Process for carbon dioxide removal from gas
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-02-02
- Publication Date
- 2026-08-13
Smart Images
Figure EP2026052590_13082026_PF_FP_ABST
Abstract
Description
[0001] 202400234 Foreign Filing 1
[0002] Process for carbon dioxide removal from gas
[0003] The invention provides a process for carbon dioxide removal from gas.
[0004] Greenhouse gas emissions, importantly those of carbon dioxide (CO2) are often associated with the (unwanted) global climate change. Therefore, the ways of reducing CO2 concentration in the atmosphere of currently roughly 400 ppm are intensively sought by the society. The so-called “direct air capture” (DAC) is one of such efforts and strategies, which focuses on a CO2 removal directly from the air.
[0005] Many techniques, including those using reversible adsorption and desorption of CO2 on solid sorbents, are known for carbon capture and particularly for DAC. Accordingly, numerous sorbent types were found to be capable of physically adsorbing CO2, such as zeolites, metal organic frameworks (MOFs) etc.
[0006] However, low concentration of CO2 in the air (-400 ppm) often makes purely physical sorption less suitable as a carbon capture method than it is for gas mixtures with higher CO2 concentrations.
[0007] Moreover, some of the above-mentioned sorbents, e.g. metal organic frameworks (MOFs), are very expensive and are less suitable for large-scale use.
[0008] Certain sorbents using chemical binding of CO2 are often more suitable for DAC than the sorbents operating by purely physical sorption. Thus, WO 2023 / 088812 A1 describes using solid sorbents having primary or secondary amine moieties immobilized on a solid support for DAC. However, WO 2023 / 088812 A1 points to an important disadvantage, which is thermal oxidative decomposition and deactivation of such amine moieties during the thermal CO2 desorption process carried out at temperatures of 60-110°C. The result of such amine degradation is decreased lifetime of the sorbent. This patent application suggests using a specific chemical regeneration method to (at least partially) restore its sorption activity. Thus, regeneration can be performed by way of reduction in the liquid phase or at the interface between liquid and solid phase by using a metal hydride such as di-isobutyl aluminium hydride (DI BAL) or lithium aluminium hydride (UAIH4) as a reduction agent. Alternatively, the use of catalytic hydrosilylation methods is described.
[0009] Such regeneration methods are complex and usually do not allow to completely restore the initial adsorption activity, which makes these methods less applicable for industrial scale processes.
[0010] Alternatively to solid sorbents, liquid absorbents, such as amines or alkaline solutions may be generally used for carbon capture. Examples of such processes for CO2 capture are described in WO 2022 / 271035 A1 and WO 2023 / 041541 A1 using potassium carbonate (K2CO3) solution for capturing CO2, which is upon reaction with CO2 converted to potassium hydrogen carbonate (KHCO3).
[0011] Subsequently, potassium hydrogen carbonate (KHCO3) can be converted back to potassium carbonate (K2CO3) upon heating. The main challenge of this process is a slow absorption rate of CO2 by carbonate, and thus, an increased CO2 partial pressure required for the process. This limits process applicability202400234 Foreign Filing 2
[0012] and leads to higher energy demand. This process is typically used for the so-called point source carbon capture, i.e. separation of relatively high concentrations of typically above 10 vol% CO2 e.g. from industrial flue gases. This process type is also typically carried out at elevated pressure of 5-20 bar to additionally increase CO2 partial pressure and thus further increase its absorption rate.
[0013] An approach for DAC using liquid absorbents is known from WO 2022 / 184840 A1 and WO 2023 / 166188 A2 describing liquid CO2 absorption from air with an absorption liquid containing 2 to 93 wt% water, 2 to 93 wt% polyethyleneglycol or polyol, and 5 to 60 wt% of compounds selected from carbonates, amines, polyethyleneglykolamine, polyethyleneimine, amine-containing sugars, amino acids or mixtures thereof.
[0014] US 8,834,822 B1 discloses a process for the separation of carbon dioxide from fluids using a solid, regenerable sorbent. The sorbent comprises a polymeric amine, such as polyethyleneimine (PEI), which is coupled with a stabilizing moiety, such as an aminosilane, and immobilized onto an inert solid substrate like silica. This document also teaches that the sorbent can be regenerated using methods suitable for solid sorbents, such as temperature swing adsorption (TSA), pressure swing adsorption (PSA), or steam-stripping. The main aim of the specific formulation in this document is to improve the stability of the solid sorbent against degradation during such thermal regeneration cycles.
[0015] From US 8,771 ,403 B2 a method and system are known, capturing carbon dioxide from a gas stream using a liquid adsorption process. In this process CO2 is absorbed by an aqueous amine and / or amino acid salt solution. Regeneration of CO2-rich liquid absorbent is achieved chemically by reacting it with a second aqueous solution containing an alkali metal carbonate This reaction regenerates the liquid amine absorbent and transfers the captured CO2 to the carbonate solution, precipitating it as an alkali metal bicarbonate. This patent teaches that this chemical regeneration approach is advantageous for reducing the energy demand and degradation associated with the thermal regeneration of conventional liquid amine solvents.
[0016] The object of the present invention is to provide an improved process for CO2 removal from a gas mixture, which overcomes the drawbacks of the known processes. Particularly, this process should be well applicable for capturing of CO2 in low concentration, i.e. for direct air capture. Such a process should use simple types of sorbents, showing minimal degradation and long service lives in the process, provide fast CO2 sorption rates and use simple operation steps and equipment.
[0017] These technical problems could be solved by a process for removal of carbon dioxide (CO2) from a gas, comprising the following steps:
[0018] (a) Feeding gas (inflow) containing CO2 in a reactor, comprising a water-insoluble unloaded sorbent having primary and / or secondary amine moieties, preferably immobilized on at least one solid carrier;
[0019] (b) Reacting the CO2 with the unloaded sorbent to form loaded sorbent containing CO2202400234 Foreign Filing 3
[0020] chemically bound to amine moieties of the sorbent;
[0021] (c) Reacting of the loaded sorbent formed in step (b) with an aqueous solution (I) containing alkali carbonate (M2CO3), wherein M is an alkali metal, and wherein the M2CO3 is at least partially converted to alkali hydrogen carbonate (MHCO3), whereby forming a solution (II) containing said MHCOsand at least partially releasing unloaded sorbent;
[0022] (d) Separating the solution (II) obtained in step (c) from the solid sorbent, and preferably withdrawing the solution (II) from the reactor.
[0023] Herein step (b) is also named “Adsorption step”, step (c) is also named “First recovery step”, and step (d) is also named “Separation step”.
[0024] The term “sorbent” means in the context of the present invention a solid material comprising primary amine (-NH2) or secondary amine (-NHR) moieties or a combination thereof, capable of reacting with CO2 gas to form CO2 chemically bound to these amine moieties.
[0025] The sorbent typically has primary and / or secondary amine moieties immobilized on at least one solid carrier. The term “solid carrier” herein also referred to as “carrier” means any kind of solid part, body, structure, configured to carry or comprise amine moieties, meaning that the solid carrier may be at least partly made of, at least partly covered with and / or at least partly filled with the substance comprising amine moieties.
