Method for producing carbon monoxide and method for producing syngas

Abstract

A method for producing carbon monoxide is specified. The method comprises electrochemical desorption of carbon dioxide and oxygen from a solution containing a metal hydrogen carbonate and forming carbon monoxide from the carbon dioxide. The carbon monoxide produced can be used in a method for forming syngas.

Description

[0001] 2024_07_Patent Family_WO July 1 , 2025 P2024 , 0513 WO N

[0002] - 1 -

[0003] Description

[0004] METHOD FOR PRODUCING CARBON MONOXIDE AND METHOD FOR PRODUCING SYNGAS

[0005] A method for producing carbon monoxide and a method for producing syngas is speci fied .

[0006] It is an obj ect to provide an ef ficient and environmentally friendly method for producing carbon monoxide and an ef ficient and environmentally friendly method for producing syngas .

[0007] According to at least one embodiment , a method for producing carbon monoxide is provided . The carbon monoxide can be used in a method for producing syngas .

[0008] According to at least one embodiment of the method, the method comprises a step of electrochemical desorption of carbon dioxide and oxygen from a solution containing a metal hydrogen carbonate . In particular, the metal of the metal hydrogen carbonate is potassium . In other words , the solution contains potassium hydrogen carbonate . For example , the electrochemical desorption produces the carbon dioxide and the oxygen in gaseous form . During electrochemical desorption, the metal hydrogen carbonate contained in the solution is trans formed into the carbon dioxide .

[0009] According to at least one embodiment of the method, the method comprises a step of forming carbon monoxide from the carbon dioxide . In particular, the carbon dioxide is reduced to carbon monoxide during forming the carbon monoxide . For example , the carbon monoxide is formed by a reverse water gas 2024_07_Patent Family_WO July 1, 2025 P2024, 0513 WO N

[0010] - 2 - shift reaction. The reverse water gas shift reaction comprises the following reaction equilibrium: CO2 + H2<-> CO + H2O.

[0011] In particular, the reverse water gas shift reaction is favored at high temperatures, for example at temperatures above 900 °C.

[0012] According to at least one embodiment, the method for producing carbon monoxide comprises

[0013] - electrochemical desorption of carbon dioxide and oxygen from a solution containing a metal hydrogen carbonate,

[0014] - forming carbon monoxide from the carbon dioxide. In particular, these steps are performed in the described order.

[0015] Due to the electrochemical desorption of the carbon dioxide, the carbon dioxide necessary for producing the carbon monoxide can advantageously be provided in a simple and efficient manner. Additionally, it is possible that the carbon dioxide obtained from the electrochemical desorption does not have to be purified, for example except of a removal of water vapor, and can be directly used in forming the carbon monoxide. In other words, the carbon dioxide and the oxygen obtained from the electrochemical desorption are advantageously not separated for forming the carbon monoxide. This makes the method less technically complex and less energy-intensive .

[0016] According to at least one embodiment of the method, during the electrochemical desorption, the carbon dioxide and the oxygen are generated in a ratio of between and including 3.0:2.0 to 4.5: 0.5, in particular between and including

[0017] 3.8:1.2 to 4.2:0.8, for example 4:1. Advantageously, with 2024_07_Patent Family_WO July 1, 2025

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[0019] 3 such a ratio of the carbon dioxide and the oxygen, addition of further carbon dioxide and / or oxygen during forming the carbon monoxide is not necessary.

[0020] According to at least one embodiment of the method, for forming the carbon monoxide, the carbon dioxide and the oxygen are provided in a ratio of between and including 3.0:2.0 to 4.5: 0.5, in particular between and including 3.8:1.3 to 4.2:0.8, for example 4:1. Advantageously, such a ratio of carbon dioxide and oxygen is obtained from the electrochemical desorption. Thus, an adjustment of the ratio of carbon dioxide and oxygen is not necessary.

[0021] According to at least one embodiment of the method, the carbon dioxide and the oxygen obtained from the electrochemical desorption are directly used in the method step of forming the carbon monoxide. In other words, no purification step for the carbon dioxide and the oxygen is performed between the electrochemical desorption and forming the carbon monoxide. In particular, the carbon dioxide and the oxygen are used without separation in forming the carbon monoxide. Thus, advantageously, no further processing steps for the carbon dioxide and the oxygen are necessary.

