A method for preparing high-purity metallic scandium

Abstract

The invention relates to the field of rare metal metallurgy and can be used to prepare high-purity scandium metal. The preparation method of high-purity scandium metal comprises reducing scandium chloride with sodium metal in two stages under the participation of a flux and under heating, wherein the reduction process is carried out in a tantalum crucible under the participation of a potassium chloride flux. In the first stage, the temperature is heated to 400°C and the vacuum degree is 1×10 ‑2 mmHg, 5-7% of the total mass of sodium is used for reduction, and the temperature is maintained for 30-60 minutes. The second stage of the reduction process is carried out in argon heated to 900-1100°C, and then the remaining molten liquid sodium is added to the surface of the melt. After all the sodium is added, the reaction mass is maintained at a temperature of 900-1100°C for 1-2 hours, and then the salts of sodium chloride and potassium chloride are precipitated and fractionated from the crucible, and the metal scandium sponge is vacuum distilled in a tantalum crucible.

Description

Technical Field

[0001] The invention relates to the field of rare metal metallurgy and can be used to prepare high-purity metal scandium. -4 -10 -5 Scandium metal is prepared by purification at 1500-1850°C, vacuum refining and distillation of the crude metal. Background Art

[0002] At present, the most common method for preparing scandium is metal thermal reduction, using anhydrous scandium fluoride or scandium chloride as raw materials, using magnesium, sodium and more commonly calcium as reducing agents. Scandium fluoride is preferred because it does not absorb moisture, and calcium chips are used as metal reducing agents (Borisakov KA "Chemistry and Technology of Rare and Dispersed Elements", Higher Education, 1976, Vol. 2, p. 351. 2. Korshunov BG et al., "Scandium", Metallurgical Press, 1987, p. 182.)

[0003] Scandium prepared by this method contains a large amount of impurities and is therefore an industrially pure metal. There are many methods for refining scandium: vacuum melting, zone melting, solid-state electrolysis, and vacuum distillation.

[0004] At a temperature of 1650°C and a vacuum of 10 -4 -10 -5 Scandium is purified by vacuum melting in an arc furnace or induction furnace at 100 mmHg (Savitsky EM, Terekhova VF, Rare Earth Metallurgy, Science Press, 1975, p. 270), and by heating at 1650-1850°C and a vacuum of 10 -4 -10 -5 Scandium was purified by vacuum distillation of crude metal under the condition of 1.5 mmHg (Korshunov BG et al., Scandium, Metallurgical Press, 1987, p. 158).

[0005] A method for preparing metallic scandium by metallothermic reduction of anhydrous scandium chloride with metallic sodium is known (Korshunov BG et al., Scandium, Metallurgical Press, 1987, p. 158). According to the known method, the process is divided into two stages. In the first stage, after degassing ScCl3 in a tantalum crucible at a temperature of 370°C and a vacuum of 0.00133 Pa, potassium is added thereto and the mixture is kept at a temperature of 400°C for 15 hours. In the second stage, sodium is added to prepare a large amount of alkali metal in the crucible and reduced to scandium at a temperature of 1000°C for 8 hours. A large amount of alkali metal-reducing agent and its chloride are removed by distillation or other means.

[0006] The disadvantages of this method are long duration, high energy consumption, and difficulty in controlling the reduction reaction in the second stage due to the rapid reaction process.

[0007] A method for preparing scandium metal by reducing scandium chloride with metallic sodium is known, wherein before the operation begins, a mixture of scandium chloride and an alkali metal is placed in a reaction cup and then reduced in two stages in the reaction cup. In the first stage of reduction, 3-7% of metallic sodium is added under stirring of the melt and kept for 30-60 minutes, after which the solid phase formed is separated and the remaining metallic sodium is added to the second stage of reduction, in which the melt is not stirred. Dispersible titanium powder is used as a reducing agent in the first stage, and the amount used is 1-3% of the total amount of reducing agent (invention application 93002042, C22B59 / 00, published in 1996).

[0008] The disadvantage of this method is that the finished product contains up to 10% impurities.

[0009] There are many known methods for purifying and refining crude metallic scandium, such as vacuum melting, zone melting, solid-state electrolysis, and vacuum distillation.

[0010] A method for preparing high-purity metallic scandium by vacuum distillation is known, wherein the scandium vapor is filtered with a tungsten-based alloy powder containing 1-25 wt.% zirconium before condensation (Russian Patent 2034075, S22B61 / 00, published in 1995).

[0011] There is also a method for preparing high-purity metal scandium, which is to -4 -10 -5 The crude metal is distilled in a vacuum of 0.1 mmHg and, after condensation, distilled at a temperature of 1850-2000°C (Russian Patent 2034080, C22B61 / 00, C22B9 / 04, published in 1995).

[0012] The disadvantage of these methods is the low efficiency of purifying gas impurities (such as nitrogen and oxygen) because the equipment cannot be absolutely sealed and the distillation process at a specified temperature lasts for a limited time. During the distillation process, the scandium vapor entering the furnace absorbs nitrogen and oxygen, resulting in a high content of gas impurities in the crude metal.

[0013] It is known that at a temperature of 1650-1850°C and a vacuum degree of 10 -4 -10 -5 A method for distilling and refining crude scandium under the condition of 1000 mmHg (Russian Patent 2034077, C22B61 / 00, C22B9 / 04, published in 1995).

[0014] The disadvantage of this method is that iron, chromium, vanadium, manganese, nickel and cobalt cannot be effectively removed because their vapor pressure values ​​are similar.

[0015] A method for preparing crystalline scandium by reducing a scandium chloride melt with molten metal sodium is known to be closest to the present invention, wherein the molten metal sodium is delivered to the surface of the scandium chloride melt in a reaction cup. Before delivering the metal sodium, a mixture of sodium chloride and potassium chloride is added to the surface of the melt, and the ratio of sodium chloride, potassium chloride to scandium chloride melt in the melt is 1:3:5 (Russian Patent 2048566, C22B59 / 00, published in 1995).

[0016] The disadvantage of this method is that the finished product contains up to 10% impurities. Summary of the invention

[0017] Problems to be solved by the invention

[0018] The purpose of the present invention is to develop a technical method for preparing high-purity metal scandium and improve the quality of the prepared metal.

[0019] The technical effect is to prepare metal scandium with a chemical purity of 99.990-99.999% (mass fraction).

[0020] Means for solving problems

[0021] A method for preparing high-purity scandium metal that can achieve the technical effect includes reducing scandium chloride with sodium metal in two stages in the presence of a flux and heating. In addition, the reduction process is carried out in a tantalum crucible with the presence of a potassium chloride flux. In the first stage, the temperature is heated to 400°C and the vacuum degree is 1×10 -2 The reduction is carried out with 5-7% metallic sodium based on the total mass of sodium under the condition of 2400-2700 mmHg, and the temperature is maintained for 30-60 minutes. The second stage of the reduction process is carried out in argon heated to 900-1100°C, and then the remaining molten liquid metallic sodium is added to the melt surface in an excess of 10-20% according to the stoichiometric ratio. After all the sodium is added, the reaction material is maintained at a temperature of 900-1100°C for 1-2 hours, and then the excess sodium vapor is removed in a vacuum to produce a metal scandium sponge in the molten salt. Then the salts of sodium chloride and potassium chloride are precipitated and fractionated from the crucible, and the metal scandium sponge is directly distilled in a tantalum crucible by vacuum.

[0022] The ratio of potassium chloride to scandium chloride is 1:1.

[0023] At a vacuum degree of 1×10 -2 mmHg, and remove excess sodium vapor at a temperature of 800-850°C.

[0024] The salt was discharged in argon gas and the vacuum was 1×10-4 -1×10 -5 mmHg, distill salt at a temperature of 1200-1300°C.

