JP4994686B2 - Carbon monoxide methanation catalyst and carbon monoxide methanation method using the catalyst - Google Patents

Description

  The present invention relates to a catalyst for removing carbon monoxide in a hydrogen-containing gas and a method for removing carbon monoxide using the catalyst. More specifically, the present invention relates to a carbon monoxide removal catalyst that exhibits high activity at a low reaction temperature, high safety, excellent selectivity and long life, and a method for removing carbon monoxide using the catalyst.

In recent years, power generation by fuel cells has been attracting attention because of its low pollution and low energy loss, and research and development for practical use is being promoted.
Various types of fuel cells are known, depending on the type of fuel and electrolyte, operating temperature, etc. Among them, hydrogen-oxygen using hydrogen as a reducing agent (active material) and oxygen or air or the like as an oxidizing agent. The development of fuel cells (low temperature operation type fuel cells) is most advanced.

  There are various types of hydrogen-oxygen fuel cells depending on the type of electrolyte, the type of electrodes, etc., and typical examples include phosphoric acid fuel cells and solid polymer fuel cells. In such fuel cells, platinum catalysts are often used for electrodes. However, platinum used in the electrode is easily poisoned by carbon monoxide (hereinafter also referred to as CO). Therefore, if the fuel contains more than a certain level of CO, the power generation performance may be reduced or depending on the concentration. There is a serious problem that power generation becomes impossible.

The deterioration of the activity of the catalyst due to the CO poisoning is remarkable especially at low temperatures, and this problem becomes particularly serious in the case of a low temperature operation type fuel cell.
Therefore, pure hydrogen is preferable as a fuel for a fuel cell using such a platinum-based electrode catalyst. However, from a practical point of view, it is inexpensive and has excellent storage properties or is already equipped with a public supply system. Fuel, for example, methane, natural gas (LNG), petroleum gas (LPG) such as propane, butane, various hydrocarbon fuels such as naphtha, gasoline, kerosene, light oil, alcohol fuel such as methanol, city gas, It has become common to use hydrogen-containing gas obtained by steam reforming of other fuels for hydrogen production or the like, and fuel cell power generation systems incorporating such reforming equipment are being promoted. However, since these reformed gases generally contain a considerable concentration of CO in addition to hydrogen, this CO is converted into a harmless to the platinum-based electrode catalyst, and the CO concentration in the fuel is reduced. There is a strong demand for the development of technologies that can be used. For example, in a polymer electrolyte fuel cell, it is desirable to reduce the CO concentration to a low concentration of usually 100 ppm by volume or less, preferably 50 ppm by volume or less, more preferably 10 ppm by volume or less.

  In order to solve the above problem, as one of means for reducing the concentration of CO in the fuel gas (hydrogen-containing gas in the reformed gas), a shift reaction represented by the following formula (1) (water gas shift) A technique using reaction) has been proposed.

_{CO + H 2 O = CO 2} + H 2 (1)
However, in the reaction using only this shift reaction, there is a limit to the reduction of the CO concentration due to restrictions on chemical equilibrium, and it is generally difficult to reduce the CO concentration to 1% or less. Therefore, as a means for reducing the CO concentration to a lower concentration, a method has been proposed in which oxygen or an oxygen-containing gas (air or the like) is introduced into the reformed gas and CO is converted to CO ₂ . However, in this case, since a large amount of hydrogen is present in the reformed gas, hydrogen is also oxidized when attempting to oxidize CO, resulting in loss of hydrogen and insufficient removal of CO.

Recently, a method of converting CO to methane by methanation with hydrogen (hereinafter also referred to as methanation) has been reviewed. For example, in JP-A-3-93602 (Patent Document 1) and JP-A-11-86892 (Patent Document 2), a catalyst in which Ru is supported on a γ-alumina carrier (Ru / γ-alumina catalyst), A method of contacting hydrogen gas containing CO is disclosed. However, if the hydrogen gas contains carbon dioxide (CO ₂ ),
Carbon dioxide methanation, which is a side reaction, also occurs and hydrogen is consumed, which is undesirable. Therefore, it is desired to develop a catalyst having high activity of CO, which is the main reaction, and high selectivity (low carbon dioxide methanation reaction).

In order to solve the above problems, a catalyst in which a Ru compound and an alkali metal compound and / or an alkaline earth metal compound are supported on an inorganic oxide carrier has been proposed (see JP 2002-068707 A and Patent Document 3). .
Japanese Patent Laid-Open No. 3-93602 JP-A-11-86892 JP 2002-068707 A

However, the above-mentioned conventional catalysts, particularly low temperature operation type fuel cell electrode catalysts, have problems such as insufficient activity and sometimes a rapid increase in reaction temperature due to runaway reaction.
For this reason, even when the reaction temperature is low, the present invention has high selectivity and activity for the methanation reaction of carbon monoxide, which is the main reaction, and can effectively remove carbon monoxide in the hydrogen-containing gas. It would be desirable to provide a catalyst and removal method.

  For this reason, as a result of intensive studies by the inventors, in a catalyst having a multilayer structure, the reaction temperature is low by arranging a catalyst layer having excellent low-temperature activity in the outer layer and a catalyst layer having lower activity than the outer layer in the inner layer. Even in such cases, the present invention was completed by finding that it showed high activity, and that the reaction temperature could be easily adjusted without problems such as a rapid increase in the reaction temperature.