[0022] According to at least one embodiment of the method, forming the carbon monoxide is performed in an oxyhydrogen flame. In particular, the oxyhydrogen flame is provided by an oxyhydrogen reaction. The oxyhydrogen reaction is also referred to as Knallgas reaction. This reaction can be described by the following equation: H2+ 1 / 2 O2-> H2O. The oxyhydrogen flame can provide the energy necessary for forming the carbon monoxide from the carbon dioxide. Additionally, the oxyhydrogen flame consumes the oxygen 2024_07_Patent Family_WO July 1, 2025

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[0024] - 4 - generated during the electrochemical desorption. Thus, separation of the oxygen generated during electrochemical desorption is advantageously not necessary.

[0025] According to at least one embodiment of the method, forming the carbon monoxide is performed without a catalyst. Thus, advantageously, expensive catalysts or regeneration of a catalyst can be avoided. This makes the method for producing carbon monoxide more environmentally friendly.

[0026] According to at least one embodiment of the method, during the electrochemical desorption of carbon dioxide, hydrogen is formed, in particular in a gaseous form. The carbon dioxide and the hydrogen are, in particular, generated in the electrochemical desorption in a ratio of between and including 1:2 and 3:1, for example between and including 1:1 and 2.5:1, for instance 2:1.

[0027] According to at least one embodiment of the method, the hydrogen is reacted with the oxygen and / or the carbon dioxide during forming the carbon monoxide. In other words, the hydrogen can be consumed in the reverse water gas shift reaction for forming the carbon monoxide and / or in the oxyhydrogen reaction. Thus, advantageously, all gaseous products formed in the electrochemical desorption are further used for forming the carbon monoxide.

[0028] According to at least one embodiment of the method, additional hydrogen to be reacted with the oxygen and / or the carbon dioxide is provided, in particular by electrolysis of water. In this way, an overall environmentally friendly method for forming the carbon monoxide can be provided. 2024_07_Patent Family_WO July 1 , 2025

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[0031] Electrolysis of water, in particular, is a simple and ef ficient method to provide hydrogen .

[0032] According to at least one embodiment of the method, the electrochemical desorption of carbon dioxide is performed in a two-chamber electrochemical desorption unit . In particular, the two-chamber electrochemical desorption unit is a two- chamber electrolyzer . In the two-chamber electrochemical desorption unit the carbon dioxide and the oxygen are , in particular, generated from the solution containing the metal hydrogen carbonate in a first chamber which is for example an anode chamber . In a second chamber which is for example a cathode chamber hydrogen can be produced . The carbon dioxide , the oxygen, and the hydrogen advantageously do not have to be separated as these gases are all used during forming the carbon monoxide .

[0033] Compared to a three-chamber electrochemical desorption unit , a bipolar membrane can be omitted . This advantageously improves the ef ficiency of the electrochemical desorption and thus the method for producing syngas . For example , the electrochemical desorption in a two-chamber electrochemical desorption unit can be operated at higher temperatures and current densities compared to a three-chamber electrochemical desorption unit while at the same time it is possible to reduce a cell voltage . Thus , the two-chamber electrochemical desorption unit is advantageously less complex and less energy-intensive and thus environmentally friendlier .

[0034] According to at least one embodiment , the electrochemical desorption of the carbon dioxide is performed with a cell voltage of between and including 1 . 9 V and 3 . 0 V . In particular, such a cell voltage allows for an ef ficient 2024_07_Patent Family_WO July 1 , 2025 P2024 , 0513 WO N

[0035] - 6 - desorption of the carbon dioxide . For example , only an additional cell voltage of 0 . 4 V is necessary for the electrochemical desorption of carbon dioxide compared to an electrolysis of an alkaline solution .

[0036] According to at least one embodiment of the method, the solution containing the metal hydrogen carbonate is provided as follows :

[0037] - contacting an absorbent with a gas stream comprising carbon dioxide , wherein the absorbent comprises a metal carbonate ,

[0038] - producing a loaded absorbent , wherein the metal carbonate is at least partially converted to a metal hydrogen carbonate ,

[0039] - precipitating at least a portion of the metal hydrogen carbonate from the loaded absorbent ,

[0040] - separating the precipitated metal hydrogen carbonate , and

[0041] - dissolving the separated metal hydrogen carbonate to form the solution containing the metal hydrogen carbonate .

[0042] In particular, the steps of contacting the absorbent and producing the loaded absorbent are performed simultaneously . For example , the metal carbonate is converted to the metal hydrogen carbonate according to the following formula : M2CO3 + CO2 + H20 -> 2 MHCO3 . For instance , the conversion of the metal carbonate to the metal hydrogen carbonate is an exothermic process .

