Ammonia production unit, production method and catalyst material

Abstract

A manufacturing unit (100) has a manufacturing device (20) and a control device (30) that controls the manufacturing device (20), the manufacturing device (20) includes a reaction tube (U) that houses a catalyst material (Q) containing a noble metal, a first supply path (R1) for supplying a raw material gas (exhaust gas) (G1) containing NOx and oxygen to the reaction tube (U), a second supply path (R2) for supplying a reducing gas (G2) not containing NOx to the reaction tube (U), and a recovery path (R3) for recovering generated ammonia from the reaction tube (U), and the control device (30) causes the manufacturing device (20) to execute a manufacturing process including a first process of causing NOx in the raw material gas (G1) to be occluded in the catalyst material (Q) by supplying the raw material gas (G1) to the catalyst material (Q), and a second process of generating ammonia from the NOx occluded in the catalyst material (Q) and recovering it by supplying the reducing gas (G2) to the catalyst material (Q) after stopping the supply of the raw material gas (G1).

Description

Technical Field

[0001] This invention relates to a technique for producing ammonia from nitrogen oxides (NOx). Background Technology

[0002] The Haber-Bosch process is a known method for producing ammonia (NH3). In the Haber-Bosch process, nitrogen and hydrogen are used as feedstocks to produce ammonia. However, this process requires high temperature and pressure (400-600°C, 200-400 atmospheres), necessitating a significant energy input.

[0003] On the other hand, in high-temperature combustion equipment, for example, nitrogen oxides (so-called thermal NOx) from combustion are present in the exhaust gas. The nitrogen oxides in the exhaust gas are neutralized and released as nitrogen. Therefore, if ammonia can be generated from the NOx in the exhaust gas, waste can be recycled. Furthermore, if the temperature of the heat engine is increased to improve energy efficiency, the amount of thermal NOx generated may further increase. However, if the generated thermal NOx can be recovered as ammonia, it is also possible to improve the energy efficiency of the heat engine without increasing the amount of nitrogen oxides released.

[0004] Here, as a harmless technology for removing NOx from exhaust gas, the ammonia selective catalytic reduction (NH3-SCR) method, which involves adding ammonia externally as a reducing agent and reducing NOx on a catalyst, is commonly used.

[0005] On the other hand, in the technology of catalyst materials used in automobiles to purify exhaust gases, Non-Patent Document 1 discloses a technology that allows NOx to be temporarily adsorbed (adsorbed) onto the catalyst, then reduced to nitrogen (N2) and released into the atmosphere.

[0006] As a result of clarifying the process for purifying exhaust gases, it was confirmed that a small amount of ammonia is generated within the system as an intermediate product. However, this small amount of ammonia is used as a reducing agent for NOx. Therefore, various techniques for using ammonia generated as an intermediate product as a reducing agent are disclosed.

[0007] For example, Patent Documents 1-3 disclose a technique for generating ammonia as an intermediate product in an internal combustion engine that supplies and combusts fuel under periodic rich / lean combustion conditions. Specifically, after NOx is adsorbed onto a catalyst and concentrated and recovered under lean conditions, the NOx adsorbed onto the catalyst is reduced under controlled rich conditions. Under rich conditions, ammonia is generated. Then, when the conditions become lean again, 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 environment with excess air and reduces NOx in a reducing environment to generate ammonia as an intermediate product. The generated ammonia is also used as a reducing agent for reducing NOx. Further, Patent Document 5 discloses a technology for converting NOx in exhaust gas discharged from a burner into ammonia. The generated ammonia is then reintroduced into the burner and used as a reducing agent for reducing NOx.

[0009] Similarly, Non-Patent Documents 2 and 3 disclose experiments in the catalyst material technology for a simulated lean-burn gasoline engine for automobiles, in which NOx-containing gas is supplied under lean conditions and a reducing gas is supplied under concentrated conditions, thereby confirming the state of nitrogen, nitrous oxide (N2O), and ammonia generated from NOx.

[0010] Furthermore, non-patent documents 4 and 5 disclose the method of simultaneously supplying NOx and reducing gas to a catalyst material under anaerobic conditions to generate ammonia.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent Application Publication No. 2009-103020.

[0014] Patent Document 2: Japanese Patent No. 4740217.

[0015] Patent document 3: Japanese Patent Application Publication No. 2005-111436.

[0016] Patent document 4: Japanese Patent No. 5431677.

[0017] Patent document 5: Japanese Patent Application Publication No. 2020-090949.

[0018] Non-patent literature

[0019] Non-patent literature 1: N. Takahashi et al., Catalysis Today, 27(1996)63.

[0020] Non-patent document 2: P.Koci, S.Bartova, D.Mracek, M.Marek, J.-S.Choi, M.-Y.Kim, JAPihl, WPPartridge, Effective model for prediction of N2O and NH3formation during the regeneration of NOx storage catalyst, Topics inCatalysis, 2013, 56, 118-124.

[0021] Non-patent document 3: D.Mracek, P.Koci, J.-S.Choi, WPPartridge, New operation strategy for driving the selectivity of NOx reduction to N2, NH3 or N2O during lean / rich cycling of a lean NOx trap catalyst, Applied Catalysis B: Environmental 2016, 182, 109-114.

[0022] Non-patent literature 4: C. Asokan, Y. Yang, A. Dang, AB Getsoian, P. Christopher, Low-temperature ammonia production during NO reduction by CO is due to atomicallydispersed rhodium active sites, ACS Catalysis, 2020, 10, 5217-5222.

[0023] Non-patent literature 5: SMPark, M.-Y.Kim, ESKim, H.-S.Han, G.Seo, H2-SCR of NO onPt-MnOx catalysts: Reaction path via NH3 formation, Applied Catalysis A, 2011, 395, 120-128. Summary of the Invention

[0024] The problem that the invention aims to solve

[0025] As stated above, in the technologies of Patent Documents 1-5 and Non-Patent Documents 2-5, the generated ammonia is used as a reducing agent for reducing NOx, without any intention to recycle the generated ammonia as a resource. Considering the above, the objective of this invention is to generate ammonia from NOx and recover it.

[0026] Methods for solving problems

[0027] [1] The manufacturing unit of the present invention is a unit for manufacturing ammonia, wherein the manufacturing unit has a manufacturing apparatus and a control device for controlling the manufacturing apparatus, the manufacturing apparatus comprising: a reaction tube containing a catalyst material comprising a precious metal; a first supply path for supplying exhaust gas containing NOx and oxygen to the reaction tube; a second supply path for supplying a reducing gas free of NOx to the reaction tube; and a recovery path for recovering the generated ammonia from the reaction tube, the control device causing the manufacturing apparatus to perform a manufacturing process comprising: a first step in which NOx in the exhaust gas is adsorbed into the catalyst material by supplying the exhaust gas to the catalyst material; and a second step in which, after stopping the supply of the exhaust gas, ammonia is generated from the NOx adsorbed into the catalyst material by supplying the reducing gas to the catalyst material and then recovered.

[0028] [2] The manufacturing unit as described in [1], wherein the manufacturing process is repeatedly performed.

[0029] [3] Another aspect of the manufacturing unit of the present invention is the manufacturing unit described in [3], which is a unit for producing ammonia, wherein the manufacturing unit has a manufacturing apparatus and a control device for controlling the manufacturing apparatus, the manufacturing apparatus comprising: N (N is a natural number greater than 2) reaction tubes, the N reaction tubes containing a catalyst material containing a precious metal; N first supply paths for supplying exhaust gas containing NOx and oxygen to the N reaction tubes respectively; N second supply paths for supplying reducing gas without NOx to the N reaction tubes respectively; and N recovery paths for recovering the generated ammonia from the N reaction tubes respectively, the control device enabling... The manufacturing apparatus repeatedly performs a manufacturing process for each of the N reaction tubes, the manufacturing process comprising: a first step in which NOx in the exhaust gas is adsorbed onto the catalyst material by supplying the exhaust gas into the reaction tube; and a second step in which, after stopping the supply of the exhaust gas, the NOx adsorbed onto the catalyst material is converted into ammonia and recovered by supplying the reducing gas into the reaction tube; the second step is performed for (NK) reaction tubes while the first step is performed for K (K is a natural number less than N) of the N reaction tubes, and the first step is performed for (NK) reaction tubes while the second step is performed for the K reaction tubes.

[0030] [4] The manufacturing unit as described in [3], wherein the manufacturing apparatus has: N first on / off valves, which respectively open and close the N first supply lines; and N second on / off valves, which respectively open and close the N second supply lines, wherein in the first process, the control device makes the first on / off valves open and the second on / off valves closed, and in the second process, the control device makes the first on / off valves closed and the second on / off valves open.

