JP2002059005A - Methanol modifying catalyst, method for manufacturing the same and methanol modifying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a methanol modifying catalyst having high activity, selectivity and durability, excellent in hydrogen manufacturing efficiency and capable of also realizing a compact fuel modifying apparatus, to provide a method for manufacturing the same and a methanol modifying method. SOLUTION: The methanol modifying catalyst is obtained by dispersing zinc oxide and/or aluminum oxide and copper oxide in a mixed solution of a water soluble compound of platinum and/or palladium and a water soluble compound of zinc to form oxides of platinum and/or palladium and zinc. Zinc oxide contained in the oxides and the water-soluble compound of platinum and/or palladium form an alloy by heat treatment. Zinc oxide and/or aluminum oxide and copper oxide are dispersed in the mixed solution of the water soluble compound of platinum and/or palladium and the water soluble compound of zinc in a predetermined ratio and this mixed solution is dried and baked to manufacture the methanol modifying catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst used in a fuel reformer for producing hydrogen-containing gas by reforming methanol. It is suitable for the production of fuels such as acid fuel cells, etc.
The present invention relates to a methanol reforming catalyst for a fuel reformer, which can reduce the amount of O) generated and can improve the startability of the fuel reformer, a method for producing the same, and a methanol reforming method.

[0002]

2. Description of the Related Art It is well known that methanol fuel is relatively easily reformed into a gas containing hydrogen as a main component in the presence of a catalyst. In particular, a high hydrogen content is obtained by a reaction represented by the following formula (1): CH ₃ OH + H ₂ O → CO ₂ + 3H ₂ -11.8 kcal / mol (1) in the presence of water called steam reforming. Reformed into a quantity of gas.

[0003] However, since the steam reforming reaction is an endothermic reaction, in a reforming apparatus that performs this reaction, a burner, a heater, or the like must be installed to perform heating to supply the heat required for the reforming reaction. In addition, there is a problem that not only the device configuration becomes complicated and large, but also the startability and the response are poor. This also means that in the reforming catalyst according to the prior art, the amount of heat required to advance the steam reforming reaction must be supplied from outside the reaction tube, and as a result, such a reforming catalyst is used. As described above, this means that the reformer becomes insufficient in compactness, startability, responsiveness, and the like.

[0004] In order to solve such a problem, the steam reforming reaction of the fuel represented by the above formula (1), which is an endothermic reaction, and the following formula (2), which is an exothermic reaction, CH ₃ OH + 1 / 2O ₂ → CO ₂ + 2H ₂ ... (2) substantially utilization of progression is to autothermal reforming reaction simultaneously an oxidation reaction and which is expressed by are promising, have been studied.

[0005] However, in this autothermal reaction, it is necessary to supply air or oxygen to the fuel and water to carry out the reaction. In this case, copper-zinc, which has a high selectivity to the steam reforming reaction and has been widely used, is required. When a system catalyst is used, activity degradation due to the presence of oxygen and thermal degradation due to an exothermic reaction occur. Particularly, when a long-time continuous operation is performed, the activity and selectivity are continuously reduced. In addition, such a problem is remarkable particularly in a reaction at a high temperature (250 ° C. or higher), and therefore, there is a problem that it is difficult to perform an autothermal reaction at a relatively high temperature for a long time.

To solve this problem, a catalyst in which noble metals such as platinum and palladium are supported on a carrier such as alumina or oxide in order to impart heat resistance to the catalyst (Japanese Patent Laid-Open No. 58-1)
74237, 58-177153 and 59-199043) and a catalyst containing nickel as a main component (JP-A-50-49021, 51-68).
488 and 51-122102) have been proposed.

[0007]

However, when the above-mentioned autothermal reaction is carried out in the presence of a catalyst containing a metal other than copper such as noble metal or nickel as an active component, the following formula (3): CH ₃ OH → The decomposition reaction of methanol represented by CO + 2H ₂ (3) mainly proceeds, and there is a problem that it is not efficient from the viewpoint of hydrogen production.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to provide high activity, selectivity, and durability, high hydrogen production efficiency, and compactness. An object of the present invention is to provide a methanol reforming catalyst capable of realizing a simple fuel reforming apparatus, a method for producing the same, and a methanol reforming method.

[0009]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have found that zinc oxide and / or aluminum oxide and copper oxide can be dissolved in platinum and / or palladium in water. Is dispersed in a mixed solution of a compound and a water-soluble compound of zinc, and then platinum and / or zinc is added in the presence of the oxide.
Or by forming an oxide of palladium and zinc,
It has high activity and high selectivity, and finds that a highly durable catalyst that maintains high stability over a long period of time can be obtained,
The present invention has been completed.

