JPH06256001A - Production of hydrogen-containing gas - Google Patents

Abstract

PURPOSE:To reduce formation of CO by bringing methanol, oxygen and water in a specific molar ratio into contact with a catalyst heated to a prescribed temperature and reacting. CONSTITUTION:An aqueous solution containing given amounts of Cu(NO3)2.3H2 O, Co(NO3)2.6H2O and Zn(NO3)2.6H2O is mixed with an aqueous solution of Na2CO3 at 50-90 deg.C, aged and precipitate is filtered and washed with water. Then the precipitate is heated, dried and burnt at 300-600 deg.C to prepare Cu- containing coprecipitation catalyst having an atomic ratio of Cu/Co/Zn=1/1-10/1-20. Then a reaction tube made of quartz glass is packed with a granular Cu-containing catalyst to form a catalytic layer and heated to 100-200 deg.C. Then a raw material gas comprising methanol/oxygen/water in the molar ratio of 1/0.01-0.5/1.0-2.5 is fed to the reaction tube at 100-100,000 (h<-1>) feed rate to give a hydrogen-containing gas in high methanol conversion ratio and with an extremely reduced amount of CO formation.

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 hydrogen-containing gas, and more particularly, it is suitable for producing fuels such as polymer electrolyte fuel cells and phosphoric acid fuel cells, and maintains a high methanol conversion rate. In addition, the present invention relates to a method for producing a hydrogen-containing gas, which can suppress the production of CO to a low level and can economically and efficiently produce a hydrogen-containing gas.

[0002]

2. Description of the Related Art Conventionally, a method for producing a hydrogen-containing gas using methanol and water as raw materials has been known. This method is used in fuel cell fuel production, on-site hydrogen production, and other processes. In the process such as fuel production of the fuel cell,
It is required to minimize the production of inhibitors in the process and keep the efficiency high.

It is known that in a process such as fuel production of the fuel cell, CO serves as a reaction inhibitor in the process. However, since CO is produced by the method for producing the hydrogen-containing gas, it is necessary to suppress the production of CO as low as possible when using this method for producing the fuel of the fuel cell. Specifically, for example, in the fuel production of a phosphoric acid fuel cell, C
It is necessary to suppress the generation of O to 1% or less, and in the fuel production of a polymer electrolyte fuel cell, the production of CO is several tens of p
It is necessary to keep it below pm.

By the way, as a conventional method for producing such a hydrogen-containing gas, methanol and water are used as raw materials,
A method for producing a hydrogen-containing gas using a copper-based catalyst is known. The reaction of this method is represented by the following formula (1), and its elementary reaction is represented by formula (2) and formula (3).

CH ₃ OH + H ₂ O → CO ₂ + 2H ₂ ... (1) CH ₃ OH → CO + 2H ₂ ... (2) CO + H ₂ O → CO ₂ + 2H ₂ ... (3) Since the reaction (2) is an endothermic reaction, it is necessary to raise the reaction temperature in order to improve the conversion rate of methanol. On the other hand, the reaction of the formula (3) is an exothermic reaction, so that the reaction does not proceed under high temperature conditions and CO
Will remain a lot. Therefore, in order to lower the CO concentration in this reaction, it is necessary to increase the water / methanol ratio or carry out the reaction under low temperature conditions.

However, in the method of increasing the water / methanol ratio, water as a raw material has to be vaporized, so that there is a problem in that the cost and energy for that purpose increase and it is not economical.

Therefore, a method for producing a hydrogen-containing gas at a low reaction temperature by using a catalyst having a high activity even under the low temperature condition has been studied. For example, in Japanese Unexamined Patent Publication No. Hei 4-139001, low temperature and high activity copper,
230 materials using zinc, chromium, iron, etc. as catalysts and having a water-methanol ratio (water / methanol) of 1.2
It is shown that when the reaction is carried out at 0 ° C., the methanol conversion rate can be maintained as high as 98.3% and the CO concentration can be suppressed as low as 1.3%.

