JP2016165712A - Steam modification catalyst, steam modification method using the same and steam modification reaction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam modification catalyst sufficiently hardly generating caulking even under environment without oxygen gas existed or a condition with low molar ratio of steam and carbon (S/C), maintaining high activity even with exposed to high temperature and capable of modifying fuel consisting of hydrocarbons by steam efficiently.SOLUTION: There is provided a steam modification catalyst for modifying fuel consisting of hydrocarbons by steam having a composite oxide carrier containing alumina, ceria and zirconia and rare earth oxide other than ceria, at least one kind of first metal element selected from a group consisting of platinum metal carried on the composite oxide carrier and having surface composition of aluminum (at%) by an X ray photoelectron spectroscopy (XPS) of the composite oxide carrier of 1.5 times as composition of aluminum (at%) of the whole composite oxide carrier.SELECTED DRAWING: None

Description

  The present invention relates to a steam reforming catalyst, a steam reforming method using the same, and a steam reforming reaction apparatus. More specifically, the present invention relates to a method for reforming a fuel comprising hydrocarbons with steam, a catalyst used therefor, and its The present invention relates to a steam reforming reaction apparatus including a catalyst.

While reduction of carbon dioxide emissions from automobiles and the like is demanded, ethanol obtained from biomass has attracted attention as a carbon neutral, particularly CO ₂ neutral fuel. However, ethanol has a small calorific value, and in order to be used as a fuel for an internal combustion engine such as an automobile, it is desirable to use a part or all of it reformed to hydrogen, carbon monoxide or the like.

  On the other hand, in an internal combustion engine such as an automobile, hydrogen or carbon monoxide is generated from part or all of the fuel by a steam reforming reaction, and these are supplied to the internal combustion engine to improve thermal efficiency and startability of the internal combustion engine. Technology is known. Since such a steam reforming reaction is usually an endothermic reaction, it is possible to improve the thermal efficiency by performing the steam reforming reaction using exhaust heat from the internal combustion engine.

As a catalyst for reforming a fuel composed of hydrocarbons such as ethanol with water vapor, Japanese Patent Application Laid-Open No. 2007-703 (Patent Document 1) uses a hydrocarbon-based raw fuel for a fuel cell as a fuel gas. A reforming catalyst for reforming, wherein an active component composed of at least one of Ru, Rh, and Ni using a hydroxide as a precursor is highly dispersed and Al ₂ O ₃ , ZrO ₂ , CeO ₂ , Nd ₂ A reforming catalyst is disclosed which is supported on a support composed of one or more of O ₃ , La ₂ O ₃ , Pr ₂ O _{3 and the} like. However, the reforming catalyst disclosed in Patent Document 1 does not have sufficient suppression of coking under conditions where the molar ratio (S / C) of water vapor to carbon is low.

  Japanese Patent Laid-Open No. 2010-207782 (Patent Document 1) discloses a carrier containing a composite oxide in which ceria and alumina are both dispersed on the nm scale, and a long-period periodic table 8 on the carrier. A steam reforming catalyst containing at least one metal element belonging to Groups 10 to 10 is disclosed. According to the description of the publication, coking is unlikely to occur even in an environment where oxygen gas is not present or in a condition where the molar ratio (S / C) of water vapor to carbon is low, and oxygen-containing hydrocarbons are efficiently reformed with water vapor. It is possible to generate hydrogen. However, in recent years, the required characteristics for the steam reforming catalyst have been increasing more and more, the environment where oxygen gas does not exist, the condition where the molar ratio (S / C) of steam and carbon is low, and further, the time or place of S Even under conditions where / C varies and S / C partially decreases, coking is not easily caused, and high activity is maintained even when exposed to high temperatures. There has been a demand for a steam reforming catalyst that can be efficiently reformed.

Japanese Patent Laid-Open No. 2007-703 JP 2010-207782 A

  The present invention has been made in view of the above-described problems of the prior art, and coking is not easily caused even in an environment where oxygen gas is not present or in a condition where the molar ratio of water vapor to carbon (S / C) is low, A steam reforming catalyst that retains high activity even when exposed to high temperatures and can efficiently reform a fuel composed of hydrocarbons with steam, and steam reforming of a fuel composed of hydrocarbons using the steam reforming catalyst It is an object to provide a quality method and a steam reforming reaction apparatus.

  As a result of intensive studies to achieve the above object, the present inventors have obtained a composite oxide support containing alumina, ceria and zirconia, and a rare earth oxide other than ceria such as praseodymium oxide, and the composite oxide. And at least one first metal element selected from the group consisting of platinum group metals supported on a material support, and the aluminum surface composition (at%) of the composite oxide support By having a high concentration of a specific ratio or more with respect to the composition of aluminum, it shows high catalytic activity in the steam reforming reaction of fuels composed of hydrocarbons, is not sufficiently prone to coking, and is exposed to high temperatures. The present inventors have found that a steam reforming catalyst having high activity can be obtained and completed the present invention.

  That is, the steam reforming catalyst of the present invention is a group consisting of a composite oxide support containing alumina, ceria and zirconia, and a rare earth oxide other than ceria, and a platinum group metal supported on the composite oxide support. At least one first metal element selected from the group consisting of: a composite oxide support having an aluminum surface composition (at%) determined by X-ray photoelectron spectroscopy (XPS) measurement; It is characterized by being a catalyst for reforming a fuel composed of hydrocarbons with water vapor, which is 1.5 times or more of the total aluminum composition (at%).

  In the steam reforming catalyst of the present invention, the rare earth oxide other than ceria is at least one selected from the group consisting of praseodymium oxide, neodymium oxide, samarium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, and ytterbium oxide. And at least one of praseodymium oxide, terbium oxide, and ytterbium oxide is more preferable. In addition, the content of ceria in the composite oxide support is preferably 50 to 95% by mass.

  In the steam reforming catalyst of the present invention, at least one of ceria in the composite oxide support and rare earth oxides other than zirconia and ceria (more preferably praseodymium oxide, terbium oxide, and ytterbium oxide). It is preferable that the seed forms a solid solution in which at least a part is in solid solution with each other.

  Furthermore, in the steam reforming catalyst of the present invention, the first metal element is preferably rhodium.

  The steam reforming catalyst of the present invention preferably further comprises at least one second metal element selected from the group consisting of alkaline earth metals supported on the composite oxide support, The second metal element is preferably at least one selected from the group consisting of magnesium, strontium, and barium.

  The method for steam reforming a fuel comprising hydrocarbons of the present invention is a method characterized by contacting a fuel comprising hydrocarbons with the steam reforming catalyst of the present invention in the presence of steam. The fuel is preferably a mixed fuel of ethanol and gasoline. The steam reforming reaction apparatus of the present invention is a steam reforming reaction apparatus provided with the steam reforming catalyst of the present invention, and can be suitably used for the method of steam reforming of fuel comprising the hydrocarbons of the present invention.

  Although the reason why the catalytic activity in the steam reforming reaction of the fuel composed of hydrocarbons is increased by the steam reforming catalyst of the present invention is not necessarily clear, the present inventors speculate as follows. That is, in the steam reforming catalyst of the present invention, even if at least one first metal element selected from platinum group metal elements that are supported metal elements is oxidized during the steam reforming reaction, In the composite oxide, ceria or a solid solution containing ceria (ceria and at least one of rare earth oxides other than zirconia and ceria (more preferably, praseodymium oxide, terbium oxide, and ytterbium oxide) are in solid solution with each other. Therefore, it is presumed that oxygen on the surface of the catalyst is absorbed by these, and the first metal element is reduced to a metal state exhibiting high catalytic activity to increase the catalytic activity.

  Further, ceria and a solid solution containing ceria (solid solution in which ceria and at least one of rare earth oxides other than zirconia and ceria (more preferably praseodymium oxide, terbium oxide, and ytterbium oxide) are in solid solution with each other) Normally, grain growth is easier in a reducing atmosphere such as a steam reforming reaction than in an oxidizing atmosphere, but in the steam reforming catalyst of the present invention, ceria and alumina that do not form a solid solution with each other or a solid solution containing ceria and alumina It is presumed that the catalytic activity is increased because the composite oxides act as a barrier to suppress the growth of complex oxide grains at high temperatures and the grain growth of the first metal element supported thereon. The In particular, ceria and solid solutions containing ceria are more likely to grow in a reducing atmosphere such as a steam reforming reaction than in an oxidizing atmosphere, and tend to grow at 600 ° C. or higher. Inferred.

  Furthermore, the reason why coking is unlikely to occur in the steam reforming catalyst of the present invention and high activity can be maintained even when exposed to high temperatures is not necessarily clear, but the present inventors speculate as follows. To do. That is, in a catalyst for reforming a fuel composed of conventional hydrocarbons with steam, an important problem of the steam reforming reaction is catalyst deterioration due to catalyst poisoning due to coking (carbon deposition) or a polymerized hydrocarbon. is there. In particular, catalyst degradation due to such catalyst poisoning becomes significant under reaction conditions with low S / C. On the other hand, in the present invention, the carrier contains alumina, ceria and zirconia, and a rare earth oxide other than ceria (more preferably, at least one of praseodymium oxide, terbium oxide, and ytterbium oxide), and By using a composite oxide support in which the surface composition of aluminum as measured by X-ray photoelectron spectroscopy (XPS) of the support is 1.5 times or more of the aluminum composition (at%) of the entire support, such a composite oxide support is used. Has a characteristic of releasing oxygen from the crystal lattice of the complex oxide when the temperature rises, so that the oxygen oxidizes and removes the carbonaceous material, and catalyst poisoning due to coking and hydrocarbon polymerized substances hardly occurs, Coking will occur sufficiently even in an environment where oxygen gas is not present or when the molar ratio of water vapor to carbon (S / C) is low. No longer it is assumed that it has become possible to become held sufficiently high activity even when exposed to high temperatures.

  Further, in the steam reforming catalyst of the present invention, even when exposed to a high temperature by supporting at least one second metal element selected from the group consisting of alkaline earth metals on the composite oxide support, The reason why the higher activity is maintained is not necessarily clear, but the present inventors speculate as follows. That is, at least one second metal element selected from the group consisting of alkaline earth metals undergoes a solid phase reaction with alumina in the composite oxide support. This suppresses at least one first metal element selected from the group consisting of platinum group metals, which are supported metal elements, from solid-state reacting with alumina to be in an oxidized state. One metal element is likely to be reduced to a metal state exhibiting high activity, and it is assumed that the catalytic activity is kept higher. Further, it is presumed that the catalytic activity is kept higher because the heat resistance of the alumina itself is increased and the barrier effect is improved.

  In addition, at least one second metal element selected from the group consisting of alkaline earth metals reacts with strong acid sites on the alumina surface to eliminate the acid sites. For this reason, the caulking which progresses on an acid point becomes difficult to occur, and even if it exposes to high temperature, it is guessed that a higher activity is hold | maintained.

