JP5494910B2 - Hydrogen production catalyst and production method thereof - Google Patents

Description

  The present invention relates to a hydrogen generation catalyst, and more particularly to a hydrogen generation catalyst used to obtain a gas containing hydrogen from ethanol and a method for producing such a hydrogen generation catalyst.

In recent years, various hydrogen-oxygen fuel cells have been developed. Among them, polymer electrolyte fuel cells that can operate at low temperatures (usually 100 ° C. or less) have attracted attention, and have been put to practical use as low-pollution power sources for automobiles. It is being considered.
In such a polymer electrolyte fuel cell, it is preferable from the viewpoint of energy efficiency to use pure hydrogen as a fuel source.

However, considering safety, widespread use of infrastructure, application to vehicles, etc., hydrocarbons such as methane gas, gasoline and light oil, and alcohols such as methanol and ethanol are used as fuel sources, and these fuels are reformed by the reformer. A method for converting to hydrogen-rich reformed gas is also a promising candidate.
Among these, ethanol has low toxicity and is an energy source that can be regenerated using biomass resources such as plants as a raw material. It is considered that ethanol can be suitably used as a fuel for obtaining a hydrogen-rich reformed gas.

Steam reforming is known as one form of fuel reforming for obtaining reformed gas. This steam reforming reaction has an advantage that the hydrogen yield is high as compared with other fuel reforming forms such as a partial oxidation reaction.
As a steam reforming catalyst for reforming fuel by a steam reforming reaction, a steam reforming catalyst is disclosed in which a catalyst component is supported on an inorganic carrier containing a perovskite oxide (see Patent Document 1). ).

JP 2006-346598 A

  However, in the steam reforming catalyst described in the above-mentioned patent document, although it is possible to achieve both the reduction of carbon deposition and the lowering of the reaction temperature, it cannot be said that the activity particularly under high SV conditions is sufficient. It cannot be said that there is no room for improvement.

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is to improve the catalytic activity and to obtain a higher concentration of hydrogen. It is in providing the production | generation catalyst and its manufacturing method.

  As a result of intensive studies aimed at achieving the above object, the present inventors have found that the above-mentioned problems can be achieved by using a catalyst containing rhodium and an acetaldehyde steam reforming catalyst in combination. It came to be completed.

That is, the present invention is based on the above knowledge, and the hydrogen generation catalyst of the present invention is a hydrogen generation catalyst used to obtain a gas containing hydrogen from ethanol, and supports Rh and Na on alumina. And a second catalyst in which an oxide of Fe and Co is supported on ceria , the first catalyst and the second catalyst are mixed, and the mass ratio of the second catalyst is More than the first catalyst .
In addition, the same first catalyst and the second catalyst are provided, and the second catalyst is coated in two layers so that the inner layer and the first catalyst become the surface layer, and the mass ratio of the second catalyst is the first And the thickness of the second catalyst layer is larger than that of the first catalyst layer.

According to the present invention, there is provided a first catalyst comprising Rh and Na supported on alumina, and a second catalyst comprising Fe and Co oxides supported on ceria which function as an acetaldehyde steam reforming catalyst. Therefore, it is possible to provide a hydrogen production catalyst capable of obtaining a hydrogen-containing gas with high hydrogen selectivity (low methane concentration) while obtaining a high ethanol conversion rate.

  Hereinafter, the hydrogen production catalyst of the present invention will be described in more detail and specifically together with the production method thereof.

As described above, the hydrogen generation catalyst of the present invention is a catalyst for obtaining a hydrogen-containing gas from ethanol, and includes a first catalyst containing rhodium and a second catalyst having an acetaldehyde steam reforming function. I have.
By adopting such a configuration, it is possible to obtain a hydrogen-containing gas with high hydrogen selectivity (low methane concentration) while obtaining a high ethanol conversion rate.

The hydrogen generation catalyst of the present invention is particularly excellent in reforming efficiency for alcohol-containing fuel. Further, ethanol is a renewable energy source obtained from biomass resources as raw material, and it is preferable to use only ethanol or an ethanol-containing fuel as a fuel from the viewpoint of reducing the burden on the environment.
The mechanism by which the above-described effect is obtained by arranging the first catalyst containing rhodium and the second catalyst having the steam reforming function of acetaldehyde is not completely clear. The following mechanism is considered.