[0026] This substance may be at least one of the following or a mixture thereof, such as but not limited to a porous or non-porous material based on an organic and / or inorganic material, preferably a polymer material, preferably selected from the group of linear or branched, cross-linked or uncross-linked polystyrene, polyethylene, polypropylene, polyamide, polyurethane, acrylate-based polymer including PMMA, polyacrylonitrile or combinations thereof, wherein preferably the polymer material is poly(styrene) or poly(styrene-co-divinylbenzene) based, cellulose, or an inorganic material including silica, alumina, activated carbon, metal organic frameworks, covalent organic frameworks, and combinations thereof, wherein preferably the material is based on a polystyrene material, preferably cross-linked polystyrene material and most preferably poly(styrene-codivinylbenzene).
[0027] The solid sorbent may be present in any suitable form used in direct air capture processes, e.g. in form of particles, e.g. of a cylindrical, spherical, or irregular form. This sorbent may also be present as a so-called “structured sorbent”, e.g. a porous monolith, or a composite of sorbent particles and any type of suitable carrying matrix, preferably having high ratio of pores or voids to ensure fast transfer of air through it.
[0028] The simplified chemical reactions occurring during the adsorption step (step (b)), reacting the CO2 with solid sorbent to form loaded sorbent containing CO2 chemically bound to amine moieties, can be202400234 Foreign Filing 4
[0029] generally described according to the following reaction equations (for simplicity, only an example with primary amine is shown below. Analogous reactions occur with secondary amine moieties):
[0030] carbamate formation:
[0031]
[0032] hydrogen carbonate formation:
[0033] R-NH2+ H2O + CO2R-NH3+HCO3-
[0034] in which R may be a linear, branched, cyclic alkyl and / or mixed aryl / alky I group, optionally further substituted with other functional groups. For secondary amines (R1R2NH), R1and R2may be the same or different substituents, both having the same meaning as described above for R. R, R1and R2may also be a part of polymer structure.
[0035] In other words, a “loaded sorbent” means in the context of the present invention a solid sorbent comprising amine moieties, wherein amine moieties are at least partially converted to one of the products of chemical reaction of amine with CO2, e.g. the corresponding carbamates, corresponding ammonium salts, hydrogen carbonates and / or carbonates as described above.
[0036] The “unloaded sorbent” means in the context of the present invention a sorbent, capable of reacting with CO2, i.e. the sorbent having free amine moieties not converted to carbamates, hydrogen carbonates etc. Adsorption capacity of the “unloaded sorbent” is preferably at least 50%, more preferably, at least 75%, more preferably at least 90%, more preferably at least 95% of the maximal adsorption capacity of this sorbent after its full regeneration.
[0037] In the current context the term "regeneration" shall mean a treatment step in which the amine moieties of the sorbent having at least partly lost their CO2adsorption (capture) activity due to contacting with carbon dioxide, are converted chemically back to free amine moieties.
[0038] The simplified chemical reaction occurring in the recovery step (desorption, step (c)), reacting loaded sorbent formed in step (b) with an aqueous solution (I) containing alkali carbonate (M2CO3) to form a solution (II) containing alkali hydrogen carbonate (MHCO3), wherein M is an alkali metal, can be generally described according to the following reaction equations:
[0039]
[0040] in which R is defined as described above.202400234 Foreign Filing 5
[0041] The “water-insoluble sorbent” refers to a solid sorbent, which is not soluble or essentially not soluble in water under process conditions. “Essentially not soluble” means that solubility of the sorbent in water at 20 °C is less than 0.5 g / L, preferably less than 0.05 g / L.
[0042] The term “gaseous” is used in its usual meaning for a skilled person, i.e. means in the context of the present invention any non-solid and non-liquid, and no-plasma form, such as but not limited to gas, steam etc. Gas containing CO2 employed in the inventive process may however carry some droplets of liquid phase, e.g. water or fine solid particles such as dust, which does not change its “gaseous” nature, or any substantial aspects of the present invention.
[0043] The reactor used in the inventive process may have any suitable form typically employed for carrying out direct air capture. For instance, the reactor may be “fixed bed reactor” filled with at least one solid sorbent. One preferred version of such fixed bed reactor is the so-called “trickle bed reactor”, wherein both the liquid phase and the gas phase are supplied from the upper part of the reactor, and the liquid is flowing down the sorbent bed forming a thin film on the sorbent’s surface, surrounded by a relatively large gas stream. The benefit of using this type of the reactor is in a high gas-to-liquid ratio and good mass transfer between solid, liquid, and gaseous phase, which is particularly useful for the present invention. Trickle bed reactors are frequently used as industrial multiphase treatment equipment, especially for exothermic catalytic reactions between gaseous and liquid components, such as, but not limited to hydrogenation, oxidation etc.
[0044] Another suitable version of a fixed bed reactor is a “packed bubble column” reactor, wherein both the liquid and the gas phase are supplied from the bottom part of the reactor and move upwards the sorbent. This variant has the benefit of prolonged residence time in the reactor.
[0045] According to a preferred embodiment of the process, step (d) is followed by step (e), which is also named “Second recovery step”:
[0046] At least partially converting MHCO3 contained in the solution (II) to M2CO3 and CO2, wherein the thus obtained solution (III) comprising M2CO3 is at least partially fed into step (c).
[0047] The thus obtained solution (III) may contain different concentration of M2CO3 than the solution (I). Small amounts of MHCO3 may still be present in solution (III) obtained in step (e).
[0048] In a preferred version of the process, the conversion of solution (II) in solution (III) may be carried out thermally or electrochemically, both variants are described in more detail below.
[0049] Even though, (virgin) solution (I), e.g. form a vessel of storage tank, is not identical to the obtained solution (III) downstream the regeneration unit, as well as a mixture of (virgin) solution (I) and said solution (III) is no identical, hereinafter the M2CO3 containing solution ready to be (re-) used by feeding into the reactor, such as the solution (III) downstream the regeneration unit, is for simplicity’s sake named “solution (I)” or “unloaded” or “active” solution (I).202400234 Foreign Filing 6
[0050] The chemical reaction of the second recovery step (desorption, step (e)), conversion of solution (II) separated in step (c) to solution (III), can be generally described according to the following reaction equation:
[0051] 2 MHCO3 -> M2CO3 + H2O + CO2,
[0052] wherein the temperature of step (e) may be in the range of 30 to 200 °C, depending on the used process, e.g. thermal or electrochemical recovery process (as described below).
[0053] According to one preferred solution, the heat needed for the second recovery step (step (e)) may be transferred to solution (II) by indirect heat transfer, via a heating jacket of a vessel or reactor containing solution (II) and / or by a heat exchanger located at the outlet and / or integrated in the outlet line of the fixed bed reactor.
[0054] The term “gas” means in the context of the present invention a gas mixture of at least two substances containing carbon dioxide (CO2), such as air, flue gas, crude process gas etc.
[0055] Present invention is applicable to any gas comprising 50 ppm-100 vol% CO2, e.g. 50 ppm - 25 vol%, preferably 50 ppm-15 vol% CO2.
[0056] According to a preferred embodiment of the process, the CO2 concentration in the gas (inflow) of step (a) and / or (b) is from 100 ppm to 1000 ppm.
[0057] The volume percentage of CO2 in the range of 350 to 500 ppm is most preferred.
[0058] Preferably the gas mixture comprises oxygen (O2), nitrogen (N2) and at least 50 ppm carbon dioxide (CO2), wherein the total volume always sums up to 100 vol%. The volume percentage of the respective gases within the gas mixture (air) are preferably as follows:
[0059] O2: 18 - 21 vol%
[0060] N2: 78 - 80 vol%
[0061] CO2: 50 ppm - 1 vol%
[0062] Other gases, such as noble gases: 0,5 - 2 vol%.
