Method for preparing high-purity metallic titanium through fused salt electrolysis one-step method

Abstract

The invention discloses a method for preparing high-purity metallic titanium through a fused salt electrolysis one-step method. The method mainly comprises the two stages of electrolytic reduction and electrolytic purification. The method comprises the following steps: firstly, by taking a mixture of TiO2 powder and C powder as a cathode and graphite as an anode, carrying out electrolysis in halide molten salt at 700-1000 DEG C under 3.0-3.2 V voltage and inert atmosphere to obtain TiCxOy; and secondly, when the current is reduced to a platform of a time current curve, a pure metal titanium rod is used for replacing a graphite rod to serve as a cathode for electrolytic purification in the next stage, TiCxOy obtained through electrolytic reduction is adjusted to be a new anode, and deep electrolysis is conducted to prepare high-purity titanium. And after electrolysis is finished, a cathode product is cleaned, dried and collected, and a high-purity titanium product is obtained. According to the method, the advantage that the cathode and the anode in the direct-current electrolytic cell can be flexibly dispatched is utilized, the titanium oxide electrolysis rapid deoxidation process and the TiCxOy electrolysis titanium extraction process are efficiently coupled, one-step method direct preparation from the titanium oxide to the high-purity titanium is achieved, the process cost for preparing the metal titanium is low, and the prepared metal titanium is high in purity.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for preparing high-purity metallic titanium by one-step molten salt electrolysis. Background Art

[0002] Titanium and titanium alloys have shown broad application prospects in many key fields such as aerospace, automotive industry, biomedicine and chemical industry due to their unique physical and chemical properties. These properties include high specific strength, excellent corrosion resistance, low thermal conductivity and excellent biocompatibility, making titanium an important strategic metal material. Although titanium is abundant in the earth's crust, second only to iron, aluminum and magnesium, the large-scale application of titanium and titanium alloys has been limited due to its complex production process, high energy consumption, high cost, and high processing and molding costs.

[0003] At present, the main process for industrial production of titanium sponge is the Kroll process. This process includes the chlorination of titanium oxide, purification and impurity removal of chloride, magnesium thermal reduction of TiCl4, distillation and refining, and MgCl2 electrolytic cycle. However, the Kroll process has problems such as long process, high energy consumption, high cost, environmental pollution, and discontinuous production. Despite continuous improvement and optimization, there is limited room for further reducing production energy consumption and costs due to the limitations of process mechanism and process.

[0004] In order to overcome the limitations of the Kroll method, researchers from all over the world have carried out a large number of basic research and application attempts on the short-process preparation of titanium sponge in the past 20 years. Among them, the molten salt electrolysis method is considered to be the most promising short-process preparation of titanium sponge technology. The main representative processes include the OS method (calcium oxide molten salt electrolysis method), the FFC method (fluoride molten salt electrolysis method) and the USTB method (soluble anode electrolysis method).

[0005] The OS method is a process of preparing titanium metal by electrolyzing CaO dissolved in CaCl2 to obtain metallic Ca, and then realizing calcium thermal reduction of TiO2. This process uses CaCl2-CaO as electrolyte, graphite as anode, and titanium metal mesh or stainless steel mesh as cathode frame. The added TiO2 powder is reduced by Ca near the cathode to obtain titanium metal, and the removed O 2- The ions dissolve in the molten salt and migrate to the graphite anode to form CO2 and CO. At the same time, the reduction product CaO near the cathode is electrolyzed again to obtain Ca, thus realizing the continuous production of sponge titanium. Although the OS method can theoretically produce metallic titanium with a low oxygen content, and the exothermic reaction can reduce some energy consumption, the low current efficiency during the electrolysis process, carbon contamination in the product, and difficulty in separating it from the electrolyte mean that the process is still in the laboratory research stage.

[0006] The FFC principle uses TiO2 as the cathode and carbonaceous material as the anode to obtain titanium sponge by electro-deoxidation in CaCl2 molten salt. This process can simplify the traditional alloy preparation process and reduce process energy consumption and production costs. However, the deoxidation process of TiO2 is relatively complicated, which is mainly divided into the early stage of rapid deoxidation to form titanium low-valent oxide TiO x and later TiO x Slow deoxidation to titanium sponge, low deoxidation efficiency, long time and high energy consumption in the later stage are the bottlenecks in the research and large-scale application of this process.

