SU1723040A1 - Method of potassium heptafluorotantalate synthesis - Google Patents

Abstract

The invention relates to a process for the preparation of potassium heptafluorotantalate and makes it possible to increase the purity of the final product. The potassium salt is introduced into the hydrofluoric solution of tantalum. The precipitate of potassium heptane fluorofluorotalate obtained as a result of the interaction of tantalum and potassium salts is separated from the solution and fluorinated in a vacuumized reactor at 20-185 ° C for 0.5-10 hours and halogen fluoride selected from the group: CIFa, CIFs, Brgr. BrFs, JFs, with the removal of gaseous reaction products. The content of impurities of oxygen, nitrogen, carbon, phosphorus, as well as tungsten, molybdenum in the final product decreased to the level (1-5). 1 tab.

Description

The invention relates to the metallurgy of rare metals, namely, to methods for producing potassium heptafluorotantalate (faTaF) - a starting material for the production of metallic tantalum by the method of sodium thermal reduction or the main component of the mixture using electrolysis.

A known method for producing potassium fluorotunate (FTC) by heat treatment at 400-800 ° C of the charge consisting of tantalum oxide Ta20s. alkali metal fluoride (KF) and ammonium bifluoride (HF). The process of heat treatment of the charge is carried out until the release of ammonium fluoride vapors.

A disadvantage of the known method is the necessity of using high purity tantalum pentoxide to obtain good quality K2TaF, since using this method does not purify PTC from niobium impurities and

other metals and silicon, as well as the fact that the use of ammonium biofluoride for the preparation of PTK may lead to a low purity of the product in terms of nitrogen content:

Ta205 + NH4F.HF + 4KF- 2K2TaF7 + 5NH3 + + 5H20

The closest to the proposed technical essence and the achieved result is a method for producing potassium heptafluorotantalate, including dissolving technical oxide of tantalum TaaOs containing niobium in concentrated (35-40%) hydrofluoric acid, taken with some excess, filtering the solution, diluting it to volume, so that the concentration of KzNbOFs niobium salt is 3-6%, and the concentration of free HF is 1-2%, precipitation of potassium fluorotanthalate (K2TaF) by adding KCI or KOC3 and separating the liquid phase.

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The disadvantage of this method is the low purity of the oxygen content (in the form of oxofluorides), carbon, tungsten, and molybdenum.

The aim of the invention is to increase the purity of the final product.

This goal is achieved in that according to the method of obtaining potassium heptafluorotantalate, which includes precipitating it from a hydrofluoric solution of tantalum compounds with potassium salt, removing the liquid phase, potassium heptafluorotantalate after separation of the liquid phase is placed in a vacuumized reactor, treated with fluorinated reagent selected from halogen fluoride class (, CIFs, BgPv, BgPz, JFs) at 20-185 ° C for 0.5-10 h with removal of gaseous reaction products.

The method involves dissolving the starting tantalum-containing product in hydrofluoric acid, precipitating KaTaFy potassium fluorotantalate by adding potassium-containing compound (KCI or K2CO3). After removing the liquid phase from the crystals, the potassium fluoro-tantalate obtained is treated with halogen fluoride (CIFa, CtFs, BrFs, BrPz, JFs) after drying and calcining the product at 250 ° C (PTC moisture content is 0.1-0.2%) after drying at 150 ° C (humidity FTC 0.3-0.5%) or. eliminating the stage of drying and calcining FTK (humidity 1.5-2.0%), at 20-185 ° C for 0.5-10 hours

The essence of the proposed method is as follows.

Potassium fluorotantalate, obtained by precipitation from an aqueous HF solution, contains significant amounts of impurities, the presence of which is associated with both adsorption on the surface of PTC and the formation of chemical compounds having low solubility or formed during the drying and calcining process as pyrohydrol products. First of all, this concerns oxygen-containing impurities that are in the form of oxyfluorides of various compositions, for example, KaTaOFs, CsTaORe. KzTaOaRz. .

Potassium fluorotantalate, obtained by heat treatment of a mixture consisting, for example, of Ta20s + KF + NH4F-HF, may contain significant amounts of nitrogen impurities. In those cases; when extraction is used during the additional purification of tantalum from niobium, the final product (KataP) can be contaminated with carbon in the form of its organic compounds, as well as phosphorus. In addition, the contamination of KataPa with carbon in the form of carbonates can occur when it is precipitated from solution using KCO3, which often has

place in industrial practice. Potassium fluoro-tantalate is contaminated with heavy metals (Mo, W) because they are satellites of tantalum and niobium in raw materials. The presence of these impurities in potassium ftorotantalate leads to an increase in their relative content in the powder of the resulting metal, which does not provide the required electrical characteristics of electronic products (electrical capacitors, etc.) made from tantalum powders and, in addition, leads to an increased consumption of expensive and metal shortage (annual global production of tantalum is 550-600 t / g).

Processing potassium fluoro-tantalate obtained by factory technology with reagents from halogen fluoride groups (CIFs,

0 CIFs. CrPr, BrFs, JFs) allows not only to remove impurities of nonmetals (Oa, C, P, N2) and metals capable of forming volatile fluorides in the highest oxidation state, but at the same time it allows qualitatively changing the phase itself, which has the name potassium fluorotantalate, bringing it closer to the strictly stoherhymetric composition of foTaF, increase the bulk density and reduce energy consumption, eliminating drying and calcining of the product.

0 The choice of the temperature range of 20–185 ° C for the treatment of fluorotantalate with potassium fluorides of halogens is determined by a number of factors, namely, the composition of the impurities, the physicochemical properties of hailide fluoride, the initial state of K2TaF (wet, dry, calcined), the reactor material (fluoroplast, metals ) and energy costs.

Halogen fluorides are highly active chemical reagents that readily react with many of the impurities contained in PTK, even at room temperature. Lowering the temperature below room temperature is impractical because of the need to create special cooling devices. In addition, below 10 ° C, the JFs are in a solid state, and Grps is solidified at + 8.8 ° C. At these temperatures, the process almost does not go. So,

5, oxygen-containing impurities in the form of water or hydroxyl groups and carbon-containing impurities in the form of organic derivatives are easily removed at room temperature. Oxygenated

0 impurities in the form of oxides, oxyfluorides, carbonates, and also carbon in the form of carbonates require higher temperatures and time of exposure to reagents, phosphorus impurities (organic and inorganic), nitrogen (in. Form

ammonium salts of silicon (provided there is no complexation process), tungsten and molybdenum are also removed at 20-185 ° C.

The upper temperature limit of 185 ° C is due to the fact that at this temperature the impurities are completely removed, i.e. an increase in temperature does not lead to an improvement in the quality of PTK, and in addition, in the case of using fluoroplastic as a construction material in the reactor in which the process is carried out (to obtain high-purity K2TaF), at a temperature above 185 ° C fluoroplastic corrosion resulting in carbon contamination of the product,

The method is carried out as follows.

A solution of potassium salt (KCI or K2CO3) is introduced into the hydrofluoric solution (1-2%) of the tantalum salt. In this case, potassium heptafluorotantalate is precipitated, which, depending on the history of origin, may contain impurities of oxygen, nitrogen, carbon, phosphorus, tungsten, molybdenum, silicon, etc. The potassium fluorotantalate precipitate obtained is separated by centrifugation from the liquid phase, then dried and calcined.

To free FTC from these impurities, it is further treated with halogen fluoride. The resulting volatile products (impurities) are removed by vacuum.

