Method for activating porous alumina carrier in preparation of palladium membrane by surface chemical plating

Abstract

A kind of carrier activation method in the process of preparing palladium membrane by electroless plating on the surface of porous alumina carrier, belong to inorganic membrane preparation technical field.Palladium membrane is prepared by amino functionalization on the surface of carrier, grafting organic ligand on the surface of carrier, carrier activation.The porous alumina is aminated by silanization reaction, organic ligand is introduced by Schiff base reaction, and Pd 2+ In solution is captured by its coordination chelation, and then Pd 2+ Is reduced by heat treatment in hydrogen atmosphere 0 , so that the surface of porous alumina carrier is activated, and finally a layer of palladium membrane is prepared on its surface by electroless plating method.The effective adsorption of Pd 2+ In activation solution by organic functional groups introduced on the surface of porous alumina carrier realizes the pre-coating of palladium seed on the surface of porous alumina carrier, which not only avoids the influence of Sn element on the stability of palladium membrane in the traditional sensitization-activation process of electroless plating, but also can significantly reduce the use amount of PdCl2 and reduce the preparation cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of inorganic membrane preparation, and particularly relates to a carrier activation method in a process of chemical plating for preparing a palladium membrane on a porous alumina carrier surface. BACKGROUND

[0002] Hydrogen energy, as a renewable clean energy, has become a hot spot in the field of new energy research because of its non-pollution, high combustion heat value and wide source. In the process of hydrogen energy utilization, hydrogen separation and purification is the key. At present, hydrogen separation and purification technologies mainly include pressure swing adsorption, cryogenic technology and membrane separation technology. Among them, membrane separation technology has been widely concerned because of its simple operation, small equipment occupation and high separation efficiency.

[0003] Palladium membrane has unique selective permeability to hydrogen and can be used as an excellent hydrogen permeation material. Palladium membrane mainly includes unsupported palladium membrane and supported palladium membrane. Unsupported palladium membrane is mainly prepared by rolling method, but the palladium membrane prepared by this method is thick, the amount of palladium is large, the cost is high, the mechanical strength is low and the hydrogen permeation rate is low. Supported palladium membrane is obtained by loading a thin palladium membrane layer on a porous carrier (such as porous ceramic, porous stainless steel and porous glass), so as to effectively reduce the thickness of the palladium membrane, significantly reduce the cost, and improve the permeation rate and mechanical strength of the palladium membrane. Therefore, supported palladium membrane has a more broad industrial application prospect. Chemical plating method is the most commonly used method for preparing supported palladium membrane because of its low preparation cost and simple operation. In the process of preparing supported palladium membrane by chemical plating method, the activation of the surface of the porous carrier (i.e. pre-coating of palladium seed) is a key step. The traditional carrier activation method is usually completed by two-step method of SnCl2sensitization / PdCl2activation. However, this method is complicated, consumes a large amount of water, uses a large amount of palladium, and it is difficult to ensure the uniform distribution of palladium seed on the surface of the carrier. Especially, the presence of Sn element will affect the operation stability and hydrogen permeability of the palladium membrane (Journal of Membrane Science, 1993, 77, 181). At present, in order to avoid the introduction of Sn element in the process of carrier activation, the method of directly loading palladium ions to the porous alumina carrier has become a new strategy for preparing palladium composite membrane. Li et al. first coated the PdCl2modified γ-AlOOH sol on the surface of the porous alumina carrier, and then reduced Pd 2 + in the modified layer to Pd 0, which realized the pre-coating of palladium seeds on the surface of the carrier (Journal of Membrane Science, 1996, 110, 257). However, the process of pre-coating palladium seeds on the alumina carrier mainly relies on the physical doping process, and the palladium seeds are unevenly distributed, and the existence of the carrier modification layer also increases the resistance of hydrogen permeation. Therefore, it is of great significance to develop a new type of porous carrier surface activation technology to prepare supported palladium membranes. SUMMARY

