Production method and production unit for producing product from nitrogen oxide

Abstract

To provide a production method and a production unit that control a target product by changing reaction temperature.SOLUTION: A production method comprises: a first step of supplying source gas containing NOx and oxygen to a catalyst material in a reaction tube to have the catalyst material occlude NOx in the source gas; and a second step of supplying reducing gas not containing NOx to the catalyst material after stopping the supply of the source gas to generate target products from the NOx occluded in the catalyst material. The catalyst material contains noble metal, at least one of alkali metal and alkaline earth metal, and TiO2, and when ammonia is the target product, the temperature in the reaction tube is 150°C or higher and 240°C or lower in both the first step and the second step, and when nitrogen is the target product, the temperature in the reaction tube is 260°C or higher and 350°C or lower in both the first step and the second step.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a technique for producing a product from nitrogen oxides (NOx).

Background Art

[0002] For example, exhaust gas containing combustion-derived nitrogen oxides (so-called thermal NOx) is discharged from high-temperature combustion equipment. Various techniques have been proposed for producing a desired product from such exhaust gas containing nitrogen oxides (NOx). For example, Patent Document 1 discloses a technique for producing ammonia as a target product from exhaust gas. Specifically, Patent Document 1 discloses a technique for producing ammonia by reducing NOx in exhaust gas using a catalyst material containing an oxide carrier, and then recovering the produced ammonia. As the oxide carrier, for example, Al 2 O 3 、CeO 2 、TiO 2 and ZrO 2 are exemplified.

[0003] Also, Non-Patent Documents 1 and 2 disclose a technique for deliberately generating NOx by plasma oxidation of air and generating ammonia at a low temperature of 200°C or lower using a catalyst material using an alumina carrier. For example, it is also assumed to produce a product such as ammonia from exhaust gas using the techniques of Non-Patent Documents 1 and 2. Here, it is known that the catalyst material may be deactivated by a sulfur component often contained in exhaust gas. However, in the techniques of Non-Patent Documents 1 and 2, the NOx generated by plasma oxidation substantially does not contain sulfur, so the sulfur resistance in the reaction is not considered.

[0004] On the other hand, among the oxide carriers disclosed in Patent Document 1, a catalyst material using titania (TiO 2 ) is known to have high sulfur resistance in NOx storage-detoxification.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] International Publication No. 2023 / 080022 [Non-Patent Document]

[0006] [Non-Patent Document 1] L. Hollevoet et al., Angew. Chem. Int. Ed., 59 (2020) 23825. doi.org / 10.1002 / anie.202011676 [Non-Patent Document 2] L. Hollevoet et al., ChemSusChem, 15 (2022) e202102526. doi.org / 10.1002 / cssc.202102526 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] However, in the technology of Patent Document 1, when using titania as the oxide carrier, the relationship between the types of products that can be produced with high efficiency and the reaction temperature has not been studied. Considering the above circumstances, an object of the present invention is to control the target product by changing the reaction temperature when using titania as the oxide carrier in the catalyst material. [Means for Solving the Problems]

[0008] [1] A first step of occluding NOx in the raw material gas into the catalyst material in the reaction tube by supplying a raw material gas containing NOx and oxygen to the catalyst material in the reaction tube, and after stopping the supply of the raw material gas, supplying a reducing gas not containing NOx to the catalyst material to generate a target product from the NOx occluded in the catalyst material. A second step, wherein the catalyst material comprises a noble metal, at least one of an alkali metal and an alkaline earth metal, and TiO 2When ammonia is used as the target product and it contains [components], the temperature inside the reaction tube is 150°C or higher and 240°C or lower in the first step and the second step. When nitrogen is used as the target product, the temperature inside the reaction tube is 260°C or higher and 350°C or lower in the first step and the second step. A manufacturing method.

[0009] [2] The reducing gas contains H 2 The manufacturing method according to [1] containing [this].

[0010] [3] The noble metal is one or more of Pt, Pd, Rh, and Ir, and the content of the noble metal is 0.1% by mass or more and 10% by mass or less based on 100% by mass of the entire catalyst material. The manufacturing method according to [1] or [2].

[0011] [4] The alkali metal is one or more selected from Li, K, Na, and Cs, the alkaline earth metal is one or more selected from Ca, Mg, Sr, and Ba, and the content of the alkali metal and the alkaline earth metal is 1% by mass or more and 30% by mass or less based on 100% by mass of the entire catalyst material. The manufacturing method according to [1] to [3].

[0012] [5] The noble metal is contained inside the TiO 2 , and the alkali metal and the alkaline earth metal are supported on the TiO 2 containing the noble metal inside. The manufacturing method according to [1] to [4].

[0013] [6] The reaction tube includes N (N is a natural number of 2 or more) reaction tubes. For each of the N reaction tubes, the first step and the second step are alternately repeated. While the first step is being performed on K (K is a natural number less than N) of the N reaction tubes, the second step is being performed on (N - K) reaction tubes, and while the second step is being performed on the K reaction tubes, the first step is being performed on the (N - K) reaction tubes. The manufacturing method according to [1] to [5].

[0014] [7] A reaction tube for accommodating a catalyst material, a first supply path for supplying a raw material gas containing NOx and oxygen to the reaction tube, a second supply path for supplying a reducing gas not containing NOx to the reaction tube, and a recovery path for recovering the generated target product from the reaction tube, and a control device for controlling the manufacturing apparatus, wherein the control device causes the manufacturing apparatus to perform a first step of occluding NOx in the raw material gas in the catalyst material by supplying the raw material gas to the catalyst material, and a second step of generating the target product from the NOx occluded in the catalyst material by supplying the reducing gas to the catalyst material after stopping the supply of the raw material gas, and the catalyst material includes a noble metal, at least one of an alkali metal and an alkaline earth metal, and TiO 2 When ammonia is the target product, the temperature in the reaction tube is 150°C or higher and 240°C or lower in the first step and the second step, and when nitrogen is the target product, the temperature in the reaction tube is 260°C or higher and 350°C or lower in the first step and the second step. Manufacturing unit.

[0015] [8] There are N (N is a natural number of 2 or more) each of the reaction tube, the first supply path, the second supply path, and the recovery path, and the control device alternately repeats the first step and the second step for each of the N reaction tubes and causes the manufacturing apparatus to execute them. While the first step is being executed for K (K is a natural number less than N) of the N reaction tubes, the second step is being executed for (N - K) reaction tubes, and while the second step is being executed for the K reaction tubes, the first step is being executed for the (N - K) reaction tubes. The manufacturing unit according to [7].

Advantages of the Invention

[0016] According to the manufacturing method and manufacturing unit of the present invention, when titania is used as the oxide carrier in the catalyst material, the target product can be controlled by changing the reaction temperature. For example, ammonia can be produced with high efficiency in a low-temperature environment, and detoxification to nitrogen proceeds with high efficiency in a high-temperature environment. The slightly generated ammonia can also be used for the detoxification of NOx.

Brief Description of Drawings

[0017]

Figure 1

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Modes for Carrying Out the Invention

[0018] [Manufacturing Method] When the manufacturing method according to the present invention uses a catalyst material with titania as the oxide carrier, the target product is controlled by changing the reaction temperature. Specifically, the manufacturing method of the present invention includes a first step of occluding NOx in the raw material gas into the catalyst material by supplying a raw material gas containing nitrogen oxides (NOx) and oxygen to the catalyst material in the reaction tube, and after stopping the supply of the raw material gas, supplying a reducing gas not containing NOx to the catalyst material to generate a product from the NOx occluded in the catalyst material.

[0019] The inventors of the present invention have found as a new finding that in a catalyst material using titania as an oxide carrier, ammonia can be produced with high efficiency in a low-temperature environment (150°C or higher and 240°C or lower), and nitrogen can be produced with high efficiency in a high-temperature environment (260°C or higher and 350°C or lower). Considering the above findings, in the present invention, an optimal reaction temperature is set according to the target product (hereinafter referred to as the "target product"). The target product is ammonia or nitrogen. When the target product is ammonia, the produced ammonia can be utilized as a resource, and when the target product is nitrogen, the detoxification of nitrogen oxides proceeds efficiently.

