JP2001129398A - Catalyst for reforming methanol and method for preparing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst for reforming methanol not requiring reduction treatment, with excellent durability and with high activity. SOLUTION: A catalyst for reforming treatment of methanol by reacting methanol with steam or a mixed gas of steam and oxygen comprises zirconium oxide and at least one active metal selected from the group consisting of platinum, palladium, ruthenium, iridium and rhodium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for producing hydrogen-containing gas by reforming methanol and a method for producing the same, and more particularly, to a methanol suitably used for a methanol reformer for producing hydrogen in a fuel cell system. The present invention relates to a reforming catalyst and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, fuel cells have been attracting attention as a method for producing electric energy efficiently and more cleanly as global environmental problems increase. Above all, exhaust gas discharged from internal combustion engines such as automobiles contains a large amount of harmful gases such as nitrogen oxides and generalized carbon, and thus various improvement measures have been taken. As one of the improvement measures, the development of a vehicle equipped with a polymer electrolyte fuel cell (PEFC) instead of an internal combustion engine has been earnestly pursued. A polymer electrolyte fuel cell diffuses hydrogen with protons in a polymer membrane, and along with this, electrons move to obtain electric energy, and an efficient hydrogen production device is needed to mount it on an automobile. is there. In the production of hydrogen, methanol is easily synthesized from fossil fuel in inexpensive liquid fuel, and has a characteristic that it can be relatively easily converted to hydrogen using a catalyst.

In order to produce hydrogen from methanol, the most significant amount of hydrogen can be produced by a steam reforming reaction as shown in the following equation (1). CH ₃ OH + H ₂ O → 3H ₂ + CO ₂ -11.8 kcal / mol (1) Here, since the above equation (1) is an endothermic reaction, it is necessary to maintain a predetermined temperature at which the catalyst acts. It is effective to apply heat energy from the outside. Therefore, adding oxygen,
There has also been proposed a method of producing hydrogen by causing partial oxidation reactions of the following formulas (2) and (3) having heat generation simultaneously. CH ₃ OH + 1 / 2O ₂ → CO + H ₂ + H ₂ O + 36.2kcal / mol ・ ・ ・ (2) CH ₃ OH + 1 / 2O ₂ → CO ₂ + 2H ₂ + 46.0kcal / mol ・ ・ ・(3) Although the above formulas (2) and (3) are both exothermic reactions,
Produces a large amount of hydrogen as fuel for PEFC,
Formula (3), in which the amount of CO, which is a poison of the F cell, is small, is a preferable reaction. The methanol reforming reaction is performed in the above (1)
An ideal reaction is a single reaction of the formula or a simultaneous reaction of the formulas (1) and (3).

On the other hand, a conventional methanol reforming catalyst is generally a composite oxide composed of copper and zinc. However, since this catalyst requires a reduction treatment as an activation treatment, it is necessary to use a methanol for transportation such as automobiles. There are many problems in terms of maintenance and the like when mounted on a reformer. In addition, voids are generated inside the reformer due to the volume reduction due to the reduction treatment, and there is a concern that the catalyst may be powdered or unreacted methanol may increase due to short-circuit. Furthermore, it is necessary to mold the honeycomb into a honeycomb shape in order to be mounted on a mobile reformer, but there are many difficulties with the current molding technology. In addition, there is a concern about the durability of the catalyst. Therefore, a reduction treatment is not required instead of a copper or zinc-based catalyst, and the emergence of a highly active methanol reforming catalyst having excellent durability has been awaited.

[0005]

In view of the above problems, the present inventors have developed a highly active methanol reforming catalyst which does not require a reduction treatment and has excellent durability. The steam reforming reaction was preferentially performed, and a catalyst system containing a large amount of hydrogen and a small amount of CO in the product was intensively studied. As a result, the present inventors have found that the above problems can be solved by using zirconium oxide as a catalyst carrier for a noble metal-based catalyst having no problems such as a copper-based catalyst. It was completed.

