WO2012050192A1

WO2012050192A1 - Carbon monoxide production method and production device

Info

Publication number: WO2012050192A1
Application number: PCT/JP2011/073674
Authority: WO
Inventors: 肇名井; 八島　勇; 菅野　明弘; 陽介柴田; 雄一妹尾; 和也木下
Original assignee: 三井金属鉱業株式会社
Priority date: 2010-10-15
Filing date: 2011-10-14
Publication date: 2012-04-19
Also published as: JP6111070B2; JPWO2012050192A1

Abstract

A carbon monoxide production method according to the present invention that brings a carbon dioxide-containing gas into contact with a metal oxide having oxide ionic conductivity and having a reversible oxygen deficiency under pressure, and reduces the carbon dioxide by stoichiometric reaction to produce carbon monoxide, is characterized in that a cerium oxide comprising bismuth or a zirconium oxide comprising bismuth is used as the metal oxide. In the cerium oxide comprising bismuth, the ratio of the number of moles of bismuth to the total amount in number of moles of cerium and bismuth is preferably 0.001~0.5. Furthermore, in the zirconium oxide comprising bismuth, the ratio of the number of moles of bismuth to the total amount in number of moles of zirconium and bismuth is also preferably 0.001~0.5.

Description

Carbon monoxide production method and production apparatus

The present invention relates to a method and apparatus for producing carbon monoxide using carbon dioxide as a raw material. Moreover, this invention relates to the conversion agent used for this manufacturing method.

Carbon dioxide is known as a greenhouse gas. The concentration of carbon dioxide in the atmosphere continues to rise, which is considered to contribute to global warming. Therefore, from the viewpoint of preventing global warming, a technique for recovering carbon dioxide released into the environment is very important.

As a technique for recovering carbon dioxide, for example, an oxygen deficient iron oxide is used to decompose carbon dioxide gas into carbon monoxide gas and oxygen gas, and the oxygen gas generated generates oxygen deficient iron oxide. A technique for returning to the original iron oxide and recovering only carbon monoxide gas has been proposed (see Patent Document 1).

The above technique is a technique for producing carbon monoxide gas from carbon dioxide by a stoichiometric reaction with carbon dioxide using an iron oxide having oxygen deficiency, whereas catalytic catalytic reduction. A technique for generating carbon monoxide gas from carbon dioxide has also been proposed. For example, in Non-Patent Document 1, carbon monoxide gas or carbon is obtained by catalytic reduction of carbon dioxide using a metal oxide such as WO ₃ , Y ₂ O ₃ , ZnO or the like as a catalyst and hydrogen or methane as a reducing agent. It has been reported that it can be generated.

Apart from these techniques, Patent Document 2 proposes a method of separating carbon dioxide into carbon monoxide and oxygen using a solid reaction membrane having an oxygen ion conductor made of CeO ₂ and a catalyst. In this method, oxygen is separated from carbon dioxide by a catalyst supported on an oxygen ion conductor made of CeO ₂ , and this oxygen is diffused in the oxygen ion conductor by a potential generated due to a difference in oxygen concentration. .

Patent Document 3 discloses an oxygen ion conductive ceramic conductor which is a ceramic material selected from the group consisting of Bi ₂ O ₃ , ZrO ₂ , CeO _{2 and the} like and mixtures thereof and doped with rare earth metal oxides. Are listed. The same document also discloses that an oxygen ion conductive ceramic conductor is brought into contact with carbon dioxide and saturated with oxygen to produce carbon monoxide, and an oxygen ion conductive ceramic conductor saturated with oxygen is brought into contact with a hydrocarbon gas. The removal of oxygen from oxygen ion conducting ceramic conductors. However, in this document, cerium oxide containing bismuth or zirconium oxide containing bismuth has a reversible oxygen deficiency in an oxygen ion conductive ceramic conductor, or a reversible oxygen deficiency for generating carbon monoxide from carbon dioxide. There is no mention of what is necessary.

Japanese Patent Laid-Open No. 5-68853 JP 2001-322958 A US2002 / 0064494A1

According to the technique described in Patent Document 1, carbon monoxide gas is certainly generated from carbon dioxide gas. However, iron oxide has low oxygen ion conductivity, and if the surface is oxidized, the oxygen deficiency will come into contact with carbon dioxide gas even if oxygen deficiency exists inside the oxide. I can't. Therefore, in order to increase the conversion efficiency from carbon dioxide gas to carbon monoxide gas, it is necessary to use a large amount of iron oxide having oxygen deficiency, which is economically disadvantageous.

In the technique described in Non-Patent Document 1, it is necessary to introduce hydrogen and methane simultaneously with carbon dioxide. In addition to carbon monoxide and carbon as a product, unreacted carbon dioxide, hydrogen, methane, and the like are mixed. Therefore, it is economically disadvantageous in that it requires a separation step in the end, and when the product is carbon, the catalytic activity tends to decrease due to the precipitation on the catalyst. .

The technique described in Patent Document 2 is economically disadvantageous because a noble metal catalyst is used to decompose carbon dioxide into carbon monoxide and oxygen. Moreover, cerium oxide carrying a noble metal catalyst is only used as an ion pump for diffusing oxygen ions, and cerium oxide is not directly involved in the production of carbon monoxide from carbon dioxide.

Therefore, an object of the present invention is to provide a method for producing carbon monoxide from carbon dioxide that can eliminate the various disadvantages of the above-described conventional technology.

In the present invention, a metal oxide having oxygen ion conductivity and a reversible oxygen deficiency is brought into contact with a carbon dioxide-containing gas under heating, and carbon dioxide is reduced by a stoichiometric reaction to produce a monoxide. A method for producing carbon monoxide that produces carbon, comprising:
A carbon monoxide production method using cerium oxide containing bismuth or zirconium oxide containing bismuth as the metal oxide is provided.

Further, the present invention provides a suitable apparatus for carrying out the manufacturing method as described above.
An outer tube, and an inner tube disposed in the outer tube,
The inner tube includes a metal oxide having oxygen ion conductivity and having a reversible oxygen deficiency,
A gas containing carbon dioxide is circulated between the outer tube and the inner tube, and a reducing gas is circulated in the inner tube, or reduction is performed between the outer tube and the inner tube. And a carbon dioxide-containing gas is circulated in the inner pipe.
An apparatus for producing carbon monoxide using cerium oxide containing bismuth or zirconium oxide containing bismuth as the metal oxide is provided.

