JP2010194534A - Catalyst for reverse shift reaction, method for producing the same and method for producing synthetic gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst for a reverse shift reaction which is excellent in durability at a high temperature, can suppress formation of a methanation reaction, efficiently forms the reverse shift reaction, is low in methane content and can efficiently produce a synthetic gas including carbon monoxide and unreacted hydrogen, and a method for producing the synthetic gas using the catalyst for the reverse shift reaction. <P>SOLUTION: A composition includes: a carbonate of an alkaline earth metal of at least one selected from the group consisting of Ca, Sr and Ba; and a composite oxide containing an alkaline earth metal of at least one selected from the group consisting of Ca, Sr and Ba and a component of at least one selected from the group consisting of Ti, Al, Zr, Fe, W and Mo. The composite oxide is ATiO<SB>3</SB>, AAl<SB>2</SB>O<SB>4</SB>, AZrO<SB>3</SB>, AFe<SB>2</SB>O<SB>4</SB>, AWO<SB>4</SB>, A<SB>2</SB>WO<SB>5</SB>and AMoO<SB>4</SB>(where A is an alkaline earth metal of at least one selected from the group consisting of Ca, Sr and Ba). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reverse shift reaction catalyst having activity for a reaction of generating carbon monoxide and water vapor from carbon dioxide and hydrogen, which is the reverse reaction of the shift reaction of generating carbon dioxide and hydrogen from carbon monoxide and water vapor. The present invention relates to a method for producing synthesis gas using the same.

  In recent years, since carbon dioxide is a major causative substance of global warming, reduction and effective use of emissions has been an urgent issue. In addition, hydrocarbon-based gases are generated from technical fields such as petroleum refining and petrochemistry, but there is a need for a method for efficiently converting them into more effective substances.

  Under such circumstances, a method has been proposed in which a reverse shift reaction is performed using hydrogen and carbon dioxide to produce a synthesis gas composed of generated carbon monoxide and unreacted hydrogen (Patent Document 1 and 2).

  Further, as shown in the prior art of Patent Document 1 (paragraph 0002), a method is known in which carbon dioxide in the gas after steam reforming is separated and returned to the reformer.

By the way, for the purpose of producing hydrogen, many catalysts have been put to practical use as catalysts for promoting the aqueous shift reaction represented by the following formula (1), that is, so-called shift reaction catalysts.
CO + H ₂ O → CO ₂ + H ₂ (1)

Further, it is considered that many of the catalysts that promote the shift reaction also have activity as a reverse shift reaction catalyst represented by the following formula (2).
CO ₂ + H ₂ → CO + H ₂ O (2)

  By the way, this reverse shift reaction is desirably performed at a high temperature of 600 ° C. or higher in view of the composition (equilibrium composition) of the synthesis gas produced by the reaction. However, since the temperature of 600 ° C. or higher is usually much higher than the temperature at which the aqueous shift reaction is performed, it is actually difficult to use a catalyst for a normal shift reaction.

In addition, the reverse shift reaction proceeds even in a general steam reforming catalyst, but under pressurized conditions, methanation of the following formula (3), which is the reverse reaction of the steam reforming reaction, occurs to produce methane. As a result, there is a problem that the concentration of carbon monoxide decreases.
CO + 3H ₂ → CH ₄ + H ₂ O (3)

Japanese Patent Laid-Open No. 6-21502 Japanese Patent Laid-Open No. 4-244035

  The present invention has been made in view of the above circumstances, can be used at high temperatures, suppresses the formation of methanation reaction, efficiently generates a reverse shift reaction, and has a low methane content. An object of the present invention is to provide a reverse shift reaction catalyst capable of obtaining a synthesis gas composed of carbon oxide and hydrogen, and a synthesis gas production method using the reverse shift reaction catalyst.

In order to solve the above problems, the reverse shift reaction catalyst of the present invention is
A reverse shift reaction catalyst used to generate carbon monoxide and water vapor from carbon dioxide and hydrogen,
At least one alkaline earth metal carbonate selected from the group consisting of Ca, Sr and Ba;
At least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba, and a composite oxide containing at least one component selected from the group consisting of Ti, Al, Zr, Fe, W and Mo. It is characterized by containing.

The composite oxide is at least one selected from the group consisting of ATiO ₃ , AAl ₂ O ₄ , AZrO ₃ , AFe ₂ O ₄ , AWO ₄ , A ₂ WO ₅ , AMoO ₄ (A is Ca, Sr and Ba). A kind of alkaline earth metal).

