A purification method for catalytic reduction of carbon dioxide to formic acid based on carbon neutralization

Abstract

The application provides a purification method for reducing carbon dioxide to formic acid based on carbon neutralization, which comprises the following steps: step 1, using treated copper-tin alloy as a catalyst, the catalyst is made into an electrochemical device and is packaged, and then is placed in an electrolyte to perform an electrocatalytic reduction carbon dioxide reaction to reduce carbon dioxide to formic acid, so that an electrolyte containing formate is obtained; step 2, the electrolyte containing formate is collected in a wide-mouth container for multiple times, and dry solar salt is obtained by evaporation through solar energy and wind energy; step 3, the collected solar salt is added into a certain volume fraction of sulfuric acid for acidification, and a boron oxide secondary purification distillation method is used to obtain a formic acid solution, wherein the main components of the solar salt are a mixture of formate and carbonate, and the concentration of formic acid in the formic acid solution is greater than or equal to 85%.

Description

Technical Field

[0001] This invention relates to a method for electrocatalytic reduction of carbon dioxide, specifically to a purification method for carbon dioxide to formic acid based on carbon neutralization catalytic reduction. Background Technology

[0002] Global climate change and energy shortages have prompted more than 120 countries to develop blueprints for "carbon neutrality." Currently, carbon emission equivalents are closely linked to economic development. Therefore, carbon emission credits will serve as an industrial currency in carbon emission trading, playing the role of "currency" (Raupach MR, Nature Climate Change, 4,873-879 (2014)). G, Nature Communications, 11, 4688 (2020)). Electrocatalytic carbon dioxide reduction (CO2RR) can reduce CO2 emissions, achieve carbon neutrality, and further lower the carbon price. Furthermore, converting CO2 into high-value-added chemicals can effectively store abundant intermittent energy in the form of liquid fuels, such as formic acid and ethanol (Dinh CT, Science, 360, 783-787 (2018)). Integrating CO2RR technology into a closed "carbon neutrality" cycle presents certain challenges due to the difficulty in preparing efficient, stable, and readily available catalysts and effectively utilizing the products. Currently, research on CO2RR catalysts is burgeoning, and related work has made industrial-scale progress.

[0003] Besides catalyst preparation, the ease of purification and utilization of electrocatalytic CO2 reduction products is another obstacle to closing the "carbon neutrality" cycle. Formic acid (HCOOH) or formate is a common product of CO2RR and is widely used in fuel cells, hydrogen storage media, or antifreeze agents. In previous studies on the electrolytic reduction of CO2 to HCOOH, the rational application of formic acid and formate has been rarely reported due to the low concentration of liquid products. Due to catalyst performance degradation, liquid products are difficult to accumulate and are inevitably diluted by the electrolyte. Therefore, there is an urgent need to develop stable and efficient electrocatalysts and green separation methods to enrich, further purify, and utilize electrocatalytic products. Summary of the Invention

[0004] This invention is made to solve the above-mentioned problems, and its purpose is to provide a purification method for carbon dioxide to formic acid by catalytic reduction based on carbon neutralization.

[0005] The application provides a purification method for reducing carbon dioxide to formic acid based on carbon neutralization, which has the following characteristics: step 1, using treated copper-tin alloy as a catalyst, the catalyst is made into an electrochemical device and is packaged, and then is placed in an electrolyte to perform an electrocatalytic reduction of carbon dioxide to reduce carbon dioxide to formic acid to obtain an electrolyte containing formate;

[0006] Step 2, the electrolyte containing formate is collected in a wide-mouth container for multiple times, and dry solar salt is obtained by evaporation through solar energy and wind energy;

[0007] Step 3, the collected solar salt is added to a certain volume fraction of sulfuric acid for acidification, and a boron oxide secondary purification distillation method is used to obtain a formic acid solution, wherein the main components of the solar salt are a mixture of formate and carbonate, and the concentration of formic acid in the formic acid solution is greater than or equal to 85%.

