Palladium alloy and method for producing the same

Abstract

The invention relates to the field of palladium alloy, and discloses a palladium alloy and a preparation method thereof. The method comprises the following steps: mixing palladium and other metals except palladium, placing the obtained mixture in an activation atmosphere, and performing heat treatment at a temperature of T1≥350 ℃, and then reducing the temperature to a temperature of T2≤230 ℃ at a temperature reduction rate of V>5 ℃ / min. The palladium alloy prepared by the method has a lower hydrogen permeation activation energy and a higher hydrogen permeation and diffusion rate.

Description

Technical Field

[0001] This invention relates to the field of palladium alloys, and more specifically to a palladium alloy and its preparation method. Background Technology

[0002] In the field of high-purity hydrogen production, palladium membrane separation technology boasts advantages such as low investment, low energy consumption, high stability, and environmental friendliness. Addressing the challenge of completely removing trace impurities (such as N2, Ar, and CO2) during traditional pressure swing adsorption (PSA) processes, palladium membrane separation, following the principle of dissolution-diffusion, perfectly solves this problem, making it a highly promising high-purity hydrogen separation and purification process. However, when the temperature is below 573 K, hydrogen dissolution in the pure palladium membrane will form α-PdH. and β-PdH Two solid solutions with different lattice parameters can lead to uneven shrinkage and expansion of the palladium film after repeated dissolution and efflux cycles, resulting in hydrogen embrittlement and cracking, which greatly limits the application of palladium films under low temperature and high pressure. Related literature reports that alloy film materials loaded on porous ceramics, porous stainless steel, and high borosilicate heat-resistant glass can be obtained through methods such as electroless plating, electroplating, chemical vapor deposition, and physical vapor deposition. However, these methods can only adjust macroscopic factors such as the composition or thickness of the alloy film material, and cannot control the microscopic crystal lattice structure and lattice parameters of the film material. The plastic deformation mode of different crystal structures will determine whether the alloy film material can exhibit high strength over a wide temperature range and under large strain conditions. In existing technologies, the cooling process after alloying is generally natural cooling (cooling rate below 5℃ / min), and the performance of palladium films obtained in this way still needs further improvement. Summary of the Invention

[0003] The purpose of this invention is to overcome the problems existing in the prior art. This invention provides a palladium alloy and its preparation method.

[0004] To achieve the above objectives, the first aspect of the present invention provides a method for preparing palladium alloys, the method comprising: mixing palladium with other metals besides palladium, placing the resulting mixture in an activating atmosphere, first performing heat treatment at a temperature of T1≥350°C, and then cooling to a temperature of T2≤230°C at a cooling rate of V>5°C / min.

[0005] The second aspect of the present invention provides a palladium alloy obtained by the method described in the first aspect.

[0006] The palladium alloy prepared by the method of this invention has a stable crystal structure and a high hydrogen permeation diffusion rate. This invention obtains a palladium alloy film with high mechanical strength, long service life, resistance to hydrogen embrittlement, and resistance to sulfur and carbon deposition by controlling the annealing conditions of the palladium alloy. Furthermore, this palladium alloy can be directly applied to the rapid separation or purification of hydrogen under different operating conditions. Detailed Implementation

[0007] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0008] The first aspect of the present invention provides a method for preparing palladium alloys, the method comprising: mixing palladium with other metals besides palladium, placing the resulting mixture in an activating atmosphere, first performing heat treatment at a temperature of T1≥350°C, and then cooling to a temperature of T2≤230°C at a cooling rate of V>5°C / min.

[0009] The present invention reduces the activation energy of hydrogen permeation of the membrane material (palladium alloy) by performing heat treatment at a specific temperature and then cooling it at a specific rate, thereby improving the hydrogen permeation efficiency and stability of the membrane material (small half-width of the characteristic peak).

[0010] According to the present invention, preferably, T1 = 350-650℃.

[0011] According to the present invention, preferably, V = 25-150℃ / min.

[0012] According to the present invention, preferably, T2 = 100-200℃.

[0013] According to the present invention, preferably, the heat treatment pressure P = 0.12-0.75 MPa.

[0014] According to the present invention, preferably, the heat treatment time (t) is 1-10 h.

[0015] According to the present invention, preferably, the gas providing the activating atmosphere comprises an alkaline gas, and the content of the alkaline gas in the gas providing the activating atmosphere is greater than or equal to 1 volume.

