JP3957116B2 - Method of converting carbon dioxide with methane - Google Patents

Description

１）比表面積保持率（％）
＝〔（試験後比表面積）／（試験前比表面積）〕×１００
【００３７】
【表２】

【００３８】
【表３】

【００３９】
表１から、本発明の方法に係る触媒Ａ、Ｂ、Ｃ、Ｄ、Ｅは、比較触媒Ｆ、Ｇ、Ｈ、Ｉに比べ、耐熱安定性が高いことが判る。
また、表２、３から、本発明の方法に係る耐熱安定性の高い触媒は、比較触媒に比べ、メタンによる二酸化炭素の、一酸化炭素及び水素への高い転化活性を長時間持続でき、更に炭素も析出し難いことが判る。
【００４０】
【発明の効果】
本発明の方法によれば、用いる触媒が、耐熱安定性が高く、かつ炭素が析出し難いばかりか、メタンによる二酸化炭素の転化活性が高く、一酸化炭素及び水素を長期間効率良く得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention uses industrially useful carbon monoxide and hydrogen (hereinafter referred to as synthesis gas) using methane, which is the main component of natural gas, and carbon dioxide, which is a major cause of global warming. It relates to a method of manufacturing.
[0002]
[Technical background]
In recent years, since carbon dioxide is one of the main causative substances of global warming, reduction of emission and effective use are regarded as urgent issues.
For this reason, various chemical conversion methods that effectively utilize carbon dioxide gas have been studied. Of these, attempts have also been made to produce synthesis gas, which is useful as a raw material for synthesizing various organic compounds or a raw material for FT synthetic oil, from methane and carbon dioxide by hydroformylation of olefins. As the catalyst used in this method, a Group VIII metal is usually mentioned.
[0003]
However, this type of catalyst has a problem that it is difficult to maintain a stable activity due to sintering of a carrier or a metal as an active component, precipitated carbon, and the like.
A catalyst (Japanese Patent Laid-Open No. 9-75728) carrying a large amount of an expensive noble metal in order to maintain the activity for a long time is economically disadvantageous.
[0004]
In addition, as in the case of noble metals, inexpensive group VIII transition metals having activity for the conversion of carbon dioxide by methane, especially catalysts carrying highly active nickel, have a strong tendency to deposit carbon, resulting in decreased activity and clogging of reaction tubes. There is a problem that it is easy.
For this reason, a method of adding an alkaline earth metal or the like (JP-A-5-170403, JP-A-9-25101) is shown, but the methane and carbon dioxide conversion activity is lowered.
[0005]
Furthermore, in order to achieve efficient conversion to synthesis gas, it is effective to use at high temperature conditions, so there is a concern that the catalyst life may be shortened by sintering, and heat stability is also improved. An excellent catalyst development is desired.
[0006]
OBJECT OF THE INVENTION
Therefore, the present invention uses a catalyst that has high heat stability, low carbon deposition, and can maintain high conversion performance for a long period of time despite the small amount of expensive metal used. Another object is to provide a method for efficiently producing carbon monoxide and hydrogen from a gas containing carbon dioxide.
[0007]
SUMMARY OF THE INVENTION
In order to achieve the above object, the carbon dioxide conversion method of the present invention is a method for producing synthesis gas (carbon monoxide and hydrogen) by bringing a gas containing methane and carbon dioxide into contact with a catalyst. The catalyst is characterized in that a rare earth metal oxide, an alkaline earth metal oxide, nickel, and a small amount of rhodium are supported in a predetermined amount and calcined at 1000 to 1100 ° C. after the rare earth metal is supported.
According to the method of the present invention, carbon monoxide and hydrogen can be produced efficiently for a long period of time without causing an economic disadvantage.
[0008]
The methane used in the present invention may be either methane alone or a methane-containing gas. Examples of the methane-containing gas include natural gas and alternative natural gas. In addition to methane, saturated hydrocarbons such as ethane and propane; unsaturated hydrocarbons such as ethylene, propylene and butene; carbon dioxide and trace amounts of hydrogen sulfide , Hydrogen, 1 to 20 mol% carbon monoxide, nitrogen, air, water vapor and the like.