  According to the present invention, coking is difficult to occur even in an environment where oxygen gas is not present or in a condition where the molar ratio (S / C) of water vapor to carbon is low, and maintains high activity even when exposed to high temperatures. It is possible to generate hydrogen by efficiently reforming a fuel composed of a kind with steam.

It is a graph which shows the steam reforming reaction activity of the fuel (E20 fuel) which consists of hydrocarbons about the monolith catalyst obtained in Examples 1-2 and Comparative Examples 1-3. It is a graph which shows the steam reforming reaction activity of the fuel (E20 fuel) which consists of hydrocarbons about the monolith catalyst obtained in Example 1, 3-5, and the comparative example 1. FIG. It is a graph which shows the steam reforming reaction activity of the fuel (E20 fuel) which consists of hydrocarbons about the monolith catalyst obtained in Examples 6-10 and Comparative Example 1. Is H _2-TPR spectrum of steam reforming catalyst obtained in Examples 1 and 2 and Comparative Example 1 in the initial state (graph showing the relationship between the concentration of H ₂ in exit gas temperature). It is H _2-TPR spectrum of steam reforming catalyst obtained in Example 3-4 and Comparative Example 1 in the initial state (graph showing the relationship between the concentration of H ₂ in exit gas temperature). It is H _2-TPR spectrum of steam reforming catalyst obtained in Example 6-8 and Comparative Example 1 in the initial state (graph showing the relationship between the concentration of H ₂ in exit gas temperature). Is H _2-TPR spectrum of steam reforming catalyst obtained in Comparative Examples 1 to 3 in the initial state (graph showing the relationship between the concentration of H ₂ in exit gas temperature). A O ₂ -TPD spectrum of steam reforming catalyst obtained in Examples 1 and 2 and Comparative Example 1 in the initial state (graph showing the relationship between the O ₂ concentration in the exit gas temperature). A O ₂ -TPD spectrum of steam reforming catalyst obtained in Example 3-5 and Comparative Example 1 in the initial state (graph showing the relationship between the O ₂ concentration in the exit gas temperature). A O ₂ -TPD spectrum of steam reforming catalyst obtained in Examples 6-8 and Comparative Example 1 in the initial state (graph showing the relationship between the O ₂ concentration in the exit gas temperature). A O ₂ -TPD spectrum of steam reforming catalyst obtained in Example 9-10 and Comparative Example 1 in the initial state (graph showing the relationship between the O ₂ concentration in the exit gas temperature). A O ₂ -TPD spectrum of steam reforming catalyst obtained in Comparative Examples 1 to 3 in the initial state (graph showing the relationship between the O ₂ concentration in the exit gas temperature).

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

[Steam reforming catalyst]
First, the steam reforming catalyst of the present invention will be described. The steam reforming catalyst of the present invention is selected from the group consisting of a composite oxide support containing alumina, ceria and zirconia, and a rare earth oxide other than ceria, and a platinum group metal supported on the composite oxide support. At least one first metal element, wherein the composite oxide support has an aluminum surface composition (at%, atomic%) determined by X-ray photoelectron spectroscopy (XPS) measurement. It is a catalyst for reforming a fuel composed of hydrocarbons with water vapor, which is 1.5 times or more the aluminum composition (at%) of the entire support.

(Composite oxide support)
The composite oxide carrier in the steam reforming catalyst of the present invention contains alumina (Al ₂ O ₃ ), ceria (CeO ₂ ) and zirconia (ZrO ₂ ), and a rare earth oxide other than ceria, and The surface composition (at%) of aluminum by X-ray photoelectron spectroscopy (XPS) measurement of the composite oxide support needs to be 1.5 times or more of the aluminum composition (at%) of the entire composite oxide support. .

  When the surface composition (at%) of aluminum as measured by X-ray photoelectron spectroscopy (XPS) of such a composite oxide support is less than 1.5 times the aluminum composition (at%) of the entire composite oxide support, It is difficult to suppress grain growth at high temperatures of ceria or a solid solution containing ceria. As the surface composition (at%) of aluminum by X-ray photoelectron spectroscopy (XPS) measurement of such a composite oxide support, the aluminum composition (at%) of the entire composite oxide support is from the viewpoint of the effect of suppressing grain growth. It is preferably 1.8 times or more, and more preferably 2.0 times or more.

  Here, the “aluminum surface” refers to a surface layer within a range of 5 nm or less from the outermost surface of the composite oxide support.

  In addition, as a method for measuring the aluminum surface composition (at%) of such a complex oxide carrier, a composite is obtained by X-ray photoelectron spectroscopy (XPS) using an XPS (photoelectron spectrometer). It can be determined by a method of measuring the surface of the oxide support. In the present invention, the measurement condition of the aluminum surface composition (at%, atomic%) by X-ray photoelectron spectroscopy (XPS) measurement of the composite oxide support was analyzed using Al Kα (monochrome) as the X-ray source. The area was 800 μm × 500 μm.

  Furthermore, the method for measuring the aluminum composition (at%) of the entire composite oxide support is not particularly limited. For example, the amount of aluminum used (preparation amount, at%) at the time of manufacturing the composite oxide support is composite oxidized. The method of making the aluminum composition (at%) of the entire material carrier is mentioned. The composition (at%) can also be calculated using the composition ratio of each metal of the composite oxide support. Furthermore, the composition (at%) of the aluminum element as an average value of the entire composite oxide support can be calculated by analyzing the composition with an ICP (High Frequency Plasma Emission Spectrometer: ICP: Inductively Coupled Plasma) or the like. Also, X-ray Fluorescence Analysis (XRF), Inductively Coupled Plasma (ICP) emission analyzer, EDX (Energy Dispersive X-ray Detector), HR-TEM (High Resolution Transmission) Type electron microscope), FE-STEM (field emission-scanning transmission electron microscope), or the like, or composition analysis appropriately combining them.

  Further, the ratio of the surface composition (at%) of aluminum by X-ray photoelectron spectroscopy (XPS) measurement of the composite oxide support to the composition (at%) of aluminum of the entire composite oxide support [(composite oxide support The surface composition of aluminum (at%) measured by X-ray photoelectron spectroscopy (XPS) / (composition of aluminum of the entire complex oxide support (at%))] is obtained as described above. The ratio (the measured XPS value (at%) of the composite oxide support surface (at%)) with respect to the composition (at%) of (for example, the amount of aluminum used (charged amount, at%)) can be obtained.

In the composite oxide support according to the steam reforming catalyst of the present invention, the content of ceria (CeO ₂ ) in the composite oxide support is preferably 50 to 95% by mass, and 60 to 90% by mass. It is more preferable that If the content of ceria in such a composite oxide support is less than the lower limit, the platinum group metal is less likely to be in a metal state, and the catalytic activity tends to decrease. On the other hand, if the upper limit is exceeded, ceria or ceria is included. The solid solution tends to grow and the heat resistance tends to decrease.

In the composite oxide support according to the steam reforming catalyst of the present invention, the content of alumina (Al ₂ O ₃ ) in the composite oxide support is preferably 2 to 40% by mass. More preferably, it is -20 mass%. If the content of alumina in such a composite oxide support is less than the lower limit, ceria or a solid solution containing ceria tends to grow and heat resistance tends to decrease. On the other hand, if the upper limit is exceeded, a platinum group metal Tends to be in a metal state and the catalytic activity tends to decrease.

Furthermore, in the composite oxide support according to the steam reforming catalyst of the present invention, the content of zirconia (ZrO ₂ ) in the composite oxide support is preferably 1 to 40% by mass, and 2 to 20 More preferably, it is mass%. If the content of zirconia in such a composite oxide support is less than the lower limit, a solid solution containing ceria and zirconia tends to grow and the heat resistance tends to decrease. It becomes difficult for the metal to be in a metal state, and the catalytic activity tends to decrease.

  In addition, the composite oxide carrier according to the steam reforming catalyst of the present invention may further contain a rare earth oxide other than ceria (hereinafter also simply referred to as “other rare earth oxide”). is necessary. Examples of such other rare earth oxides include scandium (Sc), yttrium (Y), lanthanum (La), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), and europium (Eu). , Rare earth elements other than cerium (Ce), such as gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) In particular, from the viewpoint of higher catalytic activity and prevention of catalyst deterioration in the steam reforming reaction of fuels composed of hydrocarbons, praseodymium oxide, neodymium oxide, samarium oxide, gadolinium oxide, terbium oxide, dysprosium oxide Ytterbium oxide is preferred, Jim, terbium oxide, more preferably ytterbium oxide, praseodymium oxide is particularly preferred. These other rare earth oxides may be used alone or in combination of two or more. The content of such other rare earth oxides is based on the total amount (100% by mass) of the composite oxide support from the viewpoint of high catalytic activity and prevention of catalyst deterioration in the steam reforming reaction of fuels composed of hydrocarbons. It is preferable that it is 1-40 mass%, and it is more preferable that it is 2-20 mass%.

  In the composite oxide support according to the steam reforming catalyst of the present invention, “comprising alumina, ceria and zirconia and a rare earth oxide other than ceria” means that the composite oxide support is “alumina. , Ceria and zirconia and rare earth oxides other than ceria "or mainly composed of the aforementioned" alumina, ceria and zirconia and rare earth oxides other than ceria ". It means that other components are included as long as they are not impaired. As such other components, other metal oxides and additives used as a carrier for this type of application can be used. In the latter case, the content of “alumina, ceria and zirconia and rare earth oxides other than ceria” in the support is preferably 10 to 100% by mass with respect to 100% by mass of the total mass of the support, and 50 to 100%. More preferably, it is mass%. If the content of “alumina, ceria and zirconia and rare earth oxides other than ceria” in such a support is less than the lower limit, the effects of the present invention tend not to be sufficiently obtained.

  In addition, the metal oxide used as another component that can be contained in such a support within a range not impairing the effects of the present invention may be a metal oxide that can be used as a support for a steam reforming catalyst. For example, magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), vanadium from the viewpoint of thermal stability and catalytic activity of the support. Metal oxides such as alkali metals such as (V), alkaline earth metals, and transition metals, mixtures of these metal oxides, solid solutions of these metal oxides, and composite oxides of these metals are used as appropriate. be able to.

  Furthermore, in the composite oxide support according to the steam reforming catalyst of the present invention, ceria in the composite oxide support, zirconia and other rare earth oxides (more preferably, praseodymium oxide, terbium oxide, and It is preferable that at least one of the ytterbium oxides forms a solid solution in which at least a part thereof is in solid solution (hereinafter, simply referred to as “solid solution containing ceria”). A solid solution containing such ceria (a solid solution in which ceria and at least one of zirconia and other rare earth oxides (more preferably, praseodymium oxide, terbium oxide, and ytterbium oxide) are in solid solution with each other) is platinum. It is possible to more effectively express the action of reducing the first metal element made of a group metal from an oxide state to a metal state, and an environment in which no oxygen gas is present or a molar ratio of water vapor to carbon (S / C) is a steam reforming catalyst that is sufficiently resistant to coking even under low conditions, maintains high activity even when exposed to high temperatures, and can efficiently reform a fuel comprising hydrocarbons with steam. It can be. Examples of the solid solution containing ceria include ceria-zirconia solid solution, ceria-other rare earth oxide solid solution, and ceria-zirconia-other rare earth oxide solid solution. From the viewpoint of high catalytic activity and prevention of catalyst deterioration in the reforming reaction, ceria-zirconia solid solution, ceria-praseodymium oxide solid solution, ceria-neodymium oxide solid solution, ceria-samarium oxide solid solution, ceria-gadolinium oxide solid solution, ceria-terbium oxide solid solution, Ceria-dysprosium oxide solid solution, ceria-ytterbium oxide, ceria-zirconia-praseodymium oxide solid solution, ceria-zirconia-neodymium oxide solid solution, ceria-zirconia-samarium oxide solid solution, ceria-zirconia-gadolinium oxide solid solution, ceria A-zirconia-terbium oxide solid solution, ceria-zirconia-dysprosium oxide solid solution, ceria-zirconia-ytterbium oxide are preferred, ceria-zirconia solid solution, ceria-praseodymium oxide solid solution, ceria-terbium oxide solid solution, ceria-ytterbium oxide solid solution, ceria- Zirconia-praseodymium oxide solid solution, ceria-zirconia-terbium oxide solid solution, ceria-zirconia-ytterbium oxide solid solution are more preferable, ceria-zirconia-praseodymium oxide solid solution, ceria-zirconia-terbium oxide solid solution, ceria-zirconia-ytterbium oxide solid solution, and further ceria-zirconia-terbium oxide solid solution. Ceria-zirconia-praseodymium oxide solid solution is particularly preferable. These solid solutions containing ceria may be used alone or in combination of two or more.

  In the steam reforming catalyst of the present invention, ceria and at least one of zirconia and other rare earth oxides (more preferably praseodymium oxide, terbium oxide, and ytterbium oxide) are at least partially dissolved in each other. By using a composite oxide support that forms a solid solution, a steam reforming catalyst having such a composite oxide support is a catalyst that is higher in a steam reforming reaction of a fuel composed of hydrocarbons at a high temperature. It tends to show activity. The reason for this is not necessarily clear, but the present inventors speculate as follows. That is, such a composite oxide includes ceria having a low solid phase reactivity with a platinum group metal or a solid solution containing ceria (ceria, zirconia and other rare earth oxides (more preferably praseodymium oxide, terbium oxide, And at least one of ytterbium oxide) is included in the solid solution), and the first metal element made of the platinum group metal is oxidized and exposed to a high temperature of 600 ° C. or higher. It is presumed that the catalytic activity is increased because the solid-state reaction with the composite oxide does not proceed easily and is reduced to a metal state exhibiting high catalytic activity without being stabilized in the oxide state. In addition, the first metal element composed of the complex oxide and the platinum group metal exhibits a strong interaction, and the first metal element composed of the platinum group metal on the complex oxide support even at a high temperature of 600 ° C. or higher. It is presumed that the catalytic activity is increased because the grain growth of the catalyst is suppressed. In addition, ceria and solid solution containing ceria usually grow more easily in reducing atmosphere such as steam reforming reaction than oxidizing atmosphere, but ceria and alumina or solid solution containing ceria and alumina that do not solidly dissolve each other. It is presumed that the catalytic activity is increased because it acts as a barrier against each other and the grain growth of the complex oxide at high temperatures is suppressed, and the grain growth of the first metal element supported thereon is also suppressed. . The action of reducing the first metal element composed of the platinum group metal from an oxide state to a metal state is also expressed in ceria, but ceria is zirconia and other rare earth oxides (more preferably praseodymium oxide, oxidation oxide). Terbium and ytterbium oxide) are more effectively expressed when a solid solution is formed in solid solution with each other. Accordingly, in the composite oxide used in the present invention, at least a part of ceria and at least one of zirconia and other rare earth oxides (more preferably praseodymium oxide, terbium oxide, and ytterbium oxide) It is preferable to form solid solutions that are solid-solved with each other.

  By using such a composite oxide support, the steam reforming catalyst of the present invention exhibits higher catalytic activity in the steam reforming reaction of fuels composed of hydrocarbons.

  The composite oxide support used in the present invention can be produced, for example, by the following method. First, from an aqueous solution in which an aluminum compound, a cerium compound and a zirconium compound and a rare earth compound other than the cerium compound are dissolved or a solution containing water, an alumina precursor, a ceria precursor and a zirconia precursor, and a rare earth other than the ceria precursor An oxide precursor (hereinafter, also simply referred to as “other rare earth oxide precursor”) is deposited as a precipitate. At this time, all of the compounds may be blended at the same time, or may be blended in order as appropriate, or the precursor precipitates may be individually obtained and mixed. Examples of rare earth compounds other than the cerium compound (hereinafter also simply referred to as “other rare earth compounds”) include scandium (Sc), yttrium (Y), lanthanum (La), praseodymium (Pr), neodymium (Nd), and promethium. (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium Compounds of rare earth elements other than cerium (Ce) such as (Lu) are mentioned, and among them, a steam reforming catalyst having higher catalytic activity and catalyst deterioration preventing performance in a steam reforming reaction of fuels made of hydrocarbons is obtained. Praseodymium compounds, neodymium compounds, samarium compounds Gadolinium compound, terbium compound, dysprosium compound, ytterbium compound are preferred, praseodymium compounds, terbium compounds, ytterbium compounds are more preferable, praseodymium compounds are particularly preferred. These other rare earth compounds may be used alone or in combination of two or more. A ceria precursor and at least one of a zirconia precursor and another rare earth oxide precursor (more preferably, a praseodymium oxide precursor, a terbium oxide precursor, and an ytterbium oxide precursor) are used as a precipitate. It is preferable to deposit at the same time because at least a part thereof forms a solid solution.

  As the aluminum compound, cerium compound, zirconium compound and other rare earth compounds, salts such as sulfates, nitrates, chlorides and acetates are generally used. Examples of the solvent for dissolving the salt include water and alcohols. Furthermore, for example, a mixture of aluminum hydroxide, nitric acid and water can be used as an aqueous solution containing aluminum nitrate.

  The precursor precipitate can be precipitated by adding an alkaline solution to the aqueous solution or a solution containing water to adjust the pH of the solution. At this time, each precursor is added by instantly adding an alkaline solution and vigorously stirring, or by adding a hydrogen peroxide solution or the like to adjust the pH at which each precursor starts to precipitate, and then adding an alkaline solution or the like. Body precipitates can be deposited almost simultaneously. On the other hand, the alkaline solution is added over time, for example, over 10 minutes to increase the neutralization time, or the pH of the solution is monitored and adjusted stepwise to the pH at which each precursor precipitates. Or by adding a buffer solution so that the pH of the solution is maintained at a pH at which the precipitate of each precursor precipitates (or Vice versa).

  Examples of the alkaline solution include ammonia water, an aqueous solution or an alcohol solution in which ammonium carbonate, sodium hydroxide, potassium hydroxide, sodium carbonate and the like are dissolved. Among them, ammonia water, an aqueous solution of ammonium carbonate or an alcohol solution is preferable because it volatilizes when the composite oxide is fired. Further, from the viewpoint of promoting the precipitation reaction of the precursor precipitate, the pH of the alkaline solution is preferably 9 or more.

  Thereafter, the precursor precipitate thus obtained is aged and then baked to obtain the composite oxide support according to the present invention.

  In the method for producing the composite oxide support, when the precursor precipitate is aged, dissolution and reprecipitation of the precipitate are promoted by heating heat, and the resulting composite oxide particles can be grown. A complex oxide composed of crystallites having high crystallinity and an appropriate particle size can be obtained. The aging temperature is preferably room temperature or higher, more preferably from 80 ° C to 250 ° C, even more preferably from 100 to 200 ° C, particularly preferably from 100 to 150 ° C. When the aging temperature is less than the lower limit, the aging effect is small, and the time required for aging tends to be long.On the other hand, when the upper limit is exceeded, the water vapor pressure becomes extremely high, so a more expensive pressure vessel is required and manufactured. Cost tends to be high. In addition, when heat-aging at a temperature of 100 ° C. or higher, it is preferable to age in a pressure-resistant sealed container such as an autoclave under a hydrothermal condition under a high temperature and pressure of 100 ° C. or higher.

  In the method for producing the composite oxide support, the firing of the precipitate can be performed in the air. The firing temperature is preferably 300 to 800 ° C. When the firing temperature is less than the lower limit, the resulting composite oxide tends to lack stability as a carrier, and when the upper limit is exceeded, the specific surface area of the composite oxide tends to decrease.

  In such a method for producing a composite oxide support, from the viewpoint of making the surface composition of aluminum by X-ray photoelectron spectroscopy (XPS) measurement of the composite oxide support higher than the aluminum composition of the entire support. In the process of depositing the precursor as a precipitate from an aqueous solution of the compound or a solution containing water, rare earth elements other than aluminum, cerium, zirconium and cerium are deposited as simultaneously and uniformly as possible to form a uniform precursor. In the aging of the precursor precipitate, ceria, zirconia, other rare earth oxides (more preferably, at least of praseodymium oxide, terbium oxide, and ytterbium oxide in the uniform precursor are used. 1) is in a condition that makes it easy to form a solid solution. It is preferred to precipitate the crystal surface of the body.

  As mentioned above, although the suitable manufacturing method of the complex oxide support | carrier used for this invention was demonstrated, the manufacturing method of the said complex oxide support | carrier is not limited to the said embodiment. For example, the solution containing the precursor precipitate may be heated as it is to evaporate the solvent to dry the precipitate, and then fired. In this case, since the precipitate is aged during the drying of the precipitate, the drying of the precipitate is preferably performed at the aging temperature.

(Steam reforming catalyst)
The steam reforming catalyst of the present invention comprises such a composite oxide support and at least one first metal element selected from the group consisting of platinum group metals supported thereon.

  In such a steam reforming catalyst, a platinum group metal (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) and platinum (Pt)) supported on the carrier. It is necessary to contain at least one first metal element selected from the group consisting of:

  Of the at least one first metal element selected from the group consisting of the platinum group metals, rhodium (Rh) from the viewpoint of exhibiting high catalytic activity in the steam reforming reaction of fuels composed of hydrocarbons. Is more preferable. Moreover, the 1st metal element which belongs to the said platinum group may be used individually by 1 type, or may use 2 or more types together.

  The amount of the first metal element supported is not particularly limited, and it may be supported as appropriate according to the target design. In addition, it is preferable that it is 0.1-20 mass parts with respect to 100 mass parts of said complex oxide support | carriers in metal conversion as a load of a 1st metal element. When the loading amount of the first metal element is less than the lower limit, sufficient catalytic activity tends not to be obtained in the steam reforming reaction of the fuel composed of hydrocarbons. One metal element tends to grow and the catalytic activity does not improve. The amount of the first metal element supported is more preferably 0.5 to 10 parts by mass from the viewpoint of catalyst performance and cost. In addition, the particle diameter (average particle diameter) of the first metal element thus supported on the carrier is preferably 1 to 100 nm (more preferably 2 to 50 nm). When the particle diameter of the first metal element is less than the lower limit, it tends to be difficult to be in a metal state. On the other hand, when the particle diameter exceeds the upper limit, the amount of active sites tends to be remarkably reduced.

  As the method for supporting the first metal element, for example, the composite oxide support (or the composite oxide support is used in a cordierite honeycomb or the like in a solution containing the compound of the first metal element at a predetermined concentration). Examples thereof include a method in which a catalyst carrier-supporting base material coated on a base material is dipped to impregnate the composite oxide support with a solution containing a predetermined amount of the first metal element, and this is fired.

  The solution containing the compound of the first metal element is not particularly limited, but a salt solution of the first metal element can be used. For example, when a platinum salt is used as the salt of the first metal element Platinum (Pt) acetate, carbonate, nitrate, ammonium salt, citrate, dinitrodiammine salt and the like or their complexes. Among them, from the viewpoint of easy loading and high dispersibility, dinitrodiammine salt is preferable. preferable. When rhodium salt is used as the salt of the first metal element, for example, rhodium (Rh) acetate, carbonate, nitrate, ammonium salt, citrate, dinitrodiammine salt, or a complex solution thereof is used. Among them, nitrates are preferable from the viewpoint of easy loading and high dispersibility. The solvent is not particularly limited, and examples thereof include a solvent that can be dissolved in an ionic form such as water (preferably pure water such as ion-exchanged water and distilled water). The concentration of the first metal element salt solution is not particularly limited, but is preferably 0.001 to 0.5 mol / L as the first metal element salt ion. Further, the method for supporting the first metal element on the carrier using the salt solution of the first metal element is not particularly limited. For example, the solution of the salt of the first metal element is used. Known methods such as a method of impregnating the carrier with the carrier and a method of adsorbing and supporting the salt solution of the first metal element on the carrier can be appropriately employed.

  At this time, the composite oxide support may be used in the form of powder such as pellets, or the composite oxide support is used in advance by being fixed to a known base material such as a cordierite honeycomb base material by coating or the like. May be.

  Firing in such a supporting method can be performed in the atmosphere. The firing temperature is preferably 200 to 600 ° C. When the firing temperature is less than the lower limit, the compound of the first metal element is not sufficiently thermally decomposed and becomes difficult to be in a metal state, so that the activity tends to be lowered. There is a tendency that the catalytic activity in the steam reforming reaction of the fuel composed of hydrocarbons is reduced due to grain growth of the first metal element. The firing time is preferably 0.1 to 100 hours. When the firing time is less than the lower limit, the compound of the first metal element is not sufficiently thermally decomposed and becomes difficult to be in a metal state, so that the activity tends to be low. This is not effective, leading to an increase in cost for preparing the catalyst.

  In the steam reforming catalyst of the present invention, a group consisting of alkaline earth metals (magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), etc.) supported on the composite oxide support. It is preferable to further comprise at least one second metal element selected from: As a result, the heat resistance of the steam reforming catalyst of the present invention is improved, and higher activity is maintained even when exposed to high temperatures.

  Of the at least one second metal element selected from the group consisting of alkaline earth metals supported on the composite oxide support, magnesium and strontium from the viewpoint of being hard to react with solid solution with ceria or a solid solution containing ceria. , At least one selected from the group consisting of barium is preferred.

  The amount of the second metal element to be supported is not particularly limited, and may be appropriately supported according to the target design. The supported amount of the second metal element is preferably 0.0005 to 0.5 mol, and preferably 0.001 to 0.1 mol with respect to 100 g of the composite oxide support in terms of metal. More preferred. When the amount of the second metal element supported is less than the lower limit, the heat resistance tends not to be improved. On the other hand, when the upper limit is exceeded, the first metal element is adversely affected and the catalytic activity tends to decrease. It is in.

  As a method for supporting the second metal element, for example, a composite oxide carrier (or the first metal element) in which the first metal element is supported in a solution containing the compound of the second metal element at a predetermined concentration. A solution containing a predetermined amount of the second metal element by immersing a catalyst carrier-supporting base material in which a composite oxide carrier supporting the metal element is fixed on a base material such as a cordierite honeycomb. For example, a method of impregnating a complex oxide carrier on which a metal element is supported and firing the same is used.

  The solution containing the compound of the second metal element is not particularly limited, but a salt solution of the second metal element can be used. For example, when using a magnesium salt as the salt of the second metal element , Magnesium (Mg) acetate, nitrate, citrate, malate, benzoate, hydroxide, chloride, bromide, iodide, among others, high solubility in water and easy handling From the viewpoint that no halogen remains after firing, acetate and nitrate are preferable. Further, when a strontium salt is used as the salt of the second metal element, for example, acetate, nitrate, citrate, malate, hydroxide, chloride, bromide, iodide of strontium (Sr) can be mentioned. Of these, acetates and nitrates are preferred from the viewpoints of high solubility in water, easy handling, and no halogen remaining after firing. Further, when a barium salt is used as the salt of the second metal element, for example, barium (Ba) acetate, citrate, malate, hydroxide, chloride, bromide, iodide can be mentioned, Of these, acetate is preferred from the viewpoints of high solubility in water, easy handling, and no halogen remaining after firing. The solvent is not particularly limited, and examples thereof include a solvent that can be dissolved in an ionic form such as water (preferably pure water such as ion-exchanged water and distilled water). The concentration of the second metal element salt solution is not particularly limited, but is preferably 0.01 to 1.0 mol / L as the second metal element salt ion. In addition, the method for supporting the second metal element on the carrier on which the first metal element is supported using the salt solution of the second metal element is not particularly limited. A method of impregnating a carrier carrying the first metal element with a solution of the second metal element salt, adsorbing the salt solution of the second metal element onto the carrier carrying the first metal element A known method such as a method of supporting can be appropriately employed.

  At this time, the composite oxide carrier on which the first metal element is supported may be used in the form of powder such as pellets, or may be used by being immobilized on a known substrate such as a cordierite honeycomb substrate. Also good.

  Firing in such a supporting method can be performed in the atmosphere. The firing temperature is preferably 200 to 600 ° C. When the firing temperature is less than the lower limit, the compound of the second metal element is not sufficiently thermally decomposed, and the undecomposed second metal element compound covers the first metal element, so that the catalytic activity is lowered. On the other hand, if the upper limit is exceeded, the first metal element grows even if the compound of the second metal element is thermally decomposed, so that the catalytic activity tends to decrease. The firing time is preferably 0.1 to 100 hours. When the firing time is less than the lower limit, the compound of the second metal element is not sufficiently thermally decomposed, and the undecomposed second metal element compound covers the first metal element, so that the catalytic activity is lowered. On the other hand, even if the upper limit is exceeded, no further effect is obtained, leading to an increase in cost for preparing the catalyst.

  The form of the steam reforming catalyst of the present invention is not particularly limited. For example, it can be in the form of a honeycomb-shaped monolith catalyst, a pellet-shaped pellet catalyst, etc. It can also be set as the form arrange | positioned. A method for producing such a steam reforming catalyst is not particularly limited, but a known method can be appropriately employed. For example, a pellet-shaped steam reforming catalyst is formed by forming the catalyst into a pellet. A method for obtaining a steam reforming catalyst having a form coated (fixed) on the catalyst base by coating the catalyst base with a catalyst may be appropriately employed. Such a catalyst substrate is not particularly limited, and is appropriately selected depending on, for example, the use of the obtained steam reforming catalyst. However, the honeycomb monolith substrate, pellet substrate, plate substrate A material or the like is preferably employed. Further, the material of such a catalyst base material is not particularly limited. For example, a base material made of ceramics such as cordierite, silicon carbide, mullite, or a base material made of metal such as stainless steel containing chromium and aluminum. Is preferably employed.

  Such a steam reforming catalyst of the present invention is used for reforming a fuel comprising hydrocarbons with steam, and has a high catalytic activity in a steam reforming reaction of the fuel comprising hydrocarbons. It is shown.

[Steam reforming method]
Next, a method for steam reforming a fuel comprising the hydrocarbons of the present invention will be described. The fuel steam reforming method of the present invention is a method of generating hydrogen by bringing a fuel consisting of hydrocarbons into contact with the steam reforming catalyst of the present invention in the presence of steam.

  The steam reforming reaction apparatus used in such a steam reforming method is not particularly limited as long as it includes the steam reforming catalyst of the present invention, and has conventionally been used such as a fixed bed flow type reaction apparatus and a fluidized bed type reaction apparatus. A known catalytic reactor can be used.

  The fuel comprising the hydrocarbons is not particularly limited, and examples of the hydrocarbons include those containing alkanes, alkenes, alkynes, aromatic compounds, alcohols, aldehydes, and the like. Include methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane, etc., linear or branched saturated aliphatic hydrocarbons, cyclohexane, methylcyclohexane, cyclooctane, etc. Examples thereof include gaseous or liquid hydrocarbons such as hydrocarbons, monocyclic or polycyclic aromatic hydrocarbons. Specific examples of fuels composed of such hydrocarbons include hydrocarbons such as methane, ethane, ethylene, propane, and butane, mixed gases of these two or more, city gas, natural gas, petroleum gas, Gas fuel such as coal gas, generator gas, water gas, blast furnace gas, petroleum cracking gas, etc., liquid fuel such as gasoline, light oil, kerosene, diesel oil, methanol, ethanol, etc., and mixtures of two or more of these gas fuel and liquid fuel Fuel (a mixed fuel of two or more kinds of gaseous fuels, a mixed fuel of two or more kinds of liquid fuels, a mixed fuel of at least one kind of gaseous fuel and at least one kind of liquid fuel). Further, as the fuel made of hydrocarbons, biomass fuel made of hydrocarbons such as ethanol, gasoline, diesel fuel, natural gas, hydrocarbon gas, biodiesel, etc. can be used. Furthermore, when using as fuel which consists of hydrocarbons in internal combustion engines, such as a motor vehicle, the mixed fuel of ethanol and gasoline can be used, for example. As such a mixed fuel, since ethanol has a high octane number, by mixing gasoline with a low octane number (for example, in the range of 30 to 85) and ethanol, an octane number in the range of 80 to 100 equivalent to that of ordinary gasoline fuel. Can be obtained, and can be suitably used as a fuel for an internal combustion engine such as an automobile.

  Among the fuels consisting of these hydrocarbons, the steam reforming of the present invention is easy to handle because it is liquid at room temperature, has high safety, has high affinity with water (steam), and is easily available. The method is preferably applied to natural gas, methanol, ethanol, and a mixed fuel of ethanol and gasoline, and more preferably applied to a mixed fuel of ethanol and ethanol and gasoline.

