JP2003146615A - Method for manufacturing hydrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress ammonia generation as a by-product of manufacture of hydrogen from hydrocarbon. SOLUTION: The method for manufacturing hydrogen is characterized by suppressing ammonia generation as the by-product by using a catalyst carrying platinum in the case of manufacturing hydrogen from hydrocarbon, steam and air through a steam reforming reaction and a partial oxidation reaction.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hydrogen production method for producing hydrogen from hydrocarbons such as city gas.

[0002]

2. Description of the Related Art Conventionally, when hydrogen is produced from hydrocarbons such as city gas, it is carried out only by a steam reforming reaction (endothermic reaction) as represented by the following formula (1).

CH ₄ + H ₂ O → CO + 3H ₂ (1) Further, in addition to the above formula (1), a partial oxidation reaction (exothermic reaction) such as the following formula (2) is also generated to make the apparatus compact. it can. CH ₄ + 1 / 2O ₂ → CO + 2H ₂ (2) However, in this case, in the formula (2), there is a problem that nitrogen and hydrogen in the air react with each other to produce ammonia as a poisoning substance (see below). See formula (3)).

N ₂ + 3H 2 → 2NH ₃ (3)

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is a supported platinum catalyst when hydrogen is produced from hydrocarbons, steam and air by steam reforming reaction and partial oxidation reaction. An object of the present invention is to provide a hydrogen production method capable of suppressing by-product of ammonia by using.

[0006]

The present invention is a method for producing hydrogen, which comprises using a supported platinum catalyst when producing hydrogen from a hydrocarbon, steam and air by a steam reforming reaction and a partial oxidation reaction. .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The hydrogen production method of the present invention will be described in more detail below. In the present invention, the molar ratio of hydrocarbon to water vapor is H ₂ O / hydrocarbon (Cl conversion) = 0.
1 to 10, and the molar ratio of hydrocarbon to air is preferably air / hydrocarbon (converted to Cl) = 0.1 to 5. Here, when the molar ratio of hydrocarbon to steam is less than 0.1, the change due to carbon precipitation is remarkable, and when the molar ratio exceeds 10, the energy efficiency is lowered due to the supply of excess steam. Further, when the molar ratio of hydrocarbon to air is less than 0.1, the reaction of the above formula (2) does not occur and only the reaction of the above formula (1) occurs, and when the molar ratio exceeds 5, an oxidizing atmosphere occurs and the catalyst deteriorates. It is easy to do.

In the present invention, the supported platinum catalyst is a carrier in which platinum is supported, and the carrier includes α-alumina, γ-alumina, anatase-type titania, silica,
Zirconia, at least one of zeolite oxides,
Or silica / alumina, silica / titania, titania /
Examples thereof include composite oxides such as alumina and alumina-zirconia. The reason why platinum is supported on the carrier is that the steam reforming reaction and the partial oxidation reaction are promoted, but the adsorption power of N ₂ is small, so that the by-product of NH ₃ is small. Examples of the method for supporting the supported platinum catalyst include an impregnation method and an ion exchange method.

Here, the impregnation method means that a platinum salt is dissolved in a solvent such as water, the platinum aqueous solution is immersed in a carrier, and evaporation,
This is a method of supporting platinum on a carrier by a treatment of dryness and baking. The ion exchange method is a method in which a carrier having a cation exchange site (such as zeolite) is added to a cation-exchangeable aqueous solution of platinum such as gintrodiamine platinum, and platinum ions are loaded on the carrier. is there.

The supported platinum catalyst preferably has a promoter as a metal catalyst to be supported on the carrier in addition to platinum in order to enhance durability of the catalyst. Here, as the co-catalyst, for example, tungsten (W), molybdenum (M
o), boron (B), magnesium (Mg), calcium (Ca), lanthanum (La), potassium (K).

