CN103031577B - Method for preparing titanium and titanium obtained by the method - Google Patents

Abstract

The invention discloses a method for preparing metal titanium, wherein the method comprises the following steps: (1) contacting a molten titanium-containing raw material with a carbonaceous reducing agent, and the contacting conditions are such that titanium dioxide in the titanium-containing raw material is reduced into low-valent titanium, and obtain the titanium slag of reduction product containing low-valent titanium in molten state; Titanium-containing material; the average pore diameter of the titanium-containing material with a porous structure is 1mm-10mm, and the porosity is 20%-60%; (3) the titanium-containing material obtained in step (2) is used as the anode, and the metal is the cathode , the molten salt is used as the electrolyte, and the electrolysis is carried out under electrolytic conditions to obtain the metal titanium element. The method provided by the invention has the advantages of simple process, small anode resistivity, difficult polarization, easy electrolysis, and high purity of final cathode product metal titanium.

Description

A kind of preparation method of metal titanium and metal titanium obtained by the method

technical field

The invention relates to a method for preparing metallic titanium and metallic titanium obtained by the method.

Background technique

Titanium and titanium alloys have a series of advantages such as low density, high specific strength, good heat and low temperature resistance, good corrosion resistance, and excellent biocompatibility. Therefore, they have "future metals", "space metals" and "ocean metals". reputation.

Titanium is a rare metal, however, in fact, the abundance of titanium element in the earth's crust occupies the seventh place (0.45% by weight), which is much higher than that of many common metals. However, due to the active nature of titanium and high requirements for smelting technology, people cannot produce a large amount of titanium, so it is classified as a "rare" metal. At present, the only industrial production method of titanium metal in the world is the Kroll method, which includes the main processes of making titanium chloride containing titanium dioxide, magnesium reduction-vacuum distillation, product post-treatment, and magnesium electrolysis; its advantage is that it can realize Recycling of chlorine and magnesium, but the Kroll method has defects such as long process, low reduction rate, high price of reducing agent and intermittent operation, which leads to high production cost of titanium metal. With the continuous widening of the application of titanium metal from aerospace, military industry to civil industry, research and development of new technologies for titanium smelting to reduce the production cost of titanium metal has become a research hotspot in the titanium metallurgy industry.

So far, the production of titanium by molten salt electrolysis is considered to be the most promising production method to replace the Kroll process. Molten salt electrolysis usually includes TiO ₂ molten salt electrolysis, TiCl ₄ molten salt electrolysis, and titanium TiO ₂ carbothermal reduction product molten salt electrolysis, etc.

The typical process of TiO ₂ molten salt electrolysis is the FFC Cambridge process, that is, solid TiO ₂ is used as the cathode, graphite is used as the anode, and CaCl ₂ is used as the electrolyte. When the applied voltage is lower than the decomposition voltage of the molten salt, the oxygen on the cathode enters in the form of ions The electrolyte, which diffuses to the anode, combines with carbon to produce _CO2 or CO gas, which is emitted at the anode, while metal titanium is left on the cathode. Different from the traditional molten salt electrolysis method, the FFC process is a brand-new method that directly separates titanium metal from oxygen to obtain titanium, which has the advantages of environmental friendliness, short process flow and continuous realization; but so far, the FFC process has only It has been successful in the laboratory but has not yet been industrialized. The reason is that the FFC process has the following problems: the TiO ₂ cathode has a high resistivity and it is difficult to achieve stable electrolysis; the impurities in the cathode (TiO ₂ ) will all remain in the titanium, resulting in Qualified metal titanium products require high-purity _TiO2 as raw material, resulting in a significant increase in the cost of producing titanium.

The typical process of TiCl ₄ molten salt electrolysis is the Ginatta electrolysis process. The United States, Japan, the former Soviet Union, Italy, France, China, etc. have conducted long-term and in-depth research on it, and have also established several small factories. However, due to the actual There were problems in production, such as diaphragm damage, dendrites, etc., which failed to meet the expected technical and economic indicators, and were forced to stop production.