  In the steam reforming method for fuel comprising hydrocarbons of the present invention, the fuel and steam comprising the hydrocarbons may be supplied independently to the reactor, or after mixing them in advance, You may supply.

  The mixing ratio of the fuel composed of hydrocarbons and water vapor is not particularly limited. For example, when the fuel composed of hydrocarbons is ethanol, the molar ratio (S / C) of water vapor to carbon is 0.2. It is preferable that it is -2, and it is more preferable that it is 0.4-1. By using the steam reforming catalyst of the present invention, a fuel composed of hydrocarbons can be reformed even under low S / C conditions where coking has conventionally occurred. That is, the method for steam reforming of a fuel comprising the hydrocarbons of the present invention is performed under conditions of low S / C of S / C = 0.2 to 0.6 (preferably 0.4 to 0.6). This is particularly effective for the reforming reaction.

  The temperature of the reforming reaction is preferably 250 to 650 ° C, more preferably 350 to 600 ° C. By using the steam reforming catalyst of the present invention, the reforming of the fuel made of hydrocarbons even at a low temperature of 400 ° C. or lower, which has been conventionally difficult to perform steam reforming of the fuel made of hydrocarbons. It becomes possible to make it. In addition, it is possible to maintain high activity even at a high temperature of 550 ° C. or higher, and it is possible to reform a fuel composed of hydrocarbons with steam.

[Steam reforming reactor]
Next, the steam reforming reaction apparatus of the present invention will be described. The steam reforming reaction apparatus of the present invention is characterized by comprising the steam reforming catalyst of the present invention. As described above, the steam reforming reaction apparatus of the present invention only needs to include the steam reforming catalyst of the present invention, and other configurations are not particularly limited, and the configuration of a known steam reforming reaction apparatus is appropriately used. be able to. The steam reforming catalyst of the present invention is capable of efficiently producing hydrogen by contacting a fuel composed of hydrocarbons in the presence of steam, so that the steam reforming reaction of the present invention. The apparatus preferably has a configuration that allows the fuel made of hydrocarbons to efficiently contact the steam reforming catalyst of the present invention in the presence of steam. It is preferable to further include a container capable of holding the fuel composed of hydrocarbons and the steam reforming catalyst below, and disposing the steam reforming catalyst of the present invention in the container. As such a steam reforming reaction apparatus, a conventionally known catalytic reaction apparatus such as a fixed bed flow reaction apparatus or a fluidized bed reaction apparatus can be used.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example. The physical properties of the composite oxide were measured by the following methods.

<Specific surface area>
Using a fully automatic specific surface area measuring device, the BET single point method using N ₂ adsorption at liquid nitrogen temperature (−196 ° C.) was used.

Example 1
0.2 mol (75.1 g) of aluminum nitrate nonahydrate and 0.047 mol (20.6 g) of praseodymium nitrate hexahydrate were added to 2000 ml of ion-exchanged water and stirred for 5 minutes with a propeller stirrer. Dissolved. The solution was stirred by adding the concentration of CeO ₂ in terms of 28% by weight of the aqueous cerium nitrate solution 262 g (corresponding to 0.43 mol in terms of CeO ₂₎ 5 minutes. Next, an aqueous solution in which 0.068 mol (18.1 g) of zirconyl nitrate dihydrate was dissolved in 30 g of ion-exchanged water was added to the mixed aqueous solution, followed by stirring for 5 minutes. To the obtained mixed aqueous solution, 189 g of 25% by mass ammonia water was added and stirred for 10 minutes to obtain an aqueous solution containing a precipitate. This aqueous solution was heat-treated under a pressure of 2 atm and a temperature condition of 120 ° C. for 2 hours to age the precipitate.

Next, the aged aqueous solution containing the precipitate is heated to 400 ° C. at a heating rate of 100 ° C./hour, further calcined at 400 ° C. for 5 hours, and then calcined at 600 ° C. for 5 hours to obtain a composite oxide powder. A was prepared. The obtained composite oxide powder A is composed of 10.2% by mass of alumina, 73.4% by mass of ceria, 8.3% by mass of zirconia, and 8.1% by mass of praseodymium oxide. The surface area was about 100 m ² / g.

  Next, 74.1 g of ceria sol binder (“U-15” manufactured by Taki Chemical Co., Ltd., solid content concentration of 15% by mass) is added to 100 g of the obtained composite oxide powder A, and the slurry is mixed for 20 minutes with a wet attritor. Got. The slurry was applied to a cordierite honeycomb monolith substrate (400 cells / square inch) having a diameter of 23 mm × length of 25 mm and a volume of 10.4 ml at a rate of 240 g per 1 L of the substrate (coat). Then, the catalyst carrier-supporting base material A on which a carrier made of a ceria-zirconia-alumina-praseodymium oxide composite oxide was supported was obtained by baking at 500 ° C. for 3 hours.

  Next, the ceria-zirconia-alumina-praseodymium oxide composite oxide carrier supported on the catalyst carrier supporting substrate A is impregnated with a predetermined amount of an aqueous rhodium nitrate solution in which rhodium is dissolved, and rhodium is supported by a selective adsorption method. After that, in the atmosphere, it is calcined at 500 ° C. for 3 hours to support rhodium on the carrier, and a steam reforming catalyst in a form supported on a monolith substrate (rhodium / ceria-zirconia-alumina- Praseodymium oxide composite oxide carrier) was obtained. The supported amount of rhodium per liter of monolith substrate was 4.8 g (/ L). The resulting steam reforming catalyst supported on the monolith substrate was used as a monolith catalyst sample.

(Example 2)
0.2 mol (75.1 g) of aluminum nitrate nonahydrate and 0.047 mol (20.7 g) of neodymium nitrate hexahydrate were added to 2000 ml of ion-exchanged water and stirred for 5 minutes with a propeller stirrer. Dissolved. The solution was stirred by adding the concentration of CeO ₂ in terms of 28% by weight of the aqueous cerium nitrate solution 262 g (corresponding to 0.43 mol in terms of CeO ₂₎ 5 minutes. Next, an aqueous solution in which 0.068 mol (18.1 g) of zirconyl nitrate dihydrate was dissolved in 30 g of ion-exchanged water was added to the mixed aqueous solution, followed by stirring for 5 minutes. To the obtained mixed aqueous solution, 189 g of 25% by mass ammonia water was added and stirred for 10 minutes to obtain an aqueous solution containing a precipitate. This aqueous solution was heat-treated under a pressure of 2 atm and a temperature condition of 120 ° C. for 2 hours to age the precipitate.

Next, the aged aqueous solution containing the precipitate is heated to 400 ° C. at a heating rate of 100 ° C./hour, further calcined at 400 ° C. for 5 hours, and then calcined at 600 ° C. for 5 hours to obtain a composite oxide powder. B was prepared. The obtained composite oxide powder B is composed of 10.2% by mass of alumina, 73.4% by mass of ceria, 8.4% by mass of zirconia, and 8.0% by mass of neodymium oxide. The surface area was about 100 m ² / g.

  Subsequently, using the composite oxide powder B obtained instead of the composite oxide powder A, a cordierite honeycomb monolith substrate is made of a ceria-zirconia-alumina-neodymium oxide composite oxide in the same manner as in Example 1. A catalyst carrier-supporting base material B on which a carrier is supported is obtained. Further, in the same manner as in Example 1, rhodium is supported on the carrier, and a steam reforming catalyst (rhodium / ceria-zirconia) is supported on a monolith substrate. -Alumina-neodymium oxide composite oxide carrier) was obtained. The supported amount of rhodium per liter of monolith substrate was 4.8 g (/ L). The resulting steam reforming catalyst supported on the monolith substrate was used as a monolith catalyst sample.

(Example 3)
In the same manner as in Example 1, a rhodium / ceria-zirconia-alumina-praseodymium oxide composite oxide carrier supported on a monolith substrate was prepared. The rhodium / ceria-zirconia-alumina-praseodymium oxide composite oxide support was impregnated with a predetermined amount of an aqueous solution in which magnesium acetate tetrahydrate was dissolved, dried in the atmosphere at 110 ° C. for 16 hours, Steam reforming catalyst (rhodium-magnesium / ceria-zirconia-alumina-praseodymium composite oxide) in a form in which magnesium is supported on the carrier by firing at 500 ° C. for 3 hours and supported on a monolith substrate. Carrier) was obtained. The supported amount of rhodium per liter of monolith substrate was 4.8 g (/ L), and the supported amount of magnesium was 0.024 mol (/ L). The resulting steam reforming catalyst supported on the monolith substrate was used as a monolith catalyst sample.

Example 4
A steam reforming catalyst supported on a monolith substrate in the same manner as in Example 3 except that an aqueous solution in which strontium acetate is dissolved is used instead of an aqueous solution in which magnesium acetate tetrahydrate is dissolved. (Rhodium-strontium / ceria-zirconia-alumina-praseodymium oxide composite oxide support) was prepared. The supported amount of rhodium per liter of monolith substrate was 4.8 g (/ L), and the supported amount of strontium was 0.024 mol (/ L). The resulting steam reforming catalyst supported on the monolith substrate was used as a monolith catalyst sample.

(Example 5)
A steam reforming catalyst supported on a monolith substrate in the same manner as in Example 3 except that an aqueous solution in which barium acetate was dissolved was used instead of an aqueous solution in which magnesium acetate tetrahydrate was dissolved. (Rhodium-barium / ceria-zirconia-alumina-praseodymium oxide composite oxide support) was prepared. The supported amount of rhodium per liter of monolith substrate was 4.8 g (/ L), and the supported amount of barium was 0.024 mol (/ L). The resulting steam reforming catalyst supported on the monolith substrate was used as a monolith catalyst sample.

(Example 6)
0.2 mol (75.1 g) of aluminum nitrate nonahydrate and 0.047 mol (21.1 g) of samarium nitrate hexahydrate were added to 2000 ml of ion-exchanged water and stirred for 5 minutes with a propeller stirrer. Dissolved. The solution was stirred by adding the concentration of CeO ₂ in terms of 28% by weight of the aqueous cerium nitrate solution 262 g (corresponding to 0.43 mol in terms of CeO ₂₎ 5 minutes. Next, an aqueous solution in which 0.068 mol (18.1 g) of zirconyl nitrate dihydrate was dissolved in 30 g of ion-exchanged water was added to the mixed aqueous solution, followed by stirring for 5 minutes. To the obtained mixed aqueous solution, 189 g of 25% by mass ammonia water was added and stirred for 10 minutes to obtain an aqueous solution containing a precipitate. This aqueous solution was heat-treated under a pressure of 2 atm and a temperature condition of 120 ° C. for 2 hours to age the precipitate.

Next, the aged aqueous solution containing the precipitate is heated to 400 ° C. at a heating rate of 100 ° C./hour, further calcined at 400 ° C. for 5 hours, and then calcined at 600 ° C. for 5 hours to obtain a composite oxide powder. C was prepared. The obtained composite oxide powder C is composed of 10.2% by mass of alumina, 73.2% by mass of ceria, 8.3% by mass of zirconia, and 8.3% by mass of samarium oxide. The surface area was about 100 m ² / g.

