Ruthenium trichloride and a method for its preparation

Abstract

The application belongs to the technical field of preparation of ruthenium trichloride, and discloses a preparation method of ruthenium trichloride, which comprises the following steps: step 1: heating and evaporating chlororuthenic acid under the pressure of-0.06 to-0.08 Mpa to obtain concentrated liquid with the density of 1.30 to 1.40 g / ml; step 2: vacuum filtering the concentrated liquid to obtain filtrate; and step 3: baking the filtrate to obtain finished product. Through fine control of each step in the evaporation and concentration stage, the filtering stage and the baking stage, the ruthenium content of ruthenium trichloride is synergistically and accurately controlled, the content of insoluble alpha-type ruthenium trichloride and ruthenium dioxide in the ruthenium trichloride is effectively reduced, the purity of the ruthenium trichloride is effectively improved, and the product quality is improved.

Description

Technical Field

[0001] This invention relates to the field of ruthenium trichloride preparation technology, and specifically to a ruthenium trichloride. Background Technology

[0002] Ruthenium trichloride is one of the most important compounds of ruthenium. It is an important noble metal inorganic compound that can form complexes with other reagents. It is a catalyst for heterogeneous catalysis, homogeneous catalysis, organic isomerization, polymerization, hydrogenation and other reactions. It is an important chemical raw material in electroplating and other fields, and is widely used in chemical, chemical, electronic and electroplating industries.

[0003] Ruthenium trichloride (Ru) is also a major raw material for the metal anode coating of electrolytic cells and is a catalytically active material. Its quality directly affects the quality of the metal anode coating. Solid Ruthenium trichloride has two crystal forms: α- and β-. The α-form Ruthenium trichloride is insoluble and inactive. The Ruthenium trichloride used in the production of metal anode coatings must be the soluble and active β-form. Therefore, for Ruthenium trichloride products used in the metal anode coating of electrolytic cells, it is necessary to strictly control the content of both crystal forms of Ruthenium trichloride to minimize the formation of α-form Ruthenium trichloride. If the Ruthenium content in the Ruthenium trichloride product is too high, insoluble α-form Ruthenium trichloride may be formed. At the same time, because solid Ruthenium trichloride is hygroscopic, its water content is variable. When the Ruthenium content is below a certain value, the water content is high, making Ruthenium trichloride prone to adhering to the wall, which is not conducive to use. Therefore, the Ruthenium content needs to be strictly controlled during the preparation of Ruthenium trichloride.

[0004] In the industry, the ruthenium content of solid ruthenium trichloride is generally required to be between 35% and 38%. Because the detection of the crystal form of ruthenium trichloride requires very high standards for instruments and testing techniques, the crystal form of ruthenium trichloride is not tested separately. Instead, its quality is usually determined by measuring the amount of insoluble matter. The chemical standard for ruthenium trichloride used in electrolytic cell metal anode coatings, HGT3679-2011, clearly stipulates that the content of n-butanol insoluble matter in Grade I ruthenium trichloride should not exceed 0.5%.

[0005] Prior art 1: Chinese patent application CN107540025A discloses a method for preparing hydrated ruthenium trichloride. First, ruthenium powder is mixed with sodium chloride and melted at high temperature. A trace amount of starch is added to maintain a weak reducing atmosphere during the initial heating stage. Then, chlorine gas is introduced into the molten melt to convert most of the ruthenium powder into sodium ruthenium chlororuthenate. The ruthenium tetroxide gas produced during the melting process is absorbed by a mixed solution of dilute hydrochloric acid and ethanol. The molten sodium ruthenium chlororuthenate is combined with the dilute hydrochloric acid solution that absorbed the ruthenium tetroxide, and then neutralized by adding sodium hydroxide to produce black ruthenium hydroxide or hydrated ruthenium dioxide. The product is filtered and washed multiple times to remove sodium ions. Then, hydrochloric acid is added to dissolve and concentrate the product for crystallization to prepare hydrated ruthenium trichloride crystals.

[0006] While the method described in the patent can efficiently promote the conversion of ruthenium and has the advantages of fast reaction speed and high reaction efficiency, the high-temperature chlorination conditions are harsh and there are high production safety risks. The sodium ions carried by the neutralization products, ruthenium hydroxide or hydrated ruthenium dioxide, are difficult to remove. Multiple washings generate a lot of wastewater, and hydrated ruthenium dioxide is relatively insoluble in hydrochloric acid. The efficiency of its conversion to chlororuthenic acid needs to be verified.

[0007] Similarly, prior art 2: Chinese patent application CN115745031A discloses a method for preparing ruthenium trichloride. The method involves mixing ruthenium oxide with hydrochloric acid aqueous solution in a container equipped with a reflux condenser and inlet / outlet gas pipelines, adding a co-solvent, and then heating to 100-110°C for reflux reaction. When the system changes from dark blue to reddish-brown, the reaction continues at the reflux temperature for 1 hour. Finally, the system is cooled to room temperature, and oxalic acid aqueous solution is added. After stirring at room temperature for 2 hours, the mixture is filtered, concentrated by vacuum distillation, and dried to obtain a ruthenium trichloride product with a purity greater than 99.9% and a sodium ion content of 10-20 ppm.

[0008] Compared with the prior art 1, the above technical solution has the advantage of obtaining a higher purity product. However, it is difficult to obtain ruthenium dioxide raw material without sodium ions. Since ruthenium dioxide is difficult to dissolve in hydrochloric acid, the reaction efficiency may not be high even with the addition of a solubilizing agent. In addition, the ruthenium trichloride slurry may be heated unevenly when dried in the anti-corrosion oven, and the inconsistent local temperature will lead to uneven product and difficulty in controlling insoluble matter.

[0009] Based on this, prior art 3 discloses a controllable reaction technical solution. Prior art 3: Chinese patent application CN106335932A discloses a production process for ruthenium trichloride. This process involves producing RuO4 gas according to a conventional method; then absorbing the RuO4 gas with dilute hydrochloric acid until the Ru concentration in the solution reaches 59-61 g / L, while simultaneously adjusting the pH to 1.9-2.1 to obtain a ruthenium-containing solution; adding a dispersing solvent to the ruthenium-containing solution, the volume of which is 9.8-10.2% of the volume of the ruthenium-containing solution, to obtain a dispersed ruthenium-containing solution; the dispersing solvent is a mixture of hydrogen peroxide, ethanol, and acetone in a volume ratio of 1:(7.9-8.1):(0.95-1.05); and then spray-drying the obtained dispersed ruthenium-containing solution using a spray dryer to obtain ruthenium trichloride powder.

[0010] The above method improves the traditional ruthenium trichloride production process, achieving continuous, large-scale, and mechanized production, and achieving the goals of short production cycle, low cost, and no environmental pollution. However, this method has high requirements for spray equipment and is difficult to engineer. The concentration of ruthenium in the absorbent liquid is 59-61 g / L, and the spray feed rate is 800-1000 mL / h. The calculated production rate of 37% ruthenium trichloride solid is less than 165 g / h, which is insufficient to meet the production needs of current technological development. In addition, adjusting the pH of the ruthenium-containing solution to 1.9-2.1 usually requires the addition of alkaline substances, which may introduce new impurities and affect the purity of the product.

[0011] Based on the fact that the production efficiency of the three existing technologies mentioned above is insufficient to meet the latest technological developments, and that there are problems such as insufficient production capacity, difficulty in controlling insoluble matter, or insufficient purity, after experiments, a method for preparing ruthenium trichloride was finally determined that can effectively balance production capacity, controllable insoluble matter, and controllable product purity: ruthenium chlorocyanuric acid solution is concentrated, crystallized, and dried to obtain hydrated ruthenium trichloride solid. During concentration and crystallization, a glass container is baked under an infrared lamp. However, under normal conditions, this method is prone to causing poor consistency between batches of products. The product particles are uneven, basically including lumps, granules, and powder. The ruthenium metal content of the product can only be controlled by the worker's experience, and the ruthenium content fluctuates. Low ruthenium content requires re-drying, while high ruthenium content may produce more insoluble matter, resulting in a low product qualification rate.

[0012] Therefore, further research and development is needed to develop a method for preparing ruthenium trichloride that can efficiently produce ruthenium trichloride with controllable ruthenium content and insoluble matter. Summary of the Invention

[0013] One of the objectives of this invention is to provide a method for preparing ruthenium trichloride, so as to solve the problems of insufficient production efficiency and difficulty in controlling ruthenium content and insoluble matter in the prior art.

[0014] Another objective of this invention is to provide a ruthenium trichloride prepared by the method of this invention, which has the advantage of controllable ruthenium content, low content of insoluble α-type ruthenium trichloride and ruthenium dioxide, and significantly improved production efficiency.

[0015] To achieve the above objectives, the present invention provides a method for preparing ruthenium trichloride, comprising the following steps:

[0016] Step 1: Heat and evaporate chlororuthenic acid at a pressure of -0.06 to -0.08 MPa to obtain a concentrated solution with a density of 1.30 to 1.40 g / ml;

[0017] Step 2: Vacuum filter the concentrate to obtain the filtrate;

[0018] Step 3: Bake the filtrate to obtain the finished product.

[0019] Preferably, the specific operation of step 1 is as follows: add chlororuthenic acid into a rotary evaporator, turn on the rotation speed of 20-40 RPM, then evacuate the rotary evaporator to a vacuum of -0.06 to -0.08 MPa, and then evaporate and concentrate it for a period of time at a heating temperature of 70-80°C and a condensation temperature of 10-20°C. When the density of the concentrated liquid is 1.30-1.40 g / ml, stop heating and cool down.

[0020] Preferably, in step 2, the vacuum degree of the vacuum filter is -0.06 to -0.09 MPa.

[0021] More preferably, in step 2, the funnel used for vacuum filtration is a sand core funnel with a filter membrane, the pore size of the sand core funnel is 16-30 μm, and the filter membrane is made of polytetrafluoroethylene membrane with a pore size of 0.2 μm.

[0022] Preferably, the specific operation of step 3 is as follows: the filtrate obtained in step 2 is tested to obtain the ruthenium content as W1, the filtrate is weighed to obtain the filtrate mass as M1, the filtrate is uniformly baked to form a baked material, the baked material is weighed every 5 minutes to obtain the baked material mass as M2, and the baking ends when the ruthenium content W2 of the baked material reaches the target ruthenium content, and the finished product is obtained.

[0023] Preferably, the target ruthenium content of the finished ruthenium trichloride product is 35%-38%.

[0024] The ruthenium content W2 of the baked material can be calculated using the following formula: W2 = W1 * M1 / ​​M2.

[0025] The present invention also provides ruthenium trichloride, which is prepared by the above-described method for preparing ruthenium trichloride.

[0026] Furthermore, the ruthenium trichloride contains low levels of α-type ruthenium trichloride and ruthenium dioxide.

[0027] Beneficial effects

[0028] Compared with the prior art, the present invention has at least the following advantages:

[0029] (1) This invention discloses a method for preparing ruthenium trichloride. By using a reduced pressure evaporation method in the evaporation and concentration stage to evaporate and concentrate ruthenium trichloride, a suitable vacuum degree is controlled, which effectively improves the efficiency of evaporation and concentration while preventing the evaporation of ruthenium.

[0030] (2) The present invention controls the production efficiency of the overall production steps by controlling the density of the solution during the evaporation and concentration stage, avoiding the problem that the low ruthenium content of the solution will affect the efficiency of subsequent baking, and avoiding the problem that the high ruthenium content will increase the viscosity of the solution and decrease the subsequent filtration rate, thus effectively improving the overall production efficiency.

