A composite oxide formed by the combination of NiAl2O4, γ-Al2O3, and ZrO2; an active material which is a reduced product of the composite oxide; and a method for regenerating the active material.

Abstract

To provide a novel improved complex oxide of NAO (a complex oxide of NiAl2O4 and γ-Al2O3), a complex oxide having improved material strength while holding characteristic high activity of NAO and its regenerating functions, and an active material comprising a reduced product of the complex oxide.SOLUTION: The present invention provides: a complex oxide comprising a combination of NiAl2O4, γ-Al2O3 and ZrO2, wherein the complex oxide is reduced into an active material; and an Ni / (γ-Al2O3 ZrO2)-based active material comprising a reduced product of the complex oxide, wherein at least Ni particles are dispersed on the surface of the complex oxide comprising a combination of γ-Al2O3 and ZrO2.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a composite oxide in which NiAl2O4, γ-Al2O3, and ZrO2 are combined, an active material which is a reduced product of the composite oxide, and a method for regenerating the active material.

Background Art

[0002] Conventionally, as a catalyst for hydrocarbon reforming, NiAl2O4 which is a spinel oxide (specifically, a composite oxide of NiAl2O4 and γ-Al2O3, also referred to as "NAO") has been used. It is known that this NAO becomes a highly active catalyst (Ni / γ-Al2O3 catalyst) in which Ni dissociates from the spinel structure by reduction at, for example, 700 to 800 °C and fine Ni particles are highly dispersed on the surface of γ-Al2O3.

[0003] Also, a catalyst in which Ru is further added to NAO (also referred to as "RNAO") is known. By containing Ru, the reforming activity is improved, the resistance to carbon deposition during reforming is increased, and it becomes a highly active catalyst (Ni,Ru / γ-Al2O3 catalyst) in which fine Ni particles and Ru particles are highly dispersed (partially, Ni and Ru may be alloyed. The same applies hereinafter) on the surface of γ-Al2O3 by reduction.

[0004] As described above, the Ni / γ-Al2O3 catalyst and the Ni,Ru / γ-Al2O3 catalyst are highly active catalysts for hydrocarbon reforming. However, when used at high temperature for a long time during reforming, Ni aggregation occurs and the catalyst activity decreases and deactivates. Conventionally, the Ni / γ-Al2O3 catalyst and the Ni,Ru / γ-Al2O3 catalyst have had the problem that they have to be discarded after deactivation. However, the applicant of the present application has proposed a method for regenerating them into an active material by sequentially performing an oxidation treatment and a reduction treatment on the deactivated Ni / γ-Al2O3 catalyst and the Ni,Ru / γ-Al2O3 catalyst in Patent Document 1.

[0005] The Ni / γ-Al2O3 catalyst and the Ni,Ru / γ-Al2O3 catalyst are characterized in that their toluene reforming activity is about 1.5 to 3.0 times higher than that of the Pt / γ-Al2O3 catalyst (a catalyst with fine Pt particles highly dispersed on the surface of γ-Al2O3) of the old catalyst. Also, as disclosed in Patent Document 1 above, these catalysts have the advantage that they can be regenerated and reused as the active material repeatedly.

[0006] On the other hand, NAO (including RNAO; the same shall apply hereinafter) has the problem that the material strength is low and granulation is difficult. If the strength of the material (for example, a catalyst) obtained by reduction after granulation is insufficient, the catalyst will crumble and be pulverized during use, causing problems such as pipe blockage and uneven flow in the catalyst use environment. Therefore, it is required to increase the material strength while maintaining the high-activity characteristics and regeneration function of NAO.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] The present invention improves the above problems of the prior art, and aims to provide a new composite oxide obtained by improving NAO, which is a composite oxide that increases the material strength while maintaining the high-activity characteristics and regeneration function of NAO. It is also an object of the present invention to provide an active material which is a reduced product of the composite oxide and a regeneration method of the active material.

Means for Solving the Problems

[0009] As a result of intensive studies to achieve the above object, the present inventors have found that a composite oxide having a specific composition can achieve the above object, and have completed the present invention.

[0010] That is, the present invention relates to a composite oxide in which the following NiAl2O4, γ-Al2O3, and ZrO2 are combined, an active material that is a reduced product of the composite oxide, and a method for regenerating the active material.

[0011] 1. A composite oxide in which NiAl2O4, γ-Al2O3, and ZrO2 are combined, characterized in that it becomes an active material by reduction. 2. A Ni / (γ-Al2O3·ZrO2) - based active material, characterized in that at least Ni particles are dispersed on the surface of a composite oxide in which γ-Al2O3 and ZrO2 are combined. 3. Further, platinum group particles M 2 , x , , 2 , , 1 , , 2 , 2 , , , are dispersed, and it is a Ni,M 1 / (γ-Al2O3·ZrO2) - based active material, which is the active material described in item 2 above. 4. The platinum group particles M 1 are Ru particles, and it is the active material described in item 3 above. 5. Further, a Ni,M 2 in which a metal element M 1 is combined in an oxide state, and it is a Ni,M 2 / (γ-Al2O3·ZrO2·M x O 2 )(where x represents the amount of oxygen corresponding to the metal element M 6. The M 2 is at least one selected from the group consisting of Ti, Hf, Ce, Se, Y, La, Sm, Ca, Mg, Sr, and Ba, and it is the active material described in item 5 above. 7. The active material according to any one of items 2 to 6 above, which is at least one selected from the group consisting of a catalyst for hydrocarbon reforming, a catalyst for methanation, a catalyst for wood gasification, and a fuel electrode material of a solid oxide fuel cell (SOFC). 8. A method for regenerating an active material from a deactivated material, where the active material is a Ni / (γ-Al2O3·ZrO2) - based active material in which at least Ni particles are dispersed on the surface of a composite oxide in which γ-Al2O3 and ZrO2 are combined, The deactivated material is a material in which aggregation of Ni particles occurs on the surface of the γ-Al2O3·ZrO2 due to the application of at least heat to the active material. (1) Step 1, which involves oxidizing the deactivated material to produce a spinel oxide having a NiAl2O4 structure. (2) Step 2 to obtain the active material by reducing the spinel oxide, A method for regenerating an active material, characterized by having the following features. 9. The regeneration method described in item 8 above, wherein the oxidation is carried out at a temperature of 700°C or higher. 10. The regeneration method described in item 8 or 9 above, wherein the reduction is carried out at a temperature of 500°C or higher for 1 minute or more. [Effects of the Invention]