[0020] As described above, the raw material gas used in the first step is a gas containing NOx and oxygen (O 2 ). For example, exhaust gas is used as the raw material gas. NOx is composed of NO and NO 2 oxidized by O 2 in which NO coexists. The exhaust gas is assumed to be gas discharged from various facilities (for example, combustion facilities such as waste incineration facilities and thermal power plants, or chemical factories, etc.). However, the raw material gas is not limited to exhaust gas. For example, as the raw material gas, a gas containing nitric oxide (NO) obtained by plasma oxidizing air to obtain N 2 and oxygen (O 2 ) may be used.

[0021] The concentration of NOx in the raw material gas is, for example, 50 ppm or more and 2% or less. The concentration of O 2 in the raw material gas is, for example, 1% or more and 20% or less. In addition to NOx and O 2 , the raw material gas may contain CO 2 , water vapor (H 2 O), N 2 , etc.

[0022] The reducing gas used in the second step is a gas that reduces the NOx occluded (adsorbed) in the catalyst material. Specifically, the reducing gas contains a reducing agent and does not contain NOx. Note that the fact that the reducing gas does not contain NOx includes cases where NOx is contained at an extremely low concentration (for example, 10 ppm or less) within a range that does not affect the reduction of the NOx occluded (adsorbed) in the catalyst material and also does not have an impact on the environment. However, a reducing gas that does not contain NOx at all (NOx concentration is 0%) is preferably used. From the perspective of improving the production efficiency of ammonia or nitrogen, as the reducing agent, H 2 , CO, C 3 H 6 , C 3 H 8 and CH 4 are preferably any one or more of them, and H 2 is more preferable.

[0023] The concentration of the reducing agent in the reducing gas is, for example, 100 ppm or more and 50% or less, preferably 500 ppm or more and 20% or less, and more preferably 1000 ppm or more and 5% or less. Particularly when the reducing agent is H 2 , the concentration of H 2 in the reducing gas is, for example, 0.2% or more and 100% or less, preferably 0.5% or more and 30% or less, and more preferably 1% or more and 10% or less. Note that the reducing gas may contain, in addition to the reducing agent, water vapor, carbon dioxide, nitrogen, etc.

[0024] In the first step, NOx is adsorbed on the catalyst material for concentration and recovery. For example, the NOx in the raw material gas (for example, NO) is oxidized to nitrogen dioxide (NO 2 ), reacts with the catalyst material to form nitrates or nitrites. Then, in the second step, the reducing agent reacts with the nitrates or nitrites to produce ammonia or nitrogen, which is the target product. When the target product is ammonia, the ammonia produced in the second step is recovered as a resource, for example. On the other hand, when the target product is nitrogen, the nitrogen produced in the second step is released into the atmosphere, for example.

[0025] The first step and the second step can be repeatedly executed alternately (first step → second step → first step → second step → first step → second step → ···). The time during which the first step is performed (the time during which the raw material gas is supplied to the catalyst material) is, from the viewpoint of sufficiently occluding NOx in the catalyst material, for example, 10 minutes or more and 1 hour or less, preferably 10 minutes or more and 40 minutes or less, and more preferably 15 minutes or more and 30 minutes or less. On the other hand, the time during which the second step is performed (the time during which the reducing gas is supplied) is, for example, equal to or longer than the time during which the first step is performed. From the viewpoint of converting most of the NOx occluded in the catalyst material into ammonia or nitrogen, it is, for example, 1 to 3 times the time during which the first step is performed.

[0026] When the target product is ammonia, in the first step and the second step, the temperature of the reaction tube is set to 150°C or higher and 240°C or lower. On the other hand, when the target product is nitrogen (N 2 )), in the first step and the second step, the temperature of the reaction tube is set to 260°C or higher and 350°C or lower. In consideration of the following two newly obtained findings by the present inventors, the temperature of the reaction tube is set as described above according to the target product.

[0027] First, it was newly found that when the temperature in the reaction tube is 150°C or higher and 250°C or lower, ammonia is produced more predominantly than nitrogen, and when the temperature in the reaction tube is 260°C or higher and 350°C or lower, nitrogen is produced more predominantly than ammonia. That is, it was newly found that for a catalyst material using titania as an oxide carrier, a specific target product can be selectively produced with high efficiency. The target product is typically the main product that occupies, for example, more than 50 vol%, preferably 60 vol% or more, and more preferably 65 vol% or more of the total of all products that can be produced in the second step. However, the target product is typically the main product, but is not necessarily limited to the main product.

[0028] Here, in the technology of Patent Document 1, when using a catalyst material with porous alumina as the oxide carrier, it has been confirmed that ammonia is generated with high efficiency in a high-temperature environment (300°C). However, the generation of ammonia with high efficiency in a low-temperature environment has not been studied. Using a catalyst material with titania as the oxide carrier, it has also been newly found that ammonia can be generated with high efficiency in a low-temperature environment (150°C or higher and 240°C or lower).

[0029] Taking the above two findings into consideration, in the present invention, when the target product is ammonia, the temperature of the reaction tube is set to 150°C or higher and 240°C or lower, and when the target product is nitrogen, the temperature of the reaction tube is set to 260°C or higher and 350°C or lower.

[0030] From the perspective of producing ammonia with high efficiency, the lower limit value of the temperature in the reaction tube is preferably 160°C, more preferably 165°C, still more preferably 170°C, particularly preferably 175°C, and the upper limit value of the temperature in the reaction tube is preferably 235°C, more preferably 230°C, still more preferably 225°C, particularly preferably 220°C, and most preferably 210°C. The lower limit value and the upper limit value shown above can be combined in all combinations to form the temperature range of the reaction tube.

[0031] From the perspective of producing nitrogen with high efficiency, the lower limit value of the temperature in the reaction tube is preferably 265°C, more preferably 270°C, still more preferably 280°C, particularly preferably 290°C, and the upper limit value of the temperature in the reaction tube is preferably 345°C, more preferably 340°C, still more preferably 330°C, particularly preferably 320°C, and most preferably 310°C. The lower limit value and the upper limit value shown above can be combined in all combinations to form the temperature range of the reaction tube.

[0032] The temperature inside the reaction tube becomes, for example, 150°C or higher and 240°C or lower (when ammonia is the target product) or 260°C or higher and 350°C or lower (when nitrogen is the target product) by supplying the raw material gas and the reducing gas into the reaction tube. For example, when the temperature of the raw material gas and the reducing gas is 150°C or higher and 240°C or lower or 260°C or higher and 350°C or lower, the temperature of the reaction tube to which the raw material gas is supplied can also be 150°C or higher and 240°C or lower or 260°C or higher and 350°C or lower. Further, the temperature inside the reaction tube may be controlled by adjusting the temperature of the raw material gas or the reducing gas, or the temperature inside the reaction tube may be controlled to be within the above range by heating or cooling the reaction tube.

[0033] The temperature of the reaction tube in the first step and the temperature of the reaction tube in the second step only need to be within the above ranges respectively, and they do not need to be the same. However, it is preferable that the temperature of the reaction tube in the first step and the temperature of the reaction tube in the second step are substantially the same (the temperature difference between the two is, for example, within the range of ±30°C, preferably within the range of ±10°C).

[0034] In the production method according to the present invention, the target product can be controlled according to the temperature inside the reaction tube. The production method of the present invention includes the case of producing only one of ammonia and nitrogen as the target product and the case of producing both ammonia and nitrogen as the target product.

[0035] In addition, when ammonia is the target product, nitrogen and nitrous oxide (N 2 O) are also generated in addition to ammonia. In this case, the concentration of nitrogen is preferably 40 vol% or less of the total of all the products that can be generated, and the concentration of nitrous oxide is preferably 10 vol% or less of the total of all the products that can be generated. Similarly, when nitrogen is the target product, ammonia and nitrous oxide (N 2 O) can also be generated in addition to nitrogen. In this case, the concentration of ammonia is preferably 20 vol% or less of the total of all the products that can be generated, and the concentration of nitrous oxide is preferably 20 vol% or less of the total of all the products that can be generated.