[0031] [5] The manufacturing unit as described in [3] or [4], wherein the manufacturing apparatus has: N exhaust passages for discharging exhaust gas from the N reaction tubes respectively; N third on / off valves for opening and closing the N recovery passages respectively; and N fourth on / off valves for opening and closing the N exhaust passages respectively, wherein the control device, for each of the N reaction tubes, in the first step, makes the third on / off valve closed and the fourth on / off valve open, and in the second step, the control device, for each of the N reaction tubes, makes the third on / off valve open and the fourth on / off valve closed.

[0032] [6] The manufacturing method of the present invention is a method for manufacturing ammonia, comprising: a first step, wherein the NOx in the exhaust gas containing NOx and oxygen is absorbed in the catalyst material by supplying exhaust gas containing NOx and oxygen to the catalyst material; and a second step, wherein after the supply of the exhaust gas is stopped, a reducing gas without NOx is supplied to the catalyst material to generate ammonia from the NOx absorbed in the catalyst material and the ammonia is recovered.

[0033] [7] Another aspect of the present invention is a method for manufacturing ammonia, wherein, in a manufacturing apparatus having N (N is a natural number greater than 2) reaction tubes respectively containing catalyst materials containing noble metals, a manufacturing process is repeatedly performed for each of the N reaction tubes, the manufacturing process comprising: a first step in which NOx in the exhaust gas containing NOx and oxygen is retained in the catalyst material by supplying the exhaust gas into the reaction tube; and a second step in which, after the supply of the exhaust gas is stopped, ammonia is generated from the NOx retained in the catalyst material by supplying a reducing gas without NOx into the reaction tube and recovering it, the second step being performed for (NK) reaction tubes while the first step is performed for K (K is a natural number less than N) of the N reaction tubes, and the first step being performed for (NK) reaction tubes while the second step is performed for the K reaction tubes.

[0034] [8] The manufacturing method as described in [6] or [7], wherein the reducing gas includes any one or more of H2, C3H6, C3H8 and CH4.

[0035] [9] The manufacturing method as described in [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°C to 500°C.

[0036]

[10] The manufacturing method as described in [6] to [9], wherein the catalyst material comprises: the noble metal; at least one of an alkali metal and an alkaline earth metal; and an oxide support.

[0037]

[11] The manufacturing method as described in [6] to

[10] , wherein the precious metal is one or more of platinum, palladium, rhodium and iridium, the catalyst material as a whole is set to 100% by mass, and the content of the precious metal is 0.01% to 20.0% by mass of the catalyst material as a whole.

[0038]

[12] The manufacturing method as described in

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

[0039]

[13] The manufacturing method as described in

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

[0040]

[14] The manufacturing method as described in

[10] or

[12] , wherein the oxide support is Al2O3, the noble metal is contained within the Al2O3, and the alkali metal and the alkaline earth metal are loaded onto the Al2O3 containing the noble metal.

[0041]

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

[14] , wherein the catalyst material is a nanocomposite material comprising at least one of a noble metal, an alkali metal and an alkaline earth metal, and a porous alumina with regularly arranged pores, wherein the noble metal is contained within the porous alumina, and the alkali metal and the alkaline earth metal are supported on the porous alumina containing the noble metal, and the most frequent value in the pore size distribution of the catalyst material is a diameter of 1 nm to 200 nm.

[0042] The effects of the invention

[0043] The manufacturing apparatus and method according to the present invention aim to reduce the influence of coexisting gases in the feed gas (typically exhaust gas), generate ammonia from NOx and recover it. Attached Figure Description

[0044] Figure 1 This is a configuration diagram of the manufacturing unit according to the first embodiment.

[0045] Figure 2 This is a flowchart of the processing performed by the manufacturing apparatus of the first embodiment.

[0046] Figure 3 This is a configuration diagram of the manufacturing unit according to the second embodiment.

[0047] Figure 4 This is a flowchart of the processing performed by the manufacturing apparatus according to the second embodiment.

[0048] Figure 5 This is a configuration diagram used to illustrate the operation of the manufacturing apparatus according to the second embodiment.

[0049] Figure 6This is a configuration diagram used to illustrate the operation of the manufacturing apparatus according to the second embodiment.

[0050] Figure 7 This is a configuration diagram of the manufacturing unit according to the third embodiment.

[0051] Figure 8 This is a configuration diagram used to illustrate the operation of the manufacturing apparatus according to the third embodiment.

[0052] Figure 9 This is a configuration diagram used to illustrate the operation of the manufacturing apparatus according to the third embodiment. Detailed Implementation

[0053] [First Implementation Method]

[0054] Figure 1 This is a configuration diagram of a manufacturing unit 100 for manufacturing ammonia according to an example of the first embodiment. The manufacturing unit 100 includes a manufacturing apparatus 20 and a control device 30 for controlling the manufacturing apparatus 20.

[0055] Manufacturing apparatus 20 is an apparatus for generating ammonia from NOx (e.g., NO, NO2, N2O, and N2O3) in a gas. In general, manufacturing apparatus 20 performs a process (hereinafter referred to as the "manufacturing process") in which, after supplying a NOx-containing feed gas G1 to catalyst material Q, the supply of feed gas G1 is stopped and a reducing gas G2 is supplied to catalyst material Q to produce ammonia.

[0056] Catalyst material Q is a catalyst that adsorbs and reduces NOx in the feed gas G1. It should be noted that details about catalyst material Q will be described later.

[0057] Feed gas G1 is a gas containing NOx and oxygen. For example, exhaust gas is suitable for use as feed gas G1. Exhaust gas is gas discharged from various facilities (such as waste incineration facilities, high-temperature combustion facilities like thermal power plants, and factories). The concentration of NOx in feed gas G1 is, for example, 100 ppm to 2%. The concentration of oxygen in feed gas G1 is, for example, 1% to 20%. In addition to NOx and oxygen, feed gas G1 may also contain CO2, water vapor, nitrogen, etc.

[0058] The reducing gas G2 is a gas that reduces NOx adsorbed on the catalyst material Q. Specifically, the reducing gas G2 is a gas containing a reducing agent but free of NOx. It should be noted that the NOx-free nature of the reducing gas G2 also includes cases where it contains NOx at extremely low concentrations (e.g., below 10 ppm) without affecting the reduction of NOx adsorbed on the catalyst material Q or causing no environmental impact. However, it is preferable to use a reducing gas G2 that is completely free of NOx (NOx concentration is 0%). From the viewpoint of improving ammonia production efficiency, one or more of H2, C3H6, C3H8, and CH4 are preferred as the reducing agent. It should be noted that from the viewpoint of stably generating ammonia, it is preferable that the reducing gas G2 is not a gas produced from the feed gas G1.

[0059] 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 also contain water vapor, nitrogen, etc.

[0060] like Figure 1 As shown, the manufacturing apparatus 20 of the first embodiment includes 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.

[0061] The reaction tube U is a hollow structure that contains the catalyst material Q.

[0062] The first supply path R1 is a flow path for supplying feed gas G1 to the catalyst material Q (reaction tube U). Specifically, the first supply path R1 is a tubular component, connected downstream to the reaction tube U. The upstream side of the first supply path R1 is connected, for example, to the burner 40, which discharges exhaust gas that becomes feed gas G1. It should be noted that the upstream side of the first supply path R1 can be directly connected to the burner 40, or indirectly connected to the burner 40 via other piping or devices, as long as it can supply feed gas G1 to the reaction tube U.

[0063] The second supply path R2 is a flow path for supplying reducing gas G2 to the catalyst material Q (reaction tube U). Specifically, the second supply path R2 is a tubular component, connected downstream to the reaction tube U. The upstream side of the second supply path R2 is connected, for example, to a supplier 50 containing reducing gas G2. It should be noted that the upstream side of the second supply path R2 can be directly connected to the supplier 50, or indirectly connected to the supplier 50 via other piping or devices, as long as it can supply reducing gas G2 to the reaction tube U.

[0064] As can be understood from the above description, in the first embodiment, the raw material gas G1 and the reducing gas G2 are supplied by separate and independent mechanisms (burner 40 and feeder 50). In other words, the supply sources of the raw material gas G1 and the reducing gas G2 are different.

[0065] The first on / off valve V1 is the valve that opens and closes the first supply path R1. That is, the first on / off valve V1 switches the opening and closing of the first supply path R1. When the raw material gas G1 is supplied to the reaction tube U, the first on / off valve V1 is in the open state. On the other hand, when the reducing gas G2 is supplied to the reaction tube U, the first on / off valve V1 is in the closed state.

[0066] The second on / off valve V2 is the valve that opens and closes the second supply path R2. That is, the second on / off valve V2 switches the opening and closing of the second supply path R2. When reducing gas G2 is supplied to the reaction tube U, the second on / off valve V2 is in the open state. On the other hand, when raw material gas G1 is supplied to the reaction tube U, the second on / off valve V2 is in the closed state. It should be noted that... Figure 1 For convenience, the diagram shows the case where both the first on / off valve V1 and the second on / off valve V2 are in the open state.

[0067] Recovery path R3 is a flow path used to recover ammonia produced in reaction tube U. Specifically, recovery path R3 is a tubular component connected to reaction tube U on its upstream side. It should be noted that an on / off valve can also be installed in recovery path R3. Ammonia produced in reaction tube U is released from recovery path R3.

[0068] Imagine that the ammonia released from the recovery path R3 can be used for a specified reaction, for example, by being directly supplied to a reaction tube containing any catalyst, or by being adsorbed by an adsorbent material located downstream.

[0069] The control device 30 is a computer system for overall control of the various elements of the manufacturing apparatus 20, such as having one or more processors (e.g., CPU: Central Processing Unit) to control the various elements of the manufacturing apparatus 20.

[0070] Specifically, the control device 30 controls the supply of raw material gas G1 and reducing gas G2, thereby enabling the manufacturing apparatus 20 to perform manufacturing processes. In the first embodiment, the control device 30 controls the supply of raw material gas G1 by switching the opening and closing of the first on / off valve V1, and controls the supply of reducing gas G2 by switching the opening and closing of the second on / off valve V2.

[0071] The following describes the specific processes performed by the manufacturing apparatus 20 under the control of the control device 30. Figure 2It is an example of a flowchart of the manufacturing process.

[0072] When the manufacturing process begins, the manufacturing apparatus 20 first supplies the raw material gas G1 to the catalyst material Q (reaction tube U) (Sa1). Specifically, under the control of the control device 30, the manufacturing apparatus 20 opens the first on / off valve V1, thereby supplying the raw material gas G1 to the catalyst material Q via the first supply path R1. While the raw material gas G1 is being supplied, the second on / off valve V2 is closed.

[0073] Feed gas G1 is supplied to catalyst material Q (reaction tube U) for a specified period (e.g., 5 minutes to 2 hours). By supplying feed gas G1 to catalyst material Q, NOx is converted into NO2. - Or NO3 - The NOx is adsorbed onto the catalyst material Q. It should be noted that the NOx concentration in the feed gas G1 (hereinafter referred to as "used feed gas G1e") after being supplied to the catalyst material Q is reduced. Used feed gas G1e is released, for example, via recovery path R3.

[0074] After NOx is adsorbed onto the catalyst material Q, the manufacturing apparatus 20 stops the supply of feed gas G1 (Sa2). Specifically, the manufacturing apparatus 20, under the control of the control device 30, closes the first on / off valve V1, thereby stopping the supply of feed gas G1.

[0075] Then, the manufacturing apparatus 20 supplies reducing gas G2 to the catalyst 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 reducing gas G2 to the catalyst material Q.

[0076] Reducing gas G2 is supplied to catalyst material Q (reaction tube U) for a specified period (e.g., 5 minutes to 2 hours). By supplying reducing gas G2 to the catalyst material Q, which has adsorbed NOx, the reduction of NOx proceeds to produce ammonia. The generated ammonia is recovered from the recovery circuit R3.

[0077] Then, the manufacturing apparatus 20 stops the supply of 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 reducing gas G2.

[0078] Ammonia is generated through the above manufacturing process. Figure 2 The manufacturing process can be repeated. That is, after stopping the supply of reducing gas G2 in step Sa4, the process returns to the supply of raw material gas G1 in step Sa1.

[0079] The manufacturing process performed by the manufacturing apparatus 20 can be considered a method for manufacturing ammonia (hereinafter referred to as the "manufacturing method"). Specifically, the manufacturing method includes: a first step ( Figure 2 Step Sa1), this process involves supplying the raw material gas G1 (exhaust gas) to the catalyst material Q (reaction tube U), causing the NOx in the raw material gas G1 to be adsorbed in the catalyst material Q; and the second process ( Figure 2 In step Sa3), after stopping the supply of raw material gas G1, the reducing gas G2 is supplied to the catalyst material Q, and the NOx adsorbed in the catalyst material Q is used to generate ammonia and recover it.

[0080] In the manufacturing method of the first embodiment, at least one of the temperatures of the feed gas G1 and the reducing gas G2 supplied to the catalyst material Q and the temperature of the catalyst material Q is set to 150°C to 500°C, preferably 200°C to 400°C. By setting at least one of the temperatures of the feed gas G1 and the reducing gas G2 supplied to the catalyst material Q and the temperature of the catalyst material Q within the above-mentioned temperature range, the ammonia generation efficiency can be improved.

[0081] 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 raw material gas G1 is stopped, and 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, ammonia can be recovered as a resource.

[0082] Here, in the formation of ammonia using a reducing gas (e.g., H2) obtained from exhaust gas (raw material gas) (e.g., Patent Documents 1-5), the generation of the reducing gas depends on various coexisting gases in the exhaust gas (e.g., O2, H2O, CO2, CO, HC). Moreover, the concentration of these coexisting gases is not always constant. Therefore, there is a problem that the coexisting gases in the exhaust gas affect ammonia generation. Consequently, ammonia cannot be generated stably.

[0083] In contrast, in the first embodiment, since a reducing gas G2 (not a reducing gas G2 produced from the raw material gas G1) that is independent of the raw material gas G1 is used, the influence of coexisting gases in the raw material gas G1 can be reduced, and ammonia can be generated from NOx and recovered.

[0084] It should be noted that gases other than exhaust gases can also be used as feed gas G1. As long as it contains NOx and oxygen, the type of feed gas G1 is arbitrary.

[0085] [Second Implementation]

[0086] The second embodiment will be described. It should be noted that for elements in the following examples that have the same function as those in the first embodiment, the symbols used in the description of the first embodiment are used to appropriately omit their detailed descriptions.

[0087] Figure 3 This is a configuration diagram of the manufacturing unit 100 according to the second embodiment. The manufacturing unit 100 of the second embodiment has the same manufacturing apparatus 20 and control device 30 as the first embodiment.

[0088] In the first embodiment, the manufacturing apparatus 20 is configured to have one reaction tube U. In the second embodiment, the manufacturing apparatus 20 is configured to have N (N is a natural number of 2 or more) reaction tubes U[1] to U[N].

[0089] The manufacturing apparatus 20 of the second embodiment has 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 manufacturing apparatus 20 has 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].

[0090] The upstream side (opposite to the reaction tube U) of the N first supply paths R1[1] to R1[N] is connected to the burner 40 via the first common passage K1. In other words, the N first supply paths R1[1] to R1[N] are flow paths branching from the first common passage K1 to the N reaction tubes U[1] to U[N]. The upstream side of the first common passage K1 is connected to the burner 40. Raw material gas G1 is supplied to the N first supply paths R1[1] to R1[N] via the first common passage K1.

[0091] The upstream side (opposite to the reaction tube U) of the N second supply paths R2[1] to R2[N] is connected to the burner 40 via the second common passage K2. In other words, the N second supply paths R2[1] to R2[N] are flow paths branching from the second common passage K2 to the N reaction tubes U[1] to U[N]. The upstream side of the second common passage K2 is connected to the feeder 50. Reducing gas G2 is supplied to the N second supply paths R2[1] to R2[N] via the second common passage K2. It should be noted that on / off valves can also be installed on the first common passage K1 and the second common passage K2 respectively.

[0092] In the second embodiment, the manufacturing apparatus 20 performs the same manufacturing process as in the first embodiment for each of the N reaction tubes U[1] to U[N]. In the second embodiment, the manufacturing process is repeated for each reaction tube U[n]. Figure 2 (The treatment of Sa1-Sa4).

[0093] When performing step Sa1 (first step) of supplying raw material gas G1 to 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 reaction tube U[n], the first on / off valve V1[n] is closed and the second on / off valve V2[n] is opened.

[0094] The following explanation will divide the N reaction tubes U[1] to U[N] into K (K is a natural number less than N) reaction tubes U and (NK) reaction tubes U. The timing of each step of the manufacturing process is different in the K reaction tubes U and the (NK) reaction tubes U.

[0095] Figure 4 This is a flowchart illustrating the manufacturing process repeatedly performed by the manufacturing apparatus 20 of the second embodiment for K reaction tubes U and (NK) reaction tubes U. Figure 4 For convenience, the time series of unit periods T1-T4 is illustrated. The unit periods T1-T4 repeat in the order of "T1→T2→T3→T4→…". T1 and T3, which are the periods for supplying gas (G1, G2), are, for example, 1 minute to 3 hours, preferably 5 minutes to 2 hours. T2 and T4 are the short times required to stop the gas and switch.

[0096] like Figure 4 As shown, within a unit period T1, step Sa1, which supplies feed gas G1 to catalyst material Q (reaction tube U), is performed for K reaction tubes U, and step Sa3, which supplies reducing gas G2 to catalyst material Q (reaction tube U), is performed for (NK) reaction tubes U. That is, step Sa3 in (NK) reaction tubes U is performed in parallel with the execution of step Sa1 in the K reaction tubes U.

[0097] Within unit period T2, step Sa2 is performed to stop the supply of raw material gas G1, and step Sa4 is performed to stop the supply of reducing gas G2 for (NK) reaction tubes U.

[0098] Within a unit period T3, step Sa3, which supplies reducing gas G2 to catalyst material Q (reaction tube U), is performed for K reaction tubes U, and step Sa1, which supplies feed gas G1 to catalyst material Q (reaction tube U), is performed for (NK) reaction tubes U. That is, step Sa1 in (NK) reaction tubes U is performed in parallel with the execution of step Sa3 in the K reaction tubes U.

[0099] During the unit period T4, step Sa4 is performed to stop the supply of reducing gas G2, and step Sa2 is performed to stop the supply of raw material gas G1 for (NK) reaction tubes U.

[0100] The following describes the operations within unit period T1 and unit period T3 in the manufacturing apparatus 20. Figure 5 The state of manufacturing apparatus 20 during unit period T1 is shown. Figure 6 The state of the manufacturing apparatus 20 during unit period T3 is shown.

[0101] exist Figure 5 and Figure 6 In the example, the case where K is 1 is illustrated. Specifically, the case where K (1) reaction tubes U are set as reaction tube U[1] and (NK) reaction tubes U are set as reaction tubes U[2] to U[N] other than reaction tube U[1].

[0102] like Figure 5 As shown, within a unit period T1, for reaction tube U[1], the first on / off valve V1[1] is in the open state, and the second on / off valve V2[1] is in the closed state. Therefore, raw material gas G1 is supplied to reaction tube U[1] from the first supply line R1[1], and the used raw material gas G1e is recovered from the recovery line R3[1].

[0103] On the other hand, for reaction tubes U[2]~U[N], the first on / off valve V1[2]~R1[N] is closed, and the second on / off valve V2[2]~R2[N] is open. Therefore, reducing gas G2 is supplied to reaction tubes U[2]~U[N] from the second supply path R2[2]~R2[N], and ammonia is recovered from the recovery path R3[2]~R3[N].

[0104] like Figure 6 As shown, within a unit period T3, for reaction tube U[1], the first on / off valve V1[1] is closed and the second on / off valve V2[1] is open. Therefore, reducing gas G2 is supplied to reaction tube U[1] from the second supply line R2[1], and ammonia is recovered from the recovery line R3[1].

[0105] On the other hand, for reaction tubes U[2]~U[N], the first on / off valves V1[2]~V1[N] are in the open state, and the second on / off valves V2[2]~V2[N] are in the closed state. Therefore, raw material gas G1 is supplied to reaction tubes U[2]~U[N] from the first supply path R1[2]~R1[N], and used raw material gas G1e is discharged from the recovery path R3[2]~R3[N].

[0106] The control device 30 of the second embodiment performs overall control of the manufacturing apparatus 20, thereby enabling the manufacturing apparatus 20 to perform the above-described manufacturing process for each of the N reaction tubes U[1] to U[N]. The opening and closing of the first on / off valve V1[n] and the second on / off valve V2[n] are switched under the control of the control device 30.

[0107] The second embodiment also achieves the same effect as the first embodiment.

[0108] Here, we envision a configuration of steps Sa1-Sa4 where manufacturing processes are performed simultaneously on all N reaction tubes U[1] to U[N] (hereinafter referred to as "Reference Example"). In the Reference Example, during step Sa3, which involves supplying reducing gas G2, it is necessary to stop the supply of exhaust gas to the entire manufacturing apparatus 20. However, when exhaust gas discharged from burner 40 is used as feed gas G1, there is a situation where exhaust gas generation cannot be stopped during the operation of burner 40. Therefore, the Reference Example is not suitable for using exhaust gas as feed gas G1.

[0109] In contrast, in the manufacturing apparatus 20 according to the second embodiment, among the N reaction tubes U[1] to U[N], there is one or more reaction tubes U1 for supplying the raw material gas G1. That is, it has the advantage of being able to generate ammonia without stopping the supply of the raw material gas G1 to the entire manufacturing apparatus 20. The configuration of the second embodiment is particularly suitable for cases where exhaust gas is used as the raw material gas G1. However, the present invention also includes reference examples.

[0110] Furthermore, according to the manufacturing apparatus 20 of the second embodiment, since it has N reaction tubes U[1] to U[N], it is possible to sequentially introduce reducing gas G2 from the reaction tubes U where the adsorption capacity of the catalyst material Q becomes insufficient to generate ammonia and restore the adsorption capacity. Therefore, the catalyst material Q can be reused. Furthermore, the manufacturing apparatus 20 can be operated without NOx leakage in the downstream section.

[0111] The manufacturing method of the second embodiment is as follows: a manufacturing process is repeatedly performed for each of N reaction tubes U, the manufacturing process including: a first step (step Sa1), which involves supplying a raw material gas G1 (exhaust gas) to the reaction tube U[n], causing NOx in the raw material gas G1 to be adsorbed into the catalyst material Q; and a second step (step Sa3), which involves supplying a reducing gas G2 to the reaction tube U[n] after stopping the supply of the raw material gas G1, generating ammonia from the NOx adsorbed into the catalyst material Q and recovering it; during the execution of the first step for K reaction tubes U, the second step is executed for (NK) reaction tubes U, and during the execution of the second step for K reaction tubes U, the first step is executed for (NK) reaction tubes U.

[0112] It should be noted that the configuration of the manufacturing apparatus 20 in the second embodiment is only required to perform the manufacturing method described above, and is not limited to the examples above. Furthermore, there are cases where the number of reaction tubes U divided into K and the number of reaction tubes U divided into (NK) may differ in each manufacturing process.

[0113] [Third Implementation Method]

[0114] Figure 7 This is a configuration diagram of the manufacturing unit 100 according to the third embodiment. The manufacturing unit 100 of the third embodiment has the same manufacturing apparatus 20 and control device 30 as the second embodiment.

[0115] The manufacturing apparatus 20 of the third embodiment is similar to that of the second embodiment. Each reaction tube U[n] has 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]. In addition, it also has 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 a configuration formed 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.

[0116] Exhaust path R4[n] is a flow path used to recover feed gas G1 from reaction tube U[n]. After use, feed gas G1e is recovered from exhaust path R4[n] via catalyst material Q. Specifically, exhaust path R4[n] is a tubular component connected upstream to reaction tube U[n].

[0117] The third on / off valve V3[n] is the valve that opens and closes the recovery path R3[n]. That is, the opening and closing of the recovery path R3[n] is switched by the third on / off valve V3[n]. When the raw material gas G1 is supplied to the reaction tube U[n], the third on / off valve V3[n] is in the closed state, and when the reducing gas G2 is supplied to the reaction tube U[n], the third on / off valve V3[n] is in the open state.

[0118] The fourth on / off valve V4[n] is the valve that opens and closes the exhaust path R4[n]. That is, the opening and closing of the exhaust path R4 is switched by the fourth on / off valve V4[n]. When the raw material gas G1 is supplied to the reaction tube U[n], the fourth on / off valve V4[n] is in the 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 the closed state.

[0119] The opening and closing of the third on / off valve V3[n] and the fourth on / off valve V4[n] are switched under the control of the control device 30.

[0120] Based on the above explanation, it can be understood that in the third embodiment, when performing the reaction tube U[n]... Figure 4 In step Sa1 (first process), the third on / off valve V3[n] is closed and the fourth on / off valve V4[n] is opened, and the reaction is performed on the reaction tube U[n]. Figure 4 In step Sa3 (second process), the third on / off valve V3[n] is made open and the fourth on / off valve V4[n] is made closed.

[0121] The manufacturing apparatus 20 of the third embodiment will be described below. Figure 4 Actions within unit period T1 and unit period T3. Figure 8 The state of manufacturing apparatus 20 during unit period T1 is shown. Figure 9 The state of the manufacturing apparatus 20 during unit period T3 is shown.

[0122] for Figure 8 and Figure 9 , also with Figure 5 and Figure 6 Similarly, an example is given of setting K (1) reaction tubes U as reaction tube U[1] and (NK) reaction tubes U as reaction tubes U[2] to U[N] other than reaction tube U[1].

[0123] like Figure 8 As shown, within a unit period T1, similarly to the second embodiment, for the reaction tube U[1], the first on / off valve V1[1] is in the open state and the second on / off valve V2[1] is in the closed state. Therefore, the raw material gas G1 is supplied to the reaction tube U[1] from the first supply path R1[1].

[0124] Furthermore, within the unit period T1 of the third embodiment, for the reaction tube U[1], the fourth on / off valve V4[1] is in the open state and the third on / off valve V3[1] is in the 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 released from the exhaust passage R4[1].

[0125] On the other hand, for reaction tubes U[2] to U[N], similarly to the second embodiment, 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. Therefore, reducing gas G2 is supplied to reaction tubes U[2] to U[N] from the second supply path R2[2] to R2[N].

[0126] Furthermore, within the unit period T1 of the third embodiment, for reaction tubes U[2] to U[N], the fourth on / off valve V4[2] to V4[N] is in the closed state, and the third on / off valve V3[2] to V3[N] is in the open state. That is, reducing gas G2 is supplied to reaction tubes U[2] to U[N], and ammonia is released and recovered from recovery paths R3[2] to R3[N].

[0127] like Figure 9 As shown, during the unit period T3, similarly to the second embodiment, for the reaction tube U[1], the second on / off valve V2[1] is in the open state and the first on / off valve V1[1] is in the closed state. Therefore, reducing gas G2 is supplied to the reaction tube U[1] from the second supply line R2[1].

[0128] Furthermore, within the unit period T3 of the third embodiment, for the reaction tube U[1], the third on / off valve V3[1] is in the open state, and the fourth on / off valve V4[1] is in the closed state. That is, reducing gas G2 is supplied to the reaction tube U[1], and ammonia is released and recovered from the recovery path R3[1].

[0129] On the other hand, for reaction tubes U[2] to U[N], similarly to the second embodiment, 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. Therefore, the raw material gas G1 is supplied from the first supply path R1[2] to R1[N] to the reaction tubes U[2] to U[N].

[0130] Furthermore, within the unit period T3 of the third embodiment, for reaction tubes U[2] to U[N], the third on / off valves V3[2] to V3[N] are in the closed state, and the fourth on / off valves V4[2] to V4[N] are in the open state. That is, raw material gas G1 is supplied to reaction tubes U[2] to U[N], and used raw material gas G1e is released from exhaust passages R4[2] to R4[N].

[0131] Based on the above explanation, it can be understood that in the manufacturing apparatus 20 of 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. 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.

[0132] In the third embodiment, since the reaction tube U[n] has an exhaust path R4[n] separate from the recovery path R3[n], the used raw material gas G1e and ammonia can be recovered through the separate path.

[0133] It should be noted that, in the first embodiment, an exhaust path R4 separate from the recovery path R3 may also be provided in the manufacturing apparatus 20.

[0134] [Catalyst Materials]

[0135] Hereinafter, an example of a catalyst material suitable for use in the manufacturing apparatus and manufacturing method of the present invention will be described in detail.

[0136] Catalyst materials include: noble metals; at least one of alkali metals and alkaline earth metals; and oxide supports.

[0137] Oxide supports used as catalyst materials include, for example, Al2O3, CeO2, TiO2, ZrO2, SiO2, MgO, CaO, and LaAlO3. From the viewpoint of improving catalyst activity, any one or more of Al2O3, CeO2, TiO2, and ZrO2 are preferred.

[0138] Noble metals are contained in catalyst materials either on the surface of an oxide support or within the oxide support. Here, "containing within the oxide support" refers to a composite state in which particulate noble metals are encapsulated within the spherical particles of the oxide support.

[0139] In this invention, the presence of precious metals can be either as elemental precious metals contained in an oxide support, or as precious metal compounds contained in an oxide support, and both. In the following description, the term "precious metal" includes both elemental precious metals and precious metal compounds.

[0140] The noble metal (elemental noble metal) 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 either an elemental noble metal or an oxide of these noble metals. From the viewpoint of improving catalyst activity, one or more of platinum, palladium, rhodium, and iridium are preferred, and one or more of platinum and rhodium are even more preferred. It should be noted that multiple noble metals may be contained separately in the oxide support.

[0141] The average particle size of the noble metal is, for example, 0.1 nm to 100 nm, preferably 10 nm to 50 nm. By setting the average particle size of the noble metal and the noble metal compound within the above range, it is possible to balance the oxidation reaction characteristics of the flowing gas and the durability of the catalyst.

[0142] It should be noted that the average particle size of precious metals is determined by observing and measuring the particle size of a specified number (e.g., 100) of particles using a transmission electron microscope.

[0143] In the overall catalyst material, the content of precious metals (precious metal elements in the catalyst material) is 0.01% to 20% by mass, preferably 0.05% to 15.0% by mass, and more preferably 0.1% to 10.0% by mass. By setting the content of precious metals within the above range, the catalyst activity can be improved. In addition, the amount of high-priced precious metals can also be suppressed.

[0144] Alkali metals and alkaline earth metals are contained in the catalyst material in the form of being supported on the surface of an oxide support. It should be noted that, in the case where noble metals are contained inside the oxide support, alkali metals and alkaline earth metals are supported on the surface of an oxide support that is composited with noble metals.

[0145] In this invention, alkali metals and alkaline earth metals are typically supported on oxide supports as compounds comprising at least one of alkali metals and alkaline earth metals (hereinafter referred to as "alkali metal / alkaline earth metal compounds"). However, the configuration of supporting oxide supports with elemental alkali metals and alkaline earth metals is not excluded from this invention.

[0146] Alkali metal / alkaline earth metal compounds supported on oxide supports include, for example, oxides, peroxides, carbonates, hydroxides, etc. of alkali metals and alkaline earth metals.

[0147] It should be noted that in alkali metal / alkaline earth metal compounds, when multiple alkali metals and alkaline earth metals are present, more than two alkali metals can be selected, more than two alkaline earth metals can be selected, or more than one alkali metal and more than one alkaline earth metal can be selected. It should also be noted that one alkali metal / alkaline earth metal compound can be supported on an oxide support, or multiple compounds can be supported on an oxide support.

[0148] 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 reduction efficiency of nitrogen oxides, one or more of lithium, potassium, sodium, and cesium are preferred, and one or more of potassium and sodium are even more preferred.

[0149] The alkaline earth metal used in alkali metal / alkaline earth metal compounds is one or more of beryllium, magnesium, calcium, strontium, barium, and radium. From the viewpoint of improving the reduction efficiency of nitrogen oxides, one or more of magnesium, calcium, strontium, and barium are preferred, and one or more of calcium and barium are even more preferred.

[0150] In the overall catalyst material, the content (total stoichiometry) 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% by mass, preferably 0.5% to 40.0% by mass, and more preferably 1.0% to 30.0% by mass. By setting the content of alkali metals and alkaline earth metals within the above range, a uniformly arranged microporous structure can be maintained, and the reduction efficiency of nitrogen oxides can be improved.

[0151] The specific surface area of ​​the catalyst material is, for example, 10 m². 2 / g~350m 2 / g, preferably 50m 2 / g~330m 2 / g, further preferably 150m 2 / g~300m 2 / g. Based on catalyst materials with a specific surface area within the above range, for example, they are capable of adsorbing gases (e.g., nitrogen oxides) with high efficiency. It should be noted that the specific surface area of ​​the catalyst material is determined by the BET multi-point method.

[0152] The most frequent value of the pore size distribution of the catalyst material is, for example, a diameter of 1 nm to 200 nm, preferably a diameter of 1 nm to 50 nm, and more preferably a diameter of 2 nm to 20 nm. Catalyst materials with the most frequent value of the pore size distribution within the above range can, for example, adsorb gases (e.g., nitrogen oxides) with high efficiency.

[0153] The pore volume of the catalyst material is, for example, 0.1 cm³. 3 / g~1.5cm3 / g, preferably 0.3cm 3 / g~1.2cm 3 / g, further preferably 0.5cm 3 / g~0.9cm 3 / g. Catalyst materials with average pore diameter and pore volume within the above range, for example, are capable of adsorbing gases (e.g., nitrogen oxides) with high efficiency.

[0154] The most frequent values ​​of the pore size distribution in the catalyst material can be determined, for example, using gas adsorption via NLDFT (Nonlocal Density Functional Theory). Similarly, the pore volume of the catalyst material can be determined, for example, using gas adsorption.

[0155] The following describes a catalyst material (hereinafter referred to as "composite catalyst material") that is particularly preferred in a catalyst material including at least one of noble metals, alkali metals and alkaline earth metals and an oxide support.

[0156] The composite catalyst material comprises Al2O3 as an oxide support. Noble metals are contained within the Al2O3 (i.e., composited with Al2O3), with alkali metals and alkaline earth metals supported on the Al2O3 containing the noble metals. Regarding the details of the Al2O3 (content, etc.), the oxide support is as described above. Similarly, the details of the alkali metals and alkaline earth metals are also as described above.

[0157] In the following description, "Al2O3" will be referred to as "porous alumina", and porous alumina containing precious metals will be referred to as "porous alumina containing precious metals".

[0158] The following describes an example of a method for manufacturing a composite catalyst material. In general, the composite catalyst material of the present invention is manufactured by synthesizing porous alumina (oxide support) containing noble metals and loading alkali metals or alkaline earth metals onto this oxide support.

[0159] <1> Preparation of precursor solution

[0160] A precursor solution containing precious metals (hereinafter referred to as "precursor solution") is a solution containing an alumina source, a precious metal source, an amphiphilic organic molecule, an acid, and a solvent.

[0161] As the alumina source (aluminum compound) for the precursor solution, a substance that has been calcined into a transition alumina (alumina with a crystalline structure other than α) such as γ-alumina is used. Specifically, aluminum hydroxide, aluminum nitrate, aluminum sulfate, aluminum chloride (including hydrates), aluminum alkoxides, etc., are examples of alumina sources, with aluminum alkoxides being preferred. As aluminum alkoxides, (trisec-butoxy)aluminum, (tri-n-butoxy)aluminum, (tri-tert-butoxy)aluminum, (triisopropoxy)aluminum, (triethoxy)aluminum, (triphenoxy)aluminum, etc., are examples. Among these, aluminum chloride (including hydrates), (trisec-butoxy)aluminum, and (tri-n-butoxy)aluminum are preferred from the viewpoints of reactivity and availability of hydrolysis and raw material price, and (trisec-butoxy)aluminum is particularly preferred.

[0162] Examples of noble metal sources in the precursor solution include oxides, hydroxides, chlorides, carbonates, acetates, nitrates, oxalates, phosphates, and chloride complexes of gold, silver, platinum, palladium, rhodium, iridium, ruthenium, osmium, and rhenium. From the viewpoint of improving catalyst activity, it is preferable to use one or more noble metal sources selected from platinum, palladium, rhodium, and iridium.

[0163] As platinum sources, inorganic platinum compounds such as chloroplatinic acid (including hydrates), dinitrodiaminoplatinum, hexahydroxyplatinic acid, platinum(II) chloride, platinum chloride, dichlorotetraaminoplatinum, potassium tetrachloroplatinate, and potassium hexachloroplatinum, as well as organoplatinum compounds such as di(acetylacetone)platinum, dichloro(cyclohexane)platinum dimer, dichloro(n-ethylene)Pt dimer, (n-cyclooctyl-1,5-diene)platinum dichloride, tetra(triphenylphosphite)platinum, cis-dichlorobis(triphenylphosphine)platinum, bis(benzonitrile)platinum dichloride, trans-d-cyclohexanediamine dichloride, and trans-l-cyclohexanediamine dichloride can be used. These can be used alone or in combination. From the viewpoint of solubility in solvents when preparing precursor solutions, chloroplatinic acid (including hydrates) or di(acetylacetone)platinum is particularly preferred.

[0164] Examples of palladium sources include palladium chloride, palladium acetate, tetra-triphenylphosphine palladium, tris(dibenzylacetone)dipalladium, and allyl palladium chloride dimer. Examples of ligands include bis[2-(diphenylphosphine)phenyl]ether (DPEphos), triphenylphosphine, 1,1'-bis(diphenylphosphine)ferrocene (dppf), 4,5'-bis(diphenylphosphine)-9,9'-dimethyloxanthracene (Xantphos), and 1,3-di-tert-butylimidazolium. They can be used alone or in combination.

[0165] Examples of rhodium sources include rhodium chloride, rhodium tetraacetate dihydrate, rhodium acetate, rhodium isobutyrate, rhodium 2-ethylhexanoate, rhodium benzoate, and rhodium octanoate. They can be used alone or in combination.

[0166] Examples of iridium sources include iridium chloride, iridium sulfate, iridium nitrate, iridium nitrite, ammonium hexachloroiridate, hexachloroiridate n-hydrate, chlorocarbonyl bis(triphenylphosphine)iridium, and sodium chloride n-hydrate. They can be used individually or in combination.

[0167] As the amphiphilic organic molecule for the precursor solution, one or more of the following can be used: polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer (trade name: Pluronic (registered trademark)), alkyl ammonium salt, polystyrene-polyethylene oxide block copolymer, etc. 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 particularly preferred, and Pluronic P123 and F127 are even more preferred.

[0168] The pore size of porous alumina varies significantly depending on the type of amphiphilic organic molecule. When polyethylene oxide-propylene oxide-ethylene oxide block copolymers are used as the amphiphilic organic molecule, the most frequent values ​​of the fine pore size distribution are 2 nm to 30 nm. Furthermore, when polystyrene-ethylene oxide block copolymers are used as the amphiphilic organic molecule, the most frequent values ​​of the fine pore size distribution are 25 nm to 200 nm (see: "Bulletin of the Chemical Society of Japan, 2019, 92, 1859-1866.", "Dalton Transactions, 2021, 50, 7191-7197.").

[0169] As the acid used in the precursor solution, inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, as well as organic acids such as carboxylic acids and sulfonic acids, can be used. Among these, from the viewpoint of forming a regularly arranged porous structure, at least one of hydrochloric acid and nitric acid is particularly preferred.

[0170] Alcohols, ethers, water, ketones, etc., can be used as solvents for the precursor solution. In particular, various alcohols, including ethanol, methanol, n-butanol, sec-butanol, tert-butanol, n-propanol, and isopropanol, can be used as alcohols. Among these, ethanol is particularly preferred from the viewpoint of forming a regular porous structure by optimizing the evaporation rate of the solvent.

[0171] In the precursor solution, the content of alumina source (aluminum compound) is 5% to 25% by mass, preferably 8% to 20% by mass, and more preferably 10% to 15% by mass.

[0172] In the precursor solution, the content of the noble metal source is 0.01% to 0.20% by mass, preferably 0.03% to 0.20% by mass, and more preferably 0.05% to 0.10% by mass.

[0173] In the precursor solution, the content of amphiphilic organic molecules is 1% to 20% by mass, preferably 2% to 15% by mass, and more preferably 3% to 10% by mass.

[0174] In the precursor solution, the acid content 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.

[0175] In the precursor solution, the solvent content is 50% to 93% by mass, preferably 60% to 90% by mass, and more preferably 70% to 80% by mass.

[0176] An example of a specific preparation method for the precursor solution is shown in (1) to (3) below.

[0177] (1) After adding amphiphilic organic molecules to the solvent, a noble metal source is added.

[0178] (2) Prepare a dispersion by adding an aluminum source to the solvent. While stirring the dispersion, add acid dropwise over a specified time (e.g., more than 10 minutes). Stir the dispersion over a specified time (e.g., 3 hours).

[0179] (3) A precursor solution is prepared by adding the dispersion from (2) to the solution prepared in (1).

[0180] <2> Synthesis of Porous Alumina Containing Noble Metals

[0181] An example of a method for synthesizing porous alumina containing noble metals is shown in (1) and (2) below.

[0182] (1) Recovery of a precursor (powder) of porous alumina containing precious metals from a 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; for example, one or more combinations of known methods such as spray-drying, freeze-drying, heat drying, hot air drying, vacuum drying, and natural drying can be cited. From the viewpoint of productivity and reproducibility, spray drying is particularly preferred. The precursor solution is dried to recover the precursor (powder) of porous alumina containing precious metals.

[0183] (2) Porous alumina containing noble metals is synthesized by sintering the recovered precursor. Sintering the precursor removes the amphiphilic organic molecules that form pores, thus achieving porosification, and also involves the thermal decomposition of the noble metal source and the crystallization of the alumina. The amphiphilic organic molecules disappear, resulting in a porous structure with regularly arranged fine pores. For the sintering of the precursor, the precursor is held at a desired temperature (e.g., 800°C to 900°C) under a nitrogen flow for a specified time (e.g., 1 hour to 3 hours), followed by holding at that temperature under an oxygen flow for a specified time (e.g., 2 hours to 3 hours). It should be noted that it is preferable to increase the temperature in stages (e.g., 1 to 3°C per minute) until the desired temperature is reached under a nitrogen flow.

[0184] <3> Loading of alkali metals and alkaline earth metals

[0185] At least one of alkali metals and alkaline earth metals is loaded as an alkali metal / alkaline earth metal compound onto the synthesized porous alumina containing noble metals.

[0186] The alkali metals and alkaline earth metals used in this invention are as described above.

[0187] To load alkali metals and alkaline earth metals onto porous alumina containing noble metals, a compound (hereinafter referred to as "precursor compound") primarily consisting of acetates, nitrates, carbonates, hydroxides, halides, oxides, or hydrides containing at least one of the alkali metals and alkaline earth metals is used. From the viewpoint of solubility and thermal decomposition temperature, at least one of acetates and nitrates is preferred. It should be noted that the precursor compound undergoes thermal decomposition upon heating, thereby transforming into an alkali metal / alkaline earth metal compound.

