Shaped body for reversible chemisorption of co2

Abstract

The present invention is directed to a sorbent for CO2 comprising an amorphous silica shaped body having dimensions in at least one dimension in the range from 0.5 mm to 30 mm and at least one sorption medium for CO2 with which the shaped body is functionalized, to the production of said sorbent and to use thereof as a fixed bed sorbent.

Description

[0001] Shaped bodies for reversible chemisorption of CO2

[0002] The present invention is directed to a sorbent for CO2, comprising a silica / silicon dioxide shaped body with dimensions in at least one dimension in the range from 0.5 mm to 30 mm and at least one sorbent for CO2 with which the shaped body is functionalized, the production of this sorbent and the use of this sorbent as a fixed bed sorbent in the chemisorption of CO2.

[0003] “Functionalized” in the sense of the invention means, for example, that the shaped body is impregnated and / or coated with the sorbent.

[0004] Climate change and global warming are considered to be the most serious environmental problems of our time. It is now generally accepted that the main cause of global warming is the release of so-called greenhouse gases into the atmosphere. One important greenhouse gas is carbon dioxide (CO2), which is released primarily during the combustion of fossil fuels such as coal, petroleum, and natural gas. Together, these fossil fuels cover about 80% of the world's energy needs. Because fossil fuels remain relatively cheap and easy to use, and because no satisfactory alternatives are yet available that could replace them on the required scale, fossil fuels are likely to remain our most important energy source in the long term.This makes it all the more important to channel CO2 emissions into innovative technologies capable of storing CO2 as a valuable resource and / or using it as a feedstock for further processes. "Carbon Capture and Storage" (CCS) is one such technology, in which CO2 is captured, processed, compressed, and transported to a storage site, either from the environment or directly at the sources of fossil CO2 emissions of an industrial or energy-related nature.

[0005] In contrast to the pure storage purpose of CCS, "Carbon Capture and Utilization" (CCU) concerns the separation of CO2, particularly from combustion exhaust gases, and its subsequent use in further chemical processes, such as the conversion to methanol.

[0006] Another method for extracting CO2 is "Direct Wire Capture" (DAC), in which CO2 is extracted from the ambient air.

[0007] All of these technologies require that CO2 can be reversibly sorbed onto a solid sorbent. This sorbent is typically used as a fixed-bed sorbent in sorption columns, through which the gas from which CO2 is to be removed flows.

[0008] Solid sorbent materials are currently used in the form of finely divided powders, which, however, have disadvantages for sorption columns. The use of finely divided powders in the columns leads to an undesirably high pressure drop, associated with turbulence and discharge of the sorbent from the column.

[0009] Instead of using finely divided powders, EP2102131A1 teaches larger metal oxide moldings, which, however, are not functionalized and are therefore unsuitable for selectively adsorbing CO2 from gas mixtures.

[0010] It would therefore be desirable to provide a sorbent for CO2 that overcomes the disadvantages associated with powdered sorbent materials. When used as a fixed-bed sorbent in a sorption column, it results in a low pressure drop and little turbulence or even discharge of the sorbent from the column. At the same time, CO2 should be able to be reversibly bound with high sorption efficiency and capacity.

[0011] The object of the invention is achieved by the first aspect of the present invention, namely a sorbent for CO2, in particular a solid sorbent, comprising

[0012] ( i ) a shaped body made of at least one amorphous silicon dioxide (= silica ) with dimensions in at least one dimension in the range from 0.5 mm to 30 mm, preferably 1.0 mm to 15 mm; and

[0013] ( ii ) at least one sorbent for CO2 with which the

[0014] Shaped body ( i ) is functionalized ; wherein the sorbent has a compressive strength of at least

[0015] 2 N / mm 2 , preferably at least 8 N / mm 2 , has .

[0016] A preferred sorbent comprises shaped bodies which have dimensions in one, two or three dimensions, more preferably in two or three dimensions, in particular in all three dimensions in the range from 0.5 mm to 30 mm, preferably 1.0 mm to 15 mm.

[0017] Preferably, the sorbent according to the invention has the same dimensions as the corresponding shaped body.

[0018] When a gas mixture flows through the powder beds known in the prior art, a high pressure drop occurs between the sides facing toward and away from the gas source. A coarser shaped body having the dimensions according to the invention is advantageous because the pressure loss (= pressure drop) when flowing through such a bed is reduced.

[0019] The sorbent according to the invention is therefore particularly well suited as an efficient fixed-bed sorbent for CCU, CCS, or DAC, since – in contrast to fine-particle powders – it results in a lower pressure drop and little turbulence or even discharge of the sorbent from the sorption column. Efficient CO2 adsorption is only possible with the use of the shaped bodies according to the invention.

[0020] The silica moldings according to the invention also exhibit improved mechanical stability and improved long-term stability. In contrast to powdered sorbents, the silica moldings according to the invention do not tend to agglomerate or stick together during impregnation (= functionalization with sorbent) and do not require complex grinding.

[0021] The compressive strength according to the invention can be determined using all methods known in the art, for example using the universal testing machine Z 400 E with 1 kN force transducer.

[0022] It has surprisingly been shown that particularly good adsorption ef fi ciencies in the sorption column can only be achieved if the compressive strength of the sorbent according to the invention is maintained. Shaped bodies whose compressive strength is less than 2 N / mm 2cannot adequately withstand the CCh pressure in the adsorption column and are destroyed, exhibiting, for example, flaking. Destroyed molded bodies lead to the same disadvantages that also occur when using sorption powders in the sorption column (e.g., higher pressure drop, turbulence, discharge).

[0023] The shaped body according to the invention can be highly pure. Highly pure in the sense of the invention means that it is substantially free from inorganic and organic impurities. The sum of impurities (all metals as well as carbon, phosphorus and sulfur) is preferably less than 400 ppm, more preferably less than 250 ppm, particularly preferably less than 100 ppm, even more preferably less than 50 ppm and even more preferably less than 20 ppm, even more preferably less than 10 ppm and most preferably less than 1 ppm, based on the total mass of the shaped body.

[0024] Impurities can be quantified using all common analytical methods, such as XRF, AAS, ICP-OES, or ICP-MS. If necessary, the shaped body must be dissolved in a suitable solvent, such as hydrofluoric acid, before analysis.