The typical process of molten salt electrolysis of _TiO2 carbothermal reduction products is the MER process, that is, after mixing _TiO2 and carbonaceous reducing agent by ball milling, pressing and sintering; or, after mixing _TiO2 and carbonaceous reducing agent and sintering , mixed with carbonaceous reducing agent and binder, pressed and sintered. The process is complicated, and in the process of preparing the anode, if the anode is not pressed tightly enough, it will easily fall apart and cannot meet the needs of use; if the anode is pressed too tightly, it may cause the anode to be brought into the process of electrolysis. serious problem. The anode material obtained by the above method of pressing and sintering has low porosity and porosity, which inevitably leads to limited diffusion of gases such as CO generated during the electrolysis process, and the electrolysis effect is not good.

Contents of the invention

In order to overcome the defects of complex process, limited gas diffusion, easy to cause anode polarization, and difficult to realize stable electrolysis when the existing method is used to prepare titanium metal, the present invention provides a simple process, and the gas can be easily diffused. , a method for preparing metal titanium that is not easily polarized and electrolytically stable, and the metal titanium prepared by the method.

The invention provides a method for preparing titanium metal, wherein the method comprises the following steps:

(1) contacting the molten titanium-containing raw material with a carbonaceous reducing agent under conditions such that titanium dioxide in the titanium-containing raw material is reduced to low-valent titanium, and a molten titanium slag containing low-valent titanium reduction product is obtained;

(2) cooling and molding the reduced product titanium slag containing low-valent titanium in the molten state obtained in step (1) to obtain a titanium-containing material with a porous structure; the average pore diameter of the titanium-containing material with a porous structure is 1mm- 10mm, porosity 20%-60%;

(3) The titanium-containing material obtained in step (2) is used as an anode, the metal is used as a cathode, and the molten salt is used as an electrolyte, and electrolysis is performed under electrolysis conditions to obtain metal titanium element.

In addition, the present invention also provides the elemental titanium metal prepared by the above method.

In the present invention, the molten titanium-containing raw material is contacted with a carbonaceous reducing agent, and the reduced product after contact is in a molten state by controlling the contact condition, and the molten reduced product is cooled and shaped. On the one hand, the obtained molten reduced product can be directly cooled and shaped to form an anode, without the need to mix and ball-mill titanium-containing raw materials and carbonaceous reducing agents, press into an anode and then sinter, and also do not need to combine the obtained solid reduced product with a bonded The mixture of the agent is pressed into the anode and then sintered, and the process is simple; more importantly, the inventors of the present invention unexpectedly found that the molten reduction product titanium slag obtained after contacting under the temperature and pressure of the present invention is directly cooled and formed , the formed titanium-containing material has a porous structure with an average pore diameter of 1mm-10mm and a porosity of 20%-60%, which not only ensures its demand as an anode, but also ensures that CO, CO ₂ and other gases produced by electrolysis can be In addition, the reduction product obtained by contacting titanium-containing raw materials with carbonaceous reducing agents may contain one or more of TiO, Ti ₂ O ₃ , Ti ₃ O ₅ and Ti ₄ O ₇ , by controlling the conditions The reduction product obtained after contacting is in a molten state, and the molten reduction product is directly cooled and shaped, which can ensure that the above reduction products are well dissolved together, the obtained anode components are uniform, and the electrolysis process is stable.

Other features and advantages of the present invention will be described in detail in the following detailed description.

detailed description

Specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

The preparation method of metal titanium provided by the invention comprises the following steps:

(1) contacting the molten titanium-containing raw material with a carbonaceous reducing agent under conditions such that titanium dioxide in the titanium-containing raw material is reduced to low-valent titanium, and a molten titanium slag containing low-valent titanium reduction product is obtained;

(2) cooling and molding the reduced product titanium slag containing low-valent titanium in the molten state obtained in step (1) to obtain a titanium-containing material with a porous structure; the average pore diameter of the titanium-containing material with a porous structure is 1mm- 10mm, preferably 3mm-7mm; porosity 20%-60%, preferably 40%-60%;

(3) The titanium-containing material obtained in step (2) is used as an anode, the metal is used as a cathode, and the molten salt is used as an electrolyte, and electrolysis is performed under electrolysis conditions to obtain metal titanium element.

The inventors of the present invention have discovered unexpectedly that the titanium-containing raw material in the molten state is contacted with a carbonaceous reducing agent, and by controlling the contact conditions, not only the tetravalent titanium in the titanium-containing raw material can be reduced to low-valent titanium (such as trivalent, divalent etc.), it can also ensure that the obtained product is in a molten state, and the interaction between low-valent titanium in different valence states can be well solid-solved. More importantly, after natural cooling and molding of the titanium slag, the reduction product containing low-valent titanium, the obtained titanium-containing material has a porous structure, which can effectively ensure that CO, _CO2 and other gases generated during electrolysis can It is well diffused and the electrolysis effect is very good.

