JP2002263499A - Methanol reforming catalyst and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method reforming catalyst having a function that high hydrogen production per unit volume and excellent methanol reforming activity even at a low temperature (about 250 deg.C) are attained. SOLUTION: The methanol reforming catalyst contains copper, palladium and silica and hydrogen is generated by steam-reforming of methanol. The methanol reforming catalyst is manufactured by a manufacturing method including a step for forming sol by adding an acid into a metallic alkoxide, a step for adding a catalytic metal aqueous solution to the sol and stirring the mixture, a step for drying the stirred sol by evaporation to form gel, a step for firing the gel and a step for reducing the calcined gel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a methanol reforming catalyst for producing hydrogen from methanol. More specifically, the present invention relates to a methanol reforming catalyst having excellent reforming performance and low-temperature activity.

[0002]

2. Description of the Related Art In recent years, a fuel cell using a power generation system by an electrochemical reaction has high energy efficiency and excellent environmental characteristics, and is expected to be applied to an automobile in recent years.
The principle of a fuel cell utilizes the reverse reaction of water electrolysis, that is, electric energy generated when hydrogen and oxygen combine to generate water. Attention has been paid to hydrogen generated by steam reforming of methanol as a fuel hydrogen source used in this fuel cell. This is because in recent years, technology for mass-producing methanol from many resources such as petroleum, coal, and natural gas has been established, and methanol can be obtained at low cost. In addition, transportation and storage are easy because there is less danger than hydrogen gas when handling methanol. Further, since the reforming reaction temperature is about 200 to 400 ° C., a system for easily producing hydrogen can be realized.

[0003] As a methanol reforming catalyst, a catalyst generally using copper, zinc and alumina as raw materials is well known. For example, Japanese Unexamined Patent Application Publication No.
And Japanese Patent Application Laid-Open No. 11-19516. In the production of these catalysts, methods such as coprecipitation and impregnation are used.

[0004] Here, the impregnation method uses alumina (Al ₂ O ₃ ).
This is a method for producing a catalyst by impregnating a carrier of an inorganic oxide, such as, with a catalyst metal solution and supporting it. In this impregnation method, the catalyst metal is supported only on the surface of the catalyst layer, has poor dispersibility, and the active metal is sintered (agglomerated) by heat, which causes a problem of lowering the reforming activity.

The coprecipitation method is a method for producing a catalyst by adding an acid or an alkali to an aqueous solution of an inorganic metal salt to precipitate a metal oxide or a metal hydroxide. In this coprecipitation method, there are problems that it is difficult to remove impurities contained in the raw material, it is easy to take in the salts used during precipitation as impurities, and it is difficult to prepare a homogeneous catalyst due to variations in pH during the growth of the precipitate. .

[0006] For a methanol reformer for a fuel cell electric vehicle, a reformer that is compact and has high startability is required. For this reason, the desired function of the methanol reforming catalyst is that the amount of hydrogen generated per unit volume is high and the temperature is low (about 2
(00.degree. C.), the methanol reforming activity is excellent. However, conventional methanol reforming catalysts produced from copper, zinc and alumina as raw materials by a method such as a coprecipitation method or an impregnation method have a problem that such functions are inferior. Therefore, there is a need for a methanol reforming catalyst which has a higher amount of hydrogen generation per unit volume than conventional methanol reforming catalysts and has a function of excellent methanol reforming activity even at low temperatures (about 200 ° C.).

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a function to produce a large amount of hydrogen per unit volume and to have excellent methanol reforming activity even at a low temperature (about 250 ° C.). An object of the present invention is to provide a certain methanol reforming catalyst. It is another object of the present invention to provide a methanol reforming catalyst capable of maintaining a high ability to generate hydrogen from methanol from a low temperature (about 250 ° C.) to a high temperature (about 400 ° C.).

