Dual-function catalyst and carbon recycling equipment

Abstract

In a reverse water-gas shift reaction, this invention provides a dual-function catalyst that exhibits excellent carbon dioxide storage capabilities and reduction capabilities from stored carbon dioxide to carbon monoxide, even when the gas being treated contains carbon dioxide and carbon monoxide. [Solution] A dual-function catalyst having an adsorption function for adsorbing carbon dioxide contained in a gas to be treated and a reduction function for reducing the adsorbed carbon dioxide to carbon monoxide, comprising a composite of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc, an alkali metal, and a support.

Description

[Technical Field]

[0001] The present invention relates to a dual-function catalyst having a storage function for absorbing carbon dioxide and a reduction function for reducing carbon dioxide to carbon monoxide, and to a carbon recycling facility using the same. [Background technology]

[0002] Traditionally, waste incineration facilities, biomass power generation facilities, and sewage sludge incineration facilities have emitted large amounts of combustion exhaust gas containing carbon dioxide. In recent years, while it has been recognized that reducing carbon dioxide emissions is important for curbing global warming and building a sustainable society, attempts have been made to effectively utilize combustion exhaust gas containing carbon dioxide. Such attempts are called carbon recycling technologies.

[0003] As a carbon recycling technology, a process using a catalyst to reduce carbon dioxide to carbon monoxide has been proposed, and it has been suggested to use composite oxides such as Ba2TiO4, Sr2TiO4, and Ba3Ca2Ti2O9 as this type of catalyst (see Patent Document 1). In Patent Document 1, such a catalyst is used to reduce carbon dioxide to carbon monoxide by reacting the carbon dioxide contained in the gas to be treated with hydrogen (CO2 + H2 → CO + H2O, reverse water-gas shift reaction). Furthermore, the obtained carbon monoxide is converted into methanol or hydrocarbons.

[0004] Furthermore, it has been proposed to increase the amount of reduction from carbon dioxide to carbon monoxide by the reverse water-gas shift reaction by using a dual-function catalyst that has both carbon dioxide storage (adsorption) and reduction functions. For example, it has been proposed to use (Na, K, Ca) / γ-Al2O3, Na / (ZrO2, CeO2, TiO2), etc., as absorption conversion catalysts that contain alkali metals and / or alkaline earth metals and substantially do not contain Ni, Fe, Co, Cr, Cu, Ru, In, Rh, Pt, Au, and Pd elements (see Patent Document 2). Patent Document 2 states that carbon dioxide can be efficiently reduced to carbon monoxide using such a catalyst. It also states that the obtained carbon monoxide can be directly used as a raw material for the synthesis of hydrocarbons by the already established Fischer-Tropsch (FT) reaction. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2008 / 038484 [Patent Document 2] International Publication No. 2023 / 037652 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Patent documents 1 and 2 describe the conversion of carbon monoxide obtained by a reverse water-gas shift reaction into methanol and hydrocarbons. However, if more carbon monoxide can be produced from carbon dioxide in the reverse water-gas shift reaction, the amount of methanol and hydrocarbons produced will also increase accordingly. Furthermore, if carbon monoxide can be converted into solid carbon (C) or methane (carbon resource utilization), it will be possible to apply it to a wider range of uses (chemicals, fuels, etc.).

[0007] Therefore, there is a need for catalysts that can efficiently reduce carbon dioxide to carbon monoxide.

[0008] However, if the gas being treated contains not only carbon dioxide but also carbon monoxide, the amount of carbon monoxide produced by the reverse water-gas shift reaction may decrease. Furthermore, the amount of carbon dioxide reduced to carbon monoxide may also decrease. In such cases, the amount of carbon dioxide that can be converted into a resource through carbon recycling technology may decrease.

[0009] For example, when converting carbon dioxide to solid carbon, it is conceivable to construct a system that combines the process of reducing carbon dioxide to carbon monoxide using the reverse water-gas shift reaction described above, and the process of reducing the generated carbon monoxide to solid carbon using the Booduor reaction (CO → 1 / 2C + 1 / 2CO2), thereby enabling the execution of these processes.

[0010] Here, since the off-gas after the Booduor reaction contains unreacted carbon monoxide, if this unreacted carbon monoxide can be reused as a raw material gas for the Booduor reaction without being released into the atmosphere, the amount of solid carbon produced will increase, and it is thought that a highly efficient carbon recycling technology can be realized.

[0011] However, the off-gas after the Booduor reaction contains not only unreacted carbon monoxide but also carbon dioxide, a byproduct. If this off-gas is returned to the Booduor reaction, the amount of solid carbon produced may actually decrease due to equilibrium constraints imposed by the carbon dioxide contained in the off-gas.

[0012] On the other hand, if the carbon dioxide contained in the off-gas after the Booduor reaction can be returned to the reverse water-gas shift reaction and carbon monoxide can be produced from the returned carbon dioxide, the total amount of carbon monoxide produced in the system can be increased, and as a result, the amount of solid carbon produced can be increased. However, as mentioned above, the off-gas after the Booduor reaction contains not only carbon dioxide but also unreacted carbon monoxide, so if this off-gas is returned to the reverse water-gas shift reaction, the amount of carbon monoxide produced may actually decrease due to equilibrium constraints imposed by the returned carbon monoxide. Furthermore, even when the carbon monoxide produced in the reverse water-gas shift reaction is used in a reaction other than the Booduor reaction, unreacted carbon monoxide and by-product carbon dioxide may be present in the off-gas during oxidation or reduction reactions of carbon monoxide in the reactor.

[0013] As described above, in the reverse water-gas shift reaction, if the gas to be treated contains (coexists with) carbon dioxide and carbon monoxide, the amount of reduction from carbon dioxide to carbon monoxide decreases (the reduction function of the catalyst decreases), which may reduce the amount of carbon dioxide that can be converted into a resource by carbon recycling technology.