Furthermore, the present invention provides another suitable apparatus for carrying out the above manufacturing method.
This is a carbon monoxide production apparatus in which plate-like bodies comprising a metal oxide having oxygen ion conductivity and having reversible oxygen vacancies and plate-like separators are alternately stacked. And
A plurality of ridges and ridges extending in one direction are alternately arranged on each surface of each separator,
A carbon dioxide-containing gas is circulated through a concave portion located on the opposing surface of one separator and the plate-like body in two separators facing each other with the plate-like body sandwiched therebetween, and the other separator and the plate-like body Is configured to circulate the reducing gas through the concave portion located on the opposite surface,
An apparatus for producing carbon monoxide using cerium oxide containing bismuth or zirconium oxide containing bismuth as the metal oxide is provided.

Furthermore, the present invention relates to an exhaust gas containing carbon dioxide generated from a steel mill, a smelter or a thermal power plant, and a metal oxide having oxygen ion conductivity and having a reversible oxygen deficiency, Carbon dioxide characterized in that it is brought into contact with heating using waste heat generated from a steel plant or a thermal power plant, and carbon dioxide in the exhaust gas is reduced by a stoichiometric reaction to generate carbon monoxide. Is a system for converting carbon to monoxide,
The present invention provides a system for converting carbon dioxide into carbon monoxide using cerium oxide containing bismuth or zirconium oxide containing bismuth as the metal oxide.

Furthermore, the present invention provides a carbon dioxide monooxide comprising a metal oxide having oxygen ion conductivity and having reversible oxygen deficiency, wherein the metal oxide comprises cerium oxide containing bismuth or zirconium oxide containing bismuth. A carbon conversion agent is provided.

According to the present invention, carbon monoxide can be efficiently generated using carbon dioxide as a raw material. There is no carbon by-product in the production of carbon monoxide. In particular, cerium oxide containing bismuth or zirconium oxide containing bismuth used in the present invention can lower the temperature at which the reaction for producing carbon monoxide from carbon dioxide occurs, compared to cerium oxide or zirconium oxide containing no bismuth. This is advantageous in that the temperature at which oxygen vacancies occur can be lowered. Note that the temperature at which the reaction for generating carbon monoxide occurs and the temperature at which oxygen vacancies are generated are not necessarily correlated. Factors for the efficient generation of carbon monoxide are not only the low temperature at which oxygen vacancies are generated, but also the fact that the reaction of generating carbon monoxide from carbon dioxide occurs due to the inclusion of bismuth. one of.

FIG. 1 is a schematic view showing an apparatus suitably used in the method for producing carbon monoxide of the present invention. FIG. 2 is a schematic view showing another apparatus suitably used in the method for producing carbon monoxide of the present invention. FIG. 3 is a schematic view showing still another apparatus suitably used in the method for producing carbon monoxide of the present invention. FIG. 4 is a schematic diagram showing the apparatus used in the example.

Hereinafter, the present invention will be described based on preferred embodiments thereof. In the present invention, carbon dioxide-containing gas is heated with a specific metal oxide (hereinafter, this metal oxide is also referred to as “converter to carbon monoxide” or simply “converter”). To produce carbon monoxide gas. The reaction between the conversion agent and carbon dioxide gas is a stoichiometric reaction utilizing the reducing power of the conversion agent. That is, the conversion agent made of this metal oxide is not used as a catalyst, but as a reactant itself. In the present invention, cerium oxide containing bismuth or zirconium oxide containing bismuth is used as the specific metal oxide.

As the conversion agent comprising the specific metal oxide, one having oxygen ion conductivity and having reversible oxygen vacancies is used. Since this conversion agent has a reversible oxygen deficiency, the conversion agent acquires the reducibility of carbon dioxide. A reversible defect | deletion is produced | generated when oxygen is forcibly extracted from a metal oxide by the process under strong reducing conditions. A reversible defect is a defect in which oxygen can be taken into a deficient site. For example, when the metal oxide is cerium oxide containing bismuth, in cerium oxide containing bismuth having a reversible defect, an unbalanced state of charge due to oxygen deficiency is caused by a part of tetravalent cerium. Is compensated by being reduced to trivalent. Trivalent cerium is unstable and easily returns to tetravalent. Therefore, by incorporating oxygen into the deficient site, trivalent cerium returns to tetravalent, and the charge balance is always kept at zero. By incorporating oxygen into the deficient site, the deficiency disappears, but oxygen deficiency is generated again by treatment under strong reducing conditions. “Reversible oxygen deficiency” is used in this sense. The same applies to zirconium oxide containing bismuth.

On the other hand, irreversible oxygen deficiency is also known. Irreversible oxygen deficiency is formed by doping a metal oxide with an element having a valence lower than that of the metal. Irreversible oxygen vacancies, unlike reversible oxygen vacancies, are not vacancies generated by treatment under strong reducing conditions. Irreversible oxygen vacancies include, for example, mixing a metal oxide with an oxide of a valence element lower than the valence of the metal, firing in the atmosphere, etc. To obtain. When the inorganic oxide is, for example, cerium oxide, all valences of cerium in cerium oxide having irreversible oxygen vacancies are tetravalent. Therefore, oxygen is not taken into the deficient site. For example, when 20 mol% of Ca is dissolved in CeO ₂ , the average valence of the cation is 4 × 0.8 + 2 × 0.2 = 3.6, so that the charge of oxygen is balanced with this valence. The number of necessary oxygen atoms is 3.6 ÷ 2 = 1.8. This number is less than the stoichiometric amount of oxygen atoms of 2, and oxygen vacancies are generated accordingly. However, this oxygen deficiency is not capable of absorbing oxygen. Thus, the irreversible oxygen deficiency is not caused by forced extraction of oxygen but is caused by charge compensation in the metal oxide.