[0008]

In order to achieve the above object, a methanol reforming catalyst according to the present invention comprises copper, palladium, and silica, and generates hydrogen by steam reforming of methanol. . The methanol reforming catalyst according to the present invention comprises the steps of: adding an acid to a metal alkoxide to form a sol; adding a catalytic metal aqueous solution to the sol; stirring; and evaporating and drying the stirred sol to form a gel. And a step of drying and firing the gel, and a step of subjecting the fired gel to a reduction treatment.

The methanol reforming catalyst according to the present invention preferably has a palladium: copper ratio of 1:20 to 1: 5. Further, the methanol reformer according to the present invention, the methanol reforming catalyst according to the present invention is disposed at the preceding stage of the reaction path, contains copper, zinc and alumina at the latter stage of the reaction path, the carrier of alumina, copper and alumina It is preferable to dispose a catalyst produced by a method of impregnating and supporting a solution containing zinc. The methanol reforming catalyst according to the present invention may have a reaction temperature in the range of 250 ° C. to 400 ° C. and a methanol reforming rate of 82% or more.

The present invention also provides a step of adding an acid to a metal alkoxide to form a sol, a step of adding an aqueous catalyst metal solution to the sol and stirring, and
A method for producing a methanol reforming catalyst, comprising: evaporating and drying to form a gel; drying and firing the gel; and reducing the fired gel.

[0011] A metal alkoxide is a compound obtained by substituting hydrogen of a hydroxyl group in alcohols with a metal. For example, tetraethyl orthosilicate ((C
₂ H ₅ O) ₄ Si) and the like, but not limited thereto. The sol is used almost synonymously with a colloid solution, and refers to a state in which it is dispersed in a liquid and exhibits fluidity, and particles are actively Browning. The gel refers to a state in which the colloid particles lose their independent motility and are aggregated and solidified. The reduction treatment means adding electrons to the substance to be treated. Specifically, it means adding hydrogen to a substance to be treated in a hydrogen atmosphere. The catalyst metal aqueous solution is an aqueous solution containing a metal having a catalytic function. For example, an aqueous solution of palladium nitrate, an aqueous solution of copper nitrate, an aqueous solution of zinc nitrate, and the like can be mentioned, but any aqueous solution containing a metal having a catalytic function may be used and is not limited.

As described above, according to the present invention, a methanol reforming catalyst having a function of producing a large amount of hydrogen per unit volume and having excellent methanol reforming activity even at a low temperature (about 250 ° C.). Can be provided. Further, it is possible to provide a methanol reforming catalyst capable of maintaining a high ability to generate hydrogen from methanol from a low temperature (about 250 ° C.) to a high temperature (about 400 ° C.).

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a catalyst preparation method and a catalyst component were intensively studied with the aim of further improving the hydrogen generating ability and low-temperature activity of a methanol steam reforming catalyst. As a result of this study, it was found that a catalyst composed of palladium, copper and silica prepared by the sol-gel method has excellent low-temperature activity in steam reforming of methanol and produces dimethyl ether (hereinafter also referred to as “DME”) as a by-product. The catalyst was found to be a highly active catalyst with little.

Here, the method for producing a catalyst by the sol-gel method refers to a method for producing a catalyst using the following steps. Add acid to metal alkoxide, pH 2-3
, A hydrolysis reaction occurs and a uniform sol is formed. An aqueous solution of a catalytic metal is added to the sol and sufficiently stirred.
Next, gelation is performed by evaporating and drying with an evaporator. Further, after the gel is dried and fired, a reduction treatment is performed. A method for producing a catalyst by the above steps is a method for producing a catalyst by the sol-gel method. However, in the present invention, the method for producing a catalyst by the sol-gel method is not limited to the above method, and any method may be used as long as it is a method of preparing a catalyst using the state of a sol and a gel. Here, the metal alkoxide is a compound obtained by substituting hydrogen of a hydroxyl group in alcohols with a metal, for example, tetraethyl orthosilicate ((C
₂ H ₅ O) ₄ Si) and the like. Here, the aqueous catalyst metal solution is an aqueous solution containing a metal having a catalytic function, and examples thereof include palladium nitrate aqueous solution, copper nitrate aqueous solution, and zinc nitrate aqueous solution.

