JP2006283076A - Dual phase alloy for separating/refining hydrogen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dual phase alloy for separating/refining hydrogen having excellent hydrogen separability and hydrogen embrittlement resistance without using Pd as an expensive noble metal, and usable at high temperature. <P>SOLUTION: The dual phase alloy for separating/refining hydrogen has a composition of, by atomic%, T<SB>100-(α+β+γ+δ)</SB>M<SB>α</SB>X<SB>β</SB>Z<SB>γ</SB>R<SB>δ</SB>(in the formula, T is at least one selected from the group consisting of Ti, Zr and Hf; M is at least one selected from V, Nb and Ta; X is at least one selected from the group consisting of Ag, Al, Cr, Cu, Ga, Zn and Fe; Z is at least one selected from the group consisting of B, C and P; R is at least one selected from rare earth elements including Y and La; α, β, γ and δ satisfy 15≤α≤55, 5≤β≤45, 0.1≤γ≤5 and 0≤δ≤15; and T is 5 to 60 atomic%) with inevitable impurities. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrogen separation / purification double phase alloy used for producing high purity hydrogen, and to a hydrogen separation / purification dual phase alloy having a novel alloy composition.

  In order to produce hydrogen used in a fuel cell or the like, there is a method of obtaining hydrogen by reforming from natural gas, but there is a problem that a platinum catalyst is poisoned because it contains an impurity gas such as CO. Therefore, an alloy such as PdAg is used as a separation membrane through which only hydrogen passes in order to remove an impurity gas such as CO from the mixed gas. However, since Pd belongs to a noble metal and is very expensive, an inexpensive hydrogen separation membrane material that does not contain a noble metal is required in order to spread it for industrial use. Further, hydrogen embrittlement occurs due to repeated permeation of hydrogen, resulting in a problem that the hydrogen separation membrane is broken and cannot be used for a long time. Furthermore, the PdAg hydrogen separation membrane that has been widely used in the past has a lower hydrogen permeability as the temperature becomes lower. In order to obtain a practical amount of permeation, it must be used at about 300 ° C. or higher, and it must be heated to a high temperature. It was.

For this reason, what has high hydrogen permeation performance other than Pd type is required. For example, Nb-Ni system as described in Patent Document 1 and Nb- (Ni, Co, Mo)-(V, Ti, Zr, Ta, Hf) system hydrogen permeable alloy as described in Patent Document 2 Is being considered. Patent Document 3 discloses a Zr—Ni-based amorphous alloy.
JP 2001-170460 A (0026) JP 2004-42017 A (0007 to 0011) JP 2004-167378 A (0009-0011)

  The above-mentioned Zr-Ni amorphous alloy is known as a hydrogen salt permeable membrane with excellent hydrogen separation performance and good productivity. However, when used for a long time at 300 ° C or higher, crystallization occurs and the permeable membrane breaks down. It was necessary to improve the stability of amorphous metal at high temperatures. Therefore, an object of the present invention is to provide a dual phase alloy for hydrogen separation / purification that is excellent in hydrogen separation ability and excellent in hydrogen embrittlement resistance and can be used at high temperatures without using expensive precious metal Pd. .

The multi-phase alloy for hydrogen separation / purification of the present invention that has solved the above problems is expressed in _{terms of} atomic%, T _{100- (α + β + γ + δ)} M _α X _β Z _γ R _δ (Z, where T is from Ti, Zr, Hf) One or more of the group consisting of M, one or more of the group consisting of V, Nb, Ta, X is one or more of the group consisting of Ag, Al, Cr, Cu, Ga, Zn, Fe, Z is B, C , P, one or more of rare earth elements including Y and La, wherein α, β, γ, and δ are 15 ≦ α ≦ 55, 5 ≦ β ≦ 45, 0 .Ltoreq..gamma..ltoreq.5, 0.ltoreq..delta..ltoreq.15, and T is 5 to 60 atomic%) and an alloy having a composition consisting of inevitable impurities. That is, by adding one of B, P, and C, the stability of the amorphous alloy at a high temperature has been dramatically increased, and it has become possible to withstand long-term use.

  The M element is selected from one or more of V, Nb, and Ta. The content of M element is preferably 15 to 55 atomic%. If the element M is less than 15 atomic%, the hydrogen permeability is greatly reduced. On the other hand, when the content of M element exceeds 55%, hydrogen permeability is high, but hydrogen embrittlement is severe, and the membrane is destroyed immediately after hydrogen permeation. A more preferable range is 20 to 50 atomic%. X is selected from one or more of Ag, Al, Cr, Cu, Ga, Zn, and Fe. The content of the X element is preferably 5 to 45 atomic%. If the element X is less than 5 atomic%, the hydrogen permeability is high, but the mechanical processability is inferior, and it is difficult to process into a plate shape. On the other hand, if the content of the X element exceeds 45 atomic%, it becomes very brittle and in this case, mechanical processing is difficult. A more preferable range is 10 to 40 atomic%. The T element is selected from one or more of the group consisting of Ti, Zr, and Hf. If the element T is less than 5 atomic%, the hydrogen permeability is high, but hydrogen embrittlement is severe, and the membrane breaks immediately after hydrogen permeation. On the other hand, when the content of the X element exceeds 65 atomic%, the hydrogen permeability decreases. A more preferable range is 10 to 60 atomic%.

  The Z element in the present invention is selected from one or more of B, C, and P. The content of Z element is preferably 0.1 to 5 atomic%. If the Z element is less than 0.1 atomic%, the amorphous forming ability is low, and only a crystalline alloy can be obtained even if super rapid cooling is performed. On the other hand, when the content of the Z element exceeds 5 atomic%, the hydrogen permeability is very low and it is difficult to put it to practical use. As the rapid cooling means, known methods such as water atomization, gas atomization, and melt span can be employed.

