JP2003170048A - Methanol modifying catalyst and method for manufacturing hydrogen-containing gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a methanol modifying catalyst having high activity and high selectivity, excellent in heat resistance and capable of efficiently generating modified gas based on hydrogen in heat self-supplying type reaction, and a method for manufacturing a hydrogen-containing gas using this catalyst. <P>SOLUTION: The methanol modifying catalyst contains metal platinum as the main component, cerium dioxide, zirconium dioxide and/or titanium dioxide and is characterized in that an atomic ratio [cerium/(zirconium + titanium)] is 0.1-10. The method for manufacturing the hydrogen-containing gas is characterized by reacting methanol, steam and oxygen in the presence of the catalyst to manufacture the modified gas containing hydrogen as a main component. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hydrogen-containing gas in which a reformed gas containing hydrogen as a main component is produced by a steam reforming reaction of methanol, and more particularly, a self-heat treatment for carrying out the reforming reaction in the presence of oxygen. The present invention relates to a feed type reaction and a catalyst used in the reaction.

[0002]

2. Description of the Related Art Methanol steam reforming reaction for reforming methanol to hydrogen-containing gas by using steam includes a small amount of carbon monoxide by the reverse shift reaction of formula (2) in addition to the main reaction shown by formula (1). Is a byproduct. CH ₃ OH + H ₂ O = 3H ₂ + CO ₂ + 49.5 kJ / mol (1) CO ₂ + H ₂ = CO + H ₂ O + 41.17 kJ / mol (2) (2) Carbon monoxide by-product Is difficult to remove during purification to high-purity hydrogen, and it is preferable that the amount is as small as possible. From thermodynamic equilibrium, the lower the temperature, the more the molar ratio of water vapor to methanol (hereinafter, S
The larger the / C ratio, the lower the carbon monoxide concentration in the reformed gas.

Since the main reaction of the methanol steam reforming reaction of the formula (1) is an endothermic reaction, heat must be supplied from the outside, and a heat supply facility is required and the apparatus becomes complicated. On the other hand, there is a self-heat supply type reaction in which air is introduced together with methanol and steam to oxidize a part of methanol and the heat is used to cause a steam reforming reaction of the formula (1). This method oxidizes a part of methanol into hydrogen and carbon dioxide as shown in equation (3) and utilizes this heat.
The methanol reforming reaction of the formula (1) is performed. CH ₃ OH + 1 / 2O ₂ = 2H ₂ + CO ₂ 192.3kJ / mol (3) According to this method, heat is generated when the reaction is continued, except for heat that raises the temperature to the temperature level required for starting the reaction. It has the feature that it does not require supply.

[0004] Conventional methanol reforming catalysts are generally composite oxides composed of copper and zinc, but these catalysts are
Although it exhibits high activity in the steam reforming reaction of methanol, it has a problem of poor heat resistance and durability.

On the other hand, a catalyst comprising a mixture of a heat-resistant porous inorganic compound and a base metal or a noble metal and an alkali metal or an alkaline earth metal (for example, Japanese Patent Laid-Open No. 62-250948) or an oxide of a rare earth element is used. A catalyst in which a noble metal is supported on a carrier (for example, JP-A-58-174237, JP-A-58-174237).
59-199042, etc.) and the like have been proposed. However, these catalysts have a problem that the obtained hydrogen-containing gas contains a high concentration of carbon monoxide. Equation (2) above
Since the shift reaction of is slow, the hydrogen-containing gas generally contains carbon monoxide, and particularly when the efficiency is reduced by the carbon monoxide contained in the hydrogen-containing gas, for example, in the hydrogen-containing gas. In the case of a fuel cell or the like which is poisoned by carbon monoxide, it is necessary to lower the carbon monoxide concentration in the hydrogen-containing gas.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to efficiently generate a reformed gas mainly containing hydrogen even in a self-heat supply type reaction, which has high activity, high selectivity and excellent heat resistance. The present invention provides a catalyst for reforming methanol capable of producing hydrogen, and a method for producing a hydrogen-containing gas using the catalyst.