[0008] In the purification method for reducing carbon dioxide to formic acid based on carbon neutralization provided by the application, the copper-tin alloy can be used as a catalyst after being simply treated on the surface with acetone and dilute hydrochloric acid to remove the oxide layer and organic attachments.

[0009] In the purification method for reducing carbon dioxide to formic acid based on carbon neutralization provided by the application, the electrolyte can be a carbon dioxide-saturated KHCO3 solution, and the flow rate of the CO2 raw gas can be 1-1000 sccm during the electrocatalytic reduction of carbon dioxide.

[0010] In the purification method for reducing carbon dioxide to formic acid based on carbon neutralization provided by the application, the volume fraction of the sulfuric acid can be 20-40%, and the amount of the sulfuric acid added can be determined according to the gas bubbles generated in the reaction, the boron oxide secondary purification distillation method includes primary distillation and secondary distillation, the primary distillation is performed at a distillation temperature of 106 DEG C to obtain a primary distillation formic acid solution with a formic acid concentration of 20%, and the amount of boron oxide added during the secondary distillation is 1:1.5 of the amount of water in the primary distillation formic acid solution, and a formic acid solution with a formic acid concentration of more than 85% is obtained through the secondary distillation.

[0011] The application also provides an application of an electrolyte containing formate in a silver mirror reaction, which has the following characteristics: the electrolyte containing formate is directly used as a reducing agent in the silver mirror reaction to obtain a bright and dense silver mirror, the electrolyte containing formate is prepared through step 1, the concentration of the formate in the electrolyte containing formate is 0.05-0.1 M, a fresh silver-ammonia solution is used in the silver mirror reaction, the silver-ammonia solution is strongly alkaline, and the temperature of the silver mirror reaction is 95 DEG C.

[0012] The application also provides an application of the solar salt in the field of low-temperature antifreeze or snow-melting agent, which has the characteristics that the solar salt is prepared into a series of aqueous solutions with different mass fractions, and the aqueous solution is directly used as the low-temperature antifreeze or snow-melting agent, wherein the solar salt is prepared by step 2, the mass fraction of the solar salt in the aqueous solution is 0% to 80%, and the mass fraction of potassium formate in the solar salt is 40% to 45%.

[0013] The application also provides an application of the formic acid solution in the field of fuel cells, which has the characteristics that the formic acid solution is configured into a dilute formic acid solution with a certain concentration, and is used as a liquid fuel in a hydrogen fuel cell or a formic acid fuel cell, wherein the formic acid solution is prepared by step 3, the concentration of formic acid in the dilute formic acid solution is 1M to 5M, the 10% Pd / C catalyst is added for dehydrogenation when the dilute formic acid solution is used as the liquid fuel, the catalyst addition amount is 0.1g per 20ml of the dilute formic acid solution, and the working temperature range of the dilute formic acid solution when used as the liquid fuel is 25℃ to 50℃.

[0014] Effects of the application

[0015] According to the purification method for reducing carbon dioxide to formic acid based on carbon neutralization, copper-tin alloy which is generally available, low in cost and stable in catalytic conversion efficiency is used as a catalyst, carbon dioxide is reduced to formic acid through electrolysis, an electrolyte containing formate is obtained, and the electrolyte containing formate is directly converted into solar salt by using sunlight, so that the product is effectively enriched, and the solar salt is converted into high-concentration formic acid solution through acidification and oxidation boron secondary purification distillation method. The preparation process of the application is simple and low in cost, solar salt can be obtained without additional consumption of fossil energy, and the oxidation boron used in the oxidation boron secondary purification distillation method can be recycled after vacuum dehydration. Moreover, the solid-phase product and the liquid-phase product prepared by the application can be used in different application scenarios, realize carbon neutralization circulation with industrial value, and have important significance in the carbon neutralization industry, and also have important application prospects in chemical experiment education. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a flow chart of the purification method for reducing carbon dioxide to formic acid based on carbon neutralization in an embodiment of the application;

[0017] Figure 2 is a characterization diagram of the copper-tin alloy used in an embodiment of the application;

[0018] Figure 3 is a diagram of the electrocatalytic stability of the catalyst and the product concentration in an embodiment of the application;

[0019] Figure 4 is a flow chart of the reducing agent containing formate salt in the electrolyte directly used for silver mirror reaction in the embodiment of the present application;

[0020] Figure 5 is a process schematic diagram of the solar salt in the embodiment of the present application;

[0021] Figure 6 is a physical diagram of the solar salt acquisition process in the embodiment of the present application;

[0022] Figure 7 is a performance diagram of the solar salt for reducing the freezing point of water in the embodiment of the present application;

[0023] Figure 8 is a schematic diagram of the solar salt acidification with sulfuric acid and secondary purification distillation of oxidized boron into high-concentration formic acid in the embodiment of the present application;

[0024] Figure 9 is a physical diagram of the solar salt and formic acid solution in the embodiment of the present application;

[0025] Figure 10 is a flow chart of the solar salt acidification with sulfuric acid and secondary purification distillation of oxidized boron in the embodiment of the present application;

[0026] Figure 11 is a physical diagram of the dilute formic acid solution used for a hydrogen fuel cell car model in the embodiment of the present application;

[0027] Figure 12 is a gas chromatogram of the dehydrogenation product of a commercial 10% Pd / C catalyst in the embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the technical means and effects of the present application easy to understand, the present application is specifically described below in combination with embodiments and drawings.

[0029] <EMBODIMENT>

[0030] Figure 1 is a flow chart of a purification method for catalytically reducing carbon dioxide to formic acid based on carbon neutralization in the embodiment of the present application.

[0031] As shown in Figure 1 , the purification method for catalytically reducing carbon dioxide to formic acid based on carbon neutralization in the embodiment of the present application includes the following steps:

[0032] Step 1, using treated copper-tin alloy as catalyst, the catalyst is made into an electrochemical device and packaged, and then placed in an electrolyte to carry out an electrocatalytic reduction of carbon dioxide reaction to reduce carbon dioxide to formic acid, to obtain an electrolyte containing formate salt.

[0033] In step 1, the copper-tin alloy is sequentially subjected to ultrasonic treatment in acetone and dilute hydrochloric acid to remove organic attachments and oxide layers, respectively. The volume fraction of dilute hydrochloric acid is 2%, the ultrasonic power is 200 W, and the ultrasonic time is 30 min. The treatment can be directly used as an electrocatalyst for characterization and use.

[0034] In step 1, the catalyst is made into an electrochemical device and packaged, and then placed in an electrolyte to perform the specific process of electrocatalytic reduction of carbon dioxide as follows: The conductive copper glue is tightly bonded to the surface of the catalyst, and the copper glue is used as a secondary conductive substrate to weld a wire as a working electrode. The actual contact resistance between the wire and the catalyst is measured to be 1Ω-5Ω using an ohmmeter. Then, the electrochemical device is packaged with insulating silicone glue. After the silicone glue is completely dried, the catalyst is washed three times with deionized water and dried with a nitrogen gun. Then, the catalyst is placed in an electrolyte to perform the electrocatalytic reduction of carbon dioxide. The electrolyte is a 0.2M KHCO3 solution saturated with carbon dioxide, and the flow rate of CO2 raw gas is 25sccm-100sccm.

[0035] Figure 2 is a characterization diagram of the copper-tin alloy used in the embodiments of the present application.

[0036] Figure 2 In a, it is the X-ray diffraction pattern of the copper-tin alloy, in b, it is the fine spectrum of the X-ray photoelectron spectrum of copper in the copper-tin alloy, in c, it is the fine spectrum of the X-ray photoelectron spectrum of tin in the copper-tin alloy, and in d, it is the atomic ratio of copper to tin in the copper-tin alloy.