[0016] According to the present invention, preferably, the alkaline gas is selected from at least one of ethylenediamine, NH3, PH3, and N2H4. The addition of the alkaline gas enables the palladium-based alloy film to be activated more quickly, the resulting body-centered cubic structure to be more stable, and the full width at half maximum (FWHM) of the characteristic peaks in the XRD pattern to be smaller.

[0017] According to the present invention, preferably, palladium and other metals are mixed by depositing Pd and other metals on a support.

[0018] According to the present invention, preferably, the total thickness of Pd and other metals deposited on the support is 0.5-30 μm (e.g., 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, and any two of the above), preferably 5-15 μm.

[0019] According to the present invention, preferably, the thickness of the support is 0.1-20 mm (e.g., 0.1 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 15 mm, 20 mm, and any two of the above), more preferably 2-5 mm. The support can be provided by materials commonly used in the art that can withstand the operating temperature of the present invention without affecting hydrogen permeability, that is, materials that do not deform or affect hydrogen permeability at the operating temperature of the present invention. While ensuring excellent hydrogen permeability, in order to obtain better mechanical and thermal stability and reduce the amount of palladium used (reducing costs), preferably, the support is a porous support, which can be selected from at least one of porous ceramics, porous glass, porous metals (such as porous stainless steel), porous quartz, and polymers, more preferably from at least one of porous ceramics, porous metals, and polymers. Generally, the porosity distribution of the support ranges from 15-75%, and the average pore size is 0.05-0.4 μm. To obtain a tubular membrane, the support is preferably a tubular support. The porous ceramic material can be γ-Al₂O₃, with a porosity distribution ranging from 25-66% and an average pore size of 0.12-0.4 μm. The porous stainless steel material can be 316L(Fe₂O₃). 69 Cr 17 Ni 12 Mo2 has a porosity ranging from 32% to 71% and an average pore size of 0.08 to 0.36 μm. The polymer material can be polyimide, with a porosity ranging from 15% to 37% and an average pore size of 0.05 to 0.22 μm. The "porosity range" and "average pore size" can both be determined using nitrogen physical adsorption.

[0020] According to the present invention, preferably, the molar ratio of Pd to other metals is 1:(0.01-10), more preferably 1:(0.1-2).

[0021] According to the present invention, preferably, the other metal is a Group IB metal and / or a Group VIII metal. More preferably, the other metal is at least one selected from Cu, Ag, Au, and Ni.

[0022] According to some embodiments of the present invention, the other metal is Cu, and more preferably, the molar ratio of Pd to Cu is 1:(0.8-1.3).

[0023] When the other metal is Cu, preferably, the gas providing the activation atmosphere includes H2, N2 and NH3, and the volume ratio of H2, N2 and NH3 is 1:(0.2-0.5):(0.02-0.1).

[0024] When the other metal is Cu, preferably, after treatment for 3-5 hours under the conditions of T1 = 570-600℃ and P = 0.37-0.52MPa, the temperature is reduced to T2 = 100-150℃ at a rate of V = 70-100℃ / min.

[0025] According to some embodiments of the present invention, the other metal is Ag, and more preferably, the molar ratio of Pd to Ag is 100:(25-100).

[0026] When the other metal is Ag, preferably, the gas providing the activating atmosphere includes H2 and Ar, and the volume ratio of H2 to Ar is 1:(0.8-6).

[0027] When the other metal is Ag, preferably, after treatment for 5-7 hours under the conditions of T1 = 520-550℃ and P = 0.25-0.38MPa, the temperature is reduced to T2 = 150-200℃ at a rate of V = 40-70℃ / min.

[0028] According to some embodiments of the present invention, the other metal is Au. More preferably, the molar ratio of Pd to Au is 1:(0.2-0.8).

[0029] When the other metal is Au, preferably, the content of alkaline gas in the gas providing the activating atmosphere is greater than or equal to 20% by volume.

[0030] When the other metal is Au, preferably, after treatment for 2-10 hours under the conditions of T1 = 350-650℃ and P = 0.12-0.75MPa, the temperature is reduced to T2 = 100-200℃ at a rate of V = 25-150℃ / min.

[0031] According to some embodiments of the present invention, the other metals are Cu and Au, and more preferably, the molar ratio of Pd, Cu and Au is 100:(58-95):(9-37).

[0032] When the other metals are Cu and Au, preferably, the gas providing the activation atmosphere includes hydrogen and nitrogen, and the hydrogen content in the mixture of hydrogen and nitrogen is greater than or equal to 30% by volume, more preferably 31-61% by volume; or, the gas providing the activation atmosphere includes hydrogen and alkaline gas, more preferably, the alkaline gas content in the gas providing the activation atmosphere is greater than or equal to 20% by volume, and even more preferably 22-30% by volume.

[0033] When the other metals are Cu and Au, preferably, after treatment for 5-7 hours under conditions of T1 = 380-580℃ and P > 0.2MPa, the temperature is reduced to T2 < 230℃ at a rate of V > 35℃ / min.

[0034] According to some embodiments of the present invention, the other metals are Cu and Ni. More preferably, the molar ratio of Pd, Cu and Ni is 100:(65-93):(37-62).

[0035] When the other metals are Cu and Ni, preferably, the gas providing the activation atmosphere includes H2, N2 and NH3, and the volume ratio of H2, N2 and NH3 is 100:(21-64):(1-13).

[0036] When the other metals are Cu and Ni, preferably, after treatment at T1 = 500-550℃ and P = 0.43-0.56MPa for 5-8 hours, the temperature is reduced to T2 = 100-160℃ at a rate of V = 50-70℃ / min.

[0037] In this invention, the pressure of the alloying process is generally controlled by adjusting the amount of gas used to provide the activating atmosphere. When the other metals are Cu and Ni, after being reduced to below T2 at a specific rate, they can be cooled to room temperature for later use.

[0038] The second aspect of the present invention provides a palladium alloy obtained by the method described in the first aspect.

[0039] The present invention will be described in detail below through embodiments. In the following embodiments, the inner surface of the support is sealed with polytetrafluoroethylene (PTFE) material, and therefore the PTFE material is peeled off before application or performance testing.

[0040] Example

[0041] Using porous stainless steel tubes as supports (tubular, inner diameter: 9.5-10.5 mm, outer diameter: 12.5-13.5 mm; average pore size: 0.25 μm, porosity: 65%), the supports were first soaked in anhydrous ethanol for 30 minutes to remove surface contaminants such as dust and grease. Then, the surface and inner sides of the support were rinsed with deionized water and placed in warm water for vacuum rinsing to remove residual ethanol from the pores. Finally, the supports were dried in an oven at 423 K for 4 hours. Based on Faraday's law, Pd and other active components (at least one of Cu, Ag, Au, and Ni) were deposited on the supports using electroplating. The types and molar ratios of Pd and other active components are shown in Table 1. The effective film area was 21-50 cm². 2 The electroplating conditions were as follows: using a conductive layer carrier as the working electrode, a platinum electrode (plated with Pd) and other active component electrodes (plated with other active components) as counter electrodes, and a saturated calomel electrode as the reference electrode, at a temperature of 30°C, the metal ions (Pd) in the plating bath... 2+ And other active components such as metal ions, such as Cu 2+ Au 3+ Ag + Ni 2+ The concentration of the solution was 0.01-0.3 mol / L. Electroplating experiments were conducted using cyclic voltammetry, with a working voltage range of -0.60V to -0.90V, a scan rate of 0.0075V / s, a scan period of 1000, and a sensitivity of 0.0001A / V. Simultaneously, during the electroplating process, a 0.05 mol / L solution of ammonium palladium chloride ((NH4)2PdCl4) was added to the plating solution at a rate of 1-2 ml / min; salt solutions of other active components at a rate of 0.2-1.5 ml / min; ethylenediamine (EDA, 99%, analytical grade) at a rate of 0.05-0.12 ml / min; disodium ethylenediaminetetraacetate (EDTA-2Na, 99%, analytical grade) at a rate of 0.025-0.05 ml / min; and bipyridine (C... 10H8N2 (99%, analytical grade). The plating bath was vigorously stirred (1000 r / min) while the above solution was added. Every 30 min of electroplating, the working electrode, cleaned with distilled water, was immersed for 10 min in 0.05 mol / L phosphoric acid (H3PO4) solution and 0.05 mol / L dipotassium hydrogen phosphate (K2HPO4) solution, respectively. After the cyclic voltammetry program, the working electrode was treated in distilled water at 80-100℃ for 10-15 min before removal. The support with deposited Pd and other active components was subjected to high-temperature alloying treatment. The alloying treatment was performed at an activating atmosphere, at temperature T1 and pressure P, for a period of time (t); then the temperature was reduced to T2 at a rate V. The types and volumes of the activating atmosphere gas are shown in Table 1. The amount of activating atmosphere gas provided ensured that the alloying pressure was P. Detailed parameters are shown in Table 1.