The method for producing the reverse shift reaction catalyst of the present invention comprises:
A method for producing a reverse shift reaction catalyst used for producing carbon monoxide and water vapor from carbon dioxide and hydrogen,
A composite oxide of at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba and at least one component selected from the group consisting of Ti, Al, Zr, Fe, W and Mo is synthesized. And a process of
And a step of causing the composite oxide to absorb carbon dioxide to form a carbonate.

  The method for producing a synthesis gas according to the present invention includes a source gas containing carbon dioxide and hydrogen brought into contact with the reverse shift reaction catalyst according to claim 1 or 2 under a temperature condition of 700 ° C. or higher. It is characterized by letting.

  The reverse shift reaction catalyst of the present invention comprises at least one alkaline earth metal carbonate selected from the group consisting of Ca, Sr and Ba, and at least one alkali selected from the group consisting of Ca, Sr and Ba. Containing an earth metal and a composite oxide containing at least one component selected from the group consisting of Ti, Al, Zr, Fe, W and Mo, and using this reverse shift reaction catalyst, It is possible to efficiently produce a reverse shift reaction of hydrogen and carbon dioxide while suppressing the methanation reaction under high temperature conditions, and it is possible to efficiently produce synthesis gas containing carbon monoxide and hydrogen. Become.

As described above, the shift reaction is a reaction for generating H ₂ and CO ₂ using CO and H ₂ O as raw materials as shown in the following formula (1).
CO + H ₂ O → CO ₂ + H ₂ (1)
At this time, the composition of CO ₂ , H ₂ , CO, and H ₂ O is governed by chemical equilibrium, and the hydrogen production process is performed at a low temperature at which the reaction of the above formula (1) easily proceeds.

In the high temperature range, a reaction in the opposite direction, that is, a reverse shift reaction shown by the following formula (2) occurs.
CO ₂ + H ₂ → CO + H ₂ O (2)

Therefore, when it is desired to obtain a synthesis gas having a high CO concentration using H ₂ and CO ₂ as raw materials, the reverse shift reaction of the above formula (2) may be advanced at a higher temperature than the normal shift reaction process.

In the above formula (2), CO and H ₂ O are produced. As described above, the composition of CO ₂ , H ₂ , CO, and H ₂ O is governed by the chemical equilibrium. The composition of the gas to be produced is determined by the reaction temperature and the CO ₂ / H ₂ ratio of the raw material gas. In order to obtain synthesis gas, unreacted CO ₂ and generated H ₂ O may be removed from the gas after the reaction. The higher the H ₂ ratio of the source gas, the higher the H ₂ ratio of the synthesis gas obtained.

  The reverse shift reaction catalyst of the present invention has activity as a catalyst for causing the reaction of the above formula (2) at a high temperature exceeding 700 ° C. (for example, 700 ° C. to 1100 ° C.) as described above.

In the reverse shift reaction catalyst of the present invention, ATiO ₃ , AAl ₂ O ₄ , AZrO ₃ , AFe ₂ O ₄ , AWO ₄ , A ₂ WO ₅ , AMoO ₄ (A is Ca, Sr and When containing at least one alkaline earth metal selected from the group consisting of Ba), it suppresses sintering of carbonate during use, and carbon monoxide and hydrogen from hydrogen and carbon dioxide. It becomes possible to produce the synthesis gas containing efficiently.

  Further, the method for producing a reverse shift reaction catalyst of the present invention comprises at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba, and a group consisting of Ti, Al, Zr, Fe, W and Mo. After synthesizing a composite oxide with at least one component selected from the above, carbon dioxide is absorbed into the composite oxide so as to generate carbonate, so that the carbonate is formed on the surface of the synthesized composite oxide. Is generated, and the surface is covered with carbonate, so that a reverse shift reaction catalyst having high catalytic activity can be efficiently produced.

  Further, as in the synthesis gas production method of the present invention, a raw material gas containing carbon dioxide and hydrogen is brought into contact with the reverse shift reaction catalyst according to claim 1 or 2 under a temperature condition of 700 ° C. or higher to reverse the reaction gas. By performing a shift reaction, a synthesis gas with high utility value can be efficiently produced.

In the Example of this invention, it is a figure which shows schematic structure of the test apparatus used in order to perform a reverse shift reaction test. In the Example of this invention, it is a figure which shows the gas composition after reaction in the reverse shift reaction test performed using the catalyst A and D, and the equilibrium gas composition in each condition.