[0025] At a vacuum degree of 10 -4 -10 -5 mmHg, a temperature of 1550-1600°C, and vacuum distillation of the metal scandium sponge under the conditions of maintaining the temperature for 4.5-5 hours. DETAILED DESCRIPTION

[0026] A mixture of scandium chloride and potassium chloride in a ratio of 1:1 is placed in a tantalum reaction crucible in a sealed device in the furnace along with 5-7% of the total amount of sodium metal. The reduction process is carried out in two stages. In the first stage, the initial reagents are evacuated to a vacuum of 1×10 -2 mmHg, the temperature is heated to 400°C and maintained at this temperature for 30-60 minutes; in the second stage, the device is filled with argon, the temperature is heated to 900-1100°C, and the remaining molten liquid metal sodium is added to the melt surface in an excess of 10-20% according to the stoichiometric ratio, so that the sodium dissolves and diffuses in the direction of the scandium chloride. After all the sodium is added, the mixture is maintained at a temperature of 900-1100°C for 1-2 hours.

[0027] After the above state is completed, the device is evacuated to 1×10 -2 mmHg, and maintain the temperature at 800-850°C for 10-20 minutes, and discharge the excess sodium vapor into the condenser-condenser.

[0028] Due to the slow reduction rate, scandium chloride is reduced to scandium metal sponge with extremely low impurity content in this reaction.

[0029] After cooling, the tantalum crucible containing the reduction is turned 180° and then placed on a tantalum screen for discharging salts on a metal ingot mold in the furnace. The furnace is filled with argon, heated to 1200-1300°C, and maintained at this temperature for 2-2.5 hours, so that 60-70% of the sodium chloride and potassium chloride salts are discharged from the crucible.

[0030] The tantalum crucible with the scandium sponge and salt residue was put back in place and placed in a SGV-2.4-2 / 15-IZ vacuum resistance furnace. A tantalum cover was placed on the crucible, and a copper tube water-cooled condenser-cooler was installed above the tantalum cover. The resistance furnace was evacuated to 1×10 -4 -1×10 -5 mmHg, the temperature is heated to 1200-1300℃, and then maintained at this temperature for 2-2.5 hours.

[0031] The pure, desalinated, industrial-grade scandium sponge remains in the tantalum crucible. The salt vapor is trapped on the tantalum cover.

[0032] After the resistance furnace has cooled, the tantalum cover with the salt condensate is removed from it and a copper-tube water-cooled condenser-cooler is installed in its place.

[0033] The resistance furnace was evacuated to 1×10 -4 -1×10 -5 mmHg, the temperature is heated to 1550-1600℃ and maintained at this temperature for 4.5-5 hours, and the refining vapor of metallic scandium is intercepted on the copper water-cooled condenser-cooler.

[0034] After the vacuum distillation process is completed, the resistance furnace is cooled, filled with argon and discharged in an argon box.

[0035] High-purity metallic scandium in the form of crystal clusters was prepared by vacuum distillation.

[0036] The present invention is further described by the following examples:

[0037] Example

[0038] Example 1

[0039] 1.8 kg of scandium chloride, 1.8 kg of potassium chloride and 0.066 kg of sodium metal were placed in a reaction tantalum crucible with a diameter of 180 mm and a height of 400 mm. The crucible was placed in a reaction device and sealed with a lid. The device was evacuated to 10 -2 mmHg, the temperature is heated to 400°C and maintained at this temperature for 40 minutes, then the apparatus is filled with argon, the temperature is heated to 900°C, and the remaining 0.8770 kg of molten liquid metal sodium is added to the melt surface in an excess of 15% according to the stoichiometric ratio.

[0040] After all the sodium was added, the mixture was kept at 900°C for 1 hour.

[0041] After the above state is completed, the device is evacuated to 1×10 -2 mmHg and maintained at 800°C for 20 minutes to remove excess sodium vapor to the condenser-condenser.

[0042] After cooling, the tantalum crucible containing the reduction was turned 180° and then placed on a tantalum screen for discharging salt on a metal ingot mold in the furnace. The furnace was filled with argon, heated to 1200°C, and maintained at this temperature for 2.5 hours, so that 64% of the salt was discharged from the crucible.

[0043] The tantalum crucible with the scandium sponge and salt residue was put back in place and placed in a SGV-2.4-2 / 15-IZ vacuum resistance furnace. A tantalum cover was placed on the crucible, and a copper tube water-cooled condenser-cooler was installed above the tantalum cover. The resistance furnace was evacuated to 1×10-4 mmHg, the temperature was heated to 1250°C and then kept at this temperature for 2.5 hours. After the resistance furnace cooled, the tantalum cover with salt condensate was removed from it and a copper tube water-cooled condenser-cooler was installed in its place.

[0044] The resistance furnace was evacuated to 1×10 -5 mmHg, the temperature was heated to 1555°C and maintained at this temperature for 5 hours, trapping the vapor of metallic scandium in the form of a druse on a copper water-cooled condenser-cooler.

[0045] After the vacuum distillation process is completed, the resistance furnace is cooled, filled with argon gas, and the crystal cluster of metal scandium is taken out from the copper cooler in the argon box.

[0046] The prepared metal scandium has a high chemical purity of 99.996% (mass fraction).

[0047] The chemical composition and content of impurities were determined by spark source mass spectrometry.

[0048] Table 1 shows the chemical composition of the metal scandium samples prepared according to the proposed method.

[0049] Table 1 Chemical composition of the prepared metal scandium samples (ppm)

[0050] element Content, ppm element Content, ppm element Content, ppm element Content, ppm H ND Cr 0.8 Pd <0.1 Er <0.1 Li <0.01 Mn <0.1 Ag <0.1 Tm <0.1 Be <0.1 Fe 8 Cd <0.1 Yb <0.1 S <0.1 Co <0.1 In <0.1 Lu <0.1 C ND Ni 0.3 Sn <0.1 Hf <0.1 N ND Cu <0.1 Sb <0.1 Ta <0.1 O ND Zn 1.4 Te <0.1 W <0.1 F <0.5 Ga <0.1 I <0.1 Re <0.1 Na <0.1 Ge <0.1 Cs <0.1 Os <0.1 Mg 1.5 As <0.1 Ba <0.1 Ir <0.1 Al 1.0 Se <0.1 La <0.1 Pt <0.1 Si 1.7 Br <0.1 Ce <0.1 Au <0.1 P <0.1 R <0.1 Pr <0.1 Hg <0.1 S <0.5 Sr <0.1 Nd <0.1 Ti <0.1 Cl <0.5 Y <0.1 Sm <0.1 Pb <0.1 K <0.1 Zr <0.1 Eu <0.1 Bi <0.1 Ca 2.6 Nb <0.1 G <0.1 Th <0.1 Sc MATRIX Mo <0.1 Tb <0.1 U <0.1 Ti <0.1 Ru <0.1 Dy <0.1 V <0.1 R <0.1 Ho <0.1

[0051] Example 2

[0052] 2.0 kg of scandium chloride, 2.0 kg of potassium chloride and 0.0546 kg of sodium metal were placed in a reaction tantalum crucible with a diameter of 180 mm and a height of 400 mm. The crucible was placed in a reaction device and sealed with a lid. The device was evacuated to 10 -2 mmHg, the temperature is heated to 400°C and maintained at this temperature for 30 minutes, then the apparatus is filled with argon, the temperature is heated to 1050°C, and the remaining molten liquid metal sodium 1.0374 kg is added to the melt surface in an excess of 20% according to the stoichiometric ratio.

[0053] After all the sodium was added, the mixture was kept at 900°C for 1.5 hours.

[0054] After the above state is completed, the device is evacuated to 1×10 -2 mmHg and maintained at 850°C for 15 minutes to remove excess sodium vapor to the condenser-condenser.

[0055] After cooling, the tantalum crucible containing the reduction was turned 180° and then placed on a tantalum screen for discharging salt on a metal ingot mold in the furnace. The furnace was filled with argon, heated to 1250°C, and maintained at this temperature for 2.0 hours, so that 58% of the salt was discharged from the crucible.

[0056] The tantalum crucible with the scandium sponge and salt residue was put back in place and placed in a SGV-2.4-2 / 15-IZ vacuum resistance furnace. A tantalum cover was placed on the crucible, and a copper tube water-cooled condenser-cooler was installed above the tantalum cover. The resistance furnace was evacuated to 1×10 -4 mmHg, the temperature is heated to 1300°C and then kept at this temperature for 2.5 hours. After the resistance furnace has cooled, the tantalum cover with the salt condensate is removed from it and a copper tube water-cooled condenser-cooler is installed in its place.