[0006]

That is, the present invention relates to a catalyst for reforming methanol by reacting methanol with steam or a mixed gas of steam and oxygen, the catalyst comprising zirconium oxide and an active metal. It is intended to provide a methanol reforming catalyst characterized by containing:
Here, the active metal preferably contains at least one noble metal component selected from the group consisting of platinum, palladium, ruthenium, iridium and rhodium, and the zirconium oxide is a composite oxide, ZrO ₂ .A
l ₂ O ₃ , ZrO ₂ · TiO ₂ , ZrO ₂ · SiO ₂ , ZrO
It is preferably at least one compound selected from the group consisting of ₂ · P ₂ O ₅ or ZrO ₂ · B ₂ O ₃ , and a sulfate group carrier (SO ⁴⁺ / ZrO ₂ ).

In the present invention, the raw material of the zirconium oxide is preferably at least one compound selected from the group consisting of zirconium oxychloride, zirconium oxynitrate and zirconium hydroxide, and has a specific surface area of 20 m It is preferably at least ² / g. Furthermore, the crystal structure of zirconium oxide in the catalyst is amorphous,
It is preferable to be either tetragonal or cubic. Further, the present invention is a method for producing a methanol reforming catalyst in which an active metal is supported on a carrier containing zirconium oxide, which is selected from the group consisting of zirconium oxychloride, zirconium oxynitrate and zirconium hydroxide. A precipitate obtained from an aqueous solution containing at least one compound is calcined into zirconium oxide, and then impregnated with at least one active metal selected from the group consisting of platinum, palladium, ruthenium, iridium and rhodium by ion impregnation or ion exchange. The present invention provides a method for producing a methanol reforming catalyst, which is supported by a method.

According to the methanol reforming catalyst of the present invention, extremely high methanol conversion efficiency can be realized, so that methanol can be reacted stably and a reformed gas having a high hydrogen content can be obtained. Accordingly, a hydrogen-containing gas suitably used for a fuel cell can be produced.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The catalyst of the present invention allows the methanol steam reforming reaction (formula (1)) to be carried out alone, or the methanol steam reforming reaction and the partial oxidation reaction (described above).
And (3) are highly active methanol reforming catalysts for reforming methanol. Copper-based catalysts commonly used for methanol reforming require a reduction treatment, for example, exhibiting activity by reducing CuO, which is an oxide, to Cu, and being oxidized when in contact with the atmosphere to become inactive again Therefore, the operation of the reduction treatment was complicated. In addition, the reduction treatment reduces the volume of the catalyst (volume change), forms a cavity in the catalyst container, and causes a short-circuit portion in the gas flow, or causes cracks or cracks in the catalyst pellets or the like. And so on.
As described above, generally used Cu-Zn-based catalysts have problems such as low heat resistance and poor handling.

The metal-based catalyst of the present invention does not have such a problem and is extremely active.
It has the characteristic that O does not occur. In general, with a noble metal-based catalyst, CH ₃ OH + H ₂ O → 3H ₂ + CO ₂ (1) methanol decomposition reaction of the following formula (4) is more effective than the steam reforming reaction of the following formula (1). Proceeds preferentially, so that CH ₃ OH → CO + 2H ₂ (4) The amount of hydrogen obtained decreases, and at the same time, CO, which is a catalyst poison for the fuel cell electrode, is likely to be generated.

On the other hand, the catalyst system of the present invention is a noble metal-based catalyst having no problems such as reduction treatment and volume change, and preferentially advances the steam reforming reaction (1). Is what you can do. The methanol reforming catalyst of the present invention uses zirconium oxide (ZrO ₂ ) as a carrier, whereby the reaction of the above (1) can be performed preferentially, and the problem of generating CO does not occur. . This is because, when aluminum oxide or the like is the main component of the carrier, and when zirconium oxide is the main component of the carrier, the crystal structure and the like of the catalyst obtained by the production are different, so that the action as the catalyst also changes. Because.

ZrO ₂ is usually used also as an oxygen conductive solid electrolyte, and has a feature that the surface has a surface hydroxyl group having an amphoteric function. That is, in the steam oxidation reaction or methanol partial oxidation reaction of methanol,
It is considered that CO generated by methanol decomposition effectively acts on oxygen atoms generated by dissociation of H ₂ O or O ₂ , and ZrO ₂ having oxygen conductivity contributes to this reaction. The reaction mechanism is shown below as an elementary reaction, taking the methanol steam reforming reaction as an example. CH ₃ OH → CO + 2H ₂・ ・ ・ (4 ′) H ₂ O → O + H ₂・ ・ ・ (5) CO + O → CO ₂・ ・ ・ (6) Equation (5), (6) It is presumed that the reaction of the formula occurs at the surface of ZrO ₂ . Further, the methanol reforming catalyst of the present invention has high performance without any activation treatment such as reduction treatment, because the active metals are all noble metals.