The configuration of the present invention is as follows.
[1] A catalyst for carbon monoxide methanation that has a multilayer structure of two or more layers, and the highest carbon monoxide methanation active temperature increases in order from the outer layer to the inner layer.
[2] The catalyst for carbon monoxide methanation in which the ratio of the outermost layer in the catalyst is in the range of 5 to 70% by weight.
[3] The outermost layer is NiO, CoO, Co ₃ O ₄ , ZrO ₂ , CeO ₂ , Al ₂ O ₃ , TiO ₂ , SiO ₂
One or more kinds of metals selected from Group 4B, Group 6A, Group 7A and Group 8 are supported on one or more kinds of oxides or composite oxide carriers selected from:
The outermost layer (second layer) is formed by supporting or complexing one or more metals selected from Group 4B, Group 6A, Group 7A and Group 8 on a metal oxide support [1] or [2] Catalyst for carbon monoxide methanation.
[4] The group 4B metal is Sn, the group 6A metal is Mo, W, and the group 7A metal is R.
The catalyst for carbon monoxide methanation according to any one of [1] to [3], which is e and the group 8 metal is Ru, Pt, Pd, Rh, Ir, Ni, Fe, and Co.
[5] The catalyst for carbon monoxide methanation according to any one of [1] to [4], wherein the metal contained in the outermost layer is one or more metals selected from Group 8.
[6] The catalyst for carbon monoxide methanation according to [5], wherein the metal contained in the outermost layer is Ru.
[7] The content of the metal supported in the outermost layer is in the range of 0.5 to 10% by weight, and the ratio of Ru contained in the supported metal is in the range of 20% by weight or more. ] Carbon monoxide methanation catalyst.
[8] The metal oxide support of the second layer is one or more oxides selected from ZrO ₂ , CeO ₂ , NiO, CoO, Co ₃ O ₄ , Al ₂ O ₃ , TiO ₂ and SiO ₂ , or a composite The oxide according to any one of [1] to [7], which further comprises one or more oxides or composite oxides selected from alkali metal oxides, alkaline earth metal oxides, and rare earth metal oxides. Catalyst for carbon monoxide methanation.
[9] A carbon monoxide methanation method in which the methanation catalyst according to [1] to [8] is contacted with a hydrogen gas containing carbon monoxide gas.
[10] The method for methanation of carbon monoxide, wherein the temperature (reaction temperature) at the time of contact is in the range of 120 to 200 ° C.

  According to the present invention, the catalyst has a multi-layer structure, and the highest carbon monoxide methanation active temperature increases in order from the outer layer to the inner layer, so that even if the reaction temperature is low, the main reaction is monoxide. The selectivity and activity of the carbon methanation reaction are high, the reaction temperature can be adjusted easily and safely, and therefore a catalyst and a removal method capable of effectively removing carbon monoxide in the hydrogen-containing gas can be provided.

Hereinafter, modes for carrying out the present invention will be described.
The catalyst for carbon monoxide methanation according to the present invention has a multilayer structure (outermost layer (first layer), second layer, third layer,...), And the carbon monoxide methanation maximum active temperature is It is characterized by increasing in order from the outer layer to the inner layer.

The maximum active temperature refers to a reaction temperature at which the CO removal rate is highest when the carbon monoxide methanation reaction is performed while changing the reaction temperature.
In the catalyst of the present invention, the carbon monoxide methanation reaction temperature is 120 to 200 ° C., and the maximum active temperature of adjacent layers is preferably at least 10 ° C. or more, more preferably 20 ° C. or more. When the maximum active temperature difference between adjacent layers is small, the configuration of the present invention is not achieved, and the effect of providing a catalyst layer having excellent selectivity at low temperatures at the outside and a catalyst layer having excellent selectivity at high temperatures inside is not effective. It will be enough. That is, there is no difference from using only catalyst components constituting the outermost layer or catalyst particles constituted only by the internal catalyst layer components. For example, the selectivity is lowered due to the high temperature inside the catalyst layer. It may be difficult to suppress.

  The maximum active temperature range of the outermost layer (first layer) is preferably in the range of 120 to 180 ° C., more preferably 120 to 160 ° C., and the maximum active temperature of the innermost layer is 140 to 200 ° C. It is preferable that it exists in the range of 160-200 degreeC.

Outermost layer (first layer)
The outermost layer of the catalyst for carbon monoxide methanation according to the present invention is not particularly limited as long as it has higher activity than the immediate lower layer (that is, the second layer) adjacent to the outermost layer, and the conventionally known catalyst component. However, a catalyst in which one or more metals selected from the group 4B, 6A, 7A, and 8 are supported on a metal oxide support is preferable.

  The supported amount of the metal component in the outermost layer is 0.5 to 10% by weight, preferably 1 to 7.5% by weight in terms of metal. When it is in this range, the above-mentioned carbon monoxide methanation reaction temperature is achieved.

Among them, Sn as the group 4B metal, Mo, W as the group 6A metal, Re as the group 7A metal, Ru, Pt, Pd, Rt, Ni, Fe, Co and I as the group 8 metal.
One or more metals selected from r are preferably used.

Sn is considered to promote the desorption of carbon species adsorbed on other metals such as Ru, and therefore, the activity can be promoted. Mo and W are considered to improve the activity in order to promote hydrogenation due to the adsorption dissociation of H ₂ . Re is considered to promote the desorption of carbon species adsorbed on a metal such as Ru or to adsorb carbon species on Re, and thus to improve the activity. Ru, Pt, Rh, Pd, Fe, Ni, Co, and Ir are considered to improve the activity by dissociating and adsorbing CO and H ₂ as reactants.

Among these, it is preferable that the metal component is one or more metals selected from Group 8, specifically, Ru, Pt, Pd, Rt, Ni, Co, Ir, and the like.
Furthermore, when Ru is contained as an active component, dissociative adsorption and desorption of hydrogen are promoted even when the reaction temperature is relatively low, and the catalyst of the outermost layer is excellent in CO selective methanation reaction activity. It can be suitably used as a component. In addition, the amount of heat generated by the reaction is large, and the reactivity in the second layer can be increased, so that the CO concentration can be efficiently removed.

At this time, the ratio of Ru in the supported active ingredient is preferably 20% by weight or more, more preferably 25 to 98% by weight as a metal.
If the amount of Ru supported is small, the low-temperature activity is low and the heat generated by the reaction is small, so the reactivity of the catalyst layer below the second layer is lowered, and as a result, the CO concentration may not be reduced effectively.

Next, as the metal oxide support used for the outermost layer, one or more oxides selected from ZrO ₂ , CeO ₂ , NiO, CoO, Co ₃ O ₄ , Al ₂ O ₃ , TiO ₂ and SiO ₂ , particularly A composite oxide is preferable.

Specifically, ZrO ₂ —CoO, ZrO ₂ —NiO, ZrO ₂ —CeO ₂ , ZrO ₂ —CoO—NiO, NiO—CoO, CoO—CeO ₂ , NiO—CoO—CeO ₂ , ZrO ₂ —NiO—CoO— _{CeO 2, Al 2 O 3 -Co} 3 O 4, Al 2 O 3 -CeO 2 -CoO, Al 2 O 3 -NiO, TiO 2 -CoO, TiO 2 -NiO, TiO 2 -SiO 2 -Co 3 O 4 Etc.