[0036] In addition to the first step and the second step, the manufacturing method according to this embodiment may include other steps. When ammonia is the target product, for example, the manufacturing method may include a step of recovering the ammonia produced in the second step (hereinafter referred to as "the third step").

[0037] In the third step, for example, the ammonia produced in the second step is recovered by a method of extracting only ammonia by liquefying ammonia using a cooler or a method of adsorbing only ammonia using an adsorption device.

[0038] The ammonia recovered in the third step is used for various purposes as a resource. For example, the ammonia recovered for the following Use 1 or Use 2 is used.

[0039] (1) Use 1 All of the NOx in the raw material gas supplied to the reaction tube U in the first step may not be occluded by the catalyst material. Therefore, the ammonia recovered in the third step may be used to purify the NOx that was not occluded by the catalyst material among the NOx in the raw material gas supplied to the reaction tube.

[0040] (2) Use 2 When the raw material gas is the exhaust gas discharged from the facility, a part of the exhaust gas discharged from the facility may be used for the production of ammonia, and the rest of the exhaust gas discharged from the facility may be purified with the ammonia produced in the second step.

[0041] In addition, the gas after recovering ammonia in the third step (hereinafter referred to as "the recovered gas") may contain a reducing agent that was not used for the production of ammonia among the reducing gases. Therefore, the recovered gas may be supplied to the reaction tube as a reducing gas in the second step.

[0042] When nitrogen is the target product, as described above, after the second step, the produced nitrogen is released into the atmosphere, for example.

[0043] <Catalyst Material> Hereinafter, the catalyst material used in the production method of the present invention will be described in detail. The catalyst material is a catalyst that adsorbs and reduces NOx in the raw material gas. Specifically, the catalyst material includes a noble metal, at least one of an alkali metal and an alkaline earth metal, and TiO 2 (titania). Note that the TiO 2 described here may contain partial oxygen deficiency in the range of TiO 2-δ (δ = 0.0 - 0.2).

[0044] TiO 2 functions as a carrier. By using TiO 2 , ammonia can be produced efficiently under low-temperature environments, and nitrogen can be produced efficiently under high-temperature environments. Also, TiO 2 improves the reactivity by improving the dispersibility of the noble metal, the alkali metal, and the alkaline earth metal.

[0045] The noble metal contained in the catalyst material functions as a catalyst for both the oxidation of NO to NO 2 and the reduction of NOx to the target products (ammonia, nitrogen). Specifically, the noble metal is contained in the catalyst material in a state supported on the surface of TiO 2 (oxide carrier), or in a state contained inside TiO 2 . Here, the state of being contained inside TiO 2 refers to a state in which particulate noble metal is encapsulated inside the spherical particles of TiO 2 and complexed. When using a catalyst material in which the noble metal is contained inside TiO 2 , the effects of efficiently producing ammonia under low-temperature environments and efficiently producing nitrogen under high-temperature environments become prominent.

[0046] Titania (TiO 2) is preferably porous. Specifically, for example, it is more preferable to use porous titania (mesoporous titania) whose pore walls are composed of crystalline titania as the titania. The porous titania is prepared by drying and sintering a precursor solution containing monomers or oligomer species of titania or its hydrate and amphiphilic organic molecules by the process described later. During sintering, the amphiphilic organic molecules disappear and a porous structure with regularly arranged pores is formed. The pore diameter of the porous titania is in the range of 2 - 50 nm. However, the titania is not limited to porous titania.

[0047] The titania is contained in the entire catalyst material (100% by mass) in an amount of, for example, 40% by mass or more and 99% by mass or less, preferably 45% by mass or more and 98% by mass or less, and more preferably 65% by mass or more and 95% by mass or less. Typically, it is preferable that the catalyst material is composed of at least one of an alkali metal and an alkaline earth metal, a noble metal, and titania.

[0048] The noble metal (noble metal alone) contained in the oxide carrier is preferably one or more of platinum (Pt), palladium (Pd), rhodium (Pd), and iridium (Ir). When the noble metal is contained in the oxide carrier as a noble metal compound, the noble metal compound is these noble metal alone or an oxide. From the viewpoint of improving the catalytic activity, one or more noble metals of platinum and rhodium are more preferable, and platinum (Pt) is even more preferable. Note that a plurality of types of noble metals may be contained in the oxide carrier respectively.

[0049] The average particle size of the noble metal contained in the catalyst material is, for example, 0.1 nm or more and 100 nm or less, preferably 1 nm or more and 50 nm or less. In particular, for the production of ammonia within the range where the temperature of the catalyst material is 175°C or more and 250°C or less, the average particle size of the noble metal is more preferably 3 nm or more and 30 nm or less, and particularly preferably 5 nm or more and 25 nm or less. The noble metal is nanoparticles, and the nanoparticles are contained in the catalyst material. By setting the average particle size of the noble metal and the noble metal compound within the above range, it is possible to achieve both the oxidation reaction characteristics of the gas to be circulated and the durability of the catalyst. Furthermore, by appropriately selecting the average particle size of the noble metal and the noble metal compound within the above range, it is also possible to obtain a high ammoniation rate and a nitrogenation rate within the target temperature range.

[0050] Note that the average particle size of the noble metal is the most frequent value (mode diameter) specified by measuring the particle sizes of a predetermined number (for example, 100) of particles by observation with a transmission electron microscope.

[0051] The noble metal is included in the catalyst material in a state supported on the surface of titania or in a state contained inside titania. The state of being contained inside titania refers to a state in which particulate noble metal is encapsulated inside spherical particles of titania and complexed. From the viewpoint of improving the production efficiency of the target product, it is preferable that the noble metal is in a state contained inside titania.

[0052] In the following description, titania in a state containing a noble metal inside is denoted as "noble metal-containing titania". In noble metal-containing titania, the noble metal nanoparticles may be exposed in the porous structure or embedded in the skeleton of titania.

[0053] The noble metal may be contained in titania as a simple noble metal, as a noble metal compound containing the noble metal, or both. In the following description, when denoted as "noble metal", both the case of a simple noble metal and the noble metal in the noble metal compound are included.

[0054] The content of the noble metal (noble metal element in the catalyst material) is 0.1% by mass or more and 10% by mass or less, preferably 0.2% by mass or more and 8.0% by mass or less, and more preferably 0.3% by mass or more and 5.0% by mass or less, based on the entire catalyst material. By setting the content of the noble metal within the above range, it is possible to improve the catalytic activity while suppressing the amount of expensive noble metal used.

[0055] The alkali metal and alkaline earth metal are contained in the catalyst material in a state supported on the surface of the titania (support). When the noble metal is contained inside the titania, the alkali metal and alkaline earth metal are supported on the surface of the titania complexed with the noble metal.

[0056] In the present invention, the alkali metal and alkaline earth metal are typically supported on the titania as a compound containing at least one of the alkali metal and alkaline earth metal. Such compounds are, for example, oxides, peroxides, carbonates, hydroxides, etc. of the alkali metal and alkaline earth metal. In the case of containing a plurality of types from the alkali metal and alkaline earth metal in the compound, two or more types may be selected only from the alkali metal, two or more types may be selected only from the alkaline earth metal, or one or more types from the alkali metal and one or more types from the alkaline earth metal may be selected. However, a configuration in which the alkali metal alone and the alkaline earth metal alone are supported on the oxide support is not excluded from the present invention.

[0057] The alkali metal contained in the catalyst material is preferably at least one selected from Li, K, Na, and Cs, and more preferably at least one of K and Na, from the viewpoint of improving the reduction efficiency of NOx (nitrogen oxides). The alkaline earth metal contained in the catalyst material is preferably at least one selected from Ca, Mg, Sr, and Ba, more preferably at least one of Ca and Ba, and even more preferably Ba, from the viewpoint of improving the reduction efficiency of NOx.

