CN100415940C - Method for producing pure titanium by anodic electrolysis of titanium monoxide/titanium carbide soluble solid solution - Google Patents

Abstract

The invention provides a method for preparing pure titanium by direct electrolysis of a solid solution anode TiO·mTiC with metal conductivity, using carbon and titanium dioxide or titanium carbide and titanium dioxide as raw materials, mixing them into powder according to stoichiometric reaction, and then pressing and forming, at 600 The vacuum reaction in the temperature range of ℃ ~ 1600 ℃ makes TiO·mTiC anode with metal conductivity. Use molten halide salts of alkali metals or alkaline earth metals as the electrolyte, and electrolyze at a temperature of 400 ° C to 1000 ° C; during the electrolysis process, the carbon and oxygen contained in the anode form carbon oxide gas CO, CO ₂ or oxygen, and at the same time titanium Enter the molten salt in the form of low-valent ions and deposit pure titanium at the cathode. The invention has the advantages that: the electrolysis process is carried out continuously, no anode slime is generated, and the process is simple.

Description

Method for producing pure titanium by anodic electrolysis of titanium monoxide/titanium carbide soluble solid solution

technical field

The invention belongs to the technical field of producing pure titanium by electrolysis, and in particular provides a method for producing pure titanium by anode electrolysis of titanium monoxide/titanium carbide soluble solid solution. The soluble anode TiO·mTiC (where 0≤m≤1) is directly electrolyzed in alkali metal and/or alkaline earth metal halide molten salt to prepare pure titanium. In this method, the carbon and oxygen contained in the anode are dissolved in carbon oxide gas ( CO, CO ₂ ) or oxygen is released, and titanium dissolves into the molten salt in the form of low-valent ions and is deposited on the cathode to obtain pure titanium. By adopting the method, the technological process of continuous electrolytic production of pure titanium can be completed under the premise of no anode slime, and the production cost of titanium metal will be greatly reduced.

Background technique

Metal titanium has excellent physical and chemical properties, its density is 43% lower than steel, high specific strength, high melting point, high temperature corrosion resistance and non-toxic. At present, titanium has become an excellent lightweight structural material, a new functional material and an important biomedical material. Titanium has been widely used in civilian fields such as aerospace, military industry and chemical industry, shipbuilding, automobiles, sports equipment, medical equipment, and construction. It has been hailed as "future metal" and "third metal". However, the price of titanium greatly limits the utilization of titanium. Although titanium is abundant in the earth's crust (0.44%, ranking 8th among all metal elements, second only to magnesium's 2.0%), due to the current metallurgical process of titanium cumbersome, making it impossible to lower the price.

At present, the mainstream production process of titanium metal is the Kroll method, and the sponge titanium produced can be purified by electron beam melting. The process of producing titanium metal by the Kroll method is firstly to prepare titanium tetrachloride (TiCl ₄ ) by adding carbon to titanium dioxide, and then use metal magnesium to obtain sponge titanium through thermal reduction, while metal magnesium is obtained by electrolysis of magnesium chloride. The chlorine gas is used for the production of titanium chloride, so the whole production process includes three main parts: electrolysis of magnesium chloride, chlorination of titanium oxide, and magnesium thermal reduction. The steps are cumbersome and energy consumption is large, and the core magnesium thermal reduction step is intermittent. Due to these reasons, the price of metal titanium is expensive. The price of titanium sponge produced by this method is about 5.6-10.0 US$/kg, which is much higher than the price of steel, and the price per unit weight It is also more than 3 times that of metal aluminum.

In order to reduce the price of sponge titanium, in the past nearly 70 years, metallurgists from all over the world have sought new low-cost pure titanium smelting processes, including chemical thermal reduction, electrolysis and other methods.

