JPH10244158A - Amorphous alloy catalyst for conversion of carbon dioxide into methane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accelerate the conversion of CO2 into methane by reaction with H2 by subjecting a precursor made of an amorphous alloy contg. of <= specified at.% in total amt. of >= specified at.% Zr and specified at.% a rare earth element to oxidant-reduction treatment. SOLUTION: A precursor made of an amorphous alloy consisting of <=80at.%, in total, of >=20at.% Zr and >5 to <=15at.% one or more kinds of rare earth elements selected from among Y, La, Ce, Nd, Sm, Gd, Tb and Dy and the balance essentially Co and/or Ni is subjected to oxidation-reduction treatment to obtain the objective amorphous alloy catalyst. When this catalyst is used, the conversion of CO2 into methane by reaction with H2 under atmospheric pressure can be accelerated and a large amt. of CO2 can be converted into methane at a high rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous alloy catalyst for methanation of carbon dioxide, and more particularly to a highly active amorphous alloy catalyst capable of efficiently converting carbon dioxide to methane.

[0002]

2. Description of the Related Art At present, global warming caused by carbon dioxide emitted in large quantities worldwide has become a social problem. However, it is difficult to reduce carbon dioxide emissions while maintaining the current standards of industrial activity and civil life. Therefore, there is a demand for the development of a technology for collecting the generated carbon dioxide without releasing it to the atmosphere, converting it into an effective substance such as methane, and reusing it.

Conventionally, as a method for treating carbon dioxide, research has been conducted to convert carbon dioxide into methanol by reacting it with hydrogen at a pressure of several tens of atmospheres in the presence of a catalyst.

[0004] On the other hand, the present applicants have proposed that, among those obtained by subjecting an amorphous alloy to oxidation-reduction treatment, a catalyst which functions as a catalyst for producing methane at a high speed even at atmospheric pressure by a reaction between carbon dioxide and hydrogen, Iron group metals and Zr, Ti,
We have developed an amorphous alloy catalyst for methanation of carbon dioxide by subjecting an amorphous alloy composed of valve metals such as Nb and Ta to redox treatment.

Further, iron group metals and Zr, Ti, Nb, Ta
Amorphous alloys made by adding a rare earth element with a higher affinity for oxygen to amorphous alloys made of valve metals such as, etc. It has been found that a catalyst having higher activity for methane generation by the reaction between carbon dioxide and hydrogen can be obtained than that obtained by applying the method described in Japanese Patent Application No. 8-204543 (hereinafter referred to as "the prior application"). )).

The earlier application consists of the following two claims.

Amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor made of an amorphous alloy to a redox treatment, wherein the amorphous alloy is composed of Zr, Y, La, Ce, Nd, Sm, Gd, Tb
And one or more rare earth elements selected from the group consisting of Dy and Dy, and the balance is substantially Co and / or Ni
Wherein the content of Zr is 8 atomic% or more, the content of rare earth element is 5 atomic% or less, and the total content of Zr and the rare earth element is 80 atomic% or less. Amorphous alloy catalyst for methanation.

[0008] A second aspect of the present invention is an amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor made of an amorphous alloy to an oxidation-reduction treatment, wherein the amorphous alloy is selected from the group consisting of Ti, Nb and Ta. One or more kinds, Zr, Y, La, Ce, Nd, Sm,
One or two selected from the group consisting of Gd, Tb and Dy
A rare earth element of at least one species, the balance being substantially composed of Co and / or Ni, a content of Zr of 8 atomic% or more, a content of rare earth element of 5 atomic% or less, Ti, Nb and T
An amorphous alloy catalyst for carbon dioxide methanation, characterized in that the total content of one or more selected from the group consisting of a and Zr and a rare earth element is 80 atomic% or less.

[0009]

In order to efficiently treat a large amount of carbon dioxide generated, it is desired to have a more active catalyst capable of rapidly converting a large amount of carbon dioxide into methane or the like. .

The amorphous alloy catalyst according to the prior application shows higher activity than the conventional amorphous alloy catalyst. However, in the amorphous alloy catalyst according to the prior application, when the content of the rare earth element for improving the catalytic activity is increased, In addition, since it is difficult to prepare a catalyst precursor alloy, the content of the rare earth element is limited.

In the alloy system of the amorphous alloy catalyst of the prior application, increasing the content of the rare earth element not only further enhances the catalytic activity but also expands the effective catalyst composition range. At present, the realization is awaited.

The present invention has been made in view of the above-mentioned conventional circumstances, and expands the composition range of the alloy system of the amorphous alloy catalyst of the prior application to convert carbon dioxide with hydrogen at atmospheric pressure to produce methane. Excellent in promoting the reaction of converting to
It is an object of the present invention to provide a remarkably highly active catalyst capable of converting a large amount of carbon dioxide into methane at a high speed.