[0058] The content (total amount) of alkali metals and alkaline earth metals (alkali metal elements and alkaline earth metal elements in the catalyst material) is 1% by mass or more and 30% by mass or less, preferably 5% by mass or more and 25% by mass or less, and more preferably 8% by mass or more and 20% by mass or less, based on the entire catalyst material. By setting the content of alkali metals and alkaline earth metals within the above range, it is possible to improve the reduction efficiency of NOx while maintaining a uniformly arranged pore structure.

[0059] From the perspective of improving the production efficiency of the target product, it is preferable that the alkali metals and alkaline earth metals are contained in the catalyst material in a state supported on noble metal-containing titania. The alkali metals and alkaline earth metals supported on noble metal-containing titania will be in the form of being coated from above the already formed porous structure and will mainly exist on the surfaces of titania and noble metals.

[0060] Since the catalyst material contains at least one of alkali metals and alkaline earth metals (hereinafter also referred to as "alkali metals, etc."), it is possible to strongly adsorb a large amount of NOx, and it is possible to concentrate and recover NOx as a raw material. When a reducing gas is supplied to the recovered NOx, the target product is produced as the main product and is easily released.

[0061] The average particle size of the catalyst material is, for example, 0.01 μm or more and 500 μm or less, preferably 0.1 μm or more and 100 μm or less, and more preferably 0.5 μm or more and 50 μm or less. The average particle size of the catalyst material is the volume-based cumulative average particle size (median diameter) measured by a particle size distribution measuring device. However, the catalyst material may be used, for example, after being molded into a pellet shape or the like, or after being applied to a molded body.

[0062] The specific surface area of the catalyst material is, for example, 50 m 2 / g or more and 250 m 2 / g or less, preferably 80 m 2 / g or more and 230 m 2 / g or less, and more preferably 100 m 2 / g or more and 200 m2 It is below / g. When the specific surface area of the catalyst material is within the above range, for example, the gas adsorption rate is improved. The specific surface area of the catalyst material is measured by the BET multi-point method.

[0063] The mode value of the pore size distribution of the catalyst material is, for example, 1 nm or more and 200 nm or less in diameter, preferably 1 nm or more and 50 nm or less in diameter, and more preferably 2 nm or more and 20 nm or less in diameter. When the mode value of the pore size distribution of the catalyst material is within the above range, for example, gas can be adsorbed with high efficiency.

[0064] The pore volume of the catalyst material is, for example, 0.05 cm 3 / g or more and 0.5 cm 3 / g or less, preferably 0.1 cm 3 / g or more and 0.4 cm 3 / g or less, more preferably 0.2 cm 3 / g or more and 0.3 cm 3 / g or less. When the pore volume of the catalyst material is within the above range, for example, gas can be adsorbed with high efficiency.

[0065] The mode value of the pore size distribution in the catalyst material is measured by, for example, the BJH method or the NLDFT method by the gas adsorption method. The pore volume of the catalyst material is similarly measured by, for example, the gas adsorption method.

[0066] In the catalyst material, at least one of a diffraction peak and a scattering peak corresponding to an interplanar spacing of 1 nm or more and 200 nm or less obtained by irradiating X-rays is observed. The diffraction peak is measured by the X-ray diffraction method. The scattering peak is measured by the small-angle X-ray scattering method. Specifically, in the measurement by the X-ray diffraction method, one or more diffraction peaks corresponding to an interplanar spacing of 1 nm or more and 200 nm or less are observed, and in the measurement by the small-angle X-ray scattering method, one or more scattering peaks corresponding to an interplanar spacing of 1 nm or more and 200 nm or less are observed.

[0067] As the X-ray generating tube, it is desirable to use Fe because the characteristic X-ray has a long wavelength, the diffraction peak or scattering peak appears on the high-angle side and is easy to detect, and its intensity is sufficient for the detector. However, there is no problem with tubes using other elements (such as Cu, etc.). The presence of these diffraction peaks and scattering peaks indicates a regular arrangement of pores in the porous structure.

[0068] According to the catalyst material in which one or more diffraction peaks or scattering peaks corresponding to a lattice plane spacing of 1 nm or more and 200 nm or less are observed, due to the existence of a regular arrangement of pores with a uniform pore diameter in the porous structure, a high specific surface area and a uniform diffusion behavior of gas inside the pores can be expected.

[0069] <Manufacturing method of catalyst material> For the manufacturing method of the above-mentioned catalyst material, any known method can be used. Hereinafter, an example of the manufacturing method of the catalyst material will be described. In the following description, an example of the manufacturing method of a catalyst material in which an alkaline earth metal or the like is supported on a noble metal-containing titania will be exemplified. Generally, the catalyst material is manufactured by synthesizing a porous titania containing a noble metal (noble metal-containing titania) and supporting an alkaline earth metal or the like on the noble metal-containing titania.

[0070] <1> Preparation of precursor solution The noble metal-containing precursor solution (hereinafter simply referred to as "precursor solution") is a solution containing a titania source, a noble metal source, an amphiphilic organic molecule, an acid, and a solvent.

[0071] Examples of the titania source used in the precursor solution include titanium alkoxides and their oligomers, chlorides, chelate complexes, etc.

[0072] As the titania source, titanium compounds such as tetrabutyl orthotitanate, tetrabutyl orthotitanate tetramer, tetraisopropyl orthotitanate, tetra-n-propyl orthotitanate, tetra-tert-butyl orthotitanate, dichlorotitanium diisopropoxide, titanium(IV) chloride, cyclopentadienyltitanium(IV) trichloride, titanocene dichloride, tetrakis(dimethylamino)titanium(IV), bis(2,4-pentanedionato)titanium(IV) oxide, etc. can be used. These may be used alone or in combination of multiple types. Among these, from the viewpoints of solubility in the solvent during the preparation of the precursor solution and reactivity with respect to hydrolysis, tetrabutyl orthotitanate or tetraisopropyl orthotitanate is particularly preferred.

[0073] Examples of the noble metal source contained in the precursor solution include oxides, hydroxides, chlorides, carbonates, acetates, nitrates, oxalates, phosphates, and chloride complexes of noble metals.

[0074] As the platinum source, for example, inorganic platinum compounds such as chloroplatinic acid (including hydrates), dinitrodiammineplatinum, hexahydroxyplatinic acid, platinum(I) chloride, platinum(II) chloride, tetraammineplatinum dichloride, potassium tetrachloroplatinate, potassium hexachloroplatinate, etc., and organic platinum compounds such as bis(acetylacetonato)platinum, dichloro(cyclohexane)platinum dimer, dichloro(η-ethylene)Pt dimer, dichloro(η-cycloocta-1,5-diene)platinum, tetrakis(triphenylphosphite)platinum, cis-dichlorobis(triphenylphosphine)platinum, bis(benzonitrile)dichloroplatinum, trans-d-cyclohexanediamine dichloroplatinum, trans-l-cyclohexanediamine dichloroplatinum, etc. can be used. These may be used alone or in combination of multiple types. Among these, from the viewpoint of solubility in the solvent during the preparation of the precursor solution, chloroplatinic acid (including hydrates) or bis(acetylacetonato)platinum is particularly preferred.

[0075] Examples of the palladium source include palladium chloride, palladium acetate, tetrakistriphenylphosphine palladium, tris(dibenzylideneacetone) dipalladium, allylpalladium chloride dimer, and the like. Examples of the ligand include bis[2-(diphenylphosphino)phenyl] ether (DPEphos), triphenylphosphine, 1,1'-bis(diphenylphosphino) ferrocene (dppf), 4,5'-bis(diphenylphosphino)-9,9'-dimethylxanthene (xantphos), 1,3-di-tert-butylimidazolium, and the like. These may be used alone or in combination of two or more.

[0076] Examples of the rhodium source include rhodium chloride, dirhodium tetraacetate dihydrate, rhodium acetate, rhodium isobutyrate, rhodium 2-ethylhexanoate, rhodium benzoate, and rhodium octanoate. These may be used alone or in combination of two or more.

