JP6089894B2 - Catalyst for producing synthesis gas and method for producing synthesis gas - Google Patents

Description

  The present invention relates to a synthesis gas production catalyst and a synthesis gas production method using the same.

“Syngas”, which is a mixed gas of carbon monoxide and hydrogen, is widely used as a raw material for producing methanol and dimethyl ether and for producing hydrocarbons using the Fischer-Tropsch reaction.
As a method for producing synthesis gas, a “steam reforming method” for producing from hydrocarbon (mainly methane) and water vapor and a “dry reforming method” for producing from carbon dioxide and hydrocarbon (mainly methane) are known. (Hereafter, both are collectively referred to as the “reforming method.”) The latter, in particular, can produce synthesis gas from the global warming gases methane and carbon dioxide, contributing to the prevention of global warming. It is also attracting attention as an effective means of using carbon dioxide.

The reforming method is usually performed by reacting each raw material in the presence of a catalyst, and various catalysts used at that time have been studied.
As a catalyst used in the dry reforming method, a catalyst in which Ni is supported on various supports such as alumina and silica is known. (Non-Patent Document 1)
However, since the dry reforming method has a higher carbon content ratio in the raw material than the steam reforming method, carbon deposition is likely to occur on the catalyst surface and the activity is likely to decrease. The Ni-supported catalyst has an advantage that the activity of the catalyst is high, but on the other hand, it is a catalyst in which carbon deposition easily occurs.

Therefore, studies for suppressing carbon deposition of the Ni-supported catalyst have been conducted.
Specifically, a method using a complex oxide containing Ni as a catalyst has been studied. Of these, composite oxides containing magnesium have been studied. For example, Patent Document 1 discusses a catalyst using M-Ni-Mg-Ca (M is 3B group, 4A group, 6B group, 7B group, 1A group, lanthanoid) as a composite oxide. Patent Document 2 discusses a catalyst using M-Ni-Mg (M is a metal such as Ti or Zr) as a composite oxide.

JP 2000-469 A JP 2004-900 A

CHEMTECH, vol. 29, p37 (1999)

When a Ni-supported catalyst and a composite oxide containing Ni were examined based on the prior art, there was still carbon deposition, and the performance as a catalyst was insufficient.
Therefore, in the production of synthesis gas by the dry reforming method, a catalyst that has high catalytic activity and that does not decrease its catalytic activity even if carbonaceous matter is precipitated, and a production method that maintains high production efficiency for a long time. The issue is to provide.

  The inventors have studied in detail the support of Ni-supported catalyst, and when a Mg-Al-Mn composite oxide is used as the support, a catalyst having high catalyst activity and less likely to decrease the catalyst activity can be obtained. I understood. This is because the Mg—Al—Mn composite oxide itself has the ability to oxidize and remove deposited carbon (= burn carbonaceous matter) in the presence of an oxidizing gas such as oxygen or carbon dioxide. I understood.

That is, the gist of the present invention is as follows.
[1] A synthesis gas production catalyst for producing a synthesis gas containing carbon monoxide and hydrogen by reacting a raw material gas containing hydrocarbons with carbon dioxide,
A catalyst for syngas production, wherein the catalyst is a composite oxide represented by the following general formula (1) supporting Ni:
_{Mg x Al y Mn z O δ} ··· (1)
(In the general formula (1), x, y, and z each represent a molar ratio of magnesium, aluminum, and manganese atoms contained in the composite oxide, and satisfy the following formulas (2) to (5).
0.01 ≦ x ≦ 0.99 (2)
0.01 ≦ y ≦ 0.99 (3)
z ≧ 0.1 (4)
x + y + z = 1.0 (5)
δ represents a number necessary to satisfy the charge neutrality condition. )

[2] The catalyst for syngas production according to [1], wherein z ≦ 0.3 in the general formula (1),
[3] A method for producing a synthesis gas containing carbon monoxide and hydrogen by reacting a raw material gas containing hydrocarbon and carbon dioxide, wherein the catalyst according to the above [1] or [2] is used as a reaction catalyst A method for producing synthesis gas, characterized in that:
[4] The method for producing a synthesis gas according to [3], wherein the raw material gas and carbon dioxide are reacted in the presence of oxygen.
[5] The method for producing a synthesis gas according to [3] or [4], wherein the source gas contains methane,
[6] The method for producing a synthesis gas according to the above [5], wherein the molar ratio of carbon dioxide to methane (CO ₂ / CH ₄ ) in the raw material gas is 1 or more and 5 or less. .