However, at present, the above-mentioned results described in the above-mentioned publication are limited, and it is the actual situation that the concentration of CO produced cannot be suppressed to a lower level. Therefore, even in the method described in the above publication, which uses a low-temperature and high-activity catalyst, there is a problem in that it is not possible to expect a significant reduction in CO concentration while maintaining a high methanol conversion rate.

On the other hand, a method of producing hydrogen-containing gas by reacting oxygen in the presence of a copper-based or noble metal-based catalyst at the time of methanol steam reforming is disclosed in, for example, JP-A-61-161.
No. 127601 and Japanese Patent Laid-Open No. 2-116603. However, these publications do not describe reduction of CO concentration or high methanol conversion rate, and these methods have a problem that CO generation cannot be suppressed low while maintaining high methanol conversion rate. is there.

The present invention solves the above problems and
It is suitable for producing fuels such as polymer electrolyte fuel cells and phosphoric acid fuel cells, and can keep CO production low while maintaining high methanol conversion rate, and produce hydrogen-containing gas economically and efficiently. An object of the present invention is to provide a method for producing a hydrogen-containing gas that can be used.

[0011]

According to the invention of claim 1 for solving the above-mentioned problems, 1 mol of methanol, 0.01 to 0.5 mol of oxygen and water are heated to 100 to 200 ° C. A method for producing a hydrogen-containing gas, which comprises contacting with a catalyst to cause a reaction, and the invention according to claim 2 is the hydrogen according to claim 1, wherein the catalyst is a catalyst containing copper. It is a method of producing a contained gas.

The method for producing the hydrogen-containing gas according to the present invention will be described in detail below.

In the present invention, first, the raw material components methanol, oxygen and water are allowed to coexist.

There are no particular restrictions on the raw material components, such as methanol, oxygen and water, and even if pure products are used,
Alternatively, a substance containing the raw material components such as a methanol aqueous solution and air or an oxygen-containing gas may be used. Since oxygen is a gas and methanol and water are liquids, in order to coexist the respective raw material components, first, methanol and water can be vaporized together or separately by an appropriate method and used.

As the ratio of the raw materials, the ratio of the methanol to the oxygen (mol number of oxygen / mol number of methanol)
Is usually 0.01 to 0.5, preferably 0.05.
It is-0.3, More preferably, it is 0.1-0.25. When the ratio of methanol to oxygen is within the above range, the production of CO can be reduced and the reduction of hydrogen generation amount can be suppressed, which is preferable. The ratio of the methanol to the water (the number of moles of water / the number of moles of methanol) is usually 1.0 to 2.5, and preferably 1.
2 to 2.0. When the ratio of methanol to water is within the above range, the production of CO can be reduced, which is preferable. The ratio of methanol to water was 1.
If it is less than 0, the removal of CO may not be sufficient, while if it exceeds 2.5, the energy used for vaporizing water may increase and the efficiency may decrease.

There is no particular limitation on the method of coexisting the respective raw materials, but for example, methanol and water are heated together or separately by an appropriate method and oxygen is supplied to the vaporized vapor to prepare a mixed gas. A method of coexisting can be mentioned. Specifically, for example, a method in which methanol and water are gasified using different evaporators and then coexisted by mixing air with this, a methanol aqueous solution is gasified using the evaporator, and methanol is used. A mixed gas containing water and water, and then mixed with an oxygen-containing gas to make them coexist can be mentioned.

In the present invention, next, a hydrogen-containing gas is produced by bringing a gas in which the raw material components methanol, oxygen and water are coexistent into contact with a catalyst to cause a reaction.

The catalyst is not particularly limited as long as it is a catalyst that can be generally used in a methanol steam reforming reaction, and examples thereof include a copper-containing catalyst and a Group VIII metal-supported catalyst.