[0004] In view of the above technical problems, the present application provides a carrier activation method in the process of preparing palladium membranes by chemical plating on the surface of a porous alumina carrier. The method realizes the pre-coating of palladium seeds on the surface of the porous alumina carrier through the effective adsorption of organic functional groups introduced on the surface of the porous alumina carrier to Pd 2 +, which not only avoids the influence of Sn element on the stability of the palladium membrane in the traditional chemical plating sensitization-activation process, but also significantly reduces the use amount of PdCl2 and the preparation cost of the palladium membrane.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] The present application provides a carrier activation method in the process of preparing palladium membranes by chemical plating on the surface of a porous alumina carrier, and the specific steps are as follows:

[0007] (1) Amino functionalization of the carrier surface

[0008] The porous alumina carrier is vertically placed in a three-necked flask containing 60mL-200mL of an organic solvent, 1mL-5mL of a silane coupling agent is added dropwise into the organic solvent through a constant pressure funnel, and the reaction is carried out under the protection of inert gas for 12h-36h. After cooling to 20℃-35℃, the modified carrier is obtained after drying at 80℃-100℃, and the amino-modified carrier is NH2-SM;

[0009] (2) Grafting of organic ligand on the surface of the carrier

[0010] The NH2-SM obtained in step (1) is placed in a three-necked flask containing 60mL-200mL of an organic solvent, and 0.1-0.8g of glacial acetic acid with a concentration of 0.05mol / L-0.2mol / L is added dropwise under the protection of inert gas for 12h-36h. After cooling to 20℃-35℃, the carrier surface is washed with organic solvent to remove the residual chemical reagents, and the organic ligand functionalized carrier is obtained after drying at 60℃-120℃, and the organic ligand functionalized carrier is OS-SM;

[0011] (3) Carrier activation

[0012] Preparation of 20-50 mL PdCl2 activation solution with concentration of 10-50 mg / L, and then put into a measuring cylinder. The OS-SM obtained in step (2) is vertically hung in the PdCl2 activation solution, and then taken out after stirring at 30-50 ℃ for 50-180 min. After drying at 80-120 ℃, the activated porous alumina carrier, namely A-SM, is obtained by heat treatment at 200-350 ℃ for 2-6 h in a H2 atmosphere.

[0013] (4) Preparation of palladium film

[0014] The A-SM obtained in step (3) is put into 40 mL plating solution for chemical palladium plating, wherein the chemical plating temperature is 45 ℃, the chemical plating time is 6 h, and the plating solution comprises 0.14 g of PdCl2, 1.2 g of EDTA.2Na, 4.04 mL of NH3·H2O with a mass concentration of 28%, and 0.64 mL of N2H4·H2O with a molar concentration of 1 mol / L.

[0015] Further, the organic solvent in steps (1) and (2) is anhydrous ethanol, anhydrous methanol or anhydrous toluene.

[0016] Further, the inert gas in steps (1) and (2) is nitrogen, argon or helium.

[0017] Further, the silane coupling agent in step (1) is 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane or diethylenetriaminepropyltrimethoxysilane.

[0018] Further, the organic ligand in step (2) is 2-hydroxy-1-naphthaldehyde or 2-pyridine formaldehyde.

[0019] Further, the reaction temperature in step (1) is 50-100 ℃.

[0020] Further, the reaction temperature in step (2) is 60-120 ℃.

[0021] Further, the concentration of the PdCl2 activation solution in step (3) is 10-50 mg / L.

[0022] The present application has the following beneficial effects:

[0023] The present application utilizes silanization reaction to aminoize the porous alumina, and then utilizes Schiff base reaction to introduce organic ligand, and further utilizes the coordination chelation effect to capture Pd 2 + in the solution, and then reduces Pd 2 + to Pd 0The surface of the porous alumina carrier is activated, and finally a palladium film is prepared on the surface thereof by electroless plating. The effective adsorption of Pd 2 + in the activation solution by the organic functional groups introduced on the surface of the porous alumina carrier can realize pre-coating of palladium seeds on the surface of the porous alumina carrier, which not only avoids the influence of Sn element on the stability of the palladium film in the traditional sensitization-activation process of electroless plating, but also widens the preparation method of the supported palladium film, and can significantly reduce the use amount of PdCl2 and the preparation cost of the palladium film. The method has mild reaction conditions and is easy to operate, and has a broad market prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a schematic diagram of the method for preparing a palladium film on the surface of a porous alumina carrier in Example 1 of the present application.

[0025] Figure 2 is a surface SEM diagram of the porous alumina carrier in Example 1 of the present application.

[0026] Figure 3 is a surface EDX diagram of the activated alumina carrier (OS-SM) in Example 1 of the present application.

[0027] Figure 4 is a surface SEM diagram of the palladium film obtained by electroless plating on the surface of the porous alumina carrier in Example 1 of the present application.

[0028] Figure 5 is a cross-sectional SEM diagram of the palladium film obtained by electroless plating on the surface of the porous alumina carrier in Example 1 of the present application.

[0029] Figure 6 is a SEM diagram of the palladium film obtained by electroless plating on the surface of the porous alumina carrier in the comparative example of the present application. DETAILED DESCRIPTION

[0030] The present application will be described in detail below in combination with the drawings and examples.

[0031] Example 1: A carrier activation method in the process of preparing a palladium film on the surface of a porous alumina carrier by electroless plating, the specific steps are as follows:

[0032] (1) Amino functionalization of the surface of the carrier

[0033] The porous alumina carrier is vertically placed in a three-necked flask containing 60 mL of anhydrous ethanol, 1 mL of 3-aminopropyltrimethoxysilane is placed in a constant pressure funnel and added dropwise to the anhydrous ethanol solution, and after 12 h of reaction at 50°C under the protection of nitrogen, it is taken out and cooled to 20°C, dried at 80°C, and then an amino-modified carrier is obtained, which is NH2-SM;

[0034] (2) Grafting of organic ligand on the surface of the carrier

[0035] NH2-SM obtained in step (1) was put into a three-neck flask containing 0.3g 2-hydroxy-1-naphthaldehyde in 60mL anhydrous ethanol, 0.1g glacial acetic acid with a concentration of 0.05mol / L was added dropwise, and after reaction at 60℃ for 12h under nitrogen protection, it was taken out and cooled to 20℃, the residual chemical reagents on the surface of the carrier were washed with anhydrous ethanol, and after drying at 60℃, a 2-hydroxy-1-naphthaldehyde functionalized carrier was obtained, namely OS-SM;

[0036] (3) Carrier activation

[0037] A 20mL PdCl2 activation solution with a concentration of 10mg / L was prepared and put into a measuring cylinder, and OS-SM obtained in step (2) was vertically hung in the PdCl2 activation solution, and after stirring at 30℃ for 50min, it was taken out and dried at 80℃, and then heat-treated at 300℃ under H2 atmosphere for 4h to obtain an activated porous alumina carrier, namely A-SM;

[0038] (4) Palladium membrane preparation

[0039] A-SM obtained in step (3) was put into a 40ml plating solution for chemical palladium plating, wherein the chemical plating temperature was 45℃, the chemical plating time was 6h, and the plating solution composition was: PdCl2 0.14g, EDTA.2Na 1.2g, NH3·H2O 4.04ml with a mass concentration of 28%, N2H4·H2O (1mol / L) 0.64ml.

[0040] Example 2: The preparation method of this example is as follows:

[0041] (1) Carrier surface amino functionalization

[0042] A porous alumina carrier was vertically put into a three-neck flask containing 100mL anhydrous methanol, 3mL 3-aminopropyltriethoxysilane was put into a constant pressure funnel and added dropwise into the above anhydrous methanol solution under the protection of argon, and after reaction at 70℃ for 24h, it was taken out and cooled to 30℃, and after drying at 90℃, an amino modified carrier was obtained, namely NH2-SM;

[0043] (2) Carrier surface grafting of organic ligand

[0044] NH2-SM obtained in step (1) was put into a three-neck flask containing 0.6g 2-pyridine formaldehyde in 60mL anhydrous methanol, 0.5g glacial acetic acid with a concentration of 0.1mol / L was added dropwise, and after reaction at 80℃ for 24h under argon protection, it was taken out and cooled to 30℃, the residual chemical reagents on the surface of the carrier were washed with anhydrous ethanol, and after drying at 100℃, a 2-pyridine formaldehyde functionalized carrier was obtained, namely OS-SM;

[0045] (3) Carrier activation

[0046] A 35 mL PdCl2activation solution with a concentration of 30 mg / L was prepared and placed in a measuring cylinder. The OS-SM obtained in step (2) was vertically suspended in the PdCl2activation solution, stirred at 40°C for 120 min, and then taken out. After drying at 100°C, the obtained porous alumina carrier was heat-treated at 200°C under a H2atmosphere for 2 h to obtain an activated porous alumina carrier, namely A-SM.

