Molded body for reversible chemisorption of CO2

Abstract

The invention relates to an adsorbent for CO2, to the production of said adsorbent and to the use thereof as a fixed bed adsorbent, comprising a shaped body of amorphous silica having a dimension in the range of 0.5 mm to 30 mm in at least one dimension and at least one adsorbent medium for CO2, the molded body is functionalized with at least one adsorption medium for CO2.

Description

Technical Field

[0001] This invention relates to an adsorbent for CO2, the production of such adsorbent, and the use of such adsorbent as a fixed-bed adsorbent in the chemisorption of CO2. The adsorbent comprises a silica / silica molded body and at least one adsorption medium for CO2. The silica / silica molded body has a measured value in at least one dimension ranging from 0.5 mm to 30 mm. The molded body is functionalized with at least one adsorption medium for CO2.

[0002] In the context of this invention, the term "functionalization" should be understood to mean, for example, impregnation and / or coating of an adsorbent medium onto a molded body. Background Technology

[0003] Climate change and global warming are considered the most serious environmental problems today. It is now widely acknowledged that the primary cause of global warming is the release of so-called greenhouse gases into the atmosphere. The most significant greenhouse gas is carbon dioxide (CO2), which is released particularly during the combustion of fossil fuels such as coal, oil, and natural gas. These fossil fuels together account for approximately 80% of the world's energy demand. Because fossil fuels remain relatively cheap and easy to use, and there are still no satisfactory alternatives to replace them to the required extent, it is likely that fossil fuels will remain our most important energy source for the long term. This makes it all the more important to address CO2 emissions through new technologies that enable the storage of CO2 as a valuable byproduct and / or its use as a starting material for further processes.

[0004] Carbon capture and storage (CCS) is a representative of this type of technology, in which CO2 from the environment or directly from fossil CO2 emission sources from industry or power generation is separated, processed, compressed, and transported to storage facilities.

[0005] Compared to the pure storage of CCS, "carbon capture and utilization" (CCU) involves the separation of CO2, especially from combustion exhaust gases, and its related uses in further chemical processes, such as conversion to methanol.

[0006] Another method for recovering CO2 is "direct air capture" (DAC), in which CO2 is extracted from ambient air.

[0007] All of these technical requirements necessitate that CO2 can be (reversibly) adsorbed onto a solid adsorbent. The gas from which CO2 is to be removed is typically passed through an adsorbent in a fixed-bed adsorbent column.

[0008] In the prior art, solid adsorbent materials have so far been used in the form of fine powders; however, these powders are associated with the drawbacks of adsorption columns. Therefore, the use of fine powders in columns results in undesirable high pressure drops related to fluidization and adsorbent discharge from the column.

[0009] EP 2102131 A1 teaches the use of larger metal oxide molded bodies instead of finely dispersed powders, although these are not functionalized and therefore unsuitable for selectively adsorbing CO2 from gas mixtures.

[0010] Therefore, it is desirable to provide an adsorbent for CO2 that overcomes the drawbacks associated with powdered adsorbent materials, namely, low pressure drop and low fluidization when used as a fixed-bed adsorbent, or even the adsorbent escaping from the column. Simultaneously, CO2 should reversibly bind at high adsorption efficiency and capacity. Summary of the Invention

[0011] The object of the present invention is achieved by a first aspect of the present invention, namely, an adsorbent for CO2, particularly a solid adsorbent, comprising: (i) A molded body composed of at least one amorphous silica (=silica), the molded body having a measured value of 0.5 mm to 30 mm, preferably 1.0 mm to 15 mm, in at least one dimension; and (ii) At least one adsorption medium for CO2, wherein the molded body (i) is functionalized with the adsorption medium; The adsorbent has a strength of at least 2 N / mm. 2 Preferably at least 8 N / mm 2 The compressive strength.

[0012] Preferred adsorbents include molded bodies with measured values ​​in one, two, or three dimensions, more preferably in two or three dimensions, and especially in all three dimensions, ranging from 0.5 mm to 30 mm, preferably from 1.0 mm to 15 mm.

[0013] The adsorbent according to the invention preferably has the same measurement value as the corresponding molded body.

[0014] When a gas mixture passes through a powder bed known in the prior art, this results in a high pressure drop between the sides facing and away from the gas source. A coarser molded body with these measurements according to the invention is advantageous because the pressure drop is reduced as the gas passes through such a bed.

[0015] Therefore, the adsorbent according to the invention is particularly suitable as an effective fixed-bed adsorbent for CCU, CCS, or DAC because it results in lower pressure drop and less fluidization, or even adsorbent discharge from the adsorption column, compared to finely dispersed powders. Effective CO2 adsorption is only achievable using the molded form according to the invention.

[0016] The silica molded articles according to the invention also exhibit improved mechanical stability and improved long-term stability. Compared with powdered adsorbents, the silica molded articles according to the invention do not have a tendency to agglomerate or adhere during impregnation (= functionalization with adsorbent) and do not require expensive and complex grinding.

[0017] The compressive strength according to the invention can be determined by any method known in the art, for example using a Z 400 E general-purpose testing machine with a 1kN load sensor.

[0018] It has been unexpectedly discovered that particularly good adsorption efficiency can be achieved in the adsorption column only when observing the compressive strength of the adsorbent according to the invention. Its compressive strength is less than 2 N / mm². 2 The molded body is insufficient to withstand the CO2 pressure in the adsorption column and is destroyed, i.e., exhibits spalling, for example. The destroyed molded body again leads to the same disadvantages that also occur when adsorption powder is used in the adsorption column (e.g., higher pressure drop, fluidization, emission).

[0019] The molded articles according to the invention can be ultrapure. In the context of the invention, ultrapure should be understood as meaning that it is substantially free of inorganic and organic impurities. Preferably, based on the total mass of the molded article, the total amount of impurities (all metals and carbon, phosphorus and sulfur) is less than 400 ppm, preferably less than 250 ppm, particularly preferably less than 100 ppm, even more preferably less than 50 ppm, even more preferably less than 20 ppm, even more preferably less than 10 ppm and most preferably less than 1 ppm.

[0020] Impurities can be quantified using all conventional analytical methods, such as RFA, AAS, ICP-OES, or ICP-MS. If necessary, the molded body must be dissolved in a suitable solvent (e.g., hydrofluoric acid) before analysis.