  Next, using the composite oxide powder C obtained instead of the composite oxide powder A, a cordierite honeycomb monolith substrate is made of a ceria-zirconia-alumina-samarium oxide composite oxide in the same manner as in Example 1. A catalyst carrier-supporting substrate C on which a carrier is supported is obtained, and a steam reforming catalyst (rhodium / ceria-zirconia) in a form in which rhodium is supported on the carrier and supported on a monolith substrate in the same manner as in Example 1. -Alumina-samarium oxide composite oxide support) was obtained. The supported amount of rhodium per liter of monolith substrate was 4.8 g (/ L). The resulting steam reforming catalyst supported on the monolith substrate was used as a monolith catalyst sample.

(Example 7)
0.2 mol (75.1 g) of aluminum nitrate nonahydrate and 0.047 mol (21.4 g) of gadolinium nitrate hexahydrate were added to 2000 ml of ion-exchanged water and stirred for 5 minutes with a propeller stirrer. Dissolved. The solution was stirred by adding the concentration of CeO ₂ in terms of 28% by weight of the aqueous cerium nitrate solution 262 g (corresponding to 0.43 mol in terms of CeO ₂₎ 5 minutes. Next, an aqueous solution in which 0.068 mol (18.1 g) of zirconyl nitrate dihydrate was dissolved in 30 g of ion-exchanged water was added to the mixed aqueous solution, followed by stirring for 5 minutes. To the obtained mixed aqueous solution, 189 g of 25% by mass ammonia water was added and stirred for 10 minutes to obtain an aqueous solution containing a precipitate. This aqueous solution was heat-treated under a pressure of 2 atm and a temperature condition of 120 ° C. for 2 hours to age the precipitate.

Next, the aged aqueous solution containing the precipitate is heated to 400 ° C. at a heating rate of 100 ° C./hour, further calcined at 400 ° C. for 5 hours, and then calcined at 600 ° C. for 5 hours to obtain a composite oxide powder. D was prepared. The obtained composite oxide powder D is composed of 10.2% by mass of alumina, 73.0% by mass of ceria, 8.3% by mass of zirconia, and 8.5% by mass of gadolinium oxide. The surface area was about 100 m ² / g.

  Subsequently, using the composite oxide powder D obtained instead of the composite oxide powder A, a cordierite honeycomb monolith substrate is made of a ceria-zirconia-alumina-gadolinium oxide composite oxide in the same manner as in Example 1. A catalyst carrier-supporting substrate D on which a carrier is supported is obtained, and a steam reforming catalyst (rhodium / ceria-zirconia) in a form in which rhodium is supported on the carrier and supported on a monolith substrate in the same manner as in Example 1. -Alumina-gadolinium oxide composite oxide carrier) was obtained. The supported amount of rhodium per liter of monolith substrate was 4.8 g (/ L). The resulting steam reforming catalyst supported on the monolith substrate was used as a monolith catalyst sample.

(Example 8)
0.2 mol (75.1 g) of aluminum nitrate nonahydrate and 0.047 mol (21.5 g) of terbium nitrate hexahydrate were added to 2000 ml of ion-exchanged water and stirred for 5 minutes with a propeller stirrer. Dissolved. The solution was stirred by adding the concentration of CeO ₂ in terms of 28% by weight of the aqueous cerium nitrate solution 262 g (corresponding to 0.43 mol in terms of CeO ₂₎ 5 minutes. Next, an aqueous solution in which 0.068 mol (18.1 g) of zirconyl nitrate dihydrate was dissolved in 30 g of ion-exchanged water was added to the mixed aqueous solution, followed by stirring for 5 minutes. To the obtained mixed aqueous solution, 189 g of 25% by mass ammonia water was added and stirred for 10 minutes to obtain an aqueous solution containing a precipitate. This aqueous solution was heat-treated under a pressure of 2 atm and a temperature condition of 120 ° C. for 2 hours to age the precipitate.

Next, the aged aqueous solution containing the precipitate is heated to 400 ° C. at a heating rate of 100 ° C./hour, further calcined at 400 ° C. for 5 hours, and then calcined at 600 ° C. for 5 hours to obtain a composite oxide powder. E was prepared. The obtained composite oxide powder E is composed of 10.2% by mass of alumina, 72.9% by mass of ceria, 8.3% by mass of zirconia, and 8.6% by mass of terbium oxide. The surface area was about 100 m ² / g.

  Next, using the composite oxide powder E obtained instead of the composite oxide powder A, a cordierite honeycomb monolith substrate is made of a ceria-zirconia-alumina-terbium oxide composite oxide in the same manner as in Example 1. A catalyst carrier-supporting substrate E on which a carrier is supported is obtained. Further, in the same manner as in Example 1, rhodium is supported on the carrier, and a steam reforming catalyst (rhodium / ceria-zirconia) is supported on a monolith substrate. -Alumina-terbium oxide composite oxide carrier) was obtained. The supported amount of rhodium per liter of monolith substrate was 4.8 g (/ L). The resulting steam reforming catalyst supported on the monolith substrate was used as a monolith catalyst sample.

Example 9
0.2 mol (75.1 g) of aluminum nitrate nonahydrate and 0.047 mol (21.6 g) of dysprosium nitrate hexahydrate were added to 2000 ml of ion-exchanged water and stirred for 5 minutes with a propeller stirrer. Dissolved. The solution was stirred by adding the concentration of CeO ₂ in terms of 28% by weight of the aqueous cerium nitrate solution 262 g (corresponding to 0.43 mol in terms of CeO ₂₎ 5 minutes. Next, an aqueous solution in which 0.068 mol (18.1 g) of zirconyl nitrate dihydrate was dissolved in 30 g of ion-exchanged water was added to the mixed aqueous solution, followed by stirring for 5 minutes. To the obtained mixed aqueous solution, 189 g of 25% by mass ammonia water was added and stirred for 10 minutes to obtain an aqueous solution containing a precipitate. This aqueous solution was heat-treated under a pressure of 2 atm and a temperature condition of 120 ° C. for 2 hours to age the precipitate.

Next, the aged aqueous solution containing the precipitate is heated to 400 ° C. at a heating rate of 100 ° C./hour, further calcined at 400 ° C. for 5 hours, and then calcined at 600 ° C. for 5 hours to obtain a composite oxide powder. F was prepared. The obtained composite oxide powder F is composed of 10.1% by mass of alumina, 72.8% by mass of ceria, 8.3% by mass of zirconia, and 8.8% by mass of dysprosium oxide. The surface area was about 100 m ² / g.

  Subsequently, using the composite oxide powder F obtained instead of the composite oxide powder A, a cordierite honeycomb monolith substrate is made of a ceria-zirconia-alumina-dysprosium oxide composite oxide in the same manner as in Example 1. A catalyst carrier-supporting substrate F on which a carrier is supported is obtained, and a steam reforming catalyst (rhodium / ceria-zirconia) in a form in which rhodium is supported on the carrier and supported on a monolith substrate in the same manner as in Example 1. -Alumina-dysprosium oxide composite oxide carrier) was obtained. The supported amount of rhodium per liter of monolith substrate was 4.8 g (/ L). The resulting steam reforming catalyst supported on the monolith substrate was used as a monolith catalyst sample.

(Example 10)
0.2 mol (75.1 g) of aluminum nitrate nonahydrate and 0.047 mol (21.3 g) of ytterbium nitrate pentahydrate were added to 2000 ml of ion-exchanged water and stirred for 5 minutes with a propeller stirrer. Dissolved. The solution was stirred by adding the concentration of CeO ₂ in terms of 28% by weight of the aqueous cerium nitrate solution 262 g (corresponding to 0.43 mol in terms of CeO ₂₎ 5 minutes. Next, an aqueous solution in which 0.068 mol (18.1 g) of zirconyl nitrate dihydrate was dissolved in 30 g of ion-exchanged water was added to the mixed aqueous solution, followed by stirring for 5 minutes. To the obtained mixed aqueous solution, 189 g of 25% by mass ammonia water was added and stirred for 10 minutes to obtain an aqueous solution containing a precipitate. This aqueous solution was heat-treated under a pressure of 2 atm and a temperature condition of 120 ° C. for 2 hours to age the precipitate.

Next, the aged aqueous solution containing the precipitate is heated to 400 ° C. at a heating rate of 100 ° C./hour, further calcined at 400 ° C. for 5 hours, and then calcined at 600 ° C. for 5 hours to obtain a composite oxide powder. G was prepared. The obtained composite oxide powder G is composed of 10.1% by mass of alumina, 72.5% by mass of ceria, 8.2% by mass of zirconia, and 9.2% by mass of ytterbium oxide. The surface area was about 100 m ² / g.

  Next, using the composite oxide powder G obtained instead of the composite oxide powder A, a cordierite honeycomb monolith substrate is made of a ceria-zirconia-alumina-ytterbium oxide composite oxide in the same manner as in Example 1. A catalyst carrier-supporting substrate G on which a carrier is supported is obtained. Further, in the same manner as in Example 1, rhodium is supported on the carrier, and a steam reforming catalyst (rhodium / ceria-zirconia) is supported on a monolith substrate. -Alumina-ytterbium oxide composite oxide carrier) was obtained. The supported amount of rhodium per liter of monolith substrate was 4.8 g (/ L). The resulting steam reforming catalyst supported on the monolith substrate was used as a monolith catalyst sample.

(Comparative Example 1)
0.2 mol (75.1 g) of aluminum nitrate nonahydrate was added to 2000 ml of ion-exchanged water, and dissolved by stirring for 5 minutes with a propeller stirrer. The solution was stirred by adding the concentration of CeO ₂ in terms of 28% by weight of the aqueous cerium nitrate solution 262 g (corresponding to 0.43 mol in terms of CeO ₂₎ 5 minutes. Next, an aqueous solution in which 0.068 mol (18.1 g) of zirconyl nitrate dihydrate was dissolved in 30 g of ion-exchanged water was added to the mixed aqueous solution, followed by stirring for 5 minutes. To the obtained mixed aqueous solution, 177 g of 25 mass% ammonia water was added and stirred for 10 minutes to obtain an aqueous solution containing a precipitate. This aqueous solution was heat-treated under a pressure of 2 atm and a temperature condition of 120 ° C. for 2 hours to age the precipitate.

Next, the aged aqueous solution containing the precipitate is heated to 400 ° C. at a temperature increase rate of 100 ° C./hour, further calcined at 400 ° C. for 5 hours, and then calcined at 600 ° C. for 5 hours. Oxide powder H was prepared. The obtained composite oxide powder H was composed of 11.1% by mass of alumina, 79.8% by mass of ceria and 9.1% by mass of zirconia, and the specific surface area was about 100 m ² / g. It was.

