JP7255503B2 - Reforming catalyst and method for producing the same - Google Patents

Description

The present invention relates to a reforming catalyst and a method for producing the same.

Conventionally, reforming catalysts have been used to steam reform fuel gases such as hydrocarbons and oxygen-containing hydrocarbons. For example, in the field of vehicles such as automobiles, the steam contained in the exhaust gas is used to steam reform the fuel gas. A reforming catalyst may be placed in the

Conventional reforming catalysts tend to deteriorate in catalytic performance due to the sulfur component contained in the fuel gas. Therefore, a sulfur component adsorbent that selectively adsorbs sulfur components is arranged upstream of the reforming catalyst to protect the reforming catalyst arranged downstream from the sulfur components. Also known is a technique of regenerating a reforming catalyst by heating the reforming catalyst poisoned with sulfur to release the sulfur component.

In addition, in the preceding Patent Document 1, the general formula: L _1-x Ba _x CoO _y (wherein the L component is a lanthanide (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho , Er, Tm, Yb, and Lu) and contains a material satisfying 0<x≦1, 2≦y≦4).

Japanese Patent Publication No. 2009-501078

The technique using the sulfur component adsorbent described above cannot protect the reforming catalyst when the sulfur component exceeds the amount that can be adsorbed. In addition, this technique requires a large amount of sulfur component adsorbent in order to sufficiently suppress the deterioration of the catalytic performance of the reforming catalyst. On the other hand, the technique of regenerating the reforming catalyst deteriorates fuel efficiency because reforming cannot be performed during the regeneration process. From the above, there is a demand for a reforming catalyst whose catalytic performance is less likely to deteriorate due to the sulfur component contained in the fuel gas.

The present invention has been made in view of such problems, and an object thereof is to provide a reforming catalyst whose catalytic performance is less likely to deteriorate due to sulfur components contained in fuel gas, and a method for producing the same.

One aspect of the present invention is
General formula: (BaO _1-a (CO ₃ ) _a )YM1 _4-c M2 _c O _6-b (where 0≦a≦1, 0≦b≦4.5, 0≦c<4) including a composite powder (10) and a catalyst metal (11) ,
The catalyst metal contains at least one metal selected from the group consisting of Rh, Pt, Pd, Ru, Ir, Au, Ag, Os, Ni, Co, Fe, and Cu, or an alloy of these metals. It is in the reforming catalyst (1).
However, M1 and M2 are different transition metals selected from the group consisting of Co, V, Cr, Mn, Fe, Ni, Cu, and Zn.

Another aspect of the invention is
A method for producing a reforming catalyst comprising a composite powder and a catalyst metal, comprising:
a preparation step of preparing at least the base particle powder represented by the general formula: BaYM1 _4-c M2 _c O _7+σ (where 0≦c<4, 0<σ≦1.5);
By heat-treating at least the base particle powder in a reducing gas containing CO ₂ or in a reducing gas containing no CO ₂ , the general formula: (BaO _1-a (CO ₃ ) _a )YM1 _4-c M2 _c O _6-b (where 0≦a≦1, 0≦b≦4.5, 0≦c<4) to produce the composite powder;
and
The catalyst metal contains at least one metal selected from the group consisting of Rh, Pt, Pd, Ru, Ir, Au, Ag, Os, Ni, Co, Fe, and Cu, or an alloy of these metals. A method for producing a reforming catalyst.
However, M1 and M2 are different transition metals selected from the group consisting of Co, V, Cr, Mn, Fe, Ni, Cu, and Zn.

The reforming catalyst contains the composite powder. Therefore, the reforming catalyst is less likely to deteriorate in catalytic performance due to the sulfur component contained in the fuel gas.

The method for producing the reforming catalyst includes the steps described above. Therefore, according to the method for manufacturing the reforming catalyst, it is possible to suitably manufacture the reforming catalyst whose catalytic performance is less likely to deteriorate due to the sulfur component contained in the fuel gas.

It should be noted that the symbols in parentheses described in the claims and the means for solving the problems indicate the corresponding relationship with the specific means described in the embodiments described later, and limit the technical scope of the present invention. not a thing

FIG. 1 is a diagram schematically showing an example of a reforming catalyst according to Embodiment 1. FIG. FIG. 2 is a diagram schematically showing an example of the microstructure of the reforming catalyst according to Embodiment 1. FIG. FIG. 3 is a diagram schematically showing an example of a HAADF-STEM image of a reforming catalyst obtained by a high-resolution scanning transmission electron microscope (HR-STEM).

The reforming catalyst of the present embodiment has the general formula: (BaO _1-a (CO ₃ ) _a )YM1 _4-c M2 _c O _6-b (where 0≦a≦1, 0≦b≦4.5, It contains a composite powder (10) represented by 0≦c<4). However, M1 and M2 are different transition metals selected from the group consisting of Co, V, Cr, Mn, Fe, Ni, Cu, and Zn. Therefore, the reforming catalyst of the present embodiment is less likely to deteriorate in catalytic performance due to the sulfur component contained in the fuel gas.

This is because the composite powder in the reforming catalyst of the present embodiment occludes toxic sulfur components (S, S ²⁻ , SO, SO ₂ , SO ₃ , SO ₄ ²⁻ , etc.) contained in the fuel gas. In addition, the toxic sulfur component is reacted with hydrogen and carbon monoxide generated by steam reforming of the fuel gas to produce a sulfur compound gas with a low degree of influence on catalyst deterioration (detoxification of toxic sulfur component It is thought that this is due to the fact that it is possible to Therefore, according to the reforming catalyst of the present embodiment, the catalytic function can be exhibited for a long time without using a sulfur component adsorbent. Further, according to the reforming catalyst of the present embodiment, control such as regeneration processing becomes unnecessary, and fuel efficiency can be easily improved. Hereinafter, the reforming catalyst of this embodiment will be described in detail with reference to the drawings.