The catalyst produced by the sol-gel method is generally excellent in that the active metal carried thereon has a high degree of dispersion and the particle size of the metal can be controlled to be small. It is also excellent in that the metal forms a network with the carrier and is difficult to sinter. By the way, when alumina is used as a carrier as in the prior art, there is a problem that the following dehydration reaction of methanol easily occurs because alumina has acidity, and DME is generated as a by-product.
This tendency is particularly high for alumina prepared by the sol-gel method. 2CH ₃ OH → CH ₃ OCH ₃ + H ₂ O (1)

On the other hand, when silica is used as the carrier, there is almost no difference in the low-temperature activity from the case where alumina is used. Since silica has almost no acidity, the by-product DM
As a result of earnest research, it was found that E did not occur.

In the embodiment of the present invention, a methanol reforming catalyst containing palladium, copper and silica and prepared by a sol-gel method, which has a high hydrogen generation amount, is palladium and Suitably, the total amount with copper is 5 to 30% by weight (hereinafter also referred to as "wt%") and the ratio of palladium: copper is 1:20 to 1: 5. In particular, a methanol reforming catalyst having a total amount of palladium and copper of 10 wt% and a palladium: copper ratio of 1: 9 has the best hydrogen generation amount.

Further, in order to supplement the high-temperature performance of the present catalyst, a methanol reforming catalyst excellent in low-temperature activity, comprising palladium, copper and silica prepared by a sol-gel method at the preceding stage of the reaction path of the methanol reformer. And a catalyst having excellent high-temperature activity, comprising copper prepared by a conventional impregnation method, zinc and alumina, is disposed at a later stage of the reaction path. Due to this arrangement, the activity of methanol reforming is high from a low temperature (about 250 ° C.) to a high temperature (about 400 ° C.). In particular, the amount of hydrogen generation is maximized at a temperature around 300 ° C. where the methanol reformer is normally operated. can do. Here, the impregnation method is a method for producing a catalyst by impregnating a carrier of an inorganic oxide such as alumina (Al ₂ O ₃ ) into a catalyst metal solution and supporting the carrier.

[0019]

[Example 1] Cu-Pd by sol-gel method
/ Preparation of SiO ₂ ] 0.0679 g of palladium nitrate and 40 ml of water were mixed and heated to 80 ° C. with stirring. A mixed solution of 11.0 ml of tetraethyl orthosilicate and 8.3 ml of ethylene glycol was added thereto, and the mixture was heated with stirring. The mixed solution was kept stirring at 80 ° C. for 15 minutes or more, and nitric acid was added to adjust the pH to 2 or less. A copper nitrate solution (0.282 g as copper) was added thereto, and stirring was continued at 80 ° C. for 10 minutes or more. This was depressurized by an evaporator and evaporated to dryness at 80 ° C. to obtain a gelled solid. The gelled solid is dried at 150 ° C.
After calcining at 500 ° C. for 5 hours, hydrogen reduction was carried out, and 3.1 g
Of Cu-Pd / SiO ₂ was obtained. The composition of this catalyst was 9 wt% of copper (Cu) and 1 palladium (Pd) by weight.
wt% and silica (SiO ₂ ) was 90 wt%.

Example 2: Cu-P by sol-gel method
Preparation of d / SiO ₂ catalyst] The same procedure as in Example 1 was carried out. 0.0340g of palladium nitrate and 40m of water
and heated to 80 ° C. with stirring. A mixed solution of 11.0 ml of tetraethyl orthosilicate and 8.3 ml of ethylene glycol was added thereto, and the mixture was heated with stirring. The mixed solution was kept stirring at 80 ° C. for 15 minutes or more, and nitric acid was added to adjust the pH to 2 or less. A copper nitrate solution (0.297 g as copper) was added thereto, and stirring was continued at 80 ° C. for 10 minutes or more. This was depressurized by an evaporator and evaporated to dryness at 80 ° C. to obtain a gelled solid. The gelled solid is dried at 150 ° C.
After calcination at 0 ° C. for 5 hours, hydrogen reduction was carried out, and 3.1 g of C
u-Pd / SiO ₂ was obtained. The composition ratio of copper and palladium is different from that of Example 1, Cu is 9.5 wt%, and Pd is 0.1%.
5 wt%, SiO ₂ is 90wt% Cu-Pd / S
An iO ₂ catalyst was prepared.

