Carbon-fiber moldings

Abstract

The present invention relates to carbon-fiber moldings, a method for the production thereof, the use of the carbon-fiber moldings in particular in the cleaning, enrichment, adsorption, removal or generation of gases, to gas adsorption devices which use carbon-fiber moldings, and to methods for enriching, adsorbing, removing or generating gases using the carbon-fiber moldings.

Description

[0001] Carbon fiber molded body

[0002] Description

[0003] The present invention relates to carbon fiber molded bodies, processes for their production, the use of the carbon fiber molded bodies, in particular in the purification, enrichment, adsorption, separation or recovery of gases, gas adsorption devices which use the carbon fiber molded bodies, and processes for the enrichment, adsorption, separation or recovery of gases using the carbon fiber molded bodies.

[0004] Technical background / state of the art

[0005] Gas mixtures of different compositions and origins can be separated in flow by reversible gas adsorption on suitable solids (adsorbents) to obtain pure gases or to remove impurities. For gas separation, the gas component in question (adsorbate) or, conversely, all other gas components adsorb onto the adsorbent of a gas separation device (adsorber column) and are thus removed from the gas stream to be separated. Mechanistically, the adsorbate coats the surface of the adsorbent, driven by weak chemical or physical interaction, until the surface of the adsorbent is saturated. The adsorbent can then be regenerated by thermal and / or physical processes. By changing the temperature and / or pressure and / or by electrical current, the adsorbate is released from the adsorbent with the inflow of the gas mixture switched off, and the isolated adsorbate is further processed in a downstream technical system.For efficient practical application, the adsorbent must meet several requirements. These include high adsorption selectivity for the target component, reversibility of the adsorption process, material tolerance to all gas components and especially to impurities, a high mass- and volume-specific adsorption volume for the adsorbed species, and the lowest possible pressure drop across the adsorbent packing in the adsorber column.

[0006] The separation of gas mixtures can be achieved using various processes and materials. Among the possible processes, distillation, membrane separation, and adsorptive gas separation are particularly worth mentioning. In the area of ​​adsorptive gas separation, several material classes are potentially suitable for the implementation of the application, which, depending on the material, exhibit specific selectivities towards the gas species to be separated. The most important material classes are metal-organic frameworks (MOFs), zeolites, and carbons, which can have a high adsorption capacity for gases and liquids, particularly due to their high specific surface area. A more precise specification of the materials and their application depends in particular on their chemical composition, the manufacturing process, and the dosage form. In the area of ​​carbons, some materials are known that exhibit high selectivity for specific gases, such asCO2 or CH4. After their actual production, these materials often undergo chemical or physical, and sometimes complex, activation processes until they achieve the desired material properties. Typical forms of carbon are loose powder beds or pressed molded bodies, which are placed in the adsorption columns for gas adsorption. Extrusion processes are sometimes used to produce molded bodies, in which the carbon is processed together with a binder in order to achieve a higher packing density and a lower pressure drop across the adsorption material in the adsorption column. In English-speaking countries, this is also referred to as "extruded active carbon."

[0007] Despite its potential, adsorptive gas separation has so far only been used on a large scale for a few applications for the separation of gases, and in particular not for the separation of CO2 or CH4, e.g., from combustion exhaust gases or biogas (counterexample: air separation). The reason for this is that none of the possible material classes fully meets all material requirements (specific adsorption volume, selectivity, reversibility, stability towards impurities, etc.) from an economic and / or practical perspective. MOFs generally have very good specific adsorption volumes and very good selectivities, but are too expensive for widespread application due to the materials used. Zeolites are inexpensive in comparison, but usually have a high affinity for water or moisture, which impairs the adsorption of other gases.Carbons can be produced very inexpensively using simple processes and are stable towards water and moisture. However, with simple production processes, they usually have too low adsorption selectivity and / or capacity for gases in the adsorption column to make them practically useful for adsorptive gas separation. The carbon fiber molded bodies proposed here offer a solution in this regard.

[0008] WO 2020 / 249441 A1 discloses a process for producing a carbon fiber material, comprising the steps of: a) preparing a solution of polyacrylonitrile in a suitable organic solvent b) electrospinning the solution obtained in a) and drying the resulting fiber material c) crosslinking the resulting fiber material by heating to 150 to 350°C in an air or oxygen atmosphere for 1 to 30 minutes hd) carbonizing the resulting fiber material in a protective gas atmosphere at a temperature in the range of 500 to 2,500°C. In particular, in WO 2020 / 249441 A1, nanofiber mats are obtained during electrospinning, but these are not processed into molded bodies.Although the carbon fiber materials obtained according to WO 2020 / 249441 A1 exhibit a high selective, reversible adsorption capacity for various gases at low relative pressures, they are disadvantageous in handling and for use in adsorption devices such as gas adsorption columns because the fibers are very light and electrostatically charged, making them difficult to flow or pour. Furthermore, their adsorption capacity relative to the volume of the adsorption devices is too low in practice due to their low bulk density. A bed of these fibers or fiber mats in an adsorption column leads to considerable flow resistance during gas flow and thus a significant pressure drop along the column, which is highly disadvantageous for application in common gas separation processes such as PSA or TSA.

[0009] Similarly, in DE102017127629 A1, DE102015106348A1 and DE3600063C2, carbon fiber materials are obtained by melt extrusion or melt spinning, respectively, which, however, are also not further processed into molded bodies and, due to their large fiber diameter, have a small surface area relative to their mass.

[0010] EP 2902433A1 discloses a carbon fiber pellet production process comprising cutting and / or grinding the carbon fibers to be processed into pellets to a predetermined length, mixing the carbon fibers with a solution or suspension as a sizing agent to form agglomerates in a mixer, compacting the agglomerates by contacting the agglomerates with an inclined rotating surface, and drying the agglomerates to form carbon fiber pellets. Surprisingly, it was found that pyrolyzing the carbon fibers prior to mixing results in the carbon fiber pellets being particularly free-flowing and easy to handle. The pyrolyzing step, as well as the cutting step before or after, is achieved by recycling carbon fiber composites into carbon fibers. The carbon fiber pellets produced in this way are used as modifiers for plastics or elastomers of all kinds.An application as a gas adsorption material is not described.

[0011] Task

[0012] The inventors of this patent application were faced with the task of providing a carbon fiber material that, in addition to a high selective and reversible adsorption capacity for a wide variety of gases, particularly at low relative pressures, also possesses excellent handling properties such as flowability and pourability, and, relative to its bulk volume, a high adsorption capacity. The carbon fiber material should also enable the selective adsorption of various gases from gas mixtures, high stability of gas adsorption or separation performance, adjustable selectivity, and a high volume-specific adsorption capacity with a low pressure drop in an adsorption column.

[0013] Starting from the carbon fiber materials described in WO 2020 / 249441 A1, the inventors of the present patent application developed a process for producing porous carbon fiber molded bodies, such as in particular pellets, which can be obtained from the carbon fiber materials described in WO 2020 / 249441 A1, which arise as fiber mats (carbon fiber intermediates), by a suitable agglomeration or molding process and subsequent subjection to carbonization.It was surprisingly found that the carbon fiber molded bodies according to the invention retain the high selective and reversible adsorption capacity for a large number of gases, in particular even at low relative pressures of the carbon fiber materials produced directly from the carbon fiber intermediates (without prior molding), and in addition also have excellent handleability, such as flowability and pourability, and, based on their bulk volume, also have a significantly higher adsorption capacity than molded bodies made from carbon fiber intermediates that are not subjected to carbonization after their formation.

[0014] As explained further below with regard to the effects demonstrated in the examples and figures, it is particularly advantageous according to the invention if a non-carbonized, preferably already thermally stabilized carbon fiber material is subjected to an agglomeration or shaping process as a carbon fiber intermediate, and the resulting molded body is subsequently subjected to carbonization. Thus, the molded bodies according to the invention thus obtained exhibit a significantly more ordered and thus denser arrangement of the fibers than comparative samples made of already carbonized carbon fiber material, which leads to a significant increase in the adsorption capacity relative to the volume of the molded bodies according to the invention.Furthermore, it was surprising that carbonization after the production of the molded bodies with a polymeric binder did not lead to a reduction in gas adsorption, since the polymeric binder apparently did not close the ultramicropores of the carbon fibers in the carbon fiber molded bodies, which are essentially responsible for the gas adsorption capacity.

[0015] Subject of the invention

[0016] The present patent application thus solves the aforementioned problems by providing carbon fiber molded bodies that are obtainable by a process that includes the step of carbonization after the production of the molded body from one or more carbon fiber intermediates. The process for producing the molded bodies according to the invention thus initially involves the production of a molded body from a carbon fiber intermediate and the subsequent carbonization of the resulting molded body.

[0017] The invention thus relates to carbon fiber molded bodies as shown, for example, in Figure 1, which are obtainable by a process which comprises the step of carbonization after the production of a molded body from one or more carbon fiber intermediates.

