JP7047575B2 - Methaneization catalyst and method for producing methane using it - Google Patents

Description

The present invention relates to a methaneization catalyst and a method for producing methane using the same, and more particularly to a CO ₂ occlusion reduction type methaneization catalyst and a method for producing methane using the same.

The methanation reaction using CO ₂ as a raw material has attracted attention from the viewpoint of reducing CO ₂ emissions in order to suppress global warming in recent years, and Ru, which is a precious metal, and Ni, which is a base metal element, use CO ₂ as a raw material. It is being investigated as a catalyst showing high activity in the carbon dioxide reaction.

However, when combustion exhaust gas or biogas is used as the raw material gas, these gases contain reaction-inhibiting components such as O ₂ in addition to CO ₂ , and the reaction-inhibiting components inhibit the reduction reaction of CO ₂ . , The production efficiency of methane was not always high enough. Therefore, in the conventional method for producing methane from CO ₂ , it is necessary to separate and recover CO ₂ from raw material gas such as combustion exhaust gas and biogas in advance and use it as a raw material. However, in order to separate and recover CO ₂ from raw material gas such as combustion exhaust gas and biogas in advance, heat is required, so it is necessary to input energy from the outside. Further, the CO ₂ separation / recovery device has a problem that it is complicated and large in size.

On the other hand, International Publication No. 2016/007825 (Patent Document 1) describes a catalyst in which Ru having methanation catalyst performance and CaO having CO ₂ occlusion performance are carried on a carrier such as alumina, and CO is described in this catalyst. It is described that after occluding ₂ , H ₂ is supplied to reduce CO ₂ to produce methane. Further, Japanese Patent Application Laid-Open No. 2000-254508 (Patent Document 2) describes carbon dioxide methaneization in which Ni and / or Co is supported on a tetragonal zirconia-based carrier stabilized with a stabilizing element such as Ca. The catalyst is disclosed. However, even with these catalysts, the efficiency of producing methane from CO ₂ was not always high.

International Release 2016/007825 Japanese Unexamined Patent Publication No. 2000-254508

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to efficiently produce methane from CO ₂ even when O ₂ is contained in the raw material gas containing CO ₂ . It is an object of the present invention to provide a suitable methanation catalyst and a method for producing methane using the same.

As a result of diligent research to achieve the above object, the present inventors have applied a methaneation catalyst in which a CO ₂ storage component such as an alkali metal compound and a methaneization catalyst component such as Ru are supported on an oxide carrier. By supporting a predetermined amount of Si, the ability to generate methane from CO ₂ is improved, and even when O ₂ is contained in the raw material gas containing CO ₂ , methane can be efficiently produced from CO ₂ . We have found that we can do this, and have completed the present invention.

That is, the methanation catalyst of the present invention comprises an oxide carrier other than silica.
At least one CO ₂ storage component selected from the group consisting of an alkali metal compound and an alkaline earth metal compound supported on the oxide carrier, and
At least one methanation catalyst component selected from the group consisting of Ru, Ni and Co, which is supported on the oxide carrier, and
Si supported on the oxide carrier and
Equipped with
The amount of Si supported on 100 parts by mass of the oxide carrier is 1.0 to 12.0 parts by mass.
It is characterized in that the molar ratio (Si / methanation catalyst component) of Si to the methanation catalyst component is 0.5 to 7.5.

In the methanation catalyst of the present invention, the oxide carrier is preferably a porous carrier, and the oxide carrier is at least one selected from the group consisting of an alumina carrier and a titania carrier. preferable.

The method for producing methane of the present invention is characterized in that CO ₂ and a reducing gas are brought into contact with the methaneization catalyst of the present invention. In such a method for producing methane of the present invention, the methaneation catalyst is brought into contact with a raw material gas containing CO ₂ and O ₂ to occlude CO ₂ in the methaneization catalyst, and then the methaneization catalyst is stored. It is preferable to bring the reducing gas into contact with the water.

According to the present invention, even when O ₂ is contained in the raw material gas containing CO ₂ , methane can be efficiently produced from CO ₂ .