[Example 3: Cu-P by sol-gel method]
d / SiO ₂ catalyst preparation] The same procedure as in Example 1 was carried out. 0.1358 g of palladium nitrate and 80 m of water
and heated to 80 ° C. with stirring. A mixed solution of 11.0 ml of tetraethyl orthosilicate and 8.3 ml of ethylene glycol was added thereto, and the mixture was heated with stirring. Stirring of the mixed solution was continued at 80 ° C. for 15 minutes or more, and nitric acid was added to adjust the pH to 2 or less. A copper nitrate solution (0.251 g as copper) was added thereto, and stirring was continued at 80 ° C. for 10 minutes or more. This was depressurized by an evaporator and evaporated to dryness at 80 ° C. to obtain a gelled solid. The gelled solid is dried at 150 ° C.
After calcination at 0 ° C. for 5 hours, hydrogen reduction was performed, and 3.1 g of C
u-Pd / SiO ₂ was obtained. The composition ratio of copper and palladium is different from that of Example 1, Cu is 8 wt%, and Pd is 2 wt%.
%, SiO ₂ was prepared Cu-Pd / SiO ₂ catalyst is 90 wt%.

Comparative Example 1: Cu-P by sol-gel method
d / Preparation of Al ₂ O ₃ ] 0.0679 g of palladium nitrate and 40 ml of water are mixed and heated to 70 ° C. with stirring. To this is added water at 70 ° C. in which 2.49 g of aluminum isopropoxide is dispersed. Further, the pH is adjusted from 2 to 3 by adding nitric acid to obtain a sol. To this, a copper nitrate solution (0.282 g as copper) is added, and stirring is continued at 70 ° C. for 10 minutes or more. This is reduced under reduced pressure by an evaporator and dried by evaporation at 80 ° C. to obtain a gelled solid. This was dried at 150 ° C., calcined at 500 ° C. for 5 hours, and then subjected to hydrogen reduction at 450 ° C. to obtain 3.1 g of Cu—Pd.
/ Al ₂ O ₃ was obtained. The composition of this catalyst is 9 wt% Cu,
Pd was 1 wt% and Al ₂ O ₃ was 90 wt%.

[Comparative Example 2: Cu-Zn / A by impregnation method]
Preparation of l ₂ O ₃ ] 9.5 g of copper nitrate (2.5 g as copper)
Was dissolved in 15 ml of ion-exchanged water, and 11.36 g of zinc nitrate (2.5 g as zinc) was added to the solution and dissolved with stirring. Then, γ-Al ₂
5 g of O ₃ were mixed and stirred for 12 hours or more. After drying with hot air, baking at 500 ° C for 1 hour in an oven, 450
Hydrogen reduction was performed at ℃ to obtain Cu-Zn / Al ₂ O ₃ . The composition of this catalyst is Cu 25 wt%, Zn 25 wt%,
Al ₂ O ₃ was 50 wt%.

[Comparative Example 3: Commercially available copper and zinc catalysts] Nikki Chemical's N211 was used as a commercially available copper and zinc catalyst. The composition of this catalyst had a weight ratio of Cu: Zn of 1: 1.

[Example 4: Cu-P by sol-gel method]
Methanol Reforming Catalyst Using d / SiO ₂ and Cu—Zn / Al ₂ O ₃ by Impregnation] FIG. 4 is a schematic view of a methanol reformer. As shown in FIG. 4, the Cu—Pd / SiO of Example 1 prepared by the sol-gel method at the first stage of the reaction route
₂ was placed in an amount of 0.05 g, and Cu—Zn / Al ₂ O ₃ of Comparative Example 2 prepared by impregnation in
Thus, a two-stage catalyst having a g arrangement was prepared.