[0057] The resistance furnace was evacuated to 1×10 -4 mmHg, the temperature was heated to 1600°C and maintained at this temperature for 4.5 hours, trapping the vapor of metallic scandium in the form of a druse on a copper water-cooled condenser-cooler.

[0058] After the vacuum distillation process is completed, the resistance furnace is cooled, filled with argon gas, and the crystal cluster of metal scandium is taken out from the copper cooler in the argon box.

[0059] The prepared metal scandium has a high chemical purity of 99.991% (mass fraction).

[0060] The chemical composition and content of impurities were determined by spark source mass spectrometry.

[0061] Table 2 shows the chemical composition of the metal scandium samples prepared according to the proposed method.

[0062] Table 2

[0063] Chemical composition of the prepared scandium metal sample (ppm)

[0064] element Content, ppm element Content, ppm element Content, ppm element Content, ppm H ND Cr 40 Pd <0.06 Er <0.3 Li 0.07 Mn 0.03 Ag <0.07 Tm 0.05 Be 0.04 Fe 10 Cd <0.1 Yb <0.4 V <0.007 Co <0.03 In <0.07 Lu <0.2 C ND Ni 2 Sn <0.05 Hf <0.3 N ND Cu 6 Sb <0.07 Ta <1 O ND Zn <0.06 Te <0.05 W 0.9 F 2 Ga <0.04 I <0.05 Re <0.2 Na 0.1 Ge <0.04 Cs <0.04 Os <0.3 Mg 0,04 As <0.02 Ba <0.06 Ir <0.2 Al 20 Se <0.1 La <0.07 Pt <0.3 Si 0,6 Br <0.04 Ce <0.06 Au <0.1 P <0.05 R <0.03 Pr <0.06 Hg <0.3 S 0.3 Sr <0.03 Nd <0.1 Ti <0.2 Cl 4 Y 0.6 Sm <0.2 Pb 0.5 K 2 Zr <0.1 Eu <0.05 Bi <0.1 Ca 0,5 Nb <0.02 G <0.3 Th <0.08 Sc MATRIX Mo <0.09 Tb <0.07 U <0.08 Ti 0.2 Ru <0.09 Dy <0.3 V <0.02 R <0.03 Ho <0.09

[0065] In summary, a technical method for preparing high-purity metallic scandium with a chemical purity of 99.990-99.999% (mass fraction) has been developed.

Claims

1. A method for preparing high-purity scandium metal, comprising reducing scandium chloride with sodium metal in two stages in the presence of a flux and under heating, It is characterized in that The reduction process is carried out in a tantalum crucible with the participation of potassium chloride flux. In the first stage, the temperature is heated to 400°C and the vacuum degree is 1×10 -2 The reduction is carried out with 5-7% metallic sodium based on the total mass of sodium under the condition of 2400-2700 mmHg, and the temperature is maintained for 30-60 minutes. The second stage of the reduction process is carried out in argon heated to 900-1100°C, and then the remaining molten liquid metallic sodium is added to the melt surface in an excess of 10-20% according to the stoichiometric ratio. After all the sodium is added, the reaction material is maintained at a temperature of 900-1100°C for 1-2 hours, and then the excess sodium vapor is removed in a vacuum to produce a metal scandium sponge in the molten salt. Then the salts of sodium chloride and potassium chloride are precipitated and fractionated from the crucible, and the metal scandium sponge is directly distilled in a tantalum crucible by vacuum.

2. The method according to claim 1, It is characterized in that The ratio of potassium chloride to scandium chloride is 1:

1.

3. The method according to claim 1, It is characterized in that At a vacuum degree of 1×10 -2 mmHg, and remove excess sodium vapor at a temperature of 800-850°C.

4. The method according to claim 1, It is characterized in that The salt was discharged in argon gas and the vacuum was 1×10 -4 -1×10 -5 mmHg, distill salt at a temperature of 1200-1300°C.

5. The method according to claim 1, It is characterized in that At a vacuum degree of 10 -4 -10 -5 mmHg, a temperature of 1550-1600°C, and vacuum distillation of the metal scandium sponge under the conditions of maintaining the temperature for 4.5-5 hours.