A system and method for continuous production of formic acid compounds by electroreduction of carbon dioxide

Abstract

This invention relates to the field of fine manufacturing and discloses a system and method for the continuous preparation of formic acid compounds by carbon dioxide electroreduction. The production system includes: a cathode electrolyte source, an anolyte electrolyte source, a carbon dioxide gas source, an electrochemical reaction device, a simulated moving bed, and a scrubbing liquid source. In this system and method, the present invention connects the electrochemical reactor in series with a simulated moving bed. An aqueous solution of formic acid compounds is continuously generated within the electrochemical reactor. The formic acid compounds (formates) are then separated in the simulated moving bed, and the remaining electrolyte is returned to the electrochemical reactor to continue the reaction. This overcomes the problem of non-continuous production in existing electrochemical reduction processes for formic acid preparation and also has higher production capacity, making the industrial production of formic acid by carbon dioxide electroreduction possible.

Description

Technical Field

[0001] This invention relates to the field of fine manufacturing, specifically to a system and method for the continuous preparation of formic acid compounds by carbon dioxide electroreduction. Background Technology

[0002] With the increasing prominence of environmental and energy issues, the capture and utilization of carbon dioxide has become a key research focus. Carbon dioxide is the highest oxidation state oxide of carbon, with a stable chemical structure that is not easily destroyed. Converting it into other substances requires additional energy. Commonly used methods include electrochemistry, biochemistry, photochemistry, and thermochemistry. Compared with other technologies, electrochemical methods have the advantages of being able to be carried out at room temperature and pressure, being simple to operate, and having mild reactions. Furthermore, by changing the catalyst and electrolysis conditions, various organic compounds can be selectively generated, such as formic acid, carbon monoxide, methanol, and methane. Formic acid is an important raw material in industrial production and also a very promising energy storage medium. The electroreduction of carbon dioxide to prepare formic acid or formate salts is considered the most suitable process for large-scale production.

[0003] Current research on carbon dioxide electroreduction mainly focuses on optimizing reaction conditions and designing catalyst structure and composition. The process for producing formic acid by carbon dioxide electroreduction is mostly batch-based, with limited research on formic acid separation from the electrolyte and continuous production. These factors limit the large-scale production of formic acid by carbon dioxide electroreduction.

[0004] Simulated moving bed (SMB) is a highly efficient and continuous chemical separation process that connects multiple columns in series to form a ring and uses complex valve switching to simulate the countercurrent between the stationary and mobile phases, thereby achieving continuous material separation and providing a new option for large-scale production.

[0005] Electrolytes for the preparation of formic acid from carbon dioxide include aqueous and non-aqueous systems. Aqueous systems include propylene carbonate, acetonitrile, dimethyl sulfoxide, and ionic liquids; non-aqueous systems include aqueous carbonate solutions, aqueous bicarbonate solutions, aqueous hydroxide solutions, and acidic aqueous solutions. Current research on the electroreduction of formic acid from carbon dioxide focuses on optimizing reaction conditions and preparing high-quality catalysts, with limited research on electrolyte separation. Summary of the Invention

[0006] The technical problem this invention aims to solve is the inability to achieve continuous production in the electrochemical reduction of formic acid from carbon dioxide. This invention provides a system and method for the continuous electrochemical reduction of formic acid compounds. In this system and method, an electrochemical reactor is connected in series to simulate a moving bed. An aqueous solution of formic acid compounds is continuously generated within the electrochemical reactor. The formic acid compounds (formates) are then separated in the simulated moving bed, and the remaining electrolyte is returned to the electrochemical reactor to continue the reaction. This overcomes the problem of continuous production in the existing electrochemical reduction process for formic acid, and also has higher production capacity, making the industrial production of formic acid from carbon dioxide electrochemical reduction possible.

[0007] The first aspect of the present invention is to provide a production system for the continuous preparation of formic acid compounds by carbon dioxide electroreduction, comprising:

[0008] Cathode electrolyte source, anode electrolyte source, carbon dioxide gas source, electrochemical reaction device, simulated moving bed and eluent source;

[0009] The electrochemical reaction device includes an electrolytic cell with an anode chamber and a cathode chamber at its two ends. The cathode electrolyte source and the carbon dioxide gas source are connected to the cathode chamber through a feed pipe, and the anode electrolyte source is connected to the anode chamber through a feed pipe. This is used to reduce carbon dioxide to formate ions in the cathode chamber under electrolytic reaction conditions. The formate ions permeate through the ion exchange membrane into the anode chamber, where an anolyte containing formate ions is obtained.

[0010] The outlet of the anode chamber is connected to the raw material inlet of the simulated moving bed via a discharge pipe, so as to transport the anolyte containing formate ions as raw material to the simulated moving bed. By the difference in the interaction force between formate ions and anions in the electrolyte and the adsorption column, formate compounds are separated from the anolyte to be recovered. The formate compound solution flows out from the extract outlet of the simulated moving bed, and the anolyte to be recovered flows out from the raffinate outlet. The raffinate outlet is connected to the anode chamber via a pipeline through a rinsing suppressor, so as to remove the rinsing liquid from the anolyte to be recovered and return it to the anode chamber as electrolyte recovery liquid.