[0018] As explained above, the step of carbonizing the molded bodies, or after the formation of the molded bodies, leads to an improvement in the adsorption capacity based on both the mass and the volume of the molded bodies. As a result of the process used to produce the molded bodies according to the invention, carbon fiber molded bodies are obtained which have outstanding adsorption properties with respect to various gases, which are variable, for example, depending on the carbonization temperature in the carbonization step. In particular, molded bodies with significantly increased packing densities of the carbon fibers are obtained when non-carbonized carbon fiber materials are used as the carbon fiber intermediate in the formation of the molded bodies. Particularly suitable molded bodies are therefore obtained from non-carbonized carbon fiber materials as the carbon fiber intermediate.The shaped bodies according to the invention exhibit a reduced pressure drop and an improved volume-specific adsorption capacity in a given adsorber column compared to carbon fibers not processed into shaped bodies. Furthermore, the shaped bodies according to the invention exhibit an improved mass-specific adsorption capacity in a given adsorber column compared to non-recarbonized shaped bodies. Despite the carbonization at the level of the shaped bodies, the carbonized carbon fibers obtained therein retain their carbonization temperature-dependent adsorption properties. Furthermore, the shaped bodies produced according to the invention exhibit the inherent properties of carbons for gas adsorption, i.e., comparatively low production costs and stability against moisture.The shaping during the production of the molded bodies according to the invention also results in a significant improvement in the handling of the material for producing adsorbent beds, i.e., in particular, improved abrasion resistance and transferability or flowability. Carbonization after shaping or formation of the molded bodies from the carbon fiber intermediate, particularly when shaping is carried out with non-carbonized carbon fibers as the carbon fiber intermediate, results in a material that, after carbonization, exhibits the adsorption properties of the carbon fibers contained therein, but is more densely packed overall. This results in a lower pressure drop across a bed of the molded bodies and a higher volume-specific adsorption capacity in the adsorber column.The molded bodies according to the invention are particularly advantageous if carbon fibers that are not already carbonized are used in their production, which leads to a significant increase in the packing density and thus in the volume-specific adsorption properties, and requires only one carbonization step after the molded body has been produced. In this preferred embodiment of the carbon fiber molded bodies according to the invention, a non-carbonized carbon fiber material is therefore used as the carbon fiber intermediate used to produce the molded bodies, i.e., a carbon fiber material that has not yet been subjected to carbonization (or pyrolysis), i.e., the known conversion of the starting carbon fiber material consisting of organic polymers to carbon.As the comparison of the SEM images in Figure 2 shows, molded bodies produced in this way surprisingly exhibit a much more ordered and dense arrangement of the fibers than those made using already carbonized carbon fibers. This leads, as shown in Figure 3, to a significant increase in the adsorption capacity relative to the volume of the molded bodies, and thus to a significant increase in the bulk density of the molded bodies in a given bulk volume for a given molded body shape. In addition to these surprising properties, this embodiment also makes it possible to dispense with the use of already carbonized carbon fibers, and carbonization only takes place at the level of the molded bodies or after the molded bodies have been formed.This avoids a double carbonization (i.e. at the stage of the carbon fiber intermediate stage and at the stage of the molded bodies) and the carbonization step is also facilitated due to the better handling of the molded bodies in contrast to the fibers that have not yet been subjected to carbonization.

[0019] Even if an already carbonized carbon fiber material is used as a carbon fiber intermediate in the formation of the molded bodies, its carbonization leads to an improvement in the adsorption capacity relative to the mass of the molded bodies according to the invention, and the relevant pores are not closed by the binder material.

[0020] In a preferred embodiment of the invention, the carbon fiber intermediate used is obtained by subjecting one or more polymers capable of carbonization to a fiber-forming process, such as spinning, wet spinning, dry-jet wet spinning, dry spinning, melt spinning, or electrospinning, preferably electrospinning. Such fiber-forming processes are known per se from the prior art (see, for example, Macromol. Mater. Eng. 2012, 297, 493-501; Pratima Bajpai, Carbon Fiber (Second Edition), Elsevier, 2021, J Mater Sci (2014) 49:463-480, or the aforementioned WO 2020 / 249441 A1, DE102017127629 A1, DE102015106 348A1, and DE3600063C2). In a preferred embodiment of the invention, the carbon fiber intermediate used is obtained by electrospinning a solution of one or more polymers capable of carbonization.

[0021] Preferred carbonization-capable polymers are selected in particular from the group consisting of synthetic polymers such as polyacrylonitrile, polyimides, polyetherimides, polyfurfuryl alcohols, phenolic resins, polyvinyl alcohols, and mixtures thereof. Particularly preferred is the carbonization-capable polymer polyacrylonitrile. Such polymers are commercially available.

[0022] The polyacrylonitrile particularly preferably used for electrospinning according to the invention preferably has one or more of the following features:

[0023] - polyacrylonitrile homopolymer or polyacrylonitrile copolymer with a comonomer content of 1 to 10 wt.%,

[0024] - Molecular weight in g / mol from 50,000 to 300,000, preferably 100,000 to 250,000.

[0025] The molecular weight here and in the following is in particular a number-average molecular weight determined by gel permeation chromatography with polystyrene as standard.

[0026] The carbon fiber intermediate is preferably obtained by electrospinning a solution of one or more polymers capable of carbonization, wherein the solvent is preferably selected from water and organic solvents, such as in particular amides such as dimethylformamide, dimethylacetamide, ketones such as acetone, methyl ethyl ketone, alcohols such as ethanol, and mixtures thereof, including mixtures of water and organic solvents and mixtures of organic solvents.

[0027] The preferred polyacrylonitrile (PAN) used in the fiber formation process, in particular electrospinning, is a PAN homopolymer or a PAN copolymer with up to approximately 1 to 10 wt.% of one or more comonomers. Suitable comonomers include, for example, acrylic acid, methacrylic acid, itaconic acid, and / or acrylamide. The PAN is either commercially available (e.g. from Sigma-Aldrich, Dolan GmbH, or BOC Sciences) or can be produced in a conventional manner. The molecular weight of the PAN polymer in g / mol is preferably 50,000 to 300,000, preferably 100,000 to 250,000, particularly preferably 150,000 or 200,000. Practically any organic solvent that can dissolve the polymer capable of carbonization, such as PAN, can be used as the organic solvent in electrospinning. Polar organic solvents, such as, for example,Dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAC), acetone, methyl ethyl ketone, alcohols such as ethanol, or mixtures thereof are suitable. DMF is particularly suitable. Water or mixtures of water with organic solvents can also be used. The PAN solution used in the fiber formation process, preferably by spinning, preferably has a concentration of 1 to 20 wt. %, more preferably 3 to 15 wt. %, particularly preferably 5 to 10 wt. %. It is prepared, for example, by adding the PAN to the solvent and stirring, optionally with heating, until the PAN is completely dissolved (visual control). Stirring is carried out, for example, at room temperature for 2 days.

[0028] Particularly preferably, the solution used in electrospinning consists only of the solvent and polyacrylonitrile, preferably of dimethylformamide and polyacrylonitrile.

[0029] In the electrospinning fiber formation process preferred according to the invention, electrically charged threads are drawn from polymer solutions or polymer melts in a conventional manner to a fiber diameter of a few hundred nanometers. The process requires neither the use of coagulation chemistry nor high temperatures to produce solid threads from the solution. This makes the electrospinning process particularly suitable for the production of fibers from large and complex molecules.

[0030] According to the invention, both needle electrospinning and needleless electrospinning processes can be used for the electrospinning step. Needle electrospinning processes operate with one or more needles, which can be arranged in different ways. Coaxial needles can also be used, which allow the production of core-shell fibers or wet the spun thread with solvent to stabilize the spinning process. Needleless electrospinning requires an open surface of a solution in the electric field. This can be provided as a slit in an open vessel for better process control or by wetting a cylinder or sphere (see, for example, Processes 2020, 8(6), 673; https: / / doi.org / 10.3390 / pr8060673; Advanced Materials Technologies 2021, 6(11), 2100410, DOI: 10.1002 / admt.202100410).

[0031] In one embodiment of the invention, electrospinning is carried out using a needle electrospinning process. The standard laboratory apparatus for needle electrospinning consists of a spinneret (typically one or more injection needles), for example, 4 or 16 needles, connected to a high-voltage direct current supply (e.g., 5 to 100 kV), a syringe pump, and a collector, which can be grounded or operated at negative voltages of several kV. A polymer solution, sol-gel, particulate suspension, or melt is loaded into the syringe, and this liquid is extruded from the needle tip by a syringe pump at a constant velocity. Alternatively, the droplet at the tip of the spinneret can be replenished by feeding from a collector tank at a constant discharge pressure. This constant-pressure delivery works better for low-viscosity feedstocks.When a sufficiently high voltage is applied to a liquid droplet, the liquid body becomes charged, and electrostatic attraction counteracts the surface tension, stretching the droplet; at a critical point, a liquid stream erupts from the surface. This breakout point is known as the Taylor cone. If the molecular cohesion of the liquid is sufficiently high, stalling does not occur (if it does, the droplets are electrosprayed), and a charged liquid jet is formed. As the jet dries in flight, the mode of current flow changes from resistive to convective as the charge migrates to the surface of the fiber. The jet is then elongated by bending instabilities triggered by electrostatic repulsion at small bends in the fiber until it is finally deposited on the collector.The resulting elongation and thinning of the fiber leads to the formation of uniform fibers with nanometer diameters. In a particular embodiment of the invention, the collector rotates, while the needles are also moved laterally back and forth in a horizontal orientation, resulting in a uniform thickness of the fiber mat, which is collected on the collector during the electrospinning process. Drying the fiber during spinning creates chaotic movement of the fiber and thus a disordered deposition of the spun fibers in the fiber mat. The collector can be, for example, a plate or a drum, or even (in large-scale systems) a moving mat.