  Next, using the composite oxide powder H for comparison obtained instead of the composite oxide powder A, a cordierite honeycomb monolith substrate is made of a ceria-zirconia-alumina composite oxide in the same manner as in Example 1. A comparative catalyst carrier-supporting substrate H on which a comparative carrier is supported is obtained. Further, in the same manner as in Example 1, rhodium is supported on the carrier, and the comparative steam reformer is supported on a monolith substrate. Catalyst (rhodium / ceria-zirconia-alumina composite oxide support) was obtained. The supported amount of rhodium per liter of monolith substrate was 4.8 g (/ L). The comparative steam reforming catalyst in a form supported on the obtained monolith substrate was used as a comparative monolith catalyst sample.

(Comparative Example 2)
As the nitrate compound of each component of the composite oxide powder, 0.2 mol (75.1 g) of aluminum nitrate nonahydrate, 0.43 mol (187 g) of cerium nitrate hexahydrate, 0. 068 mol (18.1 g) and praseodymium nitrate hexahydrate 0.047 mol (20.6 g) were prepared and dissolved in 2000 ml of ion-exchanged water. 189 g was added dropwise to precipitate the composite hydroxide. The aqueous solution containing the precipitate is centrifuged to remove the precipitate, and the precipitate is dried in a temperature atmosphere at 150 ° C. for 16 hours, and then calcined at 600 ° C. for 5 hours, thereby comparing the composite oxide powder. J was prepared. The obtained composite oxide powder J is composed of 10.2% by mass of alumina, 73.4% by mass of ceria, 8.3% by mass of zirconia, and 8.1% by mass of praseodymium oxide. The surface area was about 150 m ² / g.

  Next, using the composite oxide powder J for comparison obtained instead of the composite oxide powder A, the cordierite honeycomb monolith substrate was coated with the ceria-zirconia-alumina-praseodymium composite in the same manner as in Example 1. A comparative catalyst carrier-supporting base material J on which a comparative carrier made of an oxide was supported was obtained. Further, in the same manner as in Example 1, rhodium was supported on the carrier, and the carrier was supported on a monolith base material. A comparative steam reforming catalyst (rhodium / ceria-zirconia-alumina-praseodymium oxide composite oxide support) was obtained. The supported amount of rhodium per liter of monolith substrate was 4.8 g (/ L). The comparative steam reforming catalyst in a form supported on the obtained monolith substrate was used as a comparative monolith catalyst sample.

(Comparative Example 3)
As the nitrate compound of each component of the composite oxide powder, 0.2 mol (75.1 g) of aluminum nitrate nonahydrate, 0.43 mol (187 g) of cerium nitrate hexahydrate, 0. 068 mol (18.1 g) and neodymium nitrate hexahydrate 0.047 mol (20.7 g) were prepared, dissolved in 2000 ml of ion-exchanged water, and then mixed with aqueous ammonia as a coprecipitate. 189 g was added dropwise to precipitate the composite hydroxide. The aqueous solution containing the precipitate is centrifuged to remove the precipitate, and the precipitate is dried in a temperature atmosphere at 150 ° C. for 16 hours, and then calcined at 600 ° C. for 5 hours, thereby comparing the composite oxide powder. K was prepared. The obtained composite oxide powder K is composed of 10.2% by mass of alumina, 73.4% by mass of ceria, 8.4% by mass of zirconia and 8.0% by mass of neodymium oxide. The surface area was about 150 m ² / g.

  Next, using the composite oxide powder K for comparison obtained instead of the composite oxide powder A, the cordierite honeycomb monolith substrate was coated with a ceria-zirconia-alumina-neodymium oxide composite in the same manner as in Example 1. A comparative catalyst carrier-supporting base material K on which a comparative carrier made of an oxide was supported was obtained. Further, in the same manner as in Example 1, rhodium was supported on the carrier, and the carrier was supported on a monolith base material. A comparative steam reforming catalyst (rhodium / ceria-zirconia-alumina-neodymium oxide composite oxide support) was obtained. The supported amount of rhodium per liter of monolith substrate was 4.8 g (/ L). The comparative steam reforming catalyst in a form supported on the obtained monolith substrate was used as a comparative monolith catalyst sample.

[Steam reforming reaction activity test and durability test of mixed fuel of ethanol and gasoline]
The steam reforming reaction activity test and the durability test were performed on the monolith catalyst samples obtained in Examples 1 to 10 and the comparative monolith catalyst samples obtained in Comparative Examples 1 to 3.

First, E20 fuel containing 20% by volume of ethanol was prepared by mixing ethanol (anhydrous) and commercial gasoline at a volume ratio of 20:80. Next, E20 fuel and ion-exchanged water are used for a CO ₂ (14%) / N ₂ mixed gas with a gas flow rate of 4.6 L / min using a liquid pump, respectively, at 0.67 mL / min and 0.54 mL / min. A model gas used in the activity test and the durability test was prepared by adding and vaporizing at a flow rate. At this time, the water vapor / carbon ratio (S / C) was 0.93, and the gas flow rate was 5.4 L / min.

Next, the monolith catalyst sample obtained in Examples 1 to 10 and the comparative monolith catalyst sample obtained in Comparative Examples 1 to 3 were each filled into a stainless steel reaction tube having an inner diameter of 23.5 mm. A fixed bed flow reactor was installed. Next, as a pretreatment, the model gas was supplied to the monolith catalyst, and held for about 1 hour in the order of the catalyst bed temperatures of 600 ° C., 500 ° C., and 400 ° C., respectively. Thereafter, as an activity test and a durability test, the catalyst bed temperature was set to 550 ° C. and held for 120 minutes. The hydrogen (H ₂ ) generation concentration at that time was measured by a gas chromatograph method, and the change with time was examined.

The graph which shows the steam reforming reaction activity of the fuel (E20 fuel) which consists of hydrocarbons about the monolith catalyst obtained in Examples 1-10 and Comparative Examples 1-3 is shown to FIG. 1A-FIG. 1C. As is apparent from a comparison between the results of Examples 1 to 10 shown in FIGS. 1A to 1C and the results of Comparative Examples 1 to 3, generation of H _{2 for} each reaction time (minute) shown in FIGS. 1A to 1C. Considering the case where the reaction time is 10 minutes in terms of concentration as the almost initial state, the monolith catalysts of Examples 1 to 10 have the reforming reaction activity in the initial state superior to the comparative monolith catalysts of Comparative Examples 1 to 3. It was confirmed that

Moreover, although the activity of any of the catalysts of Examples 1 to 10 and Comparative Examples 1 to 3 decreased with the progress of the reaction time, the monolith catalysts of Examples 1 to 2 were the comparative monolith catalysts of Comparative Examples 1 to 3. It was confirmed that the decrease rate of the H ₂ generation concentration was smaller and the durability was high (FIG. 1A). In addition, it was confirmed that the monolith catalysts of Examples 3 to 5 had a very low durability and a very high durability even when the reaction time passed (FIG. 1B). Furthermore, the monolith catalysts of Examples 6 to 10 have a higher H ₂ generation concentration at each reaction time than the comparative monolith catalyst of Comparative Example 1, and the durability is the same as the monolith catalysts of Examples 1 and 2. Was confirmed to be high (FIG. 1C). In addition, in the comparative monolith catalysts of Comparative Examples 2 to 3, the decrease in the activity with the lapse of the reaction time was most remarkable (FIG. 1A).

  From these results, the monolith catalysts of Examples 1 to 10 are both high in E20 fuel steam reforming reaction activity in the initial state and their durability. In particular, the monolith catalysts of Examples 3 to 5 are It was confirmed that the durability was extremely high, and it was confirmed that the catalyst activity was sufficiently excellent.

[Surface analysis of composite oxide support]
Surface analysis of the composite oxide carriers obtained in Examples 1-2, 6-10 and Comparative Examples 1-3 was performed by X-ray photoelectron spectroscopy (XPS). A scanning X-ray photoelectron spectrometer (“Quantum-2000” manufactured by ULVAC-PHI) is used as the XPS apparatus, AlKα is applied to the X-ray source, the photoelectron extraction angle is 45 °, and the analysis region is 800 μm × 500 μm. X-ray photoelectron spectrum (XPS) was measured under the conditions of pass energy: 26 eV and energy step: 0.1 eV. The surface composition was calculated using 3d peaks of rare earth elements other than Al2p, Ce3d, Zr3d, and Ce. The results are shown in Table 1. For reference, Table 1 also shows the composition (charged value) of the entire carrier.

  As is clear from the comparison between the results of Examples 1-2 and 6-10 shown in Table 1 and the results of Comparative Examples 1-3, the composite oxidation of the steam reforming catalysts of Examples 1-2, 6-10 It was confirmed that the material carrier has a surface Al composition significantly higher than that of the entire sample.

  These results show that in the composite oxide carriers of Examples 1-2 and 6-10, fine alumina particles are present around the composite oxide crystal particles composed of ceria, zirconia and other rare earth oxides. This is considered to indicate that it is arranged. A composite oxide composed of ceria, zirconia, and other rare earth oxides easily grows in a reducing atmosphere, and may grow even during pretreatment (up to 600 ° C.) during an activity test. Therefore, in the catalysts of Examples 1-2 and 6-10, the initial state that the grain growth of the composite oxide composed of ceria, zirconia and other rare earth oxides during the activity test was suppressed by the barrier effect of alumina. This is considered to be one of the reasons for the high performance. Further, the catalysts of Examples 3 to 5 are considered to have exhibited high performance in the initial state for the same reason because the composite oxide support is the same as the composite oxide support of Example 1.

[Hydrogen - heating reduction test _(H 2-TPR test)
About the steam reforming catalyst obtained in Examples 1 to 4 and 6 to 8 and the steam reforming catalyst for comparison (initial state) obtained in Comparative Examples 1 to 3, a hydrogen-temperature reduction test (H ₂ -TPR) Test, Hydrogen Temperature Programmed Reduction).