[0042] Comparative Example AD1

[0043] The procedure was carried out in accordance with Example A1, except that the temperature was reduced to T2 at a rate of V = 5°C / min.

[0044] Comparative Example AD2

[0045] The process was carried out in accordance with Example A1, except that the alloying temperature T1 = 700°C.

[0046] Comparative Example AD3

[0047] The alloying process was carried out in accordance with Example A1, except that the alloying pressure P = 0.1 MPa.

[0048] Test case

[0049] (I) The materials obtained after alloying treatment in each embodiment and comparative example were characterized. The characterization method is as follows, and the crystal structure parameters of the materials are shown in Table 1.

[0050] The crystal structure analysis of the alloyed material was performed on an X'PertPRO / PANalytical automated X-ray diffractometer manufactured by Philips, Netherlands. The experimental conditions were Cu K α X-rays (λ = 0.1543 nm), tube voltage 40 kV, current 40 mA, diffraction angle 2θ scan range 10-90°. The interplanar spacing of the sample was calculated using the Bragg equation.

[0051] d=λ / 2sinθ

[0052] Where λ corresponds to Cu K α The wavelength of the radiation, θ is the angle of the diffraction peak.

[0053] The crystal structure of the alloyed material was tested at the European Synchrotron Radiation Facility (beam BM25A) in France, which has higher resolution, with synchrotron radiation λ = 0.0618886 nm or 0.077449 ​​nm and tube voltage of 10.0335 keV or 20.0335 keV. A 10 × 1 mm sample was initially taken. 2 The sample was placed in a 2mm diameter quartz capillary tube, with both ends sealed with quartz wool. The capillary tube was then mounted on a rotating sample stage (to ensure uniform temperature and a larger X-ray irradiation area). The test temperature range was 298-473K (heated by a hot air blower), and the pressure range was 10... -4 The test atmosphere was -130 kPa. Hydrogen gas was first introduced and treated for 30 minutes, then a vacuum was drawn, and helium gas was introduced as a protective gas for measurement.

[0054] Methods for testing the lattice parameters of the material obtained after alloying: Combining the above in-situ XRD tests, the cell parameters of the material obtained after alloying are obtained (represented by the three cell constants a, b, and c, and the three inter-edge angles α, β, and γ). According to the formula d1 = a / (α... 2 +β 2 +γ 2 ) 0.5 d2=b / (α) 2 +β 2 +γ 2 ) 0.5 d3=c / (α) 2 +β 2 +γ 2 ) 0.5 The interplanar spacing (d1 d2 d3) of the corresponding characteristic crystal planes is calculated. For example, the PdCu alloy material obtained in this invention belongs to the body-centered cubic (BCC) structure, and its characteristic crystal planes include (110), (111), (200), (210), and (211). At the same time, according to the X-ray diffraction results, a series of different characteristic crystal plane ratios (the intensity corresponding to different crystal planes) can be obtained. For example, in the PdCu alloy material obtained in this invention, the (110) plane corresponds to the characteristic peak at 2θ = 43° ± 1°, the (111) plane corresponds to the characteristic peak at 2θ = 53° ± 1°, the (200) plane corresponds to the characteristic peak at 2θ = 62° ± 1°, the (210) plane corresponds to the characteristic peak at 2θ = 70° ± 1°, and the (211) plane corresponds to the characteristic peak at 2θ = 79° ± 1°. The lattice parameter k of the corresponding material is obtained by converting the peak intensity of the above characteristic crystal planes using HighScorePlus analysis software.

[0055] The thickness of the material obtained after alloying is tested by measuring the thickness of the alloy film according to the corresponding scale based on the magnification obtained by scanning electron microscopy (model: JSM-7610F).

[0056] The method for testing the half-peak width (WHM) of the material obtained after alloying is as follows: based on the XRD spectrum test results, combined with HighScore Plus software analysis, the radian value of the WHM is obtained.