[0021] In specific embodiments, the molded body is generally a sphere, ellipsoid, cylinder, hollow cylinder (e.g., a small tube), or cuboid, preferably a cylinder or hollow cylinder. It will also be apparent to those skilled in the art that the specified geometry does not refer to a perfect geometry, and therefore deviations from an ideal geometry are possible.

[0022] The molded body preferably has an aspect ratio of up to 15, more preferably up to 10, and most preferably up to 6.

[0023] Further investigation revealed that the stated aspect ratio has a particularly good effect on the suitability of the molded body in the adsorption column, because the already low pressure drop can be further reduced when using the molded body according to the invention with the stated aspect ratio. Molded bodies with aspect ratios exceeding those according to the invention are no longer advantageously packaged in the reaction / adsorption column and tend to break. Cracks are undesirable because they lead to the formation of very small molded body fragments, which results in high pressure drops and fluidization within the column and discharge from the column.

[0024] The molded body is preferably composed of amorphous silica / silica agglomerates. The agglomerates are preferably composed of aggregates of multiple primary silica particles.

[0025] In a preferred embodiment, the BET surface area of ​​the adsorbent is 30-500 m². 2 Within the range of / g, especially in the 50-400m³ range. 2 Within the range of / g.

[0026] BET surface area can be determined using measurement methods known in the art. BET surface area is preferably determined using nitrogen gas according to DIN 66131.

[0027] The molded body preferably exhibits a high pore volume of 0.5 ml / g to 1.8 ml / g, more preferably 0.6 ml / g to 1.5 ml / g, and particularly preferably 0.7 ml / g to 1.2 ml / g.

[0028] If the pore volume exceeds the above range, the molded body becomes excessively fragile and tends to break when used in an adsorption column. This results in the formation of very small molded body fragments and thus high pressure drop. Fragments with smaller pore volumes than specified have excessively low internal surface areas and therefore low adsorption efficiency and capacity.

[0029] The pore volume is preferably determined according to DIN 66134 (Langmuir, p / p0 = 0.9995).

[0030] At least one amorphous silica may be selected from pyrolytic silica or precipitated silica.

[0031] To produce pyrolytic silica, a volatile silicon halide (such as silicon tetrachloride) is typically injected into a flame containing hydrogen and air as an ignition gas. This substance is hydrolyzed in the presence of water formed during the ignition gas reaction to provide silica. After leaving the flame, the silica enters a so-called condensation zone, where primary particles and primary aggregates agglomerate.

[0032] To produce precipitated silica, commercially available sodium silicate is reacted with an acid (e.g., sulfuric acid) at a pH of 7.5 to 10.5. The pH is then adjusted to 3.0 to 5.0, and the precipitated silica is filtered, washed, and dried.

[0033] In a preferred embodiment, the silica of the molded article has a mesoporous structure, particularly a mesoporous structure with irregular pore structures.

[0034] The irregular pore structure of the silica according to the preferred embodiment described above is also retained in the molded body. The pore structure of the silica forms channels that define the inner surface area of ​​the molded body.

[0035] Functionalization with an adsorption medium is preferably performed on the inner surface region of the molded body according to the invention.

[0036] According to the IUPAC definition, mesoporous solids are porous materials with pore sizes ranging from 2 nm to 50 nm.

[0037] Those skilled in the art will know that mesoporous silica is typically produced through expensive and complex template-based synthesis. Silica produced in this manner is characterized by a defined channel-like pore structure. In contrast, the molded articles according to the invention are based on silica characterized by an irregular pore structure. In this context, "irregular pore structure" should be understood as meaning that the pores within the silica extend asymmetrically and / or irregularly without identifiable repeating units (with or without at least one intersection and / or branch).

[0038] For example, silica with this irregular pore structure has an economic advantage because it is more cost-effective and easier to produce than silica with a predetermined and regular channel structure. It has also been unexpectedly found that the CO2 adsorption efficiency of the molded articles according to the invention made from silica with an irregular pore structure can significantly exceed that of molded articles made from silica with a defined uniform pore structure, because silica with an irregular pore structure has a less tendency to be blocked and have its channels closed by the adsorbed medium. Therefore, the inner surface region of the molded articles according to the invention can be more uniformly and completely functionalized, thus increasing the CO2 adsorption capacity of the molded articles according to the invention. A sufficient capacity for effective CO2 adsorption is preferably at least 20 mg CO2 / g adsorbent (corresponding to about 0.45 mmol CO2), more preferably at least 40 mg CO2 / g adsorbent.

[0039] In a preferred embodiment, at least one adsorption medium (ii) is capable of undergoing a reversible reaction with CO2, particularly a reversible adsorption reaction.

[0040] Adsorption reactions, especially chemisorption, occur in this context. In this case, CO2 binds to the inner surface region of the molded body through chemical bonding with the adsorption medium. The chemisorbed CO2 can then be released from the molded body again and thus discharged by increasing the temperature and / or reducing the pressure. This has the advantage that CO2 can therefore not only be removed from the gas phase (e.g., DAC, CCS) but can also be released again at any subsequent time and, for example, fed to processes using CO2 as a starting material (e.g., CCU), such as for conversion to methanol.

[0041] At least one adsorption medium (ii) may be an inorganic adsorption medium or an organic adsorption medium.

[0042] The inorganic adsorption medium (ii) is preferably a carbonate, especially selected from the group consisting of metal carbonates, metal bicarbonates and mixtures thereof.

[0043] The metals used here are preferably selected from alkali metals and alkaline earth metals, especially Na and K.

[0044] The organic adsorption medium can be an organic polyamine containing at least two N atoms separated by at least one C atom per molecule, particularly selected from the group consisting of ethyleneamine, aminosilane, polyethyleneimine (PEI), polyacrylamide, polyvinylpyridine, polydimethylaminoethyl methacrylate, polyamide amine, polyvinylamine and polyallylamine.

[0045] Ethyleneamine is preferably selected from the group consisting of: ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), aminoethylethanolamine (AEEA), aminoethylpiperazine (AEP), piperazine (PIP), hydroxyethylpiperazine (HEP), pentaethylenehexamine (PEHA), and polyethylenepolyamine (PEPA).

[0046] The aminosilane is preferably selected from the group consisting of: [3-(2-aminoethylamino)propyl]trialkoxysilane, 3-[2-(2-aminoethylamino)ethylamino]propyltrialkoxysilane, mixtures thereof and condensation products of 3-aminopropyltrialkoxysilane.