[0014] The present invention has been made in view of the above circumstances, and aims to provide a dual-function catalyst that excels in carbon dioxide storage function and reduction function from stored carbon dioxide to carbon monoxide, even when carbon dioxide and carbon monoxide are contained in the gas to be treated in a reverse water-gas shift reaction, and carbon recycling equipment using the same. [Means for solving the problem]

[0015] In order to solve the above problems, the inventors diligently conducted research and found that even when carbon dioxide and carbon monoxide are present (coexist) in the off-gas (gas to be treated), by using a binary functional catalyst that includes a composite of indium, copper, platinum, palladium, and zinc with alkali metals and a support, the amount of carbon dioxide absorbed can be increased, and the amount of carbon dioxide reduced to carbon monoxide can also be increased, thus completing the present invention. Furthermore, the inventors found that by performing a Boudouer reaction after a reverse water-gas shift reaction using such a binary functional catalyst, the amount of solid carbon produced can be increased, and furthermore, since the reverse water-gas shift reaction can be performed at a lower reaction temperature than the Boudouer reaction, the reverse water-gas shift reaction is not subject to equilibrium constraints and can be made energy-efficient, thus completing another aspect of the present invention.

[0016] In other words, the characteristic configuration of the dual-function catalyst according to the present invention is, A dual-function catalyst having a storage function that absorbs carbon dioxide contained in the gas to be treated, and a reduction function that reduces the absorbed carbon dioxide to carbon monoxide, The material comprises a composite of an alkali metal and a support, comprising at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc.

[0017] This dual-function catalyst, comprising a composite of at least one element selected from the group consisting of indium, copper, platinum, palladium, and zinc, an alkali metal, and a support, allows the indium and other elements, along with the alkali metal, to act as active sites, exhibiting both carbon dioxide storage and reduction functions (reducing the stored carbon dioxide to carbon monoxide) in the reverse water-gas shift reaction. Furthermore, this dual-function catalyst exhibits superior carbon dioxide storage and reduction functions (reducing the stored carbon dioxide to carbon monoxide) even when the gas to be treated contains carbon monoxide in addition to carbon dioxide. As a result, a larger amount of carbon monoxide can be produced from carbon dioxide. In addition, for example, if the carbon monoxide generated in the reverse water gas shift reaction is reduced to solid carbon by the Boudouard reaction, a large amount of solid carbon can be produced. Further, since the reaction temperature of the reverse water gas shift reaction using the binary functional catalyst is lower than that of the Boudouard reaction, the reverse water gas shift reaction is not subject to equilibrium constraints and can be made energy-efficient.

[0018] In the binary functional catalyst of this configuration, It is preferable that the alkali metal is at least one selected from the group consisting of sodium, potassium, rubidium, and cesium.

[0019] According to the binary functional catalyst of this configuration, by selecting the above elements as the alkali metal, the above storage function and the above reduction function can be further enhanced.

[0020] In the binary functional catalyst of this configuration, The content of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc is preferably 1 to 70% by mass.

[0021] According to the binary functional catalyst of this configuration, when the content of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc is within the above range, the above storage function and the above reduction function can be further enhanced.

[0022] In the binary functional catalyst of this configuration, The content of the alkali metal is preferably 1 to 70% by mass.

[0023] According to the binary functional catalyst of this configuration, when the content of the alkali metal is within the above range, the above storage function and the above reduction function can be further enhanced.

[0024] In the binary functional catalyst of this configuration, The carrier is preferably at least one selected from the group consisting of zirconium oxide, aluminum oxide, titanium oxide, and magnesium oxide.

[0025] With this dual-function catalyst configuration, by selecting the above oxide as the support, at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc can be more reliably supported with an alkali metal, forming a stronger composite, and thus the above storage function and the above reduction function can be more reliably exhibited.

[0026] In this dual-function catalyst configuration, It is preferable that the carbon dioxide storage capacity is 200 μmol / g or more.

[0027] With the dual-function catalyst of this configuration, by setting the amount of carbon dioxide absorbed per gram of the dual-function catalyst within the above range, the absorption function of the dual-function catalyst is further enhanced.

[0028] In this dual-function catalyst configuration, It is preferable that the amount of carbon monoxide produced is 90 μmol / g or more.

[0029] With this configuration of a dual-function catalyst, by setting the amount of carbon monoxide generated per gram of the dual-function catalyst within the above range, the reduction function of the dual-function catalyst is further enhanced.

[0030] In this dual-function catalyst configuration, It is preferable that the methane yield be 1% or less.

[0031] With this dual-function catalyst configuration, by setting the yield of methane, a by-product, within the above range, the yield of carbon monoxide is relatively increased, thereby further enhancing the reduction function.

[0032] In this dual-function catalyst configuration, The composite preferably contains the indium and / or the copper.

[0033] With this dual-function catalyst configuration, the indium and copper content of the complex reduces the yield of methane, a byproduct, thereby relatively increasing the yield of carbon monoxide, and consequently enhancing the reducing function described above.

[0034] Another carbon recycling facility according to the present invention, which solves the above problems, A reverse water-gas shift reactor that reduces carbon dioxide contained in the gas to be treated to carbon monoxide by a reverse water-gas shift reaction, A carbon resource conversion apparatus that converts carbon monoxide into a resource through a carbon resource conversion reaction, Equipped with, The aforementioned reverse water-gas shift reactor houses the aforementioned dual-function catalyst. The off-gas from the carbon resource recovery device is returned to the reverse water-gas shift reactor.