[0007] The USTB method is an innovative new process for preparing titanium metal from soluble anodes. The process first carbon-thermally reduces TiO2 at 1000℃-1400℃ to form TiC x O y Solid solution, and then use the solid solution as a soluble anode to electrolyze in CaCl2 molten salt to prepare sponge titanium. During the electrolysis process, titanium dissolves in the anode in the form of ions, migrates to the cathode and deposits to obtain metallic titanium, and C and O in the anode are discharged in the form of CO and CO2. Although the USTB method can prepare sponge titanium with high purity and low oxygen content, it faces problems such as high energy consumption in the preparation of soluble anodes and anode collapse during electrolysis, so it has not yet been industrialized.

[0008] In summary, although titanium and titanium alloys have broad application prospects, the complexity and high cost of their production process limit their large-scale application. Therefore, the development of a short-process, low-cost, green new sponge titanium production process has become an urgent problem to be solved. Summary of the invention

[0009] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a method for preparing high-purity metallic titanium by one-step molten salt electrolysis, so as to solve the problems of high cost, long process, high energy consumption and low product purity in the prior art of preparing metallic titanium.

[0010] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] A method for preparing high-purity metallic titanium by one-step molten salt electrolysis comprises the following steps:

[0012] (1) After the TiO2 powder and the C powder are mixed evenly, a binder is added and mixed evenly, and then the raw powder is pressed into a flaky powder block embryo, and then the flaky powder block embryo is placed in an inert atmosphere for sintering to obtain a flaky TiO2-C electrode;

[0013] (2) After the powdered CaCl2, KCl and KF are mixed evenly, they are melted and dehydrated under vacuum conditions, cooled to 140-160°C, taken out and sealed for storage, thereby obtaining a molten salt electrolyte;

[0014] (3) The molten salt electrolyte obtained in step (2) is placed in an electrolytic cell, and the temperature is raised to 700-1000° C. under an inert atmosphere. After the electrolyte is completely melted, the flaky TiO2-C electrode obtained in step (1) is used as a cathode and a graphite rod is used as an anode to perform electrolysis to obtain TiC x O y Intermediates;

[0015] (4) When the electrolysis time reaches 0.5 to 24 hours and the current intensity drops to 0.2 to 0.6 A and remains stable, adjust the electrode; x O y The intermediate is used as a new anode and the metal titanium rod is used as a new cathode to continue deep electrolysis for 4 to 24 hours. The cathode product is dried and washed to obtain high-purity metal titanium.

[0016] Furthermore, in step (1), the mass ratio of TiO2 powder to C powder is 80-90:10-20. This range can ensure that the molar ratio of Ti to C in the obtained Ti-CO soluble electrode is 1-2, thereby ensuring that the electrode has a certain strength and good conductivity.

[0017] Furthermore, in step (1), the molding pressure is 200-400 kg / cm 2 The raw material powder is pressed and molded under this molding pressure, which can ensure that the electrode has good strength during sintering.

[0018] Furthermore, in the step (1), the sintering temperature is 800-1100° C. The electrode prepared at this temperature has good electrical conductivity while ensuring strength.

[0019] Furthermore, in step (2), the mass ratio of CaCl2:KCl:KF is 70-100:0-30:0-30. By controlling the mass ratio within this range, the oxygen dissolving capacity, wettability and conductivity of the molten salt can be adjusted according to different needs. By adjusting the oxygen dissolving capacity of the molten salt, the deoxidation efficiency of TiO2 can be adjusted; by adjusting the wettability, the carbon deposition reaction can be adjusted, the CO2 gas release rate of the anode can be increased, and its reaction with O in the molten salt can be reduced. 2- ions to minimize the coexistence time of CO3 2- The generation of ions inhibits the carbon deposition reaction on the cathode; the current efficiency can be improved by adjusting the conductivity.