  Since a catalyst for syngas production with high catalytic activity can be obtained, synthesis gas can be produced with high efficiency, and it is possible to produce synthesis gas with high efficiency over a long period of time without causing a decrease in catalyst activity. .

It is a triangular composition diagram showing the composition of the constituent metal elements of the composite oxide of the present invention. 10 is an evaluation result of precipitated carbon removal ability using the catalyst of Example 7. 10 is an evaluation result of precipitated carbon removal ability using the catalyst of Comparative Example 4.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is limited to these contents. Instead, various modifications can be made within the scope of the gist.
The catalyst for producing synthesis gas of the present invention is one in which Ni is supported on an Mg—Al—Mn composite oxide. First, the composite oxide will be described. Hereinafter, the Mg, Al, and Mn elements contained in the composite oxide may be collectively referred to as “constituent metal elements”.

<Mg-Al-Mn composite oxide>
The Mg—Al—Mn composite oxide used in the present invention is a composite oxide represented by the following general formula (1) (hereinafter sometimes referred to as the composite oxide of the present invention).
_{Mg x Al y Mn z O δ} ··· (1)
(In the general formula (1), x, y, and z each represent a molar ratio of magnesium, aluminum, and manganese atoms contained in the composite oxide, and satisfy the following formulas (2) to (5).
0.01 ≦ x ≦ 0.99 (2)
0.01 ≦ y ≦ 0.99 (3)
z ≧ 0.1 (4)
δ represents a number necessary to satisfy the charge neutrality condition. )

In the general formula (1), x, y, and z each represent a molar ratio of magnesium, aluminum, and manganese atoms contained in the composite oxide, and satisfy the following formula (5).
x + y + z = 1.0 (5)

In the above general formula (1), x represents the molar ratio of magnesium atoms to the total of magnesium, aluminum, and manganese atoms contained in the composite oxide.
x satisfies the following formula (2).
0.01 ≦ x ≦ 0.99 (2)
In the above formula (2), x is preferably 0.25 or more, more preferably 0.40 or more, preferably 0.90 or less, and more preferably 0.85 or less.
If x is less than the lower limit, the activity of the catalyst may be reduced, and if it is larger than the upper limit, the ability to remove precipitated carbon may not be exhibited.

In the general formula (1), y represents the molar ratio of aluminum atoms to the total of magnesium, aluminum, and manganese atoms contained in the composite oxide.
y satisfies the following formula (3).
0.01 ≦ y ≦ 0.99 (3)
In the above formula (3), y is preferably 0.05 or more, preferably 0.60 or less, and more preferably 0.40 or less.

  If y is less than the lower limit, the activity of the catalyst may be reduced, and if it is more than the upper limit, the composite oxide is present in the form of alumina without being complexed. And the acid sites of the alumina may promote carbon deposition on the catalyst during synthesis gas production.

In the general formula (1), z represents the molar ratio of manganese atoms to the total of magnesium, aluminum, and manganese atoms contained in the composite oxide.
z satisfies the following formula (4).
z ≧ 0.1 (4)
The catalyst of the present invention contains manganese in the composite oxide, so that the carbon deposited by the reforming reaction is oxidized and removed in the presence of an oxidizing gas such as oxygen or carbon dioxide (= carbonaceous matter). Has the ability to burn).

In the above formula (4), z is preferably 0.3 or less, and more preferably 0.2 or less.
If z is less than the lower limit, the ability to remove precipitated carbon is not sufficiently exhibited, so that the reactor may be clogged. If it is more than the upper limit, the activity of the catalyst may decrease.
The relationship between x, y, and z can be represented by a triangular composition diagram (FIG. 1) with Mg, Al, and Mn as vertices.

In the general formula (1), δ represents a number necessary to satisfy the charge neutrality condition. That is, it represents the number of oxygens that satisfy the charge neutrality condition in forming the composite oxide having the above x, y, and z values.
The raw material of the Mg—Al—Mn composite oxide used in the present invention is not particularly limited, but usually, a salt, oxide, hydroxide or the like of each constituent metal element is used.