[0035] With this carbon recycling equipment configuration, the reverse water-gas shift reaction can be carried out using the aforementioned dual-function catalyst in the reverse water-gas shift reactor, thereby increasing the amount of carbon monoxide produced. As a result, a large amount of resources (solid carbon in the case of the Booduar reaction) can be obtained by using the produced carbon monoxide to carry out carbon resource recovery reactions such as the Booduar reaction. Furthermore, if the carbon resource recovery reaction is, for example, the Booduar reaction, the reverse water-gas shift reaction can be carried out at a lower reaction temperature than the Booduar reaction, so the reverse water-gas shift reaction is not subject to equilibrium constraints and energy consumption can be reduced. [Brief explanation of the drawing]

[0036] [Figure 1] Figure 1 is a block diagram showing the schematic system configuration of a carbon dioxide solid carbonization facility according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram showing the experimental apparatus used in the examples and comparative examples. [Figure 3] Figure 3 is a graph showing the results of Experiment Example 2. [Figure 4]Figure 4 is a graph showing the results of Experiment Example 3. [Modes for carrying out the invention]

[0037] The dual-function catalyst and the carbon dioxide solid carbonization equipment of the present invention will be described below with reference to the drawings as appropriate. However, the present invention is not intended to be limited to the embodiments and configurations described below or shown in the drawings.

[0038] [Dual-function catalyst]

[0039] The binary-function catalyst of this embodiment is a binary-function catalyst having an adsorption function that adsorbs carbon dioxide contained in the gas to be treated, and a reduction function that reduces the adsorbed carbon dioxide to carbon monoxide. The binary-function catalyst comprises a composite of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc, an alkali metal, and a support. More specifically, the binary-function catalyst is a composite in which at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc, and an alkali metal are supported on a support. The binary-function catalyst is usually in powder or granular form.

[0040] <Storage function> Of the two functions, the storage function is the function of absorbing (adsorbing) carbon dioxide contained in the gas being treated. If this storage function is high, the amount of carbon dioxide available for the reduction reaction will increase, and thus the amount of carbon monoxide produced can be increased.

[0041] <Reduction function> The reduction function is the ability to reduce absorbed carbon dioxide to carbon monoxide. This reduction can be carried out by a reverse water-gas shift reaction (CO2 + H2 → CO + H2O). A higher reduction function allows for a greater production of carbon monoxide.

[0042] <Indium, copper, platinum, palladium, zinc> Indium (In) is an element in Group 13, Period 5 of the periodic table. Copper (Cu) is an element in Group 11, Period 4 of the periodic table. Platinum (Pt) is an element in Group 10, Period 6 of the periodic table. Palladium (Pd) is an element in Group 10, Period 5 of the periodic table. Zinc (Zn) is an element in Group 12, Period 4 of the periodic table. At least one element selected from the group consisting of indium, copper, platinum, palladium, and zinc is supported on a carrier together with an alkali metal. At least one element selected from the group consisting of indium, copper, platinum, palladium, and zinc acts as an active site together with the alkali metal, and can exhibit the above-mentioned storage function and reduction function in the reverse water-gas shift reaction. Moreover, even when the gas to be treated contains not only carbon dioxide but also carbon monoxide, the above-mentioned storage function and reduction function are excellent, so more carbon monoxide can be produced from carbon dioxide. Of indium, copper, platinum, palladium, and zinc, indium and copper are preferred, with indium being more preferred. The inclusion of indium and copper in the composite reduces the yield of methane, a byproduct, thereby relatively increasing the yield of carbon monoxide, and consequently enhancing the reducing function. These elements can be used individually, or as a mixture of two or more.

[0043] The content of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc in the binary-function catalyst is preferably 1 to 70% by mass, more preferably 1 to 30% by mass, even more preferably 2 to 25% by mass, even more preferably 5 to 25% by mass, and particularly preferably 10 to 20% by mass. By setting the content of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc within the above ranges, the storage function and the reduction function are further enhanced.

[0044] <Alkali metals> Alkali metals are elements of Group 1 in the periodic table. Alkali metals are supported on a carrier together with at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc. The alkali metals, together with at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc, act as active sites and can exert the above-mentioned storage and reduction functions in the reverse water-gas shift reaction. Moreover, even when the gas to be treated contains carbon monoxide in addition to carbon dioxide, the above-mentioned storage and reduction functions are excellent, allowing for the generation of more carbon monoxide from carbon dioxide.

[0045] The alkali metal is not particularly limited, as long as it can serve as an active site for exhibiting the above-mentioned storage function and reduction function. Examples of alkali metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr), of which sodium, potassium, rubidium, and cesium are preferred. By selecting the above elements as alkali metals, the above-mentioned storage function and reduction function can be further enhanced. Alkali metals can be used individually, or as a mixture of two or more.

[0046] The alkali metal content in the dual-function catalyst is preferably 1 to 70% by mass, more preferably 1 to 40% by mass, even more preferably 3 to 30% by mass, even more preferably 5 to 25% by mass, and particularly preferably 10 to 20% by mass. By setting the alkali metal content within the above ranges, the storage function and the reduction function can be further enhanced. The content of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc, and the alkali metal content can be appropriately set within a range where the total content, including the content of the carrier and any other components, does not exceed 100% by mass.

[0047] <Mass ratio of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc, to an alkali metal> The mass ratio of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc to an alkali metal is preferably set to 1:0.2 to 1:20, more preferably set to 1:0.5 to 1:20, and even more preferably set to 1:5 to 1:20. By setting the mass ratio of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc to an alkali metal within the above range, the above occlusion function and the above reduction function can be further enhanced.