Example (prototype). The technical oxide of tantalum (Ta20b), wet or dried at 100-120 ° С, containing niobium impurities (NbaOs), is dissolved in concentrated (35-40%) hydrofluoric acid, filtered from the insoluble residue, diluted with the solution to the concentration of free hydrofluoric acid (1-2%), heat it up and add potassium chloride or potassium carbonate, while CaTaP precipitates. Next, the solution (center is filtered) is filtered to separate the PTK crystals (KaNbOFs remain in the mother liquor). Potassium fluorotantalate precipitate dried for three hours at 120-150 ° C and then calcined at 250-275 ° C for 2 hours. This method does not allow purification of many impurities. Together with feTaFy, all silicon (in the form of K2SiFe), 50% of titanium, and also a small fraction of niobium (5-6% of the initial content in solution) is precipitated. Additional recrystallization of the obtained teTaF from a 1-2% solution of hydrofluoric acid allows obtaining potassium fluorotantalate with a content of 0.1-0.3% 1Mb, from hundredths to a few tenths of a percent of silicon, iron and titanium. However, this method does not allow purification from non-metallic impurities: oxygen, nitrogen, carbon, phosphorus, and metals such as tungsten and molybdenum.

The content of impurities in the finished product obtained in various ways is given in the table.

The moisture content in PTC obtained after filtration of the precipitate (before drying the product) is 1.5-2.5 wt.%, And its bulk density is 1.3-1.85 g / cm3. The moisture content in the dried sample is 0.3-0.5 May,%. After calcining PTC at 250 ° C for 2 hours, the moisture content in the product is 0.1-0.2 wt.%, And the bulk density is 1.6-2.0 g / cm3

Example 2. Potassium fluorotantalate, obtained by a known method, comprising precipitating it from a tantalum-containing solution of hydrofluoric acid with a solution, potassium-containing compound and separating the liquid phase by centrifugation, with a residual moisture content of 1.5 wt.%, Was further subjected to chlorine trifluoride treatment. For this purpose, 200 g of potassium fluorotantalate were weighed into a vacuumized nickel (or stainless steel, monel metal, fluoroplastic) reactor with a capacity of 200 cm3, the reactor was sealed, evacuated to-mmHg. Art. and chlorine trifluoride in the amount of 16-20 g was introduced into it in the form of a gas (or liquid). Then the reactor was heated for 1 hour at 80 ° C and the excess chlorine trifluoride and the reaction products from the impurities contained in the initial K2TaF were pumped out in a volatile state. At the same time, chlorine trifluoride was collected into a trap cooled with liquid nitrogen or dry ice for reuse. After the treatment of PTK with oxygen, nitrogen, phosphorus, and carbon-containing chloride trifluoride, the impurities were converted into Oa, N2, and CF4, PFs, respectively, and were removed in the process of pumping in the form of gases. Possible impurities of tungsten and molybdenum turned into volatile WFe and MoFe. After the reactor was pumped out for 30 minutes, it was opened and clean potassium fluorotangatalate was discharged. The resulting product contained oxygen less than 110, nitrogen less than 1 carbon less than 1 and phosphorus Zx wt.%, I.e. all impurities of non-metals less than wt.%. At the same time, the product acquired a more uniform particle size distribution (96% of the particles had a size

about 1 micron), and its bulk density increased to 1.85-2.2 g / cm3.

The content of molybdenum and tungsten in the resulting product was below the detection limits of the emission spectral method (Mo, W less than 1 wt.%). The impurities of non-metals in the form of gases were determined by chromatography; their number was also practically at the level of sensitivity of the method.

The results of the above experiments are summarized in table.

Example 6. Wet TFA (1.5% moisture), obtained as indicated in Example 1, in an amount of 200 g was placed in a vacuum-cooled monel-metal reactor with a capacity of 200 cm3, the reactor was sealed, evacuated to mm Hg, injected 12.5-15.7 g of chlorine pentafluoride in the form of gas in it and left the reactor at 20 ° C for 8 hours to complete the reaction with impurities. After the indicated time has elapsed, an excess amount (25.6%) of chlorine pentafluoride and volatile impurities formed is pumped through a trap, OKI, which is rich in liquid nitrogen. Excess condensed CIFs are reused in the process, and volatile impurities are removed and disposed of. The purity of the obtained PTC in terms of the content of limiting impurities was at the level of the detection limit. The bulk density of the product was 1.9-2.2 g / cm

