A process for the preparation of palladium (II) sulfate

Abstract

This invention discloses a method for preparing palladium(II) sulfate, comprising: 1) placing sponge palladium powder in a saturated persulfate solution, slowly adding hydrogen peroxide dropwise under ice bath conditions, stirring, turning on ultraviolet light for irradiation, and slowly heating until the reaction solution turns reddish-brown and no more bubbles appear, thus obtaining a palladium(II) sulfate solution; 2) adding a hydrohalic acid solution to the palladium(II) sulfate solution, stirring, and then concentrating under reduced pressure, precipitating reddish-brown needle-like crystals in a rotary evaporator, filtering, and collecting the hydrated Pd. II SO4·xH2O; 3) The hydrate can be dried under vacuum to obtain anhydrous palladium sulfate or palladium sulfate dihydrate; or the hydrate can be frozen to form a solid, and then freeze-dried to obtain palladium sulfate monohydrate solid. This invention avoids the traditional cumbersome synthesis process, the reaction is simple and efficient and does not contain chloride ions. This method prepares palladium(II) sulfate under mild conditions, which meets the requirements of atom economy and green environmental protection, and is suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing palladium (II) sulfate, and the preparation method of the compound belongs to the field of chemical engineering. BACKGROUND

[0002] Palladium (II) sulfate is generally divided into Pd II SO4·2H2O, Pd II SO4·H2O and Pd II SO4. Generally speaking, the number of crystal water in palladium (II) sulfate determines the solubility of palladium sulfate solid, among which anhydrous palladium sulfate is difficult to dissolve in water, dihydrate palladium sulfate is soluble in water, and monohydrate palladium sulfate is easily soluble in water. They can all be used to prepare noble metal catalysts, non-conductor material coatings, and can also be used as important raw materials for synthesizing high-end palladium compounds or homogeneous palladium catalysts. At present, there are few reports on the synthesis method of monohydrate palladium (II) sulfate Pd II SO4·H2O, and most of the public reports are about the synthesis of dihydrate palladium (II) sulfate Pd II SO4·2H2O.

[0003] The Handbook of Noble Metal Compounds and Complexes introduces the method for preparing dihydrate palladium sulfate and monohydrate palladium sulfate. Palladium powder is dissolved in a mixture of nitric acid and excess sulfuric acid to obtain a dark red solution, which is evaporated to syrup and cooled to obtain dihydrate palladium sulfate. Palladium nitrate and sulfuric acid can also be boiled to obtain monohydrate and anhydrous compounds.

[0004] In Noble Metals and Their Alloys, it is introduced that dihydrate palladium sulfate can be prepared by fuming palladium nitrate and sulfuric acid. Palladium nitrate can be obtained by dissolving palladium in fuming nitric acid.

[0005] CN112169811A discloses a preparation method of palladium sulfate solution. First, sponge palladium is oxidized with concentrated nitric acid, and then concentrated sulfuric acid is added for nitrate removal treatment to obtain a palladium sulfate solution.

[0006] CN109295482A discloses a preparation method of palladium sulfate. Palladium powder is reacted with a mixture of concentrated nitric acid and concentrated sulfuric acid, and then high-temperature nitrate removal is performed to obtain a palladium sulfate solution.

[0007] The above preparation methods are complicated, the batch stability of palladium (II) sulfate product is poor, and the number of crystal water is uncontrollable. In addition, most palladium sources contain chloride ions or other impurities, which can easily enter the end product during the synthesis process, and the content will affect the performance of the catalyst, and also has a certain influence on the electroplating process, electroplated coating and related equipment.

[0008] Therefore, it is particularly important to develop a simple and convenient preparation method of palladium (II) sulfate without chloride and with controllable crystal water. SUMMARY

[0009] The present application aims to solve the problems of complicated process, impurity content and control of crystal water in conventional synthesis of palladium (II) sulfate, and to provide a preparation method with simple operation, green environmental protection, low impurity content and controllable crystal water, which is suitable for industrial production.