[0011] The eluent source is connected to the eluent inlet of the simulated moving bed to elute the formic acid compounds and anolyte anions, thereby obtaining an extract containing formic acid compounds. The extract containing formic acid compounds flows out through the extract outlet of the simulated moving bed.

[0012] The adsorption column of the simulated moving bed is an anion exchange resin. The matrix of the anion exchange resin is a polystyrene-divinylbenzene polymer with a crosslinking degree of 50-60%, which is surface-grafted and its ion exchange functional groups are alkyl quaternary ammonium salts or alkanol quaternary ammonium salts.

[0013] The inventors of this invention discovered through research that by applying a specific adsorption column—"anion exchange resin adsorption column, wherein the matrix of the anion exchange resin is a polystyrene-divinylbenzene polymer with a crosslinking degree of 50-60%, with a surface grafted type, and its ion exchange functional group is an alkyl quaternary ammonium salt type or an alkanol quaternary ammonium salt type"—to a simulated moving bed, and combining it with an anolyte and a eluent, a continuous preparation of formic acid compounds by carbon dioxide electroreduction using an electrochemical reactor connected in series with a simulated moving bed was achieved. This method for the continuous preparation of formic acid compounds not only allows for continuous production but also has higher production capacity.

[0014] Through research, the inventors of this invention discovered that the reason this invention achieves continuous production using a series-connected simulated moving bed is because: the adsorption column in this invention can separate formic acid compounds from the anolyte, possibly because the affinity of the adsorption column for formate ions is less than its interaction with anions in the electrolyte; and the eluent in this invention, being a system with similar compositional properties to the electrolyte, can elute the adsorbed formic acid compounds. Through the specific combination of the adsorption column, eluent, and electrolyte, this invention achieves continuous production using a series-connected simulated moving bed electrochemical reactor.

[0015] Preferably, the number of adsorption columns in the simulated moving bed is 4-12, and the number of adsorption columns in each of the four sections of the simulated moving bed is 1-3. More preferably, the number of adsorption columns in the four sections of the simulated moving bed is equal.

[0016] Preferably, the anolyte is an aqueous solution of at least one of potassium carbonate, sodium carbonate, and lithium carbonate.

[0017] Preferably, the rinsing solution is an aqueous solution of at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0018] Preferably, a cathode buffer tank and a cathode electrolyte peristaltic pump are further provided on the pipeline between the cathode electrolyte source and the cathode chamber; more preferably,

[0019] The discharge port of the cathode chamber is connected to the cathode buffer tank via a pipeline.

[0020] The cathode electrolyte, byproduct gases (such as hydrogen) produced by cathode electrolysis, and unreacted carbon dioxide can all be discharged through the cathode buffer tank exhaust pipe. Therefore, the cathode buffer tank plays a role in buffering materials and separating gas and liquid, making the system safer and more stable.

[0021] More preferably, the cathode buffer tank is provided with a gas outlet, which can, when appropriate, transport the gas in the cathode buffer tank to the outside of the system according to the gas condition inside the cathode buffer tank.

[0022] Preferably, an anode buffer tank is also provided on the pipeline between the outlet of the anode chamber and the raw material inlet of the simulated moving bed; more preferably, a gas-material outlet is provided on the anode buffer tank.

[0023] The anolyte containing formate ions and the oxygen produced by anolyte electrolysis can be discharged outside the system through the anolyte buffer tank. Therefore, the anolyte buffer tank plays a role in buffering materials and separating gas and liquid, making the system safer and more stable.

[0024] Preferably, an anolyte peristaltic pump is installed on the pipeline between the raffinate outlet and the anode chamber. More preferably, the cathode electrolyte peristaltic pump and the anolyte peristaltic pump are pumps with variable frequency function to control the flow rate of the cathode and anolyte, making the overall method and system more stable.

[0025] Preferably, a flow regulating valve is provided on the carbon dioxide inlet pipe to control the carbon dioxide flow rate;

[0026] Preferably, a flow regulating valve is installed on the rinsing liquid feed pipe to control the velocity of the mobile phase; more preferably, the flow rates of each material are automatically controlled and regulated within the control system, which helps to further improve the stability of the production system.

[0027] A simulated moving bed can separate binary mixtures by simulating countercurrent between the stationary and mobile phases using multiple adsorption columns connected in series and a valve arrangement. This is accomplished through a series of annular adsorption columns, with countercurrent between the stationary and mobile phases achieved by continuous feed injection and switching the adsorption columns synchronously with the eluent flow direction. The eluent flows through this ring, and two inlets (for feed and eluent) and two outlets (for raffinate and extract) define four separation zones, each containing several adsorption columns. The structure of the simulated moving bed itself (e.g., with switching valves) and its operating principle are well-known prior art and will not be described in detail here. This invention employs a known simulated moving bed structure, combined with specific adsorbent materials and corresponding adsorption targets and elution processes, to achieve continuous production of formic acid compounds by connecting the simulated moving bed in series with an electrochemical reactor.