Example 11 (see table). Moist PTK (1.5% moisture), obtained as indicated in Example 1, in an amount of 200 g was placed in a 200 cm stainless steel reactor, the latter was sealed, vacuumed to mm Hg, st. and filled with bromine pentafluoride gas, taken in the amount of 18.2-22.8 g. The reactor was heated at 190 ° C (e.g., direct steam) for 10 hours. The reactor was then evacuated (hot or cold) through a trap cooled with liquid nitrogen to trap and reuse excess BrF5. After pumping the reactor was opened. The purity of the obtained PTK on limiting impurities was at the level of the detection limit. The bulk density of K2TaF was 1.9-2.2 g / cm3

Example 13. Moist PTC (humidity 1.5%), obtained as indicated in example 1, in an amount of 20 ° C was placed in a fluoroplast-4 reactor and 23.7-29.6 g of bromine trifluoride was introduced into it in the form of a liquid. The reactor was sealed, cooled to 0 ° C (or lower), and air and gases of impurities that had already formed during the introduction of CrPr into the reactor were evacuated. After pumping out, the valve in the reactor was shut off and the reactor was heated at 120 ° C for 3 hours. Then the reactor (not cooled) was pumped through a trap cooled

liquid nitrogen. The reactor was pumped out for 20–30 min, after which the reactor was opened and the PTK was removed. The purity of potassium fluoro-tantalate obtained by impurities of non-metals at the level of their

detection. The bulk density of the PTK was 1.85-2.2 g / cm3

Example 15. In a 200 cm fluoroplastic reactor, 200 g of wet (1.5% moisture) PTK, prepared as indicated in Example 1, was introduced, and 23-28.8 g of iodine pentafluoride was added in the form of a liquid. The reactor was sealed, cooled to O (-76 ° C) and the gases were pumped out. Then the reactor was heated at 100 ° C for 3 hours to carry out the reaction of JFs with impurities and the gaseous products were re-evacuated. Excess JFs were condensed in a cold trap, then reused. Purity

the obtained PTK is given in the table, the bulk density is 1.85-2.2 g / cm.

Example 17. FTK, obtained by a known method, including its deposition from tantalum-containing solution

hydrofluoric acid with a solution of potassium-containing compound (KCI), separating the liquid phase, drying and then calcining at 275 ° C for 2 h (residual moisture content, wt.%), taken in

200 g., additionally treated with 5 g of chlorine trifluoride for 5 hours at 185 ° C in the same way as described in Example 2. The reactor was cooled to room temperature and the excess amount of C1P3 and volatile impurities formed were pumped through a trap cooled with liquid nitrogen. . Volatile impurities were disposed of, and excess C1P3 was reused. The purity of the obtained PTC for limiting impurities was at the level of the detection limit (see table). The bulk density of the FTC in this case became equal to 1.85-2.2 g / cm with a more uniform particle size distribution.

Thus, the use of the proposed method allows to increase the purity of the final product by reducing the impurities of oxygen, nitrogen, carbon,

phosphorus, as well as tungsten and molybdenum.

Phromu l and z obre n e Method of producing potassium heptafluorotantalate, including treatment of a solution of hydrofluoric tantalum

potassium salt and separating the precipitated potassium heptafluorotantalate precipitate, characterized in that, in order to increase the purity of the final product, the precipitated potassium heptafluorotantalate precipitate after

The divisions are treated in a vacuumized reactor with halogen fluoride selected from a series of chlorine and bromine trifluorides and chlorine pentafluoride, bromine, and iodine at 20-185 ° C for 0.5 to 10 hours.

Example

Conditions of receipt

The content of impurities in VFTK, obtained by various methods, masd

Oxygen | Nitrogen I Carbon I Phosphorus) Tungsten (Molybdenum

0.03 0.08 0.06 0.03 0.05

Bulk weight of FTK, g / cm

0.05 1.6-2.0

Claims (2)