In particular, the use of a composite oxide containing approximately 10% by weight or more, preferably 30% by weight or more of Ni and / or Co oxide can improve the activity at low temperature.
The content in the catalyst component constituting the outermost layer of such an oxide and / or composite oxide is preferably in the range of 90 to 99.5% by weight, more preferably 92.5 to 99% by weight.

  When the content of the oxide and / or composite oxide in the outermost layer is small, there are many metals that are the main active ingredients, and in this case, the metal fine particles and the high dispersibility of the metal fine particles are low, so the temperature is low. In addition, the amount of heat generated by the reaction becomes insufficient and the reaction temperature of the catalyst layer below the second layer becomes insufficient, so that the CO removal rate may be insufficient.

Even if the content of the oxide and / or composite oxide in the outermost layer is too large, the activity of the outermost layer is high and the amount of heat generated by the reaction increases, so that the methanation reaction of CO ₂ occurs in the outermost layer and the selectivity May decrease.

  The pore volume of the outermost layer is preferably in the range of 0.10 to 0.45 ml / g, more preferably 0.15 to 0.30 ml / g. When the pore volume of the outermost layer is small, gas diffusion to the second layer tends to be insufficient, the reaction at the internal catalyst layer becomes insufficient, and as a result, the CO removal rate becomes insufficient. is there. If the pore volume of the outermost layer is too large, the strength and wear resistance of the catalyst may be insufficient.

  The average pore diameter of the outermost pores is preferably in the range of 5 to 2000 nm, more preferably 50 to 500 nm. When the average pore diameter of the outermost layer is small, gas diffusion to the second layer tends to be insufficient, the reaction in the internal catalyst layer becomes insufficient, and as a result, the CO removal rate becomes insufficient. There is. Moreover, even if the average pore diameter of the outermost layer is too large, the activity tends to decrease, and the strength and wear resistance may be insufficient.

The proportion of the outermost layer in the catalyst is preferably in the range of 5 to 70% by weight, more preferably 10 to 50% by weight. If the proportion of the outermost layer is small, the reaction at low temperature is insufficient and the amount of heat generated by the reaction is reduced, so the reactivity of the catalyst below the second layer is lowered, resulting in an insufficient CO removal rate. There is. When the proportion of the outermost layer is too large, the reaction of the outermost layer becomes the main, and the effect of providing a catalyst layer having excellent selectivity at high temperature inside becomes insufficient. That is, there is no place to change as the reaction at high temperature using only the outermost layer, occur methanation reaction of CO ₂ in the outermost layer, rather selectivity may be lowered.

The second layer and the second layer can be used by supporting the same metal component as that used in the outermost layer within a range where the highest activity is exhibited at a higher temperature than the outermost layer. Such pore activity at high temperatures can be adjusted by adding a predetermined amount of alkali metal oxide, alkaline earth metal oxide, or rare earth metal oxide.

The carrier used in the second layer is selected from the same NiO, CoO, Co ₃ O ₄ , ZrO ₂ , CeO ₂ , Al ₂ O ₃ , TiO ₂ , and SiO ₂ used in the outermost metal oxide carrier 1 It is preferably composed of an oxide or composite oxide of more than one species. Furthermore, the second layer contains one or more oxides or composite oxides selected from alkali metal oxides, alkaline earth metal oxides, and rare earth metal oxides. Specifically, Na ₂ O, K ₂ O, Li ₂ O, BeO, MgO, CaO, B
Examples thereof include oxides such as aO, La ₂ O ₃ , and Sm ₂ O ₃ .

The content of alkali metal oxide or the like in the second layer is preferably in the range of 0.05 to 3% by weight, more preferably 0.1 to 2% by weight. This alkali metal oxide makes it possible to increase the maximum active temperature. In addition, if the content of alkali metal oxide or the like in the second layer is small, the temperature showing the highest activity shifts to the low temperature side, and the temperature showing the highest activity approximates that of the outermost layer. The effect of providing the catalyst layer becomes insufficient. That is, there is no difference from the case where the reaction is performed at a high temperature using only the outermost layer, and the methanation reaction of CO ₂ occurs in the outermost layer and the selectivity may be lowered. On the other hand, when the content of the alkali metal oxide exceeds 3% by weight, the alkali metal oxide is liberated during use and the specific surface area is decreased, and the catalyst life may be shortened.

The ratio of the second layer is not particularly limited. If necessary, a laminated structure of the third layer or more may be used, and in this case, the third layer or more may be set so that the maximum active temperature is similarly increased.
The shape of the catalyst for carbon monoxide methanation of the present invention is not particularly limited, but usually beads (spherical or granular) or pellets are used.

  In the case of a bead-shaped catalyst, the average particle diameter is preferably in the range of 0.5 mm to 1 cm, more preferably 1 mm to 0.8 cm. In the case of a pellet-shaped catalyst, the average diameter is 0.5 mm to 1 cm, and further 1 mm. The average length is preferably in the range of 0.8 cm and 2 mm to 2 cm.

Further, in addition to the bead-shaped catalyst or the pellet-shaped catalyst, the above-described catalyst layers can be sequentially formed and used on the honeycomb base material.
Next, in the catalyst for carbon monoxide methanation according to the present invention, first, particles of the inner layer may be prepared, and then the outer layer may be sequentially formed.

Hereinafter, the case where it consists of a 2nd layer and an outermost layer is illustrated.
Preparation of the second layer
In the case of a two-layer structure, the second layer is a core particle.

In this case, first, ZrO ₂ , CeO ₂ , NiO, CoO, Co ₃ O ₄ , Al ₂ O ₃ , TiO _{2 are used.}
Then, core particles (second layer) made of one or more oxides and / or composite oxides selected from SiO ₂ are prepared.