[0037] As shown in Figure 2 , the copper-tin ratio of the surface catalytic layer of the copper-tin alloy is 2.54:1, and both copper and tin exhibit a weak oxidized state.

[0038] Figure 3 is a diagram of the electrocatalytic stability and product concentration of the catalyst in the embodiments of the present application.

[0039] Figure 3 In a, it is a diagram of the electrocatalytic stability of the catalyst, and in b, it is a diagram of the product concentration.

[0040] As shown in Figure 3 , the Faraday efficiency of the catalyst for converting CO2 can reach 95.2%, the stability can last for 48h, the cell voltage does not increase or decrease significantly, and the concentration of the product formate can reach 0.269M in different time periods.

[0041] Figure 4 is a flowchart of the reducing agent for silver mirror reaction using the electrolyte containing formate in the embodiments of the present application.

[0042] As shown in Figure 4As shown in the figure, a is a flow chart of the electrolyte containing formate directly used as a reducing agent for silver mirror reaction, and b is a nuclear magnetic resonance hydrogen spectrum of the electrolyte used for silver mirror reaction, which is used to calibrate the concentration of formate in the solution.

[0043] The application of the electrolyte containing formate in the silver mirror reaction in the embodiment is as follows: the electrolyte containing formate is directly used as a reducing agent for silver mirror reaction to obtain a bright and dense silver mirror,

[0044] The electrolyte containing formate is prepared by step 1, the concentration of formate in the electrolyte containing formate is 0.05M-0.1M, the silver mirror reaction uses a fresh silver ammonia solution, the silver ammonia solution is strongly alkaline, and the temperature of the silver mirror reaction is 95℃.

[0045] Step 2, continuously collect 800ml of the electrolyte containing formate in a wide-mouth container, and place the container in a ventilated and directly sunlit place, evaporate to obtain dry solar salt by solar energy and wind energy, the concentration of formate in the electrolyte is 0.1M-0.3M, and the current density of the reaction is 14mA / cm 2 , and the reaction time is 5h-30h.

[0046] The main components of the solar salt are a mixture of formate and carbonate.

[0047] Figure 5 is a process schematic diagram of the solar salt in the embodiment of the application.

[0048] As shown in the figure, the electrolyte containing formate product is mainly converted into solar salt by using sustainable solar energy and wind energy. Figure 5

[0049] is a process schematic diagram of the solar salt in the embodiment of the application. Figure 6 As shown in the figure, the electrolyte containing formate is evaporated by solar energy and wind energy for 1 day, 11 days, 15 days and 26 days, and the physical state of the electrolyte and the solar salt obtained finally are shown.

[0050] Figure 6 The application of the solar salt in the field of low-temperature antifreeze or snow-melting agent in the embodiment is as follows: a series of aqueous solutions with different mass fractions of the solar salt are prepared, and the aqueous solutions are directly used as low-temperature antifreeze or snow-melting agent,

[0051] The solar salt is prepared by step 2, the mass fraction of the solar salt in the aqueous solution is 0%-80%, and the mass fraction of potassium formate in the solar salt is 40%-45%.

[0052]

[0053] Figure 7 ​​is a performance diagram of the sun salt reducing the freezing point of water in the embodiment of the present application.

[0054] As shown in Figure 7 , 80% of the solid salt water solution reaches the saturation state, and can reduce the freezing point of water to -35.2℃, so that the sun salt can be directly used as a snow melting agent in most parts of the world.

[0055] Figure 8 is a schematic diagram of the sun salt being acidified by sulfuric acid and oxidized boron secondary purification distillation to high-concentration formic acid in the embodiment of the present application.

[0056] As shown in Figure 8 , in step 3, the collected sun salt is added to a certain volume fraction of sulfuric acid for acidification, and a secondary purification distillation method using oxidized boron (B2O3) is used to obtain a formic acid solution,

[0057] The concentration of formic acid in the formic acid solution is greater than or equal to 85%.