It is a graph which shows the relationship between the amount of Si supported with respect to 100 parts by mass of an oxide carrier, 1 g of a methaneization catalyst, and the amount of methane produced per cycle. It is a graph which shows the relationship between the Si / Ru molar ratio, 1 g of a methaneization catalyst, and the amount of methane produced per cycle. 6 is a graph showing 1 g of the catalyst of the methaneization catalyst obtained in Example 9 and Comparative Examples 1 and 5 and the amount of methane produced per cycle.

Hereinafter, the present invention will be described in detail according to the preferred embodiment thereof.

[Methanation catalyst]
First, the methanation catalyst of the present invention will be described. The methanation catalyst of the present invention is at least one CO ₂ storage component selected from the group consisting of an oxide carrier other than silica and an alkali metal compound and an alkaline earth metal compound supported on the oxide carrier. Carbon dioxide comprising at least one methanation catalyst component selected from the group consisting of Ru, Ni and Co supported on the oxide carrier, and Si supported on the oxide carrier. (CO ₂ ) It is a storage reduction type methanation catalyst. Further, in the methaneization catalyst of the present invention, the amount of Si supported on 100 parts by mass of the oxide carrier is 1.0 to 12.0 parts by mass, and the molar ratio of Si to the methaneization catalyst component (Si / methane). The chemical catalyst component) is 0.5 to 7.5. Since the methaneization catalyst of the present invention has both an occlusion ability of CO ₂ and a methane production ability (reduction ability of CO ₂ ), a raw material gas containing CO ₂ (particularly, a raw material containing CO ₂ and O ₂ ). CO ₂ can be selectively occluded in the methaneization catalyst from the gas), and the reaction between the occluded CO ₂ and the reducing gas can be promoted, so that methane can be efficiently produced. ..

The oxide carrier used for the methanation catalyst of the present invention is not particularly limited as long as it is an oxide carrier other than silica, but from the viewpoint of increasing the activity of the methanation catalyst, an alumina carrier, a titania carrier, a zirconia carrier, etc. A ceria carrier and a magnesia carrier are preferable, an alumina carrier and a titania carrier are more preferable, and an alumina carrier is particularly preferable. These oxide carriers may be used alone or in combination of two or more. Further, such an oxide carrier is preferably a porous carrier from the viewpoint of realizing a high reaction rate due to the good diffusivity of the gas component and improving the CO ₂ occlusion performance and the methane production efficiency.

The average particle size of such an oxide carrier is not particularly limited, but is preferably 0.05 to 200 μm, more preferably 0.1 to 100 μm, and particularly preferably 0.2 to 50 μm. The specific surface area is also not particularly limited, but is preferably 15 to 2000 m ² / g, more preferably 20 to 1500 m ² / g, and particularly preferably 30 to 1200 m ² / g. The average particle size of the oxide carrier can be measured by, for example, a dynamic light scattering method, a small-angle X-ray scattering method, a laser diffraction method, or the like, and the specific surface area can be measured by, for example, a gas adsorption method or an air permeation method. It can be measured by law or the like.

In the methanation catalyst of the present invention, a CO ₂ occlusion component is supported on such an oxide carrier. In the methaneization catalyst of the present invention, CO ₂ is selectively occluded by the CO ₂ occlusal component, and the occluded CO ₂ and the reducing gas are reacted in the presence of the methaneization catalyst component described later. Methane can be efficiently produced from CO ₂ . In particular, when the raw material gas contains a reaction-inhibiting component such as O ₂ , the reaction-inhibiting component is removed from the raw material gas by occluding CO ₂ , so that the reduction reaction of CO ₂ is less likely to be inhibited. It becomes possible to produce methane more efficiently.

Examples of the CO ₂ occlusion component include alkali metal compounds and alkaline earth metal compounds. Examples of the alkali metal compound include Li, Na, K, Rb and Cs, and examples of the alkaline earth metal compound include Mg, Ca, Sr and Ba. These CO ₂ occlusion components may be used alone or in combination of two or more.