  As the raw material salt aqueous solution, one or more metal salt aqueous solutions or mixed metal salt aqueous solutions of zirconium salt, nickel salt, cobalt salt, cerium salt, aluminum salt, silicate, and titanium salt are prepared. Zirconium nitrate, zirconium chloride, zirconyl chloride, zirconium sulfate, zirconium acetate, zirconyl nitrate, zirconyl sulfate, zirconium carbonate, etc. are used. Nickel salts include nickel nitrate, nickel sulfate, nickel chloride, nickel acetate, nickel carbonate. As the cobalt salt, cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt acetate and the like are used. Cerium nitrate, cerium chloride, cerium sulfate, etc. are used as the cerium salt, aluminum nitrate, aluminum chloride, aluminum sulfate, sodium aluminate, etc. are used as the aluminum salt, and water glass, silicate liquid, etc. are used as the silicate. As the titanium salt, titanium tetrachloride, titanium sulfate or the like is used.

  The aqueous metal salt solution or mixed metal salt aqueous solution preferably has a concentration as an oxide or composite oxide in the range of approximately 10% by weight or less. If the concentration is too high, the specific surface area of the resulting catalyst is small, and the activity may be insufficient.

  Next, an aqueous solution of a basic compound is added to a metal salt aqueous solution or a mixed metal salt aqueous solution to neutralize it, and aged as necessary to prepare a hydrogel. In addition, when using sodium aluminate, water glass, etc., it neutralizes by adding acids, such as hydrochloric acid and a sulfuric acid, other metal salt aqueous solution, or mixed metal salt aqueous solution. As the basic compound, an aqueous alkali metal solution such as NaOH and KOH, ammonia, tetramethylammonium hydroxide and the like can be used. Furthermore, if necessary, one or more metal salt aqueous solutions or mixed metal salt aqueous solutions selected from other alkali metal salt aqueous solutions, alkaline earth metal salt aqueous solutions, and rare earth metal salt aqueous solutions may be added.

Specifically, an aqueous metal salt solution or a mixed metal salt aqueous solution such as NaOH, KOH, LiOH, BeOH, Mg (OH) ₂ , Ca (OH) ₂ , Ba (OH) ₂ , La (OH) _3, or the like is used. When such a basic compound is used, the core particles contain one or more oxides or composite oxides selected from alkali metal oxides, alkaline earth metal oxides, and rare earth metal oxides. It is possible to prepare a core particle (second layer) that suppresses the CO ₂ metamation reaction and exhibits high selectivity for the CO methanation reaction.

The temperature for aging is usually preferably in the range of 30 to 100 ° C., and the time is usually about 0.5 to 24 hours.
The hydrogel is then filtered and washed. The washing method is not particularly limited as long as excessive salts such as sodium chloride produced as a by-product can be removed, and a conventionally known method can be adopted. For example, a method of sufficiently applying warm water, a method of applying ammonia water, an ultrafiltration membrane method and the like can be suitably employed.

Nuclear particles are formed from the resulting hydrogel. The following two methods are usually employed as a method for forming the core particles.
The first is to add a molding aid such as cellulose as needed, adjust the moisture, heat and concentrate, knead, knead, etc., and then form a pellet with an extrusion molding machine, etc. Use a marumerizer, rolling granulator, etc. to make it spherical. Then, dry as necessary.

  The other method is to dry the washed gel, pulverize it, add molding aids such as cellulose as necessary, adjust the moisture, and then make it spherical with a Malmerizer, tumbling granulator, etc. Dry accordingly.

  In addition, after drying, one or more metal salt aqueous solutions selected from the other alkali metal salt aqueous solutions, alkaline earth metal salt aqueous solutions, and rare earth metal salt aqueous solutions described above are absorbed, and alkali metal oxides and alkaline earth metal oxidations are absorbed. In addition, a core particle containing at least one kind of rare earth metal oxide can be used.

Formation of outermost layer A washed hydrogel is prepared in the same manner as when the core particles are prepared. In this case, an alkaline earth metal salt aqueous solution and a rare earth metal salt aqueous solution used as necessary when preparing the core particles are not used.

Next, the washed hydrogel is dried and fired, and the obtained mixed oxide powder is pulverized.
Drying is performed at 80 to 200 ° C., usually for 1 to 24 hours. Moreover, baking is performed at 300-650 degreeC normally for 1 to 24 hours. The pulverization is performed by a sand mill, a ball mill, an attritor, a piston pulverizer, a mixer type pulverizer, or the like. The average particle size of the fine powder after pulverization is preferably in the range of 0.1 to 500 μm, more preferably 0.2 to 100 μm. If the average particle size of the fine powder after pulverization is too small, it may be difficult to attach the fine powder whose moisture has been adjusted, which will be described later, to the core particles.

If the average particle size of the fine powder after pulverization exceeds 500 μm, the strength of the outermost layer may be insufficient, and the resulting catalyst may have insufficient wear resistance.
A metal salt aqueous solution to be a metal component as an active component is supported on the pulverized fine powder.

  The supporting method is not particularly limited as long as the metal component can be supported. Usually, a metal salt aqueous solution roughly corresponding to the pore volume of the fine powder for metal oxide support is prepared, and the fine powder for metal oxide support is prepared. Absorb to body and then dry.

  As the metal salt for active ingredient, it is preferable to use a salt of one or more metals selected from Group 4B, Group 6A, Group 7A and Group 8. Specifically, tin chloride, tin acetate, tin sulfate, tin oxalate, molybdenum chloride, ammonium molybdate, tungstic acid, ammonium tungstate, rhenium chloride, ammonium perrhenate, ruthenium chloride, ruthenium nitrate, chloroplatinic acid, Dichlorotetraamine platinum, palladium nitrate, palladium chloride, rhodium nitrate, rhodium chloride, nickel nitrate, nickel sulfate, nickel chloride, cobalt nitrate, cobalt chloride, cobalt sulfate and the like are preferably used.

  The concentration of the metal salt aqueous solution is usually a predetermined amount, that is, a concentration that can be supported so that the content of the metal as the active component in the obtained catalyst is 0.5 to 10.0% by weight. Absorption and drying can be repeated when the concentration of is low or when the loading is large.

The drying conditions are not particularly limited, but are usually dried at 80 to 200 ° C. In addition, after drying, especially when a chloride is used as the metal salt, it is preferable to wash and remove Cl after drying. As a method for washing, the dried carrier is dispersed in warm water or warm water containing a basic substance such as ammonia or sodium carbonate, and then filtered, and if necessary, warm water or a basic substance such as ammonia or sodium carbonate is further added. A method of washing with warm water containing water and drying at 80 to 200 ° C. is common. When such washing is performed, particle growth of the metal fine particles after reduction, which will be described later, is suppressed, and thus a carbon monoxide methanation catalyst having excellent activity can be obtained. It can then be reduced as needed. The reduction conditions can be the same as the reduction performed after forming the outermost layer on the core particles.

