.g. with a concentration of 0.1-0.5% CO2 by volume, so generally speaking, preferably the input CO2 concentration of the input gas mixture is in the range of 0.01-0.5% by volume.

[0075] The present invention relates to such a method for separating gaseous carbon dioxide from a gas mixture having the above-mentioned steps using an adsorber structure made as described further above, but it also relates to a method of producing an adsorber structure in a method as described further above and then carrying out the above-mentioned method for separating gaseous carbon dioxide from a gas mixture having the above-mentioned steps.

[0076] The sorbent material contained in or forming the thermoplastic sheets is a porous material that can adsorb and desorb gases in relevant amounts for the application through physisorption or more preferably chemisorption. Most preferably, the sorbent material is a porous support material functionalized with amines that can adsorb CO2 in relevant amounts for capturing it from ambient air.

[0077] Adsorption Material or a sorbent sheet generally speaking in this disclosure is an arrangement of at least one porous sheet with functionality to adsorb / desorb gases, for example CO2, for example from ambient air, and comprising or consisting of Sorbent Material and (optionally) secondary materials such as a support material.

[0078] More specifically, the adsorption material comprises or consists of a sorbent material or precursor of a sorbent material, that is in a second step structured to form a sheet. This may or may not require the use of additives / structuring supports / binders. The sorbent material provides the functionality to adsorb gases. The structuring into a porous sheet can be done either before or after functionalization of the sorbent material.

[0079] The final adsorption material consists of the sorbent material and a not necessarily different material that can be plastically deformed under the influence of mechanical force and / or temperature and / or pressure.

[0080] For example: a) the sorbent material itself is thermoplastic. b) the adsorption material contains a thermoplastic second material (including also bicomponent or multicomponent fibers, including such where not all components are thermoplastic, including such that have a non-thermoplastic core, and a thermoplastic shell). Preferably, the thermoplastic second material is used as a binder to give the sorbent material the shape of a sheet, and also acts as a support for mechanical stability.

[0081] Also in case a), a second and / or even third material that can be thermoplastic or nonthermoplastic, may be added, if needed sequentially, for structural support or to include other favorable properties (conductivity, anti-aging, anti-oxidant, ..).

[0082] Thermoplastic second material can for example be provided in the form of powder or beads or fibers or already processed fibers in form of a fibrous material, for example a porous sheet-like nonwoven or woven material, or other porous sheet-like materials including 3D- printed materials w / o the sorbent material. In this case, the sorbent material has to be added in a secondary step, for example a wet or dry impregnation step. The thermoplastic second material may in itself already be a composite, for example using bi-component fibers or mixtures of different kinds of already processed fibers to form a porous sheet-like material. Other non-thermoplastic additives like glass or carbon fibers or anti-aging additives or antioxidants may be added.

[0083] The sorbent material may be an ion exchange resin, a MOF, an activated carbon, a zeolite, a functionalized porous ceramic like alumina or silica, or precursors thereof. Sorbent Material can be provided for example in the form or powder or beads or fibers or already processed fibers or precursors thereof (functionalized or non-functionalized), most favorably it is provided in the form of powder or fibers.

[0084] Typically and preferably, sorbent material is functionalized (on the surface and / or in the bulk) with primary or secondary or tertiary amines, or a combination thereof, capable of reversibly binding carbon dioxide, are ion exchange resin (I ER) particles, which can either be manufactured at the desired size or which can be ground before the sheet-manufacturing (e.g. including sintering) process to the desired size.

[0085] In another embodiment, sorbent material refers to a solid porous substance that can adsorb CO2, in particular when used for DAC, the solid porous substance comprising amines or polyamines covalently attached to the backbone of a polymeric or copolymeric support.

[0086] In yet another embodiment, sorbent material takes the form of particles or fibers of support material functionalized on the surface and / or in the bulk with primary or secondary or tertiary amines, or a combination thereof.

[0087] According to yet another preferred embodiment, the mean particle size (D50, volumebased) of the particles of support material functionalized on the surface and / or in the bulk with primary or secondary or tertiary amines, or a combination thereof, capable of reversibly binding carbon dioxide is in the range of 1 and 300 microns, more preferably between 3 and 250 microns, or 10 and 200 microns, or 15 and 150 microns, or 20 and 120 microns, or 30 and 100 microns, or 40 and 80 microns, or 50 and 70 microns.

[0088] Alternatively or additionally, the mean particle size (D50) of the preferably nonfunctionalised thermoplastic second particles preferably is in the range of 1-300 pm, preferably in the range of or 10-250 microns, or 15-200 microns, or 20-180 microns, or 25- 150 microns, or 30-120 microns, or 40-100 microns, or 50-80 microns.

