Preparation method of chloroiridic acid and preparation method of iridium trichloride hydrate
Through the oxidation reaction of oxalic acid iridium acid, hydrochloric acid and gas oxidant, combined with the reduction reaction of formaldehyde, chloroiridium acid and hydrated iridium trichloride were prepared, which solved the problem of nitrate and nitrite residues in the existing methods and achieved high purity iridium chloride preparation improves product quality and performance.
Patent Information
- Application Number
- CN202411514569.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-29
- Publication Date
- 2025-02-18
AI Technical Summary
The use of nitrogen-containing reagents in the existing iridium chloride preparation methods leads to residual nitrate and nitrite in the product, reducing the purity of iridium chloride, affecting the product quality and the performance of subsequent iridium functional complexes and iridium-containing catalysts.
oxalic acid, hydrochloric acid and gas oxidants (such as chlorine and/or ozone) are used to prepare chloroiridium acid, and then reduce the reaction with formaldehyde to prepare hydrated iridium trichloride. No nitrogen-containing reagents are used throughout the process to avoid the introduction of nitric acid. Root and nitrite.
The chloroiridium acid and hydrated iridium trichloride do not contain nitrate and nitrite, and are highly purified. They are suitable for subsequently produced iridium functional complexes and iridium-containing catalysts, improving the quality and performance of the product.
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Figure CN119461518A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of precious metal compounds, and in particular to a method for preparing chloroiridic acid and a method for preparing hydrated iridium trichloride. Background Art
[0002] Iridium chloride mainly includes chloroiridic acid and hydrated iridium trichloride, etc. It is an important basic raw material for the preparation of iridium functional compounds (such as iridium functional complexes and iridium-containing catalysts), and has important applications in the fields of petrochemicals, organic synthesis, electrode materials, phosphorescent materials, catalytic precursors and nanomaterial precursors. The purity of iridium chloride has an extremely important influence on the performance of preparing other iridium functional complexes and iridium-containing catalysts, and the preparation method, preparation device and impurity removal device will affect the purity of iridium chloride.
[0003] At present, the preparation methods of iridium chloride mainly include alkali fusion method and high-temperature chlorination method. Among them, the alkali fusion method is to heat and melt iridium powder, alkaline earth metal hydroxide and peroxide in a crucible, cool the melt in the crucible after the reaction is completed, and then leach it with hydrochloric acid to obtain ammonium chloroiridate, then dissolve the ammonium chloroiridate with aqua regia, drive out the nitrate, and distill under reduced pressure to obtain chloroiridic acid, and reduce the chloroiridic acid with hydrazine hydrate or hydrazine hydrochloride to obtain iridium trichloride; the high-temperature chlorination method is to mix iridium powder and sodium chloride, pass chlorine gas to carry out high-temperature chlorination reaction, after the reaction is completed, leach the reaction mixture with water, oxidize it with chlorine gas and nitric acid, add ammonium chloride solution to obtain ammonium chloroiridate precipitate, dissolve the ammonium chloroiridate precipitate with aqua regia, drive out the nitrate and distill under reduced pressure to obtain chloroiridic acid, add hydrazine hydrate, hydrazine hydrochloride or alcohol reducing agent to the chloroiridic acid to reduce it, and obtain hydrated iridium trichloride.
[0004] However, the above-mentioned preparation methods of iridium chloride all involve the use of nitrogen-containing reagents (such as nitric acid as an oxidizing agent, nitric acid in aqua regia, and hydrazine hydrate or hydrazine hydrochloride as a reducing agent), which will result in residual nitrogen-containing impurities such as nitrate and nitrite in the prepared iridium chloride product. The nitrogen-containing impurities are easily coordinated with the iridium chloride, reducing the purity of the iridium chloride, thereby affecting the product quality of the iridium chloride and the performance of other iridium functional complexes and iridium-containing catalysts prepared subsequently. Summary of the invention
[0005] In view of this, the object of the present invention is to provide a method for preparing chloroiridic acid and a method for preparing hydrated iridium trichloride. The chloroiridic acid and hydrated iridium trichloride prepared by the preparation method provided by the present invention do not contain nitrate and nitrite, and have high purity.
[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:
[0007] The present invention provides a method for preparing chloroiridic acid, comprising the following steps:
[0008] Mixing iridium oxalate, hydrochloric acid and a gaseous oxidant to carry out an oxidation reaction to obtain iridium chloroate;
[0009] The gaseous oxidant includes chlorine and / or ozone.
