A method and device for preparing chlorine-free and nitrate-free palladium sulfate with high purity and high stability

Abstract

The present application discloses a method and device for preparing chlorine-free and nitrate-free palladium sulfate with high purity and high stability. Palladium powder or palladium sheet is reacted with concentrated sulfuric acid under high temperature conditions to form palladium sulfate in situ to obtain a concentrated sulfuric acid solution of palladium sulfate; then, heat filtration, cooling, crystallization, filtration, and drying are performed in sequence to obtain palladium sulfate crystals; the palladium sulfate crystals are dissolved in dilute sulfuric acid to obtain a palladium sulfate solution. The preparation device is connected to the reactor through the lower end of a reflux condenser, the reactor and the crystallization kettle are connected through a sand filter membrane, the crystallization kettle and the sulfuric acid storage tank are connected through a sand filter membrane, and the sulfuric acid storage tank and the reactor are connected by a pipeline and are provided with a sulfuric acid pump. The present invention avoids the Cl ‑ and NO3 ‑ The palladium sulfate liquid obtained has high stability and no precipitation occurs after storage for one year. The preparation device of the present invention can realize continuous automatic production with low investment and operation costs.

Description

Technical Field

[0001] The present application relates to the field of preparation of precious metal compounds, and in particular to a method and device for preparing chlorine-free and nitrate-free palladium sulfate with high purity and high stability. Background Art

[0002] The palladium sulfate electroplating activation solution currently on the market is mainly prepared by dissolving palladium in aqua regia and then adding sulfuric acid to drive out nitrate (such as patent CN112169811B), which inevitably leaves a large amount of Cl - and NO 3 - In addition, the academic and industrial communities have no clear understanding of the mechanism of the instability of palladium sulfate solution and its easy irreversible precipitation, which poses a huge challenge to the preparation of highly stable electroplating activation solution and the improvement of palladium sulfate's anti-precipitation performance. Summary of the invention

[0003] The present application provides a method and device for preparing chlorine-free and nitrate-free palladium sulfate with high purity and high stability. By directly reacting elemental palladium (such as palladium powder or palladium sheet) with concentrated sulfuric acid, elemental palladium is oxidized into divalent palladium, avoiding the use of oxidants such as hydrochloric acid and nitric acid, and the prepared palladium sulfate is chlorine-free and nitrate-free. The present invention adopts a high-temperature route to prepare palladium sulfate, and the prepared palladium sulfate has high stability after being prepared into a solution, and no precipitation is formed when stored at room temperature for one year. The palladium sulfate preparation device provided by the present invention organically combines a reflux condenser, a reactor, a crystallization kettle, and a sulfuric acid storage tank through a pipeline / sand core filter membrane, and provides material transportation power through a pump, so as to realize the continuous production of palladium sulfate.

[0004] A method for preparing chlorine-free and nitrate-free palladium sulfate with high purity and high stability comprises the following steps:

[0005] Step (1): reacting palladium powder or palladium sheet with concentrated sulfuric acid under certain pressure and high temperature conditions for a period of time to form palladium sulfate in situ, thereby obtaining a concentrated sulfuric acid solution of palladium sulfate;

[0006] Step (2): hot filtering the concentrated sulfuric acid solution of palladium sulfate to remove unreacted palladium powder or palladium flakes, and then cooling, crystallizing, filtering, and drying to obtain palladium sulfate crystals. The filtered concentrated sulfuric acid can be reused;

[0007] Step (3): The palladium sulfate crystals obtained in step (2) are dissolved in dilute sulfuric acid of a certain concentration to obtain a palladium sulfate solution.

[0008] In step (1), concentrated sulfuric acid is used as both a solvent and a reactant, and the concentrated sulfuric acid is selected from 98% concentrated sulfuric acid, 105% oleum, or a mixture of the two.

[0009] In a preferred embodiment, the concentrated sulfuric acid in step (1) is a mixture of 98% concentrated sulfuric acid and 105% oleum in a mass ratio of 1:1.

[0010] In step (1), before the reaction is heated, a certain amount of initiator needs to be added to the concentrated sulfuric acid, and the mass ratio of the initiator to the concentrated sulfuric acid is 1:1000-2000, preferably 1:1200-1600, and more preferably 1:1400-1500.

[0011] In a preferred embodiment, the initiator in step (1) is 30% hydrogen peroxide, and the mass ratio of the initiator to concentrated sulfuric acid is 1:1500.

