Carbon dioxide gas generator

Abstract

A carbon dioxide gas generator relates to the field of carbon dioxide gas preparation. The battery is connected with an anode and a cathode to form a potential difference; the anodic oxidation electrode enables the carbon source to be subjected to oxidation reaction to be converted into carbon dioxide, and hydrogen ions are generated in the process; a cathode reduction electrode for performing an oxygen reduction reaction, consuming hydrogen ions and generating water; and the electrolyte contains ionic salt, an acidic substance, a water-soluble liquid phase catalyst and water, provides a suitable liquid state environment for diffusion of hydrogen ions, and reduces the oxidation potential of the carbon source electrode. The invention provides a novel carbon dioxide gas generator which can directly oxidize and convert a carbon source on an anode into high-purity carbon dioxide under a mild condition. And meanwhile, the cathode is subjected to oxygen reduction reaction to consume oxygen in the air. The carbon dioxide gas generator can be widely applied to the fields of food preservation, agricultural gas fertilizers, mosquito trapping, dry ice cleaning machines and the like.

Description

Technical Field

[0001] The invention relates to the technical field of carbon dioxide gas preparation, and in particular to a carbon dioxide gas generator. Background Art

[0002] Carbon dioxide (CO2) is a colorless, odorless gas that plays an irreplaceable role in the metabolic activities of organisms. It has a wide range of applications, such as the food industry, chemical raw materials, flower cultivation, medical energy, sanitation and fire protection, entertainment and stage design, etc.

[0003] Existing methods for preparing carbon dioxide can be divided into physical methods and chemical methods, among which physical methods include cryogenic distillation, pressure swing adsorption, and membrane separation, while chemical methods mainly include chemical reaction, direct carbon combustion, electrochemical method and other methods. Among them, cryogenic distillation is suitable for extracting high-purity carbon dioxide from mixed gases, and has the characteristics of high purity, high production efficiency, continuous production, and environmental friendliness, but the collection process is relatively complex, technically difficult, requiring high maintenance, and limited scope of application. The pressure swing adsorption method absorbs carbon dioxide in the gas through an adsorbent, and then releases carbon dioxide by heating or decompression. It has the advantages of low energy consumption, low working pressure, and no solvent recovery and consumption problems. However, the system requires gas storage tanks, adsorption towers and compressors, and the overall volume and noise are large, making it difficult to achieve miniaturization and portability. The membrane separation method uses the permeability of polymers to different gases to selectively separate gases. It has the advantages of compact equipment, low cost, and simple operation, but the concentration of enriched carbon dioxide is low, and it is heavily dependent on the performance of the membrane, and the long-term reliability is poor. The preparation of carbon dioxide by chemical reaction is usually based on the principles of acid-base reaction, redox reaction or decomposition reaction, and has the advantages of high purity, controllable reaction, simple operation and low cost, but there are risks of large equipment, leakage of reaction liquid and environmental pollution, and the reaction process is out of control, which may cause chemical accidents. The direct carbon combustion method is a simple method for preparing carbon dioxide. Carbon (usually in solid form, such as charcoal, coal, coke, etc.) is burned in oxygen or air. It has the advantages of simple reaction process, abundant raw materials, high carbon conversion rate and low cost, but there are problems such as incomplete combustion, dust pollution, low energy efficiency, high temperature in the reaction process, etc., which is not suitable for use in most scenarios.

[0004] The electrochemical method is a method of generating carbon dioxide using electrochemical reactions. It has the advantages of being environmentally friendly, flexible in operation, relatively low in energy consumption, and controllable in process. However, it has the disadvantages of high equipment cost, use of precious metal catalysts, low product purity, and complex maintenance, which limit its further application scenarios. The device for preparing carbon dioxide by electrochemical method is generally similar to the traditional electrolytic cell, which mainly consists of a cathode, an anode, and an electrolyte. Under the action of potential difference, an oxidation reaction occurs at the anode to generate carbon dioxide, and a reduction reaction occurs at the cathode to generate hydrogen. The conductive ions in the electrolyte migrate under the action of the electric field and concentration gradient. However, the production process consumes a lot of energy, has low production efficiency, requires the replenishment of liquid carbon source at any time, and the whole process is accompanied by the production of hydrogen as a byproduct, which poses a great safety hazard.