When a salt of a constituent metal element is used as a raw material, the type of the salt is not particularly limited. For example, inorganic salts such as nitrates, sulfates, phosphates, and hydrochlorides, carbonates, acetates, oxalates, and the like. Organic acid salt etc. are mentioned. Of these, nitrates and acetates are preferred because of their easy reaction.
When an oxide of a constituent metal element is used as a raw material, either an oxide containing one kind of constituent metal element or a composite oxide containing two or more kinds can be used.

  As a method for producing the Mg—Al—Mn composite oxide used in the present invention, a preferred method can be used as appropriate depending on the molar ratio of each constituent metal element in the composite oxide and the preferred catalyst shape, and particularly limited. However, it is usually manufactured by preparing a precursor material of a composite oxide (hereinafter sometimes simply referred to as a precursor) using various preparation methods, and firing the precursor.

The method for preparing the precursor is not particularly limited, and methods such as a solid phase reaction method, an inorganic salt decomposition method, an organic acid complex polymerization method, and a coprecipitation method can be used.
In the solid-phase reaction method, a salt, oxide, hydroxide or the like of each constituent metal element is appropriately selected, and the constituent metal elements contained therein are mixed so as to have a desired stoichiometric ratio, and ethanol or A precursor is obtained by adding water.

In the inorganic salt decomposition method, the salt of each constituent metal element is mixed so that the constituent metal elements contained in the constituent metal element have the desired stoichiometric ratio, and water is further added and stirred to prepare a raw salt aqueous solution. . Next, this raw material salt aqueous solution is heated and evaporated to dryness to obtain a precursor.
In the organic acid complex polymerization method, the salt of each constituent metal element is mixed so that the constituent metal elements contained in the constituent metal element have the desired stoichiometric ratio, water is added, and the raw salt aqueous solution is added by stirring. Prepare. Next, a complexing agent is added to this raw salt aqueous solution to form a precipitate, thereby obtaining a precursor.

Although it does not specifically limit as an organic acid salt which forms an organic complex, For example, a citric acid, malic acid, ethylenediaminetetraacetate sodium etc. can be used.
In the coprecipitation method, the salt of each constituent metal element is mixed so that the constituent metal elements contained in the constituent metal element have the desired stoichiometric ratio, and water is further added and stirred to prepare a raw salt aqueous solution. . Next, a precipitant is obtained by adding a precipitant to the raw salt aqueous solution to form a precipitate.

  Although it does not specifically limit as a precipitating agent, For example, organic bases, such as inorganic bases, such as ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, a triethylamine, a pyridine, etc. can be used.

The obtained composite oxide precursor material is sufficiently dried, pulverized, and then fired to obtain the composite oxide used in the present invention.
The firing temperature of the precursor is not particularly limited as long as it is higher than the temperature at which the salt of each constituent metal element is decomposed, but is usually 500 ° C. or higher, preferably 700 ° C. or higher, and usually 1200 ° C. or lower, preferably 1000 ° C. or lower. Range. If the firing temperature is too lower than the lower limit, the compounding may not proceed sufficiently. On the other hand, if the firing temperature is too higher than the upper limit, the specific surface area of the composite oxide may be reduced, and the catalytic activity may be lowered.

<Ni supported catalyst>
The catalyst of the present invention is one in which Ni is supported on the Mg—Al—Mn composite oxide represented by the general formula (1).
The method for supporting Ni on the composite oxide of the present invention is not particularly limited, and can be appropriately selected from known methods such as an impregnation method and a coprecipitation method.

The raw material compound used for supporting Ni is not particularly limited as long as it can be supported on the composite oxide of the present invention. For example, inorganic compounds such as nickel oxide, nickel nitrate, nickel sulfate, and nickel chloride are used. What is necessary is just to select suitably from organic acid salts, such as acid salt, nickel carbonate, and nickel acetate.
The amount of Ni supported is not particularly limited, but is usually 0.5% by weight or more, preferably 1% by weight or more, more preferably 3%, based on the total weight of the composite oxide of the present invention and Ni. % By weight or more, usually 30% by weight or less, preferably 20% by weight or less, and more preferably 10% by weight or less. When the supported amount of Ni is too small than the lower limit value, the catalytic activity may be insufficient. When it is more than the upper limit value, the catalytic activity may be reduced due to aggregation.

<Catalyst components other than Ni>
The synthesis gas production catalyst of the present invention may further contain a metal element other than Ni. Specifically, there is a method in which a metal element other than Ni is further supported on a catalyst supporting Ni so as to coexist as a promoter for Ni. Thereby, effects such as further improvement in catalytic activity and suppression of carbon deposition can be expected.

  As the metal element other than Ni, for example, at least one metal element selected from the group consisting of alkali metal elements, alkaline earth metal elements, noble metal elements, rare earth elements and transition metal elements may be added.

  Specifically, Na, K, Rb, Cs, Ca, Sr, Ba, Ru, Rh, Pd, Os, Ir, Pt, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Ti, V, Cr, Fe, Co, Cu, Zr, Nb, Mo, Tc, Hf, Ta, W, Re, Au, etc., among which Na, K, Rb, Cs, Ca, Ba, Ru, Rh, Pd, Os, Ir, Pt, La, Ce, Pr, Nd, Sm, V, Cr, Fe, Co, Cu, Zr, Mo, W, and Au are preferable.

These other catalyst components may be used individually by 1 type, and may use 2 or more types together. In the synthesis gas production catalyst of the present invention, even if a metal component other than the above is contained, it is acceptable as long as the object and effect of the present invention are not impaired.
The catalyst of the present invention is one in which Ni is supported on the Mg—Al—Mn composite oxide represented by the general formula (1). The composite oxide after supporting Ni is usually subjected to a reduction treatment in advance when used in the synthesis gas production described later. This is because the catalytic activity is improved by raising the degree of reduction of Ni supported by the reduction treatment and bringing it closer to the metallic state.

The method of the reduction treatment can be optimized as appropriate depending on the composition of the catalyst, but the reduction treatment is usually performed in a reducing gas.
Although reducing gas is not specifically limited, Hydrogen, carbon monoxide, etc. are used normally, Preferably hydrogen is used. These may be used alone or in combination. In the production method of the present invention, the reducing gas may be mixed with an inert gas such as nitrogen or argon. Usually, the reducing gas is diluted with an inert gas. The inert gas at this time may be referred to as balance gas. The reducing gas may contain a raw material gas containing a hydrocarbon such as methane.

The temperature of the reduction treatment is not particularly limited, but is usually 500 ° C. or higher, preferably 600 ° C. or higher, usually 1000 ° C. or lower, preferably 900 ° C. or lower.
The reduction time can be appropriately adjusted to the time required for the supported Ni atoms to be reduced according to the amount of catalyst used and the catalyst composition, and is usually from 30 minutes to 5 hours, for example.

<Catalyst shape>
The shape of the catalyst for producing synthesis gas of the present invention is not particularly limited, and for example, it is used in the form of powder, granules, columns, cylinders, spheres, etc., and the shape depends on the catalyst bed system used. It can be appropriately selected depending on the case. Further, the catalyst itself may be formed into the above shape, but may be supported on a support base material. The support substrate is not particularly limited, and silica, alumina, magnesia, calcia, zirconia, ceria, zeolite, and the like can be used.

The catalyst of the present invention can be used in a synthesis gas production method by a reforming method, and is used in a “dry reforming method”. The “dry reforming method” has a higher carbon content ratio in the raw material than the “steam reforming method”, so that carbon deposition is likely to occur on the catalyst surface and the activity tends to decrease. This is because the effect of easily removing carbon is remarkable. Further, carbon dioxide can be used effectively due to its characteristics.

<Method for producing synthesis gas>
Next, a synthesis gas production method using the synthesis gas production catalyst of the present invention will be described.
The synthesis gas production method of the present invention is a method for producing a synthesis gas containing carbon monoxide and hydrogen by reacting a raw material gas containing hydrocarbons with carbon dioxide by using the catalyst of the present invention as a reaction catalyst. is there.