Generally speaking, titanium dioxide has little or no solubility in molten salt electrolytes, so using it directly as an anode does not perform well in electrolysis. However, after reducing high-valent titanium to low-valent titanium, the low-valent reduction product can show a certain solubility in molten salt, that is, titanium ions are electrolytically eluted from the anode and reduced to metal titanium at the cathode.

According to the present invention, the purpose of contacting the titanium-containing raw material with a carbonaceous reducing agent is to reduce the high-valence state in the titanium-containing raw material to low-valent titanium, and the low-valent titanium has holes in it, making its properties between a conductor and a semiconductor Among them, it can improve the conductivity and dissolve in the molten salt electrolyte. The conditions of the contact include the temperature of the contact, the pressure of the contact and the time of the contact, wherein the conditions of the contact are as long as the titanium dioxide in the titanium-containing raw material can be reduced to low-valent titanium, and the low-valent titanium in the molten state is obtained. The reduction product of titanium valence is titanium slag. Preferably, the contact temperature can be 1650-2000°C, the contact pressure can be -100Pa to 100Pa (absolute pressure), and the contact time can be 2-10 hours; more preferably, the contact temperature is 1650-1750°C, the contact pressure is -50Pa to 50Pa (absolute pressure), and the contact time is 3-5 hours.

According to the present invention, the ratio of the amount of tetravalent titanium in the titanium-containing raw material to the amount of carbon in the carbonaceous reducing agent can vary within a wide range, but since the titanium-containing raw material usually also contains other reducing substances, such as iron Ions, etc., therefore, in order to further improve the reduction effect, the carbonaceous reducing agent often needs to be slightly excessive, preferably, in terms of titanium dioxide, the molar ratio of the tetravalent titanium in the titanium-containing raw material to the carbon in the carbonaceous reducing agent is 1:1-3, more preferably 1:1.5-2.5.

According to the present invention, the titanium-containing raw material can be selected from various existing titanium-containing raw materials, for example, the titanium-containing raw material can be titanium concentrate and/or titanium-containing slag. The titanium concentrate is extracted from ilmenite or titanomagnetite, and its main components are titanium dioxide (content: 42-65% by weight), ferric oxide (content: 5-40% by weight), Iron oxide (the content is 5-40% by weight), and other compounds containing a small amount of phosphorus, sulfur, magnesium, and calcium elements (the sum of the contents is 2-10% by weight). The titanium-containing slag refers to the residue after smelting and extracting other valuable metals from titanium-containing minerals, and its main components are titanium dioxide (15-30% by weight), calcium oxide (10-25% by weight), alumina (content is 10-20% by weight) and silicon dioxide (content is 10-28% by weight).

According to the present invention, the carbonaceous reducing agent can be various existing carbonaceous reducing agents, as long as the high-valent titanium in the titanium-containing raw material can be reduced to low-valent titanium. For example, the carbonaceous reducing agent can be selected from One or more of anthracite, bituminous coal, charcoal, coke and petroleum coke. The anthracite is the coal with the deepest degree of coalification, and has a high carbon content, which can reach more than 80% by weight; and a low volatile matter, which is less than 10% by weight. The carbon content of the bituminous coal is 75-90% by weight. The carbon content of the charcoal is 65-95% by weight. The coke refers to the bituminous coal heated to 950-1050°C under the condition of isolation from the air, and it is made through drying, pyrolysis, melting, bonding, solidification, shrinkage and other processes, and its carbon content is 75-85 weight%. The petroleum coke refers to the crude oil that is distilled to separate the light and heavy oils, and then the heavy oils are thermally cracked to convert the products. From the appearance, the cokes are black lumps of irregular shapes and sizes (or Particles) with metallic luster, the particles of coke have a porous structure, the carbon content can reach more than 90% by weight, and the rest are hydrogen, oxygen, nitrogen, sulfur and metal elements.

The present invention has no particular limitation on the type of metal used as the cathode, as long as it can be used in conjunction with the anode of the present invention to electrolyze the metal titanium element. However, in order to increase the service life of the anode and improve the purity of the titanium metal obtained, preferably, the metal used as the cathode can be selected from one or more of carbon steel, molybdenum, copper and nickel.

