Preparation method and application of inert anode for ionic liquid low-temperature electrolysis of aluminum

Abstract

The application discloses a preparation method and application of an inert metal tungsten anode for low-temperature electrolytic aluminum of ionic liquid, and relates to the technical field of electrolysis. The preparation method of the porous tungsten inert anode provided by the application comprises raw material proportioning, raw material mixing, vacuum sintering and electrode purification. The method combines a discharge plasma sintering process with an electrochemical dissolution process to prepare the porous tungsten anode with a pore diameter of 1-10 microns. The anode has excellent electrochemical stability and corrosion resistance, can effectively promote the desorption of anode chlorine gas bubbles in the electrolysis process, and can effectively reduce the voltage of the low-temperature electrolytic aluminum system of ionic liquid.

Description

Technical Field

[0001] This invention relates to the field of electrolysis technology, and in particular to a method for preparing and applying an inert anode for low-temperature electrolysis of aluminum using ionic liquids. Background Technology

[0002] Aluminum, a silvery-white lightweight metal, possesses excellent ductility and electrical conductivity, as well as corrosion resistance due to the formation of a dense oxide film in air. It plays an irreplaceable role in aerospace, transportation, building materials, packaging, power transmission, and daily necessities, and is a crucial basic material in modern industry and daily life.

[0003] Currently, the industrial production of aluminum mainly relies on the Hall-Heroo process, which involves producing aluminum through high-temperature electrolysis of alumina. This method is extremely energy-intensive, requiring approximately 13,500 kWh of electricity to produce one ton of aluminum. During electrolysis, the consumed carbon anode is directly converted into carbon dioxide, and fluorine-containing gases are also released, creating environmental pollution challenges. Against the backdrop of the global push for "dual-carbon" goals, the green and low-carbon transformation of aluminum electrolysis technology has become an urgent need for the industry's development.

[0004] Ionic liquids, with their wide electrochemical window, high ionic conductivity, and low volatility, can serve as highly efficient electrolytes for low-temperature aluminum electrolysis. The operating temperature for low-temperature aluminum electrolysis with ionic liquids is typically below 150 °C, significantly reducing energy consumption. More importantly, this process does not produce carbon dioxide, and the chlorine gas generated at the anode can be used for the chlorination of alumina, making it a highly promising green aluminum smelting process. However, this technology still faces key challenges in practical applications: the chlorine gas generated at the anode not only corrodes the electrode materials but also easily adheres to the electrode surface and is difficult to desorb, leading to increased electrolytic cell voltage and thus limiting electrolysis efficiency and stability.

[0005] To address the aforementioned problems, this invention provides a method for preparing an inert tungsten anode for low-temperature electrolytic aluminum using ionic liquids. This method aims to overcome the technical bottlenecks of anodic corrosion and bubble desorption difficulties in existing ionic liquid electrolytic aluminum processes, and promote the industrial application of this green process. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing an inert anode for low-temperature electrolytic aluminum using ionic liquids, in order to overcome the deficiencies in the existing technology.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing an inert anode for low-temperature aluminum electrolysis using ionic liquids includes the following steps: S1: Raw material ratio: Weigh tungsten powder, iron powder and carbon powder according to a mass ratio of 0.5-1.5 : 0.5-1.5 : 0.001-0.003; S2: Raw material mixing: Mix the tungsten powder, iron powder and carbon powder after the proportioning is completed; S3: Vacuum sintering: The mixed powder is placed in a vacuum environment and sintered into shape by spark plasma sintering. The sintering temperature is 800-1000 ℃ and the pressure is 10-30 MPa. S4: Purification electrode: The obtained sintered body is used as the anode and the aluminum sheet is used as the cathode. It is placed in a chloroaluminate ion liquid electrolyte and electrochemically dissolved under DC voltage until the iron component is completely removed to obtain a porous tungsten matrix. S5: Cleaning the electrode: The porous tungsten substrate is cleaned and dried using organic solvents and ethanol respectively to obtain a micron-sized porous tungsten inert anode.

[0008] Furthermore, in step S1, the tungsten powder is pure tungsten powder, the iron powder is pure iron powder, and the carbon powder is nano carbon powder. The specific mass ratio of pure tungsten powder, pure iron powder, and nano carbon powder is 1:1:0.002, and the raw material ratio forms a tungsten-iron pseudo-alloy structure.

[0009] Furthermore, in step S1, the average particle size of the tungsten powder is 1-5 micrometers, the average particle size of the iron powder is 3-7 micrometers, and the particle size of the carbon powder is 30-60 nanometers.

[0010] Furthermore, in step S2, the raw material mixing time is 10-20 hours, and the mixing speed is 80-120 rpm.

[0011] Furthermore, in step S4, the cation of the aluminochloroaluminate ionic liquid is a C1-C4 alkyl-substituted imidazolium ion, and the anion is AlCl4. - and Al2Cl7 - .

[0012] Furthermore, in step S5, the organic solvent is an organic reagent capable of dissolving chloroaluminate ionic liquids, such as dichloromethane or acetonitrile.

[0013] The application of an inert anode for low-temperature electrolytic aluminum using an ionic liquid prepared by the above method in the electrolysis process of aluminochloride ionic liquid.

[0014] Beneficial effects

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes spark plasma sintering and electrochemical dissolution to prepare an inert tungsten anode. The tungsten anode obtained by this method has high purity, a rod-like or sheet-like appearance, a uniformly dispersed micron-sized porous structure, and good electrical conductivity.

[0016] The metallic inert tungsten anode obtained by this invention has good corrosion resistance and electrochemical stability. It can effectively promote the removal of chlorine bubbles during the electrolysis of aluminum with ionic liquids, thereby improving current efficiency. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0018] Figure 1 These are surface morphology and elemental distribution diagrams after spark plasma sintering.

[0019] Figure 2 These are surface morphology and elemental distribution diagrams of the electrodes after 10 hours of electrolysis.

[0020] Figure 3 These are the anodic polarization curves of the low-temperature electrolytic aluminum process using ionic liquids with porous tungsten sheet electrodes and non-porous tungsten sheet electrodes.

[0021] Figure 4 These are the it curves of the low-temperature electrolysis of aluminum by ionic liquid using porous tungsten sheet electrodes and non-porous tungsten sheet electrodes. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0023] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] Example 1: A method for preparing an inert tungsten metal anode for low-temperature electrolysis of aluminum with ionic liquids is as follows: Raw material preparation: Weigh 50 g of tungsten powder with an average particle size of about 1 micrometer, 50 g of iron powder with an average particle size of about 5 micrometers, and 0.1 g of carbon powder with an average particle size of about 50 nanometers. The purity of all three materials is greater than 99%.

[0025] Mixing: Thorough mixing is carried out using a three-dimensional mixer at a speed of 80 rpm for 15 hours.

[0026] Sintering: The mixed powder was subjected to discharge plasma sintering at 1000 ℃ in a vacuum atmosphere, with a heating rate of 100 ℃ / min and a pressure of 20 MPa.

[0027] Cutting: The cylindrical material obtained from sintering was cut into 1×1.5 cm electrode sheets for morphology testing, such as... Figure 1 At this point, the electrode morphology is indeterminate, and the three materials are mixed relatively evenly.

[0028] Electrochemical dissolution: Using this electrode as the anode and the aluminum sheet as the cathode, the electrode is placed in a chloroaluminate ionic liquid and electrochemical dissolution is performed using a DC voltage. When the iron is fully dissolved, a large number of bubbles will emerge from the anode. At this point, the main component of the anode is metallic tungsten. The chloroaluminate ionic liquid is prepared by mixing imidazole halide and aluminum chloride in a molar ratio of 1:1.5. The imidazole halide is 1-ethyl-3-methylimidazolium (EMIC).

[0029] Cleaning and Drying: The tungsten anode was thoroughly cleaned with dichloromethane and ethanol to remove residual ionic liquid, and then dried at room temperature in a vacuum oven. The surface morphology and elemental distribution of the obtained tungsten metal with a micron-scale porous structure are shown in the following figures. Figure 2 .

[0030] Performance Testing: The prepared tungsten anode was electrochemically tested using an electrochemical workstation. A platinum sheet electrode was used as the counter electrode, and an aluminum wire electrode as the reference electrode. Polarization curves were measured at a scan rate of 10 mV / s, and electrochemical stability was tested at 3.5 V.

[0031] Example 2

[0032] A method for preparing an inert tungsten anode for low-temperature electrolysis of aluminum with ionic liquids differs from Example 1 in that the macroscopic morphology of the porous tungsten electrode is altered. A tungsten cylinder with a diameter of 6 mm is obtained by cutting, and then connected to a carbon rod or aluminum rod, etc., using conductive adhesive or solder. Other steps are the same as in Example 1.

[0033] Example 3

[0034] A method for preparing an inert tungsten anode for low-temperature electrolysis of aluminum using ionic liquids differs from Example 1 in that the imidazole halide salt used in the electrochemical dissolution step is changed. Instead, a pre-cut tungsten electrode sheet is used as the anode, and an aluminum sheet as the cathode, which is then placed in a chloroaluminate ionic liquid electrolyte for electrochemical dissolution. This ionic liquid is prepared by mixing 1-butyl-3-methylimidazolium chloride (BMIC) and anhydrous aluminum chloride at a molar ratio of 1:1.5. Other steps are the same as in Example 1.

[0035] Example 4

[0036] A method for preparing an inert tungsten anode for low-temperature electrolysis of aluminum with ionic liquids differs from Example 1 in that the ratio of imidazole halide to aluminum chloride used in the electrochemical dissolution step is changed. The ionic liquid is prepared by mixing EMIC and anhydrous aluminum chloride in a molar ratio of 1:2. Other steps are the same as in Example 1.

[0037] Application Example 1: An application method for an inert metal tungsten anode used in low-temperature electrolysis of aluminum with ionic liquids is as follows: Electrochemical tests were performed on porous tungsten sheet electrodes and non-porous tungsten anodes using an electrochemical workstation. A platinum sheet electrode was used as the counter electrode, and an aluminum wire electrode as the reference electrode. An EMIC-AlCl3 ionic liquid with a molar ratio of 1:2 was used as the electrolyte at room temperature. Polarization curves were measured at a scan rate of 10 mV / s. Figure 3 The porous tungsten electrode fabricated exhibits a lower overpotential than the non-porous tungsten electrode. Electrochemical stability tests were conducted at 3.5 V. Figure 4 During the 10-hour electrolysis period, the activity of the porous tungsten electrode did not decrease, and the current was always greater than that of the non-porous tungsten metal sheet.

[0038] Application Example 2: An application method for an inert metal tungsten anode used in low-temperature electrolysis of aluminum with ionic liquids is as follows: Electrochemical tests were conducted using an electrochemical workstation on a porous tungsten sheet electrode and a 300-mesh tungsten mesh anode. A platinum sheet electrode was used as the counter electrode, and an aluminum wire electrode as the reference electrode. An EMIC-AlCl3 ionic liquid with a molar ratio of 1:2 was used as the electrolyte at 80 °C. Electrochemical stability tests were performed at 3.5 V. During electrolysis, numerous bubbles were generated and detached from the porous tungsten surface. Over an electrolysis period of up to 10 hours, the activity of the porous tungsten electrode showed no decline, and the current remained consistently higher than that of the non-porous tungsten sheet electrode.

[0039] Application Example 3

[0040] An application method for an inert metal tungsten anode used in low-temperature electrolysis of aluminum with ionic liquids is as follows: Electrochemical tests were performed on the porous tungsten rod electrode and the non-porous tungsten metal rod anode prepared in Example 4 using an electrochemical workstation. A platinum electrode was used as the counter electrode, and an aluminum wire electrode as the reference electrode. At room temperature, a BMIC-AlCl3 ionic liquid with a molar ratio of 1:2 was used as the electrolyte. Polarization curves were tested at a scan rate of 10 mV / s. The porous tungsten rod junction showed a lower overpotential than the non-porous tungsten metal rod anode electrode. Electrochemical stability tests were conducted at 3 V. During an electrolysis period of up to 10 hours, the activity of the porous tungsten rod electrode showed no decline, and the current remained higher than that of the non-porous tungsten metal rod anode.

[0041] Application Example 4

[0042] An application method for an inert metal tungsten anode used in low-temperature electrolysis of aluminum with ionic liquids is as follows: Electrolytic cell voltage tests were conducted on porous tungsten sheet electrodes and non-porous metallic tungsten sheet electrodes using a DC power supply. An EMIC-AlCl3 ionic liquid with a molar ratio of 1:2 was used as the electrolyte at 80 °C. A voltage of 50 mA / cm² was applied. 2 The electrolysis was conducted using a constant current, with a pure aluminum cathode and a 2 cm anode-cathode distance. During electrolysis, the cell voltage of the porous tungsten electrode was 2.5-3 V, while that of the non-porous tungsten electrode was 3-3.5 V. Throughout the 10-hour electrolysis period, the voltage of the porous tungsten electrode remained consistently lower than that of the non-porous tungsten rod anode.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing an inert anode for low-temperature electrolytic aluminum using ionic liquids, characterized in that, Includes the following steps: S1: Raw material ratio: Weigh tungsten powder, iron powder and carbon powder according to a mass ratio of 0.5-1.5 : 0.5-1.5 : 0.001-0.003; S2: Raw material mixing: Mix the tungsten powder, iron powder and carbon powder after the proportioning is completed; S3: Vacuum sintering: The mixed powder is placed in a vacuum environment and sintered into shape by spark plasma sintering. The sintering temperature is 800-1000 ℃ and the pressure is 10-30 MPa. S4: Purification electrode: The obtained sintered body is used as the anode and the aluminum sheet is used as the cathode. It is placed in a chloroaluminate ion liquid electrolyte and electrochemically dissolved under DC voltage until the iron component is completely removed to obtain a porous tungsten matrix. S5: Cleaning the electrode: The porous tungsten substrate is cleaned and dried using organic solvents and ethanol respectively to obtain a micron-sized porous tungsten inert anode.

2. The method for preparing an inert anode for low-temperature electrolytic aluminum using ionic liquids according to claim 1, characterized in that, In step S1, the tungsten powder is pure tungsten powder, the iron powder is pure iron powder, and the carbon powder is nano carbon powder. The specific mass ratio of pure tungsten powder, pure iron powder, and nano carbon powder is 1:1:0.

002. The raw material ratio forms a tungsten-iron pseudo-alloy structure.

3. The method for preparing an inert anode for low-temperature electrolytic aluminum using ionic liquids according to claim 1, characterized in that, In step S1, the average particle size of the tungsten powder is 1-5 micrometers, the average particle size of the iron powder is 3-7 micrometers, and the particle size of the carbon powder is 30-60 nanometers.

4. The method for preparing an inert anode for low-temperature electrolytic aluminum using ionic liquids according to claim 1, characterized in that, In step S2, the raw material mixing time is 10-20 hours and the mixing speed is 80-120 rpm.

5. The method for preparing an inert anode for low-temperature electrolytic aluminum using ionic liquids according to claim 1, characterized in that, In step S4, the cation of the aluminochloroaluminate ionic liquid is a C1-C4 alkyl-substituted imidazolium ion, and the anion is AlCl4. - and Al2Cl7 - .

6. The method for preparing an inert anode for low-temperature electrolytic aluminum using ionic liquids according to claim 1, characterized in that, In step S5, the organic solvent is an organic reagent capable of dissolving chloroaluminate ionic liquids, such as dichloromethane or acetonitrile.

7. The application of an inert anode for low-temperature electrolytic aluminum production using an ionic liquid prepared by any one of claims 1 to 6 in the electrolysis process of aluminochloride ionic liquid.

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