[0047] The polyamine can be silylated, for example, by reacting one or more amino groups of the polyamine with a suitably functionalized alkoxysilane, such as selected from the group consisting of 3-chloropropyltrialkoxysilane, 3-chloropropyltrialkoxysilane, glycidoxypropyltrialkoxysilane and isocyanopropyltrialkoxysilane.

[0048] In the context of this application, "alkoxy group" is preferably understood to mean a C1 to C4 alkoxy group, and particularly preferably an ethoxy or methoxy group.

[0049] Silylated polyamines can be obtained by silylation alone or in situ.

[0050] In a preferred embodiment, the adsorbent according to the present invention further comprises: (iii) At least one auxiliary agent selected from the group consisting of polymeric adhesives, silicone-containing adhesives such as silicates and silica sols, spreaders and wetting agents.

[0051] Polyamines can exist in combination with at least one amino-functionalized alkoxysilane.

[0052] At least one amino-functionalized alkoxysilane is preferably selected from the group consisting of: 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane and 3-aminopropyltriisopropoxysilane.

[0053] Based on the total amount of polyamine and amino-functionalized alkoxysilane, the amount of polyamine is preferably at least 50 by weight.

[0054] In preferred adsorbents, the amount of at least one adsorption medium (ii) is 10%-90% by weight, preferably 25%-80% by weight, based on the total weight of the adsorbent.

[0055] In specific embodiments, the molded body of the adsorbent does not contain inorganic or organic chemical binders, such as glycerol, kaolin, sugar, starch, urea, wax, methylcellulose, magnesium stearate, graphite, aluminum stearate, polyethylene glycol, or polyethylene oxide.

[0056] Another aspect of the present invention relates to a method for producing an adsorbent for CO2 according to the present invention, the method comprising the following steps in a specified sequence: (A) Provide a molded body composed of at least one amorphous silica, the molded body having a measurement value in the range of 0.5 mm to 30 mm in at least one dimension; (B) Impregnate the provided molded body with at least one adsorption medium for CO2 to functionalize the molded body with at least one adsorption medium.

[0057] The molded articles according to the invention can be ultrapure. In the context of the invention, ultrapure should be understood as meaning that it is substantially free of inorganic and organic impurities. Preferably, based on the total mass of the molded article, the total amount of impurities (all metals and carbon, phosphorus and sulfur) is less than 400 ppm, preferably less than 250 ppm, particularly preferably less than 100 ppm, even more preferably less than 50 ppm, even more preferably less than 20 ppm, even more preferably less than 10 ppm and most preferably less than 1 ppm.

[0058] In specific embodiments, the molded body is generally a sphere, ellipsoid, cylinder, hollow cylinder, or cuboid, preferably a cylinder or hollow cylinder. It is also clear to those skilled in the art that the specified geometry does not refer to a perfect geometry, and therefore deviations from an ideal geometry are possible.

[0059] The molded body preferably has an aspect ratio of up to 15, more preferably up to 10, and most preferably up to 6.

[0060] The molded body can be composed of amorphous silica agglomerates.

[0061] The agglomerates are preferably composed of aggregates of multiple primary silica particles.

[0062] The BET surface area of ​​the provided molded body is preferably between 30 and 500 m². 2 In the range of / g, especially in the range of 50 to 400m 2 Within the range of / g.

[0063] At least one amorphous silica is preferably selected from pyrolyzed or precipitated silica.

[0064] The silica of the molded body preferably has a mesoporous structure, especially a mesoporous structure with irregular pore structure.

[0065] In a preferred embodiment, the molded body is provided in step (A) by the following production molding process: (A1) Provides at least one type of silica in an aqueous solution with a pH of 2.0 to 10.0, preferably 3.0 to 8.0; (A2) Adjust the pH of the dispersion at least once; (A3) Molding; and (A4) Proceed with the subsequent drying.

[0066] In another preferred embodiment, the molded body is provided in step (A) by the following production molding process: (A1) Provides at least one type of silica in an aqueous solution with a pH of 2.0 to 10.0, preferably 3.0 to 8.0; (A2) Adjust the pH of the dispersion at least once; (A3) Molding; (A4) Proceed with the subsequent drying, and (A5) The sintering step is carried out at 400°C to 1500°C.

[0067] In a specific implementation, the pH in step (A1) is in the range of 2.0 to 4.0 or in the range of greater than 7.0 to at most 10.0.

[0068] The silica provided in step (A1) is preferably in powder form. The powdered silica preferably has an aggregate size of 100 nm to 500 nm as measured by dynamic light scattering.

[0069] The silica provided in step (A1) is preferably blended with the aqueous solution to form a dispersion.

[0070] Dispersion can be performed using various dispersing devices. Silica powder is initially stirred into water, for example, using a dissolving pan or planetary dissolving pan, and further stirred for at least 25 minutes at a circumferential speed of at least 5 m / s, preferably at least 8 m / s. This is pre-dispersion. At this point, the silica powder should have been wetted with water. Subsequent fine dispersion achieves the pulverization of particles, aggregates, and agglomerates, and is carried out for at least 25 minutes, for example using a dissolving pan, rotor-stator mixer, ultrasonic flow cell, planetary dissolving pan, wet jet mill, or optionally an ultrapure ball mill. Preferably, the dispersion is subjected to fine dispersion for at least 25 minutes using a dissolving pan, ultrasonic flow cell, planetary dissolving pan, or wet jet mill. The dispersion is particularly preferably subjected to fine dispersion for at least 25 minutes using a rotor-stator mixer, dissolving pan, or planetary dissolving pan at a circumferential speed of at least 10 m / s.

[0071] At the end of the dispersion, the dispersion can also be sieved to remove non-dispersible, unwetted and other coarse particles.

[0072] The pH adjustment in step (A2) is preferably carried out by adding a suitable acid and / or base, especially a base, to the aqueous solution from step (A1). Suitable acids include, for example, HCl, HNO3, H2SO4, H3PO4, or mixtures thereof. Suitable bases include, for example, alkali metal and alkaline earth metal hydroxides, carbonates, and mixtures thereof, such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, magnesium carbonate, basic magnesium carbonate, NH3, or mixtures thereof.

[0073] In a preferred embodiment, the pH adjustment according to step (A2) is performed twice, for example, by initially acidifying to achieve a pH < 4.0 and then subsequently increasing the pH of the reaction mixture to > 4.0 with alkali.

[0074] If the pH adjustment in step (A2) is performed only once, an aqueous solution with pH < 4.0 may have already been used in step (A1), and then the pH is increased to a value > 4.0 in step (A2).