[0063] It was found that a CO2 capture rate achieved by the inventive process may reach at least 60%, preferably at least 70%, more preferably at least 80%, more preferably 80-99%. Therein, the CO2 capture rate is defined according to the following formula:
[0064] CO2 capture rate [in %] =
[0065] (1 - (CO2 volume outflow rate [in m3 / h] / CO2 inflow rate [in m3 / h]) ) * 100%
[0066] The inflow rate can be measured at the inlet of the reactor used in step (a) of the process, while the202400234 Foreign Filing 7
[0067] outflow rate can be measured at the outlet of this reactor.
[0068] According to a further preferred embodiment of the process, M is lithium (Li), sodium (Na) or potassium (K), wherein M is most preferably potassium (K). Thus, the preferred aqueous solution (I) comprises potassium carbonate (K2CO3).
[0069] Advantageously, potassium is a non-toxic, and largely available alkali metal, while potassium carbonate shows suitable CO2 absorption rates in the process, which is very important for industrial applicability thereof.
[0070] According to a further preferred embodiment of the process, the concentration of
[0071] - M2CO3 in solution (I) is 0.5-50 wt%; and / or of
[0072] - MHCO3 in solution (II) is 0.5-50 wt%.
[0073] Thus, for the following case:
[0074] - steps (a) to (d) are carried out continuously, wherein CO2 containing gas and solution (I) are simultaneously fed into reactor (200), while solution (II) is continuously separated from sorbent (212), wherein both the CO2 containing gas and solution (I) are fed into the reactor at the top end (202), while solution (II) is withdrawn from the reactor at the bottom end (204),
[0075] a relatively low M2CO3 concentration in solution (I), e.g. 0.5-10 wt% may be selected due to a very large gas to liquid ratio in the reactor and the fact that water may be evaporated from solution (I). However, in the above-described case, if
[0076] solvent (II) is recycled into the reactor, i.e. mixed with solution (I), and fed back into reactor for further CO2 sorption, and
[0077] relatively high recycling rates (i.e. volume ratios of solution (II) to solution (I) fed into reactor) of at least 5 are selected, then
[0078] a higher M2CO3 concentration in solution (I), e.g. 10-50 wt% may be more advantageous.
[0079] An alternative embodiment of the inventive process including stepwise CO2 sorption on a sorbent followed by subsequent regeneration is preferably carried out with higher M2CO3 concentrations in solution (I), e.g. 10-50 wt%, resulting in higher MHCO3 concentrations in the solution (II) of e.g. 10-50 wt%.
[0080] Higher M2CO3 concentrations in the solution (I) and higher concentration of MHCO3 in the solution (II) are generally beneficial for decreasing overall energy demand of the process, e.g. for the second recovery step (e).
[0081] According to a further preferred embodiment of the process, steps (a) to (d) or (a) to (e) are repeated at least twice by reusing the recovered active sorbent released during step (c) in step (b), and the recovered aqueous solution (I) obtained in step (e) is reused in step (c). This is particularly advantageous in discontinuous or semi-continuous versions of the process.
[0082] According to a further preferred embodiment of the process, step (a) is carried out at relatively mild conditions, such as202400234 Foreign Filing 8
[0083] - at a temperature of 0-60°C, preferably 10-50°C, more preferably 15-40°C;
[0084] and / or
[0085] - under pressure of 0.8-2 bar, more preferably 0.9-1.5 bar, more preferably about 1 bar.
[0086] According to a further preferred embodiment of the process, at least steps (a) to (c) are carried out simultaneously and / or continuously.
[0087] According to a preferred embodiment of the inventive process, steps (a) to (d) are carried out continuously, wherein CO2 containing gas and solution (I) are simultaneous fed into reactor, while solution (II) is continuously separated from sorbent and, and optionally followed by step (e), wherein solution (III) obtained in step (e) is continuously fed back to the reactor.
[0088] In other words, surprisingly it was found, that CO2 reaction with the solid sorbent (step (b)), reaction of the loaded sorbent with the solution (I) to form a solution (II) and reactivation of the sorbent (step (c)), can occur simultaneously in the same fixed bed packed with the sorbent, while solution (II) preferably exits the reactor (step (d)) continuously.
[0089] There are two conceivable ways of chemically binding CO2 from the gas, either by
[0090] - initial reaction of CO2 with amine moieties of the sorbent followed by subsequent reaction of the loaded sorbent with M2CO3 solution to obtain MHCO3 or
[0091] - direct reaction of CO2 with dissolved M2CO3 to obtain MHCO3.
[0092] Though both processes may theoretically occur, based on a much faster kinetics of the first process, it is strongly believed that this first process predominantly takes place.
[0093] In a further preferred embodiment of the process according to present invention, the reactor has a top end and a bottom end, and both the CO2 containing gas and solution (I) are fed into the reactor at the top end, while solution (II) is withdrawn from the reactor at the bottom end of the reactor. In the context of the present invention, the term “top end” (of the reactor) shall not be considered as limiting and shall also include an upper segment of the reactor. Analogously, the term “bottom end” (of the reactor) shall not be considered limiting and shall also include a lower segment of the reactor.
[0094] Given the relatively high gas-to-liquid ratio which would be typically required for the air capture in the present process, this variant of the inventive process may be advantageously carried out in the so-called trickle bed reactor type, wherein the liquid flows slowly down the sorbent bed forming a very thin film around sorbent particles, while the gas is blown with a very high flow rate downwards the reactor.
[0095] According to a further preferred embodiment of the inventive process, the volume flow ratio of gas flow [L / h] to solution (I) flow [L / h] is in the range 100-100,000, more preferably 500-50,000, more preferably 1 ,000-20,000. These are the preferred parameters of the process where steps (a) to (d) carried out continuously.202400234 Foreign Filing 9
[0096] Gas feed is typically carried once through a sorbent bed, while the liquid phase is preferably circulated over the sorbent. Thus, fresh solution (I) feed may be provided from one side of the reactor, e.g. from the upper side, and withdrawn from the other, e.g. from the bottom side, recirculated (e.g. by means of a pump), and re-fed again to the reactor together with the fresh feed. In this case, a longer residence time of the liquid phase on the sorbent and higher liquid-to-gas ratio may be realized. In view of the very low CO2 concentration typically used in the process, this embodiment of the process may be particularly beneficial.
[0097] Thus, in a preferred version of the process, the solution (II) from the reactor is mixed with solution (I) and / or solution (III) and recycled back to the reactor, wherein the volume flow ratio of
[0098] i) solution (I) flow [L / h] to solution (II) flow [L / h] recycled to the reactor (200) or
[0099] ii) the mixed solutions (I) and (III) flow [L / h] to solution (II) flow [L / h] recycled to the reactor (200) is in the range 1 : 1 to 1 OO, more preferably 1 : 1 to 1 : 30, more preferably 1 : 1 to 1 : 15.
[0100] According to a further preferred embodiment of the inventive process, step (a) and step (b) are carried out until at least 20%, preferably at least 30%, more preferably at least 50% of the maximal CO2 adsorption capacity of the sorbent is achieved, before step (c) is started.