[0188] An example of a method for loading alkali metals and alkaline earth metals onto porous alumina containing noble metals is shown below (1)-(3). For example, alkali metals and alkaline earth metals are loaded onto porous alumina containing noble metals by an impregnation loading method.

[0189] (1) Disperse porous alumina containing precious metals in distilled water, and add an aqueous solution of the precursor compound dropwise while stirring vigorously.

[0190] An aqueous solution of the precursor compound is added dropwise to make the content of alkali metal and alkaline earth metal elements in the composite catalyst material, for example, 0.1% to 50% by mass, preferably 0.5% to 40% by mass, and more preferably 1% to 30%. By adding the aqueous solution of the precursor compound dropwise to make the mass ratio of alumina to alkali metal / alkaline earth metal compound in the porous alumina containing noble metals within the above range, the adsorption characteristics and reduction efficiency of nitrogen oxides can be improved.

[0191] (2) The dispersion of (1) is heated under reduced pressure to remove distilled water and obtain powder. For example, distilled water is removed from the dispersion by reduced pressure distillation at 30–80°C.

[0192] (3) The composite catalyst material of the present invention is obtained by drying the powder obtained in (2) and then calcining it. The powder obtained in (2) is dried, for example, at 80°C to 120°C for 6 to 20 hours. The dried powder is then calcined, for example, in a tubular furnace at 400°C to 700°C for 2 to 5 hours.

[0193] Composite catalyst materials are manufactured using the above-described manufacturing method. The manufacturing method according to the present invention has the advantage of enabling the productive manufacture of composite catalyst materials in a short time, compared to methods such as spreading the precursor solution in a container like a petri dish and drying it at a predetermined temperature for several days.

[0194] The composite catalyst material manufactured using the above method achieves a pore size distribution with a diameter ranging from 1 nm to 200 nm. Furthermore, this composite catalyst material, with its pore size distribution exhibiting a pore size distribution with a diameter ranging from 1 nm to 200 nm, allows for uninterrupted diffusion or adsorption of nitrogen oxides in the gas phase. Moreover, by selecting the type of amphiphilic organic molecule and considering the synthesis conditions, the pore size distribution of the composite catalyst material can be controlled, and the balance between the diffusion of nitrogen oxides within the pores and the specific surface area of ​​the composite catalyst material can be adjusted.

[0195] In the composite catalyst material of the present invention, by loading at least one of an alkali metal and an alkaline earth metal onto porous alumina containing a noble metal, the adsorption capacity of nitrogen oxides can be increased, and the reduction efficiency of nitrogen oxides can be improved.

[0196] The composite catalyst material of this invention can maintain a regularly arranged microporous structure. Therefore, it is possible to maintain a high specific surface area.

[0197] For the composite catalyst material manufactured by the above method, at least one of a diffraction peak and a scattering peak corresponding to a lattice plane spacing of 1 nm to 200 nm, obtained by X-ray irradiation, was observed. The diffraction peak was determined by X-ray diffraction. The scattering peak was determined by small-angle X-ray scattering. Specifically, in the X-ray diffraction determination, at least one diffraction peak corresponding to a lattice plane spacing of 1 nm to 200 nm was observed, and in the small-angle X-ray scattering determination, at least one scattering peak corresponding to a lattice plane spacing of 1 nm to 200 nm was observed.

[0198] As a tube for generating X-rays, Fe is preferred because the characteristic X-rays have a longer wavelength, and the diffraction or scattering peaks appear at high angles, making them easy to detect. Moreover, the intensity is sufficient for the detector. However, tubes using other elements (such as Cu) are also acceptable. The presence of these diffraction and scattering peaks indicates a regular arrangement of pores in the porous structure.

[0199] Based on the observation of composite catalyst materials with more than one diffraction peak or scattering peak corresponding to the lattice plane spacing of 1 nm to 200 nm, due to the existence of the regular arrangement of pores with uniform pore size in the porous structure, it is expected that there will be a high specific surface area and uniform diffusion behavior of gas inside the pores.

[0200] Based on the above description, it can be understood that, in particular, the composite catalyst material is a nanocomposite material containing at least one of a noble metal, an alkali metal, and an alkaline earth metal, and porous alumina. The noble metal is contained within the porous alumina, and the alkali metal and alkaline earth metal are supported on the porous alumina containing the noble metal. The most frequent value in the pore size distribution is preferably a diameter of 1 nm to 200 nm. Based on the above composite catalyst material, ammonia can be produced efficiently. The porous alumina used in the composite catalyst material is preferably particulate porous alumina (mesoporous alumina) with a crystalline structure, possessing a regularly arranged porous structure.

[0201] Example

[0202] The catalyst materials used in this invention are described in more detail below through examples, but the invention is not limited to these examples.

[0203] <Example 1>

[0204] Example 1 is a catalyst material prepared by supporting barium on porous alumina containing platinum. The mass ratio of platinum to barium to porous alumina (platinum:barium:porous alumina) is 1:10:100.

[0205] Example 1 was prepared as described in <1> to <3> below.

[0206] <1> Preparation of Platinum-Containing Porous Alumina Precursor Solution

[0207] (1) Weigh 15g of Pluronic P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer), an amphiphilic organic molecule, and place it in a stoppered Erlenmeyer flask. Add 120mL of ethanol and 0.135g of chloroplatinic acid hexahydrate. Then stir with a magnetic stirrer and a stir bar.

[0208] (2) Add 60 mL of ethanol and 24.6 g of (trisec-butoxy)aluminum to a three-necked flask to prepare a dispersion. While continuing to stir the dispersion, add concentrated hydrochloric acid (14.5 mL) dropwise over a period of more than 10 minutes, and stir for 3 hours.

[0209] (3) Add the dispersion of (2) to the solution of (1) to prepare a porous alumina precursor solution containing platinum.

[0210] <2> Synthesis of Platinum-Containing Porous Alumina

[0211] (1) A platinum-containing porous alumina precursor solution was introduced into a spray dryer (Yamato Scientific Co., Ltd., Japan, ADL311) to remove ethanol-containing water by hot air drying while spraying the precursor solution. The inlet temperature of the spray dryer was set to 170°C. Then, the platinum-containing porous alumina precursor was recovered by a cyclone separator.

[0212] (2) The precursor recovered by the cyclone separator was sintered in a tubular furnace to remove the Pluronic P123 mold that served as the pores, thereby achieving porosification. Thermal decomposition of the platinum compound (chloroplatinic acid hexahydrate) and crystallization of alumina were also performed. For sintering, the temperature was increased to 850°C at a rate of 2°C per minute under a nitrogen flow, held at the same temperature for 1 hour, and then held at the same temperature for another 2 hours under an oxygen flow.

[0213] <3> Barium supported on platinum-containing porous alumina

[0214] As described above, barium is loaded onto platinum-containing porous alumina as a barium compound (which is a barium compound generated by the thermal decomposition of barium acetate in Example 1, such as barium carbonate, barium oxide, and barium hydroxide).

[0215] Specifically, barium compounds are loaded onto porous alumina containing platinum using an impregnation loading method.

[0216] (1) Disperse platinum-containing porous alumina in distilled water, and add barium acetate aqueous solution dropwise while stirring vigorously. Add barium acetate aqueous solution dropwise so that the mass ratio of platinum-containing porous alumina to barium in the barium acetate aqueous solution (platinum-containing porous alumina:barium) is 101:10.

[0217] (2) After shaking the dispersion from (1) for 1 hour, the dispersion was transferred to a flask and the distilled water was removed by distillation at 60°C under reduced pressure using a rotary evaporator to recover the powder. The powder was then dried at 110°C for more than 10 hours and then calcined in a tubular furnace at 500°C for 3 hours (heating rate: 10°C per minute, under dry air flow) to obtain a catalyst material composed of platinum-containing porous alumina loaded with barium compounds.

[0218] It should be noted that the average particle size of platinum (nanoparticles) in the platinum-containing porous alumina is 24 nm. The average particle size of platinum was observed using a transmission electron microscope manufactured by JEOL Ltd. (JEM-2010). The length of the noble metal nanoparticles was measured at 100 points to determine the most frequent value (mode particle size) of this particle size.

[0219] <Example 2>

[0220] Example 2 is a catalyst material prepared by supporting calcium on porous alumina containing platinum. The mass ratio of platinum to calcium to porous alumina (platinum:calcium:porous alumina) is 1:10:100.

[0221] The process is the same as in Example 1, except that an aqueous solution of calcium acetate monohydrate is used instead of an aqueous solution of barium acetate.

[0222] It should be noted that, in Example 2, calcium was also loaded onto porous alumina containing platinum as a calcium compound using an impregnation loading method.

[0223] Examples 1 and 2 are examples of the composite catalyst material described above.

