JP4705375B2 - Method for stabilizing and activating CO removal catalyst - Google Patents

Description

  The present invention relates to a method for stabilizing and activating a CO removal catalyst for selectively removing CO carrying ruthenium using a nitrogen-containing ruthenium compound.

  In recent years, new energy technology has attracted attention due to environmental problems, and fuel cells are attracting attention as one of the new energy technologies. This fuel cell converts chemical energy into electrical energy by electrochemically reacting hydrogen and oxygen, and has a feature of high energy use efficiency. Or, practical research has been actively conducted for automobiles and the like.

In the case of producing hydrogen using petroleum-based hydrocarbons as a hydrogen source, generally, a method of subjecting hydrocarbons to steam reforming or partial oxidation reforming in the presence of a reforming catalyst is used. The hydrogen-containing gas obtained in these reactions usually contains CO together with the target hydrogen gas. If this CO is contained in a certain level or more, a serious problem arises that the power generation performance of the fuel cell is lowered, or power generation cannot be performed at all depending on the concentration. Therefore, there is a strong demand for the development of a technique for converting this CO into harmless CO ₂ or the like and reducing the CO concentration in the hydrogen-containing gas supplied to the fuel cell.

As one means for reducing the concentration of CO in the reformed gas, a method of converting CO into CO ₂ by introducing oxygen or an oxygen-containing gas (such as air) into the fuel gas has been proposed. At this time, it is desirable to use a catalyst that selectively oxidizes only CO without oxidizing hydrogen as much as possible. As selective oxidation catalysts for CO, Patent Documents 1 to 3 disclose catalysts in which ruthenium is supported on alumina using ruthenium nitrate.

These catalysts are reduced at a high temperature of 300 ° C. or higher before use. However, when the catalyst is actually used in the CO removing device, there is a problem that the catalyst is oxidized by oxygen in the air when the CO removing device is filled and deactivated.
In addition, in view of the safety of the CO removal device, it is necessary to purge the reformed gas remaining after the operation is completed. When purging, it is preferable to use nitrogen gas so as not to damage the catalyst, but there is a problem that a nitrogen gas cylinder or the like is required and it is not economical.
JP 2001-239169 A JP 2001-239170 A JP 2001-327868 A

  An object of the present invention is to provide a method for stabilizing and activating a CO removal catalyst in which ruthenium is supported using a nitrogen-containing ruthenium compound.

As a result of diligent research, the inventors of the present invention have found that a CO removal catalyst in which ruthenium is supported using a nitrogen-containing ruthenium compound is deactivated by contact with air after specific stabilization after reduction at 300 ° C. or higher. However, it was not necessary to reduce at 300 ° C. or higher for reactivation, and it was found that reduction at 120 ° C. or higher was possible, that is, the air resistance was high, and the present invention was completed.
According to the present invention, the following CO removal catalyst stabilization method and activation method are provided.
1. A CO removal catalyst in which ruthenium is supported on a refractory oxide support using a nitrogen-containing ruthenium compound is reduced at 300 ° C. to 600 ° C. in a hydrogen-containing gas atmosphere, and the temperature is lowered in the hydrogen-containing gas or inert gas atmosphere. And then stabilizing the oxidation of the catalyst in a state maintained at 120 ° C. or lower in an oxygen-containing gas.
2. 2. The stability of a CO removal catalyst according to 1, wherein the refractory oxide support is at least one selected from alumina, titania, silica, zirconia and ceria, and the nitrogen-containing ruthenium compound is ruthenium nitrate. Method.
3. A CO removal catalyst stabilized by the method for stabilizing a CO removal catalyst according to 1 or 2.
4). Activation of a CO removal catalyst charged in a CO removal apparatus in a hydrogen production system having a reformer that generates a hydrogen-rich reformed gas from hydrocarbons and a CO removal device that removes CO contained in the reformed gas A method for activating a CO removal catalyst, comprising filling the CO removal apparatus with the CO removal catalyst according to 3, and then reducing the CO removal catalyst at 150 ° C or higher.
5. Activation of a CO removal catalyst charged in a CO removal apparatus in a hydrogen production system having a reformer that generates a hydrogen-rich reformed gas from hydrocarbons and a CO removal device that removes CO contained in the reformed gas A method comprising: operating a CO removal device filled with the CO removal catalyst according to 3 and then stopping the operation, purging the CO removal device with air, and then reducing the CO removal catalyst at 150 ° C. or higher. A method for activating a CO removal catalyst characterized by the above.
6). The reduction at 120 ° C. or higher is a reduction under a hydrogen-containing gas atmosphere, a reduction under introduction of a reformed gas, or a reduction under introduction of air used for reforming gas and selective oxidation. The method for activating a CO removal catalyst according to claim 4 or 5.

  ADVANTAGE OF THE INVENTION According to this invention, the stabilization method and activation method of the CO removal catalyst which carry | supported ruthenium using the nitrogen containing ruthenium compound can be provided.

A system for producing hydrogen using a hydrocarbon as a raw material for a hydrogen-containing gas usually comprises a desulfurization device, a reforming device, a shift device, and a CO removal device (if a raw material not containing sulfur is used, a desulfurization device is used). In addition, when using hydrocarbons that can be reformed at low temperatures such as methanol and dimethyl ether as raw materials, the shift device may be omitted.)
Here, the desulfurization apparatus is an apparatus for removing sulfur contained in the hydrocarbon raw material, and the reforming apparatus is an apparatus for obtaining hydrogen from the desulfurized hydrocarbon raw material. Since CO is generated together with hydrogen during reforming, CO is converted into CO ₂ and H ₂ by a converter. The CO removal device is a device that removes CO that has not been transformed by the transformation device, and the CO removal catalyst of the present invention is used in this device.
The CO removal catalyst of the present invention contributes to the reaction of generating CO ₂ from CO in the presence of oxygen, but also to the reaction (methanation) of generating CH ₄ and H ₂ O from CO and H ₂ together with this reaction. Has contributed.

The CO removal catalyst used in the present invention is a catalyst in which ruthenium is supported on a carrier using a nitrogen-containing ruthenium compound.
Examples of the refractory oxide carrier used in the CO removal catalyst of the present invention include those selected from alumina, titania, silica, zirconia and ceria. These may be used alone or in combination of two or more. Among these, alumina is preferably used from the viewpoint of catalytic activity.

Examples of the nitrogen-containing ruthenium compound used in the CO removal catalyst of the present invention include Ru (NO ₃ ) ₃ , Ru (NO) (NO ₃ ) ₃ , Ru ₂ (OH) ₂ Cl ₄ .7NH ₃ .3H ₂ O , (Ru ₃ O ₂ (NH ₃ ) ₁₄ ) C ₁₆ • H ₂ O, (NH ₄ ) ₂ (RuCl ₅ (H ₂ O)), K ₂ (RuCl ₅ (NO)), K ₄ (Ru (CN) ) ₆ ) · nH ₂ O, K ₂ (Ru (NO ₂ ) ₄ (OH) (NO)), (Ru (NH ₃ ) ₆ ) Cl ₃ , (Ru (NH ₃ ) ₆ ) Br ₃ , (Ru ( NH ₃ ) ₆ ) Cl ₂ , (Ru (NH ₃ ) ₆ ) Br ₂ , (Ru (NO) (NH ₃ ) ₅ ) Cl ₃ , (Ru (OH) (NO) (NH ₃ ) ₄ ) (NO ₃ ) ₂ etc. are mentioned. Among these ruthenium compounds, Ru (NO ₃ ) ₃ , Ru (NO) (NO ₃ ) ₃ , (Ru (NH ₃ ) ₆ ) Cl ₃ , (Ru (NH ₃ ) are preferable from the viewpoint of availability. ₆ ) Cl ₂ , more preferably Ru (NO ₃ ) ₃ is used.

In the CO removal catalyst of the present invention, a ruthenium compound is brought into contact with a carrier and then dried / calcined (supported).
First, the above-described ruthenium compound is dissolved in water, ethanol or the like to prepare a catalyst preparation solution. Using this catalyst preparation solution, the ruthenium compound is brought into contact with the support by the usual impregnation method, coprecipitation method, or competitive adsorption method. At this time, the treatment conditions may be appropriately selected according to various methods. Usually, the support is brought into contact with the catalyst preparation solution at a temperature of room temperature to 90 ° C. for 1 minute to 10 hours. The amount of the ruthenium compound supported is not particularly limited, but is usually preferably 0.05 to 10% by weight as Ru with respect to the support.

  After contact, the carrier is dried. As the drying method, for example, natural drying, evaporation to dryness, drying using a rotary evaporator or an air dryer can be used. When baking is performed after drying, the baking is usually performed at 350 to 550 ° C. for 1 to 6 hours.

  The supported metal of the CO removal catalyst prepared as described above is usually present in the state of the salt used, or in the state of hydroxide or oxide. In the present invention, the catalyst is reduced at 300 ° C. to 600 ° C. in a hydrogen-containing gas atmosphere before use. As the hydrogen-containing gas, 100% hydrogen or a mixed gas of inert gas such as nitrogen or helium and hydrogen can be used. The reduction is usually performed at 300 to 600 ° C., preferably 350 to 500 ° C. in a hydrogen stream for 1 to 5 hours, preferably 1 to 2 hours.

  After the reduction, the catalyst is cooled. The purpose of cooling is to lower the temperature to the temperature at the time of oxidation stabilization, which will be described later, and it is desirable that the temperature be lower than the temperature at the time of oxidation stabilization in consideration of heat generation during the oxidation stabilization. Usually, it is carried out at 120 ° C. or lower, preferably room temperature to 100 ° C., more preferably room temperature to 80 ° C. in an inert gas atmosphere such as hydrogen-containing gas or nitrogen helium.

After cooling, the catalyst is oxidized and stabilized in an oxygen-containing gas. As the oxygen-containing gas, air, a gas obtained by mixing an inert gas and air, or the like can be used. The oxidation is performed at 120 ° C. or less, preferably at room temperature to 100 ° C., more preferably at room temperature to 60 ° C. until no heat generation is observed. Usually 30 minutes to 2 hours. If the temperature exceeds 120 ° C., the supported ruthenium may aggregate.
For example, this oxidation is preferably initially performed in a gas having a low oxygen concentration in order to suppress heat generation, and the oxygen concentration is gradually increased.

  When stabilized in this way, even if the air is subsequently touched, it is not necessary to perform hydrogen reduction at 300 ° C. or higher again, and activation can be achieved by reduction at 120 ° C. or higher. Normally, it is expected that the catalyst cannot be activated unless hydrogen reduction at 300 ° C. or higher is performed again in a state where the catalyst is filled in the CO removal apparatus. However, the CO removal catalyst of the present invention has good air stability and is reduced at 120 ° C. or higher. Can be activated. Since the reduction at a high temperature in a state where the CO removing apparatus is filled is difficult, the activation method of the present invention is very advantageous.

The CO removal catalyst stabilized by the above method is charged into a CO removal apparatus.
Since CO removal catalyst contacts air at the time of filling, it is necessary to activate the CO removal catalyst after filling and before operating the CO removal apparatus. Once the CO removal catalyst has been exposed to air, the activity is reproduced by reduction at 120 ° C. or higher, preferably 120 to 200 ° C., more preferably 150 to 180 ° C.

For example, a reformed gas having a temperature high enough to heat the catalyst to 120 ° C. or higher, or a gas in which reformed gas is mixed with air for selective oxidation of CO is allowed to flow. In addition, the activity of the CO removal catalyst can be reproduced by reducing in a hydrogen-containing gas atmosphere instead of the reformed gas. These reductions are preferably performed for 1 to 60 minutes, more preferably 2 to 30 minutes.
After this activation, the CO removal device is activated. If it is after activation, it can be operated even at a temperature below the activated temperature.

