Palladium ball for three-way catalysis and preparation method thereof

Abstract

The invention discloses a palladium ball for three-way catalysis and a preparation method thereof, the palladium ball takes a modified silicon ball as an inner core, the surface of the modified silicon ball is sequentially coated with a metal nickel layer and a palladium layer by adopting a chemical deposition method, the particle size of the palladium ball is 2.5-150 mu m, the thickness of the nickel layer is 0.15 + / -0.05 mu m, and the total thickness of the nickel layer and the palladium layer is 0.2 + / -0.05 mu m. The palladium material content of the prepared palladium ball is 5-20%, the consumption of palladium metal can be effectively reduced, and the consumption of the palladium material can be saved by about 90% under the same catalytic effect, so that the cost is greatly reduced; the palladium balls are uniformly dispersed and are of a spherical structure, the conversion specific surface area is greatly increased, and the catalytic efficiency can be remarkably improved; according to the palladium ball, a chemical deposition method of silicon ball palladium plating is adopted, numerous groups exist on the surface of the ball body, the ball body can be easily combined with a carrier, combination is firmer, and the service life of a three-way catalyst can be effectively prolonged.

Description

Technical Field

[0001] The invention belongs to the field of catalysts, and particularly relates to a palladium ball for three-way catalysis and a preparation method thereof. Background Art

[0002] With the development of new energy, electric vehicles have grown exponentially in recent years, and the incentive policies for fuel vehicles have undoubtedly brought new hope and opportunities to the fuel vehicle industry. Judging from the market reaction, many consumers still prefer traditional fuel vehicles. Data shows that although the sales of electric vehicles are continuing to grow, the market share of fuel vehicles remains at a relatively high level. For example, in the market sales in 2024, fuel vehicles still accounted for more than half of the share. This situation not only reflects consumers' recognition of fuel vehicles, but also helps related companies to further develop in this field.

[0003] In the course of daily use, fuel vehicles will inevitably produce mechanical wear and aging, resulting in excessive emissions and increased fuel consumption. With the continuous and dramatic increase in the number of fuel vehicles, automobile exhaust pollution to the atmosphere will become more and more serious. With the development of my country's low-carbon economy, higher and stricter standards have been put forward for motor vehicle exhaust emissions. Motor vehicle emission control is still an important task in the current battle against pollution. The three-way catalytic converter is the main component for pollutant emission purification. Its carrier component is a porous ceramic material installed in a special exhaust pipe. It is called a carrier because it does not participate in the catalytic reaction itself, but is covered with a layer of precious metals and rare earth coatings such as platinum, rhodium, palladium, etc. It is the most important off-board purification device installed in the automobile exhaust system. It can convert harmful gases such as CO, HC and NOx in exhaust gas into harmless carbon dioxide (CO2), water (H2O) and nitrogen (N2) through oxidation and reduction. Its working principle is to use three precious metals, platinum (Pt), rhodium (Rh) and palladium (Pd), as catalysts to carry out oxidation-reduction reactions on carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) in exhaust emissions to generate carbon dioxide (CO2), nitrogen (N2) and water (H2O), thereby achieving the purpose of purifying exhaust emissions. However, the traditional palladium metal used in three-way catalysis is a solid rod structure made by sintering and coated on the carrier by van der Waals force. Therefore, reducing the consumption of precious metal palladium materials, reducing enterprise costs, and improving the coating firmness are currently a technical task. Summary of the invention

[0004] The purpose of the present invention is to provide a palladium ball for three-way catalysis and a preparation method thereof in view of the defects of the prior art.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a palladium ball for three-way catalysis, the palladium ball has a modified silicon ball as the inner core, and the surface is coated with a metal nickel layer and a palladium layer in sequence by chemical deposition method, the particle size of the palladium ball is 2.5 to 150 μm, the thickness of the nickel layer is 0.15±0.05 μm, and the total thickness of the nickel layer and the palladium layer is 0.2 μm±0.05 μm.

