CN115747889B - A method for preparing an electrolyte for titanium electrolytic refining and a method for electrolytic titanium extraction - Google Patents

Abstract

The present invention provides a method for preparing an electrolyte for titanium electrolytic refining, comprising the following steps: (1) mixing molybdenum pentachloride with a mixture of one or more alkali metal halides and/or alkaline earth metal halides and melting to obtain a matrix molten salt; (2) adding titanium carbide to the matrix molten salt for heat preservation treatment, and obtaining a reactant after reaction; (3) performing solid-liquid separation on the reactant to obtain a molten mixture, and using the molten mixture as an electrolyte for titanium electrolytic refining. The present invention also provides a method for electrolytic titanium extraction, wherein the obtained titanium electrolytic refining electrolyte is electrolyzed to obtain metallic titanium at the cathode. The method of the present invention does not use TiCl ₄ , thereby avoiding TiCl ₄ from corroding the reactor material and causing electrolyte contamination, and thus it is not easy to introduce other impurities. Titanium carbide is used as a Ti ion introduction source, and its chemical properties are more stable than TiCl ₄ , and the operation is safer and easier to implement. The titanium carbide used is lower in cost than sponge titanium, and the comprehensive preparation cost of the electrolyte is reduced by about 40%.

Description

A method for preparing an electrolyte for titanium electrolytic refining and a method for electrolytic titanium extraction

Technical Field

The invention belongs to the technical field of rare metal refining, and specifically relates to a method for preparing an electrolyte for titanium electrolytic refining. The invention also relates to a method for electrolytically extracting titanium using the electrolyte for titanium electrolytic refining.

Background Art

Molten salt electrolysis to extract titanium or molten salt electrorefining to prepare high-purity titanium usually uses titanium-containing compounds, crude titanium, etc. as soluble anodes, a molten salt mixture containing low-valent titanium ions as an electrolyte, and a metal material as a cathode. During the electrolysis process, the titanium in the soluble anode enters the molten salt in the form of ions. Under the action of direct current, titanium ions are electrochemically deposited at the cathode to obtain high-purity metallic titanium or titanium powder, while impurities remain in the anode or electrolyte, so as to achieve the purpose of extracting or purifying metallic titanium.

The medium for realizing this process - molten salt electrolyte is usually an alkali metal or alkaline earth metal halide containing a certain amount of low-valent ions. One or more alkali metals or alkaline earth metal halides are used as the matrix molten salt. In order to ensure the quality of cathode titanium precipitation obtained in the titanium extraction or refining process, low-valent titanium ions need to be introduced into the matrix molten salt before electrolysis. For example, the electrolyte preparation method involved in the disclosed patent document CN201410126996.0 is: using NaCl-KCl as the matrix molten salt, _TiCl4 is used to react with sponge titanium in the matrix molten salt to introduce low-valent titanium ions into the electrolyte to form a molten salt electrolyte. The process includes the following main reactions:

Ti+3TiCl ₄ =4TiCl ₃

Ti+TiCl ₄ =2TiCl ₂

The above reaction is usually carried out at a temperature above 700°C. At high temperatures, _TiCl4 vaporizes into gas, which is very easy to corrode the conduit material and reactor material, causing electrolyte pollution. Moreover, _TiCl4 is a hazardous chemical, which is prone to leakage and smoke accidents during use, and is extremely difficult to control. Furthermore, during preparation, due to the low efficiency of the gas-solid reaction, gaseous _TiCl4 is easy to emerge from the molten salt and be discharged to the outside of the reactor with the tail gas, and the utilization rate is low. In addition, since sponge titanium is used as a reaction raw material, the cost is relatively high.

Therefore, a safe and effective method for extracting titanium is urgently needed.

Summary of the invention

In view of the shortcomings of the prior art, the present invention aims to provide a method for preparing an electrolyte for titanium electrolytic refining, and the present invention also relates to a method for electrolytically extracting titanium using the electrolyte for titanium electrolytic refining. More specifically, the present invention relates to a method for obtaining an electrolyte for electrolytic refining titanium by reacting molybdenum pentachloride with titanium carbide to introduce low-valent titanium ions (Ti ²⁺ , Ti ³⁺ ) into a matrix molten salt, and also relates to a method for electrolytically extracting titanium using the electrolyte.

In order to achieve the above object, the present invention adopts the following technical solutions:

The present invention provides a method for preparing an electrolyte for titanium electrolytic refining, comprising the following steps:

(1) mixing molybdenum pentachloride with a mixture of one or more alkali metal halides and/or alkaline earth metal halides and melting the mixture to obtain a matrix molten salt;

(2) adding titanium carbide to the matrix molten salt for heat preservation treatment, and obtaining a reactant after reaction;

(3) The reactants are subjected to solid-liquid separation to obtain a molten mixture, and the molten mixture is used as an electrolyte for titanium electrolytic refining.

Furthermore, in step (1), the mass concentration C of molybdenum pentachloride in the matrix molten salt is: 0<C≤28%.

Furthermore, in step (1),

The alkali metal halide is a fluoride and/or chloride of an alkali metal;

The alkaline earth metal halide is a fluoride and/or chloride of an alkaline earth metal.

Further,

The alkali metal fluoride is selected from one or more of lithium, sodium and potassium fluorides; the alkali metal chloride is selected from one or more of lithium, sodium and potassium chlorides;

The alkaline earth metal fluoride is selected from one or more of the fluorides of magnesium, barium and calcium; the alkaline earth metal chloride is selected from one or more of the chlorides of magnesium, barium and calcium.

Furthermore, at least two alkali metal chlorides are mixed with molybdenum pentachloride and melted to form a matrix molten salt, wherein the mixture of at least two alkali metal chlorides is a mixture of KCl and NaCl or LiCl.

Furthermore, in step (2), the molar ratio of the titanium carbide to the molybdenum pentachloride in the matrix molten salt is 1.7:1-3:1.

Furthermore, in step (2), the temperature of the heat preservation treatment is 460-1050° C., and the heat preservation reaction time is 1-4 hours.

Furthermore, in step (3), solid-liquid separation is performed by hot filtration or static sedimentation.

The present invention also provides a method for extracting titanium by electrolysis, wherein the electrolyte for titanium electrolytic refining obtained above is electrolyzed to obtain metallic titanium at the cathode.

Furthermore, the electrolysis process is carried out in a closed electrolytic cell, the anode of the electrolytic cell is sponge titanium or carbon oxytitanium or a titanium rod, and the cathode is a carbon steel rod or a stainless steel rod or a titanium rod.

Compared with the prior art, the beneficial technical effects of the present invention are as follows: the method of the present invention does not use TiCl ₄ , thus avoiding TiCl ₄ from corroding the reactor material and causing electrolyte contamination, and thus not easily introducing other impurities. Secondly, titanium carbide is used as the Ti ion introduction source, which has a more stable chemical property than TiCl ₄ , and is safer and easier to operate. Furthermore, the titanium carbide used is less expensive than titanium sponge, and the comprehensive preparation cost of the electrolyte is reduced by about 40%.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

FIG. 1 is a schematic process flow chart of a method for preparing an electrolyte for titanium electrolytic refining and a method for electrolytically extracting titanium using the electrolyte for titanium electrolytic refining according to the present invention.

DETAILED DESCRIPTION

In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

The endpoints and any values of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article.

As shown in FIG1 , the present invention provides a method for preparing an electrolyte for titanium electrolytic refining, comprising the following steps:

(1) Molybdenum pentachloride is mixed with a mixture of one or more alkali metal halides and/or alkaline earth metal halides and melted to obtain a matrix molten salt.

(2) Adding titanium carbide to the matrix molten salt for heat preservation treatment, and obtaining a reactant after reaction.

(3) The reactants are subjected to solid-liquid separation to obtain a molten mixture, and the molten mixture is used as an electrolyte for titanium electrolytic refining.

In step (1), the mass concentration C of molybdenum pentachloride in the matrix molten salt is: 0<C≤28%. Controlling a reasonable mass concentration range of molybdenum pentachloride is conducive to reacting with titanium carbide added in step (2). If the concentration of molybdenum pentachloride is too high, it is easy to volatilize and lose.

In step (1), the alkali metal halide is a fluoride and/or chloride of an alkali metal, and the alkaline earth metal halide is a fluoride and/or chloride of an alkaline earth metal. In a preferred embodiment, the fluoride of the alkali metal is selected from one or more of the fluorides of lithium, sodium, and potassium, and the chloride of the alkali metal is selected from one or more of the chlorides of lithium, sodium, and potassium. The fluoride of the alkaline earth metal is selected from one or more of the fluorides of magnesium, barium, and calcium, and the chloride of the alkaline earth metal is selected from one or more of the chlorides of magnesium, barium, and calcium.

Because single-component salts generally have higher melting points, two or more salts have a eutectic point, which can reduce the melting point of the mixed salt. Therefore, for example, molybdenum pentachloride can be mixed with two or more alkali metal chlorides and melted as a matrix molten salt. In a preferred embodiment, for example, the mixture of at least two alkali metal chlorides is a mixture of KCl and NaCl or LiCl.

In step (2), the molar ratio of titanium carbide to molybdenum pentachloride in the matrix molten salt is 1.7:1-3:1, the temperature of the insulation treatment is 460-1050° C., and the insulation reaction time is 1-4 hours.

Titanium carbide and molybdenum pentachloride react mainly according to the following three reaction equations:

MoCl ₅ +5/3TiC＝5/3TiCl ₃ +Mo+5/3C

MoCl ₅ +2.5TiC=2.5TiCl ₂ +Mo+2.5C

MoCl ₅ +1.25TiC=1.25TiCl ₄ +Mo+1.25C

In step (3), solid-liquid separation is performed by hot filtration (for example, filtering using a metal nickel wire mesh) or static sedimentation to remove the solid phase metal molybdenum and carbon generated in the reaction in step (2), and finally an electrolyte containing low-valent titanium ions for titanium electrolytic refining is obtained.

As shown in Figure 1, the present invention also provides a method for electrolytic titanium extraction, which is to electrolyze the electrolyte for titanium electrolytic refining obtained above, so as to obtain metallic titanium at the cathode. In a preferred embodiment, the electrolysis process is carried out in a closed electrolytic cell, the anode of the electrolytic cell is sponge titanium or carbon oxytitanium or a titanium rod, and the cathode is a carbon steel rod or a stainless steel rod or a titanium rod.

The present invention is described in detail below by way of examples, but the protection scope of the present invention is not limited thereto.

Example 1

Weigh 800 g of NaCl and KCl in an equal molar ratio after drying and 141 g of MoCl _{5 5} , mix them evenly and melt them in a closed electrolytic cell under the protection of inert gas to obtain a matrix molten salt, wherein the mass concentration C of molybdenum pentachloride in the matrix molten salt is 14.98%.

92.8 g of titanium carbide (the molar ratio of titanium carbide to molybdenum pentachloride is 3:1) was added to the above-mentioned matrix molten salt, and the mixture was kept at 750° C. for 4 h. During the process, argon was bubbled in the molten salt for stirring. After the heat preservation reaction was completed, the reactant was obtained.

The reactant is subjected to heat filtration and solid-liquid separation to obtain a molten mixture, which is used as an electrolyte for titanium electrolytic refining, and an electrolytic cell is formed with sponge titanium as an anode and a carbon steel rod as a cathode to obtain metallic titanium with a purity greater than 99.5%.

Example 2

1120g LiCl, 1960g KCl and 53.3g MoCl ₅ after drying are mixed evenly, and melted in a closed electrolytic cell under the protection of inert gas to obtain a matrix molten salt, wherein the mass concentration C of molybdenum pentachloride in the matrix molten salt is 1.7%.

23.4 g of titanium carbide (the molar ratio of titanium carbide to molybdenum pentachloride is 2:1) was added to the above-mentioned matrix molten salt, and the mixture was kept at 460° C. for 4 h. During the process, argon gas was bubbled in the molten salt for stirring. After the heat preservation reaction was completed, the reactant was obtained.

The reactant is subjected to heat filtration and solid-liquid separation to obtain a molten mixture, which is then extracted and used as an electrolyte for titanium electrolytic refining in an electrolytic cell composed of a titanium rod as an anode and a stainless steel rod as a cathode to obtain metallic titanium with a purity greater than 99.6%.

Example 3

130g LiF, 290.5g KF and 46.7g MoCl ₅ after drying are mixed evenly, and melted in a closed electrolytic cell under the protection of inert gas to obtain a matrix molten salt, wherein the mass concentration C of molybdenum pentachloride in the matrix molten salt is 10%.

17.4 g of titanium carbide (the molar ratio of titanium carbide to molybdenum pentachloride is 1.7:1) was added to the above-mentioned matrix molten salt, and the mixture was kept at 550° C. for 4 h. During the process, argon gas was bubbled in the molten salt for stirring. After the heat preservation reaction was completed, the reactant was obtained.

The reactant is subjected to heat filtration and solid-liquid separation to obtain a molten mixture, which is used as an electrolyte for titanium electrolytic refining, and an electrolytic cell is formed with carbon dioxide titanium as an anode and a titanium rod as a cathode to obtain metallic titanium with a purity greater than 99.6%.

Example 4

168g NaF, 348.6g KF and 50g MoCl ₅ after drying are mixed evenly, and melted in a closed electrolytic cell under the protection of inert gas to obtain a matrix molten salt, wherein the mass concentration C of molybdenum pentachloride in the matrix molten salt is 8.8%.

32.9 g of titanium carbide (the molar ratio of titanium carbide to molybdenum pentachloride is 3:1) was added to the above-mentioned matrix molten salt, and the mixture was kept at 750° C. for 1 h. During the process, argon was bubbled in the molten salt for stirring. After the heat preservation reaction was completed, the reactant was obtained.

The reactant is subjected to heat filtration and solid-liquid separation to obtain a molten mixture, which is used as an electrolyte for titanium electrolytic refining, and an electrolytic cell is composed of carbon dioxide titanium as an anode and a stainless steel rod as a cathode to obtain metallic titanium with a purity greater than 99.5%.

Example 5

623g of MgF ₂ , 781g of CaF ₂ and 546g of MoCl ₅ after drying are mixed evenly, and melted in a closed electrolytic cell under the protection of inert gas to obtain a matrix molten salt, wherein the mass concentration C of molybdenum pentachloride in the matrix molten salt is 28%.

240 g of titanium carbide (the molar ratio of titanium carbide to molybdenum pentachloride is 2:1) is added to the above-mentioned matrix molten salt, and the mixture is kept at 1050° C. for 2 h. During the process, argon gas is bubbled in the molten salt for stirring. After the insulation reaction is completed, the reactant is obtained.

The reactants are allowed to settle and solid-liquid separation is performed to obtain a molten mixture, which is used as an electrolyte for titanium electrolytic refining, and an electrolytic cell is formed with carbon dioxide titanium as an anode and a stainless steel rod as a cathode to obtain metallic titanium with a purity greater than 99.6%.

Example 6

542.6 g of MgCl ₂ , 895.3 g of BaCl ₂ and 253.7 g of MoCl ₅ after drying are uniformly mixed and melted in a closed electrolytic cell under the protection of an inert gas to obtain a matrix molten salt, wherein the mass concentration C of molybdenum pentachloride in the matrix molten salt is 15%.

167 g of titanium carbide (the molar ratio of titanium carbide to molybdenum pentachloride is 3:1) was added to the above-mentioned matrix molten salt, and the mixture was kept at 650° C. for 2 h. During the process, argon gas was bubbled in the molten salt for stirring. After the heat preservation reaction was completed, the reactant was obtained.

The reactants are allowed to settle and solid-liquid separation is performed to obtain a molten mixture, which is used as an electrolyte for titanium electrolytic refining, and an electrolytic cell is formed with carbon dioxide titanium as an anode and a stainless steel rod as a cathode to obtain metallic titanium with a purity greater than 99.5%.

Example 7

711.5 g of CaCl ₂ , 747.4 g of BaCl ₂ and 76.8 g of MoCl ₅ after drying are mixed evenly and melted in a closed electrolytic cell under the protection of an inert gas to obtain a matrix molten salt, wherein the mass concentration C of molybdenum pentachloride in the matrix molten salt is 5%.

28.6 g of titanium carbide (the molar ratio of titanium carbide to molybdenum pentachloride is 1.7:1) was added to the above-mentioned matrix molten salt, and the mixture was kept at 700° C. for 1 hour. During the process, argon gas was bubbled in the molten salt for stirring. After the heat preservation reaction was completed, the reactant was obtained.

The reactant is subjected to heat filtration and solid-liquid separation to obtain a molten mixture, which is used as an electrolyte for titanium electrolytic refining, and an electrolytic cell is composed of carbon oxide titanium as an anode and a stainless steel rod as a cathode to obtain metallic titanium with a purity greater than 99.6%.

Example 8

332.9g NaCl, 410.3g _MgCl2 and 64.6g _MoCl5 after drying are mixed evenly, and melted in a closed electrolytic cell under the protection of inert gas to obtain a matrix molten salt, wherein the mass concentration C of molybdenum pentachloride in the matrix molten salt is 8%.

35.4 g of titanium carbide (the molar ratio of titanium carbide to molybdenum pentachloride is 2.5:1) was added to the above-mentioned matrix molten salt, and the mixture was kept at 550° C. for 4 h. During the process, argon gas was bubbled in the molten salt for stirring. After the heat preservation reaction was completed, the reactant was obtained.

The reactant is subjected to heat filtration and solid-liquid separation to obtain a molten mixture, which is used as an electrolyte for titanium electrolytic refining, and an electrolytic cell is composed of carbon oxide titanium as an anode and a stainless steel rod as a cathode to obtain metallic titanium with a purity greater than 99.6%.

Embodiment 9

325.9g NaF, 139.6g _MgF2 and 24.5g _MoCl5 after drying are mixed evenly and melted in a closed electrolytic cell under the protection of inert gas to obtain a matrix molten salt, wherein the mass concentration C of molybdenum pentachloride in the matrix molten salt is 5%.

16.1 g of titanium carbide (the molar ratio of titanium carbide to molybdenum pentachloride is 3:1) was added to the above-mentioned matrix molten salt, and the mixture was kept at 900° C. for 3 h. During the process, argon gas was bubbled in the molten salt for stirring. After the heat preservation reaction was completed, the reactant was obtained.

The reactant is subjected to heat filtration and solid-liquid separation to obtain a molten mixture, which is used as an electrolyte for titanium electrolytic refining, and an electrolytic cell is composed of carbon oxide titanium as an anode and a stainless steel rod as a cathode to obtain metallic titanium with a purity greater than 99.6%.

It should be particularly pointed out that the various components or steps in the above-mentioned embodiments can be cross-linked, replaced, added, or deleted. Therefore, the combinations formed by these reasonable permutations and combinations should also fall within the scope of protection of the present invention, and the scope of protection of the present invention should not be limited to the embodiments.

A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims (9)

1. A method for preparing an electrolyte for titanium electrolytic refining, characterized in that it comprises the following steps: (1) mixing molybdenum pentachloride with a mixture of one or more alkali metal halides and/or alkaline earth metal halides and melting the mixture to obtain a matrix molten salt; (2) adding titanium carbide to the matrix molten salt for heat preservation treatment, and obtaining a reactant after reaction, wherein the molar ratio of the titanium carbide to the molybdenum pentachloride in the matrix molten salt is 1.7:1-3:1; (3) The reactants are subjected to solid-liquid separation to obtain a molten mixture, and the molten mixture is used as an electrolyte for titanium electrolytic refining. 2. The method according to claim 1, characterized in that, in step (1), the mass concentration C of molybdenum pentachloride in the matrix molten salt is: 0<C≤28%. 3. The method according to claim 1, characterized in that in step (1), The alkali metal halide is a fluoride and/or chloride of an alkali metal; The alkaline earth metal halide is a fluoride and/or chloride of an alkaline earth metal. 4. The method according to claim 3, characterized in that The alkali metal fluoride is selected from one or more of lithium, sodium and potassium fluorides; the alkali metal chloride is selected from one or more of lithium, sodium and potassium chlorides; The alkaline earth metal fluoride is selected from one or more of the fluorides of magnesium, barium and calcium; the alkaline earth metal chloride is selected from one or more of the chlorides of magnesium, barium and calcium. 5. The method according to claim 4, characterized in that at least two alkali metal chlorides are mixed with molybdenum pentachloride and melted to form a matrix molten salt, wherein the mixture of at least two alkali metal chlorides is a mixture of KCl and NaCl or LiCl. 6. The method according to claim 1, characterized in that in step (2), the temperature of the heat preservation treatment is 460-1050°C, and the heat preservation reaction time is 1-4 hours. 7. The method according to claim 1, characterized in that in step (3), solid-liquid separation is performed by hot filtration or static sedimentation. 8. A method for extracting titanium by electrolysis, characterized in that the electrolyte for titanium electrolytic refining obtained according to any one of claims 1 to 7 is electrolyzed to obtain metallic titanium at the cathode. 9. The method according to claim 8 is characterized in that the electrolysis process is carried out in a closed electrolytic cell, the anode of the electrolytic cell is sponge titanium or carbon oxytitanium or a titanium rod, and the cathode is a carbon steel rod or a stainless steel rod or a titanium rod.