[0077] Examples of the iridium source include iridium chloride, iridium sulfate, iridium nitrate, iridium nitrite, ammonium hexachloroiridate, iridium hexachloride n-hydrate, chlorocarbonylbis(triphenylphosphine) iridium, sodium chloride iridium n-hydrate, and the like. These may be used alone or in combination of two or more.

[0078] As amphiphilic organic molecules used in the precursor solution, one or more of polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymers (trade name: Pluronic (registered trademark)), alkylammonium salts, polystyrene-polyethylene oxide block copolymers, poly(methyl methacrylate)-polyethylene oxide block copolymers, etc. can be used. Among them, from the viewpoint of forming a regularly arranged porous structure, at least one of polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer and polystyrene-polyethylene oxide block copolymer is preferable, and further Pluronic P123 and F127 are preferable.

[0079] Note that the pore diameter of the obtained noble metal-containing titania varies greatly depending on the type of amphiphilic organic molecule. For example, when a polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer is used as the amphiphilic organic molecule, the mode value of the pore size distribution is 2 nm or more and 30 nm or less. Furthermore, when a polystyrene-polyethylene oxide block copolymer is used as the amphiphilic organic molecule, the mode value of the pore size distribution is 25 nm or more and 200 nm or less (see: "Bulletin of the Chemical Society of Japan, 2019, 92, 1859-1866.", "Dalton Transactions, 2021, 50, 7191-7197.").

[0080] As the acid used in the precursor solution, inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as carboxylic acids and sulfonic acids can be used.

[0081] As the solvent used in the precursor solution, alcohol, ether, water, ketone, etc. can be utilized. In particular, as the alcohol, various alcohols such as ethanol, methanol, n-butanol, sec-butanol, tert-butanol, n-propanol, and iso-propanol can be used. Among them, from the viewpoint of forming a regular porous structure by optimizing the evaporation rate of the solvent, ethanol is particularly preferred.

[0082] The content of the titania source is 5% by mass or more and 25% by mass or less in the precursor solution, preferably 8% by mass or more and 20% by mass or less, and more preferably 10% by mass or more and 15% by mass or less.

[0083] The content of the noble metal source is 0.01% by mass or more and 0.20% by mass or less in the precursor solution, preferably 0.03% by mass or more and 0.20% by mass or less, and more preferably 0.05% by mass or more and 0.10% by mass or less.

[0084] The content of the amphiphilic organic molecule is 1% by mass or more and 20% by mass or less in the precursor solution, preferably 2% by mass or more and 15% by mass or less, and more preferably 3% by mass or more and 10% by mass or less.

[0085] The content of the acid is 0.1% by mass or more and 3.0% by mass or less in the precursor solution, preferably 0.3% by mass or more and 2.0% by mass or less, and more preferably 0.5% by mass or more and 1.5% by mass or less.

[0086] The content of the solvent is 50% by mass or more and 93% by mass or less in the precursor solution, preferably 60% by mass or more and 90% by mass or less, and more preferably 70% by mass or more and 80% by mass or less.

[0087] As an example of a specific method for preparing a precursor solution, first, a solution prepared by adding a titania source to a solvent is stirred, and an acid is added dropwise over a predetermined time (for example, 1 minute or more). The hydrolysis of the titania source is carried out by stirring this solution for a predetermined time (for example, 1 to 3 hours). Next, an amphiphilic organic molecule is added to and dissolved in this solution, and then a platinum source is further added and stirred to obtain a precursor solution (mesoporous titania precursor solution).

[0088] <2>Synthesis of noble metal-containing titania An example of a method for synthesizing noble metal-containing titania is as follows.

[0089] First, a precursor (powder) of noble metal-containing titania is recovered from the precursor solution. Specifically, the solvent and moisture are removed from the precursor solution by drying. The method for drying the precursor solution is not particularly limited, and examples include one or a combination of two or more known methods such as spray drying, freeze drying, heat drying, hot air drying, vacuum drying, and natural drying. Among them, spray drying is particularly preferable from the viewpoints of productivity and reproducibility. The precursor solution is dried to recover the precursor (powder) of noble metal-containing titania.

[0090] Next, the recovered precursor is calcined to synthesize noble metal-containing titania. Specifically, by calcining the precursor, the amphiphilic organic molecules that served as the template for the pores are removed and the material becomes porous, and at the same time, the thermal decomposition of the noble metal source and the crystallization of the titania skeleton into anatase are carried out. The calcination of the precursor is carried out by holding it at a desired temperature (for example, 300 to 500 °C) for a predetermined time (for example, 1 to 3 hours) under a dry air stream. It is preferable to raise the temperature stepwise (for example, 1 to 3 °C per minute) until the desired temperature is reached under the dry air stream.

[0091] <3>Loading of alkali metals and alkaline earth metals At least one of an alkali metal and an alkaline earth metal (such as an alkali metal) is loaded onto the synthesized noble metal-containing titania.

[0092] To support an alkali metal or the like on a noble metal-containing titania, compounds including acetates, nitrates, carbonates, hydroxides, halides, oxides, hydrides, etc. of an alkali metal or the like (hereinafter referred to as "alkali metal or the like compounds") are used. Among these, from the viewpoints of solubility and thermal decomposition temperature, at least one or more of acetates and nitrates are preferable. Note that the precursor compound changes into an alkali metal or the like compound by being thermally decomposed by heating.

[0093] An example of a method for supporting an alkaline earth metal or the like on a noble metal-containing titania is as follows. For example, an alkaline earth metal or the like is supported on a noble metal-containing titania by an impregnation method.

[0094] First, a noble metal-containing titania is dispersed in distilled water, and an aqueous solution of an alkali metal or the like compound is dropped while stirring to obtain a dispersion. From the viewpoint of improving the NOx occlusion characteristics and reduction efficiency, the weight ratio (weight of alkali metal element and alkaline earth metal element / TiO 2 ) of the mass (total amount) of the alkali metal element and the alkaline earth metal element to the mass of titania (TiO 2 ) is, for example, 1 / 30 to 1 / 3, preferably 1 / 20 to 1 / 5, and an aqueous solution of an alkali metal or the like compound is dropped.

[0095] Next, after stirring the obtained dispersion, it is heated under reduced pressure to remove distilled water and obtain a powder. For example, distilled water is removed from the dispersion by vacuum distillation at 30 to 80°C.

[0096] Then, the obtained powder is fired in a dry air stream to obtain the catalyst material according to the present invention. For example, it is fired in a tubular furnace at 400 to 700°C for 2 to 5 hours.

[0097] According to the catalyst material in which an alkali metal or the like is supported on a noble metal-containing titania, it is possible to improve the NOx adsorption amount and also improve the NOx reduction efficiency.

[0098] In the above description, a method for manufacturing a catalyst material in which an alkali metal or the like is supported on a noble metal-containing titania has been exemplified. However, the catalyst material used in the present invention is arbitrary as long as it contains a noble metal, an alkali metal or the like, and titania. For example, a catalyst material in which a noble metal and an alkali metal or the like are supported on the surface of titania may be used. Note that, as a method for manufacturing a catalyst material in which both an alkaline earth metal or the like and a noble metal are supported on the surface of titania, any known method is adopted.

[0099] According to the manufacturing method according to the present embodiment, when the raw material gas is exhaust gas, the temperature of the target reaction tube (150°C or higher and 240°C or lower, or 260°C or higher and 350°C or lower) is close to the temperature of the exhaust gas discharged from the facility, and the temperature for NOx adsorption and the production of the target product may be the same or close. Therefore, the energy input for heat management is unnecessary or extremely small. Further, in the manufacturing method according to the present embodiment, by making the first step of introducing the raw material gas and recovering NOx and the second step of catalytically converting and releasing the recovered NOx into the target product independent steps, it is possible to sufficiently reduce the influence of co-existing gas species present in the raw material gas (exhaust gas). Therefore, the conditions for producing the target product can be optimized.