[0047] (4) Palladium membrane preparation

[0048] The palladium membrane was prepared in the same manner as in Example 1.

[0049] Example 3: The preparation method of this example is as follows:

[0050] (1) Carrier surface amino functionalization

[0051] The porous alumina carrier was vertically placed in a three-necked flask containing 200 mL of anhydrous toluene. 5 mL of diethylenetriamine propyl trimethoxysilane was placed in a constant pressure funnel and added dropwise to the anhydrous toluene solution. After reaction at 100°C for 36 h under the protection of helium, the obtained product was cooled to 35°C and dried at 100°C to obtain an amino-modified carrier, namely NH2-SM.

[0052] (2) Carrier surface grafting of organic ligand

[0053] The NH2-SM obtained in step (1) was placed in a three-necked flask containing 200 mL of anhydrous toluene and 1 g of 2-pyridine formaldehyde. 0.8 g of glacial acetic acid with a concentration of 0.2 mol / L was added dropwise. After reaction at 100°C for 36 h under the protection of helium, the obtained product was cooled to 35°C, washed with anhydrous toluene to remove residual chemical reagents on the surface of the carrier, and dried at 120°C to obtain a 2-pyridine formaldehyde functionalized carrier, namely OS-SM.

[0054] (3) Carrier activation

[0055] A 50 mL PdCl2activation solution with a concentration of 50 mg / L was prepared and placed in a measuring cylinder. The OS-SM obtained in step (2) was vertically suspended in the PdCl2activation solution, stirred at 50°C for 180 min, and then taken out. After drying at 120°C, the obtained porous alumina carrier was heat-treated at 350°C under a H2atmosphere for 6 h to obtain an activated porous alumina carrier, namely A-SM.

[0056] (4) Palladium membrane preparation

[0057] The palladium membrane was prepared in the same manner as in Example 1.

[0058] The functionalized alumina carrier OS-SM prepared by the present application is used for loading of palladium ions, and the specific steps are as follows: the OS-SM obtained in Example 1, Example 2 and Example 3 and the unmodified alumina carrier as a comparative example are weighed respectively and placed in a graduated cylinder containing 20 ml of 50 mg / L palladium ion activation solution, and after stirring at 30℃ for 180 min, the OS-SM loaded with palladium ions is taken out, the concentration of residual palladium ions in the solution is detected by an atomic absorption spectrometer, the utilization rate of palladium ions in the activation solution is calculated, and the results are shown in Table 1. As can be known from Table 1, according to the technical scheme provided by the present application, the OS-SM obtained can realize efficient adsorption of palladium ions, thereby providing uniform catalytic active centers for chemical plating to prepare a palladium membrane, and being conducive to depositing a uniform and dense palladium membrane on the surface of the alumina carrier.

[0059] Table 1: Utilization rate of palladium ions in the activation solution

[0060]

[0061]

[0062] As can be known from Table 1, the utilization rate of palladium ions in the activation solution for the unmodified alumina carrier of Example 1-3 and the comparative example shows that the palladium ions in the activation solution can be effectively loaded on the OS-SM prepared by the present application, because the functionalized porous alumina carrier has -C=N- functional groups on the surface which can coordinate and chelate with the palladium ions in the activation solution.

[0063] As can be known from Figure 2 , the porous alumina carrier is sintered by a large number of alumina particles, and a large number of pores exist on the surface and are uniformly distributed.

[0064] As can be known from Figure 3 , the 2-hydroxy-1-naphthaldehyde functionalized alumina carrier (OS-SM) contains not only oxygen and aluminum elements, but also carbon, oxygen, silicon and nitrogen elements, indicating that the 2-hydroxy-1-naphthaldehyde is successfully grafted onto the surface of the alumina carrier. In particular, the presence of palladium element shows that the 2-hydroxy-1-naphthaldehyde functionalized alumina carrier (OS-SM) can successfully capture the palladium ions in the activation solution, thereby realizing the activation of the alumina carrier.