  Examples of the present invention will be described below to describe the features of the present invention in more detail.

[Production of reverse shift reaction catalyst]
(1) Production of reverse shift reaction catalyst A
(a) BaCO ₃ and TiO ₂ were weighed so as to have a molar ratio of 2.0: 1.0, mixed by a ball mill, and then dried.
(b) Next, a binder was added to this mixture and granulated into a spherical shape having a diameter of 2 to 5 mm.
(c) The obtained granular material was fired in air at 1100 ° C. for 1 h to obtain a composite oxide (Ba ₂ TiO ₄ ).
(d) Then, this composite oxide (Ba ₂ TiO ₄ ) is fired in a 20% CO _2, 80% N ₂ stream under conditions of 700 ° C. and 1 h to obtain a mixture of BaCO ₃ and BaTiO ₃ . A reverse shift reaction catalyst A was obtained.

Incidentally, the results calcined weight change and XRD measurements before and after the sample, in the above described process (d), all Ba ₂ TiO ₄ was decomposed into BaCO ₃ and BaTiO _3, the molar ratio of BaCO ₃ and BaTiO ₃ as a result It was confirmed that a 1.0: 1.0 mixture (catalyst for reverse shift reaction) was obtained.

(2) Production of reverse shift catalyst B
(a) SrCO ₃ and TiO ₂ were weighed so as to have a molar ratio of 2.0: 1.0, mixed by a ball mill, and then dried.
(b) Next, a binder was added to this mixture and granulated into a spherical shape having a diameter of 2 to 5 mm.
(c) The obtained granular material was fired in air at 1100 ° C. for 1 h to obtain a composite oxide (Sr ₂ TiO ₄ ).
(d) Then, this composite oxide (Sr ₂ TiO ₄ ) is fired in a 20% CO _2, 80% N ₂ stream under conditions of 700 ° C. and 1 h to obtain a mixture of SrCO ₃ and SrTiO ₃ . The reverse shift reaction catalyst B was obtained.

Incidentally, the results calcined weight change and XRD measurements before and after the sample, in the above described process (d), all of Sr ₂ TiO ₄ was decomposed into SrCO ₃ and SrTiO _3, the molar ratio of SrCO ₃ and SrTiO ₃ as a result It was confirmed that a 1.0: 1.0 mixture (catalyst for reverse shift reaction) was obtained.

(3) Production of catalyst C for reverse shift reaction
(a) BaCO ₃ and Al ₂ O ₃ were weighed so as to have a molar ratio of 2.0: 1.0, mixed by a ball mill, and then dried.
(b) Next, a binder was added to this mixture and granulated into a spherical shape having a diameter of 2 to 5 mm.
(c) The obtained granular material was fired in air at 1100 ° C. for 1 h to obtain a composite oxide (Ba ₂ Al ₂ O ₅ ).
(d) Then, this composite oxide (Ba ₂ Al ₂ O ₅ ) is baked under conditions of 700 ° C. and 1 h in a 20% CO _2, 80% N ₂ stream to obtain BaCO ₃ and BaAl ₂ O. A reverse shift reaction catalyst C, which was a mixture of ₄ , was obtained.

From the weight change of the sample before and after firing and the XRD measurement results, in the step (d), all of Ba ₂ Al ₂ O ₅ was decomposed into BaCO ₃ and BaAl ₂ O ₄ , and as a result, BaCO ₃ and BaAl It was confirmed that a mixture (catalyst for reverse shift reaction) having a molar ratio of ₂ O ₄ of 1.0: 1.0 was obtained.

(4) Preparation of Comparative Catalyst (Comparative Example) D For comparison, quartz sand having no catalytic activity for reverse shift reaction was prepared, and this was designated as Comparative Catalyst D.
(5) Preparation of catalyst for comparison (comparative example) E A methane steam reforming catalyst (commercially available product) comprising Al ₂ O ₃ and Ni as main components was prepared, and this was used as catalyst E of comparative example. .

[Reverse shift reaction test and evaluation of characteristics]
(1) Reverse shift reaction test at atmospheric pressure Using a reverse shift reaction catalyst A according to an example of the present invention and a catalyst D of a comparative example, from a source gas containing carbon dioxide and hydrogen at atmospheric pressure, A reverse shift reaction test for generating carbon monoxide and water vapor was performed, and the characteristics of Catalyst A and Catalyst D were compared and evaluated.