Generally speaking, an electrolyte refers to a compound that can conduct electricity (electrolyte dissociate into cations and anions) when dissolved in an aqueous solution or in a molten state. In the present invention, in order to increase the concentration of the obtained metal titanium element and reduce the introduction of impurities, molten salt is used as the electrolyte. Preferably, the molten salt is a molten salt formed by melting alkali metal chlorides and/or alkaline earth metal chlorides.

According to the present invention, although the electrolysis conditions will not have a significant impact on the purity of the obtained titanium metal, in order to balance efficiency and yield, preferably, the electrolysis conditions include an anode current density of 0.05-2A/cm ² , The cathode current density is 0.05-2A/cm ² ; more preferably, the anode current density is 0.1-1A/cm ² , and the cathode current density is 0.1-1A/cm ² .

According to the present invention, the temperature of the molten salt, that is, the temperature of electrolysis can vary in a wide range, as long as it is higher than the melting point of the salt forming the molten salt and lower than the gasification temperature and decomposition temperature of the salt forming the molten salt. Yes, for example, the temperature of the electrolysis may be 600-900°C, preferably 600-800°C. The time of electrolysis can be reasonably selected according to the amount of low-valent titanium to be electrolyzed and the conditions of electrolysis, so that at least 90% of the low-valent titanium is transformed into metallic titanium element.

According to the present invention, the metal titanium produced by electrolysis is easy to react with oxygen in the air at the electrolysis temperature. Therefore, in order to improve the purity of the obtained metal titanium, preferably, the electrolysis is carried out in an inert gas. The inert gas may be selected from one or more of nitrogen and group zero gases of the periodic table, preferably argon.

In addition, the present invention also provides metal titanium prepared by the above method.

The present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

In addition, various combinations of different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the idea of the present invention, they should also be regarded as the disclosed content of the present invention.

The present invention will be described in more detail by way of examples below.

In the examples and comparative examples, the average pore diameter of the titanium-containing material was measured using a scanning electron microscope (purchased from Hitachi, model number S-4700); and the corresponding porosity was measured using a nitrogen adsorption method.

Example 1

This example is used to illustrate the preparation of the titanium metal element provided by the present invention.

The Panzhihua titanium concentrate of 100g molten state (wherein, the content of TiO ₂ is 47.5% by weight, the content of Fe ₂ O ₃ is 5.74% by weight, the content of FeO is 34.48% by weight, the content of CaO is 1.42% by weight, the content of MgO content is 6.22% by weight) and 14g of anthracite (wherein, the content of carbon is 78.5% by weight) are added in the electric furnace, and the temperature is 1750 ℃, the pressure is -50Pa (absolute pressure) under the condition of smelting for 5 hours, obtain molten titanium slag . The above molten titanium slag was injected into a Φ400×600 cast steel mold, cooled and formed to obtain a titanium-containing material with a porous structure, wherein the average pore diameter of the titanium-containing material was 5.75mm, and the porosity was 45%. The titanium-containing material is used as the anode, the Φ80×600 carbon steel rod is used as the cathode, and NaCl-KCl is used as the molten salt electrolyte, and the electrolysis is performed at 820°C for 300 minutes under the protection of argon, and the anode current density is 0.2A/cm ² , the cathode current density is 0.2A/cm ² . After the electrolysis is completed, the negative electrode is taken out, cooled naturally, washed with 0.5% by weight of dilute hydrochloric acid and deionized water, and dried to obtain 22.5 g of the product containing the elemental titanium metal. The elemental composition of the product is as follows: the content of Ti is 98.5% by weight, the content of Fe is 0.95% by weight, the content of O is 0.37% by weight, and the content of H is 0.18% by weight.

Example 2

This example is used to illustrate the preparation of the titanium metal element provided by the present invention.

The Panzhihua titanium concentrate of 60g molten state (wherein, the content of TiO ₂ is 47.5% by weight, the content of Fe ₂ O ₃ is 5.74% by weight, the content of FeO is 34.48% by weight, the content of CaO is 1.42% by weight, the content of MgO content is 6.22% by weight), 40g of Yunnan titanium concentrate (wherein, the content of TiO ₂ is 49.85% by weight, the content of Fe ₂ O ₃ is 9.68% by weight, the content of FeO is 36.50% by weight, and the content of CaO is 0.24% by weight %, the content of MgO is 1.99% by weight) and 20g of anthracite (wherein, the content of carbon is 78.5% by weight) is added in the electric furnace, and the temperature is 1650 ℃, and the pressure is smelting under the condition of 50Pa (absolute pressure) for 3 hours to obtain molten titanium slag. The above-mentioned titanium slag was injected into a Φ300×600 cast steel mold, cooled and formed to obtain a titanium-containing material with a porous structure, wherein the average pore diameter of the titanium-containing material was 6.5mm, and the porosity was 55.3%. The titanium-containing material was used as the anode, the Φ60×600 carbon steel rod was used as the cathode, and NaCl-KCl was used as the molten salt electrolyte, and electrolyzed at 900°C for 300 minutes under an inert atmosphere, wherein the anode current density was 2A/cm ² , and the cathode current density 1A/cm ² . After the electrolysis was completed, the negative electrode was taken out, cooled naturally, washed with 0.5% by weight of dilute hydrochloric acid and deionized water, and dried to obtain 23 g of the product containing the elemental titanium metal. The element composition of the product was as follows: the content of Ti was 97.78% by weight, the content of Fe was 0.85% by weight, the content of O was 1.25% by weight, and the content of H was 0.12% by weight.

Example 3

This example is used to illustrate the preparation of the titanium metal element provided by the present invention.

With 100g molten Yunnan titanium concentrate (wherein, the content of TiO ₂ is 49.85% by weight, the content of Fe ₂ O ₃ is 9.68% by weight, the content of FeO is 36.50% by weight, the content of CaO is 0.24% by weight, the content of MgO Content is 1.99% by weight) and 22g of coke (wherein, the content of carbon is 85.5% by weight) is added in the electric furnace, is smelted under the condition of temperature 1700 ℃, pressure is 5Pa (absolute pressure) 4 hours, obtains molten titanium slag. The above-mentioned titanium slag was injected into a Φ200×400 cast steel mold, cooled and formed to obtain a titanium-containing material with a porous structure, wherein the average pore diameter of the titanium-containing material was 3.5mm, and the porosity was 60%. The titanium-containing material is used as the anode, the Φ50×400 carbon steel rod is used as the cathode, and NaCl-KCl is used as the molten salt electrolyte, and electrolyzed at 850°C for 210 minutes under an inert atmosphere, wherein the anode current density is 1A/cm ² , and the cathode current density It is 1.5A/cm ² . After the electrolysis was completed, the cathode was taken out, cooled naturally, washed and dried with 0.5% by weight of dilute hydrochloric acid and deionized water, and dried to obtain 23.5 g of a product containing elemental titanium metal, which was measured by X-ray fluorescence analysis. The elemental composition of the product is as follows: the content of Ti is 98.28% by weight, the content of Fe is 0.55% by weight, the content of O is 1.05% by weight, and the content of H is 0.12% by weight.

Example 4

This example is used to illustrate the preparation of the titanium metal element provided by the present invention.

Titanium metal was prepared according to the method of Example 2, except that the temperature at which the molten Panzhihua titanium concentrate was in contact with anthracite was 1600°C. After the electrolysis is completed, the negative electrode is taken out, cooled naturally, washed with 0.5% by weight of dilute hydrochloric acid and deionized water, and dried to obtain 20 g of the product containing the elemental titanium metal, which is measured by semi-quantitative analysis. The elemental composition of the alloy is as follows: the content of Ti is 97.5% by weight, the content of Fe is 1.55% by weight, the content of O is 1.25% by weight, and the content of H is 0.12% by weight.

Comparative example 1

This comparative example is used to illustrate the preparation of the reference metal titanium element.

Metal titanium was prepared according to the method of Example 1, the difference was that the anode used for the preparation of metal titanium was prepared by the following method:

With 100g Panzhihua titanium concentrate (wherein, the content of TiO ₂ is 47.5% by weight, the content of Fe ₂ O ₃ is 5.74% by weight, the content of FeO is 34.48% by weight, the content of CaO is 1.42% by weight, and the content of MgO is 6.22% by weight. % by weight) and 14g of anthracite (wherein, the carbon content is 78.5% by weight) are added in the electric furnace, and the temperature is 1750 ℃, and the pressure is smelting under the condition of -50Pa (absolute pressure) for 5 hours to obtain molten titanium slag. The obtained molten titanium slag was cooled and put into a Φ400×600 cast steel mold, and pressed under a pressure of 50,000 psi to obtain a titanium-containing material. Wherein, the average pore diameter of the titanium-containing material is 200 nm, and the porosity is 10%. After the electrolysis was completed, the negative electrode was taken out, cooled naturally, washed and dried with 0.5% by weight of dilute hydrochloric acid and deionized water, and dried to obtain 11.9 g of a product containing elemental titanium metal, which was measured by X-ray fluorescence analysis. The element composition of the product is as follows: the content of Ti is 97% by weight, the content of Fe is 1.95% by weight, the content of O is 0.57% by weight, and the content of H is 0.48% by weight.

Comparative example 2

This comparative example is used to illustrate the preparation of the reference metal titanium element.

Metal titanium was prepared according to the method of Example 1, the difference was that the anode used for the preparation of metal titanium was prepared by the following method:

With 100g Panzhihua titanium concentrate (wherein, the content of TiO ₂ is 47.5% by weight, the content of Fe ₂ O ₃ is 5.74% by weight, the content of FeO is 34.48% by weight, the content of CaO is 1.42% by weight, and the content of MgO is 6.22% by weight. % by weight) and 14g of anthracite (wherein, the content of carbon is 78.5% by weight) are ball-milled in a ball mill tank for 60min, injected into a cast steel mold of Φ200×400, pressed and formed under a pressure of 50,000psi, at 1750°C, pressure The titanium-containing material was obtained by sintering for 5 hours under the condition of -50 Pa (absolute pressure). Wherein, the average pore diameter of the titanium-containing material is 300 nm, and the porosity is 15%. After the electrolysis was completed, the negative electrode was taken out, cooled naturally, washed and dried with 0.5% by weight of dilute hydrochloric acid and deionized water, and dried to obtain 12.1 g of a product containing elemental titanium metal, which was measured by X-ray fluorescence analysis. The elemental composition of the product is as follows: the content of Ti is 97.08% by weight, the content of Fe is 1.45% by weight, the content of O is 0.57% by weight, and the content of H is 0.48% by weight.

Claims (9)

1. a preparation method of metal titanium, is characterized in that, the method comprises the following steps: (1) contacting the molten titanium-containing raw material with a carbonaceous reducing agent under conditions such that titanium dioxide in the titanium-containing raw material is reduced to low-valent titanium, and a molten titanium slag containing low-valent titanium reduction product is obtained; (2) cooling and molding the reduced product titanium slag containing low-valent titanium in the molten state obtained in step (1) to obtain a titanium-containing material with a porous structure; the average pore diameter of the titanium-containing material with a porous structure is 1mm- 10mm, porosity 20%-60%; (3) The titanium-containing material obtained in step (2) is used as an anode, the metal is used as a cathode, and the molten salt is used as an electrolyte, and electrolysis is performed under electrolysis conditions to obtain metal titanium. 2. method according to claim 1, wherein, in step (1), the condition of described contact comprises: the temperature of contact is 1650-2000 ℃; The absolute pressure of contact is-100Pa to 100Pa; The time of contact is 2 -10 hours. 3. The method according to claim 1, wherein, in step (1), in terms of titanium dioxide, the mol ratio of the tetravalent titanium in the titanium-containing raw material and the carbon in the carbonaceous reducing agent is 1:1-3 . 4. The method according to claim 1 or 3, wherein, in step (1), the titanium-containing raw material is titanium concentrate and/or titanium-containing slag. 5. The method according to claim 1 or 3, wherein, in step (1), the carbonaceous reducing agent is selected from one or more of anthracite, bituminous coal, charcoal, coke and petroleum coke. 6. The method according to claim 1, wherein, in step (2), the average pore diameter of the titanium-containing material having a porous structure is 3mm-7mm, and the porosity is 40%-60%. 7. The method according to claim 1, wherein, in step (3), the metal as the cathode is selected from one or more of carbon steel, molybdenum, copper and nickel. 8. The method according to claim 1, wherein, in step (3), the molten salt is an alkali metal chloride and/or an alkaline earth metal chloride in a molten state. 9. The method according to claim 1, wherein, in step (3), the electrolysis conditions include that the anode current density is 0.05-2A/cm ² ; the cathode current density is 0.05-2A/cm ² ; the electrolysis temperature is 600 -900°C.