Next, water is added to the fine powder for outermost layer so that the water content is in the range of 10 to 60% by weight, preferably 25 to 50% by weight, and the fine powder for outermost layer is adjusted.
The amount of water at this time varies depending on the particle diameter, pore volume and the like of the fine powder for outermost layer, but usually 1.05 to 1.2 times the volume of pore volume is added.

  When the water content of the outermost layer fine powder is low, the outermost layer fine powder does not adhere to the formed core particles, and it may be difficult to form the outermost layer. Moreover, even if there is too much water, there are cases where the water particles are too much and the core particles may aggregate, and the desired outermost layer cannot be formed.

  Next, while rotating the rolling granulator containing the pellets or bead-shaped core particles, the outermost layer fine powder is gradually added and adhered to the surface of the core particles to form the outermost layer. In addition, when adding the fine powder for outermost layers, you may spray water separately as needed.

The ratio of the core particles and the fine powder for outermost layer at this time is used so that the ratio of the outermost layer in the obtained catalyst is in the range of 5 to 70% by weight, preferably 10 to 50% by weight.
After the outermost layer is formed on the core particles, the carbon monoxide methanation according to the present invention is usually dried at 80 to 200 ° C. and then reduced to 100 to 700 ° C., preferably 150 to 400 ° C. in a reducing gas atmosphere. The catalyst for use can be obtained.

As the reducing gas, hydrogen gas or a mixed gas of hydrogen gas and inert gas such as nitrogen gas is usually used.
If the temperature during the reduction is less than 100 ° C., the metal salt may not be sufficiently reduced and sufficient activity may not be obtained.

If the temperature during the reduction exceeds 700 ° C., the particle size of the metal fine particles becomes too large and the activity becomes insufficient, or sintering occurs, and the specific surface area of the resulting catalyst becomes small, resulting in insufficient activity. May be.

Next, the carbon monoxide methanation method according to the present invention will be described.

The methanation method for carbon monoxide according to the present invention is characterized in that the methanation catalyst is brought into contact with a hydrogen gas containing carbon monoxide gas.
As the methanation catalyst, the aforementioned catalyst is used.

  As the carbon monoxide gas-containing hydrogen gas, a fuel gas (hydrogen-containing gas in the reformed gas) is used, and this gas usually contains hydrogen gas, carbon monoxide gas, carbon dioxide gas, water vapor, and the like. May contain methane.

  The hydrogen gas concentration in the fuel gas used in the present invention is 71 to 89 vol%, the carbon monoxide gas concentration is 0.3 to 1.0 vol%, the carbon dioxide gas concentration is 10 to 25 vol%, and the methane gas concentration is 0 to 3.0 vol. % (Gas composition). Furthermore, it contains water vapor at a ratio of 20 vol% to 70 vol% with respect to the gas in the fuel.

  The temperature at which the methanation catalyst is brought into contact with the carbon monoxide gas-containing hydrogen gas (hereinafter referred to as reaction temperature) is preferably in the range of 120 to 200 ° C, more preferably 130 to 190 ° C.

When the reaction temperature is low, the water vapor contained in the reaction gas condenses and it is difficult to carry out the reaction continuously. If the reaction temperature is too high, the temperature shifts to the CO shift reaction (CO + H ₂ O → CO ₂ + H ₂ ), and carbon monoxide that can be converted by the CO shift reaction is methanated by the methanation reaction. The hydrogen concentration contained in the gas is significantly reduced.

The fuel gas treated by such a carbon monoxide methanation method according to the present invention has a carbon monoxide gas concentration of 20 ppm or less, preferably 10 ppm or less.
[Example]
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited to these Examples at all.
[Example 1]
Preparation of core particles (1) 46.6 g of cobalt nitrate hexahydrate, zirconyl nitrate aqueous solution (ZrO ₂ concentration: 25%)
A mixed aqueous solution (1) was prepared by adding 232.0 g and 109.0 g of nickel nitrate hexahydrate to 1240.5 g of water.

A hydrogel was prepared by dissolving 80.5 g of sodium hydroxide in 1519.5 g of water and adding the mixed aqueous solution (1) thereto while stirring, and then aging at 80 ° C. for 2 hours.
The aged hydrogel was filtered, washed with sufficient warm water, and dried at 120 ° C. overnight. Further, a solution obtained by dissolving 12.7 g of magnesium nitrate hexahydrate in 48.0 g of water was absorbed into the dried product, dried at 120 ° C. for 5 hours, and then at 550 ° C. for 1 hour in the air. Fine powder for core particles composed of cobalt oxide, nickel oxide, magnesium oxide and zirconium oxide with firing and pulverization with a mixer-type pulverizer and an average particle size of 1 μm (1)
Got.

Next, a cellulose organic plasticizer was added to the core particle fine powder (1), the water content was adjusted to 35 to 45%, and granulated by a Malmerizer to prepare the core particle (1).
The average particle diameter after firing a part of the core particles (1) at 450 ° C. was 2.0 mm.

Measurement of the maximum active temperature of core particle (1) 4.2 ml of core particle (1) is packed in a stainless steel reaction tube with an inner diameter of 12 mm, and the catalyst layer temperature is 400 ° C. with a hydrogen-nitrogen mixed gas (H ₂ concentration 10 vol%). Reduced for 1.5 hours under distribution, then mixed gas for reaction (carbon monoxide 0.6vol%, carbon dioxide 20.0vol%, methane 2.0vol%, hydrogen 51.37vol%, water vapor 33.3vol%) SV = 4000 ^-1 The reaction temperature was raised from 100 to 200 ° C. in 5 degree increments, and the reaction tube outlet CO concentration at each temperature was analyzed by gas chromatography and an infrared spectroscopic gas concentration meter. The temperature at which the CO concentration was the lowest was defined as the maximum active temperature, and the results are shown in Table 1.