[0100] [Manufacturing Unit] Hereinafter, an example of a manufacturing unit for performing the manufacturing method according to the present invention will be described.

[0101] FIG. 1 is a configuration diagram illustrating a manufacturing unit 100 for manufacturing a target product according to the present embodiment. The manufacturing unit 100 includes a manufacturing apparatus 20, a control apparatus 30, and a feeder 50. The manufacturing apparatus 20 is an example of an apparatus for implementing the above-described manufacturing method (the first step and the second step).

[0102] The manufacturing apparatus 20 includes, for example, a reaction tube U, a first supply path R1, a second supply path R2, a first on-off valve V1, a second on-off valve V2, and a recovery path R3. The reaction tube U is a hollow structure, and a catalyst material Q is accommodated therein. In the following description, a case where exhaust gas discharged from a combustion facility is used as the raw material gas will be exemplified.

[0103] The first supply path R1 is a flow path for supplying the raw material gas G1 to the catalyst material Q (reaction tube U). Specifically, the first supply path R1 is a tubular member, and the downstream side is connected to the reaction tube U. The upstream side of the first supply path R1 is connected to, for example, a combustor 40 that discharges the raw material gas G1 (exhaust gas). Note that as long as the raw material gas G1 can be supplied to the first supply path R1 (catalyst material Q), the supply source of the raw material gas G1 is not limited to the combustor 40. The raw material gas G1 may be supplied from a container filled with the raw material gas G1 to the first supply path R1.

[0104] The second supply path R2 is a flow path for supplying the reducing gas G2 to the catalyst material Q (reaction tube U). Specifically, the second supply path R2 is a tubular member, and the downstream side is connected to the reaction tube U. The upstream side of the second supply path R2 is connected to, for example, a supplier 50 filled with the reducing gas G2.

[0105] As understood from the above description, in the present embodiment, the raw material gas G1 and the reducing gas G2 are supplied from independent mechanisms (the combustor 40 and the supplier 50), respectively. In other words, the supply sources of the raw material gas G1 and the reducing gas G2 are different.

[0106] The first on-off valve V1 is a valve that opens and closes the first supply path R1. That is, the opening and closing of the first supply path R1 is switched by the first on-off valve V1. When supplying the raw material gas G1 to the reaction tube U, the first on-off valve V1 is opened. On the other hand, when supplying the reducing gas G2 to the reaction tube U, the first on-off valve V1 is closed.

[0107] The second on-off valve V2 is a valve that opens and closes the second supply path R2. That is, the opening and closing of the second supply path R2 is switched by the second on-off valve V2. When supplying the reducing gas G2 to the reaction tube U, the second on-off valve V2 is opened. On the other hand, when supplying the raw material gas G1 to the reaction tube U, the second on-off valve V2 is closed. In FIG. 1, for convenience, the case where both the first on-off valve V1 and the second on-off valve V2 are in the open state is illustrated.

[0108] The recovery path R3 is a flow path for recovering the target product produced in the reaction tube U. Specifically, the recovery path R3 is a tubular member, and the upstream side is connected to the reaction tube U. Note that an on-off valve may be provided in the recovery path R3. The target product produced in the reaction tube U is discharged from the recovery path R3.

[0109] When the target product is ammonia, the ammonia discharged from the recovery path R3 is recovered as a resource. For example, ammonia is directly supplied to a reaction tube containing an arbitrary catalyst inside and used for a predetermined reaction, or it is assumed to be recovered by being adsorbed by an adsorbent or the like arranged in the subsequent stage. On the other hand, when the target product is nitrogen, the nitrogen discharged from the recovery path R3 is discharged into the atmosphere, for example.

[0110] Note that the manufacturing apparatus 20 may include an exhaust path for discharging the gas discharged from the reaction tube U (that is, the gas that has passed through the catalyst material Q) in the first step.

[0111] The control device 30 is a computer system for comprehensively controlling each element of the manufacturing apparatus 20, and is composed of, for example, one or a plurality of processors (for example, CPU: Central Processing Unit) that control each element of the manufacturing apparatus 20.

[0112] Specifically, the control device 30 causes the manufacturing apparatus 20 to execute the first step and the second step. The control device 30 of the present embodiment causes the manufacturing apparatus 20 to execute the first step and the second step by controlling the supply of the raw material gas G1 and the reducing gas G2. The control device 30 controls the supply of the raw material gas G1, for example, by switching the opening and closing of the first on-off valve V1, and controls the supply of the reducing gas G2 by switching the opening and closing of the second on-off valve V2. Further, the control device 30 also controls the flow rate of the raw material gas G1 from the combustor 40 and the reducing gas G2 from the supplier 50.

[0113] FIG. 2 is a configuration diagram of a manufacturing unit 100 according to another example of the present embodiment. The manufacturing apparatus 20 in FIG. 2 includes N (N is an integer of 2 or more) reaction tubes U[1] to U[N], N first supply paths R1[1] to R1[N], N second supply paths R2[1] to R2[N], N first on-off valves V1[1] to V1[N], N second on-off valves V2[1] to V2[N], and N recovery paths R3[1] to R3[N].

[0114] It can also be said that for each reaction tube U[n] (n = 1 to N), a first supply path R1[n], a second supply path R2[n], a first on-off valve V1[n], a second on-off valve V2[n], and a recovery path R3[n] are provided. Note that the first on-off valve V1[n], the second on-off valve V2[n], and the recovery path R3[n] may be appropriately omitted depending on the configuration of the manufacturing apparatus 20. The first step and the second step are repeatedly executed in each reaction tube U[n]. In FIG. 2 as well, the case where both the first on-off valve V1[n] and the second on-off valve V2[n] are in the open state is illustrated for convenience.

[0115] Here, it is assumed that the raw material gas G1 from various facilities is continuously discharged without stopping during the operation of the facility (combustor 40). Therefore, when producing a target product using the raw material gas G1 as a raw material, it is necessary to continuously supply the raw material gas G1 to the catalyst material Q without stopping. Thus, during the period when the raw material gas G1 is discharged from the combustor 40 (that is, during the operation of the combustor 40), it is preferable that the first step (supply of the raw material gas G1) is performed in at least one of the N reaction tubes U.

[0116] The above manufacturing method is expressed as a method in which, for each of the N reaction tubes U, in a first step, a raw material gas G1 is supplied to the reaction tube U[n], and NOx in the raw material gas G1 is occluded in the catalyst material Q, and after the supply of the raw material gas G1 is stopped, in a second step, a reducing gas G2 is supplied to the reaction tube U[n], and a target product is generated and recovered from the NOx occluded in the catalyst material Q, and the first step and the second step are alternately and repeatedly executed, and while the first step is being executed for K reaction tubes U, the second step is being executed for (N-K) reaction tubes U, and while the second step is being executed for K reaction tubes U, the first step is being executed for (N-K) reaction tubes U.

[0117] Hereinafter, an example of a specific configuration for causing the first step to be performed in at least one of the N reaction tubes U will be described.

[0118] For the sake of convenience, assume a configuration in which the time during which the second step is performed (hereinafter referred to as the "second time") is twice the time during which the first step is performed (hereinafter referred to as the "first time") (for example, when the first time is 1 hour and the second time is 2 hours). First, in order to cause the first step to be performed in at least one of the plurality of reaction tubes, it is necessary to set the number of reaction tubes (that is, N) according to the first time and the second time.

[0119] FIG. 3 is a table schematically showing the operations of the respective reaction tubes U in the case where the first time is 1 hour, the second time is 2 hours, and there are three reaction tubes U[1] to [3]. In FIG. 3, the time series of the unit period T (1 hour) is illustrated.

[0120] As illustrated in FIG. 3, by making the start times of the manufacturing process (first step) different among the three reaction tubes U[1] to U[3], one of the three reaction tubes U[1] to U[3] performs the first step in order. For example, when the first step of reaction tube U[1] ends, the first step of reaction tube U[2] starts, and when the first step of reaction tube U[2] ends, the first step of reaction tube U[3] starts. Then, there is one reaction tube U that executes the first step for the three reaction tubes U[1] to U[3]. Therefore, the raw material gas G1 continuously discharged from the facility can be continuously supplied to the manufacturing apparatus 20.

