Method for manufacturing hydrogen separation filter, and hydrogen separation filter

Abstract

To provide a method for manufacturing a hydrogen separation filter capable of reducing the usage amount of palladium, and to provide a hydrogen separation filter manufactured by the method.SOLUTION: A method for manufacturing a hydrogen separation filter including a porous substrate composed of oxide material and a palladium layer provided on the porous substrate includes the steps of (a) adsorbing a hydrophilic palladium compound to the porous substrate, (b) reducing the adsorbed hydrophilic palladium compound to palladium, (c) adsorbing a palladium complex to the porous substrate to which palladium is attached, and (d) reducing the adsorbed palladium complex to palladium, in this order.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a method for producing a hydrogen separation filter, and a hydrogen separation filter. [Background technology]

[0002] As a method for purifying hydrogen, a membrane separation method using a metal membrane is known. Patent Document 1 describes a porous filter characterized in that only defects larger than the micropores that open on one side of a porous ceramic membrane having micropores are blocked by metal, and the micropores in the porous ceramic membrane are not blocked by the metal, and a hydrogen separation membrane in which a thin palladium film or a thin palladium alloy film is formed on one side of the porous filter. Patent Document 1 describes that a porous filter is produced using a porous ceramic membrane with an average pore size of 0.1 μm, and a thin palladium film with an average thickness of 0.8 μm or more is formed on the outer surface by plating. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5891512 specification Summary of the Invention [Problem to be solved by the invention]

[0004] Palladium is expensive, so it is desirable to reduce the amount of palladium used. However, when attempting to form a thin palladium layer (for example, 20 nm or less) on a porous substrate using conventional membrane formation methods such as plating, it has been impossible to form a palladium layer with sufficient hydrogen separation performance. Therefore, the present disclosure provides a method for producing a hydrogen separation filter that can reduce the amount of palladium used, and a hydrogen separation filter that can be produced thereby. [Means for solving the problem]

[0005] Aspects of the present disclosure include the following. [Aspect 1] A method for producing a hydrogen separation filter comprising a porous substrate made of an oxide material and a palladium layer provided on the porous substrate, the method comprising: (a) adsorbing a hydrophilic palladium compound onto the porous substrate; (b) reducing the adsorbed hydrophilic palladium compound to palladium; (c) adsorbing a palladium complex onto the porous substrate having palladium attached thereto; (d) reducing the adsorbed palladium complex to palladium; A method for producing a hydrogen separation filter, comprising the steps of: [Aspect 2] After step (d), (e) adsorbing a hydrophilic palladium compound onto the porous substrate having palladium attached thereto; (f) reducing the adsorbed hydrophilic palladium compound to palladium; (g) adsorbing a palladium complex onto the porous substrate having palladium attached thereto; (h) reducing the adsorbed palladium complex to palladium; in that order, A method for producing a hydrogen separation filter according to aspect 1, comprising carrying out steps (e) to (h) one or more times. [Aspect 3] The average pore diameter of the porous substrate is 5 to 20 nm; 3. The method for producing a hydrogen separation filter according to aspect 1 or 2, wherein the palladium layer has a thickness of 75 to 500 nm. [Aspect 4] A method for producing a hydrogen separation filter according to any one of Aspects 1 to 3, wherein the hydrophilic palladium compound is palladium acetate or palladium chloride, and the palladium complex is palladium acetylacetonate, palladium hexafluoroacetylacetonate, bis(2,2,6,6-tetramethyl-3,5-heptanedionato)palladium, dichlorobis(triphenylphosphine)palladium, cyclopentadienylallylpalladium, or tetrakis(triphenylphosphine)palladium. [Aspect 5] A porous substrate having an average pore size of 5 to 20 nm; A palladium layer having a thickness of 75 to 500 nm provided on the porous substrate; A hydrogen separation filter comprising: Effect of the Invention

[0006] The hydrogen separation filter manufacturing method and hydrogen separation filter disclosed herein can reduce the amount of palladium required to manufacture the hydrogen separation filter, enabling the hydrogen separation filter to be manufactured at low cost. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view of a hydrogen separation filter according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments will be described with reference to the drawings as appropriate. In the drawings referred to in the following description, the dimensional ratios and shapes of each member are exaggerated for the convenience of explanation and may differ from the actual dimensional ratios and shapes. In addition, in this application, a numerical range expressed using the symbol "~" includes the numerical values ​​written before and after the symbol "~" as the lower limit and upper limit, respectively. The upper limit and lower limit of the numerical range described in this application can be used alone or in any combination to define a preferred range.