In the present invention, hydrogen is produced by supplying an autothermal reaction, which is a combined reaction of steam reforming reaction / partial oxidation reaction, by supplying hydrocarbon, steam and air to the catalyst layer comprising a supported platinum catalyst. However, it is preferable to supply air to the catalyst layer in multiple stages. Although the reason why the by-product of ammonia is eliminated by using the supported platinum catalyst as in the present invention is still unknown, the present catalyst can selectively adsorb hydrocarbons, oxygen, and water vapor, but has poor nitrogen adsorption power. It is thought to be because.

The hydrocarbon reformer using this catalyst is compact and can be started for a short time, and is effective as a reformer for vehicle-mounted and distributed power PEFC systems. Specifically, a hydrogen-containing gas produced from steam reforming / partial oxidation reaction using this catalyst (mainly hydrogen, other 10 pp
m including CO, N ₂ , H ₂ O, and CO ₂ )
If it is supplied to the FC fuel cell, the reformed gas after CO removal can be directly supplied to the PEFC cell because there is no by-product of ammonia.

[0013]

EXAMPLES Examples of the present invention will be described below. (Example 1) Preparation of catalyst 1: First, as a carrier, a specific surface area of 150 m ² /
g of γ-type alumina powder was placed in an evaporation dish, a platinum chloride aqueous solution was dropped on α-alumina, and the dropped water was evaporated on a hot plate at 100 ° C. (Pt was carried by an impregnation method). Next, while stirring the powder, platinum was uniformly supported, and 1% by weight of platinum (Pt) was supported on the carrier by an impregnation method. Next, this γ-alumina carrier Pt
After drying the catalyst powder at 120 ° C for 12 hours, 550 ° C
Calcination was performed for 5 hours in an air atmosphere. Furthermore, 2% of alumina sol binder was added to the present Pt catalyst powder supporting γ-alumina.
Was added to mold a 3 mmφ catalyst, and then 500 ° C.,
It was baked for 5 hours. This granular catalyst is referred to as catalyst 1.

Preparation of catalysts 2 to 6: In the preparation method of the above catalyst 1, a specific surface area of 10 m ² / instead of γ-alumina.
g of α-alumina, anatase type titania, silica, zirconia, pentasil type zeolite (SiO ₂ / Al ₂
Powder catalysts 2 to 6 were prepared by carrying platinum in the same manner as the catalyst 1 using O ₃ ratio = 200). Next, catalyst 1
A 3 mmφ granular catalyst was prepared by the same method as described above, and then calcined at 500 ° C. for 5 hours to obtain catalysts 2 to 6.

Preparation of catalysts 7-11: Method for preparing catalyst 1 above
In place of γ-alumina,_Two・ SiO
_TwoComplex oxide (TiO_Two: SiO_Two= 80: 20, ratio table
Area 150m^Two/ G), TiO_Two・ Al2O_ThreeComplex oxidation
Thing (TiO_Two: Al_TwoO_Three= 50: 50, specific surface area 16
0m^Two/ G), Al_TwoO_Three・ ZrO_TwoComplex oxide (Al
_TwoO_Three: ZrO_Two= 90:10, specific surface area 200 m_Two/
g), TiO_Two・ ZrO_TwoComplex oxide (TiO _Two: Zr
O_Two= 50: 50, specific surface area 100 m^Two/ G), SiO
_Two・ Al_TwoO_ThreeComplex oxide (SiO_Two: Al_TwoO_Three= 9
0:10, specific surface area 150m^Two/ G) was prepared.

The preparation method was as follows. First, ammonia was added dropwise to the aqueous metal nitrate or chloride solution, and a composite hydroxide was obtained by a coprecipitation method at about pH = 7. Next, after drying, baking was performed at 600 ° C. for 5 hours. Then, powder catalysts 7 to 11 were prepared by carrying platinum in the same manner as the catalyst 1. Further, a granular catalyst having a diameter of 3 mm was prepared in the same manner as the catalyst 1 to obtain catalysts 7 to 11.