The studied titanium electrolysis methods mainly include TiCl ₄ electrolysis and titanium oxide electrolysis (document: MVGinatta.Process for the electrolytic production of metals[P].US6074545,2000; MVGinatta, G.Orsello, R.Berruti.Method and cell for the electrolytic production of a polyvalent metal[P]. US5015342, 1991; Ni Fusheng, Lu Qingtao, Chen Shiguan. The equilibrium between titanium and low-valent chlorides in the LiCl-NaCl-KCl system. Rare Metals, .111(1984): 23-28; Du Jihong, Qi Heshu. Electrochemical Reduction of Ti(IV) in Chloride Melt. Rare Metal Materials and Engineering, 27(1998): 165-168.).

Because TiCl ₄ is a covalent bond molecule, its solubility in molten salt is low, and it is difficult to meet the needs of industrial production. In addition, titanium is a typical transition metal element. The incomplete discharge of titanium ions at the cathode and the migration of ions in different valence states between the cathode and the anode can reduce the current efficiency of the electrolysis process.

At the beginning of this century, a research team headed by DJFray at the University of Cambridge proposed a new process for producing sponge titanium by cathodic deoxidation in molten calcium chloride using _TiO2 as raw material (document: GZChen, DJFray, TWFarthing.Direct electrochemical reduction of titanium Dioxide to titanium in molten calcium chloride. Nature, 407 (2000): 361-364). This method has a lower estimated cost than the Kroll method and is considered non-toxic. Thus, the direct production of titanium sponge by oxide electrolysis has become a research hotspot in titanium metal smelting (document: GZChen, DJFray, TWFarthing.Direct electrochemical reduction of titaniumdioxide to titanium in molten calcium chloride.Nature, 407(2000):361-364; . Emerging molten salt technologies for metals production. JOM, 53(2001): 26-31; GZ Chen, DJFray. Electro-deoxidation of metal oxides. Light Metals, 2001: 1147-1151). However, recent research on the FFC process has proved that the production of sponge titanium by this method has the following problems:

(1) The use of _CaCl2 molten salt system with high oxygen solubility makes the oxygen content of the generated sponge titanium too high, and excessive electrolysis must be carried out to reduce the oxygen content, which causes the current efficiency to be extremely low;

(2) It is very inconvenient to prepare the raw material cathode. TiO ₂ is a semiconductor. In the initial stage of electrolysis, other metal materials must undertake the conduction of the electrode. If the raw material cathode is too large, it will naturally cause a large voltage drop and hinder the progress of the electrode process;

(3) The solid-phase diffusion rate of oxygen ions is too slow, resulting in polarization so that the current density of the cathode is very low, and the electrode area gradually changes with the progress of electrolysis, even if the electrolysis current is carried out in a constant potential mode, it will be reduced with TiO ₂ Therefore, it is difficult to achieve stable electrolysis in industrial production;

(4) Since the raw material TiO ₂ and the product metal titanium are the same cathode, the whole process can only be intermittent, that is to say, even if the electrolysis is successful, the electrode can only be taken out after the end of a cathode electrolysis, and after another TiO ₂ electrode is replaced Re-electrolysis.

(5) The product metal titanium is obtained by gradually reducing the raw material TiO ₂ , and most of the impurities in the raw material will enter the product metal titanium. To obtain high-purity metals, high-purity raw material TiO ₂ must be used. However, the cost of producing high-purity _TiO2 is not low, which will increase the production cost of the whole process.

Therefore, the possibility of the industrialization of the FFC process still needs to be discussed, and it is only possible to put it into practical use after solving the above problems, but in reality it is difficult to see the way to solve these problems in essence (MFLiu, ZCGuo, WCLu.An investigation into electrochemical reduction of TiO ₂ pellet. Transaction of the institute of mining and metallurgy, sectrion C. In press).

Japanese researchers Okabe and Ono also used molten calcium chloride as electrolyte to electrolyze titanium metal (document: THOkabe, M.Nakamura, T.Oishi et al.Electrochemicaldeoxidation of titanium.Met.Trans. , 24B(1993): 449-455; K.Ono, ROSuzuki.a new concept for producing Ti sponge: calciothermic reduction. JOM, 54(2002)(2): 59-61), the difference is that they did not use raw materials TiO ₂ is in direct contact with the cathode, so they believe that metal calcium is obtained by electrolysis and then reduced to obtain metal titanium. This method is a combination of electrolysis and thermal reduction. This method saves the preparation of the TiO ₂ cathode in the FFC method. Steps, but there are problems such as how to properly mix the metal calcium of the cathode product and the _TiO2 of the raw material and extract the product titanium; and the problems of other parts of the FFC method also exist in this method.