In general, rhodium-containing catalysts are known to activate hydrocarbons. This hydrogen generation reaction from ethanol is considered to be due to the following formulas (1) to (3).
That is, ethanol is activated, hydrogen is stripped from ethanol to generate acetaldehyde (1), and then a reaction (2) in which acetaldehyde is decomposed into methane and carbon monoxide and a shift reaction (3) are assumed to proceed. .
CH ₃ CH ₂ OH⇒CH ₃ CHO + H ₂ (1)
CH ₃ CHO⇒CH ₄ + CO (2)
CO + H ₂ O => CO ₂ + H ₂ (3)

In the first catalyst containing rhodium, the above reaction, particularly the decomposition reaction of acetaldehyde, reacts promptly to produce methane having an almost equilibrium concentration. Moreover, since the catalyst containing rhodium has high activity, ethanol can be converted at a high conversion rate even under relatively high SV conditions, and the performance stability is also high.
However, the price of precious metals such as rhodium has been rising in recent years, and we want to avoid using a lot of rhodium.

On the other hand, in the second catalyst, that is, the acetaldehyde steam reforming catalyst, a steam reforming reaction of acetaldehyde as shown in the following formula (4) proceeds to obtain a gas having a low methane concentration (high hydrogen concentration). be able to.
However, the ethanol conversion activity in the second catalyst is generally not so high, and there is also a problem of performance degradation due to carbon deposition.
CH ₃ CHO + H ₂ O => 3H ₂ + 2CO (4)

In the present invention, by arranging a rhodium-containing catalyst (first catalyst) and an acetaldehyde steam reforming catalyst (second catalyst), it is possible to take advantage of the good functions of both, and to achieve ethanol conversion activity. An excellent hydrogen production catalyst having high hydrogen selectivity and low cost can be obtained.
That is, by combining the first and second catalysts, the first catalyst containing rhodium converts ethanol, and the steam reforming reaction of acetaldehyde proceeds in the second catalyst. A highly efficient gas can be obtained at a high conversion rate.

As a combination method, it is desirable to mix both catalysts or to form a two-layer coat. More preferably, the second catalyst is arranged in the inner layer and the first catalyst containing rhodium is arranged in the surface layer. It is to be.
By arranging the second catalyst in the inner layer, it is considered that acetaldehyde converted by the rhodium catalyst in the surface layer can be adsorbed and the steam reforming reaction of acetaldehyde can be promoted more efficiently.

Further, it is desirable that the ratio of the first catalyst containing rhodium and the second catalyst functioning as a steam reforming catalyst for acetaldehyde is larger in the second catalyst. That is, when the first catalyst is more, the ethanol conversion reaction proceeds at a high conversion rate, but methane production due to the decomposition reaction from acetaldehyde cannot be suppressed, and a gas with low hydrogen selectivity can be obtained. become.
Therefore, it is desired to arrange a large amount of the second catalyst and convert as much acetaldehyde as possible into hydrogen and carbon monoxide by the steam reforming reaction.

  Further, in the acetaldehyde steam reforming reaction, activation of water is important. However, since activation of water is relatively difficult, it is necessary to dispose more second catalyst. Therefore, it is desirable to dispose a large amount of the second catalyst in terms of mass, or to increase the thickness of the coat layer of the second catalyst in the case of two-layer coating.

As the first catalyst, one in which rhodium is supported on alumina is used .
In the case of a catalyst in which the base material (support) has an acid point, ethylene is generated by the dehydration reaction of ethanol, leading to carbon precipitation. It is desirable to use a material. Specifically, a method of adding an alkali metal, an alkaline earth metal, or the like and removing acid sites can be applied.

In the present invention, it is desirable to use an Rh—Na / Al ₂ O ₃ catalyst in which sodium which is an alkali metal is added and the acid point of alumina is reduced as much as possible. By using such a catalyst, a rhodium-containing catalyst having excellent ethanol conversion performance and excellent performance stability can be obtained.
As a method for preparing the catalyst, a general method may be applied. However, by carrying by co-impregnation, a catalyst having more excellent ethanol conversion performance and excellent performance stability can be obtained.

  Further, the supported amount of rhodium is preferably 0.5 to 10% by mass in terms of metal with respect to the total amount of the base material and the rhodium. If the supported amount of rhodium is too small, sufficient catalytic activity may not be obtained. On the other hand, when the loading amount of rhodium is too large, an increase in activity commensurate with the increase in the loading amount is not recognized, and the production cost may be increased. However, even if rhodium in an amount outside the above range is supported, there is basically no problem as long as rhodium is supported.