[0057] E act (Hydrogen permeation activation energy, unit: kJ·mol) -1 The test method involves measuring the hydrogen permeation rate from 573 K to 773 K under a transmembrane pressure difference of 0.1 MPa, combined with the Arrhenius equation J. H2 =J H2 °exp(-E act / RT), calculated through measurement, where J H2 It is the hydrogen permeation diffusion rate, J H2 ° is the hydrogen permeation diffusion coefficient, R is the gas constant, and T is the absolute temperature. The higher the hydrogen permeation activation energy, the higher the hydrogen mass transfer resistance of the composite membrane material, and the more difficult it is for hydrogen to permeate and diffuse through the composite membrane.

[0058] J H2 (Hydrogen permeation diffusion rate, unit: mol·m) -2 ·s -1 The test method involves measuring the volume of hydrogen passing through the palladium-based composite membrane per minute (liters) at 20℃ and a transmembrane pressure difference of 0.1 MPa, and then normalizing it to the hydrogen permeation rate (mol·m²) based on the membrane area (square meters). -2 ·s -1 ).

[0059] J N2 (Nitrogen permeation diffusion rate, unit: mmol·m) -2 ·s -1 The test method involves measuring the volume (mL) of nitrogen gas passing through the palladium-based composite membrane per minute at 20℃ and a transmembrane pressure difference of 0.1 MPa, and then normalizing it to the hydrogen permeation rate (mmol·m²) based on the membrane area (m²). -2 ·s -1 ).

[0060] Table 1

[0061]

[0062] Note: In Table 1, BCC+FCC indicates that it includes both body-centered cubic packing and face-centered cubic close packing. "--" indicates that the parameter is the same as A1.

[0063] Table 1 (continued)

[0064]

[0065]

[0066] A comparison of the examples and comparative examples in Table 1 shows that the palladium alloy prepared using the preferred embodiment of the present invention has a lower hydrogen permeation activation energy and a higher hydrogen permeation diffusion rate.

[0067] The palladium alloy prepared by the method of this invention exhibits high hydrogen-nitrogen selectivity α(H2 / N2) (H2 / N2 selectivity refers to the ratio between the hydrogen permeation and diffusion rate at defects in the palladium membrane and the nitrogen permeation and diffusion rate at defects; a higher value indicates higher mechanical structural stability of the palladium membrane and fewer defects in the composite membrane material). It can be applied to the separation or purification of hydrogen under various operating conditions, such as in other forms of hydrogen fuel cell systems including methanol fuel cell systems, hydrogen production through hydrocarbon steam reforming, water-steam shift hydrogen production, and rapid separation of high-purity hydrogen, as well as in the production of monocrystalline and polycrystalline silicon in the electronics and semiconductor industries. Furthermore, the palladium alloy of this invention is not prone to hydrogen embrittlement even at low temperatures, exhibits strong resistance to carbon deposition, and has a long service life (the hydrogen permeation rate remains unchanged even after long-term operation).

[0068] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing palladium alloys, characterized in that, The method includes: mixing palladium with other metals besides palladium, placing the resulting mixture in an activating atmosphere, first heat-treating it at a temperature of T1=350-650℃, and then cooling it down to a temperature of T2=100-200℃ at a cooling rate of V=25-150℃ / min; the heat treatment pressure is P=0.12-0.75MPa.

2. The method according to claim 1, wherein, The gas providing the activating atmosphere includes alkaline gas, and the content of alkaline gas in the gas providing the activating atmosphere is greater than or equal to 1 volume.

3. The method according to claim 2, wherein, The alkaline gas is selected from at least one of ethylenediamine, NH3, PH3 and N2H4.

4. The method according to claim 1, wherein, The method of mixing palladium with other metals is to deposit Pd and other metals on a support.

5. The method according to claim 4, wherein, The total thickness of Pd and other metals deposited on the support is 0.5-30µm; And / or, the thickness of the support is 0.1-20 mm.

6. The method according to claim 4, wherein, The total thickness of Pd and other metals deposited on the support is 5-15µm.

7. The method according to claim 4, wherein, The thickness of the support is 2-5mm.

8. The method according to claim 1, wherein, The molar ratio of Pd to other metals is 1:(0.01-10).

9. The method according to claim 1 or 8, wherein, The other metals are Group IB metals and / or Group VIII metals.

10. The method according to claim 9, wherein, The other metal is at least one of Cu, Ag, Au, and Ni.

11. The palladium alloy prepared by the method according to any one of claims 1-10.

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