[0012] The composite oxide of the present invention is a composite oxide (also called "NAZO") formed by the combination of NiAl2O4, γ-Al2O3, and ZrO2, characterized in that it becomes an active material upon reduction. This composite oxide is a composite oxide in which ZrO2 is further combined with the conventional NAO (a composite oxide of NiAl2O4 and γ-Al2O3), and the material strength of NAO is improved by the combination of ZrO2. ZrO2 has multiple crystal systems such as monoclinic, tetragonal, and cubic, and it is thought that the material strength is improved compared to NAO because the crystal system changes when stress is applied to NAZO, allowing for stress relaxation. In addition, since the cubic crystal is stable at high temperatures, it is thought to contribute to the improvement in strength in ways other than the phase change mentioned above. The composite oxide of the present invention becomes an active material upon reduction and can be used as a catalyst for hydrocarbon reforming, a fuel electrode material for SOFCs, etc. After the active material is deactivated by heat, it can be regenerated into an active material by sequentially performing oxidation treatment and reduction treatment on the deactivated material. [Brief explanation of the drawing]

[0013] [Figure 1]This diagram schematically illustrates the function of the Ni / (γ-Al2O3·ZrO2) system active material in which at least Ni particles are dispersed on the surface of a composite oxide (γ-Al2O3·ZrO2) formed by the combination of γ-Al2O3 and ZrO2, in the present invention, to be regenerated back to the original active material by sequentially performing oxidation treatment and reduction treatment after deactivation. [Figure 2] This figure shows the appearance of 1:5:5NAZO / α-Al2O3 containing Ni1Al5Zr5Ox (also known as "1:5:5NAZO") before and after reduction, and the fine structure observed by energy-dispersive X-ray spectroscopy (EDX) before and after reduction (EDX mapping results for Ni and Al) in Test Example 1. [Figure 3] This figure shows the repeated sequential temperature-reducing (TPR) characteristics of 1:5:5 NAZO in Test Example 2. [Figure 4] This figure shows the X-ray diffraction (XRD) patterns of 1:5:5 NAZO obtained in Test Example 2, where the fourth oxidation in the oxidation-reduction cycle was performed at 350°C, 500°C, 600°C, 700°C, 780°C, and 850°C. [Figure 5] This figure shows the XRD patterns (particularly regarding the ZrO2 peak) of 1:5:5 NAZO obtained in Test Example 2, where the fourth oxidation in the oxidation-reduction cycle was performed at 350°C, 500°C, 600°C, 700°C, 780°C, and 850°C. [Figure 6] This figure shows STEM (scanning transmission electron microscope) and EDX observation images of the 1:5:5 NAZO reduced product after reduction at 850°C for 2 hours in Test Example 2. [Figure 7] This figure shows the STEM and EDX observation images of 1:5:5 NAZO oxide in Test Example 2. [Figure 8] This figure shows the results of the strength test (compression test) in Test Example 3. [Figure 9] This figure shows the Arrhenius plot of the LNG reforming rate of the methane reforming catalyst in Test Example 4. [Figure 10] This figure shows the Arrhenius plots of the gasification (C1 conversion) rates with and without the wood gasification catalyst in Test Example 5. [Modes for carrying out the invention]

[0014] 1. NiAl 2 O 4 and γ-Al 2 O 3 and ZrO 2 A composite oxide formed by the combination of these two elements. The composite oxide of the present invention is a composite oxide (NAZO) formed by the combination of NiAl2O4, γ-Al2O3, and ZrO2, characterized in that it becomes an active material upon reduction. The composite oxide of the present invention having the above characteristics is a composite oxide in which ZrO2 is further combined with conventional NAO (a composite oxide of NiAl2O4 and γ-Al2O3), and the material strength of NAO is improved by the combination of ZrO2. ZrO2 has multiple crystal systems such as monoclinic, tetragonal, and cubic, and it is thought that the material strength is improved compared to NAO because the crystal system changes when stress is applied to NAZO, allowing for stress relaxation. In addition, since the cubic crystal is stable at high temperatures, it is thought to contribute to the improvement in strength in ways other than the phase change mentioned above. The composite oxide of the present invention becomes an active material upon reduction and can be used as a catalyst for hydrocarbon reforming, a fuel electrode material for SOFCs, etc. After the active material is deactivated by heat, it can be regenerated into an active material by sequentially performing oxidation treatment and reduction treatment on the deactivated material.

[0015] The forms of composite formation between NiAl2O4, γ-Al2O3, and ZrO2 in composite oxides (NAZO) are not limited to specific forms. Examples include a form in which each oxide particle is completely dissolved, and a form in which the composite is formed by solid solution and necking of parts of the surfaces of each oxide particle.

[0016] The molar ratio of Ni, Al, and Zr in the composite oxide (NAZO) can be adjusted by the mixing ratio of the raw materials used to prepare the composite oxide. When the molar ratio of each element is expressed as the proportion of the raw materials, Ni:Al:Zr = 1 or more:1 to 40:0 to 40 is preferred, and 1 to 2:10 to 40:1 to 10 is more preferred. Furthermore, from the viewpoint of increasing the material strength of NAZO compared to NAO, if the total amount of each oxide constituting the composite oxide (NAZO) (NiAl2O4, γ-Al2O3, and ZrO2) is set to 100% by mass, and the ZrO2 content is 1% by mass or more, the material strength can be increased. The ZrO2 content is preferably 5% by mass or more, more preferably 10% by mass or more, and the preferred upper limit, determined from the relationship between strength improvement and the properties of the composite oxide (properties of the active material after reduction), is approximately 90% by mass.