[0058] Figure 9 is a physical diagram of the sun salt and the formic acid solution in the embodiment of the present application.

[0059] As shown in Figure 9 , the sun salt is 31.25g, and the mass fraction of the high-concentration formic acid solution is 86.2%, and the volume is 2.9ml.

[0060] Figure 10 is a flowchart of the sun salt being acidified by sulfuric acid and oxidized boron secondary purification distillation in the embodiment of the present application.

[0061] As shown in Figure 10 , in step 3, the volume fraction of sulfuric acid is 40%, and the amount of sulfuric acid added is determined according to the gas bubbles generated by the reaction, and the secondary purification distillation method using oxidized boron includes primary distillation and secondary distillation,

[0062] The primary distillation is to obtain a primary distillation formic acid solution with a formic acid concentration of 20% by distillation at a distillation temperature of 106℃, and when the secondary distillation is performed, the amount of oxidized boron added is 1:1.5 compared to the amount of water in the primary distillation formic acid solution, and by secondary distillation, a formic acid solution with a concentration of 86.2% is obtained, and the oxidized boron can be reused after calcination at 300℃ for 5h under vacuum in a tube furnace.

[0063] The application of a formic acid solution in the embodiment in the field of fuel cells has the following: the formic acid solution is configured into a certain concentration of dilute formic acid solution as a liquid fuel in a hydrogen fuel cell or a formic acid fuel cell,

[0064] The formic acid solution is prepared in step 3. The formic acid concentration of the dilute formic acid solution is 1M-5M. When the dilute formic acid solution is used as a liquid fuel, 10% Pd / C catalyst is added to carry out the dehydrogenation reaction. The amount of catalyst added per 20ml of dilute formic acid solution is 0.1g. The operating temperature range of the dilute formic acid solution as a liquid fuel is 25℃-50℃. There is no CO gas in the catalytic dehydrogenation product.

[0065] Figure 11 This is a physical image of a hydrogen fuel cell vehicle model using dilute formic acid solution in an embodiment of the present invention.

[0066] like Figure 11 As shown, 20 ml of 3M dilute formic acid solution, under the dehydrogenation action of 10% Pd / C catalyst, releases hydrogen gas into the anode to undergo a hydrogenation reaction, while oxygen in the air undergoes an oxygen reduction reaction at the cathode. The energy released by this fuel cell can ignite LED lights and drive the movement of a fuel cell vehicle model.

[0067] Figure 12 This is a gas chromatogram of the dehydrogenation products of a commercial 10% Pd / C catalyst in an embodiment of the present invention.

[0068] like Figure 12 As shown, there is no CO gas in the catalytic dehydrogenation products.

[0069] In summary, this embodiment presents a purification method for carbon dioxide to formic acid based on carbon neutralization catalytic reduction. It proposes a purification and utilization process for solar salt and formic acid solution, and the prepared solid and liquid products can be used in different application scenarios, enabling carbon neutralization recycling.

[0070] The role and effect of the embodiments

[0071] According to the purification method for carbon neutralization-based catalytic reduction of carbon dioxide to formic acid involved in this embodiment, a readily available, low-cost, and highly efficient and stable copper-tin alloy is used as a catalyst. Carbon dioxide is reduced to formic acid through an electrolytic reaction, yielding an electrolyte containing formate. This electrolyte, containing formate, is then converted into solar salt using sunlight in a green manner, achieving effective enrichment of the product. Further, the solar salt is converted into a high-concentration formic acid solution through acidification and a secondary purification distillation method using boron oxide. The preparation process of this invention is simple and low-cost, allowing the acquisition of solar salt without additional fossil energy consumption. Furthermore, the boron oxide used in the secondary purification distillation method can be recycled after vacuum dehydration. Moreover, the solid and liquid products prepared in this embodiment can be used in different application scenarios, realizing an industrially valuable carbon neutrality cycle, which is of great significance in the carbon neutrality industry and also has important application prospects in chemical experimental education.