  Usually, the CO removing device filled with the activated CO removing catalyst is repeatedly operated after being operated and then stopped again. For example, a CO removal device provided in a hydrogen production system linked to a fuel cell is repeatedly operated and stopped every time the fuel cell is used or stopped. When stopping the CO removal device, it is necessary to purge the reformed gas remaining in the CO removal device from the viewpoint of safety. Conventionally, it was purged with nitrogen gas, but it can also be purged with air. Although air purge does not require a gas cylinder like nitrogen gas purge, it is economical, but the CO removal catalyst is oxidized by air.

In the present invention, after the air purge, the CO removal catalyst can be reused by reducing it at 120 ° C. or higher. The reduction is performed at a temperature of 120 ° C. or more, preferably 120 to 120 ° C., preferably in a hydrogen-containing gas atmosphere or while introducing a reformed gas or a mixed gas of reformed gas and selective oxidation air, as in the above-described reduction after filling. 200 degreeC, More preferably, it is 150-180 degreeC, Preferably it is 1 to 60 minutes, More preferably, it carries out for 2 to 30 minutes.
The air purge is preferably performed at 200 ° C. or less, more preferably at room temperature to 150 ° C., and even more preferably at room temperature to 100 ° C. If it exceeds 200 ° C., the activity of the catalyst may be reduced. Here, 200 degrees C or less means that the maximum temperature in a catalyst layer is 200 degrees C or less.

The CO removal catalyst treated by the method of the present invention selectively removes CO in a hydrogen-based gas (reformed gas) obtained by reforming or partially oxidizing a raw material for hydrogen production. Is suitably used.
Hydrogen produced in this way is preferably used for a fuel cell, but is not limited thereto.

Preparation example (catalyst preparation)
7 ml of a ruthenium nitrate solution (manufactured by Kojima Chemical Co., Ltd., ruthenium content = 50 g / liter (as ruthenium metal)) was placed in a beaker, and 1 ml of ion-exchanged water was added thereto and stirred until uniform. In another beaker, 20 g of γ-alumina carrier (KHD24, manufactured by Sumitomo Chemical Co., Ltd., spherical shape having a diameter of 2 to 4 mm) was weighed.
The diluted ruthenium nitrate solution was added dropwise while stirring the alumina support well with a glass rod, and the stirring was continued for 5 minutes until most of the ruthenium nitrate solution was absorbed by the alumina support. The alumina carrier that absorbed the ruthenium nitrate solution was recovered in a baking dish, and this was left to stand at 120 ° C. for 3 hours to obtain a ruthenium catalyst.

Reference Example 2.5 cc of the catalyst prepared in the above preparation example was weighed and charged into a reactor. Hydrogen reduction was performed in the reactor at 450 ° C. under the following conditions (initial reduction). Thereafter, the temperature was lowered in a hydrogen stream, and the raw material gas was introduced to initiate the CO removal reaction. The reaction conditions are as follows.
1. Hydrogen reduction conditions Temperature: 450 ℃
Pressure: Atmospheric pressure Time: 1 hour Hydrogen concentration: 100%
GHSV: 6,000 h ⁻¹
2. Reaction conditions Temperature: 115 ° C
Pressure: Atmospheric pressure GHSV: 14,000 h ⁻¹
Raw material gas composition _{(volume%): CO / CO 2 /} O 2 / N 2 / H 2 O / H 2
= 0.6 / 15 / 0.9 / 3.5 / 20 / Balance
Reaction time: 45 minutes GHSV in the above conditions is a value (gas space velocity) divided by the apparent volume of the catalyst layer using the supply volume velocity in the standard state of the feed gas.
The outlet CO concentration during the reaction was 15 ppm.

Example 1
10 cc of catalyst was weighed and charged into the reactor. It was subjected to hydrogen reduction under the same conditions as in Reference Example (initial reduction). At this time, since the amount of catalyst was large, the hydrogen flow rate was increased in order to align GHSV.
Thereafter, the temperature was lowered to 39 ° C. under the condition of 100% hydrogen. After purging hydrogen with nitrogen gas, air (21% oxygen, 79% nitrogen) was allowed to flow at 200 cc / min for 30 minutes to stabilize the catalyst. The fever disappeared in 30 minutes. The maximum temperature of the catalyst layer at this time was 59 ° C.
The catalyst was removed from the reactor and left in the air for one day.
Next, 2.5 cc of the catalyst was weighed and charged into the reactor. Hydrogen reduction was carried out under the same conditions as in the reference example except that the reduction temperature was changed to 200 ° C.
Then, reaction was implemented on the same conditions as a reference example.
The outlet CO concentration during the reaction was 16 ppm.

Example 2
In this example, the stabilization start temperature was set to 74 ° C. The maximum temperature of the catalyst layer at the time of stabilization was 100 ° C. Otherwise, the initial reduction-stabilization-reduction-reaction was carried out under the same conditions as in Example 1.
The outlet CO concentration during the reaction was 3 ppm.

Example 3
In this example, the stabilization start temperature was 103 ° C. The maximum temperature of the catalyst layer at the time of stabilization was 120 ° C. Otherwise, the initial reduction-stabilization-reduction-reaction was carried out under the same conditions as in Example 1.
The outlet CO concentration during the reaction was 19 ppm.

Example 4
In this example, the stabilization start temperature was 39 ° C., which was the same as in Example 1. However, the maximum temperature of the catalyst layer during stabilization was 60 ° C. Subsequent pre-reaction reduction was carried out at 150 ° C. Otherwise, the initial reduction-stabilization-reduction-reaction was carried out under the same conditions as in Example 1.
The outlet CO concentration during the reaction was 16 ppm.

Example 5
In this example, the pre-reaction reduction was performed at 120 ° C. Otherwise, the initial reduction-stabilization-reduction-reaction was carried out under the same conditions as in Example 1.
The outlet CO concentration during the reaction was 20 ppm.

Example 6
In this example, the initial reduction temperature was changed from 450 ° C. to 300 ° C. Moreover, the maximum temperature of the catalyst layer at the time of stabilization was 57 degreeC. Otherwise, the initial reduction-stabilization-reduction-reaction was carried out under the same conditions as in Example 1.
The outlet CO concentration during the reaction was 17 ppm.

Comparative Example 1
In this example, the stabilization start temperature was 117 ° C. The maximum temperature of the catalyst layer at the time of stabilization was 142 ° C. Otherwise, the initial reduction-stabilization-reduction-reaction was carried out under the same conditions as in Example 1.
The outlet CO concentration during the reaction was 33 ppm.

Comparative Example 2
In this example, the stabilization start temperature was 137 ° C. The maximum temperature of the catalyst layer at the time of stabilization was 165 ° C. Otherwise, the initial reduction-stabilization-reduction-reaction was carried out under the same conditions as in Example 1.
The outlet CO concentration during the reaction was 36 ppm.

Comparative Example 3
In this example, the initial reduction temperature was 250 ° C. The stabilization start temperature was 39 ° C., which was the same as in Example 1. However, the maximum temperature during stabilization was 56 ° C. Otherwise, the initial reduction-stabilization-reduction-reaction was carried out under the same conditions as in Example 1.
The outlet CO concentration during the reaction was 54 ppm.

Comparative Example 4
In this example, the pre-reaction reduction was performed at 80 ° C. Otherwise, the initial reduction-stabilization-reduction-reaction was carried out under the same conditions as in Example 1.
The outlet CO concentration during the reaction was 41 ppm.