(Embodiment 1)
A reforming catalyst of Embodiment 1 will be described with reference to FIG. As illustrated in FIG. 1 , the reforming catalyst 1 of this embodiment contains composite powder 10 . The composite powder 10 has the general formula: (BaO _1-a (CO ₃ ) _a ) YM1 _4-c M2 _c O _6-b (where 0 ≤ a ≤ 1, 0 ≤ b ≤ 4.5, 0 ≤ c <4). However, M1 and M2 are Co (cobalt), V (vanadium), Cr (chromium), Mn (manganese), Fe (iron), Ni (nickel), Cu (copper), and , Zn (zinc).

In the general formula of the composite powder 10, a is a sulfur compound gas SG that makes it easy to suppress the change in the fuel reforming rate over time and has an excessive adsorption force for the toxic sulfur component Sc and has a low degree of influence on catalyst deterioration. From the viewpoint of improving the activity of the denaturing reaction, it is preferably greater than 0, more preferably 0.1 or more, still more preferably 0.2 or more, still more preferably 0.3 or more, and even more Preferably, it can be 0.4 or more. In addition, a is preferably less than 1 from the viewpoint of suppressing the decrease in the frequency of reaction to transform into sulfur compound gas SG, which has a low degree of influence on catalyst deterioration, due to an excessively low adsorption force of the toxic sulfur component Sc. , more preferably 0.9 or less, still more preferably 0.8 or less, still more preferably 0.7 or less, and even more preferably 0.6 or less.

In the general formula of the composite powder 10, b is the activity of the reaction that transforms the toxic sulfur component Sc into a sulfur compound gas SG that has a low degree of influence on catalyst deterioration, which makes it easier to suppress the change in the fuel reforming rate over time. From the viewpoint of improving the be able to. In addition, b is preferably less than 4.5, more preferably less than It can be 4 or less, more preferably 3.5 or less, and even more preferably 3 or less.

In the general formula of composite powder 10, M2 is an element substituted for M1. When c=0, M1 is not replaced by M2. When 0<c<4, part of M1 is replaced by M2. In this case, c is preferably 0.3 or more, more preferably 0.6 or more, and still more preferably 0.8 or more from the viewpoint of enhancing the shape retention ability in a fuel reforming environment. can be done. In this case, c is preferably 2 or less, more preferably 1.5 or less, and still more preferably 1.2 or less from the viewpoint of increasing the shape retention ability in a fuel reforming environment. can be done.

In the general formula of the composite powder 10, preferably M1 can be Co. That is, the composite powder 10 has the general formula: (BaO _1-a (CO ₃ ) _a )YCo _4-c M2 _c O _6-b (where 0≦a≦1, 0≦b≦4.5, 0 ≤c<4). However, M2 is a transition metal selected from the group consisting of V, Cr, Mn, Fe, Ni, Cu, and Zn. According to this configuration, it is possible to reliably suppress the deterioration of the catalyst performance due to the sulfur component Sc contained in the fuel gas FG.

In the general formula of the composite powder 10, more preferably, M1 is Co and c=0. That is, the composite powder 10 has a structure represented by the general formula: (BaO _1-a (CO ₃ ) _a )YCo ₄ O _6-b (where 0≦a≦1, 0≦b≦4.5) can be According to this configuration, it is possible to more reliably suppress the deterioration of the catalyst performance due to the sulfur component Sc contained in the fuel gas FG.

Composite powder 10 includes base particles 101, BaCO ₃ fine particles 102 adhering to the surfaces of base particles 101, and at least M1 fine particles and M2 fine particles adhering to the surfaces of base particles 101, as illustrated in FIG. and a transition metal fine particle 103 composed of one. According to this configuration, it is possible to reliably suppress the deterioration of the catalyst performance due to the sulfur component Sc contained in the fuel gas FG. This is because the BaCO ₃ fine particles 102 and the transition metal fine particles 103 are highly dispersed and arranged on the surface of the base particle 101, and the adsorption of the sulfur component Sc, which is considered to be mainly contributed by the BaCO ₃ fine particles 102, and the Generation of sulfur compound gas SG which has a low degree of influence on catalyst deterioration due to reaction with H ₂ and CO gas (generated in the atmosphere by steam reforming) in reformed gas RG, which is considered to contribute to transition metal fine particles 103 is assumed to occur with high efficiency in a desired temperature range (for example, 300° C. or higher and 900° C. or lower).

Specifically, the base particle 101 can have a structure represented by the general formula: BaYM1 _4-c M2 _c O _7+σ (0≦c<4, 0<σ≦1.5). M1, M2 are each a transition metal selected from the group consisting of Co, V, Cr, Mn, Fe, Ni, Cu, and Zn, different from each other. Note that Y (yttrium) in the base particles 101 is difficult to be reduced by a reducing gas (details will be described later) when producing the composite powder 10, and maintains the state of an oxide, allowing the BaCO ₃ fine particles 102 and the transition metal It is suitable for holding fine particles 103 .

In the general formula of the base particle 101, M2 is a substituting element for M1. When c=0, M1 is not replaced by M2. When c is 0<c<4, part of M1 is replaced with M2. In this case, c is preferably 0.3 or more, more preferably 0.6 or more, and still more preferably 0.8 or more from the viewpoint of enhancing the shape retention ability in a fuel reforming environment. can be done. In this case, c is preferably 2 or less, more preferably 1.5 or less, and still more preferably 1.2 or less from the viewpoint of increasing the shape retention ability in a fuel reforming environment. can be done.

In the general formula of the base particles 101, σ is preferably greater than 0, more preferably 0.1 or more, from the viewpoint of improving the fuel reforming rate. Also, σ is preferably less than 1.5, more preferably 1 or less, still more preferably 0.5 or less, still more preferably 0.2 or less, from the viewpoint of improving the fuel reforming rate. can be

In the general formula of the base particle 101, preferably M1 can be Co. In other words, the base particles 101 can have a structure represented by the general formula: BaYCo _4-c M2 _c O _7+σ (0≦c<4, 0<σ≦1.5). However, M2 is a transition metal selected from the group consisting of V, Cr, Mn, Fe, Ni, Cu, and Zn. According to this configuration, it is possible to reliably suppress the deterioration of the catalyst performance due to the sulfur component Sc contained in the fuel gas FG.