[0020] Furthermore, in step (3), the electrolysis voltage is 2.9 to 3.2 V. Controlling the voltage in the deoxidation stage within this range can efficiently deoxidize TiO2 and ensure that the molten salt does not undergo electrolysis reaction.

[0021] Furthermore, in step (4), the cathode current density of deep electrolysis is 0.2-1A / cm2. In the purification stage, constant current electrolysis is performed with a cathode current density of 0.2-1A / cm2, which can controllably dissolve the anode and deposit the cathode, thereby obtaining a controllable average particle size of crystalline titanium and a higher current efficiency.

[0022] Furthermore, in step (2), the melting temperature is 600-700°C and the dehydration time is 2-3 hours. By controlling the melting temperature and dehydration time within this range, impurities in the molten salt can be removed while reducing the volatilization of the molten salt and ensuring its uniformity.

[0023] Furthermore, in step (4), the diameter of the metal titanium rod is 5 mm, and it is polished with 1000-mesh sandpaper to remove the oxide film on the surface before use, and then cleaned with alcohol and dried.

[0024] The present invention takes advantage of the flexible scheduling of the cathode and anode in the DC electrolyzer, and combines the rapid deoxidation process of titanium oxide electrolysis with the TiC x O y The electrolytic titanium extraction process is efficiently coupled to achieve a one-step direct preparation of high-purity titanium from titanium oxide; this continuous preparation technology effectively avoids the low deoxidation efficiency of traditional electrolytic processes of metal oxides and the high purity of TiC x O y The problems of long preparation process and high energy consumption can be effectively improved by improving the process electrolysis efficiency and reducing the process cost. Compared with the existing high-melting-point refractory metal molten salt electrolysis preparation process, the present invention effectively combines the efficient deoxidation of metal oxide electrolysis, the preparation of soluble metal carbon oxide compounds and the soluble anode electrolysis purification, which can achieve the continuous, efficient and low-cost preparation of high-purity titanium metal, and provides a new idea for the short-process and low-cost preparation of high-melting-point refractory high-purity metals.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention combines the rapid deoxidation process of titanium oxide electrolysis with TiC x O y The electrolytic titanium extraction process is efficiently coupled, realizing the one-step direct preparation from titanium oxide to high-purity titanium. This innovative method not only significantly shortens the traditional preparation process, but also greatly reduces process energy consumption and costs. By utilizing the high-efficiency zone of TiO2 electrochemical deoxidation, the present invention can efficiently obtain TiC x O y The intermediate is then electrolyzed to produce high-purity titanium products. The optimization of this process makes the entire preparation process more efficient, energy-saving and cost-effective.

[0027] 2. The present invention makes full use of the advantages of flexible scheduling of the anode and cathode in the DC electrolytic cell, and effectively combines the FFC method in the high-efficiency section of metal oxide electrolytic deoxidation with the USTB method of soluble anode electrolytic purification. This combination not only avoids the problems of low current efficiency and high energy consumption in the later stage of the FFC method, but also solves the difficult problems of high energy consumption and easy collapse in the preparation of soluble anodes in the USTB method. Through this innovative method, the present invention realizes the one-step preparation from oxide to high-purity titanium, which not only improves production efficiency, but also significantly reduces production costs. At the same time, the application of continuous preparation technology further reduces the loss of titanium and molten salt consumption in the traditional electrolytic deoxidation and purification process, and further improves the overall economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the main process principle diagram of the present invention.

[0029] Figure 2 It is the main process flow chart of the present invention.

[0030] Figure 3 The XRD spectra of the cathode products of Example 1, Comparative Example 1 and Comparative Example 2 of the present invention are shown. DETAILED DESCRIPTION

[0031] The specific implementation modes of the present invention are further described in detail below in conjunction with specific examples.

[0032] The numerical ranges in the present invention are understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any intermediate value in the stated value or stated range and any other stated value or intermediate value in the stated range is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded in the range.

[0033] Unless otherwise stated, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art described in the present invention are generally understood. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of conflict with any incorporated document, the content of this specification shall prevail. Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open terms, which means including but not limited to.