[0025] In a particular embodiment, the shaped bodies are essentially spheres, ellipsoids, cylinders, hollow cylinders (e.g., tubes), or cuboids, preferably cylinders or hollow cylinders. It is also clear to the person skilled in the art that the specified geometry does not represent perfect geometric bodies, so deviations from the ideal geometry are possible.

[0026] The shaped bodies preferably have an aspect ratio of at most 15, more preferably of at most 10, most preferably of at most 6.

[0027] It has further been found that the aspect ratio mentioned has a particularly positive effect on the suitability of the shaped body in a sorption column, since the already low pressure drop when using the shaped bodies according to the invention can be reduced even further due to the aspect ratio mentioned. Shaped bodies whose aspect ratio exceeds that of the invention can no longer be effectively packed in reaction / sorption columns and tend to break. Breakage points are disadvantageous because they result in very small shaped body fragments, which result in a high pressure drop and turbulence in the column, as well as discharge from the column.

[0028] The shaped body is preferably constructed from agglomerates of amorphous silicon dioxide / silica. The agglomerates are preferably constructed from aggregates of a plurality of primary silica particles.

[0029] In a preferred embodiment, the BET surface area of ​​the sorbent is in the range of 30 to 500 m 2 / g, especially in the range from 50 to 400 m 2 / g .

[0030] The BET surface area can be determined using standard measurement methods. The BET surface area is preferably determined using nitrogen according to DIN 66131.

[0031] The shaped bodies are preferably characterized by a high pore volume which is between 0.5 ml / g and 1.8 ml / g, preferably between 0.6 ml / g and 1.5 ml / g and particularly preferably between 0.7 ml / g and 1.2 ml / g.

[0032] If the pore volume exceeds the above-mentioned ranges, the shaped bodies are too fragile and tend to break during use in a sorption column. This results in the formation of very small shaped body fragments and thus a high pressure drop. Fragments with a pore volume smaller than specified have an insufficient internal surface area and thus lead to low sorption efficiencies and capacities.

[0033] The pore volume is preferably determined according to DIN 66134 (Langmuir, p / pO = 0.9995).

[0034] The at least one amorphous silicon dioxide may be selected from pyrogenic or precipitated silicon dioxide.

[0035] To produce pyrogenic silicon dioxide, a volatile silicon halide (e.g., silicon tetrachloride) is usually injected into an oxyhydrogen flame consisting of hydrogen and air. This substance hydrolyzes to silicon dioxide under the influence of the water produced during the oxyhydrogen reaction. After leaving the flame, the silicon dioxide enters a so-called coagulation zone, where the primary particles and primary aggregates agglomerate.

[0036] To produce precipitated silica, for example, commercially available sodium silicate is reacted with an acid (e.g., sulfuric acid) at a pH between 7.5 and 10.5. The pH is then adjusted to 3.0 to 5.0, and the precipitated silica is filtered, washed, and dried.

[0037] In a preferred embodiment, the silicon dioxide of the shaped body has a mesoporous structure, in particular a mesoporous structure with an irregular pore structure.

[0038] The irregular pore structure of the silica according to the above preferred embodiment is also retained in the molded body. The pore structure of the silica creates channels within the molded body, which define the inner surface of the molded body. Functionalization with the sorbent preferably occurs on the inner surfaces of the molded bodies according to the invention.

[0039] Mesoporous solids are, according to the IUPAC definition, porous

[0040] Materials with pore diameters between 2 nm and 50 nm.

[0041] It is known to those skilled in the art that mesoporous silica is usually produced by a complex template-based synthesis. Silica produced in this way is characterized by a defined, channel-like pore structure. In contrast, the molded articles according to the invention are based on silica, which is characterized by an irregular pore structure. "Irregular pore structure" in this context means that the pores within the silica extend asymmetrically and / or randomly without any recognizable repeating sections, either with or without at least one branching and / or branching.

[0042] Silica with such an irregular pore structure, for example, has economic advantages because it is far cheaper and easier to produce than silica with a predefined and regular channel structure. Furthermore, it has surprisingly been shown that the CO2 adsorption efficiency of the inventive shaped bodies made of silica with an irregular pore structure can significantly exceed the adsorption efficiency of shaped bodies made of silica with a defined, uniform pore structure because silica with an irregular pore structure is less prone to clogging and closure of the channels by sorbents. Thus, the inner surfaces of the inventive shaped bodies can be more homogeneously and completely functionalized, thereby increasing the adsorption capacity of the inventive shaped bodies for CO2.Sufficient capacities for efficient CO2 sorption are preferably at least 20 mg CO2 per gram of sorbent (corresponding to about 0.45 mmol CO2), more preferably at least.

[0043] 40 mg CO2 per gram of sorbent.

[0044] In a preferred embodiment, the at least one sorbent (11) is capable of entering into a reversible reaction with CO2, in particular a reversible sorption reaction.

[0045] The sorption reaction is, in particular, a chemisorption. In this case, the CO2 is bound to the inner surface of the molded body by chemical bonding with the sorbent. By increasing the temperature and / or decreasing the pressure, the chemisorbed CO2 can be released from the molded body and thus expelled. This has the advantage that the CO2 can not only be removed from the gas phase (e.g., DAC, CCS), but can also be released again at any time thereafter and, for example, fed into a process that uses CO2 as a starting material (e.g., CCU), such as the conversion to methanol.

[0046] The at least one sorbent (11) can be an inorganic or an organic sorbent.

[0047] The inorganic sorbent (ii) is preferably a carbonate, in particular selected from the group consisting of metal carbonate, metal bicarbonate and mixtures thereof.

[0048] Preferably, the metal here is selected from alkali metals and alkaline earth metals, in particular from Na and K.

[0049] The organic sorbent may be an organic polyamine comprising at least two N atoms per molecule separated by at least one C atom, in particular selected from the group consisting of ethyleneamine, aminosilane, polyethyleneimine (PEI), polypropyleneamine, polyvinylpyridine, polydimethylaminoethyl methacrylate, polyamidoamine, polyvinylamine and polyallylamine.