[0101] The state of remaining adsorption capacity, i.e. % of maximal adsorption capacity of the sorbent may be determined by measuring the amounts of CO2 in the inflow and in the outflow from the reactor followed by calculating the total amount of the adsorbed CO2 and finally comparing this amount with the maximal CO2 adsorption capacity of the sorbent known from the manufacturer or from measuring the corresponding adsorption curves.
[0102] This solution refers to a discontinuous or semi-continuous process, wherein in the first step adsorption of CO2-containing gas occurs in the reactor and subsequent regeneration of the sorbent by treatment with solution (I) happens in the following second step. In one version of this process, steps (a) and (b) of the process are conducted until the mentioned adsorption capacity is reached, and gas feeding is stopped, the sorbent is then regenerated according to step (c) by means of reacting with solution (I). The thus formed solution (II) containing MHCO3 exits the reactor and may be stored and / or at least partially recovered to solution (III) containing M2CO3.
[0103] The M2CO3 containing solution (I) may be circulated through the sorbent bed of the reactor several times to increase residence time, ensuring better solid / liquid contact and eventually, higher conversion rate of M2CO3 to MHCO3.
[0104] In a semi-continuous process, the process may be carried out in a reactor unit comprising at least two reactors, such as fixed bed reactors, connected in parallel. These at least two reactors are controlled in such a way, that steps (a), (b) and / or (c) can be done at least partially in parallel and / or sequentially. According to this variant, CO2-containing gas is blown through the fixed bed of one of the202400234 Foreign Filing 10
[0105] reactors containing the sorbent (sorption mode) until the maximum or a defined adsorption capacity is achieved, e.g. until at least 50% of maximal adsorption capacity is achieved. Then, the loaded sorbent in this first reactor is washed and reacted with the alkali carbonate solution (I) to regenerate the sorbent (regeneration mode), while CO2-containing gas is further fed into the second reactor (sorption mode). Thus, one of the two reactors may be operated continuously, while the other is regenerated. According to a further preferred version of the process, step (e) can be carried out
[0106] - at a temperature of 70-200 °C, preferably 80-150°C, more preferably 90-140°C, more preferably 100-130 °C.
[0107] During this version of step (e), which may be called “thermal recovery”, MHCO3 is thermally decomposed into M2CO3 and CO2 according to the following reaction equation:
[0108] 2MHCO3 -> M2CO3 + CO2
[0109] The process pressure during this “thermal recovery” step (e) can be 1.1-15 bar, more preferably 1.2-10 bar, more preferably 1.5-6 bar.
[0110] Alternatively to “thermal recovery”, step (e) of the process may be carried out electrochemically, preferably at 20-80 °C.
[0111] This electrochemical process can be done according to a further preferred version of the process, when step (c) is carried out electrochemically in an electrolyser having at least three chambers, wherein at least two of the at least three chambers are separated by a bipolar membrane and / or a semipermeable membrane.
[0112] The temperature of electrochemical reaction in step (e) may be in the range of 15 to 100 °C, preferably 20 to 90 °C, most preferably 20 to 80 °C.
[0113] The electrochemical reaction of the second recovery step (desorption, step (e)), can be done in a recovery unit configured as a three-chamber electrolyser (as exemplary shown in Figure 4) for electrolysis of solution (II) (containing MHCO3) to solution (III) containing M2CO3, before recycling this solution to the fixed bed reactor. Water is fed to the anode chamber, solution (II) is fed to the middle chamber of the electrolyser. The middle chamber is separated from the anode chamber by a bipolar membrane and from the cathode chamber by means of a membrane permeable to the alkali metal ions M+, preferably potassium ions (K+). By applying a voltage, oxygen is evolved in the anode chamber, hydrogen in the cathode chamber and carbon dioxide in the middle chamber. The individual gas streams O2, H2 and CO2 can be collected separately. The carbon dioxide-depleted solution in the middle chamber now has a higher carbonate and a lower hydrogen carbonate content. This recycled solution (III) can be recycled to the reactor and used again for sorbent recovery as solution (I).
[0114] In terms of reaction equations, the following conversions occur at the different reaction sites:
[0115] At the anode: 2 OH- H2O + 1 O2 + 2e202400234 Foreign Filing 11
[0116] At the bipolar membrane: H2O H++ OH-
[0117] In the middle chamber:
[0118]
[0119] At the cathode:
[0120]
[0121] Overall, the result for the cathode chamber is thus:
[0122]
[0123] The anode is preferably made of or contains Ni(OH)2.
[0124] In an alternative embodiment, see also Figure 5, the process comprises an alternative recovery step (d), wherein an electrolyser configured for two-chamber electrolysis is included. Therein solution (II) is fed in the anode chamber and contacted with a nickel hydroxide anode. The alkali carbonate is converted, at least partially, to hydrogen carbonate, in the first chamber where the anode is located (anode chamber).
[0125] The electrolysis cell has an alkali-permeable membrane separating the anode chamber from the cathode chamber. The anode is a porous anode, configured to bind oxygen at its surface. In this respect, only the carbon dioxide formed leaves the anode chamber.
[0126] Hydrogen (H2) is formed in the second chamber (cathode chamber), separated from the first chamber by a semi permeable diaphragm, permeable for alkali metal ions. Thus, CO2 exits the anode chamber and H2 exits the cathode chamber. The regeneration of anodes and / or cathode can be done if required, e.g. by a thermal treatment or any adequate cleaning step. Due to the fixation of O2 at the anode, this embodiment of the process is preferably suitable for smaller plants or process units.
[0127] In terms of reaction equations within the two-chamber electrolyser, the following conversions occur at the different reaction sites:
[0128] At the anode:
[0129]
[0130] HCO3 -^CO2+ OH- Ni(OH)2+ OH- NiOOH + H2O + e-
[0131] The overall reaction at the anode is:
[0132]
[0133] The following reactions take place at the cathode:202400234 Foreign Filing 12
[0134] 2 H2O H3O++ OH-
[0135]
[0136] Overall, the result for the cathode chamber is thus:
[0137]
[0138] According to another preferred version of the process, the sorbent is selected from at least one of the following substances:
[0139] - organic polymers, such as polystyrene, poly(meth)acrylate, or phenol-formaldehyde resin having primary and / or secondary amine moieties;
[0140] - metal and metalloid oxides, such as silica, alumina, mixed oxides, zeolites, having primary and / or secondary amine moieties.
[0141] An example of a suitable for use in the process organic polymer is LEWATIT® VP OC 1065 manufactured by Lanxess®. Polymers of this type can be prepared e.g. by a process described in US 2006 / 0173083 A1. Another suitable for the inventive process polymer system having amine moieties is described in WO 2024 / 056715 A1.
[0142] Examples of suitable for the process amines supported on oxide carriers can be found in
[0143] WO 2016 / 114991 . Content of the above-mentioned patent applications related to the corresponding sorbents is incorporated herein by reference.
[0144] According to another preferred version of the process, the sorbent has a CO2 sorption capacity of 1-20 mmol CO2 / g related to dry sorbent, more preferably 1-10 mmol CO2 / g, more preferably 1-6 mmol CO2 / g.
[0145] A further advantage can be achieved, when the sorbent has BET surface area of 5 - 300 m2 / g, preferably 10-200 m2 / g, more preferably 15-150 m2 / g.
[0146] The specific surface area, also referred to simply as BET surface area, can be determined according to DIN 9277:2014 by nitrogen adsorption in accordance with the Brunauer-Emmett-Teller method. With BET lower than 5 m2 / g, the sorbent may show insufficient CO2 sorption capacity, while with BET > 300 m2 / g, lower mechanical stability and shorter service life are often observed.
[0147] The sorbent preferably has a pore volume for pores > 4nm of 0.1-2.0 mL / g, more preferably 0.2-1 .8, more preferably 0.3-1.5 mL / g.
[0148] The term "pore volume for pores > 4nm" relates to a cumulative pore volume of pores > 4nm, which can be determined by the mercury intrusion method according to DIN ISO 15901 -1.
[0149] It has been found that the specified pore volume range show optimal results of high CO2 sorption rate and long service life.202400234 Foreign Filing 13
[0150] The sorbent preferably has an average pore diameter of 10-300 nm, more preferably 20-200 nm. Pore diameter can be determined by the mercury intrusion method according to DIN ISO 15901-1 . Pore diameter in the above-specified range has shown the best performance in CO2 capturing process.
[0151] As another preferred characteristic of the solid sorbent, the sorbent has a number average particle size (dso) of 0.1 to 5 mm, preferably 0.2 to 3 mm, more preferably 0.3 to 3 mm.
[0152] A number average particle size can be determined according to ISO 13320:2009 by laser diffraction particle size analysis. The resulting measured particle size distribution is used to define the average value d5o, which reflects the particle size not exceeded by 50% of all particles, as the number average particle size.
[0153] Sorbent particle size of less than 0.1 mm is impractical due to difficult handling and high-pressure buildup in the reactor, while the average particle size exceeding 3 mm is less suitable for the process due to relatively low accessibility of the amino moieties in the inner parts of large particles for CO2.
[0154] Sorbent particles preferably have spherical or nearly spherical shape, wherein better packing density in fixed bed reactors and more homogeneous distribution of the sorbent may be achieved.
[0155] A key advantage of the process according to the present invention, is that both CO2 sorption (step (b)) and desorption / sorbent regeneration (step (c)), are carried out under mild conditions at or near to ambient temperatures. Thus, both steps (b) and (c) can be carried out at a temperature in the range of 15-80°C, e.g. 20-40 °C, and under pressure of about 1 bar. Consequently, practically no thermal degradation of amines occurs, and a prolonged lifetime of the sorbent is reached.
[0156] In step (c), the regeneration of solution (I), safe and easily available reagents such as K2CO3 or Na2COs are used further supporting the use of the inventive process on an industrial scale.
[0157] Additionally, also amine-containing sorbents like ion exchange resins or amines bound to metal oxides, are safe, relatively inexpensive and easily available.
[0158] The process of the present invention and suitable equipment shall be illustrated in more detail by means of the following figures. These figures only represent some exemplary suitable forms of e.g., the used reactor comprising a fixed bed or trickle bed and should not be understood as in any way limiting the scope of the invention itself.
[0159] Description of the Figures:
[0160] Fig. 1 : A first process flow chart with a trickle bed reactor.
[0161] Fig. 2: A second process flow chart with equipment adapted for operation at elevated temperature. Fig. 3: A third process flow chart with reactor series.
[0162] Fig. 4: A fourth process flow chart with a three-chamber electrochemical second recovery step.
[0163] Fig. 5: A fifth process flow chart with a two-chamber electrochemical second recovery step.202400234 Foreign Filing 14
[0164] The illustrated example of the process as shown in Figure 1 is conducted in plant 100, plant segment, or plant unit. The plant 100 comprises central reactor 200, regeneration unit 190, and two tanks 110, 112 for the solvent. The reactor 200 is connected to an external production unit 300, e.g. a compressor or any other air-circulating device delivering CO2 containing gas to the reactor 200. The reactor 200 is a trickle bed reactor, comprising a fixed bed 202 formed by or filled with a solid, heterogenous, sorbent 212, having primary and / or secondary amine moieties immobilized on solid carrier 210. The reactor 200 further comprises a (top) inlet side 216, a (bottom) outlet side 218, a gas inlet element 222, a distributor element 223 for liquids, an outlet for liquids, and an outlet for gas. Only selected valves are shown by symbols, wherein some pieces of commonly known equipment for running and (automatically) controlling such a plant 100 and / or reactor 200, are not shown, such as, but not limited to pumps, compressor, sensors, actors, data control units, data lines, electrical power supply / lines, fluid energy supply equipment, heat exchanger, pipes etc.
[0165] The gas inlet element 222 of the reactor 200 is connected to the external production unit 300 by line 120, feeding the CO2 -containing air into the gas inlet element 222 and subsequently into the reactor 200. Fed air flows in main flow direction (downwards), symbolized by an arrow. At the outlet side 218 air depleted in CO2 is released through line 220, and fluid is released through outlet line 140. The liquid effluent, e.g. solvent (II), released through line 140 can be either fed into the recovery unit 190 or sent through line 141 to a storage tank 113. The tanks 110, 112, 113 may be parts of a storage unit of plant 100. As another alternative, the liquid effluent, e.g. solvent (II), may at least partially be directly recycled to the reactor 200 via outlet line 140, further via line 147 and subsequent via lines 196 and 132.
[0166] The distributor element 223 at the inlet side 216 of the reactor 200 is connected to tank 112, which serves as a storage tank for solution (I). Solution (I) is provided from tank 112 through lines 130, 132 and is at least to some extent distributed radially over the fixed bed 202 with sorbent 212 and flows in main flow direction through the fix bed 202, symbolized by an arrow.
[0167] The solid, heterogenous sorbent 212 is symbolised by a number of cylindrical pellets. In the detailed view on the right side of Fig. 1 surrounded by a dotted line, it can be seen, that carrier 210 is covered by primary and / or secondary amine moieties immobilized on the carrier 210 forming solid sorbent 212. For demonstration reasons only, the area of the carrier 210, covered with amine moieties is shown as hatched area on the part of the surface of the carrier 210. However, such amine moieties in the sorbent 212 would usually cover more or less the entire surface of the solid carrier 210 and / or at least partially its inner volume, e.g. at least partially fill the pores of the carrier 210.
[0168] When the process starts in a continuous manner, a gas containing CO2, e.g. air is fed through line 120 into the gas inlet 222 of the reactor 100 (step a), distributed by means of a gas distributor (not shown) and penetrates through the fixed bed of solid sorbent 212, while CO2 reacts with primary and / or secondary amine moieties of the sorbent 212. The thus resulting air depleted in gaseous CO2 exits the reactor 200 via line 220, while sorbent 212 is at least partially saturated and thus inactivated by chemically binding CO2 (step b). Simultaneously to the above-described CO2 sorption process, a liquid202400234 Foreign Filing 15
[0169] solution (I) containing alkali carbonate M2CO3 (e.g. K2CO3) is distributed at the inlet side 216 by means of the distributor element 223, also goes through the sorbent fixed bed, and directly reacting with CO2 bound to the sorbent 212 and forming liquid solution (II), containing alkali hydrogen carbonate MHCO3 (e.g. KHCO3) by the reaction as described above (step c). The process temperature in steps (a) and (b) is typically an ambient temperature of - 21 °C, while the maintained pressure is about 1 bar.
[0170] Finally, solvent (II), containing alkali hydrogen carbonate, is released from the reactor 200 and send via line 140 to the recovery unit 190. Therein, solution (II), containing alkali hydrogen carbonate MHCO3, is converted at least partially back to alkali carbonate M2CO3 and gaseous CO2 (step e). The resulting recovered solution (III) is subsequently sent back through lines 192, 194 to tank 112 or directly through lines 192, 196 as solution (I) into the feed line 132 to the inlet of the reactor 200. The solution (I) fed to the reactor might be a 100% recovered solution (III) coming from the recovery unit 190 ora mixture of recovered solution (III) and solution (I) supplied from tank 112. Alternatively, recovered solution (III) can either be stored in a separate tank 113 or released elsewhere through line 193. Concentrated gaseous CO2 stream typically containing > 90 vol% CO2 exits the recovery unit 190 via line 195 and can be further transported, compressed, stored, and / or chemically utilized. The recovery unit 190 receives the needed reactants for the recovery from tank 110 through line 114, wherein tank 110 can by a group of tanks, storing a number of different reactants. Said reactants can be preferably an acid or caustic for pH-control inside the recovery unit 190.
[0171] The illustrated example of the process as shown on Figure 2 is similar to that shown on Figure 1.
[0172] However, this process, particularly its second recovery step, is designed for operating at elevated temperatures of e.g. from 80 to 150 °C. The process and plant 100 differ from the one referred to in Figure 1 , in that the reactor 200 comprises a gas-liquid-separation element 204, ensuring that less liquid and / or droplets of solvent (II) in the air is released from the reactor 200. Additionally, the recovery unit 190 comprises as central element a vessel 198, comprising a motor driven stirrer and a jacket heating element. Furthermore, in feed line 132 of solvent (I), a heat exchanger 150 is integrated and another heat exchanger 152 is integrated downstream the reactor 100 in line 140. Heat exchangers 150 and 152 may be connected with each other, therefore providing beneficial for the process heat integration. Thus, the energy required for heating up solution (II) exiting the reactor 200 via line 140 prior to its thermal recovery in the recovery unit 190, may be obtained by collecting the energy released by cooling of the solution (III) fed via line 132 to reactor 200. The air feed line 140 comprises a sensor 102, which may comprise at least one physical sensor, monitoring at least one of the main process parameters related to the fed air, such as temperature, pressure, concentration of CO2 etc. Sensor 102 is in cable-based or wireless communication with a central control unit 310.
[0173] Analogously, another sensor 104 sensor is placed at the air outlet line 220 and may comprise at least one physical sensor monitoring at least one of the main process parameters related to the released air, such as temperature, pressure, concentration of CO2 etc.202400234 Foreign Filing 16
[0174] The illustrated example of the process as shown in Figure 3 is similar to the ones shown on Figures 1 and 2. However, three reactors 200.1 , 200.2, 200.3 form the central reaction unit. The three reactors 200.1 , 200.2, 200.3 are built identically or analogously as further described above for a single reactor 200.
[0175] Additionally, the plant 100 comprise:
[0176] - a valve unit 160, configured to send air in alternating way to at least one of the three reactors 200.1 , 200.2, 200.3;
[0177] - a valve unit 170, configured to send solvent (I) in alternating way to at least one of the three reactors 200.1 , 200.2, 200.3; and
[0178] - a valve unit 180, configured to collect the liquid outflows from at least one of the three reactors 200.1 , 200.2, 200.3 and lead solvent (II) to the stirred vessel 198 of recovery unit 190.
[0179] The air controlling valve unit 160 is integrated in line 120, connected to the production unit 300, the solvent (I) control valve unit 170 is integrated in feed line 130, leading to the distributor elements 223 of the three reactors; and the solvent (II) receiving valve unit 180 is integrated in line 182 leading to the recovery unit 190 and its vessel 198. The air control valve unit 160 is connected with each of the reactors 200.1. 200.2, 200.3 by one line: 122, 124, and 126, respectively. The solvent (I) control valve unit 170 is connected with each of the three reactors 200.1 , 200.2, 200.3 and / or the respective distributor elements 223 by one single feed line 132, 134, and 136, respectively, and the solvent (II) receiving valve unit 180 is analogously connected with each of the three reactors 200.1 , 200.2, 200.3 by one single outlet line 142, 144, 146, respectively. Furthermore, outlet heat exchanger 152 is integrated downstream of the valve unit 180 for setting the intended feed temperature of vessel 198.
[0180] Thus, one can run inter alia the following processes:
[0181] First reactor is being fed with CO2 containing air, while the sorbent 212 of the second reactor is recovered with solvent (I) and the third reactor is inactive in waiting position, receiving neither loaded air nor solvent (I). Next, shift of air feed from the first reactor to the third reactor occurs, as soon as maximal or target CO2 loading is reached, and second reactor stays in (inactive) waiting position.
[0182] The first and the second reactors are fed with CO2 loaded air, while the sorbent 212 of the third reactor is recovered with solvent (I), wherein the first and the second reactors may have different CO2 loadings of the sorbent 212. Next, shift from the CO2-loaded reactor to the recovered reactor (sorbent) is done.
[0183] First reactor is being fed with CO2 loaded air, while the sorbent 212 of the second reactor is recovered with solvent (I) and the third reactor is inactive in waiting position, receiving neither loaded air nor solvent (I). Next, shift of air feed from the first reactor to the second reactor occurs, as soon as maximal or target loading of the first reactor and / or recovery of the second reactor is finished. The third reactor is only used (activated) in case of maintenance and / or emergency.
[0184] The progress of CO2 sorption can be indirectly monitored by means of sensor 104, which can be a pH-meter, a CO2-gas sensor, a conductivity sensor, or any other suitable sensor, responding to a directly or indirectly to CO2 content and / or concentration.202400234 Foreign Filing 17
[0185] In the example shown in Figure 4, the regeneration unit 190 comprises an electrolyser 199, having three chambers 250, 252, 254, The electro-chemical reaction in the second recovery step (desorption, step (e)), can be done in a recovery unit configured as a three-chamber electrolyser for electrolysis of solution (II) comprising MHCO3 to solution (III) comprising M2CO3, before recycling to the reactor 200. Water is fed via line 114 into the anode chamber 250 wherein an electrochemical FhO-dissociation is initiated. The solution (II), comprising MHCO3 (and M2CO3) delivered from the reactor outlet via line 140, is fed into the middle chamber 252 of the electrolyser. The middle chamber is separated from the anode chamber by a bipolar membrane and from the cathode chamber by means of a membrane permeable to the alkali metal ions M+, preferably potassium ions (K+). By applying a voltage, oxygen is evolved in the anode chamber 250, hydrogen in the cathode chamber and (concentrated) carbon dioxide in the middle chamber 252. A transfer line 274 connects the middle chamber 252 with the cathode chamber 254, leading the aqueous outlet stream from the middle chamber 252 to the cathode chamber 254. The outlet stream is depleted in CO2, which is released as gas from this middle chamber. The outlet stream is further at least partially depleted in cations M+, which are transferred through the membrane into the cathode chamber 254. The hydrogen ions received from the anode chamber 250, may also further travel into the cathode chamber 254. The individual gas streams O2, H2 and CO2 can be separately collected from different chambers of the electrolyser. The depleted aqueous outlet stream from the middle chamber 252 is introduced in the cathode chamber 254 and solution (III) comprising M2CO3 as a major salt component is formed by releasing electro-chemically formed hydrogen gas. This thus obtained solution (III) can be recycled to the reactor 200 and used again for sorbent recovery as solution (I).