A catalyst containing a cobalt oxide is used as the second catalyst having an acetaldehyde steam reforming catalyst function. However, like the above-described catalyst containing rhodium, it is desirable that the substrate does not have acid sites.
In this case, since it is important to be a cobalt oxide, it is desirable that the substrate is easy to form a cobalt oxide. Specifically, a ceria base material that does not have a very high surface area is used.

Further, the catalyst containing the cobalt oxide described above is not so high in activity and has a large amount of carbon deposition, so it is more preferable to add an additive.
In the catalyst containing the cobalt oxide (second catalyst), the additive functions as one that keeps the activation of water and the oxidation state of the cobalt oxide appropriately. When this additive is contained in the catalyst, the steam reforming reaction of acetaldehyde proceeds, and at the same time, carbon deposition can be suppressed.

  However, the above mechanism is based on estimation. Therefore, it goes without saying that even if the above-described effect is obtained by a mechanism other than the above-described mechanism, it is included in the technical scope of the present invention.

The supported amount of the additive is preferably 0.03 to 2% by mass, more preferably 0.03 to 1.5% by mass in terms of metal with respect to the total amount of the base material, cobalt, and additive. %, And more preferably 0.05 to 1.2% by mass.
By setting the loading amount of the additive within the above range, it is possible to obtain a catalyst (second catalyst) from which the risk of carbon deposition is further reduced and a reformed gas with higher hydrogen selectivity can be obtained.

As the above-mentioned additives, for example, those containing iron (Fe), chromium (Cr), manganese (Mn), and the like are conceivable.
However, as an additive to cobalt oxide, it seems that the effect of adding iron (Fe) is high, and this is because the combination with iron can reinforce the function that is insufficient with only cobalt oxide, Specifically, it is considered that this is because the function of activating water and the function of appropriately maintaining the oxidation state of the cobalt oxide are excellent. On the other hand, although chromium (Cr), manganese (Mn), etc. have the same function, they are not as good as iron (Fe) and seem to be less effective.

Here, whether or not the catalyst having a cobalt oxide has a cobalt oxide can be specified by a technique called an X-ray diffraction (XRD) method, for example.
In cobalt oxide, an XRD pattern peculiar to Co ₃ O ₄ can be obtained.

  Hereinafter, the method for producing the hydrogen production catalyst described above will be described with some examples, but the hydrogen production catalyst of the present invention is not limited to those produced by these production methods.

First, an inorganic oxide serving as a support substrate is prepared. As the inorganic oxide serving as the base material, an originally prepared inorganic oxide may be used, and when a suitable one is commercially available, the commercially available product may be purchased and used.
The raw material of the inorganic carrier used in this stage is not particularly limited as long as it can be a desired inorganic carrier by firing. Taking alumina as an example, aluminum hydroxide such as boehmite alumina and gibbsite, or γ-alumina, aluminum sulfate, aluminum nitrate, aluminum chloride and the like can be mentioned.

  In the production of the first catalyst containing rhodium, the inorganic carrier powder is preliminarily subjected to a calcination treatment to adjust the specific surface area, and then the Rh component is supported on the inorganic carrier powder. Only the inorganic carrier having a desired particle size may be selected by pulverizing and sieving the obtained inorganic carrier.

Next, various methods are effective as a method for supporting Rh. Typically, an impregnation method using a catalyst preparation solution in which Rh is dissolved is simple and often used.
In the step of preparing the catalyst preparation solution, first, an Rh compound such as rhodium nitrate is prepared as an Rh raw material. Furthermore, a solvent for dissolving these compounds is prepared. Thereafter, the Rh compound as a raw material is added to the prepared solvent, and the mixture is stirred if necessary to prepare a catalyst preparation solution.

  Examples of the Rh compound that is a raw material for Rh include compounds in the form of metal salts, such as nitrates, carbonates, ammonium salts, and chlorides. These salts are easily available, are widely used as raw materials for preparing catalysts, and are easy to handle when supported on a carrier.

Examples of the solvent used in the preparation of the catalyst preparation solution include water and ethanol, but are not limited thereto.
The concentration of Rh in the catalyst preparation solution is not particularly limited, and can be adjusted as appropriate in consideration of the amount of inorganic support used in the supporting stage described later, a desired supporting amount, a supporting method, and the like.