The conversion agent comprising the metal oxide used in the present invention has oxygen ion conductivity as described above. The oxygen ion conductivity may be developed at a temperature at which the production method of the present invention is performed. Since this conversion agent has oxygen ion conductivity, almost all of the reversible oxygen vacancies present in this conversion agent can be effectively utilized for the reaction with carbon dioxide. The reason is as follows. That is, since the production method of the present invention is a reaction between a solid metal oxide and a gaseous carbon dioxide gas, the reaction mainly proceeds on the solid surface. And the oxygen deficiency which exists in the surface of a metal oxide couple | bonds with the oxygen in a carbon dioxide, The oxygen deficiency in this surface lose | disappears, and a carbon dioxide is converted into carbon monoxide. In this case, since the metal oxide has oxygen ion conductivity, oxygen associated with oxygen vacancies existing on the surface of the metal oxide is in the state of oxygen ions (O ²⁻ ). The oxygen vacancies disappear inside the metal oxide, and reversible oxygen vacancies are generated again on the surface of the metal oxide. By repeating this, almost all of the reversible oxygen vacancies present in the conversion agent can contribute to the reaction with carbon dioxide. On the other hand, for example, the iron oxide having oxygen vacancies described in Patent Document 1 described in the background section does not have oxygen ion conductivity, so that oxygen vacancies remain in the oxide. Even so, when all the oxygen vacancies present on the surface of the oxide disappear, the reactivity with carbon dioxide is greatly reduced.

The conversion agent comprising the metal oxide used in the present invention has oxygen ion conductivity and has the following advantages. That is, in this conversion agent, the reversible oxygen deficiency present in the converter can also contribute to the reaction with carbon dioxide, so that the reactivity with carbon dioxide can be achieved without excessively increasing the specific surface area of this conversion agent. Is hard to decline. Therefore, there is a degree of freedom that the reactant containing the conversion agent can be formed into a desired shape such as a granular shape, a pellet shape, a plate shape, or a cylindrical shape. On the other hand, a metal oxide that does not have oxygen ion conductivity, for example, an iron oxide having an oxygen vacancy described in Patent Document 1 described in the background section, has an oxygen vacancy existing therein. Since it hardly contributes to the reaction with carbon dioxide, it is necessary to increase the specific surface area of the oxide in order to effectively utilize the oxygen deficiency. In other words, it is indispensable to use it in the state of fine powder, resulting in low handleability and flexibility in designing the reactor.

As described above, the conversion agent comprising the metal oxide used in the production method of the present invention is essential to have oxygen ion conductivity and to have reversible oxygen vacancies. In the present invention, as described above, cerium oxide containing bismuth or zirconium oxide containing bismuth is used as the metal oxide having bismuth. Bismuth may exist as a solid solution in cerium oxide and zirconium oxide, or may exist in an oxide state. Generally speaking, when the proportion of bismuth in cerium oxide and zirconium oxide is low, bismuth tends to exist as a solid solution.

When cerium oxide containing bismuth (hereinafter referred to as bismuth-containing cerium oxide) is used as the metal oxide used in the production method of the present invention, the ratio of the number of moles of bismuth to the total number of moles of cerium and bismuth is preferably It is 0.001 to 0.5, more preferably 0.02 to 0.5, particularly preferably 0.02 to 0.2. On the other hand, when zirconium oxide containing bismuth (hereinafter referred to as bismuth-containing zirconium oxide) is used as the metal oxide used in the production method of the present invention, the ratio of the number of moles of bismuth to the total number of moles of zirconium and bismuth. Is preferably 0.001 to 0.5, more preferably 0.02 to 0.2. When the ratio of bismuth in the bismuth-containing cerium oxide and bismuth-containing zirconium oxide is within this range, carbon monoxide can be efficiently generated using carbon dioxide as a raw material. Moreover, as will be described later, the temperature of the heat treatment in a reducing atmosphere performed when oxygen deficiency is generated again in bismuth-containing cerium oxide and bismuth-containing zirconium oxide whose oxygen deficiency has disappeared by reaction with carbon dioxide can be reduced. There are also advantages. In order to obtain bismuth-containing cerium oxide and bismuth-containing zirconium oxide having a bismuth ratio in the above range, the amount of cerium, zirconium and bismuth used should be adjusted during the production of bismuth-containing cerium oxide and bismuth-containing zirconium oxide, which will be described later. That's fine.

Bismuth-containing cerium oxide and bismuth-containing zirconium oxide can be suitably produced, for example, by the following method. Cerium carbonate or zirconium carbonate and Bi ₂ O ₃ are pulverized and mixed using a media mill such as a ball mill. The obtained mixed powder is calcined in an air atmosphere, preferably at 150 to 600 ° C., more preferably at 250 to 500 ° C., preferably for 0.5 to 10 hours, more preferably for 2 to 10 hours. The obtained calcined product is pulverized with a mortar or the like, and the pulverized product is main-fired at 400 to 1400 ° C., more preferably 730 to 820 ° C. in an air atmosphere. The temperature for the main baking is set higher than the temperature for the preliminary baking. The firing time is preferably 0.5 to 10 hours, more preferably 2 to 10 hours, provided that the firing temperature is within the above range. By this operation, bismuth-containing cerium oxide and bismuth-containing zirconium oxide in which reversible oxygen deficiency has not yet occurred can be obtained.

Bismuth-containing oxidation having reversible oxygen deficiency used in the production method of the present invention by strongly reducing the bismuth-containing cerium oxide and bismuth-containing zirconium oxide obtained by the above-described method to generate reversible oxygen deficiency Cerium and bismuth-containing zirconium oxide can be obtained. In strong reduction, a hydrogen-containing atmosphere having a hydrogen concentration of not less than the lower explosion limit, preferably not less than 20% by volume, is used as the reducing atmosphere. Of course, the hydrogen concentration may be 100% by volume. As a result of the examination by the present inventors, it was found that a relatively low temperature is sufficient for the strong reduction. The present inventors believe that this reason is due to the addition of bismuth to cerium oxide and zirconium oxide. In particular, when bismuth is dissolved in cerium oxide and zirconium oxide, it is advantageous in that reversible oxygen vacancies can be successfully generated even if the temperature during strong reduction is set low. Specifically, the temperature during strong reduction is preferably 300 to 1050 ° C., more preferably 320 to 820 ° C. The time for strong reduction is preferably 0.5 to 10 hours, more preferably 2 to 10 hours, provided that the temperature is in the above-mentioned range.

By the way, in addition to the metal oxide having reversible oxygen deficiency used in the present invention, an OSC (oxygen storage and release capability) material is known as a metal oxide capable of absorbing oxygen. OSC materials are often used as promoters for automotive catalysts. The OSC material uses oxygen ion conductivity and valence change of cerium oxide, releases oxygen for oxidation reaction and absorbs oxygen for reduction reaction, so that the gas composition in exhaust gas Is used for the purpose of stably purifying exhaust gas with a three-way catalyst. Therefore, the OSC material is a co-catalyst for converting carbon monoxide in the exhaust gas to carbon dioxide, and is used in a reaction process opposite to the production method of the present invention that generates carbon monoxide from carbon dioxide. Is.

The reaction between the conversion agent and the carbon dioxide-containing gas used in the production method of the present invention is performed under heating. For example, the heating temperature is set to 400 to 1000 ° C., particularly 400 to 800 ° C., particularly 400 to 600 ° C., to increase the conversion efficiency from carbon dioxide to carbon monoxide and to the action of carbon monoxide once generated. From the viewpoint of effectively preventing the conversion agent from being reduced and carbon dioxide from being regenerated. The reaction may be carried out batchwise or continuously. Since the reaction of this production method is a stoichiometric reaction, the amount of the conversion agent and the carbon dioxide-containing gas is 1 equivalent or more with respect to 1 equivalent of carbon dioxide when the reaction is carried out batchwise. In particular, it is preferably 3 equivalents or more. Here, 1 equivalent means that, for example, the conversion agent is represented by Ce _(1-y) Bi _y O _{(2-y / 2-x)} (where 0 <y <1, 0 ≦ x <2). In the case of bismuth-containing cerium oxide, x / 2 mol of carbon dioxide reacts with the bismuth-containing cerium oxide.

The conversion agent can be brought into contact with the carbon dioxide-containing gas in various forms. For example, in the case of a batch reactor, the powdered conversion agent can be allowed to stand (or filled) to carry out the reaction, and the conversion agent can be granulated, pelletized, massive, or plate-shaped. It is also possible to use a product formed into a shape such as a honeycomb shape, a Raschig ring shape, or a bell saddle shape by leaving (or filling). On the other hand, in the case of a continuous reaction apparatus, a reaction surface that converts carbon dioxide into carbon monoxide is separated from a regeneration surface that generates oxygen deficiency with a reducing gas by a dense membrane such as a cylinder, plate, or disk. Any structure can be used. The present inventors have confirmed that carbon is not produced as a by-product due to the reaction between the conversion agent and carbon dioxide in any case.

The carbon dioxide-containing gas brought into contact with the conversion agent may be composed of 100% by volume of carbon dioxide gas, or composed of carbon dioxide gas and one or more other gases. Also good. Examples of other gases include oxygen gas, nitrogen gas, carbon monoxide gas, methane gas, and acetylene gas. When the carbon dioxide-containing gas contains other gases, the carbon dioxide-containing gas is not particularly limited in the concentration of carbon dioxide gas, but considering the cost, carbon dioxide gas is contained in an amount of 1% by volume or more. It is preferable that it is contained, and it is more preferable that it is contained by 15% by volume or more. When the other gas is oxygen gas, it is desirable that the ratio of oxygen gas to the total amount of gas to be supplied is as small as possible.

Specific examples of the carbon dioxide-containing gas including other gases include blast furnace gas and converter gas. Blast furnace gas is a gas generated when pig iron is produced in a blast furnace, and its main components are nitrogen, carbon monoxide and carbon dioxide. The blast furnace gas contains about 52 to 53% by volume of nitrogen, about 18 to 25% by volume of carbon monoxide, and about 20 to 24% by volume of carbon dioxide. Converter gas is a gas generated when steel is produced in the converter, and its main components are carbon monoxide and carbon dioxide. The converter gas contains about 50 to 80% by volume of carbon monoxide and about 15 to 17% by volume of carbon dioxide.

In the production method of the present invention, it is preferable to regenerate the conversion agent by bringing the conversion agent oxidized by contact with carbon dioxide into contact with a reducing gas. The temperature at which the conversion agent and the reducing gas are brought into contact with each other is preferably set to, for example, 300 to 1050 ° C., particularly 320 to 820 ° C. As the reducing gas, for example, a hydrogen-containing gas or an acetylene-containing gas described later can be used. Examples of the hydrogen-containing gas include coke oven gas. The coke oven gas is a gas generated when coke is produced in the coke oven, and its main components are hydrogen and methane. The coke oven gas contains about 50 to 60% by volume of hydrogen and about 25 to 30% by volume of methane.

FIG. 1 schematically shows a carbon monoxide production apparatus suitably used in the production method of the present invention. The apparatus shown in the figure is of a continuous type and has a double tube structure. Specifically, the apparatus 10 shown in the figure includes an outer tube 11 and an inner tube 12 disposed in the outer tube 11. A heating device 13 such as a heater is disposed in the inner tube 12. The inner tube 12 contains the conversion agent. In this apparatus, a carbon dioxide-containing gas is circulated in the space between the outer tube 11 and the inner tube 12. While the carbon dioxide-containing gas circulates in the space, carbon dioxide and the conversion agent contained in the inner tube 12 react to generate carbon monoxide.