[0013]

The amorphous alloy catalyst for methanation of carbon dioxide according to claim 1 is an amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor comprising an amorphous alloy to a redox treatment. The amorphous alloy is composed of Zr, Y, La, Ce, Nd, Sm,
One or two selected from the group consisting of Gd, Tb and Dy
A rare earth element of at least one kind, the balance substantially consisting of Co and / or Ni, and the content of Zr is at least 20 atomic%;
The rare earth element content is more than 5 atomic% and 15 atomic% or less, and the total content of Zr and the rare earth element is 80 atomic% or less.

An amorphous alloy catalyst for methanation of carbon dioxide according to claim 2 is an amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor made of an amorphous alloy to a redox treatment, wherein the amorphous alloy comprises: T
one or more selected from the group consisting of i, Nb and Ta, Zr, Y, La, Ce, Nd, Sm, Gd,
One or two or more rare earth elements selected from the group consisting of Tb and Dy, the balance substantially consisting of Co and / or Ni, a Zr content of 10 atomic% or more, Ti,
When the total content of one or more selected from the group consisting of Nb and Ta and Zr is 20 at% or more, the content of the rare earth element is more than 5 at% and 15 at% or less, and Ti, N
The total content of one or more selected from the group consisting of b and Ta, Zr and a rare earth element is 80 atomic% or less.

The amorphous alloy catalyst for methanation of carbon dioxide according to claim 3 is an amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor made of an amorphous alloy to an oxidation-reduction treatment, wherein the amorphous alloy comprises: Z
r and Mg, the balance being substantially Co and / or Ni
Wherein the content of Zr is 20 at% or more, the content of Mg is 15 at% or less, and the total content of Zr and Mg is 80 at% or less.

An amorphous alloy catalyst for methanation of carbon dioxide according to claim 4 is an amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor comprising an amorphous alloy to a redox treatment, wherein the amorphous alloy comprises: T
one or two or more selected from the group consisting of i, Nb and Ta, and Zr and Mg, the balance substantially consisting of Co and / or Ni, and a Zr content of 10 atomic% or more;
One or two selected from the group consisting of Ti, Nb and Ta
The total content of the species and Zr is 20 atomic% or more, and Mg
Is not more than 15 atomic%, and the total content of one or more selected from the group consisting of Ti, Nb and Ta, Zr and Mg is not more than 80 atomic%.

An amorphous alloy catalyst for methanation of carbon dioxide according to claim 5 is an amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor made of an amorphous alloy to a redox treatment, wherein the amorphous alloy comprises: Z
r, Y, La, Ce, Nd, Sm, Gd, Tb and D
one or two or more rare earth elements selected from the group consisting of y and Mg, and the balance is substantially Co and / or N
i, the content of Zr is 20 at% or more, the total content of rare earth elements and Mg is 15 at% or less, and the total content of Zr, rare earth elements and Mg is 80 at% or less. It is characterized by the following.

The amorphous alloy catalyst for methanation of carbon dioxide according to claim 6 is an amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor made of an amorphous alloy to a redox treatment, wherein the amorphous alloy comprises: T
one or more selected from the group consisting of i, Nb and Ta, Zr, Y, La, Ce, Nd, Sm, Gd,
It contains one or more rare earth elements selected from the group consisting of Tb and Dy, and Mg, and the balance substantially consists of Co and / or Ni. The content of Zr is 10 atom% or more, Ti, A total content of one or more selected from the group consisting of Nb and Ta and Zr and 20 atomic% or more;
The total content of the rare earth element and Mg is 15 atomic% or less, and the total content of one or more selected from the group consisting of Ti, Nb and Ta, Zr, the rare earth element and Mg is 80 atomic%. % Or less.

That is, the amorphous alloy catalyst of the present invention comprises:
An amorphous alloy containing at least one of Co and Ni, Zr and a rare earth element as essential components, and a part of the Zr
a, Nb, an amorphous alloy substituted with Ti, and C
an amorphous alloy containing at least one of o and Ni, and Zr and Mg as essential components;
This is obtained by subjecting an amorphous alloy substituted with b and Ti, and an amorphous alloy containing a rare earth element as an essential component together with Mg to an oxidation-reduction treatment.