That is, the methanol reforming catalyst of the present invention comprises a zinc oxide and / or aluminum oxide and a copper oxide in a mixed solution of a water-soluble compound of platinum and / or palladium and a water-soluble compound of zinc. And forming an oxide of platinum and / or palladium and zinc.

A preferred embodiment of the methanol reforming catalyst of the present invention is characterized in that the zinc oxide contained in the oxide and the water-soluble compound of platinum and / or palladium form an alloy by heat treatment. And

Further, the method for producing a methanol reforming catalyst according to the present invention is a method for producing the above methanol reforming catalyst, wherein zinc oxide and / or aluminum oxide and copper oxide are mixed at a predetermined ratio. Dispersed in a mixed solution of a water-soluble compound of platinum and / or palladium and a water-soluble compound of zinc,
The mixed solution is dried and fired.

Furthermore, a methanol reforming method of the present invention is characterized by using the above-mentioned methanol reforming catalyst.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the methanol reforming catalyst of the present invention will be described in detail. In this specification, “%” indicates mass percentage unless otherwise specified. As described above, this methanol reforming catalyst disperses zinc oxide and / or aluminum oxide and copper oxide in a mixed solution of a water-soluble compound of platinum and / or palladium and a water-soluble compound of zinc. , Platinum and / or oxides of palladium and zinc. Here, the oxide dispersed in the mixed solution, that is, zinc oxide and / or aluminum oxide and copper oxide is not particularly limited as long as it is an oxide containing zinc and / or aluminum component and copper component. Although not specifically described, specifically, a mixture of copper oxide and zinc oxide, a mixture of copper oxide and aluminum oxide, a composite oxide of copper-zinc, a composite oxide of copper-aluminum, and a mixed system thereof In this case, unavoidable impurities and other additional components may be appropriately contained.

Although the details of the excellent properties of the methanol reforming catalyst of the present invention are not always clear, it is presumed as follows at present. First, oxidation (or further oxidation) of copper is suppressed by highly dispersing platinum or palladium on copper or copper oxide, and thus the durability of the catalyst is improved. Further, since platinum and palladium form a tightly mixed or bound state with zinc oxide, it is considered that active species composed of platinum and / or palladium and zinc oxide are generated.

Incidentally, these phenomena are significantly manifested in platinum and / or palladium, the above-mentioned zinc oxide and / or aluminum oxide and copper oxide, and other than these, for example, platinum and palladium supported on alumina. In the catalyst, a methanol decomposition reaction represented by the above formula (3) is mainly performed, and carbon monoxide is generated. On the other hand, the methanol reforming catalyst of the present invention selectively promotes the reactions of the above formulas (1) and (2), thereby suppressing the reaction for producing carbon monoxide and improving the selectivity.

In the present invention, an aluminum component can be added to the above oxide. In this case, specific examples of the oxide include a mixture of copper oxide, zinc oxide and aluminum oxide. , Copper-zinc-aluminum composite oxides and their mixed systems. The use of such a three-component oxide also provides a methanol reforming catalyst having excellent heat resistance and durability.

In the reforming methanol reforming catalyst of the present invention, zinc oxide contained in the above-described two-component oxide of copper-zinc and the three-component oxide of copper-zinc-aluminum, and platinum and / or palladium It is desirable that zinc oxide and platinum and / or palladium formed together with the oxide of the above form an alloy with the zinc by heat treatment. Such alloying selectively promotes the reactions of the above formulas (1) and (2), thereby suppressing the production of carbon monoxide. Further, since the oxidation of copper or copper oxide described above is further suppressed, the durability of the catalyst is further improved.

Next, the mixing amounts of various components in the methanol reforming catalyst of the present invention will be described. In this methanol reforming catalyst, the mixing ratio of various components is not particularly limited as long as intended reduction of methanol conversion and carbon monoxide concentration can be realized.
%, The content of platinum and / or palladium is 0.5 to 10%.
%, And the balance is preferably zinc. Copper content is 10
%, The methanol conversion may decrease and the CO concentration may increase, and if it exceeds 60%, the CO concentration may increase. If the content of platinum and / or palladium is less than 0.5%, the methanol conversion may decrease, and if it exceeds 10%, the CO concentration may increase.