[0089] Alternatively or additionally, the ratio of the particle size (D50) of the particles of support material functionalized on the surface and / or in the bulk with primary or secondary or tertiary amines, or a combination thereof, capable of reversibly binding carbon dioxide to the particle size (D50) of the preferably non-functionalised thermoplastic second particles is preferably in the range of 0.1-10, more preferably in the range of 0.2-5, or 0.25 - 4, or 0.3 to 3, or 0.4 to 2, or 0.3 - 1.4 or 0.5 to 1.5, or 0.6 to 1.3.

[0090] The sorbent material and / or the adsorption material and / or the embossed sorbent sheet preferably have a nitrogen content in the range 4-50 wt.%, preferably in the range or 5 - 25 wt.% or 5 - 15 wt.% or 6 - 12 wt.%, in each case for dry sorbent material.

[0091] The final Adsorption Material may be produced through processes including but not limited to any or all or a combination of typical non-woven manufacturing methods like wet-laying, dry-laying, melt-blowing, (E-)spinning; and / or through yarn-making and / or weaving and / or through sintering, and / or through impregnation and / or coating of an already existing porous sheet-like material with the Sorbent Material (and subsequent functionalization, in case a precursor of the sorbent material is used).

[0092] The final composite sheet material typically consists of 30-100 % sorbent material, and of 0-70 % preferably thermoplastic binder / support / glue and of 0-30 % additives (including nonthermoplastic binders / supports / glues). Lower sorbent material loadings are possible, but not preferably for the application of capturing CO2 out of ambient are due to the high parasitic thermal mass that has to be heated in a temperature-swing regeneration process. The amount of preferably thermoplastic second material should be chosen in a way to provide enough stability and support to form a stable sheet-like material, and to make the whole adsorption material formable under the influence of temperature and / or pressure in case the sorbent material itself is not thermoplastic. The thickness of such material is typically in the range of 0.1 - 2 mm. The melting point (or melting range) of the thermoplastic second material or of a component of the thermoplastic second material is typically in the range of 100-300°C, more favorably in the range of 110-240°C, and most favorably in the range of 120-180°C. More specifically, the melting point of the thermoplastic material should be chosen in a way to be a) higher than the maximum operating temperature and b) below the temperature at which the sorbent material decomposes or degrades significantly already at the short exposure times required for thermoforming. Thermoplastic materials suitable include for example PE; PP, PET, PA, TPU, or combinations thereof. The final sheet would typically have a density of 0.200-0.800 g / cc, and a porosity of 50 to 90 %.

[0093] A sheet preferably has a thickness in the range of 0.05-3 mm, or 0.1 to 2 mm, or, more preferably has a thickness of 0.2 to 1.8 mm, or 0.3 - 1.5 mm, or 0.4 - 1.3 mm, or 0.5-1.0 mm

[0094] Alternatively and / or additionally preferably the sheet has a length in adsorption flow direction in the range of 0.1-3 m.

[0095] Further embodiments of the invention are laid down in the dependent claims.

[0096] BRIEF DESCRIPTION OF THE DRAWINGS

[0097] 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,

[0098] Fig. 1 shows in a) cross sections of a raw sheet and an embossed sheet (right); and frontal views of a parallel-passage contactors made from several embossed sheets, wherein b) shows a single direction embossing example, c) a bidirectional embossing example, and d) and interlocking embossing example;

[0099] Fig. 2 shows in a) a top view (top) and a side view (bottom) of a pointwise embossed sheet, and in b) a top view (top) and a side view (bottom) of an pleated embossed sheet;

[0100] Fig. 3 shows various spacer geometries and arrangements, wherein in the top row from left to right a prismatic embossing, around conical embossing, a bridge like embossing, and another bridge like / pleated embossing with cutouts is shown, in the middle row from left to right a smoothened embossing, an eye or lens shaped embossing, a raceway shaped and an arrangement of several sheets with glued contact points is shown, and in the lowermost row from left to right circular embossings are shown including on the right side lateral view, bidirectional embossings alternating with flat sheets, and embodiments with embossings cut to form wire retainer possibilities, and on the very right again bidirectional embossings alternating with flat sheets including horizontal wire connection;

[0101] Fig. 4 shows an optimized protrusion shape on the left in a side view along the plane of the sheet interviewing direction perpendicular to the airflow direction (arrow) and on the right in a side view in a direction parallel to the airflow direction;

[0102] Fig. 5 shows a mold for producing an embossed sheet, wherein on the right side of magnification of the feature illustrated by the circle a on the left side is given;

[0103] Fig. 6 shows a graphical representation of the relationship between compressive force exerted on emboss (y-axis) and displacement (x-axis);

[0104] Fig. 7 shows a graphical representation of the relationship between pull force (y-axis) and displacement (x-axis);

[0105] Fig. 8 shows the deformation due to steaming / subsequent drying for three different embossings;

[0106] Fig. 9 shows a graphical representation of the relationship between compressive force (y-axis) applied to steamed embossings and displacement (x-axis).