[0028] The main function of an eluent suppressor is to eliminate eluent as much as possible, and it is a commonly used device in chromatographic separation. In this invention, it is used to remove anions from the eluent, thereby stabilizing the anolyte.

[0029] More preferably, such asFigure 1 As shown, the present invention provides a production system for the continuous preparation of formic acid compounds by carbon dioxide electroreduction, comprising:

[0030] Cathode electrolyte source, anode electrolyte source, carbon dioxide gas source, electrochemical reaction device, simulated moving bed, eluent suppressor and eluent source;

[0031] The electrochemical reaction device includes an electrolytic cell 22, with an anode chamber and a cathode chamber at its two ends, respectively.

[0032] The cathode electrolyte source supplies cathode electrolyte to the cathode through the cathode electrolyte supply pipe 1. Along the path between the cathode electrolyte source and the cathode chamber inlet, in the direction of cathode electrolyte feeding, the following are sequentially arranged: cathode electrolyte supply pipe 1, cathode buffer tank inlet pipe 2, cathode buffer tank 4, cathode electrolyte outlet pipe 5, cathode electrolyte peristaltic pump 6, and electrolytic cell cathode inlet pipe 7. The electrolytic cell cathode inlet pipe 7 is connected to the cathode chamber inlet. Furthermore, the cathode buffer tank 4 is equipped with a cathode buffer tank exhaust pipe 3 that connects to external equipment.

[0033] The outlet of the cathode chamber is connected to the cathode buffer tank 4 through the cathode electrolyte return pipe 9 and the cathode buffer tank inlet pipe 2;

[0034] A carbon dioxide gas source is connected to the feed inlet of the cathode chamber through a carbon dioxide gas inlet pipe 8 to provide carbon dioxide to the cathode;

[0035] An anode electrolyte source supplies anode electrolyte to the anode via an anode electrolyte supply pipe 11. Along the path between the anode electrolyte source and the anode chamber inlet, following the direction of electrolyte feeding, are sequentially arranged the following components: anode electrolyte supply pipe 11, anode buffer tank 13, anode electrolyte outlet pipe 14, a simulated moving bed 15, anode electrolyte recovery pipe 19, a rinsing liquid suppressor 23, anode electrolyte peristaltic pump 20, and an electrolytic cell anode feed pipe 21. The electrolytic cell anode feed pipe 21 is connected to the anode chamber inlet. The anode electrolyte outlet pipe 14 is connected to the raw material inlet of the simulated moving bed 15, and the raffinate outlet of the 15 is connected to the anode electrolyte recovery pipe 19. An anode buffer tank exhaust pipe 12 is also provided on the anode buffer tank 13 to connect to external equipment.

[0036] The outlet of the anode chamber is connected to the inlet of the anode buffer tank 13 through the anode electrolyte return pipe 10;

[0037] The eluent source is connected to the eluent inlet of the simulated moving bed 15 through the eluent feed pipe 18 to provide eluent to the simulated moving bed 15; the extract outlet of the simulated moving bed 15 is connected to external equipment through the formic acid compound outlet pipe 17.

[0038] Preferably, the production system includes two electrochemical reactors connected in parallel via pipelines, with one in standby mode and the other in operation via a switching valve installed on the pipelines. When the parameters of the electrochemical reactor show abnormalities and replacement is required, the electrochemical reactor is switched via a power switch to further ensure the continuous operation of the reaction system.

[0039] Preferably, each of the anode and cathode chambers is equipped with a gas concentration detection probe. This probe monitors the gas concentration and issues an alarm signal when the gas concentration reaches a target threshold. During operation, the electrochemical reaction system produces oxygen and byproduct gases hydrogen and carbon monoxide, and unreacted carbon dioxide is also emitted. Therefore, simultaneously installing hydrogen, carbon monoxide, and oxygen concentration detection probes within the system can trigger an audible and visual alarm when the concentration of flammable or toxic gases exceeds the threshold, or (simultaneously) shut down the entire operating system. This further enhances the safety of the entire system and method.

[0040] Preferably, the production system further includes a purification device, comprising one or a combination of a separation membrane, a distillation column, and a crystallization device connected to the extract outlet of the simulated moving bed, so that formic acid or formate can be prepared as needed.

[0041] In this system and method, the present invention connects an electrochemical reactor in series to simulate a moving bed. An aqueous solution of formic acid compounds is continuously generated within the electrochemical reactor. Subsequently, the formic acid compounds (formate salts) are separated in the simulated moving bed, and the remaining electrolyte is returned to the electrochemical reactor to continue the reaction. This solves the problems of continuous production and safety issues in the electrochemical reduction of carbon dioxide to produce formic acid. It provides a possibility for the industrial-scale production of formic acid by the electroreduction of carbon dioxide.