A “dry reforming method” in which a raw material gas containing hydrocarbon and carbon dioxide are reacted is represented by the following reaction formula (6).
CH ₄ + CO ₂ → 2CO + 2H ₂ ΔH ₂₉₈ = +247 kJ / mol (6)
The “steam reforming method” in which a raw material gas containing hydrocarbon and water are reacted is represented by the following reaction formula (7).
CH ₄ + H ₂ O → CO + 3H ₂ ΔH ₂₉₈ = + 206 kJ / mol (7)

Although it does not specifically limit as hydrocarbon used for source gas, The thing containing C1-C5 hydrocarbon is preferable, and as C1-C5 hydrocarbon, for example, methane, ethane, propane, butane etc. are included. Although used, methane is more preferable. This is because natural gas, coke by-product gas (COG), and the like are abundant as hydrocarbons containing methane, and can be effectively used as a raw material gas.

The reaction temperature during syngas production is not particularly limited, but is usually 500 ° C. or higher, preferably 550 ° C. or higher, more preferably 600 ° C. or higher, usually 1100 ° C. or lower, preferably 1000 ° C. or lower, more preferably 900 ° C. or lower. It is. If the lower limit is too low, the reforming reaction is an endothermic reaction as shown in the above reaction formulas (5) and (6), which leads to a decrease in the conversion rate of the raw material and a decrease in the reaction rate. May cause a decline. On the other hand, if it is higher than the upper limit, catalyst sintering may occur or the reaction vessel may be damaged.

The reaction pressure is not particularly limited, but is usually 3 kg / cm ² G or more, preferably 5 kg / cm ² G or more, usually 40 kg / cm ² G or less, preferably 30 kg / cm ² G. If it is smaller than the lower limit value, the productivity may be lowered, and if it is larger than the upper limit value, the cost of manufacturing equipment necessary for the high-pressure reaction may be increased.

The reaction mode of the production method of the present invention is not particularly limited. For example, a fixed bed reactor, a fluidized bed reactor, a moving bed reactor, a suspension bed reactor, or the like can be used, and a fixed bed reactor is preferable. .
When carrying out the production method of the present invention in a fixed bed reactor, the gas space velocity (GHSV) is not particularly limited, usually 1000 hr ^-1 or more, preferably 2000 hr ^-1 or more, and usually 30000 hr ^-1 or less, preferably Is 10,000 hr ⁻¹ or less.
When the dry reforming method is performed, the molar ratio of carbon dioxide to hydrocarbon in the raw material gas is not particularly limited, but when the hydrocarbon in the raw material gas is methane, the molar ratio of carbon dioxide to methane (CO ₂ / CH ₄ ), usually 1 or more, usually 5 or less, preferably 3 or less. When CO ₂ / CH ₄ is too smaller than the lower limit, carbon deposition is likely to occur, which may cause a decrease in catalyst activity or a clogging of the reactor. On the other hand, when it is larger than the upper limit value, unreacted CO ₂ increases, so that the recycling load increases and the process economy is lowered.

In the synthesis gas production method of the present invention, water (steam) may be further introduced together with carbon dioxide, and the ratio of steam to carbon dioxide (H ₂ O / CO ₂ ) is not particularly limited, but is usually 0.1 or more. 10 or less. When H ₂ O / CO ₂ is too smaller than the lower limit, it is difficult to obtain the effect of introducing steam, and carbon may be easily deposited. On the other hand, if H ₂ O / CO ₂ is too larger than the upper limit, the amount of steam used increases, which may be disadvantageous from the viewpoint of process economy.

The synthesis gas production method of the present invention may be carried out in the presence of oxygen, and is preferably carried out in the presence of oxygen. The reaction used in the synthesis gas production method of the present invention is a large endothermic reaction as described in the above reaction formulas (5) and (6). Therefore, it is preferable in terms of reaction efficiency that the endothermic component is supplemented with the combustion heat obtained by oxidizing part of the hydrocarbon as the raw material. In this case, the ratio (C / O ₂ ) between the number of moles of hydrocarbon carbon and the number of moles of oxygen molecules in the raw material gas is not particularly limited, but is usually 0.1 or more, preferably 0.5 or more, usually 5 Hereinafter, it is preferably 4 or less.

  The oxygen source in the production of the synthesis gas of the present invention is not particularly limited, and examples thereof include oxygen gas and air, and these oxygen sources can be introduced into the reaction system.