[0010] The synthesis method of the present application comprises:

[0011] Step (1), sponge palladium powder is placed in a saturated solution of persulfate, and an appropriate amount of hydrogen peroxide with a concentration of 30% is slowly added dropwise under ice bath conditions, and after stirring for a few minutes, a UV lamp (UV) is turned on for irradiation, and the reaction solution is slowly heated to red-brown color while no more bubbles appear, to obtain a palladium (II) sulfate solution;

[0012] Step (2), a certain amount of hydrogen halide acid solution is added to the above red-brown solution, and after sufficient stirring, a vacuum concentration treatment is performed, a large amount of red-brown needle-shaped crystalline substance is precipitated in the rotary evaporation flask, and the hydrate Pd II SO4·xH2O (x is an integer from 0 to 2) is collected by filtration;

[0013] Step (3), the hydrate is dried at 80°C under vacuum conditions to obtain red-brown palladium (II) sulfate dihydrate Pd II SO4·2H2O solid;

[0014] or

[0015] The hydrate is dried at 120°C under vacuum conditions to obtain dark red anhydrous palladium (II) sulfate Pd II SO4 solid.

[0016] or

[0017] The hydrate Pd II SO4·xH2O (x is an integer from 0 to 2) is placed in a freeze-drying machine equipment for low-temperature freezing to obtain frozen Pd II SO4·xH2O (x is an integer from 0 to 2) solid, which is frozen for 3-5h below the crystallization temperature of-50°C, and then the temperature is increased from-50°C to-25°C for low-temperature sublimation drying, the material temperature is-25°C to-20°C, the vacuum value is not more than 30Pa, and the drying is stopped immediately when the red-brown color changes to olive green, to obtain olive green palladium (II) sulfate monohydrate Pd II SO4·H2O solid.

[0018] The present application uses common sponge palladium as raw material, and adopts the method of H2O2-persulfate-UV light (UV) synergistic oxidation to directly convert sponge palladium into Pd II SO4, and the technical route is:

[0019]

[0020] The beneficial effects of the present application include:

[0021] (1) The method of the present application is simple and efficient, effectively avoiding the influence of impurities such as chloride ions.

[0022] (2) The present application adopts a one-step freeze-drying method to realize the controllable preparation of high-purity palladium sulfate (II) Pd II SO4·H2O solid.

[0023] (3) The present application prepares palladium (II) sulfate under mild conditions, which meets the requirements of atomic economy, green environmental protection, and industrial production. DETAILED DESCRIPTION

[0024] Example 1: Synthesis of palladium (II) sulfate monohydrate Pd II SO4·H2O

[0025] Take 5.0 g of sponge palladium powder and add 100 g of ice-cold ammonium persulfate saturated solution. While stirring in an ice bath, slowly add 5 mL of 30% concentration hydrogen peroxide. After stirring for a few moments, turn on the ultraviolet lamp (UV) irradiation. Slowly heat to 60°C. Under this condition, react for 0.5 h. After the red-brown solution is obtained and no more bubbles appear, cool to room temperature. Add 20 mL of 48% hydrobromic acid. Stir thoroughly. Concentrate under reduced pressure to 60 mL. A large amount of red-brown needle-shaped crystalline material is precipitated in the rotary evaporation flask. Filter to obtain the hydrate Pd II SO4·xH2O (x is an integer from 0 to 2). Place the above hydrate in a freeze-drying machine device for low-temperature freezing to obtain the frozen Pd II SO4·xH2O (x is an integer from 0 to 2) solid. Freeze at a crystallization temperature of -50°C or lower for 3-5 h. Then, perform low-temperature sublimation drying by increasing the temperature from -50°C to -25°C. The material temperature is about -25°C to -20°C. The vacuum value is 25-28 Pa. Dry for about 6 h. The red-brown color changes to olive green. Immediately stop to obtain olive green palladium (II) sulfate monohydrate Pd II SO4·H2O solid 9.95 g, yield 96%.

[0026] Elemental analysis:

[0027] The measured values are S 14.32%, H 1%, Pd 48.06%, which are consistent with the theoretical values of S 14.55%, H 0.91%, and Pd 48.28%.

[0028] The synthesis route of this example is:

[0029]

[0030] Example 2: Pd II Synthesis of Pd

[0031] Pd II Pd SO4xH2O (x is an integer from 0 to 2) was prepared according to the procedure of Example 1, and the above Pd II Pd SO4xH2O (x is an integer from 0 to 2) was dried at 80°C under vacuum to obtain red-brown Pd II Pd SO4xH2O (x is an integer from 0 to 2) was dried at 80°C under vacuum to obtain red-brown Pd

[0032] Elemental analysis:

[0033] Found: S 13.25%, H 1.84%, Pd 44.35%; Caled: S 13.45%, H 1.68%, Pd 44.62%.