In order to add Na as a component other than Rh to the produced fuel reforming catalyst, a desired component may be added simultaneously to the catalyst preparation solution at this stage. In that case, it is good to add and dissolve in a solvent in the form of a metal salt as exemplified above. Thereafter, Rh dissolved in the catalyst preparation solution is supported on the inorganic carrier.
As a specific method for supporting, a conventionally known method in the field of catalyst preparation such as an impregnation method, a coprecipitation method, and a competitive adsorption method can be employed. The treatment conditions can be appropriately selected according to the method employed, but usually the inorganic support and the catalyst preparation solution may be brought into contact at room temperature to 80 ° C. for about 0.5 to 4 hours.

  After the catalyst metal is supported on the inorganic support, it is dried as necessary. Specific methods for drying include, for example, natural drying, evaporation to dryness, and drying using a rotary evaporator, a blower dryer, or the like. The drying time can be appropriately set according to the method employed. In some cases, this drying step may be omitted, and drying may be performed in the firing step described later.

Subsequently, the inorganic carrier carrying Rh is fired. The apparatus and conditions (calcination atmosphere, calcination temperature, calcination time) used for calcination are not particularly limited, and conventionally known knowledge can be appropriately referred to in the catalyst preparation field. As an example, the firing conditions are 1 to 4 hours at 400 to 600 ° C. in a nitrogen or air atmosphere. Through this firing, a catalyst powder carrying Rh is obtained.
In order to employ the catalyst obtained by the above method for a desired application, the obtained catalyst may be further subjected to processing such as pulverization and sieving.

Next, in the production of the second catalyst having an acetaldehyde steam reforming catalyst function, in the case of supporting cobalt oxide, nitrate, acetate, carbonate, ammonium salt, Various salts such as acetylacetonato complex and chloride can be used as starting materials.
Specifically, cobalt acetate, cobalt nitrate, etc. can be used, and these are thermally decomposed. For example, after dissolving in water once and drying, it bakes and an oxide is produced | generated. The obtained cobalt oxide-supported powder may be further subjected to processing such as pulverization and sieving.

When adding Fe to the catalyst powder containing cobalt oxide, it is desirable to employ a method in which the additive is added later using the cobalt oxide-supported powder obtained by firing.
As a method for adding these additives, there are a method of adding an additive at the same time when the cobalt oxide is supported, and a method of adding the additive first and then supporting the cobalt oxide later. It is desirable to carry the additive as described above after carrying the product.

As a method for adding an additive, various salts such as nitrates, acetates, carbonates, ammonium salts, acetylacetonato complexes, and chlorides can be used as starting materials, as in the Rh loading method.
To add Fe, iron nitrate or the like can be used as a raw material and is dissolved in a solvent such as water. In this solution, the cobalt oxide-supported powder is dispersed and impregnated. Then, an iron addition cobalt oxide catalyst powder can be obtained by passing through drying and baking.

In addition, although the additive addition method by the impregnation method was described here, conventionally well-known various methods may be used. The treatment conditions can be appropriately selected according to the method employed, but usually, the cobalt oxide catalyst powder and the additive preparation solution may be brought into contact at room temperature to 80 ° C. for about 0.5 to 4 hours. .

After the additive is supported on the cobalt oxide catalyst powder, it is dried as necessary.
Specific methods for drying include, for example, natural drying, evaporation to dryness, and drying using a rotary evaporator, a blower dryer, or the like. The drying time can be appropriately set according to the method employed. In some cases, this drying step may be omitted, and drying may be performed in the baking step described later.

  Subsequently, the powder is fired. The apparatus and conditions (calcination atmosphere, calcination temperature, calcination time) used for calcination are not particularly limited, and conventionally known knowledge can be appropriately referred to in the catalyst preparation field. As an example, firing conditions of 1 to 4 hours at 400 to 600 ° C. in a nitrogen or air atmosphere can be employed. Through this calcination, a cobalt oxide catalyst powder carrying an additive is obtained.

  By such a method, the preparation of the second catalyst powder containing the desired cobalt oxide is completed and processed into a shape suitable for the use environment.

The first and second catalysts produced as described above are each prepared as a slurry, and applied to, for example, a honeycomb carrier to obtain one form of the hydrogen generation catalyst of the present invention.
As the honeycomb carrier, a metal honeycomb can be used in addition to a normal ceramic honeycomb. Furthermore, it is also effective to apply to ceramic or various metal foams or microreactors.

When applying to a honeycomb or the like, by using a slurry, a more uniform catalyst layer with no peeling can be obtained. There is no restriction | limiting in particular in the method to make a slurry, A general method may be sufficient.
For example, the catalyst powder, the binder, and the solvent can be obtained together with a ball for grinding into a ball milling pot and ground for a predetermined time. The obtained slurry is applied to a honeycomb, dried and fired, whereby the hydrogen generation catalyst of the present invention can be obtained.

