JP2003010684A - Catalyst for manufacturing hydrogen and hydrogen manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a catalyst capable of manufacturing hydrogen in a high yield by a reduced amount of the catalyst, and to provide a hydrogen manufacturing method. SOLUTION: Hydrogen is manufactured by allowing the catalyst comprising a copper-containing substance and a solid acidic substance to act on mixed gas of dimethyl ether and steam.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a catalyst for producing hydrogen and a method for producing a gas containing hydrogen by allowing a mixed gas of dimethyl ether and water vapor to flow through the catalyst.

[0002]

2. Description of the Related Art Heretofore, there have been known some methods for producing a gas containing hydrogen from a mixed gas of dimethyl ether and steam in the presence of a catalyst, and catalysts therefor.

For example, Japanese Patent No. 3124035 discloses a method for producing a gas containing hydrogen by using a catalyst containing at least 20% of copper and containing no alkali metal. Further, JP-A-9-118501 discloses a method for producing a gas containing hydrogen by reacting dimethyl ether with steam in the presence of an ether hydration catalyst selected from the group consisting of solid acids and a methanol decomposition catalyst. Is disclosed. Japanese Unexamined Patent Publication (Kokai) No. 10-174870 discloses a catalyst for producing hydrogen from dimethyl ether and steam, which contains copper.

[0004]

However, in the method disclosed in Japanese Patent No. 3124035, 350 ° C.
There is a problem that the conversion rate of dimethyl ether does not increase unless the temperature is higher than the above. Further, in the method disclosed in Japanese Patent Application Laid-Open No. 9-118501, the reaction proceeds at a low temperature of 350 ° C. or lower, but W / F (g-catalyst) showing the amount of catalyst per flow rate of dimethyl ether as a reaction raw material. * Hr / m
(ol-DME) is a very high value of about 86, which is not practical.

It is an object of the present invention to solve the above conventional problems and provide a catalyst capable of producing a high yield of hydrogen with a small amount of catalyst, and a method for producing hydrogen.

[0006]

Means for Solving the Problems As a result of extensive studies to solve the above-mentioned problems, the present invention proposes a substance containing copper and a substance having solid acidity as a catalyst for reacting dimethyl ether with water vapor to produce hydrogen. The present invention has been completed by finding that those physically mixed are extremely effective, and hydrogen can be efficiently produced at low temperature.

That is, according to the present invention, a catalyst comprising a mixture of a substance containing copper and a substance having solid acidity for producing hydrogen from dimethyl ether and steam, and the above catalyst are brought into contact with a mixed gas containing dimethyl ether and steam. The present invention relates to a method for producing hydrogen characterized by the above.

A feature of the present invention is that a substance obtained by physically mixing a substance containing copper but not zinc and a substance having solid acidity is used as a catalyst. This is because alumina having solid acidity and a catalyst containing copper element as a main component cause the reaction cycle described below to proceed rapidly,
This is to improve the yield of hydrogen. The reaction of producing hydrogen from dimethyl ether and steam by the catalyst of the present invention proceeds as follows. First, dimethyl ether is hydrated in the presence of alumina having solid acidity according to the following formula. CH ₃ OCH ₃ + H ₂ O → 2CH ₃ OH (1)

Next, methanol reacts with water vapor in the presence of elemental copper according to the following formula. 2CH ₃ OH + 2H ₂ O → 2CO ₂ + 6H ₂ (2)

The overall reaction is given by the following equation. CH ₃ OCH ₃ + 3H ₂ O → 2CO ₂ + 6H ₂ (3)

When a substance containing zinc is used here, it affects the solid acid properties of alumina and the like, so that the reaction of (1) is hindered and the conversion rate of dimethyl ether is presumed to be low.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The substance containing copper in the catalyst of the present invention is a metal and / or compound of copper or those containing these. The copper compound is preferably a copper oxide, and the copper oxide is cuprous oxide (Cu ₂ O), cupric oxide (CuO), or a mixture thereof.

The substance containing copper may be supported on a catalyst carrier. Preferred catalyst carriers are oxides of alumina, silica gel, silica-alumina, zeolite, titania, zirconia, etc. Among them, alumina is preferable because of high hydrogen yield. The content of copper in the material containing copper is about 1 to 50% by weight, preferably 2 to 30% by weight. When the copper content is less than about 1% by weight and 50% by weight or more, the yield of synthesis gas decreases. The average particle size of the substance containing copper is 0.001 to 50.
mm, preferably about 0.005 to 30 mm, particularly preferably about 0.010 to 20 mm.

This material is characterized by the fact that it does not contain zinc, and a high dimethyl ether conversion rate can be obtained by not containing zinc. Therefore, the content of zinc in this substance is 1.0% by weight or less, preferably 0.5% by weight or less, and particularly preferably 0.1% by weight or less.

A general catalyst preparation method can be applied to the production of the substance containing copper. For example, the raw material for the production of this substance, as the copper compound, each nitrate, carbonate,
Inorganic acid salts such as halides and organic acid salts such as copper acetate and copper oxalate are used. In addition, for the operation of supporting copper on the catalyst carrier, ordinary techniques such as a precipitation method, a kneading method, an impregnation method and an ion exchange method can be used. The catalyst composition thus prepared is calcined by a conventional method if necessary. The firing is preferably performed by heating in nitrogen or air at a temperature of 300 to 800 ° C. for 1 to 10 hours.

The other catalyst component constituting the catalyst of the present invention is a substance having solid acidity. The solid acid is one that exhibits the characteristics of a Bronsted acid or a Lewis acid even though it is a solid, and specifically, it is alumina, silica-alumina, silica-titania, zeolite, aluminum phosphate or the like. Of these, alumina is preferable because it has a high hydrogen yield. The average particle size of the substance having solid acidity is about 0.001 to 50 mm, preferably 0.00
About 5 to 30 mm, particularly preferably 0.010 to 20 m
It is about m.

In the method of mixing the above two kinds of catalyst components, both components may be pelletized and then physically mixed, or both components may be made into powder and physically mixed and then compression-molded into pellets. May be turned into. The mixing ratio of both components is not particularly limited and may be appropriately selected according to the type of each component or reaction conditions, etc., but usually the ratio of the substance containing copper and the substance having solid acidity is the weight ratio. So 1:
It is about 20 to 10: 1, preferably 1:10 to 5:
It is about 1. The particle size of the substance containing copper and the substance having solid acidity is about 0.005 to 30 mm, preferably 0.01
It is about 20 mm.

By passing a mixed gas of dimethyl ether and water vapor through the catalyst thus prepared,
Hydrogen is obtained in high yield.

In the present invention, steam is supplied together with dimethyl ether as a raw material. In terms of stoichiometry, the mixing ratio of dimethyl ether and water vapor is three times that of dimethyl ether according to the above formula (3), but it is preferable that this stoichiometric amount or a slight excess of the stoichiometric amount be used.
It is ˜7 mol times, preferably 3˜5 mol times. The raw material gas may contain components other than dimethyl ether and water vapor. Other components may include a gas inert to the reaction, such as nitrogen or an inert gas.
It is appropriate that the content of these is 30% by volume or less, and if the content is more than 30% by volume, the decrease in reaction rate becomes a problem. On the other hand, since air (oxygen) burns dimethyl ether, it is better to remove it as much as possible, and the allowable content is 5% as air.
It is the following.

The reaction temperature is 200 to 350 ° C, preferably 200 to 300 ° C. If the reaction temperature is lower than 200 ° C, a high dimethyl ether conversion cannot be obtained, and 350 ° C
If it is higher, the production of methane increases and the yield of hydrogen decreases, and when the obtained hydrogen-containing gas is used in a fuel cell or the like, the production of carbon monoxide that poisons the catalyst of the fuel cell increases, Not preferable.

The reaction pressure is preferably atmospheric pressure to 10 kg / cm ² . When the reaction pressure is higher than 10 kg / cm ² , the conversion rate of dimethyl ether decreases.

W / F (g catalyst * hr / mol) showing the amount of catalyst per flow rate of dimethyl ether as a reaction raw material
-DME) is preferably 0.1 to 50 g · hr / mol, particularly 1 to 20 g · hr / mol. When W / F is less than 0.1 g · hr / mol, the conversion rate of dimethyl ether is low, and when it is more than 50 g · hr / mol, the amount of catalyst used is large and the reactor becomes extremely large, which is not economical.

In the method of the present invention, a fixed bed,
Any device of the fluidized bed may be used.

[0024]

EXAMPLE I. Preparation of catalyst 1) Preparation of Cu-Al ₂ O ₃ catalyst About 200 ml of deionized water was added with copper acetate (Cu (CH ₃ CO ₃
After dissolving 15.7 g of O) ₂ · H ₂ O) and adding 95 g of γ-alumina (“N612” manufactured by JGC Chemical Co., Ltd.) to this,
Evaporated to dryness. Then, this was dried in air at 120 ° C. for 24 hours and then calcined in air at 450 ° C. for 4 hours. Further, it was treated at 400 ° C. for 3 hours in a steam flow to obtain a catalyst. The composition of this is Cu: Al ₂ O ₃ = 5: 95.
(Weight ratio).