  In order to improve hydrogen permeability, it is preferable to contain R element. The R element is selected from one or more rare earth elements including Y and La. Content of R element shall be 15 atomic% or less. If the content is small, the effect of improving the hydrogen permeability is diminished, but if the content of R element exceeds 15 atomic%, the hydrogen permeability is high but hydrogen embrittlement is severe, and the membrane breaks immediately after hydrogen permeation. A preferable content is 5 to 13 atomic%.

  This alloy is prepared by melting by, for example, an arc melting method in an inert gas atmosphere, a high-frequency induction heating melting method in an inert gas atmosphere or in a vacuum, an electron beam melting method in a vacuum, or a laser heating melting method. can do. It is also possible to form a Pd film or a Pd alloy film on both sides of the surface of the multiphase alloy for hydrogen separation / purification on the side where the raw material to be treated is flowed and on the side where the purified hydrogen is taken out to obtain a final form. It is also attractive that it is much cheaper than Pd-based alloys.

  The double phase alloy for hydrogen separation / purification of the present invention has good hydrogen permeability, in particular, low temperature permeability as compared with conventional Pd-based hydrogen separation membranes, and is excellent in hydrogen embrittlement and practical. Because of its excellent amorphous performance, it is possible to prepare a thin band by roll cooling or the like, and it is possible to obtain an unprecedented thin film for hydrogen separation / purification in mass production.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

Example 1
The dual phase alloy for hydrogen separation / purification rotates at a peripheral speed of 15 m / s after arc melting the alloys of Examples 1 to 7 and the alloys of Comparative Examples 1 to 7 having the composition shown in Table 1 in an Ar atmosphere. A thin ribbon having a thickness of 100 μm was prepared by spraying 0.02 MPa Ar gas on a Cu roll. A diameter of about 10 mm was cut out from the ribbon to prepare a hydrogen separation membrane test piece. The test piece was sputtered with a Pd film of about 100 nm on both sides to prevent oxidation. Judgment whether it became amorphous was performed by the X-ray diffraction pattern.
After setting the hydrogen separation membrane in a predetermined reaction tube and flowing He, and confirming that there is no leakage from the membrane, the reaction tube is heated to a predetermined temperature, and when one reaches the predetermined temperature, one primary side Hydrogen was allowed to flow through and pressure was applied, and the flow rate of hydrogen flowing to the secondary side on the reaction side was measured. The temperature was 300 ° C. The hydrogen permeation coefficient representing the hydrogen permeation capacity was determined using the following equation.

  The hydrogen embrittlement resistance was evaluated based on the time during which hydrogen permeation was continuously performed and the hydrogen separation membrane was broken.

As is apparent from the results in Table 1, the test pieces of Examples 1 to 7 showed a hydrogen permeability superior to that of the conventionally used PdAg alloy of Comparative Example 1, and also had a high hydride generation temperature, and were resistant to hydrogen. It turns out that it is excellent in brittleness. In the examples shown in Comparative Examples 2 to 7, the hydrogen permeability may be higher than that of the PdAg alloy, but it can be seen that the hydride generation temperature is low and the hydrogen embrittlement resistance is inferior to PdAg. FIGS. 1 and 2 show these ternary composition diagrams. From now on, the composition range having high hydrogen permeability and excellent resistance to hydrogen embrittlement is atomic%, and T _{100− (α + β)} M _α X _β (wherein , T is one or more of the group consisting of Ti, Zr or Hf, M is one or more of the group consisting of V, Nb, Ta, X is a group consisting of Ag, Al, Cr, Cu, Ga, Zn, Fe It is understood that α and β are 15 ≦ α ≦ 55, 5 ≦ β ≦ 45, and T is in the composition range of 10 to 70 atomic%.

(Example 2)
Evaluation was performed in the same manner as in Example 1 using an alloy of a system other than the La-Ti-V-Ag-B system of Example 1. As is apparent from the results in Table 2, the test pieces of Examples 8 to 14 show a hydrogen permeability that is superior to the PdAg alloy of Comparative Example 1 that is conventionally used, and the time required for the hydrogen permeable membrane to break is 10,000. It turns out that it is excellent in hydrogen embrittlement resistance over time.

It is a figure which shows the relationship between a composition and hydrogen permeability coefficient (PHI). It is a figure which shows the relationship between a composition and the time until a hydrogen permeable film breaks.

Claims (3)

In _{atomic%, T 100- (α + β} + γ + δ) M α X β Z γ R δ (Z However Shikichu, T is Ti, Zr, 1 or more of the group consisting of Hf, M is V, Nb, of the group consisting of Ta One or more, X is one or more of the group consisting of Ag, Al, Cr, Cu, Ga, Zn and Fe, Z is one or more of the group consisting of B, C and P, R is a rare earth containing Y and La 1 or more elements, wherein α, β, γ, δ are 15 ≦ α ≦ 55, 5 ≦ β ≦ 45, 0.1 ≦ γ ≦ 5, 0 ≦ δ ≦ 15, and T is 5 A double phase alloy for hydrogen separation / purification characterized in that it is composed of an alloy having a composition consisting of ˜60 atomic%) and inevitable impurities. The multiphase alloy for hydrogen separation / purification according to claim 1, wherein the structure of the alloy is amorphous. The multiphase alloy for hydrogen separation and purification according to claim 2, wherein the alloy has a ribbon-like shape formed by roll cooling and has a thickness of 0.01 to 1 mm.