[0048] <Support> The support is one that supports at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc having active sites and an alkali metal, and a composite is formed by supporting these on the support. Examples of the support include metal oxides. In this case, the dual-functional catalyst will contain a composite oxide of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc, an alkali metal, and a metal oxide. When the content of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc in the dual-functional catalyst is X (mass %), the alkali metal is A, the content of the alkali metal A in the dual-functional catalyst is Y (mass %), the metal in the metal oxide is B, its molar number is m, and the molar number of oxygen is n, the dual-functional catalyst is In(X)A(Y) / B m O n , Cu(X)A(Y) / B m O n , Pt(X)A(Y) / B m O n , Pd(X)A(Y) / B m O n , Zn(X)A(Y) / B m O n , In(X1)Cu(X2)A(Y) / B m O nIt can be expressed by structural formulas such as the following. Note that " / " indicates that the element on the left is supported in the compound on the right. Also, if multiple elements are selected from indium, copper, platinum, palladium, and zinc, "X" is the total content, and the content of each element can be expressed as "X1", "X2", "X3", and "X4" depending on the number of elements selected (1 to 4). In such metal oxides, as described above, the content X of at least one element selected from the group consisting of indium, copper, platinum, palladium, and zinc, the content Y of alkali metals, and the mass ratio (X:Y) of at least one element selected from indium, copper, platinum, palladium, and zinc to alkali metals can be set as described above.

[0049] Preferred metal oxides for the support are zirconium oxide, aluminum oxide, titanium oxide, and magnesium oxide. Zirconium oxide is ZrO2, which corresponds to the case where B is Zr, m is 1, and n is 2 in the above structural formula. Aluminum oxide (Al2O3) corresponds to the case where B is Al, m is 2, and n is 3 in the above structural formula. Titanium oxide (TiO2) corresponds to the case where B is Ti, m is 1, and n is 2 in the above structural formula. Magnesium oxide (MgO) corresponds to the case where B is Mg, m is 1, and n is 1 in the above structural formula. By selecting the above metal oxides as the support, at least one selected from indium, copper, platinum, palladium, and zinc, which have active sites, and an alkali metal can be more reliably supported, forming a stronger composite, and thus the above storage function and the above reduction function can be more reliably exhibited. The support can be used individually, or as a mixture of two or more types.

[0050] <Specific examples of dual-function catalysts> Specific examples of dual-function catalysts are listed below. In(1)Cs(10) / ZrO2(X:Y=1:10) In(2)Cs(10) / ZrO2(X:Y=1:5) In(5)Cs(10) / ZrO2(X:Y=1:2) In(10)Cs(10) / ZrO2(X:Y=1:1) In(15)Cs(10) / ZrO2(X:Y=1:0.67) In(10)Cs(5) / ZrO2(X:Y=1:0.5) In(10)Cs(16) / ZrO2(X:Y=1:1.6) In(10)Cs(28) / ZrO2(X:Y=1:2.8) In(2)Cs(5) / ZrO2(X:Y=1:2.5) In(2)Cs(15) / ZrO2(X:Y=1:7.5) In(2)Cs(20) / ZrO2(X:Y=1:10) In(2)Cs(10) / Al2O3(X:Y=1:5) In(2)Cs(10) / TiO2(X:Y=1:5) In(2)Cs(10) / MgO(X:Y=1:5) In(20)Cs(5) / ZrO2(X:Y=1:0.25) In(2)Na(1.7) / ZrO2(X:Y=1:0.85) In(2)K(3) / ZrO2(X:Y=1:1.5) In(2)Rb(6.5) / ZrO2(X:Y=1:3.25) Pt(1)Cs(10) / ZrO2(X:Y=1:10) Pd(1)Cs(10) / ZrO2(X:Y=1:10) Cu(1)Cs(10) / ZrO2(X:Y=1:10) Cu(10)Cs(10) / ZrO2(X:Y=1:1) Zn(10)Cs(10) / ZrO2(X:Y=1:1)

[0051] <Other ingredients> The dual-function catalyst may contain indium, copper, platinum, palladium, zinc, alkali metals, and a support, as long as it does not interfere with the effect of the dual-function catalyst.

[0052] <Characteristics of a dual-function catalyst> The dual-function catalyst preferably has a carbon dioxide storage capacity of 200 μmol / g or more per gram of catalyst, and more preferably 300 μmol / g or more. By setting the carbon dioxide storage capacity within the above range, the storage function is further enhanced. There is no particular upper limit to the carbon dioxide storage capacity, but for example, it can be around 600 μmol / g.

[0053] The dual-function catalyst preferably produces 90 μmol / g or more of carbon monoxide per gram of catalyst, and more preferably 170 μmol / g or more. By setting the amount of carbon monoxide produced within the above range, the reduction function is further enhanced. The upper limit of the amount of carbon monoxide produced is not particularly limited, but for example, it can be around 500 μmol / g.

[0054] The dual-function catalyst preferably has a carbon monoxide yield of 8% or more, and more preferably 10% or more. By setting the carbon monoxide yield within the above range, the reduction function is further enhanced.

[0055] In a dual-function catalyst, it is preferable that the methane yield is 1% or less. By setting the yield of methane, a by-product, within the above range, the relative yield of carbon monoxide is increased, thereby further enhancing the reduction function.

[0056] As described above, the binary-function catalyst of this embodiment includes a composite of at least one element selected from the group consisting of indium, copper, platinum, palladium, and zinc, an alkali metal, and a support. As a result, the elements such as indium and the alkali metal act as active sites, and in the reverse water-gas shift reaction, they can exhibit carbon dioxide storage function and reduction function of stored carbon dioxide to carbon monoxide in the gas to be treated. Moreover, even when the gas to be treated contains carbon monoxide in addition to carbon dioxide, this binary-function catalyst exhibits excellent carbon dioxide storage function and reduction function of stored carbon dioxide to carbon monoxide. Consequently, more carbon monoxide can be produced from carbon dioxide. In addition, for example, if the carbon monoxide produced in the reverse water-gas shift reaction is reduced to solid carbon by the Boudouar reaction, a large amount of solid carbon can be produced. Furthermore, since the reverse water-gas shift reaction using this dual-function catalyst has a lower reaction temperature than the Boudouar reaction, the reverse water-gas shift reaction is not subject to equilibrium constraints, and energy consumption can be reduced.