The present applicants have conducted intensive studies on the characteristics of amorphous alloys, and as a result, have found that conventional iron group metals and Zr,
An amorphous alloy made of a valve metal such as Ti, Nb, Ta or the like added with a rare earth element having a high affinity for oxygen is produced and subjected to oxidation-reduction treatment to obtain a conventional iron group metal-valve metal. It has been found that a catalyst having higher activity against methane generation by the reaction between carbon dioxide and hydrogen can be obtained than the one obtained by subjecting an amorphous alloy to oxidation-reduction treatment, and the invention of the prior application has been achieved.

The performance equivalent to that of the prior application should be obtained by further adding a rare earth element, but as described above, there was a drawback that in this case, it was difficult to prepare an alloy.

However, as a result of further study on an amorphous alloy, Zr, which is an essential element of the present invention, is oxidized in the state of coexisting with a rare earth element or Mg.
When oxidized, ZrO ₂ having a tetragonal structure, which is stable only at a high temperature, is stabilized, and a large amount of ZrO ₂ having a tetragonal structure is generated in addition to ZrO ₂ having a monoclinic structure having a stable structure.
When at least one of Co and Ni is supported on this,
It has been found that a catalyst having a particularly high activity for the production of methane by the reaction between carbon dioxide and hydrogen can be obtained. Further, they have found that the content of a rare earth element that can be produced can be increased by increasing the lower limit of the valve metal added to an amorphous alloy composed of an iron group metal and a valve metal such as Zr, Ti, Nb, and Ta. The present invention has been completed based on such findings.

To obtain a catalyst with high selective catalytic activity for a particular chemical reaction, alumina, titania,
It is more advantageous to use an alloy containing a necessary amount of an effective element as a precursor than to carry a platinum group element or the like on ceramics such as silica. However, in the case of crystalline metals made by ordinary methods, the addition of a large amount of various alloy metals often results in a multiphase structure with different chemical properties,
In addition to being unable to have the predetermined characteristics, it is difficult to obtain a material having a large specific surface area required as a catalyst because of its brittleness.

On the other hand, in the amorphous alloy of the composition of the present invention, the constituent elements are not allowed to be localized, and the predetermined elements are uniformly dissolved. When such an amorphous alloy is manufactured using a liquid quenching method, a sputtering method, a mechanical alloying method, etc., it has excellent catalytic activity unique to the amorphous alloy of the present invention, which has not been realized in the past, and rapidly converts carbon dioxide into methane. A catalyst which can be converted to

According to the catalyst of the present invention obtained by subjecting an amorphous alloy having the above composition to an oxidation-reduction treatment, carbon dioxide can be rapidly converted to methane at atmospheric pressure.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

In the present invention, the composition of the amorphous alloy serving as the catalyst precursor is as shown in the following table.

[0028]

[Table 1]

The reasons for limiting the composition of each component of the amorphous alloy according to the present invention will be described below.

Ni and Co are elements that form the basis of the amorphous alloy according to the present invention. Zr or a part of Zr as a valve metal is replaced with Ta or T as another valve metal.
It is an element that forms an amorphous structure in coexistence with one substituted by one or more of i and Nb. For the formation of this amorphous structure, Ni and / or Co are 20 atomic%.
Therefore, the total of other elements is set to 80 atomic% or less.

Ni and Co are also elements that contribute to the catalytic reaction as active elements.

Zr is an essential element that forms ZrO ₂ and acts as a carrier for Ni and Co.

Rare earth elements and Mg are elements that increase the amount of tetragonal structure ZrO ₂ acting as a carrier having particularly high catalytic activity.

However, in the prior application, Zr or a part of Zr was replaced with at least one of Ta, Ti, and Nb as another valve metal, and the lower limit was set at 8 atomic%. The amount of the rare earth element had to be 5 atomic% or less. On the other hand, in the present invention, Zr or a part of Zr is replaced with another valve metal such as Ta, Ti, N
Since the lower limit of those substituted with one or more kinds of b was set to 20 atomic%, addition of a rare earth element exceeding 5 atomic% was realized.
However, addition of a certain amount or more of rare earth elements is unnecessary,
Also, the addition of a large amount makes it difficult to form an amorphous alloy. Therefore, in claim 1 and claim 2 of the present invention, the amount of the rare earth element is set to more than 5 atomic% and 15 atomic% or less.

Ti, Nb, and Ta are effective elements that form an amorphous structure with Ni and / or Co by substituting Zr. When they function as an oxide and serve as a carrier, they exert an effect of ZrO _{2 on} the catalytic activity. Since it cannot surpass, Zr in claims 2, 4 and 6 of the present invention
Is 10 atomic% or more, and Zr and Ti, Nb, Ta
Is 20 atomic% or more.

