Method for producing iridium chloride hydrate and method for producing iridium chloride

Abstract

The present invention provides a method for producing iridium chloride hydrate, the method including: a mixing step of preparing a mixture of iridium metal powder and an alkali metal compound; a calcination step of calcining the mixture to produce alkali-containing iridium oxide; a hydrochloric acid aqueous solution washing step of washing the alkali-containing iridium oxide with an aqueous hydrochloric acid solution to obtain iridium oxide; and a hydrochloric acid dissolution reaction step of dissolving the iridium oxide in hydrochloric acid under pressure and then reacting the iridium oxide.

Description

[Technical Field]

[0001] The present invention relates to a method for producing iridium chloride hydrate and iridium chloride from iridium metal powder. [Background technology]

[0002] The most common commercially available form of iridium is as a metal powder. However, unlike platinum or palladium, iridium metal powder does not dissolve in acid solutions, alkaline solutions, or aqua regia (a mixture of concentrated hydrochloric acid and concentrated nitric acid).

[0003] To produce an iridium aqueous solution by dissolving iridium metal powder, it is mixed with an alkali metal (such as Na or K) and then heat-treated to convert it into an oxide, which is then dissolved in aqua regia.

[0004] However, even with this method, it is difficult to completely dissolve iridium metal, and the yield of the product is not high. Therefore, the undissolved iridium metal must be recovered and the same process must be repeated starting from the heat treatment step.

[0005] In addition, the process of dissolving iridium oxide in aqua regia is carried out at high temperatures, and the nitric acid contained in the aqua regia is released as steam, which can cause environmental pollution. Summary of the Invention [Problem to be solved by the invention]

[0006] One embodiment of the present invention provides a method for producing iridium chloride hydrate, which has a high conversion rate of iridium metal, no unreacted iridium due to the high solubility of iridium metal, a low alkali metal content resulting in a high product purity, and no nitrogen oxides are generated, making it environmentally friendly.

[0007] Another embodiment of the present invention provides a method for producing iridium chloride using the produced iridium chloride hydrate. [Means for solving the problem]

[0008] According to one embodiment of the present invention, there is provided a method for producing iridium chloride hydrate, including: a mixing step of preparing a mixture of iridium metal powder and an alkali metal compound; a calcination step of calcining the mixture to produce alkali-containing iridium oxide; a hydrochloric acid aqueous solution washing step of washing the alkali-containing iridium oxide with a hydrochloric acid aqueous solution to obtain iridium oxide; and a hydrochloric acid dissolution reaction step of dissolving the iridium oxide in hydrochloric acid under pressure and then reacting the iridium oxide.

[0009] The alkali metal compound can include an alkali metal hydroxide, an alkali metal peroxide, or a mixture thereof.

[0010] The alkali metal hydroxide may include sodium hydroxide, potassium hydroxide, lithium hydroxide, or mixtures thereof.

[0011] The alkali metal peroxide may include sodium peroxide, potassium peroxide, lithium peroxide, or mixtures thereof.

[0012] The alkali metal hydroxide may include a mixture of sodium hydroxide and sodium peroxide.

[0013] The mixture may contain 0.5 to 1 part by weight of the alkali metal compound per 1 part by weight of the iridium metal powder.

[0014] The mixture may contain 1 to 3 parts by weight of alkali metal peroxide per 1 part by weight of iridium metal powder.

[0015] The alkali-containing iridium oxide may include a compound represented by the following Chemical Formula 1:

[0016] [Chemical formula 1]

[0017] Nax Ir y O z

[0018] In Chemical Formula 1, x is an integer of 2 to 4, y is an integer of 1 to 3, and z is an integer of 3 to 8.

[0019] The alkali-containing iridium oxide may include Na2IrO3, Na4IrO4, Na4Ir3O8, or mixtures thereof.

[0020] In the firing step, firing is carried out at a high temperature of 750°C or more.

[0021] Between the calcination step and the hydrochloric acid aqueous solution washing step, a water washing step of washing the alkali-containing iridium oxide with water at 60°C to 70°C for 2 to 4 hours may be further included.

[0022] In the hydrochloric acid aqueous solution washing step, the concentration of the hydrochloric acid aqueous solution is 5% to 10%.

[0023] The method may further include a step of drying the iridium oxide that has been washed with the aqueous hydrochloric acid solution to obtain a cake.