[0005] Therefore, the electrochemical method is an important method for preparing carbon dioxide, but further technical development and optimization are needed to overcome the above shortcomings and improve its economy and practicability. Summary of the invention

[0006] The purpose of the present invention is to provide a carbon dioxide gas generator, which can effectively realize the synchronous regulation of carbon and oxygen dual atmospheres by rationally designing the generator structure.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A carbon dioxide gas generator capable of synchronously controlling the generation of carbon dioxide gas and the consumption of oxygen gas, specifically comprising the following components:

[0009] Battery: connect the anode and cathode to form a potential difference;

[0010] Anodic oxidation electrode: contains a sacrificial carbon source inside and is connected to an external wire. Its main function is to oxidize the carbon source and convert it into carbon dioxide, generating hydrogen ions in the process.

[0011] Cathode reduction electrode: It contains a three-phase interface gas reaction electrode and is connected to an external wire. Its main function is to carry out oxygen reduction reaction, consume hydrogen ions and generate water;

[0012] Electrolyte: It is in direct contact with the cathode and anode, and contains ionic salts, acidic substances, water-soluble liquid phase catalysts and water. The main function of the electrolyte is to provide a suitable liquid environment for the diffusion of hydrogen ions and reduce the oxidation potential of the carbon source electrode.

[0013] As a preferred technical solution of the present invention, in the carbon dioxide gas generator:

[0014] The anodized electrode adopts a graphite plate or metal platinum, and one or more of activated carbon, graphite particles, hard carbon or soft carbon are bonded to the anode as a solid sacrificial carbon source through a binder, or one or more of alcohol, acetic acid, oxalic acid, glycerol, ethylene glycol, cellulose, acrylic acid, succinic acid and polyvinyl alcohol are added to the electrolyte as a liquid sacrificial carbon source.

[0015] The cathode reduction electrode is selected from one of an aqueous aluminum-air battery, an aqueous zinc-air battery, and an aqueous lithium-air battery.

[0016] The ionic salt in the electrolyte is selected from one or a combination of potassium sulfate, sodium sulfate, magnesium sulfate, zinc sulfate, iron sulfate and copper sulfate, and the concentration of the ionic salt in the electrolyte is set to a sulfate ion concentration exceeding 0.06 mol / L but not exceeding the maximum solubility of the ionic salt.

[0017] The acidic substance in the electrolyte is selected from one or a combination of sulfuric acid, acetic acid, oxalic acid, lactic acid and citric acid; the concentration of hydrogen ions generated by the acid after hydrolysis is in the range of 0.02mol / L-0.08mol / L.

[0018] The water-soluble liquid-phase catalyst in the electrolyte is a salt that can form ferric ions, ferrous ions, nickel ions or cerium ions, and the concentration in the electrolyte is 0.08mol / L-60mmol / L. Preferably, one or a combination of ferric sulfate, nickel sulfate, cerium sulfate, ferric chloride, nickel chloride, ferric acetate, ferrous acetate, ferrous sulfate and potassium ferrocyanide is used. The addition of a water-soluble liquid-phase catalyst can increase the generation rate and output of carbon dioxide and reduce energy consumption.

[0019] The carbon dioxide gas generator proposed by the present invention is used by first filling the generator with electrolyte, assembling the anode oxidation electrode and the cathode reduction electrode, and connecting the battery to realize the generation of carbon dioxide gas at the anode oxidation electrode, and at the same time, realizing the consumption of oxygen gas at the cathode reduction electrode. In addition, the generated carbon dioxide gas is separated and collected to realize the preparation of high-purity carbon dioxide gas.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] The present invention proposes a novel carbon dioxide gas generator, which can directly oxidize the carbon source on the anode into high-purity carbon dioxide under mild conditions. At the same time, an oxygen reduction reaction occurs at the cathode to consume oxygen in the air. The carbon dioxide gas generator can be widely used in the fields of food preservation, agricultural gas fertilizer, mosquito trapping, dry ice cleaning machines, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1This is a working principle diagram of a carbon dioxide gas generator proposed by the present invention, wherein A represents a catalyst cation, x represents a valence state; B represents a corresponding anion, and y represents a valence state.