[0034] Example 3: Pd II Synthesis of Pd

[0035] Pd II Pd SO4xH2O (x is an integer from 0 to 2) was prepared according to the procedure of Example 1, and the above Pd II Pd SO4xH2O (x is an integer from 0 to 2) was dried at 120°C under vacuum to obtain dark red Pd II Pd SO4xH2O (x is an integer from 0 to 2) was dried at 120°C under vacuum to obtain dark red Pd

[0036] Elemental analysis:

[0037] Found: S 15.78%, Pd 52.49%; Caled: S 15.81%, Pd 52.57%.

[0038] Example 4: Pd II Synthesis of Pd

[0039] Pd SO4xH2O (x is an integer from 0 to 2) was prepared according to the procedure of Example 1, and the above Pd IISO4.xH2O (x is an integer from 0 to 2). The hydrate is placed in a freeze-drying machine at low temperature to obtain frozen Pd II SO4.xH2O (x is an integer from 0 to 2) solid is frozen for 3-5 h at a crystallization temperature of -50°C or less, then the temperature is raised from -50°C to -25°C for low-temperature sublimation drying, the material temperature is about -25°C to -20°C, the vacuum value is 25-28 Pa, and the drying is performed for about 6 h, the red-brown color is changed to olive green, and the drying is immediately stopped to obtain olive green Pd II SO4.xH2O (x is an integer from 0 to 2) solid is frozen for 3-5 h at a crystallization temperature of -50°C or less, then the temperature is raised from -50°C to -25°C for low-temperature sublimation drying, the material temperature is about -25°C to -20°C, the vacuum value is 25-28 Pa, and the drying is performed for about 6 h, the red-brown color is changed to olive green, and the drying is immediately stopped to obtain olive green Pd

[0040] Elemental analysis:

[0041] Measured values S 14.34%, H 1%, Pd 48.03%, which are consistent with the theoretical values S 14.55%, H 0.91%, Pd 48.28%.

Claims

1. A process for the preparation of palladium sulfate, characterized in that, Comprise the following steps: Step (1), the sponge palladium powder is placed in the persulfate saturated solution, stirring under ice bath conditions while slowly adding the appropriate concentration of 30% hydrogen peroxide, stirring for a few moments after turning on the ultraviolet lamp irradiation, slowly heated to the reaction liquid red brown color, while no more bubbles, get the sulfuric acid solution of palladium; Step (2), a certain amount of hydrogen halide acid solution is added into the red-brown palladium sulfate solution, after fully stirring, the solution is concentrated under reduced pressure, a large amount of red-brown needle-shaped crystalline substance is precipitated in the rotary evaporation flask, the hydrate PdSO4·xH2O is collected by filtration II SO4·xH2O, wherein x is an integer from 0 to 2; the hydrogen halide acid includes hydriodic acid, hydrobromic acid, hydrofluoric acid; the mass ratio of the sponge palladium to the hydrogen halide acid solution is 1:3-6; the hydrogen halide acid has a concentration of 20%-70%; Step (3), the hydrate Pd II SO4.xH2O is dried at 80°C under vacuum to obtain red-brownish palladium sulfate dihydrate Pd II SO4.2H2O solid; or The hydrate Pd II SO4.xH2O is dried at 120°C under vacuum to obtain dark red anhydrous palladium sulfate Pd II SO4 solid; Or The hydrate Pd II SO4.xH2O is placed in a freeze-drying machine apparatus for low-temperature freezing to obtain frozen Pd II SO4.xH2O solid is frozen at a crystallization temperature of -50°C or lower for 3-5 hours, and then the temperature is raised from 50°C to 25°C for low-temperature sublimation drying, the material temperature is 25°C-20°C, the vacuum value is not more than 30 Pa at the highest, and the drying is stopped immediately after the red-brown color turns into olive green, to obtain olive green Pd II SO4.H2O solid.

2. The method according to claim 1, characterized in that: In step (1), the mass ratio of sponge palladium to persulfate is 1:5~11.

3. The method according to claim 1, characterized in that: In step (1), the heating temperature is 50~80℃, and the reaction time is 0.5~5 h.

4. The method according to claim 1, characterized in that: In step (1), the mass ratio of sponge palladium to 30% concentration hydrogen peroxide is 1:0.04~0.

11.

5. The method according to claim 1, characterized in that: In step (2), the temperature of the reduced pressure concentration treatment is 50~80℃.

6. The method according to any one of claims 1-5, characterized in that: The persulfate includes ammonium persulfate, sodium persulfate, potassium persulfate, barium persulfate.

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