[0065] As can be known from Figure 4 and Figure 5 , the palladium membrane prepared on the surface of the 2-hydroxy-1-naphthaldehyde functionalized alumina carrier is dense, flat, defect-free and pinhole-free, and the thickness of the palladium membrane is about 7 μm.

[0066] As can be known from Figure 6It can be seen that the palladium film prepared on the surface of the unmodified alumina carrier has only some palladium particles deposited on the surface, and no continuous and dense palladium film is formed, which indicates that direct activation of the alumina carrier cannot successfully introduce palladium seeds, resulting in limited self-catalytic active centers on the surface of the alumina carrier, and the dense palladium film cannot be obtained by using the chemical plating method.

[0067] It can be understood that the above specific description of the present application is only used to illustrate the present application and is not limited to the technical solutions described in the embodiments of the present application. Those skilled in the art should understand that the present application can still be modified or replaced equivalently to achieve the same technical effect; as long as the use needs are met, it is within the protection scope of the present application.

Claims

1. A method for activating a porous alumina support during electroless plating of palladium onto the surface of the support, characterized in that: The specific steps are as follows: (1) carrier surface amino functionalization Put the porous alumina carrier vertically into a three-necked flask containing 60 mL-200 mL of an organic solvent, put 1 mL-5 mL of a silane coupling agent into a constant pressure funnel for dropwise addition to the organic solvent, under the protection of an inert gas, after reaction for 12 h-36 h, take out and cool to 20 ℃-35 ℃, dry at 80 ℃-100 ℃, and obtain the amino-modified carrier, namely NH2-SM; (2) carrier surface grafting of an organic ligand Put the NH2-SM obtained in step (1) into a three-necked flask containing 60 mL-200 mL of an organic solvent containing an organic ligand, the organic ligand being 2-hydroxy-1-naphthaldehyde or 2-pyridinecarboxaldehyde, dropwise add 0.1-0.8 g of glacial acetic acid with a concentration of 0.05 mol / L-0.2 mol / L, under the protection of an inert gas, after reaction for 12 h-36 h, take out and cool to 20 ℃-35 ℃, wash the residual chemical reagents on the surface of the carrier with an organic solvent, dry at 60 ℃-120 ℃, and obtain the organic ligand functionalized carrier, namely OS-SM; (3) carrier activation Prepare 20 mL-50 mL of a PdCl2 activation solution with a concentration of 10 mg / L-50 mg / L, put into a graduated cylinder, vertically suspend the OS-SM obtained in step (2) in the PdCl2 activation solution, stir at 30 ℃-50 ℃ for 50 min-180 min, take out, dry at 80 ℃-120 ℃, and heat treat under a H2 atmosphere at 200 ℃-350 ℃ for 2 h-6 h, to obtain the activated porous alumina carrier, namely A-SM; (4) palladium membrane preparation Put the A-SM obtained in step (3) into a 40 ml plating solution for chemical palladium plating, wherein the chemical plating temperature is 45 ℃, the chemical plating time is 6 h, and the plating solution composition is: PdCl2 is 0.14 g, EDTA.2Na is 1.2 g, NH3·H2O is 4.04 ml, the mass concentration is 28%, N2H4·H2O is 0.64 ml, and the molar concentration is 1 mol / L.

2. The method for activating the support in the process of electroless plating of palladium film on the surface of porous alumina support according to claim 1, characterized in that: The organic solvent in steps (1) and (2) is anhydrous ethanol, anhydrous methanol, or anhydrous toluene.

3. The method for activating the support in the process of electroless plating palladium film on the surface of porous alumina support according to claim 1, characterized in that: The inert gas in steps (1) and (2) is nitrogen, argon, or helium.

4. The method for activating the support in the process of electroless plating palladium film on the surface of porous alumina support according to claim 1, characterized in that: The silane coupling agent in step (1) is 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, or diethylenetriaminepropyltrimethoxysilane.

5. The method for activating the support in the process for preparing a palladium membrane by electroless plating on the surface of a porous alumina support according to claim 1, characterized in that: The reaction temperature in step (1) is 50 ℃-100 ℃.

6. The method for activating the support in the process for preparing a palladium membrane by electroless plating on the surface of a porous alumina support according to claim 1, characterized in that: The reaction temperature in step (2) is 60 ℃-120 ℃.

Images