[0024] The iridium oxide cake has an alkali metal content of 10 ppm or less.

[0025] In the hydrochloric acid dissolution reaction step, the content of hydrochloric acid is 5 to 15 parts by weight per 1 part by weight of iridium oxide.

[0026] The hydrochloric acid dissolution reaction step can be carried out under pressure of 5 to 10 pressures.

[0027] The hydrochloric acid dissolution reaction step can be carried out under pressure at 130°C to 170°C for 2 to 6 hours.

[0028] The method may further include a step of filtering the iridium chloride hydrate produced in the hydrochloric acid dissolution reaction step.

[0029] The iridium chloride hydrate produced has an alkali metal content of 10 ppm or less.

[0030] According to another embodiment of the present invention, there is provided a method for producing iridium chloride, in which the obtained iridium chloride hydrate is concentrated to produce iridium chloride. [Effects of the Invention]

[0031] The method for producing iridium chloride hydrate according to one embodiment of the present invention has a high conversion rate of iridium metal, no unreacted iridium exists due to the high solubility of iridium metal, a low alkali metal content results in a high product purity, and no nitrogen oxides are generated, making it environmentally friendly. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a process flow chart illustrating steps for producing iridium chloride hydrate and iridium chloride according to one embodiment.

[0033] [Figure 2] 1 is a graph showing the results of XRD analysis of alkali-containing iridium oxides produced at different firing temperatures in Experimental Example 1.

[0034] [Figure 3] 1 is a graph showing the results of XRD analysis of iridium oxide produced under different cleaning conditions in Experimental Example 2.

[0035] [Figure 4] 1 is a graph showing the results of XRD analysis of iridium chloride hydrate measured in Experimental Example 3.

[0036] [Figure 5] 1 is a photograph showing the iridium chloride hydrate and iridium chloride produced in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0037] The advantages and features of the techniques described below, and the manner in which they are achieved, will become apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the embodied forms are not limited to the embodiments disclosed below. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the meaning commonly understood by one of ordinary skill in the art. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless specifically defined otherwise. Throughout the specification, when a part is said to "comprise" a certain element, this means that it may further include other elements, but not to the exclusion of other elements, unless otherwise specified.

[0038] Also, the singular includes the plural unless the phrase specifically states otherwise.

[0039] FIG. 1 is a process flow diagram illustrating steps for producing iridium chloride hydrate and iridium chloride according to one embodiment of the present invention.

[0040] Referring to FIG. 1, the method for producing iridium chloride hydrate and iridium chloride will be described in detail.

[0041] The method for producing iridium chloride hydrate includes a mixing step (S1-1), a calcination step (S1-2), a hydrochloric acid aqueous solution washing step (S1-4), and a hydrochloric acid dissolution reaction step (S1-5).

[0042] In the mixing step (S1-1), a mixture of iridium metal powder and an alkali metal compound is prepared.

[0043] The alkali metal compound can include an alkali metal hydroxide, an alkali metal peroxide, or a mixture thereof, for example, a solid mixture of an alkali metal hydroxide and an alkali metal peroxide.

[0044] The alkali metal hydroxide can include sodium hydroxide, potassium hydroxide, lithium hydroxide, or mixtures thereof, for example, the alkali metal hydroxide is sodium hydroxide (NaOH).

[0045] The alkali metal peroxide can include sodium peroxide, potassium peroxide, lithium peroxide, or mixtures thereof; for example, the alkali metal peroxide can be sodium peroxide (Na2O2).

[0046] As an example, the alkali metal hydroxide may include a mixture of sodium hydroxide and sodium peroxide.

[0047] The mixture may contain 0.5 to 1 part by weight, for example 0.6 to 0.7 parts by weight, of the alkali metal compound per 1 part by weight of the iridium metal powder. If the content of the alkali metal compound is less than 0.5 parts by weight per 1 part by weight of iridium metal powder, the amount of alkali component adsorbed on the surface of the iridium metal may be insufficient, resulting in uneven oxidation during the firing process. If the content exceeds 1 part by weight, the excess alkali metal compound may cover the surface of the iridium metal, preventing the oxidizing agent from coming into contact with the iridium metal.

[0048] Alternatively, the mixture may contain 1 to 3 parts by weight, for example 1.75 to 2.25 parts by weight, of the alkali metal peroxide in the alkali metal compound per part by weight of the iridium metal powder. If the content of alkali metal peroxide is less than 1 part by weight per part by weight of iridium metal powder, the iridium metal may remain even after calcination due to a lack of oxidizing agent, and if it exceeds 3 parts by weight, the iridium metal may be peroxidized to form iridium nanoparticles, which may make it difficult to pass through the filter paper in the subsequent filtration process to obtain the product.

[0049] In this case, when the alkali metal compound contains a mixture of an alkali metal hydroxide and an alkali metal peroxide, the weight ratio of the alkali metal hydroxide to the alkali metal peroxide is 1:2 to 1:4, for example, 1:2.5 to 1:3.5. If the weight ratio of alkali metal peroxide is less than 2, iridium metal may remain even after calcination due to a lack of oxidizing agent, and if it exceeds 4, iridium metal may be overoxidized to form iridium nanoparticles, making it difficult to pass through the filter paper in the subsequent filtration process to obtain the product.

[0050] In the calcination step (S1-2), the mixture is calcined to produce alkali-containing iridium oxide.

[0051] The firing is carried out at 750°C or higher. If the calcination temperature is below 750°C, unreacted iridium metal may remain, whereas at temperatures above 750°C, the iridium metal may be completely converted to alkali-containing iridium oxide. For example, the firing is carried out by raising the temperature to 750° C. or higher over a period of 5 to 10 hours and maintaining the temperature at 750° C. or higher for 2 to 4 hours.

[0052] The alkali-containing iridium oxide produced by calcination may include a compound represented by the following Chemical Formula 1:

[0053] [Chemical formula 1]

[0054] Na x Ir y O z

[0055] In Chemical Formula 1, x is an integer of 2 to 4, y is an integer of 1 to 3, and z is an integer of 3 to 8.

[0056] For example, the alkali-containing iridium oxide represented by Chemical Formula 1 can include Na2IrO3, Na4IrO4, Na4Ir3O8, or a mixture thereof.

[0057] Optionally, the alkali-containing iridium oxide obtained in the calcination step may be washed with water before the hydrochloric acid aqueous solution washing step (S1-3).

[0058] The water may be deionized water, distilled water, or ultrapure water, and for example, deionized water may be used.

[0059] As an example, the water washing step may be carried out by washing iridium oxide with water containing alkali at 60°C to 70°C for 2 to 4 hours. If the temperature in the water washing step is below 60°C, the washing will not be complete and residual alkaline ions may remain after washing. If the temperature exceeds 70°C, the washing water may evaporate and become concentrated. If the water washing step is done for less than two hours, the washing may not be complete, and if it is done for more than four hours, the working time may be unnecessarily long.

[0060] Optionally, a further filtration step can be included after the water washing step. For example, filtration can be performed hot using a paper filter on a water-washed solution.

[0061] Optionally, after the filtration step, a water washing step may be further performed, for example, washing with pre-prepared hot water at 60°C to 70°C may be performed after filtration.

[0062] The water washing step can remove some of the alkali metal ions from the alkali-containing iridium oxide, thereby obtaining some iridium oxide. However, even after the water washing step, about 400 ppm or more of alkali metal components may remain.

[0063] Therefore, in the hydrochloric acid aqueous solution washing step (S1-4), the iridium oxide containing alkali is washed with a hydrochloric acid aqueous solution to reduce the content of the remaining alkali metal component to 10 ppm or less, thereby producing iridium oxide.

[0064] The concentration of the aqueous hydrochloric acid solution may be 5% to 10%. If the concentration of the hydrochloric acid solution is less than 5%, the cleaning effect will not be good and alkali metals may still remain, while if it exceeds 10%, some iridium metal may also be dissolved in addition to alkali metals.

[0065] Optionally, a filtration step can be further included after the aqueous hydrochloric acid washing step. For example, filtration is performed by using a paper filter at a high temperature to remove the solution washed with an aqueous hydrochloric acid solution.

[0066] Alternatively, the iridium oxide that has been washed with the aqueous hydrochloric acid solution can be dried to produce a cake.

[0067] Drying is carried out at 100°C or higher for 12 to 24 hours. If the drying temperature is less than 100°C, not only will the drying time be longer, but residual moisture may remain even after drying.

[0068] The content of residual alkali metal components can be reduced through the step of washing with an aqueous hydrochloric acid solution. As a result, the iridium oxide cake can have an alkali metal content of 10 ppm or less, for example, 0 ppm to 5 ppm.

[0069] If the content of alkali metal exceeds 10 ppm, the purity of the final product iridium chloride will decrease, which may have a negative effect on the catalytic reaction when producing a catalyst using this.

[0070] In the hydrochloric acid dissolution reaction step (S1-5), iridium oxide is dissolved in hydrochloric acid under pressure and then reacted to produce iridium chloride hydrate.

[0071] The content of hydrochloric acid relative to 1 part by weight of iridium oxide can be 5 parts by weight to 15 parts by weight, for example, 8 parts by weight to 10 parts by weight. If the content of hydrochloric acid per 1 part by weight of iridium oxide is less than 5 parts by weight, the content of chloride ions necessary for the reaction may be insufficient, and 100% conversion of iridium oxide to iridium chloride may not be achieved. If the content exceeds 15 parts by weight, excessive energy costs may be required to evaporate the hydrochloric acid aqueous solution in the subsequent concentration process.

[0072] The hydrochloric acid dissolution reaction step is carried out under pressure, and is illustratively carried out in a pressurized vessel. The pressure during pressurization is 5 to 10 pressures, for example, 6 to 8 pressures. Since the pressure increases in proportion to the reaction temperature, there is no need to separately adjust the pressure within the following temperature range.

[0073] The hydrochloric acid dissolution reaction step is carried out under pressure at 130°C to 170°C for 2 to 6 hours, for example, at 150°C to 170°C for 2 to 4 hours. If the temperature in the hydrochloric acid dissolution reaction step is below 130°C, it may be difficult to convert iridium oxide to iridium chloride 100%. If it exceeds 170°C, the conversion to iridium chloride is easy, but the pressure vessel may corrode or deform, making commercial application difficult. If the time is less than 2 hours, the conversion reaction rate of iridium chloride may decrease, and if it exceeds 6 hours, excessive energy costs may be incurred.

[0074] Optionally, a filtration step may be further included after the hydrochloric acid dissolution reaction step.

[0075] Through the filtration step, the iridium chloride hydrate produced in the hydrochloric acid dissolution reaction step can be obtained. For example, filtration is carried out by using a paper filter to filter the solution that has undergone the hydrochloric acid dissolution reaction at a high temperature. At this time, a minimum amount of rinse solution, such as deionized water, is used to recover the remaining solution.

[0076] The produced iridium chloride hydrate may be, for example, a compound represented by H2IrCl6·xH2O. The iridium chloride hydrate obtained in the hydrochloric acid dissolution reaction step is substantially completely dissolved, for example, 99.9% or more dissolved, and has an alkali metal content of 10 ppm or less.

[0077] In one embodiment of the method for producing iridium chloride hydrate, the calcination step (S2-1) induces complete oxidation of iridium metal, thereby increasing the production yield; the hydrochloric acid aqueous solution washing step (S1-4) uses a single solvent, hydrochloric acid, to prevent the generation of nitrogen oxides; the alkali metal component used as an oxidant is removed using hydrochloric acid before the pressure reaction, resulting in an alkali metal content of 10 ppm or less in the obtained iridium chloride; and the hydrochloric acid dissolution reaction step (S1-5) results in a solubility of 99.9% or more through the pressure reaction, and the absence of unreacted iridium results in extremely high product purity.

[0078] In another embodiment of the method for producing iridium chloride, the produced iridium chloride hydrate is concentrated to produce iridium chloride (S2-1).

[0079] For example, the concentration can be performed by vacuum distillation.

[0080] The iridium chloride produced can be, for example, a compound represented by IrCl4·xH2O. [Example]

[0081] Specific examples of the invention will be presented below. However, the examples described below are merely for the purpose of specifically illustrating and explaining the invention, and should not be construed as limiting the scope of the invention.

[0082] [Production Example: Production of Iridium Chloride Hydrate]

[0083] Example 1

[0084] 13.3 g of NaOH powder and 40.2 g of Na2O2 powder are added to 20 g of Ir metal powder and then physically mixed.

[0085] The mixed powder is placed in a crucible and fired at 750°C, then allowed to cool slowly. The firing is carried out in stages, with the temperature raised to 750°C for 6 hours and maintained at that temperature for 2.5 hours. During firing, the lid of the crucible is left open.