[0107] Fig. 10 shows the CO2 uptake curve of a parallel passage contactor made from embossed sheets normalized by the CO2 uptake after 150 minutes,

[0108] Fig. 11 shows different embodiments of embossing tools, wherein in a) and b) implementations are shown where the protrusions are essentially dome-shaped and the counter plates have correspondingly rounded indentations, while in c) - h) implementations are shown, where the counter elements are not indentations but through openings,

[0109] Fig. 12 in a) shows an embossing tool with surrounding platforms and in b) an embossing tool without surrounding platforms.

[0110] DESCRIPTION OF PREFERRED EMBODIMENTS

[0111] The invention relates to sheets for a parallel-passage contactor for gas adsorption processes, preferably for the adsorption of CO2 and / or water from ambient air. More specifically, the parallel-passage contactor comprises or consists of several parallel embossed sheets of adsorbent material, that are stacked together and operated preferably in a vertical, i.e. hanging configuration.

[0112] A schematic of a sheet 1 (left) and an embossed sheet 2 (right) is shown in Fig. 1a) and modules made from several embossed sheets are shown in Fig. 1b)-d). An embossed sheet 2 comprises at least one protrusion, normally a multitude of protrusions which are distributed over the full area of the sheet. The distribution can be regular or irregular.

[0113] As can be seen from Fig. 1 , the emboss can be single-directional, or bi-directional (in which case only every second sheet will have to be embossed) or have an interlocking feature for additional stability.

[0114] Examples of possible emboss geometries and of the interlocking are provided in Fig. 2 and Fig. 3. The airflow in Fig. 2 is perpendicular to the shown faces, i.e. air will flow in between two parallel sheets.

[0115] Fig. 2 a) shows the emboss pattern of a single-side embossed sheet with oval cross-section of the embosses. In contrast, Fig. 2 b) shows a pleated geometry, that can be facilitated though thermoformability, but does not necessarily require thermoformable sheets.

[0116] Fig 3 shows from top left to bottom right an emboss with a tetrahedron shape, a conical shape, an soft-edge half-cylinder emboss shape, a prism embossed shape with cuts on the side that allows for airflow through the cut-open sides (which can be favorable regarding pressure drop) and also allows for less smooth edges, a soft-edge conical emboss, an emboss with a rhombus cross-section (increased stability), an soft-edge half cylinder emboss, an emboss pattern where the emboss of one sheet and the next sheet are conjoint (different conjoining options are possible including but not limited to welding, use of adhesives, sewing, clamping), emboss with an ring-shape cross-section, bi-directional emboss, a prism embossed shape with cuts on the side interlocking with a cut-out in the next sheet, a double-sided emboss with an interlocking feature (for example a string or wire). In contrast to the state of the art, the spacing elements are formed in an embossing process, preferably through application of temperature and / or pressure, out of the adsorption material itself. This is in contrast to the state of the art, where spacing elements on top of the adsorbent material (that may also be made from adsorbent material itself) are used.

[0117] The configuration described here has the advantages that a) no additional thermal mass is added to the structure for keeping the sheets spaced apart. This is essential for example when a thermal regeneration is employed, as is typically done for capturing CO2 out of ambient air in an adsorption-based process.

[0118] And b) the manufacturing can be simplified significantly compared to the addition of separate spacing elements, where the spacing elements have to be manufactured and attached to the sheets. In contrast, with embossed sheets, the sheet-form adsorbent material, typically on a roll, can simply be embossed in a single post-treatment step. Moreover, such configuration is fundamentally different from an overall corrugated or pleated material. In those cases, the corrugation results in continuous channels for airflow. In contrast, the emboss details are non-continuous and take up a low fraction of the overall sheets, preferably < 30%, more preferably < 10%, and most preferably < 1 % of the sheet area. The air flows essentially in between two parallel sheets, and airflow is obstructed by the emboss details. Hence, the pressure drop is dominated by the pressure drop between two parallel sheets with obstructions, whereas the pressure drop for the corrugated / pleated sheet is that within a triangular or sinusoidal channel. The difference is shown schematically in Fig.2 for an embossed sheet and a pleated sheet.

[0119] Another advantage especially compared to a corrugated or pleated configuration is that any water can drain between two parallel sheets if they are arranged in a non-horizontal parallel passage contactor.