The method for producing the methanol reforming catalyst of the present invention is not particularly limited, and a catalyst in which platinum, palladium, ruthenium, iridium, rhodium or the like as an active metal is supported on zirconium oxide as a carrier. If it is, it can be used effectively. Hereinafter, an example of a specific manufacturing method will be described. An aqueous ammonia solution is added to an aqueous solution containing at least one compound selected from the group consisting of zirconium oxychloride, zirconium oxynitrate, and zirconium hydroxide to obtain a precipitate. This precipitate is usually calcined at 300 to 800 ° C. for 30 minutes to 12 hours to obtain a zirconium oxide. The obtained oxide is pulverized and then immersed in an aqueous solution of an active metal such as platinum, palladium, ruthenium, iridium or rhodium. After impregnating and drying, usually at 300 to 800 ° C for 30 minutes to 1
By calcining for 2 hours, the target catalyst is obtained. here,
Although the active metal is supported by the impregnation method, a method such as an ion exchange method may be used. The methanol reforming catalyst of the present invention obtained as described above is a high-performance catalyst that does not require an activation treatment such as a reduction treatment. The catalyst of the present invention can be used both in the case of the steam reforming reaction alone (Example 2) and in the case of the simultaneous partial oxidation reaction (Example 3). Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0014]

EXAMPLES Example 1 [Catalyst preparation 1] Zirconium oxychloride (ZrOCl ₂ .2H ₂ O)
1 mol is added to 5 liters of water and the temperature is kept at 70 ° C. 1% ammonia solution in solution A
While stirring the mixture, the mixture was added dropwise until the pH became 7, thereby obtaining a precipitate. Stir for 1 hour in the state of PH7, and wash this solution with water.
Filtration was performed to obtain a precipitate 1, and the precipitate 1 was dried at 100 ° C. The dried product 1 was calcined at 500 ° C. for 5 hours to obtain zirconium oxide 1 (ZrO ₂ ). The resulting oxide 1 was ground in a dry ball mill, the platinum concentration 0.1 wt% of chloroplatinic acid in pulverized product (H ₂ PtCl ₆₎ aqueous solution was dipped, supported platinum of 1% by weight of platinum relative to ZrO ₂ Is added with stirring, and 1
Evaporation to dryness was performed at 00 ° C. The dried product 1 prepared by the impregnation method was calcined at 500 ° C. for 5 hours to prepare a platinum-supported ZrO ₂ catalyst (catalyst 1).

[Catalyst Preparation 2] In the same manner as in Catalyst Preparation 1, simultaneously with zirconium oxychloride, 1 mol of aluminum trichloride (AlCl ₃ ), 1 mol of titanium tetrachloride (TiCl ₄ )
l, the SiO ₂ 1 mol in silica sol (SiO ₂ ... 20% by weight containing)
Added to 5 liters of water. Composite precipitates 2, 3, and 4 were obtained in the same manner as in preparation of catalyst 1, and the precipitate was calcined to obtain composite oxides 1 (ZrO ₂ .Al ₂ O ₃ ), 2 (ZrO ₂ .TiO ₂ ), and 3 ( (ZrO ₂・ SiO ₂ )
I got Further, in the same manner as in Catalyst Preparation 1, platinum was added so as to be able to carry 1% by weight per oxide, and dried and calcined to obtain Catalyst 2, Catalyst 3, and Catalyst 4. Further, in the same manner as in catalyst preparation 1, an aqueous solution of oil phosphoric acid (H ₃ PO ₄ ) and boric acid (H ₃ BO ₃ ) is immersed in zirconium oxide 1 (ZrO ₂ ), and the mixture is stirred and evaporated to dryness. while, with respect to ZrO _2, the P ₂ O ₅ 10
%, And 10% by weight of B ₂ O ₃ . 500 samples
At 5 ° C. for 5 hours to obtain a composite oxide 5 (ZrO ₂ .P ₂ O ₅ ), 6 (ZrO 2
₂ · B ₂ O ₃₎ was obtained. And, 1% by weight of platinum per oxide
Add in the same manner as in Catalyst Preparation 1 so that it can be supported, and
Calcination gave Catalysts 5 and 6.