Examples of the copper-containing catalyst include CuO-
MeO _x (in the Formula, MeO _x represents a metal oxide, Me represents Mn, represents a metal such as Si.) Copper oxide kneaded catalyst represented by, Cu ion exchange MeO _x (where
In the formula, MeO _x represents a metal oxide such as SiO ₂ , ZnO ₂ , and Al ₂ O ₃ . ) Copper ion exchange catalyst, Cu / Al ₂ O ₃ , Cu / SiO _{2 and} other copper oxide-supported catalysts, CuO.ZnO, CuO.ZnO.Al ₂ O ₃ ,
CuO / Cr ₂ O ₃ , CuO / NiO, CuO / NiO
A copper-containing coprecipitation catalyst such as ZnO may be mentioned.

Examples of the Group VIII metal-supported catalyst include metals such as Co, Ni, Pt, and Pd, and SiO ₂ and Z.
A catalyst having a metal oxide such as rO ₂ or Al ₂ O ₃ can be mentioned.

Among these, copper-containing catalysts are preferable, and copper-containing coprecipitation catalysts are particularly preferable. These are preferable because they have high activity at low temperatures and can reduce by-products such as aldehyde and formic acid.

The copper-containing catalyst is, for example, a combination of copper-nickel-zinc, and the copper-containing coprecipitation catalyst is, for example, a combination of copper-cobalt-zinc or a combination of copper-nickel-lanthanum. Can be mentioned.

As the copper-containing catalyst comprising the combination of copper-nickel-zinc, for example, an alloy containing 5 to 30% by weight of copper, 5 to 50% by weight of nickel and 30 to 90% by weight of zinc is developed. As a result, a catalyst obtained by eluting inactive zinc with an alkali can be used. The zinc elution amount is usually 10 to 90% by weight of the zinc content in the alloy. The development can be performed according to a usual development method in which the alloy is treated with an alkaline solution such as an aqueous caustic soda solution, an aqueous caustic potash solution, and an aqueous potassium carbonate solution at a temperature of usually 20 to 100 ° C.

In the expanded alloy obtained by the above expansion,
The content ratio of copper, nickel and zinc is 10 to 50% by weight of copper, 20 to 80% by weight of nickel and 10 to 6 of zinc.
It is 0% by weight. When the contents of the copper, nickel and zinc are within the above ranges, the activity can be maintained for a long time and the production of by-products can be suppressed to a low level, which is preferable.

This copper-containing catalyst can be prepared, for example, by separating the developed alloy, separating, washing with water, drying, shaping, and reducing.

The separation can be carried out by a usual solid-liquid separation method such as filtration, centrifugation, decantation and the like. The washing with water is performed for the purpose of removing the alkaline solution, and can be performed by, for example, a gradient method using distilled water or ion-exchanged water. The drying can be performed by air-drying for 3 to 12 hours. The molding may be performed in various shapes such as a tablet shape, a pellet shape, a granular shape, a strip shape, and a plate shape by adding graphite as a lubricant to the spread alloy by, for example, a press molding method, a tablet molding method, or the like. You can The reduction can be usually performed in a hydrogen atmosphere at 200 to 500 ° C., or can be performed by diluting with an inert gas such as helium gas, neon gas, argon gas or nitrogen gas.

As the copper-containing coprecipitation catalyst composed of the combination of copper-cobalt-zinc, for example, the ratio of each element, that is, the atomic ratio is Cu: Co: Zn = 1: 0.01-5.
0: 0.1 to 1000, preferably Cu: Co: Zn =
There may be mentioned 1: 1 to 10: 1 to 20. When the atomic ratio is within the above range, a copper-containing coprecipitated catalyst having desired performance can be obtained, which is preferable.

As the copper-containing coprecipitation catalyst comprising the combination of copper-nickel-lanthanum, for example, the ratio of each element, that is, the atomic ratio is Cu: Ni: La = 1: 1.
0.01-50: 0.1-1000, preferably Cu:
Examples thereof include Ni: La = 1: 1 to 10: 1 to 20. When the atomic ratio is within the above range, a copper-containing coprecipitated catalyst having desired performance can be obtained, which is preferable.