Any carbon dioxide may be used, and examples thereof include natural gas containing CO ₂ and thermal power generation exhaust gas. In addition to CO ₂ , saturated hydrocarbons such as methane, ethane, and propane; ethylene, propylene, butene Unsaturated hydrocarbons such as hydrogen sulfide, hydrogen, carbon monoxide, air, water vapor and the like.
[0009]
The gas containing methane and carbon dioxide, which is the raw material gas of the present invention, is a mixed gas of methane or methane-containing gas as described above and carbon dioxide or carbon dioxide-containing gas, or methane-containing gas or carbon dioxide-containing gas. In addition, when carbon dioxide or methane is contained in a predetermined amount, it can be used as it is.
The molar ratio of methane / carbon dioxide in the gas containing methane and carbon dioxide is suitably 0.05 to 25, preferably 0.1 to 20, and more preferably 0.2 to 10.
If it is less than 0.05, the amount of carbon dioxide increases and the amount of hydrogen produced decreases, and if it exceeds 25, a sufficient carbon monoxide production rate cannot be obtained, and carbon deposition also increases.
[0010]
Further, in order to obtain a synthesis gas having a wide range of hydrogen / carbon monoxide ratio, water vapor can be supplied simultaneously with the raw material gas.
That is, in the method of the present invention, if water vapor is present together with carbon dioxide and methane in the reaction system, in addition to methane, water vapor can also act as a hydrogen source, so by adjusting the water vapor concentration, A synthesis gas having a composition corresponding to various uses can be obtained.
The supply amount of water vapor is S / C (water vapor / methane molar ratio), 0.1 to 3, preferably 0.5 to 1.5.
If it is less than 0.1, the amount of hydrogen produced decreases, and if it exceeds 3, the conversion rate of carbon dioxide decreases and the production efficiency decreases.
[0011]
The catalyst carrier used in the present invention is preferably alumina with a high surface area such as γ-alumina or η-alumina.
As the alumina, in addition to alumina alone, a metal oxide such as silica, zirconia, titania, niobia, crystalline alumina silicate and the like may be included.
[0012]
Of the components supported on the carrier (hereinafter sometimes referred to as “supported component”, “active component”, “active metal”, etc.), the rare earth metal oxide is preferably yttrium oxide or lanthanum oxide.
The molar ratio of the rare earth metal oxide to nickel (rare earth metal oxide / Ni) is 0.01 to 1, preferably 0.03 to 0.3, and the supported amount of the rare earth metal oxide in the entire catalyst is: 1-5 mass%, Preferably it is 2-4.5.
If the rare earth metal oxide / Ni molar ratio is less than 0.01 or the amount of the rare earth metal oxide supported in the total catalyst is less than 1% by mass, the effect of supporting the rare earth metal oxide becomes insufficient, and the rare earth metal oxide Even when the / Ni molar ratio exceeds 1 or the supported amount of rare earth metal oxide in all the catalysts exceeds 5% by mass, the supporting effect is saturated.
[0013]
The method for adding the rare earth metal oxide is not particularly limited, and for example, a known supporting method such as an impregnation method, a coprecipitation method, or a sol / gel method can be used.
For example, a method in which an alumina molding is immersed in an aqueous solution containing a rare earth metal salt, dried and fired; a method in which ammonium is added to an aqueous solution containing aluminum and a rare earth metal salt to form a precipitate, and the resulting gel is dried and fired A method of hydrolyzing aluminum alkoxide using a rare earth metal salt aqueous solution to obtain a precipitate, drying and baking, and the like.
The firing temperature at this time is set to 1000 to 1100 ° C. in order to keep the catalyst having high heat stability.
[0014]
Of the supported components, the alkaline earth metal oxide is preferably magnesium oxide, calcium oxide, strontium oxide, or barium oxide.
The molar ratio of alkaline earth metal oxide to nickel (alkaline earth metal oxide / Ni) is 0.3 to 20, preferably 0.3 to 3, and more preferably 0.3 to 1.
If it is less than 0.3, the effect of supporting alkaline earth metal is insufficient, and if it exceeds 20, the catalytic activity is decreased.
[0015]
The method for supporting the alkaline earth metal oxide is not particularly limited, and known supporting methods such as an impregnation method, a coprecipitation method, and a sol / gel method can be used.
For example, a method in which an alumina molded article supporting a rare earth metal oxide by the above method is dipped in an aqueous solution containing an alkaline earth metal salt, dried and fired; an aqueous solution containing aluminum, a rare earth metal salt and an alkaline earth metal salt A method in which ammonium is added to form a precipitate, and the resulting gel is dried and fired; aluminum alkoxide is hydrolyzed using an aqueous solution containing a rare earth metal salt and an alkaline earth metal salt to obtain a precipitate, and then dried and fired. And the like.
[0016]
Among the active ingredients, nickel and rhodium have a molar ratio of rhodium to nickel (Rh / Ni) of 0.005 to 0.4, preferably 0.005 to 0.1, more preferably 0.01 to 0.1. It is made to carry so that it may become.
If it is less than 0.005, the effect of carrying Rh is small, and if it exceeds 0.4, the effect of carrying Rh is saturated, which is economically disadvantageous.
The method for supporting nickel and rhodium is not particularly limited, and known methods such as an impregnation method, a coprecipitation method, and a sol-gel method can be used.
For example, a method in which an alumina molded product supporting a rare earth metal oxide and an alkaline earth metal oxide by the above method is immersed in an aqueous solution containing a nickel salt, a rhodium salt, etc., dried and fired; aluminum (support), rare earth Examples include a method in which an alkaline earth metal aqueous solution is added to an aqueous solution containing a metal salt, nickel and rhodium salt to form a precipitate, and the resulting gel is dried and fired.
[0017]
Finally, the total supported amount of the rare earth metal oxide, alkaline earth metal oxide, nickel oxide, and rhodium metal or rhodium oxide in the catalyst is 5 to 30% by mass. If it is less than 5% by mass, sufficient catalyst performance cannot be obtained, and if it exceeds 30% by mass, the expected loading effect cannot be obtained.
[0018]
In the method of the present invention, the catalyst is used after being reduced, and this reduction may be performed with a reducing gas, and may be performed in the catalyst preparation step as described above (specifically, after the calcination step). The previous catalyst may be fixed in a reactor for carrying out the process of the present invention, and may be carried out in the reactor after drying.
As the reducing gas, pure hydrogen, carbon monoxide, or a mixed gas containing these can be used, and hydrogen gas is particularly preferable.
The reduction can be performed at a reaction temperature when methane and carbon dioxide are brought into contact with the catalyst, but can also be performed at a low temperature of about 100 to 180 ° C. so that the active metal to be supported does not aggregate.
[0019]
The method of the present invention is carried out by bringing a gas containing methane and carbon dioxide into contact with the catalyst described above.
The reaction temperature at this time is preferably in the range of 300 to 400 ° C. for the lower limit and 1000 to 900 ° C. for the upper limit (in other words, 300 to 1000 ° C., preferably 400 to 900 ° C.). If the temperature is lower than 300 ° C., sufficient conversion rates of methane and carbon dioxide cannot be obtained, and if it exceeds 1000 ° C., there is a concern that the activity may be reduced due to sintering of the catalyst.
The reaction pressure is not particularly limited, and the lower limit is about normal pressure, and the upper limit is about 40 to 20 atmospheres (in other words, normal pressure to 40 atmospheres, preferably normal pressure to 40 atmospheres). .
The feed rate of the source gas is GHSV, and the lower limit value is in the range of 500 to 5,000 h ⁻¹ and the upper limit value is in the range of 500,000 to 300,000 h ⁻¹ (in other words, 500 to 500,000 h. ^-1 , preferably 5,000 to 300,000 h ^-1 ). Small production rate of carbon monoxide is less than 500h ^-1, feed conversion ratio decreases exceeds 500,000 ^-1.
The reaction method is not particularly limited as long as the catalyst and the raw material can be efficiently contacted, and for example, a fixed bed, a fluidized bed, or a moving bed can be adopted.
[0020]
【Example】
Example 1
After immersing 20 g of alumina (trade name “GB-45” manufactured by Mizusawa Chemical Co., Ltd.) adjusted to 16 to 28 mesh in an aqueous solution of 2.8 g of lanthanum nitrate hexahydrate dissolved in 15 ml of pure water at 60 ° C. for 30 minutes. The mixture was evaporated to dryness with a rotary evaporator, then dried at 110 ° C. for 11 hours, and calcined at 1000 ° C. for 3 hours to obtain an alumina support carrying lanthanum oxide.
Next, the entire amount of the lanthanum oxide-added alumina carrier was immersed in an aqueous solution in which 6.7 g of magnesium nitrate hexahydrate was dissolved in 10 ml of pure water at 60 ° C. for 30 minutes, and then evaporated to dryness with a rotary evaporator. It was dried for 11 hours and calcined at 900 ° C. for 3 hours to carry magnesium oxide.
Subsequently, the entire amount of the lanthanum oxide and magnesium oxide-supported alumina carrier was immersed in an aqueous solution in which 12.5 g of nickel nitrate hexahydrate and 0.35 g of rhodium acetate were dissolved in 10 ml of pure water at 60 ° C. for 30 minutes. 3. Evaporate to dryness with an evaporator, then dry at 110 ° C. for 11 hours, and calcined at 900 ° C. for 3 hours to obtain nickel oxide 10% by mass, rhodium 0.5% by mass, magnesium oxide 4.5% by mass, lanthanum oxide. Catalyst A comprising 2% by mass and 80.8% by mass of alumina was obtained.
Catalyst A has a Rh / Ni molar ratio of 0.04, a MgO / Ni molar ratio of 0.8, and a La ₂ O ₃ / Ni molar ratio of 0.1.
[0021]
About 1 g of Catalyst A was weighed into an evaporating dish and subjected to a heat resistance test for 24 hours at 1100 ° C. in air under atmospheric pressure.
Using about 0.3 g of catalyst A before and after the test, the specific surface area was measured by the nitrogen adsorption method. The results are shown in Table 1.
[0022]
Example 2
3. Nickel oxide 10% by mass, rhodium 0.5% by mass, magnesium oxide 4.5% by mass, lanthanum oxide 4. The calcination treatment after supporting lanthanum nitrate was changed to 1100 ° C. for 1 hour. Catalyst B consisting of 2% by mass and 80.8% by mass of alumina was obtained.
The Rh / Ni molar ratio is 0.04, the MgO / Ni molar ratio is 0.8, and the La ₂ O ₃ / Ni molar ratio is 0.1.
Using 1 g of Catalyst B, the heat resistance test was performed in the same manner as in Example 1. The results are shown in Table 1.
[0023]
Example 3
Instead of lanthanum nitrate hexahydrate, nickel oxide 10% by mass, rhodium 0.5% by mass, magnesium oxide 4.5% in the same manner as in Example 1 except that 5.7 g of yttrium nitrate hexahydrate was used. Catalyst C consisting of 4% by mass, 4.2% by mass of yttrium oxide, and 80.8% by mass of alumina was obtained.
The Rh / Ni molar ratio is 0.04, the MgO / Ni molar ratio is 0.8, and the Y ₂ O ₃ / Ni molar ratio is 0.14.
A heat resistance test was conducted in the same manner as in Example 1 using 1 g of Catalyst C. The results are shown in Table 1.
[0024]
Example 4
10% by mass of nickel oxide, 0.5% by mass of rhodium, 4.5% of calcium oxide were used in the same manner as in Example 1 except that 4.4 g of calcium nitrate tetrahydrate was used instead of magnesium nitrate hexahydrate. A catalyst D consisting of 4% by mass, 4.2% by mass of lanthanum oxide, and 80.8% by mass of alumina was obtained.
The Rh / Ni molar ratio is 0.04, the CaO / Ni molar ratio is 0.6, and the La ₂ O ₃ / Ni molar ratio is 0.1.
A heat resistance test was conducted in the same manner as in Example 1 using 1 g of the catalyst D. The results are shown in Table 1.
[0025]
Example 5
Instead of magnesium nitrate hexahydrate, nickel oxide 10% by mass, rhodium 0.5% by mass, strontium oxide 4.5% by mass, except that 2.2 g of anhydrous strontium nitrate was used. A catalyst E composed of 4.2% by mass of lanthanum oxide and 80.8% by mass of alumina was obtained.
The Rh / Ni molar ratio is 0.04, the SrO / Ni molar ratio is 0.3, and the La ₂ O ₃ / Ni molar ratio is 0.1.
A heat resistance test was conducted in the same manner as in Example 1 using 1 g of Catalyst E. The results are shown in Table 1.
[0026]
Comparative Example 1
The carrier alumina was calcined at 1000 ° C. for 3 hours and the same procedure as in Example 1 except that lanthanum nitrate was not used. Nickel oxide 10% by mass, rhodium 0.5% by mass, magnesium oxide 4.5% by mass, alumina Catalyst F consisting of 85.0% by mass was obtained.
The Rh / Ni molar ratio is 0.04, the MgO / Ni molar ratio is 0.8, and the La ₂ O ₃ / Ni molar ratio is 0.
A heat resistance test was conducted in the same manner as in Example 1 using 1 g of Catalyst F. The results are shown in Table 1.
[0027]
Comparative Example 2
10% by mass of nickel oxide, 0.5% by mass of rhodium, 4.5% by mass of magnesium oxide, alumina, except that lanthanum nitrate was not used and the firing temperature after supporting magnesium was 1000 ° C. A catalyst G consisting of 85.0% by mass was obtained.
The Rh / Ni molar ratio is 0.04, the MgO / Ni molar ratio is 0.8, and the La ₂ O ₃ / Ni molar ratio is 0.
Using 1 g of catalyst G, a heat resistance test was performed in the same manner as in Example 1. The results are shown in Table 1.
[0028]
Comparative Example 3
Except for setting the calcination temperature after supporting lanthanum to 900 ° C., in the same manner as in Example 1, nickel oxide 10% by mass, rhodium 0.5% by mass, magnesium oxide 4.5% by mass, lanthanum oxide 4.2% by mass, And the catalyst H which consists of 80.8 mass% of alumina was obtained.
The Rh / Ni molar ratio is 0.04, the MgO / Ni molar ratio is 0.8, and the La ₂ O ₃ / Ni molar ratio is 0.1.
Using 1 g of catalyst H, the heat resistance test was performed in the same manner as in Example 1. The results are shown in Table 1.
[0029]
Comparative Example 4
10% by mass of nickel oxide, 0.5% by mass of rhodium, 4.5% by mass of magnesium oxide in the same manner as in Example 1 except that the firing temperature after supporting each of lanthanum, magnesium, nickel and rhodium was 700 ° C. Then, Catalyst I consisting of 4.2% by mass of lanthanum oxide and 80.8% by mass of alumina was obtained.
The Rh / Ni molar ratio is 0.04, the MgO / Ni molar ratio is 0.8, and the La ₂ O ₃ / Ni molar ratio is 0.1.
A heat resistance test was conducted in the same manner as in Example 1 using 1 g of Catalyst I. The results are shown in Table 1.
[0030]
Examples 6-10
15 mg of catalyst A (Example 6), B (Example 7), C (Example 8), D (Example 9), and E (Example 10) were weighed on a thermobalance. Reduction treatment was performed at 900 ° C. for 1 hour in an atmosphere.
Next, after switching to a helium atmosphere and setting the conditions to 850 ° C. and 10 atm, the helium supply is stopped, so that the methane / carbon dioxide molar ratio = 1 / 0.5 and the water vapor / methane molar ratio = 0.5 / 1. A raw material gas (120 ml / min) in which pure water was vaporized and mixed was introduced, and a reaction test was conducted for 3 hours.
The amount of carbon deposition was evaluated from the amount of increase in the catalyst weight, and the production amounts of hydrogen and carbon monoxide were evaluated by a quadrupole mass spectrometer.
The production amounts of hydrogen and carbon monoxide were relatively evaluated based on the production amounts of each gas of Comparative Example 5 below. The results are shown in Table 2.