[0086] The calcined powder is placed in 500 ml of deionized water and the solution is heated to 65° C. with ultrasonic mixing. Once the temperature reaches 65°C, the mixture is stirred using a magnetic spin bar for 2 hours.

[0087] The stirred solution is filtered hot using a paper filter. After filtration, the mixture is washed with 2 L of pre-prepared hot water at 65°C.

[0088] In addition, 200 g of 10% HCl solution (180 g of deionized water + 20 g of HCl) is prepared and then washed.

[0089] After the cleaning was completed, the cleaning solution was subjected to ICP analysis, and the results confirmed that no Ir component was present in the cleaning solution.

[0090] After washing, the powder was dried at 120°C for 12 hours or more to remove Na x IrO y Collect the cake.

[0091] The dried cake is placed in a pressure vessel and mixed with 242 g of HCl.

[0092] The prepared pressure vessel is placed in a heat treatment furnace, and subjected to a high-temperature pressure reaction at 150°C for 4 hours, followed by cooling.

[0093] The dissolved solution is filtered using a paper filter. Use a minimum amount of rinse solution (deionized water) to recover any residual solution.

[0094] (Examples 2 to 11 and Comparative Examples 1 and 2)

[0095] Iridium chloride hydrate was produced in the same manner as in Example 1, except that the reaction conditions in Example 1 were changed as shown in Table 1 below.

[0096] For reference, in Comparative Examples 1 and 2, aqua regia (hydrochloric acid:nitric acid=3:1 volume ratio) is used in place of hydrochloric acid in the dissolution reaction stage.

[0097] [Table 1]

[0098] [Experimental Example 1: XRD analysis results of products at different firing temperatures]

[0099] The state of the alkali-containing iridium oxides produced by changing the firing temperature to 750°C, 650°C, 700°C, and 800°C in Examples 1 and 4 to 6, respectively, was analyzed by XRD, and the results are shown in Figure 2.

[0100] Referring to FIG. 2, it can be seen that at firing temperatures below 750°C, iridium metal that did not react with the oxidizing agent Na2O2 remained, and IrO2, a simple oxide form without being bound to Na ions, was also produced.

[0101] On the other hand, under firing conditions of 750°C or higher, the iridium metal completely combines with the Na ions and oxidizing agent, and the Na x IrO yIt can be confirmed that it is converted into

[0102] [Experimental Example 2: XRD analysis results of products according to washing conditions]

[0103] The state of iridium oxide produced by changing the washing conditions in Examples 1, 7, and 8 was analyzed by XRD, and the results are shown in FIG.

[0104] Example 1 is the result of first washing with deionized water and second washing with 10% hydrochloric acid aqueous solution, Example 8 is the result of first washing with deionized water and second washing with 5% hydrochloric acid aqueous solution, and Example 7 is the result of first washing with deionized water but not second washing with hydrochloric acid aqueous solution.

[0105] Referring to FIG. 3, most of the Na ions contained in the iridium oxide are removed by washing with deionized water, but some remain in the iridium oxide.

[0106] It can be seen that if a secondary cleaning is performed using an additional 5% to 10% aqueous hydrochloric acid solution after cleaning with deionized water, most of the Na ions in the iridium oxide are finally removed.

[0107] Specifically, when the XRD analysis results were examined, the Na content was 0.001%. x IrO y The peak of Na is still present, but after additional washing with aqueous hydrochloric acid, x IrO y It can be seen that the peak disappears.

[0108] Furthermore, elemental analysis (ICP analysis) was performed on the oxide from which the sodium ions had been removed. As a result, after additional washing with a hydrochloric acid solution, the sodium ions in the iridium oxide were measured to be at the 10 ppm level when washed with a 5% hydrochloric acid solution, and at the 4 ppm level when washed with a 10% hydrochloric acid solution.

[0109] [Experimental Example 3: Confirmation of the produced iridium chloride hydrate]

[0110] The iridium content of the product prepared in Example 1 is measured by ICP analysis.

[0111] As a result, a yield of 99.9% or more was confirmed based on the initial Ir powder, and the residual Na content in the product was 4.1 ppm, confirming that it had been almost completely removed.

[0112] The product was dried at 80°C to remove moisture and then subjected to XRD analysis. The results are shown in Figure 4. In Figure 4, Reference Example 1 shows the results for reagent grade (manufactured by Aldrich) H2IrCl6·xH2O. Referring to Figure 4, it was confirmed that the crystals exhibited the same shape as reagent grade H2IrCl6·xH2O (manufactured by Aldrich).

[0113] The product produced is dried at 100°C for 4 hours and the dried product is recovered. The dried product was analyzed by ion chromatography and found to have a Cl / Ir molar ratio of 4.2.

[0114] The results of the thermogravimetric analysis are shown in Table 2.

[0115] [Table 2]

[0116] Referring to Table 2, Example 1 and Reference Example 1 had almost the same residual amounts after thermal analysis at 900°C. This confirmed that the dried product was produced using IrCl4.

[0117] The resulting product was diluted 1000 times and the color was compared with that of commercially available Reference Example 1. The results are shown in FIG. In Figure 5, (A) is a photograph of iridium metal powder, (B) is a photograph of the product H2IrCl6 solution, (B') is a photograph of the product H2IrCl6 solution after 1000-fold dilution and dissolution, and (Ref. B') is a photograph of Reference Example 1. (C) is a photograph of IrCl4, which is the dried product, (C') is a photograph of IrCl4, which is the dried product, after being diluted 1000 times and dissolved, and (Ref. C') is a photograph of Reference Example 1. In Figure 5, Reference Example 1 shows reagent grade (manufactured by Aldrich) H2IrCl 6· Results for xH2O.

[0118] Referring to Figure 5, the product was identified as H2IrCl6·xH2O, and the dried product was identified as IrCl4·xH2O.

[0119] [Experimental Example 4: Measurement of yield and Na content of produced iridium chloride hydrate]

[0120] The yield and Na content of the iridium chloride hydrates produced in Examples 1 to 11 and Comparative Examples 1 and 2 were measured, and the results are shown in Table 3.

[0121] [Table 3]

[0122] Referring to Table 3, Examples 1 to 3 are the cases where catalysts were prepared by adjusting the ratio of alkali metal compound to iridium metal during calcination. In Example 2, the iridium metal was not completely oxidized, and therefore, complete dissolution did not occur in the final oxide dissolution reaction stage. In Example 3, an excessive amount of alkali metal compound was added, causing the iridium oxide to dissolve and be eluted in deionized water during the cleaning process.

[0123] In Example 1 and Examples 4 to 6, the catalysts were produced at different calcination temperatures. When the firing temperature is below 750°C, unoxidized iridium exists, and the dissolution rate is low during the dissolution reaction stage. Only when firing is performed at a temperature above 750°C can the single Na x IrO y It can be seen that a complex oxide form is formed.

[0124] Examples 1, 7, and 8 are results of comparing the amount of Na ions in the product depending on the degree of washing with the aqueous hydrochloric acid solution in the washing step. In Example 7, the secondary washing using an aqueous hydrochloric acid solution was not carried out, and as a result, it was confirmed that a large amount of Na ions remained in the final product. Example 8 shows the results of washing with a hydrochloric acid solution prepared with a concentration of 5%, and it was confirmed that even a small amount of hydrochloric acid provided excellent washing effects.

[0125] In Example 1 and Examples 9 to 11, the dissolution reaction temperatures were varied during the dissolution reaction stage. It was confirmed that when pressure dissolution was performed at temperatures below 150°C, a low dissolution rate was observed, but complete dissolution occurred at temperatures above 150°C.

[0126] Example 1, Comparative Example 1, and Comparative Example 2 are produced using different dissolution methods in the dissolution reaction stage. In the case of the aqua regia dissolution method, the temperature cannot be raised above 100°C when performed at normal pressure, and low solubility is shown. In particular, Comparative Example 1 shows low solubility and a high residual rate of Na ions in the product because washing with a hydrochloric acid aqueous solution was not performed in the washing step.

[0127] Therefore, as in Example 1, iridium oxide is produced by additionally removing Na ions using a 5% to 10% hydrochloric acid solution at a weight ratio of iridium metal to alkali metal compound of 2.6, a calcination temperature of 750°C or higher, and a pressurized reaction at 150°C or higher from the iridium oxide produced in this manner, and an iridium chloride solution with a dissolution rate of 99% or higher can be produced.

[0128] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the claims also fall within the scope of the present invention. [Industrial Applicability]

[0129] One embodiment provides a method for producing iridium chloride hydrate that is environmentally friendly because it has a high conversion rate of iridium metal, no unreacted iridium due to the high solubility of iridium metal, a low alkali metal content resulting in a high product purity, and no nitrogen oxides are generated.

[0130] Another embodiment provides a method for producing iridium chloride utilizing the produced iridium chloride hydrate.

Claims

1. a mixing step of preparing a mixture of iridium metal powder and an alkali metal compound; a calcination step of calcining the mixture to produce alkali-containing iridium oxide; a step of washing the alkali-containing iridium oxide with an aqueous hydrochloric acid solution to obtain iridium oxide; a hydrochloric acid dissolution reaction step of dissolving the iridium oxide in hydrochloric acid under pressure and then reacting the iridium oxide; The alkali metal compound includes an alkali metal hydroxide and an alkali metal peroxide.

2. the alkali metal hydroxide comprises sodium hydroxide, potassium hydroxide, lithium hydroxide, or a mixture thereof; 2. The method for producing iridium chloride hydrate according to claim 1, wherein the alkali metal peroxide comprises sodium peroxide, potassium peroxide, lithium peroxide, or a mixture thereof.

3. 3. The method for producing iridium chloride hydrate according to claim 2, wherein the alkali metal compound comprises a mixture of the sodium hydroxide and the sodium peroxide.

4. 2. The method for producing iridium chloride hydrate according to claim 1, wherein the mixture contains 0.5 to 1 part by weight of the alkali metal compound per 1 part by weight of the iridium metal powder.

5. 2. The method for producing iridium chloride hydrate according to claim 1, wherein the mixture contains 1 to 3 parts by weight of the alkali metal peroxide per 1 part by weight of the iridium metal powder.

6. 2. The method for producing iridium chloride hydrate according to claim 1, wherein the alkali-containing iridium oxide comprises a compound represented by the following Chemical Formula 1: [Chemical formula 1] Na ｘ Ir ｙ O ｚ (In the above Chemical Formula 1, x is an integer of 2 to 4, y is an integer of 1 to 3, and z is an integer of 3 to 8.)

7. The alkali-containing iridium oxide is Na ２ IrO ３ , Na ４ IrO ４ , Na ４ Ir ３ O ８ 2. The method for producing iridium chloride hydrate according to claim 1, wherein the iridium chloride hydrate comprises:

8. 2. The method for producing iridium chloride hydrate according to claim 1, wherein the calcination is performed at a high temperature of 750° C. or higher.

9. Between the calcination step and the hydrochloric acid aqueous solution washing step, 2. The method for producing iridium chloride hydrate according to claim 1, further comprising a water washing step of washing the alkali-containing iridium oxide with water at 60 to 70° C. for 2 to 4 hours.

10. 2. The method for producing iridium chloride hydrate according to claim 1, wherein the concentration of the aqueous hydrochloric acid solution in the washing step is 5% to 10%.

11. 2. The method for producing iridium chloride hydrate according to claim 1, further comprising the step of drying the iridium oxide that has been washed with the aqueous hydrochloric acid solution to obtain a cake.

12. 2. The method for producing iridium chloride hydrate according to claim 1, wherein the iridium oxide cake has an alkali metal content of 10 ppm or less.

13. 2. The method of claim 1, wherein the amount of hydrochloric acid in the hydrochloric acid dissolution reaction step is 5 to 15 parts by weight per 1 part by weight of the iridium oxide.

14. 2. The method for producing iridium chloride hydrate according to claim 1, wherein the hydrochloric acid dissolving reaction step is carried out under pressure of 5 to 10 pressures.

15. 2. The method for producing iridium chloride hydrate according to claim 1, wherein the hydrochloric acid dissolution reaction step is carried out under pressure at 130 to 170° C. for 2 to 6 hours.

16. 2. The method for preparing iridium chloride hydrate according to claim 1, further comprising the step of filtering the iridium chloride hydrate prepared in the hydrochloric acid dissolution reaction step.

17. 2. The method for producing iridium chloride hydrate according to claim 1, wherein the produced iridium chloride hydrate has an alkali metal content of 10 ppm or less.

18. A method for producing iridium chloride, comprising concentrating the iridium chloride hydrate obtained by the method for producing iridium chloride hydrate according to claim 1.

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