<Analysis conditions of gas chromatograph (GC)>
Apparatus: GC-2014 manufactured by Shimadzu Corporation
Column: Molecular Sieve 5A
Porapak Q
Column temperature: 93 ° C
Detector temperature: 120 ° C
Carrier gas: Ar 40ml / min
Analysis time: 12 minutes <Analysis conditions for micro gas chromatograph (micro GC)>
Apparatus: CP-4900 manufactured by VARIAN
Column: Molecular Sieve 5A
Porapak Q
Column temperature: 80 ° C
Carrier gas: Ar 200 kPa (Molecular Sieve 5)
190 kPa (Porapak Q)
Analysis time: 1 minute

<Catalyst preparation>
Example 1
The Mg—Al—Mn composite oxide was prepared by the following procedure. Magnesium nitrate hexahydrate (Kishida Chemical Co., Ltd.) 19.04 g, Aluminum nitrate nonahydrate (Kishida Chemical Co., Ltd.) 2
. 37 g and 3.20 g of manganese nitrate hexahydrate (manufactured by Kishida Chemical Co., Ltd.) were dissolved in 30 ml of pure water. This mixed aqueous solution was evaporated to dryness and 850 ° C. under an air flow of 200 ml / min.
After firing for 5 hours, an Mg—Al—Mn composite oxide (Mg: Al: Mn (molar ratio) = 0.82: 0.09: 0.09, FIG. 1: A) was obtained. Ni was supported on the Mg—Al—Mn composite oxide by the following procedure. To a nickel acetate aqueous solution in which 0.13 g of nickel acetate tetrahydrate (manufactured by Kishida Chemical Co., Ltd.) was dissolved in 1.87 ml of pure water, 1.00 g of Mg—Al—Mn composite oxide was added, After evaporating to dryness, the catalyst of Example 1 (3 wt% Ni / Mg _0.82 Al _0.09 Mn _0.09 O _δ ) was obtained by calcination in Air at 600 ° C. for 2 hours.

<Catalyst activity evaluation>
The catalyst was molded into a spherical tablet having a diameter of 250 to 600 μm. After 0.025 g of the molded catalyst was filled in a glass reaction tube, reduction treatment was performed at 700 ° C. for 30 minutes in an 8% by volume H ₂ stream using nitrogen gas as a balance gas. After the reduction treatment, methane is used as a raw material gas, and a mixed gas of CH ₄ / CO ₂ = 1/1 (molar ratio) is applied to the catalyst layer at a reaction temperature of 750 ° C. and a gas space velocity of GHSV = 24000 hr ⁻¹ under atmospheric pressure. Circulated. The gas that passed through the catalyst layer every 2 hours from the start of the reaction was analyzed by a gas chromatograph (GC) under the above conditions. From the GC analysis results, the CH ₄ conversion was determined. The CH ₄ conversion rate was calculated from the following formula, assuming that the conversion rate after the lapse of α time was [CH ₄ conversion rate] _α .

[CH ₄ conversion ratio] _α = (1- (number of moles of CH _{4 in} the product) / (CH _{4 in} raw material gas)
Number of moles)) x 100 (%)
Further, [CH ₄ conversion rate] ₁₀ and [CH ₄ conversion rate] ₂₀ which are CH ₄ conversion rates after 10 hours and 20 hours are obtained, and the difference between the conversion rates is calculated as [ΔCH ₄ conversion rate] = [CH _{4 conversion]} 20 - [calculated as CH _{4 conversion] 10.}
[ΔCH ₄ conversion] represents the degree of activity decrease, and the smaller the value, the better.

(Examples 2 to 10, Comparative Examples 1 to 3)
Hereinafter, similarly, catalysts having the composition ratios shown in Table 1 were prepared, and the catalytic activity was evaluated.

As shown in Table 1, when a composite oxide containing 0.1 or more of Mn in molar ratio was used as in Examples 1 to 10, the activity was high and the degree of activity decrease was small.
Furthermore, when a complex oxide having a molar ratio of Mn of 0.1 or more and 0.3 or less is used, it can be seen that [CH ₄ conversion] ₁₀ is high and [ΔCH ₄ conversion] is small, It can be seen that the degree of decrease in activity is smaller.