In such an H ₂ -TPR test, first, the catalyst in a powder state coated on the monolith substrate in each monolith catalyst sample was scraped off to obtain a test catalyst powder. Next, about 40 mg of the obtained test catalyst powder was filled in a quartz reaction tube (inner diameter: 10 mm) of a fixed bed flow type reaction apparatus (trade name “TP5000” manufactured by Henmi Kakushakusha) and tested as an oxidation pretreatment. A mixed gas (A) composed of O ₂ (60% by volume) / Ar (remainder) is supplied to the catalyst powder at a rate of 50 mL / min, and the bed temperature of the catalyst is 300 at a rate of temperature increase of 60 ° C./min. The temperature was raised to 0 ° C., and the mixture gas (A) was supplied at 50 mL / min and maintained at 300 ° C. for 20 minutes. Next, the mixed gas (A) is used to cool the catalyst until the bed temperature of the catalyst reaches room temperature, and then the gas species (B) is switched to a gas (B) made of Ar (100% by volume), so that the gas (B) is 50 mL / A supply process (purge process) was performed for 30 minutes at a supply speed of 1 minute. Next, the supply gas species is switched to a mixed gas (C) composed of H ₂ (1% by volume) / Ar (remainder), and the mixed gas (C) is supplied at a supply rate of 50 mL / min for 5 minutes, and then mixed. While supplying gas (C), the bed temperature of the catalyst was increased from 30 ° C. to 810 ° C. at a rate of temperature increase of 20 ° C./min. Then, such quadrupole mass spectrometer of _{H 2} concentration of the outgoing gas in the heated (QMS: Quadrupol Mass Spectrometer, Q squares) was used for the measurement. As a graph showing the relationship between the H ₂ concentration (%) in the output gas and the temperature (° C.), the steam reforming catalysts obtained in Examples 1-4, 6-8 and Comparative Examples 1-3 in the initial state were used. H ₂ -TPR spectra are shown in FIGS. 2A is an H ₂ -TPR spectrum (a graph showing the relationship between the H ₂ concentration in the output gas and the temperature) of the steam reforming catalyst obtained in Examples 1-2 and Comparative Example 1 in the initial state, and FIG. H ₂ -TPR spectrum of the steam reforming catalyst obtained in Examples 3 to 4 in the initial state and Comparative Example 1 (a graph showing the relationship between the H ₂ concentration in the output gas and the temperature), FIG. 2C shows the initial state. H ₂ -TPR spectrum of the steam reforming catalyst obtained in Examples 6 to 8 and Comparative Example 1 (a graph showing the relationship between the H ₂ concentration in the output gas and the temperature), FIG. 2D shows Comparative Example 1 in the initial state. 4 is an H ₂ -TPR spectrum (a graph showing the relationship between the H ₂ concentration in the output gas and the temperature) of the steam reforming catalyst obtained in -3. Note that the ease of reduction of the Rh active species in the catalyst is known from the temperature at which consumption of H ₂ is started, and the reduction amount of the Rh active species is known from the consumption of H ₂ . In the H ₂ -TPR test, H ₂ consumption was observed in a temperature range of about 40 ° C. to about 200 ° C. This is considered to be due to the reduction of Rh oxidized in the pre-oxidation treatment. Table 2 shows the results of calculating the H ₂ consumption amount and the H ₂ consumption center temperature. Note that with H ₂ consumption core temperature is a temperature at which the H ₂ 50% of the total H ₂ consumption is consumed.

  As apparent from the comparison of the results of Examples 1 to 4 and 6 to 8 shown in FIGS. 2A to 2D and Table 2 with the results of Comparative Examples 1 to 3, the water vapor of Examples 1 to 4 and 6 to 8 was used. It was confirmed that the reforming catalyst is in a state where the active species Rh in the catalyst is easily reduced. That is, in the steam reforming catalysts of Examples 1 to 4 and 6 to 8, Rh is reduced at a lower temperature than the steam reforming catalyst for comparison in Comparative Examples 1 to 3, and Rh is easily reduced. I understand that. Therefore, in the steam reforming catalysts of Examples 1 to 4 and 6 to 8, Rh, which is a platinum group metal, is likely to be in a metal state effective for steam reforming reaction activity. It is thought that it is one of.

[Oxygen-temperature programmed desorption test (O ₂ -TPD test)]
About the steam reforming catalyst obtained in Examples 1-10 and the steam reforming catalyst for comparison (initial state) obtained in Comparative Examples 1-3, an oxygen-temperature-programmed desorption test (O ₂ -TPD test, Oxygen) (Temperature Programmed Desorption) was performed.

In such an O ₂ -TPD test, first, the catalyst in a powder state coated on the monolith substrate in each monolith catalyst sample was scraped off to obtain a test catalyst powder. Next, about 160 mg of the obtained test catalyst powder was charged into a temperature programmed desorption analyzer (trade name “TP5000”, manufactured by Henmi Kakusha Co., Ltd.). First, as a pretreatment, O ₂ gas was added to the test catalyst powder. After heating at 600 ° C. for 20 minutes while supplying (O ₂ : 100% by volume) at 20 mL / min, the supply gas species is switched to Ar gas (Ar: 100% by volume), and Ar gas is supplied at a rate of 20 mL / min. Then, a treatment (purging treatment) was performed at 600 ° C. for 10 minutes, followed by cooling with Ar gas until the bed temperature of the catalyst reached room temperature of 200 ° C. Next, as an oxidation treatment, heating was performed at 200 ° C. for 20 minutes while supplying O ₂ gas (O ₂ : 100% by volume) at 20 mL / min, and then the catalyst was cooled to room temperature with O ₂ gas. Thereafter, the supply gas species was switched to Ar gas (Ar: 100% by volume), and a process of supplying Ar gas at a supply rate of 20 mL / min for 30 minutes (purge process) was performed. Next, while supplying Ar gas at a supply rate of 20 mL / min, the temperature was increased at a rate of temperature increase of 20 ° C./min, and the catalyst during such temperature increase was passed between 30 and 850 ° C. out the amount of _{O 2} contained in the gas _{(O 2} concentration) a quadrupole mass spectrometer (QMS: Quadrupol mass spectrometer, Q squares) was used for the measurement. As a graph showing the relationship between the O ₂ concentration (%) in the outgas and the temperature (° C.), the O ₂ -TPD of the steam reforming catalyst obtained in the initial Examples 1 to 10 and Comparative Examples 1 to 3 The spectra are shown in FIGS. 3A-3E. FIG. 3A is an O ₂ -TPD spectrum (a graph showing the relationship between the O ₂ concentration in the output gas and the temperature) of the steam reforming catalyst obtained in Examples 1-2 and Comparative Example 1 in the initial state, and FIG. The O ₂ -TPD spectrum of the steam reforming catalyst obtained in Examples 3 to 5 and Comparative Example 1 in the initial state (a graph showing the relationship between the O ₂ concentration in the output gas and the temperature), FIG. 3C shows the initial state. O ₂ -TPD spectrum of the steam reforming catalyst obtained in Examples 6 to 8 and Comparative Example 1 (a graph showing the relationship between the O ₂ concentration in the output gas and the temperature), FIG. 3D shows Example 9 in the initial state. 10 and the O ₂ -TPD spectrum of the steam reforming catalyst obtained in Comparative Example 1 (a graph showing the relationship between the O ₂ concentration in the outgas and the temperature), FIG. 3E shows Comparative Examples 1 to 3 in the initial state. _O 2 -TPD spectrum of the steam reforming catalyst (outgoing gas _{O 2} Is a graph) showing a relationship between the degree and temperature. In the O ₂ -TPD test, two O ₂ desorption peaks were observed in a low temperature range of about 150 ° C. to about 500 ° C. and a high temperature range of about 550 ° C. or higher. The O ₂ desorption peak on the high temperature side is considered to be oxygen release from the crystal grains of the composite oxide. On the other hand, the details of the O ₂ desorption peak on the low temperature side are unknown, but Examples 1 and 3 containing praseodymium oxide, which is known to be stable from tetravalent to trivalent as the temperature increases. Since a large peak was obtained at ˜5, this is also considered to be due to oxygen release from the crystal particles of the composite oxide support. From these peaks, the amount of O ₂ desorption on the low temperature side and the high temperature side was calculated by integrating the area. The results are shown in Table 3.

  As is clear from the comparison between the results of Examples 1 to 10 shown in FIGS. 3A to 3E and Table 3 and the results of Comparative Examples 1 to 3, the steam reforming catalysts of Examples 1, 3 to 5 and 8 are It was confirmed that a large amount of oxygen was released from the complex oxide support on the low temperature side. Furthermore, it was confirmed that the steam reforming catalyst of Example 2 released a large amount of oxygen from the composite oxide support on the high temperature side. Therefore, the steam reforming catalysts of Examples 1 to 10 are considered to be the cause of high durability performance because the carbonaceous material on which the oxygen released from the crystal particles of the composite oxide support is deposited is oxidized and removed. It is done. In particular, in the steam reforming catalysts of Examples 3 to 5, since a large amount of oxygen is released on the low temperature side, a carbonaceous material in which oxygen released from the crystal particles of the composite oxide support is deposited is used. It is thought that this is the cause of the extremely high durability performance because the ability to oxidize and remove is very high.

  As described above, according to the present invention, coking is not likely to occur even in an environment where oxygen gas is not present or in a condition where the molar ratio (S / C) of water vapor to carbon is low, and even when exposed to high temperatures. High activity can be maintained, and hydrogen can be generated by efficiently reforming a fuel composed of hydrocarbons with steam.

  Therefore, the steam reforming catalyst of the present invention has high catalytic activity in the steam reforming reaction of fuels composed of hydrocarbons, is excellent in coking resistance, and exhibits high activity even when exposed to high temperatures. When a fuel composed of hydrocarbons is used in such an internal combustion engine, it is useful as a catalyst or the like when reforming this with steam to generate hydrogen.

Claims (12)

A composite oxide support containing alumina, ceria and zirconia, and a rare earth oxide other than ceria, and
At least one first metal element selected from the group consisting of platinum group metals supported on the composite oxide support;
With
The surface composition (at%) of aluminum by X-ray photoelectron spectroscopy (XPS) measurement of the composite oxide support is 1.5 times or more of the aluminum composition (at%) of the entire composite oxide support. A steam reforming catalyst for reforming a fuel comprising hydrocarbons with steam.   2. The rare earth oxide other than ceria is at least one selected from the group consisting of praseodymium oxide, neodymium oxide, samarium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, and ytterbium oxide. The steam reforming catalyst according to 1.   The steam reforming catalyst according to claim 2, wherein the rare earth oxide other than ceria is at least one of praseodymium oxide, terbium oxide, and ytterbium oxide.   The steam reforming catalyst according to any one of claims 1 to 3, wherein the content of ceria in the composite oxide support is 50 to 95 mass%.   The ceria in the composite oxide support and at least one of rare earth oxides other than zirconia and ceria form a solid solution in which at least a part thereof is in solid solution with each other. 4. The steam reforming catalyst according to claim 1.   The ceria in the composite oxide support and at least one of zirconia, praseodymium oxide, terbium oxide, and ytterbium oxide form a solid solution in which at least a part thereof is in solid solution with each other. Item 6. The steam reforming catalyst according to Item 5.   The steam reforming catalyst according to any one of claims 1 to 6, wherein the first metal element is rhodium.   8. The method according to claim 1, further comprising at least one second metal element selected from the group consisting of alkaline earth metals supported on the composite oxide support. The steam reforming catalyst as described.   The steam reforming catalyst according to claim 8, wherein the second metal element is at least one selected from the group consisting of magnesium, strontium, and barium.   Steam reforming of a fuel comprising hydrocarbons, wherein the fuel comprising hydrocarbons is brought into contact with the steam reforming catalyst according to any one of claims 1 to 9 in the presence of steam. Method.   The steam reforming method according to claim 10, wherein the fuel is a mixed fuel of ethanol and gasoline.   A steam reforming reaction apparatus comprising the steam reforming catalyst according to any one of claims 1 to 9.