Preparation of fine powder (1) for outermost layer 100.9 g of cobalt nitrate hexahydrate, aqueous zirconyl nitrate (ZrO ₂ concentration: 25%
) 168.0 g, 46.7 g of nickel nitrate hexahydrate and 50.2 g of cerium nitrate hexahydrate were added to 1381.2 g of water to prepare a mixed aqueous solution (2).

A hydrogel was prepared by dissolving 86.51 g of sodium hydroxide in 1489.4 g of water and adding the mixed aqueous solution (2) thereto while stirring, and then aging at 80 ° C. for 2 hours.
The aged hydrogel was filtered, washed with sufficient warm water, dried overnight at 120 ° C., then calcined at 550 ° C. for 1 hour in the atmosphere to obtain cobalt oxide, cerium oxide, nickel oxide, and A powder (1) for metal oxide support made of zirconium oxide was obtained.

The metal oxide carrier powder (1) is pulverized with a mixer-type pulverizer, and the average particle size of the powder is 1.
A fine powder (1) for metal oxide carrier having a size of 1 μm was obtained.
Ruthenium chloride and palladium chloride are mixed with 100 g of the obtained fine powder for metal oxide carrier (1) so that the metal weight ratio is Ru: Pd = 1: 0.4, and the metal concentration becomes 10% by weight. 36.26 g of the dissolved solution was absorbed, allowed to stand for 1 hour, dried at 120 ° C. for 8 hours, then dispersed in 2 L of sodium hydrogen carbonate solution adjusted to pH 10-11 and stirred. Thereafter, it was washed with sufficient warm water and dried at 120 ° C. for 5 hours to prepare an outermost layer fine powder (1).

Measurement of maximum active temperature of outermost layer fine particles (1) Fill outermost layer fine particles (1) into a tablet molding machine, press mold at 50 kg / cm ² , and then grind, particle size 20-42 mesh Adjusted.

Next, 4.2 ml of the molded fine particles for outermost layer (1) is filled into a stainless steel reaction tube with an inner diameter of 12 mm, and the catalyst layer temperature is 400 ° C. under the flow of a hydrogen-nitrogen mixed gas (H ₂ concentration 10 vol%). , Reduced for 1.5 hours, then the reaction gas mixture (carbon monoxide 0.6 vol%, carbon dioxide 20.0 vol%, methane 2.0 vol%, hydrogen 51.37 vol%, water vapor 33.3 vol%) becomes SV = 4000 hr ^-1 The reaction temperature was increased from 100 to 200 ° C in 5 ° C increments, and the reaction tube outlet CO concentration at each temperature was analyzed by gas chromatography and an infrared spectroscopic gas concentration meter. Is the highest active temperature at which the temperature became the lowest, and the results are shown in Table 1.

Preparation of catalyst for methanation (1) Core powder obtained by granulating powder with water content adjusted to 35-45% by adding fine powder (1) for outermost layer to cellulosic organic plasticizer The outermost layer was formed by gradually adding to (1). At this time, the outermost layer fine powder (1) was added so that the ratio of the outermost layer was 30% by weight in the final catalyst.

Then, after drying at 120 ° C. for 4 hours, calcining in the atmosphere at 500 ° C. for 3 hours, and reducing treatment in a hydrogen stream at 400 ° C. for 1.5 hours, the catalyst for methanation (1) Was prepared.

Table 1 shows the weight ratio, the weight average particle diameter, the weight ratio of the outermost layer, and the thickness of the core particles (1) in the methanation catalyst (1).
The catalyst for activity test methanation (1) (4.2 ml) was filled in a stainless steel reaction tube with an inner diameter of 12 mm, and again for 1 hour under a flow of hydrogen-nitrogen mixed gas (H ₂ concentration 10 VOL%) at a catalyst layer temperature of 250 ° C. Then, after reducing the catalyst layer temperature to 120 ° C., the reaction gas mixture (carbon monoxide 0.6 vol%, carbon dioxide 20.0 vol%, methane 2.0 vol%, hydrogen 51.37 vol%) , Water vapor 33.3 Vol%) is circulated so that SV = 4,000 h ^−1, and the product gas in a steady state after about 1 hour is analyzed by gas chromatography and an infrared spectroscopic gas densitometer. The results of measuring the tube outlet CO concentration, CO ₂ concentration, and CH ₄ concentration are shown in Table 1.

As the selectivity, the increase or decrease in CO ₂ from 20.0 Vol% of carbon dioxide in the reaction gas is shown in Table 1.
To indicate, when little increase or decrease in CO ₂ was evaluated as excellent in selectivity.
Similarly, the reaction temperature was 150 ° C. and 180 ° C., and the results are shown in Table 1.
[Example 2]
Preparation of catalyst for methanation (2) In Example 1, the fine particle for outermost layer was adjusted so that the average particle diameter of the core particles was 1.6 mm (core particle (2)) and the proportion of the outermost layer was 45% by weight. A methanation catalyst (2) was prepared in the same manner except that (1) was added.

Table 1 shows the weight ratio, weight average particle diameter, outermost layer weight ratio, and thickness of the core particles (2) in the methanation catalyst (2).
Measurement of Maximum Active Temperature In the same manner as in Example 1, the maximum active temperature of the outermost layer and the core particles was measured.

Activity test An activity test was conducted in the same manner as in Example 1, and the changes in CO concentration, CH ₄ concentration and CO ₂ concentration are shown in Table 1.
[Example 3]
Preparation of fine powder (2) for outermost layer 166.9 g of cobalt nitrate hexahydrate, aqueous zirconyl nitrate solution (ZrO ₂ concentration: 25%)
204.0 g and 23.4 g of nickel nitrate hexahydrate were added to 1421.4 g of water to prepare a mixed aqueous solution (3).
A hydrogel was prepared by dissolving 86.51 g of sodium hydroxide in 1489.4 g of water and adding the mixed aqueous solution (3) thereto while stirring, and then aging at 80 ° C. for 2 hours.

  The aged hydrogel was filtered, washed with sufficient warm water, and dried at 120 ° C. overnight. Subsequently, firing was performed in the air at 550 ° C. for 1 hour to obtain a metal oxide carrier powder (2) composed of cobalt oxide, nickel oxide, and zirconium oxide.