[0009] (1) Hydrogen separation filter 1 includes a porous substrate 10 and a palladium layer 60 provided on the porous substrate 10. The palladium layer 60 may be formed directly on the porous substrate 10.

[0010] The porous substrate 10 is composed of an oxide material such as a metal oxide, a semi-metal oxide, or a mixture thereof, and is preferably composed of an oxide material. In this application, "composed of" means that in addition to the materials described, additional components that do not substantially adversely affect the performance of the hydrogen separation filter 1 may be included. "Consisting of" means that only the materials described are included, but does not exclude the inclusion of unavoidable impurities. Examples of oxide materials include aluminum oxide, zirconium oxide, titanium oxide, and mixtures thereof.

[0011] The porous substrate 10 may have any shape having a first surface 12 and a second surface 14, such as a plate, a sheet, a cylinder, or the like. The porous substrate 10 has pores that are connected from the first surface 12 to the second surface 14 and through which hydrogen can pass. The pores are blocked by the palladium layer 60. The average diameter (average pore diameter) of the pores of the porous substrate 10 may be preferably 5 to 20 nm, more preferably 5 nm or more and less than 20 nm, and particularly 5 to 15 nm. When the average pore diameter is within the above range, the porous substrate 10 has sufficient hydrogen permeability and the pores can be blocked by the thin palladium layer 60. The average pore diameter of the porous substrate 10 is determined based on the pore diameter distribution obtained by mercury intrusion porosimetry in accordance with JIS R 1655:2003. Mercury intrusion porosimetry is a method in which mercury is forced into open pores under pressure, the relationship between the volume of mercury that has penetrated into the open pores and the pressure applied at that time is determined, and the diameter of the open pores is calculated based on the result using the Washburn formula, assuming that the open pores are cylindrical.

[0012] The palladium layer 60 may have a thickness of 75 to 500 nm. This is a smaller value than the thickness of conventional palladium for hydrogen separation. When the thickness of the palladium layer 60 is small, the hydrogen permeation rate per unit area of ​​the palladium layer 60 is improved, so that the target hydrogen permeation rate can be achieved with a smaller area than in the conventional technology. Therefore, the hydrogen separation filter 1 according to the embodiment can reduce the amount of palladium used and can be manufactured at low cost.

[0013] (2) Manufacturing method of hydrogen separation filter The method for producing a hydrogen separation filter according to the embodiment includes, in this order, step a of adsorbing a hydrophilic palladium compound to a porous substrate, step b of reducing the adsorbed hydrophilic palladium compound to palladium, step c of adsorbing a palladium complex to the porous substrate to which palladium is attached, and step d of reducing the adsorbed palladium complex to palladium. The method for producing a hydrogen separation filter may further include, after step d, step e of adsorbing a hydrophilic palladium compound to the porous substrate to which palladium is attached, step f of reducing the adsorbed hydrophilic palladium compound to palladium, step g of adsorbing a palladium complex to the porous substrate to which palladium is attached, and step h of reducing the adsorbed palladium complex to palladium, in this order. Steps e to h may not be performed, may be performed once, or may be performed repeatedly two or more times.

[0014] Step a) Adsorption of hydrophilic palladium compounds A gas of a hydrophilic palladium compound is introduced into a film-forming chamber in which a porous substrate is placed, whereby the hydrophilic palladium compound is adsorbed onto the surface of the porous substrate.

[0015] In the present application, the term "hydrophilic palladium compound" refers to a palladium compound having a solubility of 0.8 g / L or more in water at 20° C. Examples of hydrophilic palladium compounds include palladium acetate and palladium chloride. Palladium acetate is preferred because it is easy to handle.

[0016] The hydrophilic palladium compound has a high affinity for the hydrophilic surface of the porous substrate made of an oxide material, and therefore can coat the surface of the porous substrate well.

[0017] The gas of the hydrophilic palladium compound may be produced by heating and vaporizing the hydrophilic palladium compound, which is a solid or liquid at room temperature.