[0017] The method for preparing composite oxides (NAZOs) is not limited. For example, nickel salts, aluminum salts, and zirconium salts can be dissolved in deionized water to prepare aqueous solutions. A predetermined amount of the mixture of these aqueous solutions can be titrated with an alkali source, such as sodium hydroxide or ammonia water, to obtain a precipitate by coprecipitation. After drying the precipitate, the composite oxide (NAZO) can be obtained by calcining it under air. The method of preparing composite oxides by obtaining a precipitate of, for example, hydroxide by coprecipitation, drying the precipitate, and calcining it under air is a well-known technique to those skilled in the art, and the conditions for obtaining the precipitate and the drying and calcining conditions can be those of conventional methods.

[0018] As raw materials, nickel salts, aluminum salts, and zirconium salts can be used, for example, sulfates and nitrates of each element. In addition, platinum group elements M can be used in NAZO. 1 (For example, Ru), metallic element M 2 If an oxide of (at least one selected from the group consisting of Ti, Hf, Ce, Sc, Y, La, Sm, Ca, Mg, Sr, and Ba) is included, then platinum group element M 1 , metallic element M 2A composite can be formed by coprecipitating an aqueous solution of a salt (e.g., nitrate, sulfate, chloride) together with aqueous solutions of nickel salt, aluminum salt, and zirconium salt. NAZO contains platinum group elements M 1 When (for example, Ru) is included, in the active material (reduced state) of the present invention described later, Ru readily alloys with Ni to form Ni-Ru, which has the advantage of improving modification activity, improving carbon deposition resistance during modification, and in the regeneration method of the active material of the present invention described later, the oxidation temperature and reduction temperature can be set lower when the deactivated material is sequentially subjected to oxidation treatment and reduction treatment. 2 is an oxide (M 2 O x )(However, x is a metallic element M 2 It forms a complex oxide in a state that indicates the amount of oxygen corresponding to it, and it is not active itself, but contains platinum group element M 1 This has the effect of further increasing the diversification.

[0019] Since the obtained composite oxide (NAZO) has improved material strength compared to NAO, the composite oxide (NAZO) may be molded into a desired shape by directly granulating it, for example by tort granulation. Alternatively, it may be molded into a desired shape by supporting it on a known carrier such as α-Al2O3. When supporting NAZO on α-Al2O3 (carrier), for example, a primary granule (carrier precursor) can be obtained by tort granulating α-Al2O3 together with water (binder), a desired amount of the aforementioned precipitate (after drying) can be added to the primary granule and further tort granulation can be performed to obtain a secondary granule (carrier precursor), and a carrier on which NAZO is supported can be obtained by calcining the secondary granule. Tort granulation is a method known to those skilled in the art, and the conditions for obtaining NAZO granules or carriers on which NAZO is supported can be followed according to conventional methods.

[0020] Composite oxides (NAZOs) become active materials upon reduction. The reduction conditions are not limited as long as the reduced product of NAZO exhibits activity in applications such as hydrocarbon reforming catalysts, methane catalysts, wood gasification catalysts, and fuel electrode materials for solid oxide fuel cells (SOFCs), but can be explained as follows with reference to Figure 1.

[0021] Figure 1 schematically illustrates the function of a Ni / (γ-Al2O3·ZrO2) system active material (the active material of the present invention, described later) in which at least Ni particles are dispersed on the surface of a composite oxide formed by the combination of γ-Al2O3 and ZrO2, to be regenerated back to the original active material by sequentially performing oxidation and reduction treatments after deactivation. In the schematic diagram of the regeneration cycle, NAZO in the lower left is the composite oxide of the present invention, representing a composite oxide formed by the combination of NiAl2O4, γ-Al2O3, and ZrO2. Spinel oxides are generally represented by the compositional formula AB2O4 (A is a divalent metal, B is a trivalent metal), and among the oxides constituting NAZO, NiAl2O4 is the spinel oxide (crystal structure diagram in the upper left of Figure 1). When NAZO is reduced, Ni dissociates from the NiAl2O4 spinel crystal and precipitates as fine Ni particles on the surface of the composite oxide formed by the combination of γ-Al2O3 and ZrO2, resulting in high dispersion. Figure 1 shows an energy-dispersive X-ray spectrometer (EDX) image of NAZO, which reveals that Ni and Al are distributed in almost the same locations in the spinel oxide. However, after Ni dissociates from the spinel crystal, it is found that Ni is dispersed as Ni particles. Thus, the activity for each of the above applications is exhibited in a highly dispersed state of Ni particles. On the other hand, when Ni particles are oxidized from the state in which they have dissociated from the NiAl2O4 spinel crystal, Ni becomes NiO, and then reacts with γ-Al2O3 to form NiAl2O4 spinel oxide again. This reversible oxidation-reduction behavior is the mechanism of the regeneration method for the active material of the present invention, which will be described later. Details of the oxidation-reduction conditions will be explained in a later section.

[0022] 2. active material The active material of the present invention is a Ni / (γ-Al2O3·ZrO2) system active material characterized by the fact that Ni is dissociated from the NiAl2O4 spinel crystal by reducing the composite oxide (NAZO) of the present invention, and then precipitated as fine Ni particles on the surface of the composite oxide formed by the combination of γ-Al2O3 and ZrO2, resulting in high dispersion, and at least Ni particles are dispersed on the surface of the composite oxide formed by the combination of γ-Al2O3 and ZrO2. Here, the notation "Ni / (γ-Al2O3·ZrO2)" means that Ni particles are dispersed on the surface of the composite oxide of γ-Al2O3 and ZrO2.

[0023] The active material of the present invention exhibits improved material strength compared to conventional reduced NAO, due to the presence of ZrO2 in the composite oxide constituting the active material. As mentioned in the section on the composite oxide (NAZO) of the present invention, the reason for the improved material strength is thought to be that ZrO2 has multiple crystal systems such as monoclinic, tetragonal, and cubic, and stress can be relieved by the change in crystal system when stress is applied to the active material. In particular, the change in crystal system from tetragonal (t-ZrO2) to monoclinic (m-ZrO2) is accompanied by volume expansion, which is thought to have the effect of suppressing the propagation of cracks and other damage caused by stress on the active material and thereby increasing material strength. Furthermore, since the cubic crystal is stable at high temperatures, it is thought to contribute to the improvement in strength in ways other than the aforementioned phase change.