The metal oxide carrier powder (2) is pulverized with a mixer-type pulverizer, and the average particle size of the powder is 1.
A fine powder (2) for a metal oxide carrier having a thickness of μm was obtained.
In 100 g of the obtained fine powder (2) for metal oxide support, 52.6 g of a solution in which ruthenium chloride was dissolved so that its concentration as Ru was 10% by weight was absorbed, and allowed to stand for 1 hour, then 120 ° C. For 8 hours, and then dispersed in 2 L of sodium hydrogen carbonate solution adjusted to pH 10 to 11, stirred, washed with sufficient warm water, dried at 120 ° C. for 5 hours and dried. The outer layer fine powder (2) was prepared.
Preparation of catalyst for methanation (3) Fine powder for outermost layer (2) is mixed with cellulose organic plasticizer, and the moisture adjusted to 35-45% is granulated with Malmerizer in Example 1. The outermost layer was formed by gradually adding to the core particles (1). At this time, the outermost layer fine powder (2) was added so that the ratio of the outermost layer was 30% by weight in the final catalyst.

Then, after drying at 120 ° C. for 4 hours, calcining in the air at 500 ° C. for 3 hours, and reducing treatment in a hydrogen stream at 400 ° C. for 1.5 hours, a catalyst for methanation (3) Was prepared.

Measurement of Maximum Active Temperature In the same manner as in Example 1, the maximum active temperature of the outermost layer and the core particles was measured.
Activity test An activity test was conducted in the same manner as in Example 1, and the changes in CO concentration, CH ₄ concentration and CO ₂ concentration are shown in Table 1.
[Example 4]
Preparation of methanation catalyst (4) In Example 2, the methanation catalyst (4) was prepared in the same manner except that the outermost layer fine powder (2) was added so that the ratio of the outermost layer was 45% by weight. Prepared. Table 1 shows the weight ratio, weight average particle diameter, outermost layer weight ratio, and thickness of the core particles (2) in the methanation catalyst (4).

Measurement of Maximum Active Temperature In the same manner as in Example 1, the maximum active temperature of the outermost layer and the core particles was measured.
Activity test An activity test was conducted in the same manner as in Example 1, and the changes in CO concentration, CH ₄ concentration and CO ₂ concentration are shown in Table 1.
[Example 5]
Preparation of core particles (3) Zirconyl nitrate aqueous solution (ZrO ₂ concentration: 25% by weight) 204.0 g, nickel nitrate hexahydrate 116.8 g, lanthanum nitrate hexahydrate 3.56 g and iron nitrate 9 water A mixed aqueous solution (4) was prepared by adding 60.5 g of the Japanese product to 1300.0 g of water.

A hydrogel was prepared by dissolving 91.6 g of sodium hydroxide in 1621.5 g of water and adding the mixed aqueous solution (4) thereto while stirring, and then aging at 80 ° C. for 2 hours.
The aged hydrogel was filtered, washed with sufficient warm water, and dried at 120 ° C. overnight. Further, a solution obtained by dissolving 6.4 g of magnesium nitrate hexahydrate in 49.0 g of water was absorbed into the dried product, dried at 120 ° C. for 5 hours, and then at 550 ° C. for 1 hour in the air. Firing was performed, and the mixture was further pulverized by a mixer-type pulverizer to obtain fine particles (2) for core particles composed of lanthanum oxide, nickel oxide, iron oxide, magnesium oxide and zirconium oxide having an average particle size of 1 μm.

Next, a cellulose organic plasticizer was added to the fine powder for core particles (2), the water content was adjusted to 35 to 45%, and granulated with a Malmerizer to prepare the core particles (3).
The average particle diameter after firing a part of the core particles (3) at 450 ° C. was 2.0 mm.
Preparation of catalyst for methanation (5) A catalyst for methanation (5) was prepared in the same manner as in Example 1 except that the core particles (3) were used.

Measurement of Maximum Active Temperature In the same manner as in Example 1, the maximum active temperature of the outermost layer and the core particles was measured.
Activity test An activity test was conducted in the same manner as in Example 1, and the changes in CO concentration, CH ₄ concentration and CO ₂ concentration are shown in Table 1.
[Example 6]
Preparation of catalyst for methanation (6) In Example 5, the fine particle for outermost layer was adjusted so that the average particle diameter of the core particles was 1.6 mm (core particle (4)) and the proportion of the outermost layer was 45% by weight. A methanation catalyst (6) was prepared in the same manner except that (1) was added.

Table 1 shows the weight ratio, weight average particle diameter, outermost layer weight ratio, and thickness of the core particles (4) in the methanation catalyst (6).
Measurement of Maximum Active Temperature In the same manner as in Example 1, the maximum active temperature of the outermost layer and the core particles was measured.

Activity test An activity test was conducted in the same manner as in Example 1, and the changes in CO concentration, CH ₄ concentration and CO ₂ concentration are shown in Table 1.
[Example 7]
Preparation of methanation catalyst (7) A methanation catalyst (7) was prepared in the same manner as in Example 5, except that the outermost layer fine powder (2) was used.

Measurement of Maximum Active Temperature In the same manner as in Example 1, the maximum active temperature of the outermost layer and the core particles was measured.
Activity test An activity test was conducted in the same manner as in Example 1, and the changes in CO concentration, CH ₄ concentration and CO ₂ concentration are shown in Table 1.
[Example 8]
Preparation of catalyst for methanation (8) A catalyst for methanation (8) was prepared in the same manner as in Example 6 except that the fine powder for outermost layer (2) was used.

Measurement of Maximum Active Temperature In the same manner as in Example 1, the maximum active temperature of the outermost layer and the core particles was measured.
Activity test An activity test was conducted in the same manner as in Example 1, and the changes in CO concentration, CH ₄ concentration and CO ₂ concentration are shown in Table 1.
[Comparative Example 1]
Preparation of catalyst for methanation (R1) A fine powder for core particles (1) was prepared in the same manner as in Example 1, and then a cellulose organic plasticizer was added to the fine powder for core particles (1). %, And granulated with a Malmerizer, then dried at 120 ° C. for 4 hours, calcined at 500 ° C. in the air for 3 hours, and 1.400 ° C. Reduction treatment was carried out in a hydrogen stream for 5 hours to prepare a methanation catalyst (R1). The average particle size of the methanation catalyst (R1) was 3 mm.