The above-mentioned elements contained in the copper-containing coprecipitation catalyst are
Usually, those obtained from water-soluble salts are preferable. Examples of such salts include nitrates, acetates, sulfates, oxalates, formates and the like. More specifically, copper nitrate, copper acetate, copper sulfate, copper oxalate, copper formate, cobalt nitrate, cobalt acetate, cobalt sulfate, cobalt oxalate, cobalt formate, zinc nitrate, zinc acetate, zinc sulfate, zinc oxalate. Examples thereof include zinc formate, nickel nitrate, nickel acetate, nickel sulfate, nickel oxalate, nickel formate, lanthanum nitrate, lanthanum acetate, lanthanum sulfate, lanthanum oxalate, and lanthanum formate.

For the preparation of these copper-containing coprecipitated catalysts,
This will be described below.

First, a mixture of a water-soluble salt of copper, a water-soluble salt of cobalt and a water-soluble salt of zinc, or a mixture of a water-soluble salt of copper, a water-soluble salt of nickel and a water-soluble salt of lanthanum and a precipitant. A precipitate is deposited by mixing with an aqueous solution of (sodium carbonate, potassium carbonate, caustic soda, caustic potash, etc.).

The concentration of the water-soluble salt in the mixed solution is usually 0.1 to 10 mol / L, preferably 0.5 to 5 mol / L. The precipitating agent is not particularly limited, but sodium carbonate is preferred. The concentration of the precipitating agent in the aqueous solution is preferably 0.05 to 5 mol / L. The liquid amount ratio (volume ratio) of the mixed liquid and the precipitant aqueous solution is preferably 0.1 to 10. When the mixed solution and the precipitant aqueous solution are mixed, the temperature of both solutions is usually 50 to
The temperature is 90 ° C, preferably 60 to 85 ° C. It is preferable that the mixed solution and the precipitant aqueous solution are mixed rapidly.

After mixing, the mixed solution is aged. It is known that if the new precipitate immediately after co-precipitation is brought into contact with the mother liquor, the precipitate particles grow and grow further, and the sharp parts and edges of the precipitate disappear and become smooth. Precipitation of various particles can be obtained. In addition, since the pH of the solution changes during aging, it is considered that the crystal structure and chemical composition have changed, and aging operation is necessary to obtain a catalyst with good reproducibility. As the aging conditions, the temperature is 50 to 90 ° C., the aging time is 1 to 10 hours, and p
H is preferably 8 to 11.

The copper-containing coprecipitated catalyst can be obtained by washing the coprecipitate obtained as described above with water, drying it, and calcining it sufficiently. The drying temperature is usually 100 to 120 ° C., and the drying time is
It is usually 5 to 20 hours. The firing temperature is usually 300 to 600 ° C., and the firing time is usually 1 to 10 hours.

In the present invention, the mode of using the catalyst is not particularly limited, and for example, it may be used in the state of the catalyst film or in the state of the catalyst layer. Among these, the embodiment used in the state of the catalyst layer is preferable. In such a case, the contact area with the source gas and the time can be increased, and the reaction efficiency can be improved.

As a mode of use in the state of the catalyst layer,
For example, an appropriately selected mode to be used by filling a reactor such as a reformer known per se, a mode to be used by supporting on a honeycomb, or a mode to be used by supporting on a tube wall inside a reaction tube, etc. You can In addition, it is preferable that the reactor has a function of controlling the temperature of the catalyst that is filled in the reactor and that forms the catalyst layer.

The length and cross-sectional area of the catalyst layer are such that the temperature raised by the exothermic reaction at the catalyst layer inlet portion, that is, upstream of the catalyst layer can be radiated to a predetermined temperature of 200 ° C. or less. The cross-sectional area is required and can be appropriately selected depending on the conditions such as heat transfer in the reactor, feed rate of raw materials, and reaction pressure.

The pressure in the above reaction is usually from atmospheric pressure to 30 Kg / cm ² G, preferably from atmospheric pressure to 10
It is Kg / cm ² G. When the pressure is within the above range, the conversion rate of methanol can be kept high, which is preferable.

The temperature of the catalyst layer in the above reaction is
The temperature is usually 100 to 200 ° C., and preferably 120 to 160 ° C. for the reason described below.