[0043] In particular, the gas stream comprising carbon dioxide is air, for example ambient air with a carbon dioxide concentration of at most 10 % or greater than or equal to 100 ppm and less than or equal to 650 ppm . In particular, the precipitated metal hydrogen carbonate comprises at least

[0044] 90 wt . -% of the metal hydrogen carbonate . In particular, the 2024_07_Patent Family_WO July 1 , 2025

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[0046] - 7 - precipitated metal hydrogen carbonate is separated from the aqueous phase of the loaded absorbent using a centri fuge , a hydrocyclone , a belt filter, or combinations thereof .

[0047] By providing the solution as described herein, the method of fers an environmentally friendly option for trans forming carbon dioxide into carbon monoxide . Furthermore , by providing the solution as described above , the carbon dioxide in the gas stream can be stored as metal hydrogen carbonate and used at a di f ferent time to produce the carbon monoxide .

[0048] According to at least one embodiment of the method, waste heat produced during forming the carbon monoxide is used to pre-heat the carbon dioxide , the oxygen and / or the hydrogen used during forming the carbon monoxide . In this way, advantageously, the overall energy ef ficiency of the method for producing the carbon monoxide can be improved .

[0049] According to at least one embodiment of the method, the carbon monoxide produced is passed through heat exchangers to pre-heat the carbon dioxide , the oxygen and / or the hydrogen used for forming the carbon dioxide . Advantageously, in this way it is possible that no further heat supply is necessary to pre-heat the carbon dioxide , the oxygen and / or the hydrogen . Thus , the overall ef ficiency of the method for producing the carbon dioxide can be improved . In particular, the heat exchangers allow for an autothermal or an almost autothermal method for producing the carbon monoxide .

[0050] Furthermore , a method for producing syngas is speci fied . In particular, the carbon monoxide produced by the method for producing carbon monoxide described herein is used during the method for producing syngas . Thus , features and embodiment of 2024_07_Patent Family_WO July 1, 2025 P2024, 0513 WO N

[0051] - 8 - the method for producing the carbon monoxide also apply to the method for producing syngas and vice versa.

[0052] According to at least one embodiment, the method for producing syngas produces syngas. Syngas can also be referred to as synthesis gas. In particular, syngas is a mixture of hydrogen and carbon monoxide. For example, the syngas can be used in a Fischer-Tropsch synthesis to produce liquid hydrocarbons. For instance, the syngas formed comprises carbon monoxide and hydrogen in a ratio of between and including 1.5 to 0.5 and 0.5: 1.5, for example of 1:1.

[0053] According to at least one embodiment of the method for producing syngas, carbon monoxide is provided by the method described herein. The carbon monoxide is then mixed with hydrogen to produce the syngas.

[0054] According to at least one embodiment of the method for producing syngas, the hydrogen is provided by electrolysis of water. Advantageously, electrolysis of water is an environmentally friendly method to produce hydrogen.

[0055] Advantageous embodiments and developments of the method for producing syngas will become apparent from the exemplary embodiments described below in conjunction with the figures.

[0056] In the figures:

[0057] Figure 1 schematically shows a step of a method for producing carbon monoxide according to an exemplary embodiment.

[0058] Figure 2 schematically shows steps of a method for producing carbon monoxide according to an exemplary embodiment. 2024_07_Patent Family_WO July 1 , 2025

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[0060] Figure 3 schematically shows steps of a method for producing carbon monoxide according to an exemplary embodiment .

[0061] In the exemplary embodiments and figures , similar or similarly acting constituent parts are provided with the same reference signs . The elements illustrated in the figures and their si ze relationships among one another should not be regarded as true to scale . Rather, individual elements may be represented with an exaggerated si ze for the sake of better representability and / or for the sake of better understanding .

[0062] Figure 1 schematically shows an electrochemical desorption of carbon dioxide from a solution containing potassium hydrogen carbonate as a metal hydrogen carbonate . This step is a first step of a method for producing carbon monoxide according to an exemplary embodiment . The electrochemical desorption of carbon dioxide from the solution containing the metal hydrogen carbonate is performed in an electrochemical desorption unit 4 . The electrochemical desorption unit 4 comprises a first chamber 41 , for example an anode chamber, and a second chamber 42 , for example a cathode chamber . In other words , the electrochemical desorption unit 4 is a two- chamber electrochemical desorption unit .