[0057] <Application of dual-function catalysts> The dual-function catalyst of this embodiment can be applied to various uses. For example, as described above, the dual-function catalyst of this embodiment can produce a large amount of carbon monoxide from carbon dioxide in a reverse water-gas shift reaction. Therefore, for example, by constructing a reaction system that combines a reverse water-gas shift reaction with a Boudouar reaction that reduces the carbon monoxide produced in the reverse water-gas shift reaction to solid carbon, it becomes possible to produce a large amount of solid carbon with low energy. In addition, it can be applied to carbon recycling equipment that includes carbon resource conversion reactions that convert the produced carbon monoxide into various chemicals, fuels, etc. Such application examples will be described below.

[0058] [Carbon Recycling Facility] The following describes a carbon recycling facility, which is another aspect of the present invention and also an application example of the dual-function catalyst of this embodiment, with reference to the drawings. In the following embodiments, a carbon recycling facility that converts the gas to be treated into a resource (solid carbon) by an oxidation-reduction reaction will be described as an example of a carbon resource conversion reaction. However, the present invention is not intended to be limited to the embodiments and configurations described in the drawings below. In the following description, the treatment gas line 9 and the off-gas outlet / inlet line 11 are gas pipelines composed of necessary piping and ducts.

[0059] Figure 1 is a block diagram showing the schematic system configuration of the carbon recycling facility 1 according to this embodiment. The carbon recycling facility 1 shown in Figure 1 comprises a reverse water-gas shift reactor 5 that reduces carbon dioxide in the gas to be treated to carbon monoxide by a reverse water-gas shift reaction using a dual-function catalyst, and a redox reactor 7 that oxidizes and reduces (redox) carbon monoxide. Furthermore, the carbon recycling facility 1 includes a carbon dioxide recovery device 3 that receives the gas to be treated, such as combustion exhaust gas discharged from an incinerator of a waste incineration facility with an attached power generation facility, and recovers the carbon dioxide contained in the gas to be treated. The reverse water-gas shift reactor 5 and the redox reactor 7 are arranged on a treatment gas line 9 through which the gas to be treated flows from the carbon dioxide recovery device 3. The reverse water-gas shift reactor 5 is configured to be supplied with hydrogen gas generated by an electrolytic device or the like.

[0060] <Carbon dioxide capture device> Examples of carbon dioxide recovery devices 3 include devices utilizing chemical absorption, membrane separation, physical absorption, and solid absorption methods. A carbon dioxide recovery device 3 using the chemical absorption method, for example, utilizes an amine absorbent and is configured to chemically bond (react) carbon dioxide in the gas to be treated with an amine to separate and recover only the carbon dioxide. A carbon dioxide recovery device 3 using the membrane separation method uses a solid thin film with separation capabilities and is configured to separate and recover carbon dioxide from the gas to be treated by utilizing its permeation selectivity. A carbon dioxide recovery device 3 using the physical absorption method is configured to separate and recover carbon dioxide in the gas to be treated by dissolving it in a liquid. A carbon dioxide recovery device 3 using the solid absorption method is configured to separate and recover carbon dioxide in the gas to be treated by adsorbing it onto the adsorbent, using zeolite or activated carbon as a physical adsorbent, or using an inorganic porous material supporting alkali metals or amines as a chemical adsorbent.

[0061] <Reverse water-gas shift reactor> The reverse water-gas shift reactor 5 receives carbon dioxide from the gas to be treated and hydrogen, and generates carbon monoxide and water from carbon dioxide and hydrogen through the reverse water-gas shift reaction shown in the following equation (1). CO2 + H2 → CO + H2O ... (1)

[0062] The reverse water-gas shift reactor 5 is mainly composed of a reactor filled with the binary-function catalyst of this embodiment described above as a catalyst to promote the reaction shown in formula (1) above, and performs carbon dioxide absorption and reduction to carbon monoxide (oxidation of hydrogen) inside the reactor. In the reverse water-gas shift reactor 5, carbon dioxide and hydrogen are passed inside the reactor, generating carbon monoxide and water (water vapor) inside the reactor, and carbon monoxide and water (water vapor) are discharged from the reactor. The gas temperature inside the reverse water-gas shift reactor 5 is set to, for example, 300 to 1000°C, preferably 300 to 500°C.

[0063] The reverse water-gas shift reactor 5 can be configured, for example, as shown in Figure 2(b) below, by housing a dual-function catalyst in a flow-through reactor C, connecting a three-way valve to the inlet side of reactor C, and connecting the remaining two sides to the flow paths for the gas to be treated (including off-gas) from the carbon dioxide recovery device 3 and hydrogen gas, so that the gas flows out from the outlet of reactor C and the treated gas containing carbon monoxide is sent to the redox reactor 7 as the gas to be treated (reaction device (b)). Furthermore, the reactor can be configured so that the inflow of the mixed gas and the inflow of hydrogen gas can be switched by switching the valve on the inlet side of reactor C.

[0064] Furthermore, as shown in Figure 2(a) below, the reverse water-gas shift reactor 5 can also be configured such that, for example, two parallel-installed flow-through reactors A and B each contain a dual-function catalyst, the inlet sides of reactors A and B are connected to two sides of a four-way valve (inlet valve), the remaining two sides are connected to the flow paths of the gas to be treated (including off-gas) and hydrogen gas from the carbon dioxide recovery device 3, the outlet sides of reactors A and B are connected to two sides of a four-way valve (outlet valve), and the remaining two sides allow gas to flow out from the outlet of reactor A and the outlet of reactor B, sending the treated gas containing carbon monoxide to the oxidation-reduction reactor 7 as the gas to be treated (reaction device (a)). In addition, by switching the valves on the inlet sides of reactors A and B, it is also possible to configure the reactor so that when the gas to be treated flows into reactor A, hydrogen gas flows into reactor B at the same time, and when hydrogen gas flows into reactor A, the gas to be treated flows into reactor B at the same time. By switching the gases flowing into reactors A and B in this way, the storage function and the reduction function can be further enhanced.

[0065] <Redox reaction apparatus> The redox reactor 7 redoxes the carbon monoxide produced by the reverse water-gas shift reactor 5. For example, the solid carbonization reaction (Boudouer reaction) shown in equation (2) below converts the carbon monoxide produced by the reverse water-gas shift reactor 5 into carbon, and incidentally produces carbon dioxide (as a byproduct). 2CO → C + CO2···(2)

[0066] The redox reactor 7 is mainly composed of a reactor filled with a catalyst (for example, an iron-based metal catalyst) that promotes the reaction of formula (2) above, and performs both reduction and oxidation of carbon monoxide inside the reactor. In the redox reactor 7, carbon monoxide is passed through the reactor, causing oxidation and reduction inside the reactor, and carbon is deposited on the catalyst surface. The gas temperature inside the redox reactor 7 is set higher than the gas temperature inside the reverse water-gas shift reactor 5, for example, 300 to 1000°C, preferably 450 to 850°C.

[0067] In the carbon recycling facility 1, the off-gas containing unreacted carbon monoxide and the by-product carbon dioxide is mixed with the gas to be treated flowing through the processing gas line 9 between the hydrogen gas supply section in the processing gas line 9 and the reverse water-gas shift reactor 5 (in the reverse water-gas shift reactor 5 in Figure 1). In this way, the off-gas containing unreacted carbon monoxide and the by-product carbon dioxide can be returned to the reverse water-gas shift reactor 5 and recycled as a raw material for solid carbon. The reverse water-gas shift reactor 5 can carry out the reverse water-gas shift reaction using the binary-function catalyst described above.

[0068] The off-gas from the redox reactor 7 contains unreacted carbon monoxide and by-product carbon dioxide. Therefore, when this off-gas is returned to the reverse water-gas shift reactor 5, a mixed gas containing carbon dioxide and carbon monoxide flows into the reverse water-gas shift reactor 5. However, even in such a case, by performing the reverse water-gas shift reaction using the dual-function catalyst of this embodiment described above in the reverse water-gas shift reactor 5, the amount of carbon monoxide produced can be increased. As a result, depending on the type of redox reaction occurring in the redox reactor 7, a large amount of solid carbon can be obtained, improving the yield of the redox reaction. Furthermore, if the redox reaction is a Booduar reaction, the reverse water-gas shift reaction can be performed at a lower reaction temperature than the Booduar reaction, so the reverse water-gas shift reaction is not subject to equilibrium constraints, and energy consumption can be reduced. In addition, the amount of carbon dioxide that is wasted without being redoxed can be reduced.

[0069] In addition to the above, the carbon recycling facility 1 may also be equipped with a preheater for preheating the gas to be treated supplied to the reverse water-gas shift reactor 5, a heater, an electrolytic device for generating hydrogen gas by electrolyzing water, a cooler for cooling the off-gas, a water remover for removing water if the off-gas contains water, and a hydrogen separator for separating hydrogen if the off-gas contains hydrogen. Furthermore, each reactor may be of the heat exchange type.

[0070] In the carbon recycling facility 1 configured as described above, the reverse water-gas shift reaction step and the carbon resource conversion reaction step (for example, the oxidation-reduction reaction step) are carried out. Thus, the carbon recycling facility 1 can be used in a carbon recycling method that includes these steps. [Examples]

[0071] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0072] [Gas used] The following mixed gas (gas to be treated) and hydrogen (H2) gas were used. In the following, gaseous carbon monoxide, i.e., carbon monoxide gas, may be referred to as "carbon monoxide," gaseous carbon dioxide, i.e., carbon dioxide gas, as "carbon dioxide," gaseous hydrogen, i.e., hydrogen gas, as "hydrogen," and gaseous helium, i.e., helium gas, as "helium." • Mixed gas: A mixed gas containing 10% by volume of carbon monoxide (CO), 10% by volume of carbon dioxide (CO2), and 80% by volume of helium (He) (10%CO / 10%CO2 / 80%He)

[0073] [Experimental apparatus (reaction apparatus)] • Reaction apparatus (a) In the experimental example 2 below, as shown in Figure 2(a), two parallel-installed flow-through reactors (capacity 5.8 mL), A and B, each housed a dual-function catalyst. The inlets of reactors A and B were connected to two sides of a four-way valve (inlet valve). The remaining two sides were connected to the flow paths for the mixed gas and hydrogen gas. The outlets of the reactors were connected to two sides of the four-way valve (outlet valve), and the reaction apparatus (a) was configured to collect the gas flowing out of the outlet of reactor A and the gas flowing out of the outlet of reactor B from the remaining two sides. Furthermore, the reaction apparatus (a) is configured so that, by switching the valves on the inlet sides of reactors A and B, when the mixed gas is introduced into reactor A, hydrogen gas is introduced into reactor B simultaneously, and vice versa. • Reactor (b) In experimental examples 1 and 3 below, as shown in Figure 2(b), a dual-function catalyst was housed in a flow-through reactor (capacity 5.8 mL) C. A three-way valve was connected to the inlet side of reactor C, and the remaining two sides were connected to flow paths for the mixed gas and hydrogen gas, respectively. Reactor (b) was configured to collect the gas flowing out from the outlet side of reactor C. Furthermore, reactor (b) was configured so that the inflow of the mixed gas and the inflow of hydrogen gas could be switched by switching the valve on the inlet side of reactor C.

[0074] [Experimental Example 1] The catalysts of Examples 1 to 26 and Comparative Examples 1 to 12 shown in Table 1 were used. Each catalyst was placed in reactor C of reaction apparatus (b), and the temperature inside reactor C was set to the temperatures shown in Table 1. A mixed gas was introduced into reaction vessel C at a flow rate of 20 mL / min for 5 minutes, then the three-way valve was switched, and hydrogen gas was introduced at a flow rate of 20 mL / min for 15 minutes (total of 20 minutes). At the point when the mixed gas had been introduced for 15 minutes (20 minutes had elapsed from the start), the concentrations of carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4) in the processed gas, which had been treated in reactor C and was flowing out from the outlet side, were measured using an infrared spectrometer (product name: Fourier transform infrared spectrophotometer FT / IR-4600, manufactured by JASCO Corporation). Using the measurement results, for Examples 1-17, 21-26, and Comparative Examples 1-6 and 12, the amount of carbon dioxide (CO2) absorbed per gram of catalyst, the amount of carbon monoxide (CO) produced per gram of catalyst, the yield of carbon monoxide (CO) relative to the carbon dioxide (CO2) adsorbed on the catalyst during the flow of the mixed gas, and the yield of methane (CH4) were calculated. For Examples 18-20 and Comparative Examples 7-11, the amount of carbon dioxide (CO2) absorbed per gram of catalyst, the amount of carbon monoxide (CO) produced per gram of catalyst, and the yield of carbon monoxide (CO) relative to the carbon dioxide (CO2) adsorbed on the catalyst during the flow of the mixed gas were calculated. The results are shown in Table 1.

[0075] [Table 1]

[0076] [Experimental Example 2] The catalyst shown in Example 5 of Table 1 was used as the dual-function catalyst. A reaction apparatus (a) having reactors A and B was used, and the temperatures in reactors A and B were set to 300°C, 350°C, 400°C, 450°C, and 500°C. Mixed gas and hydrogen gas were alternately introduced into reaction vessels A and B at a flow rate of 20 mL / min. Specifically, when the mixed gas was introduced into reactor A, hydrogen gas was simultaneously introduced into reactor B, and the valves were switched. When hydrogen gas was introduced into reactor A, the mixed gas was simultaneously introduced into reactor B, and this switching was repeated at 1-minute intervals. Using the infrared spectrometer described above, the concentrations of carbon dioxide (CO2) and carbon monoxide (CO) in the treatment gases discharged from reactors A and B were continuously measured over time. Using the measurement results, the ratio (percentage) of the concentration of generated carbon monoxide (CO) to the concentration of carbon dioxide (CO2) in the treatment gas was calculated as the conversion rate (%) of carbon dioxide (CO2) to carbon monoxide (CO). The results are shown in Figure 3 (solid line graph). Furthermore, using a reaction apparatus (b) equipped with reactor C, carbon monoxide (10%), carbon dioxide (10%), and hydrogen gas (80%) were alternately introduced into the inlet of reactor C at a flow rate of 20 mL / min at 20-minute intervals, as described above. The concentration of carbon monoxide (CO) in the processed gas flowing out of reactor C was continuously measured over time, and the ratio (percentage) of the concentration of generated carbon monoxide (CO) to the concentration of carbon dioxide (CO2) flowing through the catalyst was calculated as the conversion rate (%) of carbon dioxide (CO2) to carbon monoxide (CO). The results are shown in Figure 3 (solid line graph). In Figure 3, the chemical equilibrium (Equilibrium) in the reverse water-gas shift reaction (hydrogen reduction) under the conditions of carbon monoxide (10%), carbon dioxide (10%), and hydrogen gas (80%) is calculated from the equilibrium constant and shown as the equilibrium conversion rate by a dashed line.

[0077] [Experimental Example 3] As a reverse water-gas shift reactor, reactor (b) having reactor C, similar to that in Experimental Example 1, was used. The catalyst from Example 4 was placed in reactor C, and the mixed gas was treated under the same conditions as in Experimental Example 1. The carbon monoxide produced in reactor C was introduced into the redox reactor (in this case, a solid carbonization reactor) as described above to carry out a Boudouard reaction and produce solid carbon. At this time, the volume ratio of carbon dioxide to carbon monoxide (CO2 / CO) in the mixed gas introduced into reactor C was varied to 0, 0.25, 0.5, 0.75, and 1, and the amount of solid carbon produced for each mixed gas was measured. The results are shown in Figure 4. In the graph in Figure 4, the vertical axis shows the amount of solid carbon produced at each volume ratio (CO2 / CO) as a percentage of the amount of solid carbon produced when the volume ratio (CO2 / CO) is 0 (i.e., when no carbon dioxide (CO2) is introduced) (100%).

[0078] As shown in Table 1, when comparing catalysts with the same mass ratio of content (X:Y), when using the catalysts of Examples 1 to 4, the process gas discharged from the outlet of reactor C contained generated carbon monoxide (CO) and water (H2O), unreacted hydrogen (H2), helium, and methane (CH4). However, the yield of methane (CH4) was significantly lower than the yield of carbon monoxide (CO). In contrast, the catalysts of Comparative Examples 1 to 3 showed a significantly higher yield of methane (CH4) than the yield of carbon monoxide (CO).