[Reformation experiment of each prepared methanol reforming catalyst] The methanol reforming experiment was carried out by a fixed bed flow-through methanol reformer. The prepared catalyst powder was placed in a reaction tube, and all were vaporized with argon gas at 16 mmol / g- so that the molar ratio of vaporized water and methanol was 1: 1.
The amount was adjusted to the amount of catalyst / hour and introduced into the reaction tube. The reaction temperature was set at 200 ° C. to 400 ° C., and the analysis of the reaction gas and the product was performed by gas chromatography.

FIG. 1 is a graph showing the relationship between the reaction temperature and the amount of hydrogen generated in the catalysts of the examples and comparative examples. As is clear from FIG. 1, the Cu—Pd / SiO _{2 of} Example 1 prepared by the sol-gel method and the Cu—Pd / SiO ₂ of Comparative Example 1 were better than the Cu—Zn / Al ₂ O _{3 of} Comparative Example 2 prepared by the impregnation method. Cu-Pd / Al ₂ O ₃ was superior in low-temperature activity of the methanol reforming reaction. Cu-Pd / SiO of Example 1
₂ is a reaction temperature range of 250 ° C to 400 ° C, a methanol reforming rate of 64% or more, and a hydrogen generation amount of 36 mmol / g-
A catalyst amount / hour or more was obtained.

FIG. 2 is a graph showing the relationship between the reaction temperature and the by-product DME generation rate in the catalysts of the examples and comparative examples. As is clear from FIG. 2, the Cu—Pd / Al ₂ O of Comparative Example 1 prepared by the sol-gel method was used.
No. ₃ has a high generation rate of dimethyl ether as a by-product because alumina has acidity. On the other hand, the Cu—Pd / SiO _{2 of} Example 1 prepared by the sol-gel method
Is hardly generated. Therefore, as the methanol reforming catalyst, Cu-Pd / Si prepared by the sol-gel method was used.
O ₂ is best.

In FIG. 1, prepared by the sol-gel method
Cu-Pd / SiO of Example 1 _TwoHas excellent low-temperature activity
When the temperature rises (about 400 ° C), the impregnation method
Prepared Cu-Zn / Al of Comparative Example 2_TwoO_ThreeIs hydrogen-producing
Great yield. Therefore, as shown in FIG.
Example prepared by the sol-gel method in the first stage of the reaction route
Cu-Pd / SiO 1_TwoAnd the latter 2 of the reaction path
Cu—Zn / Al of Comparative Example 2 prepared by impregnation_Two
O_ThreeWas placed in a methanol reformer. It is clear from FIG.
When the reaction temperature is in the range of 250 ° C to 400 ° C,
Tanol reforming rate 82% or more, hydrogen production 39 mmol /
g-catalyst amount / hour or more and low temperature (about 250 ° C)
To a high temperature (about 400 ° C.). Ma
In addition, the temperature around 300 ° C where the methanol reformer is normally operated
The amount of hydrogen generated at temperature is 44 mmol / g-catalyst amount / hour.
Could be maximized.

FIG. 3 is a graph showing the relationship between the Pd content of the Cu-Pd / SiO ₂ catalyst prepared by the sol-gel method of Examples 1 to 3 and the amount of hydrogen generated when the Pd content was changed. The vertical axis of FIG. 3 indicates the amount of hydrogen generated [mmol / g-catalyst amount /
Time], and the horizontal axis represents Cu and Pd with respect to Pd in the catalyst.
Represents the ratio to the total amount of The value of Pd / (Cu + Pd) on the horizontal axis is 0.05 for Example 2, 0.10 for Example 1, and 0.20 for Example 3. In order to maintain a high hydrogen generation amount for the methanol reforming catalyst, Pd: Cu
From 1: 5 (0.17 on the horizontal axis in FIG. 3) to 1:20 (FIG.
It was found from FIG. 3 that the range of 0.05) was good on the horizontal axis. Pd: Cu is 1: 9 (0.1 in the horizontal axis of FIG. 3).
It was found from FIG. 3 that the amount of hydrogen generation was highest at 0).

