Ammonia production unit and production method

Abstract

A production unit 100 comprises: a production device 20 comprising a reaction pipe U in which a noble-metal-containing catalyst material Q is to be accommodated, a first feed passage R1 for feeding a feed gas (discharge gas) G1 including NOx and oxygen to the reaction pipe U, a second feed passage R2 for feeding a reducing gas G2 containing no NOx to the reaction pipe U, and a collection passage R3 for collecting produced ammonia from the reaction pipe U; and a control unit 30 which controls the production device 20. The control unit 30 makes the production device 20 perform production treatments including a first step, in which the feed gas G1 is fed to the catalyst material Q to thereby cause the catalyst material Q to occlude the NOx contained in the feed gas G1, and a second step, in which, after the feeding of the feed gas G1 is stopped, the reducing gas G2 is fed to the catalyst material Q to thereby produce ammonia from the NOx occluded in the catalyst material Q and the ammonia is collected.

Description

[Technical Field]

[0001] The present invention relates to a technology for producing ammonia from nitrogen oxides (NOx). [Background technology]

[0002] The Haber-Bosch process is a well-known method for producing ammonia (NH3). In the Haber-Bosch process, ammonia is produced using nitrogen and hydrogen as raw materials. However, ammonia must be produced under high temperatures and pressures (400-600°C, 200-400 atmospheres), which requires a large input of energy.

[0003] On the other hand, for example, in high-temperature combustion equipment, nitrogen oxides (so-called thermal NOx) resulting from combustion are present in the exhaust gas. The nitrogen oxides in the exhaust gas are detoxified into nitrogen and then released. Therefore, if ammonia can be produced from the NOx in the exhaust gas, it will be possible to recycle waste materials. Furthermore, increasing the temperature of a heat engine to improve its energy efficiency may further increase the amount of thermal NOx produced. However, if the produced thermal NOx can be recovered as ammonia, it may be possible to improve the energy efficiency of the heat engine without increasing the amount of nitrogen oxides emitted.

[0004] Here, ammonia selective catalytic reduction (NH3-SCR) is a commonly used method for removing NOx from exhaust gases to make them harmless. This method involves adding ammonia as a reducing agent from outside and reducing NOx on a catalyst.

[0005] Meanwhile, in catalytic material technology for purifying automobile exhaust gases, Non-Patent Document 1 discloses a technology in which NOx is temporarily stored (adsorbed) in a catalyst, then reduced to nitrogen (N2) and released into the atmosphere.

[0006] As the exhaust gas purification process has been elucidated, it has been confirmed that a small amount of ammonia is generated as an intermediate product in the system. However, the small amount of ammonia generated is used as a reducing agent for NOx. Therefore, various technologies have been disclosed that use ammonia generated as an intermediate product as a reducing agent.

[0007] For example, Patent Documents 1 to 3 disclose technologies for generating ammonia as an intermediate product in an internal combustion engine that supplies and burns fuel under cyclic rich / lean combustion conditions. Specifically, NOx is adsorbed onto a catalyst under lean conditions and concentrated and recovered, and then the NOx adsorbed onto the catalyst is reduced by controlling the engine to rich conditions. Under rich conditions, ammonia is generated. Then, when the lean condition is restored, the generated ammonia reacts with NOx in the exhaust gas and is reduced to harmless nitrogen. As described above, ammonia is used as a reducing agent for reducing NOx.

[0008] Furthermore, Patent Document 4 discloses an exhaust gas purification device that temporarily adsorbs NOx in an excess air atmosphere and reduces the NOx in a reducing atmosphere to produce ammonia as an intermediate product. The produced ammonia is used as a reducing agent for further reducing NOx. Furthermore, Patent Document 5 discloses a technology for converting NOx in exhaust gas emitted from a combustor into ammonia. The produced ammonia is fed back into the combustor and used as a reducing agent for reducing NOx.

[0009] Similarly, Non-Patent Documents 2 and 3 disclose experiments using catalyst material technology simulating a lean-burn gasoline engine for automobiles, in which nitrogen, nitrous oxide (NO) and ammonia are produced from NOx by supplying a gas containing NOx under lean conditions and then supplying a reducing gas under rich conditions.

[0010] Furthermore, Non-Patent Documents 4 and 5 disclose that ammonia is produced by simultaneously supplying NOx and a reducing gas to a catalyst material in the absence of oxygen.

Prior Technical Literature

Charter Documents

[0011] [Patent Document 1] Japanese Patent Publication No. 2009-103020 [Patent Document 2] Patent No. 4740217 [Patent Document 3] Japanese Patent Publication No. 2005-111436 [Patent Document 4] Patent No. 5431677 [Patent Document 5] Japanese Patent Publication No. 2020-090949

Non-licensed literature

[0012]

Non-patent document 1

Non-patent document 2

Non-patent document 3

[0013] As described above, in the techniques of Patent Documents 1-5 and Non-Patent Documents 2-5, it is assumed that the generated ammonia will be used as a reducing agent for reducing NOx, and it is not anticipated that it will be recovered as a resource. In consideration of the above circumstances, the present invention aims to generate and recover ammonia from NOx. [Means for solving the problem]

[0014] [1] A production unit according to the present invention is a unit for producing ammonia, and includes a production apparatus including a reaction tube containing a catalytic material containing a precious metal, a first supply path for supplying an exhaust 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 ammonia from the reaction tube, and a control device for controlling the production apparatus, wherein the control device causes the production apparatus to perform a production process including: a first step of supplying the exhaust gas to the catalytic material to cause the catalytic material to occlude NOx in the exhaust gas; and a second step of generating and recovering ammonia from the NOx occluded in the catalytic material by supplying the reducing gas to the catalytic material after stopping the supply of the exhaust gas.

[0015] [2] The manufacturing unit of [1], in which the manufacturing process is repeatedly executed.

[0016] [3] A production unit according to another aspect of the present invention is a unit for producing ammonia, comprising: a production apparatus including N (N is a natural number of 2 or more) reaction tubes each containing a catalytic material containing a noble metal; N first supply paths for supplying an exhaust gas containing NOx and oxygen to the N reaction tubes, respectively; N second supply paths for supplying a reducing gas not containing NOx to the N reaction tubes, respectively; and N recovery paths for recovering ammonia produced in the N reaction tubes, respectively; and a control device for controlling the production apparatus, wherein the control device controls the production apparatus to supply the exhaust gas to each of the N reaction tubes. and a second step of generating and recovering ammonia from the NOx occluded in the catalytic material by supplying the reducing gas to the reaction tube after stopping the supply of the exhaust gas, wherein the manufacturing apparatus is caused to repeatedly execute a manufacturing process, and the manufacturing process includes: a first step of supplying a reducing gas to the reaction tube, thereby occluding the NOx in the exhaust gas in the catalytic material; and a second step of generating and recovering ammonia from the NOx occluded in the catalytic material by supplying the reducing gas to the reaction tube after stopping the supply of the exhaust gas; and while the first step is being executed for K (K is a natural number less than N) reaction tubes out of the N reaction tubes, the second step is being executed for (NK) reaction tubes, and while the second step is being executed for the K reaction tubes, the first step is being executed for the (NK) reaction tubes. [3]

[0017] [4] The manufacturing unit of [3], wherein the manufacturing apparatus has N first on-off valves that open and close the N first supply paths, respectively, and N second on-off valves that open and close the N second supply paths, and the control device opens the first on-off valves and closes the second on-off valves in the first step, and closes the first on-off valves and opens the second on-off valves in the second step.

[0018] [5] The manufacturing unit of [3] or [4], wherein the manufacturing apparatus has N exhaust paths for exhausting exhaust gas from the N reaction tubes, N third on-off valves for opening and closing the N recovery paths, respectively, and N fourth on-off valves for opening and closing the N exhaust paths, respectively, and the control device closes the third on-off valve and opens the fourth on-off valve in the first step, and opens the third on-off valve and closes the fourth on-off valve in the second step, for each of the N reaction tubes.

[0019] [6] The manufacturing method of the present invention is a method for manufacturing ammonia, and includes a first step of supplying exhaust gas containing NOx and oxygen to a catalytic material containing a precious metal, thereby occluding the NOx in the exhaust gas in the catalytic material, and a second step of generating and recovering ammonia from the NOx occluded in the catalytic material by supplying a reducing gas not containing NOx to the catalytic material after stopping the supply of the exhaust gas.

[0020] [7] A production method according to another aspect of the present invention is a method for producing ammonia, in which a production apparatus includes N (N is a natural number equal to or greater than 2) reaction tubes, each containing a catalytic material containing a precious metal, and for each of the N reaction tubes, a production process including a first step of supplying an exhaust gas containing NOx and oxygen to the reaction tube, thereby occluding the NOx in the exhaust gas into the catalytic material, and a second step of producing and recovering ammonia from the NOx occluded in the catalytic material by supplying a reducing gas not containing NOx to the reaction tube after stopping the supply of the exhaust gas, is repeatedly performed, and while the first step is performed for K (K is a natural number less than N) reaction tubes out of the N reaction tubes, the second step is performed for (NK) reaction tubes, and while the second step is performed for the K reaction tubes, the first step is performed for the (NK) reaction tubes.

[0021] [8] The method according to [6] or [7], wherein the reducing gas contains at least one of H2, C3H6, C3H8, and CH4.

[0022] [9] The production method according to any one of [6] to [8], wherein at least one of the temperature of the exhaust gas and the reducing gas and the temperature of the catalyst material is 150 to 500°C.

[0023]

[10] The method according to any one of [6] to [9], wherein the catalytic material comprises the noble metal, at least one of an alkali metal and an alkaline earth metal, and an oxide support.

[0024]

[11] The manufacturing method according to any one of [6] to

[10] , wherein the noble metal is one or more of platinum, palladium, rhodium, and iridium, and the content of the noble metal is 0.01 to 20.0 mass% of the entire catalyst material, taken as 100 mass%.

[0025]

[12] The manufacturing method according to

[10] , wherein the alkali metal is one or more selected from lithium, potassium, sodium, and cesium, and the alkaline earth metal is one or more selected from calcium, magnesium, strontium, and barium, and the content of the alkali metal and the alkaline earth metal is 0.1 to 50.0 mass % of the entire catalyst material, taken as 100 mass %.

[0026]

[13] The method according to

[10] , wherein the oxide support is one or more of Al2O3, CeO2, TiO2, and ZrO2.

[0027]

[14] The manufacturing method according to

[10] or

[12] , wherein the oxide support is Al2O3, the precious metal is contained within the Al2O3, and the alkali metal and the alkaline earth metal are supported on the Al2O3 containing the precious metal therein.

[0028]

[15] The catalyst material according to the present invention is a catalyst material used in the manufacturing methods of [6] to

[14] , and is a nanocomposite material having regularly arranged pores, the nanocomposite material including a precious metal, at least one of an alkali metal and an alkaline earth metal, and porous alumina, wherein the precious metal is contained within the porous alumina, the alkali metal and the alkaline earth metal are supported on the porous alumina containing the precious metal therein, and the mode in the pore size distribution is a diameter of 1 to 200 nm. [Effects of the Invention]

[0029] The manufacturing apparatus and manufacturing method according to the present invention aim to reduce the influence of coexisting gases in the raw material gas (typically exhaust gas) and generate and recover ammonia from NOx. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 2 is a configuration diagram of a manufacturing unit according to the first embodiment. [Figure 2] 3 is a flowchart of a process executed by the manufacturing apparatus according to the first embodiment. [Figure 3] FIG. 10 is a configuration diagram of a manufacturing unit according to a second embodiment. [Figure 4] 10 is a flowchart of a process executed by a manufacturing apparatus according to a second embodiment. [Figure 5] FIG. 10 is a configuration diagram for explaining the operation of a manufacturing apparatus according to a second embodiment. [Figure 6] FIG. 10 is a configuration diagram for explaining the operation of a manufacturing apparatus according to a second embodiment. [Figure 7] FIG. 10 is a configuration diagram of a manufacturing unit according to a third embodiment. [Figure 8] FIG. 10 is a configuration diagram for explaining the operation of a manufacturing apparatus according to a third embodiment. [Figure 9] FIG. 10 is a configuration diagram for explaining the operation of a manufacturing apparatus according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] [First embodiment] 1 is a configuration diagram illustrating a production unit 100 for producing ammonia according to the first embodiment. The production unit 100 includes a production apparatus 20 and a control device 30 that controls the production apparatus 20.

[0032] The production apparatus 20 is an apparatus that produces ammonia from NOx (e.g., NO, NO2, N2O, and N2O3) in a gas. Schematically, the production apparatus 20 supplies a raw material gas G1 containing NOx to a catalyst material Q, stops the supply of the raw material gas G1, and supplies a reducing gas G2 to the catalyst material Q, thereby producing ammonia (hereinafter referred to as the "production process").

[0033] The catalytic material Q is a catalyst that occludes and reduces NOx in the raw material gas G1. Details of the catalytic material Q will be described later.

[0034] The raw material gas G1 is a gas containing NOx and oxygen. For example, exhaust gas is suitably used as the raw material gas G1. Exhaust gas is a gas emitted from various facilities (for example, high-temperature combustion facilities such as waste incineration facilities or thermal power plants, and factories). The NOx concentration in the raw material gas G1 is, for example, 100 ppm to 2%. The oxygen concentration in the raw material gas G1 is, for example, 1 to 20%. In addition to NOx and oxygen, the raw material gas G1 may contain CO2, water vapor, nitrogen, etc.

[0035] The reducing gas G2 is a gas that reduces NOx occluded (adsorbed) in the catalytic material Q. Specifically, the reducing gas G2 is a gas that contains a reducing agent but does not contain NOx. Note that the term "reducing gas G2 not containing NOx" also includes a case where the reducing gas G2 contains NOx at an extremely low concentration (e.g., 10 ppm or less) that does not affect the reduction of NOx occluded (adsorbed) in the catalytic material Q and does not have an environmental impact. However, a reducing gas G2 that does not contain NOx at all (NOx concentration is 0%) is preferably used. From the viewpoint of improving the ammonia production efficiency, the reducing agent is preferably one or more of H2, C3H6, C3H8, and CH4. Note that from the viewpoint of stably producing ammonia, the reducing gas G2 is preferably not a gas produced from the raw material gas G1.

[0036] The concentration of the reducing agent in the reducing gas G2 is, for example, 100 ppm to 50%, preferably 500 ppm to 20%, and more preferably 1000 ppm to 5%. In addition to the reducing agent, the reducing gas G2 may contain water vapor, nitrogen, etc.

[0037] As illustrated in FIG. 1, the production apparatus 20 of the first embodiment includes a reaction tube U, a first supply line R1, a second supply line R2, a first on-off valve V1, a second on-off valve V2, and a recovery line R3.

[0038] The reaction tube U is a hollow structure in which a catalyst material Q is accommodated.

[0039] The first supply path R1 is a flow path for supplying the raw material gas G1 to the catalytic material Q (reaction tube U). Specifically, the first supply path R1 is a tubular member, and its 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 exhaust gas to be used as the raw material gas G1. Note that the upstream side of the first supply path R1 may be directly connected to the combustor 40 or may be indirectly connected to the combustor 40 via another pipe or device, as long as the upstream side can supply the raw material gas G1 to the reaction tube U.

[0040] 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 its downstream side is connected to the reaction tube U. The upstream side of the second supply path R2 is connected to, for example, a supply device 50 containing the reducing gas G2. Note that the upstream side of the second supply path R2 may be directly connected to the supply device 50 or indirectly connected to the supply device 50 via another pipe or device, as long as it can supply the reducing gas G2 to the reaction tube U.

[0041] As can be understood from the above description, in the first embodiment, the raw material gas G1 and the reducing gas G2 are supplied from independent mechanisms (the combustor 40 and the supply device 50). In other words, the raw material gas G1 and the reducing gas G2 are supplied from separate sources.

[0042] The first on-off valve V1 is a valve that opens and closes the first supply path R1. That is, the first on-off valve V1 switches between opening and closing the first supply path R1. When a raw material gas G1 is supplied to the reaction tube U, the first on-off valve V1 is opened. On the other hand, when a reducing gas G2 is supplied to the reaction tube U, the first on-off valve V1 is closed.

[0043] The second on-off valve V2 is a valve that opens and closes the second supply path R2. That is, the second on-off valve V2 switches between opening and closing the second supply path R2. When the reducing gas G2 is supplied to the reaction tube U, the second on-off valve V2 is opened. On the other hand, when the raw material gas G1 is supplied to the reaction tube U, the second on-off valve V2 is closed. For convenience, FIG. 1 illustrates a case where both the first on-off valve V1 and the second on-off valve V2 are open.

[0044] The recovery line R3 is a flow path for recovering the ammonia produced in the reaction tube U. Specifically, the recovery line R3 is a tubular member, and an upstream side of the recovery line R3 is connected to the reaction tube U. An on-off valve may be provided in the recovery line R3. The ammonia produced in the reaction tube U is released from the recovery line R3.

[0045] The ammonia released from the recovery line R3 is expected to be used for a predetermined reaction by being directly supplied to a reaction tube containing an arbitrary catalyst therein, or to be recovered by being adsorbed by an adsorbent or the like placed in a downstream stage.

[0046] The control device 30 is a computer system for controlling each element of the manufacturing device 20 in an integrated manner, and includes, for example, one or more processors (for example, CPU: Central Processing Unit) that control each element of the manufacturing device 20.

[0047] Specifically, the control device 30 controls the supply of the raw material gas G1 and the reducing gas G2, thereby causing the manufacturing apparatus 20 to perform the manufacturing process. The control device 30 of the first embodiment controls the supply of the raw material gas G1 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.

[0048] The following describes specific manufacturing processes that are executed by the manufacturing apparatus 20 under the control of the control device 30. Fig. 2 is a flowchart illustrating the manufacturing processes.

[0049] When the manufacturing process starts, first, the manufacturing apparatus 20 supplies the raw material gas G1 to the catalyst material Q (reaction tube U) (Sa1). Specifically, the manufacturing apparatus 20 opens the first on-off valve V1 under the control of the control device 30, thereby supplying the raw material gas G1 to the catalyst material Q via the first supply path R1. When supplying the raw material gas G1, the second on-off valve V2 is in a closed state.

[0050] The raw material gas G1 is supplied to the catalyst material Q (reaction tube U) for a predetermined period (for example, 5 minutes to 2 hours). By supplying the raw material gas G1 to the catalyst material Q, NOx is converted to NO2 - or NO3 - The NOx is absorbed (adsorbed) into the catalyst material Q. The NOx concentration in the raw material gas G1 after being supplied to the catalyst material Q (hereinafter referred to as "used raw material gas G1e") decreases. The used raw material gas G1e is released, for example, via a recovery path R3.