[0079] The catalysts of Examples 1 to 26, which are composites of indium, copper, platinum, palladium, zinc, and alkali metals supported on a carrier, showed significantly higher carbon dioxide storage capacity and reduction of stored carbon dioxide to carbon monoxide compared to Comparative Examples 1 to 3, which are composites of elements other than those listed above supported on a carrier together with alkali metals; Comparative Examples 4, 7 to 10, which contain the same amount of indium (X) but do not contain alkali metals; and Comparative Examples 5, 6, 11, and 12, which contain only alkali metals. This demonstrated that they are dual-function catalysts with superior carbon dioxide storage and reduction capabilities. Even when experimental conditions (reactor temperature) were changed, the catalysts of Examples 22 to 25 were shown to be dual-function catalysts with superior storage and reduction capabilities compared to the catalyst of Comparative Example 12. A comparison of Examples 5 and 12-14 showed that when zirconium oxide (ZrO2) is used as a support, it tends to exhibit superior storage and reduction functions compared to when aluminum oxide (Al2O3), titanium oxide (TiO2), or magnesium oxide (MgO).

[0080] As shown in Figure 3, when Example 5 from Examples 1 to 26 was used as a representative example and compared with the equilibrium conversion rate in the reverse water-gas shift reaction (hydrogen reduction), Example 5 showed superior adsorption and reduction functions when using a reactor (a) with reactors A and B, resulting in a higher carbon monoxide production rate than the chemical equilibrium rate. Furthermore, when using a reactor (b) with only one reactor C, the carbon monoxide production rate was lower than the equilibrium conversion rate. Similar results were obtained when using the catalysts of other Examples 1 to 4 and 6 to 26, although they are not shown in the figures. As a result, the dual-function catalyst of the present invention is shown to be particularly superior in adsorption and reduction functions when using reactors A and B.

[0081] The reason why using two reactors, A and B, increases carbon dioxide (CO2) storage, carbon monoxide (CO) production, and carbon monoxide (CO) yield is presumed to be as follows: Since there is a limit to the amount of carbon dioxide (CO2) that a dual-function catalyst can absorb, when processing carbon dioxide (CO2) over time, there is a limit to the time during which high carbon dioxide (CO2) storage capacity can be obtained. After this period, the carbon dioxide (CO2) storage capacity of the dual-function catalyst tends to decrease. However, by using two reactors and periodically switching the gas to be treated, which contains carbon dioxide (CO2), carbon dioxide (CO2) can be released from the dual-function catalyst, and it is presumed that high carbon dioxide (CO2) storage capacity can be continuously exhibited. Furthermore, as shown in Experimental Example 1, if the amount of carbon dioxide (CO2) absorbed by the dual-function catalyst is large when measured in a single reactor C, the instantaneous peak (maximum peak) of that absorbed amount will also be high. Therefore, it is presumed that using two reactors instead of a single reactor can result in a higher carbon dioxide (CO2) storage capacity.

[0082] As shown in Figure 4, it has been demonstrated that applying the dual-function catalyst of the present invention to a carbon dioxide solid carbonization facility can generate more solid carbon.

[0083] The dual-function catalyst and carbon recycling equipment of the present invention have been described above based on embodiments. However, the present invention is not limited to the configurations described in the above embodiments, and the configuration can be modified as appropriate without departing from the spirit of the invention, such as by appropriately combining the configurations described in the embodiments. [Industrial applicability]

[0084] The dual-function catalyst and carbon recycling equipment of the present invention can be used, for example, in applications such as generating carbon dioxide contained in exhaust gas generated by the combustion of fossil fuels in thermal power plants, steel mills, petroleum refineries, etc., in hydrogen production facilities, in carbon dioxide contained in exhaust gas generated by the combustion of off-gas, in general waste incineration facilities, in carbon dioxide contained in exhaust gas generated by the combustion of waste, and in biomass power generation facilities, in carbon monoxide from carbon dioxide contained in exhaust gas generated by the combustion of biomass fuel, and generating solid carbon, methane, hydrocarbons, and other chemicals and fuels through carbon resource conversion reactions (e.g., oxidation-reduction reactions) of said carbon monoxide. [Explanation of Symbols]

[0085] 1. Carbon Recycling Facility 3. Carbon dioxide capture device 5. Reverse water-gas shift reactor 7. Redox Reaction Apparatus (Carbon Resource Recovery Apparatus)

Claims

1. A dual-function catalyst having a storage function that absorbs carbon dioxide contained in the gas to be treated, and a reduction function that reduces the absorbed carbon dioxide to carbon monoxide, A dual-function catalyst comprising a composite of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc, an alkali metal, and a support.

2. The binary functional catalyst according to claim 1, wherein the alkali metal is at least one selected from the group consisting of sodium, potassium, rubidium, and cesium.

3. The binary functional catalyst according to claim 1, wherein the content of at least one selected from the group consisting of indium, copper, platinum, palladium, and zinc is 1 to 70% by mass.

4. The dual-function catalyst according to claim 1, wherein the alkali metal content is 1 to 70% by mass.

5. The dual-function catalyst according to claim 1, wherein the carrier is at least one selected from the group consisting of zirconium oxide, aluminum oxide, titanium oxide, and magnesium oxide.

6. The dual-function catalyst according to claim 1, wherein the carbon dioxide storage capacity is 200 μmol / g or more.

7. The dual-function catalyst according to claim 1, wherein the amount of carbon monoxide produced is 90 μmol / g or more.

8. The dual-function catalyst according to claim 1, wherein the methane yield is 1% or less.

9. The composite comprises the indium and / or the copper, as described in claim 1, a binary functional catalyst.

10. A reverse water-gas shift reactor that reduces carbon dioxide contained in the gas to be treated to carbon monoxide by a reverse water-gas shift reaction, A carbon resource conversion apparatus that converts carbon monoxide into a resource through a carbon resource conversion reaction, Equipped with, The reverse water-gas shift reactor contains the binary-function catalyst described in any one of claims 1 to 9. A carbon recycling facility in which off-gas from the carbon resource recovery device is returned to the reverse water-gas shift reactor.

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