[0025] _{2) CuO-ZnO-Al 2} O 3 catalyst prepared copper nitrate _{(Cu (NO 3) 2 ·} 3H 2 O) 185g, zinc nitrate _{(Zn (NO 3) 2 ·} 6H 2 O) 117g, and nitric acid aluminum _{(Al (NO 3) 3 ·} 9H 2 O) 52g was dissolved in deionized water of about 1l. About 1.4 kg of this aqueous solution and sodium carbonate (Na ₂ CO ₃ ) was added to about 1 part of deionized water.
The pH of the solution prepared by dissolving the aqueous solution of 7.1 in a stainless steel container containing about 3 1 of ion-exchanged water kept at about 60 ° C.
The solution was added dropwise over about 2 hours while adjusting it so that it was maintained at 0 ± 0.5. After the completion of dropping, the mixture was kept for about 1 hour for aging. During this period, the pH is 7.0 ± 0.5.
If it comes out of the range, an about 1 mol / l nitric acid aqueous solution or an about 1 mol / l sodium carbonate aqueous solution was added dropwise to adjust the pH to 7.0 ± 0.5. Next, the generated precipitate was filtered and then washed with ion-exchanged water until nitrate ions were not detected in the washing liquid. The cake obtained was dried at 120 ° C. for 24 hours, and then dried in air 35
The target catalyst was obtained by calcination at 0 ° C. for 5 hours.

The composition of the resulting catalyst was CuO: ZnO: A.
_{l 2 O 3 = 61: 32} : 7 was (weight ratio).

Examples 1, 2, 3 (Catalyst A) The above CuO-Al ₂ O ₃ catalyst crushed to 0.5 to 1 mm and commercially available alumina crushed to 0.5 to 1 mm (manufactured by JGC Chemicals, " N612 ″) was physically mixed in a weight ratio of 1: 2 to obtain a catalyst A.

Examples 4, 5, 6 (Catalyst B) The above CuO-Al ₂ O ₃ catalyst crushed to 0.5 to 1 mm and commercially available alumina crushed to 0.5 to 1 mm (manufactured by JGC Chemicals, " N612 ″) was physically mixed at a weight ratio of 1: 1 to obtain catalyst B.

Comparative Examples 1, 2 and 3 (Catalyst C) Only the above-mentioned CuO-Al ₂ O ₃ catalyst was used as catalyst C.

Comparative Examples 4, 5, 6 (Catalyst D) The above CuO-ZnO-Al crushed to 0.5 to 1 mm.
₂ O ₃ catalyst and commercially available alumina pulverized to 0.5 to 1 mm (“N612” manufactured by JGC Chemical Co., Ltd.) were physically mixed at a weight ratio of 1: 2 to obtain a catalyst D.

II. Reaction Method A stainless steel reaction tube having an inner diameter of 20 mm was filled with a predetermined amount of the above catalyst. Dimethyl ether and water vapor were supplied to the reaction tube in predetermined amounts and reacted at a predetermined temperature.

The reaction products and unreacted products obtained by the above operation were analyzed by gas chromatography.

III. Reaction conditions and experimental results The reaction conditions and experimental results are shown in Tables 1 to 4.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

Hydrogen yield (%) = (1/6 × H ₂ production rate / dimethyl ether feed rate) × 100 CO ₂ yield (%) = (1/2 × CO ₂ production rate / dimethyl ether feed rate) × 100 CO yield (%) = (1/2 × CO production rate / dimethyl ether supply rate) × 100 CH ₄ yield (%) = (1/2 × CH ₄ production rate / dimethyl ether supply rate) × 100 Unit of each rate Are all [mol / g-cat · h]

[0039]

In the method for producing hydrogen using the catalyst of the present invention, the mixed gas of dimethyl ether and steam is mixed with 200 to
By contacting a catalyst in which a substance containing copper and a substance having solid acidity are physically mixed at a low temperature of 350 ° C., a high hydrogen yield can be obtained.

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Claims (2)

[Claims] 1. A catalyst for producing hydrogen from dimethyl ether and steam comprising a mixture of a substance containing copper and a substance having solid acidity. 2. A method for producing hydrogen, characterized in that the catalyst according to claim 1 is brought into contact with a mixed gas containing dimethyl ether and steam.