[0010] Preferably, the ratio of the mass of the iridium oxalate to the volume of the hydrochloric acid is 1000 g: 500-1000 mL.
[0011] Preferably, the concentration of the hydrochloric acid is 6 to 12 mol / L.
[0012] Preferably, the ratio of the amount of iridium oxalate to the flow rate of the gaseous oxidant is 1 mol: 10-30 mL / min.
[0013] Preferably, the oxidation reaction is carried out under reflux conditions; the oxidation reaction time is 2 to 5 hours.
[0014] Preferably, after the oxidation reaction, the process further comprises concentrating the oxidation liquid obtained from the oxidation reaction to obtain chloroiridic acid.
[0015] The present invention provides a method for preparing hydrated iridium trichloride, comprising the following steps:
[0016] The chloroiridic acid prepared by the preparation method described in the above technical solution is mixed with formaldehyde and subjected to a reduction reaction to obtain hydrated iridium trichloride.
[0017] Preferably, the molar ratio of the chloroiridic acid to formaldehyde is 0.5-0.55:1.
[0018] Preferably, the reduction reaction is carried out under reflux conditions; the reduction reaction time is 30 to 50 minutes.
[0019] Preferably, after the reduction reaction, the process further comprises concentrating the reducing liquid obtained from the reduction reaction to obtain iridium trichloride.
[0020] The invention provides a method for preparing chloroiridic acid, comprising the following steps: mixing iridic oxalate, hydrochloric acid and a gaseous oxidant, and performing an oxidation reaction to obtain chloroiridic acid; the gaseous oxidant comprises chlorine and / or ozone. The invention uses chlorine and / or ozone as a gaseous oxidant to oxidize iridic oxalate, and during the oxidation process, oxalate is oxidized and decomposed into carbon dioxide, and iridium (IV) ions and chloride ions combine to generate chloroiridic acid, and there is no nitrogen-containing compound in the reaction raw material, and no nitrogen element and impurity metal ions are introduced during the reaction process. The obtained chloroiridic acid does not contain nitrogen-containing impurities such as nitrate and nitrite, and the obtained chloroiridic acid has high purity. Moreover, the invention uses cheap and easily available iridic oxalate as a preparation raw material, has low cost, and the conversion rate of iridium is 100%, which is high; the preparation steps are simple, and no additional complicated impurity removal steps need to be designed, and the invention is suitable for industrial production.
[0021] The present invention also provides a method for preparing hydrated iridium trichloride, comprising the following steps: mixing chloroiridic acid obtained by the preparation method described in the above technical solution with formaldehyde, and performing a reduction reaction to obtain hydrated iridium trichloride. In the present invention, formaldehyde is used as a reducing agent, and during the preparation process, formaldehyde is oxidized and decomposed into carbon dioxide and water, and the obtained hydrated iridium trichloride does not contain nitrogen-containing impurities such as nitrate and nitrite, and the obtained hydrated iridium trichloride has high purity. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 Flow chart of the preparation method of chloroiridic acid and hydrated iridium trichloride in the examples. DETAILED DESCRIPTION
[0023] The invention provides a method for preparing chloroiridic acid, comprising the following steps: mixing oxalic iridic acid, hydrochloric acid and a gas oxidant, and performing an oxidation reaction to obtain chloroiridic acid; the gas oxidant comprises chlorine and / or ozone.
[0024] Unless otherwise specified, the reagents used in the present invention are all commercially available products in the art.
[0025] In the present invention, the ratio of the mass of the iridium oxalate to the volume of the hydrochloric acid can be 1000g:500-1000mL. In a specific embodiment, it can be 1000g:500mL, 1000g:600mL, 1000g:700mL, 1000g:800mL, 1000g:900mL or 1000g:1000mL; the concentration of the hydrochloric acid can be 6-12mol / L. In a specific embodiment, it can be 6mol / L, 7mol / L, 8mol / L, 9mol / L, 10mol / L, 11mol / L or 12mol / L.
[0026] In the present invention, the ratio of the amount of iridium oxalate to the flow rate of the gaseous oxidant can be 1 mol: 10-30 mL / min. In a specific embodiment, it can be 1 mol: 10 mL / min, 1 mol: 15 mL / min, 1 mol: 20 mL / min, 1 mol: 25 mL / min or 1 mol: 30 mL / min.
