Method for recovering ruthenium from ruthenium-containing catalyst

Abstract

The invention relates to the field of ruthenium-containing catalysts, and discloses a method for recovering ruthenium from a ruthenium-containing catalyst, which comprises the following steps: 1) carrying out first roasting on the ruthenium-containing catalyst; 2) mixing the first roasted product with a composite alkali flux, and performing second roasting; 3) performing ultrasonic extraction on the second roasted product in the presence of water, performing first solid-liquid separation on the extracted product to obtain a first liquid phase, contacting the first liquid phase with a reducing agent, and performing second solid-liquid separation to obtain a second solid phase; and 4) performing oxygenolysis on the second solid phase obtained in the step 3). According to the present invention, it is possible to provide a method for recovering ruthenium from a ruthenium-containing catalyst, the method being capable of efficiently leaching metal ruthenium from the ruthenium-containing catalyst, having a short leaching time, a low leaching temperature, a small amount of water used, and being capable of directly preparing beta-RuCl3.H2O crystals, and having a high ruthenium recovery rate.

Description

Technical Field

[0001] The present invention relates to the technical field of ruthenium-containing catalysts, and particularly to a method for recovering ruthenium from ruthenium-containing catalysts. Background Art

[0002] The research and application of ruthenium-containing catalysts in the chemical industry are concentrated in the production processes such as benzene hydrogenation to cyclohexene, ammonia synthesis, Fischer-Tropsch synthesis, and catalytic oxidation of hydrogen chloride to chlorine for caprolactam and adipic acid (caprolactam and adipic acid are raw materials for the production of nylon 6 and nylon 66). In recent years, the annual consumption of ruthenium in the chemical industry is mostly above 10 tons, accounting for a relatively large proportion of the newly increased production of ruthenium.

[0003] However, at present, there are problems of low recovery rate of ruthenium, long recovery time, and large water consumption in recovering ruthenium from ruthenium-containing catalysts. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems of low ruthenium recovery rate, long recovery time, and large water consumption existing in the existing ruthenium recovery methods, and provide a method for recovering ruthenium from ruthenium-containing catalysts. This method can effectively leach metallic ruthenium from ruthenium-containing catalysts (such as ruthenium-containing waste catalysts), with a short leaching time, a low leaching temperature, a small water consumption, and can be directly prepared into β-RuCl 3 ·H 2 O crystals, and the ruthenium recovery rate is high.

[0005] To achieve the above purpose, on the one hand, the present invention provides a method for recovering ruthenium from ruthenium-containing catalysts, wherein the method includes the following steps,

[0006] 1) A step of subjecting the ruthenium-containing catalyst to a first calcination;

[0007] 2) A step of mixing the first calcination product obtained in step 1) with a KOH / KNO 3 composite alkali flux and performing a second calcination;

[0008] 3) A step of subjecting the second calcination product obtained in step 2) to ultrasonic extraction in the presence of water, performing a first solid-liquid separation on the extraction product, and then contacting the first liquid phase obtained from the first solid-liquid separation with a reducing agent and performing a second solid-liquid separation to obtain a second solid phase;

[0009] 4) A step of subjecting the second solid phase obtained in step 3) to oxidative decomposition.

[0010] Preferably, in step 1), the conditions of the first calcination include: the temperature is 200 - 500 °C, and the time is 1 - 3 h; more preferably, the conditions of the first calcination include: the temperature is 200 - 300 °C, and the time is 1.5 - 2 h.

[0011] Preferably, in step 2), the KOH / KNO 3 In the composite alkali flux, relative to 1 mol of the KOH content, the KNO 3 content is 2 - 4 mol, preferably 2.5 - 3.5 mol.

[0012] Preferably, relative to the ruthenium-containing catalyst, the amount of the composite alkali flux used is 100 - 300% by weight, preferably 125 - 150% by weight.

[0013] Preferably, in step 2), the conditions for the second calcination include: the temperature is 550 - 700 °C and the time is 1 - 5 h; more preferably, the conditions for the second calcination include: the temperature is 600 - 650 °C and the time is 2 - 3 h.

[0014] Preferably, in step 3), relative to the second calcination product, the amount of water used is 2 - 7 times the volume.