The feed rate (gas space velocity) of the raw materials in the above reaction is usually 100 to 100,00.
0 (h ^-1 ), preferably 1,000 to 10,000
It is 0 (h ^-1 ).

The mechanism of the reaction for producing the hydrogen-containing gas in the present invention is considered as follows. That is, when a gas containing the raw materials methanol, oxygen and water is introduced into the catalyst layer which has been heated to 100 to 200 ° C. in advance, methanol and oxygen are present on the catalyst near the inlet of the catalyst layer (hereinafter referred to as the upstream). And react as in formula (4) shown below.

CH ₃ OH + 3 / 2O ₂ → CO ₂ + 2H ₂ O (4) Since the reaction of the above formula (4) is a large exothermic reaction, the temperature of the upstream of the catalyst layer rises by this reaction.
The heat generated by this exothermic reaction promotes the endothermic reaction represented by the above formula (2), and the methanol introduced into the catalyst layer is almost completely converted.

Then, the oxygen introduced into the catalyst layer is not immediately consumed upstream of the catalyst layer, and the above formula (4)
Since the exothermic reaction represented by (3) becomes less likely to occur, the temperature increased in the upstream of the catalyst layer and the temperature in the region (hereinafter, referred to as “medium / downstream”) that follows the upstream of the catalyst layer and is increased together with the temperature increase. Then, the temperature is rapidly lowered to a temperature of the preset catalyst layer (100 to 200 ° C.). Then, in the middle and downstream of the catalyst layer, the reaction mainly represented by the formula (3) occurs. Since the reaction represented by the above (3) is an exothermic reaction, at a temperature (100 to 200 ° C.) in the middle and downstream of the catalyst layer,
The reaction proceeds to the right side and CO is converted to CO ₂ . Therefore, the CO concentration is greatly reduced.

As described above, according to the present invention, the production of CO can be suppressed to a low level while maintaining a high methanol conversion rate, and the amount of heat supplied from the outside can be reduced. The hydrogen-containing gas can be efficiently produced.

However, when the preset temperature of the catalyst layer exceeds 200 ° C., the reaction represented by the formula (3) does not easily proceed to the right side, so that a large effect of reducing the CO concentration cannot be expected. On the other hand, when the temperature is lower than 100 ° C, methanol and water in the gas introduced into the catalyst layer may be liquefied, and the reaction may not be allowed to proceed smoothly. Further, when the ratio of the number of moles of oxygen to 1 mole of methanol is less than 0.01, the exothermic reaction represented by the above formula (4) does not sufficiently occur, so that the endothermic reaction represented by the above formula (2) occurs. Since sufficient heat cannot be supplied and the conversion of methanol may not be sufficient, on the other hand, when it exceeds 0.5 mol, the conversion of methanol due to the reaction of the above formula (4) greatly increases. It is not preferable because the amount of hydrogen produced from the reaction represented by 1) is greatly reduced and the hydrogen production efficiency is reduced.

[0046]

Embodiments of the present invention will be described below. The present invention is not limited to the following embodiments.

(Preparation of catalyst) An aqueous sodium carbonate solution was added to an aqueous solution containing copper nitrate (trihydrate), zinc nitrate (hexahydrate) and aluminum nitrate (hexahydrate) to form a precipitate. . Then, this precipitate was filtered and washed with water. The obtained precipitate was dried at a temperature of 120 ° C. for about 12 hours and then calcined at 450 ° C. for 2 hours to prepare a copper-containing coprecipitation catalyst composed of a combination of copper-zinc-aluminum.

The ratio of each element in this copper-containing coprecipitation catalyst was Cu: Zn: Al = 1: 2: 0.5 (molar ratio). This catalyst was used in the following examples and comparative examples.

(Example 1) 5 cc of the copper-containing coprecipitated catalyst molded to 16 to 32 mesh and 10 cc of inactive silicon carbide (SiC) were mixed and filled in a reaction tube made of quartz glass to form a catalyst layer. Formed. At this time, the length of the catalyst layer was about 8 cm. Then, the reaction tube made of quartz glass was placed in an electric furnace capable of controlling a predetermined temperature. The catalyst layer was hydrogen-reduced at 300 ° C. for 2 hours before being used, and then preliminarily kept at a predetermined temperature in N ₂ gas.

Further, by inserting a thermocouple protective tube into the central portion of the catalyst layer in the quartz glass reaction tube, and further inserting a thermocouple into the protective tube and moving it up and down, the inside of the catalyst layer From the inlet of the catalyst layer at
The temperature at each point of cm (catalyst layer inlet), 4 cm, and 7 cm (catalyst layer outlet) was measured. The average value of the temperature at each point was defined as the average catalyst temperature.

The temperatures at which the experiment was conducted (average catalyst temperature before the reaction) were 150 ° C, 170 ° C, 180 ° C and 200 ° C.

After the temperature of the catalyst layer was measured, it consisted of methanol, oxygen and water, and water / methanol (molar ratio) = 1.
2. Oxygen / methanol (molar ratio) = 0.25, the feed rate (LHSV) of methanol is 4.3 h for the source gas.
^-1 , The hydrogen-containing gas was produced by introducing into the catalyst layer and reacting under the condition that the reaction pressure was normal pressure. Methanol and water were vaporized in advance in the evaporator and then mixed with the raw material gas.

After measuring the temperature of the catalyst layer during the reaction, the produced gas and liquid were analyzed. The results are shown in Table 1. As a result, the average catalyst layer temperature before the reaction is 100 to
At 200 ° C., the CO concentration in the dry gas could be kept as low as less than 1.0% while maintaining a high methanol conversion rate of 98.8% or more.

(Comparative Example 1) A hydrogen-containing gas was produced in the same manner as in Example 1 except that the temperature at which the experiment was conducted (average catalyst temperature before the reaction) was changed to 220 ° C and 260 ° C. The results are shown in Table 1. As a result, when the average catalyst layer temperature before the reaction is 220 ° C. and 260 ° C., not only the temperature of the upstream of the catalyst layer but also the temperature of the middle and downstream of the catalyst layer becomes high, so the methanol conversion rate becomes high at 100%, but in the dry gas. The CO concentration of 1 was as high as 1.5% or more.

(Comparative Example 2) A hydrogen-containing gas was produced in the same manner as in Example 1 except that only methanol and water were used as raw material gases. The results are shown in Table 1.

As a result, the average catalyst temperature before the reaction was 3
When the temperature was 00 ° C, although the methanol conversion rate was as high as 100%, the CO concentration in the dry gas was as high as 3.7%. Then, when the average catalyst layer temperature was set to 250 ° C., the CO concentration in the dry gas was lowered to 1.0%, but the methanol conversion rate was also lowered to less than 80%.

This result shows that when the average catalyst temperature is increased,
Although the methanol conversion rate is improved, the CO concentration is also increased. On the other hand, when the average catalyst layer temperature is lowered, the CO concentration is decreased but the methanol conversion rate is also decreased.

From the above, when the reaction is carried out under the conditions of the present invention, the CO conversion is maintained at a high value of 99% or more, even if the water / methanol ratio is as low as 1.2.
It can be seen that the hydrogen-containing gas can be efficiently and economically obtained by suppressing the concentration as low as 0.7 to 0.9%.

[0059]

[Table 1]

[0060]

According to the present invention, it is suitable for producing fuels such as polymer electrolyte fuel cells and phosphoric acid fuel cells, and it is possible to keep CO generation low while maintaining a high methanol conversion rate. Since the amount of heat supplied from the outside can be reduced, it is possible to provide a method for producing a hydrogen-containing gas that can produce a hydrogen-containing gas economically and efficiently.

Claims (2)

[Claims] 1. 1 mol of methanol and 0.01 to 0.
A method for producing a hydrogen-containing gas, which comprises bringing 5 mol and water into contact with a catalyst heated to 100 to 200 ° C. to cause a reaction. 2. The method for producing a hydrogen-containing gas according to claim 1, wherein the catalyst is a catalyst containing copper.