[0186] In terms of reaction equations, the following conversions occur at the different reaction sites:
[0187] At the anode:
[0188]
[0189] At the bipolar membrane 256: H2O -> H++ OH-
[0190] In the middle chamber 252:
[0191]
[0192] CO2 + H2O
[0193] The following reactions take place at the cathode:
[0194]
[0195] Overall, the result for the cathode chamber is thus:
[0196] 2 KHCO3 + 2 K++ 2e 2K2CO3 + H2
[0197] In an alternative solution, shown in Figure 5, the process comprises an alternative recovery step (e), wherein an electrolyser 199 configured for two-chamber electrolysis is included. Therein solution (II) is fed into the anode chamber 250 and contacted with anode 258, e.g. made of nickel hydroxide. The alkali hydrogen carbonate (MHCO3) is converted, at least partially, to carbonate (M2CO3), in the first202400234 Foreign Filing 18
[0198] chamber 250 where the anode 258 is located (anode chamber). (Concentrated) CO2 gas is evolved in the same chamber. A transfer line 274 connects the anode chamber 250 with the cathode chamber 254, leading the aqueous outlet stream comprising MHCO3 and M2CO3 to the cathode chamber 254. The outlet stream is further depleted from at least a portion of the cations M+, which are transferred through the membrane into the cathode chamber 254.
[0199] The electrolysis cell has an alkali-permeable membrane 256 separating the anode chamber 250 from the cathode chamber 254. The anode 258 is a porous anode, configured to bind oxygen at its surface.
[0200] Hydrogen gas (H2) is formed in the second chamber, the cathode chamber 254, separated from the first chamber by a semi permeable diaphragm 256, permeable for alkali metal ions. Thus, CO2 exits the anode chamber 250 and H2 exits the cathode chamber 254. The regeneration of anode 258 and / or cathode 260 can be done if required, e.g. by a thermal treatment or any adequate cleaning step. Due to the fixation of O2 at the anode 258, this solution of the process is preferably suitable for smaller plant 100 or process units.
[0201] In terms of reaction equations within the two chambers electrolyser, the following conversions occur at the different reaction sites:
[0202] At the anode:
[0203]
[0204] HCO3 -^CO2+ OH- Ni(OH)2+ OH- NiOOH + H2O + e-
[0205] The overall reaction at the anode is:
[0206]
[0207] The following reactions take place at the cathode:
[0208]
[0209] Overall, the result for the cathode chamber is thus:
[0210]
[0211] The inputs and outputs of two typical variants of the inventive process carried out with a single fixed bed reactor in a production unit build according to Figure 1 were calculated with the following materials:
[0212] • Sorbent: LEWATIT® VP OC 1065 (commercially available from Lanxess®). A macroporous, divinylbenzene crosslinked polymer in spherical bead form with primary amine groups. Spherical beads with an average particle size of ~0.5 mm.
[0213] • Solution (I): Aqueous solution of potassium carbonate (K2CO3), concentration as specified below.202400234 Foreign Filing 19
[0214] Fixed bed reactor’s inner volume: 300 mL, sorbent fixed bed height: 1 cm.
[0215] Total mass of the (dry) sorbent: 100 g
[0216] Example 1 (sequential sorption / sorbent regeneration)
[0217] Step 1 :
[0218] Air containing 400 ppm CO2 is fed from the top inlet side (216) of the reactor (200) downwards through a sorbent’s fixed bed to react CO2 with amine moieties of the sorbent (steps (a) - (b) of the inventive process) with a flow rate of 10,000 (standard) L / h. The temperature in the reactor is kept at 20 °C and the pressure is 1 bar (abs). CO2 concentration in the reactor outlet (220) is monitored, and when its value increases over 200 ppm (corresponds to decreasing CO2 adsorption rate to < 50%), step 1 of the process is stopped, which takes about 0.8 h.
[0219] Step 2:
[0220] Aqueous solution (I) containing 20 wt% K2CO3 is fed for 4 h with a flow rate of 50 mL / h from the top inlet side (216) of the reactor (200) downwards through a sorbent’s fixed bed (202) to partially convert the carbonate (K2CO3) into hydrogen carbonate (KHCO3) and simultaneously regenerate the sorbent (step (c) of the inventive process). Liquid phase withdrawn via line (140) from the bottom section (218) of the reactor (200) is re-fed via lines (140, 147, 196, 132) to the upper reactor side so that a circulation rate of 500 mL / h through the reactor bed and feed-to-recycle ratio of 1 :10 is realized. The thus obtained solution (II) containing KHCO3 is withdrawn (via 152) from the bottom part of the reactor (200) and sent to the second recovery step (190), wherein solution (II) is heated to 140 °C for 1 h to convert KHCO3 to CO2 and K2CO3.
[0221] Example 2 (simultaneous sorption / sorbent regeneration)
[0222] The parallel flow of solution (I) and air downwards trough trickle bed from the top inlet side (216) of the reactor (200) in steps (a) to (d) is carried out continuously.
[0223] Air was fed from the top side of the reactor (216), and the CO2-depleted air was withdrawn from a side outlet (220) located in the lower part of the reactor (200). The loaded solvent (II) was withdrawn from the reactor 200 at the bottom end (via line 140).
[0224] Liquid phase withdrawn from the bottom section of the reactor is re-fed on the upper reactor side so that a circulation feed-to-recycle ratio of 1 :10 is realized.
[0225] Table 1 shows reactor inputs and outputs in example 2.
[0226] The columns 1-10 of Table 1 show the following information:
[0227] 1 : Air flow rate of air into reactor (200) [in standard L / h]
[0228] 2: CO2 concentration in the inflow stream (via 120) into the reactor [in vol ppm]202400234 Foreign Filing 20
[0229] 3: CO2 capture rate (in %) = (amount of CO2 fed per h in reactor inflow (via 120) - amount of CO2 per h in reactor outflow (via 220)) *100% / (amount of CO2 fed per h in reactor inflow (via 120)) 4: CO2 concentration in the outflow stream from the reactor (200) [in vol ppm]
[0230] 5: CO2 amount adsorbed = standard volume of CO2 [in L / h] chemically bound in the reactor (200) to sorbent (212) and thus removed from the inflow stream
[0231] 6: CO2 amount adsorbed = amount of CO2 [in mmol / h] chemically bound in the reactor (200) to sorbent (212) and thus removed from the inflow stream
[0232] 7: Solution (I) (aqueous solution containing K2CO3) inflow (via 132) in L / h
[0233] 8: Concentration of K2CO3 (in wt%) in inflow (via 132)
[0234] 9: Amount of K2CO3 (in mmol / h) fed into reactor 200 (via 132)
[0235] 10: Molar ratio of the amount of K2CO3 provided into reactor (via 132) to the amount of CO2 adsorbed in the reactor.
[0236] One important benefit of the process according to the invention, as demonstrated in the abovedescribed example, is that an efficient capturing of low CO2 concentrations from air with high CO2 capture rate, at ambient temperature and using cheap, commercially available sorbent and alkali carbonate solution is possible. Another very important aspect is that regeneration of the loaded with CO2 sorbent also happens under ambient conditions, simultaneously with loading the sorbent. This nearly eliminates any amine degradation and leads to greatly prolonged service time for the sorbent. Another benefit compared to classical amine sorbent desorption methods, is that the sorbent may remain wet in the whole process, as water does not have to be removed during the desorption. This saves energy and eliminates mechanical and chemical stress on the sorbent. Additionally, overall process time may be significantly reduced, especially in continuous variant as described in example 2.202400234 Foreign Filing 21
[0237]
[0238] Table 1 : Reactor inflows and outflows202400234 Foreign Filing 22
[0239] References
[0240] 100 Process unit
[0241] 102 Sensor
[0242] 104 Sensor
[0243] 110 Tank
[0244] 112 Tank
[0245] 113 Tank
[0246] 120 Line, air
[0247] 122 Line, air to 200.1
[0248] 124 Line, air to 200.2
[0249] 126 Line, air tO 200.3
[0250] 130 Line, solution (I)
[0251] 132 Line, solution (I) to 200.2
[0252] 134 Line, solution (I) to 200.3
[0253] 136 Line, solution (I) to 200.1
[0254] 140 Line, solution (II)
[0255] 141 Line, solution (II) to 113
[0256] 142 Line, solution (II) out 200.1
[0257] 144 Line, solution (II) out 200.2
[0258] 146 Line, solution (II) out 200.3
[0259] 147 Line, solution (II) out 140, directly feed to 200
[0260] 150 Heat exchanger, feed (solution (I))
[0261] 152 Heat exchanger, outlet (solution (II))
[0262] 160 Valve unit (air, to 200)
[0263] 170 Valve unit (solution (I), to 200)
[0264] 180 Valve unit (solution (II), from 200) 182 Line, to 190 from 180
[0265] 190 Regeneration unit
[0266] e.g. vessel 198, electrolyser 199
[0267] 192 Line, from 190
[0268] 193 Line, from 190
[0269] 194 Line, to 112
[0270] 195 Line, from 190 (CO2)202400234 Foreign Filing 23
[0271] 196 Line to 170, 200
[0272] 198 Vessel, stirred
[0273] 199 Electrolyser
[0274] 200 Reactor
[0275] 202 Fixed bed
[0276] 204 Gas / liquid separation element in 200
[0277] 206 Valve
[0278] 210 Carrier
[0279] 212 Sorbent
[0280] 216 Reactor inlet, feed side
[0281] 218 Reactor outlet, product side
[0282] 220 Line, air from reactor also 220.1 , 220.2, 220.3 222 Gas inlet
[0283] 223 Distributor element
[0284] 250 Electrolysis chamber, first (anode chamber) 252 Electrolysis chamber, second (middle chamber) 254 Electrolysis chamber, third (cathode chamber) 256 Diaphragm or membrane
[0285] 258 Anode
[0286] 260 Cathode
[0287] 262 Outlet gas, O2
[0288] 264 Outlet gas, CO2
[0289] 266 Outlet gas, H2
[0290] 268 Feed connection, solution (II) from reactor 200 270 Feed connection, H2O
[0291] 272 Outlet, solution (I)
[0292] 300 Production unit
[0293] 310 Control unit
[0294] 312 Data line
Claims
202400234 Foreign Filing 24Claims1. Process for removal of carbon dioxide (CO2) from a gas, comprising the following steps:(a) Feeding gas (inflow) containing CO2 in a reactor (200), comprising a water-insoluble unloaded sorbent (212) having primary and / or secondary amine moieties, preferably immobilized on at least one solid carrier (210);(b) (Adsorption step)Reacting the CO2 with the unloaded sorbent (212) to form loaded sorbent (212) containing CO2 chemically bound to amine moieties of the sorbent (212);(c) (First recovery step)Reacting of the loaded sorbent (212) formed in step (b) with an aqueous solution (I) containing alkali carbonate (M2CO3), wherein M is an alkali metal, and wherein the M2CO3 is at least partially converted to alkali hydrogen carbonate (MHCO3), whereby forming a solution (II) containing said MHCOsand at least partially releasing unloaded sorbent (212);(d) Separating the solution (II) obtained in step (c) from the solid sorbent (212), and preferably withdrawing the solution (II) from the reactor (200).
2. Process according to claim 1 , wherein step (d) is followed by step (e) (Second recovery step):At least partially converting MHCO3 contained in the solution (II) to M2CO3 and CO2, and wherein the thus obtained solution (III) comprising M2CO3 is at least partially fed into step (c).
3. Process according to any of the preceding claims, wherein the CO2 concentration in the gas (inflow) of step (a) and / or (b) is from 100 ppm to 1000 ppm.
4. Process according to any of the preceding claims, wherein M is lithium (Li), sodium (Na) or potassium (K), preferably potassium (K).
5. Process according to any of the preceding claims, wherein- the concentration of M2CO3 in solution (I) is 0.5-50 wt%; and / or- the concentration of MHCO3 in solution (II) is 0.5-50 wt%.
6. Process according to any of the preceding claims, wherein steps (a) to (d) are carried out continuously, wherein CO2 containing gas and solution (I) are simultaneously fed into reactor (200), while solution (II) is continuously separated from sorbent (212), and steps (a) to (d) further optionally followed by step (e), wherein solution (III) obtained in step (e) is continuously fed back to the reactor (200).202400234 Foreign Filing 257. Process according to claim 6, wherein the reactor (200) has a top end (202) and a bottom end (204), and wherein both the CO2 containing gas and solution (I) are fed into the reactor at the top end (202), while solution (II) is withdrawn from the reactor at the bottom end (204).
8. Process according to any of claims 6 or 7, wherein the volume flow ratio of gas flow [L / h] to solution (I) flow [L / h] is in the range 100-100,000, more preferably 500-50,000, more preferably 1 ,000-20,000.
9. Process according to any of claims 1 to 5, whereinstep (a) and step (b) are carried out until at least 20%, preferably at least 30%, more preferred at least 50% of the maximal CO2 adsorption capacity of the sorbent is achieved, before step (c) is started.
10. Process according to any of the preceding claims 2 to 9, wherein step (e) is carried out - at a temperature of 70-200 °C, more preferably 80-150°C, more preferably 90-140°C, more preferably 100-130 °C; and- under pressure of 1.1-15 bar, preferably 1.2-10 bar, more preferably 1.5-6 bar.
11. Process according to any of the preceding claims 2 to 10, wherein step (e) is carried out electrochemically, preferably at 20-80 °C.
12. Process according to any of the preceding claims, wherein the sorbent (212) is selected from at least one of the following substances:- organic polymers, such as polystyrene, polyacrylate, or phenol-formaldehyde resin, having primary and / or secondary amine moieties;- metal and / or metalloid oxides, such as silica, alumina, mixed oxides, or zeolites, having primary and / or secondary amine moieties.
13. Process according to any of the preceding claims, wherein the sorbent (212) has a maximal CO2 sorption capacity related to dry sorbent of 1-20 mmol CO2 / g,more preferably 1-10 mmol CO2 / g, more preferably 1-6 mmol CO2 / g.
14. Process according to any of the preceding claims, wherein the solution (II) from the reactor (200) is mixed with solution (I) and / or solution (III) and recycled back to the reactor (200), wherein the volume flow ratio ofi) solution (I) flow [L / h] or the mixed solutions (I) and (III) flow [L / h] toii) solution (II) flow [L / h] recycled to the reactor (200)is in the range 1 : 1 to 1 : 100, more preferably 1 : 1 to 1 : 30, more preferably 1 : 1 to 1 : 15.