[0075] In a preferred embodiment of step (A1), the aqueous solution has a pH of 2.0 to 4.0.

[0076] The pH adjustment in step (A2) is preferably characterized in that the pH difference before and after the pH adjustment in step (A2) is 0.5 to 5.5, wherein the target pH after the pH adjustment in step (A2) is preferably in the range of 4.0 to 7.5, particularly preferably in the range of 4.5 to 7.0.

[0077] The pH adjustment in step (A2) is preferably performed with stirring and / or kneading. This can be done using, for example, a planetary mixer or a centrifugal mixer.

[0078] The pH adjustment in step (A2) is typically accompanied by an increase in viscosity, and thus typically results in high viscosity quality.

[0079] The production of molded articles from the silica dispersion provided in steps (A1) to (A2) by forming in step (A3) is preferably carried out by extrusion, tableting, or pressing. All apparatuses known to those skilled in the art are conceivable here, such as extruders, tableting machines, or piston extrusion presses. The geometry of the molded article is determined by the forming tool selected in each case. Geometric shapes such as rings, granules, cylinders, wheels, spheres, etc., can be produced. The length of rings and granules is preferably defined directly after forming using a cutting device.

[0080] After molding, the molded article is dried in step (A4). This is preferably carried out using methods known to those skilled in the art (drying oven, IR heating, microwave oven). Drying can be carried out at a temperature preferably from 25°C to 200°C, more preferably from 30°C to 100°C, and very particularly preferably from 40°C to 80°C. The drying time depends on the ratio of silica to water, but is preferably 2 to 24 hours. Step (A4) can be carried out at a standard pressure of 1013 mbar or below atmospheric pressure. If the drying of the molded article in step (A4) is carried out below atmospheric pressure, then the pressure can be 10... -3 millibars to standard pressure, especially 10 -1 Millibars to 800 millibars.

[0081] The sintering step (A5), also known as calcination, can be carried out at 800°C to 1200°C, particularly 850°C to 1150°C. Calcination is preferably performed in a furnace in an air atmosphere. The air may be mixed with another gas. Various protective gases are suitable for this purpose. Suitable protective gases include all those known to those skilled in the art, with nitrogen, argon, or helium being particularly preferred. Air can also be completely replaced by a protective gas. The calcination time is 0.5 to 10 hours, and a typical calcination time is 2 hours. Calcination can be carried out at standard pressure or under vacuum.

[0082] Calcination can be used to produce fine-pore shaped bodies from finely ground silica. The proportion of pores with a diameter of 10 nm to 20 nm is typically greater than 50%, preferably greater than 70%, and particularly preferably greater than 80%.

[0083] In step (A1), at least one type of silica may be selected from pyrolytic silica or precipitated silica.

[0084] In the method according to the present invention, at least one adsorption medium may be an inorganic or organic adsorption medium.

[0085] The inorganic adsorption medium in the method according to the invention can be a carbonate, particularly selected from the group consisting of metal carbonates, metal bicarbonates and mixtures thereof.

[0086] The organic adsorption medium in the method according to the invention can be an organic polyamine in which each molecule contains at least two N atoms separated by at least one C atom, particularly selected from the group consisting of: ethyleneamine, aminosilane, polyethyleneimine (PEI), polyacrylamine, polyvinylpyridine, polydimethylaminoethyl methacrylate, polyamide amine, polyvinylamine and polyallylamine.

[0087] The ethyleneamine used in the method according to the present invention can be selected from the group consisting of: ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), aminoethylethanolamine (AEEA), aminoethylpiperazine (AEP), piperazine (PIP), hydroxyethylpiperazine (HEP), pentaethylenehexamine (PEHA), and polyethylenepolyamine (PEPA).

[0088] The aminosilane used in the method according to the invention may be selected from the group consisting of: [3-(2-aminoethylamino)propyl]trialkoxysilane, 3-[2-(2-aminoethylamino)ethylamino]propyltrialkoxysilane, mixtures thereof, and condensation products of 3-aminopropyltrialkoxysilane.

[0089] The polyamine in the method according to the invention may be silylated, for example, by reacting one or more amino groups of the polyamine with a suitably functionalized alkoxysilane, such as selected from the group consisting of 3-chloropropyltrialkoxysilane, 3-chloropropyltrialkoxysilane, glycidoxypropyltrialkoxysilane and isocyanopropyltrialkoxysilane.

[0090] Polyamines can be obtained, in particular, by silylation, which can be carried out alone or in situ.

[0091] At least one adsorbent medium is preferably present in liquid form during impregnation in step (B), for example as a solution, emulsion, or dispersion in a solvent / liquid medium, or in pure form. In the context of this invention, the adsorbent medium is also referred to as the impregnation medium. The solvent / liquid medium is preferably removed after impregnation.

[0092] In the method according to the invention, at least one adsorption medium may be a solution of a metal carbonate, especially potassium carbonate and / or sodium carbonate in water, or a solution of a metal bicarbonate, especially potassium bicarbonate and / or sodium bicarbonate in water.

[0093] In a preferred method, at least one adsorption medium is a saturated aqueous solution of potassium carbonate, sodium carbonate, potassium bicarbonate and / or sodium bicarbonate, preferably a saturated aqueous solution of potassium carbonate and / or potassium bicarbonate, and more preferably a saturated aqueous solution of potassium carbonate.

[0094] In a preferred method, the amount of metal carbonate or metal bicarbonate is 15-40% by weight, preferably 15-33% by weight, based on the total weight of the aqueous solution.

[0095] In a preferred method, the adsorption medium is in the form of a solution of an organic adsorption medium, such as an organic amine, in a suitable solvent, wherein the amount of dissolved organic adsorption medium is preferably at least 30% by volume, more preferably at least 60% by volume.

[0096] The organic solvent preferably has a boiling point of up to 200°C, more preferably up to 150°C, and in each case at 1013 mbar.

[0097] Examples of suitable solvents include water; alcohols such as methanol, ethanol, n-propanol, isopropanol, n-pentanol, and isopentanol; ethers such as dioxane, tetrahydrofuran, diethyl ether, isopropyl ether, and diethylene glycol dimethyl ether; chlorinated hydrocarbons such as dichloromethane, chloroform, tetrachloromethane, 1,2-dichloroethane, and trichloroethylene; hydrocarbons such as pentane, n-hexane, mixtures of hexane isomers, heptane, octane, gasoline, petroleum ether, benzene, toluene, and xylene; ketones such as acetone, methyl ethyl ketone, diisopropyl ketone, and methyl isobutyl ketone (MIBK); esters such as ethyl acetate, butyl acetate, propyl propionate, ethyl butyrate, and ethyl isobutyrate; carbon disulfide and nitrobenzene, or mixtures of these solvents.