The apparatus 10 shown in FIG. 1 is configured to circulate a reducing gas in the inner pipe 12 in addition to circulating the carbon dioxide-containing gas in the space between the outer pipe 11 and the inner pipe 12. (In FIG. 1, hydrogen, which is a typical example of a reducing gas, is described.) As a result, oxygen is extracted from the conversion agent oxidized by contact with carbon dioxide, and lost oxygen vacancies are generated again. As described above, when the apparatus 10 shown in the figure is used, the conversion agent brought into contact with carbon dioxide to generate carbon monoxide, and then the conversion agent oxidized by the contact with carbon dioxide is reduced to a reducing gas. The metal oxide can be regenerated by carrying out strong reduction by contacting with the metal. The reason why such repeated regeneration treatment is possible is that the conversion agent has oxygen ion conductivity. As the reducing gas, for example, a hydrogen-containing gas or an acetylene-containing gas can be used. It is particularly preferable to use a hydrogen-containing gas. The concentration of hydrogen gas in such a reducing gas is preferably not less than the lower limit of explosion to 100% by volume, more preferably 20% to 100% by volume. As described above, a relatively low temperature is sufficient for the processing temperature. The reason for this is that bismuth is added to cerium oxide and zirconium oxide as described above. Specifically, the treatment temperature is preferably 300 to 1050 ° C, more preferably 320 to 820 ° C. Strong reducing gas is generally at atmospheric pressure.

In the apparatus shown in FIG. 1, the heating device 13 is disposed inside the inner tube 12, but a heating device may be disposed around the outer tube 11 instead. In general, since the temperature at which oxygen is forcibly extracted from the oxidized conversion agent 24 is higher than the temperature at which the reaction between carbon dioxide and the conversion agent 24 occurs, the heating device 13 is disposed inside the inner tube 12. It is advantageous in terms of ease of forced extraction of oxygen. However, in the present invention, because the conversion agent 24 contains bismuth, the temperature for forced extraction of oxygen can be set lower than when bismuth is not contained, The temperature at which the conversion agent 24 reacts with carbon dioxide and the temperature at which the oxidized conversion agent 24 is strongly reduced can also be set to be approximately the same. Therefore, there are few restrictions on the arrangement position of the heating device 13. That is, the device 10 has a high degree of design freedom.

In the apparatus shown in FIG. 1, the flow direction of the carbon dioxide-containing gas and the flow direction of the reducing gas are the same direction, but instead, the flow direction of the carbon dioxide-containing gas and the flow direction of the reducing gas are changed. It may be in the opposite direction. Further, as a modification of the apparatus shown in FIG. 1, a configuration may be adopted in which a reducing gas is circulated in the space between the outer tube 11 and the inner tube 12 and a carbon dioxide-containing gas is circulated in the inner tube 12. it can. In this case, in order to efficiently regenerate the conversion agent contained in the inner tube 12, it is preferable to arrange a heating device around the outer tube 11.

The apparatus 20 shown in FIG. 2 includes two batch-

type reaction apparatuses

21 and 22. Furthermore, the device 20 includes a switching valve 23. The switching valve 23 has

input parts

23a and 23b respectively connected to a carbon dioxide-containing gas source and a reducing gas source (in FIG. 2, hydrogen, which is a representative example of the reducing gas, is described). Yes. Furthermore, the switching valve 23 has

output parts

23c and 23d connected to the

reaction devices

21 and 22, respectively. The conversion agent 24 can be disposed in the reaction apparatuses 21 and 22. A heating device 25 is disposed around each of the

reaction devices

21 and 22.

In the apparatus 20 shown in FIG. 2, the carbon dioxide-containing gas or the reducing gas is alternatively and simultaneously supplied to the reaction apparatuses 21 and 22 via the switching valve 23. In addition to this, the type of gas supplied to each reactor can be switched by switching the switching valve 23.

When the apparatus shown in FIG. 2 is operated, first, the switching valve 23 is set to the position shown in FIG. 2, the carbon dioxide-containing gas is supplied to the second reactor 22, and the reducing gas is supplied to the first reactor. 21 to be supplied. And each

reaction apparatus

21 and 22 is heated with the heating apparatus 25, and reducing gas and a carbon dioxide containing gas are supplied to each

reaction apparatus

21 and 22. FIG. In this way, in the first reaction device 21, the conversion agent 24 placed inside is strongly reduced, oxygen is forcibly extracted, and a reversible oxygen deficiency is generated in the conversion agent 24. . On the other hand, in the second reactor 22, carbon monoxide is generated by the reaction between carbon dioxide and the conversion agent 24 that has been strongly reduced in advance, and the number of oxygen vacancies in the conversion agent 24 gradually decreases. When the amount of carbon monoxide produced in the second reactor 22 decreases, the switching valve 23 is switched so that the carbon dioxide-containing gas is supplied to the first reactor 21 and the reducing gas is supplied to the second reactor 22. To be supplied to. Since the conversion agent 24 that is left in the first reactor 21 is highly active that is not in contact with carbon dioxide, the amount of carbon monoxide produced increases by bringing this into contact with carbon dioxide. . On the other hand, in the second reactor 22, the conversion agent 24 whose activity is reduced due to a decrease in the number of oxygen vacancies is strongly reduced, oxygen is forcibly extracted, and a reversible oxygen vacancy is generated again in the conversion agent 24. .

In the apparatus 20 shown in FIG. 2, the heating temperatures of the first reaction apparatus 21 and the second reaction apparatus 22 may be set to the same or different temperatures. Generally, the temperature at which oxygen is forcibly extracted from the oxidized conversion agent 24 is higher than the temperature at which the reaction between carbon dioxide and the conversion agent 24 occurs. It is preferable to set the heating temperature higher than the heating temperature of the reactor that produces carbon monoxide. However, in the apparatus 20 using the conversion agent 24, due to the fact that the conversion agent 24 contains bismuth, the temperature at which the conversion agent 24 reacts with the carbon dioxide-containing gas, and the oxidized conversion agent 24 are strengthened. The temperature at which the reduction treatment is performed can be set to be substantially the same. Therefore, the heating temperature of the first reactor 21 and the second reactor 22 can be determined without any particular limitation. That is, the device 20 has a high degree of design freedom.

In this manner, the carbon dioxide gas and the conversion agent 24 are alternately reacted in the first reaction device 21 and the second reaction device 22 to regenerate the conversion agent 24 and generate carbon monoxide. Semi-continuous operation is possible. In the apparatus 20 shown in FIG. 2, two batch reactors are used, but three or more reactors may be used instead.

The apparatus 30 shown in FIG. 3 has a structure in which plate-like bodies 31 including the conversion agent and plate-like separators 32 are alternately stacked. A plurality of convex portions 33 and concave portions 34 extending in one direction are alternately arranged on each surface of each separator 32. As a result, a space is formed between the plate-like body 31 and the pair of separators that are opposed to each other with the gas formed by the concave portions 34. Moreover, although not shown in figure, the apparatus 30 is equipped with the heating apparatus arrange | positioned around the stack structure.

When the apparatus 30 shown in FIG. 3 is operated, in the two

separators

32a and 32b facing each other with the plate-like body 31 interposed therebetween while the stack structure is heated to a predetermined temperature by a heating device (not shown). A carbon dioxide-containing gas is circulated through the concave portion 34a located on the opposing surface of the one separator 32a and the plate-like body 31. While the carbon dioxide-containing gas flows through the recess 34a, the carbon dioxide and the conversion agent contained in the plate-like body 31 react to generate carbon monoxide. In addition to this, the reducing gas is circulated through the concave portion 34b located on the opposing surface of the other separator 32b and the plate-like body 31 (in FIG. 3, a representative example of reducing gas). Some hydrogen is described.) As a result, oxygen is extracted from the conversion agent oxidized by contact with carbon dioxide, and lost oxygen vacancies are generated again. As described above, when the apparatus 30 is used, as in the apparatus 10 shown in FIG. 1 described above, after the conversion agent is brought into contact with the carbon dioxide-containing gas to generate carbon monoxide, the carbon dioxide-containing gas is used. The metal oxide can be regenerated by carrying out strong reduction by bringing the conversion agent oxidized by contact with the catalyst into contact with a reducing gas.

In each separator 32 of the device 30 shown in FIG. 3, the extending direction of the convex portion 33 and the concave portion 34 formed on one surface and the other surface is shifted by 90 degrees. However, the extending direction of the convex portion 33 and the concave strip portion 34 formed on each surface of the separator 32 is not limited to this. For example, the extending direction of the convex part 33 and the concave line part 34 formed on each surface of the separator 32 may intersect at an angle other than 90 degrees, or the same direction. When the extending direction of the convex part 33 and the concave line part 34 formed on each surface of the separator 32 is the same direction, the direction of the gas flowing through the concave line part 34 on one surface side of the separator 32 and the other The direction of the gas flowing through the groove 34 on the surface side may be the same direction or the opposite direction.

Note that, regarding the device shown in FIGS. 2 and 3, the description regarding the device shown in FIG.

Further, according to the present invention, a system for converting carbon dioxide into carbon monoxide using the conversion agent is also provided. In this system, an exhaust gas containing carbon dioxide generated from an ironworks, a smelter, or a thermal power plant, which is a main source of carbon dioxide, is contacted with the conversion agent. Examples of the exhaust gas containing carbon dioxide generated from a steel mill, a smelter, or a thermal power plant include blast furnace gas and converter gas. At this time, it is advantageous that the energy efficiency can be increased if the waste heat generated from the steelworks, the smelter or the thermal power plant is contacted under heating. Carbon monoxide is produced by the contact under heating. According to this system, not only carbon dioxide is prevented from being released into the atmosphere, but also there is an advantage that the produced carbon monoxide can be effectively used as a raw material for C1 chemistry. Alternatively, the produced carbon monoxide can be fed back to, for example, a blast furnace at a steel mill and reused.

In the steelworks or smelter, in addition to generating gas exhaust gas containing carbon dioxide, hydrogen-containing gas is also generated. Particularly in steelworks, a large amount of hydrogen-containing gas is generated. If this hydrogen-containing gas is used to regenerate the conversion agent oxidized by contact with carbon dioxide, the conversion agent having a reversible oxygen deficiency can be obtained without preparing a separate hydrogen gas. Therefore, energy efficiency is further increased, which is advantageous. Examples of the hydrogen-containing gas produced in the steelworks or smelter include coke oven gas. Moreover, since the conversion agent used in the present invention contains bismuth, the temperature for generating reversible oxygen vacancies in the conversion agent can be set low. Alternatively, there is an advantage that the conversion agent can be successfully regenerated using waste heat generated from the thermal power plant. The facility to which the present system is applied is not limited to a steel mill or a smelter, but can be advantageously applied to a facility that produces a large amount of hydrogen as a by-product, such as a facility having a coke oven.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” means “% by weight”.

[Example 1]
(1) Production of bismuth-containing cerium oxide having reversible oxygen deficiency (a) Synthesis of bismuth-containing cerium oxide Cerium carbonate octahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dried at 120 ° C. for 12 hours to obtain cerium carbonate. Got. The obtained cerium carbonate 92.0308 g and Bi ₂ O ₃ (manufactured by Wako Pure Chemical Industries, Ltd., purity 99.9%) 0.0932 g were pulverized and mixed in a ball mill for 12 hours. The ratio of bismuth to the total amount of cerium and bismuth was 0.001. 50 g of the obtained mixed powder was allowed to stand in a heating furnace, and heated and calcined while circulating air. Heating was started from room temperature, heated at a rate of temperature increase of 5 ° C./min, and after reaching 300 ° C., this temperature was maintained for 2 hours. The air flow rate was 0.5 L / min. The calcined product obtained by calcining was further pulverized and mixed with a mortar. This pulverized product was left in a heating furnace and heated while circulating air to perform main firing. Heating was started at room temperature and performed at a rate of temperature increase of 5 ° C./min. After reaching 750 ° C., this temperature was maintained for 2 hours. Thereafter, it was naturally cooled to obtain bismuth-containing cerium oxide having no reversible oxygen deficiency. The air flow rate was 0.5 L / min. In the measurement by XRD, in this bismuth-containing cerium oxide, the diffraction peak derived from Bi ₂ O ₃ was not observed, but only the diffraction peak derived from CeO ₂ was observed. From this result, it was confirmed that bismuth was dissolved in cerium oxide.

(B) Synthesis of bismuth-containing cerium oxide having reversible oxygen deficiency The bismuth-containing cerium oxide (50 g) obtained in the previous item (a) was left in an atmosphere-controlled heating furnace, and 100% by volume of hydrogen gas was supplied. The reduction was performed by heating while circulating. Heating was started from room temperature, heated at a rate of temperature increase of 5 ° C./min, and after reaching 600 ° C., this temperature was maintained for 3 hours. Then, it naturally left to cool. The flow rate of hydrogen gas was 1.5 L / min. In this way, bismuth-containing cerium oxide having reversible oxygen vacancies was obtained.