[0031] (3) The present invention adds a filtration step before baking, which effectively reduces the content of insoluble matter in the ruthenium trichloride obtained in production;

[0032] (4) This invention discloses a method for preparing ruthenium trichloride. By controlling the ruthenium content through the calculation method of ruthenium content in the baking stage, the content of α-type ruthenium trichloride and ruthenium dioxide in the prepared ruthenium trichloride is low, thereby further improving the quality of the prepared ruthenium trichloride product.

[0033] (5) This invention achieves precise control of the ruthenium content of ruthenium trichloride through meticulous control at each step of the evaporation and concentration stage, filtration stage and baking stage, and effectively reduces the content of insoluble α-type ruthenium trichloride and ruthenium dioxide in ruthenium trichloride, thereby effectively improving the purity of ruthenium trichloride and improving product quality. Detailed Implementation

[0034] The present invention will be further described below with reference to embodiments, but this does not constitute any limitation on the present invention. Any limited modifications made within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0035] To illustrate the technical content of the present invention in detail, the following description is provided in conjunction with the embodiments.

[0036] In the following examples and comparative examples, the funnel used for vacuum filtration is a sand core funnel with a filter membrane. The pore size of the sand core funnel is 16 μm, and the filter membrane is made of polytetrafluoroethylene membrane with a pore size of 0.2 μm.

[0037] It should be noted that in the following examples and comparative examples, during the evaporation and concentration stage in step 1, the density of the concentrate is tested every 5 minutes.

[0038] Example 1

[0039] A ruthenium trichloride is prepared by the following steps:

[0040] Step 1: Add 35 kg of chlororuthenic acid to a rotary evaporator, wherein the ruthenic acid contains 3.70% ruthenic acid. Start the rotation speed at 30 RPM, then evacuate the rotary evaporator to a vacuum of -0.07 MPa. Then, evaporate and concentrate the solution at a heating temperature of 75°C and a condensation temperature of 15°C for a period of time. When the density of the concentrate is 1.35 g / ml, stop heating and cool down. The ruthenic acid content in the condensate is found to be less than 0.2 ppm.

[0041] Step 2: Vacuum filter the concentrate to obtain the filtrate. The vacuum degree of the vacuum filter is -0.08 MPa.

[0042] Step 3: The filtrate obtained in Step 2 was tested and found to have a ruthenium content W1 of 18.5%. The filtrate was weighed and found to have a mass M1 of 7 kg. The filtrate was then uniformly baked to form a baked material with a mass M2 of 3.477 kg.

[0043] The target ruthenium content W2 for baking ruthenium trichloride was set at 37.25%, and the mass M2 of the baked material was calculated to be 3.477 kg according to W2 = W1 * M1 / ​​M2.

[0044] Example 2

[0045] A ruthenium trichloride is prepared by the following steps:

[0046] Step 1: Add 30 kg of chlororuthenic acid to a rotary evaporator, wherein the ruthenic acid contains 5.33% ruthenic acid. Turn on the rotary evaporator at a rotation speed of 40 RPM, and then evaporate the rotary evaporator to a vacuum of -0.08 MPa. Then, evaporate and concentrate the evaporator at a heating temperature of 80°C and a condensation temperature of 10°C for a period of time. When the density of the concentrate is 1.40 g / ml, stop heating and cool down. The ruthenic acid content in the condensate is found to be less than 0.2 ppm.

[0047] Step 2: Vacuum filter the concentrate to obtain the filtrate. The vacuum degree of the vacuum filter is -0.08 MPa.

[0048] Step 3: The filtrate obtained in Step 2 was tested and found to have a ruthenium content W1 of 20.0%. The filtrate was weighed and found to have a mass M1 of 8 kg. The filtrate was then uniformly baked to form a baked material with a mass M2 of 4.244 kg.

[0049] The target ruthenium content W2 for baking ruthenium trichloride was set at 37.70%, and the mass M2 of the baked material was calculated to be 4.244 kg according to W2 = W1 * M1 / ​​M2.