As described above, Mg is an element that increases the amount of ZrO ₂ having a tetragonal structure that acts as a carrier having a particularly high catalytic activity. However, it is not necessary to add a certain amount or more. In order to make it difficult to form an alloy, the content of Mg in claims 3 and 4 of the present invention is 1
5 at% or less.

The coexistence of Mg and a rare earth element is also effective in increasing the amount of tetragonal ZrO ₂ acting as a carrier having a particularly high activity, but it is not necessary to add a certain amount or more. Since the addition of a large amount makes the formation of an amorphous alloy difficult, in the fifth and sixth aspects of the present invention, M
The total content of g and the rare earth element is 15 atomic% or less.

It should be noted that substituting a part of Ni and / or Co with a small amount of Fe in the amorphous alloy according to the present invention does not affect the object of the present invention.

The amorphous alloy catalyst for methanation of carbon dioxide of the present invention is obtained by subjecting an amorphous alloy having the above composition obtained by a liquid quenching method, a sputtering method, a mechanical alloying method or the like to a precursor, and subjecting the same to a redox treatment. Is obtained by

The oxidation-reduction treatment of this amorphous alloy is performed by
For example, an amorphous alloy is placed in an oxygen atmosphere at 300-70.
After oxidizing by heating at 0 ° C. for 1 to 12 hours, reduction can be performed by heating at 100 to 500 ° C. for 1 to 24 hours in a hydrogen atmosphere.

The thus obtained amorphous alloy catalyst for methanation of carbon dioxide of the present invention exhibits high catalytic activity as a catalyst for methanation reaction in which carbon dioxide and hydrogen are reacted at a predetermined molar ratio.

In order to methanize carbon dioxide using the amorphous carbon dioxide methanation catalyst of the present invention, for example, a reaction filled with 1 g of the carbon dioxide methanation amorphous alloy catalyst of the present invention is performed. A gas in which carbon dioxide and hydrogen are mixed in a ratio of CO ₂ : H ₂ = 1: 1 to 4 (molar ratio) in a tube at 15 to 300 ° C. at 100 to 300 ° C.
The reaction may be carried out at a flow rate of ml / min.

[0043]

The present invention will be described more specifically below with reference to examples and comparative examples.

Examples 1, 2 and Comparative Example 1 Raw materials were mixed to have the compositions shown in Table 2, and raw material alloys were produced by argon arc melting. This alloy was re-melted in an argon atmosphere and was rapidly quenched and solidified by the single roll method shown in FIG.
m, a width of 1 to 3 mm, and a length of 3 to 20 m were obtained.

In FIG. 1, 1 is a quartz tube, 2 is a raw material insertion port, and 3 is a vertical nozzle at the tip. The raw material alloy 4 put in the quartz tube 1 is heated and melted in a heating furnace 5 in an argon gas atmosphere. Obtain a thin plate. In FIG. 1, a portion surrounded by a broken line is installed in a vacuum chamber.

The formation of an amorphous structure in the obtained thin plate was confirmed by X-ray diffraction.

Next, the sample of the obtained amorphous alloy thin plate was oxidized in an oxygen atmosphere at 500 ° C. for 3 hours, and then reduced in a hydrogen atmosphere at 300 ° C. for 1 hour to obtain a catalyst.

1 g of the obtained catalyst was packed in a glass tube having an inner diameter of 8 mm to a length of 5 cm to form a reaction tube, which was placed in an electric furnace. CO ₂ and H ₂ are added to the reaction tube at a predetermined temperature.
Was flowed at a flow rate of 60 ml / min, and the amounts of CO ₂ , H ₂ , CH ₄ , and other detected substances at the outlet of the reaction tube were measured by gas chromatography.
As a result, it was confirmed that only the detected substances were CO ₂ , H ₂ , and CH ₄ , and CH ₄ was generated at a selectivity of 100%. Table 2 shows the conversion from CO ₂ to CH _{4 at} each reaction temperature.

[0049]

[Table 2]

From Table 2, it can be seen that the catalyst of the present invention obtained by subjecting the Ni-30 atomic% Zr-10 atomic% Y and Ni-30 atomic% Zr-10 atomic% Sm alloys to oxidation-reduction treatment is CO ₂
It is clear that from a conversion highly active catalyst into CH _4.

[0051] In Example 3-25 Example 1, the alloy composition in the same manner except for using the composition shown in Table 3 to prepare a catalyst, likewise performed methanation reaction of carbon dioxide, from the CO ₂ at that time The conversion to CH ₄ was determined and the results are shown in Table 3.

[0052]

[Table 3]

From Table 3, it is clear that the amorphous alloy catalyst for methanation of carbon dioxide of the present invention has extremely high activity.