[0121] The number (N) of reaction tubes U is set according to the first time and the second time so that the first step is performed in at least one of the N reaction tubes U while the raw material gas G1 is discharged from the combustor 40. For example, N is set according to the value [(first time + second time) / first time] obtained by dividing the sum of the first time and the second time by the first time. It can also be said that N is set according to the ratio (first time: second time) of the first time and the second time. Specifically, N is set to a value equal to or greater than the value obtained by dividing the sum of the first time and the second time by the first time. For example, in the example of FIG. 3, [(first time + second time) / first time] is 3, so N is set to 3. Also, when [(first time + second time) / first time] includes a decimal part (for example, in the case of 2.5), N is set to a value equal to or greater than the integer obtained by rounding up the decimal part (that is, 3).

[0122] As understood from the above description, the number N of reaction tubes U is set according to the time when the first step is performed and the time when the second step is performed, and it is preferable that the first step is performed in at least one of the N reaction tubes U while the raw material gas G1 is discharged from the combustor 40.

[0123] In the above configuration, the case where the exhaust gas discharged from the combustion facility is used as the raw material gas is exemplified. However, for example, as the raw material gas, air is plasma-oxidized to obtain N 2 and oxygen (O 2When using a gas containing nitric oxide (NO) obtained from

[0124] The production unit 100 according to the present embodiment includes a configuration for producing either ammonia or nitrogen as a target product, and a configuration for producing both ammonia and nitrogen as target products. When mainly producing ammonia as the target product, ammonia is produced as the target product in all the reaction tubes U in the production unit 100 (nitrogen is hardly produced as the target product). When producing nitrogen as the target product, nitrogen is produced as the target product in all the reaction tubes U in the production unit 100 (ammonia is hardly produced as the target product).

[0125] When producing both ammonia and nitrogen as target products, for example, a configuration is exemplified in which ammonia is produced as the target product in one or more of the N reaction tubes U, and nitrogen is produced as the target product in the remaining reaction tubes U. Also, in each reaction tube, a configuration is adopted in which ammonia and nitrogen are selectively produced by switching the temperature of the reaction tube U.

Examples

[0126] Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

[0127] [Catalyst Material 1] First, the following catalyst material 1 was prepared. The preparation of catalyst material 1 involved synthesizing mesoporous titania encapsulating platinum particles, and then impregnating and supporting barium species for complexation.

[0128] (1) Synthesis of mesoporous titania encapsulating platinum particles To a solution of butyl titanate (3.4 g) in ethanol (11 mL), acetic acid (2.3 mL) and concentrated hydrochloric acid (1.1 mL) were added dropwise, and the mixture was stirred for 2 hours to hydrolyze butyl titanate. To this solution, amphiphilic organic molecule Pluronic F127 (2.52 g) was added, and the solution was immersed in a water bath at 40 °C for 5 minutes to completely dissolve Pluronic F127. Further, a dispersion of platinum acetylacetonate (16.3 mg) in ethanol (1 mL) was added and stirred for 1 hour to prepare a mesoporous titania precursor solution.

[0129] The mesoporous titania precursor solution was introduced into a spray dryer (ADL311S-A type manufactured by Yamato Scientific Co., Ltd.), spray-dried at an inlet temperature of 130 °C, and the powder was recovered with a cyclone separator. The recovered powder was heated to 400 °C at a rate of 2 °C / min in a dry air stream and held at that temperature for 3 hours to remove the amphiphilic organic molecule Pluronic F127 and crystallize the titania skeleton into anatase, obtaining mesoporous titania encapsulating platinum particles (Pt@mTiO 2 ).

[0130] (2) Complexation of barium species Mesoporous titania encapsulating platinum particles (Pt@mTiO 2 )(0.30 g) was added to distilled water (20 mL) and dispersed by stirring. An aqueous barium acetate solution (1.485 mL, containing 1 mg of Ba in 0.05 mL of aqueous solution) was added so that the weight ratio of Ba / TiO 2 was 1 / 10. The dispersion was stirred for 1 hour and dried under reduced pressure at 60 °C using a rotary evaporator to recover the powder. The recovered powder was heated to 500 °C at a rate of 10 °C / min in a dry air stream and held at that temperature for 3 hours to thermally decompose barium acetate, obtaining a catalyst material 1 (Ba / Pt@mTiO 2 ) in which barium species were complexed. In catalyst material 1, the weight ratio of Ba / TiO 2 is 1 / 10.

[0131] [Catalyst Material 2] The preparation of the catalyst material 2 was carried out by synthesizing mesoporous alumina containing platinum particles and then impregnating and supporting barium species for complexation.

[0132] <1>Preparation of Platinum-Containing Porous Alumina Precursor Solution (1) Weighed 15 g of Pluronic P123 (a polyethylene oxide - polypropylene oxide - polyethylene oxide block copolymer) as an amphiphilic organic molecule into a three-necked flask with a stopper, added 120 mL of ethanol, and further added 0.135 g of chloroplatinic acid hexahydrate. After that, it was stirred with a magnetic stirrer and a stir bar.

[0133] (2) Added 60 mL of ethanol and 24.6 g of aluminum (tri-sec-butoxide) to a three-necked flask to prepare a dispersion. While continuously stirring the dispersion, concentrated hydrochloric acid (14.5 mL) was added dropwise over 10 minutes or more and then stirred for 3 hours.

[0134] (3) Added the dispersion from (2) to the solution from (1) to prepare a platinum-containing porous alumina precursor solution.

[0135] <2>Synthesis of Platinum-Containing Porous Alumina (1) Introduced the platinum-containing porous alumina precursor solution into a spray dryer (ADL311 manufactured by Yamato Scientific Co., Ltd.), and removed the moisture containing ethanol by hot air drying while spraying the precursor solution. The inlet temperature of the spray dryer was set at 170 °C. After that, the precursor of platinum-containing porous alumina was recovered by a cyclone separator.

[0136] (2) The precursor recovered by the cyclone separator was calcined in a tubular furnace to remove Pluronic P123 that served as a pore template to make it porous, and at the same time, thermal decomposition of the platinum compound (chloroplatinic acid hexahydrate) and crystallization of alumina were carried out. The calcination was carried out by raising the temperature to 850 °C at a rate of 2 °C per minute under a nitrogen stream, holding at the same temperature for 1 hour, and then holding at the same temperature for 2 hours under an oxygen stream.

[0137] <3>Loading of Barium onto Platinum-Containing Porous Alumina

[0138] Barium is supported on platinum-containing porous alumina as a barium compound (in Example 1, it is a barium compound produced by thermal decomposition of barium acetate, such as barium carbonate, barium oxide, and barium hydroxide).

[0139] The loading of the barium compound onto the platinum-containing porous alumina was carried out by an impregnation method in the same manner as in Example 1 to obtain Catalyst Material 2. In Catalyst Material 2, the weight ratio of Ba / Al 2 O 3 is 1 / 10.