[0024] Furthermore, the active material of the present invention contains ZrO2, and since ZrO2 has oxygen ion conductivity through oxygen vacancies, the ZrO2 in contact with the Ni particles, which are the active sites, acts as a promoter in the catalytic reaction. In particular, it can exhibit superior activity compared to conventional reduced NAO products in applications such as hydrocarbon reforming catalysts, methane catalysts, and wood gasification catalysts. Moreover, it can be used as a fuel electrode material for solid oxide fuel cells (SOFCs).

[0025] The active material of the present invention is not limited to any Ni / (γ-Al2O3·ZrO2) system active material in which at least Ni particles are dispersed on the surface of a composite oxide of γ-Al2O3 and ZrO2, but the application embodiments are also limited to, for example, (1) An active material in which Ni particles are dispersed on the surface of (γ-Al2O3·ZrO2), (2) At least Ni particles and platinum group particles M on the surface of (γ-Al2O3·ZrO2) 1 Dispersed Ni,M 1 / (γ-Al2O3·ZrO2) based active material (however, platinum group particles M 1 (at least one particle selected from the group consisting of Ru particles, Rh particles, Pd particles, Os particles, Ir particles, and Pt particles), (3) In the above (2), further, the metal element M 2 is an oxide (M 2 O x )(However, x is a metallic element M 2 Ni, M compounded in a state that indicates the amount of oxygen corresponding to 1 / (γ-Al2O3·ZrO2·M 2 O x ) System active materials (however, M 2 (at least one selected from the group consisting of Ti, Hf, Ce, Se, Y, La, Sm, Ca, Mg, Sr, and Ba), These are some examples.

[0026] In other words, the term Ni / (γ-Al2O3·ZrO2)-based active materials includes not only the above embodiment (1) in which only Ni particles are dispersed on the (γ-Al2O3·ZrO2) surface, but also platinum group particles M 1 The above embodiment (2) is further dispersed, and in the above embodiment (2), the metal element M 2 is an oxide (M 2 O x )(However, x is a metallic element M 2 This also includes the above embodiment (3) which is compounded in a state that indicates the amount of oxygen corresponding to ).

[0027] As a catalyst for hydrocarbon reforming, for example, in the case of the catalyst in which Ni particles are dispersed on the surface of (γ-Al2O3·ZrO2) as described in (1) above, Ni is dissociated from the spinel structure by reducing NAZO containing the spinel oxide NiAl2O4 at 800-900°C, resulting in a catalyst in which fine Ni particles are highly dispersed on the surface of (γ-Al2O3·ZrO2).

[0028] (2) above, further platinum group particles M 1 If the catalyst is dispersed, then NAZO can be further mixed with platinum group particles M 1 Added raw materials (M 1 In the case of Ru particles, by reducing RNAZO (γ-Al2O3·ZrO2), fine Ni particles and platinum group particles M are formed on the surface. 1 Examples include catalysts in which Ni and platinum group particles M are highly dispersed. In the case of this catalyst as well, reduction releases Ni and platinum group particles M. 1 The spinel structure dissociates, and fine Ni particles and platinum group particles M form on the (γ-Al2O3·ZrO2) surface. 1 It acts as a dispersed catalyst.

[0029] Platinum group particles M 1 The platinum group particle M can be at least one selected from the group consisting of Pt, Ru, Rh, Pd, Os, and Ir, but among these, Ru particles are preferred because they readily alloy with Ni in the reduced state to form Ni-Ru, and are more cost-effective than other platinum group metal elements. 1 Further dispersion of the compound leads to improved modification activity and enhanced resistance to carbon precipitation during modification.

[0030] (3) above, further metal element M 2 is an oxide (M 2 O x )(However, x is a metallic element M 2 If the catalyst is compounded in a state that indicates the amount of oxygen corresponding to the above (2), then the raw material of the catalyst (e.g., RNAZO) is mixed with metal particles M 2 By further adding (γ-Al2O3·ZrO2·M 2 O x) An example is a catalyst in which fine platinum group particles are dispersed on the surface in addition to fine Ni particles. Here, the metal particles M 2 It itself is inactive, but it has the effect of improving strength and further enhancing catalytic activity.

[0031] The active materials (1) to (3) exemplified above can also be used as fuel electrode materials for SOFCs. Generally, the fuel electrode of an SOFC is used in the form of a porous cermet containing one of the active materials (1) to (3) above, Ni, and an electrolyte (such as YSZ). Therefore, when obtaining a fuel electrode, a porous cermet containing one of the raw materials (e.g., NAZO, RNAZO, etc.), NiO, and an electrolyte (such as YSZ) is prepared by a known method, and then the cermet is subjected to a reduction treatment.

[0032] The active material of the present invention, when used, for example, as a catalyst for hydrocarbon reforming or as a fuel electrode material for SOFCs, will experience a decrease in activity due to the aggregation of Ni particles on its surface (γ-Al2O3·ZrO2) when heat is applied to the active material. In the schematic diagram of the regeneration cycle in Figure 1, the "Ni aggregation" in the lower right indicates a state of reduced activity. In the present invention, for example, materials whose catalytic activity or fuel electrode performance has decreased from the start of use (initial) in each of the applications exemplified above are referred to as deactivated materials. However, this includes not only materials that have completely lost their activity, but also materials in which the aggregation of Ni particles has occurred and the activity has decreased compared to the initial state. In the case of a catalyst for hydrocarbon reforming, the deactivated catalyst with reduced activity can be directly applied to the regeneration method of the present invention described later, and in the case of a fuel electrode material for SOFCs, the porous cermet containing the deactivated material can be directly applied to the regeneration method of the present invention.

[0033] 3. Method for regenerating active materials The present invention provides a method for regenerating an active material from a deactivated material, The aforementioned active material is a Ni / (γ-Al2O3·ZrO2) system active material in which at least Ni particles are dispersed on the surface of (γ-Al2O3·ZrO2). The deactivated material is a material in which aggregation of Ni particles occurs on the (γ-Al2O3·ZrO2) surface due to the application of at least heat to the active material. (1) Step 1, which involves oxidizing the deactivated material to produce a spinel oxide having a NiAl2O4 structure. (2) Step 2 to obtain the active material by reducing the spinel oxide, It is characterized by having the following features.

[0034] According to the regeneration method of the present invention having the above characteristics, by using a Ni / (γ-Al2O3·ZrO2) system active material in which at least Ni particles are dispersed on the (γ-Al2O3·ZrO2) surface as a catalyst for hydrocarbon reforming, a fuel electrode material for SOFCs, etc., the material (deactivated material) in which Ni particles have aggregated on the (γ-Al2O3·ZrO2) surface due to at least heat being applied to the active material can be regenerated into an active material by subjecting it to a simple process including oxidation and reduction steps. Oxidation of the deactivated material is preferably carried out at a temperature of 700°C or higher. Furthermore, reduction following oxidation is preferably carried out at a temperature of 500°C or higher for 1 minute or more. The active material of the present invention is highly useful in that it can be regenerated into an active material by a simple process even after deactivation, and is expected to be applied to reformers of maintenance-free distributed power sources.

[0035] Furthermore, the deactivated material to which the regeneration process of the present invention can be applied is a material to which aggregation of Ni particles occurs on the (γ-Al2O3·ZrO2) surface (i.e., deactivated) due to the application of heat to the active material by using an active material [Ni / (γ-Al2O3·ZrO2) system active material] in which at least Ni particles are dispersed on the (γ-Al2O3·ZrO2) surface, for example, as a catalyst for hydrocarbon reforming or a fuel electrode material for SOFCs. Here, regarding the term Ni / (γ-Al2O3·ZrO2) system active material, in addition to the above embodiment (1) in which only Ni particles are dispersed on the (γ-Al2O3·ZrO2) surface, platinum group particles M 1 In the above embodiment (2) in which the particles are further dispersed, platinum group particles M 1 (γ-Al2O3·ZrO2·M 2 O xAs mentioned above, this also includes the configuration described in (3) above, which is distributed on top of the above.

[0036] The method for regenerating the active material of the present invention will be described step by step below.

[0037] Step 1 (Step to oxidize the deactivating material) In step 1, the deactivated material is oxidized to produce a spinel oxide having a NiAl2O4 structure.

[0038] The oxidation process can be any process that produces a spinel oxide having a NiAl2O4 structure by oxidizing the deactivated material, and the oxidation method is not limited, but in the present invention, a method of supplying air as an oxidizing gas in an amount greater than or equal to the amount required for the oxidation of Ni and causing contact oxidation with the deactivated material is preferred. The oxidation process is the process of producing ZnAO from the "Ni aggregation" (deactivated state) in the lower right of the schematic diagram of the regeneration cycle in Figure 1.

[0039] (For use as a catalyst for hydrocarbon reforming) The oxidation process is preferably carried out at a temperature of 800°C or higher, more preferably 800-900°C, and even more preferably 850-900°C, when used as a catalyst for hydrocarbon reforming, in the case of the material described in (1) above. The time required for the oxidation process varies depending on the flow rate of the oxidizing gas, temperature, etc., but when oxidation is carried out by the above method, it is preferably 2 hours or more, and more preferably 2-8 hours.

[0040] On the other hand, in the case of materials (2) or (3) above used as catalysts for hydrocarbon reforming, it is preferable to carry out the process at a temperature of 750°C or higher, more preferably 750 to 900°C, and even more preferably 750 to 800°C. The time required for the oxidation process varies depending on the flow rate of the oxidizing gas, temperature, etc., but when oxidation is carried out by the above method, it is preferable to take 2 hours or more, and more preferably 2 to 8 hours. In other words, platinum group particles M 1 If it contains platinum group particles M 1 The oxidation temperature for the regeneration process can be set lower than when it is not included.

[0041] (For use as fuel electrode material in SOFCs) For fuel electrode material applications, the oxidation process is preferably carried out at a temperature of 750°C or higher, more preferably 750 to 1000°C, and even more preferably 800 to 900°C. The time required for the oxidation process varies depending on the flow rate and temperature of the oxidizing gas, but when oxidized by the above method, it is preferably 1 minute or more, and more preferably 3 to 60 minutes.

[0042] On the other hand, in the case of materials (2) or (3) above for fuel electrode material applications, it is preferable to carry out the process at a temperature of 700°C or higher, more preferably 700 to 900°C, and even more preferably 750 to 850°C. The time required for the oxidation process varies depending on the flow rate of the oxidizing gas, temperature, etc., but when oxidized by the above method, it is preferable to 1 minute or more, and more preferably 3 to 60 minutes. In other words, platinum group particles M 1 If it contains platinum group particles M 1 The oxidation temperature for the regeneration process can be set lower than when it is not included.

[0043] In the oxidation process described above, the aggregated Ni particles first become nickel oxide, and then react with γ-Al2O3 to become spinel oxide again, having a NiAl2O4 structure. In the case of materials (2) and (3) above, platinum group particles M 1 It is presumed that this substance is not incorporated into the structure of the spinel oxide but remains on the surface of the spinel oxide.

[0044] Step 2 (Step to obtain the active material by reduction) In step 2, the spinel oxide produced in step 1 is reduced to regenerate the active material [Ni / (γ-Al2O3·ZrO2) system active material].

[0045] The reduction process involves using the spinel oxide (platinum group particles M) produced in step 1. 1 The process is not limited to any step that regenerates the active material (Ni / (γ-Al2O3·ZrO2) system active material) to its pre-deactivation state by reducing the spinel oxide (including cases where it remains on the spinel oxide surface), but in this invention, hydrogen is used as the reducing gas at a rate of 10 ml·min. -1A method of supplying at the above flow rate to regenerate the material into an active state is preferred. Note that, even without using hydrogen added externally as a reducing gas, self-reformation and reduction by hydrocarbon reforming gas is possible in the case of hydrocarbon reforming catalyst applications. Similarly, in SOFC fuel electrode material applications, internal reformation and reduction by hydrocarbon reforming is also possible. In this case, reduction is possible when the hydrogen concentration in the reforming gas is 20 mol% or higher, and ideally, a hydrogen concentration of 40 mol% or higher is preferred. The reduction step is the process of regenerating NAZO into a Ni / (γ-Al2O3·ZrO2) system active material by reduction, starting from the NAZO in the lower left of the schematic diagram of the regeneration cycle in Figure 1.

[0046] (For use as a catalyst for hydrocarbon reforming) The reduction process is preferably carried out at a temperature of 800°C or higher, more preferably between 800°C and 950°C, and even more preferably between 850°C and 950°C, when used as a catalyst for hydrocarbon reforming, in the case of the material described in (1) above. The time required for the reduction process varies depending on the flow rate and temperature of the reducing gas, but when reduction is carried out by the above method, it is preferably 1 minute or more.

[0047] On the other hand, in the case of materials (2) or (3) above used as catalysts for hydrocarbon reforming, it is preferable to carry out the process at a temperature of 700°C or higher, more preferably 700 to 850°C, and even more preferably 750 to 800°C. The time required for the reduction process varies depending on the flow rate of the reducing gas, temperature, etc., but when reduction is carried out by the above method, it is preferable to take 1 minute or more. In other words, platinum group particles M 1 If it contains platinum group particles M 1 The reduction temperature for the regeneration process can be set lower than when platinum group particles M are not included. This is because platinum group particles M 1 If it contains platinum group particles M 1 The hydrogen atoms adsorbed on top dissociate to produce atomic hydrogen, which is a platinum group particle M 1 It is presumed that increasing the reduction frequency of Ni in its vicinity will increase the reduction rate and lower the reduction temperature.

[0048] (For use as fuel electrode material in SOFCs) The reduction process is preferably carried out at a temperature of 550°C or higher, more preferably 650 to 1000°C, and even more preferably 700 to 900°C, when used as a fuel electrode material. The time required for the reduction process varies depending on the flow rate and temperature of the reducing gas, but when reduction is performed by the above method, it is preferably 1 minute or more.

[0049] On the other hand, for fuel electrode material applications, the material described in (2) or (3) above is preferably carried out at a temperature of 500°C or higher, more preferably 600 to 950°C, and even more preferably 650 to 850°C. The time required for the reduction process varies depending on the flow rate and temperature of the reducing gas, but when reduction is carried out by the above method, it is preferable to do so for 1 minute or more. In other words, platinum group particles M 1 If it contains platinum group particles M 1 The reduction temperature for the regeneration process can be set lower than when it is not included. [Examples]

[0050] The present invention will be specifically described below with reference to preparation examples and test examples. However, the present invention is not limited to these illustrative descriptions.

[0051] Preparation Examples 1-6 (Preparation of NAO complex oxide precursors and NAZO complex oxide precursors) (Preparation Example 1: Comparative Product) 1:2NAO (Molar ratio: Ni:Al = 1:2) (Preparation Example 2: Comparative Product) 1:10 NAO (Molar ratio: Ni:Al = 1:10) (Preparation Example 3: Comparative Product) 1:20 NAO (Molar ratio: Ni:Al = 1:20) (Preparation Example 4: Actual Product) 1:2:3 NAZO (Molar ratio is Ni:Al:Zr = 1:2:3) (Preparation Example 5: Actual Product) 1:3:3 NAZO (Molar ratio is Ni:Al:Zr = 1:3:3) (Preparation Example 6: Actual Product) 1:5:5 NAZO (Molar ratio is Ni:Al:Zr = 1:5:5) Each of the composite oxide precursors was prepared.

[0052] The preparation methods for each precursor are as follows.

[0053] αg of nickel sulfate hexahydrate (NiSO4·6H2O), βg of aluminum sulfate octahydrate (Al2(SO4)3·H2O), and γg of zirconium sulfate tetrahydrate (Zr(SO4)2·4H2O) were dissolved in Xg of water while heating and stirring. This yielded a NiAlZr sulfate mixed solution. A 25% sodium hydroxide solution was prepared as an alkali source for producing the hydroxide. The NiAlZr sulfate mixed solution was added dropwise to a beaker containing 300g of water over 2 hours using a pump. During the addition of the mixed solution, the 25% sodium hydroxide solution was added dropwise using a pump to maintain the pH of the beaker solution at 7. The reaction was carried out at a temperature of 90°C with stirring at 800 rpm. After the addition was complete, the mixture was aged for 1 hour while maintaining the temperature and stirring. The mixture was filtered and washed, and dried at 110°C for 12 hours to prepare a Yg complex oxide precursor (before calcination). The values ​​of α, β, γ, X, and Y are as shown in Table 1 below. In Preparation Examples 1 to 6, the target product was a composite oxide precursor. The composite oxide precursor was separately calcined at 1000°C for 5 hours under air to obtain each NAO composite oxide or each NAZO composite oxide.

[0054] [Table 1]

[0055] Preparation Examples 7-9 (Preparation of NAZO Composite Oxide Supports) (Preparation Example 7: Actual Product) 1:2:3NAZO / α-Al2O3 (Preparation Example 8: Actual Product) 1:3:3NAZO / α-Al2O3 (Preparation Example 9: Actual Product) 1:5:5NAZO / α-Al2O3 Each of the NAZO composite oxide supports was prepared. Note that the notation "1:2:3NAZO / α-Al2O3" refers to a support in which 1:2:3NAZO is supported on the α-Al2O3 support.

[0056] The preparation methods for each NAZO composite oxide support are as follows.

[0057] Granulation was performed by adding water (binder) to α-Al2O3 while rolling the α-Al2O3, in a mass ratio of α-Al2O3:water = 9:1. Primary granules (carrier precursors) were obtained by granulation at room temperature, a rotation speed of approximately 70 rpm, and for more than 1 hour. Approximately 2% by mass of a composite oxide precursor was added to the obtained primary granules for each preparation example, and rolling granulation was performed under the same conditions as above to obtain secondary granules (support precursors). Each NAZO composite oxide support was prepared by calcining the obtained secondary granules at 1000°C for 5 hours under air. The particle size of each NAZO composite oxide support was approximately 3 to 10 mm.

[0058] Test Example 1 (1:5:5NAZO / α-Al 2 O 3 (Appearance before and after reduction, etc.) Figure 2 shows the appearance of 1:5:5NAZO / α-Al2O3 obtained in Preparation Example 9 before and after reduction, and the microstructure observed before and after reduction using an energy-dispersive X-ray spectrometer (EDX) (HITACHI, HD-2700, EDAX Genesis XM2) (EDX mapping results for Ni and Al).

[0059] Figure 2 shows the NAZO / α-Al2O3 before use, which is the NAZO composite oxide support before reduction. The NAZO / α-Al2O3 after use (reduction) is the reduced product (active material) obtained by reducing the NAZO composite oxide support with H2 at 850°C for 2 hours. In the pre-reduction photograph, the surface of the support is white, but in the reduced product, the surface of the support has turned gray due to the precipitation and dispersion of Ni particles. In addition, EDX mapping results showed that the distribution of Ni and Al was similar before reduction, but in the reduced product, the presence of Ni particles ranging from 5 to 20 nm was confirmed due to the precipitation and dispersion of Ni particles. Figure 2 also includes a photograph showing the contents after breaking the reduced product, and it was confirmed that the surface portion of the support (NAZO composite oxide) was particularly hard when broken. This is thought to be due to the presence of ZrO2 in the NAZO composite oxide.

[0060] Test Example 2 (Evaluation of repeated regeneration function and crystal structure analysis of 1:5:5 NAZO composite oxide) The reduction properties of 1:5:5NAZO (composite oxide) were evaluated by sequential temperature-progressive reduction (TPR) using H2 as the reducing agent. 4.0g of 1:5:5NAZO was used, and the supply flow rate of the reducing gas H2 was 100ml·min. -1 The temperature range is from room temperature to 850°C, at 10°C / min. -1 TPR was performed under the specified heating rate conditions. After removing moisture from the outlet gas using a desiccant, the gas flow rate was measured and the H2 consumption characteristics were analyzed.

[0061] In the above TPR (Total Pressure Refining) procedure, after the temperature reached 850°C, the N2 substitution was performed while maintaining the temperature, and then air was supplied for 2 hours to oxidize the 1:5:5 NAZO reduction product. This reduction-oxidation cycle using TPR was repeated four times, and the TPR characteristics of each cycle were analyzed.

[0062] Furthermore, the 1:5:5NAZO reduced product, after completing three reduction-oxidation cycles and up to the fourth reduction, was oxidized in an air atmosphere for 2 hours at temperatures of 350°C, 500°C, 600°C, 700°C, 780°C, and 850°C. The 1:5:5NAZO oxidized at each of these temperatures was analyzed using an X-ray diffractometer (XRD, Rigaku, SmartLab) with a CuKα source, output of 40kV, 150mA, and angular velocity of 10°·min. -1 The crystal structure was investigated under these conditions.

[0063] The 1:5:5 NAZO reduced product, which underwent H2 reduction (4th time) at 850°C for 2 hours, and the 1:5:5 NAZO oxide, which underwent a subsequent 5th oxidation, were observed using a scanning transmission electron microscope (STEM) and an energy-dispersive X-ray spectrometer (EDX) (HITACHI, HD-2700, EDAX Genesis XM2) to investigate their fine structure.

[0064] <Results and Discussion> (Evaluation of 1:5:5NAZO characteristics) Figure 3 shows the repeatable TPR characteristics of 1:5:5NAZO.

[0065] As shown in Figure 3, in 1:5:5NAZO, the peak at 750-800°C indicates the reduction reaction of NiAl2O4 spinel oxide (NiAl2O4 + H2 → Ni + Al2O3 + H2O), and all peaks originating from the reduction of NiAl2O4 were confirmed even after repeated oxidation and reduction. This suggests that when Ni / (γ-Al2O3·ZrO2), which is generated by the precipitation of fine Ni particles from the composite oxide (NiAl2O4·γ-Al2O3·ZrO2) upon reduction, is oxidized back to (NiAl2O4·γ-Al2O3·ZrO2).

[0066] Furthermore, it was confirmed that the reduction peak area of ​​NiAl2O4 remained stable even after repeated oxidation-reduction cycles in 1:5:5NAZO. This indicates that the oxidation-reduction cycle of 1:5:5NAZO is stable.

[0067] Furthermore, when the 1:5:5NAZO reduced product, after completing the fourth reduction, was oxidized in an air atmosphere for 2 hours at temperatures of 350°C, 500°C, 600°C, 700°C, 780°C, and 850°C, the 1:5:5NAZO particles were gray at 350°C because the dispersion of Ni particles remained. However, as the oxidation temperature increased, the dispersed Ni particles returned to (NiAl2O4·γ-Al2O3·ZrO2), and at 850°C, the 1:5:5NAZO particles changed to light blue.

[0068] (XRD pattern of 1:5:5NAZO) Figures 4 and 5 show the XRD patterns of 1:5:5 NAZO obtained after the fourth oxidation in the oxidation-reduction cycle at 350°C, 500°C, 600°C, 700°C, 780°C, and 850°C.

[0069] As shown in Figure 4, an oxidation reaction of Ni(N, 44.5°) occurred above 450°C, and a reaction between NiO(NO, 43°) and γ-Al2O3(A, 37.5°) occurred above 700°C, causing a decrease in the corresponding peak heights. At 850°C, the formation of NiAl2O4(S, 19.2°) was confirmed by the appearance of a peak. This confirmed the regeneration function of 1:5:5NAZO through oxidation and reduction.

[0070] Figure 5 confirms that the ZrO2 constituting 1:5:5NAZO can be represented by two crystal systems: monoclinic (27.2°) and tetragonal (33° and 35.4°).

[0071] (STEM and EDX images of 1:5:5 NAZO after the 4th reduction and 4th oxidation) Figure 6 shows STEM and EDX images of the 1:5:5NAZO reduced product after reduction at 850°C for 2 hours. On the surface of the reduced 1:5:5NAZO, Ni and Al were not necessarily present in the same location, and fine Ni particles of approximately 5-10 nm were observed, confirming high dispersibility.

[0072] Figure 7 shows STEM and EDX images of 1:5:5NAZO oxide. In contrast to Figure 6, Ni and Al are distributed in almost the same locations on the surface of 1:5:5NAZO, suggesting that when Ni / (γ-Al2O3·ZrO2) is oxidized, it returns to (NiAl2O4·γ-Al2O3·ZrO2).

[0073] Test Example 3 (1:2:3NAZO / α-Al 2 O 3 and 1:3:3NAZO / α-Al 2 O 3 (Evaluation of strength characteristics) The strength properties of the 1:2:3NAZO / α-Al2O3 support and the 1:3:3NAZO / α-Al2O3 support were evaluated in comparison with the strength properties of Al2O3 (support) granules and 1:2NAO composite oxide granules. The size of each support and each granule was approximately the same. A strength test was conducted in which one granule was sandwiched between two ceramic plates, and one plate was pressed down while keeping the plates parallel to each other, measuring the maximum force that could be applied before the granule collapsed.

[0074] The results of the strength test (compression test) are shown in Figure 8. From Figure 8, it was confirmed that the crush strength of the 1:2:3 NAZO / α-Al2O3 support and the 1:3:3 NAZO / α-Al2O3 support are more than five times greater than that of the Al2O3 (carrier) granules and the 1:2 NAO granules. This means that the NAZO composite oxide has higher material strength than conventional NAO composite oxides and Al2O3 (carrier) due to the presence of ZrO2.

[0075] Test Example 4 (Evaluation of LNG reforming activity of NAZO in comparison with NAO) As composite oxides, 1.0 g each of 1:10NAO, 1:20NAO, 1:5:5NAZO, 1:3:3NAZO, and 1:2:3NAZO was prepared. Each composite oxide was reduced by supplying H2 gas for 30 minutes or more to serve as a methane reforming catalyst.

[0076] Each methane reforming catalyst is packed into a tubular furnace and heated to 850°C. The volume ratio is LNG:water vapor = 1:2.9, and the space velocity SV = 6700 Lkg is based on the mass of each methane reforming catalyst. -1 h -1 The LNG reforming activity was investigated under the following conditions. Specifically, the LNG reforming activity was investigated at a predetermined temperature of 850°C to 350°C, with an LNG flow rate of 111 ml / min, a water vapor flow rate of 0.26 g / min, and an N2 flow rate of 150 ml / min.

[0077] Figure 9 shows the Arrhenius plots of the LNG reforming rates for each methane reforming catalyst. From Figure 9, it was confirmed that NAZO has LNG reforming activity equal to or greater than NAO when the amount of Ni is the same. Also from Figure 9, it was confirmed that although 1:5:5 NAZO and 1:20 NAO have the same amount of the active metal Ni, 1:5:5 NAZO has higher methane reforming activity than 1:20 NAO. This result suggests that NAZO has the effect of promoting oxygen transport and reaction in methane reforming (promoter effect) due to the high oxygen ion conductivity of ZrO2.

[0078] Test Example 5 (Evaluation of NAZO's wood gasification activity) RNAO and 1:3:3NAZO were prepared as composite oxides. Each composite oxide was reduced by supplying H2 gas for 30 minutes or more to form a wood gasification catalyst. In addition, Pt / γ-Al2O3 was prepared as a conventional wood gasification catalyst (Pt / γ-Al2O3 is a Pt-supported catalyst on a γ-Al2O3 support).

[0079] Each wood gasification catalyst was packed into a tubular furnace so that the amount of active metal was equal. After heating to 850°C, the wood gasification activity was investigated under conditions where cypress chips were used as the raw material and air was used as the gasifying agent, with the temperature controlled by external heating. Specifically, the temperature was set to a predetermined range of 850°C to 350°C, with an air flow rate of 180 ml / min and biomass of 6 gh. -1 We investigated the wood gasification activity by gasifying cypress chips under the specified conditions and analyzing the composition of the resulting gas.

[0080] Figure 10 shows the Arrhenius plots of the gasification (C1 conversion) rates for each wood gasification catalyst and without a catalyst. From Figure 10, it was confirmed that NAZO has equivalent wood gasification activity (tar modifying activity) to NAO.

Claims

1. NiAl ２ O ４ and γ-Al ２ O ３ and ZrO ２ A composite oxide formed by the combination of these, which becomes an active material upon reduction. The aforementioned composite oxide has a molar ratio of Ni, Al, and Zr in the range of 1 or more: 1 to 40: greater than 0 to 40, The active material is at least one selected from the group consisting of hydrocarbon reforming catalysts, methane catalysts, wood gasification catalysts, and fuel electrode materials for solid oxide fuel cells (SOFCs). A composite oxide characterized by the following features.

2. γ-Al ２ O ３ and ZrO ２ This is an active material in which at least Ni particles are dispersed on the surface of a composite oxide formed by the combination of the two. The active material has a composition molar ratio of Ni, Al, and Zr in the range of 1 or more: 1 to 40: greater than 0 to 40, The active material is at least one selected from the group consisting of hydrocarbon reforming catalysts, methane catalysts, wood gasification catalysts, and fuel electrode materials for solid oxide fuel cells (SOFCs). characterized Ni / (γ - Al ２ O ３ ·ZrO ２ ) - based active material

3. Furthermore, platinum group particles M １ Ni, M are distributed １ / (γ-Al ２ O ３ ・ZrO ２ The active material according to claim 2, which is a ) system active material.

4. The platinum group particles M １ The active material according to claim 3, wherein the active material is Ru particles.

5. A method for regenerating active material from deactivated material, The active material is γ-Al ２ O ３ and ZrO ２ Ni / (γ-Al) is a composite oxide in which at least Ni particles are dispersed on the surface of the composite oxide formed by the combination of Ni and (γ-Al ２ O ３ ・ZrO ２ ) is a system-based active material, The active material has a composition molar ratio of Ni, Al, and Zr in the range of 1 or more: 1 to 40: greater than 0 to 40, The active material is at least one selected from the group consisting of hydrocarbon reforming catalysts, methane catalysts, wood gasification catalysts, and fuel electrode materials for solid oxide fuel cells (SOFCs). The deactivating material is activated by the application of at least heat to the active material, thereby removing the γ-Al ２ O ３ ・ZrO ２ This material has aggregates of Ni particles on its surface. (1) By oxidizing the deactivating material, NiAl ２ O ４ Step 1 for producing a spinel oxide having a structure, (2) Step 2, which involves reducing the spinel oxide to obtain the active material. A method for regenerating an active material, characterized by having the following features.

6. The regeneration method according to claim 5, wherein the oxidation is carried out at a temperature of 700°C or higher.

7. The regeneration method according to claim 5 or 6, wherein the reduction is carried out under conditions of 500°C or higher and for 1 minute or more.

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