Therefore, in order to obtain high-quality titanium metal, it is still necessary to isolate oxygen from the product titanium metal, and to continuously provide the raw material titanium into the electrolyte. In fact, high-purity titanium is obtained by electrolytic refining of molten salt (mostly chloride) with sponge titanium as the anode, but these raw material anodes are obtained by the Kroll method, which means that this is just a refining process, and there is no Reductive extraction is achieved in any sense. Since TiC is a compound with metal conductivity, it can also be used as a soluble anode for molten salt electrolysis to prepare high-purity titanium. During the electrolysis process, titanium enters the molten salt in the form of low-valent ions and deposits pure titanium at the cathode. However, the residual carbon in the anode area seriously affects the electrolysis. In order to solve the problem of remaining carbon in the anode, in the 1950s, E.Wainer (document: E.Wainer.Cell feed material for the production of titanium[P].US2868703, 1959.; E.Wainer, C.Heights, O. Assignor.Production of titanium[P].US2722509, 1955.) After mixing TiC and TiO as raw materials, heat treatment at a high temperature of 2100°C to form a solid solution of TiC and TiO (TiC TiO), which is used as an anode when the chloride melts In salt electrolysis, it is found that CO gas is released from the anode and there is no remaining product (anode slime) in the anode area. After electrolysis, pure titanium can be deposited on the cathode. The TiO used here is a metal conductive compound similar to TiC, so TiC and TiO solid solutions can be used in soluble anodes similar to metals, and the anode product is carbon oxide gas (CO, CO ₂ ) under appropriate conditions, Titanium dissolves into the electrolyte in the form of ions. However, the scheme proposed by Wainer needs to use TiC and TiO as raw materials, among which TiO is not easy to prepare and control, and the solid solution melting he proposed is completed at high temperature (>2100°C) by arc melting, which obviously still exists in the sense of practical application. question.

Japanese researcher Y. Hashimoto mixed excess carbon and TiO ₂ as raw materials, made oxygen-doped titanium carbide (TiC doped by Oxygen) at high temperature (>1700°C) in the arc, and used it as an anode Electrolysis, molten salt electrolytic cathodic deposition to obtain pure titanium (document: Hashimoto Yongyan. Ti-CO alloy またはを anode and するTi の melting 塩 electrolysis. Journal of the Japanese Society for Metals, 32 (1968): 1327-1333.; Hashimoto Yongyan. チタンの烧食塩制錬におけるLow-grade (δ)-Ti-CO soluble anode のちタン anode dissolution. Journal of the Japanese Society for Metals, 35(1971): 480-486.; Extraction of anode よりのTiの. The Journal of the Japanese Society for Metals, 35(1971): 282-289. ): 487-493.; Hashimoto Yuhiko. Research on high-purity TiC powder manufacturing に关する (1st report)--TiO ₂の vacuum carbonization による fine powder TiC manufacturing について. Powder および powder metallurgy, 17(1970): 168-175. ). However, the preparation process of its anode still relies on very high temperature reducing conditions, and it does not essentially achieve the purpose of extracting titanium at low cost. Moreover, the electrolysis experiments are all based on low-oxygen titanium carbide. If the carbon content of the anode is too high, a large amount of anode slime will be generated, and continuous electrolysis cannot be carried out normally.