[0051] After NOx has been occluded in the catalytic material Q, the production apparatus 20 stops the supply of the raw material gas G1 (Sa2). Specifically, under the control of the control device 30, the production apparatus 20 closes the first on-off valve V1 to stop the supply of the raw material gas G1.

[0052] Next, the manufacturing apparatus 20 supplies the reducing gas G2 to the catalytic material Q (reaction tube U) (Sa3). Specifically, the manufacturing apparatus 20 opens the second on-off valve V2 under the control of the control device 30, thereby supplying the reducing gas G2 to the catalytic material Q.

[0053] The reducing gas G2 is supplied to the catalytic material Q (reaction tube U) for a predetermined period (for example, 5 minutes to 2 hours). By supplying the reducing gas G2 to the catalytic material Q in which NOx has been occluded, the reduction of NOx progresses and ammonia is produced. The produced ammonia is recovered from the recovery line R3.

[0054] Then, the manufacturing apparatus 20 stops the supply of the reducing gas G2 (Sa4). Specifically, the manufacturing apparatus 20 closes the second on-off valve V2 under the control of the control device 30, thereby stopping the supply of the reducing gas G2.

[0055] 2 may be repeatedly performed. That is, after the supply of the reducing gas G2 is stopped in step Sa4, the process returns to the process of supplying the raw material gas G1 in step Sa1.

[0056] The manufacturing process executed by the manufacturing apparatus 20 can also be thought of as a method for manufacturing ammonia (hereinafter referred to as the "manufacturing method"). Specifically, the manufacturing method includes a first step (step Sa1 in FIG. 2) of supplying a raw material gas G1 (exhaust gas) to a catalytic material Q (reaction tube U) to cause NOx in the raw material gas G1 to be occluded in the catalytic material Q, and a second step (step Sa3 in FIG. 2) of generating and recovering ammonia from the NOx occluded in the catalytic material Q by supplying a reducing gas G2 to the catalytic material Q after stopping the supply of the raw material gas G1.

[0057] In the production method according to the first embodiment, at least one of the temperature of the raw material gas G1 and reducing gas G2 supplied to the catalytic material Q and the temperature of the catalytic material Q is set to 150 to 500° C., and preferably 200 to 400° C. By setting at least one of the temperature of the raw material gas G1 and reducing gas G2 supplied to the catalytic material Q and the temperature of the catalytic material Q within the above temperature range, the efficiency of ammonia production can be improved.

[0058] As can be understood from the above description, according to the manufacturing apparatus 20 (manufacturing method) of the first embodiment, after the raw material gas G1 is supplied to the catalyst material Q, the supply of the raw material gas G1 is stopped and a reducing gas G2 is supplied to the catalyst material Q, thereby generating and recovering ammonia. That is, since the raw material gas G1 and the generated ammonia do not coexist in the reaction tube U, it becomes possible to recover ammonia as a resource.

[0059] In the configurations (e.g., Patent Documents 1-5) in which a reducing gas (e.g., H) obtained from exhaust gas (raw material gas) is used to generate ammonia, the generation of the reducing gas depends on various coexisting gases (e.g., O, HO, CO, CO, and HC) in the exhaust gas. The concentrations of the coexisting gases are not always constant. Therefore, there is also the problem that the coexisting gases in the exhaust gas affect the generation of ammonia. As a result, ammonia cannot be generated stably.

[0060] In contrast, in the first embodiment, a reducing gas G2 independent of the raw material gas G1 (a reducing gas G2 not produced from the raw material gas G1) is used, thereby reducing the influence of coexisting gases in the raw material gas G1 and enabling ammonia to be produced and recovered from NOx.

[0061] It should be noted that gases other than exhaust gas may be used as the raw material gas G1. The type of raw material gas G1 is arbitrary as long as it contains NOx and oxygen.

[0062] [Second embodiment] A second embodiment will be described. In the following examples, elements that have the same functions as those in the first embodiment will be designated by the same reference numerals as those in the first embodiment, and detailed descriptions thereof will be omitted where appropriate.

[0063] 3 is a configuration diagram of a manufacturing unit 100 according to the second embodiment. The manufacturing unit 100 according to the second embodiment includes a manufacturing device 20 and a control device 30, similar to the first embodiment.

[0064] In the first embodiment, a configuration in which the production apparatus 20 includes one reaction tube U is exemplified. However, in the second embodiment, a configuration in which the production apparatus 20 includes N reaction tubes U[1] to U[N] (N is a natural number of 2 or more) is exemplified.

[0065] The production apparatus 20 of the second embodiment is provided with 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] for each reaction tube U[n] (n = 1 to N). That is, the production apparatus 20 is provided with N 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].

[0066] The upstream sides (opposite side to the reaction tube U) of the N first supply passages R1[1] to R1[N] are connected to the combustor 40 via the first common passage K1. In other words, the N first supply passages R1[1] to R1[N] are flow paths branching from the first common passage K1 toward the N reaction tubes U[1] to U[N]. The upstream side of the first common passage K1 is connected to the combustor 40. A raw material gas G1 is supplied to each of the N first supply passages R1[1] to R1[N] via the first common passage K1.

[0067] The upstream sides (opposite side to the reaction tube U) of the N second supply passages R2[1] to R2[N] are connected to the combustor 40 via the second common passage K2. In other words, the N second supply passages R2[1] to R2[N] are flow paths branching from the second common passage K2 toward the N reaction tubes U[1] to U[N]. The upstream side of the second common passage K2 is connected to the supply device 50. A reducing gas G2 is supplied to each of the N second supply passages R2[1] to R2[N] via the second common passage K2. An on-off valve may also be provided in each of the first common passage K1 and the second common passage K2.

[0068] The manufacturing apparatus 20 of the second embodiment performs the same manufacturing process as that of the first embodiment for each of the N reaction tubes U[1] to U[N]. In the second embodiment, the manufacturing process (the processes Sa1 to Sa4 in FIG. 2) is repeatedly performed for each reaction tube U[n].

[0069] When performing step Sa1 (first step) of supplying raw material gas G1 to the reaction tube U[n], the first on-off valve V1[n] is opened and the second on-off valve V2[n] is closed. When performing step Sa3 (second step) of supplying reducing gas G2 to the reaction tube U[n], the first on-off valve V1[n] is closed and the second on-off valve V2[n] is opened.

[0070] Hereinafter, N reaction tubes U[1] to U[N] will be described by dividing them into K (K is a natural number less than N) reaction tubes U and (NK) reaction tubes U. The K reaction tubes U and the (NK) reaction tubes U have different timings for performing each step in the production process.

[0071] FIG. 4 is a flowchart illustrating a manufacturing process that the manufacturing apparatus 20 according to the second embodiment repeatedly executes for K reaction tubes U and (NK) reaction tubes U. For convenience, FIG. 4 illustrates a time series of unit periods T1-T4. The unit periods T1-T4 are repeatedly repeated in the order of "T1 → T2 → T3 → T4 → ...". The periods T1 and T3 during which the gases (G1, G2) are supplied are, for example, 1 minute to 3 hours, preferably 5 minutes to 2 hours. The periods T2 and T4 are short periods required to stop and switch the gases.

[0072] 4, in a unit period T1, step Sa1 of supplying a raw material gas G1 to the catalytic material Q (reaction tubes U) is performed for K reaction tubes U, and step Sa3 of supplying a reducing gas G2 to the catalytic material Q (reaction tubes U) is performed for (NK) reaction tubes U. That is, step Sa3 is performed for the (NK) reaction tubes U in parallel with the execution of step Sa1 for the K reaction tubes U.

[0073] In the unit period T2, step Sa2 of stopping the supply of the source gas G1 is performed, and step Sa4 of stopping the supply of the reducing gas G2 to the (NK) reaction tubes U is performed.

[0074] In the unit period T3, step Sa3 of supplying the reducing gas G2 to the catalytic material Q (reaction tubes U) is performed for K reaction tubes U, and step Sa1 of supplying the raw material gas G1 to the catalytic material Q (reaction tubes U) is performed for (NK) reaction tubes U. That is, step Sa1 is performed for the (NK) reaction tubes U in parallel with the execution of step Sa3 for the K reaction tubes U.

[0075] In the unit period T4, step Sa4 of stopping the supply of the reducing gas G2 is performed, and step Sa2 of stopping the supply of the raw material gas G1 to the (NK) reaction tubes U is performed.

[0076] The following describes the operation of the manufacturing equipment 20 during the unit period T1 and the unit period T3. Fig. 5 shows the state of the manufacturing equipment 20 during the unit period T1, and Fig. 6 shows the state of the manufacturing equipment 20 during the unit period T3.

[0077] 5 and 6 show an example where K is 1. Specifically, an example is shown in which K (one) reaction tubes U are defined as the reaction tube U[1], and (NK) reaction tubes U are defined as reaction tubes U[2] to U[N] other than the reaction tube U[1].

[0078] 5, in the unit period T1, the first on-off valve V1[1] is open and the second on-off valve V2[1] is closed for the reaction tube U[1]. Therefore, the raw material gas G1 is supplied to the reaction tube U[1] from the first supply path R1[1], and the used raw material gas G1e is recovered from the recovery path R3[1].

[0079] On the other hand, for the reaction tubes U[2] to U[N], the first on-off valves V1[2] to R1[N] are closed, and the second on-off valves V2[2] to R2[N] are open. Therefore, the reducing gas G2 is supplied to the reaction tubes U[2] to U[N] from the second supply paths R2[2] to R2[N], and ammonia is recovered from the recovery paths R3[2] to R3[N].

[0080] 6, in the unit period T3, for the reaction tube U[1], the first on-off valve V1[1] is closed and the second on-off valve V2[1] is open. Therefore, the reducing gas G2 is supplied to the reaction tube U[1] from the second supply path R2[1], and ammonia is recovered from the recovery path R3[1].

[0081] On the other hand, for the reaction tubes U[2] to U[N], the first on-off valves V1[2] to V1[N] are open, and the second on-off valves V2[2] to V2[N] are closed. Therefore, the raw material gas G1 is supplied to the reaction tubes U[2] to U[N] from the first supply paths R1[2] to R1[N], and the used raw material gas G1e is discharged from the recovery paths R3[2] to R3[N].

[0082] The control device 30 of the second embodiment comprehensively controls the manufacturing apparatus 20, thereby causing the manufacturing apparatus 20 to perform the above-mentioned manufacturing process for each of the N reaction tubes U[1] to U[N]. The first on-off valve V1[n] and the second on-off valve V2[n] are switched between open and closed states under the control of the control device 30.

[0083] The second embodiment also achieves the same effects as the first embodiment.

[0084] Here, we consider a configuration (hereinafter referred to as "reference example") in which each step Sa1-Sa4 of the manufacturing process is performed simultaneously across N reaction tubes U[1] to U[N]. In the reference example, while step Sa3 of supplying reducing gas G2 is being performed, it is necessary to stop the supply of exhaust gas to the entire manufacturing apparatus 20. However, when the exhaust gas discharged from the combustor 40 is used as the raw material gas G1, there is a circumstance in which the generation of exhaust gas cannot be stopped while the combustor 40 is operating. Therefore, the reference example is not suitable for the case where exhaust gas is used as the raw material gas G1.

[0085] In contrast, according to the production apparatus 20 of the second embodiment, there are at least one reaction tube U among the N reaction tubes U[1] to U[N] to which the raw material gas G1 is supplied. That is, there is an advantage that ammonia can be produced without stopping the supply of the raw material gas G1 to the entire production apparatus 20. The configuration of the second embodiment is particularly suitable when exhaust gas is used as the raw material gas G1. However, the present invention also includes reference examples.

[0086] Furthermore, according to the production apparatus 20 of the second embodiment, since it is equipped with N reaction tubes U[1] to U[N], it is possible to sequentially introduce the reducing gas G2 into the reaction tube U in which the storage capacity of the catalytic material Q has become insufficient, thereby generating ammonia and recovering the storage capacity. Therefore, it is possible to repeatedly use the catalytic material Q. Furthermore, it is possible to operate the production apparatus 20 without leaking NOx to the downstream stage.

[0087] The manufacturing method according to the second embodiment is a method of repeatedly executing a manufacturing process including a first step (step Sa1) of supplying a raw material gas G1 (exhaust gas) to the reaction tube U[n] for each of N reaction tubes U, whereby NOx in the raw material gas G1 is occluded by the catalytic material Q, and a second step (step Sa3) of generating and recovering ammonia from the NOx occluded by the catalytic material Q by supplying a reducing gas G2 to the reaction tube U[n] after stopping the supply of the raw material gas G1, and executing the second step for (NK) reaction tubes U while executing the first step for K reaction tubes U, and executing the first step for (NK) reaction tubes U while executing the second step for K reaction tubes U.

[0088] The configuration of the manufacturing apparatus 20 according to the second embodiment is not limited to the above example, as long as it can execute the above manufacturing method. In addition, the reaction tube U divided into K pieces and the reaction tube U divided into (NK) pieces may be different for each manufacturing process.

[0089] [Third embodiment] 7 is a configuration diagram of a manufacturing unit 100 according to the third embodiment. The manufacturing unit 100 according to the third embodiment includes a manufacturing device 20 and a control device 30, similar to the second embodiment.

[0090] The manufacturing apparatus 20 of the third embodiment, like the second embodiment, is equipped with 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] for each reaction tube U[n], and is also equipped with an exhaust path R4[n], a third on-off valve V3[n], and a fourth on-off valve V4[n]. That is, the manufacturing apparatus 20 of the third embodiment is configured by adding N exhaust paths R4[1] to R4[N], N third on-off valves V3[1] to V3[N], and N fourth on-off valves V4[1] to V4[N] to the manufacturing apparatus 20 of the second embodiment.

[0091] The exhaust path R4[n] is a flow path for recovering the raw material gas G1 from the reaction tube U[n]. The used raw material gas G1e after passing through the catalyst material Q is recovered from the exhaust path R4[n]. Specifically, the exhaust path R4[n] is a tubular member, and its upstream side is connected to the reaction tube U[n].

[0092] The third on-off valve V3[n] is a valve that opens and closes the recovery line R3[n]. That is, the third on-off valve V3[n] switches the recovery line R3[n] between open and closed. When the raw material gas G1 is supplied to the reaction tube U[n], the third on-off valve V3[n] is closed, and when the reducing gas G2 is supplied to the reaction tube U[n], the third on-off valve V3[n] is open.

[0093] The fourth on-off valve V4[n] is a valve that opens and closes the exhaust passage R4[n]. That is, the fourth on-off valve V4[n] switches the exhaust passage R4 between open and closed states. When the raw material gas G1 is supplied to the reaction tube U[n], the fourth on-off valve V4[n] is in an open state, and when the reducing gas G2 is supplied to the reaction tube U[n], the fourth on-off valve V4[n] is in a closed state.

[0094] The third on-off valve V3[n] and the fourth on-off valve V4[n] are switched between open and closed states under the control of the control device 30.

[0095] As can be understood from the above description, in the third embodiment, when step Sa1 (first step) in FIG. 4 is performed for the reaction tube U[n], the third on-off valve V3[n] is closed and the fourth on-off valve V4[n] is opened, and when step Sa3 (second step) in FIG. 4 is performed for the reaction tube U[n], the third on-off valve V3[n] is opened and the fourth on-off valve V4[n] is closed.

[0096] Hereinafter, the operation of the manufacturing apparatus 20 according to the third embodiment will be described in the unit period T1 and the unit period T3 in Fig. 4. Fig. 8 shows the state of the manufacturing apparatus 20 in the unit period T1, and Fig. 9 shows the state of the manufacturing apparatus 20 in the unit period T3.

[0097] Similarly to Fig. 5 and Fig. 6 , Fig. 8 and Fig. 9 also illustrate the case where K (one) reaction tubes U are defined as the reaction tube U[1] and (N-K) reaction tubes U are defined as reaction tubes U[2] to U[N] other than the reaction tube U[1].

[0098] 8, in the unit period T1, as in the second embodiment, the first on-off valve V1[1] is open and the second on-off valve V2[1] is closed for the reaction tube U[1]. Therefore, the source gas G1 is supplied from the first supply path R1[1] to the reaction tube U[1].

[0099] Furthermore, in the unit period T1 of the third embodiment, for the reaction tube U[1], the fourth on-off valve V4[1] is in an open state, and the third on-off valve V3[1] is in a closed state. That is, the raw material gas G1 is supplied to the reaction tube U[1], and the used raw material gas G1e is discharged from the exhaust path R4[1].

[0100] On the other hand, for the reaction tubes U[2] to U[N], the first on-off valves V1[2] to V1[N] are closed and the second on-off valves V2[2] to V2[N] are open, as in the second embodiment. Therefore, the reducing gas G2 is supplied to the reaction tubes U[2] to U[N] from the second supply paths R2[2] to R2[N].

[0101] Furthermore, in the unit period T1 of the third embodiment, for the reaction tubes U[2] to U[N], the fourth on-off valves V4[2] to V4[N] are closed, and the third on-off valves V3[2] to V3[N] are open. That is, the reducing gas G2 is supplied to the reaction tubes U[2] to U[N], and ammonia is released and recovered from the recovery paths R3[2] to R3[N].

[0102] 9, in the unit period T3, as in the second embodiment, the second on-off valve V2[1] is in an open state and the first on-off valve V1[1] is in a closed state for the reaction tube U[1]. Therefore, the reducing gas G2 is supplied to the reaction tube U[1] from the second supply path R2[1].

[0103] Furthermore, in the unit period T3 of the third embodiment, for the reaction tube U[1], the third on-off valve V3[1] is in an open state, and the fourth on-off valve V4[1] is in a closed state. That is, the reducing gas G2 is supplied to the reaction tube U[1], and ammonia is released and recovered from the recovery line R3[1].

[0104] On the other hand, for the reaction tubes U[2] to U[N], the second on-off valves V2[2] to V2[N] are closed and the first on-off valves V1[2] to V1[N] are open, as in the second embodiment. Therefore, the source gas G1 is supplied to the reaction tubes U[2] to U[N] from the first supply paths R1[2] to R1[N].

[0105] Furthermore, in the unit period T3 of the third embodiment, for the reaction tubes U[2] to U[N], the third on-off valves V3[2] to V3[N] are closed, and the fourth on-off valves V4[2] to V4[N] are open. That is, the source gas G1 is supplied to the reaction tubes U[2] to U[N], and the used source gas G1e is released from the exhaust paths R4[2] to R4[N].

[0106] As can be understood from the above explanation, in the manufacturing apparatus 20 according to the third embodiment, when the first process (step Sa1) is performed, the third on-off valve V3[n] is closed and the fourth on-off valve V4[n] is open, and when the second process (step Sa3) is performed, the third on-off valve V3[n] is open and the fourth on-off valve V4[n] is closed.

[0107] In the third embodiment, the reaction tube U[n] is provided with an exhaust path R4[n] separate from the recovery path R3[n], so that the used raw material gas G1e and ammonia can be recovered through separate paths.

[0108] In the first embodiment, the manufacturing apparatus 20 may also be configured to have an exhaust path R4 separate from the recovery path R3.

[0109] [Catalyst materials] An example of a catalyst material that can be suitably used in the production apparatus and production method according to the present invention will be described in detail below.

[0110] The catalytic material includes a noble metal, at least one of an alkali metal and an alkaline earth metal, and an oxide support.

[0111] Examples of oxide supports used in catalytic materials include Al2O3, CeO2, TiO2, ZrO2, SiO2, MgO, CaO, LaAlO3, etc. From the viewpoint of improving catalytic activity, one or more of Al2O3, CeO2, TiO2, and ZrO2 are preferred.

[0112] The precious metal is contained in the catalyst material in a state where it is supported on the surface of an oxide support or in a state where it is contained inside the oxide support. Here, the state where it is contained inside the oxide support refers to a state where particulate precious metal is encapsulated inside spherical particles of the oxide support to form a composite.

[0113] In the present invention, the noble metal may be contained in the oxide support as a noble metal alone, or as a noble metal compound containing the noble metal, or both. In the following description, the term "noble metal" includes both the noble metal alone and the noble metal in a noble metal compound.

[0114] The noble metal (noble metal element) contained in the oxide support is one or more of gold, silver, platinum, palladium, rhodium, iridium, ruthenium, osmium, and rhenium. When the noble metal is contained in the oxide support as a noble metal compound, the noble metal compound is one or more of these noble metal elements or oxides. From the viewpoint of improving catalytic activity, one or more noble metals selected from platinum, palladium, rhodium, and iridium are preferred, and one or more noble metals selected from platinum and rhodium are more preferred. Note that a plurality of each noble metal may be contained in the oxide support.

[0115] The average particle size of the noble metal is, for example, 0.1 to 100 nm, and preferably 10 to 50 nm. By setting the average particle size of the noble metal and noble metal compound within the above range, it is possible to achieve both oxidation reaction characteristics of the gas being passed through and durability of the catalyst.

[0116] The average particle size of the noble metal is the mode diameter determined by measuring the particle sizes of a predetermined number of particles (for example, 100 particles) through observation with a transmission electron microscope.

[0117] The content of the noble metal (noble metal element in the catalyst material) is 0.01 to 20 mass % of the entire catalyst material, preferably 0.05 to 15.0 mass %, and more preferably 0.1 to 10.0 mass %. By keeping the content of the noble metal within the above range, the catalytic activity can be improved. Furthermore, the amount of expensive noble metal used can be reduced.

[0118] The alkali metal and alkaline earth metal are contained in the catalyst material in a state supported on the surface of an oxide support. When a noble metal is contained inside the oxide support, the alkali metal and alkaline earth metal are supported on the surface of the oxide support in which the noble metal is composited.

[0119] In the present invention, the alkali metal and alkaline earth metal are typically supported on the oxide support as a compound containing at least one of the alkali metal and alkaline earth metal (hereinafter referred to as "alkali metal-alkaline earth metal compound"). However, the present invention does not exclude the configuration in which the alkali metal or alkaline earth metal is supported on the oxide support as a single element.

[0120] The alkali metal and alkaline earth metal compounds supported on the oxide carrier include, for example, oxides, peroxides, carbonates, hydroxides, etc. of alkali metals and alkaline earth metals.

[0121] When the alkali metal / alkaline earth metal compound contains multiple alkali metals and alkaline earth metals, two or more alkali metals may be selected, two or more alkaline earth metals may be selected, or one or more alkali metals and one or more alkaline earth metals may be selected. One or more alkali metal / alkaline earth metal compounds may be supported on an oxide support.

[0122] The alkali metal used in the alkali metal / alkaline earth metal compound is one or more of lithium, sodium, potassium, rubidium, cesium, and francium. From the viewpoint of improving the efficiency of reducing nitrogen oxides, one or more of lithium, potassium, sodium, and cesium are preferred, and one or more of potassium and sodium are more preferred.

[0123] The alkaline earth metal used in the alkali metal-alkaline earth metal compound is one or more of beryllium, magnesium, calcium, strontium, barium, and radium. From the viewpoint of improving the efficiency of nitrogen oxide reduction, one or more of magnesium, calcium, strontium, and barium are preferred, and one or more of calcium and barium are more preferred.

[0124] The total content of alkali metals and alkaline earth metals (alkali metal elements and alkaline earth metal elements in the catalyst material) is 0.1 to 50.0 mass %, preferably 0.5 to 40.0 mass %, and more preferably 1.0 to 30.0 mass % of the total catalyst material. By keeping the alkali metal and alkaline earth metal contents within the above ranges, it is possible to improve the efficiency of reducing nitrogen oxides while maintaining a uniformly arranged pore structure.

[0125] The specific surface area of ​​the catalyst material is, for example, 10 to 350 m 2 / g, preferably 50 to 330m 2 / g, and more preferably 150 to 300m2 / g. A catalyst material having a specific surface area within the above range can, for example, adsorb gases (such as nitrogen oxides) with high efficiency. The specific surface area of ​​the catalyst material is measured by the BET multipoint method.

[0126] The mode of the pore size distribution of the catalyst material is, for example, 1 to 200 nm, preferably 1 to 50 nm, and more preferably 2 to 20 nm. A catalyst material having a mode of the pore size distribution within the above range can adsorb, for example, gases (such as nitrogen oxides) with high efficiency.

[0127] The pore volume of the catalyst material is, for example, 0.1 to 1.5 cm 3 / g, preferably 0.3 to 1.2 cm 3 / g, and more preferably 0.5 to 0.9 cm 3 / g. A catalyst material having an average pore diameter and pore volume within the above ranges can adsorb, for example, gases (such as nitrogen oxides) with high efficiency.

[0128] The mode of the pore size distribution in the catalyst material is measured, for example, by the NLDFT method using gas adsorption. The pore volume of the catalyst material is also measured, for example, by gas adsorption.

[0129] Hereinafter, a particularly preferred embodiment of a catalyst material (hereinafter referred to as a "composite catalyst material") will be described among catalyst materials containing a noble metal, at least one of an alkali metal and an alkaline earth metal, and an oxide support.

[0130] The composite catalyst material contains Al2O3 as an oxide support. The precious metal is contained within the Al2O3 (i.e., composited with the Al2O3), and the alkali metal and alkaline earth metal are supported on the Al2O3 containing the precious metal. Details of the Al2O3 (content, etc.) are as described above for the oxide support. Similarly, details of the alkali metal and alkaline earth metal are as described above.

[0131] In the following description, "Al2O3" will be referred to as "porous alumina", and porous alumina containing a noble metal therein will be referred to as "noble metal-containing porous alumina".

[0132] An example of a method for producing a composite catalyst material will be described below. In summary, the composite catalyst material according to the present invention is produced by synthesizing porous alumina (oxide support) containing a noble metal and then supporting an alkali metal or alkaline earth metal on the oxide support.

[0133] <1> Preparation of precursor solution The noble metal-containing precursor solution (hereinafter simply referred to as "precursor solution") is a solution containing an alumina source, a noble metal source, an amphiphilic organic molecule, an acid, and a solvent.

[0134] Used in precursor solutions The alumina source (aluminum compound) used is one that becomes a transition alumina (alumina with a crystal structure other than α) such as γ-alumina upon calcination. Specific examples of the alumina source include aluminum hydroxide, aluminum nitrate, aluminum sulfate, aluminum chloride (including hydrates), and aluminum alkoxides, with aluminum alkoxides being preferred. Examples of aluminum alkoxides include aluminum tri-sec-butoxide, aluminum tri-n-butoxide, aluminum tri-tert-butoxide, aluminum tri-iso-propoxide, aluminum tri-ethoxide, and aluminum tri-phenoxide. Among these, aluminum chloride (including hydrates), aluminum tri-sec-butoxide, and aluminum tri-n-butoxide are preferred, with aluminum tri-sec-butoxide being particularly preferred, from the standpoints of reactivity to hydrolysis, availability, and raw material cost.

[0135] Examples of the noble metal source contained in the precursor solution include oxides, hydroxides, chlorides, carbonates, acetates, nitrates, oxalates, phosphates, chloride complexes, etc. of one or more of gold, silver, platinum, palladium, rhodium, iridium, ruthenium, osmium, and rhenium. From the viewpoint of improving catalytic activity, it is preferable to use a noble metal source of one or more of platinum, palladium, rhodium, and iridium.

[0136] Examples of platinum sources that can be used include inorganic platinum compounds such as chloroplatinic acid (including hydrates), dinitrodiammine platinum, hexahydroxyplatinic acid, platinous chloride, platinic chloride, tetraammineplatinum dichloride, potassium tetrachloroplatinate, and potassium hexachloroplatinate, 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-cyclohexanediaminedichloroplatinum, and trans-l-cyclohexanediaminedichloroplatinum. These may be used alone or in combination. Among these, chloroplatinic acid (including hydrate) or bis(acetylacetonato)platinum is particularly preferred from the viewpoint of solubility in the solvent when preparing the precursor solution.

[0137] Examples of palladium sources include palladium chloride, palladium acetate, tetrakistriphenylphosphinepalladium, tris(dibenzylideneacetone)dipalladium, and allylpalladium chloride dimer. Examples of ligands include bis[2-(diphenylphosphino)phenyl]ether (DPEphos), triphenylphosphine, 1,1'-bis(diphenylphosphino)ferrocene (dppf), 4,5'-bis(diphenylphosphino)-9,9'-dimethylxanthene (Xantphos), and 1,3-di-tert-butylimidazolium. These may be used alone or in combination.

[0138] Examples of rhodium sources 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.

[0139] Examples of iridium sources include iridium chloride, iridium sulfate, iridium nitrate, iridium nitrite, ammonium hexachloroiridate, hexachloroiridate n-hydrate, chlorocarbonylbis(triphenylphosphine)iridium, sodium iridium chloride n-hydrate, etc. These may be used alone or in combination.

[0140] The amphiphilic organic molecules used in the precursor solution may be one or more of polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymers (trade name: Pluronic (registered trademark)), alkylammonium salts, polystyrene-polyethylene oxide block copolymers, etc. Among these, from the viewpoint of forming a regularly arranged porous structure, at least one of polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymers and polystyrene-polyethylene oxide block copolymers is particularly preferred, with Pluronic P123 and F127 being more preferred.

[0141] The pore size of porous alumina varies significantly depending on the type of amphiphilic organic molecule. When polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer is used as the amphiphilic organic molecule, the mode of the pore size distribution is 2 to 30 nm. Furthermore, when polystyrene-polyethylene oxide block copolymer is used as the amphiphilic organic molecule, the mode of the pore size distribution is 25 to 200 nm (see Bulletin of the Chemical Society of Japan, 2019, 92, 1859-1866, and Dalton Transactions, 2021, 50, 7191-7197).

[0142] The acid used in the precursor solution may be an inorganic acid such as hydrochloric acid, sulfuric acid, or nitric acid, or an organic acid such as carboxylic acid or sulfonic acid. Among these, from the viewpoint of forming a regularly arranged porous structure, it is particularly preferable that the precursor solution contains at least one of hydrochloric acid and nitric acid.

[0143] The solvent used in the precursor solution may be alcohol, ether, water, ketone, or the like. In particular, various alcohols, including ethanol, methanol, n-butanol, sec-butanol, tert-butanol, n-propanol, and isopropanol, can be used. Among these, ethanol is particularly preferred from the viewpoint of optimizing the evaporation rate of the solvent to form a regular porous structure.

[0144] The content of the alumina source (aluminum compound) in the precursor solution is 5 to 25 mass %, preferably 8 to 20 mass %, and more preferably 10 to 15 mass %.

[0145] The content of the noble metal source in the precursor solution is 0.01 to 0.20 mass %, preferably 0.03 to 0.20 mass %, and more preferably 0.05 to 0.10 mass %.

[0146] The content of the amphiphilic organic molecule in the precursor solution is 1 to 20% by mass, preferably 2 to 15% by mass, and more preferably 3 to 10% by mass.

[0147] The content of the acid in the precursor solution is 0.1 to 3.0% by mass, preferably 0.3 to 2.0% by mass, and more preferably 0.5 to 1.5% by mass.

[0148] The content of the solvent in the precursor solution is 50 to 93 mass %, preferably 60 to 90 mass %, and more preferably 70 to 80 mass %.

[0149] An example of a specific method for preparing the precursor solution is as follows (1) to (3).

[0150] (1) After adding the amphiphilic organic molecule to a solvent, a noble metal source is further added. (2) An aluminum source is added to a solvent to prepare a dispersion. While stirring the dispersion, an acid is added dropwise over a predetermined period of time (e.g., 10 minutes or more). The dispersion is stirred for a predetermined period of time (e.g., 3 hours). (3) The dispersion liquid of (2) is added to the solution prepared in (1) to prepare a precursor solution.

[0151] <2> Synthesis of porous alumina containing noble metals An example of a method for synthesizing the noble metal-containing porous alumina is as follows (1) and (2).

[0152] (1) A precursor (powder) of the noble metal-containing porous alumina is recovered from the precursor solution. First, the solvent and water are removed from the precursor solution by drying. The method for drying the precursor solution is not particularly limited, but examples include one or a combination of two or more of any known methods such as spray drying, freeze drying, heat drying, hot air drying, reduced pressure drying, and natural drying. Among these, spray drying is particularly preferred from the viewpoints of productivity and reproducibility. The precursor solution is dried, and the precursor (powder) of the noble metal-containing porous alumina is recovered.

[0153] (2) The recovered precursor is calcined to synthesize a noble metal-containing porous alumina. Calcining the precursor removes the amphiphilic organic molecules that served as pore templates, resulting in porosity, while also thermally decomposing the noble metal source and crystallizing the alumina. The disappearance of the amphiphilic organic molecules results in a porous structure with regularly arranged pores. The precursor is calcined by first maintaining the desired temperature (e.g., 800-900°C) under a nitrogen stream for a predetermined time (e.g., 1-3 hours), and then maintaining the same temperature under an oxygen stream for an additional predetermined time (e.g., 2-3 hours). It is preferable to increase the temperature stepwise (e.g., 1-3°C per minute) until the desired temperature is reached under a nitrogen stream.

[0154] <3> Alkali metal and alkaline earth metal loading At least one of an alkali metal and an alkaline earth metal is supported on the synthesized noble metal-containing porous alumina as an alkali metal-alkaline earth metal compound.

[0155] The alkali metals and alkaline earth metals used in the present invention are as described above.

[0156] To support alkali metals and alkaline earth metals on precious metal-containing porous alumina, compounds containing at least one of alkali metals and alkaline earth metals, such as acetates, nitrates, carbonates, hydroxides, halides, oxides, and hydrides (hereinafter referred to as "precursor compounds"), are used. Among these, at least one of acetates and nitrates is preferred from the viewpoints of solubility and thermal decomposition temperature. Furthermore, the precursor compounds are converted into alkali metal / alkaline earth metal compounds by thermal decomposition upon heating.

[0157] Examples of methods for supporting alkali metals and alkaline earth metals on noble metal-containing porous alumina are as follows (1) to (3): For example, alkali metals and alkaline earth metals are supported on noble metal-containing porous alumina by impregnation.

[0158] (1) The noble metal-containing porous alumina is dispersed in distilled water, and an aqueous solution of the precursor compound is added dropwise to the dispersion while vigorously stirring.

[0159] The aqueous solution of the precursor compounds is added dropwise so that the content of alkali metal and alkaline earth metal elements in the composite catalyst material is, for example, 0.1 to 50 mass %, preferably 0.5 to 40 mass %, and more preferably 1 to 30. By adding the aqueous solution of the precursor compounds dropwise so that the mass ratio of alumina to alkali metal / alkaline earth metal compounds in the noble metal-containing porous alumina is within the above range, it is possible to improve the nitrogen oxide absorption characteristics and reduction efficiency.

[0160] (2) The dispersion liquid of (1) is heated under reduced pressure to remove the distilled water, thereby obtaining a powder. For example, the distilled water is removed from the dispersion liquid by distillation under reduced pressure at 30 to 80°C.

[0161] (3) The powder obtained in (2) is dried and then calcined to obtain the composite catalyst material of the present invention. The powder obtained in (2) is dried, for example, at 80 to 120°C for 6 to 20 hours. The dried powder is calcined, for example, in a tubular furnace at 400 to 700°C for 2 to 5 hours.

[0162] The composite catalyst material is produced by the above-described production method. The production method according to the present invention has the advantage that the composite catalyst material can be produced in a short period of time with high productivity, compared to, for example, a method in which a precursor solution is spread in a container such as a petri dish and dried at a predetermined temperature for several days.

[0163] By producing a composite catalyst material using the above-described production method, the mode of the pore size distribution becomes 1 to 200 nm in diameter. Furthermore, a composite catalyst material with a mode of 1 to 200 nm in diameter in the pore size distribution allows smooth diffusion and occlusion of nitrogen oxides in the gas phase. Furthermore, the pore size distribution of the composite catalyst material can be controlled depending on the type of amphiphilic organic molecule selected and the synthesis conditions, and the balance between the diffusion of nitrogen oxides in the pores and the specific surface area of ​​the composite catalyst material can also be adjusted.

[0164] In the composite catalyst material according to the present invention, by supporting at least one of an alkali metal and an alkaline earth metal on the precious metal-containing porous alumina, it is possible to improve the adsorption amount of nitrogen oxides and the efficiency of reducing nitrogen oxides.

[0165] The composite catalyst material according to the present invention can maintain a regularly arranged pore structure, and therefore can maintain a high level of specific surface area.

[0166] The composite catalyst material produced by the above-described production method is irradiated with X-rays, and at least one of a diffraction peak and a scattering peak corresponding to a lattice spacing of 1 to 200 nm is observed. The diffraction peak is measured by X-ray diffraction. The scattering peak is measured by small-angle X-ray scattering. Specifically, in the measurement by X-ray diffraction, one or more diffraction peaks corresponding to a lattice spacing of 1 to 200 nm are observed, and in the measurement by small-angle X-ray scattering, one or more scattering peaks corresponding to a lattice spacing of 1 to 200 nm are observed.

[0167] It is desirable to use Fe as the tube that generates the X-rays, as the wavelength of the characteristic X-rays is long and the diffraction or scattering peaks appear at high angles, making them easy to detect, and their intensity is sufficient for the detector, but tubes made of other elements (such as Cu) are also acceptable. The presence of these diffraction and scattering peaks indicates the regular arrangement of pores in the porous structure.

[0168] A composite catalyst material in which one or more diffraction or scattering peaks corresponding to lattice spacings of 1 to 200 nm are observed can be expected to have a high specific surface area and uniform gas diffusion behavior within the pores due to the presence of a regular arrangement of pores with uniform pore diameters in the porous structure.

[0169] As can be understood from the above explanation, the composite catalyst material is a nanocomposite material particularly containing a precious metal, at least one of an alkali metal and an alkaline earth metal, and porous alumina, wherein the precious metal is contained within the porous alumina, and the alkali metal and alkaline earth metal are supported on the porous alumina containing the precious metal therein, and the mode in the pore size distribution is preferably a diameter of 1 to 200 nm. The composite catalyst material described above enables highly efficient production of ammonia. The porous alumina used in the composite catalyst material is preferably particulate porous alumina (mesoporous alumina) having a crystalline structure, and this porous alumina has a regularly arranged porous structure. [Example]

[0170] The catalyst material used in the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0171] Example 1 Example 1 is a catalyst material in which barium is supported on platinum-containing porous alumina. The mass ratio of platinum, barium, and porous alumina (platinum:barium:porous alumina) is 1:10:100.

[0172] Example 1 is the following <1> - <3> It was prepared as follows.

[0173] <1> Preparation of platinum-containing porous alumina precursor solution (1) 15 g of Pluronic P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer) was weighed into a stoppered Erlenmeyer flask as an amphiphilic organic molecule, 120 mL of ethanol was added, and 0.135 g of chloroplatinic acid hexahydrate was then added, followed by stirring using a magnetic stirrer and a stirring bar.

[0174] (2) 60 mL of ethanol and 24.6 g of aluminum tri-sec-butoxide were added to a three-neck flask to prepare a dispersion. While continuing to stir the dispersion, concentrated hydrochloric acid (14.5 mL) was added dropwise over 10 minutes, and the mixture was stirred for 3 hours.

[0175] (3) The dispersion liquid of (2) was added to the solution of (1) to prepare a platinum-containing porous alumina precursor solution.

[0176] <2> Synthesis of platinum-containing porous alumina (1) The platinum-containing porous alumina precursor solution was introduced into a spray dryer (Yamato Scientific ADL311), and the precursor solution was sprayed and the water content, including ethanol, was removed by hot air drying. The inlet temperature of the spray dryer was set to 170°C. The platinum-containing porous alumina precursor was then recovered using a cyclone separator.

[0177] (2) The precursor recovered by the cyclone separator was calcined in a tubular furnace to remove the Pluronic P123 that formed the pores, and to make it porous. The platinum compound (chloroplatinic acid hexahydrate) was thermally decomposed and alumina crystallized. The calcination was carried out by heating the material to 850°C at a rate of 2°C per minute under a nitrogen stream, holding it at that temperature for 1 hour, and then holding it at that temperature for another 2 hours under an oxygen stream.

[0178] <3> Barium loading on platinum-containing porous alumina

[0179] As described above, barium is supported on the 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, or barium hydroxide).

[0180] Specifically, the barium compound was supported on the platinum-containing porous alumina by an impregnation method.

[0181] (1) Platinum-containing porous alumina was dispersed in distilled water, and an aqueous solution of barium acetate was added dropwise to the dispersion while vigorously stirring. The barium acetate solution was added dropwise so that the mass ratio of the platinum-containing porous alumina to the barium in the aqueous solution (platinum-containing porous alumina:barium) was 101:10.

[0182] (2) After shaking the dispersion from (1) for 1 hour, the dispersion was transferred to an eggplant-shaped flask, and the distilled water was removed under reduced pressure at 60°C using a rotary evaporator to recover the powder. The powder was further dried at 110°C for 10 hours or more, and then calcined in a tubular furnace at 500°C for 3 hours (heating rate: 10°C per minute, under a dry air stream) to obtain a catalyst material consisting of platinum-containing porous alumina carrying a barium compound.

[0183] The average particle size of the platinum (nanoparticles) in the platinum-containing porous alumina was 24 nm. The average particle size of platinum was determined by observing with a transmission electron microscope using a JEOL JEM-2010, measuring the size of 100 noble metal nanoparticles, and determining the mode diameter of the particle size.

[0184] <Example 2> Example 2 is a catalyst material in which calcium is supported on platinum-containing porous alumina, with the mass ratio of platinum to calcium to porous alumina (platinum:calcium:porous alumina) being 1:10:100.

[0185] The procedure was the same as in Example 1, except that an aqueous solution of calcium acetate monohydrate was used instead of the aqueous solution of barium acetate.

[0186] In Example 2, calcium is also supported as a calcium compound on platinum-containing porous alumina by impregnation support.

[0187] Examples 1 and 2 are examples of the above-mentioned composite catalyst material.

[0188] Example 3 Example 3 is a material in which both platinum (nanoparticles) and barium are supported on commercially available gamma alumina (manufactured by Strem Chemicals). Example 3 was prepared as follows (1)-(4).

[0189] (1) Gamma alumina was pretreated in a dry air stream at 500°C for 2 hours. (2) An ethanol solution of chloroplatinic acid hexahydrate was used and mixed with the gamma alumina of (1) and platinum so that the mass ratio was 100:1. (3) After evaporating the ethanol to dryness, the mixture was calcined in a dry air stream at 600°C for 3 hours to prepare platinum-supported gamma alumina. (4) Barium species were supported on the platinum-supported γ-alumina obtained in (3) in the same manner as in Example 1. The mass ratio of platinum-supported γ-alumina to barium atoms was 101:10.

[0190] Example 4 Example 4 is a material in which both platinum and barium are supported on commercially available CeO2 (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) Example 4 was prepared as follows (1)-(3).

[0191] (1) CeO2 was pretreated in a dry air stream at 500°C for 2 hours. (2) Using a dinitrodiammine platinum nitrate solution and an aqueous solution of barium acetate, the CeO2 in (1) was mixed with platinum and barium atoms in a mass ratio of 100:1:10. (3) (2) was evaporated to dryness, and the resulting powder was dried at 100°C and then calcined at 600°C for 2 hours in a dry air stream to prepare barium and platinum-supported CeO2.

[0192] <Example 5> Example 5 is a material in which platinum is supported on commercially available CeO2 (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) The material is the same as Example 4 except that no barium source is used and the CeO2 and platinum are mixed at a mass ratio of 100:1.

[0193] Example 6 Example 6 is a catalyst material in which calcium is supported on platinum-containing porous alumina. It is the same as Example 2 except that the mass ratio of platinum to calcium to porous alumina (platinum:calcium:porous alumina) is 1:4:100.

[0194] Example 7 Example 7 is a catalyst material in which strontium is supported on platinum-containing porous alumina. The mass ratio of platinum, strontium, and porous alumina (platinum:strontium:porous alumina) is 1:9:100. Example 7 is the same as Example 1, except that an aqueous solution of strontium acetate 0.5 hydrate is used instead of the aqueous solution of barium acetate.

[0195] <Comparative Example 1> Comparative Example 1 is a material in which barium is supported on commercially available gamma alumina (manufactured by Strem Chemicals). It is the same as Example 4 except that no platinum source was used and the gamma alumina and barium were mixed at a mass ratio of 100:10.

[0196] <1> Mode of pore size distribution The mode of the pore size distribution was measured for Examples 1 and 2, which are examples of composite catalyst materials among the catalyst materials used in the present invention. The samples were heated at 110°C for 6 hours under reduced pressure to remove adsorbed moisture and other substances, and then nitrogen adsorption isotherms were measured using a Quantachrome Autosorb-1 or Autosorb-iQ. The pore size distribution was calculated from the adsorption isotherm using the NLDFT method (software: Quantachrome AS1Win; NLDFT method kernel: N2 at 77K on carbon, slit pore, NLDFT equilibrium model), and the mode of the pore size distribution was identified.

[0197] <2> X-ray diffraction measurements The sample (Example 1-2) was subjected to X-ray diffraction measurement using a Rigaku RINT 2100 (Fe radiation source, scanning angle: 0.6 degrees to 12 degrees, scanning speed: 2 degrees per minute) to confirm whether diffraction peaks corresponding to lattice spacings of 1 to 200 nm could be detected.

[0198] <3> Testing the production of ammonia from nitrogen oxides (NOx) The test was carried out using a fixed-bed flow reactor. 100 mg of the sample (Examples 1-7 and Comparative Example 1) was placed in a quartz reaction tube, and both ends were fixed with quartz wool. The gas flow rate was fixed at 100 mL / min throughout the test.

[0199] As a pretreatment step, the sample temperature was raised to 500°C and held in a nitrogen gas stream containing 10% oxygen for 1 hour to remove any remaining moisture or organic matter.

[0200] Next, for the NOx adsorption process, the sample temperature was raised to 300°C and held for 1 hour in a nitrogen gas stream containing 1000 ppm nitric oxide (NO) and 10% oxygen. After that, for the ammonia production process, the sample was held for 1 hour in a nitrogen gas stream containing 1% hydrogen.

