Preparation process of palladium chloride dehydrate

Abstract

The invention provides a preparation process of palladium chloride dihydrate, which comprises the following steps: S1, respectively adding palladium powder, high-purity water and a reducing agent into a reactor, stirring and heating, and carrying out constant-temperature reaction and standing for layering to obtain activated palladium powder; s2, hydrochloric acid is added into the activated palladium powder, then stirring and heating are conducted, hydrogen peroxide is dropwise added, a reaction is conducted till the palladium powder is completely dissolved, and a dissolved solution is filtered; s3, transferring the filtrate into an evaporator for dissolving, and then carrying out vacuum concentration; s4, repeating the step S3 for 3-5 times until the pH value of the solution reaches 1-5.5; and S5, carrying out vacuum concentration on the solution, and obtaining palladium chloride dihydrate when the palladium content reaches a set value. The direct recovery rate of the preparation process is high, the raw material loss can be effectively reduced, the production benefit is improved, the operation process is simple, and the prepared palladium chloride dihydrate has the nitrate-free characteristic, also has good water solubility and can meet the use requirements in different scenes.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, and in particular to a preparation process for palladium chloride dihydrate. Background Technology

[0002] Palladium chloride, a key palladium compound, has a wide range of applications across multiple fields. In catalysis, it can directly serve as a catalyst for the oxidation of ethylene to acetaldehyde, and also as a precursor for cross-coupling catalysts such as Suzuki and Heck. In sensing and detection, it is an important raw material for gas-sensitive elements and a commonly used analytical reagent. In materials processing, it can be used to formulate coatings for non-conductive materials and is a commonly used raw material for palladium plating. In polymer synthesis, it can participate in the synthesis of metal polymers. Therefore, palladium chloride plays an important role in many fields.

[0003] There are two main conventional methods for preparing palladium chloride. The first is the direct gas-solid phase synthesis method, which involves the direct reaction of palladium powder with chlorine at 500°C to produce palladium dichloride. Although this method can produce a product without nitrate residue, it has significant drawbacks: the direct yield of the target product is low, unreacted palladium powder is easily mixed into the product, and the resulting palladium chloride is insoluble in water. Furthermore, the raw material chlorine has strong oxidizing and highly toxic properties, requiring stringent production equipment and making it difficult to meet the needs of large-scale production. Therefore, it is rarely used in actual production. The second method is the aqua regia dissolution method, which uses pure palladium as a raw material. Through steps such as dissolution in aqua regia, denitration, and concentration, palladium chloride is finally obtained by evaporation at a temperature not lower than 100°C. This method is simple and suitable for large-scale production; however, a small amount of nitrate ions remain in the product. It is worth noting that palladium chloride prepared by both conventional methods is insoluble in water, and there are currently few reports on the preparation process of water-soluble palladium chloride. Since palladium dichloride is mostly used in aqueous solution form in subsequent applications, this significantly limits the application of palladium chloride prepared by conventional methods. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a preparation process for palladium chloride dihydrate with high direct yield, simple operation process, no need for complex equipment and special conditions, and easy to realize large-scale industrial production; the produced product is free of nitrate impurities and has good water solubility, which can meet the needs of multiple scenarios.

[0005] The technical solution adopted in this invention is: A process for preparing palladium chloride dihydrate, comprising the following steps: Step S1. Add palladium powder, high-purity water and reducing agent to the reactor, then stir and heat. After heating to the set temperature, carry out a constant temperature reaction. After the reaction is completed, let it stand to separate into layers and remove the supernatant to obtain activated palladium powder. Step S2. Add hydrochloric acid to the activated palladium powder obtained in step S1, then stir and heat. After heating to the set temperature, add hydrogen peroxide dropwise. After the addition is complete, react until the palladium powder is completely dissolved to obtain a solution, and filter the solution. Step S3. Transfer the filtrate obtained in step S2 to an evaporator for vacuum concentration. When the palladium concentration reaches 400~500g / L, add high-purity water to the evaporator for dilution, and then continue vacuum concentration. Step S4. Adjust the pH by removing acid multiple times. Repeat step S3 3 to 5 times to remove acid until the solution pH reaches 1 to 5.5, thus completing the acid removal process. Step S5. The solution obtained in step S4 is concentrated under vacuum. When the palladium content reaches the set value, palladium chloride dihydrate is obtained.

[0006] Preferably, in the preparation process of palladium chloride dihydrate, the heating temperature in step S1 is 60~80℃, the constant temperature reaction time is 1~2h, and the standing time is 0.5~1h.

[0007] Preferably, in the preparation process of palladium chloride dihydrate, the mass ratio of palladium powder, high-purity water, and reducing agent in step S1 is 1:1~2:0.1~0.2, and the reducing agent is selected from one or two of formic acid and hydrazine hydrate; the purity of the palladium powder is not less than 99.95%.

[0008] Preferably, in the preparation process of palladium chloride dihydrate, the concentration of hydrochloric acid in step S2 is 36%~38%, the heating temperature is 60~80℃, the concentration of hydrogen peroxide is 30%, and the reaction time is 8~12h.

[0009] Preferably, in the preparation process of palladium chloride dihydrate, the mass ratio of palladium powder, hydrochloric acid, and hydrogen peroxide in step S2 is 1:10~20:5~10.

[0010] Preferably, in the preparation process of palladium chloride dihydrate, the vacuum concentration temperature in step S3 is 55~85℃, and the mass ratio of palladium to high-purity water in the filtrate is 1:1~2. Preferably, in the preparation process of palladium chloride dihydrate, the pH value of the solution in step S4 is 4-5.

[0011] Preferably, in the preparation process of palladium chloride dihydrate, the vacuum concentration temperature in step S5 is 55~85℃, and the palladium content in palladium chloride dihydrate is 49.80%~49.99%.

[0012] Advantages of this invention: (1) The preparation process of palladium chloride dihydrate of the present invention has a high direct yield, which can effectively reduce raw material loss and improve production efficiency; the operation process is simple, no complex equipment or special operating conditions are required, and it is easy to realize large-scale industrial production; the palladium chloride dihydrate prepared by this process has nitrate-free characteristics, which avoids the influence of nitrate impurities on subsequent applications, and at the same time has good water solubility, which can meet the needs of different scenarios. Attached Figure Description

[0013] Figure 1 This is a flowchart of the preparation process of palladium chloride dihydrate according to the present invention. Detailed Implementation

[0014] The present invention will be further described below with reference to specific embodiments.

[0015] Example 1 like Figure 1 A process for preparing palladium chloride dihydrate, comprising the following steps: Step S1. Add 50g of palladium powder with a purity of 99.95%, 50g of high-purity water and 10g of formic acid to the reactor. Then turn on the stirring device and heating system to raise the system temperature to 60℃ and react at a constant temperature for 1h. After the reaction is completed, turn off the stirring and heating, let it stand for 0.5h and then extract the supernatant to obtain activated palladium powder. Step S2. Add 500 ml of high-purity hydrochloric acid to the activated palladium powder obtained in step S1, start stirring and heating, raise the system temperature to 60°C, add 250 g of 30% high-purity hydrogen peroxide dropwise, continue the reaction for 8 hours, stop heating and stirring after the palladium powder is completely dissolved, wait for the system temperature to drop to room temperature, and filter the solution. Step S3. Transfer the filtrate obtained from filtration to a rotary evaporator. The filter residue is dried to a net weight of 0.49g. Turn on the rotary evaporator and vacuum system, raise the temperature in the rotary evaporator to 55°C, and perform vacuum concentration. When the palladium concentration reaches 400g / L, add 50g of high-purity water to the evaporator for dilution, and then continue vacuum concentration. Step S4. Repeat the acid removal operation of step S3 3 times, and check the pH value of the solution to 1 to complete the acid removal process; Step S5. The solution obtained in step S4 is further concentrated under vacuum at 55°C. When the net weight of the material is 99.40g, heating is stopped, and after cooling to room temperature, the product is packaged into a special packaging barrel to obtain the target product, palladium chloride dihydrate. The palladium content is 49.81%, and nitrate is not detected. The palladium chloride dihydrate prepared in this example is dissolved in water, and the resulting solution is clear and free of residue. The calculated yield is 99.0%.

[0016] Example 2 like Figure 1A process for preparing palladium chloride dihydrate, comprising the following steps: Step S1: Add 50g of palladium powder (99.95% purity), 100g of high-purity water, and 5g of hydrazine hydrate to the reactor. Then, turn on the stirring device and heating system to raise the system temperature to 80℃ and react at a constant temperature for 2 hours. After the reaction is completed, turn off the stirring and heating, let it stand for 1 hour, and then extract the supernatant to obtain activated palladium powder. Step S2. Add 1000 ml of high-purity hydrochloric acid to the activated palladium powder obtained in step S1, start stirring and heating, raise the system temperature to 80°C, add 500 g of 30% high-purity hydrogen peroxide dropwise, continue the reaction for 12 h, stop heating and stirring after the palladium powder is completely dissolved, wait for the system temperature to drop to room temperature, and filter the solution. Step S3. Transfer the filtrate obtained from filtration to a rotary evaporator. After filtration, the filtrate obtained from filtration is transferred to a rotary evaporator. There is no filter residue and the palladium powder is completely dissolved. Turn on the rotary evaporator and the vacuum system, raise the temperature to 85°C, and perform vacuum concentration. When the palladium concentration reaches 500 g / L, add 100 g of high-purity water to the evaporator for dilution, and then continue vacuum concentration. Step S4. Repeat the acid removal operation of step S3 5 times, and check that the pH value of the solution is 5.5 to complete the acid removal process; Step S5. The solution obtained in step S4 is further concentrated under vacuum at 55°C. When the net weight of the material is 100.02g, heating is stopped, and after cooling to room temperature, the product is packaged into a special packaging barrel to obtain the target product, palladium chloride dihydrate. The palladium content is 49.99%, and nitrate is not detected. The palladium chloride dihydrate prepared in this example is dissolved in water, and the resulting solution is clear and free of residue. The yield is calculated to be 100%.