[0006] Furthermore, the modified silicon sphere is modified silicon powder containing hydroxyl groups.

[0007] Furthermore, the mass content of the modified silicon ball in the palladium ball is 20% to 60%, the nickel metal content is 15% to 45%, and the palladium metal content is 5% to 20%.

[0008] Furthermore, the coefficient of variation CV value of the palladium ball is ≤3%; the recovery rate is between 50% and 85%; and the 10% K value is greater than or equal to 5000N / mm 2 And less than or equal to 90000N / mm 2 .

[0009] A method for preparing the above-mentioned palladium ball for three-way catalysis comprises the following steps:

[0010] (1) Spherical silicon powder is modified to obtain modified silicon spheres;

[0011] (2) After roughening, sensitizing and activating the surface of the modified silicon sphere, a metal nickel layer is coated on the surface of the modified silicon sphere by chemical deposition;

[0012] (3) After being coated with a metal nickel layer, the modified silicon ball is coated with a metal palladium layer by a chemical deposition method to prepare a palladium ball.

[0013] Furthermore, the modified silicon spheres in step (1) are prepared by the following steps:

[0014] 1.1 Add spherical silicon micropowder into ethanol solvent to obtain a uniform solution, then add 1% to 10% of silane coupling agent to react at a temperature of 50 to 90°C for 3 to 8 hours. Centrifuge the solution at room temperature to separate the silicon micropowder modified by the coupling agent;

[0015] 1.2 Add the silicon micropowder separated in step 1.1 to a mixture of 95% ethanol / 5% water, adjust the pH value to 4-6.5, hydrolyze at room temperature, react for 30-90 minutes, then centrifuge, wash, and dry to obtain hydroxyl-containing modified silicon micropowder.

[0016] Furthermore, the coarsening in step (2) specifically adopts HNO3 solution to treat the modified silicon balls, the mixed solution speed is 50-200r / min, after stirring evenly, the temperature is raised to 30-80°C, the reaction is carried out for 10-60min, and the modified silicon balls are washed with deionized water until neutral; the sensitization specifically adopts SnCl2 solution as a sensitizer, and HCl is added dropwise to adjust the pH value to 4-7, the temperature is heated to 30-80°C, the speed is 100r / min, and stirring is continued for 10-60min; the activation treatment specifically adopts PdCl2 for activation treatment, the solution pH value is adjusted to 4-7, the modified silicon balls and PdCl2 solution are mixed, the temperature is 30-80°C, the reaction is stirred for 10-60min, and then washed with deionized water.

[0017] Furthermore, the step (2) of coating the surface of the modified silicon ball with a metal nickel layer by chemical deposition method specifically adopts the following steps:

[0018] 2.1 Prepare a nickel salt / sodium phosphite solution, wherein the molar ratio of nickel salt to sodium phosphite is 0.1 to 1.5, and then add a complexing agent to ensure the stability of the nickel salt and mix;

[0019] 2.2 Take the sedimentation liquid prepared in step 2.1 and react it with the treated modified silica spheres, heat the temperature to 30-80°C, control the pH value at 2-7 during the reaction, react for 60-240 minutes, and filter and clean.

[0020] Furthermore, the nickel salt is nickel sulfate, nickel acetate or nickel chloride; and the complexing agent is sodium citrate.

[0021] Furthermore, the metal palladium layer is coated in step (3) by the following specific steps: 100-2000 mL of sedimentation liquid, 1-10 g of palladium salt, and 10-100 g of sodium citrate are mixed with water, and the pH value is adjusted to 2-7, and then the modified silicon balls coated with the metal nickel layer obtained in step (2) are added and stirred and dispersed, and the temperature is raised to 30-80° C., and the reaction is stirred for 30-120 min. After the reaction is completed, the mixture is filtered with a sand funnel, washed, and dried into powder; the sedimentation liquid is a mixture of nickel salt, sodium phosphite and sodium citrate.

[0022] The palladium balls prepared by the present invention have the following advantages: (1) the palladium content is 5-20%, which can effectively reduce the amount of palladium metal used. With the same catalytic effect, the palladium material consumption can be saved by about 90%, which greatly reduces the cost; (2) the palladium balls are evenly dispersed and have a spherical structure. The conversion specific surface area is greatly increased, which can significantly improve the catalytic efficiency; (3) the palladium metal in the conventional three-way catalytic converter is a rod-shaped structure directly coated on the carrier, which relies entirely on the intermolecular force, and the van der Waals force connection is not strong. The palladium balls of the present invention adopt the chemical deposition method of palladium plating on silicon balls. The surface of the ball itself has many groups, which is easy to combine with the carrier, and the combination is more firm, which can effectively increase the service life of the three-way catalytic converter. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiment of the present application will be clearly and completely described below in combination with the embodiment of the present application. Obviously, the described embodiment is only a part of the embodiment of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0024] It should be noted that the specification and claims of the present application and the above-mentioned terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0025] (1) Modification of silicon micropowder: Weigh 200 g of silicon micropowder and add it to 1 L of ethanol solvent. Ultrasonicate at room temperature for 30 min to obtain a uniform solution. Then add 3% of silane coupling agent KBM-403 and continue ultrasonicating for 10 min. Set the oil bath temperature to 80 °C and react for 6 h. After the reaction, centrifuge the solution at 1500 r / min at room temperature to obtain silicon micropowder modified with the coupling agent.

[0026] (2) Add the above silicon micropowder to a mixture of 95% ethanol / 5% water (mass fraction), add a small amount of acetic acid, adjust the pH value to 5, hydrolyze at room temperature, react for 40 minutes, then centrifuge, wash, and dry to obtain hydroxyl-containing modified silicon micropowder.

[0027] (3) Take 100g of the modified silicon balls and stir them with 1L HNO3 solution at a speed of 50r / min. After stirring evenly, heat to 70℃. , after reacting for 30 minutes, the sphere was washed with deionized water until it was neutral; 1L of SnCl2 solution was added to the modified silicon sphere, wherein the concentration of SnCl2 was 30g / L, and HCl was added dropwise to adjust the pH value to 6, the temperature was heated to 50°C, the speed was 100r / min, and the reaction was stirred for 30 minutes, and then washed with deionized water; then 1L of PdCl2 solution was added, wherein the concentration of PdCl2 was 3g / L, the pH value of the solution was adjusted to 6, heated to 50°C, stirred for 30 minutes, and washed with deionized water; 1L of chemical precipitant was added to the modified silicon sphere after the above treatment, wherein the molar ratio of nickel sulfate nickel salt / sodium hypophosphite solution was 0.7, and the mass ratio of trisodium citrate was 0.3g / L, heated to 50°C, reacted for 60 minutes, filtered and washed, and the pH value was controlled to 4 during the reaction.

[0028] (4) Take 500 mL of the above nickel sulfate / sodium hypophosphite / trisodium citrate sediment solution, 2 g of palladium salt, 40 g of sodium citrate and mix with 3 L of water, and adjust the pH value to 5. After heating to 50°C, mix and stir for 30 minutes; then add 100 g of the above nickel balls, stir and disperse, heat to 60°C, stir and react for 40 minutes. After the reaction is completed, filter with a sand funnel, wash, and dry into powder.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A palladium ball for three-way catalysis, characterized in that: The palladium ball has a modified silicon ball as its core, and its surface is coated with a metal nickel layer and a palladium layer in sequence by chemical deposition. The particle size of the palladium ball is 2.5 to 150 μm, the thickness of the nickel layer is 0.15±0.05 μm, and the total thickness of the nickel layer and the palladium layer is 0.2 μm±0.05 μm.

2. The palladium ball for three-way catalysis according to claim 1, characterized in that: The modified silicon sphere is modified silicon micropowder containing hydroxyl groups.

3. The palladium ball for three-way catalysis according to claim 1, characterized in that: The mass content of the modified silicon ball in the palladium ball is 20% to 60%, the nickel metal content is 15% to 45%, and the palladium metal content is 5% to 20%.

4. The palladium ball for three-way catalysis according to claim 1, characterized in that: The coefficient of variation CV value of the palladium ball is ≤3%; the recovery rate is between 50% and 85%; the 10% K value is greater than or equal to 5000N / mm 2 And less than or equal to 90000N / mm 2 .

5. A method for preparing palladium balls for three-way catalysis according to any one of claims 1 to 4, characterized in that The following steps are involved: (1) Spherical silicon powder is modified to obtain modified silicon spheres; (2) After roughening, sensitizing and activating the surface of the modified silicon sphere, a metal nickel layer is coated on the surface of the modified silicon sphere by chemical deposition; (3) After being coated with a metal nickel layer, the modified silicon ball is coated with a metal palladium layer by a chemical deposition method to prepare a palladium ball.

6. The preparation method according to claim 5, characterized in that: The modified silicon spheres in step (1) are prepared by the following steps: 1.1 Add spherical silicon micropowder into ethanol solvent to obtain a uniform solution, then add 1% to 10% of silane coupling agent to react at a temperature of 50 to 90°C for 3 to 8 hours. Centrifuge the solution at room temperature to separate the coupling agent-modified silicon micropowder; 1.2 Add the coupling agent-modified silicon micropowder separated in step 1.1 to a mixture of 95% ethanol / 5% water by mass concentration, adjust the pH value to 4-6.5, hydrolyze at room temperature, react for 30-90 minutes, and then centrifuge, wash, and dry to obtain hydroxyl-containing modified silicon micropowder.

7. The preparation method according to claim 5, characterized in that: The coarsening in step (2) is carried out by treating the modified silicon balls with HNO3 solution, the mixed solution is rotated at a speed of 50 to 200 r / min, and after being stirred evenly, the temperature is raised to 30 to 80°C, and after reacting for 10 to 60 minutes, the modified silicon balls are washed with deionized water until they are neutral; the sensitization is carried out by using a sensitizer SnCl2 solution, and HCl is added dropwise to adjust the pH value to 4 to 7, the temperature is heated to 30 to 80°C, the speed is 100 r / min, and stirring is continued for 10 to 60 minutes; the activation treatment is carried out by using PdCl2 for activation treatment, the pH value of the solution is adjusted to 4 to 7, the modified silicon balls and the PdCl2 solution are mixed, the temperature is 30 to 80°C, the reaction is stirred for 10 to 60 minutes, and then washed with deionized water.

8. The preparation method according to claim 5, characterized in that: The step (2) of coating the surface of the modified silicon ball with a metal nickel layer by chemical deposition method specifically adopts the following steps: 2.1 Prepare a nickel salt / sodium phosphite solution, wherein the molar ratio of nickel salt to sodium phosphite is 0.1 to 1.5, and then add a complexing agent to ensure the stability of the nickel salt and mix; 2.2 Take the sedimentation liquid prepared in step 2.1 and react it with the treated modified silica spheres, heat the temperature to 30-80°C, control the pH value at 2-7 during the reaction, react for 60-240 minutes, and filter and clean.

9. The preparation method according to claim 8, characterized in that: The nickel salt is nickel sulfate, nickel acetate or nickel chloride; and the complexing agent is sodium citrate.

10. The preparation method according to claim 5, characterized in that: The metal palladium layer is coated in step (3) by the following specific steps: 100-2000 mL of sedimentation liquid, 1-10 g of palladium salt, and 10-100 g of sodium citrate are mixed with water, and the pH value is adjusted to 2-7, and then the modified silicon balls coated with the metal nickel layer obtained in step (2) are added, stirred and dispersed, and the temperature is raised to 30-80° C., and stirred for reaction for 30-120 min. After the reaction is completed, the mixture is filtered with a sand funnel, washed, and dried into powder; the sedimentation liquid is a mixture of nickel salt, sodium phosphite and sodium citrate.