  At this time, when the first and second catalysts described above are mixed, at the time of slurry preparation, the above two kinds of catalyst powders are mixed with a binder and a solvent together with balls into a pulverizing pot, pulverized, and mixed together. After forming a slurry, it is applied to a honeycomb or the like.

Further, when the first and second catalysts are formed in a two-layer coating, first, a catalyst slurry as an inner layer is prepared, applied to a honeycomb, dried and fired, and then a catalyst slurry as a surface layer is prepared. Then, the honeycomb is coated, dried and fired. In addition, after applying the slurry containing the second catalyst (acetaldehyde steam reforming catalyst) to the inner layer side, it is desirable to apply the slurry containing the first catalyst (rhodium-containing catalyst) as a surface layer. As described in.
At this time, it is desirable to change the type of the binder, or appropriately change the binder mixing ratio, pulverization time, etc. in consideration of the adhesion to the carrier such as a honeycomb depending on the type of catalyst powder of the inner layer and the surface layer.

It is desirable that the ratio of the first catalyst containing rhodium and the second catalyst having a steam reforming catalyst function of acetaldehyde is larger in mass than the first catalyst in the second catalyst.
When the first catalyst containing rhodium is large, a high ethanol conversion ratio can be obtained, but a large amount of methane is produced, and as a result, a gas having a low hydrogen concentration is obtained. Therefore, a gas having a low methane concentration and a high hydrogen concentration can be obtained by mixing more second catalyst.
In addition, when the loading amount of the catalyst metal is different between the first catalyst and the second catalyst, it is desirable to have the above-mentioned relationship in terms of the metal conversion value relating to the catalyst metal contained in each catalyst. become.

As for the ratio of the thickness of the catalyst coat layer, it is desirable that the coat thickness of the second catalyst is larger than the thickness of the first catalyst. This is because the second catalyst is inferior in ethanol conversion activity, and therefore it is necessary to ensure space velocity (SV) = reaction gas flow rate (L / h) / catalyst volume (L).
The first catalyst containing rhodium exhibits high reactivity even at a relatively high space velocity (SV), but the second catalyst may not exhibit sufficient performance at a high space velocity (SV). That is, since it is important to obtain a gas having a high hydrogen concentration that the second catalyst can exhibit sufficient performance, in order to secure the catalyst layer volume of the second catalyst, as described above, It is desirable to make the coat thickness of the second catalyst larger than that of the catalyst.

The hydrogen generation catalyst of the present invention is disposed, for example, in a hydrogen generator.
The hydrogen generation apparatus in which the hydrogen generation catalyst of the present invention is disposed is used, for example, for producing a hydrogen-containing gas supplied to a solid polymer fuel cell.
Moreover, the combustion efficiency can be improved by supplying the hydrogen-containing gas obtained by such an apparatus to the internal combustion engine. Furthermore, it can also be used to improve the exhaust gas purification rate by supplying it to the exhaust gas purification unit.

In addition, the form in particular at the time of arrange | positioning the hydrogen-producing catalyst of this invention in a hydrogen generator is not restrict | limited, A conventionally well-known technique and its improvement technique can be employ | adopted suitably.
For example, the form of the honeycomb carrier obtained by preparing a slurry containing the hydrogen generation catalyst of the present invention and applying the slurry to the honeycomb carrier is exemplified. As the honeycomb, a metal honeycomb can be applied in addition to a normal ceramic honeycomb. Furthermore, it is also effective to apply to ceramic or various metal foams or microreactors.

  Hereinafter, the present invention will be described more specifically based on examples and comparative examples. The present invention is not limited to these examples.

[Preparation of Rh-Na / Al ₂ O ₃ catalyst (first catalyst)]
A predetermined amount of sodium carbonate was dissolved in a 10% nitric acid solution. After confirming dissolution of sodium carbonate, a rhodium nitrate solution was added, and alumina was impregnated with rhodium and sodium. At this time, it was impregnated so that the supported amounts of rhodium and sodium were 4% by mass (in terms of metal) with respect to the total amount of the catalyst (alumina, rhodium and sodium) obtained.
Thereafter, the obtained powder was dried at 150 ° C. overnight and then calcined in a muffle furnace at 500 ° C. for 1 hour to prepare a Rh—Na / Al ₂ O ₃ catalyst as a first catalyst.