The reverse shift reaction test was performed by the method described below using the test apparatus shown in FIG.
As shown in FIG. 1, the test apparatus used here includes a stainless steel reaction tube 1 having an inner diameter of 22 mm and a length of 300 mm provided with a heater 2, and a gas inlet 4 for supplying gas to the reaction tube 1. And a gas outlet 5 for discharging gas from the reaction tube 1 and a pressure regulator 6 for adjusting the pressure in the reaction tube.

Then, 5 cc of each of the reverse shift reaction catalysts (catalysts A and D) 3 produced as described above was filled in the reaction tube 1, and the heaters 2 used the predetermined temperatures (700 ° C., 750 ° C., was heated to 800 ° C.), (mixture gas of H ₂₎ and carbon dioxide _{(CO 2) (H 2:} CO 2 = 63: 37 ( volume ratio) hydrogen from a gas inlet 4 of the reaction tube 1) of 5 NL / h It was circulated for 2 hours at a ratio (SV (space velocity) = 1000 h ⁻¹ ).
During the test, the pressure regulator 6 was opened, and the reverse shift reaction test for 2 hours was performed under the atmospheric pressure (1 atm) condition as described above.

  During the test, the gas discharged from the gas outlet 5 of the reaction tube 1 is introduced into the analyzer to analyze the gas composition, and the obtained gas composition (measured value) is the equilibrium gas obtained by performing the equilibrium calculation. It was compared with the composition (calculated value).

Table 1 shows the relationship between the reaction temperature and the gas composition after the reaction in the reverse shift reaction test conducted using the catalysts A and D.
FIG. 2 shows the gas composition (measured value) after the reaction in the reverse shift reaction test conducted using the catalysts A and D and the equilibrium gas composition (calculated value) under each condition.

That is, the top graph in FIG. 2 shows the relationship between the H ₂ concentration in the gas after reaction and the temperature and the equilibrium concentration of H ₂ at each temperature when the catalysts A and D are used. Yes.
The second graph from the top in FIG. 2 shows the relationship between the CO ₂ concentration in the gas after reaction and the temperature, and the equilibrium concentration of CO ₂ at each temperature when the catalysts A and D are used. .
The third graph from the top in FIG. 2 shows the relationship between the CO concentration in the gas after reaction and the temperature, and the equilibrium concentration of CO at each temperature when the catalysts A and D are used.
The fourth graph from the top in FIG. 2 shows the relationship between CH ₄ concentration and temperature in the gas after reaction and the equilibrium concentration of CH ₄ at each temperature when catalysts A and D are used. .
In each graph of FIG. 2, the dotted line indicates the equilibrium concentration (calculated value) for each component.

As shown in Table 1 and 2, when using a catalyst D (activity without quartz sand), the gas after the reaction, each ingredient concentration deviates significantly from the equilibrium concentration (calculated value), BaCO ₃ When the catalyst A composed of BaTiO ₃ is used, a gas almost in equilibrium composition is obtained, and the reverse shift reaction catalyst A according to the example of the present invention has catalytic activity for the reverse shift reaction. You can see that

(2) Reverse shift reaction test under pressure of 5 atm Using the catalysts A, B, and C for reverse shift reaction according to the examples of the present invention and the catalyst E of Comparative Example, carbon dioxide was added under pressure of 5 atm. A reverse shift reaction test for generating carbon monoxide and water vapor from a raw material gas containing carbon and hydrogen was conducted, and the characteristics of the catalysts A, B, C and the catalyst E were compared and evaluated.

In the reverse shift reaction test, 5 cc each of the reverse shift reaction catalysts (catalysts A, B, C, and E) 3 produced as described above were filled in the reaction tube 1 using the test apparatus shown in FIG. 2 is heated to 700 ° C., and a mixed gas of hydrogen (H ₂ ) and carbon dioxide (CO ₂ ) (H ₂ : CO ₂ = 63: 37 (volume ratio)) is supplied from the gas inlet 4 of the reaction tube 1 to 10 NL / It was carried out by circulating for 2 hours at a ratio of h (SV (space velocity) = 2000 h ⁻¹ ).
During the test, the pressure in the reaction tube 1 was maintained at 5 atm by operating the pressure regulator 6.
In addition, during the test, the gas discharged from the gas outlet 5 of the reaction tube 1 is introduced into the analyzer to analyze the gas composition, and the obtained gas composition (measured value) is the equilibrium gas obtained by performing the equilibrium calculation. It was compared with the composition (calculated value).