In the general formula of the base particle 101, more preferably, M1 is Co and c=0. In other words, the base particle 101 can have a structure represented by the general formula: BaYCo ₄ O _{7 +σ} (where 0<σ≦1.5). According to this configuration, it is possible to more reliably suppress the deterioration of the catalyst performance due to the sulfur component Sc contained in the fuel gas FG. This is because the presence of the transition metal fine particles 103 composed of Co fine particles around the BaCO ₃ fine particles 102 on the surface of the base particle 101 causes the sulfur component Sc adsorbed on the BaCO ₃ fine particles 102 and the water vapor of the fuel gas FG to It is believed that this is because the generation of the sulfur compound gas SG, which has a low degree of influence on the deterioration of the catalyst due to the reaction with the H ₂ and CO gas in the atmosphere generated by the reforming, is promoted.

Both the composite powder 10 and the base particles 101 are oxides. The amount of oxygen in the general formula of each oxide can be identified by inert gas fusion-infrared absorption method. Specifically, when a graphite crucible is pressed between the upper and lower electrodes of an extraction furnace in a helium gas atmosphere as an inert gas and a large current is applied, the temperature of the crucible itself rises rapidly due to Joule heat. An oxide sample is put into a graphite crucible that has been degassed once in a high temperature state, and the oxide sample is thermally decomposed in a high temperature state again. Oxygen contained in the oxide sample reacts with carbon in the graphite crucible to form carbon monoxide (CO) gas, and the generated CO gas is transported to a carrier gas and detected by a non-dispersive infrared detector. The amount of oxygen in the oxide sample can be identified from the amount of CO detected.

The atomic number ratio of each metal element in the general formula of the composite powder 10 and the base particle 101 can be measured by high frequency inductively coupled plasma atomic emission spectrometry (ICP-AES).

When the composite powder 10 contains the base particles 101, the _BaCO3 fine particles 102, and the transition metal fine particles 103, the average particle diameter of the _BaCO3 fine particles 102 is 10 nm or more and 50 nm or less, and the average particle diameter of the transition metal fine particles 103 is 0.5 nm or more. It can be 30 nm or less. According to this configuration, it is possible to more reliably suppress deterioration of the catalyst performance over time due to the sulfur component Sc contained in the fuel gas FG. The average particle diameter of the BaCO ₃ fine particles 102 is preferably 10 nm or more, more preferably 15 nm or more, and still more preferably 20 nm or more, from the viewpoint of enhancing the shape retention ability in a fuel reforming environment. . The average particle diameter of the BaCO ₃ fine particles 102 is preferably 45 nm or less, more preferably 40 nm or less, and even more preferably 30 nm or less, from the viewpoint of improving the fuel reforming rate. In addition, the average particle diameter of the transition metal fine particles 103 is preferably 1 nm or more, more preferably 2 nm or more, and still more preferably 4 nm or more, from the viewpoint of increasing the shape retention ability in a fuel reforming environment. can be done. From the viewpoint of improving the fuel reforming rate, the transition metal microparticles 103 are preferably 25 nm or less, more preferably 20 nm or less, and still more preferably 10 nm or less.

The average particle size can be measured using a high resolution scanning transmission electron microscope (HR-STEM) and an energy dispersive X-ray spectrometer (EDS). Specifically, using a high-resolution scanning transmission electron microscope, an observation image (HAADF-STEM image) of the reforming catalyst 1 as shown in FIG. 3 is obtained. Next, EDS analysis is performed on each particle on the surface of the base particle 101 in the obtained observed image. Particles from which elements Ba and C are detected are determined to be BaCO ₃ fine particles 102 . Particles in which a transition metal element is detected are determined to be transition metal fine particles 103 . Next, each particle size is calculated from the scale in the observed image. Next, the arithmetic average value of the particle diameters of the 30 BaCO ₃ fine particles 102 in the observed image is taken as the average particle diameter of the BaCO ₃ fine particles 102 . Also, the arithmetic average value of the particle diameters of the 30 transition metal fine particles 103 in the observed image is taken as the average particle diameter of the transition metal fine particles 103 .

When composite powder 10 contains base particles 101, BaCO ₃ fine particles 102, and transition metal fine particles 103, the amount of BaCO ₃ fine particles 102 attached to the surface of base particles 101 is determined by placing a sample of composite powder 10 in an inert gas atmosphere. can be identified from the amount of carbon dioxide released at 400° C. or higher and 1500° C. or lower, which is the decomposition temperature range of barium carbonate.

The reforming catalyst 1 contains catalyst metal 11 in addition to composite powder 10 . In this case, the composite powder 10 can function as a carrier that supports the catalytic metal 11 . Further, the reforming catalyst 1 can include a catalyst metal 11 and a carrier 12 supporting the catalyst metal 11, as illustrated in FIG. According to this configuration, steam reforming of the fuel gas FG and detoxification of the sulfur component Sc (conversion into a sulfur compound gas SG having a low degree of influence on catalyst deterioration) can be ensured. In addition, according to this configuration, compared to the case where the composite powder 10 is used as a carrier for the catalytic metal 11, the degree of freedom in carrier selection is increased, so that the electronic state of the catalytic metal 11 can be made more suitable for steam reforming. There are also advantages. It should be noted that the above-mentioned carrying includes the case where the catalyst metal 11 is contained inside the carrier 12 in addition to the case where the catalyst metal 11 is carried on the surface of the carrier 12 . Note that FIG. 1 shows an example in which the catalyst metal 11 is supported on the surface of the carrier 12 . Further, the reforming catalyst 1 can include gaps 13 through which the fuel gas FG and the reformed gas RG flow.

Specific examples of the catalyst metal 11 include Rh (rhodium), Pt (platinum), Pd (palladium), Ru (ruthenium), Ir (iridium), Au (gold), Ag (silver), and Os (osmium). , Ni, Co, Fe, and Cu, or at least one metal selected from the group consisting of Cu, or an alloy of these metals. According to this configuration, it is possible to ensure the reforming activity of the reforming catalyst 1 . The catalyst metal 11 is preferably at least one metal selected from the group consisting of Rh, Pt, Pd, Ru, Ir, Au, Ag, and Os, or an alloy of these metals, more preferably , Rh.