[0012] In step (1), the reaction temperature is 240-360°C, preferably 260-320°C, and more preferably 280-300°C.

[0013] In step (1), the reaction pressure is 0.1 MPa, i.e., normal pressure.

[0014] In step (1), the reaction time is 30 to 60 min, preferably 30 to 45 min, and more preferably 35 to 45 min.

[0015] In a preferred embodiment, the reaction temperature in step (1) is 300° C., the reaction pressure is 0.1 MPa, and the reaction time is 40 min.

[0016] In step (1), the mass ratio of palladium powder or palladium sheet to concentrated sulfuric acid in the reaction system is 1:5-20, preferably 1:8-12.

[0017] In step (2), the temperature of cooling and crystallizing the concentrated sulfuric acid solution of palladium sulfate is 30-50°C.

[0018] In step (2), an initiator needs to be added to the filtered concentrated sulfuric acid before reuse, and the mass ratio of the initiator to the concentrated sulfuric acid is 1:1000-2000, preferably 1:1200-1600, and more preferably 1:1400-1500.

[0019] In step (2), the drying temperature is 100-150°C.

[0020] In step (2), the drying time is 0.5 to 2 hours.

[0021] In step (3), the dilute sulfuric acid is a mixture of 98% concentrated sulfuric acid and water, and the mass content of sulfuric acid in the dilute sulfuric acid is 20-70%, preferably 35-50%.

[0022] In a preferred embodiment, the mass content of sulfuric acid in the dilute sulfuric acid in step (3) is 40-45%.

[0023] According to another aspect of the present application, a device for preparing chlorine-free and nitrate-free palladium sulfate having both high purity and high stability is provided.

[0024] The device for preparing high-purity and high-stability chlorine-free and nitrate-free palladium sulfate comprises the following components from top to bottom: a reflux condenser, a reactor, a crystallization kettle, a sulfuric acid storage tank and a sulfuric acid pump; the lower end of the reflux condenser is connected to the reactor, the reactor and the crystallization kettle are connected by a sand filter membrane, the crystallization kettle and the sulfuric acid storage tank are connected by a sand filter membrane, the sulfuric acid storage tank is connected to the sulfuric acid pump by a pipeline, and the sulfuric acid pump is connected to the reactor by a pipeline.

[0025] Preferably, the reactor is electrically heated for temperature control, the reflux condenser and the crystallization kettle are cooled and temperature controlled by a water bath jacket, and the sulfuric acid pump is a peristaltic pump.

[0026] The device for preparing high-purity and high-stability chlorine-free and nitrate-free palladium sulfate does not require human intervention from the initial feeding to the completion of the preparation of palladium sulfate crystals, thereby realizing continuous and automated production of palladium sulfate crystals.

[0027] The beneficial effects that the present invention can produce include:

[0028] 1) In the present invention, sulfuric acid is used as the reaction solvent and reactant, and sulfuric acid is used as the oxidant of elemental palladium, avoiding the use of conventional hydrochloric acid and nitric acid, and fundamentally solving the problem of palladium sulfate Cl - and NO 3 - The residues lay the foundation for the preparation of high-quality electroplating activation solution downstream.

[0029] 2) In the present invention, palladium sulfate is prepared by reacting elemental palladium with concentrated sulfuric acid at a relatively high reaction temperature of 240 to 360° C. Therefore, the palladium sulfate inherently has relatively high thermal stability, has good precipitation resistance after being configured into a solution, and can be stored at room temperature for more than one year without precipitation.

[0030] 3) The high-purity and high-stability chlorine-free and nitrate-free palladium sulfate preparation device provided by the present invention is easy to carry out large-scale industrial continuous automated production and is easy to accurately control the purity and yield of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the structure of a continuous automated reaction device for high-purity and high-stability chlorine-free and nitrate-free palladium sulfate.

[0032] Figure numerals: 1-reflux condenser; 2-feed port; 3-reactor; 4-electric heating wire; 5-sand filter membrane; 6-crystallization kettle; 7-sulfuric acid storage tank; 8-flow control valve; 9-sulfuric acid pump. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Unless otherwise specified, the palladium powder and palladium sheet used in the present invention are purchased from Guiyan Platinum Co., Ltd.; 98% concentrated sulfuric acid, 105% oleum, and 30% hydrogen peroxide are purchased from China National Pharmaceutical Group Corporation.