[0034] Unless otherwise specified, the experimental methods used in the present invention are all conventional methods.

[0035] Unless otherwise specified, the materials, reagents, etc. used in the present invention can be purchased or synthesized by known methods.

[0036] The quantitative tests in the present invention were all repeated three times, and the results were averaged.

[0037] 1. Implementation

[0038] Example 1

[0039] This embodiment provides a method for preparing high-purity titanium metal by one-step molten salt electrolysis. The reaction principle is as follows: Figure 1 As shown, the process flow is as follows Figure 2 As shown, the following steps are included:

[0040] (1) Preparation of TiO2-C flake electrodes

[0041] First, TiO2 powder and C powder were accurately weighed in a mass ratio of 90:10 and mixed evenly to obtain a mixture. Next, a binder (PVA and water in a mass ratio of 5:100) accounting for 7wt.% of the mixture was added to the mixture to enhance the binding force and formability of the powder. Then, a mold was used at 400kg / cm 2 The mixed powder is pressed into a flaky powder block under a molding pressure of . Finally, the flaky powder block is sintered at 1000° C. in an argon atmosphere to obtain a flaky TiO2-C electrode with stable structure and good conductive performance.

[0042] (2) Preparation of halide molten salt electrolyte

[0043] In a glove box, the halide powders CaCl2, KCl and KF are accurately weighed in a mass ratio of 100:0:0 (in this case, the amount of KCl and KF added is 0, so the main component is CaCl2). After the weighed halide powders are mixed evenly, they are placed in a 600°C vacuum electrolysis furnace. Under vacuum conditions, the mixture is melted and dehydrated for 2 hours to remove moisture and impurities. When the molten salt is cooled to about 150°C, it is taken out and sealed for storage to prevent it from absorbing moisture and oxygen in the air. This avoids the adverse effects of moisture in the electrolysis process, including reducing electrolysis efficiency, affecting product quality, and causing equipment damage.

[0044] (3) Electrolytic preparation of TiC x O y Intermediates

[0045] Place the prepared halide molten salt electrolyte into the electrolytic cell and heat it to 900°C under an inert atmosphere (such as argon). After the electrolyte is completely melted, use the previously prepared TiO2-C flaky electrode as the cathode and the high-purity graphite rod as the anode. Set the electrolysis voltage to 3.2V and start electrolysis to obtain TiC x O yIntermediate.

[0046] (4) Preparation of high-purity titanium by deep electrolysis

[0047] When the electrolysis time reaches 2 hours and the current intensity drops to 0.6A, the electrode adjustment is performed. x O y The intermediate is used as a new anode, and a titanium rod (5 mm in diameter, polished with 1000-grit sandpaper to remove the oxide film on the surface before use, and then cleaned with alcohol and dried) is used as a new cathode. A constant current of 0.6 A / cm2 is used to continue deep electrolysis to obtain high-purity titanium. The duration of deep electrolysis is 4 hours to ensure the full reduction of titanium ions and further improvement of purity.

[0048] (5) Product processing

[0049] After the electrolysis is completed, turn off the power and wait for the electrolytic cell to cool to room temperature. Then, take out the cathode product (i.e., high-purity titanium product), and clean and dry it. The purpose of cleaning is to remove the molten salt and impurities attached to the surface of the titanium product, while the drying process is to ensure the dry state of the titanium product for subsequent storage and use. Finally, the purity of the obtained metallic titanium was measured to be 99.9947% through component analysis, meeting the high purity requirements.

[0050] Example 2

[0051] This embodiment provides a method for preparing high-purity titanium metal by one-step molten salt electrolysis, which is mainly the same as that in Embodiment 1, except that CaCl2:KCl:KF is weighed and mixed at a mass ratio of 90:0:10. When the electrolysis time is about 3 hours and the current intensity drops to 0.6A, the electrode is adjusted.

[0052] The purity of titanium metal is 99.9962%

[0053] Example 3

[0054] This embodiment provides a method for preparing high-purity titanium metal by one-step molten salt electrolysis, the difference being that CaCl2:KCl:KF are weighed and mixed at a mass ratio of 80:10:10. When the electrolysis time is about 2.5 hours and the current intensity drops to 0.6A, the electrode adjustment is performed.