On the other hand, in the case where the Mn content molar ratio is small as in Comparative Example 1, the reaction tube was clogged by carbon deposition within 10 hours from the start of the reaction, which clearly shows that the catalyst performance is low.
In addition, the Al—Mn composite oxide of Comparative Example 2 and the Mg—Mn composite oxide of Comparative Example 3 have [CH ₄ conversion ratio] ₁₀ lower than that of the Mg—Al—Mn composite oxide catalyst. It can be seen that the activity is not sufficient. On the other hand, the Mg—Al based composite oxide has high catalytic activity but does not contain Mn, and therefore does not have the ability to remove precipitated carbon as shown in Comparative Example 4 described later.
Therefore, in order to obtain the effect of the present invention, the composition of the support Mg—Al—Mn based composite oxide is very important. It can be said that it is necessary to make the composition range include a certain amount or more.

<Evaluation of deposited carbon removal ability>
As Comparative Example 4, a composite oxide was prepared in the same manner as in Example 1 except that the ratio of each component of the composite oxide was adjusted to be Mg _0.8 Al _0.2 O _δ .
The composite oxide of Comparative Example 4 and the composite oxide used in the catalyst of Example 7 were compared in terms of the ability to oxidize and remove the deposited carbon by carbon dioxide using carbon black as a simulated substance of the precipitated carbon.

0.005 g of carbon black (Mitsubishi Carbon Black # 40) was mixed with 0.095 g of each catalyst and charged into a glass reaction tube. While flowing a mixed gas of CO ₂ and N ₂ (CO ₂ : 1 cc / min, N ₂ : 9 cc / min) through the mixture phase of carbon black and catalyst, the temperature was raised to 800 ° C. at 25 ° C./min, Hold for 2 hours at ° C. The reaction gas was analyzed by micro GC under the above conditions to evaluate the carbon black removal ability.

First, when only a carbon black is filled in a glass reaction tube and a mixed gas of CO ₂ and N ₂ is circulated and the temperature is raised, no generation of CO is observed, and carbon black alone is not oxidized by CO _2. confirmed. Next, the results of evaluation by mixing a catalyst with carbon black are shown in FIGS. From FIG. 3, it can be seen that when the catalyst of Comparative Example 4 containing no Mn is used, there is almost no generation of CO, and therefore the oxidation reaction of carbon black hardly proceeds. On the other hand, from FIG. 2, when the catalyst of Example 7 containing Mn was used, the generation of CO was recognized, so it is considered that carbon was oxidized using CO ₂ as an oxidizing agent by the catalytic action of Mn. From the above results, the catalyst in which Ni is supported on the Mg—Al—Mn composite oxide of the present invention can oxidize and remove the deposited carbon even with CO _{2, so} even if carbon deposition occurs in a dry reforming reaction atmosphere, It is considered that high catalytic activity can be maintained for a long time because precipitated carbon can be removed quickly.

  Since the catalyst for syngas production of the present invention provides a catalyst for syngas production with high catalytic activity, the synthesis gas can be produced with high efficiency, and the activity of the catalyst does not decrease, and it is highly efficient for a long time. Syngas can be produced.

Claims (6)

A synthesis gas production catalyst for producing a synthesis gas containing carbon monoxide and hydrogen by reacting a raw material gas containing hydrocarbons with carbon dioxide,
A catalyst for syngas production, wherein the catalyst is a composite oxide represented by the following general formula (1) supporting Ni.
_{Mg x Al y Mn z O δ} ··· (1)
(In the general formula (1), x, y, and z each represent a molar ratio of magnesium, aluminum, and manganese atoms contained in the composite oxide, and satisfy the following formulas (2) to (5).
0.01 ≦ x ≦ 0.9 0 (2)
0.01 ≦ y ≦ 0. 60 ... (3)
z ≧ 0.1 (4)
x + y + z = 1.0 (5)
δ represents a number necessary to satisfy the charge neutrality condition. ) In the said General formula (1), it is z <= 0.3, The catalyst for syngas production of Claim 1 characterized by the above-mentioned .   A method of producing a synthesis gas containing carbon monoxide and hydrogen by reacting a raw material gas containing hydrocarbon and carbon dioxide, wherein the catalyst according to claim 1 or 2 is used as a reaction catalyst. A method for producing synthesis gas.   The method for producing a synthesis gas according to claim 3, wherein the raw material gas and carbon dioxide are reacted in the presence of oxygen.   The method for producing synthesis gas according to claim 3 or 4, wherein the source gas contains methane. The molar ratio of carbon dioxide to methane (CO ₂ / CH ₄ ) in the source gas is 1 or more and 5
The method for producing synthesis gas according to claim 5, wherein: