JP2001246251A - Method for preparing catalyst used in synthesis of ammonia and method for synthesizing ammonia - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing a highly active ruthenium catalyst having ruthenium carried on active carbon which is used for synthesis of ammonia and a method for synthesizing ammonia using the same. SOLUTION: The catalyst having ruthenium carried on active carbon is prepared by a process comprising the steps of adding an alkaline metal salt or an alkaline earth metal salt to the catalyst precursor having ruthenium carried on active carbon treated with hydrogen, then raising the temperature to 350 to 400 deg.C under hydrogen atmosphere, followed by heating the resultant catalyst precursor to 500 to 600 deg.C at a heating speed of 10-60 deg.C to subject to an activation treatment. The synthesis of ammonia is conducted by using the catalyst having ruthenium carried on active carbon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an activated carbon-supported ruthenium catalyst for ammonia synthesis and a method for ammonia synthesis using the catalyst.

[0002]

2. Description of the Related Art In a conventional ammonia synthesis, an iron-based catalyst containing iron as a main component and adding alumina, potassium oxide and the like as a promoter is used. However, since this catalyst has a low ammonia synthesis activity in a low temperature range, in an industrial apparatus using this catalyst, the reaction temperature is set to 400 to 500 ° C. in order to increase the reaction rate.
And the synthesis reaction must be performed in a temperature range that is disadvantageous in terms of equilibrium theory. When the synthesis reaction is performed under such conditions, the circulation ratio of the reaction gas increases, and
Equipment such as a reactor, a separator for separating generated ammonia from unreacted gas, and a compressor for returning unreacted gas to the ammonia synthesis reactor becomes large. In addition, compressor power, gas cooling,
Requires a lot of energy for heating.

In response to the above problems, a ruthenium-based catalyst capable of synthesizing ammonia even at low temperature and low pressure has been developed as a catalyst replacing the iron-based catalyst. These catalysts are disclosed in JP-A-7-256104,
No. 168,739, Japanese Patent Application Laid-Open No. 9-239272, etc., have properties such as high activity at low temperature and low pressure and less inhibition by carbon monoxide and water as compared with iron-based catalysts. Have.

[0004] For this reason, a ruthenium catalyst supported on activated carbon, which is one of the ruthenium-based catalysts, has attracted attention as one of the most practically suitable catalysts for ammonia synthesis.

Conventionally, activated carbon-supported ruthenium catalysts have been produced by the following method. The activated carbon was heated under a hydrogen atmosphere to remove impurities (hereinafter referred to as hydrogen-treated activated carbon or HTAC), impregnated with an organic solvent in which a ruthenium complex such as acetylacetonatoruthenium was dissolved, and dried. Thereafter, the precursor is heated in a helium or nitrogen atmosphere to produce a precursor of a ruthenium catalyst supported on activated carbon.

Next, the precursor is added to an aqueous solution in which an alkali metal or alkaline earth metal salt as a promoter is dissolved, dried, and then activated in a hydrogen atmosphere to perform an activation treatment. A ruthenium catalyst has been obtained.

[0007]

Under the circumstances described above, in order to reduce the construction cost and operation cost of the ammonia synthesizing apparatus, it has been desired to develop an activated carbon-supported ruthenium catalyst with further improved ammonia synthesis activity. I have.

It is an object of the present invention to provide a method for producing a highly active ruthenium catalyst supported on activated carbon and a method for synthesizing ammonia using the catalyst.

[0009]

The above object is achieved by the following invention. The method for producing a catalyst according to the first invention comprises:
An alkali metal salt or an alkaline earth metal salt was added to a precursor of an activated carbon-supported ruthenium catalyst for ammonia synthesis in which ruthenium was supported on hydrogen-treated activated carbon, and then heated to 350 ° C. to 400 ° C. under a hydrogen atmosphere. After 10 ℃
It is characterized in that it is heated to a temperature of 500 ° C. to 600 ° C. at a rate of temperature rise of 60 ° C./h to perform an activation treatment.

[0010] The method for producing a catalyst according to the second aspect of the present invention comprises the steps of:
In the invention, the precursor of the activated carbon-supported ruthenium catalyst for ammonia synthesis is impregnated with a solvent obtained by dissolving a ruthenium complex in the hydrogen-treated activated carbon, and the hydrogen-treated activated carbon containing the ruthenium complex is placed in a nitrogen or inert gas atmosphere for 200 hours.
It is characterized by being heated to a temperature of from 450C to 450C.

[0011] The method for producing a catalyst according to a third aspect of the present invention comprises the steps of:
In the invention, the precursor of the activated carbon-supported ruthenium catalyst for ammonia synthesis is impregnated with a solvent obtained by dissolving ruthenium chloride in the hydrogen-treated activated carbon, and the hydrogen-treated activated carbon containing the ruthenium chloride is heated to 350 ° C. to 500 ° C. under a hydrogen atmosphere. It is characterized by being heated.

[0012] A fourth aspect of the present invention provides a method for synthesizing ammonia.
The present invention is characterized in that ammonia is synthesized by using an activated carbon-supported ruthenium catalyst for ammonia synthesis manufactured by any one of the first to third inventions.

The present inventors have been conducting research to develop a highly active ruthenium catalyst supported on activated carbon for ammonia synthesis. In the process, a salt of a promoter such as an alkali metal was added to a catalyst precursor. It has been found that the activity of the obtained catalyst varies greatly depending on the conditions of the activation treatment performed after the above. In particular, the hydrogenolysis of the alkali metal salt or alkaline earth metal salt added as a promoter is completed.
The rate of temperature rise from around 5 ° C. to the predetermined heating holding temperature has a very large effect. That is, by performing the heating in this temperature range at a gentle heating rate, an extremely highly active catalyst can be obtained.

In order to obtain a highly active catalyst, first, a catalyst obtained by adding a salt of a promoter to a precursor is heated to a temperature near the completion of hydrogenolysis of the salt of the promoter (365 ° C.), ie, 350 ° C.
C. to 400.degree. C., preferably 360.degree. During the heating period up to this temperature, water evaporation, ruthenium re-reduction, hydrogenolysis of the promoter salt, etc. occur, but the main reaction related to the construction of the active site, which greatly affects the catalytic function, does not occur. However, the heating does not necessarily have to be carried out slowly.

Then, the temperature is gradually increased at a heating rate of 10 ° C. to 60 ° C./h, preferably 20 ° C. to 40 ° C./h until the temperature reaches a predetermined heating holding temperature. The holding temperature after heating at a gradual heating rate is 500 ° C to 600 ° C, preferably 530 ° C to 570 ° C. By such a treatment operation, a highly active ruthenium catalyst carrying activated carbon can be obtained. The activation processing conditions are determined based on the results of experiments performed by the present inventors, and will be described later.

The mechanism by which a highly active catalyst can be obtained under the above-mentioned activation treatment conditions is considered to be as follows. In the activation treatment, the generation of methane due to the reaction between activated carbon and hydrogen by the catalytic action of ruthenium starts around a temperature entering a temperature region where the temperature must be increased slowly from 350 ° C. to 400 ° C., and from around 500 ° C. Methane production increases sharply. Then, it is considered that methane generation by the reaction between activated carbon and hydrogen plays an important role in enhancing the function of the catalyst. That is, by appropriately reacting the surface of the activated carbon as a carrier and releasing methane, the arrangement (dispersed state) of ruthenium supported on the activated carbon and the promoter is optimized, and ammonia synthesis activity is improved. it is conceivable that. And the degree of this methane production was different depending on the heating rate.

As described above, the activated carbon-supported ruthenium catalyst for ammonia synthesis can be obtained by adding an accelerator to a precursor obtained by supporting ruthenium on hydrotreated activated carbon, and then performing an activation treatment in a hydrogen atmosphere. . The precursor serving as the base is impregnated with a solvent obtained by dissolving a ruthenium compound in hydrogen-treated activated carbon, and is subjected to heat treatment.In the present invention, the precursor is used for producing the precursor. As the ruthenium source, ruthenium chloride can be selected in addition to the ruthenium complex. In terms of the price of both, for example, the price per unit amount of ruthenium chloride is less than 1/6 that of the conventionally used acetylacetonatoruthenium. For this reason, if ruthenium chloride can be used as a ruthenium source, the production cost of the catalyst will be greatly reduced.

Conventionally, when ruthenium chloride is used as a ruthenium source, chlorine remaining in the catalyst attracts electrons from ruthenium on the catalyst, so that even if an accelerator such as an alkali metal having a high electronegativity is added, It is believed that the catalyst activity cannot be increased. Therefore, when using ruthenium chloride as a ruthenium source, a method must be developed that can remove chlorine and disperse ruthenium on the catalyst. In this regard, the present inventors have found a method by which chlorine can be efficiently removed and ruthenium can be well dispersed on the catalyst. That is, by heating the hydrogen-treated activated carbon impregnated with ruthenium chloride in a hydrogen atmosphere and maintaining it at a predetermined temperature, chlorine is efficiently removed and ruthenium can be well dispersed on the catalyst.

When ruthenium chloride is used as the ruthenium source, the temperature and time for dechlorination of the hydrogen-treated activated carbon impregnated with ruthenium chloride are determined according to the temperature and time.
The activity of the final catalyst is significantly different. This is because during the temperature rise process during the dechlorination treatment, hydrogen chloride is generated and chlorine is removed in the initial stage, and when the temperature is further raised, methane is generated by the reaction of activated carbon and hydrogen, and ruthenium is formed on the catalyst. This is because they can be well dispersed. Dechlorination due to the production of hydrogen chloride starts around 200 ° C. and ends around 300 ° C. When the temperature is further increased, as described above, the generation of methane starts, and the amount of the generated methane rapidly increases from around 500 ° C. and becomes excessive. For this reason, in the present invention, the dechlorination treatment for producing the catalyst precursor is performed at 350 ° C to 500 ° C.
Do with. This temperature range is higher than the temperature at which the dechlorination reaction is completed, and lower than the temperature at which the rapid generation of methane at which the ruthenium particles on the catalyst agglomerates and enlarges occurs.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION A method for producing a ruthenium catalyst supported on activated carbon for ammonia synthesis according to the present invention is as follows.

1) Production method when the ruthenium source is a ruthenium complex Production of hydrogen-treated activated carbon Activated carbon is heated under a hydrogen atmosphere at 500 ° C. to 915 ° C., preferably at about 900 ° C., for 50 hours to 500 hours, preferably 90 hours. By heating to a certain degree, hydrogen-treated activated carbon from which impurities have been removed is obtained. When the heating temperature is 1000 ° C. or higher,
Since the graphitization of activated carbon proceeds and the properties of the carrier change, the heating temperature must be lower than 1000 ° C.

Impregnation of ruthenium Acetylacetonate ruthenium as a ruthenium source is dissolved in an aprotic polar organic solvent such as tetrahydrofuran, acetone or acetonitrile, and this solution is impregnated into the hydrogenated activated carbon produced by the above method.
The impregnated amount of acetylacetonate ruthenium is 0.5 to 10% by weight, preferably about 3% by weight in terms of ruthenium, based on activated carbon. Then, the solvent is distilled off under reduced pressure. This solvent distillation is performed at a temperature of 5 ° C to 120 ° C, preferably at room temperature. The pressure is from 10 ^{-3 to} 750 Torr, preferably 50 Torr.

Preparation of Catalyst Precursor The hydrogen-treated activated carbon impregnated with the ruthenium complex by the above-mentioned method and then dried is placed in a nitrogen or inert gas atmosphere at 200 ° C. to 450 ° C., preferably at about 400 ° C. for 1 hour. By heating for about 30 hours, preferably about 4 hours, a precursor of the activated carbon-supported ruthenium catalyst whose ruthenium source is a ruthenium complex is obtained.

Addition of Accelerator To the precursor produced by the above method, an aqueous solution of an alkali metal salt or an alkaline earth metal salt, which is a salt of the accelerator, is added, and the mixture is heated to 50 ° C. to 120 ° C. and dried. I do.

As the alkali metal, cesium, rubidium, potassium, sodium and the like can be used. Further, as the alkaline earth metal, barium, calcium and the like can be used. The salt to be added may be in the form of nitrate, acetate, formate, or the like. Of these, nitrate is preferred because it is most easily hydrocracked.

In the case of barium and calcium, the amount of the accelerator is 0.01 to 10 times the molar amount of ruthenium,
Preferably, the molar amount is about twice. In the case of cesium and rubidium, the molar amount is preferably 1 to 50 times, preferably about 20 times the amount of ruthenium. In the case of potassium and sodium, the molar amount is preferably 1 to 30 times, preferably about 15 times the molar amount of ruthenium.

Activation Treatment The precursor obtained by adding an accelerator to the precursor by the above method is
The temperature is increased from 350 ° C. to 400 ° C. by heating in a hydrogen atmosphere. Subsequently, 10 ° C. to 60 ° C./h, preferably 2 ° C.
Heat to 500 ° C to 600 ° C, preferably 530 ° C to 570 ° C at a heating rate of 0 ° C to 40 ° C / h.
Hold for about 20 hours, preferably about 5 hours. By this treatment, a highly active ruthenium catalyst carrying activated carbon for ammonia synthesis can be obtained.

The pressure during the activation process is 0.1 to 20.
It is good to be more than MPaG, preferably 0.2MPaG.

2) Production method when the ruthenium source is ruthenium chloride Production of hydrotreated activated carbon Same as in the case where the ruthenium source is a ruthenium complex.

Ruthenium impregnation Ruthenium chloride is dissolved in a strong polar solvent such as acetone, water, methanol, etc., and this solution is impregnated into the hydrotreated activated carbon produced by the above method. The impregnation amount of ruthenium chloride is 0.1 to 20 w
t%, preferably about 5 wt%. Then, the solvent is distilled off under reduced pressure. The solvent is distilled off at a temperature of 5 ° C to 120 ° C.
C., preferably at room temperature. Pressure is 10 ^{-3 to} 750 Torr
r, preferably at 50 Torr.

Preparation of Catalyst Precursor The hydrogen-treated activated carbon impregnated with ruthenium chloride according to the method described above and then dried was placed in a hydrogen atmosphere for 400 hours.
By heating at 6 to 60 hours, preferably about 12 hours at about 500 to about 500 ° C., preferably about 450 ° C., chlorine of ruthenium chloride is removed as hydrogen chloride. By this dechlorination treatment, a precursor of an activated carbon-supported ruthenium catalyst in which the ruthenium source is ruthenium chloride is obtained.

Addition of accelerator Same as when the ruthenium source is a ruthenium complex.

Activation Treatment By the same method as in the case where the ruthenium source is a ruthenium complex, a highly active ruthenium catalyst carrying activated carbon for ammonia synthesis can be obtained.

The activated carbon-supported ruthenium catalyst produced by the above method is charged into a reactor of an ammonia synthesis apparatus,
If ammonia synthesis is performed, very efficient ammonia synthesis can be performed. The reaction conditions at this time are preferably set as follows. Composition of reaction gas: molar ratio of hydrogen to nitrogen is 1: 3 to 4:
1, preferably 2.5: 1 or less Reaction temperature: 300 ° C to 500 ° C, preferably 350 ° C to
400 ° C. Reaction pressure: 0 to 30 MPaG, preferably 0.5 MPaG or more

[0035]

EXAMPLES (Example 1) (Production of ruthenium catalyst supporting activated carbon) A ruthenium complex was used as a ruthenium source to produce a ruthenium catalyst supporting activated carbon. A commercially available activated carbon was heated to 900 ° C. in a hydrogen atmosphere to obtain a hydrogen-treated activated carbon from which impurities were removed. The hydrogenated activated carbon was impregnated with tetrahydrofuran in which acetylacetonatoruthenium was dissolved, and the solvent was distilled off. Next, heat treatment was performed in a helium atmosphere to obtain a precursor of a ruthenium catalyst supporting activated carbon. An aqueous solution of ruthenium nitrate or barium nitrate as a salt of the accelerator was added to the precursor, and the precursor was dried. Then, a precursor obtained by adding a promoter to a precursor was heated to 365 ° C. in a hydrogen atmosphere, and then slowly heated to obtain a ruthenium catalyst carrying activated carbon for ammonia synthesis. At this time, the heating rate was 20 ° C. /
h to 600 ° C / h, heat treatment temperature 300 to 600 ° C
, And catalysts having different activation treatment conditions were prepared. At this time, methane generated under a certain condition was analyzed by a mass spectrometer, and the relative amount of methane generated under each condition using an arbitrary unit was compared.

(Measurement of Ammonia Synthesis Activity) The above catalyst was charged into a high pressure fixed bed flow reactor, and a mixed gas of hydrogen and nitrogen (H ₂ : N ₂ = 3: 1) was passed therethrough. ° C, reaction pressure at normal pressure or 1.0 MPaG, space velocity 1
The ammonia synthesis reaction was performed at 5000 to 18000. The ammonia synthesis activity was calculated from the decrease in the electric conductivity of the absorbing solution by absorbing the ammonia by blowing the gas after passing through the catalyst layer into dilute sulfuric acid.

(Experimental Results) FIG. 1 is a diagram showing the relationship between the activation treatment temperature and the ammonia synthesis activity. The catalyst used in this experiment was a catalyst produced by the above method, and the promoter was cesium. The catalyst activity greatly varies depending on the activation treatment temperature, and when the activation treatment temperature is 550 ° C., an extremely high value (about 5000 μmol / g / g) is obtained.
h) and reached the maximum value. As described above, when the catalyst is heated above a certain temperature, the activated carbon reacts with activated carbon and hydrogen to react with hydrogen to generate methane. It is considered that the disappearance plays an important role in enhancing the function of the catalyst. The value of the activity of the catalyst obtained when the activation treatment temperature was set to 550 ° C. (about 5000 μmol / g / h)
Is about 2.5 times the value obtained when a ruthenium catalyst supported on cerium oxide, which has been regarded as one of the most active ruthenium catalysts, is extremely high.

FIG. 2 is a graph showing the results of examining the relationship between the activation treatment temperature and the amount of methane produced for a precursor obtained by adding cesium nitrate to a precursor. As shown in FIG.
The methane starts to be generated by the reaction between activated carbon and hydrogen around the temperature range of over 400C to 400C. The amount of methane generated increases more at around 450 ° C. and sharply increases at around 500 ° C. And
By performing the activation treatment in a temperature range where the amount of methane production starts to rapidly increase, an extremely high catalytic activity as shown in FIG. 1 is obtained.

Table 1 shows the results of examining the effect of the rate of temperature increase during the activation treatment on the activity of the catalyst. As shown in Table 1, the activity of the obtained catalyst becomes higher as the heating rate becomes slower. Therefore, the temperature should be raised as slowly as possible. However, if the temperature is too slow, it takes a long time for the activation treatment. Therefore, it is considered appropriate to set the heating rate to about 10 ° C./h or more. Also, increasing the heating rate
Since the activity of the obtained catalyst is reduced, the heating rate is 60 ° C.
/ H or less.

[0040]

[Table 1]

Table 2 shows the relationship between the pressure during the activation treatment and the ammonia synthesis activity of the catalyst. As shown in Table 2, when the pressure during the activation treatment is increased, a catalyst having a high ammonia synthesis activity can be obtained.

[0042]

[Table 2]

Example 2 (Production of Ruthenium Catalyst Supported on Activated Carbon) Ruthenium chloride was used as a ruthenium source, and the ruthenium catalyst was supported on the hydrotreated activated carbon used in Example 1 to produce a ruthenium catalyst supported on activated carbon. Manufacturing method in Embodiment 2 and Embodiment 1
Are different in a step of impregnating the hydrogen-treated activated carbon with a ruthenium source and a step of dechlorination for producing a catalyst precursor.

The hydrogen-treated activated carbon used in Example 1 was impregnated with acetone in which ruthenium chloride was dissolved, and dried. Next, the precursor was heated and dechlorinated in a hydrogen stream for 12 hours to obtain a precursor of an activated carbon-supported ruthenium catalyst. Then, in the same manner as in Example 1, an aqueous solution of ruthenium nitrate or barium nitrate was added, followed by heating and activation in a hydrogen atmosphere to obtain a ruthenium catalyst carrying activated carbon for ammonia synthesis. At this time, the heat treatment temperature is set to 400 ° C to 50 ° C.
The treatment was performed at 0 ° C. to prepare catalysts having different activation treatment conditions.

(Measurement of Ammonia Synthesis Activity) The measurement was performed in the same manner and under the same conditions as in Example 1.

(Experimental Results) Table 3 and FIG. 3 show the relationship between the dechlorination temperature and the activity of the obtained catalyst when a catalyst precursor is obtained using ruthenium chloride as a ruthenium source.
However, the catalyst produced in this experiment had barium added as a promoter. As shown in this table and figure, the ammonia synthesis activity of the obtained catalyst was greatly affected by the dechlorination treatment temperature. The activity of the catalyst became maximum when the dechlorination treatment temperature was set to about 450 ° C.
Factors that may vary with changes in treatment temperature include the surface area of the catalyst, the size of the ruthenium particles on the catalyst, the amount of residual chlorine, the extent of loss of activated carbon, and the rate of each reaction that results in each. This is probably because the treatment corresponding to the sum of the effects of these factors becomes the highest in the treatment at 450 ° C. for about 12 hours.

[0047]

[Table 3]

Table 4 shows the relationship between the dechlorination temperature and the activity of the obtained catalyst when a catalyst precursor is obtained using ruthenium chloride as a ruthenium source. However, the catalyst produced in this experiment had cesium added as a promoter. As shown in this table, the ammonia synthesis activity of the obtained catalyst showed the same tendency as that of the barium-added catalyst shown in Table 1 and FIG. 3, and became maximum when the dechlorination treatment temperature was set to about 450 ° C.

[0049]

[Table 4]

Table 5 shows the relationship between the dechlorination time and the activity of the obtained catalyst when a catalyst precursor is obtained using ruthenium chloride as a ruthenium source. However, the catalyst produced in this experiment had barium added as a promoter. In this table, the dechlorination treatment temperature is 400 ° C.
In the case of the above, the highest ammonia synthesis activity was obtained when the dechlorination treatment time was 24 hours, and the dechlorination treatment temperature was 45 hours.
In the case of 0 ° C., the highest ammonia synthesis activity was obtained when the dechlorination treatment time was 12 hours. Thus, the activity of the resulting catalyst depends on the dechlorination time,
Although a high value is obtained when processing is performed for an appropriate time, the appropriate processing time further differs depending on the processing temperature.

[0051]

[Table 5]

Table 6 shows the results of comparing the ammonia synthesis activities of two types of catalysts having different ruthenium sources.
The catalysts compared were a catalyst made using ruthenium chloride as the ruthenium source and a catalyst made using the ruthenium complex. As shown in Table 6, the use of ruthenium chloride makes it possible to relatively easily increase the ruthenium content, which is difficult when using a ruthenium complex, and to produce a more active catalyst. About 6 times the activity was achieved.

[0053]

[Table 6]

[0054]

According to the present invention, an alkali metal salt or an alkaline earth metal salt is added to a precursor of a catalyst in which ruthenium is supported on hydrogen-treated activated carbon, and then the resultant is added under hydrogen atmosphere.
After raising the temperature to 0 ° C to 400 ° C, 10 ° C to 60 ° C / h
A method for producing an ammonia synthesis catalyst, characterized in that the catalyst is heated to 500 ° C. to 600 ° C. at a rate of temperature rise and activated.

According to the present invention, in the activation treatment of the catalyst precursor, an extremely high ammonia concentration is obtained by heating to a predetermined temperature at a predetermined heating rate under the activation processing conditions found by the present inventors. A catalyst having synthetic activity can be produced.

Further, according to the present invention, inexpensive ruthenium chloride can be used as a source of ruthenium to be supported on the hydrotreated activated carbon, so that the production cost of the catalyst is greatly reduced.

Further, according to the ammonia synthesis method of the present invention, since the above-mentioned highly active ammonia synthesis catalyst is used, a very high conversion rate of ammonia can be obtained. For this reason, since the recycle ratio of the raw material gas can be reduced, the size of the ammonia synthesizing apparatus is reduced and the construction cost is reduced, and the power required for recycling the unreacted gas and the energy required for heating and cooling are reduced. It can be significantly reduced.

When ammonia is synthesized using the catalyst produced according to the present invention, the ammonia synthesis reaction can be carried out at low temperature and low pressure, so that the energy consumption can be further reduced.

Further, when the catalyst produced according to the present invention is used, the ammonia gas synthesis reaction can be carried out at a low temperature and a low pressure by reducing the recycle ratio of the raw material gas. The device can be made compact. For this reason, it becomes possible to mount the reaction apparatus on a ship or the like, and it is possible to use the reaction apparatus for a new application that has not been used before.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the activation treatment temperature and the ammonia synthesis activity of a catalyst.

FIG. 2 is a diagram showing a relationship between an activation treatment temperature and a methane generation amount.

FIG. 3 is a graph showing the relationship between the dechlorination temperature and the ammonia synthesis activity of a catalyst.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masakazu Okubo 1-2-1 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 4G069 AA03 AA08 AA09 BA08A BA08B BA27C BB08C BB12C BC01A BC08A BC13B BC13C BC70A BC70B BC70C BD01C BD12C BE11C CB82 DA06 FA02 FA08 FB14 FB19 FB20 FB30 FC04 FC07

Claims (4)

[Claims] An alkali metal salt or an alkaline earth metal salt is added to a precursor of an activated carbon-supported ruthenium catalyst for ammonia synthesis in which ruthenium is supported on hydrotreated activated carbon,
Next, the temperature is raised to 350 ° C. to 400 ° C. in a hydrogen atmosphere, and then 500 ° C. to 6 ° C. at a rate of 10 ° C. to 60 ° C./h.
A method for producing an ammonia synthesis catalyst, comprising heating to 00 ° C. and performing an activation treatment. 2. A precursor of an activated carbon-supported ruthenium catalyst for ammonia synthesis is impregnated with a solvent obtained by dissolving a ruthenium complex in the hydrogen-treated activated carbon, and the hydrogen-treated activated carbon containing the ruthenium complex is subjected to a nitrogen or inert gas atmosphere for 200 hours. ° C
The method for producing an activated carbon-supported ruthenium catalyst for ammonia synthesis according to claim 1, wherein the catalyst is heated to -450 ° C. 3. A precursor of an activated carbon-supported ruthenium catalyst for ammonia synthesis is impregnated with a solvent obtained by dissolving ruthenium chloride in hydrogenated activated carbon, and the hydrogenated activated carbon containing ruthenium chloride is heated to 350 ° C. to 500 ° C. in a hydrogen atmosphere. The method for producing an activated carbon-supported ruthenium catalyst for ammonia synthesis according to claim 1, wherein the catalyst is heated to a maximum temperature. 4. An ammonia synthesis method, characterized in that ammonia is synthesized using a ruthenium catalyst supported on activated carbon for ammonia synthesis produced by the production method according to any one of claims 1 to 3.