[0055] The purity of titanium metal is 99.9428%.

[0056] Example 4

[0057] This embodiment provides a method for preparing high-purity metallic titanium by one-step molten salt electrolysis, comprising the following steps:

[0058] (1) Preparation of TiO2-C flake electrodes

[0059] First, TiO2 powder and C powder were accurately weighed in a mass ratio of 85:15 and mixed evenly. Then, a binder (PVA and water in a mass ratio of 5:100) accounting for 7wt.% of the mixture was added to enhance the binding force and formability of the powder. Then, a mold was used at 300kg / cm 2 The mixed powder is pressed into a flaky powder block under a molding pressure of . Finally, the flaky powder block is sintered in an argon atmosphere at 850° C. to obtain a flaky TiO2-C electrode with stable structure and good conductive performance.

[0060] (2) Preparation of halide molten salt electrolyte

[0061] In a glove box, the halide powders CaCl2, KCl and KF are accurately weighed in a mass ratio of 90:0:10. After the weighed halide powders are mixed evenly, they are placed in a 600°C vacuum electrolysis furnace. Under vacuum conditions, the mixture is melted and dehydrated for 3 hours to remove moisture and impurities. When the molten salt is cooled to 145°C, it is taken out and sealed to prevent it from absorbing moisture and oxygen in the air. This avoids the adverse effects of moisture in the electrolysis process, including reducing electrolysis efficiency, affecting product quality, and causing equipment damage.

[0062] (3) Electrolytic preparation of TiC x O y Intermediates

[0063] Place the prepared halide molten salt electrolyte into the electrolytic cell and heat it to 750°C under an inert atmosphere (such as argon). After the electrolyte is completely melted, use the previously prepared TiO2-C flaky electrode as the cathode and the high-purity graphite rod as the anode. Set the electrolysis voltage to 3.0V and start electrolysis to obtain TiC x O y Intermediate.

[0064] (4) Preparation of high-purity titanium by deep electrolysis

[0065] When the electrolysis time reaches 4 hours and the current intensity drops to 0.4A, the electrode adjustment is performed. x O y The intermediate is used as a new anode, and a titanium rod (5 mm in diameter, polished with 1000-grit sandpaper to remove the oxide film on the surface before use, and then cleaned with alcohol and dried) is used as a new cathode. A constant current of 0.4 A / cm2 is used to continue deep electrolysis to obtain high-purity titanium. The duration of deep electrolysis is 7 hours to ensure the full reduction of titanium ions and further improvement of purity.

[0066] (5) Product processing

[0067] After the electrolysis is completed, turn off the power and wait for the electrolytic cell to cool to room temperature. Then, take out the cathode product (i.e., high-purity titanium product), and wash and dry it. The purpose of cleaning is to remove the molten salt and impurities attached to the surface of the titanium product, while the drying process is to ensure the dry state of the titanium product for subsequent storage and use. Finally, the purity of the obtained metallic titanium was measured to be 99.8814% through component analysis, meeting the high purity requirements.

[0068] Example 5

[0069] This embodiment provides a method for preparing high-purity metallic titanium by one-step molten salt electrolysis, comprising the following steps:

[0070] (1) Preparation of TiO2-C flake electrodes

[0071] First, TiO2 powder and C powder were accurately weighed in a mass ratio of 80:20 and mixed evenly. Next, a binder (PVA and water in a mass ratio of 5:100) accounting for 7wt.% of the mixture was added to enhance the binding force and formability of the powder. Then, a mold was used at 200kg / cm 2 The mixed powder is pressed into a sheet powder block embryo under a molding pressure of . Finally, the sheet powder block embryo is sintered at 900° C. in an argon atmosphere to obtain a sheet TiO2-C electrode with stable structure and good conductive performance.