[0035] The analysis method in the examples of this application is as follows:

[0036] The impurity element content of the product was determined using a NexIon 300Q inductively coupled plasma mass spectrometer (ICP for short) from PE Company of the United States.

[0037] The chlorine and nitrate content of the product was detected using the ELEMENTRAC ONH-P 2 oxygen and nitrogen analyzer and the Dionex ICS3000 ion chromatograph from the German ELTRA company.

[0038] The solution turbidity was detected using a Shanghai Xinrui portable WGZ-1B / 200B turbidity meter.

[0039] Example 1

[0040] Preparation and purity test of chlorine-free and nitrate-free palladium sulfate crystals

[0041] Preparation of palladium sulfate crystals: Weigh 100g of palladium powder, 500g of 98% concentrated sulfuric acid, 500g of 105% fuming sulfuric acid, and 1.5g of 30% hydrogen peroxide, and put the above materials into the reactor in turn. Open the reflux condenser and the cooling water of the crystallization kettle, and control the cooling water temperature to 40°C; turn on the electric heating of the reactor and control the reaction temperature to 300°C. When sulfuric acid passes through the sand filter membrane into the sulfuric acid storage tank, open the flow control valve and the sulfuric acid pump to circulate sulfuric acid into the reactor. After 40 minutes of reaction, stop heating the reactor and turn off the sulfuric acid pump. At this time, there are palladium sulfate crystals in the crystallization kettle. Take out the palladium sulfate crystals, place them in a blast drying oven at 120°C and dry them for 1h to obtain 185.3g of product palladium sulfate crystals, and the yield of palladium sulfate is 97.5%.

[0042] The impurity content of the above palladium sulfate crystals was tested, and the results are shown in the following table.

[0043] Table 1 Impurity content of palladium sulfate crystals (wt%)

[0044] Pd 52.53 Cu 0.0003 Mg 0.0005 Fe 0.0005 Pb 0.0008 Ca 0.0009 Pt 0.0011 Sn 0.0003 Bi 0.0012 Au 0.0014 Al 0.0001 Sb 0.0007 Na 0.0005 Si 0.0005 Ag 0.0003 Cl none <![CDATA[NO 3 - ]]> none

[0045] Example 2

[0046] Preparation and purity test of chlorine-free and nitrate-free palladium sulfate crystals

[0047] Preparation of palladium sulfate crystals: Weigh 100g of palladium powder, 2000g of 98% concentrated sulfuric acid, and 1g of 30% hydrogen peroxide, and put the above materials into the reactor in turn. Open the reflux condenser and the cooling water of the crystallization kettle, and control the cooling water temperature to 50°C; turn on the electric heating of the reactor and control the reaction temperature to 360°C. When sulfuric acid passes through the sand filter membrane into the sulfuric acid storage tank, open the flow control valve and the sulfuric acid pump to circulate sulfuric acid into the reactor. After 60 minutes of reaction, stop heating the reactor and turn off the sulfuric acid pump. At this time, there are palladium sulfate crystals in the crystallization kettle. Take out the palladium sulfate crystals, place them in a blast drying oven at 150°C and dry them for 0.5h to obtain 187.7g of product palladium sulfate crystals, and the yield of palladium sulfate is 98.7%.

[0048] The impurity content of the above palladium sulfate crystals was tested, and the results are shown in the following table.

[0049] Table 2 Impurity content of palladium sulfate crystals (wt%)

[0050] Pd 52.54 Cu 0.0003 Mg 0.0007 Fe 0.0002 Pb 0.0005 Ca 0.0009 Pt 0.0008 Sn 0.0006 Bi 0.0011 Au 0.0007 Al 0.0002 Sb 0.0008 Na 0.0006 Si 0.0004 Ag 0.0002 Cl none <![CDATA[NO 3 - ]]> none

[0051] Example 3

[0052] Preparation and purity test of chlorine-free and nitrate-free palladium sulfate crystals

[0053] Preparation of palladium sulfate crystals: Weigh 100g of palladium powder, 500g of 105% fuming sulfuric acid, and 0.5g of 30% hydrogen peroxide, and put the above materials into the reactor in turn. Open the reflux condenser and the cooling water of the crystallization kettle, and control the cooling water temperature to 30°C; turn on the electric heating of the reactor and control the reaction temperature to 240°C. When sulfuric acid passes through the sand filter membrane into the sulfuric acid storage tank, open the flow control valve and the sulfuric acid pump to circulate sulfuric acid into the reactor. After 30 minutes of reaction, stop heating the reactor and turn off the sulfuric acid pump. At this time, there are palladium sulfate crystals in the crystallization kettle. Take out the palladium sulfate crystals, place them in a blast drying oven at 100°C and dry them for 2 hours to obtain 188.6g of product palladium sulfate crystals, and the yield of palladium sulfate is 99.2%.

[0054] The impurity content of the above palladium sulfate crystals was tested, and the results are shown in the following table.

[0055] Table 3 Impurity content of palladium sulfate crystals (wt%)

[0056] Pd 52.55 Cu 0.0004 Mg 0.0004 Fe 0.0004 Pb 0.0004 Ca 0.0007 Pt 0.0010 Sn 0.0003 Bi 0.0007 Au 0.0011 Al 0.0003 Sb 0.0004 Na 0.0007 Si 0.0001 Ag 0.0003 Cl none <![CDATA[NO 3 - ]]> none

[0057] Example 4

[0058] Preparation and stability test of palladium sulfate solutions with different palladium contents

[0059] Preparation of palladium sulfate crystals: Weigh 500g of palladium powder, 5000g of 98% concentrated sulfuric acid, and 8g of 30% hydrogen peroxide, and put the above materials into the reactor in turn. Open the reflux condenser and the cooling water of the crystallization kettle, and control the cooling water temperature to 30°C; turn on the electric heating of the reactor and control the reaction temperature to 290°C. When sulfuric acid passes through the sand filter membrane into the sulfuric acid storage tank, open the flow control valve and the sulfuric acid pump to circulate sulfuric acid into the reactor. After 45 minutes of reaction, stop heating the reactor and turn off the sulfuric acid pump. At this time, there are palladium sulfate crystals in the crystallization kettle. Take out the palladium sulfate crystals, place them in a blast drying oven at 140°C and dry them for 2 hours to obtain 928.7g of product palladium sulfate crystals, and the yield of palladium sulfate is 97.7%.

[0060] The impurity content of the above palladium sulfate crystals was tested, and the results are shown in the following table.

[0061] Table 4 Impurity content of palladium sulfate crystals (wt%)

[0062] Pd 52.52 Cu 0.0002 Mg 0.0006 Fe 0.0007 Pb 0.0005 Ca 0.0007 Pt 0.0008 Sn 0.0001 Bi 0.0002 Au 0.0009 Al 0.0003 Sb 0.0006 Na 0.0004 Si 0.0006 Ag 0.0004 Cl none <![CDATA[NO 3 - ]]> none

[0063] Preparation of dilute sulfuric acid: Take 3245g of deionized water and 3245g of 98% concentrated sulfuric acid in a beaker, slowly add concentrated sulfuric acid into the deionized water to prepare 50% dilute sulfuric acid.

[0064] For palladium sulfate crystals, there is no problem of storage stability. However, when palladium sulfate is configured into a solution, since palladium sulfate will hydrolyze and produce precipitation in the solution, its solution stability is a problem of general concern in the industry. The palladium content of commercial palladium sulfate solutions in industry is generally between 4% and 9%. Therefore, the present invention configures the above-prepared palladium sulfate crystals into a 1% to 15% palladium sulfate solution, stores it at room temperature without being protected from light, and examines its stability. The following is the preparation process and stability test data of palladium sulfate solution.

[0065] Preparation of palladium sulfate solutions with different palladium contents:

[0066] (1) Preparation of 1% palladium sulfate solution: 10 g of palladium sulfate crystals were slowly added into 515.2 g of 50% dilute sulfuric acid and stirred until the palladium sulfate was completely dissolved. The turbidity of the solution was detected to be 0.12.

[0067] (2) Preparation of 3% palladium sulfate solution: 30 g of palladium sulfate crystals were slowly added into 495.2 g of 50% dilute sulfuric acid and stirred until the palladium sulfate was completely dissolved. The turbidity of the solution was detected to be 0.01.

[0068] (3) Preparation of 5% palladium sulfate solution: 50 g of palladium sulfate crystals were slowly added into 475.2 g of 50% dilute sulfuric acid and stirred until the palladium sulfate was completely dissolved. The turbidity of the solution was detected to be -0.11.

[0069] (4) Preparation of 7% palladium sulfate solution: 70 g of palladium sulfate crystals were slowly added into 455.2 g of 50% dilute sulfuric acid and stirred until the palladium sulfate was completely dissolved. The turbidity of the solution was detected to be 0.15.

[0070] (5) Preparation of 9% palladium sulfate solution: 90 g of palladium sulfate crystals were slowly added into 435.2 g of 50% dilute sulfuric acid and stirred until the palladium sulfate was completely dissolved. The turbidity of the solution was detected to be -0.02.

[0071] (6) Preparation of palladium sulfate solution with 12% palladium content: 120 g of palladium sulfate crystals were slowly added into 405.2 g of 50% dilute sulfuric acid and stirred until the palladium sulfate was completely dissolved. The turbidity of the solution was detected to be 0.08.

[0072] (7) Preparation of palladium sulfate solution with 15% palladium content: 150 g of palladium sulfate crystals were slowly added into 375.2 g of 50% dilute sulfuric acid and stirred until the palladium sulfate was completely dissolved. The turbidity of the solution was detected to be 0.05.

[0073] The above palladium sulfate solutions with a palladium content of 1% to 15% were placed in quartz bottles and sealed, and stored at room temperature for one year. After one year of storage, the solutions were shaken and then sampled, and the turbidity of the palladium sulfate solutions was tested, and the results are shown in Table 5.

[0074] Table 5 Changes in appearance and turbidity of palladium sulfate solutions with different palladium contents after one year of storage

[0075]

[0076]

[0077] It can be seen from Table 5 that the above 7 palladium sulfate solutions with palladium contents of 1% to 15% are relatively stable and no precipitation is produced after being stored for one year.

[0078] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing chlorine-free and nitrate-free palladium sulfate with high purity and high stability, characterized in that: The following steps are involved: Step (1): reacting palladium powder or palladium sheet with concentrated sulfuric acid under certain pressure and high temperature conditions for a period of time to form palladium sulfate in situ, thereby obtaining a concentrated sulfuric acid solution of palladium sulfate; Step (2): hot filtering the concentrated sulfuric acid solution of palladium sulfate to remove unreacted palladium powder or palladium flakes, and then cooling, crystallizing, filtering, and drying to obtain palladium sulfate crystals. The filtered concentrated sulfuric acid can be reused; Step (3): dissolving the palladium sulfate crystals obtained in step (2) in dilute sulfuric acid of a certain concentration to obtain a palladium sulfate solution; the dilute sulfuric acid is a mixture of 98% concentrated sulfuric acid and water, and the mass content of sulfuric acid in the dilute sulfuric acid is 20-70%; In the step (1), the mass ratio of palladium powder or palladium sheet to concentrated sulfuric acid in the reaction is 1:5-20; the reaction temperature is 240-360°C, the reaction pressure is 0.1 MPa, and the reaction time is 30-60 min; In the step (1), the concentrated sulfuric acid is selected from 98% concentrated sulfuric acid, 105% oleum, or a mixture of the two; the concentrated sulfuric acid in the step (1) contains an initiator, the initiator is 30% hydrogen peroxide, and the mass ratio of the initiator to the concentrated sulfuric acid is 1:1000-2000; In the step (2), the cooling temperature is 30-50°C; the crystallization temperature is 30-50°C; the drying temperature is 100-150°C and the drying time is 0.5-2h; The device of the preparation method comprises the following components from top to bottom: a reflux condenser, a reactor, a crystallization kettle, a sulfuric acid storage tank and a sulfuric acid pump; the lower end of the reflux condenser is connected to the reactor, the reactor and the crystallization kettle are connected by a sand filter membrane, the crystallization kettle and the sulfuric acid storage tank are connected by a sand filter membrane, the sulfuric acid storage tank is connected to the sulfuric acid pump by a pipeline, and the sulfuric acid pump is connected to the reactor by a pipeline.

2. A method for preparing a chlorine-free and nitrate-free palladium sulfate having both high purity and high stability according to claim 1, characterized in that: In step (2), the filtered concentrated sulfuric acid needs to be supplemented with an initiator before reuse, and the mass ratio of the initiator to the concentrated sulfuric acid is 1:1000-2000.

3. A method for preparing a chlorine-free and nitrate-free palladium sulfate having high purity and high stability according to claim 1, characterized in that: The mass content of sulfuric acid in the dilute sulfuric acid is 40-45%.

4. A method for preparing a chlorine-free and nitrate-free palladium sulfate having high purity and high stability according to claim 1, characterized in that: The reactor is electrically heated for temperature control, the reflux condenser and the crystallization kettle are cooled and temperature controlled by a water bath jacket, and the sulfuric acid pump is a peristaltic pump.

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