[0032] In one embodiment of the invention, a standard process is used for electrospinning. For example, a needle electrospinner, e.g. from IME Technologies, is used at 10 to 60%, preferably 15 to 35%, particularly preferably 20 or 30% relative humidity and 20 to 50 °C, preferably 25 °C. However, the ambient parameters have no significant influence on the properties of the carbon fiber material obtained after the subsequent carbonization. The flow rate of the polymer solution during electrospinning is, for example, 20 to 60, preferably 30 to 50 and particularly preferably 40 pl / min per needle used, the volume 1.5 to 20 ml, preferably 2 to 15 ml. The spinning time depends on the initial polymer volume and is, for example, 1 h or 2 h for 2.2 ml and 6 h for 14.6 ml. The voltage is, for example, 21 kV at the anode and -4 kV at the cathode. The collector rotates at 1000 to 2000 rpm, preferably 1500 rpm.The needle-collector distance is, for example, 100 to 200 mm, preferably 130 to 190 mm, in particular 140 or 180 mm. The inner needle diameter is, for example, 0.5 to 1 mm, preferably 0.7 to 0.9 mm, in particular 0.8 mm. The lateral movement of the needle in a horizontal orientation occurs over a total distance of 80 to 150 mm, preferably 90 to 130 mm, particularly preferably 100 or 120 mm. The speed of the lateral needle movement is, for example, 20 mm / s, and the reversal delay is, for example, 500 ms. In this way, a fiber mat is obtained.

[0033] Particular preference is given to using the process described in WO 2020 / 249441, to which reference is made in its entirety. According to the invention, the fiber mat obtained by electrospinning is preferably first dried, e.g. at 25°C to 200°C, preferably approximately 150°C, for 1 to 24 hours, preferably 1 to 2 hours, particularly preferably for approximately 1 hour in an air atmosphere. It is then preferably stabilized in an air or oxygen atmosphere, e.g. at 150 to 300°C, preferably 180 to 300°C, particularly preferably 250°C, preferably for 1 to 24 hours, particularly preferably overnight, preferably at heating rates of 1 to 10 K / min. In this way, a stabilized fiber mat, the carbon fiber intermediate, is obtained, which can be used particularly preferably for producing the molded bodies according to the invention.

[0034] The fiber material obtained during electrospinning and preferably dried as described above is preferably crosslinked (or stabilized) by heating, e.g., at approximately 250°C for 3 to 30 hours, preferably 8 to 20 hours, even more preferably overnight. When using PAN, heating results in the cyclization shown schematically in Figure 7, resulting in crosslinking of the polymer chains in the fibers, which stabilizes the PAN fibers. Furthermore, surface oxidation and partial elimination of nitrogen compounds occur during crosslinking.

[0035] A preferred carbon fiber intermediate is obtained as a stabilized fiber mat after electropinning and crosslinking. The thickness of the fiber mat obtained after the crosslinking or stabilization step, when produced on a laboratory scale, is typically 100 to 2000 μm, preferably 400 to 1000 μm, more preferably 600 to 900 μm, and most preferably 800 μm, depending on the spinning time. However, the size and thickness of the fiber mat can be adjusted to much larger values ​​after adjusting the electrospinning system.

[0036] The carbon fiber intermediate obtained by the fiber formation process preferably has fibers with an average fiber diameter in the range of about 5 to about 100,000 nm, preferably from about 10 nm to 10,000 nm, more preferably from about 20 nm to about 1,000 nm. This average fiber diameter can be determined, for example, by scanning electron microscopy (SEM), for example according to the method described in Biomaterials Volume 61, August 2015, pages 327-338. The average fiber diameter is determined using scanning electron microscopy (SEM) and the ImageJ® software and is based, for example, on average values ​​from 20-30 measurements.

[0037] The fiber material obtained as explained above exhibits particularly good gas adsorption properties after its carbonization, particularly depending on the carbonization temperature, i.e., a gas molecule size-selective gas adsorption capacity, wherein, in particular, neither surface modification nor surface activation of the fibers after the fiber formation process by treatment with chemical reagents and / or application of tensile stress is necessary to achieve these properties. The fiber material obtained after the fiber formation process is, after its carbonization, particularly porous with pores of various sizes, with ultramicropores (pore size < 0.35 nm) representing the largest proportion of the pores present in the fibers, while fewer mesopores or macropores are present. Figure 4, for example, shows the cumulative pore size distribution of a molded body particularly preferred according to the invention.Regardless of the further processing of the non-carbonized fibers, it has surprisingly been shown that the aforementioned gas adsorption properties of the carbon fibers obtained, in particular by electrospinning, are retained even after carbonization of the resulting molded bodies, and the added binder apparently does not close the ultramicropores. The molded bodies produced as described below accordingly retain the carbonization temperature-dependent adsorption properties described for the carbonized fibers.

[0038] The pore size of the pores in the fibers of the carbon fiber molded bodies according to the invention is defined here, for example, as in the IUPAC Technical Report (https: / / doi.org / 10.1515 / pac-2014-1117; part 2, general definitions and terminology). It is:

[0039] Ultramicropores < 0.7 nm

[0040] Micropores < 2 nm

[0041] Mesopores 2-50 nm

[0042] Macropores > 50 nm.

[0043] In a preferred embodiment, the carbon fiber intermediate obtained in the fiber formation process, for example, a stabilized fiber mat obtained by electrospinning, is optionally subjected to a comminution step. In this comminution step, the preferably stabilized fiber mat is comminuted, for example, using a knife mill. During comminution, the carbon fiber intermediate is obtained as a coarse powder consisting of agglomerated fiber pieces. The length of the resulting fiber pieces is preferably on average about 1 to about 50 μm, preferably about 1 to about 15 μm.

[0044] The production of the carbon fiber molded bodies preferably takes place following the production of the carbon fiber intermediate, preferably by subjecting a dispersion of the comminuted carbon fiber intermediate in a dispersing medium to an agglomeration or shaping process. In principle, all known processes for forming molded bodies from dispersions can be used. In particular, this involves an agglomeration process in which the bulk density of the carbon fiber intermediate is increased. Particularly preferably, the molded bodies of the carbon fiber intermediate are obtained by extruding a dispersion of the comminuted carbon fiber intermediate in a dispersing medium through a die, followed by drying and dividing the extruded strand.Alternatively, it is also possible to obtain the shaped bodies of the carbon fiber intermediate, for example, by granulating the carbon fiber intermediate, preferably by wet granulation of a dispersion of the comminuted carbon fiber intermediate in a dispersing medium, as described, for example, in EP2902433A1. Such processes are known per se from the prior art.

[0045] For example, conventional processes such as those used to produce pharmaceutical pellets can be used (see, for example, Peter Kleinebudde, "Pharmaceutical Pellets - Production, Properties and Application," Yearbook of the Heinrich Heine University Düsseldorf, 2003). These include moist extrusion at room temperature (approximately 23°C) with a liquid dispersing medium, followed, if necessary, by solidifying the extrudate by removing the dispersing medium in a drying step. The extrudate strands can, for example, be cut into cylindrical pellets or rounded in a subsequent step. Conventional machine types are available for extrusion, such as piston, perforated shell, and screw extruders, as well as single-screw or twin-screw extruders.By adjusting the extrusion parameters, such as the carbon fiber intermediate dosing rates, dispersing medium, liquid dosing rate, and extruder screw speed, the properties of the extrudate and the resulting molded articles or extrudates can be influenced. The extrusion process is preferably carried out continuously.

[0046] Furthermore, it is also possible to pour or inject the dispersions of the carbon fiber intermediate in the dispersing medium into molds, for example made of plastics such as Teflon, and to dry the resulting molded bodies if necessary and then subject them to carbonization.

[0047] In a preferred embodiment, the shaped bodies of the carbon fiber intermediate are obtained by a process in which a dispersion of the comminuted carbon fiber intermediate in a dispersing medium is subjected to an agglomeration or shaping process, wherein the dispersing medium preferably contains one or more polymeric binders. The dispersing medium used is preferably selected from water or organic solvents, in particular amides such as dimethylformamide, dimethylacetamide, ketones such as acetone, methyl ethyl ketone, alcohols such as ethanol, and mixtures thereof, including mixtures of water and organic solvents and mixtures of organic solvents. In principle, the same solvents as described for electrospinning can be used.The polymeric binders mentioned are preferably selected from the group of polymers capable of carbonization, as already described in the fiber-forming process, and which are selected from the group consisting of: synthetic polymers, such as polyacrylonitrile, polyimides, polyetherimides, polyfurfuryl alcohols, phenolic resins, polyvinyl alcohols, and mixtures thereof, preferably polyacrylonitrile. Such polymers are commercially available. In a particularly preferred embodiment, the polymeric binder used in the agglomeration or molding process corresponds to the polymer used for the production of the carbon fiber intermediate, as described above.Therefore, it is particularly preferred to use a polyacrylonitrile as a polymeric binder in the agglomeration or forming process, and in the production of the carbon fiber intermediate in the fiber formation process, a polyacrylonitrile is also used as a polymer capable of carbonization.