[0050] Example 3

[0051] A ruthenium trichloride is prepared by the following steps:

[0052] Step 1: Add 25 kg of chlororuthenic acid to a rotary evaporator, wherein the ruthenic acid contains 5.33% ruthenic acid. Turn on the rotary evaporator at a rotation speed of 20 RPM, then evacuate the rotary evaporator to a vacuum of -0.06 MPa. Then, evaporate and concentrate the solution at a heating temperature of 70°C and a condensation temperature of 20°C for a period of time. When the density of the concentrate is 1.36 g / ml, stop heating and cool down. The ruthenic acid content in the condensate is found to be less than 0.2 ppm.

[0053] Step 2: Vacuum filter the concentrate to obtain the filtrate. The vacuum degree of the vacuum filter is -0.08 MPa.

[0054] Step 3: The filtrate obtained in Step 2 was tested and found to have a ruthenium content W1 of 19.6%. The filtrate was weighed and found to have a mass M1 of 6.8 kg. The filtrate was then uniformly baked to form a baked material with a mass M2 of 3.652 kg.

[0055] The target ruthenium content W2 for baking ruthenium trichloride is set at 36.5%, and the mass M2 of the baked material is calculated to be 3.652 kg according to W2 = W1 * M1 / ​​M2.

[0056] Comparative Example 1

[0057] It is largely the same as Example 1, except that step 2 is omitted.

[0058] Comparative Example 2

[0059] The process is largely the same as in Example 1, except that step 1 is changed to: adding 35 kg of chlororuthenium acid into a rotary evaporator, wherein the ruthenium content of the chlororuthenium acid is 3.70%, starting the rotation speed at 30 RPM, and then evaporating and concentrating at a heating temperature of 105°C and a condensation temperature of 15°C for a period of time. When the density of the concentrated liquid is 1.35 g / ml, heating is stopped, and the liquid is cooled down. The ruthenium content in the condensate is measured to be 10 ppm. This process takes twice as long as in Example 1, which affects production efficiency and causes ruthenium loss or increases the cost of secondary recovery.

[0060] Comparative Example 3

[0061] The process is largely the same as in Example 1, except that step 1 is modified as follows: 35 kg of chlororuthenic acid is added to a rotary evaporator, wherein the ruthenic acid contains 3.70% ruthenic acid, the rotation speed is set to 30 RPM, the rotary evaporator is then evacuated to a vacuum of -0.07 MPa, and then the mixture is evaporated and concentrated at a heating temperature of 75°C and a condensation temperature of 15°C for a period of time. When the density of the concentrated liquid is 1.25 g / ml, heating is stopped, the mixture is cooled down, and the ruthenic acid content in the condensate is measured to be less than 0.2 ppm.

[0062] The low density of the concentrate significantly increased the baking time in step 3, affecting production efficiency.

[0063] Comparative Example 4

[0064] The process is largely the same as in Example 1, except that step 1 is modified as follows: 35 kg of chlororuthenic acid is added to a rotary evaporator, wherein the ruthenic acid contains 3.70% ruthenic acid, the rotation speed is set to 30 RPM, the rotary evaporator is then evacuated to a vacuum of -0.07 MPa, and then the mixture is evaporated and concentrated at a heating temperature of 75°C and a condensation temperature of 15°C for a period of time. When the density of the concentrated liquid is 1.45 g / ml, heating is stopped, the mixture is cooled down, and the ruthenic acid content in the condensate is measured to be less than 0.2 ppm.

[0065] The high density of the concentrate significantly increased the time required for vacuum filtration in step 2, affecting production efficiency.

[0066] Comparative Example 5

[0067] It is largely the same as Example 1, except that step 3 is changed to: instead of controlling the ruthenium content by calculating the ruthenium content during the baking stage, the endpoint of the baking of the material is determined by the experience of the personnel.

[0068] Results Test

[0069] Method for determining ruthenium content in ruthenium trichloride products: The ruthenium content in ruthenium trichloride is determined using the hydrogen reduction gravimetric method commonly used in the industry. The allowable tolerance range for ruthenium content determination is ±0.2%.

[0070] The method for detecting insoluble matter in ruthenium trichloride products is as follows: Refer to Section 6.3 of the HGT3679-2011 Chemical Standard for Ruthenium Trichloride for Electrolytic Cell Metal Anode Coating.