[0050] The ethyleneamine is preferably selected from the group consisting of ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetraamine (TETA), tetraethylenepentamine (TEPA), aminoethylethanolamine (AEEA), aminoethylpiperazine (AEP), piperazine (PIP), hydroxyethylpiperazine (HEP), pentaethylenehexamine (PEHA) and polyethylenepolyamine (PEPA).

[0051] 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.

[0052] The polyamine may be silylated, for example obtainable by reacting one or more amino groups of the polyamine with suitably functionalized alkoxysilanes, for example selected from the group consisting of 3-chloropropyl-trialkoxysilane, 3-chloropropyl-trialkoxysilane, glycidoxypropyl-trialkoxysilane and isocyanatopropyl-trialkoxysilane.

[0053] "Alkoxy radical" in the sense of this application preferably means a C 1 -C 4 alkoxy radical, particularly preferably an ethoxy or methoxy radical

[0054] The silylated polyamine can be obtained by silylation, which can be carried out in isolation or in situ.

[0055] In a preferred embodiment, the inventive

[0056] Sorbent further (iii) at least one auxiliary agent selected from the group consisting of polymeric binders, silicon-containing binders such as silicates and silica sol, spreading agents and wetting agents.

[0057] The polyamine can be present in combination with at least one aminofunctional alkoxysilane.

[0058] The at least one amino-functional alkoxysilane is preferably selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane and 3-aminopropyltriisoproxysilane.

[0059] The amount of polyamine is preferably at least 50 wt.% based on the total amount of polyamine and amino-functional alkoxysilane.

[0060] In a preferred sorbent, the amount of at least one sorbent (ii) is 10 to 90 wt.%, preferably 25 to 80 wt.%, based on the total weight of the sorbent.

[0061] In a special version, the molded body of the sorbent is free of inorganic and organic chemical binders, such as glycerin, kaolin, sugar, starch, urea, wax, methylcellulose, magnesium stearate, graphite, aluminum stearate,

[0062] Polyethylene glycol or polyethylene oxide.

[0063] A further aspect of the present invention is directed to a process for producing the sorbent for CO2 according to the invention, comprising the following steps in the order given: (A) providing a shaped body of at least one amorphous silicon dioxide having dimensions in at least one dimension in the range of 0.5 mm to 30 mm;

[0064] (B) Impregnating the provided shaped body with at least one sorbent for CO2 in order to functionalize the shaped body.

[0065] The shaped body according to the invention can be highly pure. Highly pure in the sense of the invention means that it is substantially free from inorganic and organic impurities. The sum of impurities (all metals as well as carbon, phosphorus and sulfur) is preferably less than 400 ppm, more preferably less than 250 ppm, particularly preferably less than 100 ppm, even more preferably less than 50 ppm and even more preferably less than 20 ppm, more preferably less than 10 ppm and most preferably less than 1 ppm, based on the total mass of the shaped body.

[0066] In a particular embodiment, the shaped bodies are essentially spheres, ellipsoids, cylinders, hollow cylinders, or cuboids, preferably cylinders or hollow cylinders. It is also clear to a person skilled in the art that the specified geometry does not represent perfect geometric bodies, so deviations from the ideal geometry are possible.

[0067] The shaped bodies preferably have an aspect ratio of at most 15, more preferably of at most 10, most preferably of at most 6.

[0068] The shaped body can be composed of agglomerates of amorphous silicon dioxide. The agglomerates are preferably composed of aggregates of a plurality of primary silica particles.

[0069] The BET surface area of ​​the provided molded body is preferably in the range of 30 to 500 m 2 / g, especially in the range of 50 to 400 m 2 / G.

[0070] The at least one amorphous silicon dioxide is preferably selected from pyrogenic or precipitated silicon dioxide.

[0071] The silicon dioxide of the shaped body preferably has a mesoporous structure, in particular a mesoporous structure with an irregular pore structure.

[0072] In a preferred embodiment, the molded body is provided in step (A) by

[0073] (Al) at least one silicon dioxide is provided in an aqueous solution having a pH of 2.0 to 10.0, preferably 3.0 to 8.0;

[0074] (A2) this dispersion is subjected to a change in pH at least once;

[0075] (A3) shaping takes place; and

[0076] (A4) subsequent drying is carried out to produce the shaped body.

[0077] In a further preferred embodiment, the provision of the shaped body in step (A) is carried out by

[0078] (Al) at least one silicon dioxide is provided in an aqueous solution having a pH of 2.0 to 10.0, preferably 3.0 to 8.0;

[0079] (A2) this dispersion is subjected to a change in pH at least once; (A3) shaping takes place;

[0080] (A4) subsequent drying takes place, and

[0081] (A5) a sintering step is carried out at 400 °C to 1500 °C to produce the shaped body.

[0082] In a particular embodiment, the pH value in step (A1) is either in the range of 2.0 to 4.0 or in the range of more than 7.0 to a maximum of 10.0.

[0083] The silicon dioxide provided in step (A1) is preferably in powder form. The powdered silicon dioxide preferably has aggregate sizes of 100 nm to 500 nm, as measured by dynamic light scattering.

[0084] By mixing the silicon dioxide provided in step (Al) with the aqueous solution, a dispersion is preferably formed.

[0085] Dispersal can be carried out using various dispersing devices. For example, the silicon dioxide powder is first stirred into water using a dissolver disk or planetary dissolver disk and then stirred for at least 25 minutes at a peripheral speed of at least 5 m / s, preferably at least 8 m / s. This is a pre-dispersion step. The wetting of the silicon dioxide powder by water should already be complete at this point. The subsequent fine dispersion serves to reduce the size of particles, aggregates and agglomerates and is carried out, for example, using a dissolver, rotor-stator mixer, ultrasonic flow cell, planetary dissolver, wet jet mill or, if necessary, a high-purity ball mill for at least 25 minutes. The dispersion is preferably finely dispersed using a dissolver, ultrasonic flow cell, planetary dissolver or wet jet mill for at least 25 minutes.Particularly preferably, the dispersion is finely dispersed by means of a rotor-stator mixer, dissolver or planetary dissolver for at least 25 minutes at a peripheral speed of the dissolver disk of at least 10 m / s.

[0086] At the end of the dispersion process, the dispersions can also be freed from non-dispersible, non-wetted and other coarse particles by sieving.

[0087] The pH value in step (A2) is preferably changed by adding suitable acids and / or bases, especially bases, to the aqueous solution from step (A1). Suitable acids are, for example, HCl, HNO3, H2SO4, H3PO4, or mixtures thereof. Suitable bases are, for example, alkali and alkaline earth metal hydroxides, carbonates, and mixtures thereof, such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, magnesium carbonate, magnesium hydroxide carbonate, NH3, or mixtures thereof.

[0088] In a preferred embodiment, the pH value is changed according to step (A2) twice, for example by first acidifying to achieve a pH value < 4.0 and then raising the reaction mixture to a value > 4.0 with a base.

[0089] In the event that the pH value is to be changed only once in step (A2), an aqueous solution with a pH of < 4.0 can be used in step (A1) before the pH value is then raised to a value of > 4.0 in step (A2).

[0090] In a preferred embodiment of step (A1), the aqueous solution has a pH of 2.0 to 4.0. The change in the pH in step (A2) is preferably characterized in that the difference in the pH before and after the change in the pH in step (A2) is 0.5 to 5.5, wherein the target pH after the change in the pH in step (A2) is preferably in the range from 4.0 to 7.5, particularly preferably in the range from 4.5 to 7.0.

[0091] The pH change in step (A2) is preferably carried out by stirring and / or kneading. Planetary mixers or centrifugal mixers can be used for this purpose, for example.

[0092] The change in pH in step (A2) is typically accompanied by an increase in viscosity, so that a highly viscous mass is typically obtained.

[0093] The production of shaped bodies by shaping in step (A3) the dispersion of the silicon dioxide prepared in steps (A1) to (A2) is preferably carried out by extrusion, tableting, or pressing. All equipment known to the person skilled in the art, such as extruders, tabletting machines, or piston extruders, is conceivable. The geometry of the shaped body results from the selected shaping tool. Geometries such as rings, pellets, cylinders, wagon wheels, spheres, etc. can be produced. The length of rings and pellets is preferably defined using a cutting device directly after shaping.

[0094] After shaping, the molded body is dried in process step (A4). This is preferably carried out using methods known to those skilled in the art (drying cabinet, IR heating, microwave). Drying can take place at temperatures between 25°C and 200°C, preferably between 30°C and 100°C, and most preferably between 40°C and 80°C. The drying time depends on the ratio of silicon dioxide to water, but is preferably between 2 and 24 hours. Process step (A4) can be carried out at atmospheric pressure at 1013 mbar or under reduced pressure. If the drying of the molded body in step (A4) takes place under reduced pressure, the pressure can be 10~ 3 mbar to normal pressure, especially 10 -1 mbar to 800 mbar.

[0095] The sintering step (A5) is also called calcination and can be carried out at temperatures between 800°C and 1200°C, particularly between 850°C and 1150°C. Calcination in a furnace under air atmosphere is preferred. Another gas can be admixed with the air. Various protective gases are suitable for this purpose. All protective gases known to those skilled in the art are suitable; nitrogen, argon, or helium are particularly preferred. The air can also be completely replaced by the protective gas. The calcination time is between 0.5 and 10 hours; a typical calcination time is 2 hours. Calcination can be carried out under atmospheric pressure or under vacuum.

[0096] By calcining, fine-pored molded bodies can be formed from the finely divided silica. The proportion of pores with a diameter between 10 nm and 20 nm is typically more than 50%, preferably more than 70%, and particularly preferably more than 80%.

[0097] The at least one silicon dioxide in step (Al) can be selected from a pyrogenic silicon dioxide or a precipitated silicon dioxide. The at least one sorbent in the inventive

[0098] Process can be an inorganic or an organic

[0099] sorbents.

[0100] The inorganic sorbent in the process according to the invention can be a carbonate, in particular selected from the group consisting of metal carbonate, metal bicarbonate and mixtures thereof.

[0101] The organic sorbent in the process according to the invention can be an organic polyamine comprising at least two N atoms per molecule which are separated by at least one C atom, in particular selected from the group consisting of ethyleneamine, aminosilane, polyethyleneimine (PEI), polypropyleneamine, polyvinylpyridine, polydimethylaminoethyl methacrylate, polyamidoamine, polyvinylamine and polyallylamine.

[0102] The ethyleneamine in the process according to the 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).

[0103] The aminosilane in the process according to the invention can 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. The polyamine in the process according to the invention can be silylated, for example obtainable by reacting one or more amino groups of the polyamine with suitably functionalized alkoxysilanes, for example selected from the group consisting of 3-chloropropyltrialkoxysilane, 3-chloropropyltrialkoxysilane, glycidoxypropyltrialkoxysilane and isocyanatopropyltrialkoxysilane.

[0104] The polyamine is particularly obtainable by silylation, which can be carried out in isolation or in situ.

[0105] The at least one sorbent is preferably in liquid form during the impregnation in step (B), for example as a solution, emulsion or dispersion in a solvent or liquid medium or in pure form. The sorbent is also referred to in the context of this invention as impregnating agent. The solvent or liquid medium is preferably removed after impregnation. In the process according to the invention, the at least one sorbent can be a solution of a metal carbonate, in particular potassium carbonate and / or sodium carbonate, in water or a solution of a metal bicarbonate, in particular potassium bicarbonate and / or sodium bicarbonate, in water.

[0106] In a preferred process, the at least one sorbent is a saturated aqueous solution of potassium carbonate, sodium carbonate, potassium bicarbonate and / or sodium bicarbonate, preferably of potassium carbonate and / or potassium bicarbonate, more preferably of potassium carbonate. In a preferred process, the amount of metal carbonate or metal bicarbonate is 15-40 wt.%, preferably 15-33 wt.% of the total weight of the aqueous solution.

[0107] In a preferred process, the sorbent is in the form of a solution of an organic sorbent, for example an organic amine, in a suitable solvent, wherein the amount of dissolved organic sorbent is preferably at least 30 vol%, more preferably at least 60 vol%.

[0108] The organic solvent preferably has a boiling point of not more than 200 °C, more preferably not more than 150 °C, in each case at 1013 mbar.