The methanol reforming catalyst of the present invention comprises the above-mentioned components such as copper, zinc and palladium as essential components. Other components such as alumina and silica which can increase the reaction specific surface area are also used. It is possible to add a high specific surface area substrate such as. Further, the shape of the catalyst is not particularly limited, and may be in the form of granules or pellets.
It is also possible to use a ceramic or metal integrated structure type carrier (monolithic carrier or the like). In addition, when using such a monolithic carrier, 100 to 300 g of the catalyst component is used.
/ L is preferably supported.

The method for preparing the methanol reforming catalyst of the present invention is not particularly limited either. Conventional methods such as coprecipitation, impregnation, and precipitation, and methods substantially the same as these methods are used. Can be applied.

Next, a method for producing the methanol reforming catalyst of the present invention will be described. This reforming catalyst comprises an oxide containing Zn and / or Al and Cu at a predetermined ratio in P
It is obtained by dispersing in a mixed solution of a water-soluble compound of t and / or Pd and a water-soluble compound of Zn, and drying and firing this mixed solution. Specifically, for example, an alkaline substance (for example, sodium carbonate) is dropped into an aqueous solution of a nitrate of Zn and / or Al and Cu to generate a precipitate. This precipitate is sufficiently washed with water, filtered, dried, and
Calcination at 0 ° C. to obtain a metal oxide. Pt and / or Pd
The metal oxide is added to a mixed solution obtained by dissolving zinc nitrate in an aqueous solution, and sufficiently stirred and mixed. Then, it is dried and calcined at 300 to 600 ° C. to obtain a catalyst powder. Next, the obtained catalyst powder is pulverized and mixed, and a slurry is prepared.
Get. Thereafter, the obtained slurry is applied to an integrated carrier, and then calcined at 300 to 600 ° C. in air, whereby a methanol reforming catalyst having stable performance can be obtained.

In the methanol reforming method of the present invention, the production of carbon monoxide is suppressed by selectively promoting the reactions of the above formulas (1) and (2) using the above-mentioned methanol reforming catalyst. It reforms methanol by efficiently producing hydrogen. Thus, a reformed gas having high combustion efficiency can be obtained, and can be used as a fuel for a combustion engine or the like.

[0024]

EXAMPLES Hereinafter, 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.

(Example 1) A CuO-ZnO powder having a copper content of 30% was prepared from zinc nitrate and copper nitrate by a coprecipitation method. Next, this powder was dispersed and supported in an aqueous solution of palladium nitrate and zinc nitrate, dried and calcined to obtain a catalyst powder having a Pd loading of 1% and a Zn loading of 5%. A slurry was obtained by mixing 195 g of this catalyst powder and 5 g of 8% nitric acid acidic alumina sol, and the obtained slurry was applied to the surface of a ceramic monolith carrier so that the catalyst powder weight was 200 g / L, and the temperature was 150 ° C. And dried at 400 ° C. in air to form a catalyst layer, thereby obtaining a catalyst of this example.

(Example 2) The same operation as in Example 1 was repeated except that the amount of Pd supported was 2% and the amount of Zn supported was 10%, to obtain a catalyst of this example.

Example 3 The same operation as in Example 1 was repeated, except that the amount of Pd supported on the catalyst powder was 10% and the amount of Zn supported was 30%, to obtain a catalyst of this example.

Example 4 The same as Example 1 except that the Cu content in the CuO-ZnO powder was 10%, the amount of Pd supported on the catalyst powder was 2%, and the amount of Zn supported was 10%. Was repeated to obtain a catalyst of this example.

Example 5 The same as Example 1 except that the Cu content in the CuO-ZnO powder was 60%, the Pd loading on the catalyst powder was 2%, and the Zn loading was 10%. Was repeated to obtain a catalyst of this example.

Comparative Example 1 The same operation as in Example 1 was repeated except that the amount of Pd supported on the catalyst powder was changed to 0.1% and the amount of supported Zn was changed to 0.5% to obtain the catalyst of this example. Was.

Comparative Example 2 The same operation as in Example 1 was repeated, except that the amount of Pd supported was 20% and the amount of Zn supported was 30%, to obtain a catalyst of this example.

(Comparative Example 3) The Cu content in the CuO-ZnO powder was set to 5%, and the Pd carrying amount of the catalyst powder was set to 2%.
% And the amount of supported Zn were set to 10%, and the same operation as in Example 1 was repeated to obtain a catalyst of this example.

(Comparative Example 4) The same as Example 1 except that the Cu content in the CuO-ZnO powder was 70%, the supported amount of Pd in the catalyst powder was 2%, and the supported amount of Zn was 10%. Was repeated to obtain a catalyst of this example.