[0018] After the hydrophilic palladium compound is adsorbed onto the surface of the porous substrate, the membrane formation chamber may be evacuated to remove residual gas of the hydrophilic palladium compound from the membrane formation chamber.

[0019] Step b) Reduction of the hydrophilic palladium compound The hydrophilic palladium compound adsorbed on the porous substrate is then reduced with a reducing agent to produce palladium.

[0020] Examples of the reducing agent include reducing radicals such as hydrogen radicals and ammonia radicals. For example, hydrogen gas or ammonia gas is supplied to a film formation chamber, and high frequency waves are applied to generate plasma, whereby hydrogen radicals or ammonia radicals can be generated.

[0021] After the hydrophilic palladium compound has been reduced to palladium, the deposition chamber may be evacuated to remove the remaining reducing agent and the source gas of the reducing agent from the deposition chamber.

[0022] Step c) Adsorption of palladium complexes Next, a gas of a palladium complex is introduced into the film formation chamber. As a result, the palladium complex is adsorbed onto the surface of the porous substrate to which palladium is attached obtained in step b (hereinafter, the porous substrate to which palladium is attached will be appropriately referred to as the "palladium-adhered porous substrate"). The palladium complex is easily adsorbed onto the palladium attached to the porous substrate, and can also be adsorbed onto the surface of the porous substrate.

[0023] Examples of palladium complexes include palladium acetylacetonate (Pd(acac)), palladium hexafluoroacetylacetonate (Pd(hfac)), bis(2,2,6,6-tetramethyl-3,5-heptanedionate)palladium (Pd(btmhd)), dichlorobis(triphenylphosphine)palladium, cyclopentadienylallylpalladium, and tetrakis(triphenylphosphine)palladium. It is preferable that the palladium complex has high hydrophilicity. Therefore, it is preferable that the ligand of the palladium complex does not have a fluoroalkyl group, and examples of such palladium complexes include Pd(acac), Pd(btmhd), dichlorobis(triphenylphosphine), cyclopentadienylallylpalladium, and tetrakis(triphenylphosphine)palladium. Furthermore, in order to make the palladium complex more hydrophilic, it is preferable that the ligand of the palladium complex has neither a fluoroalkyl group nor a branched alkyl group, and examples of such palladium complexes include Pd(acac), dichlorobis(triphenylphosphine), cyclopentadienylallylpalladium, and tetrakis(triphenylphosphine)palladium. Pd(acac) is particularly preferred because it has high hydrophilicity.

[0024] The gas of the palladium complex may be produced by heating and vaporizing the palladium complex, which is a solid or liquid at room temperature.

[0025] After the palladium complex is adsorbed onto the surface of the palladium-attached porous substrate, the deposition chamber may be evacuated to remove any remaining palladium complex gas from the deposition chamber.

[0026] Step d) Reduction of the palladium complex Next, the palladium complex adsorbed on the palladium-attached porous substrate is reduced with a reducing agent to produce palladium.

[0027] As an example of the reducing agent, the same reducing agent as used in step b can be used.

[0028] After the palladium complex has been reduced to palladium, the deposition chamber may be evacuated to remove the remaining reducing agent and the source gas of the reducing agent from the deposition chamber.

[0029] Step e) Adsorption of hydrophilic palladium compounds Next, a gas of a hydrophilic palladium compound may be introduced into the film formation chamber. This causes the hydrophilic palladium compound to be adsorbed onto the surface of the palladium-attached porous substrate obtained in the previous step. Details are the same as in step a, so the explanation is omitted.

[0030] The reduction of the hydrophilic palladium compound, the adsorption of the palladium complex, and the reduction of the palladium complex in steps fh are also carried out in the same manner as in steps bd, and therefore a description thereof will be omitted.

[0031] In each step of the present manufacturing method, the film formation chamber may be at a reduced pressure relative to atmospheric pressure.

[0032] By the above-described manufacturing method, the hydrogen separation filter is manufactured.

[0033] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above-described embodiments, and various design modifications can be made without departing from the technical scope described in the claims. EXAMPLES

[0034] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples.

[0035] (1) Preparation of hydrogen separation filter Examples 1 to 7 A porous aluminum oxide substrate (NGK Insulators, Ltd. "Microfiltration Membrane MF0.1", average pore size 100 nm) was coated with aluminum particles or titanium oxide particles to prepare a porous substrate having the average pore size shown in Table 1. The average pore size was determined based on the pore size distribution determined by mercury intrusion porosimetry in accordance with JIS R 1655:2003.