[0098] The impregnation in step (B) is preferably carried out by contacting the molded body with at least one adsorption medium for CO2.

[0099] Suitable methods for impregnating silica molded articles generally include any existing techniques for surface treatment of fillers or particles. This is an advantage of silica molded articles according to the invention, as they are mechanically stable enough and do not tend to agglomerate or adhere when drying due to their size and shape.

[0100] In a preferred method, impregnation is performed by mixing, spraying, or immersing the molded body with at least one adsorbent medium in liquid form, or by initial wetting with at least one adsorbent medium in liquid form, particularly by initial wetting.

[0101] In the context of this invention, "impregnation" should be understood as immersion treatment with a liquid, dissolved, emulsified, or dispersed impregnation medium. The impregnation medium may be physically deposited on the inner and outer surface regions of the porous molded body, or may undergo complete or partial chemical bonding.

[0102] The “initial wetting process” is known in the literature to relate to the coating of a support material with a catalyst, and the principle is described in Marceau, E.; Carrier, X.; Chet, M., Impregnation and Drying, Synthesis of Solid Catalysts, 2009, pp. 59-82. It has been unexpectedly found that the initial wetting process is also suitable for coating molded articles according to the invention with an adsorption medium for CO2 in such a way that CO2 binding sites are uniformly distributed over the entire surface area of ​​the molded article. This allows for particularly high adsorption efficiencies in the adsorbent. In the initial wetting process, the adsorption medium is typically dissolved or dispersed in a solution (e.g., an aqueous or organic solution). This mixture can then be added to a support material, which preferably has the same pore volume as the added mixture. Capillary action causes the mixture to be drawn into the pores and results in functionalization there.

[0103] Compared to the wet process (“wet impregnation”), the initial wet process does not cause particle adhesion and the impregnation medium is deposited very uniformly on the internal and external surface areas of the molded body.

[0104] The impregnation in step (B) is preferably carried out in a temperature range of 0-150°C, and more preferably in a temperature range of 15-120°C.

[0105] The impregnation in step (B) is preferably carried out under standard pressure, under elevated pressure, or under pressure below atmospheric pressure.

[0106] The standard pressure is typically 1013 millibars.

[0107] If the impregnation in step (B) is carried out under increased pressure, that pressure may be up to 2 bar.

[0108] If the impregnation in step (B) is carried out at a pressure below atmospheric pressure, that pressure can be 10. -3 millibars to standard pressure, especially 10 -1 Millibars to 500 millibars.

[0109] The preferred method is characterized in that the molded body has a mesoporous structure, and the volume used for at least one adsorption medium for CO2 is 80% to 120%, preferably 90% to 110%, more preferably 95% to 105%, based on the total pore volume of the molded body.

[0110] Using this amount of adsorption medium ensures that the inner surface area of ​​the molded body is uniformly and completely functionalized by the adsorption medium. This achieves high adsorption efficiency.

[0111] In the preferred method, the molded body is at 10 3 -10 2 Treated at a pressure below atmospheric pressure and / or dried before impregnation.

[0112] In step (B), the provided molded body is impregnated with at least one adsorption medium for CO2 to functionalize the molded body, preferably together with at least one impregnation aid selected from wetting agents, emulsifiers, dyes, adhesives, adhesion promoters, higher functional alcohols and higher functional polyols.

[0113] In a preferred embodiment, the molded body retains the shape defined by the molding tool / molding process during production. Deformation during and immediately after molding creates density differences and stresses, which lead to defects (stripping, fine dust) on the molded body during drying and sintering. According to the invention, the produced carrier exhibits a stripping ratio preferably less than 5% by weight, more preferably less than 1% by weight, and very particularly preferably less than 0.5% by weight. Stripping is undesirable because it causes a high pressure drop when used in a column / reactor.

[0114] Therefore, the present invention particularly relates to an adsorbent for CO2 obtainable by a method according to the invention for producing an adsorbent for CO2, wherein impregnation is preferably carried out by an initial wetting process. This has the advantages of a particularly uniform distribution of CO2 adsorption sites, as detailed above, and the associated exceptional adsorption efficiency for CO2.

[0115] Another aspect of the invention relates to the use of the adsorbent for CO2 according to the invention for the reversible binding of CO2 from a gas mixture, particularly in the form of a fixed-bed adsorbent, for example for CCU, CCS and / or DAC.

[0116] Reversible bonding is achieved, in particular, through chemisorption. In this case, CO2 binds to the inner surface region of the molded body by chemically bonding with silica. The chemisorbed CO2 can then be released from the molded body again, and thus discharged by increasing the temperature and / or reducing the pressure. This has the advantage that CO2 can therefore not only be removed from the gas phase (e.g., DAC, CCS), but can also be released again at any time thereafter, and fed, for example, to processes that use CO2 as a starting material (e.g., CCU). Detailed Implementation

[0117] The following examples were carried out at ambient atmospheric pressure (i.e., about 1013 mbar) and room temperature (i.e., about 23°C), or at a temperature established when the reactants are combined at room temperature without additional heating or cooling, and describe how the invention can be practiced in principle, but do not limit the invention to what is disclosed herein.

[0118] Determination of CO2 adsorption capacity

[0119] CO2 adsorption capacity was determined using a BELCAT II gas adsorption analyzer from Microtrac. Temperature programmed desorption (TPD) was typically employed.

[0120] For sample preparation, the support to be studied was heated to 200°C at a constant helium flow rate of 10 K / min and held at this temperature for 35 minutes.

[0121] For analysis, the sample was initially purged with helium at 40°C. Then, CO2 was passed through the sample at 40°C for 90 min. If desired, the CO2 could be humidified using a commercially available steam injection device (“bubbler”).

[0122] The sample was treated in a helium stream at 40°C for 30 minutes.

[0123] Helium was used as the desorption gas for desorption. The temperature of the carrier was increased to 200°C at a rate of 10 K / min (linear temperature gradient) and held for 20 minutes.

[0124] The gas mixture was passed through a dry molecular sieve (3 Å) to remove water, and analyzed using a thermal conductivity detector (TCD) and mass spectrometry (MS). This allowed the amount of CO2 desorbed to be determined.

[0125] Silica Molded Body

[0126] The following is made from hydrophilic pyrolytic silica HDK® T40 (BET surface area: 400 m²). 2 / g, compaction density: 40 g / ml; available from Wacker Chemie AG) for the production of silica molded bodies: First, 1155g of double-distilled H2O was placed into a 4-liter plastic beaker. Using a plastic-coated dissolving pan, 345g of pyrolytic silica (BET surface area 400 m²) was dissolved at 1000 rpm. 2 The mixture was stirred in a solution of 1% NH3 (g / g). The mixture was then subjected to further stirring at a circumferential speed of 14 m / s for 40 min. The slurry was transferred to a planetary mixer with two plastic-coated rod stirrers. 7.5 g of 1% NH3 solution was added dropwise at 100 rpm. Once the addition was complete, the mixture was stirred for another 5 min. The mixture was then introduced into a piston extruder. The rheology and pH of random samples were simultaneously measured: G' = 200,000, G” = 25,000, pH = 6.1.

[0127] The material (mass) is extruded in a piston extruder using suitable tools to form the desired shape and cut into the required length of the molded body. The resulting molded body—in this case, granules with a length of 6 mm and a diameter of 6 mm—is dried at 85°C for 24 hours. The carrier is then sintered at 1060°C.

[0128] The silica molded body has 205m 2 / g BET surface area and 0.75cm 3 / g pore volume.

[0129] The pore volume was determined by nitrogen adsorption according to DIN 66134 (Langmuir, p / po=0.9995).

[0130] Potassium content determination

[0131] Potassium content was determined by ICP-OES (inductively coupled plasma optical emission spectrometry). For this purpose, the weighed sample was evaporated to dryness with hydrofluoric acid at approximately 150°C, the dried residue was redissolved with nitric acid, and then the potassium content was measured by ICP-OES (radial) after calibration.

[0132] Functionalization of silica carriers

[0133] Example 1

[0134] Functionalization of the carrier is performed by spraying a commercially available rotary evaporator with a functionalizing medium. The silica molded body is dried in a rotary evaporator flask at an oil bath temperature of 140°C and 25 mbar for 6 hours prior to the addition of the functionalizing medium. For functionalization, the rotary evaporator's exhaust nozzle has a Teflon hose connected thereto, through which the functionalizing medium is drawn from an external source by applying sub-atmospheric pressure, and delivered through another Teflon hose inside the rotary evaporator, reaching the evaporator flask.

[0135] After the functionalizing medium was applied directly by spray, the silica molded body subjected to spray application was post-treated by rotating in an evaporator flask at room temperature and standard pressure for 1 hour, and then dried in an oil bath at 80°C and 25 mbar.

[0136] Example 2

[0137] 12.7 g of silica preform was functionalized according to Example 1 by introducing a solution of 28.0 g of potassium carbonate in water at a concentration of 30% by weight. 20.7 g of functionalized preform was obtained after functionalization. The potassium content was 5.6 mmol / g preform (average of three individual values). The adsorption capacity, determined by chemisorption, was 2.8 mmol CO2 / g preform.

[0138] Example 3

[0139] 10.0 g of silica molded body was impregnated according to Example 1 by introducing 7.5 ml of pentaethylenehexamine (available from Merck KGaA, Darmstadt, Germany). The nitrogen content was 7.9 mmol / g molded body (average of three individual values). The adsorption capacity, determined by chemisorption, was 2.51 mmol CO2 / g molded body.

[0140] Example 4

[0141] 10.0 g of silica molded body was functionalized according to Example 1 by introducing 7.5 ml of 3-aminopropyltrimethoxysilane (available from Fisher Scientific GmbH, ImHeiligen Feld 17, 58239 Schwerte, Germany). The nitrogen content was 2.7 mmol / g molded body (average of three individual values). The adsorption capacity, determined by chemisorption, was 0.46 mmol CO2 / g molded body.

[0142] Example 5: A general procedure for impregnating a carrier with polyamines in methanol solution

[0143] The carrier was impregnated with a methanol solution in a three-necked flask. Before adding the functionalizing medium, the silica molded body was dried in the three-necked flask at room temperature and under a vacuum of 1.6 mbar for 2 hours. The vacuum was then broken with argon. For functionalization, a solution of methanol and the functionalizing medium was introduced into an argon-filled three-necked flask. The reaction solution was stirred at 70°C under reflux and argon inertization for 6 hours. The solvent was then removed using a commercially available rotary evaporator at 40°C and 337 mbar. The functionalized silica molded body was then dried in a drying oven at 100°C for 1 hour under a nitrogen atmosphere.

[0144] Example 6

[0145] According to Example 5, 10.0 g of silica molded body was functionalized by impregnation with a methanol solution of 7.5 g pentaethylenehexamine (available from Merck KGaA, Darmstadt, Germany) in 40 ml of methanol. The nitrogen content was 10.4 mmol / g molded body (average of three individual values). The adsorption capacity, determined by chemisorption, was 1.81 mmol CO2 / g molded body.

[0146] The invention is further characterized by the following points: 1. Adsorbents for CO2, including (i) A molded body composed of at least one amorphous silica, the molded body having a measured value of 0.5 mm to 30 mm, preferably 1.0 mm to 15 mm, in at least one dimension; and (ii) At least one adsorption medium for CO2, the molded body (i) being functionalized with the adsorption medium; The adsorbent has a strength of at least 2 N / mm. 2 Preferably at least 8 N / mm 2 The compressive strength.

[0147] 2. The adsorbent according to point 1, wherein the shaped body is composed of amorphous silica agglomerates.

[0148] 3. Based on point 1 or 2, the adsorbent has a BET surface area of ​​30-500 m². 2 Within the range of / g, especially in the 50-400m³ range 2 Within the range of / g.

[0149] 4. For any of the above points, at least one amorphous silica is selected from pyrolyzed or precipitated silica.

[0150] 5. The adsorbent according to any of the above points, wherein the silica of the shaped body has a mesoporous structure, especially a mesoporous structure with an irregular pore structure.

[0151] 6. An adsorbent according to any of the points above, wherein at least one adsorption medium (ii) is capable of undergoing a reversible reaction with CO2, particularly a reversible adsorption reaction.

[0152] 7. The adsorbent according to any of the points above, wherein at least one adsorption medium (ii) is an inorganic adsorption medium or an organic adsorption medium.

[0153] 8. The adsorbent according to point 7, wherein the inorganic adsorbent medium (ii) is a carbonate, particularly selected from the group consisting of metal carbonates, metal bicarbonates and mixtures thereof.