[0031]
Comparative Example 5
Except that rhodium acetate was not used, in the same manner as in Example 1, a catalyst J comprising 10% by mass of nickel oxide, 4.5% by mass of magnesium oxide, 4.2% by mass of lanthanum oxide, and 81.3% by mass of alumina was obtained. Obtained.
The Rh / Ni molar ratio is 0, the MgO / Ni molar ratio is 0.8, and the La ₂ O ₃ / Ni molar ratio is 0.1.
The same evaluation test as in Example 6 was performed using 15 mg of Catalyst J. The results are shown in Table 2.
[0032]
Comparative Example 6
Except not using magnesium nitrate, the catalyst K which consists of nickel oxide 10 mass%, rhodium 0.5 mass%, lanthanum oxide 4.2 mass%, and alumina 85.3 mass% was obtained in the same manner as in Example 1. It was.
The Rh / Ni molar ratio is 0.04, the MgO / Ni molar ratio is 0, and the La ₂ O ₃ / Ni molar ratio is 0.1.
An evaluation test was carried out in the same manner as in Example 6 using 15 mg of Catalyst K. The results are shown in Table 2.
[0033]
Comparative Examples 7 and 8
An evaluation test was carried out in the same manner as in Example 6 using 15 mg of Catalyst F (Comparative Example 7) and I (Comparative Example 8). The results are shown in Table 2.
[0034]
Examples 11-13
1.5 g of catalyst A (Example 11), D (Example 12), and E (Example 13) were each placed in an Inconel reaction tube having an inner diameter of 19 mm and quartz having the same particle size as the catalyst so as to have a layer height of 20 mm. Diluted and filled with a piece, a reduction treatment was performed at 900 ° C. for 2 hours in a hydrogen atmosphere.
Subsequently, pure water was vaporized and mixed so that the methane / carbon dioxide molar ratio = 1/1 and the water vapor / methane molar ratio = 1/1, and introduced into the reaction tube under the condition of GHSV 210,000 h ⁻¹ .
Performance evaluation was performed at a reaction temperature of 850 ° C. and a reaction pressure of 10 atm.
The reaction product gas at this time was analyzed with a gas chromatograph after removing moisture contained therein. The results are shown in Table 3.
[0035]
Comparative Examples 9-11
An evaluation test was conducted in the same manner as in Example 11 using 1.5 g of Catalyst F (Comparative Example 9), H (Comparative Example 10), and J (Comparative Example 11). The results are shown in Table 3.
[0036]
[Table 1]

1) Specific surface area retention rate (%)
= [(Specific surface area after test) / (Specific surface area before test)] x 100
[0037]
[Table 2]

[0038]
[Table 3]

[0039]
From Table 1, it can be seen that the catalysts A, B, C, D and E according to the method of the present invention have higher heat stability than the comparative catalysts F, G, H and I.
In addition, from Tables 2 and 3, the heat-resistant and stable catalyst according to the method of the present invention can maintain a high conversion activity of carbon dioxide by methane to carbon monoxide and hydrogen for a long time as compared with the comparative catalyst. It can be seen that carbon is difficult to deposit.
[0040]
【The invention's effect】
According to the method of the present invention, the catalyst used has high heat stability and is difficult to precipitate carbon, and also has high carbon dioxide conversion activity by methane, and can efficiently obtain carbon monoxide and hydrogen for a long period of time. it can.

Claims (1)

For the support, rare earth metal oxide, alkaline earth metal oxide, nickel, and rhodium, a molar ratio of rhodium to nickel of 0.005 to 0.4, a molar ratio of rare earth metal oxide to nickel of 0.01 to 1, Supported at a molar ratio of alkaline earth metal oxide to nickel of 0.3-20,
The total supported amount of rare earth metal oxide, alkaline earth metal oxide, nickel oxide, and rhodium metal or rhodium oxide in the catalyst is 5 to 30% by mass,
A method for converting carbon dioxide with methane, comprising bringing a gas containing carbon dioxide and methane into contact with a catalyst obtained by calcining at 1000 to 1100 ° C. after supporting the rare earth metal.