Specific examples of the carrier 12 include ceria-zirconia composite oxide, titania (TiO ₂ ), and alumina (Al ₂ O ₃ ). These can be used alone or in combination of two or more. Specifically, the ceria-zirconia composite oxide has the general formula: Ce _1-x Zr _x O ₂ (where 0.05≦X≦0.5, preferably 0.1≦X≦0.4, and Preferably, those represented by 0.2≦X≦0.3) can be suitably used.

When the reforming catalyst 1 is composed of a mixture containing the composite powder 10, the catalyst metal 11, and the carrier 12, the mass ratio of the composite powder 10 to the carrier 12 can be 20% or more and 80% or less. . According to this configuration, the catalytic function can be exerted for a long period of time, so it becomes easy to suppress the change in the fuel reforming rate over time. The mass ratio of the composite powder 10 to the carrier 12 can be preferably 25% or more, more preferably 30% or more. Also, the mass ratio of the composite powder 10 to the carrier 12 can be preferably 75% or less, more preferably 70% or less. The mass ratio of the composite powder 10 is the mass percentage of the mass of the composite powder 10 with respect to the total mass of the composite powder 10 and the carrier 12 (= 100 × (mass of the composite powder 10) / (composite powder 10 and total mass of the carrier 12)).

As the fuel gas FG to be steam-reformed by the reforming catalyst 1, at least one of hydrocarbons and oxygen-containing hydrocarbons can be mentioned. Hydrocarbons may basically contain carbon atoms and hydrogen atoms, for example, alkanes represented by C _n H _2n+2 (n: natural number) such as methane, ethane, propane, butane, and can be exemplified. Also, the hydrocarbon may be cyclic, or may contain a double bond, a benzene ring, or the like. Oxygen-containing hydrocarbons are hydrocarbons containing oxygen atoms, and examples thereof include alcohols such as methanol and ethanol, ethers, epoxides, and carboxylic acids. These can be used alone or in combination of two or more. Hydrocarbons and oxygenated hydrocarbons also include gasoline, light oil, and ethanol-blended gasoline.

The form of the reforming catalyst 1 is not particularly limited, and can be appropriately selected depending on the application. Examples of the shape of the reforming catalyst 1 include a honeycomb shape, a pellet shape, a plate shape, a powder shape, and a film shape. The reforming catalyst 1 can also be coated (fixed) on a substrate such as a honeycomb substrate, pellet substrate, or plate substrate. In this case, examples of materials for the substrate include ceramics such as cordierite, silicon carbide, and mullite, and metal materials such as stainless steel containing chromium and aluminum.

(Embodiment 2)
A method for producing the reforming catalyst of Embodiment 2 will be described. It should be noted that, of the reference numerals used in the second and subsequent embodiments, the same reference numerals as those used in the previously described embodiments represent the same components and the like as those in the previously described embodiments, unless otherwise specified.

The method for producing a reforming catalyst according to the present embodiment (hereinafter sometimes referred to as the present production method) is a method for producing a reforming catalyst containing composite powder and a catalyst metal, comprising a preparation step and a production step. have

The preparation step is a step of preparing at least the base particle powder represented by the general formula: BaYM1 _4-c M2 _c O _7+σ (where 0≤c<4, 0<σ≤1.5). However, M1 and M2 are transition metals selected from the group consisting of Co, V, Cr, Mn, Fe, Ni, Cu, and Zn, respectively, different from each other. Since the general formula of the base particle powder in this production method is the same as that of the base particles 101 in the composite powder 10 described above in Embodiment 1, the explanation is omitted.

For the base particle powder, for example, Ba salt, Y salt, M1 salt, and M2 salt are weighed so that Ba, Y, M1, and M2 have a predetermined molar ratio, and these are dissolved in water to form an aqueous solution. is produced, the aqueous solution is sprayed and dried to form granulated powder, and the obtained granulated powder is calcined in an air atmosphere. Examples of salts of the above metals include acetates, nitrates, sulfates and chlorides.

In the production step, by heat-treating at least the base particle powder in a reducing gas containing CO ₂ or in a reducing gas containing no CO ₂ , the general formula: (BaO _1-a (CO ₃ ) _a )YM1 _{4 -c} M2 _c O _6-b (where 0≤a≤1, 0≤b≤4.5, 0≤c<4).

The reducing gas containing CO ₂ can specifically contain a CO ₂ gas, a reducing gas, and a base gas consisting of an inert gas. The _CO2 -free reducing gas can specifically include a reducing gas and a base gas consisting of an inert gas. Examples of the reducing gas include hydrogen gas, carbon monoxide gas, hydrocarbon gas, and ammonia gas. Examples of inert gas include nitrogen gas, helium gas, and argon gas. The reducing gas containing CO ₂ is used when manufacturing the composite powder 10 where 0<a. On the other hand, a reducing gas that does not contain CO ₂ is used when manufacturing composite powder 10 where a=0.

The reducing gas concentration contained in the reducing gas can be, for example, 1% by volume or more and 10% by volume or less. The CO ₂ gas concentration contained in the reducing gas can be, for example, 1% by volume or more and 90% by volume or less.

The heat treatment temperature can be, for example, 800° C. or higher and 1000° C. or lower. Also, the heat treatment time can be, for example, 0.5 hours or more and 10 hours or less. The heat treatment pressure can be, for example, 0.1 atmosphere or more and 5 atmospheres or less.

When manufacturing a reforming catalyst containing a composite powder, a catalyst metal, and a carrier, for example, a mixed powder in which the base particle powder and the carrier powder are mixed can be prepared in the preparation step. In this case, at least a step of supporting the catalyst metal on the carrier powder can be added before the above-described production step. At this time, the catalyst metal can be supported on the mixed powder, that is, the catalyst metal can be supported not only on the carrier powder but also on the base particle powder. In addition, for example, a step of mixing the composite powder and the carrier powder supporting the catalyst metal can be added after the production step.

When manufacturing a reforming catalyst that contains composite powder and a catalyst metal and does not contain a support, a step of supporting the catalyst metal on the base particle powder can be added before the above-described production step. In addition, for example, a step of supporting the catalyst metal on the composite powder can be added after the above-described production step. In these cases, the composite powder functions as a carrier.

The mixing method in the above is not particularly limited. can be exemplified by a method of drying after wet mixing with a mixer. As a solvent for wet mixing, water or an organic solvent can be used, and a desired amount of binder can be mixed to improve the dispersion state.

In addition, as a method for supporting the catalytic metal, for example, a method of impregnating the carrier or the carrier and the composite powder with a solution of the catalytic metal salt and then calcining the solution; A method of calcining after adsorbing and supporting the material may be used. For example, when Pt is used as the catalyst metal, the platinum salt includes platinum acetate, carbonate, nitrate, ammonium salt, citrate, dinitrodiammine salt, or solutions of their complexes. Dinitrodiammine salts are preferred from the standpoint of ease and high dispersibility. For example, when Rh is used as the catalyst metal, rhodium salts include rhodium acetates, carbonates, nitrates, ammonium salts, citrates, dinitrodiammine salts, and solutions of their complexes. Nitrates are preferred because of their ease and high dispersibility. As the solvent, for example, water (preferably pure water such as ion-exchanged water or distilled water) or the like, which is capable of dissolving the catalyst metal salt in the form of ions, is suitable.

Firing in such a supporting method can be carried out in the air. The firing temperature is preferably 200 to 600°C. When the calcination temperature is lower than the above lower limit, the platinum group metal compound is not sufficiently thermally decomposed, and it becomes difficult to enter a metallic state exhibiting catalytic activity, so the activity tends to decrease. On the other hand, when the above upper limit is exceeded, grain growth of the supported platinum group metal tends to lower the catalytic activity in the steam reforming reaction of the fuel gas. Also, the firing time is preferably 0.1 to 100 hours. If the calcination time is less than the above lower limit, the platinum group metal compound is not sufficiently thermally decomposed, and it becomes difficult to enter a metal state exhibiting catalytic activity, so the activity tends to decrease. On the other hand, even if the above upper limit is exceeded, no further effect can be obtained, leading to an increase in the cost for preparing the catalyst.

In this production method, the composite powder produced in the producing step is composed of base particles, _BaCO3 fine particles adhering to the surfaces of the base particles, and at least one of M1 fine particles and M2 fine particles adhering to the surfaces of the base particles. and transition metal fine particles. That is, in the production step, the BaCO ₃ fine particles and the transition metal fine particles can be precipitated on the surface of the base particles by heat-treating the base particle powder in a reducing gas atmosphere.

According to this configuration, it is possible to reliably suppress the deterioration of the catalyst performance due to the sulfur component contained in the fuel gas. Since the general formula of the base particles is the same as that of the base particles 101 in the composite powder 10 described above in Embodiment 1, description thereof is omitted.

This manufacturing method has the above steps. Therefore, according to this production method, it is possible to suitably produce the reforming catalyst of Embodiment 1 whose catalytic performance is less likely to deteriorate due to the sulfur component contained in the fuel gas.

(Experimental example)
- Preparation of reforming catalysts of samples 1 to 26 -
Y( _CH3COO )3.4H2O, Ba( _CH3COO ) _{2 and} Co( _CH3COO ) _2.4H2O were weighed so that the molar ratio of Y:Ba:Co=1:1:4 was obtained _. bottom. Then, these were dissolved in pure water to prepare an aqueous acetate solution. The prepared acetate aqueous solution was spray-dried to obtain a powder. The obtained powder was calcined in the air at 600° C. for 7 hours to prepare a BaYCo ₄ O _7.1 powder as a base particle powder used for preparing the composite powder.

Further, each base particle powder was prepared by substituting a part of Co in BaYCo ₄ O _7.1 with V, Cr, Mn, Fe, Ni, Cu, and Zn. At this time, _VCl3 , Mn( _CH3COO ) _2.4H2O , Fe( _NO3 ) _{3.9H2O ,} Ni _{( CH3COO} ) ₂ , Cu( _CH3COO ) ₂ , Zn( _CH3COO ) ) ₂ was used and the Co to V, Cr, Mn, Fe, Ni, Cu, Zn was weighed out in a molar ratio of 3:1. As a result, BaYCo ₃ V ₁ O _7.1 powder, BaYCo ₃ Cr ₁ O _7.1 powder, BaYCo ₃ Mn ₁ O _7.1 powder, and BaYCo ₃ Fe ₁ O powder were used as the base particle powder used for producing the composite powder. _7.1 powder, BaYCo ₃ Ni ₁ O _7.1 powder, BaYCo ₃ Cu ₁ O _7.1 powder, and BaYCo ₃ Zn ₁ O _7.1 powder were prepared.

In addition, a base particle powder was prepared by replacing all of the Co in the BaYCo ₄ O _7.1 powder with Fe. At this time, Fe(NO ₃ ) _{3.9H 2} O was used, and the same procedure as described above was performed except that the molar ratio of Y:Ba:Fe was 1:1:4. As a result, BaYFe ₄ O _7.1 powder was produced as the base particle powder used for producing the composite powder.

Next, 3 g of BaYCo ₄ O _7.1 powder as base particle powder and 7 g of CeO—ZrO powder (Ce _0.75 Zr _0.25 O ₂ powder) as carrier powder were added to 25 g of ion-exchanged water, This was mixed with 150 g of zirconia balls with a diameter of 5 mm, and mixed by ball milling in a 250 cc pot for 3 hours. As a result, a mixed powder for producing the reforming catalyst of sample 1 was produced, in which the base particle powder and the carrier powder were mixed. Similarly, mixed powders for producing reforming catalysts of Samples 2 to 26 were produced by mixing base particle powder and carrier powder in the combinations shown in Tables 1 and 2 below. The base particle powder and the carrier powder in each mixed powder were mixed so that the mass ratio of the composite powder and the mass ratio of the carrier were the values shown in Tables 1 and 2 below.

Next, a cordierite honeycomb substrate (400 cells/square inch) having a diameter of 23 mm and a length of 25 mm was coated with the mixed powder in an amount of 240 g per 1 L of the honeycomb substrate. Next, the honeycomb substrate coated with the mixed powder was immersed in 20 cc of an aqueous solution of rhodium nitrate containing 50 mg of rhodium for 12 hours, and then dried at 120° C. for 10 minutes. Then, the mixture was calcined at 500° C. for 3 hours in an air atmosphere to support the catalyst metal on the mixed powder. The amount of rhodium, which is a catalyst metal, supported was 4.8 g/L.

Next, each mixed powder coated on the honeycomb substrate contains a predetermined concentration of _CO2 gas, a predetermined concentration of _H2 gas, and a predetermined base gas, as shown in Tables 3 and 4 below. Heat treatment was performed at a predetermined heat treatment temperature and heat treatment time in a reducing gas atmosphere. As a result, reforming catalysts of Samples 1 to 26 were obtained. The reforming catalysts of Samples 1 to 13 and Samples 15 to 26 contain a catalyst metal, a carrier, and a composite powder. Also, the reforming catalyst of sample 14 contains catalyst metal and composite powder.

The detailed structure of the composite powder in the reforming catalyst of each sample was measured by the measurement method described above. The results are collectively shown in Tables 1 and 2 below.

An inert gas fusion-infrared absorption analyzer "EMGA-620W" manufactured by Horiba, Ltd. was used as an analyzer for analyzing the amount of oxygen in the general formula of each oxide. As a flux, 0.5 g of tin pellets of a decomposition accelerator manufactured by Horiba Ltd. was used. The graphite crucible was a double crucible by inserting an inner crucible with a diameter of 14 mm and a height of 20 mm and an inner crucible with a diameter of 10 mm and a height of 12 mm. The analytical sample was dried at 110° C. for 2 hours to remove moisture, and then allowed to cool to room temperature in a desiccator. 10 mg of a sample was weighed, enclosed in a flux and compressed to sufficiently remove air, and subjected to analysis. A calibration curve was prepared from the analysis values of iron oxide (Fe ₂ O ₃ ) (O: 30.06%) JSS-009-2 as a standard substance and the blank test results. Measurements and evaluations were made in an inert gas (helium gas) atmosphere at a melting temperature of 3.4 kW (1634°C).

In addition, in the measurement of the atomic number ratio of each metal element in the general formula of the composite powder and base particles, after drying the sample at 110 ° C. for 3 hours, 0.3 g was weighed and placed in a pressurized polytetrafluoroethylene put into the container. 10 ml of 24% by mass sulfuric acid was added thereto, and the pressurized container was introduced into the pressurized decomposition apparatus. "Multiwave 7000" manufactured by Anton Paar Japan was used as a pressure decomposition apparatus, and treatment was performed at 230°C and 15 atm for 24 hours. After the treatment, it was confirmed that the sample in the pressurized container was dissolved, and the content liquid and the washing liquid in the pressurized container were transferred to a plastic beaker and filled with pure water to a constant volume of 100 ml. About the fixed volume solution, the atomic number ratio of each metal element was measured using "ICPE-9820" by Shimadzu Corporation.

In addition, the composite powders in Samples 1 to 3, Samples 5 to 7, and Samples 9 to 26 using a reducing gas containing CO ₂ gas had BaCO ₃ fine particles and predetermined transition metal fine particles on the surface of the base particles. was precipitated. In addition, in the composite powders of Samples 4 and 8 using reducing gas containing no CO ₂ gas, predetermined fine transition metal particles were deposited on the surfaces of the base particles. A high-resolution scanning transmission electron microscope and an energy dispersive X-ray spectroscope "JEM-ARM300F" manufactured by JEOL Ltd. were used to measure the average particle sizes of the BaCO ₃ fine particles and the transition metal fine particles. At this time, the methanol dispersion liquid of the sample powder was dropped onto a copper microgrid, heated under vacuum, and dried. The particle size was measured at a magnification of 1,000,000 times.

Further, the analysis of the adhesion amount of BaCO ₃ fine particles in the general formula of each oxide (a value in the general formula of the composite powder) was specifically performed as follows. After putting 1.0 g of the sample in a platinum boat and setting it in a zirconia heating tube, the temperature was raised to 1500 ° C. at 10 ° C./min under a nitrogen flow of 500 ccm. It was carried out by measuring using a _two- concentration analyzer. "VA-3000" manufactured by Horiba, Ltd. was used as a CO ₂ concentration analyzer.

- Preparation of reforming catalysts of samples 1C to 3C -
In the preparation of the reforming catalysts of Samples 1 to 26, instead of the mixed powder, CeO—ZrO powder, TiO ₂ powder, or Al ₂ O ₃ powder was used, and heat treatment was performed in a reducing gas atmosphere. The reforming catalysts of Samples 1C to 3C shown in Tables 1 and 2 below were produced in the same manner except that the sample was not used.

Tables 1 and 2 collectively show the detailed structure of the reforming catalyst of each sample. Tables 3 and 4 collectively show the heat treatment conditions under the reducing gas atmosphere.

-Evaluation test-
The reforming catalyst of each sample was subjected to a steam reforming reaction activity test and a durability test.
Specifically, first, E20 fuel containing 20% by volume of anhydrous ethanol was prepared by mixing anhydrous ethanol and commercially available gasoline at a volume ratio of 20:80. E20 fuel and deionized water were then added to 1.35 mL/min and 1.09 mL/min respectively using a liquid pump against a _CO2 (14%)/ _N2 mixed gas at a gas flow rate of 9.2 L/min. A model gas was prepared as a base for use in the activity test and endurance test by adding it at a flow rate and vaporizing it. Further, as a gas for accelerating deterioration due to a sulfur component, a sulfur component-containing gas was prepared by introducing 100 ppm by mass of sulfur dioxide (SO ₂ ) into a model gas. Their steam/carbon ratio (S/C) was 0.80 and the gas flow rate was 10.8 L/min.