[0154] 9. The adsorbent according to point 7, wherein the organic adsorbent medium is an organic polyamine containing at least two N atoms separated by at least one C atom per molecule, particularly selected from the group consisting of ethyleneamine, aminosilane, polyethyleneimine (PEI), polyacrylamine, polyvinylpyridine, polydimethylaminoethyl methacrylate, polyamide amine, polyvinylamine and polyallylamine.

[0155] 10. According to point 9, the adsorbent wherein the ethyleneamine is selected from the group consisting of: ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), aminoethylethanolamine (AEEA), aminoethylpiperazine (AEP), piperazine (PIP), hydroxyethylpiperazine (HEP), pentaethylenehexamine (PEHA), and polyethylenepolyamine (PEPA).

[0156] 11. The adsorbent according to point 9, wherein the aminosilane is selected from the group consisting of: [3-(2-aminoethylamino)propyl]trialkoxysilane, 3-[2-(2-aminoethylamino)ethylamino]propyltrialkoxysilane, mixtures thereof and condensation products of 3-aminopropyltrialkoxysilane.

[0157] 12. An adsorbent according to any one of points 9 to 11, wherein the polyamine is silylated, for example, by reaction of one or more amino groups of the polyamine with a suitably functionalized alkoxysilane, the alkoxysilane being selected, for example, from the group consisting of: 3-chloropropyltrialkoxysilane, 3-chloropropyltrialkoxysilane, glycidoxypropyltrialkoxysilane and isocyanopropyltrialkoxysilane.

[0158] 13. According to the adsorbent of point 12, the silanized polyamine can be obtained by silanization alone or in situ.

[0159] 14. The adsorbent according to any one of the above points further includes

[0160] (iii) At least one auxiliary agent selected from the group consisting of polymeric adhesives, silicone-containing adhesives such as silicates and silica sols, spreaders and wetting agents.

[0161] 15. The adsorbent according to any one of points 9 to 14, wherein the polyamine is present in combination with at least one amino-functionalized alkoxysilane.

[0162] 16. The adsorbent according to point 15, wherein at least one amino-functionalized alkoxysilane is selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane and 3-aminopropyltriisopropoxysilane.

[0163] 17. The adsorbent according to point 15 or 16, wherein the amount of polyamine is at least 50 by weight, based on the total amount of polyamine and amino-functionalized alkoxysilane.

[0164] 18. An adsorbent according to any of the above points, wherein, based on the total weight of the adsorbent, the amount of at least one adsorbent medium (ii) is 10% to 90% by weight, preferably 25% to 80% by weight.

[0165] 19. A method for producing an adsorbent for CO2 according to any one of points 1-18, the method comprising the following steps in a specified order: (A) Provide a molded body composed of at least one amorphous silica, the molded body having a measurement value in the range of 0.5 mm to 30 mm in at least one dimension; (B) Impregnate the provided molded body with at least one adsorption medium for CO2 to functionalize the molded body with at least one adsorption medium.

[0166] 20. According to the method of point 19, wherein providing the molded body in step (A) is achieved by producing the molded body in the following manner: (A1) Provides at least one type of silica in an aqueous solution with a pH of 2.0 to 10.0, preferably 3.0 to 8.0; (A2) Adjust the pH of the dispersion at least once; (A3) Molding; and (A4) Proceed with the subsequent drying.

[0167] 21. According to the method of point 20, wherein providing the molded body in step (A) is achieved by producing the molded body in the following manner: (A1) Provides at least one type of silica in an aqueous solution with a pH of 2.0 to 10.0, preferably 3.0 to 8.0; (A2) Adjust the pH of the dispersion at least once; (A3) Molding; (A4) Proceed with the subsequent drying, and (A5) The sintering step is carried out at 400°C to 1500°C.

[0168] 22. According to the method of point 21, the sintering step is carried out at 800°C to 1200°C, especially at 850°C to 1150°C.

[0169] 23. The method according to any one of points 20 to 22, wherein at least one silica in step (A1) is selected from pyrolytic silica or precipitated silica.

[0170] 24. The method according to any one of points 20 to 23, wherein the aqueous solution in step (A1) has a pH of 2.5 to 4.0.

[0171] 25. The method according to any one of points 20 to 24, wherein the pH adjustment in step (A2) is characterized in that the pH difference before and after the pH adjustment in step (A2) is 0.5 to 5.5, wherein the target pH after the pH adjustment in step (A2) is preferably in the range of 4.0 to 7.5, particularly preferably in the range of 4.5 to 7.0.

[0172] 26. The method according to any one of points 19 to 25, wherein at least one adsorption medium is an inorganic or organic adsorption medium.

[0173] 27. According to the method of point 26, wherein the inorganic adsorption medium is a carbonate, particularly selected from the group consisting of metal carbonates, metal bicarbonates and mixtures thereof.

[0174] 28. According to the method of point 26, wherein the organic adsorbent is an organic polyamine containing at least two N atoms separated by at least one C atom per molecule, particularly selected from the group consisting of: ethyleneamine, aminosilane, polyethyleneimine (PEI), polyacrylamine, polyvinylpyridine, polydimethylaminoethyl methacrylate, polyamide amine, polyvinylamine and polyallylamine.

[0175] 29. According to the method of point 28, wherein the ethyleneamine is selected from the group consisting of: ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), aminoethylethanolamine (AEEA), aminoethylpiperazine (AEP), piperazine (PIP), hydroxyethylpiperazine (HEP), pentaethylenehexamine (PEHA), and polyethylenepolyamine (PEPA).

[0176] 30. According to the method of point 29, wherein the aminosilane is selected from the group consisting of: [3-(2-aminoethylamino)propyl]trialkoxysilane, 3-[2-(2-aminoethylamino)ethylamino]propyltrialkoxysilane, mixtures thereof and condensation products of 3-aminopropyltrialkoxysilane.

[0177] 31. The method according to any one of points 28 to 30, wherein the polyamine is silylated, for example, by reacting one or more amino groups of the polyamine with a suitably functionalized alkoxysilane, the alkoxysilane being selected, for example, from the group consisting of: 3-chloropropyltrialkoxysilane, 3-chloropropyltrialkoxysilane, glycidoxypropyltrialkoxysilane, and isocyanopropyltrialkoxysilane.

[0178] 32. The method according to point 31, wherein the polyamine can be obtained by silylation, which can be carried out alone or in situ.