[Preparation of Fe / Co / CeO ₂ catalyst (second catalyst)]
Ceria was impregnated with a cobalt-containing solution in which cobalt nitrate hexahydrate was dissolved in distilled water. The impregnation amount at this time was such that the supported amount of cobalt was 10% by mass (in terms of metal) with respect to the total amount of the obtained catalyst (iron, cobalt oxide and ceria). Thereafter, the obtained powder was dried at 150 ° C. overnight and then calcined in a muffle furnace at 500 ° C. for 1 hour to obtain a catalyst supporting Co oxide on ceria (hereinafter referred to as Co / CeO _2). ).
Subsequently, using an iron-containing solution obtained by dissolving iron nitrate nonahydrate in distilled water, the Co / CeO ₂ catalyst obtained above was used with respect to the total amount of the obtained catalyst (iron, cobalt oxide, and ceria). Then, the impregnation was carried out so that the amount of iron supported was 0.22% by mass (in terms of metal). Thereafter, the impregnated powder thus obtained was dried at 150 ° C. overnight and then calcined in a muffle furnace at 500 ° C. for 1 hour to obtain a catalyst having Fe / O ₂ supported on Co / CeO ₂ as a _second catalyst. (Hereinafter referred to as Fe / Co / CeO ₂ ).

( Reference Example 1)
The Rh—Na / Al ₂ O ₃ catalyst powder and Fe / Co / CeO ₂ catalyst powder (mass ratio, 3: 1) prepared above were put together with alumina sol as a binder and water as a solvent into a magnetic ball mill pot. The slurry was prepared by charging and mixing and grinding for 1 hour.
Next, the prepared slurry was applied to a ceramic honeycomb as a monolith support, dried by ventilation at 130 ° C., and fired at 400 ° C. for 1 hour to obtain a hydrogen generation catalyst of this example. In addition, about the slurry application quantity at this time, it adjusted so that the mass (except for alumina sol as a binder) of the catalyst contained in a slurry might be 200 g / L with respect to the volume of a monolith support | carrier.

( Reference Example 2)
The same operation as in Reference Example 1 was repeated except that the mass ratio of the Rh—Na / Al ₂ O ₃ catalyst powder prepared above and the Fe / Co / CeO ₂ catalyst powder was 1: 1. Thus, a hydrogen generation catalyst of this example was obtained.

(Example 1 )
The same operation as in Reference Example 1 was repeated except that the mass ratio of the Rh—Na / Al ₂ O ₃ catalyst powder prepared above and the Fe / Co / CeO ₂ catalyst powder was 1: 3. Thus, a hydrogen generation catalyst of this example was obtained.

( Reference Example 3 )
First, the Rh—Na / Al ₂ O ₃ catalyst powder prepared as described above was charged into a magnetic ball mill pot together with alumina sol as a binder and water as a solvent, and mixed and pulverized for 1 hour to prepare a slurry. Next, the prepared slurry was applied to a ceramic honeycomb as a monolith support, dried by ventilation at 130 ° C., and fired at 400 ° C. for 1 hour, and the lower layer Rh—Na / Al ₂ O ₃ catalyst was formed on the ceramic honeycomb. A layer was formed.
The amount of slurry applied at this time was adjusted so that the mass of the catalyst contained in the slurry (excluding alumina sol as a binder) was 150 g / L with respect to the volume of the monolith support.

Next, the Fe / Co / CeO ₂ catalyst powder prepared above was charged into a magnetic ball mill pot together with alumina sol as a binder and water as a solvent, and mixed and pulverized for 0.5 hour to prepare a slurry. Then, an Rh—Na / Al ₂ O ₃ catalyst layer as a lower layer was applied on the formed monolith support so as to be a surface layer, dried by ventilation at 130 ° C., and calcined at 400 ° C. for 1 hour. A hydrogen generation catalyst was obtained.
At this time, the slurry coating amount was adjusted so that the mass of the catalyst contained in the slurry (excluding alumina sol as a binder) was 50 g / L with respect to the volume of the monolith support. The ratio t1 / t2 between the thickness t1 of the coat layer containing the Rh—Na / Al ₂ O ₃ catalyst and the thickness t2 of the coat layer containing the Fe / Co / CeO ₂ catalyst was 2.5.

( Reference Example 4 )
Except that the Rh—Na / Al ₂ O ₃ catalyst layer as the lower layer was adjusted to 100 g / L with respect to the volume of the monolith support, and the Fe / Co / CeO ₂ catalyst layer as the surface layer was also adjusted to 100 g / L. By repeating the same operation as in Reference Example 3 , the hydrogen production catalyst of this example was obtained.
At this time, the thickness ratio t1 / t2 of both coat layers was 0.9.