[0048] In one embodiment, it is also possible to use a preferably low-molecular-weight oligomeric or polymeric binder as the sole dispersing medium, which is suitable for dispersing the carbon fiber intermediate in the shaping process, such as the extrusion process. It is also possible to dispense with drying the extrudates and subject them directly to carbonization. The low-molecular-weight oligomeric or polymeric binders are expediently the polymeric binders as described above, but they are expediently selected such that they are liquid during shaping, preferably at room temperature.

[0049] According to the invention, the carbon fiber molded bodies obtained from the carbon fiber intermediate in the agglomeration or molding process are subjected to carbonization. The molded body of the carbon fiber intermediate is carbonized, preferably at a temperature in the range of approximately 400 to approximately 2500°C, preferably in the range of approximately 500 to approximately 1800°C, and more preferably in the range of approximately 500 to approximately 1500°C, under an inert gas atmosphere.

[0050] The carbonization of the molded bodies or the carbon fiber intermediates contained therein represents an essential step in achieving the desired properties of the carbon fiber molded bodies of the invention. The carbonization temperature, in particular, is an important parameter. It is comparatively easy to adjust and control and has a significant influence on the exact size of the ultramicropores in the fibers. Carbonization involves pyrolysis. For example, the polyacrylonitrile fibers are converted through cyclization, dehydrogenation, and N2 elimination, as schematically shown in Figure 7.

[0051] Cyclization can partially occur during the crosslinking or stabilization step. Depending on the progress of the carbonization reactions, nitrogen atoms can be present on the fiber surface in different hybridization states. These can be determined, for example, by XPS (X-ray photoelectron spectroscopy).

[0052] The carbonization temperatures can also depend on the type of carbon fibers used, i.e., on the choice of the polymer capable of carbonization. According to the invention, preference is given, for example, to carbonizing the carbon fiber moldings in an oven at 400 to 2500°C, preferably 500 to 1800°C, more preferably 500 to 1500°C, and particularly preferably at approximately 600 to 1000°C. Alternatively, carbonization can also be carried out using laser or IR heating or microwave treatment. The type of heating is less important, but care must be taken to maintain the temperatures during carbonization in order to achieve the desired adsorption properties of the fiber material or the moldings produced therefrom. For example, the pore size of the pores in the fibers decreases from low to higher carbonization temperatures.Above a carbonization temperature of 850 °C, for example, the pore size, starting with polyacrylonitrile (PAN) as a polymer capable of carbonization, can become too small, so that CO2 or NH3, for example, can no longer diffuse sufficiently into the pores of the carbon fibers. As a result, from this temperature onwards a sudden change in the adsorption properties of the material with regard to CO2 or NH3 can be observed. Therefore, a carbonization temperature of 800 to 850 °C is particularly suitable for adjusting the adsorption properties of the carbon fiber molded bodies starting from PAN for the selective adsorption of CO2 or NH3, in particular from a gas mixture, since after carbonization at temperatures of 800 to 850 °C CO2 or NH3 still adsorb well, but the pores of the fiber material are already too small for larger molecules such as CH4 or N2.In this way, for example, CO2 or NH3 can be selectively removed from a gas mixture of, for example, CO2 or NH3 with, for example, CH4 or N2 by adsorption on the carbon fiber moldings. In each individual case, the carbonization temperatures for a given fiber material and the adsorption of the desired gas must be determined or optimized.

[0053] For carbon fiber moldings based on PAN fiber material preferred according to the invention and for the adsorption of CO2, carbonization temperatures of less than 1000 °C are therefore preferred, even more preferably less than 900 °C. Carbonization of PAN fiber materials is particularly preferably carried out in the range from 600 to 850 °C in order to generate a significant proportion of pores with a pore diameter of < 0.35 nm, especially if carbon dioxide is to be absorbed. The following list provides examples of particularly preferred carbonization temperatures for the carbonization of PAN fiber materials depending on the application. The conductivity of the fibers in the resulting carbon fiber moldings also depends on the carbonization temperature. For example, the electrical conductivity during the carbonization of PAN fiber materials in the temperature range from 800 to 850 °C is higher than, for example,during carbonization at 600 °C or 700 °C, which makes the material obtained at 800 to 850 °C particularly suitable for use in electric swing adsorption, in which the adsorbent is regenerated by applying an electric current. Here, too, the appropriate conductivities can be determined or optimized by selecting suitable carbonization temperatures for given fiber materials and adsorbing the desired gas.

[0054] The carbonization of the carbon fiber moldings carried out according to the invention is carried out under a protective gas (inert gas). Suitable gases include nitrogen, argon, or helium, with argon being most preferred. The protective gas can be introduced into the furnace, for example, and a gas flow can be maintained throughout the reaction time. Before carbonization, the furnace is preferably evacuated and flooded with a protective gas, such as argon, to prevent the entry of air. The atmosphere in the furnace is as free as possible from O2 and CO2 by means of a protective gas atmosphere. According to the invention, the carbonization is carried out, for example, at atmospheric pressure in a protective gas atmosphere, typically under argon at a flow rate of, for example, approximately 200 l / h. It is expected that other flows or pressures can be used without significant effects on the product being observed. The duration of the carbonization is typically 1.5 to 5 hours, preferably 2 to 4 hours, particularly preferably 3 hours.The heating rate is typically 200 to 400 K / h, preferably 250 to 350 K / h, most preferably 300 K / h. The cooling rate is typically 150 to 250 K / h, preferably 200 K / h. The heating and cooling times are not included in the specified carbonization time, but are additional.

[0055] The carbon fiber molded bodies according to the invention are generally three-dimensional objects which have been produced by a specific shaping as described above and which generally have a uniform macroscopic appearance as described below.

[0056] Due to their production by molding from carbon fiber intermediates, the carbon fiber moldings according to the invention are, after molding or agglomeration, carbonized fiber agglomerates made from the carbon fiber intermediates and the polymeric binders optionally used in production. The carbon fiber moldings according to the invention thus exhibit high porosity, expressed, for example, by the macropore volume (volume of the fiber interstices per unit mass). The shape of the carbon fiber moldings according to the invention is not subject to any particular restriction. The moldings are preferably selected from the group consisting of pellets, spheres, cuboids, tablets, extrudates, cylinders, granules, monolithic shapes, complex or irregular shapes, or mixtures thereof.Particularly preferred are extrudates which are obtained by cutting a preferably round extrudate strand (circular die), i.e. which have a cylindrical shape.

[0057] The carbon fiber molded bodies according to the invention advantageously have one or more of the following features: a) a shape selected from the group consisting of cylinders and spheres, b) a size, expressed as the longest distance between two points within the molded body, in the range from about 0.1 to about 10 cm, c) a volume in the range of about 3 mm 3 up to about 520 cm 3 , d) a bulk density (determined, for example, according to DIN EN ISO 60: 1977) in the range from about 150 to about 1000, preferably about 250 to about 500 kg / m 3, e) an adsorption capacity for CO2 (carbon dioxide) at a temperature of 0 °C and a pressure of 1 bar (determined using a static-manometric gas adsorption device as described, for example, here: Lowell, Shields et al., Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density, Kluwer Academic Publishers, Dordrecht 2004, ISBN 978-1-4020-2303-3) in the range from about 2 to about 7 mmol / g, f) an adsorption capacity for CH4 (methane) at a temperature of 0 °C and a pressure of 1 bar (determined using a static-manometric gas adsorption device as described, for example, here: Lowell, Shields et al., Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density, Kluwer Academic Publishers, Dordrecht 2004, ISBN 978-1-4020-2303-3) in the range of about 0.2 to about 3.0 mmol / g.

[0058] According to the invention, a process for producing the carbon fiber molded articles according to the invention is further provided, which process comprises the steps of: a) providing a carbon fiber intermediate by a fiber formation process, preferably by spinning from one or more polymers capable of carbonization, b) optionally subjecting the carbon fiber intermediate to a drying step, c) optionally subjecting the carbon fiber intermediate to a crosslinking or

[0059] Stabilization step, d) Optionally subjecting the carbon fiber intermediate to a comminution step, e) Dispersing the carbon fiber intermediate in a dispersing medium which optionally contains one or more polymeric binders, f) Subjecting the dispersed carbon fiber intermediate to an agglomeration or shaping process, in particular an extrusion process, whereby a shaped body of the carbon fiber intermediate is obtained, g) Optionally drying the obtained carbon fiber intermediate shaped body, h) Optionally subjecting the carbon fiber intermediate to a further crosslinking or stabilization step to stabilize / crosslink the polymeric binder, i) Optionally dividing the dried carbon fiber intermediate shaped body, j) Carbonizing the optionally divided dried carbon fiber intermediate shaped body.

[0060] Steps a) to j) can be performed in the order listed. However, the order of the steps can also be interchanged as needed. For example, it is possible to first carbonize the carbon fiber intermediate molded bodies and then divide them.

[0061] In a preferred embodiment of the invention, all steps a) to j) as mentioned above, i.e. including the optional steps, are carried out in the order mentioned.

[0062] The process according to the invention for producing the carbon fiber molded bodies according to the invention preferably meets one or more of the following conditions: a) For step a) (formation of the carbon fiber intermediate):

[0063] 1) Preferred fiber formation process: electrospinning

[0064] 2) Preferred electrospinning parameters: a. Polymer capable of carbonization: i. Polyacrylonitrile (PAN) b. Solvent: i. Dimethylformamide (DMF) ii. Dimethyl sulfoxide (DMSO) c. Concentration of the polymer in the spinning solution (based on its mass) i. From about 5 to about 25 wt.%, preferably about 5 to about 15 wt.%, particularly for polyacrylonitrile d. Relative humidity during spinning: i. From about 20 to about 40% e. Temperature during spinning: about 20 to about 50 °C f. Electrode voltage: From about 15 to about 30 kV g. Electric field strength: From about 0.75 to about 5 kV / cm h. Distance between nozzle and collector: From about 6 to about 20 cm i. Flow rate per spinning needle: from about 1 to about 100 pl / min. b) For step b) (drying the carbon fiber intermediate):

[0065] 1) Preferred drying method: circulating air drying cabinet,

[0066] 2) Drying temperature: From about 25 to about 200 °C,

[0067] 3) Drying time: From about 1 to about 24 hc) To step c) (crosslinking or stabilization of the carbon fiber intermediate):

[0068] 1) Preferred conditions of the crosslinking or stabilization step: a. Temperature: from about 180 to about 300 °C, b. Time: from about 1 to about 24 h, c. Heating rate: from about 1 to about 10 K / min. d) For step d) (comminution of the carbon fiber intermediate):

[0069] 1) Preferred conditions of the comminution step a. Equipment: Knife mill with star blade b. Product obtained: Agglomerated fiber pieces c. Average fiber piece lengths achieved from 1 to 50, preferably 1 to

[0070] 15 pm e) For step e) (dispersion step):

[0071] 1) Dispersing medium: a. Organic solvent selected from i. Dimethylformamide (DMF) ii. Dimethyl sulfoxide (DMSO)

[0072] 2) Polymeric binders: a. Polyacrylonitrile

[0073] 3) Weight ratios of the components: a. preferred carbon fiber intermediate / solvent ratio (preferably DMF): from 1 / 1 to 1 / 2, b. preferred carbon fiber intermediate / binder ratio (preferably PAN): from 20 / 1 to 5 / 1,

[0074] (The carbon fiber intermediate / binder ratio used in the dispersion step allows for the gas adsorption to be adjusted or finely controlled to a certain extent. When using non-carbonized carbon fiber materials as the carbon fiber intermediate used in the production of the molded bodies, smaller amounts of solvent, thus higher carbon fiber intermediate / solvent ratios, can generally be used.) f) For step f) (agglomeration or molding process):

[0075] 1) Preferred agglomeration or forming process: Extrusion a. Nozzle geometry: Circular b. Nozzle size: Diameter: about 0.2 mm to about 5 mm c. Temperature: Between 0 °C and 200 °C, preferably between 20 °C and 120 °C g) For step g) (drying of the carbon fiber intermediate molded body):

[0076] Preferred drying conditions:

[0077] 1) Temperature of about 50 to about 80 °C (preferred for DMF, depending on the solvent),

[0078] 2) Time from about 30 to about 90 minutes,

[0079] 3) Drying device: hot plate (30 min) and drying cabinet (60 min),

[0080] 4) Heating rate: pre-tempered, h) To step h) (crosslinking or stabilization of the polymer binder)

[0081] 2) Preferred conditions of the crosslinking or stabilization step: a. Temperature from about 180 to about 300 °C, b. Time from about 1 to about 24 h, c. Heating rate from about 1 to about 10 K / min. i) For step i) (division of the dried carbon fiber intermediate molded body):

[0082] 1) Cutting device: knife

[0083] 2) Length of the sections: about 2 to about 10, preferably about 3 to about 4 mm. j) For step j) (Carbonization of the optionally divided dried carbon fiber intermediate molded body):

[0084] Preferred carbonization conditions:

[0085] 1) Shielding gas a. Argon b. Nitrogen c. Helium

[0086] 2) (Optional) Activation by adding an activating gas selected from a. carbon dioxide (CO2), b. water (H2O), (If appropriate, it is also possible according to the invention to activate the fibers during carbonization by adding further gases. Such activating gases include, for example, carbon dioxide (CO2) or water (H2O)).

[0087] 3) Temperature range: a. From about 400 to about 2500°C, preferably about 500 to about 1800°C, more preferably about 500 to about 1500°C, most preferably about 600 to about 1000°C.

[0088] (In principle, the carbonization temperature, as already described in WO 2020 / 249441 A1, influences in particular the pore size of the carbonized fiber material present in the molded bodies according to the invention. The pore sizes, in turn, influence the adsorption properties of the molded bodies for the gases used, so that the adsorption properties of the molded bodies can be adjusted or optimized by setting a suitable carbonization temperature for a desired gas adsorption or gas separation operation.

[0089] Starting from PAN fiber materials, the carbonization temperature is preferably less than 1000 °C, more preferably less than 900 °C, particularly preferably the PAN fiber materials are carbonized in the range of 600 to 850 °C in order to produce a significant proportion of pores with a pore diameter of < 0.35 nm, especially if carbon dioxide is to be adsorbed).

[0090] 4) Time / Duration a. From 1 to 6 hours,

[0091] 5) Heating rate a. From 1 to 10 K / min.

[0092] The process according to the invention results in carbon fiber molded bodies that possess outstanding adsorption properties with respect to various gases, which vary depending on the carbonization temperature. In particular, the use of non-carbonized carbon fiber materials for the production of molded bodies results in a significant increase in the packing density of the carbon fibers, and, compared to carbon fibers not processed into molded bodies, thus results in a reduction in pressure drop and a significant increase in the volume-specific adsorption capacity in the adsorber column.Despite the advanced shaping and subsequent carbonization of the molded bodies, the carbonized polymer fibers contained in the molded bodies retain their adsorption properties, which are particularly dependent on the carbonization temperature, which are particularly pronounced on the suitable carbon fibers in the molded bodies compared to other carbons. Furthermore, the molded bodies exhibit the inherent properties of carbons for gas adsorption, i.e., their comparatively low production costs and stability against moisture. Shaping, such as pelleting, also significantly improves the handling of the material for producing adsorbent beds, i.e., improved abrasion resistance and transferability or flowability.

[0093] The final carbonization of the shaped body, in particular the shaped bodies made of non-carbonized carbon fiber materials, surprisingly results in a material which, after its carbonization, i.e. its further processing into the carbon fiber shaped bodies according to the invention, has the adsorption properties of the carbon fibers contained therein, but is overall much more densely packed. This results in particular in a lower pressure drop across a bed of the shaped bodies according to the invention and a higher volume-specific adsorption capacity in the adsorber column compared to carbon fibers not processed into shaped bodies. The production process must be distinguished in particular from the simple shaping of already carbonized fibers, whose packing density, and thus their volume-specific adsorption properties, do not achieve the adsorption properties of the carbon fiber shaped bodies according to the invention.Furthermore, in a preferred embodiment, only one carbonization step instead of two is required to produce the carbon fiber molded bodies according to the invention. The final carbonization of the molded body according to the invention leads to an improvement in the mass-specific adsorption behavior compared to molded bodies that were not subjected to final carbonization, even when already carbonized fibers are used to produce the molded body.

[0094] The present invention further relates to the use of the carbon fiber molded bodies according to the invention in the purification, enrichment, adsorption, separation, or recovery of one or more gases. The gases can be selected, for example, from the following group, and one or more gases can be purified, enriched, adsorbed, separated, or recovered simultaneously with the carbon fiber molded bodies according to the invention:

[0095] CO2 (carbon dioxide), (see Figure 5),

[0096] CO (carbon monoxide),

[0097] H2 (hydrogen),

[0098] NH3 (ammonia),

[0099] Hydrocarbons such as selected from:

[0100] • CH4 (methane, natural gas, biogas), (see Figure 5),

[0101] • C2H2 (acetylene), • C2H4 (ethylene),

[0102] • C2H6(ethane),

[0103] • C3H6 (propene), and

[0104] • C3H8 (propane),

[0105] N2 (nitrogen), see Figure 5),

[0106] O2 (oxygen),

[0107] Air pollutants selected from: NO, NO2, H2S and SO2,

[0108] Noble gases selected from: He, Ne, Ar, Kr and Xe,

[0109] H2O (water adsorption / gas drying, see Figure 6).

[0110] Examples of applications and particularly preferred carbonization temperatures (starting in particular from PAN fiber material) for their production for the use of the carbon fiber molded bodies according to the invention include in particular the purification, enrichment, adsorption, separation or recovery of gases from the gas mixtures, as listed below by way of example:

[0111] CO2 / N2 (600 °C, CO2 separation from exhaust gases of combustion engines),

[0112] CO2 / CH4 (800 °C, CO2 separation from biogas),

[0113] CH4 / N2 (800 °C, N2 separation from natural gas),

[0114] O2 / N2 (900 °C, O2 separation from air),

[0115] CO2 / CO (600 °C, CO2 separation from CO2 / CO mixtures),

[0116] C2H4 / C2H6 (750 °C, separation of ethylene and ethane after petrochemical cracking), C3H6 / C3H8 (600 °C, separation of propene and propane after petrochemical cracking), NH3 / N2 (600 °C, separation of ammonia and N2 after ammonia synthesis), CO2 / CO / H2 (600 °C, separation of impurities from hydrogen), and

[0117] Kr / Xe (800 °C, separation of Kr and Xe (or other noble gases in air liquefaction)).

[0118] The present invention further relates to a gas adsorption device, preferably selected from gas adsorbers, columns, and fixed bed reactors, containing one or more beds of the carbon fiber molded bodies according to the invention.

[0119] The present invention further relates to a process for the purification, enrichment, adsorption, separation, or recovery of gases or gas mixtures, which comprises bringing gases or gas mixtures into contact with the carbon fiber moldings according to the invention. In a preferred embodiment of this process, it further comprises the step of desorbing one or more gases from the carbon fiber moldings according to the invention or regenerating the carbon fiber moldings according to the invention, for example at elevated temperatures (temperature swing adsorption, TSA, optionally by directly heating the adsorbent with electric current, ESA) or reduced pressures (pressure swing adsorption with or without vacuum, PSA or VPSA). Adsorption and desorption preferably take place alternately.

[0120] In a further embodiment of the invention, the carbon fiber moldings according to the invention can also be used to reinforce materials such as thermoplastic or thermosetting plastics, elastomers, rubber and caoutchouc, or inorganic composites such as those made of ceramic or concrete, which in turn find applications in device, vehicle, boat, or aircraft construction, as described, for example, in EP 2902433 A1. The present invention further relates to carbon fiber moldings made of one or more non-carbonized carbon fiber materials. These represent, in a sense, the intermediate product in the production of the carbon fiber moldings according to the invention. The above naturally applies to the production of this intermediate product, with the exception of the last carbonization step j).

[0121] Description of the illustrations

[0122] Figure 1 shows a photo of the carbon fiber molded bodies according to the invention produced according to Example 1a.

[0123] Figure 2 shows SEM images (magnification 10,000x) of the carbon fiber molded bodies according to the invention, which were obtained according to Example 1a, Example 2, and Comparative Example 1. The preferred material obtained according to Example 1a, which was obtained from a carbon fiber material that had not been previously carbonized, surprisingly shows a significantly denser packing of the fiber fragments compared to Example 2 and Comparative Example 1, which were obtained from an already carbonized carbon fiber material. The fiber fragments are also significantly shorter, which favors denser packing of the fibers. Furthermore, an image of the carbon fiber intermediate (carbon fiber material) according to WO 2020 / 249441 A1 is shown, wherein the significantly higher volume between the individual fibers and the associated lower density are striking.

[0124] Figure 3 shows the weight- and volume-specific CO2 adsorption of the molded bodies produced in Example 1a, Example 2, and Comparative Example 1. Both the molded bodies according to Example 1a and Example 2 show higher mass- and volume-specific adsorption than the molded bodies according to Comparative Example 1. Furthermore, the molded bodies according to Example 1a show higher volume-specific adsorption than the molded bodies according to Example 2 and Comparative Example 1. It is surprising that the volume-specific adsorption capacity of the molded bodies according to Example 2 is increased by a factor of about 2 compared to that of Comparative Example 1, despite similar bulk densities, since the mass-specific adsorption is also surprisingly higher.

[0125] Figure 4 shows the cumulative pore size distribution of the molded bodies according to Example 1b. The material preferably obtained according to Example 1b has a predominant proportion of ultramicropores, particularly in the range < 0.35 nm.

[0126] Figure 5 shows adsorption isotherms of the molded bodies according to Example 1b compared for CO2, N2, and CH4. The material obtained according to Example 1b exhibits different adsorption properties for different gases, which forms the basis for the selective separation of gas mixtures.

[0127] Figure 6 shows the adsorption isotherm of the shaped bodies according to Example 1b for H2O. The adsorption isotherm demonstrates the suitability of the shaped bodies for water adsorption.

[0128] Figure 7 shows a schematic representation of the cyclization and cross-linking of polymer chains in polyacrylonitrile (PAN) fibers. Examples

[0129] General procedure

[0130] In a typical process of the invention, for example, about 10 wt. % polyacrylonitrile is dissolved in dimethylformamide, and the resulting polymer solution is spun in an electrospinner. The resulting fibers are dried in air and then cross-linked, for example, for about 15 h at temperatures between about 200 and about 300°C, preferably about 250°C, in a circulating air drying cabinet. The resulting carbon fiber intermediate is comminuted, for example, in a knife mill to a coarse powder of fiber pieces with a size in the range of about 1 to about 50 μm, preferably about 1 to about 15 μm, and the comminuted carbon fiber intermediate is admixed with a dilute polyacrylonitrile solution in dimethylformamide in a weight ratio of approximately between 1:1 and 1:2 to produce a dispersion of comminuted carbon fiber intermediate and polyacrylonitrile solution.The dispersion is pressed through a nozzle that is, for example, approximately 2 mm wide and then dried. Drying takes place for example for 30 minutes at approximately 60°C on a preheated hot plate and then for several hours at approximately 100°C in a vacuum drying cabinet. The extrudate is then divided into shaped bodies that are, for example, approximately 2 to approximately 10 mm long, preferably approximately 3 to approximately 4 mm long, and have a diameter of approximately 2 mm. Finally, the shaped bodies are carbonized at temperatures between, for example, approximately 600 and, for example, approximately 1400°C, preferably, for example, at approximately 600°C, in an argon protective gas atmosphere for, for example, 3 hours at a heating rate of, for example, approximately 1 to, for example, approximately 20 K / min, preferably, for example, approximately 5 K / min.

[0131] Alternative embodiments include the use of other polymers capable of carbonization (e.g. other synthetic polymers such as those mentioned above), changed weight proportions of the polymers in the polymer solution (preferably in the range of, for example, about 1 to, for example, about 15 wt.% based on the polymer solution), the type of solvent (depending on the polymer used), spinning parameters, drying times and conditions, dispersion media for the non-carbonized carbon fiber intermediate during molding or agglomeration, carbon fiber intermediate proportions in the polymer mass during molding or agglomeration (which are selected so that the flowability of the polymer mass (dispersion) is maintained), extrusion conditions (e.g.Nozzle diameter, temperature), drying and carbonization conditions of the molded bodies, such as the extrudates, such as the choice of carbonization temperatures depending on the target adsorbate), sizes of the molded bodies (e.g., depending on the required bulk density). Various examples are explained below and, for a better overview, are initially presented in the table below with the sequence of typical process steps:

[0132] Example 1a

[0133] A polyacrylonitrile (PAN) from BOC Sciences with a molecular weight of 150,000 g / mol was used. The carbon fiber intermediate was produced by needle electrospinning and subsequent cross-linking or stabilization. First, a solution of 10 wt. % PAN in dimethylformamide (DMF) was prepared. For this purpose, 4 g of PAN was dissolved in 36 g of DMF while stirring with a magnetic stirrer at room temperature for two days. The solution was spun directly into fiber mats in an IME Technologies electrospinner in a controlled atmosphere. The parameters shown in Table 1 were used. Table 1: Electrospinning parameters After the electrospinning process, the resulting fiber material was dried in air and cross-linked or stabilized overnight in a circulating air drying cabinet at 250 °C in an air atmosphere, thus producing the carbon fiber intermediate.

[0134] The resulting carbon fiber intermediate was then ground in a knife mill from IKA (IKA A 10 basic with star knife and grinding chamber reduction) within 3 minutes. After every 1 minute, the grinding process was interrupted in order to loosen any deposits on the edge or lid of the grinding chamber with a spatula. To produce the extrusion mass, 3 g of the ground carbon fiber intermediate were mixed with 6 g of an approximately 5 wt. % PAN in DMF solution, using the same PAN as in fiber production. The ground carbon fiber intermediate was placed in a 100 ml beaker, mixed with approximately 14 g of the PAN solution, and stirred with a spatula for 1-2 minutes. This process was repeated three times to obtain a homogeneous, dough-like dispersion. The dispersion was then transferred into a 2 ml syringe from IKA.Braun (Injekt) and extruded manually at room temperature using the plunger through the 2 mm wide nozzle of the syringe into 6 to 10 cm long cylinders onto a suitable substrate (here a Petri dish). To remove the solvent, the extrudate was first dried for 30 minutes on a preheated hot plate at 60 °C and finally in a vacuum drying oven at 100 °C for at least 1 hour. This was followed by cross-linking of the added PAN binder from the dispersion step at 250 °C for 15 hours in air in a circulating air drying oven. The cured extrudate was cut into 2 to 7 mm long pellets using a scalpel. Finally, after reaching the target temperature, the molded bodies were carbonized for 3 hours at 600 °C in a previously evacuated and argon-flushed oven and then cooled. The heating rate of the carbonization furnace was 300 K / h, the cooling rate 200 K / h, and the argon flow rate 200 L / h.The result of the process described above are the molded bodies according to the invention shown in Figure 1 and Figure 2 (left).

[0135] Example 1 b

[0136] The production of the molded articles according to Example 1b was repeated as in Example 1a, whereby 3 g of the comminuted carbon fiber intermediate was mixed with 5.4 g of an approximately 3.3 wt.% PAN in DMF solution to produce the extrusion mass. Example 2

[0137] The molded bodies were produced as in Example 1a up to the production of the carbon fiber intermediate. However, unlike Example 1a, this intermediate was subjected to carbonization before comminution, as described below.

[0138] After reaching the target temperature, the carbon fiber intermediate was carbonized for 3 hours at 600 °C in a previously evacuated and argon-flushed furnace. The heating rate of the carbonization furnace was 300 K / h, the cooling rate 200 K / h, and the argon flow rate 200 L / h. The carbonized fibers were then ground within 3 minutes in an IKA knife mill (IKA A 10 basic with star-shaped blades and grinding chamber reduction) analogous to Example 1a. The grinding process was interrupted after 1 minute to remove any deposits on the edge or lid of the grinding chamber with a spatula. To prepare the extrusion mass, 3 g of the ground carbon fiber intermediate were mixed with 6 g of an approximately 5 wt.% PAN in DMF solution, using the same PAN as used for fiber production. The crushed carbon fiber intermediate was placed in a 100 ml beaker with approx.14 of the PAN solution and stirred with a spatula for 1-2 minutes. This procedure was repeated three times to obtain a homogeneous, dough-like dispersion. The dispersion was then filled into a 2 ml syringe from Braun (Injekt) and manually extruded at room temperature using the plunger through the 2 mm wide nozzle of the syringe into 6 to 10 cm long cylinders onto a suitable substrate (here a Petri dish). To remove the solvent, the extrudate was first dried for 30 minutes on a preheated hotplate at 60 °C and finally in a vacuum drying cabinet at 100 °C for at least 1 hour. This was followed by crosslinking of the added PAN binder from the dispersion step at 250 °C for 15 hours in air. The cured extrudate was cut into 2 to 7 mm long pellets using a scalpel.Finally, after reaching the target temperature, the molded bodies were carbonized again for 3 hours at 600 °C in a previously evacuated and argon-flushed furnace, and then cooled. The heating rate was again 300 K / h, the cooling rate 200 K / h, and the argon flow rate 200 L / h. The result of the process described above is the molded bodies shown in Figure 2 (center).

[0139] Comparison example 1

[0140] Comparative Example 1 corresponds to Example 2, except that no further carbonization of the molded bodies made from the already carbonized carbon fibers was carried out according to the invention. The adsorption properties of the molded bodies produced in Examples 1a and b, as well as in Example 2 and Comparative Example 1, were determined as follows:

[0141] The gas adsorption isotherms in Figures 3, 5, and 6 were determined using a static manometric gas adsorption device, as described, for example, by Lowell, Shields et al., Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density, Kluwer Academic Publishers, Dordrecht 2004, ISBN 978-1-4020-2303-3, either with an Autosorb iQ2 device equipped with a Cryocooler (Quantachrome, USA), a 3P Micro (3P Instruments GmbH, Germany) equipped with one Cryotune (3P Instruments GmbH, Germany) per station, or a Quadrasorb (Quantachrome, USA) equipped with one Cryotune per station. The carbon fiber molded bodies were transferred to a glass tube for the measurement. The samples were degassed under vacuum at 200 °C for 8 h. The sample weight was determined by calculating the difference between the weight of the filled and empty sample tube.

[0142] Table 2: Bulk density of the molded bodies of Example 1a as well as Example 2 and Comparative Example 1

Claims

Patent claims 1. Carbon fiber molded body obtainable by a process comprising the step of carbonization after the production of the molded body from one or more carbon fiber intermediates.

2. Carbon fiber molded body according to one or more of the preceding claims, wherein the carbon fiber intermediate is a non-carbonized carbon fiber material.

3. Carbon fiber molded body according to one or more of the preceding claims, wherein the carbon fiber intermediate is obtained by subjecting one or more polymers capable of carbonization to a fiber formation process such as spinning, such as wet spinning, dry jet wet spinning, dry spinning, melt spinning or electrospinning, preferably electrospinning.

4. Carbon fiber molded body according to one or more of the preceding claims, wherein the carbon fiber intermediate is obtained by electrospinning a solution of one or more polymers capable of carbonization.

5. Carbon fiber molded body according to one or more of the preceding claims, wherein the carbon fiber intermediate is obtained from polymers capable of carbonization, which are selected from the group consisting of: synthetic polymers, such as polyacrylonitrile (PAN), polyimides, polyetherimides, polyfurfuryl alcohols, phenolic resins, polyvinyl alcohols and mixtures thereof, preferably polyacrylonitrile.

6. Carbon fiber molded body according to one or more of the preceding claims, wherein the carbon fiber intermediate is obtained from polyacrylonitrile, which preferably has one or more of the following features: Polyacylnitrile homopolymer or polyacrylonitrile copolymer with a comonomer content of 1 to 10 wt.%, Molecular weight in g / mol from 50,000 to 300,000, preferably 100,000 to 250,000.

7. Carbon fiber molded body according to one or more of the preceding claims, wherein the carbon fiber intermediate is obtained by electrospinning a solution of one or more polymers capable of carbonization, wherein the solvent is selected from water and organic solvents, such as in particular amides such as dimethylformamide, dimethylacetamide, ketones such as acetone, methyl ethyl ketone, alcohols such as ethanol, and mixtures thereof.

8. Carbon fiber molded body according to one or more of the preceding claims, wherein the carbon fiber intermediate has been subjected to a crosslinking or stabilization step.

9. Carbon fiber molded body according to one or more of the preceding claims, wherein the carbon fiber intermediate has been subjected to a comminution step.

10. Carbon fiber molded body according to one or more of the preceding claims, wherein the carbon fiber intermediate has an average fiber diameter in the range from about 5 to about 100,000 nm, preferably from about 10 nm to about 10,000 nm, more preferably from about 15 to about 4,500 nm, even more preferably from about 20 nm to about 1,000 nm. 11 . Carbon fiber molded bodies according to one or more of the preceding claims, wherein the molded bodies of the carbon fiber intermediate are obtained by subjecting a dispersion of the carbon fiber intermediate in a dispersing medium to an agglomeration or molding process.

12. Carbon fiber molded body according to one or more of the preceding claims, wherein the molded bodies of the carbon fiber intermediate stage are obtained by extruding a dispersion of the carbon fiber intermediate stage in a dispersing medium through a nozzle and subsequently drying and dividing the extruded strand.

13. Carbon fiber molded body according to one or more of the preceding claims, wherein the molded bodies of the carbon fiber intermediate stage are obtained by granulation of the carbon fiber intermediate stage, preferably by wet granulation of a dispersion of the carbon fiber intermediate stage in a dispersing medium.

14. Carbon fiber molded bodies according to one or more of the preceding claims, wherein the molded bodies of the carbon fiber intermediate stage are obtained by subjecting a dispersion of the carbon fiber intermediate stage in a dispersing medium to an agglomeration or molding process, wherein the dispersing medium contains one or more polymeric binders.

15. Carbon fiber molded body according to one or more of the preceding claims, wherein the molded bodies of the carbon fiber intermediate stage are obtained by subjecting a dispersion of the carbon fiber intermediate stage in a dispersing medium to an agglomeration or molding process, wherein the dispersing medium is selected from water or organic solvents, such as in particular amides such as dimethylformamide, dimethylacetamide, ketones such as acetone, methyl ethyl ketone, alcohols such as ethanol, and mixtures thereof.

16. Carbon fiber molded body according to one or more of the preceding claims, wherein the molded body of the carbon fiber intermediate stage is produced by extrusion of a dispersion of the carbon fiber intermediate stage in a dispersing medium containing tend one or more polymeric binders, wherein the polymeric binder is selected from the group of polymers capable of carbonization, which are selected from the group consisting of: synthetic polymers, such as polyacrylonitrile (PAN), polyimides, polyetherimides, polyfurfuryl alcohols, phenolic resins, polyvinyl alcohols and mixtures thereof, preferably polyacrylonitrile.

17. Carbon fiber molded bodies according to one or more of the preceding claims, wherein the molded bodies of the carbon fiber intermediate are obtained by subjecting a dispersion of the carbon fiber intermediate in a dispersing medium to an agglomeration or molding process, wherein the dispersing medium contains one or more polymeric binders, wherein the polymeric binder corresponds to the polymer used for the production of the carbon fiber intermediate.