[0027] In the present invention, the oxidation reaction can be carried out under reflux conditions; the temperature of the oxidation reaction can be 80-100°C, and in specific embodiments, can be 80°C, 82°C, 85°C, 88°C, 90°C, 92°C, 95°C, 98°C or 100°C; the time of the oxidation reaction can be 2-5h, and in specific embodiments, can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h.
[0028] In the present invention, when the gas oxidant includes chlorine, the chemical reaction involved is: H2IrC2O4+3Cl2=H2IrCl6+2CO2; when the gas oxidant includes ozone, the chemical reaction involved is: H2IrC2O4+2O3+6HCI=H2IrCl6+3H2O+2CO2.
[0029] After the oxidation reaction is completed, the present invention may further include concentrating the oxidation liquid obtained by the oxidation reaction (referred to as the first concentration) to obtain chloroiridic acid. In the present invention, the first concentration may include first rotary evaporation concentration; the temperature of the first rotary evaporation concentration may be 60°C; the pressure of the first rotary evaporation concentration may be 70Pa. In the present invention, the first concentration process may further include testing the first concentrated solution obtained by the first concentration, and stopping the concentration when the mass percentage of iridium in the first concentrated solution is 35-36%, to obtain chloroiridic acid.
[0030] In the present invention, the carbon dioxide and acid gas (formed by the reaction of carbon dioxide and water) obtained by the oxidation reaction can be absorbed by alkali solution. In the present invention, the alkali in the alkali solution can include alkali metal hydroxides, which can be sodium hydroxide and / or potassium hydroxide in a specific embodiment; the mass percentage of the alkali solution can be 10-30%, and in a specific embodiment, it can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28% or 30%. The present invention achieves zero emission of harmful gases by absorbing byproduct carbon dioxide and acid gas through alkali solution.
[0031] The invention also provides a method for preparing hydrated iridium trichloride, comprising the following steps: mixing chloroiridic acid obtained by the preparation method described in the above technical scheme with formaldehyde, and performing a reduction reaction to obtain hydrated iridium trichloride.
[0032] In the present invention, the chemical reaction involved in the preparation method of hydrated iridium trichloride is as follows:
[0033] H2IrCl6+HCHO→IrCl3·nH2O+H2O+CO2.
[0034] In the present invention, the molar ratio of the chloroiridic acid and formaldehyde can be 0.5-0.55:1, and in a specific embodiment, can be 0.5:1, 0.51:1, 0.52:1, 0.53:1, 0.54:1 or 0.55:1. In the present invention, the formaldehyde can be used in the form of a formaldehyde aqueous solution; the mass percentage of formaldehyde in the formaldehyde aqueous solution can be 10-30%. In the present invention, the reduction reaction can be carried out under reflux conditions; the temperature of the reduction reaction can be 80-100°C, and in a specific embodiment, can be 80°C, 82°C, 85°C, 88°C, 90°C, 92°C, 95°C, 98°C or 100°C; the time of the reduction reaction can be 30-50min, and in a specific embodiment, can be 30min, 35min, 40min, 45min or 50min.
[0035] In the present invention, the carbon dioxide obtained by the reduction reaction can be absorbed by alkali solution. The alkali in the alkali solution can include alkali metal hydroxides, which can be sodium hydroxide and / or potassium hydroxide in a specific embodiment; the mass percentage of the alkali solution can be 10-30%, and in a specific embodiment, it can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28% or 30%. The present invention uses formaldehyde as a reducing agent to carry out a reduction reaction. During the reaction, formaldehyde is oxidized to carbon dioxide, and excess formaldehyde can also be converted into carbon dioxide by heating, thereby avoiding the introduction and residue of acid radicals other than carbon dioxide caused by the use of other aldehydes, and also avoiding the residue of nitrate radicals and nitrite radicals caused by the use of reducing agents such as hydrazine hydrate or hydrazine hydrochloride, which is beneficial to improving the purity of hydrated iridium trichloride.
[0036] After the reduction reaction is completed, the present invention may further include concentrating the reduced raw material liquid obtained by the reduction reaction (referred to as the second concentration) to obtain hydrated iridium trichloride. In the present invention, the second concentration may include a second rotary evaporation concentration; the temperature of the second rotary evaporation concentration may be 60° C.; the pressure of the second rotary evaporation concentration may be 70 mbar. The present invention has no particular limitation on the time of the second concentration, as long as the solvent can be evaporated to dryness.
[0037] In order to further illustrate the present invention, a method for preparing chloroiridic acid and a method for preparing iridium trichloride provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0038] Example 1
[0039] Figure 1 The preparation method flow chart of chloroiridic acid and hydrated iridium trichloride in the embodiment. The specific steps are as follows:
[0040] 2000g of iridium oxalate (the mass percentage of iridium is 41.95%) was added, and 1L of hydrochloric acid with a concentration of 6mol / L was added under stirring. Ozone (the flow rate of ozone is 10mL / min) was introduced into the above solution, and the solution was heated to reflux for oxidation reaction for 2h. After the reaction was completed, the obtained oxidation reaction liquid was concentrated by rotary evaporation at 60°C and 70mbar to evaporate the solvent to obtain 2397.14g of chloroiridic acid, the mass percentage of iridium in the chloroiridic acid was 35%, and the yield was 100%.
[0041] 720.2 g of a 10% formaldehyde aqueous solution was added to the obtained chloroiridic acid, and the mixture was heated to reflux for a reduction reaction for 30 min. After the reaction was completed, the obtained reduction reaction liquid was concentrated and evaporated to dryness by rotary evaporation at 60° C. and 70 mbar to obtain 1544.55 g of hydrated iridium trichloride (solid), wherein the mass percentage of iridium in the hydrated iridium trichloride was 54.32%, and the yield was 100%.
[0042] The impurity metal content in chloroiridic acid and hydrated iridium trichloride was determined by ICP-MS, and the nitrate and nitrite content in chloroiridic acid and hydrated iridium trichloride was determined by ion chromatography. The results are shown in Tables 1 and 2 (unit: impurity metal: wt%; nitrate and nitrite: ppm).
[0043] Table 1 Contents of impurity metals, nitrates and nitrites in the chloroiridic acid obtained in Example 1
[0044] Impurities content Impurities content Impurities content Pt <0.003 Pd <0.002 R <0.003 Ru <0.002 Au <0.001 Ag <0.001 Na <0.004 Cu <0.003 Mn <0.002 Fe <0.003 Mg <0.003 Si <0.002 Ca <0.001 Al <0.002 Pb <0.001 Nitrate Not detected Nitrite Not detected
[0045] Table 2 Contents of impurity metals, nitrates and nitrites in iridium trichloride obtained in Example 1
[0046] Impurities content Impurities content Impurities content Ca <0.002 Fe <0.005 Na <0.002 Cu 0.002 Mg <0.003 Pb <0.001 Mn <0.003 Al <0.001 Si <0.005 Nitrate Not detected Nitrite Not detected
[0047] It can be seen from Table 1 and Table 2 that the content of impurity metals in the chloroiridic acid and hydrated iridium trichloride prepared by the preparation method provided by the present invention is lower than the requirements of the YS-T 595-2022 and YST 643-2007 standards, and does not contain nitrate and nitrite, and has high purity.
[0048] Example 2
[0049] 3000g of iridium oxalate (the mass percentage of iridium is 41.95%) was added, and 1.5L of hydrochloric acid with a concentration of 6mol / L was added under stirring. Chlorine gas (the flow rate of chlorine gas is 30mL / min) was passed into the above solution, and the solution was heated to reflux for oxidation reaction for 2h. After the reaction was completed, the obtained oxidation reaction feed liquid was concentrated by rotary evaporation at 60°C and 70mbar to evaporate the solvent to obtain 3595.71g of chloroiridic acid, the mass percentage of iridium in the chloroiridic acid was 35%, and the yield was 100%.
[0050] 360.1 g of a 30% formaldehyde aqueous solution was added to the obtained chloroiridic acid, and the mixture was heated to reflux for a reduction reaction for 30 min. After the reaction was completed, the obtained reduction reaction liquid was concentrated and evaporated to dryness by rotary evaporation at 60° C. and 70 mbar to obtain 2310.44 g of hydrated iridium trichloride (solid), wherein the mass percentage of iridium in the hydrated iridium trichloride was 54.47%, and the yield was 100%.
[0051] The impurity metal content in chloroiridic acid and hydrated iridium trichloride was determined by ICP-MS, and the nitrate and nitrite content in chloroiridic acid and hydrated iridium trichloride was determined by ion chromatography. The results are shown in Tables 3 and 4 (unit: impurity metal: wt%; nitrate and nitrite: ppm).
[0052] Table 3 Contents of impurity metals, nitrates and nitrites in the chloroiridic acid obtained in Example 2
[0053] Impurities content Impurities content Impurities content Pt <0.002 Pd <0.003 R <0.002 Ru <0.001 Au <0.001 Ag <0.001 Na <0.003 Cu <0.002 Mn <0.001 Fe <0.002 Mg <0.002 Si <0.003 Ca <0.002 Al <0.003 Pb <0.002 Nitrate Not detected Nitrite Not detected
[0054] Table 4 Contents of impurity metals, nitrates and nitrites in iridium trichloride obtained in Example 2
[0055] Impurities content Impurities content Impurities content Ca <0.001 Fe <0.005 Na <0.003 Cu 0.002 Mg <0.002 Pb <0.001 Mn <0.001 Al <0.001 Si <0.004 Nitrate Not detected Nitrite Not detected
[0056] It can be seen from Table 3 and Table 4 that the content of impurity metals in the chloroiridic acid and hydrated iridium trichloride prepared by the preparation method provided by the present invention is lower than the requirements of YS-T 595-2022 and YST 643-2007 standards, and does not contain nitrate and nitrite, and has high purity.
[0057] Comparative Example 1
[0058] 500g iridium powder, 500g sodium peroxide and 1500g sodium hydroxide were mixed uniformly, heated and roasted at 650°C for 5h. After the roasting was completed, the calcined product obtained was water-soaked, repeatedly washed, and undissolved iridium powder was removed by filtration to obtain a water immersion liquid. Chlorine (the flow rate of chlorine was 30mL / min) was introduced into the water immersion liquid obtained, and the reaction was carried out for 10min. Excessive ammonium chloride was added to the reaction liquid obtained, and the precipitation and washing were performed to obtain an ammonium chloroiridate precipitate. The ammonium chloroiridate precipitate obtained was dissolved with aqua regia, and nitre was removed. The chloroiridic acid 1357.14g was concentrated, and the mass percentage of iridium in the chloroiridic acid was 35%, and the yield was 95%.
[0059] 70 g of hydrazine hydrate was added to the obtained chloroiridic acid, heated to reflux, and a reduction reaction was carried out for 1 h. After the reaction was completed, the obtained reduction reaction liquid was concentrated and evaporated to dryness to obtain 874.77 g of iridium trichloride hydrate, the mass percentage of iridium in the iridium trichloride hydrate was 54.23%, and the yield was 95% (calculated from the iridium powder).
[0060] The impurity metal content in chloroiridic acid and hydrated iridium trichloride was determined by ICP-MS, and the nitrate and nitrite content in chloroiridic acid and hydrated iridium trichloride was determined by ion chromatography. The results are shown in Tables 5 and 6 (unit: impurity metal: wt%; nitrate and nitrite: ppm).
[0061] Table 5 Contents of impurity metals, nitrates and nitrites in chloroiridic acid obtained in Comparative Example 1
[0062] Impurities content Impurities content Impurities content Pt <0.004 Pd <0.003 R <0.004 Ru <0.003 Au <0.002 Ag <0.002 Na <0.005 Cu <0.005 Mn <0.003 Fe <0.004 Mg <0.003 Si <0.006 Ca <0.003 Al <0.004 Pb <0.003 Nitrate 67 Nitrite 39
[0063] Table 6 Contents of impurity metals, nitrates and nitrites in iridium trichloride obtained in Comparative Example 1
[0064] Impurities content Impurities content Impurities content Ca <0.007 Fe <0.005 Na <0.004 Cu 0.003 Mg <0.003 Pb <0.002 Mn <0.004 Al <0.003 Si <0.005 Nitrate 45 Nitrite 27
[0065] It can be seen from Table 5 and Table 6 that the chloroiridic acid and hydrated iridium trichloride prepared in Comparative Example 1 (alkali fusion method) have high impurity metal content, and have residual nitrate and nitrite, and the product purity is low.