Contents of the invention

The object of the present invention is to: provide the method for producing pure titanium by anode electrolysis of titanium monoxide/titanium carbide soluble solid solution, that is, a kind of solid solution anode TiO mTiC (wherein 0≤m≤1) with metal conductivity directly electrolytically prepares pure titanium method. Realized the preparation of TiO mTiC (where 0≤m≤1) solid solution soluble anode with low energy consumption, and electrolyzed it in halide molten salt, the carbon and oxygen contained in the anode combined into carbon and oxygen gas (CO, CO ₂ ) The form or oxygen is released, and the contained titanium enters the molten salt in the form of low-valent ions and deposits pure titanium at the cathode.

In the present invention, carbon and titanium dioxide or titanium carbide and titanium dioxide are used as raw materials, mixed into powder according to the stoichiometric reaction, then pressed and formed, and vacuum-reacted in a temperature range of 600 ° C to 1600 ° C to produce a TiO mTiC anode with metal conductivity. , where 0≤m≤1; the molten salt of alkali metal or alkaline earth metal halide is used as the electrolyte, and electrolyzed at a temperature of 400 ° C to 1000 ° C; during the electrolysis process, the carbon and oxygen contained in the anode form carbon oxide gases CO, CO ₂ or oxygen is released, and titanium enters the molten salt in the form of low-valent ions and deposits pure titanium on the cathode; after the electrolysis is completed, the cathode product is removed at room temperature, and the chloride from the electrolyte is washed out with deionized water 5 to 8 times ; The electrolysis process is carried out continuously, and no anode slime is produced. The specific process is as follows:

1. Using stoichiometric carbon and TiO ₂ as raw materials, molding at a pressure of 100kg/cm ² to 1000kg/cm ² , the molding pressure is preferably 600kg/cm ² to 1000kg/cm ² ; at a temperature range of 600°C to 1600°C The internal vacuum reaction makes a TiO·mTiC (where 0≤m≤1) anode with metal conductivity.

2. Use carbon and titanium dioxide or titanium carbide and titanium dioxide as raw materials to uniformly mix the raw materials according to the stoichiometric ratio of the following reactions;

2TiO ₂ +4C=Ti ₂ CO+3CO

3TiO ₂ +5C＝Ti ₃ CO ₂ +4CO

4TiO ₂ +6C＝Ti ₄ CO ₃ +5CO

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TiO ₂ +C=TiO+CO

or

2TiO ₂ +4TiC＝3Ti ₂ CO+CO

4TiO ₂ +5TiC＝3Ti ₃ CO ₂ +2CO

2TiO ₂ +2TiC＝Ti ₄ CO ₃ +CO

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2TiO ₂ +TiC＝3TiO+CO

3. Using stoichiometric TiC and TiO ₂ as raw materials, molding at a pressure of 100kg/cm ² to 1000kg/cm ² , the molding pressure is preferably 600kg/cm ² to 1000kg/cm ² ; at a temperature range of 600°C to 1600°C The internal vacuum reaction makes a TiO·mTiC (where 0≤m≤1) anode with metal conductivity.

4. Select alkali metal or alkaline earth metal halide molten salt system, preferably fluoride or chloride, more preferably chloride eutectic system.

5. The TiO·mTiC (where 0≤m≤1) prepared in steps 1 and 2 is used as the anode, and a metal material is selected as the cathode, preferably titanium, carbon steel, and nickel as the cathode.

6. Use the molten salt selected in step 3 as the electrolyte, and the electrode selected in step 4 to form an electrolytic cell, and perform electrolysis at a temperature of 400°C to 1000°C.

7. The range of current density during electrolysis is: anode, 0.05A/cm ² ~ 1.00A/cm ² , preferably 0.20A/cm ² ~ 0.5A/cm ² ; cathode, 0.10A/cm ² ~ 1.00A/cm 2 ² , preferably 0.10A/cm ² to 0.4A/cm ² .

8. Continuously add soluble solid solution anode, and check the cathode product after 15 hours of electrolysis each time.

9. After the electrolysis is completed, remove the cathode product at room temperature, and wash it with deionized water six times to remove the chloride from the electrolyte.