Next, the reforming catalyst of each sample was filled in a stainless steel reaction tube having an inner diameter of 23.5 mm, and this reaction tube was installed in a fixed bed flow reactor. Next, as a pretreatment, the model gas was supplied to the reforming catalyst at a space velocity of about 60000 hr ^-1 , and the catalyst bed temperatures were maintained in the order of 400°C, 500°C and 600°C for about 1 hour. After that, as an activity test and an endurance test, the catalyst bed temperature was set to 500° C. and held for 120 minutes. The generated concentrations of hydrogen (H ₂ ) and carbon monoxide (CO) at that time were measured by gas chromatography to calculate the fuel reforming rate, and its change over time was investigated. Five points were evaluated every 30 minutes at the start, 30 minutes, 60 minutes, 90 minutes, and 120 minutes. At this time, the evaluation up to the 60th minute was performed with the above model gas, and the sulfur component-containing gas containing sulfur dioxide was introduced after the 60th minute sampling was completed. In other words, the sulfur component-containing gas was evaluated for the latter half of 60 minutes. Then, the rate of change was calculated from the following formula.
Change rate [%] = 100 x (fuel reforming rate at start - fuel reforming rate at 120 minutes) / (fuel reforming rate at start)
When the rate of change was 30% or less, it was rated as A+ because the effect of suppressing deterioration of catalyst performance over time due to the sulfur component contained in the fuel gas was high. When the rate of change was more than 30% and 40% or less, it was rated as A because it has an effect of suppressing deterioration of catalytic performance over time due to the sulfur component contained in the fuel gas. When the rate of change was more than 40%, it was evaluated as C because there was no effect of suppressing deterioration of catalyst performance over time due to the sulfur component contained in the fuel gas. The results are summarized in Table 5.

Tables 1 to 5 show the following.
The reforming catalysts of Samples 1C-3C do not contain composite powders as defined in this disclosure. Therefore, the catalyst performance deteriorated due to the sulfur component contained in the fuel gas. The sulfur component contained in the catalyst made it difficult for the catalytic performance to deteriorate.

Further, when the reforming catalysts of Samples 1 to 26 are compared with each other, the following can be said. According to Samples 1 to 3, deterioration of catalytic performance due to sulfur components can be suppressed even when the carriers are different. According to Samples 4 to 9, even when the degree of carbonation of BaO and the degree of oxidation of Co in the composite powder are different, the deterioration of the catalytic performance due to the sulfur component can be suppressed. Further, by changing the reduction treatment conditions, it is possible to change the degree of carbonation of BaO and the degree of oxidation of Co. According to Samples 10 to 14, deterioration of the catalytic performance due to the sulfur component can be suppressed even when the mass ratio of the composite powder is different. In particular, when the mass ratio of the composite powder is 20% or more and 80% or less, the catalytic function can be exhibited for a long time, and it becomes easy to suppress the change in the fuel reforming rate over time. According to Samples 15 to 18, it is possible to change the average particle size of the BaCO ₃ fine particles and the transition metal fine particles by changing the reduction treatment conditions. According to Samples 19 to 26, even when the M1 transition metal in the composite powder is replaced with the M2 transition metal different from M1, the deterioration of the catalytic performance due to the sulfur component can be suppressed.

The present invention is not limited to the above-described embodiments and experimental examples, and various modifications can be made without departing from the scope of the invention. Moreover, each configuration shown in each embodiment and each experimental example can be combined arbitrarily.
Examples of reference forms are added below.
Section 1.
General formula: (BaO _1-a (CO ₃ ) _a )YM1 _4-c M2 _c O _6-b (where 0≦a≦1, 0≦b≦4.5, 0≦c<4) A reforming catalyst (1) comprising a composite powder (10).
provided that M1 and M2 are different transition metals selected from the group consisting of Co, V, Cr, Mn, Fe, Ni, Cu, and Zn, respectively.
Section 2.
The above composite powder has the general formula: (BaO _1-a (CO ₃ ) _a )YCo _4-c M2 _c O _6-b (where 0 ≤ a ≤ 1, 0 ≤ b ≤ 4.5, 0 ≤ c Item 1. The reforming catalyst according to Item 1, represented by <4).
provided that M2 is a transition metal selected from the group consisting of V, Cr, Mn, Fe, Ni, Cu, and Zn
Item 3.
The above composite powder is represented by the general formula: (BaO _1-a (CO ₃ ) _a )YCo ₄ O _6-b (where 0 ≤ a ≤ 1, 0 ≤ b ≤ 4.5), item 1 The reforming catalyst according to .
Section 4.
The composite powder is composed of base particles (101) represented by the general formula: BaYM1 _4-c M2 _c O _7+σ (where 0 ≤ c < 4, 0 < σ ≤ 1.5), and the surface of the base particle Item 2. The improvement according to item 1, comprising BaCO 3 fine particles (102) attached to the surface of the base particles, and transition metal fine particles (103) composed of at least one of M1 fine particles and M2 fine particles attached to the surface of the base particle _. quality catalyst.
provided that M1 and M2 are different transition metals selected from the group consisting of Co, V, Cr, Mn, Fe, Ni, Cu, and Zn, respectively.
Item 5.
The composite powder consists of a base particle (101) represented by the general formula: BaYCo _4-c M2 _c O _7+σ (where 0≦c<4, 0<σ≦1.5), and the surface of the base particle Item 3. The improvement according to item 2, comprising _BaCO3 fine particles (102) attached to the base particles, and transition metal fine particles (103) composed of at least one of Co fine particles and M2 fine particles attached to the surface of the base particles. quality catalyst.
provided that M2 is a transition metal selected from the group consisting of V, Cr, Mn, Fe, Ni, Cu, and Zn
Item 6.
The composite powder consists of base particles (101) represented by the general formula: BaYCo ₄ O _{7 +σ} (where 0<σ≦1.5) and BaCO ₃ fine particles (102) adhering to the surface of the base particles. and transition metal fine particles (103) composed of Co fine particles adhering to the surface of the base particles.
Item 7.
Item 7. The reforming catalyst according to any one of Items 4 to 6, wherein the BaCO 3 fine particles have an average particle size of 10 nm or more and 50 nm or less, and the transition metal fine particles have an average particle size of 0.5 nm or more and 30 nm or less _. .
Item 8.
Item 8. The reforming catalyst according to any one of items 1 to 7, comprising a catalyst metal (11) and a carrier (12) supporting the catalyst metal.
Item 9.
Item 9. The reforming catalyst according to Item 8, wherein the mass ratio of the composite powder is 20% or more and 80% or less.
Item 10.
a preparation step of preparing at least the base particle powder represented by the general formula: BaYM1 _4-c M2 _c O _7+σ (where 0≦c<4, 0<σ≦1.5);
By heat-treating at least the base particle powder in a reducing gas containing CO ₂ or in a reducing gas containing no CO ₂ , the general formula: (BaO _1-a (CO ₃ ) _a )YM1 _4-c M2 a production step of producing a composite powder represented by _c O _6-b (where 0≦a≦1, 0≦b≦4.5, 0≦c<4);
A method for producing a reforming catalyst.
provided that M1 and M2 are different transition metals selected from the group consisting of Co, V, Cr, Mn, Fe, Ni, Cu, and Zn, respectively.
Item 11.
The composite powder is composed of base particles represented by the general formula: BaYM1 _4-c M2 _c O _7+σ (where 0 ≤ c < 4, 0 < σ ≤ 1.5), and adhered to the surface of the base particles Item 11. The method for producing a reforming catalyst according to Item 10, comprising BaCO ₃ fine particles and transition metal fine particles composed of at least one of M1 fine particles and M2 fine particles attached to the surface of the base particles.
provided that M1 and M2 are different transition metals selected from the group consisting of Co, V, Cr, Mn, Fe, Ni, Cu, and Zn, respectively.