Formula A method for producing potassium heptafluorotantalate, comprising treating a solution of a tantalum hydrofluoric compound with a potassium salt and separating the formed i precipitate of potassium heptafluorotantalate, characterized in that, in order to increase the purity of the final product , the obtained precipitate of potassium heptafluorotantalate after separation is treated in a vacuum reactor with halogen fluoride selected from a number of chlorine trifluorides and bromine, bromine, iodine pentafluorides at 20-185 ° C for 5 for 0.5-10 hours. Example Production conditions C the content of impurities vFTC obtained by various methods, wt.% Bulk weight of FTC, g / cm3 Oxygen | Nitrogen | Carbon | Phosphorus | Tungsten | Molybdenum 1.5 wt.%) Reagent Temperature, * С Time, Ch. 1 According to the prototype (calcination of FTK at 275 ** C) 0.03 0.08 0.06 0.03 0.05 0.05 1.6-2.0 Treatment conditions for wet FTK halogen fluorides (humidity 2 Cifj 80 1 1-10-3 1-y ' ³ VIO-s 3 -ΙΟ * ³ 1-s-s 1.10'3 3 Cifj 20 10 1-10-3 I-Yu-z 1 -10'3 1-10 * s 1 .10 * 3 1-10 * 3 4 C1F ₃ 20 eleven 1-ΙΟ ' ³ MO ' ³ 1-10'z 1-10 ^: s 1-10 * s 1.10 * 3 5 C1F, 185 . 0.8 1 ΊΟ * ³ 1 Ί0 * 3 1 * 10 * 3 S-u-z 1 '10 * 3 1-10 * 3 6 cif ₅ 20 8 1 · 10 “3 1 ΊΟ ' ³ 1-y ' ³ 3-10 * 3 1.10 * 3 1.10 * 3 7 C1F _S 90 1 1-2 -10-3 1-10'3 1-10'3 3 "Yu-s 1-10 * s 1.10 * 3 ' 8 C1F ₅ 185 0.5 1-u- ³ 1- Yu'z 1 -10'3 3-10-e 1 * 10 * 3 1 ΊΟ'3 \ > 1.85-2.2 9 Btf _s 100 2 2-10'3 1 ΊΟ * ³ 1-10'3 4-10'z 1.10 * 3 Yo-s 10 Btfg 150 1,5 2-10 * 3 2'10 * 3 Z-Yu'z 4-s 1-10 * 3 1.10 * s eleven Brf _s 185 10 1 .10-3 1 · 10 * 3 1-10 * s 3-10 * s 1 * 10 * s 1> 10'3 12 Brfj 60 2 2-10-3 2-10-3 3-10 ' ³ 4Ί0 * 3 1-10 * s YO’Z thirteen Brf ₃ 120 3 1-10-3 1 * Yu-s 1-10‘z 4-10 * 3 1-10 * s 1 Yu * s. 14 Brfj 200 * 12 1-s-s 1-10'3 1-10 * s 4 · 10'3 1 .10 * 3 1.10 * 3 fifteen ^Jf 5 100 5 3-10-3 5 · Yu-e 5-10 * s 6'10 ^g s 1-10 * 3 B10 * s 16 jf ₅ 200 * 2Ί0-3 5> 10-s 5-10‘z 6-10'3 1 .10'3 B10'3_ FTK processing conditions fluorides halogen dried at 275 C 17 C1F ₃ 185 5 Yo-s 1st- ^3rd * ³ 1-10 * s 3rd * ’ M-10 * 3 41 H0 * s 18 Cifj 150 4 1-u- ³ 1.10'3 1-10'3 3-U'Z 4 ΊΟ * ’ 41-10 * 3 19 Brfj 170 3,5 1-10-3 1.10 * s 1-10 * s Z'U'Z 41.10 * 3 Λ1.10 * 3 1.85-2.2 20 BrF _& 190 6 1 Yu-s 1 · 10 * ³ 1-10 * 3 4'10 * s .10 * 3 4Y0 * s 21 Jf _e 200 16 Yo-s 1-10 * 3 1-Yu'z 4 · U’s C.YU'Z A1'10 * 3 22 JF ₅ . 8 10 Process not going 23 Jfj 180 0.25 50.10 * 3 80-10-3 70.10GZ ZO'KGZ 50-10'3 5O'TO-e 1.6-1.9 Substances polluted products corrosion reactor