[0042] A second aspect of the present invention is to provide a method for the continuous preparation of formic acid compounds by electroreduction of carbon dioxide using the production system described in the first aspect, comprising:

[0043] Under electrolysis conditions, carbon dioxide is reduced to formate ions in the cathode chamber. The formate ions permeate through the ion membrane into the anode chamber, where an anolyte containing formate ions and oxygen are obtained.

[0044] The anolyte containing formate ions is used as the extraction raw material and transported to the simulated moving bed.

[0045] Formic acid compounds are separated from the anolyte by the difference in the interaction forces between formate ions and anions in the electrolyte and the adsorption column. The anolyte flows out from the raffinate outlet. The raffinate, as the anolyte to be recovered, is returned to the anode chamber as the electrolyte recovery liquid after the raffinate is eliminated by the raffinate suppressor.

[0046] The adsorption column containing formic acid compounds is eluted with an eluent to remove the formic acid compounds and anolyte anions, yielding an extract containing formic acid compounds.

[0047] The extract containing formic acid compounds flows out through the extract outlet of the simulated moving bed;

[0048] The anolyte is an aqueous solution of at least one of potassium carbonate, sodium carbonate, and lithium carbonate;

[0049] The rinsing solution is an aqueous solution of at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0050] The process described in this invention, which involves "reducing carbon dioxide to formate ions in the cathode chamber under electrolytic reaction conditions, with the formate ions permeating through the ion-exchange membrane into the anode chamber, and obtaining an anolyte containing formate ions and oxygen in the anode chamber," is existing technology. For example, one can refer to the method described in Li Fajun's "Electrochemical Reduction of Carbon Dioxide to Formic Acid".

[0051] Preferably, the cathode electrolyte is at least one of potassium carbonate, sodium carbonate, and lithium carbonate aqueous solution; more preferably, the concentration of the cathode electrolyte is 0.1-0.5 mol / L.

[0052] Preferably, the concentration of the anolyte is 0.1-0.5 mol / L.

[0053] Preferably, the concentration of the rinsing solution is 0.01-0.5 mol / L.

[0054] Preferably, the formic acid compound is at least one of potassium formate, sodium formate, and lithium formate.

[0055] Preferably, the operating temperature of the adsorption column of the simulated moving bed is 20-30℃, and / or the operating pressure is 0.3-1MPa.

[0056] Preferably, the feed flow rate of the anolyte containing formate ions to the simulated moving bed is 0.2-50 ml / min.

[0057] Preferably, the flow rate of the rinsing solution is 1-100 ml / min;

[0058] Preferably, the flow rate of the extract is 1-100 ml / min;

[0059] Preferably, the flow rate of the raffinate is 0.2-50 ml / min.

[0060] The formate solution separated by this invention can be converted into other formic acid compounds according to product requirements. For example, adding an acidification step can yield formic acid.

[0061] More preferably, the method for the continuous preparation of formic acid compounds by carbon dioxide electroreduction using this production system includes:

[0062] Start-up procedure: The cathode electrolyte is added to the cathode buffer tank 4 through the cathode electrolyte feed pipe 1 and the cathode buffer tank feed pipe 2. The anode electrolyte is added to the anode buffer tank 13 through the anode electrolyte feed pipe 11. The anode electrolyte peristaltic pump 20 and the cathode electrolyte peristaltic pump 6 are started. The carbon dioxide inlet pipe 8 is opened to allow the reaction medium and electrolyte to flow in the reaction system.

[0063] Working procedure: Turn on the power to the electrolytic cell 22 to start energizing the cathode and anode, and the electrolysis reaction will occur. Formate ions will be continuously generated at the cathode, pass through the ion membrane to the anode, and obtain an anolyte containing formate ions. The anolyte containing formate ions and the oxygen generated by the anolyte electrolysis enter the anode buffer tank 13 through the anolyte return pipe 10. The oxygen in the anode buffer tank 13 is discharged through the anode buffer tank exhaust pipe 12. The by-product gas generated by the cathode electrolysis and the unreacted carbon dioxide are discharged in the cathode buffer tank 4 through the cathode buffer tank exhaust pipe 3.

[0064] Separation process: The anolyte containing formate ions enters the simulated moving bed 15 through the anolyte outlet pipe 14. The anolyte containing formate ions is transported to the simulated moving bed 15 as raw material. Due to the difference in the interaction force between the formate ions and the anions in the electrolyte and the adsorption column in the simulated moving bed 15, the formate compounds are separated from the anolyte to be recovered. The anolyte to be recovered is returned to the anode from the raffinate outlet via the anolyte recovery pipe 19, the eluent suppressor 23, the anolyte peristaltic pump 20, and the electrolytic cell anode feed pipe 21. During this process, the anolyte to be recovered is flushed out by the eluent suppressor 23.

[0065] The eluent source is connected to the eluent inlet of the simulated moving bed through the eluent feed pipe 18. The eluent washes away the formic acid compounds and the anolyte anions to obtain an extract containing formic acid compounds. The extract containing formic acid compounds flows out of the extract outlet of the simulated moving bed through the formic acid compound outlet pipe 17 to separate the electrolysis system.

[0066] The advantages of this invention are:

[0067] As previously stated, this invention relates to a system and method for the continuous preparation of formic acid compounds by carbon dioxide electroreduction. The present invention addresses the problem of the inability to achieve continuous production in the process of preparing formic acid compounds by carbon dioxide electrochemical reduction. Currently, the common practice in the industry is to stop the electrochemical reaction after the formic acid compounds have accumulated to a certain concentration, and then perform a separation operation, which affects the production capacity of formic acid compounds. This invention combines an electrochemical reactor with a simulated moving bed, allowing for the direct separation of formic acid compounds from the electrolyte system. Preferably, a standby electrochemical reactor is used to facilitate the continuous operation of the reaction when changing reactors. Preferably, a gas concentration detection probe is installed within the reactor device to improve the safety of the system and method. The system and method of this invention not only achieve continuous preparation of formic acid compounds by carbon dioxide electroreduction but also have higher efficiency, production capacity, and safety, making the industrial production of formic acid by carbon dioxide electroreduction possible. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of the production system for the continuous preparation of formic acid compounds by carbon dioxide electroreduction according to the present invention.

[0069] Figure 1 In the diagram: 1 is the cathode electrolyte feed pipe, 2 is the cathode buffer tank feed pipe, 3 is the cathode buffer tank exhaust pipe, 4 is the cathode buffer tank, 5 is the cathode electrolyte discharge pipe, 6 is the cathode electrolyte peristaltic pump, 7 is the electrolytic cell cathode feed pipe, 8 is the carbon dioxide inlet pipe, 9 is the cathode electrolyte return pipe, 10 is the anode electrolyte return pipe, 11 is the anode electrolyte feed pipe, 12 is the anode buffer tank exhaust pipe, 13 is the anode buffer tank, 14 is the anode electrolyte discharge pipe, 15 is the simulated moving bed, 16 is the simulated moving bed switching valve, 17 is the formic acid compound discharge pipe, 18 is the eluent feed pipe, 19 is the anode electrolyte recovery pipe, 20 is the anode electrolyte peristaltic pump, 21 is the electrolytic cell anode feed pipe, 22 is the electrolytic cell, and 23 is the eluent suppressor. Detailed Implementation

[0070] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0071] Example 1

[0072] like Figure 1 As shown, the production system for the continuous preparation of formic acid compounds by carbon dioxide electroreduction includes:

[0073] Cathode electrolyte source, anode electrolyte source, carbon dioxide gas source, electrochemical reaction device, simulated moving bed, eluent suppressor and eluent source;

[0074] The electrochemical reaction device includes an electrolytic cell 22, with an anode chamber and a cathode chamber at its two ends, respectively.

[0075] The cathode electrolyte source supplies cathode electrolyte to the cathode through the cathode electrolyte supply pipe 1. Along the path between the cathode electrolyte source and the cathode chamber inlet, in the direction of cathode electrolyte feeding, the following are sequentially arranged: cathode electrolyte supply pipe 1, cathode buffer tank inlet pipe 2, cathode buffer tank 4, cathode electrolyte outlet pipe 5, cathode electrolyte peristaltic pump 6, and electrolytic cell cathode inlet pipe 7. The electrolytic cell cathode inlet pipe 7 is connected to the cathode chamber inlet. Furthermore, the cathode buffer tank 4 is equipped with a cathode buffer tank exhaust pipe 3 that connects to external equipment.

[0076] The outlet of the cathode chamber is connected to the cathode buffer tank 4 through the cathode electrolyte return pipe 9 and the cathode buffer tank inlet pipe 2;

[0077] A carbon dioxide gas source is connected to the feed inlet of the cathode chamber through a carbon dioxide gas inlet pipe 8 to provide carbon dioxide to the cathode.

[0078] An anode electrolyte source supplies anode electrolyte to the anode via an anode electrolyte supply pipe 11. Along the path between the anode electrolyte source and the anode chamber inlet, following the direction of electrolyte feeding, are sequentially arranged the following components: anode electrolyte supply pipe 11, anode buffer tank 13, anode electrolyte outlet pipe 14, a simulated moving bed 15, anode electrolyte recovery pipe 19, a rinsing liquid suppressor 23, anode electrolyte peristaltic pump 20, and an electrolytic cell anode feed pipe 21. The electrolytic cell anode feed pipe 21 is connected to the anode chamber inlet. The anode electrolyte outlet pipe 14 is connected to the raw material inlet of the simulated moving bed 15, and the raffinate outlet of the 15 is connected to the anode electrolyte recovery pipe 19. An anode buffer tank exhaust pipe 12 is also provided on the anode buffer tank 13 to connect to external equipment.

[0079] The outlet of the anode chamber is connected to the inlet of the anode buffer tank 13 through the anode electrolyte return pipe 10;

[0080] The eluent source is connected to the eluent inlet of the simulated moving bed 15 through the eluent feed pipe 18 to provide eluent to the simulated moving bed 15; the extract outlet of the simulated moving bed 15 is connected to external equipment through the formic acid compound outlet pipe 17.

[0081] This embodiment adopts Figure 1 The production system shown includes a method for the continuous preparation of formic acid compounds by carbon dioxide electroreduction, comprising:

[0082] Start-up procedure: The cathode electrolyte is added to the cathode buffer tank 4 through the cathode electrolyte feed pipe 1 and the cathode buffer tank feed pipe 2. The anode electrolyte is added to the anode buffer tank 13 through the anode electrolyte feed pipe 11. The anode electrolyte peristaltic pump 20 and the cathode electrolyte peristaltic pump 6 are started. The carbon dioxide inlet pipe 8 is opened to allow the reaction medium and electrolyte to flow in the reaction system.

[0083] Working procedure: Turn on the power to the electrolytic cell 22 to start energizing the cathode and anode, and the electrolysis reaction will occur. Formate ions will be continuously generated at the cathode, pass through the ion membrane to the anode, and obtain an anolyte containing formate ions. The anolyte containing formate ions and the oxygen generated by the anolyte electrolysis enter the anode buffer tank 13 through the anolyte return pipe 10. The oxygen in the anode buffer tank 13 is discharged through the anode buffer tank exhaust pipe 12. The by-product gas generated by the cathode electrolysis and the unreacted carbon dioxide are discharged in the cathode buffer tank 4 through the cathode buffer tank exhaust pipe 3.

[0084] Separation process: The anolyte containing formate ions enters the simulated moving bed 15 through the anolyte outlet pipe 14. The anolyte containing formate ions is transported to the simulated moving bed 15 as raw material. Due to the difference in the interaction force between the formate ions and the anions in the electrolyte and the adsorption column in the simulated moving bed 15, the formate compounds are separated from the anolyte to be recovered. The anolyte to be recovered is returned to the anode from the raffinate outlet via the anolyte recovery pipe 19, the eluent suppressor 23, the anolyte peristaltic pump 20, and the electrolytic cell anode feed pipe 21. During this process, the anolyte to be recovered is flushed out by the eluent suppressor 23.

[0085] The eluent source is connected to the eluent inlet of the simulated moving bed through the eluent feed pipe 18. The eluent washes away the formic acid compounds and the anolyte anions to obtain an extract containing formic acid compounds. The extract containing formic acid compounds flows out of the extract outlet of the simulated moving bed through the formic acid compound outlet pipe 17 to separate the electrolysis system.

[0086] Electrolysis conditions in this embodiment:

[0087] The electrolytic cell is loaded with approximately 50 mg of Bi-based nanomaterials as cathode catalyst, approximately 25 mg of IrO2 as anode catalyst, and an ion-exchange membrane in a single charge; the current density is 5 A / cm². 2 .

[0088] The cathode electrolyte is a potassium carbonate solution with a concentration of 0.1 mol / L;

[0089] The anolyte is a potassium carbonate solution with a concentration of 0.1 mol / L;

[0090] The rinsing solution was a 0.01 mol / L potassium hydroxide solution;

[0091] The operating temperature of the adsorption column in the simulated moving bed is 25℃, and the operating pressure is 0.5MPa.

[0092] The flow rate of the simulated moving bed feed material is 2 ml / min; and / or,

[0093] The flow rate of the rinsing solution is 7 ml / min;

[0094] The flow rate of the extract is 6 ml / min;

[0095] The flow rate of the raffinate is 3 ml / min.

[0096] The adsorbent material in the simulated moving bed adsorption column is a polystyrene-divinylbenzene polymer with a crosslinking degree of 55% as its matrix, with a surface grafting type and alkyl quaternary ammonium salt ion exchange functional groups (adsorption column model SH-AP-1, manufacturer: Qingdao Shenghan Chromatography Technology Co., Ltd.).

[0097] The simulated moving bed contains 8 adsorption columns, and each of the four sections of the simulated moving bed contains 2 adsorption columns.

[0098] The adsorption column is switched synchronously with the flow direction of the eluent and the raw material injection, with a switching time of 2.5 min.

[0099] In this embodiment, the potassium formate extract obtained after separation and purification has a potassium formate mass concentration of 98%.

[0100] The entire process is continuous, and the production capacity of potassium formate is 3g / h.

[0101] Calculations show that the annual production capacity of potassium formate using the production system and method of this invention can reach 7.2 kg / a, while the annual production capacity of potassium formate using the same electrochemical reaction without using a simulated moving bed discontinuous scheme is <5 kg / a. This invention has a higher production capacity.

[0102] Example 2

[0103] Formic acid compounds were produced according to the method of Example 1, except that the potassium ion system was replaced with a sodium ion system: i.e.

[0104] The cathode electrolyte is a sodium carbonate solution with a concentration of 0.1 mol / L;

[0105] The anolyte is a sodium carbonate solution with a concentration of 0.1 mol / L;

[0106] The rinsing solution is a 0.01 mol / L sodium hydroxide solution.

[0107] The formic acid compound obtained is sodium formate, and the production capacity of sodium formate is 3 g / h.

[0108] Example 3

[0109] Potassium formate was produced according to the method of Example 1; the difference was that the number of adsorption columns was 12, the operating pressure was changed to 0.8 MPa, and the concentration of potassium formate was increased, with the mass concentration of potassium formate increasing from 98% in Example 1 to 98.5%.

[0110] Comparative Example 1

[0111] Traditional discontinuous methods for preparing formic acid compounds using electrochemical reactors require manual operation for material input and output. Once the electrolyte concentration containing formic acid compounds reaches a certain level, the material must be transferred out of the reactor for separation, resulting in a discontinuous reaction. Furthermore, manual material input and output can lead to leaks in the reactor's exhaust gas system, causing hydrogen, carbon monoxide, and carbon dioxide gases to accumulate within the reaction equipment. If these gases reach a certain concentration, there is a risk of explosion or poisoning of personnel.

[0112] As can be seen from the above embodiments 1-3, during operation, material feeding and discharging are automated. Formate continuously flows out from the formic acid compound discharge pipe 17, and the anolyte after removing the formic acid compounds returns to the anode of the electrolytic cell 22. There is no need to wait for formate to accumulate to a certain amount before separately separating the formate and electrolyte. During operation, material feeding and discharging are automated. If a malfunction occurs in the exhaust gas emission from the electrochemical reactor, the gas concentration detector will alarm, which can trigger an interlock to shut down the equipment and terminate the electrolysis reaction, preventing the entire system from being in a dangerous state. The system of the present invention is safer.

[0113] It is evident that the system and method of this invention not only achieve continuous preparation of formic acid compounds by carbon dioxide electroreduction, but also have higher efficiency, production capacity and safety.

[0114] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

[0115] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0116] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0117] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0118] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

[0119] Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or technical ideas shall be regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination to be obviously unreasonable.

Claims

1. A production system for the continuous preparation of formic acid compounds by carbon dioxide electroreduction, comprising: Cathode electrolyte source, anode electrolyte source, carbon dioxide gas source, electrochemical reaction device, simulated moving bed, eluent suppressor and eluent source; The electrochemical reaction device includes an electrolytic cell with an anode chamber and a cathode chamber at its two ends. The cathode electrolyte source and the carbon dioxide gas source are connected to the cathode chamber through a feed pipe, and the anode electrolyte source is connected to the anode chamber through a feed pipe. This is used to reduce carbon dioxide to formate ions in the cathode chamber under electrolytic reaction conditions. The formate ions permeate through the ion exchange membrane into the anode chamber, where an anolyte containing formate ions is obtained. The outlet of the anode chamber is connected to the raw material inlet of the simulated moving bed via a discharge pipe, so as to transport the anolyte containing formate ions as raw material to the simulated moving bed. By the difference in the interaction force between the formate ions and the anions in the electrolyte and the adsorption column in the simulated moving bed, the formate compounds are separated from the anolyte to be recovered. The anolyte to be recovered flows out from the raffinate outlet. The raffinate outlet is connected to the anode chamber via a pipeline through a leaching liquid suppressor, so as to return the anolyte to be recovered to the anode chamber as electrolyte recovery liquid after removing the leaching liquid. The eluent source is connected to the eluent inlet of the simulated moving bed to elute the formic acid compounds and anolyte anions, thereby obtaining an extract containing formic acid compounds. The extract containing formic acid compounds flows out through the extract outlet of the simulated moving bed. The adsorption column of the simulated moving bed is an anion exchange resin. The matrix of the anion exchange resin is a polystyrene-divinylbenzene polymer with a crosslinking degree of 50%-60%, which is surface-grafted and its ion exchange functional groups are alkyl quaternary ammonium salts or alkanol quaternary ammonium salts.

2. The production system according to claim 1, characterized in that: The simulated moving bed contains 4-12 adsorption columns, and each of the four sections of the simulated moving bed contains 1-3 adsorption columns; and / or, The anolyte is an aqueous solution of at least one of potassium carbonate, sodium carbonate, and lithium carbonate; and / or, The rinsing solution is an aqueous solution of at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

3. The production system according to claim 1, characterized in that: The pipeline connecting the cathode electrolyte source and the cathode chamber is further equipped with a cathode buffer tank and a cathode electrolyte peristaltic pump; preferably, The discharge port of the cathode chamber is connected to the cathode buffer tank via a pipeline; and / or, The cathode buffer tank is equipped with a gas discharge port.

4. The production system according to claim 1, characterized in that: An anode buffer tank is also provided on the pipeline between the outlet of the anode chamber and the raw material inlet of the simulated moving bed; preferably, the anode buffer tank is provided with a gas-material outlet. And / or, An anode electrolyte peristaltic pump is installed on the pipeline between the raffinate outlet and the anode chamber.

5. The production system according to claim 1, characterized in that: The production system includes two electrochemical reaction units connected in parallel via pipelines, with one unit in standby mode and the other in use via switching valves installed on the pipelines; and / or, Each of the anode and cathode chambers is equipped with a gas concentration detection probe, which monitors the gas concentration and issues an alarm signal when the gas concentration reaches a target threshold; and / or, The production system also includes a purification device, comprising one or a combination of a separation membrane, a distillation column, and a crystallization device connected to the extract outlet of the simulated moving bed.

6. The production system according to any one of claims 1-5, characterized in that, The production system includes: a cathode electrolyte source, an anode electrolyte source, a carbon dioxide gas source, an electrochemical reaction device, a simulated moving bed, a rinsing liquid suppressor, and a rinsing liquid source; The electrochemical reaction device includes an electrolytic cell, with an anode chamber and a cathode chamber at each end. The cathode electrolyte source provides cathode electrolyte to the cathode through a cathode electrolyte replenishment pipe. Along the path between the cathode electrolyte source and the cathode chamber inlet, in the direction of cathode electrolyte feeding, are sequentially arranged a cathode electrolyte replenishment pipe, a cathode buffer tank inlet pipe, a cathode buffer tank, a cathode electrolyte outlet pipe, a cathode electrolyte peristaltic pump, and an electrolytic cell cathode inlet pipe. The electrolytic cell cathode inlet pipe is connected to the cathode chamber inlet. Furthermore, the cathode buffer tank is equipped with a cathode buffer tank exhaust pipe that connects to external equipment. The outlet of the cathode chamber is connected to the cathode buffer tank through the cathode electrolyte return pipe and the cathode buffer tank inlet pipe; The carbon dioxide gas source is connected to the feed inlet of the cathode chamber through a carbon dioxide gas inlet pipe to provide carbon dioxide to the cathode; The anode electrolyte source provides anode electrolyte to the anode through an anode electrolyte feed pipe. Along the path between the anode electrolyte source and the anode chamber inlet, arranged sequentially in the direction of anode electrolyte feeding, are the following components: an anode electrolyte feed pipe, an anode buffer tank, an anode electrolyte outlet pipe, a simulated moving bed, an anode electrolyte recovery pipe, a rinsing solution suppressor, an anode electrolyte peristaltic pump, and an electrolytic cell anode feed pipe. The electrolytic cell anode feed pipe is connected to the anode chamber inlet. The anode electrolyte outlet pipe is connected to the raw material inlet of the simulated moving bed, and the raffinate outlet is connected to the anode electrolyte recovery pipe. The anode buffer tank is also equipped with an anode buffer tank exhaust pipe that connects to external equipment. The outlet of the anode chamber is connected to the inlet of the anode buffer tank through an anode electrolyte return pipe; The eluent source is connected to the eluent inlet of the simulated moving bed via an eluent feed pipe to provide eluent to the simulated moving bed; the extract outlet of the simulated moving bed is connected to external equipment via a formic acid compound outlet pipe.

7. A method for the continuous preparation of formic acid compounds by electroreduction of carbon dioxide using the production system according to any one of claims 1-6, comprising: Under electrolysis conditions, carbon dioxide is reduced to formate ions in the cathode chamber. The formate ions permeate through the ion membrane into the anode chamber, where an anolyte containing formate ions and oxygen are obtained. The anolyte containing formate ions is used as the extraction raw material and transported to the simulated moving bed. The formate compounds are separated from the anolyte by the difference in the interaction forces between the formate ions and the anions in the electrolyte and the adsorption column. The anolyte flows out from the raffinate outlet. The raffinate is used as the anolyte to be recovered. After the raffinate is eliminated by the raffinate suppressor, it is returned to the anode chamber as the electrolyte recovery liquid. The adsorption column containing formic acid compounds is eluted with an eluent to remove the formic acid compounds and anolyte anions, yielding an extract containing formic acid compounds. The extract containing formic acid compounds flows out through the extract outlet of the simulated moving bed; The anolyte is an aqueous solution of at least one of potassium carbonate, sodium carbonate, and lithium carbonate; The rinsing solution is an aqueous solution of at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

8. The method according to claim 7, characterized in that: The cathode electrolyte is at least one of potassium carbonate, sodium carbonate, and lithium carbonate aqueous solution; preferably, The concentration of the cathode electrolyte is 0.1-0.5 mol / L; and / or, The concentration of the anolyte is 0.1-0.5 mol / L.

9. The method according to claim 7, characterized in that: The concentration of the eluent is 0.01-0.5 mol / L; and / or, The formic acid compound is at least one selected from potassium formate, sodium formate, and lithium formate; and / or, The operating temperature of the adsorption column of the simulated moving bed is 20-30℃, and / or the operating pressure is 0.3-1MPa.

10. The method according to any one of claims 7-9, characterized in that: The feed flow rate of the anolyte containing formate ions to the simulated moving bed is 0.2-50 ml / min; and / or, The flow rate of the rinsing solution is 1-100 ml / min; The flow rate of the extract is 1-100 ml / min; The flow rate of the raffinate is 0.2-50 ml / min.

Images