[0072] The above embodiments are preferred cases of the present application and are not intended to limit the scope of protection of the present application.

Claims

1. A purification method for carbon neutral-based catalytic reduction of carbon dioxide to formic acid, characterized by, It comprises the following steps: Step 1: Using the treated copper-tin alloy as a catalyst, the catalyst is made into an electrochemical device and packaged, and then placed in an electrolyte for electrocatalytic reduction of carbon dioxide to reduce carbon dioxide to formic acid to obtain an electrolyte containing formate; Step 2: Collecting the electrolyte containing formate in a wide-mouth container for several times in succession, evaporating to obtain dry solar salt by solar energy and wind energy; Step 3: Adding the collected solar salt to a certain volume fraction of sulfuric acid for acidification, the volume fraction is 20%-40%, and the amount of sulfuric acid added is determined according to the gas bubbles generated by the reaction, and a boron oxide secondary purification distillation method is used to obtain a formic acid solution, Wherein, the main components of the solar salt are a mixture of formate and carbonate, The concentration of formic acid in the formic acid solution is greater than or equal to 85%, The copper-tin ratio of the surface catalytic layer of the copper-tin alloy is 2.54:1, and both copper and tin exhibit weak oxidation state, The copper-tin alloy is treated with acetone and dilute hydrochloric acid to remove the oxide layer and organic attachments before being used as the catalyst.

2. The purification method of claim 1, wherein: the electrolyte is a KHCO3 solution saturated with CO2, and the flow rate of the CO2 raw gas is 1-1000 sccm during the electrocatalytic reduction of CO2. wherein 3. The purification method of claim 1, wherein: the boron oxide secondary purification distillation method comprises primary distillation and secondary distillation, the primary distillation is carried out at a distillation temperature of 106°C to obtain a primary distillation formic acid solution with a formic acid concentration of 20%, and the amount of boron oxide added during the secondary distillation is 1:1.5 of the amount of water in the primary distillation formic acid solution, and the secondary distillation obtains the formic acid solution with a formic acid concentration of more than 85%.

4. Use of an electrolyte containing formate in a silver mirror reaction, wherein: the electrolyte containing formate is directly used as a reducing agent in a silver mirror reaction to obtain a bright and dense silver mirror, wherein, Wherein, the electrolyte containing formate is prepared by step 1 of claim 1, The concentration of formate in the electrolyte containing formate is 0.05-0.1 M, and a fresh silver ammonia solution is used in the silver mirror reaction, which is strongly alkaline, and the temperature of the silver mirror reaction is 95°C.

5. Use of solar salt in the field of low-temperature antifreeze or snow-melting agent, wherein: the solar salt is prepared into a series of aqueous solutions with different mass fractions, and the aqueous solution is directly used as a low-temperature antifreeze or snow-melting agent, Wherein, the solar salt is prepared by step 2 of claim 1, The mass fraction of the solar salt in the aqueous solution is 80%, and the mass fraction of potassium formate in the solar salt is 40%-45%. ​ ​ ​ ​ 6. Use of a formic acid solution in the field of fuel cells, characterized in that: The formic acid solution is configured as a dilute formic acid solution with a certain concentration as a liquid fuel in a hydrogen fuel cell or a formic acid fuel cell, The formic acid solution is prepared by the step 3 of claim 1, The formic acid concentration of the dilute formic acid solution is 1 M-5 M, the dilute formic acid solution is used as the liquid fuel and added with a 10% Pd / C catalyst for a dehydrogenation reaction, the catalyst addition amount is 0.1 g per 20 ml of the dilute formic acid solution, and the working temperature range of the dilute formic acid solution used as the liquid fuel is 25℃-50℃.

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