The advantage of the present invention is that: the anode TiO mTiC (where 0≤m≤1) with metal conductivity is prepared under the condition of lower than 1600°C and electrolyzed in halide molten salt, the cathode obtains pure titanium and the anode area has no anode mud produced. In this way, a continuous electrolysis process can be completed.

Description of drawings

Fig. 1 is the X-ray diffraction diagram of the anode material prepared in Example 1 of the present invention.

Fig. 2 is an X-ray diffraction pattern of the anode material prepared in Example 2 of the present invention.

Figure 3 is a scanning electron micrograph of the cathode product of Example 3 of the present invention.

Fig. 4 is the X-ray diffraction diagram of the cathode product of Example 3 of the present invention.

Fig. 5 is the X-ray diffraction pattern of the cathode product of example 4 of the present invention

Fig. 6 is a scanning electron micrograph of the cathode product of Example 5 of the present invention.

Fig. 7 is a scanning electron micrograph of the cathode product of Example 6 of the present invention.

Detailed ways

Example 1

Anode preparation

Raw materials: carbon powder, titanium dioxide are mixed in the following reaction stoichiometric ratio.

2TiO ₂ +4C=Ti ₂ CO+3CO

Preparation process conditions (see the table below)

The electrical resistance of the pressed block was 38 ohm·cm before heat treatment, and the resistance dropped sharply to 0.1 ohm·cm after heat treatment. The elemental analysis of the material after heat treatment shows that its atomic proportion form should be Ti ₂ CO, and the structural composition of the material is analyzed by means of X-ray diffraction. The results are shown in Figure 1, and the structure of the material after heat treatment can be seen from the figure. Obvious changes, mainly TiC TiO solid solution with metal conductivity.

Example 2

Anode preparation

Raw materials: Titanium carbide, titanium dioxide powder mixed in the following reaction stoichiometric ratio.

2TiO ₂ +4TiC＝3Ti ₂ CO+CO

Preparation process conditions (see the table below)

The resistance of the pressed block was 72 ohm·cm before heat treatment, and the resistance dropped sharply to 0.05 ohm·cm after heat treatment. The structural composition of the material was analyzed by means of X-ray diffraction, and the results are shown in Figure 2. It can be seen from the figure that it is a TiC·TiO solid solution after heat treatment.

Example 3

The bulk material obtained in Example 1 is used as the anode, the carbon steel is used as the cathode, and the NaCl-KCl molten salt is used as the electrolyte for electrolysis. The specific implementation process is shown in the table below:

In order to illustrate the mechanism of the anode reaction, a gas chromatographic analysis instrument is used to detect the gas generated in the anode process during the electrolysis process. The carrier gas used is argon, and the concentrations of various gases are shown in the table below.

The data in the above table shows that carbon oxide gas is generated at the anode during the electrolysis process, and CO is the main form under the experimental conditions. After the electrolysis is completed, the cathodic deposition obtains pure titanium, which is washed with dilute hydrochloric acid (1wt%) and then cleaned with deionized water for 5 times and stored in natural drying. Calculated by Faraday's law, the cathode current efficiency is 90%; accompanying drawing 3 example 3 cathode Scanning electron micrograph of the product. Accompanying drawing 4 example 3 is the X-ray diffraction pattern of cathode product, as can be seen from the figure, cathode product has the crystal structure of pure titanium.

Example 4

The bulk material obtained in Example 2 is used as the anode, the carbon steel is used as the cathode, and the LiCl-KCl molten salt is used as the electrolyte for electrolysis. The specific implementation process is shown in the table below:

After the electrolysis is completed, the pure titanium obtained by the negative electrode is washed with dilute hydrochloric acid (1wt%) and stored for 8 times with deionized water. It is calculated by Faraday's law that the cathode current efficiency is 85%; Scanning electron microscope photo.

Example 5

Anode preparation

Raw materials: carbon powder, titanium dioxide are mixed in the following reaction stoichiometric ratio.

3TiO ₂ +5C＝Ti ₃ CO ₂ +4CO

Preparation process conditions (see the table below)

The resistance of the pressed block before heat treatment was 46 ohm·cm, and the resistance dropped sharply to 0.07 ohm·cm after heat treatment.

The block material is used as the anode, and the carbon steel is used as the cathode. NaCl-KCl molten salt is used as the electrolyte, and the electrolytic gas chromatography is used to detect the anode gas analysis results as follows:

The current efficiency calculated by Faraday's theorem is 89%, and the scanning electron microscope photo of the cathode product in Example 5 of the accompanying drawing 6. Elemental analysis results showed that the oxygen content in the cathode product was 210 ppm.

Example 6

Anode preparation

Raw materials: carbon powder, titanium dioxide are mixed in the following reaction stoichiometric ratio.

TiO ₂ +C=TiO+CO

Preparation process conditions (see the table below)

The electrical resistance of the pressed block was 43 ohm·cm before heat treatment, and the resistance dropped sharply to 0.2 ohm·cm after heat treatment.

The block material is used as the anode, the carbon steel is used as the cathode, and the LiF-NaF-KF molten salt is used as the electrolyte. The electrolysis conditions in the following table are used to detect the anode gas by electrolytic gas chromatography. The analysis results are as follows.

The current efficiency calculated by Faraday's theorem is 87%, and the scanning electron micrograph of the cathode product in Example 6 of the accompanying drawing 7. Elemental analysis results showed that the oxygen content in the cathode product was 380 ppm.

Claims (6)

1. method that titanium monoxide/titanium carbide solubility sosoloid anode electrolysis is produced pure titanium is characterized in that: with carbon and titanium dioxide or with titanium carbide and titanium dioxide is raw material, is mixed into powder by the chemical reaction metering, then with 100kg/cm ²～1000kg/cm ²Pressure forming, vacuum reaction is made the TiOmTiC anode with metallic conduction performance, wherein 0≤m≤1 in 600 ℃～1600 ℃ temperature range; Halogenide fused salt with basic metal or alkaline-earth metal is an electrolytic solution, electrolysis under 400 ℃～1000 ℃ temperature; Contained carbon and the oxygen of anode forms carbon oxide gas CO, CO in the electrolytic process ₂Or oxygen emits, and titanium enters fused salt and obtains pure titanium in cathodic deposition with the low price ionic species simultaneously; After electrolysis is finished cathode product is removed down the muriate of clearing out from electrolytic solution for 5～8 times with deionized water; This electrolytic process carries out continuously, and does not have anode sludge generation; With carbon and titanium dioxide or with titanium carbide and titanium dioxide be raw material respectively by the stoichiometric ratio of following reaction with the raw material uniform mixing;

2TiO ₂+4C＝Ti ₂CO+3CO

3TiO ₂+5C＝Ti ₃CO ₂+4CO

4TiO ₂+6C＝Ti ₄CO ₃+5CO

TiO ₂+C＝TiO+CO

Or

2TiO ₂+4TiC＝3Ti ₂CO+CO

4TiO ₂+5TiC＝3Ti ₃CO ₂+2CO

2TiO ₂+2TiC＝Ti ₄CO ₃+CO

2TiO ₂+TiC＝3TiO+CO。

2. the method for claim 1, it is characterized in that: forming pressure is 600kg/cm ²～1000kg/cm ²

3. the method for claim 1, it is characterized in that: the halogenide fused salt of described basic metal or alkaline-earth metal is fluorochemical or muriate.

4. the method for claim 1, it is characterized in that: with TiOmTiC is anode, selects a kind of metallic substance as negative electrode, described metallic substance is titanium, carbon steel or nickel.

5. the method for claim 1 is characterized in that: as electrolytic solution and electrode composition electrolyzer, the current density range during electrolysis is respectively: anode is 0.05A/cm with fused salt ²～1.00A/cm ², negative electrode is 0.10A/cm ²～1.00A/cm ²

6. the method for claim 1, it is characterized in that: the current density range during electrolysis is respectively: anode is 0.20A/cm ²～0.5A/cm ²Negative electrode is 0.10A/cm ²～0.4A/cm ²

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