Table 2 shows the gas composition (measured value) and the equilibrium gas composition (calculated value) after the reaction in the reverse shift reaction test conducted under the pressure of 5 atm using each catalyst.
The conditions of 5 atm and 700 ° C. are conditions in which methane (CH ₄ ) produced by the methanation reaction is present at a rate of 5.9% (vol%) even in the equilibrium gas composition.

From Table 2, when using the catalyst E of Comparative Example is a steam reforming catalyst commercially available methane product gas after reaction is seen to contain 5.7% of CH _4.
This is because the catalyst E of the comparative example which is a commercially available CH ₄ steam reforming catalyst has catalytic activity for the reverse shift reaction, but also has an activity for methanation which is the reverse reaction of the reforming reaction. Therefore, it is considered that the product gas after the reaction has almost the same gas composition as the equilibrium composition including methanation (that is, a gas composition containing 5.7% methane (CH ₄ )).

On the other hand, when using the catalyst A through C, the product gas after the reaction it can be seen that hardly contains CH _4. This is because the catalysts A to C according to the examples of the present invention having no methane reforming activity allow only the reverse shift reaction to proceed selectively. It is thought that the generation of (CH ₄ ) could be suppressed.
Moreover, it can be seen from Table 2 that when catalysts A to C are used, synthesis gas having a low methane (CH ₄ ) concentration, a high H ₂ concentration, and a high utility value can be obtained.

In addition, in chemical synthesis of liquid fuel or the like using synthesis gas as a raw material, it is generally known that the conversion rate increases as the synthesis pressure increases. For this reason, it is desirable to employ a pressurization process in the synthesis gas production process (reverse shift reaction process) before the chemical synthesis process. However, according to the present invention, it is possible to meet the demand. .
Further, by performing the entire process from the synthesis gas production process (reverse shift reaction process) to the chemical synthesis process in the previous stage under a pressurized condition, it is possible to reduce the size of the entire facility.

Therefore, the production of methane (CH ₄ ) is suppressed even under high temperature and pressure conditions, and the present invention is capable of efficiently producing a synthesis gas having a low methane content and a high proportion of carbon monoxide and hydrogen. It can be said that the production method of the catalyst and the synthesis gas of the present invention is extremely significant.

  In the above embodiment, the case where Ba or Sr is used as the alkaline earth metal is described as an example. However, it is confirmed that the same effect can be obtained when Ca is used as the alkaline earth metal. ing.

  In the above-described embodiment, the case where Ti and Al are used as the components constituting the composite oxide together with the alkaline earth metal has been described. However, Zr, Fe, W, and Mo were used instead of Ti and Al. Even in this case, it has been confirmed that the same effect can be obtained.

  The present invention is not limited to the above examples in other respects as well, and is a specific example of a method for producing a reverse shift reaction catalyst or a reverse shift reaction when using the reverse shift reaction catalyst of the present invention. With respect to conditions and the like, various applications and modifications can be made within the scope of the invention.

DESCRIPTION OF SYMBOLS 1 Reaction tube 2 Heater 3 Reverse shift reaction catalyst 4 Gas inlet of reaction tube 5 Gas outlet of reaction tube 6 Pressure regulator

Claims (4)

A reverse shift reaction catalyst used to generate carbon monoxide and water vapor from carbon dioxide and hydrogen,
At least one alkaline earth metal carbonate selected from the group consisting of Ca, Sr and Ba;
At least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba, and a composite oxide containing at least one component selected from the group consisting of Ti, Al, Zr, Fe, W and Mo. A reverse shift reaction catalyst characterized by containing. The composite oxide is at least one selected from the group consisting of ATiO ₃ , AAl ₂ O ₄ , AZrO ₃ , AFe ₂ O ₄ , AWO ₄ , A ₂ WO ₅ , AMoO ₄ (A is Ca, Sr and Ba). The catalyst for reverse shift reaction according to claim 1, wherein the catalyst is an alkaline earth metal). A method for producing a reverse shift reaction catalyst used for producing carbon monoxide and water vapor from carbon dioxide and hydrogen,
A composite oxide of at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba and at least one component selected from the group consisting of Ti, Al, Zr, Fe, W and Mo is synthesized. And a process of
And a step of causing the composite oxide to absorb carbon dioxide to produce a carbonate.   A method for producing a synthesis gas, comprising subjecting a raw material gas containing carbon dioxide and hydrogen to a reverse shift reaction catalyst according to claim 1 or 2 under a temperature condition of 700 ° C. or more to cause a reverse shift reaction.

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