The amount of such CO ₂ occlusion component supported is preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass, and particularly preferably 1.5 to 15 parts by mass with respect to 100 parts by mass of the oxide carrier. preferable. When the amount of the CO ₂ storage component carried is less than the above lower limit, the CO ₂ storage performance of the methaneization catalyst is lowered and CO ₂ cannot be efficiently reduced, so that the production efficiency of methane from CO ₂ tends to be lowered. On the other hand, if the upper limit is exceeded, the CO ₂ storage component is coarsened, the pores of the oxide carrier are clogged, and the like, so that the CO ₂ storage performance and the methane production efficiency tend to decrease.

Further, in the methanation catalyst of the present invention, at least one kind of methanation catalyst component selected from the group consisting of Ru, Ni and Co is supported on the oxide carrier. The amount of such a methanation catalyst component supported is preferably 0.5 to 50 parts by mass, more preferably 1 to 40 parts by mass, and particularly preferably 2 to 30 parts by mass with respect to 100 parts by mass of the oxide carrier. When the amount of the methaneation catalyst component supported is less than the lower limit, the reduction reaction of CO ₂ is not sufficiently promoted, and the efficiency of producing methane from CO ₂ tends to decrease. On the other hand, when the upper limit is exceeded, methane is produced. The CO ₂ storage performance and the methane production efficiency tend to decrease due to the coarsening of the chemical catalyst component and the clogging of the pores of the oxide carrier.

Further, in the methanation catalyst of the present invention, Si is supported on the oxide carrier. By supporting Si, the reducing power of the methanogenesis catalyst component is improved, and the rate of methane production from CO ₂ is increased ₍ that is, the ability to generate methane from CO ₂ is improved). It can be manufactured efficiently. In the methanation catalyst of the present invention, the amount of Si supported is required to be 1.0 to 12.0 parts by mass with respect to 100 parts by mass of the oxide carrier. When the amount of supported Si is less than the above lower limit, the effect of supporting Si is not sufficiently obtained, and the reducing power of the methaneization catalyst component is not sufficiently improved, so that the efficiency of producing methane from CO ₂ is lowered. On the other hand, if the amount of supported Si exceeds the upper limit, coarsening of Si, blockage of pores of the oxide carrier, and the like occur, so that the efficiency of producing methane from CO ₂ decreases. Further, from the viewpoint that the effect of supporting Si is sufficiently obtained and the efficiency of producing methane from CO ₂ is further improved, the amount of Si supported on 100 parts by mass of the oxide carrier is 2.0 to 10.0 mass by mass. Parts are preferable, 3.0 to 9.0 parts by mass are more preferable, and 4.0 to 8.0 parts by mass are particularly preferable.

Further, in the methanation catalyst of the present invention, the molar ratio (Si / methanation catalyst component) of Si to the methanation catalyst component needs to be 0.5 to 7.5. When the Si / methanation catalyst component is less than the above lower limit, the effect of supporting Si is not sufficiently obtained, and the reducing power of the methanation catalyst component is not sufficiently improved, so that the production efficiency of methane from CO ₂ is lowered. On the other hand, when the Si / methanation catalyst component exceeds the upper limit, the CO ₂ occlusion component and the methanation catalyst component are covered with Si, so that the production efficiency of methane from CO ₂ is lowered. Further, from the viewpoint that the supporting effect of Si can be sufficiently obtained and the production efficiency of methane from CO ₂ is further improved, the Si / methaneization catalyst component is preferably 0.5 to 7.0, preferably 1.5. ~ 6.0 is more preferable, and 2.0 to 5.5 is particularly preferable.

[Manufacturing method of methanation catalyst]
The methanation catalyst of the present invention can be produced, for example, by the following method. That is, first, a CO ₂ storage component precursor is attached to an oxide carrier other than silica so that a predetermined amount of the CO ₂ storage component is supported, and the CO 2 storage component precursor is dried and fired. As a result, a predetermined amount of CO ₂ occlusion component is supported on the oxide carrier. Next, a Si precursor is attached to the oxide carrier on which the CO ₂ occlusion component is supported so that a predetermined amount of Si is supported, and the Si precursor is dried and fired. As a result, a predetermined amount of Si is supported on the oxide carrier. Next, the methaneization catalyst component precursor is attached to the oxide carrier supported by the CO ₂ occlusion component and Si so that a predetermined amount of the methaneation catalyst component is supported, and this is dried and calcined. As a result, the methaneization catalyst of the present invention is obtained in which a predetermined amount of the methanation catalyst component is supported on the oxide carrier and a predetermined amount of the CO ₂ storage component, the methanation catalyst component and Si are carried on the oxide carrier.