Measurement of Maximum Active Temperature As in Example 1, the maximum active temperature of the core particles was measured.
Activity test An activity test was conducted in the same manner as in Example 1, and the changes in CO concentration, CH ₄ concentration and CO ₂ concentration are shown in Table 1.
[Comparative Example 2]
Preparation of catalyst for methanation (R2) Fine powder (2) for core particles was prepared in the same manner as in Example 5, and then cellulose organic plasticizer was added to fine powder (2) for core particles. %, And granulated with a Malmerizer, then dried at 120 ° C. for 4 hours, calcined at 500 ° C. in the air for 3 hours, and 1.400 ° C. Reduction treatment was performed in a hydrogen stream for 5 hours to prepare a methanation catalyst (R2). The average particle size of the methanation catalyst (R2) was 3 mm.

Measurement of Maximum Active Temperature As in Example 1, the maximum active temperature of the core particles was measured.
Activity test An activity test was conducted in the same manner as in Example 1, and the changes in CO concentration, CH ₄ concentration and CO ₂ concentration are shown in Table 1.
[Comparative Example 3]
Preparation of catalyst for methanation (R3) Fine powder for outermost layer (1) was prepared in the same manner as in Example 1, and cellulose organic plasticizer was added to fine powder for outermost layer (1). %, And granulated with a Malmerizer, then dried at 120 ° C. for 4 hours, calcined at 500 ° C. in the air for 3 hours, and 1.400 ° C. Reduction treatment was performed in a hydrogen stream for 5 hours to prepare a methanation catalyst (R3). The average particle size of the methanation catalyst (R3) was 3 mm.

Measurement of Maximum Active Temperature In the same manner as in Example 1, the maximum active temperature of the outermost layer particles was measured.
Activity test An activity test was conducted in the same manner as in Example 1, and the changes in CO concentration, CH ₄ concentration and CO ₂ concentration are shown in Table 1.
[Comparative Example 4]
Preparation of catalyst for methanation (R4) Fine powder for outermost layer (2) was prepared in the same manner as in Example 3, and then cellulose organic plasticizer was added to fine powder for outermost layer (2). %, And granulated with a Malmerizer, then dried at 120 ° C. for 4 hours, calcined at 500 ° C. in the air for 3 hours, and 1.400 ° C. Reduction treatment was carried out in a hydrogen stream for 5 hours to prepare a methanation catalyst (R4). The average particle size of the methanation catalyst (R4) was 3 mm.

Measurement of Maximum Active Temperature In the same manner as in Example 1, the maximum active temperature of the outermost layer particles was measured.
Activity test An activity test was conducted in the same manner as in Example 1, and the changes in CO concentration, CH ₄ concentration and CO ₂ concentration are shown in Table 1.
[Reference Example 1]
Preparation of catalyst for methanation (R5) In Example 1, fine powder for outermost layer so that the average particle diameter of the core particles is 0.8 mm (core particle (5)) and the proportion of the outermost layer is 80% by weight. A methanation catalyst (R5) was prepared in the same manner except that (1) was added.

Table 1 shows the weight ratio, weight average particle diameter, outermost layer weight ratio, and thickness of the core particles (5) in the methanation catalyst (R5).
Measurement of Maximum Active Temperature In the same manner as in Example 1, the maximum active temperature of the outermost layer and the core particles was measured.

Activity test An activity test was conducted in the same manner as in Example 1, and the changes in CO concentration, CH ₄ concentration and CO ₂ concentration are shown in Table 1.
[Reference Example 2]
Preparation of catalyst for methanation (R6) In Example 1, the average particle diameter of the core particles was 2.94 mm (core particles (6)), and the ratio of the outermost layer was 3.5% by weight. A methanation catalyst (R6) was prepared in the same manner except that the fine powder (1) was added.

Table 1 shows the weight ratio, weight average particle diameter, outermost layer weight ratio, and thickness of the core particles (6) in the methanation catalyst (R6).
Activity test An activity test was conducted in the same manner as in Example 1, and the changes in CO concentration, CH ₄ concentration and CO ₂ concentration are shown in Table 1.

Claims (7)

A catalyst for carbon monoxide methanation that has a multilayer structure of two or more layers, and the maximum active temperature of carbon monoxide methanation increases sequentially from the outer layer to the inner layer ,
The outermost layer is Ru or Ru and Pd on at least one oxide or composite oxide support selected from NiO, CoO, Co ₃ O ₄ , ZrO ₂ , CeO ₂ , Al ₂ O ₃ , TiO ₂ , and SiO _2. Metal is supported,
The outermost layer (second layer) is composed of one or more metals selected from Group 4B, Group 6A, Group 7A and Group 8, ZrO ₂ , CeO ₂ , NiO, CoO, Co ₃ O ₄ , Al _2. One or more oxides selected from O ₃ , TiO ₂ and SiO ₂ , or composite oxides, and one or more oxidations selected from alkali metal oxides, alkaline earth metal oxides, and rare earth metal oxides. A catalyst for carbon monoxide methanation, wherein the catalyst is supported or complexed on a metal oxide support containing a product or a complex oxide . _{2. The} catalyst for carbon monoxide methanation according to claim 1, wherein the outermost layer carrier is one or more oxides or composite oxides selected from NiO, CoO, ZrO ₂ , and CeO ₂ .   The catalyst for carbon monoxide methanation according to claim 1 or 2, wherein the ratio of the outermost layer in the catalyst is in the range of 5 to 70% by weight.   The group 4B metal is Sn, the group 6A metal is Mo, W, the group 7A metal is Re, and the group 8 metal is Ru, Pt, Pd, Rh, Ir, Ni, Fe and Co. The catalyst for carbon monoxide methanation according to any one of claims 1 to 3, wherein   The content of the metal supported in the outermost layer is in the range of 0.5 to 10% by weight, and the ratio of Ru contained in the supported metal is in the range of 20% by weight or more. The catalyst for carbon monoxide methanation according to claim 4.   A methanation method for carbon monoxide, comprising contacting the methanation catalyst according to any one of claims 1 to 5 with a hydrogen gas containing carbon monoxide gas.   7. The carbon monoxide methanation method according to claim 6, wherein the temperature (reaction temperature) at the time of contact is in the range of 120 to 200 ° C.