[0036] The porous substrate was placed in the film-forming chamber. After the film-forming chamber was evacuated, palladium acetate gas was introduced into the film-forming chamber to adsorb palladium acetate on the surface of the porous substrate. After the film-forming chamber was evacuated, hydrogen gas was introduced into the film-forming chamber and high frequency was applied to generate plasma, and the palladium acetate adsorbed on the porous substrate was reduced to palladium. After the film-forming chamber was evacuated, palladium (II) acetylacetonate (Pd(acac)) gas was introduced into the film-forming chamber to adsorb Pd(acac) on the porous substrate to which palladium was attached. After the film-forming chamber was evacuated, hydrogen gas was introduced into the film-forming chamber and high frequency was applied to generate plasma, and the adsorbed Pd(acac) was reduced to palladium. Furthermore, the above-mentioned adsorption and reduction of palladium acetate and adsorption and reduction of Pd(acac) were set as one cycle, and this cycle was repeated. As a result, a Pd layer having a thickness as shown in Table 1 was formed on the porous substrate, and the hydrogen separation filters of Examples 1 to 7 were obtained. The thickness of the Pd layer was measured using a cross-sectional TEM image of the hydrogen separation filter.

[0037] (2) Hydrogen permeation rate measurement The hydrogen permeation rates (unit: mmol s ) of the hydrogen separation filters of Examples 1 to 7 were measured by gas chromatography in accordance with JIS K7126:2006 (Plastics - Films and sheets - Gas permeability test method - Part 1: Differential pressure method). -1 m -2 ·Pa -0.5 ) was measured. The results are shown in Table 1. For comparison with the prior art, the hydrogen permeation rate of the hydrogen separation membrane of Example 3 of Patent Document 1 is also shown in Table 1. The hydrogen separation filters of Examples 1 to 7 had higher hydrogen permeation rates than the hydrogen separation membrane of Patent Document 1. In addition, the hydrogen permeation rate was divided by the palladium membrane thickness to determine an index of the cost performance of the hydrogen separation filter. The results are shown in Table 1. It can be seen that the hydrogen separation filters of Examples 1 to 7 have high cost performance.

[0038] [Table 1] [Explanation of symbols]

[0039] 1: hydrogen separation filter, 10: porous substrate, 12: first surface, 14: second surface, 60: palladium layer

Claims

1. A method for producing a hydrogen separation filter comprising a porous substrate made of an oxide material and a palladium layer provided on the porous substrate, the method comprising: (a) adsorbing a hydrophilic palladium compound onto the porous substrate; (b) reducing the adsorbed hydrophilic palladium compound to palladium; (c) adsorbing a palladium complex onto the porous substrate having palladium attached thereto; (d) reducing the adsorbed palladium complex to palladium; A method for producing a hydrogen separation filter, comprising the steps of:

2. After step (d), (e) adsorbing a hydrophilic palladium compound onto the porous substrate having palladium attached thereto; (f) reducing the adsorbed hydrophilic palladium compound to palladium; (g) adsorbing a palladium complex onto the porous substrate having palladium attached thereto; (h) reducing the adsorbed palladium complex to palladium; in that order, The method for producing a hydrogen separation filter according to claim 1, wherein steps (e) to (h) are carried out one or more times.

3. The average pore diameter of the porous substrate is 5 to 20 nm; The method for producing a hydrogen separation filter according to claim 1 or 2, wherein the palladium layer has a thickness of 75 to 500 nm.

4. 3. The method for producing a hydrogen separation filter according to claim 1 or 2, wherein the hydrophilic palladium compound is palladium acetate or palladium chloride, and the palladium complex is palladium acetylacetonate, palladium hexafluoroacetylacetonate, bis(2,2,6,6-tetramethyl-3,5-heptanedionato)palladium, dichlorobis(triphenylphosphine)palladium, cyclopentadienylallylpalladium, or tetrakis(triphenylphosphine)palladium.

5. A porous substrate having an average pore size of 5 to 20 nm; A palladium layer having a thickness of 75 to 500 nm provided on the porous substrate; A hydrogen separation filter comprising:

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