[0072] (2) Preparation of halide molten salt electrolyte

[0073] In a glove box, the halide powders CaCl2, KCl and KF are accurately weighed in a mass ratio of 70:0:30. After the weighed halide powders are mixed evenly, they are placed in a 600°C vacuum electrolysis furnace. Under vacuum conditions, the mixture is melted and dehydrated for 3 hours to remove moisture and impurities. When the molten salt is cooled to 150°C, it is taken out and sealed to prevent it from absorbing moisture and oxygen in the air. This avoids the adverse effects of moisture in the electrolysis process, including reducing electrolysis efficiency, affecting product quality, and causing equipment damage.

[0074] (3) Electrolytic preparation of TiC x O y Intermediates

[0075] Place the prepared halide molten salt electrolyte into the electrolytic cell and heat it to 1000°C under an inert atmosphere (such as argon). After the electrolyte is completely melted, use the previously prepared TiO2-C flaky electrode as the cathode and the high-purity graphite rod as the anode. Set the electrolysis voltage to 3.1V and start electrolysis to obtain TiC x O y Intermediate.

[0076] (4) Preparation of high-purity titanium by deep electrolysis

[0077] When the electrolysis time reaches 5 hours and the current intensity drops to 0.4A, the electrode adjustment is performed. x O y The intermediate is used as a new anode, and a titanium rod (5 mm in diameter, polished with 1000-grit sandpaper to remove the oxide film on the surface before use, and then cleaned with alcohol and dried) is used as a new cathode. A constant current of 0.6 A / cm2 is used to continue deep electrolysis to obtain high-purity titanium. The duration of deep electrolysis is 7 hours to ensure the full reduction of titanium ions and further improvement of purity.

[0078] (5) Product processing

[0079] After the electrolysis is completed, turn off the power and wait for the electrolytic cell to cool to room temperature. Then, take out the cathode product (i.e., high-purity titanium product), and wash and dry it. The purpose of cleaning is to remove the molten salt and impurities attached to the surface of the titanium product, while the drying process is to ensure the dry state of the titanium product for subsequent storage and use. Finally, the purity of the obtained metallic titanium was measured to be 99.8865% through component analysis, meeting the high purity requirements.

[0080] Example 6

[0081] This embodiment provides a method for preparing high-purity metallic titanium by one-step molten salt electrolysis, comprising the following steps:

[0082] (1) Preparation of TiO2-C flake electrodes

[0083] First, TiO2 powder and C powder were accurately weighed in a mass ratio of 80:20 and mixed evenly. Next, a binder (PVA and water in a mass ratio of 5:100) accounting for 7wt.% of the mixture was added to enhance the binding force and formability of the powder. Then, a mold was used at 200kg / cm 2 The mixed powder is pressed into a sheet powder block embryo under a molding pressure of . Finally, the sheet powder block embryo is sintered at 900° C. in an argon atmosphere to obtain a sheet TiO2-C electrode with stable structure and good conductive performance.

[0084] (2) Preparation of halide molten salt electrolyte

[0085] In a glove box, the halide powders CaCl2, KCl and KF are accurately weighed in a mass ratio of 80:10:10. After the weighed halide powders are mixed evenly, they are placed in a 600°C vacuum electrolysis furnace. Under vacuum conditions, the mixture is melted and dehydrated for 3 hours to remove moisture and impurities. When the molten salt is cooled to 150°C, it is taken out and sealed to prevent it from absorbing moisture and oxygen in the air. This avoids the adverse effects of moisture in the electrolysis process, including reducing electrolysis efficiency, affecting product quality, and causing equipment damage.

[0086] (3) Electrolytic preparation of TiC x O y Intermediates

[0087] Place the prepared halide molten salt electrolyte into the electrolytic cell and heat it to 900°C under an inert atmosphere (such as argon). After the electrolyte is completely melted, use the previously prepared TiO2-C flaky electrode as the cathode and the high-purity graphite rod as the anode. Set the electrolysis voltage to 3.1V and start electrolysis to obtain TiC x O y Intermediate.