Example 7
Under the same conditions as in Example 1, initial reduction-stabilization was performed. Then, instead of hydrogen reduction, the raw material gas (reformed gas) having the above-described composition was circulated at 150 ° C. for 30 minutes, and then the temperature was lowered to 115 ° C. to carry out the reaction.
The outlet CO concentration during the reaction was 15 ppm.
Thereafter, the reaction gas was stopped, and the temperature was lowered to 100 ° C. without any flow. Next, when the residual gas was purged with air at 50 cc / min, heat was generated up to 119 ° C.
Subsequently, the air was switched to the above-described source gas, and the temperature was raised to 150 ° C. and allowed to flow for 30 minutes. Thereafter, the temperature was lowered to 115 ° C. to carry out the reaction.
The outlet CO concentration during the second reaction was 18 ppm.

As described above, in the examples, the outlet CO concentration during the reaction decreased to 20 ppm or less, and very good CO removal activity was obtained.
On the other hand, as in Comparative Examples 1 and 2, when the maximum temperature of the catalyst layer during oxidation stabilization exceeded 120 ° C, the outlet CO concentrations during the reaction were 33 and 36 ppm, respectively, and 30 ppm. Beyond.
Further, even when the initial reduction temperature is lower than 300 ° C. as in Comparative Example 3, even when the subsequent oxidation stabilization and reduction are performed in the same manner as in Example 1, the outlet CO concentration during the reaction is as high as 54 ppm. .
In Comparative Example 4, the conditions until the initial reduction-oxidation stabilization were the same as in Example 1, but since the pre-reduction reduction was performed at 80 ° C., activation was not sufficient and the CO concentration during the reaction was 41 ppm. . However, since the reaction was carried out at 115 ° C. and the reaction time was 45 minutes, it can be said that the reduction before the reaction was carried out at 115 ° C.

The method for stabilizing and activating a CO removal catalyst of the present invention can be used in a system for producing hydrogen used in fuel cells and the like.
Further, the hydrogen-containing gas obtained by the CO removal catalyst treated by the method of the present invention can be suitably used as a fuel for various H ₂ combustion type fuel cells, and particularly at least the fuel electrode (negative electrode). To various H ₂ combustion type fuel cells (Phosphate type fuel cells, KOH type fuel cells, polymer electrolyte fuel cells and other low temperature operation type fuel cells) using platinum (platinum catalyst) as an electrode It can be used as a supply fuel.

Claims (6)

A CO removal catalyst in which ruthenium is supported using a nitrogen-containing ruthenium compound on a refractory oxide carrier,
Reduction at 300 ° C. to 600 ° C. in a hydrogen-containing gas atmosphere,
Lowering the temperature in the hydrogen-containing gas or inert gas atmosphere,
Thereafter, the method for stabilizing a CO removal catalyst is characterized in that the catalyst is oxidized and stabilized in an oxygen-containing gas at 120 ° C. or lower until no heat is generated . The refractory oxide carrier is at least one selected from alumina, titania, silica, zirconia and ceria;
The method for stabilizing a CO removal catalyst according to claim 1, wherein the nitrogen-containing ruthenium compound is ruthenium nitrate.   A CO removal catalyst stabilized by the method for stabilizing a CO removal catalyst according to claim 1 or 2. Activation of a CO removal catalyst charged in a CO removal apparatus in a hydrogen production system having a reformer that generates a hydrogen-rich reformed gas from hydrocarbons and a CO removal device that removes CO contained in the reformed gas A method,
The CO removal apparatus is filled with the CO removal catalyst according to claim 3,
Then, the CO removal catalyst is reduced at 120 ° C. or higher, and the CO removal catalyst activation method. Activation of a CO removal catalyst charged in a CO removal apparatus in a hydrogen production system having a reformer that generates a hydrogen-rich reformed gas from hydrocarbons and a CO removal device that removes CO contained in the reformed gas A method,
After operating the CO removal device filled with the CO removal catalyst according to claim 3, stop,
Purging the CO remover with air;
Then, the CO removal catalyst is reduced at 120 ° C. or higher, and the CO removal catalyst activation method. The reduction at 120 ° C. or higher
Reduction under a hydrogen-containing gas atmosphere,
Reduction with introduction of reformed gas, or
6. The method for activating a CO removal catalyst according to claim 4 or 5, wherein the reduction is performed by introducing reformed gas and air used for selective oxidation.