[0071] The ruthenium content and insoluble matter of the ruthenium trichloride obtained in Examples 1-3 and Comparative Examples 1-5 were tested (samples were taken from different parts and tested twice to fully verify the uniformity of the product). The production rate of ruthenium trichloride during the baking stage of Examples 1-3 and Comparative Examples 1-5 was statistically analyzed. The results are shown in Table 1.

[0072] Table 1. Test results of ruthenium trichloride content and insoluble matter content obtained from Examples 1-3 and Comparative Examples 1-5.

[0073]

[0074] According to Table 1:

[0075] A comparison of the data from Example 1 and Comparative Example 1 shows that the filtration step of the present invention can effectively reduce the content of insoluble matter in the finished product; after the filtration step was eliminated in Comparative Example 1, the content of ruthenium trichloride insoluble matter in the product was too high, and the product quality was significantly reduced.

[0076] As can be seen from the data comparison of Example 1 and Comparative Example 2, although the quality of the final ruthenium trichloride product was not affected, a small amount of ruthenium escaped into the condensate due to the high evaporation temperature, resulting in ruthenium loss or increased secondary recovery costs. Furthermore, the evaporation time was extended, wasting energy and affecting the production efficiency of this process.

[0077] Although the quality of the final ruthenium trichloride product obtained in Comparative Example 3 was not affected, the low density of the concentrate led to a significant increase in the baking time in step 3, which affected production efficiency.

[0078] Similarly, although the quality of the final ruthenium trichloride product obtained in Comparative Example 4 was not affected, the high density of the concentrate led to a significant increase in the vacuum filtration time in step 2, which affected production efficiency.

[0079] As can be seen from the comparison between Example 1 and Comparative Example 5, the present invention controls the ruthenium content by controlling the quality of ruthenium trichloride obtained by drying, which can accurately control the ruthenium content and uniformity of the finished product and effectively avoid the problem of inconsistent ruthenium trichloride quality.

[0080] The embodiments presented herein are merely selected implementations based on combinations of all possible embodiments. The appended claims should not be limited to the embodiments described herein. Some numerical ranges used in the claims include sub-ranges within them, and variations within these ranges should also be covered by the appended claims.

Claims

1. A process for the preparation of ruthenium trichloride, characterized in that, Includes the following steps: Step 1: Heat and evaporate chlororuthenic acid at a pressure of -0.06 to -0.08 MPa to obtain a concentrated solution with a density of 1.30 to 1.40 g / ml; Step 2: Vacuum filter the concentrate to obtain the filtrate; Step 3: Bake the filtrate to obtain the finished product; The specific operation of step 3 is as follows: the filtrate obtained in step 2 is tested to obtain the ruthenium content as W1, the filtrate is weighed to obtain the filtrate mass as M1, the filtrate is uniformly baked to form a baked material, the baked material is weighed every 5 minutes to obtain the baked material mass as M2, and when the ruthenium content W2 of the baked material reaches the target ruthenium content, the baking is completed and the finished product is obtained. The ruthenium content W2 of the baked material is calculated using the following formula: W2=W1*M1 / M2; In step 2, the vacuum degree of vacuum filtration is -0.06 to -0.09 MPa, the funnel used for vacuum filtration is a sand core funnel with a filter membrane, the pore size of the sand core funnel is 16 to 30 μm, and the filter membrane is made of polytetrafluoroethylene membrane with a pore size of 0.2 μm.

2. The method for preparing ruthenium trichloride according to claim 1, characterized in that, The specific operation of step 1 is as follows: add chlororuthenic acid into the rotary evaporator, turn on the rotation speed of 20~40 RPM, then evacuate the rotary evaporator to a vacuum of -0.06~-0.08 MPa, and then evaporate and concentrate it for a period of time at a heating temperature of 70~80℃ and a condensation temperature of 10~20℃. When the density of the concentrated liquid is 1.30~1.40 g / ml, stop heating and cool down.

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