[0201] In the second and subsequent tests, the pretreatment process was omitted, and only the NOx adsorption process and ammonia production process were repeatedly tested. The amount of NOx adsorption and ammonia production were quantified using a Thermo Fisher Scientific Nicolet iS 20 infrared spectrophotometer and a PIKE Technologies multi-reflection gas cell.

[0202] Table 1 shows the mode of the pore size distribution and the lattice spacing indicated by the diffraction peaks obtained by X-ray diffraction measurement.

[0203] [Table 1]

[0204] As can be seen from Table 1, in Examples 1 and 2, which are examples of the composite catalyst material, the mode of the pore size distribution was in the diameter range of 1 to 200 nm, and a diffraction peak corresponding to a lattice spacing of 1 to 200 nm was observed. That is, it was confirmed that the pores were regularly arranged in Examples 1 and 2. In Examples 1 and 2, the regular arrangement of the pores is thought to be due to the self-organization of the amphiphilic organic molecules that chemically interacted with the alumina source, followed by the removal of the amphiphilic organic molecules by calcination.

[0205] Table 2 shows the results of a test to produce ammonia from nitrogen oxides (NOx). Table 2 shows the amount of NOx adsorbed, the amount of ammonia produced from NOx, the ammonia yield (amount of ammonia produced / amount of NOx adsorbed), and the maximum NH3 concentration. The amount of NOx adsorbed and the amount of NH3 produced per mass were calculated from the catalyst weight after the ammonia production test.

[0206] [Table 2]

[0207] As shown in Table 2, it was confirmed that ammonia was produced in Examples 1-7, which contained noble metals. In contrast, ammonia was not produced in Comparative Example 1, which did not contain noble metals.

[0208] It can be seen that Examples 1-4, 6, and 7, which contain both a precious metal and at least one of an alkali metal and an alkaline earth metal, have higher ammonia production amounts and maximum ammonia concentrations than Example 5, which contains only a precious metal without containing an alkali metal or alkaline earth metal.

[0209] In particular, in Examples 1, 2, 6, and 7, which are examples of the composite catalyst material, the ammonia yield does not decrease even after the second use, compared to Examples 3 and 4. In particular, in Examples 2, 6, and 7, the ammonia yield increases in the second and third uses compared to the first use. As described above, among catalyst materials, the use of a composite catalyst material in which at least one of an alkali metal and an alkaline earth metal is supported on the surface of precious metal-containing porous alumina makes it possible to repeatedly produce ammonia with high efficiency.

[0210] Moreover, the amount of N2O produced was sufficiently low in Example 4, and in particular, no N2O production was confirmed in Examples 1-3 and 5-7.

[0211] A technology has been proposed for reducing nitrogen oxides (NOx) in exhaust gases to nitrogen using catalytic materials (NSR catalysts). It is known that this process generates ammonia as an intermediate product, as well as NO. However, because NO has a greenhouse effect approximately 300 times that of CO, the less NO produced, the better. However, the amount of NO produced can sometimes be large depending on the catalytic material used.

[0212] By using the composite catalyst material as a catalyst material, it is possible to sufficiently reduce the amount of NO produced and produce ammonia from nitrogen oxides (NOx) (in other words, reduce nitrogen oxides to ammonia). Specifically, when the composite catalyst material is used, the concentration of NO produced together with ammonia is below the measurable concentration range, and even if it is detected, it is approximately 5% or less of the ammonia concentration.

[0213] However, in the production apparatus and production method according to the present invention, any catalyst material can be used, and any known catalyst material can be used as appropriate as long as it is capable of producing ammonia. [Explanation of symbols]

[0214] 20: Manufacturing equipment 30: Control device 40: Combustor 50:Supplier 100: Manufacturing units G1: Raw material gas G1e: Used raw gas G2: Reducing gas K1: 1st common road K2: 2nd common road Q: Catalyst material R1: 1st supply path R2: 2nd supply path R3: Recovery route R4: Exhaust duct U: Reaction tube V1: First shut-off valve V2: Second shut-off valve V3: Third shut-off valve V4: 4th shut-off valve

Claims

1. 1. A unit for producing ammonia, comprising: a reaction tube containing a catalytic material including a precious metal; a first supply passage for supplying an exhaust gas containing NOx and oxygen to the reaction tube; a second supply passage for supplying a reducing gas not containing NOx to the reaction tube; a production apparatus including a recovery line for recovering the produced ammonia from the reaction tube; a control device for controlling the manufacturing apparatus, The control device a first step of supplying the exhaust gas to the catalytic material to cause the catalytic material to occlude NOx in the exhaust gas; a second step of generating and recovering ammonia from the NOx occluded in the catalytic material by supplying the reducing gas to the catalytic material after stopping the supply of the exhaust gas; The reducing gas includes at least one of H 2 , C 3 H 6 , C 3 H 8 and CH 4 . Manufacturing unit.

2. The manufacturing process is carried out repeatedly. The manufacturing unit of claim 1.

3. 1. A unit for producing ammonia, comprising: N (N is a natural number of 2 or more) reaction tubes each containing a catalytic material containing a precious metal; N first supply passages for supplying an exhaust gas containing NOx and oxygen to the N reaction tubes, respectively; N second supply passages for supplying a reducing gas not containing NOx to the N reaction tubes, respectively; a production apparatus including N recovery paths for recovering the ammonia produced from each of the N reaction tubes; a control device for controlling the manufacturing apparatus, The control device For each of the N reaction tubes, a first step in which the exhaust gas is supplied to the reaction tube, thereby occluding NOx in the exhaust gas into the catalytic material; a second step of generating and recovering ammonia from the NOx occluded in the catalytic material by supplying the reducing gas to the reaction tube after stopping the supply of the exhaust gas, and the first step is performed for K (K is a natural number less than N) reaction tubes out of the N reaction tubes, while the second step is performed for (N−K) reaction tubes; while the second step is performed for the K reaction tubes, the first step is performed for the (N−K) reaction tubes; The reducing gas includes at least one of H 2 , C 3 H 6 , C 3 H 8 and CH 4 . Manufacturing unit.

4. The manufacturing apparatus includes: N first on-off valves that open and close the N first supply paths, respectively; N second on-off valves that open and close the N second supply paths, respectively; The control device In the first step, the first on-off valve is opened and the second on-off valve is closed, In the second step, the first on-off valve is closed and the second on-off valve is opened. The manufacturing unit of claim 3.

5. The manufacturing apparatus includes: N exhaust paths for exhausting exhaust gases from the N reaction tubes, respectively; N third on-off valves that open and close the N recovery paths, respectively; N fourth on-off valves that open and close the N exhaust paths, respectively; The control device For each of the N reaction tubes, In the first step, the third on-off valve is closed and the fourth on-off valve is opened, In the second step, the third on-off valve is opened and the fourth on-off valve is closed. The manufacturing unit of claim 3.

6. 1. A method for producing ammonia, comprising: a first step of supplying an exhaust gas containing NOx and oxygen to a catalytic material containing a precious metal, thereby causing the catalytic material to occlude NOx in the exhaust gas; a second step of generating and recovering ammonia from the NOx occluded in the catalytic material by supplying a reducing gas not containing NOx to the catalytic material after stopping the supply of the exhaust gas; The reducing gas includes at least one of H 2 , C 3 H 6 , C 3 H 8 and CH 4 . Manufacturing method.

7. 1. A method for producing ammonia, comprising: A manufacturing apparatus including N (N is a natural number of 2 or more) reaction tubes each containing a catalytic material containing a precious metal, For each of the N reaction tubes, a first step in which exhaust gas containing NOx and oxygen is supplied to the reaction tube, so that NOx in the exhaust gas is occluded by the catalytic material; a second step of generating and recovering ammonia from the NOx occluded in the catalytic material by supplying a reducing gas not containing NOx to the reaction tube after stopping the supply of the exhaust gas; while the first step is performed for K (K is a natural number less than N) reaction tubes out of the N reaction tubes, the second step is performed for (N−K) reaction tubes; while the second step is performed for the K reaction tubes, the first step is performed for the (N−K) reaction tubes; The reducing gas includes at least one of H 2 , C 3 H 6 , C 3 H 8 and CH 4 . Manufacturing method.

8. At least one of the temperature of the exhaust gas and the reducing gas and the temperature of the catalytic material is 150 to 500°C. The method according to claim 6 or 7.

9. The catalytic material includes the noble metal, at least one of an alkali metal and an alkaline earth metal, and an oxide support. The method according to claim 6 or 7.

10. the noble metal is one or more of platinum, palladium, rhodium, and iridium; The content of the noble metal is 0.01 to 20.0 mass % of the entire catalyst material, which is 100 mass %. The method according to claim 6 or 7.

11. the alkali metal is at least one selected from lithium, potassium, sodium, and cesium; the alkaline earth metal is at least one selected from calcium, magnesium, strontium, and barium; The content of the alkali metal and the alkaline earth metal is 0.1 to 50.0 mass % of the entire catalyst material, which is 100 mass %. The method of claim 9.

12. The oxide support is Al ２ O ３ , CeO ２ , TiO ２ and ZrO ２ One or more of the following The method of claim 9.

13. The oxide support is Al ２ O ３ and The noble metal is Al ２ O ３ Contained within The alkali metal and the alkaline earth metal are the Al containing the noble metal therein. ２ O ３ Carried by The method of claim 9.

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