[0015] Preferably, the temperature of the water is 25 - 50 °C, preferably 25 - 35 °C;

[0016] Preferably, the conditions for the ultrasonic extraction include: the ultrasonic frequency is 10 - 180 kHz, preferably 20 - 100 kHz; the ultrasonic power is 0.01 - 20 W / mL based on the volume of the solution, preferably 0.05 - 10 W / mL.

[0017] Preferably, in step 3), the reducing agent is ethanol.

[0018] Preferably, the molar ratio of the ruthenium-containing catalyst in terms of ruthenium element to the reducing agent is 1:2 - 6, preferably 1:3 - 4.

[0019] Preferably, step 4) includes: subjecting the second solid obtained by the second solid-liquid separation to oxidative decomposition treatment with an acidic oxidant; more preferably, absorbing the generated ruthenium tetroxide gas with a hydrochloric acid solution to obtain chlororuthenic acid, and then heating and decomposing the chlororuthenic acid to obtain ruthenium chloride.

[0020] Preferably, the acidic oxidant is a mixture of concentrated sulfuric acid and saturated NaClO solution; more preferably, in the acidic oxidant, the volume ratio of concentrated sulfuric acid to saturated NaClO solution is 1:0.9 - 5, preferably 1:1 - 1.2.

[0021] Preferably, in step 4), relative to 1 mol of the ruthenium element contained in the ruthenium-containing catalyst, the amount of the acidic oxidant used is 10 - 40 mL, preferably 20 - 30 mL.

[0022] Preferably, in step 4), the temperature of the oxidative decomposition treatment is 50 - 100 °C, preferably 60 - 70 °C.

[0023] Preferably, the ruthenium-containing catalyst is a supported catalyst, and its carrier is alumina or titanium oxide.

[0024] Through the above technical solution, the present invention can provide a method for recovering ruthenium from a ruthenium-containing catalyst. This method can effectively leach metallic ruthenium from the ruthenium-containing catalyst (such as a spent ruthenium-containing catalyst), with a short leaching time, a low leaching temperature, a small amount of water used, and can be directly prepared into β-RuCl 3 ·H 2 O crystals, and the recovery rate of ruthenium is high.

[0025] Moreover, the obtained β-RuCl 3 ·H 2 O crystals meet the HG / 3679-2011 standard and can be used as raw materials to re-prepare ruthenium catalysts, thus realizing the recovery and recycling of resources and reducing production costs. Detailed Embodiments

[0026] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0027] According to the first aspect of the present invention, a method for recovering ruthenium from a ruthenium-containing catalyst is provided, wherein the method includes the following steps:

[0028] 1) A step of subjecting the ruthenium-containing catalyst to a first calcination;

[0029] 2) A step of mixing the first calcination product obtained in step 1) with a KOH / KNO 3 composite alkali flux and performing a second calcination;

[0030] 3) A step of performing ultrasonic extraction on the second calcination product obtained in step 2) in the presence of water, performing a first solid-liquid separation on the extraction product, and then contacting the first liquid phase obtained from the first solid-liquid separation with a reducing agent and performing a second solid-liquid separation to obtain a second solid phase;

[0031] 4) A step of subjecting the second solid phase obtained in step 3) to oxidative decomposition.

[0032] In the present invention, there is no particular limitation on the ruthenium-containing catalyst. For example, it can be a supported ruthenium-containing catalyst, and its carrier can be alumina or titanium oxide, preferably an alumina-supported ruthenium catalyst. As a specific example of the alumina-supported ruthenium catalyst, it can be an alumina-supported ruthenium catalyst used in the petrochemical industry for synthesizing cyclohexanol, cyclohexanone, caprolactam, adipic acid, etc. Among them, for the alumina-supported ruthenium catalyst, even if the ruthenium content is low, the method of the present invention can achieve good recovery effects.

[0033] In the present invention, the ruthenium-containing catalyst is particularly preferably a used ruthenium-containing catalyst.

[0034] According to the present invention, in the ruthenium-containing catalyst, the content of ruthenium element can be, for example, 0.5 - 10 wt%, preferably 0.5 - 2 wt%, and more preferably 1 - 1.2 wt%. The method of the present invention especially has good recovery effects for ruthenium-containing catalysts with low ruthenium content (such as below 5 wt%, below 2 wt% or below 1 wt%), and can achieve a ruthenium recovery rate of more than 98%.