18. Carbon fiber molded body according to one or more of the preceding claims, wherein the carbonization of the molded body of the carbon fiber intermediate stage takes place at a temperature in the range of about 400 to about 2500 °C, preferably in the range of about 500 to about 1800 °C, more preferably in the range of about 500 to about 1500 °C, particularly preferably in the range of about 600 to about 1000 °C under an inert gas atmosphere.

19. Carbon fiber molded bodies according to one or more of the preceding claims, wherein the molded bodies are selected from the group consisting of pellets, tablets, extrudates, granules, monolithic shapes, complex shapes, or mixtures thereof.

20. Carbon fiber molded body according to one or more of the preceding claims, which have one or more of the following features: a) a shape selected from the group consisting of cylinders and spheres, b) a size, expressed as the longest distance between two points of the molded body, in the range of about 0.1 to about 10 cm, c) a volume in the range of about 3 mm 3 up to about 520 cm 3 , d) a bulk density (determined, for example, according to DIN EN ISO 60: 1977) in the range from about 150 to about 1000, preferably about 250 to about 500 kg / m 3, e) an adsorption capacity for CO2 (carbon dioxide) at a temperature of 0 °C and a pressure of 1 bar (determined using a static-manometric gas adsorption device as described, for example, in: Lowell, Shields et al., Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density, Kluwer Academic Publishers, Dordrecht 2004, ISBN 978-1-4020-2303-3) in the range from about 2 to about 7 mmol / g, f) an adsorption capacity for CH4 (methane) at a temperature of 0 °C and a pressure of 1 bar (determined using a static manometric gas adsorption device as described, for example, in: Lowell, Shields et al., Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density, Kluwer Academic Publishers, Dordrecht 2004, ISBN 978-1-4020-2303-3) in the range from about 0.2 to about 3.0 mmol / g.

21. A process for producing the carbon fiber molded bodies according to one or more of the preceding claims, comprising the steps of: a) providing a carbon fiber intermediate by a fiber-forming process, preferably by spinning, from one or more polymers capable of carbonization, b) optionally subjecting the carbon fiber intermediate to a drying step, c) optionally subjecting the carbon fiber intermediate to a crosslinking or stabilizing step, d) optionally subjecting the carbon fiber intermediate to a comminution step, e) dispersing the carbon fiber intermediate in a dispersing medium, which optionally contains one or more polymeric binders, f) subjecting the dispersed carbon fiber intermediate to an agglomeration or molding process, in particular an extrusion process, whereby a molded body of the carbon fiber intermediate is obtained,g) Optionally drying the resulting carbon fiber intermediate molded body, h) Optionally subjecting the carbon fiber intermediate to a further crosslinking or stabilization step to stabilize / crosslink the polymeric binder, i) Optionally dividing the dried carbon fiber intermediate molded body, j) Carbonizing the optionally divided dried carbon fiber intermediate molded body.

22. A process for producing the carbon fiber molded bodies according to one or more of the preceding claims, wherein steps a) to j) are carried out in the order mentioned, preferably wherein all steps a) to j), including the optional steps, are carried out in the order mentioned.

23. A process for producing the carbon fiber molded bodies according to one or more of the preceding claims, wherein one or more of the following conditions are met: a) For step a) (formation of the carbon fiber intermediate stage): 1) Preferred fiber formation process: electrospinning 2) Preferred electrospinning parameters: a. Polymer capable of carbonization: i. Polyacrylonitrile b. Solvent: i. Dimethylformamide (DMF), ii. Dimethyl sulfoxide (DMSO) c. Concentration of the polymer in the spinning solution (based on its mass) i. From about 5 to about 25 wt.%, preferably about 5 to about 15 wt.%, especially for polyacrylonitrile, d. Relative humidity during spinning: i. From about 20 to about 40%, e. Temperature during spinning: From about 20 to about 50 °C, f. Electrode voltage: From about 15 to about 30 kV, g. Electric field strength: From about 0.75 to about 5 kV / cm, h. Distance between nozzle and collector: From about 6 to about 20 cm, i. Flow rate per spinning needle: From about 1 to about 100 pl / min. b) For step b) (drying the carbon fiber intermediate): 1) Preferred drying method: circulating air drying cabinet, 2) Drying temperature: From about 25 to about 200 °C, 3) Drying time: From about 1 to about 24 h, c) To step e) (crosslinking or stabilization of the carbon fiber intermediate): 1) Preferred conditions of the crosslinking or stabilization step: a. Temperature from about 180 to about 300 °C, b. Time from about 1 to about 24 h, c. Heating rate from about 1 to about 10 K / min. d) For step d) (comminution of the carbon fiber intermediate): 1) Preferred conditions of the comminution step: a. Equipment: Knife mill with star blades, b. Product obtained: Agglomerated fiber pieces, c. Average fiber piece lengths achieved from about 1 to about 50 pm, e) For step e) (dispersion step): 1) Dispersing medium: a. Organic solvent selected from: i. Dimethylformamide (DMF), ii. Dimethyl sulfoxide (DMSO), 2) Polymeric binders: a. Polyacrylonitrile (PAN), 3) Weight ratios of the components: a. preferred carbon fiber intermediate / solvent ratio (preferably DMF): from 1 / 1 to 1 / 2, b. preferred carbon fiber intermediate / binder ratio (preferably PAN): from 20 / 1 to 5 / 1, f) For step f) (agglomeration or molding process): 1) Preferred agglomeration or forming process: Extrusion a. Nozzle geometry: Circular, b. Nozzle size: Diameter: about 0.2 mm to about 5 mm, c. Temperature between 0 °C and 200 °C, preferably between 20 °C and 120 °C g) For step g) (drying of the carbon fiber intermediate molded body): Preferred drying conditions: 1) Temperature of about 50 to about 80 °C, 2) Time from about 30 to about 90 minutes, 3) Drying device: hot plate (30 min) and drying cabinet (60 min), 4) Heating rate: pre-tempered, h) To step h) (stabilization / crosslinking of the polymeric binder) 1) Preferred conditions of the crosslinking or stabilization step: a. Temperature from about 180 to about 300 °C, b. Time from about 1 to about 24 h, c. Heating rate from about 1 to about 10 K / min. i) Regarding step i) (division of the dried carbon fiber intermediate molded body): 1) Cutting device / equipment: knife, 2) Length of the sections: about 2 to about 10 mm, preferably about 3 to about 4 mm, j) For step j) (carbonization of the optionally divided dried carbon fiber intermediate molded body): Preferred carbonization conditions: 1) Shielding gas a. Argon, b. Nitrogen, c. Helium, 2) Activation by adding an activating gas selected from a. carbon dioxide (CO2), b. water (H2O), 3) Temperature range: a. From about 400 to about 2500 °C, preferably about 500 to about 1800 °C, more preferably about 500 to about 1500 °C, most preferably about 600 to about 1000 °C 4) Time / Duration a. From about 1 to about 6 hours 5) Heating rate a. From about 1 to about 10 K / min.

24. Use of the carbon fiber molded bodies according to one or more of the preceding claims in the purification, enrichment, adsorption, separation or recovery of one or more of the following gases: CO2 (carbon dioxide), CO (carbon monoxide), H2 (hydrogen), NH3 (ammonia), Hydrocarbons selected from: • CH4 (methane, natural gas, biogas), • C2H2 (acetylene), • C2H4 (ethylene), • C2H6(ethane), • C3H6 (propene), and • C3H8 (propane), N2 (nitrogen), O2 (oxygen), Air pollutants selected from: NO, NO2, H2S and SO2 Noble gases selected from: He, Ne, Ar, Kr, and Xe H2O (water adsorption / gas drying), 25. Use of the carbon fiber molded bodies according to one or more of the preceding claims for application or separation in the following gas mixtures: CO2 / N2 (CO2 separation from exhaust gases of combustion engines), CO2 / CH4 (CO2 separation from biogas), CH4 / N2 (N2 separation from natural gas), O21 N2 (O2 separation from air), CO21 CO (CO2 separation from CO2 / CO mixtures), C2H41 C2H6 (separation of ethylene and ethane after petrochemical cracking), C3H61 C3H8 (separation of propene and propane after petrochemical cracking), NH3 / N2 (separation of ammonia and N2 after ammonia synthesis), CO2 / CO / H2 (separation of impurities from hydrogen), and Kr / Xe (separation of Kr and Xe (or other noble gases in air liquefaction)).

26. Gas adsorption device, preferably selected from gas adsorbers, columns, and fixed bed reactors, containing one or more beds of the carbon fiber molded bodies according to one or more of the preceding claims.

27. Use of the carbon fiber molded body according to one or more of the preceding claims for reinforcing materials such as thermoplastic or thermosetting plastics, elastomers, rubber and caoutchouc or inorganic composites such as ceramic or concrete.

28. A process for the purification, enrichment, adsorption, separation or recovery of gases or gas mixtures, which comprises bringing gases or gas mixtures into contact with the carbon fiber molded bodies according to one or more of the preceding claims.

29. A method according to the preceding claim, which comprises the step of desorbing one or more gases from the carbon fiber molded bodies according to one or more of the preceding claims or of regenerating the carbon fiber molded bodies according to one or more of the preceding claims.

30. Carbon fiber molded articles made from one or more non-carbonized carbon fiber materials.

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