(2) Conversion evaluation of carbon monoxide gas from carbon dioxide gas A tubular furnace using the apparatus shown in FIG. 4 was installed in a glove box in a nitrogen gas atmosphere. In the tubular furnace, 8.5 g of bismuth-containing cerium oxide powder having reversible oxygen vacancies obtained in (1) above is placed. First, the valve V5 was closed, all other valves were opened, and the inside of the tubular furnace was vacuumed. In this state, the valve V1 was closed and the tubular furnace was heated to 600 ° C. Next, after the valves V2 and V3 were closed, the suction in the tubular furnace was stopped. The valve V4 was closed and carbon dioxide gas (100% by volume) was supplied into the tubular furnace. The supply amount was 280 mL (0 ° C., 1 atm conversion value). The valve V1 was closed and left for 1 hour. Thereafter, the valve V2 was opened, and nitrogen gas was supplied into the tubular furnace until the gas recovery bag was slightly expanded. Next, the valve V2 was closed and the gas recovery bag was heat sealed and separated from the tube. In this state, the temperature of the tubular furnace was lowered and cooled to room temperature. After completion of cooling, the valve V1 was opened and nitrogen gas was supplied into the tubular furnace. The supply was continued until the pressure in the tubular furnace reached atmospheric pressure. Finally, the valves V3 and V5 were opened, and carbon monoxide in the tubular furnace was extruded with nitrogen gas. The recovered gas after the reaction was qualitatively and quantitatively analyzed using gas chromatography, and the conversion from carbon dioxide to carbon monoxide at 600 ° C. was evaluated according to the following criteria. Apart from this evaluation, the conversion from carbon dioxide to carbon monoxide at 400 ° C. was evaluated in the same manner as described above except that the heating temperature of the tubular furnace was lowered to 400 ° C. These results are shown in Table 1 below.
○: 0.5% or more of carbon dioxide was converted to carbon monoxide.
X: Less than 0.5% of carbon dioxide was converted to carbon monoxide.

(3) Oxygen deficiency generation temperature The temperature at which the bismuth-containing cerium oxide having no reversible oxygen deficiency and the cerium oxide having no oxygen deficiency used in Example 1 generate reversible oxygen deficiency (hereinafter, “T _red Was measured by the following method. The results are shown in Table 1 below.

Reduction of bismuth-containing cerium oxide without reversible oxygen vacancies and cerium oxide without reversible oxygen vacancies 30-35 mg using differential thermothermal gravimetric simultaneous measurement device (TG / DTA) (EXSTAR6000 manufactured by SII) The temperature was raised under a gas atmosphere. The temperature at which a weight change due to oxygen desorption was observed was defined as T _red . As the reducing gas, a hydrogen / nitrogen mixed gas (hydrogen 4 vol%, nitrogen 96 vol%) was used. The flow rate of the reducing gas was 300 mL / min, and the heating rate was 20 ° C./min. In the TG curve, the temperature at the intersection of the tangent line before the weight loss starts to occur and the tangent line after the weight loss starts to occur was defined as T _red .

[Examples 2 to 9 and Reference Example 1]
A bismuth-containing cerium oxide was obtained in the same manner as in Example 1 except that the mixing ratio of cerium carbonate and Bi ₂ O ₃ was adjusted so that the ratio of bismuth to the total amount of cerium and bismuth was the value shown in Table 1. It was. In the measurement by XRD, in the bismuth-containing cerium oxide of each Example, the diffraction peak derived from Bi ₂ O ₃ was not observed, but only the diffraction peak derived from CeO ₂ was observed. From these results, it was confirmed that bismuth was dissolved in cerium oxide in the bismuth-containing cerium oxide of each example. Except this, bismuth-containing cerium oxide having reversible oxygen vacancies (cerium oxide having reversible oxygen vacancies in Reference Example 1) was obtained in the same manner as in Example 1. The obtained bismuth-containing cerium oxide (Examples 2 to 9) and cerium oxide (Reference Example 1) were _{subjected to} the same conversion evaluation and T _red measurement as in Example 1. The results are shown in Table 1 below.

[Reference Example 2]
In Example 6, bismuth-containing cerium oxide having no reversible oxygen vacancies was directly subjected to reaction with carbon dioxide gas without hydrogen reduction. The results are shown in Table 1 below.

As is clear from the results shown in Table 1, it is understood that carbon dioxide can be converted to carbon monoxide by using the conversion agent obtained in each example. In particular, as is clear from the comparison between Example 1 and Reference Example 1 at a temperature of 400 ° C., it can be seen that carbon monoxide can be produced from carbon dioxide even at a lower temperature by adding bismuth to cerium oxide. Further, as is clear from the results shown in Reference Example 2, it can be seen that the reaction with carbon dioxide gas does not occur when bismuth-containing cerium oxide does not cause reversible oxygen deficiency.

Further, as is apparent from the results shown in the table, it can be seen that T _red decreases as the amount of bismuth added increases, and the temperature at which oxygen vacancies are generated can be lowered. T _red, the ratio of added bismuth is minimized when the 0.1 and more than that will increase the amount of bismuth, T _red it can be seen that starts to rise.

Although not shown in the table, no carbon by-product was observed in each example.

Example 10
In this example, bismuth-containing zirconium oxide is used as a metal oxide having reversible oxygen vacancies. Zirconium carbonate hydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dried at 120 ° C. for 12 hours to obtain zirconium carbonate. The obtained zirconium carbonate and 100 g of Bi ₂ O ₃ (manufactured by Wako Pure Chemical Industries, purity 99.9%) were pulverized and mixed in a ball mill for 12 hours. The ratio of bismuth to the total amount of zirconium and bismuth was 0.02. 50 g of the obtained mixed powder was allowed to stand in a heating furnace, and heated and calcined while circulating air. Heating was started from room temperature, heated at a rate of temperature increase of 5 ° C./min, and after reaching 300 ° C., this temperature was maintained for 2 hours. The air flow rate was 0.5 L / min. The calcined product obtained by calcining was further pulverized and mixed with a mortar. This pulverized product was left in a heating furnace and heated while circulating air to perform main firing. Heating was started at room temperature and performed at a rate of temperature increase of 5 ° C./min. After reaching 750 ° C., this temperature was maintained for 2 hours. Thereafter, it was naturally cooled to obtain bismuth-containing zirconium oxide having no reversible oxygen deficiency. The air flow rate was 0.5 L / min. In the measurement by XRD, in this bismuth-containing zirconium oxide, the diffraction peak derived from Bi ₂ O ₃ was not observed, but only the diffraction peak derived from ZrO ₂ was observed. From this result, it was confirmed that bismuth was dissolved in zirconium oxide. From the obtained bismuth-containing zirconium oxide, a bismuth-containing zirconium oxide having a reversible oxygen deficiency was obtained in the same manner as in Example 1. The obtained bismuth-containing zirconium oxide was subjected to the same conversion evaluation and T _red measurement as in Example 1. The results are shown in Table 2 below.

[Reference Example 3]
Zirconium oxide having a reversible oxygen deficiency was obtained in the same manner as in Example 10 except that the ratio of bismuth to the total amount of zirconium and bismuth was 0. The obtained zirconium oxide was subjected to the same conversion evaluation and T _red measurement as in Example 1. The results are shown in Table 2 below.

[Reference Example 4]
In Example 10, the bismuth-containing zirconium oxide having no reversible oxygen deficiency was directly subjected to the reaction with carbon dioxide gas without hydrogen reduction. The results are shown in Table 2 below.

From the results shown in Table 2, it can be seen that carbon dioxide can be converted to carbon monoxide when the conversion agent obtained in Example 10 is used. In particular, as is clear from the comparison between Example 10 and Reference Example 3 at a temperature of 400 ° C., it can be seen that by adding bismuth to zirconium oxide, carbon monoxide can be generated from carbon dioxide even at a lower temperature. Further, as is clear from the results shown in the table, it can be seen that T _red can be reduced by adding bismuth, and the temperature at which oxygen vacancies are generated can be lowered. Further, as is clear from the results shown in Reference Example 4, it can be seen that the reaction with carbon dioxide gas does not occur when bismuth-containing zirconium oxide does not cause reversible oxygen deficiency.

Although not shown in Table 2, no carbon by-product was observed in Example 10 as well.

Claims

A metal oxide having oxygen ion conductivity and reversible oxygen deficiency is brought into contact with a carbon dioxide-containing gas under heating, and carbon dioxide is reduced by a stoichiometric reaction to generate carbon monoxide. A method for producing carbon monoxide, comprising:
A method for producing carbon monoxide using cerium oxide containing bismuth or zirconium oxide containing bismuth as the metal oxide.
In the cerium oxide containing bismuth, the ratio of the number of moles of bismuth to the total amount of moles of cerium and bismuth is 0.001 to 0.5,
The production method according to claim 1, wherein in the zirconium oxide containing bismuth, the ratio of the number of moles of bismuth to the total number of moles of zirconium and bismuth is 0.001 to 0.5.
The production method according to claim 2, wherein cerium oxide in which bismuth is dissolved or zirconium oxide in which bismuth is dissolved is used as the metal oxide.
The manufacturing method according to any one of claims 1 to 3, wherein a blast furnace gas or a converter gas is used as the carbon dioxide-containing gas.
The metal oxide is brought into contact with a carbon dioxide-containing gas to produce carbon monoxide, and then the metal oxide oxidized by the contact with the carbon dioxide-containing gas is brought into contact with a reducing gas to form the metal oxide. The manufacturing method according to any one of claims 1 to 4 which reproduces.
The manufacturing method according to claim 5, wherein coke oven gas is used as the reducing gas.
An outer tube, and an inner tube disposed in the outer tube,
The inner tube includes a metal oxide having oxygen ion conductivity and having a reversible oxygen deficiency,
A gas containing carbon dioxide is circulated between the outer tube and the inner tube, and a reducing gas is circulated in the inner tube, or reduction is performed between the outer tube and the inner tube. And a carbon dioxide-containing gas is circulated in the inner pipe.
A carbon monoxide production apparatus using cerium oxide containing bismuth or zirconium oxide containing bismuth as the metal oxide.
This is a carbon monoxide production apparatus in which plate-like bodies comprising a metal oxide having oxygen ion conductivity and having reversible oxygen vacancies and plate-like separators are alternately stacked. And
A plurality of ridges and ridges extending in one direction are alternately arranged on each surface of each separator,
A carbon dioxide-containing gas is circulated through a concave portion located on the opposing surface of one separator and the plate-like body in two separators facing each other with the plate-like body sandwiched therebetween, and the other separator and the plate-like body Is configured to circulate the reducing gas through the concave portion located on the opposite surface,
A carbon monoxide production apparatus using cerium oxide containing bismuth or zirconium oxide containing bismuth as the metal oxide.
The exhaust gas containing carbon dioxide generated from steelworks, smelters or thermal power plants and metal oxides having oxygen ion conductivity and having reversible oxygen vacancies are used for smelters, steelworks or thermal power plants. The carbon dioxide in the exhaust gas is brought into contact with heating using waste heat generated from the plant and the carbon dioxide in the exhaust gas is reduced by a stoichiometric reaction to produce carbon monoxide. A system for converting,
A system for converting carbon dioxide to carbon monoxide using cerium oxide containing bismuth or zirconium oxide containing bismuth as the metal oxide.
The system according to claim 9, wherein a blast furnace gas or a converter gas is used as the exhaust gas.
The metal oxide oxidized by contact with carbon dioxide is brought into contact with a hydrogen-containing gas generated from a smelter or an ironworks, thereby causing reversible oxygen deficiency in the metal oxide. The described system.
The system according to claim 11, wherein coke oven gas is used as the hydrogen-containing gas.
An agent for converting carbon dioxide to carbon monoxide comprising a metal oxide having oxygen ion conductivity and having a reversible oxygen deficiency, wherein the metal oxide comprises cerium oxide containing bismuth or zirconium oxide containing bismuth. .