[0035] According to the present invention, in step 1), by subjecting the ruthenium-containing catalyst to a first calcination, the residual organic substances in the ruthenium-containing catalyst can be removed. The first calcination is preferably carried out in an inert atmosphere (such as a nitrogen atmosphere and / or an inert gas atmosphere such as argon). When carried out in an inert atmosphere, the gas flow can also carry out the organic substances in the ruthenium-containing catalyst out of the container.

[0036] In the present invention, the first calcination can be carried out using a muffle furnace, for example.

[0037] Preferably, in step 1), the conditions of the first calcination include: the temperature is 200 - 500 °C, and the time is 1 - 3 h; more preferably, in step 1), the conditions of the first calcination include: the temperature is 200 - 300 °C, and the time is 1.5 - 2 h.

[0038] Preferably, in step 1), the first calcination product can also be washed, dried, and then subjected to the treatment of step 2). Among them, the washing can be carried out with water, and the drying temperature can be, for example, 60 - 100 °C, preferably 80 - 90 °C.

[0039] According to the present invention, in step 2), the first calcination product obtained in step 1) is mixed with a KOH / KNO 3 composite alkali flux and subjected to a second calcination, the purpose of which is to oxidize and convert the ruthenium in the ruthenium-containing catalyst into soluble ruthenate.

[0040] According to the present invention, as the above KOH / KNO 3 in the composite alkali flux, relative to 1 mol of the KOH content, KNO3 The content can be, for example, 2 - 4 mol, preferably 2.5 - 3.5 mol, and can be, for example: 2 mol, 2.5 mol, 3 mol, 3.5 mol, 4 mol, etc., as well as the ranges formed by any two of the above values.

[0041] To improve the ruthenium recovery effect, preferably, relative to the ruthenium-containing catalyst, the dosage of the composite alkali flux is 100 - 300% by weight; more preferably, relative to the ruthenium-containing catalyst, the dosage of the composite alkali flux is 125 - 150% by weight.

[0042] Preferably, the composite alkali flux is mixed with the first calcination product in solid form and subjected to a second calcination.

[0043] In the present invention, the second calcination can be carried out using a muffle furnace, for example. Preferably, in step 2), the conditions of the second calcination treatment include: the temperature is 550 - 700 °C and the time is 1 - 5 h; more preferably, the conditions of the second calcination include: the temperature is 600 - 650 °C and the time is 2 - 3 h.

[0044] According to the present invention, step 3) is carried out under the strengthening effect of ultrasonic waves. In step 3), first, by utilizing the solubility of the second calcination product (such as soluble potassium ruthenate) and the strengthening effect of ultrasonic waves, it is dissolved and then the impurities are removed by the first solid-liquid separation; then a reducing agent is used to precipitate the ruthenium element, and ruthenium is reduced to ruthenium hydroxide and precipitated, so as to be separated by the second solid-liquid separation.

[0045] According to the present invention, in step 3), the frequency of the ultrasonic waves can be 10 - 180 kHz, preferably 20 - 100 kHz, more preferably 25 - 80 kHz. In addition, the ultrasonic power can be 0.01 - 20 W / mL based on the volume of the solution, preferably 0.05 - 10 W / mL, more preferably 0.05 - 3 W / mL.

[0046] According to the present invention, in step 3), the temperature of the water used to dissolve the second calcination product can be 25 - 50 °C, preferably 25 - 35 °C.

[0047] According to the present invention, preferably, relative to the second calcination product, the dosage of water is 2 - 7 times the volume; more preferably, relative to the second calcination product, the dosage of water is 2 - 6 times the volume; further preferably, relative to the second calcination product, the dosage of water is 2 - 3 times the volume.

[0048] In addition, in the ultrasonic extraction, it is preferably carried out under stirring conditions to accelerate the dissolution process. The rotation speed of the stirring at this time can be 50 - 150 rpm, preferably 60 - 90 rpm.

[0049] According to the present invention, preferably, in step 3), the extraction time can be 10 - 60 min; more preferably, in step 3), the extraction time is 10 - 40 min; further preferably, in step 3), the extraction time is 10 - 15 min.

[0050] In addition, the first solid-liquid separation can be carried out by methods such as filtration, centrifugation, and static liquid separation, as long as a liquid phase can be obtained, and filtration is preferably used.

[0051] According to the present invention, in step 3), the reducing agent is preferably ethanol.

[0052] In order to better precipitate ruthenium elements, preferably, the molar ratio of the ruthenium-containing catalyst to the reducing agent in terms of ruthenium elements is 1:2 - 6; more preferably, the molar ratio of the ruthenium-containing catalyst to the reducing agent in terms of ruthenium elements is 1:3 - 4.

[0053] In the present invention, through the above reducing agent, ruthenium is reduced to ruthenium hydroxide and precipitated, and then the second solid-liquid separation and washing are carried out. The second solid-liquid separation can be carried out by methods such as filtration, centrifugation, and static liquid separation, as long as a precipitate can be obtained, and filtration is preferably used.

[0054] The washing is used to wash away impurities such as adsorbed ions on the solid phase of the solid-liquid separation, and water is preferably used for washing. The amount of water used during the washing process can be 1 - 5 times the volume, preferably 2 - 3 times the volume.

[0055] According to the present invention, preferably, step 4) includes: performing oxidative decomposition treatment on the second solid obtained from the second solid-liquid separation with an acidic oxidant; more preferably, absorbing the generated ruthenium tetroxide gas with a hydrochloric acid solution to obtain chlororuthenic acid, and then heating and decomposing the chlororuthenic acid to obtain ruthenium chloride.

[0056] In a preferred embodiment of the present invention, in step 4), an acidic oxidant is added dropwise to the second solid obtained in step 3) until the solution color becomes colorless and transparent, and at the same time, it is heated in a water bath until no RuO 4 golden-yellow gas is generated.

[0057] According to the present invention, preferably, the acidic oxidant is a mixture of concentrated sulfuric acid and saturated NaClO solution.

[0058] Preferably, in the acidic oxidant, the volume ratio of concentrated sulfuric acid to saturated NaClO solution is 1:0.9 - 5; more preferably, in the acidic oxidant, the volume ratio of concentrated sulfuric acid to saturated NaClO solution is 1:1 - 1.2. The above concentrated sulfuric acid refers to a sulfuric acid aqueous solution with a mass fraction of more than 70%, preferably more than 80%, more than 90%, more than 95%, or more than 98%.

[0059] In the present invention, in order to enhance the oxidation effect, preferably, in step 4), relative to 1 mol of ruthenium element contained in the ruthenium-containing catalyst, the amount of the acidic oxidant used is 10 - 40 mL, more preferably 20 - 30 mL.

[0060] According to the present invention, preferably, in step 4), the temperature of the oxidative decomposition treatment is 50 - 100 °C, preferably 60 - 70 °C.

[0061] According to the present invention, preferably, in the step of absorbing ruthenium tetroxide with a hydrochloric acid solution, the concentration of the hydrochloric acid can be 15 - 36.5 wt%, preferably 18 - 30 wt%. In addition, in order to ensure the recovery rate of ruthenium, an excessive amount of hydrochloric acid solution is preferably used.

[0062] In a particularly preferred embodiment of the present invention, during the oxidative decomposition treatment, the ruthenium chlorate is preferably decomposed by heating in a water bath, and the temperature can be 50 - 100 °C, preferably 60 - 70 °C. In order to increase the rate of thermal decomposition, it is preferred to use a rotary evaporator for thermal decomposition. By decomposing ruthenium chlorate by heating, ruthenium element can be recovered in the form of ruthenium chloride (β-RuCl 3 ·H 2 O) crystals.

[0063] By the above technical solution, the present invention can provide a method for recovering ruthenium from a ruthenium-containing catalyst, which can effectively leach metallic ruthenium from the ruthenium-containing catalyst (such as a ruthenium-containing waste catalyst), with a short leaching time, a low leaching temperature, a small amount of water used, and can be directly prepared into β-RuCl 3 ·H 2 O crystals, and the recovery rate of ruthenium is high.

[0064] Moreover, the obtained β-RuCl 3 ·H 2 O crystals meet the HG / 3679 - 2011 standard and can be used as a raw material to re-prepare a ruthenium catalyst, thereby realizing the recovery and recycling of resources and reducing production costs.

[0065] The present invention will be described below by way of examples, but the present invention is not limited to the following examples.

[0066] Example 1

[0067] Put 50 g of an alumina-supported ruthenium waste catalyst into a muffle furnace, introduce nitrogen, heat to 300 °C, roast for 2 h, and stop introducing nitrogen. After sufficient cooling, add a composite alkali flux KOH / KNO 3 (relative to 1 g of the waste catalyst, the total amount used is 1.5 g, KOH / KNO 3The molar ratio is 1 / 3). After mixing, it is put into a muffle furnace, heated to 650 °C, and kept at a constant temperature for 3 h. After the material is cooled, 3 times the volume of water at 25 °C is added and it is placed in an ultrasonic transducer for stirring and dissolution. The ultrasonic transducer is controlled to emit power of 200 W and frequency of 25 kHz and run for 10 min. After the dissolved aqueous solution becomes clear, it is filtered with filter cloth. Then, a reducing agent ethanol is added to the filtrate to extract ruthenium (the dosage of the reducing agent is the molar ratio of ruthenium element to the reducing agent of 1:4). Ruthenium is reduced to ruthenium hydroxide and precipitated, and then it is filtered and washed. An acidic oxidizing agent solution (a mixed solution of concentrated sulfuric acid and saturated NaClO solution with a volume ratio of 1:1.2; relative to 1 mol of ruthenium element contained in the waste catalyst, the dosage of the acidic oxidizing agent solution is 20 mL) is dropped into the obtained ruthenium hydroxide solid, and it is heated in a water bath at 60 °C to generate yellow ruthenium tetroxide gas. The ruthenium tetroxide is absorbed by a hydrochloric acid solution with a mass fraction of 18% to generate chlororuthenic acid (H 6 RuCl 3 ), and chlororuthenic acid is decomposed by rotary evaporation under normal pressure to obtain β-RuCl 3 ·H 2 O crystals, and the recovery rate of ruthenium is 99.8%.

[0068] Example 2

[0069] 50 g of a waste catalyst (a waste catalyst for producing chlorine from hydrogen chloride), with a Ru element mass fraction of 2%, RuO 2 / Al 2 O 3 -TiO 2 is placed in a muffle furnace, nitrogen is introduced, heated to 300 °C, calcined for 1.5 h, and then the introduction of nitrogen is stopped. After sufficient cooling, a composite alkali flux KOH / KNO 3 (relative to 1 g of the waste catalyst, the total dosage is 1.25 g, and the KOH / KNO 3 molar ratio is 1 / 3) is added. After mixing, it is put into a muffle furnace, heated to 650 °C, and kept at a constant temperature for 3 h. After the material is cooled, 3 times the volume of water at 25 °C is added and it is placed in an ultrasonic transducer for stirring and dissolution. The ultrasonic transducer is controlled to emit power of 200 W and frequency of 25 kHz and run for 15 min. After the dissolved aqueous solution becomes clear, it is filtered with filter cloth. Then, a reducing agent ethanol is added to the filtrate to extract ruthenium (the dosage of the reducing agent is the molar ratio of ruthenium element to the reducing agent of 1:3). Ruthenium is reduced to ruthenium hydroxide and precipitated, and then it is filtered and washed. An acidic oxidizing agent solution (a mixed solution of concentrated sulfuric acid and saturated NaClO solution with a volume ratio of 1:1; relative to 1 mol of ruthenium element contained in the waste catalyst, the dosage of the acidic oxidizing agent solution is 20 mL) is dropped into the obtained ruthenium hydroxide solid, and it is heated in a water bath at 60 °C to generate yellow ruthenium tetroxide gas. The ruthenium tetroxide is absorbed by a hydrochloric acid solution with a mass fraction of 18% to generate chlororuthenic acid (H 6 RuCl 3), decompose chlororuthenic acid by atmospheric pressure rotary evaporation to obtain β-RuCl 3 ·H 2 O crystal, and the recovery rate of ruthenium is 98.5%.

[0070] Example 3

[0071] Compared with Example 1, change the transmitting power of the ultrasonic transducer to 50 W and the frequency to 80 kHz, and the dosages of other materials and operating conditions are the same as those in Example 1. The recovery rate of ruthenium is 99.4%.

[0072] Example 4

[0073] Compared with Example 1, change the transmitting power of the ultrasonic transducer to 800 W and the frequency to 50 kHz, and the dosages of other materials and operating conditions are the same as those in Example 1. The recovery rate of ruthenium is 99.6%.

[0074] Comparative Example 1

[0075] Recover ruthenium according to the method of Example 1, with the only difference being that ultrasonic intensification is not applied in the leaching and reduction step. The final recovery rate of ruthenium is 95.9%.

[0076] Comparative Example 2

[0077] Recover ruthenium according to the method of Example 2, with the only difference being that ultrasonic intensification is not applied in the leaching and reduction step. The final recovery rate of ruthenium is 95.2%.

[0078] It can be seen from the results of the above examples that the method of the present invention can recover ruthenium elements in waste catalysts with a high recovery rate. Specifically, through the comparison of Examples 1-2 and Comparative Examples 1-2, it can be seen that the method of the present invention has a better recovery effect on alumina-supported ruthenium catalysts. Even when the ruthenium content in the alumina-supported ruthenium catalyst is low, it can be recovered with a high recovery rate.

[0079] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for recovering ruthenium from a ruthenium-containing catalyst, characterized in that, this method comprises the following steps, 1) a step of subjecting the ruthenium-containing catalyst to a first calcination; 2) The step of mixing the first calcined product obtained in step 1) with a KOH / KNO 3 composite alkali flux and performing a second calcination; 3) a step of subjecting the second calcination product obtained in step 2) to ultrasonic extraction in the presence of water, after performing a first solid-liquid separation on the extraction product, bringing the first liquid phase obtained from the first solid-liquid separation into contact with a reducing agent and performing a second solid-liquid separation to obtain a second solid phase; 4) a step of subjecting the second solid phase obtained in step 3) to oxidative decomposition.

2. The method according to claim 1, wherein, in step 1), the conditions of the first calcination include: the temperature is 200 - 500 °C, and the time is 1 - 3 h; preferably, the conditions of the first calcination include: the temperature is 200 - 300 °C, and the time is 1.5 - 2 h.

3. The method according to claim 1, wherein, In step 2), in the KOH / KNO 3 complex alkali flux, relative to 1 mol of the KOH content, the KNO 3 content is 2 - 4 mol, preferably 2.5 - 3.5 mol; preferably, relative to the ruthenium-containing catalyst, the dosage of the composite alkali flux is 100 - 300% by weight, preferably 125 - 150% by weight.

4. The method according to any one of claims 1 - 3, wherein, in step 2), the conditions of the second calcination include: the temperature is 550 - 700 °C, and the time is 1 - 5 h; preferably, the conditions of the second calcination include: the temperature is 600 - 650 °C, and the time is 2 - 3 h.

5. The method according to any one of claims 1 - 3, wherein, in step 3), relative to the second calcination product, the dosage of water is 2 - 7 times the volume; preferably, the temperature of the water is 25 - 50 °C, preferably 25 - 35 °C.

6. The method according to any one of claims 1 - 5, wherein, the conditions of the ultrasonic extraction include: the ultrasonic frequency is 10 - 180 kHz, preferably 20 - 100 kHz; the ultrasonic power is 0.01 - 20 W / mL based on the volume of the solution, preferably 0.05 - 10 W / mL.

7. The method according to any one of claims 1 - 3, wherein, in step 3), the reducing agent is ethanol; preferably, the molar ratio of the ruthenium-containing catalyst to the reducing agent in terms of ruthenium element is 1:2 - 6, preferably 1:3 - 4.

8. The method according to any one of claims 1 - 3, wherein, step 4) includes: subjecting the second solid phase obtained from the second solid-liquid separation to oxidative decomposition treatment with an acidic oxidant; preferably, absorbing the generated ruthenium tetroxide gas with a hydrochloric acid solution to obtain chlororuthenic acid, and then heating and decomposing the chlororuthenic acid to obtain ruthenium chloride; preferably, the acidic oxidant is a mixture of concentrated sulfuric acid and saturated NaClO solution; preferably, in the acidic oxidant, the volume ratio of concentrated sulfuric acid to saturated NaClO solution is 1:0.9 - 5, preferably 1:1 - 1.

2.

9. The method according to claim 8, wherein, in step 4), relative to 1 mol of ruthenium element contained in the ruthenium-containing catalyst, the dosage of the acidic oxidant is 10 - 40 mL, preferably 20 - 30 mL.

10. The method according to claim 8, wherein, In step 4), the temperature of the oxidative decomposition treatment is 50-100°C, preferably 60-70°C.

11. According to the method described in any one of claims 1-3, wherein, the ruthenium-containing catalyst is a supported catalyst, and its carrier is alumina or titanium oxide.