( Reference Example 5 )
Except that the Rh—Na / Al ₂ O ₃ catalyst layer as the lower layer was adjusted to 50 g / L with respect to the volume of the monolith support, and the Fe / Co / CeO 2 catalyst layer as the surface layer was adjusted to 150 g / L. By repeating the same operation as in Reference Example 3 , the hydrogen generation catalyst of this example was obtained.
At this time, the thickness ratio t1 / t2 of both coat layers was 0.5.

( Reference Example 6 )
First, the Fe / Co / CeO ₂ catalyst powder prepared above was charged into a magnetic ball mill pot together with alumina sol as a binder and water as a solvent, and mixed and pulverized for 0.5 hour to prepare a slurry. Next, the prepared slurry is applied to a ceramic honeycomb that is a monolith support, dried by ventilation at 130 ° C., and fired at 400 ° C. for 1 hour to form a lower Fe / Co / CeO ₂ catalyst layer on the ceramic honeycomb. Formed.
At this time, the slurry coating amount was adjusted so that the mass of the catalyst contained in the slurry (excluding alumina sol as a binder) was 50 g / L with respect to the volume of the monolith support.

Next, the Rh—Na / Al ₂ O ₃ catalyst powder prepared above was charged into a magnetic ball mill pot together with alumina sol as a binder and water as a solvent, and mixed and pulverized for 1 hour to prepare a slurry. Then, a Fe / Co / CeO ₂ catalyst layer as a lower layer is applied on the formed monolith support so as to be a surface layer, dried by ventilation at 130 ° C., and baked at 400 ° C. for 1 hour to generate hydrogen in this example A catalyst was obtained.
The amount of slurry applied at this time was adjusted so that the mass of the catalyst contained in the slurry (excluding alumina sol as a binder) was 150 g / L with respect to the volume of the monolith support. Here, the ratio t1 / t2 of the thickness t1 of the coat layer containing the Rh—Na / Al ₂ O ₃ catalyst and the thickness t2 of the coat layer containing the Fe / Co / CeO ₂ catalyst was 2.1.

( Reference Example 7 )
Except that the Fe / Co / CeO ₂ catalyst layer as the lower layer was adjusted to 100 g / L with respect to the volume of the monolith support, and the Rh—Na / Al ₂ O ₃ catalyst layer as the surface layer was similarly adjusted to 100 g / L. By repeating the same operation as in Reference Example 6 , the hydrogen generation catalyst of this example was obtained.
The thickness ratio t1 / t2 between the two coating layers was 0.7.

(Example 2 )
Except that the Fe / Co / CeO ₂ catalyst layer as the lower layer was adjusted to 50 g / L with respect to the volume of the monolith support, and the Rh—Na / Al ₂ O ₃ catalyst layer as the surface layer was adjusted to 150 g / L, By repeating the same operation as in Reference Example 6 , the hydrogen generation catalyst of this example was obtained.
At this time, the thickness ratio t1 / t2 of both coat layers was 0.4.

( Reference Example 8 )
A hydrogen generation catalyst of this example was obtained by repeating the same operation as in Example 1 except that the Co ₃ O ₄ reagent (manufactured by Wako Pure Chemical Industries) was used as it was as the second catalyst.

( Reference Example 9 )
A hydrogen generation catalyst of this example was obtained by repeating the same operation as in Reference Example 5 except that the Co ₃ O ₄ reagent (manufactured by Wako Pure Chemical Industries) was used as it was as the second catalyst. The ratio t1 / t2 between the thickness t1 of the coat layer containing the Rh—Na / Al ₂ O ₃ catalyst and the thickness t2 of the coat layer containing the Co ₃ O ₄ catalyst was 0.5.

( Reference Example 10 )
A hydrogen generation catalyst of this example was obtained by repeating the same operation as in Example 2 except that the Co ₃ O ₄ reagent (manufactured by Wako Pure Chemical Industries) was used as it was as the second catalyst. In addition, the thickness ratio t1 / t2 of both coat layers was 0.6.

(Comparative Example 1)
The Rh—Na / Al ₂ O ₃ catalyst prepared as described above was charged into a magnetic ball mill pot together with alumina sol as a binder and water as a solvent, and mixed and pulverized for 1 hour to prepare a slurry.
Next, the prepared slurry was applied to a ceramic honeycomb as a monolith support so that the catalyst mass contained was 200 g / L with respect to the volume of the monolith support, dried by ventilation at 130 ° C., and fired at 400 ° C. for 1 hour. As a result, a hydrogen generation catalyst of this example not containing the second catalyst was obtained.