(Example 6) CuO-ZnO-Al ₂ O having a copper content of 30% and an aluminum content of 5% from zinc nitrate, copper nitrate and aluminum nitrate by coprecipitation method
_Three powders were prepared. Next, an aqueous solution of palladium nitrate and zinc nitrate was sprayed, dried and fired on the powder to obtain a catalyst powder having a Pd loading of 2% and a Zn loading of 10%. A slurry was obtained by mixing 195 g of this catalyst powder and 5 g of 8% nitric acid acidic alumina sol, and the obtained slurry was applied to the surface of a ceramic monolith carrier so that the catalyst powder weight was 200 g / L, and the temperature was 150 ° C. And dried at 400 ° C. in air to form a catalyst layer, thereby obtaining a catalyst of this example.

(Comparative Example 5) P was added to the above CuO-ZnO powder.
The same operation as in Example 1 was repeated, except that d and Zn were not supported and the catalyst powder was used as it was, to obtain a catalyst of this example.

[Evaluation of Performance] The catalysts of the above examples were placed in a hydrogen stream.
After reducing at 400 ° C for 1 hour, fixed bed normal pressure flow type reaction equipment
To perform an autothermal reforming reaction of methanol.
Was. At this time, the reaction temperature was 350 ° C., and the S / C ratio (water
Steam / methanol molar ratio) is 1.5, O ₂/ C (oxygen
/ Mole ratio of methanol) to 0.15. Obtained breaks
Gas composition of gaseous gas analyzed by gas chromatograph.
The results obtained are shown in Tables 1 and 2 as CO concentration and conversion.
did. In addition, about the catalyst of Example 6 and the comparative example 5,
The CO concentration and conversion after 50 hours of the reaction were shown. Ma
For reference, the catalyst composition of each example is also shown.

[0037]

[Table 1]

[0038]

[Table 2]

As is clear from the results shown in Tables 1 and 2, the methanol reforming catalysts of the examples belonging to the scope of the present invention include the catalyst of Comparative Example 1 having a small palladium content of 0.1%, The catalyst of Comparative Example 2 having a high palladium content of 20%, the catalyst of Comparative Example 3 having a low copper content of 5%, the catalyst of Comparative Example 4 having a high copper content of 70%, CuO and ZnO
As compared with the catalyst of Comparative Example 5, it was confirmed that the catalyst was a methanol reforming catalyst having a low CO concentration, excellent catalytic activity, and excellent durability.

Although the present invention has been described in detail with reference to preferred embodiments, the present invention is not limited to these embodiments, and various modifications can be made within the scope of the present invention. For example, when the reforming catalyst of the present invention is used, a fuel reforming device that does not require an external heating device such as a heater can be easily obtained, and the fuel reforming device can be made compact, and high startup performance and high responsiveness can be realized. .

[0041]

As described above, according to the present invention, a zinc oxide and / or an aluminum oxide and a copper oxide are combined with a water-soluble compound of platinum and / or palladium and a water-soluble compound of zinc. Since it is dispersed in a mixed solution and then forms an oxide of platinum and / or palladium and zinc in the presence of this oxide, it has high activity, selectivity and durability, and is excellent in hydrogen production efficiency and compact. It is possible to provide a methanol reforming catalyst capable of realizing a simple fuel reforming device, a method for producing the same, and a methanol reforming method.

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Claims (6)

[Claims] A zinc oxide and / or aluminum oxide and a copper oxide are dispersed in a mixed solution of a water-soluble compound of platinum and / or palladium and a water-soluble compound of zinc. A methanol reforming catalyst obtained by forming an oxide of zinc and zinc. 2. The methanol reforming catalyst according to claim 1, wherein the zinc oxide contained in the oxide and the water-soluble compound of platinum and / or palladium form an alloy by heat treatment. 3. The methanol reforming catalyst according to claim 1, wherein the content of copper is 10 to 60%. 4. The methanol reforming catalyst according to claim 1, wherein the content of platinum and / or palladium is 0.5 to 10%. 5. The method for producing a methanol reforming catalyst according to claim 1, wherein zinc oxide and / or aluminum oxide and copper oxide are mixed at a predetermined ratio. A method for producing a methanol reforming catalyst, comprising dispersing in a mixed solution of a water-soluble compound of platinum, palladium and / or palladium and a water-soluble compound of zinc, and drying and calcining the mixed solution. 6. A methanol reforming method using the methanol reforming catalyst according to claim 1. Description: