Preparation process and application of nano-palladium powder for membrane reactor

Abstract

The present invention relates to the field of nanomaterial technology, in particular to the field of IPCB22F1, and more specifically to a preparation process and application of nano palladium powder for membrane reactor. The preparation process comprises the following steps: S1, dissolving a palladium source with aqua regia, adding hydrochloric acid solution and deionized water, and heating to obtain a chloropalladic acid solution; S2, adding concentrated ammonia water to the chloropalladic acid solution to obtain a tetraamine palladium dichloride solution; S3, adding a dispersant to the tetraamine palladium dichloride solution to obtain a dispersed solution; S4, dripping a reducing agent into the dispersed solution and stirring, reacting to obtain a nano palladium powder mixed solution; S5, filtering the nano palladium powder mixed solution to obtain a precipitate; S6, washing the precipitate with deionized water, and drying to obtain nano palladium powder. When the speed of the dropping of the reducing agent is 10-22 mL / min, the particle size of the nano palladium powder can be controlled to be 50-100 nm, and the tap density is 1.3-1.8 g / mL.

Description

Technical Field

[0001] The present invention relates to the field of nanomaterial technology, in particular to the field of IPCB22F1, and more specifically to a preparation process and application of nano palladium powder for a membrane reactor. Background Art

[0002] Nano palladium has high surface activity and has been widely used in microelectronic materials, such as the preparation of thick film slurries and thick film palladium-palladium conductor slurries in the electronics industry, and internal and external electrode materials for multilayer ceramic capacitors. There are two main methods for preparing palladium nanoparticles: physical and chemical. The physical method mainly includes ultrasonic chemical method, including ultrasonic and microwave method. The palladium nanoparticles prepared by physical method have higher purity, but the size and uniform dispersion of nanoparticles are difficult to control by physical method; the chemical method mainly includes chemical reduction method and electrochemical method, among which the chemical reduction method has simple production process and is widely used.

[0003] He Wuqiang: Preparation of nano-palladium by reduction of chloropalladic acid with sodium borohydride. A method for reducing palladium chloroacid with sodium borohydride at room temperature is disclosed to obtain small and evenly distributed palladium metal nanoparticles. The optimal conditions for obtaining palladium metal nanoparticles under this method are discussed. However, the invention uses polyvinyl pyrrolidone as a dispersant to reduce the agglomeration of palladium powder. However, the prepared palladium powder has low sphericity and the polyvinyl pyrrolidone is not easy to wash and remove, which affects the use of the final product. Summary of the invention

[0004] The present invention provides a preparation process and application of nano palladium powder for a membrane reactor. By adjusting the ratio between palladium salt, reducing agent and dispersant, the prepared nano palladium powder has excellent particle size uniformity, high purity and high tap density, and can be applied to palladium membrane reactors.

[0005] To achieve the purpose of the present invention, the first aspect of the present invention provides a process for preparing nano palladium powder for a membrane reactor, comprising the following steps:

[0006] S1, dissolving a palladium source with aqua regia, adding hydrochloric acid solution and deionized water, and heating to obtain a chloropalladic acid solution;

[0007] S2, adding concentrated ammonia water to the chloropalladic acid solution to obtain a tetraamminepalladium dichloride solution;

[0008] S3, adding a dispersant to the tetraamminepalladium dichloride solution to obtain a dispersed solution;

[0009] S4, adding a reducing agent to the dispersed solution and stirring to react to obtain a nano-palladium powder mixed solution;

[0010] S5, filtering the nano-palladium powder mixed solution to obtain a precipitate;

[0011] S6, washing the precipitate with deionized water, and drying to obtain nano palladium powder.

[0012] The palladium source is one of sponge palladium and metal palladium powder.

[0013] Preferably, the palladium source is metallic palladium powder with a mesh size of 325, purchased from Zhuozhou Yourong New Material Technology Co., Ltd.

[0014] The reducing agent is one of hydrazine hydrate, hydrogen peroxide, ascorbic acid, sodium borohydride, glucose, fatty aldehyde and fatty amine.

[0015] Preferably, the reducing agent is sodium borohydride (CAS: 16940-66-2).

[0016] The molar ratio of the palladium source to the reducing agent is 1:(2-3).

[0017] Preferably, the molar ratio of the palladium source to the reducing agent is 1:2.5.

[0018] The dispersant is at least one of hexadecyltrimethylammonium bromide, sodium polyacrylate, sodium dodecyl sulfate, polyethylene glycol and Tween.

[0019] Preferably, the dispersant is hexadecyltrimethylammonium bromide (CAS: 57-09-0) and sodium polyacrylate, and the sodium polyacrylate is purchased from Zhengzhou Shengyu Chemical Products Co., Ltd.

[0020] The weight ratio of hexadecyltrimethylammonium bromide to sodium polyacrylate is 1:(2-4).

[0021] Preferably, the weight ratio of hexadecyltrimethylammonium bromide to sodium polyacrylate is 1:3.

[0022] The weight ratio of the dispersant to the palladium source is 1:(100-250).

[0023] Preferably, the weight ratio of the dispersant to the palladium source is 1:120.

[0024] Preferably, the tap density of the nano palladium powder is 1.3-1.8 g / mL.

[0025] Preferably, the particle size of the nano palladium powder is 50-100 nm.

[0026] When the speed of reducing agent dripping is 10-22mL / min, the particle size of nano palladium powder can be controlled to be 50-100nm. It may be the interaction between the crystal nucleus generation speed and the crystal nucleus growth speed. When the crystal nucleus growth speed is greater than the growth speed, a large number of crystal nuclei are generated. When the crystal nucleus growth speed is greater than the growth speed, the crystal nucleus will grow. If the reducing agent is added too fast, the crystal nucleus generation speed and growth speed are both relatively large, resulting in some particles not having time to be wrapped by the protective agent and growing, resulting in excessively large particle size and uneven distribution, which is not conducive to the preparation of nanoparticles. When the speed of reducing agent dripping is 10-22mL / min, and the weight ratio of dispersant to palladium source is 1:(100-250), a balance can be achieved between the crystal nucleus growth speed and the growth speed, which not only makes the palladium powder particle size 50-100nm, but also improves the particle size uniformity of palladium powder, thereby improving the palladium powder packing density, which can be used to prepare a high-density palladium membrane reactor. Too much dispersant will increase the viscosity of the reaction solution, increase the subsequent washing process, and reduce the efficiency of palladium powder preparation.

[0027] The speed of dropping the reducing agent is 10-22 mL / min.

[0028] Preferably, the reducing agent is added at a rate of 20 mL / min.

[0029] The reaction temperature is 20-30°C, and the reaction time is 1-2h.

[0030] Preferably, the reaction temperature is 25° C. and the reaction time is 1.5 h.

[0031] A second aspect of the present invention provides an application of a process for preparing nano-palladium powder for a membrane reactor, which is applied to a palladium membrane reactor.

[0032] Beneficial effects:

[0033] 1. The dispersant is hexadecyltrimethylammonium bromide (CAS: 57-09-0) and sodium polyacrylate, and polyvinyl pyrrolidone is not used, which simplifies the post-processing steps.

[0034] 2. When the speed of reducing agent dropping is 10-22 mL / min, the particle size of nano-palladium powder can be controlled to be 50-100 nm, and the tap density can be 1.3-1.8 g / mL.

[0035] 3. When the weight ratio of the dispersant to the palladium source is 1:(100-250), a balance can be achieved between the nucleus growth rate and the growth rate, which not only makes the palladium powder particle size 50-100nm, but also improves the particle size uniformity of the palladium powder. DETAILED DESCRIPTION

[0036] Example 1

[0037] A process for preparing nano palladium powder for a membrane reactor comprises the following steps:

[0038] S1, dissolve 106.4 g of palladium source in 200 mL of aqua regia, add 50 mL of hydrochloric acid solution (36 wt%) and 200 mL of deionized water, heat to 55 ° C, and obtain chloropalladic acid solution after 0.5 h;

[0039] S2, add 200mL concentrated ammonia water (20wt%) to the chloropalladic acid solution to obtain tetraaminochloride

[0040] Palladium (CAS: 13933-31-8) solution;

[0041] S3, adding 0.88 g of a dispersant to the tetraamminepalladium dichloride solution to obtain a dispersed solution;

[0042] S4, add 189 mL of sodium borohydride (CAS: 16940-66-2) aqueous solution (50 wt%) to the dispersed solution.

[0043] The temperature was kept at 25 °C for 1.5 h to obtain nanoparticles.

[0044] Palladium powder mixed solution;

[0045] S5, filtering the nano-palladium powder mixed solution to obtain a precipitate;

[0046] S6, washing the precipitate with 500 mL of deionized water, and drying at 60° C. for 2 h to obtain nano palladium powder.

[0047] The palladium source is metallic palladium powder with a mesh size of 325, purchased from Zhuozhou Yourong New Material Technology Co., Ltd.

[0048] The dispersant is hexadecyltrimethylammonium bromide (CAS: 57-09-0) and sodium polyacrylate, and the sodium polyacrylate is purchased from Zhengzhou Shengyu Chemical Products Co., Ltd.

[0049] The weight ratio of hexadecyltrimethylammonium bromide to sodium polyacrylate is 1:3.

[0050] The invention discloses a preparation process of nano palladium powder for a membrane reactor, which is applied to a palladium membrane reactor.

[0051] Example 2

[0052] The specific implementation is the same as that of Example 1; the difference is that the weight ratio of hexadecyltrimethylammonium bromide to sodium polyacrylate in Example 2 is 1:3.

[0053] Example 3

[0054] The specific implementation method is the same as that of Example 1; the difference is that the

[0055] Comparative Example 1

[0056] The specific implementation is the same as Example 1; the difference is that the weight ratio of hexadecyltrimethylammonium bromide to sodium polyacrylate in Comparative Example 1 is 1:1.

[0057] Comparative Example 2

[0058] The specific implementation is the same as in Example 1; the difference is that the dropping speed in step S2 in Comparative Example 2 is 10 mL / min.

[0059] Comparative Example 3

[0060] The specific implementation is the same as Example 1; the difference is that the dropping speed in step S2 in Comparative Example 3 is 40 mL / min.

[0061] Performance Testing Methods

[0062] The performance of the nano-palladium powder obtained in the embodiment and the comparative example was tested, and the test data are listed in Table 1.

[0063] Average particle size: The average particle size of the palladium powder was measured using a Mastersize 2000 laser particle size analyzer.

[0064] Tap density: The tap density of palladium particles was measured using a PF-100B intelligent tap density meter.

[0065] Performance test data

[0066] Table 1

[0067]

[0068]

Claims

1. A process for preparing nano palladium powder for membrane reactor, characterized in that: The following steps are involved: S1, dissolving a palladium source with aqua regia, adding hydrochloric acid solution and deionized water, and heating to obtain a chloropalladic acid solution; S2, adding concentrated aqueous ammonia to the chloropalladic acid solution to obtain a tetraamminepalladium dichloride solution; S3, adding a dispersant to the tetraamminepalladium dichloride solution to obtain a dispersed solution; S4, adding a reducing agent dropwise to the dispersed solution and stirring to react to obtain a nano-palladium powder mixed solution; S5, filtering the nano-palladium powder mixed solution to obtain a precipitate; S6, washing the precipitate with deionized water, and drying to obtain nano palladium powder; The dispersant is hexadecyltrimethylammonium bromide and sodium polyacrylate, and the weight ratio of the hexadecyltrimethylammonium bromide to the sodium polyacrylate is 1:(2-4); the weight ratio of the dispersant to the palladium source is 1:(100-250). The dropping speed of the reducing agent is 10-22 mL / min.

2. The preparation process of nano palladium powder for membrane reactor according to claim 1, characterized in that: The molar ratio of the palladium source to the reducing agent is 1:(2-3).

3. A process for preparing nano palladium powder for membrane reactor according to claim 1, characterized in that: The tap density of the nano palladium powder is 1.3-1.8 g / mL.

4. The preparation process of nano palladium powder for membrane reactor according to claim 1, characterized in that: The particle size of the nano palladium powder is 50-100 nm.

5. The preparation process of nano palladium powder for membrane reactor according to claim 1, characterized in that: The reaction temperature is 20-30°C, and the reaction time is 1-2h.

6. An application of the preparation process of nano palladium powder for membrane reactor according to any one of claims 1 to 5, characterized in that: Applied to palladium membrane reactors.

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