1 reforming catalyst 10 composite powder

Claims (11)

General formula: (BaO _1-a (CO ₃ ) _a )YM1 _4-c M2 _c O _6-b (where 0≦a≦1, 0≦b≦4.5, 0≦c<4) including a composite powder (10) and a catalyst metal (11) ,
The catalyst metal contains at least one metal selected from the group consisting of Rh, Pt, Pd, Ru, Ir, Au, Ag, Os, Ni, Co, Fe, and Cu, or an alloy of these metals. Reforming catalyst (1).
provided that M1 and M2 are different transition metals selected from the group consisting of Co, V, Cr, Mn, Fe, Ni, Cu, and Zn, respectively. The above composite powder has the general formula: (BaO _1-a (CO ₃ ) _a )YCo _4-c M2 _c O _6-b (where 0 ≤ a ≤ 1, 0 ≤ b ≤ 4.5, 0 ≤ c The reforming catalyst according to claim 1, represented by <4).
provided that M2 is a transition metal selected from the group consisting of V, Cr, Mn, Fe, Ni, Cu, and Zn The composite powder is represented by the general formula: (BaO _1-a (CO ₃ ) _a )YCo ₄ O _6-b (where 0≦a≦1, 0≦b≦4.5). 2. The reforming catalyst according to 1. The composite powder is composed of base particles (101) represented by the general formula: BaYM1 _4-c M2 _c O _7+σ (where 0 ≤ c < 4, 0 < σ ≤ 1.5), and the surface of the base particle and transition metal fine particles (103) composed of at least one of _M1 fine particles and M2 fine particles attached to the surface of the base particles. reforming catalyst.
provided that M1 and M2 are different transition metals selected from the group consisting of Co, V, Cr, Mn, Fe, Ni, Cu, and Zn, respectively. The composite powder consists of a base particle (101) represented by the general formula: BaYCo _4-c M2 _c O _7+σ (where 0≦c<4, 0<σ≦1.5), and the surface of the base particle and transition metal fine particles (103) composed of at least one of Co fine particles and M2 _fine particles attached to the surface of the base particles. reforming catalyst.
provided that M2 is a transition metal selected from the group consisting of V, Cr, Mn, Fe, Ni, Cu, and Zn The composite powder consists of base particles (101) represented by the general formula: BaYCo ₄ O _{7 +σ} (where 0<σ≦1.5) and BaCO ₃ fine particles (102) adhering to the surface of the base particles. 4. The reforming catalyst according to claim 3, comprising: , transition metal fine particles (103) composed of Co fine particles adhered to the surface of said base particles. 7. The improvement according to any one of claims 4 to 6, wherein the average particle size of the _BaCO3 fine particles is 10 nm or more and 50 nm or less, and the average particle size of the transition metal fine particles is 0.5 nm or more and 30 nm or less. quality catalyst. 8. A reforming catalyst according to any one of claims 1 to 7, comprising a carrier (12 ) supporting said catalytic metal. The reforming catalyst according to claim 8, wherein the mass ratio of the composite powder is 20% or more and 80% or less. A method for producing a reforming catalyst comprising a composite powder and a catalyst metal, comprising:
a preparation step of preparing at least the base particle powder represented by the general formula: BaYM1 _4-c M2 _c O _7+σ (where 0≦c<4, 0<σ≦1.5);
By heat-treating at least the base particle powder in a reducing gas containing CO ₂ or in a reducing gas containing no CO ₂ , the general formula: (BaO _1-a (CO ₃ ) _a )YM1 _4-c M2 _c O _6-b (where 0≦a≦1, 0≦b≦4.5, 0≦c<4) to produce the composite powder;
and
The catalyst metal contains at least one metal selected from the group consisting of Rh, Pt, Pd, Ru, Ir, Au, Ag, Os, Ni, Co, Fe, and Cu, or an alloy of these metals. A method for producing a reforming catalyst.
provided that M1 and M2 are different transition metals selected from the group consisting of Co, V, Cr, Mn, Fe, Ni, Cu, and Zn, respectively. The composite powder is composed of base particles represented by the general formula: BaYM1 _4-c M2 _c O _7+σ (where 0 ≤ c < 4, 0 < σ ≤ 1.5), and adhered to the surface of the base particles 11. The method for producing a reforming catalyst according to claim 10, comprising BaCO ₃ fine particles and transition metal fine particles composed of at least one of M1 fine particles and M2 fine particles attached to the surface of the base particles.
provided that M1 and M2 are different transition metals selected from the group consisting of Co, V, Cr, Mn, Fe, Ni, Cu, and Zn, respectively.

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