[0063] In the electrochemical desorption unit 4 the following reaction occurs :

[0064] 4 KHCOa -> 2 K2CO3 + H2O + 2 CO2+ H2+ 1 / 2 O2.

[0065] In other words , the metal hydrogen carbonate is trans formed to metal carbonate , water, the carbon dioxide , hydrogen, and oxygen . The carbon dioxide and the oxygen are produced in the first chamber 41 , whereas the hydrogen is produced in the 2024_07_Patent Family_WO July 1 , 2025

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[0067] - 10 - second chamber 42 . The carbon dioxide and the oxygen are presently generated in a ratio of about 4 : 1 .

[0068] The solution containing the metal hydrogen carbonate is presently provided by contacting an absorbent with a gas stream comprising carbon dioxide in an absorption unit 1 . The absorbent comprises a metal carbonate such as potassium carbonate . In the absorption unit 1 a loaded absorbent is produced from the absorbent . During this process the metal carbonate is at least partially converted to a metal hydrogen carbonate . This reaction can be described by the following equation : 2 K2CO3+ 2 CO2+ 2 H2O -> 4 KHCO3.

[0069] The loaded absorbent comprising the metal carbonate and the metal hydrogen carbonate is then trans ferred to a precipitation unit 2 . In the precipitation unit 2 , at least a portion of the metal hydrogen carbonate is precipitated from the loaded absorbent . In particular, the metal hydrogen carbonate crystalli zes in the precipitation unit 2 during precipitating . After precipitation, the metal hydrogen carbonate is separated from the remaining loaded absorbent . The remaining loaded absorbent comprises metal hydrogen carbonate and metal carbonate .

[0070] The precipitated and separated metal hydrogen carbonate is then trans ferred to a dissolving unit 3 . In the dissolving unit 3 , the metal hydrogen carbonate is dissolved such that the solution containing the metal hydrogen carbonate is formed which is used in the electrochemical desorption unit 4 . Presently, the solution containing the metal hydrogen carbonate is provided in the first chamber 41 of the electrochemical desorption unit 4 . The remaining loaded absorbent obtained after separation of the precipitated metal 2024_07_Patent Family_WO July 1 , 2025

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[0072] - 11 - hydrogen carbonate in the precipitation unit 2 can be provided in the second chamber 42 of the electrochemical desorption unit 4 .

[0073] After the electrochemical desorption of carbon dioxide and oxygen in the electrochemical desorption unit 4 , the products apart from the carbon dioxide , the oxygen and the hydrogen can be recycled . For example , a solution obtained in the first chamber 41 after electrochemical desorption can be reused in the dissolving unit 3 to form the solution containing the metal hydrogen carbonate . A solution obtained in the second chamber 42 after electrochemical desorption comprises metal carbonate and metal hydrogen carbonate and can be reused as absorbent in the absorption unit 1 .

[0074] In Figure 2 , further steps of a method for producing carbon monoxide according to an exemplary embodiment are shown . In an electrochemical desorption unit 4 comprising a first chamber 41 and a second chamber 42 , carbon dioxide and oxygen are electrochemically desorbed from a solution containing a metal hydrogen carbonate . The metal of the metal hydrogen carbonate is , for example , potassium . The electrochemical desorption unit 4 is an electrolyzer . For example , the electrochemical desorption is performed at a voltage of about 2 . 5 V . For an ef fectivity of 90% about 434 kJ of energy can be consumed in the electrochemical desorption unit 4 .

[0075] In the first chamber 41 , the carbon dioxide and the oxygen are generated from the solution containing the metal hydrogen carbonate . In the second chamber 42 , hydrogen is generated by the electrochemical desorption . The carbon dioxide and the oxygen are generated in a ratio of about 4 : 1 . The carbon 2024_07_Patent Family_WO July 1 , 2025 P2024 , 0513 WO N

[0076] - 12 - dioxide and the hydrogen are generated in a ratio of about 2 : 1 .

[0077] The carbon dioxide , the oxygen, and the hydrogen generated during electrochemical desorption are directly provided to a reduction unit 5 . No puri fication or other separation processing is performed on the carbon dioxide , the oxygen, and the hydrogen after the electrochemical desorption, except for a possible removal of water vapor, for example by condensation . Furthermore , the ratio of the carbon dioxide and the oxygen is not changed .

[0078] In the reduction unit 5 , the carbon dioxide is reacted to carbon monoxide at a temperature T of at least 1000 ° C . The following table 1 gives exemplary caloric heats necessary to pre-heat the carbon dioxide , the oxygen, and the hydrogen to a temperature of about 1000 ° C .

[0079] Table 1 : caloric heat / kJ carbon dioxide 105 oxygen 34 hydrogen 88

[0080] The carbon monoxide produced may comprise traces of hydrogen . During forming the carbon monoxide from the carbon dioxide , no catalyst is used . The carbon monoxide is formed by a reverse water gas shi ft reaction from the carbon dioxide . In other words , the carbon monoxide is formed according to the following equation : 2 CO2 + 2 H2-> 2 CO + 2 H2O .

[0081] The energy that has to be expended to perform the reverse water gas shi ft reaction is provided by an oxyhydrogen flame . The oxyhydrogen flame is produced by the reaction of the 2024_07_Patent Family_WO July 1 , 2025

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[0083] 13 oxygen and the hydrogen . The overall reaction, that is the combination of the reaction in the oxyhydrogen flame and the reverse water gas shi ft , leads to a released enthalpy of - 170 kJ . This energy can be used to pre-heat the gas streams leading into the reduction unit 5 , that is the carbon dioxide , the oxygen, and the hydrogen .

[0084] Presently, additional hydrogen is provided to the reduction unit 5 from an electrolysis unit 6 . In the electrolysis unit 6 , water is electrolyzed to give oxygen and water . The electrolysis of water can be described by the following equation : 6 H2O -> 6 H2+ 3 O2. The electrolysis is , for example , performed at a voltage of 1 . 9 V . For an ef fectivity of 90% about 1980 kJ of energy can be consumed in the electrolysis unit 6 .

[0085] The additional hydrogen is also reacted with the carbon dioxide and / or the oxygen in the reduction unit 5 . That is , the additional hydrogen is used in forming the carbon monoxide from the carbon dioxide and / or in generating the oxyhydrogen flame . Presently, only one third of the hydrogen generated in the electrolysis unit 6 is provided as additional hydrogen to the reduction unit 5 . The oxygen generated in the electrolysis unit 6 is lead away . In other words , the oxygen generated in the electrolysis unit 6 can be used in a method other than forming carbon monoxide .

[0086] The other two thirds of the hydrogen generated in the electrolysis unit 6 can be provided to produce syngas . Syngas is a mixture of carbon monoxide and hydrogen which can be used to form hydrocarbons in a Fischer-Tropsch unit 7 . 2024_07_Patent Family_WO July 1 , 2025

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[0088] - 14 -

[0089] For forming the syngas , the carbon monoxide producing in the reduction unit 5 is mixed with hydrogen, for example at least a part of the other two thirds of the hydrogen generated in the electrolysis unit 6 . Forming the syngas occurs presently in the Fischer-Tropsch unit 7 . In the Fischer-Tropsch unit 7 , the syngas is reacted to liquid hydrocarbons . In the Fischer- Tropsch unit 7 , a ratio of carbon monoxide and hydrogen in the syngas is , for example , about 2 : 4 .

[0090] Water generated during forming the carbon monoxide in the reduction unit 5 can be separated before the carbon monoxide is mixed with hydrogen to form the syngas .

[0091] Figure 3 shows a further exemplary embodiment of the method for producing carbon monoxide and the method for producing syngas . The method is performed in principle as described in combination with figure 2 . However, presently, heat of the carbon monoxide and water generated in the reduction unit 5 is used to pre-heat the carbon dioxide , the oxygen, and the hydrogen which are fed into the reduction unit 5 . The heat trans fer from the carbon monoxide and the water to the carbon dioxide , the oxygen, and the hydrogen are performed in heat exchangers 81 , 82 , 83 .

[0092] In particular, in a first heat exchanger 81 , heat is trans ferred from the carbon monoxide and the water produced in the reduction unit 5 to the carbon dioxide and the oxygen generated in the electrochemical desorption unit 4 . In a second heat exchanger 82 , for example arranged downstream of the first heat exchanger 81 , the heat of the carbon monoxide and the water produced in the reduction unit 5 is trans ferred to the hydrogen generated in the electrochemical desorption unit 4 . In a third heat exchanger 83 , for example arranged 2024_07_Patent Family_WO July 1 , 2025

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[0094] - 15 - downstream of the first heat exchanger 81 and the second heat exchanger 82 , the heat of the carbon monoxide and the water produced in the reduction unit 5 is trans ferred to the hydrogen generated in the electrolysis unit 6 . It is also possible that the heat exchangers 81 , 82 , 83 are arranged in a di f ferent order .

[0095] In a fourth heat exchanger 84 which is operated with a cooling liquid 9 and which is , for example , arranged downstream of the first to third heat exchangers 81 , 82 , 83 , the remaining heat of the carbon monoxide and the water is removed such that the water condenses and is separated from the carbon monoxide . The carbon monoxide puri fied by this method is then used to form syngas by mixing with hydrogen, for example provided by the electrolysis unit 6 . The syngas can then be used in the Fischer-Tropsch unit 7 for forming liquid hydrocarbons .

[0096] The features and exemplary embodiments described in connection with the figures can be combined with each other according to further exemplary embodiments , even i f not all combinations are explicitly described . Furthermore , the exemplary embodiments described in connection with the figures may have alternative or additional features as described in the general part .

[0097] The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary embodiments . Rather, the invention encompasses any new feature and also any combination of features , which in particular comprises any combination of features in the patent claims and any combination of features in the exemplary embodiments , even i f this feature or this 2024_07_Patent Family_WO July 1, 2025

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[0099] - 16 - combination itself is not explicitly specified in the patent claims or exemplary embodiments.

[0100] This patent application claims the priority of DE patent application 10 2024 122 674.9, the disclosure content of which is hereby incorporated by reference.

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[0104] List of reference signs

[0105] 1 absorption unit

[0106] 2 precipitation unit

[0107] 3 dissolving unit

[0108] 4 electrochemical desorption unit

[0109] 41 first chamber

[0110] 42 second chamber

[0111] 5 reduction unit

[0112] 6 electrolysis unit

[0113] 7 Fischer-Tropsch unit

[0114] 81 first heat exchanger

[0115] 82 second heat exchanger

[0116] 83 third heat exchanger

[0117] 84 fourth heat exchanger

[0118] 9 cooling liquid

[0119] T temperature

Claims

2024_07_Patent Family_WO July 1, 2025 P2024, 0513 WO N- 18 -Claims1. Method for producing carbon monoxide comprising- electrochemical desorption of carbon dioxide and oxygen from a solution containing a metal hydrogen carbonate,- forming carbon monoxide from the carbon dioxide, wherein- during the electrochemical desorption of carbon dioxide, hydrogen is formed, and- the hydrogen is reacted with the oxygen and / or the carbon dioxide during forming the carbon monoxide.

2. Method according to claim 1, wherein during the electrochemical desorption, the carbon dioxide and the oxygen are generated in a ratio of between and including 3.0:2.0 to 4.5:0.5.

3. Method according to any of the previous claims, wherein for forming the carbon monoxide, the carbon dioxide and the oxygen are provided in a ratio of between and including3.0:2.0 to 4.5:0.5.

4. Method according to any of the previous claims, wherein the carbon dioxide and the oxygen are directly used in the method step of forming the carbon monoxide.

5. Method according to any of the previous claims, wherein forming the carbon monoxide is performed in an oxyhydrogen flame .

6. Method according to any of the previous claims, wherein forming the carbon monoxide is performed without a catalyst.2024_07_Patent Family_WO July 1 , 2025 P2024 , 0513 WO N- 19 -7 . Method according to any of the previous claims , wherein additional hydrogen to be reacted with the oxygen and / or the carbon dioxide is provided by electrolysis of water .8 . Method according to any of the previous claims , wherein the electrochemical desorption of carbon dioxide is performed in a two-chamber electrochemical desorption unit .9 . Method according to any of the previous claims , wherein the solution containing the metal hydrogen carbonate is provided as follows :- contacting an absorbent with a gas stream comprising carbon dioxide , wherein the absorbent comprises a metal carbonate ,- producing a loaded absorbent , wherein the metal carbonate is at least partially converted to a metal hydrogen carbonate ,- precipitating at least a portion of the metal hydrogen carbonate from the loaded absorbent ,- separating the precipitated metal hydrogen carbonate , and- dissolving the separated metal hydrogen carbonate to form the solution containing the metal hydrogen carbonate .10 . Method for producing syngas comprising- providing carbon monoxide by the method according to any of the previous claims ,- mixing the carbon monoxide with hydrogen to produce the syngas .

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