Preparation of catalysts 12 to 17: In the preparation method of the above catalyst 1, in order to carry W, Mo, B, Ca, Mg, and K using the γ-alumina-supported platinum powder catalyst as a co-catalyst, an aqueous ammonium salt or nitrate solution is prepared. And 0.5% of each was supported by a metal, dried and baked at 600 ° C. for 5 hours. Further, a granular catalyst having a diameter of 3 mm was prepared in the same manner as the catalyst 1 to obtain catalysts 12 to 17.

Preparation of catalyst 18: In the preparation method of the above catalyst 1, an ion exchange method was used as a method for supporting platinum supported on γ-alumina. First, using 100 cc of dinitroamine aqueous solution (0.1 M solution) as a platinum raw material, 10 g of γ-alumina was added and stirred at 40 ° C. for 3 hours to perform cation exchange. Next, after filtration, washing with ion-exchanged water, drying and firing in the same manner as the catalyst 1, and further adjusting to 3 mmφ,
A catalyst 18 was obtained. The amount of platinum supported on the catalyst 18 was 1.
It was 2% by weight.

Preparation of catalysts 19 and 20: In the preparation method of catalyst 1 above, 0.3 as platinum supported on γ-alumina was used.
%, 2% supported catalyst was prepared. Granular catalysts were prepared in the same manner as the catalysts to obtain catalysts 19 and 20.

Comparative catalyst: In the method for preparing Catalyst 1 above,
As a catalyst supported on α-alumina, instead of chloroplatinic acid, each aqueous solution of ruthenium chloride and nickel chloride is impregnated to form a powder catalyst, and each metal is Ru: 1%, Ni: 1
Supported 3%. Further, in the same manner as the catalyst 1, 3 mm
Comparative catalysts 1 and 2 were obtained by preparing a granular catalyst of φ.

[0021] (Example 2) autothermal reaction conditions 1: the catalyst 1 to 17, Comparative Catalyst 1 was used to reforming test was conducted under the following conditions, the raw material is city gas 13A _(CH 4: 88 %, C ₂ H ₆ : 6
%, C ₃ H ₈ : 4%, C ₄ H ₁₀ : 2%) and steam and air (steam / city gas (Cl base) = 2.5 (molar ratio), air / city gas (Cl base) = 2.5 (molar ratio)) and 20 cc filled catalyst layer (3
mmφ pellet filling, cylindrical type: diameter 26 mmφ, length 25
mm) was maintained at a catalyst layer average temperature of 740 ° C., and the above raw materials were supplied at GHSV 1000 h ⁻¹ (flow rate 200 L / h). Hydrocarbons having a gas composition at the outlet of the reaction tube were analyzed by a gas chromatogram. The hydrocarbon conversion rate (η) can be obtained by η = (1-outlet hydrocarbon / inlet hydrocarbon (Cl base) × 100. Also, the amount of NH ₃ produced as a by-product is obtained by an ion chromatogram method. The results of the activity evaluation test of the above catalyst are shown in Table 1 below.

[0022]

[Table 1]

From Table 1, it was confirmed that all the catalysts produced a city gas conversion rate of 95% or more and a hydrogen concentration of 48% or more. However, with the comparative catalyst, the by-product of ammonia is 60
About 1 ppm is recognized, while the catalyst 1
20 is hardly recognized. From this, it is considered that the prototype catalyst has no ammonia by-product, and thus PEFC has almost no poisoning effect.

The reason why the catalysts 1 to 20 have sufficient hydrogen production activity and no ammonia by-product is that Pt, which has a weak nitrogen adsorption force, is used as the active metal and the adsorption ability of water and oxygen is increased. The combination with a strong carrier is considered to be effective.

Example 3 The catalyst 1 was used under the autothermal conditions of Example 2 under the conditions shown in Table 2 below for the composition of water vapor / city gas and air / city gas (Run No23- 26).

[0026]

[Table 2]

From Table 2, it was confirmed that steam / city gas and air / city gas have no NH ₃ by-product even in the above molar ratio and can produce sufficient hydrogen.

Example 4 The temperature distribution of the catalyst layer was measured under the test conditions of RUN No. 1 of Example 2. As a result, although the average temperature of the catalyst layer was 740 ° C., heat was mainly generated at the catalyst inlet and heat was mainly absorbed at the outlet, so that the catalyst layer temperature distribution was about 150 ° C. Therefore, in order to solve the above-mentioned problems, the catalyst average temperature is set to 740 ° C., the amount of air supplied to the catalyst layer is divided into three, and the upstream side of the catalyst layer and the 1/3 and 2/3 intermediate layers each have 1 The temperature distribution and activity evaluation test of the catalyst layer were performed (Run N
o27).

Further, the amount of air supplied to the catalyst layer was divided into five, and the activity evaluation was conducted by supplying 1/5 each to the upstream of the catalyst layer and the 1/5, 2/5, 3/5, 4/5 intermediate layers. I went (Ru
n No 28). Furthermore, Run1 of Example 2 was continuously operated for 500 hours, and an activity evaluation test after 500 hours was performed (Run No29). Table 3 below shows Run No.
1,27,28,29 hydrocarbon conversion (%), NH ₃
The amount of by-product, hydrogen concentration (%) dry base, and catalyst layer temperature distribution (° C) are shown.

[0030]

[Table 3]

From Table 3, it was confirmed that the temperature distribution of the catalyst layer was smaller than that of Run Nos. 27 and 28 by the split air supply. In addition, it was confirmed that in Run No. 29, a stable activity is exhibited even after 500 hours have passed in the autothermal test using this catalyst.

[0032]

As described in detail above, according to the present invention, when a hydrogen is produced from hydrocarbons, steam and air by a steam reforming reaction and a partial oxidation reaction, by using a supported platinum catalyst, ammonia by-product It is possible to provide a method for producing hydrogen that can suppress the raw material. Therefore, the hydrocarbon reformer using this catalyst is compact and can be started in a short time, and is effective as a reformer for vehicle-mounted and distributed power PEFC systems.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoru Watanabe             4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture               Mitsubishi Heavy Industries Ltd. Hiroshima Research Center (72) Inventor Masanao Yonemura             4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture               Mitsubishi Heavy Industries Ltd. Hiroshima Research Center F term (reference) 4G040 EA03 EA06 EA07 EB03 EB22                       EC01 EC03 EC04 EC05

Claims (6)

[Claims] 1. A method for producing hydrogen, which comprises using a supported platinum catalyst when producing hydrogen from a hydrocarbon, steam and air by a steam reforming reaction and a partial oxidation reaction. 2. The molar ratio of hydrocarbon to water vapor is H ₂ O / hydrocarbon (converted to Cl) = 0.1 to 10, and the molar ratio of hydrocarbon to air is air / hydrocarbon (converted to Cl) = 0.1. The method for producing hydrogen according to claim 1, wherein 3. The carrier of the supported platinum catalyst is at least one of α-alumina, γ-alumina, silica, titania, zirconia and zeolite, or at least one of silica-alumina, silica-titania, titania-alumina and alumina-zirconia. The method for producing hydrogen according to claim 1 or 2, wherein the method is provided. 4. The method for producing hydrogen according to claim 1, wherein the method for supporting the supported platinum catalyst is an impregnation method or an ion exchange method. 5. The method for producing hydrogen according to claim 1, wherein the air is supplied to the catalyst layer made of the supported platinum catalyst in multiple stages. 6. The method for producing hydrogen according to claim 1, wherein at least one of tungsten, molybdenum, boron, magnesium, calcium, lanthanum, and potassium is supported as a cocatalyst for the supported platinum catalyst.