[0140] Ammonia was synthesized as follows using Catalyst Material 1 and Catalyst Material 2. Specifically, the catalyst material was placed in a quartz reaction tube, heated to 300 °C, and pretreated for 1 hour under a flowing 1% H 2 . Thereafter, the reaction tube was maintained at a predetermined temperature (175 °C, 200 °C, 250 °C, 300 °C), and a simulated exhaust gas containing 1000 ppm of nitrogen monoxide (NO) and 10% oxygen (O 2 ) was passed through this quartz reaction tube for 1 hour to contact with the catalyst, and the discharged outlet gas was analyzed by infrared spectroscopy. When NO was oxidized, nitrogen dioxide (NO 2 ) was generated and adsorbed strongly on the alkaline earth metal. The NO 2 species or nitrate (NO 3 ― species) was recovered. Subsequently, the gas was switched and 1% H 2 was supplied for 1 hour, so that the recovered NOx was converted to ammonia and desorbed, and ammonia was effectively extracted into the gas phase. Similarly, ammonia was synthesized using 5% H 2 . FIG. 4 is a graph showing the ammoniation rate for each temperature when using 1% H 2 , and FIG. 5 is a graph showing the ammoniation rate for each temperature when using 5% H 2It is a graph showing the ammoniation rate for each temperature when [used]. The ammoniation rate is the ammonia production rate with respect to the NOx storage amount. The NOx storage amount was determined by analyzing the outlet gas. The outlet gas was quantified using a Nicolet iS 20 infrared spectrophotometer manufactured by Thermo Fisher Scientific and a multiple reflection gas cell manufactured by PIKE Technologies.

[0141] In the case of the catalyst material 1, the following reactions occur during the storage of NOx: 2NO + O 2 → 2NO 2 BaO + 3NO 2 → Ba(NO 3 ) 2 + NO During the synthesis of NH after NOx storage 3 the following reactions occur. Ba(NO 3 ) 2 + 8H 2 → BaO + 2NH 3 + 5H 2 O During the synthesis of N after NOx storage 2 the following reactions occur. Ba(NO 3 ) 2 + 5H 2 → BaO + N 2 + 5H 2 O 3Ba(NO 3 ) 2 + 10NH 3 → 3BaO + 8N 2 + 15H 2 O When N 2 O is generated after NOx storage, the following reactions occur. Ba(NO 3 ) 2 + 4H 2 → BaO + N 2 O + 4H 2 O

[0142] As can be understood from FIGS. 4 and 5, when the temperature was 250° C. or higher, the catalyst material 2 produced ammonia with higher efficiency than the catalyst material 1. On the other hand, when the temperature was 240° C. or lower, it was confirmed that the catalyst material 1 produced ammonia with higher efficiency than the catalyst material 2.

[0143] FIG. 6 shows the analysis results ((a) nitrogen adsorption isotherm, (b) pore size distribution, (c) low-angle XRD, (d) XRD) for the catalyst material 1 for reference. (a) The nitrogen adsorption isotherm was measured by Autosorb-iQ manufactured by Anton Paar. As a pretreatment of the sample, it was heated at 110° C. for 6 hours under reduced pressure to remove surface moisture and the like. (b) The pore size distribution was calculated using the NLDFT method from the desorption-side isotherm of the nitrogen adsorption isotherm. (c) Low-angle XRD was measured by X-ray diffraction using RINT 2100 manufactured by Rigaku (Fe radiation source, scanning angle: 0.6 degrees to 12 degrees, scanning speed: 2 degrees per minute). (d) XRD was measured by X-ray diffraction using RINT 2000 manufactured by Rigaku (Cu radiation source, scanning angle: 10 degrees to 80 degrees, scanning speed: 2 degrees per minute).

[0144] The above results were obtained because the spillover of H (the diffusion of atomic hydrogen generated by the dissociation of the H bond to the catalyst surface) from titania to alumina was fast, and the conversion to ammonia and nitrogen proceeded rapidly. 2 of 2 to the catalyst surface was fast, and the conversion to ammonia and nitrogen proceeded rapidly.

[0145] Table 1 is a graph showing the selectivity of the products when 1% H 2 was used for the catalyst material 1.

[0146]

Table 1

[0147] As can be understood from Table 1, it was confirmed that when the reaction temperatures were 175 °C, 200 °C, and 250 °C, ammonia was produced as the main product, and when the reaction temperature was 300 °C, nitrogen was produced as the main product.

[0148] From the above results, it can be said that when the reaction temperature (the temperature of the reaction tube) is 150 °C or higher and 240 °C or lower, ammonia can be produced with high efficiency, and when the reaction temperature is 260 °C or higher and 350 °C or lower, nitrogen can be produced with high efficiency. That is, when using titania as the oxide carrier in the catalyst material, the target product can be controlled by changing the reaction temperature. Specifically, ammonia can be produced with high efficiency in a low-temperature environment, and the detoxification to nitrogen proceeds with high efficiency in a high-temperature environment, and the slightly generated ammonia can also be used for the detoxification of NOx.

Explanation of Signs

[0149] 20: Manufacturing apparatus 30: Control apparatus 40: Combustor 50: Feeder 60: Recovery apparatus 100: Manufacturing unit G1: Raw material gas G2: Reducing gas K1: First common passage K2: Second common passage Q: Catalyst material R1: First supply path R2: Second supply path R3: Recovery path U: Reaction tube V1: First on-off valve V2: Second on-off valve V3: Third on-off valve

Claims

1. A first step of occluding NOx in the raw material gas in the catalyst material by supplying a raw material gas containing NOx and oxygen to the catalyst material in the reaction tube; A second step of generating a target product from the NOx occluded in the catalyst material by supplying a reducing gas not containing NOx to the catalyst material after stopping the supply of the raw material gas, The catalyst material includes a noble metal, at least one of an alkali metal and an alkaline earth metal, and TiO ２ and When ammonia is the target product, the temperature in the reaction tube is 150°C or higher and 240°C or lower in the first step and the second step, When nitrogen is the target product, the temperature in the reaction tube is 260°C or higher and 350°C or lower in the first step and the second step Manufacturing method.

2. The reducing gas contains H ２ and The manufacturing method according to Claim 1.

3. The noble metal is one or more of Pt, Pd, Rh, and Ir, The content of the noble metal is 0.1% by mass or more and 10% by mass or less based on 100% by mass of the entire catalyst material The manufacturing method according to Claim 1.

4. The alkali metal is one or more selected from Li, K, Na, and Cs, The alkaline earth metal is one or more selected from Ca, Mg, Sr, and Ba, The content of the alkali metal and the alkaline earth metal is 1% by mass or more and 30% by mass or less based on 100% by mass of the entire catalyst material The manufacturing method according to Claim 1.

5. The noble metal is contained inside the TiO ２ and The alkali metal and the alkaline earth metal are supported on the TiO ２ containing the noble metal therein The manufacturing method according to Claim 1.

6. The reaction tube includes N (N is a natural number of 2 or more) reaction tubes, For each of the N reaction tubes, the first step and the second step are alternately repeated, While the first step is being performed on K (K is a natural number less than N) of the N reaction tubes, the second step is being performed on (N - K) reaction tubes, While the second step is being performed on the K reaction tubes, the first step is being performed on the (N - K) reaction tubes The manufacturing method according to Claim 1.

7. A reaction tube containing a catalyst material, A first supply path for supplying a raw material gas containing NOx and oxygen to the reaction tube, A second supply path for supplying a reducing gas not containing NOx to the reaction tube, A manufacturing apparatus including a recovery path for recovering the generated target product from the reaction tube, A control device for controlling the manufacturing apparatus, The control device is A first step of occluding NOx in the raw material gas into the catalyst material by supplying the raw material gas to the catalyst material; After stopping the supply of the raw material gas, a second step of generating the target product from the NOx occluded in the catalyst material by supplying the reducing gas to the catalyst material is executed by the manufacturing apparatus. The catalyst material includes a noble metal, at least one of an alkali metal and an alkaline earth metal, and TiO ２ and When ammonia is the target product, the temperature in the reaction tube is 150°C or higher and 240°C or lower in the first step and the second step. When nitrogen is the target product, the temperature in the reaction tube is 260°C or higher and 350°C or lower in the first step and the second step. Manufacturing unit. **Claim 8** There are N (N is a natural number of 2 or more) each of the reaction tube, the first supply path, the second supply path, and the recovery path. The control device is For each of the N reaction tubes, the manufacturing apparatus is made to alternately repeat the first step and the second step. While the first step is being executed for K (K is a natural number less than N) of the N reaction tubes, the second step is being executed for (N - K) reaction tubes. While the second step is being executed for the K reaction tubes, the first step is being executed for the (N - K) reaction tubes. The manufacturing unit according to claim 7.

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