[0007]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that a catalyst containing metal platinum and cerium dioxide and zirconium dioxide and / or titanium dioxide as a main component is suitable for a self-heat supply type reaction. And
Further, they have found that the concentration of carbon monoxide in the obtained hydrogen-containing gas is low and have reached the present invention.

That is, the present invention contains metallic platinum and cerium dioxide as main components, zirconium dioxide and / or titanium dioxide, and has an atomic ratio of cerium to zirconium and titanium (cerium / (zirconium + titanium)) of 0.1 to. A catalyst for reforming methanol in the range of 10 and a method for producing a hydrogen-containing gas, characterized in that a reformed gas containing hydrogen as a main component is produced by reacting methanol with steam and oxygen in the presence of the catalyst. It is about.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As a platinum source of the catalyst of the present invention,
Platinum oxide, chloroplatinic acid and its alkali metal salts, acetylacetonato platinum, dinitrodiammine platinum and the like can be used. When the catalyst is prepared by dissolving it in water, it is preferable to use potassium chloroplatinate.

The cerium source, zirconium source and titanium source of the catalyst of the present invention are not particularly limited as long as they are compounds which become cerium dioxide, zirconium dioxide and titanium dioxide after firing or reduction or during the reaction.

The catalyst preparation method in the present invention is not particularly limited as long as it is a catalyst preparation method in which metallic platinum, cerium dioxide and zirconium dioxide and / or titanium dioxide coexist. Impregnation method, coprecipitation method, precipitation method A preparation method such as a precipitation method can be used. For example, a method of coprecipitating a mixed solution of potassium chloroplatinate with cerium nitrate and zirconyl nitrate using a suitable precipitant, cerium dioxide prepared by coprecipitation from cerium nitrate and zirconyl nitrate.
A method of supporting potassium chloroplatinate on the zirconium dioxide calcined powder can be used. As the precipitating agent, an alkali compound such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate or sodium hydrogen carbonate is used. The amount of precipitating agent is 1-2 times the chemical equivalent, preferably 1.1-1.6 times. The temperature at the time of preparation of the precipitate is 20 to 90 ° C, preferably 35 to 85 ° C. The precipitate obtained by the precipitation method is preferably washed with ion-exchanged water, distilled water or the like.

The atomic ratio of cerium to zirconium and titanium contained in the catalyst of the present invention (cerium / (zirconium + titanium)) is 0.1 to 10, preferably 0.5 to 4.0.
Is the range. The atomic ratio of cerium to zirconium and titanium contained in the catalyst (cerium / (zirconium +
Titanium)) is adjusted within this range to produce a hydrogen-containing reformed gas by the steam reforming reaction of methanol, and in particular the self-heating for reforming reaction in the presence of oxygen. In the feed-type reaction, the concentration of carbon monoxide in the obtained hydrogen-containing gas can be reduced.

The platinum content contained in the catalyst of the present invention is
It is preferably in the range of 1 to 50% by weight, more preferably 10 to 30% by weight, based on the total amount of metallic platinum, cerium dioxide, zirconium dioxide and titanium dioxide. When the platinum content is less than 1% by weight, the activity and selectivity are insufficient, and when it exceeds 50% by weight, it becomes difficult to support the platinum.

The precipitate obtained by the above method is dried, or dried and calcined, and then crushed to a uniform size or molded. Also, it can be used by pulverizing a dried product of a slurry, or a product obtained by drying and firing, suspending it in water, adding a binder such as alumina sol if necessary, and supporting it on a carrier and a carrier structure. You can In this case, it can be used after being carried and dried, or after firing. Drying temperature is 50-1
50 ° C is preferred. The firing method is not particularly limited, and is generally 180-800
It is preferable to carry out the treatment at a temperature range of ℃, preferably 350 to 450 ℃.

In the method of the present invention, methanol is reacted with steam and air in the presence of the catalyst for reforming methanol prepared as described above, and the reforming mainly comprising hydrogen is carried out by an autoheat supply type reaction. Produce gas. In this reaction, the methanol reforming catalyst may be activated by, for example, hydrogen or a carbon monoxide-containing gas as in the case of steam reforming, or the reaction may be performed without activation. You can also offer it. Air is usually used as the oxygen source. The reaction conditions for reacting methanol with water vapor and air include a water vapor / methanol ratio (S / C ratio) of 1.0 to 2.0 and an air / methanol ratio of 0.3 to 3.0.
Therefore, conditions are selected so that the heat generated by the combustion reaction and the heat absorbed by the methanol reforming reaction are balanced. The liquid hourly space velocity (LHSV) per unit catalyst volume is 0.1 to 60 (hr ⁻¹ ). The reaction temperature is 200-500 ℃, and the reaction pressure is atmospheric pressure-0.5M.
Selected in the range of Pa.

[0016]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In the following examples and comparative examples, the catalytic activity was evaluated by the methanol reaction rate from the reactor outlet gas composition and the CO selectivity according to the following formula. Methanol reaction rate (%) = ([CO] + [CO ₂ ]) / ([CO] + [CO ₂ ] + [CH ₃
OH]) × 100 CO selectivity (%) = [CO] / ([CO] + [CO ₂ ]) × 100 where [CO], [CO ₂ ], and [CH ₃ OH] are reactors, respectively. It is the molar concentration of CO, CO ₂ and CH ₃ OH in the outlet gas.

Example 1 A slurry prepared by mixing a commercially available titania sol with an aqueous cerium nitrate solution so that the atomic ratio of cerium and titanium was 1 was obtained.
Honeycomb made of cordierite (400 cells / cm2)
The steps of dipping, blowing off the excess amount, and drying were repeated, the catalyst was loaded so that the loading amount after drying was 200 g / L, and the mixture was baked at 400 ° C. for 10 minutes. Acetylacetonato platinum (Pt (C ₅ H ₇ O ₂ )) acetone solution was impregnated therein as platinum metal so that the supported amount after drying was 3.5 g / L.
After drying at ℃, Pt-Ce-Ti catalyst was obtained. This is designated as catalyst A.

Example 2 A slurry prepared by mixing a commercially available zirconia sol with an aqueous cerium nitrate solution so that the atomic ratio of cerium and zirconium was 1 was dipped in a cordierite honeycomb (400 cells / cm 2) and the excess amount was added. The steps of blowing off and drying were repeated, and the catalyst was loaded so that the loaded amount after drying was 200 g / L, and the mixture was baked at 400 ° C. for 10 minutes. Acetylacetonato platinum (Pt (C ₅ H ₇ O ₂ )) acetone solution was impregnated as platinum metal so that the supported amount after drying was 3.5 g / L, and this was dried at 80 ° C., and Pt- A Ce-Zr catalyst was obtained. This is designated as catalyst B.

Example 3 500 ml of a 60 ° C. aqueous solution in which 33.64 g of potassium carbonate (K ₂ CO ₃ ) was dissolved
, Potassium chloroplatinate (K ₂ PtCl ₄ ) 3.57 g, cerium nitrate
_{(Ce (NO 3) 3 ·} 6H 2 O) 22.50g and zirconyl nitrate (ZrO (N
_{O 3) 2 · 2H 2 O} ) was slowly added to 60 ° C. mixed aqueous solution 1000ml of 13.72g over about 30 minutes, and stirred for 60 minutes. After that, the solution was filtered, and washing with water was repeated until chlorine in the filtrate became 1 ppm or less. Then, it was dried at 80 ° C. for 15 hours and then calcined at 380 ° C. for 2 hours to obtain a Pt-Ce-Zr catalyst having an atomic ratio of cerium to zirconium of 1 and a platinum metal content of 10% by weight. This 10wt% Pt
-Ce-Zr catalyst was wet pulverized and mixed with alumina sol to form a slurry, and then a cordierite honeycomb (400 cells /
The process of dipping, blowing off the excess amount, and drying was repeated in a square centimeter, and the catalyst was loaded so that the amount of the catalyst loaded after drying was 200 g / L. This is designated as catalyst C.

Comparative Example 1 Commercially available titania sol was mixed with cordierite honeycomb (4
(00 cells / square centimeter), soak, blow off excess
The drying and drying process is repeated, and the supported amount after drying is 200 g / L.
The catalyst was supported so as to become, and calcined at 400 ° C. for 10 minutes. Acetylacetonato platinum (Pt (C ₅ H ₇ O ₂ )) acetone solution was impregnated as platinum metal so that the supported amount after drying was 3.5 g / L, and this was dried at 80 ° C., and Pt- A Ti catalyst was obtained. This is designated as catalyst D.

Comparative Example 2 A commercially available zirconia sol was added to a cordierite honeycomb.
Repeat the steps of dipping, blowing off the excess amount, and drying in (400 cells / square centimeter), and the supported amount after drying is 20
The catalyst was supported so that the concentration would be 0 g / L, and the mixture was baked at 400 ° C. for 10 minutes. Acetylacetonato platinum (Pt (C ₅ H ₇ O ₂ )) acetone solution was impregnated as platinum metal so that the supported amount after drying was 3.5 g / L, and this was dried at 80 ° C., and Pt- A Zr catalyst was obtained. This is designated as catalyst E.

Comparative Example 3 Commercially available ceria sol was added to a cordierite honeycomb (400
The steps of dipping, blowing off excess amount, and drying were repeated in (cell / square centimeter), the catalyst was carried so that the carried amount after drying was 200 g / L, and the mixture was baked at 400 ° C. for 10 minutes. Acetylacetonato platinum (Pt (C ₅ H ₇ O ₂ )) acetone solution was impregnated as platinum metal so that the supported amount after drying was 3.5 g / L, and this was dried at 80 ° C., and Pt- A Ce catalyst was obtained.
This is designated as catalyst F.

Comparative Example 4 700 m of a 60 ° C. aqueous solution in which 36.29 g of sodium carbonate (anhydrous) was dissolved
500 ml of a 60 ° C. aqueous solution of 77.18 g of cerium nitrate (Ce (NO ₃ ) ₃ .6H ₂ O) was slowly added to 1 l, and the mixture was stirred for 30 minutes. The slurry thus prepared was filtered, and the obtained precipitate was washed with 6 L of ion-exchanged water. It is then dried at 80 ° C and then 380
By firing at ℃ for 2 hours, cerium dioxide was obtained. 7.5 g of this cerium dioxide powder was crushed with a ball mill and dispersed in 250 ml of a 60 ° C. aqueous solution, and potassium chloroplatinate was added.
Add (K ₂ PtCl ₄ ) 1.79 g of 60 ° C aqueous solution 250 ml, and after 30 minutes, add 1NK
8 ml of OH was added and stirred for 60 minutes. After that, the solution was filtered, and washing with water was repeated until chlorine in the filtrate became 1 ppm or less. Then, after drying at 80 ° C. for 15 hours, it was calcined at 380 ° C. for 2 hours to obtain a Pt—Ce catalyst having a platinum metal content of 10% by weight. This 10
The wt% Pt-Ce catalyst is wet pulverized, mixed with alumina sol to form a slurry, and then dipped in a cordierite honeycomb (400 cells / square centimeter), the excess is blown off, and the drying process is repeated to dry it. The catalyst was loaded so that the amount of the catalyst loaded later was 200 g / L. This is designated as catalyst G.