[0179] 33. The method according to any one of points 19 to 32, wherein at least one adsorbent medium is present in liquid form during impregnation in step (B), for example as a solution, emulsion or dispersion in a solvent / liquid medium or in pure form.

[0180] 34. According to the method of point 33, at least one of the adsorption media is a solution of a metal carbonate, especially potassium carbonate and / or sodium carbonate in water, or a solution of a metal bicarbonate, especially potassium bicarbonate and / or sodium bicarbonate in water.

[0181] 35. According to the method of point 33 or 34, wherein at least one adsorption medium is a saturated aqueous solution of potassium carbonate, sodium carbonate, potassium bicarbonate and / or sodium bicarbonate, preferably a saturated aqueous solution of potassium carbonate and / or potassium bicarbonate, more preferably a saturated aqueous solution of potassium carbonate.

[0182] 36. According to the method of point 34 or 35, wherein the amount of metal carbonate or metal bicarbonate is 15-40% by weight, preferably 15-33% by weight, based on the total weight of the aqueous solution.

[0183] 37. The method according to any one of points 19 to 36, wherein the adsorption medium is in the form of a solution of an organic adsorption medium such as an organic amine in a suitable solvent, wherein the amount of dissolved organic adsorption medium is preferably at least 30% by volume, more preferably at least 60% by volume.

[0184] 38. The method according to any one of points 19 to 37, wherein the impregnation in step (B) is carried out by contacting the molded body with at least one adsorption medium for CO2.

[0185] 39. The method according to any one of points 19 to 38, wherein the impregnation in step (B) is carried out in a temperature range of 0-150°C, preferably in a temperature range of 15-120°C.

[0186] 40. The method according to any one of points 19 to 39, wherein the impregnation in step (B) is carried out at standard pressure, elevated pressure or below atmospheric pressure.

[0187] 41. The method according to any one of points 19 to 40, wherein impregnation is carried out by mixing, spraying or immersing the molded body with at least one adsorbent medium in liquid form, or by initial wetting with at least one adsorbent medium in liquid form, particularly by initial wetting.

[0188] 42. The method according to any one of points 19 to 41, wherein the molded body has a mesoporous structure, and the volume of at least one adsorption medium for CO2 is 80% to 120%, preferably 90% to 110%, more preferably 95% to 105%, based on the total pore volume of the molded body.

[0189] 43. According to any one of points 19 to 42, wherein the molded body

[0190] -in 10 -3 Up to 10 2 Treatment at pressures below atmospheric pressure (mbar); and / or

[0191] -Dry before impregnation.

[0192] 44. The method according to any one of points 19 to 43, wherein in step (B), the provided molded body is impregnated with at least one adsorption medium for CO2 to functionalize the molded body together with at least one impregnation aid selected from wetting agents, emulsifiers, dyes, adhesives, adhesion promoters, higher functional alcohols and higher functional polyols.

[0193] 45. The use of an adsorbent for CO2 according to any of points 1 to 18 for the reversible binding of CO2 from a gas mixture, particularly in the form of a fixed-bed adsorbent, for example for CCU, CCS and / or DAC.

Claims

1. An adsorbent for CO2, comprising: (i) A molded body composed of at least one amorphous silica, said molded body having a measured value in the range of 0.5 mm to 30 mm in at least one dimension; and (ii) At least one adsorption medium for CO2, wherein the molded body (i) is functionalized with the adsorption medium; in, The adsorbent has a concentration of at least 2 N / mm. 2 The compressive strength.

2. The adsorbent according to claim 1, wherein, The molded body is composed of amorphous silica agglomerates.

3. The adsorbent according to any one of the preceding claims, wherein, The molded body is in the form of a sphere, ellipsoid, cylinder, hollow cylinder or cuboid, and / or has an aspect ratio of not more than 15.

4. The adsorbent according to any one of the preceding claims, wherein, The at least one amorphous silica is selected from pyrolytic or precipitated silica.

5. The adsorbent according to any one of the preceding claims, wherein, The silicon dioxide of the molded body has a mesoporous structure.

6. The adsorbent according to any one of the preceding claims, wherein, The silicon dioxide of the molded body has a mesoporous structure, and the mesoporous structure has an irregular pore structure.

7. The adsorbent according to any one of the preceding claims, wherein, The at least one adsorption medium (ii) is an inorganic adsorption medium or an organic adsorption medium.

8. The adsorbent according to claim 7, wherein, The inorganic adsorption medium (ii) is a carbonate, particularly selected from the group consisting of metal carbonates, metal bicarbonates and mixtures thereof.

9. The adsorbent according to claim 7, wherein, The organic adsorption medium is an organic polyamine containing at least two N atoms separated by at least one C atom per molecule, particularly selected from the group consisting of ethyleneamine, aminosilane, polyethyleneimine (PEI), polyacrylamine, polyvinylpyridine, polydimethylaminoethyl methacrylate, polyamide amine, polyvinylamine and polyallylamine.

10. The adsorbent according to any one of the preceding claims, further comprising: (iii) At least one auxiliary agent selected from the group consisting of polymeric adhesives, silicone-containing adhesives such as silicates and silica sols, spreaders and wetting agents.

11. A method for producing an adsorbent for CO2 according to any one of claims 1-10, the method comprising the following steps in a specified sequence: (A) Provides a molded body composed of at least one amorphous silica, said molded body having a measurement value in the range of 0.5 mm to 30 mm in at least one dimension; (B) Impregnate the provided molded body with at least one adsorption medium for CO2 to functionalize the molded body with said at least one adsorption medium.

12. The method according to claim 11, wherein, Providing the molded body in step (A) is achieved by producing the molded body in the following way: (A1) Provides at least one type of silica in an aqueous solution with a pH of 2.0 to 10.0; (A2) Adjust the pH of the dispersion at least once; (A3) Molding; and (A4) Proceed with the subsequent drying; and optional (A5) Sintering steps are carried out at 400°C to 1500°C.

13. The method according to claim 11 or 12, wherein, The at least one adsorbent medium is present in liquid form during impregnation in step (B), for example as a solution, emulsion, or dispersion in a solvent / liquid medium, or in pure form.

14. The method according to any one of claims 11-13, wherein, The impregnation is performed by mixing, spraying, or immersing the molded body with at least one of the adsorbent media in liquid form, or by initial wetting with at least one of the adsorbent media in liquid form.

15. Use of the adsorbent for CO2 according to any one of claims 1-10 for reversibly binding CO2 from a gas mixture.