[0088] (4) Preparation of high-purity titanium by deep electrolysis

[0089] When the electrolysis time reaches 5 hours and the current intensity drops to 0.4A, the electrode adjustment is performed. x O y The intermediate is used as a new anode, and a titanium rod (5 mm in diameter, polished with 1000-grit sandpaper to remove the oxide film on the surface before use, and then cleaned with alcohol and dried) is used as a new cathode. A constant current of 0.6 A / cm2 is used to continue deep electrolysis to obtain high-purity titanium. The duration of deep electrolysis is 7 hours to ensure the full reduction of titanium ions and further improvement of purity.

[0090] (5) Product processing

[0091] After the electrolysis is completed, turn off the power and wait for the electrolytic cell to cool to room temperature. Then, take out the cathode product (i.e., high-purity titanium product), and clean and dry it. The purpose of cleaning is to remove the molten salt and impurities attached to the surface of the titanium product, while the drying process is to ensure the dry state of the titanium product for subsequent storage and use. Finally, the purity of the obtained metallic titanium was measured to be 99.9167% through component analysis, meeting the high purity requirements.

[0092] Comparative Example 1

[0093] Comparative Example 1 provides a method for preparing metallic titanium by molten salt electrolysis (electrolytic deoxidation of TiO2 in CaCl2 molten salt), comprising the following steps:

[0094] (1) Preparation of TiO2 electrode: After the TiO2 powder is mixed with the binder, the raw material powder is pressed into a flaky powder block using a mold, where the molding pressure is 400kg / cm 2 The flaky powder block was then sintered in an argon atmosphere at 1000° C. to obtain a flaky TiO2 electrode.

[0095] (2) Preparation of CaCl2 molten salt electrolyte: Melt CaCl2 in a vacuum electrolytic furnace at 600°C and dehydrate for 2 h. When cooled to 150°C, take it out and seal it for storage.

[0096] (3) The CaCl2 molten salt electrolyte prepared above was placed in an electrolytic cell and heated to 900°C under an inert atmosphere. After the electrolyte was completely melted, the prepared TiO2 flake electrode was used as the cathode and the high-purity graphite rod was used as the anode. The voltage was set to 3.2V and the electrolysis was started for 9 hours.

[0097] (4) After the electrolysis is completed, the cathode product is cleaned and dried.

[0098] The analysis showed that the cathode product was mainly low-valent oxide of titanium Ti6O.

[0099] Comparative Example 2

[0100] Comparative Example 2 provides a method for preparing metallic titanium by molten salt electrolysis (electrolytic deoxidation of a TiO2-C electrode in a CaCl2 molten salt), comprising the following steps:

[0101] (1) Preparation of TiO2-C flaky electrode: TiO2 powder and C powder were weighed and mixed in a mass ratio of 90:10, a binder was added, and the raw powder was pressed into a flaky powder block using a mold, wherein the molding pressure was 400 kg / cm 2 The flaky powder block was then sintered in an argon atmosphere at 1000° C. to obtain a flaky TiO2-C electrode.

[0102] (2) Preparation of CaCl2 molten salt electrolyte: Melt CaCl2 in a vacuum electrolytic furnace at 600°C and dehydrate for 2 h. When cooled to 150°C, take it out and seal it for storage.

[0103] (3) The CaCl2 molten salt electrolyte prepared above was placed in an electrolytic cell and heated to 900°C under an inert atmosphere. After the electrolyte was completely melted, the prepared flaky TiO2-C electrode was used as the cathode and the high-purity graphite rod was used as the anode. The voltage was set to 3.2V and the electrolysis was started for 9 hours.

[0104] (4) After the electrolysis is completed, the cathode product is cleaned and dried.

[0105] The analysis shows that the cathode product is mainly composed of titanium low-valent oxides Ti6O and TiC.

[0106] 2. Data Analysis

[0107] Table 1 is a comparison of the oxygen content of the products of Examples 1 to 3 and Comparative Examples 1 to 2.