Examples of the CO ₂ storage component precursor include salts of alkali metals such as Li, Na, K, Rb and Cs (for example, acetates, nitrates and carbonates), and alkaline earths such as Mg, Ca, Sr and Ba. Examples include metal salts (eg, acetates, nitrates).

Examples of the Si precursor include alkoxysilanes such as tetramethyl orthosilicate and tetraethyl orthosilicate, Si-containing water-soluble compounds such as sodium silicate, and silica colloids.

Examples of the methanation catalyst component precursor include ruthenium compounds such as ruthenium nitrosyl nitrate, ruthenium nitrate, ruthenium chloride and ruthenium carbonyl, nickel salts such as nickel nitrate and nickel acetate, and cobalt salts such as cobalt nitrate and cobalt acetate. Be done.

The method for adhering the CO ₂ occlusion component precursor, Si precursor, and methanation catalyst component precursor to the oxide carrier is not particularly limited, but the precursor is used on the oxide carrier from the viewpoint of simple operation. A method (impregnation method) of impregnating the containing solution and then removing the solvent by drying or the like is preferable.

The drying temperature of the oxide carrier to which the precursor is attached is not particularly limited, but is preferably 40 to 250 ° C, more preferably 50 to 200 ° C, for example. The drying time is also not particularly limited, but is preferably 1 to 48 hours, more preferably 3 to 24 hours, for example.

The firing temperature of the oxide carrier after drying is not particularly limited, but is preferably 300 to 1000 ° C, more preferably 500 to 800 ° C, for example. The firing time is also not particularly limited, but is preferably 1 to 24 hours, more preferably 3 to 12 hours, for example.

[Methane production method]
The method for producing methane of the present invention is a method in which CO ₂ and a reducing gas are brought into contact with the methaneization catalyst of the present invention to reduce CO ₂ to obtain methane. In particular, in the method for producing methane of the present invention, since the methaneization catalyst of the present invention can selectively occlude CO ₂ , a gas containing CO ₂ and a reaction-inhibiting component such as O ₂ is used as a raw material gas. It is effective for. That is, a raw material gas containing CO ₂ and a reaction-inhibiting component such as O ₂ is brought into contact with the methaneization catalyst of the present invention to occlude CO ₂ in the methaneation catalyst, and then the reducing gas is stored in the methaneation catalyst. By contacting with methane, the occluded CO ₂ is reduced and methane can be obtained.

The CO ₂ concentration in the raw material gas is not particularly limited, but is preferably 0.1 to 20 vol%, preferably 0.2 to 20 vol%, from the viewpoint of improving the CO ₂ storage efficiency and enabling long-term CO ₂ storage. 15 vol% is more preferable. When O ₂ is contained in the raw material gas, the O ₂ concentration is preferably 20 vol% or less, more preferably 10 vol% or less, from the viewpoint of suppressing the oxidation of the methanation catalyst component.

The reducing gas is not particularly limited as long as it reduces CO ₂ to produce methane, but pure H ₂ gas and H ₂ -containing gas are preferable. The other gas contained in the H ₂ -containing gas is not particularly limited as long as it does not inhibit the CO ₂ reduction reaction, but an inert gas such as He gas or N ₂ gas is preferable. The H ₂ concentration in the H ₂ -containing gas is preferably 5 vol% or more, more preferably 10 vol% or more, from the viewpoint of shortening the reduction time and producing high-concentration methane.

The temperature at which CO ₂ is occluded in the methanation catalyst is preferably 50 to 500 ° C, more preferably 75 to 400 ° C from the viewpoint of suppressing the condensation of water on the catalyst and the oxidation of the methanation catalyst component. The temperature at which the occluded CO ₂ reacts with the reducing gas is 150 from the viewpoint of improving the methane production rate, suppressing CO ₂ desorption during reduction, and obtaining high methane production efficiency. It is preferably to 500 ° C, more preferably 200 to 400 ° C.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

(Example 1)
First, calcium acetate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in ion-exchanged water, and alumina powder (“TN4” manufactured by Nikki Universal Co., Ltd., specific surface area: 150 m ² /) was used as an oxide carrier in the obtained calcium acetate aqueous solution. g, average particle size: 1 μm) was added and immersed, and calcium acetate was attached to the alumina powder. The alumina powder to which calcium acetate was attached was dried at 110 ° C. for 12 hours and then fired in air at 500 ° C. for 5 hours to obtain a CaO-supported alumina powder (hereinafter referred to as “CaO-supported alumina powder”). .. The concentration of the calcium acetate aqueous solution and the amount of the alumina powder added were adjusted so that the amount of CaO supported on 100 parts by mass of the alumina powder was 8.0 parts by mass based on Ca.

Next, tetraethyl orthosilicate (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was dissolved in ethanol (manufactured by Wako Pure Chemical Industries, Ltd.), and the CaO-supported alumina powder was added to the obtained ethanol solution of tetraethyl orthosilicate and immersed. , Tetraethyl orthosilicate was attached to the CaO-supported alumina powder. The CaO-supported alumina powder to which tetraethyl orthosilicate is attached is dried at 60 ° C. for 8 hours and then calcined in air at 600 ° C. for 5 hours to carry the alumina powder supported by Si and CaO (hereinafter, “(Si + CaO) -supported alumina). "Powder") was obtained. The concentration of the ethanol solution of tetraethyl orthosilicate and the amount of CaO-supported alumina powder added were adjusted so that the amount of Si supported on 100 parts by mass of the alumina powder was 2.0 parts by mass.

Next, the (Si + CaO) -supported alumina powder was added to a ruthenium nitrosyl nitrate solution (manufactured by Wako Pure Chemical Industries, Ltd., Ru concentration: 1.5% by mass) and immersed, and the ruthenium nitrosyl nitrate was immersed in the (Si + CaO) -supported alumina powder. Was attached. The (Si + CaO) -supported alumina powder on which nitrosyl ruthenium nitrate was attached was dried at 110 ° C. for 12 hours and then calcined in air at 400 ° C. for 5 hours to carry the alumina powder on which Ru, Si and CaO were supported (hereinafter, "(. A methanation catalyst composed of "Ru + Si + CaO) supported alumina powder") was obtained. The amount of the (Si + CaO) -supported alumina powder added was adjusted so that the amount of Ru supported on 100 parts by mass of the alumina powder was 5.3 parts by mass. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si and Ru (Si / Ru) of the obtained methanation catalyst.

(Example 2)
A methanation catalyst composed of (Ru + Si + CaO) -supported alumina powder was obtained in the same manner as in Example 1 except that the amount of Si supported on 100 parts by mass of the alumina powder was changed to 5 parts by mass. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si to Ru (Si / Ru) for this methanation catalyst.

(Example 3)
A methanation catalyst composed of (Ru + Si + CaO) -supported alumina powder was obtained in the same manner as in Example 1 except that the amount of Si supported on 100 parts by mass of the alumina powder was changed to 7.5 parts by mass. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si to Ru (Si / Ru) for this methanation catalyst.

(Example 4)
A methanation catalyst composed of (Ru + Si + CaO) -supported alumina powder was obtained in the same manner as in Example 1 except that the amount of Si supported on 100 parts by mass of the alumina powder was changed to 10 parts by mass. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si to Ru (Si / Ru) for this methanation catalyst.

(Example 5)
Examples except that each component was supported so that the ratio of CaO to the total obtained methanation catalyst was 7.0% by mass based on Ca and the molar ratio of Si to Ru (Si / Ru) was 1.0. In the same manner as in No. 1, a methanation catalyst composed of (Ru + Si + CaO) -supported alumina powder was obtained. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si to Ru (Si / Ru) for this methanation catalyst.

(Example 6)
A methanation catalyst composed of (Ru + Si + CaO) -supported alumina powder was obtained in the same manner as in Example 5 except that the molar ratio (Si / Ru) of Si and Ru was changed to 2.5. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si to Ru (Si / Ru) for this methanation catalyst.

(Example 7)
A methanation catalyst composed of (Ru + Si + CaO) -supported alumina powder was obtained in the same manner as in Example 5 except that the molar ratio (Si / Ru) of Si and Ru was changed to 5.0. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si to Ru (Si / Ru) for this methanation catalyst.

(Example 8)
A methanation catalyst composed of (Ru + Si + CaO) -supported alumina powder was obtained in the same manner as in Example 5 except that the molar ratio (Si / Ru) of Si and Ru was changed to 7.0. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si to Ru (Si / Ru) for this methanation catalyst.

(Example 9)
With Ru in the same manner as in Example 1 except that titanium powder (“AEROXIDE TiO ₂ P25” manufactured by Nippon Aerodil Co., Ltd., specific surface area: 50 m ² / g, average particle size: 0.5 μm) was used as the oxide carrier. A methanation catalyst composed of a titania powder supported by Si and CaO (hereinafter referred to as “(Ru + Si + CaO) supported titania powder”) was obtained. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si to Ru (Si / Ru) for this methanation catalyst.

(Comparative Example 1)
A methanation catalyst composed of an alumina powder supported by Ru and CaO (hereinafter referred to as “(Ru + CaO) supported alumina powder”) was obtained in the same manner as in Example 1 except that Si was not supported. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si to Ru (Si / Ru) for this methanation catalyst.

(Comparative Example 2)
A methanation catalyst composed of (Ru + Si + CaO) -supported alumina powder was obtained in the same manner as in Example 1 except that the amount of Si supported on 100 parts by mass of the alumina powder was changed to 12.5 parts by mass. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si to Ru (Si / Ru) for this methanation catalyst.

(Comparative Example 3)
A methanation catalyst composed of (Ru + Si + CaO) -supported alumina powder was obtained in the same manner as in Example 1 except that the amount of Si supported on 100 parts by mass of the alumina powder was changed to 15.0 parts by mass. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si to Ru (Si / Ru) for this methanation catalyst.

(Comparative Example 4)
A methanation catalyst composed of (Ru + Si + CaO) -supported alumina powder was obtained in the same manner as in Example 5 except that the molar ratio (Si / Ru) of Si and Ru was changed to 9.0. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si to Ru (Si / Ru) for this methanation catalyst.

(Comparative Example 5)
A methanation catalyst composed of a titania powder supported by Ru and CaO (hereinafter referred to as “(Ru + CaO) supported titania powder”) was obtained in the same manner as in Example 9 except that Si was not supported. Table 1 shows the amount of each component supported on 100 parts by mass of the oxide carrier, the ratio of each component to the entire catalyst, and the molar ratio of Si to Ru (Si / Ru) for this methanation catalyst.

<Catalyst performance evaluation>
Each methanation catalyst obtained in Examples and Comparative Examples was formed into pellets having a particle size of 0.5 to 1.0 mm by a cold isotropic press molding method (CIP). 0.5 g of this pellet-shaped methanation catalyst was filled in a quartz reaction tube, and this was mounted on a catalyst evaluation device (“TP-5000” manufactured by Henmi Measuring Scale Co., Ltd.). He (100%) purge gas was circulated through this methanation catalyst at a flow rate of 20 ml / min for 180 seconds at a temperature of 320 ° C. [Step 1], and then CO ₂ (10%) + O at a temperature of 320 ° C. ₂ (3%) + He (remaining) of the raw material gas was circulated at a flow rate of 20 ml / min for 420 seconds, and CO ₂ was occluded in the methanation catalyst [Step 2]. Next, a He (100%) purge gas was circulated through the methaneization catalyst occluded by CO ₂ at a flow rate of 20 ml / min for 180 seconds at a temperature of 320 ° C. [Step 3], and then at a temperature of 320 ° C. A reducing gas of H ₂ (100%) was circulated at a flow rate of 10.5 ml / min for 140 seconds to reduce the occluded CO ₂ and generate methane [step 4]. Steps 1 to 4 are repeated, and when the steady state is reached, the methane concentration in the catalyst exhaust gas is measured with a mass analyzer, and the amount of methane produced during steps 1 to 4 (1 cycle) is measured. The amount of methane produced per 1 g of catalyst and one cycle was calculated. The results are shown in Table 1.

Based on the results shown in Table 1, 1 g of the catalyst of the methaneization catalyst obtained in Examples 1 to 4 and Comparative Examples 1 to 3 and the amount of methane produced per cycle were supported on 100 parts by mass of the oxide carrier with Si. Plotted against quantity. The results are shown in FIG. As shown in FIG. 1, it was confirmed that the amount of methane produced increased by supporting Si in the range of 1.0 to 12.0 parts by mass of Si supported on 100 parts by mass of the alumina carrier. On the other hand, it was found that when the amount of Si carried exceeds 12.0 parts by mass, the amount of methane produced decreases as compared with the case where Si is not supported (Comparative Example 1). From this result, it was confirmed that the methane-producing ability was improved by supporting a predetermined amount of Si on the alumina carrier.

Further, based on the results shown in Table 1, 1 g of the catalyst of the methaneization catalyst obtained in Examples 5 to 8 and Comparative Examples 1 and 4 and the amount of methane produced per cycle were calculated with respect to the Si / Ru molar ratio. And plotted. The results are shown in FIG. As shown in FIG. 2, it was confirmed that the amount of methane produced increased by supporting Si in the range of Si / Ru molar ratio of 0.5 to 7.5. On the other hand, it was found that when the Si / Ru molar ratio exceeds 7.5, the amount of methane produced decreases as compared with the case where Si is not supported (Comparative Example 1). From this result, it was confirmed that the methane-producing ability was improved by supporting Si and Ru in a predetermined amount of Si / Ru molar ratio on the alumina carrier.

Further, FIG. 3 is a graph showing 1 g of the catalyst of the methaneization catalyst obtained in Examples 9 and Comparative Examples 1 and 5 and the amount of methane produced per cycle, which were prepared based on the results shown in Table 1. be. As shown in FIG. 3, when titania powder is used as the oxide carrier and Si is supported (Example 9), alumina powder (Comparative Example 1) or titania powder (Comparative Example 5) is used as the oxide carrier. It was confirmed that the amount of methane produced was increased compared to the case where Si was not supported, and that the effect of improving the methane production ability by supporting Si can be obtained even when a titania carrier is used as the oxide carrier. Was done.

As described above, according to the present invention, it is possible to obtain a methaneization catalyst having a CO ₂ occlusion ability and an excellent methane production ability from CO ₂ . Therefore, since the method for producing methane of the present invention uses such the methaneization catalyst of the present invention, even when O ₂ is contained in the raw material gas containing CO ₂ , CO ₂ is produced from the raw material gas. Is useful as a method that can selectively occlude methane and efficiently produce methane from CO ₂ .

Claims (5)

With oxide carriers other than silica,
At least one CO ₂ storage component selected from the group consisting of an alkali metal compound and an alkaline earth metal compound supported on the oxide carrier, and
At least one methanation catalyst component selected from the group consisting of Ru, Ni and Co, which is supported on the oxide carrier, and
Si supported on the oxide carrier and
Equipped with
The amount of Si supported on 100 parts by mass of the oxide carrier is 1.0 to 12.0 parts by mass.
A methanation catalyst characterized in that the molar ratio (Si / methanation catalyst component) of Si to the methanation catalyst component is 0.5 to 7.5. The methanation catalyst according to claim 1, wherein the oxide carrier is a porous carrier. The methanation catalyst according to claim 1 or 2, wherein the oxide carrier is at least one selected from the group consisting of an alumina carrier and a titania carrier. A method for producing methane, which comprises contacting CO ₂ with a reducing gas with the methaneization catalyst according to any one of claims 1 to 3. The claim is characterized in that the raw material gas containing CO ₂ and O ₂ is brought into contact with the methaneization catalyst to occlude CO ₂ in the methaneization catalyst, and then the reducing gas is brought into contact with the methaneization catalyst. Item 4. The method for producing methane according to Item 4.

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