[0109] Examples of suitable solvents are water; alcohols such as methanol, ethanol, n-propanol, iso-propanol, n-amyl alcohol, i-amyl alcohol; ethers such as dioxane, tetrahydrofuran, diethyl ether, diisopropyl ether, diethylene glycol dimethyl ether; chlorinated hydrocarbons such as dichloromethane, trichloromethane, tetrachloromethane, 1, 2-dichloroethane, trichloroethylene; hydrocarbons such as pentane, n-hexane, hexane isomer mixtures, heptane, octane, white spirit, petroleum ether, benzene, toluene, xylenes; ketones such as acetone, methyl ethyl ketone, diisopropyl ketone, methyl isobutyl ketone (MIBK); esters such as ethyl acetate, butyl acetate, propyl propionate, ethyl butyrate, ethyl isobutyrate; Carbon disulfide and nitrobenzene, or mixtures of these solvents.

[0110] Impregnation in step (B) is preferably carried out by contacting the molded body with the at least one sorbent for CO2. In principle, any prior art method used for the surface treatment of fillers or particles is suitable for impregnating the silica molded body. This is an advantage of the silica molded bodies according to the invention, because they are sufficiently mechanically stable and, due to their size and shape, do not tend to agglomerate or stick together during drying.

[0111] In a preferred method, the impregnation is carried out by mixing, spraying or soaking the shaped body or the incipient wetness method with the at least one sorbent in liquid form, in particular by means of the incipient wetness method.

[0112] "Impregnation" in the sense of this invention means the impregnating treatment with liquid, dissolved, emulsified or dispersed impregnating agents. The impregnating agent can be physically deposited on the inner and outer surface of the porous molded body or can be chemically bonded in whole or in part.

[0113] The "incipient wetness method" is known in the literature in connection with the coating of carrier materials with a catalyst and the principles are described in Marceau, E .; Carrier, X .; Chet , M ., Impregnation and Drying . In Synthesis of Solid Catalysts , 2009 ; pp 59- 82 . Surprisingly, it has been found that the incipient wetness method is also suitable for coating the shaped bodies according to the invention with the sorbent for CO2 in such a way that CO2 binding sites are homogeneously distributed over the entire surface of the shaped body. This makes it possible to achieve particularly high sorption ef fi ciencies in the sorbent. In the incipient wetness method, the sorbent is usually dissolved or dispersed in a solution (e.g. aqueous or organic). This mixture can then be added to the carrier material, which preferably has the same pore volume as the volume of the added mixture.Due to the capillary action, the mixture is sucked into the pores and leads to functionalization.

[0114] In contrast to the wet method ("wet impregnation"), the incipient wetness method does not result in the particles sticking together and the impregnating agent is deposited very homogeneously on the inner and outer surface of the molded body.

[0115] The impregnation in step (B) is preferably carried out in a temperature range of 0-150 °C, preferably in a temperature range of 15-120 °C.

[0116] The impregnation in step (B) is preferably carried out at normal pressure, under elevated pressure or under reduced pressure.

[0117] The normal pressure is usually 1013 mbar.

[0118] In the event that the impregnation in step (B) is carried out at increased pressure, the pressure may be a maximum of 2 bar.

[0119] In case the impregnation in step (B) is carried out under negative pressure, the pressure can be 10~ 3 mbar to normal pressure, especially IO -1 mbar to 500 mbar .

[0120] A preferred method is characterized in that the shaped body has a mesoporous structure and the volume of the at least one sorbent used for CO2 is 80 to 120%, preferably 90 to 110%, more preferably 95-105%, based on the total pore volume of the shaped body. By using such amounts of sorbent, it can be ensured that the inner surface of the shaped body is homogeneously and completely functionalized with the sorbent. This achieves high sorption ef fi ciencies.

[0121] In a preferred process, the molded body is impregnated at a vacuum of 10~ 3 up to 10 2 mbar treated; and / or dried.

[0122] The impregnation in step (B) of the provided shaped body with at least one sorbent for CO2 in order to functionalize the shaped body is preferably carried out together with at least one impregnation aid selected from wetting agent, emulsifier, dye, binder, adhesion promoter, higher-functional alcohols and higher-functional polyols.

[0123] In a preferred embodiment, the shaped body retains its shape defined by the molding tool / shaping process at the time of production. Deformations during and immediately after shaping cause density differences and stresses which lead to defects (scaling, fine dust) on the shaped body during the drying and sintering process. According to the invention, the supports produced have a spalling content of preferably less than 5% by weight, more preferably less than 1% by weight, and most preferably less than 0.5% by weight. Spalling is disadvantageous because it leads to high pressure losses in a column or reactor during use.

[0124] The present invention is therefore particularly directed to a sorbent for CO2 obtainable by the inventive process for producing a sorbent for CO2, wherein the impregnation is preferably carried out using the incipient wetness method. This has the advantages already detailed above of a particularly homogeneous distribution of the CO2 sorption sites and an associated outstanding sorption efficiency for CO2.

[0125] A further aspect of the present invention is directed to the use of the sorbent according to the invention for CO2 for the reversible binding of CO2 from a gas mixture, in particular in the form of a fixed bed sorbent, for example for CCU, CCS and / or

[0126] DAC .

[0127] Reversible binding is achieved in particular by chemisorption. In this case, the CO2 is bound by chemical bonding with the silica on the inner surface of the molded body. By increasing the temperature and / or reducing the pressure, the chemisorbed CO2 can be released from the molded body and thus expelled. This has the advantage that the CO2 can not only be removed from the gas phase (e.g. DAC, CCS), but can also be released again at any time afterwards and, for example, fed into a process that uses CO2 as a starting material (e.g. CCU).

[0128] Examples of implementation

[0129] The following examples were carried out at a pressure of the ambient atmosphere, i.e. at about 1013 mbar, and at room temperature, i.e. about 23°C or a temperature which is reached when the reactants come together at room temperature without additional heating or cooling, and describe the basic feasibility of the present invention, without, however, limiting it to the contents disclosed therein.

[0130] Determination of CO2 adsorption capacity

[0131] The BELCAT II gas adsorption analyzer from Microtrac is used to determine CO2 adsorption capacity. Typically, the temperature-programmed desorption (TPD) method is used, which works as follows.

[0132] For sample preparation, the carrier to be examined is heated to 200 °C under a continuous helium flow at a rate of 10 K / min and kept at this temperature for 35 min.

[0133] For analysis, the sample is first purged with helium at 40 °C. Then, CO2 is passed over the sample for 90 minutes at 40 °C. If necessary, the CO2 can be humidified using a commercially available vapor injection device ("bubbier").

[0134] The sample is treated in a helium stream at 40 °C for 30 min.

[0135] Helium is used as the desorption gas for desorption. The temperature of the carrier is increased to 200 °C at a rate of 10 K / min (linear temperature gradient) and held for 20 min. The gas mixture is passed through dry molecular sieves (3 Å) to remove water and analyzed using a thermal conductivity detector (TCD) and mass spectrometry (MS). This allows the desorbed amount of CO2 to be determined.

[0136] Silica molded body

[0137] The silica molding was made from hydrophilic fumed silica HDK® T40 (BET surface area: 400 m 2 / g, tamped density: 40 g / ml; available from WACKER Chemie AG) as follows:

[0138] In a 4-liter plastic beaker, 1155 g of bidistilled H2O are placed. Using a plastic-coated dissolver disc, 345 g of fumed silica (BET surface area 400 m 2 / g) at 1000 rpm. Stirring is then continued for 40 minutes at a peripheral speed of 14 m / s. The slurry is transferred to a planetary mixer equipped with two plastic-coated bar stirrers. 7.5 g of 1% NH3 solution are added dropwise at 100 rpm. After the addition, stirring is continued for a further 5 minutes. The mixture is then introduced into a piston extrusion press. In parallel, the rheology and pH of a sample are measured: G' = 200,000, G" = 25,000, pH = 6.1.

[0139] The mass is extruded into the desired shapes using a suitable tool in a piston extrusion press and cut to the desired length. The resulting molded bodies—in this case, pellets with a length of 6 mm and a diameter of 6 mm—are dried for 24 hours at a temperature of 85 °C. The support is then sintered at 1060 °C. The silica molded body has a BET surface area of ​​205 m². 2 / g and a pore volume of 0.75 cm 3 / g on .

[0140] The pore volume is determined by nitrogen adsorption according to DIN 66134 (Langmuir, p / po= 0.9995).

[0141] Potassium content determination

[0142] The potassium content is determined using ICP-OES (inductively coupled plasma with optical emission spectrometry). For this purpose, the weighed sample is fumed with hydrofluoric acid at approximately 150 °C, the dried residue is redissolved with nitric acid, and the potassium content is then measured after calibration using ICP-OES (radial).

[0143] Functionalization of the silica carrier

[0144] Example 1

[0145] The functionalization of the support takes place by spraying the functionalizing agent using a commercially available rotary evaporator. The silica molded body is located in the rotating evaporation flask and is dried for 6 hours at an oil bath temperature of 140 °C and 25 mbar before the functionalizing agent is added. For functionalization, a Teflon tube is connected to the vent tap of the rotary evaporator. The functionalizing agent is sucked in from the outside by applying negative pressure and is passed on via another Teflon tube, which is located inside the rotary evaporator and reaches into the evaporation flask. Immediately after spraying the functionalizing agent, the sprayed silica molded body is post-treated by rotation under atmospheric pressure at room temperature in the evaporation flask for one hour and then dried at an oil bath temperature of 80 °C and 25 mbar.

[0146] Example 2

[0147] 12.7 g of the silica molded body are functionalized according to Example 1 by introducing 28.0 g of 30 wt% potassium carbonate into water. After functionalization, 20.7 g of the functionalized molded body are obtained. The potassium content is 5.6 mmol per gram of molded body (average of three individual values). The adsorption capacity, determined by chemisorption, is 2.8 mmol CO2 per gram of molded body.

[0148] Example 3

[0149] 10.0 g of the silica moldings are impregnated according to Example 1 by introducing 7.5 mL of pentethylenehexamine (available from Merck KGaA, Darmstadt, Germany). The nitrogen content is 7.9 mmol per gram of molding (average of three individual values). The adsorption capacity, determined by chemisorption, is 2.51 mmol CO2 per gram of molding.

[0150] Example 4

[0151] 10.0 g of the silica moldings are functionalized according to Example 1 by introducing 7.5 mL of 3-aminopropyltrimethoxysilane (available from Fisher Scientific GmbH, Im Heiligen Feld 17, 58239 Schwerte, Germany). The nitrogen content is 2.7 mmol per gram of molding (average of three individual values). The adsorption capacity determined by chemisorption is 0.46 mmol CO2 per gram of molding. Example 5: General procedure for impregnation of the

[0152] carrier with polyamine in methanolic solution

[0153] The support is impregnated with a methanolic solution in a three-necked flask. The silica moldings are placed in the three-necked flask and dried for 2 hours at room temperature and under a vacuum of 1.6 mbar before the functionalizing agent is added. The vacuum is then broken with argon. For functionalization, a solution of methanol and functionalizing agent is poured into the three-necked flask blanketed with argon. The reaction solution is stirred for 6 hours at 70 °C under reflux and inerted with argon. The solvent is then removed using a commercially available rotary evaporator at 40 °C and 337 mbar. The functionalized silica moldings are then dried for one hour in a drying oven at 100 °C under a nitrogen atmosphere.

[0154] Example 6

[0155] 10.0 g of the silica molded body are functionalized by impregnation according to Example 5 with a methanolic solution of 7.5 g of pentethylenehexamine (available from Merck KGaA, Darmstadt, Germany) in 40 ml of methanol. The nitrogen content is 10.4 mmol per gram of molded body (average of three individual values). The adsorption capacity determined by chemisorption is 1.81 mmol CO2 per gram of molded body. The present invention is further characterized by the following points:

[0156] 1. Sorbent for CO2, comprising

[0157] (i) a shaped body of at least one amorphous silicon dioxide having dimensions in at least one dimension in the range from 0.5 mm to 30 mm, preferably 1.0 mm to 15 mm; and

[0158] (ii) at least one sorbent for CO2, with which the shaped body (i) is functionalized; wherein the sorbent has a compressive strength of at least 2 N / mm 2 , preferably at least 8 N / mm2 , has.

[0159] 2. Sorbent according to item 1, wherein the shaped body is constructed from agglomerates of amorphous silicon dioxide.

[0160] 3. Sorbent according to point 1 or 2, wherein the BET surface area of ​​the sorbent is in the range of 30 to 500 m 2 / g, especially in the range of 50 to 400 m 2 / G.

[0161] 4. Sorbent according to one of the preceding points, wherein the at least one amorphous silicon dioxide is selected from pyrogenic or precipitated silicon dioxide.

[0162] 5. Sorbent according to one of the preceding points, wherein the silicon dioxide of the shaped body has a mesoporous structure, in particular a mesoporous structure with an irregular pore structure. Sorbent according to one of the preceding points, wherein the at least one sorbent (ii) is capable of entering into a reversible reaction with CO2, in particular a reversible sorption reaction. Sorbent according to one of the preceding points, wherein the at least one sorbent (ii) is an inorganic or an organic sorbent. Sorbent according to point 7, wherein the inorganic sorbent

[0163] (ii) is a carbonate, in particular selected from the group consisting of metal carbonate,

[0164] Metal bicarbonate and mixtures thereof. Sorbent according to item 7, wherein the organic sorbent is an organic polyamine comprising at least two N atoms per molecule separated by at least one C atom, in particular selected from the group consisting of ethyleneamine, aminosilane, polyethyleneimine (PEI), polypropyleneamine, polyvinylpyridine,

[0165] Polydimethylaminoethyl methacrylate, polyamidoamine,

[0166] Polyvinylamine and polyallylamine. Sorbent according to item 9, wherein the ethyleneamine is selected from the group consisting of ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetraamine (TETA), tetraethylenepentamine (TEPA), aminoethylethanolamine (AEEA), aminoethylpiperazine (AEP), piperazine (PIP),

[0167] Hydroxyethylpiperazine (HEP), pentaethylenehexamine (PEHA) and polyethylenepolyamine (PEPA). Sorbent according to item 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. Sorbent according to any one of items 9-11, wherein the polyamine is silylated, for example obtainable by reacting one or more amino groups of the polyamine with suitably functionalized alkoxysilanes, for example selected from the group consisting of 3-chloropropyltrialkoxysilane, 3-chloropropyltrialkoxysilane, glycidoxypropyltrialkoxysilane and isocyanatopropyltrialkoxysilane. Sorbent according to item 12, wherein the silylated polyamine is obtainable by silylation, which is carried out in isolation or in situ. Sorbent according to any one of the preceding items, further comprising

[0168] (iii) at least one auxiliary agent selected from the group consisting of polymeric binders, silicon-containing binders such as silicates and silica sol, spreading agents and wetting agents. Sorbent according to one of items 9-14, wherein the polyamine is present in combination with at least one amino-functional alkoxysilane. Sorbent according to item 15, wherein the at least one amino-functional alkoxysilane is selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-

[0169] Aminopropyl triethoxysil and 3-

[0170] Aminopropyl triisoproxysilane. Sorbent according to item 15 or 16, wherein the amount of polyamine is at least 50 wt.% based on the total amount of polyamine and amino-functional alkoxysilane. Sorbent according to any one of the preceding items, wherein the amount of the at least one sorbent (ii) is 10 to 90 wt.%, preferably 25 to 80 wt.%, based on the total weight of the sorbent. Process for producing a sorbent for CO2 according to any one of items 1-18, comprising the following steps in the given order:

[0171] (A) providing a shaped body of at least one amorphous silicon dioxide having dimensions in at least one dimension in the range of 0.5 mm to 30 mm;

[0172] (B) Impregnating the provided shaped body with at least one sorbent for CO2 in order to functionalize the shaped body. The process according to item 19, wherein the provision of the shaped body in step (A) is carried out by

[0173] (Al) at least one silicon dioxide is provided in an aqueous solution having a pH of 2.0 to 10.0, preferably 3.0 to 8.0;

[0174] (A2) this dispersion is subjected to a change in pH at least once;

[0175] (A3) shaping takes place; and

[0176] (A4) subsequent drying is carried out to produce the shaped body. Process according to item 20, wherein the provision of the shaped body in step (A) is carried out by

[0177] (Al) at least one silicon dioxide is provided in an aqueous solution having a pH of 2.0 to 10.0, preferably 3.0 to 8.0;

[0178] (A2) this dispersion is subjected to a change in pH at least once;

[0179] (A3) shaping takes place;

[0180] (A4) subsequent drying takes place, and

[0181] (A5) a sintering step is carried out at 400°C to 1500°C to produce the shaped body. The process according to item 21, wherein the sintering step is carried out at 800°C to 1200°C, in particular at 850°C to 1150°C. The process according to any one of items 20-22, wherein the at least one silicon dioxide in step (A1) is selected from a pyrogenic silicon dioxide or a precipitated silicon dioxide. The process according to any one of items 20-23, wherein in step (A1), the aqueous solution has a pH of 2.5 to 4.0. Method according to one of items 20-24, wherein the change in the pH value in step (A2) is characterized in that the difference in the pH value before and after the change in the pH value in step (A2) is 0.5 to 5.5, wherein preferably the target pH value after the change in the pH value in step (A2) is in the range from 4.0 to 7.5, particularly preferably in the range from 4.5 to 7.0.The process according to any one of items 19-25, wherein the at least one sorbent is an inorganic or an organic sorbent. The process according to item 26, wherein the inorganic sorbent is a carbonate, in particular selected from the group consisting of metal carbonate, metal bicarbonate, and mixtures thereof. The process according to item 26, wherein the organic

[0182] Sorbent is an organic polyamine comprising at least two N atoms per molecule, which are separated by at least one C atom, in particular selected from the group consisting of ethyleneamine, aminosilane, polyethyleneimine (PEI), polypropyleneamine, polyvinylpyridine, polydimethylaminoethyl methacrylate, polyamidoamine,

[0183] Polyvinylamine and polyallylamine. The process according to item 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),

[0184] Hydroxyethylpiperazine (HEP), pentaethylenehexamine (PEHA) and polyethylenepolyamine (PEPA). The process according to item 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

[0185] Condensation products of 3-aminopropyltrialkoxysilane. Process according to one of points 28-30, wherein the polyamine is silylated, for example obtainable by reacting one or more amino groups of the polyamine with suitably functionalized alkoxysilanes, for example selected from the group consisting of 3-chloropropyltrialkoxysilane, 3-chloropropyltrialkoxysilane, glycidoxypropyltrialkoxysilane and isocyanatopropyltrialkoxysilane. Process according to point 31, wherein the polyamine is obtainable by silylation, which can be carried out in isolation or in situ. Process according to one of points 19-32, wherein the at least one sorbent is present in liquid form during the impregnation in step (B), for example as a solution, emulsion or dispersion in a solvent or liquid medium or in pure form. Process according to point 33, wherein the at least one

[0186] Sorbent a solution of a metal carbonate , in particular potassium carbonate and / or sodium carbonate , in water or a solution of a metal bicarbonate , in particular potassium bicarbonate and / or

[0187] Sodium bicarbonate, in water. Process according to item 33 or 34, wherein the at least one sorbent is a saturated aqueous solution of potassium carbonate, sodium carbonate, potassium bicarbonate and / or sodium bicarbonate, preferably of potassium carbonate and / or potassium bicarbonate, more preferably of potassium carbonate. Process according to item 34 or 35, wherein the amount of metal carbonate or metal bicarbonate is 15-40 wt.%, preferably 15-33 wt.% of the total weight of the aqueous solution. Process according to any one of items 19-36, wherein the sorbent is in the form of a solution of an organic sorbent, for example an organic amine, in a suitable solvent, the amount of dissolved organic sorbent preferably being at least 30 vol.%, more preferably at least 60 vol.%.Process according to one of points 19-37, wherein the impregnation in step (B) takes place by bringing the shaped body into contact with the at least one sorbent for CO2. Process according to one of points 19-38, wherein the impregnation in step (B) takes place in a temperature range of 0-150 °C, preferably in a temperature range of 15-120 °C. Process according to one of points 19-39, wherein the impregnation in step (B) takes place at atmospheric pressure, under elevated pressure or under reduced pressure. Process according to one of points 19-40, wherein the impregnation is carried out by mixing, spraying or soaking the shaped body or the incipient wetness method with the at least one sorbent in liquid form, in particular by means of the incipient wetness method.Process according to one of points 19-41, wherein the shaped body has a mesoporous structure and the volume of the at least one sorbent for CO2 is 80 to 120%, preferably 90 to 110%, more preferably 95-105%, based on the total pore volume of the shaped body. Process according to one of points 19-42, wherein the shaped body before impregnation.

[0188] - at a suppression of 10~ 3 up to 10 2 mbar; and / or

[0189] - is dried. Process according to one of points 19-43, wherein in step (B) the provided shaped body is impregnated with at least one sorbent for CO2 in order to functionalize the shaped body, together with at least one impregnation aid selected from wetting agent, emulsifier, dye, binder, adhesion promoter, higher-functionality alcohols and higher-functionality polyols. Use of the sorbent for CO2 according to one of points 1-18 for the reversible binding of CO2 from a gas mixture, in particular in the form of a fixed bed sorbent, for example for CCU, CCS and / or DAC.

Claims

Claims 1. Sorbent for CO2, comprising (i) a shaped body of at least one amorphous silicon dioxide having dimensions in at least one dimension in the range from 0.5 mm to 30 mm; and (ii) at least one sorbent for CO2 with which the Shaped body (i) is functionalized; wherein the sorbent has a compressive strength of at least 2 N / mm 2 has.

2. Sorbent according to claim 1, wherein the shaped body consists of Agglomerates of amorphous silicon dioxide.

3. Sorbent according to one of the preceding claims, wherein the shaped body has the shape of spheres, ellipsoids, cylinders, hollow cylinders or cuboids, and / or has an aspect ratio of at most 15.

4. Sorbent according to one of the preceding claims, wherein the at least one amorphous silicon dioxide is selected from pyrogenic or precipitated silicon dioxide.

5. Sorbent according to one of the preceding claims, wherein the silicon dioxide of the shaped body has a mesoporous structure.

6. Sorbent according to one of the preceding claims, wherein the silicon dioxide of the shaped body has a mesoporous structure with an irregular pore structure.

7. Sorbent according to one of the preceding claims, wherein the at least one sorbent (ii) is an inorganic or an organic sorbent.

8. Sorbent according to claim 7, wherein the inorganic Sorbent (ii) is a carbonate, in particular selected from the group consisting of metal carbonate, metal bicarbonate and mixtures thereof.

9. Sorbent according to claim 7, wherein the organic sorbent is an organic polyamine comprising at least two N atoms per molecule separated by at least one C atom, in particular selected from the group consisting of ethyleneamine, aminosilane, polyethyleneimine (PEI), polypropyleneamine, polyvinylpyridine, polydimethylaminoethyl methacrylate, polyamidoamine, Polyvinylamine and polyallylamine.

10. Sorbent according to one of the preceding claims, further comprising (iii) at least one auxiliary agent selected from the group consisting of polymeric binders, silicon-containing binders such as silicates and silica sol, spreading agents and wetting agents.

11. A process for producing a sorbent for CO2 according to any one of claims 1-10, comprising the following steps in the order given: (A) providing a shaped body of at least one amorphous silicon dioxide having dimensions in at least one dimension in the range of 0.5 mm to 30 mm; (B) Impregnating the provided shaped body with at least one sorbent for CO2 in order to functionalize the shaped body.

12. The method according to claim 11, wherein the provision of the shaped body in step (A) is carried out by (Al) at least one silicon dioxide is provided in an aqueous solution having a pH of 2.0 to 10.0; (A2) this dispersion is subjected to a change in pH at least once; (A3) shaping takes place; and (A4) subsequent drying takes place; and if necessary (A5) a sintering step is carried out at 400 °C to 1500 °C to produce the shaped body.

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

14. The method according to any one of claims 11-13, wherein the impregnation is carried out by mixing, spraying, soaking the shaped body or the incipient wetness method with the at least one sorbent in liquid form.

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