(Methanol reforming reaction) Examples 4 and 5 and Comparative Examples 5 to 7 An aqueous methanol solution having a water / methanol ratio of 1.5 was added to methanol L.
It was introduced into the evaporator at HSV = 5 hr ⁻¹ , air was mixed after the evaporator outlet, and the temperature of the introduction line was adjusted so as to enter the catalyst layer at 200 ° C. The reaction was controlled by the amount of air so that the outlet temperature of the catalyst layer was 350 ° C. at LHSV = 20 hr ⁻¹ . The gas composition after the reaction was analyzed by gas chromatography. Table 1 shows the results of activity evaluation at the outlet temperature of the catalyst layer of 350 ° C.

[0025] Table 1 (Catalyst layer outlet temperature 350 ° C)                 Catalyst type Methanol reaction rate CO selectivity Example 4 Catalyst A (Pt-Ce-Ti) 96.4 46.7 Example 5 Catalyst B (Pt-Ce-Zr) 98.3 38.0 Comparative Example 5 Catalyst D (Pt-Ti) 97.6 77.4 Comparative Example 6 Catalyst E (Pt-Zr) 95.7 65.4 Comparative Example 7 Catalyst F (Pt-Ce) 94.4 65.2

As can be seen from Table 1, in Examples 4 and 5 using the catalyst according to the present invention, the outlet temperature of the catalyst layer was 350 ° C.
In all, the CO selectivity was lower than in Comparative Examples 5 to 7, and the selectivity of the steam reforming reaction was improved.

Example 6 and Comparative Example 8 A methanol / water solution having a water / methanol ratio of 1.5 was added to methanol L.
It was introduced into the evaporator at HSV = 5 hr ⁻¹ , air was mixed after the evaporator outlet, and the temperature of the introduction line was adjusted so as to enter the catalyst layer at 200 ° C. The reaction was controlled by the amount of air so that a predetermined conversion was obtained at LHSV = 15 hr ⁻¹ . The gas composition after the reaction was analyzed by gas chromatography. Table 2 shows the results of activity evaluation at each reaction time described.

Table 2 (LHSV = 15 hr ⁻¹ ) (Initial reaction → After each reaction time) Type of catalyst Methanol CO selectivity Reaction time Reaction rate (%) (%) (hr) Example 6 Catalyst C (10 wt% Pt -Ce-Zr) 98.8 → 98.2 10.8 → 11.3 67 Comparative Example 8 Catalyst G (10wt% Pt-Ce) 98.1 → 96.4 29.7 → 37.5 44

As can be seen from Table 2, Example 6 using the catalyst according to the present invention is superior in heat resistance to Comparative Example 8,
Moreover, the CO concentration in the obtained hydrogen-containing gas can be kept low.

[0030]

EFFECTS OF THE INVENTION According to the method of the present invention, hydrogen is mainly produced by a self-heat supply reaction by reacting methanol with steam and oxygen by using a highly active catalyst for reforming methanol with excellent heat resistance. The hydrogen-containing gas can be produced industrially advantageously by efficiently generating the reformed gas as described below and reducing the carbon monoxide concentration in the reformed gas.

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Claims (3)

[Claims] 1. A metal containing platinum and cerium dioxide as main components, zirconium dioxide and / or titanium dioxide, and having an atomic ratio of cerium to zirconium and titanium (cerium / (zirconium + titanium)) of 0.1.
Catalyst for methanol reforming in the range of ~ 10. 2. The catalyst for reforming methanol according to claim 1, wherein the amount of metallic platinum is in the range of 1 to 50% by weight based on the total amount of metallic platinum, cerium dioxide, zirconium dioxide and titanium dioxide. 3. In the presence of the catalyst according to claim 1 or 2,
A method for producing a hydrogen-containing gas, which comprises reacting methanol with water vapor and oxygen to produce a reformed gas containing hydrogen as a main component.