[0031]

As described above, the methanol reforming catalyst according to the present invention is superior in activity at low temperatures and produces DME as a by-product as compared with a catalyst comprising copper, zinc and alumina. Can be reduced. Further, since the methanol reforming catalyst according to the present invention is produced by using a sol-gel method, the degree of dispersion of copper and palladium that contribute to the catalytic activity is improved, and the ability to generate hydrogen can be improved. Further, the methanol reforming catalyst according to the present invention can maintain a high ability to generate hydrogen from methanol from a low temperature (about 250 ° C.) to a high temperature (about 400 ° C.). The hydrogen generation amount can be maximized at the temperature before and after. Furthermore, since the catalyst is prepared by the sol-gel method, sintering of the active metal does not easily occur, and the catalyst life becomes longer.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the reaction temperature and the amount of hydrogen generated in catalysts of an example according to the present invention and comparative examples.

FIG. 2 is a graph showing the relationship between the reaction temperature and the by-product DME generation rate in the catalysts of Examples according to the present invention and Comparative Examples.

FIG. 3 shows a Pd / (Cu + P) in a Cu—Pd / SiO ₂ catalyst prepared by a sol-gel method according to an embodiment of the present invention.
It is a graph showing the relationship between the ratio of d) and the amount of generated hydrogen.

FIG. 4 is a diagram in which Cu-Pd / SiO ₂ prepared by the sol-gel method is arranged at the first stage of the reaction route, and Cu-Zn / Al ₂ O ₃ prepared by the impregnation method is arranged at the second stage of the reaction route. It is a schematic diagram of a stage catalyst.

[Explanation of symbols]

1 Cu-Pd / SiO prepared by sol-gel method
It was prepared by ₂ 2 impregnation Cu-Zn / Al ₂ O ₃

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuhisa Konagai 300, Takatsukacho, Hamamatsu-shi, Shizuoka Suzuki Co., Ltd. (72) Inventor Fumika Kimata 300, Takatsukacho, Hamamatsu-shi, Shizuoka Suzuki Co., Ltd. Person Yukio Yamamoto 300 Takatsuka-cho, Hamamatsu-shi, Shizuoka Suzuki Co., Ltd. F-term (reference) 4G040 EA02 EA06 EC01 EC03 4G069 AA03 AA08 BA01B BA02A BA02B BA21C BC31A BC31B BC35B BC72A BC72B BD05C BE06FB40 FB FB FB FB FB FB FB FB FB FB FB FB FB FB FB FB FB40 EA02 EA06 EC01 EC03 5H027 AA02 BA01

Claims (6)

[Claims] 1. A methanol reforming catalyst comprising palladium, copper, and silica, for producing hydrogen by steam reforming of methanol. 2. The methanol reforming catalyst according to claim 1, wherein the catalyst is produced by a sol-gel method. 3. A step of adding an acid to the metal alkoxide to form a sol; a step of adding a catalytic metal aqueous solution to the sol and stirring; and a step of evaporating and drying the stirred sol to form a gel; 2. The methanol reforming catalyst according to claim 1, wherein the catalyst is produced by a production method including a step of drying and calcining the gel, and a step of reducing the calcined gel. 3. 4. The methanol reforming catalyst according to claim 1, wherein the ratio of palladium: copper is in the range of 1:20 to 1: 5. 5. The method according to claim 1, wherein the methanol reforming catalyst according to any one of claims 1 to 4 is arranged at a stage preceding the reaction path, and a catalyst obtained by impregnating a carrier of alumina with copper and zinc is arranged at a stage subsequent to the reaction path. A methanol reformer characterized by the following. 6. A step of adding an acid to the metal alkoxide to form a sol; a step of adding a catalytic metal aqueous solution to the sol and stirring; a step of evaporating and drying the stirred sol to form a gel; A method for producing a methanol reforming catalyst, comprising: a step of drying and calcining the gel; and a step of reducing the calcined gel.