[0108] Table 1 Comparison of oxygen content of products of Examples 1 to 3 and Comparative Examples 1 to 2

[0109]

[0110] From the comparison of Examples 1 to 3, it can be seen that the effect of KF on molten salt modification is to increase the solubility of titanium ions, which will increase the purity of the titanium product we finally obtain, but will sacrifice some current efficiency. The effect of KCl on molten salt modification is to improve its wettability, which reduces the carbon deposition reaction and improves the current efficiency, so that TiC x O y The electrolysis time required for the intermediate is reduced, but KCl will reduce the solubility of the molten salt to titanium ions, resulting in a lower purity of the final titanium product.

[0111] Figure 3 The cathode product XRD spectra of Example 1, Comparative Example 1 and Comparative Example 2 of the present invention are shown. By comparing Example 1 with Comparative Examples 1-2, it can be seen that Example 1 produces high-purity titanium metal, but the cathode products obtained in Comparative Examples 1-2 are low-valent oxides of titanium Ti6O and TiC, and high-purity titanium metal cannot be effectively prepared. It can be seen that electrolytic deoxidation of TiO2 in CaCl2 molten salt or electrolytic deoxidation of TiO2-C electrode in CaCl2 molten salt cannot produce high-purity titanium metal.

[0112] In summary, the process for preparing high-purity titanium metal by molten salt electrolysis of the present invention can efficiently prepare titanium metal products with higher purity, and the purity of the product is closely related to the process systems such as electrode composition, electrode scheduling and molten salt composition.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing high-purity titanium metal by one-step molten salt electrolysis, characterized in that: The following steps are involved: (1) After the TiO2 powder and the C powder are mixed evenly, a binder is added and mixed evenly, and then the raw powder is pressed into a flaky powder block embryo, and then the flaky powder block embryo is placed in an inert atmosphere for sintering to obtain a flaky TiO2-C electrode; (2) After the powdered CaCl2, KCl and KF are mixed evenly, they are melted and dehydrated under vacuum conditions, cooled to 140-160°C, taken out and sealed for storage, thereby obtaining a molten salt electrolyte; (3) The molten salt electrolyte obtained in step (2) is placed in an electrolytic cell, and the temperature is raised to 700-1000° C. under an inert atmosphere. After the electrolyte is completely melted, the flaky TiO2-C electrode obtained in step (1) is used as a cathode and a graphite rod is used as an anode to perform electrolysis to obtain TiC x O y Intermediates; (4) When the electrolysis time reaches 0.5 to 24 hours and the current intensity drops to 0.2 to 0.6 A and remains stable, adjust the electrode; x O y The intermediate is used as a new anode and the metal titanium rod is used as a new cathode to continue deep electrolysis for 4 to 24 hours. The cathode product is dried and washed to obtain high-purity metal titanium.

2. The method for preparing high-purity titanium metal by one-step molten salt electrolysis according to claim 1, characterized in that: In the step (1), the mass ratio of TiO2 powder to C powder is 80-90:10-20.

3. The method for preparing high-purity titanium by one-step molten salt electrolysis according to claim 1, characterized in that: In the step (1), the molding pressure is 200-400 kg / cm 2 .

4. The method for preparing high-purity titanium by one-step molten salt electrolysis according to claim 1, characterized in that: In the step (1), the sintering temperature is 800-1100°C.

5. The method for preparing high-purity titanium by one-step molten salt electrolysis according to claim 1, characterized in that: In the step (2), the mass ratio of CaCl2:KCl:KF is 70-100:0-30:0-30.

6. The method for preparing high-purity titanium by one-step molten salt electrolysis according to claim 1, characterized in that: In the step (3), the voltage of electrolysis is 2.9 to 3.2V.

7. The method for preparing high-purity titanium by one-step molten salt electrolysis according to claim 1, characterized in that: In the step (4), the cathode current density of deep electrolysis is 0.2 to 1 A / cm2.

8. The method for preparing high-purity titanium by one-step molten salt electrolysis according to claim 1, characterized in that: In the step (2), the melting temperature is 600-700° C. and the dehydration time is 2-3 hours.

9. The method for preparing high-purity titanium by one-step molten salt electrolysis according to claim 1, characterized in that: In the step (4), the metal titanium rod has a diameter of 5 mm and is polished with 1000-mesh sandpaper to remove the oxide film on the surface before use, and is then cleaned with alcohol and dried.

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