[Catalyst Preparation 3] In the same manner as in Catalyst Preparation 1, 1N sulfuric acid is immersed in the precipitate 1 at room temperature for 1 hour, filtered, dried at 110 ° C. for 12 hours, and further dried at 550 ° C.
Sintering in air for 5 hours at room temperature, and sulfated ZrO ₂ (SO ⁴⁺ / Zr
O ₂ ) was obtained. To the above substance, platinum was added in the same manner as in Catalyst Preparation 1 so as to support 1% by weight of the oxide, and dried and calcined to obtain Catalyst 7.

[Catalyst Preparation 4] In the same manner as in Catalyst Preparation 1, as the active metal supported on zirconium oxide (ZrO ₂ ), an aqueous solution of palladium nitrate containing 0.1% by weight of each metal was used instead of the aqueous solution of chloroplatinic acid. Ruthenium, iridium chloride and rhodium chloride aqueous solutions were immersed and evaporated to dryness, and 1% by weight of each metal was supported. Further, each substance was calcined at 500 ° C. for 5 hours to obtain catalysts 8, 9, 10, and 11.

[Catalyst Preparation 5] In the same preparation method as in Catalyst Preparation 1, 1 mol of zirconium oxynitrate (ZrO (NO ₃ ) ₂ ) was added instead of zirconium oxychloride, and platinum was supported in the same manner as in Catalyst Preparation 1. A ZrO ₂ catalyst (12) was prepared. Further, in the same preparation method as in catalyst preparation 1, zirconium hydroxide (manufactured by Hanoi Chemical: Zr (O
H) Using ₄ ), platinum-supported ZrO
₂ (catalyst 13) was obtained.

[Catalyst Preparation 6] In a preparation method similar to Catalyst Preparation 1, when preparing a platinum-supported ZrO ₂ catalyst, an aqueous solution of a platinum chloride ammine complex (Pt (NH 3) ₄ Cl ₄ ) was used instead of chloroplatinic acid. Then, ZrO ₂ crushed at a platinum concentration of 1% by weight was added at room temperature, and 1% by weight of platinum was supported on ZrO ₂ by an ion exchange method.
₂ (catalyst 14) was obtained. Table 1 shows the specific surface areas and the crystal structures of the catalysts 1 to 14 produced as above.

[0020]

[Table 1] An aqueous sodium hydroxide solution was added at 70 ° C. to an aqueous solution containing zinc nitrate and copper nitrate (Cu: Zn = 1: 1) at 70 ° C. to form a precipitate. The precipitate is filtered and washed with water,
Then, baking was performed at 300 ° C. for 3 hours. This catalyst is referred to as Comparative Catalyst 1.

Example 2 Catalyst 1 produced as a trial in Catalyst Preparations 1 to 6 and Comparative Catalyst Preparation 1
To 14, a comparative catalyst 1 was subjected to a methanol reforming test. In the test method, the catalyst was formed into pellets of 2 to 4 mm, and the catalyst was filled in a reactor of a fixed bed flow type test apparatus.
Then, the catalyst inlet temperature is 300 ° C, 440 ° C, and the pressure is 3at.
a, GHSV: 10000 h ^-1 , H ₂ O / CH ₃ OH molar ratio 2.2
Under the conditions described above, a methanol steam reaction was performed. Table 2 shows, as test results at catalyst inlet temperatures of 300 ° C. and 400 ° C., outlet catalyst temperature, methanol conversion, and outlet CO concentration. From these results, it can be seen that the comparative catalyst shows almost no activity under the present test conditions without reduction treatment, whereas the catalysts of the present invention all have a high methanol conversion and a low exit CO concentration, indicating that It was proved to be a methanol reforming catalyst.