[0066] Comparative Example 2
[0067] 500g iridium powder and 1000g sodium chloride were mixed uniformly, chlorine gas (chlorine flow rate was 20min / mL), and heated and calcined at 650°C for 5h. After the calcination was completed, the calcined product was immersed in water, filtered to remove the undissolved iridium powder, and a water infusion was obtained. Excess ammonium chloride was added to the obtained water infusion for precipitation, and the mixture was repeatedly washed with water and filtered to obtain ammonium chloroiridate. The obtained ammonium chloroiridate precipitate was dissolved in aqua regia, and nitrate was removed, and concentrated to obtain 1000g of chloroiridic acid, in which the mass percentage of iridium in the chloroiridic acid was 35%, and the yield was 70%.
[0068] 52 g of hydrazine hydrate was added to the obtained chloroiridic acid, heated to reflux, and a reduction reaction was carried out for 1 h. After the reaction was completed, the obtained reduction reaction liquid was concentrated and evaporated to dryness to obtain 644.81 g of iridium trichloride hydrate, the mass percentage of iridium in the iridium trichloride hydrate was 54.20%, and the yield was 70% (calculated from the iridium powder).
[0069] Table 7 Contents of impurity metals, nitrates and nitrites in chloroiridic acid obtained in Comparative Example 2
[0070] Impurities content Impurities content Impurities content Pt <0.003 Pd <0.004 R <0.002 Ru <0.004 Au <0.001 Ag <0.003 Na <0.006 Cu <0.004 Mn <0.004 Fe <0.005 Mg <0.002 Si <0.005 Ca <0.004 Al <0.003 Pb <0.002 Nitrate 75 Nitrite 42
[0071] Table 8 Contents of impurity metals, nitrates and nitrites in iridium trichloride obtained in Comparative Example 2
[0072] Impurities content Impurities content Impurities content Ca <0.006 Fe <0.004 Na <0.005 Cu 0.004 Mg <0.002 Pb <0.003 Mn <0.003 Al <0.005 Si <0.006 Nitrate 52 Nitrite 38
[0073] It can be seen from Table 7 and Table 8 that the chloroiridic acid and hydrated iridium trichloride prepared in Comparative Example 2 (high temperature chlorination method) have high impurity metal content, and have residual nitrate and nitrite, and the product purity is low.
[0074] In summary, compared with the current alkali fusion method and high-temperature chlorination method, the preparation method provided by the present invention has a low content of impurity metals in the prepared chloroiridic acid and iridium trichloride, especially does not contain nitrate and nitrite, has high purity, and is beneficial to improving the performance of other iridium functional complexes and iridium-containing catalysts prepared subsequently.
[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A method for preparing chloroiridic acid, characterized in that: The following steps are involved: Mixing iridium oxalate, hydrochloric acid and a gaseous oxidant to carry out an oxidation reaction to obtain iridium chloroate; The gaseous oxidant includes chlorine and / or ozone.
2. The preparation method according to claim 1, characterized in that: The ratio of the mass of the iridium oxalate to the volume of the hydrochloric acid is 1000 g: 500-1000 mL.
3. The preparation method according to claim 1 or 2, characterized in that: The concentration of the hydrochloric acid is 6-12 mol / L.
4. The preparation method according to claim 1, characterized in that: The ratio of the amount of iridium oxalate to the flow rate of the gaseous oxidant is 1 mol: 10-30 mL / min.
5. The preparation method according to claim 1, 2 or 4, characterized in that: The oxidation reaction is carried out under reflux conditions; the oxidation reaction time is 2 to 5 hours.
6. The preparation method according to claim 1, characterized in that: After the oxidation reaction, the method further comprises concentrating the oxidation liquid obtained by the oxidation reaction to obtain chloroiridic acid.
7. A method for preparing hydrated iridium trichloride, characterized in that: The following steps are involved: The chloroiridic acid prepared by the preparation method according to any one of claims 1 to 6 is mixed with formaldehyde and subjected to a reduction reaction to obtain hydrated iridium trichloride.
8. The preparation method according to claim 7, characterized in that: The molar ratio of the chloroiridic acid to formaldehyde is 0.5-0.55:
1.
9. The preparation method according to claim 7 or 8, characterized in that: The reduction reaction is carried out under reflux conditions; the reduction reaction time is 30 to 50 minutes.
10. The preparation method according to claim 7, characterized in that: After the reduction reaction, the method further comprises concentrating the reduction liquid obtained by the reduction reaction to obtain hydrated iridium trichloride.