[0120] Specific examples of adsorption materials:

[0121] Adsorption sheet materials:

[0122] Example 1 : Sintered lER-binder sheets are produced from a mixture of 50 w% (wet, -85% solid content) ion exchange resin (I ER) powder at a mean particle size of 55 microns (D50, volume based, measured using a particle size analyzer 1190LD by Anton Paar, 5.5 bar air pressure for dispersion, a Fraunhofer reconstruction mode, 70% vibrator duty, an 5-30% obscuration range) and a glass transition temperature of approximately 180°C, and 50 w% Ultra-high-molecular-weight polyethylene (UHMWPE) at a mean particle size of 150 microns (D50). The two powders are mixed by shaking for -1 minute. Approximately 0.7 g of powder mixture are filled in an aluminum mold with inner dimensions of 22x36x2 mm.

[0123] The I ER powder employed is based on porous divinyl benzene crosslinked polystyrene beads (d~0.3-1.5 mm) functionalized with amino methyl-groups to form benzyl amine moieties which can be introduced e.g. in an chloromethylation reaction followed by amination with urotropine. I ER powder was obtained from such beads by jet-milling.

[0124] The IER beads used can by synthesized as follows: In a 1 L reactor, 1% (mass ratio) of gelatin and 2% (mass ratio) of sodium chloride are dissolved in 340 mL of water at 45°C for 1h. In another flask, 1 g of benzoyl peroxide is dissolved in a mixture of 59.7 g of styrene, 3.9 g of divinylbenzene (content 80%) and 65.3 g of C11-C13 iso-paraffin. 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 3 h, and then raised to 90°C for 6 h. 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 washed with toluene and dried in rotavapor.

[0125] The polystyrene-divinylbenzene beads are functionalized using the chloromethylation reaction. 5 g of so obtained beads are added to a 3-neck flask containing 50 mL of chloromethyl methyl ether. The mixture is stirred for 1 h, 2 g of zinc chloride is added and is heated to 40°C and kept it for 24 h. After that, the beads are filtered off and wash with 25% HCI and water to obtain chloromethylated beads. To obtain benzylamine units, the chloromethylated beads are aminated using the following procedure. The chloromethylated beads are added to a three-necked flask with 27 g of methylal and the mixture is stirred for 1 h. To this mixture, 16 g of hexamethylenetetramine and 13 g of water are added and kept under gentle reflux for 24 h. The beads are filtered off and washed with water. To have a primary amine, a hydrolysis step followed by a treatment with a bases 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.

[0126] 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 with 1 h at 80°C. The aminated beads are filter off and washed to neutral pH with demineralized water.

[0127] The LIHMWPE powder used was the following: Mean particle size (D50): -150 microns, Molecular weight: 3-6 million, melting point range 104 - 138°C, density 0.945 g / cm3, possible commercial source: Alfa Aesar, CAS 9002-88-4.

[0128] The mold is closed, and the powder is distributed and compacted by placing it on a shaker. Subsequently, the aluminum mold is placed on a metal plate that is heated to 220°C, and a light pressure (0.2 bar) and heat are applied from the top by placing a steel rod of 40 mm diameter, that was pre-heated to 220°C, on top of the mold. This pressure is then transferred from the top part of the mold to the powder, as the powder height in the bottom part of the mold is such that the lid of the top part is not in direct contact with the frame of the bottom part. The mold is heated for 4 minutes, i.e., for 2 minutes from each side.

[0129] It was independently determined that after at most 5 seconds on the metal plate forming the contact surface of the mold and the corresponding aluminum plate in contact with the metal plate approximately reached the melting temperature of the LIHMWPE powder. After -30 s, the temperature of the aluminum / metal plate reaches ~210°C, whilst it takes -60s for the aluminum / metal plate to reach 220°C.

[0130] Afterwards, the mold is removed from the heated plate and left to cool in ambient air to reach room temperature (approximately 6 minutes). The mold is opened, and a sheet of IER bound together by LIHMWPE with a cross-section of 22x36 mm is removed. The sheet has a density in the range of 550-620 kg / mA3.

[0131] Example 1b): Alternatively, the sheets can be produced from a mixture of 50 wt% (wet, -85% solid content) ion exchange resin (IER) powder at a mean particle size of 75 microns (D50, volume based and 50 wt% ultra-high-molecular-weight polyethylene (LIHMWPE, 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.

[0132] Example 2: In another example 2, the sheet is produced in the same way, but the mold is placed into a hydraulic press directly after removing it from the hot plate, and a pressure of approximately 600 bar is applied. Afterwards, the mold is left to cool, and the IER-UHMWPE sheet is removed. The sheet has a density in the range of 600-700 kg / mA3 (example 2). Both examples result each in a mechanically stable sheet, that remains stable also when stirred for at least 2 hours in room-temperature water.

[0133] Example 3: In another example 3, an adsorbent material is produced from 70% by weight I ER powder as given above and 30 % by weight bi-component fibers, leading to a stable sheet with a density of approximately 0.3-0.4 g / cc.

[0134] Example 4: In another example, a fleece was produced according to WO 2023 / 001810 in a wet-laying process and using thermoplastic auxiliary fibers and was then embossed as described below.

[0135] Embossed adsorption sheet material manufacturing

[0136] Example 1 : For the protrusions geometry shown in Fig. 4, produce a corresponding mold from steel. Heat the mold in an oven until it reaches a temperature of ~150°C. Take out the mold, place an adsorption material example 1 , 2, 3 or 4 as described above and a thickness of approximately 0.2-2 mm in the mold and clamp for approximately 10s, open the mold and take out the material. This results in an embossed protrusion with a height approximately 30% below the height of the tool.

[0137] Example 2: For a protrusion pattern similar to the one shown in Fig. 2a, produce a corresponding mold from steel as illustrated in Fig. 5. Heat the mold in an oven until it reaches a temperature of ~150°C. Take out the mold, place an adsorption material example 1 , 2, 3 or 4 as described above and a thickness of approximately 0.2-2 mm in the mold and clamp for approximately 10s, open the mold and take out the material. This results in an embossed protrusion with a height approximately 20% below the height of the tool. Example 3: Provide the adsorption material of example 3 and the mold of example 2. Heat to mold in an oven until it reaches the desired temperature. Put the Adsorption Material w / o preheating onto the female part of the tool, put the male part on top and close it applying a pressure of approximately 1 N / mm2 and leave for approximately a few s. Remove the male upper part and the embossed sheet.

[0138] Variants: for a given tool and sheet, the main optimization parameters are the temperature and time. In the specific tested case, it was found that a temperature of ~150°C worked best. Higher temperatures were avoided to prevent shrinkage of the sheet. At 130°C, the height of the embossed structure was lower. Moreover, the time of exposure was optimized in order to provide optimal embossing results without having the sheets adhere to the tool. In this case, a time of approximately 5 s was found to be optimal. Demolding agents can be used if needed depending on the material. Longer exposure times may result in the adsorption material adhering to the tool, which makes removal difficult, and may even result in heat-induced degradation (color change and shrinkage).

[0139] That the time that elapses between removing the tool of the oven and removing the embossed adsorption material was up to 2 min. It was measured that during this time, the temperature of the tool drops by <10 K.

[0140] Example 4: Produce an adsorption material according to any of the methods described before. Use the molds show attached to a heat press, pre-heat the molds to a temperature of ~120°C, then emboss the sheets for a duration of ~6s at a pressure of < 100N. As a variant, turn the sheet around after embossing one side, offset the embosses by approximately half the distance between two embosses, then emboss the sheet again to form a sheet with bi-directional embosses.

[0141] Protrusion stability: Several stability tests were carried out on an embossed sheet as described above in Example 3 with emboss heights in the range of 1-3mm. Protrusion heights of 2.6 / 2.3 / 2 / 1 .7 mm were used for the three steam stability tests (emboss 1 / 2 / 3) and the compressive strength / extension test, respectively. For the steam stability tests, a tool with geometry as shown in Fig. 4 was used, but with three different heights to result in embosses 1 / 2 / 3 with three different emboss heights in the range of 1-3 mm with emboss 1 > emboss 2 > emboss 3.

[0142] Compressive strength: measure the compressive strength of the protrusion by placing it underneath a load cell and measuring the applied load vs displacement. This results in the plot given in Fig. 6.

[0143] Extension Test: Load cell was clamped onto the sorbent sheet on its top edge and clamped into place on its bottom edge. The sheet was then stretched at a constant rate until the sheet was fully flattened. The results are shown in the graph given in Fig. 7.

[0144] The embossed feature can withstand approximately 20 N before deforming. After the sheet was removed from the clamp, the emboss returned slightly.

[0145] Steam stability: Test procedure steaming: place an embossed sorbent sheet produced according to Example 3 in a ~45 ° angle ~20cm away from a 1800 W clothes steamer and steam for 20 minutes. For subsequent drying, the embossed sheet was dried for at least 17 hours at ambient conditions. The height of the embossed protrusions was measured before and after steaming. The trends are shown in the graph given in Fig. 8. As shown in the figure, the embossed change significantly during the initial steaming / drying cycles, but only marginally for steaming cycle 2 and drying cycle 2.

[0146] Compressive strength after steaming: Immediately after steaming a sheet with embossed 1 / 2 / 3 as described above, the compressive strength was measured. The result is shown in the graphs given in Fig. 9.

[0147] As shown in the figure, the stability of the emboss after steaming does not change significantly compared to the stability before steaming shown in Fig. 6.

[0148] Process stability testing: a parallel passage contactor built from the embossed material produced according to Example 4 above was tested in an accelerated adsorptiondesorption process running a similar process as described below for the cyclic adsorption performance testing, but with accelerated heating and cooling steps, short adsorption steps and higher flows, which accelerates the cycles by an order of magnitude and cycle for > 3000 cycles to test protrusion stability before / after. The protrusion after cycling show no visible deformation or measurable change in protrusion height.

[0149] Cyclic adsorption performance, a parallel passage contactor with 100 cc volume was build using 16 sheets of a material produced according to Example 4 above with a singlesided emboss feature. The parallel passage adsorption contactor was tested in an experimental rig. For comparison, a similar parallel passage contactor with 20 sheets without any embossed was tested in the same rig. The cyclic adsorption / desorption capacity was measured in consecutive runs at relative humidity of the ambient air of approximately 60% and temperature of approximately 15°C at a flow of approximately 9 Nl / min (norm liter, at 0°C at 1013.25 Pa). The desorption process was performed using a warm fluid to increase the temperature of the sorbent. In this specific example, saturated steam was employed. The sorbent bed was first adsorbed for 150 min using ambient air. Once the adsorption was completed, the pressure of the system was brought down to <400 mbarabs. As soon as the pressure is reached, saturated steam is supplied to the sorbent bed up to reaching a temperature of ca 95°C. After that, the sorbent was brought to <400 mbarabs.

[0150] Fig. 10 shows the CO2 uptake over time for the embossed sample, normalized by the uptake after -150 min. The CO2 uptake and kinetics are in line with those measured for the flat sheets, which shows that the embossing did not results in a significant reduction in CO2 capacity or CO2 uptake kinetics.

[0151] As illustrated in Fig. 11 , showing cross-sections perpendicular to the plane of the sheet through embossing elements, going through the center axis of the corresponding protrusion

[0152] 10 provided on a first embossing plate 8, which is designated as convex embossing plate in this case, because it carries a protrusion 10.

[0153] As illustrated in a) and b), according to one implementation, for the generation of an embossing in the sheet of a height h, a dome-shaped protrusion 10 can be provided for each embossing on the first embossing plate 8, while a corresponding counter indentation

[0154] 11 with essentially the complementary form is provided in the counter plate 9.

[0155] To take account of different types and / or thicknesses of sheet material, also different embossing elements can be used as illustrated in c)-h). The embossing elements are provided as separate structural elements to the embossing plate 8, and embossing elements with protrusions of different shape and / or height can be used as inserts in the same embossing plate to take account of different materials and / or thicknesses or to generate embossings of different height in the resulting sheet. Also, it is possible to use spacer elements between the embossing plate and the embossing elements (e.g. between a shoulder of the embossing element and a contact face on the embossing plate) to change the resulting height of the protrusion of the embossing elements mounted in the embossing plate. The embossing elements can be fixed in the embossing plate by form fit (e.g. snap in), force fit (screwing), or material connection (e.g. adhesive), or a combination thereof.

[0156] In this case the counter plate 9 does not carry indentations but is provided with through openings 12. Instead of the through openings 12, it is also possible to have the same structures, but which are closed on the bottom; what is important is that in the facing circumferential region facing the respective protrusion 10, the circumferential edge portion of the side wall 13 of the through opening 12 is progressively widening, so is essentially trumpet-shaped.

[0157] As one can see from the illustrations in this figure, depending on the materials, temperatures and embossing times chosen, the diameter of the protrusions and of the openings as well as the rounding of the protrusions and / or of the widening of the openings can be chosen in different ways to optimize the manufacturing conditions and the stability of the embossings. Fig. 12 illustrates, how, if heating of the sorbent sheet 1 outside of the areas where the protrusions are to be generated, is to be avoided by providing surrounding platforms on the protrusions 10 as well as on the indentations 11. a) represents a schematic representation of a cut through a mold in which such surrounding platforms 14, 15 are provided, while b) for illustration purposes shows a cut through a conventional mold.

[0158] As one can see, the sheet 1 is provided between the convex embossing plate 8 and the concave embossing plate 9. The convex embossing plate 8 has protrusions 10 to form the above-mentioned embossed protrusions in the sorbent sheet, and the concave embossing plate 9 has corresponding indentations 11 for the proper shaping of the embossed protrusions in the sorbent sheet 1 on both sides. If the mold according to the representation in b) is closed, there is a full-surface contact between both embossing plates 8 and 9 not only in the region of the protrusions 10 and indentations 11 but also in the areas in between. This can lead to problems due to prolonged heating in these areas and corresponding degradation of sorbent sheet material or functionalization thereof.

[0159] If the mold according to a) is closed, the sheet 1 will be embossed between the protrusion 10 and the indentation 11 but the embossing plates 8 and 9 will only close to an extent that between the surrounding platform 14 of the protrusion 10 and the surrounding platform 15 of the indentation 11 the sheet is only slightly or not at all pressed or contacted.

[0160] Like that in the intermediate regions 16 there is no contact between the sheet and the respective embossing plate 8,9 and correspondingly also no heat influence. Further optimized heat management can be provided in such a mold by, during the molding process, circulating cold air through the gap in the mold on both sides of the sheet 1 to avoid noncontact irradiative heat transfer between the intermediate regions 16 of the embossing plates 8 and 9 and the sorbent sheet 1 .

[0161] LIST OF REFERENCE SIGNS

[0162] 1 sorbent sheet 12 through opening in 9

[0163] 2 embossed sorbent sheet 13 progressively widening

[0164] 3 air flow sidewall of 12

[0165] 4 obstruction 14 platform surrounding 10

[0166] 5 embossed protrusion 15 platform surrounding 11 ,

[0167] 6 adsorber structure countersurface for 14

[0168] 7 contact with next sheet 16 intermediate noncontact

[0169] 8 convex embossing plate regions of 8 and 9

[0170] 9 concave embossing plate

[0171] 10 protrusion on 8 h height of protrusion

[0172] 11 indentation in 9

Claims

CLAIMS1. Method of producing an embossed sorbent sheet (2) for use in 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 said sorbent structure adsorbing said gaseous carbon dioxide, wherein the method comprises the following steps: provision of a thermoplastic sheet (1) of sorbent material comprising at least one of particles, fibers and a coating of a material adsorbing said gaseous carbon dioxide, subjecting said thermoplastic sheet (1) to a temperature in the range of 50-300°C and embossing at least one protrusion (5) into said thermoplastic sheet (1) to form an embossed sorbent sheet (2).

2. Method according to claim 1 , wherein said particles, fibers and a coating of a material adsorbing said gaseous carbon dioxide are particles, fibers or a coating of a material functionalized with primary or secondary or tertiary amines, or a combination thereof, capable of reversibly binding carbon dioxide, or wherein said thermoplastic sheet (1) comprises or consists of at least one heat- treated or sintered or extruded or wet-laid porous structure from a mixture of first particles and / or fibres of support material functionalized with primary or secondary or tertiary amines, or a combination thereof, capable of reversibly binding carbon dioxide, with thermoplastic second particles and / or fibres different from the first particles and not functionalized with primary or secondary or tertiary amines, including bi- and multicomponent fibers and / or particles, or wherein said thermoplastic sheet (1) comprises or consists of at least one layered and / or fibrous support material coated and / or impregnated and / or functionalized with primary or secondary or tertiary amines, or a combination thereof, or wherein said thermoplastic sheet (1) comprises or consists of at least one layered and / or fibrous support material coated and / or impregnated with particles and / or fibres of support material functionalized with primary or secondary or tertiary amines, or a combination thereof, capable of reversibly binding carbon dioxide.

3. Method according to any of the preceding claims, wherein embossing takes place batch wise in a mold / die comprising an interior cavity structure with mold / dieindentations / corresponding mold / die protrusions embossing the protrusions, and / or wherein embossing takes place in a continuous process between at least two rolls and / or belts, preferably heated rolls and / or belts, with roll / belt indentations / corresponding roll / belt protrusions embossing the protrusions.

4. Method according to any of the preceding claims, wherein the thermoplastic sheet (1) during embossing is subjected to a temperature in the range of 60-240°C or 60- 180°C or 80-160°C, preferably in the range of 100-140°C, and / or wherein a multitude of more than two, or more than 5, or more than 10, or more than 20 protrusions (5) or more than 100, or more than 500, or more than 1000 protrusions (5) per sheet are formed in the embossing step, wherein the protrusions (5) are preferably arranged regularly and / or wherein further preferably the protrusions (5) are pointing all in one direction or are pointing, preferably alternatingly, in opposite directions, and wherein further preferably the protrusions (5) take the form of point wise protrusions (5) or pleating, with sharp or rounded edges, and wherein further preferably essentially the full surface of the sheet is provided with a pattern of protrusions (5), and / or wherein an embossing density in the range of 20 - 40000 protrusions per m2, preferably in the range of 50-5000 protrusions per m2, more preferably in the range of 100-3000 or 300-2000 protrusions per m2 or 500-1000 protrusions per m2.

5. Method according to any of the preceding claims, wherein at least two embossed sheets (2) are obtained in the method batch wise or in a continuous process, combined with cutting as needed, and wherein they are assembled in an adsorber structure (6) in an essentially parallel arrangement of said embossed sheets (2), in which the protrusions (5) of said embossed sheets (2) are not overlapping, seen in a direction perpendicular to the planes of the sheets (2), such that the protrusions (5) of said embossed sheets (2) are contacting the flat portions of the other contacting sheet, and the distance between said embossed sheets (2) is defined by the height of the protrusions (5).

6. Method according to any of the preceding claims, wherein alternatingly sheets (1) without protrusions and embossed sheets (2) with bidirectional protrusions are arranged in the absorber structure, wherein preferably an arrangement of at least two sheets is rolled to form a rolled adsorber structure, or wherein sheets with monodirectional protrusions are arranged all with protrusions pointing in the same direction, wherein preferably at least one sheet or an arrangement of several sheets is rolled to form a rolled adsorber structure.

7. Method according to any of the preceding claims 5 or 6, wherein the sheets are oriented in a vertical direction and wherein the protrusions have a length in an airflow direction which is less than 20 cm or less than 5 cm or less than 3 cm or less than 1 cm, and / or have a length perpendicular to the airflow direction which is less than 5 cm or less than 3 cm or less than 1 cm or less than 0.5 cm.

8. Method according to any of the preceding claims 5 - 7, wherein the protrusions in each of the sheets have the same shape, and are preferably bell-shaped or dome-shaped or tear-shaped or wing-shaped or drop-shaped or in the form of bridge- like / pleated protrusions or protrusions with cutouts.

9. Method according to any of the preceding claims 5-8, wherein an arrangement of at least 4 or at least 8 or at least 12 or at least 20 sheets is arranged in one adsorber structure (6) which further comprises a cage, preferably a cage with walls parallel to the airflow direction which are air impermeable and air permeable walls perpendicular to the airflow direction or without walls perpendicular to the airflow direction.

10. Method according to any of the preceding claims, wherein the embossed sheet is attached to at least one further embossed or non-embossed sheet by way of the protrusions of the embossed sheet being attached to the further embossed or nonembossed sheet, wherein the attachment can be by way of force fit, by way of form fit, by way of adhesive bonding, or a combination thereof.

11. Method according to any of the preceding claims, wherein the embossing / forming features (10,11) in each mold / roller / die / belt have a protruded surrounding platform (14,15) to only allow punctual heating and hence to avoid unwanted heating of material that is not to be deformed, and / or wherein an isolating material around the forming feature surrounding platforms (14,15) is placed to furthermore avoid unwanted heating of material that is not to be deformed.

12. Method according to any of the preceding claims, wherein there is provided a multitude of more than two, or more than 5, or more than 10, or more than 20 protrusions (5) or more than 100, and wherein the protrusions (5) take the form of point wise protrusions (5) or the protrusions (5) have a length of which are smaller than a maximum extension ofsaid sheet (2), preferably the length of which are at most one third of said maximum extension of said sheet (2).

13. Embossed sorbent sheet (2) obtained using a method according to any of the preceding claims 1-4 or at least two embossed sheets (2) obtained using a method according to any of the preceding claims 5-12.

14. Adsorber structure (6) with at least one or at least two embossed sorbent sheet (2) according to claim 13, preferably with at least two embossed sheets (2) obtained using a method according to any of claims 5-12.

15. Adsorber structure (6) according to claim 14, wherein it comprises an arrangement of at least 4 or at least 8 or at least 12 or at least 20 sheets in a cage, preferably a cage with walls parallel to the airflow direction which are air impermeable and air permeable walls perpendicular to the airflow direction or without walls perpendicular to the airflow direction.

16. 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 an adsorber structure (6) according to any of claims 13 or 14 adsorbing said gaseous carbon dioxide in a unit, wherein the method comprises at least the following sequential and in this sequence repeating steps (a) - (e):(a) contacting said gas mixture with the adsorber structure (6) to allow at least said gaseous carbon dioxide to adsorb on the adsorber structure (6) by flow-through through said unit essentially under ambient atmospheric pressure conditions and ambient atmospheric temperature conditions in an adsorption step;(b) isolating said adsorber structure (6) with adsorbed carbon dioxide in said unit from said flow-through;(c) inducing an increase of the temperature of the adsorber structure (6), preferably to a temperature between 60 and 110°C, starting the desorption of CO2;(d) extracting at least the desorbed gaseous carbon dioxide from the unit and separating gaseous carbon dioxide in or downstream of the unit;(e) optionally bringing the adsorber structure (6) essentially to ambient atmospheric temperature conditions and ambient atmospheric pressure conditions.

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