[0022]

[Table 2]

Example 3 In the same manner as in Example 2, the catalysts 1 to 1
4. Using the comparative catalyst 1 and methano
A reforming test was conducted. In the same manner as in Example 2.
And the catalyst inlet temperature 300 ° C, 440 ° C, pressure 3ata, G
HSV: 10000h ^-1, H_TwoO / CH_ThreeOH molar ratio 2.2, air
/ CH_ThreeUnder the condition of CH mole ratio 0.8, methanol steam
Reaction of the hydrogen reaction (1) and the methanol partial oxidation reaction (3)
Responded. Inlet catalyst temperature 300 ℃, 400 ℃
As test results, the outlet catalyst temperature, methanol conversion and
Table 3 shows the outlet CO concentration.

[0024]

[Table 3]

From these results, the comparative catalyst showed almost no activity as in Example 2. On the other hand, all of the experimental catalysts of the present invention exhibited high methanol conversion and low exit CO concentration. Further, in Example 2, the outlet catalyst temperature is significantly lower than the inlet catalyst temperature,
Under the test conditions, the outlet catalyst temperature and the inlet catalyst temperature were almost the same, and it was found that the methanol steam reaction and the partial oxidation reaction occurred simultaneously, and even under such conditions, the catalyst of the present invention had a high performance. It proved to be a methanol reforming catalyst.

[0026]

According to the present invention, a highly active methanol reforming catalyst which does not require a reduction treatment and has excellent durability can be obtained. According to the catalyst of the present invention, methanol can be converted to a hydrogen-containing gas with high efficiency, and the amount of generated CO can be reduced and the amount of hydrogen can be increased. When the catalyst of the present invention is used, extremely high methanol conversion efficiency can be realized, so that all methanol can be reacted stably, and a reformed gas having a high hydrogen content can be obtained, which is suitable for a fuel cell system or the like. Used for

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 23/46 311 B01J 23/46 311M 27/053 27/053 M 27/185 27/185 M 35/10 301 35/10 301 J 37/02 101 37/02 101Z C01B 3/32 C01B 3/32 A F term (reference) 4G040 EA02 EA06 EA07 EC03 EC08 4G069 AA03 AA08 AA09 AA12 BA01A BA01B BA02A BA02B BA04A BA04B BA20A BA05B BAA BB04C BB06A BB06B BB10A BB10B BB20C BC51A BC51B BC51C BC70A BC70B BC71A BC71B BC72A BC72B BC74A BC74B BC75A BC75B BD02A BD02B BD02C BD03A BD03B BD06C BD07A BD07B BD12C CC25 EC02X EC02 EC02 EC04 EC05

Claims (7)

[Claims] 1. A catalyst for reforming methanol by reacting methanol with steam or a mixed gas of steam and oxygen, the catalyst comprising zirconium oxide and an active metal. Quality catalyst. 2. The catalyst for methanol reforming according to claim 1, wherein the active metal contains at least one metal component selected from the group consisting of platinum, palladium, ruthenium, iridium and rhodium. 3. The method according to claim 1, wherein the zirconium oxide is a composite oxide of ZrO ₂ .Al ₂ O ₃ , ZrO ₂ .TiO ₂ , ZrO _2.
SiO ₂ , ZrO ₂ · P ₂ O ₅ or ZrO ₂ · B ₂ O ₃ ,
_2. The methanol reforming catalyst according to claim 1, wherein the catalyst is at least one compound selected from the group consisting of and a sulfate support (SO4 ⁺ / ZrO2). 4. The methanol reforming method according to claim 1, wherein the raw material of the zirconium oxide is at least one compound selected from the group consisting of zirconium oxychloride, zirconium oxynitrate, and zirconium hydroxide. catalyst. 5. The catalyst for methanol reforming according to claim 1, wherein the specific surface area is 20 m ² / g or more. 6. The methanol reforming catalyst according to claim 1, wherein the crystal structure of zirconium oxide in the catalyst is one of amorphous, tetragonal, and cubic. 7. A method for producing a methanol reforming catalyst in which an active metal is supported on a support containing zirconium oxide, comprising: at least one selected from the group consisting of zirconium oxychloride, zirconium oxynitrate and zirconium hydroxide. A precipitate obtained from an aqueous solution containing one compound is calcined to form zirconium oxide, and the zirconium oxide is impregnated with at least one active metal selected from the group consisting of platinum, palladium, ruthenium, iridium and rhodium. A method for producing a methanol reforming catalyst, wherein the catalyst is supported by a method or an ion exchange method.