(Comparative Example 2)
By repeating the same operation as in Comparative Example 1 except that a Fe / Co / CeO ₂ catalyst was used instead of the Rh—Na / Al ₂ O ₃ catalyst, the first catalyst was not included. A hydrogen generation catalyst was obtained.

(Comparative Example 3)
By repeating the same operation as in Comparative Example 1 except that the Co ₃ O ₄ reagent (manufactured by Wako Pure Chemical Industries) was used as it was instead of the Rh—Na / Al ₂ O ₃ catalyst, the first catalyst was The hydrogen generation catalyst of this example which does not contain was obtained.

[Performance evaluation]
<Preprocessing>
The hydrogen production catalysts obtained in the above Examples and Comparative Examples were allowed to stand for 1 hour in a 10% by volume H ₂ / N ₂ balance gas stream at 500 ° C.

<Evaluation test>
Next, the mixture (reaction liquid) of ethanol and water was adjusted to S / C = 2.0, and liquid space velocity (LHSV: flow rate of ethanol (cm ³ / h) / monolith catalyst volume (cm ³ )) = 20 h ^{− 1} was supplied to the catalyst of each of the above examples.
“S / C” means the ratio of the water supply rate to the ethanol (carbon atom conversion) supply rate, that is, H ₂ O supply rate (mol / sec) / (ethanol supply rate (mol / sec) × 2).

  The inlet gas temperature was maintained at 500 ° C., and the outlet gas composition was analyzed 1 hour after the temperature was stabilized (steady state). As a result, ethanol conversion and methane concentration are shown in Table 1.

As is clear from Table 1, the hydrogen generation catalysts of Reference Examples 1 to 10 including the first catalyst containing rhodium and the second catalyst containing cobalt oxide are excellent in ethanol conversion performance and have a methane concentration. Is low. A low methane concentration indicates a high hydrogen concentration. Further, it has been confirmed that there is little carbon deposition on the catalyst surface during reforming, and stable performance can be maintained for a long time.

Regarding Reference Examples 1 and 2 and Example 1, the mixing ratio of the second catalyst is increased in this order, and the ratio of the second catalyst is increased in the order of Example 3, Reference Example 2, and Reference Example 1. This shows that a gas having a low concentration, in other words, a gas having a high hydrogen concentration is obtained.
Similarly , in Reference Examples 3 to 8 and Example 2 , as the ratio of the second catalyst increases, a gas with a lower methane concentration and a higher hydrogen concentration is obtained.

In addition, in the mixed catalysts of Reference Examples 1 and 2 and Example 1 , when the ratio of the second catalyst is large, the ethanol conversion tends to decrease, but Reference Examples 3 to 5, 6, This tendency does not necessarily apply to the two-layer coat catalyst of No. 7 , and particularly in Example 2 , a gas having a low methane concentration and a high hydrogen concentration can be obtained without causing a decrease in the ethanol conversion rate.

By incorporating the hydrogen generation catalyst of the present invention into a hydrogen generation device, a fuel cell system, an internal combustion engine system, or the like, the size of these devices can be reduced.
In addition, the hydrogen generation catalyst of the present invention can reduce the amount of rhodium, which is a noble metal, so that the cost can be reduced.

Claims (3)

A hydrogen generation catalyst used to obtain a gas containing hydrogen from ethanol, the first catalyst comprising Rh and Na supported on alumina, and the first catalyst comprising Fe and Co oxides supported on ceria . And a second catalyst, wherein the first catalyst and the second catalyst are mixed, and the mass ratio of the second catalyst is larger than that of the first catalyst. A hydrogen generation catalyst used to obtain a gas containing hydrogen from ethanol, the first catalyst comprising Rh and Na supported on alumina, and the first catalyst comprising Fe and Co oxides supported on ceria . The second catalyst is coated in two layers so that the second catalyst is an inner layer and the first catalyst is a surface layer, and the mass ratio of the second catalyst is larger than that of the first catalyst. A hydrogen generating catalyst, wherein the thickness of the catalyst is thicker than that of the first catalyst layer . In preparing the second catalyst, the ceria is impregnated with cobalt-containing solution, the manufacturing method of the hydrogen generating catalyst of claim 1 or 2, characterized in that impregnating the iron-containing solution.