[0017] Example 3 like Figure 1 A process for preparing palladium chloride dihydrate, comprising the following steps: Step S1. Add 50g of palladium powder with a purity of 99.95%, 75g of high-purity water and 10g of formic acid to the reactor. Then turn on the stirring device and heating system to raise the system temperature to 80℃ and keep the temperature constant for 1.5h. After the reaction is completed, turn off the stirring and heating, let it stand for 0.75h and then extract the supernatant to obtain activated palladium powder. Step S2. Add 750 ml of high-purity hydrochloric acid to the activated palladium powder obtained in step S1, start stirring and heating, raise the system temperature to 70°C, add 375 g of 30% high-purity hydrogen peroxide dropwise, continue the reaction for 1.5 h, stop heating and stirring after the palladium powder is completely dissolved, wait for the system temperature to drop to room temperature, and filter the solution. Step S3. Transfer the filtrate obtained from filtration to a rotary evaporator. The filter residue is dried to a net weight of 0.25g. Turn on the rotary evaporator and vacuum system, raise the temperature to 70℃, and perform vacuum concentration. When the palladium concentration reaches 450g / L, add 75g of high-purity water to the evaporator for dilution, and then continue vacuum concentration. Step S4. Repeat the acid removal operation of step S3 4 times, and check that the pH value of the solution is 4 to complete the acid removal process; Step S5. The solution obtained in step S4 is further concentrated under vacuum at 70°C. When the net weight of the material is 99.74g, heating is stopped, and after cooling to room temperature, the product is packaged into a special packaging barrel to obtain the target product, palladium chloride dihydrate. The palladium content is 49.88%, and nitrate is not detected. The palladium chloride dihydrate prepared in this example is dissolved in water, and the resulting solution is clear and free of residue. The calculated yield is 99.5%.

[0018] The test results from Examples 1-3 show that the preparation process of palladium chloride dihydrate of the present invention not only has low equipment requirements but also a simple process route, fully demonstrating that this method has good prospects for industrial production and is suitable for industrial promotion. By reducing and activating palladium powder, even when using hydrogen peroxide as an oxidant, good dissolution of palladium powder can be achieved without the need to add nitric acid, thus completely eliminating the introduction of nitrate ions and making the process more environmentally friendly. The direct recovery rate of the prepared palladium chloride dihydrate all exceeded 99%, and nitrates were not detected. The solution was clear and residue-free in the water dissolution experiment, indicating that the product has the advantages of being nitrate-free and having good water solubility.

[0019] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A process for preparing palladium chloride dihydrate, characterized in that, Includes the following steps: Step S1. Add palladium powder, high-purity water and reducing agent to the reactor, then stir and heat. After heating to the set temperature, carry out a constant temperature reaction. After the reaction is completed, let it stand to separate into layers and remove the supernatant to obtain activated palladium powder. Step S2. Add hydrochloric acid to the activated palladium powder obtained in step S1, then stir and heat. After heating to the set temperature, add hydrogen peroxide dropwise. After the addition is complete, react until the palladium powder is completely dissolved to obtain a solution, and filter the solution. Step S3. Transfer the filtrate obtained in step S2 to an evaporator for vacuum concentration. When the palladium concentration reaches 400~500g / L, add high-purity water to the evaporator for dilution, and then continue vacuum concentration. Step S4. Repeat step S3 3 to 5 times until the solution pH reaches 1 to 5.5; Step S5. The solution obtained in step S4 is concentrated under vacuum. When the palladium content reaches the set value, palladium chloride dihydrate is obtained.

2. The preparation process of palladium chloride dihydrate according to claim 1, characterized in that: In step S1, the heating temperature is 60~80℃, the constant temperature reaction time is 1~2h, and the standing time is 0.5~1h.

3. The preparation process of palladium chloride dihydrate according to claim 1, characterized in that: In step S1, the mass ratio of palladium powder, high-purity water, and reducing agent is 1:1~2:0.1~0.

2. The reducing agent is selected from one or two of formic acid and hydrazine hydrate. The purity of the palladium powder is not less than 99.95%.

4. The preparation process of palladium chloride dihydrate according to claim 1, characterized in that: In step S2, the mass concentration of hydrochloric acid is 36%~38%, the heating temperature is 60~80℃, the concentration of hydrogen peroxide is 30%, and the reaction time is 8~12h.

5. The preparation process of palladium chloride dihydrate according to claim 1, characterized in that: In step S2, the mass ratio of activated palladium powder, hydrochloric acid, and hydrogen peroxide is 1:10~20:5~10.

6. The preparation process of palladium chloride dihydrate according to claim 1, characterized in that: In step S3, the vacuum concentration temperature is 55~85℃, and the mass ratio of palladium to high-purity water in the filtrate is 1:1~2.

7. The preparation process of palladium chloride dihydrate according to claim 1, characterized in that: The pH value of the solution in step S4 is 4~5.

8. The preparation process of palladium chloride dihydrate according to claim 1, characterized in that: In step S5, the vacuum concentration temperature is 55~85℃, and the palladium content in palladium chloride dihydrate is 49.80%~49.99%.

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