[0054]

As described in detail above, according to the amorphous alloy catalyst for methanation of carbon dioxide of the present invention, a large amount of carbon dioxide can be efficiently converted to methane by a reaction under atmospheric pressure. ing.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an apparatus for producing an amorphous alloy according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw material insertion port 2 Quartz tube 3 Vertical nozzle 4 Raw material alloy 5 Heating furnace 6 Motor 7 High-speed rotating roll

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B01D 53/86 B01D 53/36 Z (72) Inventor Kazuo Shimamura 5-6-4 Tsukiji, Chuo-ku, Tokyo Mitsui Engineering Ship Inc. (72) Inventor Ken Yoshida 2-14-18, Sanjinmine, Taihaku-ku, Sendai City, Miyagi Prefecture (72) Inventor Hiroki Hirosaki 8-2-131 Nagamachi, Taishiro-ku, Sendai City, Miyagi Prefecture (72) Eiji Akiyama Miyagi 13-5 Mukaiyama, Taihaku-ku, Sendai City, Japan

Claims (6)

[Claims] 1. An amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor made of an amorphous alloy to a redox treatment, wherein the amorphous alloy comprises Zr, Y, La, Ce, and N.
one or more rare earth elements selected from the group consisting of d, Sm, Gd, Tb and Dy, and the balance substantially consisting of Co and / or Ni, with a Zr content of 20 atomic% or more The content of the rare earth element is more than 5 atomic% and not more than 15 atomic%, and the total content of Zr and the rare earth element is 80%.
An amorphous alloy catalyst for methanation of carbon dioxide, which is at most atomic%. 2. An amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor comprising an amorphous alloy to a redox treatment, wherein the amorphous alloy is one selected from the group consisting of Ti, Nb and Ta. Or two or more, Zr, Y, La,
One or more rare earth elements selected from the group consisting of Ce, Nd, Sm, Gd, Tb and Dy, and the balance substantially consisting of Co and / or Ni, and a Zr content of 10 atoms % Or more, and the total content of one or more selected from the group consisting of Ti, Nb and Ta and Zr is 2%.
0 atomic% or more, rare earth element content exceeds 5 atomic% and 1
Methane of carbon dioxide, wherein the total content of one or more selected from the group consisting of Ti, Nb and Ta, Zr and a rare earth element is 80 atomic% or less. Amorphous alloy catalyst. 3. An amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor made of an amorphous alloy to a redox treatment, wherein the amorphous alloy contains Zr and Mg, and the balance is substantially Co. And / or Ni, and the Zr content is 2
0 atomic% or more, Mg content is 15 atomic% or less, Zr
An amorphous alloy catalyst for methanation of carbon dioxide, characterized in that the total content of Mg and Mg is 80 atomic% or less. 4. An amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor made of an amorphous alloy to a redox treatment, wherein the amorphous alloy is one selected from the group consisting of Ti, Nb and Ta. Or Zr and Mg, the balance being substantially composed of Co and / or Ni;
Is not less than 10 atomic%, the total content of one or more selected from the group consisting of Ti, Nb and Ta and Zr is not less than 20 atomic%, and the Mg content is not more than 15 atomic%. , Ti, Nb and Ta, the total content of one or more selected from the group consisting of Zr and Mg is 80 atomic%.
An amorphous alloy catalyst for methanation of carbon dioxide, characterized in that: 5. An amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor made of an amorphous alloy to a redox treatment, wherein the amorphous alloy comprises Zr, Y, La, Ce, and N.
one or more rare earth elements selected from the group consisting of d, Sm, Gd, Tb, and Dy, and Mg, and the balance substantially consisting of Co and / or Ni; Carbon dioxide methanation, characterized in that the total content of rare earth elements and Mg is 15 atomic% or less, and the total content of Zr, rare earth elements and Mg is 80 atomic% or less. For amorphous alloy catalyst. 6. An amorphous alloy catalyst for methanation of carbon dioxide obtained by subjecting a precursor made of an amorphous alloy to a redox treatment, wherein the amorphous alloy is one selected from the group consisting of Ti, Nb and Ta. Or two or more, Zr, Y, La,
One or more rare earth elements selected from the group consisting of Ce, Nd, Sm, Gd, Tb and Dy, and Mg, and the balance substantially consisting of Co and / or Ni;
Is 10 atomic% or more, the total content of one or more selected from the group consisting of Ti, Nb and Ta and Zr is 20 atomic% or more, and the total content of rare earth elements and Mg is Is not more than 15 atomic%, and the total content of one or more selected from the group consisting of Ti, Nb and Ta, Zr, a rare earth element and Mg is not more than 80 atomic%. Amorphous alloy catalyst for methanation of carbon.