[0023] Figure 2 This is a schematic diagram of a carbon dioxide gas generator proposed by the present invention.

[0024] Figure 3 The graph is a graph showing the relationship between the concentration of carbon dioxide and oxygen and the change in voltage in Example 1. The values ​​on the detector were read after working for 5 minutes at each voltage.

[0025] Figure 4 This is a graph showing the relationship between the concentrations of carbon dioxide and oxygen changing with time at an operating voltage of 3.0 V in Example 1. DETAILED DESCRIPTION

[0026] See also Figure 1 As shown, a carbon dioxide gas generator can synchronously control the generation of carbon dioxide gas and the consumption of oxygen gas, and specifically includes the following components:

[0027] Battery: connect the anode and cathode to form a potential difference;

[0028] Anodic oxidation electrode: contains a sacrificial carbon source inside and is connected to an external wire. Its main function is to oxidize the carbon source and convert it into carbon dioxide, generating hydrogen ions in the process.

[0029] Cathode reduction electrode: It contains a three-phase interface gas reaction electrode and is connected to an external wire. Its main function is to carry out oxygen reduction reaction, consume hydrogen ions and generate water;

[0030] Electrolyte: It is in direct contact with the cathode and anode, and contains ionic salts, acidic substances, water-soluble liquid phase catalysts and water. The main function of the electrolyte is to provide a suitable liquid environment for the diffusion of hydrogen ions and reduce the oxidation potential of the carbon source electrode.

[0031] See also Figure 2 As shown, first fill the generator with electrolyte, assemble the anode oxidation electrode and cathode reduction electrode, and connect the battery to generate carbon dioxide gas at the anode oxidation electrode, while consuming oxygen gas at the cathode reduction electrode. In addition, separate and collect the generated carbon dioxide gas to achieve the preparation of high-purity carbon dioxide gas.

[0032] The carbon dioxide gas generator proposed by the present invention is further described below through embodiments:

[0033] Example 1

[0034] In this embodiment, a graphite plate is selected as the anode oxidation electrode, and a commercially available aqueous zinc air electrode is used as the cathode reduction electrode. The electrolyte is prepared as a 0.15 mol / L potassium sulfate solution, with additional additions of 0.12 mmol / L acetic acid and 1.2 mmol / L ferrous sulfate. The specific device structure is described in detail in Figure 2 .

[0035] At different working voltages (0.5, 1, 1.5, 2, 2.5, 3, 3.5 V), the system was run for 5 min each. Then, the gas concentration in the sealed chamber was measured using a CO2 / O2 tester. The relevant data are presented in Figure 3 It can be seen that: with the increase of the working voltage (in the range of 0.5V to 3.0V), the rate of CO2 generation and O2 consumption gradually increases, indicating that the rate of chemical reaction in this generator system has increased significantly, and the reaction kinetics is regulated by voltage. The higher the voltage, the more intense the reaction. When the voltage reaches 3.0V, the CO2 generation rate increases significantly, which verifies that the CO2 generator system can effectively drive the CO2 generation reaction at an operating voltage of ≥3V, providing key parameters for the subsequent design of electrochemical CO2 generation. Continuing to use the same device, operating at an operating voltage of 3.0V, and collecting gas concentrations at different time periods, the results are shown in Figure 4 . It can be seen that the continuous electrochemical action leads to a cumulative increase in CO2 concentration (the average increase is about 1.02% / h), and the O2 concentration shows a corresponding downward trend (the average decrease is about 1.6% / h). The change in gas concentration is time-dependent, indicating that the CO2 generator reaction has good stability and self-sustainability. The reaction mechanism is speculated to be: CO2 production originates from the anode carbon oxidation reaction (C+2H2O→CO2+4H + +4e - ), O2 consumption comes from the cathode oxygen reduction reaction (O2+4H + +4e - →2H2O), which is consistent with the characteristics of electrocatalytic oxidation reaction. The CO2 generator system can operate continuously and efficiently at 3.0V. The rapid and continuous CO2 generation and O2 consumption characteristics are suitable for food preservation, anaerobic fermentation or inhibition of aerobic pathogens.

[0036] Comparative Example:

[0037] The difference from Example 1 is that ferrous sulfate is not added as a catalyst.

[0038] Example 2

[0039] In this embodiment, the anode oxidation electrode is a graphite plate, the cathode reduction electrode is a commercially available aqueous zinc air electrode, the electrolyte is a 0.2 mol / L potassium sulfate solution, and 0.1 mmol / L acetic acid and 1 mmol / L cerium sulfate are added.

[0040] Example 3

[0041] In this embodiment, the anodic oxidation electrode uses metal platinum, the cathode reduction electrode is also a commercially available aqueous zinc air electrode, and the electrolyte is a 0.2 mol / L potassium sulfate solution, with 0.1 mmol / L acetic acid and 1 mmol / L ferrous sulfate added. In addition, 10 mg / mL of activated carbon powder is added to the electrolyte as a sacrificial carbon source.

[0042] Example 4

[0043] In this embodiment, the anodic oxidation electrode is also made of metal platinum, the cathode reduction electrode is a commercially available aqueous zinc air electrode, the electrolyte is a 0.2 mol / L potassium sulfate solution, and 0.1 mmol / L acetic acid and 1 mmol / L ferrous sulfate are added. 10% (volume percentage) of ethanol is also added to the electrolyte as a sacrificial carbon source.

[0044] After working in a confined space for 5 minutes (working voltage 3.0 V), the concentrations of carbon dioxide and oxygen were compared. The results are shown in Table 1.

[0045] Table 1

[0046]

[0047] By comparing Example 1 and the comparative example in Table 1, it can be seen that the O2 concentration in the comparative example (20.1%) is consistent with the air background value (20.1%), indicating that no effective oxidation reaction occurs. In addition, the bubbles on the surface of the graphite plate electrode in the comparative example may be side reactions (such as water electrolysis: 2H2O→2H2↑+O2↑), which do not promote the target reaction (CO2 generation). When no catalyst is added to the electrolyte of the CO2 generator, the reaction efficiency is extremely low, and the electrolysis of water is dominant, resulting in energy waste and no target product (CO2).

[0048] Comparison of Examples 1, 2, 3 and 4 shows that the catalyst ferrous sulfate (Fe 2+ ) or cerium sulfate (Ce 4+ ) increased the CO2 concentration (0.19% to 0.41%) and decreased the O2 concentration (20.21% to 19.28%), proving that the catalyst is the core factor driving the redox reaction. It can be seen that adding a catalyst to the CO2 generator electrolyte can significantly improve the reaction activity.

[0049] Comparison of Examples 1, 3 and 4 shows that activated carbon has the best effect, with the highest CO2 concentration (0.41%) and the highest O2 consumption (19.28%), which is attributed to the high specific surface area and porous structure of activated carbon, which provide more reactive sites and accelerate the oxidation of carbon sources. Graphite plate is second, with a CO2 concentration (0.27%) lower than that of activated carbon, indicating that its surface reactivity is limited. Ethanol is the least efficient as a carbon source, with CO2 concentration (0.19%) and O2 concentration (20.21%) slightly higher than that of air. Possible reasons: incomplete oxidation of ethanol generates intermediate products (such as acetaldehyde and acetic acid) instead of CO2. The molecular structure of ethanol is stable, and higher voltage or different catalysts are required for effective oxidation.

[0050] Comparison between Example 1 and Example 2 shows that: CO2 concentration increased from 0.27% to 0.29%, O2 concentration decreased from 19.56% to 19.50%, and the catalytic efficiency of cerium sulfate (Ce 4+ ) is slightly better than ferrous sulfate (Fe 2+ ), indicating that Ce 4+ It may have stronger oxidation ability or more stable catalytic activity. It can be seen that when different liquid catalysts and carbon sources work in a closed space for 5 minutes, ferrous sulfate and cerium sulfate can effectively drive CO2 generation and O2 consumption, and activated carbon has the best effect when used as a carbon source.

[0051] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A carbon dioxide gas generator, characterized in that: It can synchronously control the generation of carbon dioxide gas and the consumption of oxygen gas, including the following components: Battery: Connect the anode and cathode to form a potential difference; Anodic oxidation electrode: contains or has a sacrificial carbon source inside and is connected to an external wire. Its main function is to oxidize the carbon source and convert it into carbon dioxide, generating hydrogen ions in the process. Cathode reduction electrode: It contains a three-phase interface gas reaction electrode and is connected to an external wire. Its main function is to carry out oxygen reduction reaction, consume hydrogen ions and generate water; Electrolyte: It is in direct contact with the cathode and anode, and contains ionic salts, acidic substances, water-soluble liquid phase catalysts and water. The main function of the electrolyte is to provide a suitable liquid environment for the diffusion of hydrogen ions and reduce the oxidation potential of the carbon source electrode.

2. The carbon dioxide gas generator according to claim 1, characterized in that: The anodized electrode adopts a graphite plate or metal platinum, and one or more of activated carbon, graphite particles, hard carbon or soft carbon are bonded to the anode as a solid sacrificial carbon source through a binder, or one or more of alcohol, acetic acid, oxalic acid, glycerol, ethylene glycol, cellulose, acrylic acid, succinic acid and polyvinyl alcohol are added to the electrolyte as a liquid sacrificial carbon source.

3. The carbon dioxide gas generator according to claim 1, characterized in that: The cathode reduction electrode is selected from one of an aqueous aluminum-air battery, an aqueous zinc-air battery, and an aqueous lithium-air battery.

4. The carbon dioxide gas generator according to claim 1, characterized in that: The ionic salt in the electrolyte is selected from one or a combination of potassium sulfate, sodium sulfate, magnesium sulfate, zinc sulfate, iron sulfate and copper sulfate, and the concentration of the ionic salt in the electrolyte is set to a sulfate ion concentration exceeding 0.06 mol / L but not exceeding the maximum solubility of the ionic salt.

5. The carbon dioxide gas generator according to claim 1, characterized in that: The acidic substance in the electrolyte is selected from one or a combination of sulfuric acid, acetic acid, oxalic acid, lactic acid and citric acid; the concentration of hydrogen ions generated by the acid after hydrolysis is in the range of 0.02 mol / L-0.2 mol / L.

6. The carbon dioxide gas generator according to claim 1, characterized in that: The water-soluble liquid-phase catalyst in the electrolyte is a salt that can form ferric ions, ferrous ions, nickel ions or cerium ions, and the concentration in the electrolyte is 0.08 mol / L-60 mmol / L.

7. The carbon dioxide gas generator according to claim 6, characterized in that: The water-soluble liquid phase catalyst in the electrolyte is selected from one or a combination of ferric sulfate, nickel sulfate, cerium sulfate, ferric chloride, nickel chloride, ferric acetate, ferrous acetate, ferrous sulfate, and potassium ferrocyanide.

8. The carbon dioxide gas generator according to any one of claims 1 to 7, characterized in that: Fill the generator with electrolyte, assemble the anode oxidation electrode and cathode reduction electrode, and connect the battery to generate carbon dioxide gas at the anode oxidation electrode and consume oxygen gas at the cathode reduction electrode.

9. The carbon dioxide gas generator according to claim 8, characterized in that: The generated carbon dioxide gas is separated and collected to achieve the preparation of high-purity carbon dioxide gas.

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