[0224] <Example 3>

[0225] Example 3 describes a material prepared by loading platinum (nanoparticles) and barium onto commercially available γ-alumina (manufactured by Strem Chemicals). Example 3 was prepared as described in (1) to (4) below.

[0226] (1) Pre-treat γ-alumina at 500°C for 2 hours in a dry air stream.

[0227] (2) Mix with an ethanol solution of chloroplatinic acid hexahydrate so that the mass ratio of γ-alumina to platinum in (1) is 100:1.

[0228] (3) After the ethanol is evaporated and dried, it is calcined at 600°C for 3 hours in a dry air stream to prepare platinum-supported γ-alumina.

[0229] (4) Barium seeds were loaded onto the platinum-loaded γ-alumina obtained in (3) in the same manner as in Example 1. The mass ratio of platinum-loaded γ-alumina to barium atoms was 101:10.

[0230] <Example 4>

[0231] Example 4 is a material prepared by loading platinum and barium onto commercially available CeO2 (produced by First Rare Element Chemical Industry). Example 4 was prepared as described in (1) to (3) below.

[0232] (1) Pre-treat CeO2 at 500°C for 2 hours in a dry air stream.

[0233] (2) Use dinitrodiammineplatinum nitric acid solution and barium acetate aqueous solution and mix them so that the mass ratio of CeO2 and platinum and barium atoms in (1) is 100:1:10.

[0234] (3) Evaporate and dry (2), dry the obtained powder at 100°C, and then calcine it at 600°C for 2 hours in a dry air stream to prepare barium and platinum supported CeO2.

[0235] <Example 5>

[0236] Example 5 is a material prepared by loading platinum onto commercially available CeO2 (manufactured by First Rare Element Chemical Industry). It is identical to Example 4 except that the mixing is performed without a barium source to achieve a CeO2 to platinum mass ratio of 100:1.

[0237] <Example 6>

[0238] Example 6 is a catalyst material prepared by supporting calcium on porous alumina containing platinum. Example 6 is the same as Example 2 except that the mass ratio of platinum to calcium to porous alumina (platinum:calcium:porous alumina) is set to 1:4:100.

[0239] <Example 7>

[0240] Example 7 is a catalyst material prepared by supporting strontium on porous alumina containing platinum. The mass ratio of platinum to strontium to porous alumina (platinum:strontium:porous alumina) is 1:9:100. Example 7 is the same as Example 1 except that an aqueous solution of 0.5 hydrate of strontium acetate is used instead of an aqueous solution of barium acetate.

[0241] <Comparative Example 1>

[0242] Comparative Example 1 is a material made by loading barium onto commercially available γ-alumina (manufactured by Strem Chemicals). Comparative Example 1 is the same as Example 4 except that the mixing is performed without using a platinum source to make the mass ratio of γ-alumina to barium 100:10.

[0243] <1> The most frequent value of fine pore size distribution

[0244] For Examples 1 and 2, which are examples of composite catalyst materials used in this invention, the most frequent values ​​of the pore size distribution were determined. The sample was heated at 110°C for 6 hours under reduced pressure to remove adsorbed moisture, etc., and then nitrogen adsorption isotherms were measured using Autosorb-1 or Autosorb-iQ instruments manufactured by Quanta Chrome. Based on the adsorption isotherms, the pore size distribution was calculated using the NLDFT method (software: AS1Win, Quanta Chrome; NLDFT core: N2 on carbon at 77K, slit pores, NLDFT equilibrium model), and the most frequent values ​​in this pore size distribution were determined.

[0245] <2> X-ray diffraction measurement

[0246] X-ray diffraction measurements were performed on the samples (Examples 1-2) using a RINT2100 (Fe-ray source, scanning angle: 0.6°–12°, scanning speed: 2° per minute) manufactured by Rigaku Corporation of Japan to confirm whether diffraction peaks corresponding to lattice plane spacing of 1 nm–200 nm could be detected.

[0247] <3> Experiment on the production of ammonia from nitrogen oxides (NOx)

[0248] The experiment was conducted using a fixed-bed flow-through reactor. 100 mg of the sample (Examples 1-7 and Comparative Example 1) was placed inside a quartz reaction tube, which was secured at both ends with quartz wool. Throughout the experiment, the gas flow rate was kept constant at 100 mL / min.

[0249] As a pretreatment step, the sample temperature was set to 500℃ and kept in a nitrogen gas flow containing 10% oxygen for 1 hour to remove residual moisture and organic matter.

[0250] Then, as a NOx adsorption step, the sample temperature was set to 300°C and maintained for 1 hour in a nitrogen gas stream containing 1000 ppm nitric oxide (NO) and 10% oxygen. Then, as an ammonia production step, the sample was maintained for 1 hour in a nitrogen gas stream containing 1% hydrogen.

[0251] In subsequent tests, no pretreatment process was performed; only the NOx adsorption and ammonia production processes were repeated. The NOx adsorption and ammonia production were quantified using a Thermo Fisher Scientific Nicolet iS 20 infrared spectrophotometer and a PIKE Technologies multi-reflection gas unit.

[0252] Table 1 shows the most frequent values ​​of the fine aperture distribution and the lattice spacing indicated by the diffraction peaks determined by X-ray diffraction.

[0253] Table 1

[0254] Example 1 6.0 8.3 Example 2 7.1 8.8

[0255] As can be seen from Table 1, in Examples 1 and 2, which are examples of composite catalyst materials, the most frequent values ​​of the pore size distribution are in the range of diameter 1 nm to 200 nm, and diffraction peaks corresponding to the lattice plane spacing of 1 nm to 200 nm were observed. That is, it can be confirmed that the pores in Examples 1 and 2 are regularly arranged. It can be considered that in Examples 1 and 2, the pores are regularly arranged through the self-assembly of amphiphilic organic molecules that chemically interact with the alumina source and the subsequent removal by sintering of the amphiphilic organic molecules.

[0256] Table 2 shows the experimental results of ammonia production from nitrogen oxides (NOx). Table 2 illustrates the NOx adsorption amount, the amount of ammonia generated from NOx, the ammonia yield (ammonia generated / NOx adsorption amount), and the maximum NH3 concentration. It should be noted that the NOx adsorption amount and NH3 generation amount per unit mass are calculated based on the catalyst weight after the ammonia production experiment.

[0257] Table 2

[0258]

[0259] As shown in Table 2, it can be confirmed that ammonia was generated in Examples 1-7, which contained precious metals. In contrast, no ammonia was generated in Comparative Example 1, which did not contain precious metals.

[0260] It can be confirmed that, compared with Example 5 which contains only precious metals and no alkali metals or alkaline earth metals, Examples 1-4, 6, and 7, which contain at least one of precious metals and alkali metals and alkaline earth metals, have higher ammonia production and maximum ammonia concentration.

[0261] In particular, in Examples 1, 2, 6, and 7, which are examples of composite catalyst materials, the ammonia yield does not decrease even after the second use, compared to Examples 3 and 4. Specifically, in Examples 2, 6, and 7, the ammonia yield increases in the second and third uses compared to the first. As described above, when using a composite catalyst material formed by supporting at least one of an alkali metal and an alkaline earth metal on the surface of porous alumina containing a noble metal, ammonia can be produced repeatedly with high efficiency.

[0262] Moreover, the amount of N2O generated in Example 4 was sufficiently low. In particular, no N2O generation was observed in Examples 1-3 and 5-7.

[0263] Previously, techniques were proposed to reduce nitrogen oxides (NOx) in exhaust gas to nitrogen using catalytic materials (NSR catalysts). In these cases, ammonia is known to be generated as an intermediate product, and N2O is also produced. However, the greenhouse effect of N2O is approximately 300 times that of CO2; therefore, lower production levels are preferred. Furthermore, the amount of N2O produced can sometimes increase depending on the catalytic material used.

[0264] By using a composite catalyst material, the amount of N2O generated can be significantly reduced, and ammonia can be produced from nitrogen oxides (NOx) (in other words, nitrogen oxides are reduced to ammonia). Specifically, if a composite catalyst material is used, the concentration of N2O generated along with ammonia is below the measurable concentration range, and even if it is detected, the concentration relative to ammonia is approximately 5% or less.

[0265] However, the catalyst material used in the manufacturing apparatus and method of the present invention is arbitrary. Any known catalyst material may be used if ammonia can be generated.

[0266] Explanation of reference numerals in the attached figures

[0267] 20: Manufacturing equipment.

[0268] 30: Control device.

[0269] 40: Burner.

[0270] 50: Feeder.

[0271] 100: Manufacturing unit.

[0272] G1: Raw material gas.

[0273] G1e: Raw material gas after use.

[0274] G2: Reducing gas.

[0275] K1: First common pathway.

[0276] K2: Second common pathway.

[0277] Q: Catalyst materials.

[0278] R1: First supply route.

[0279] R2: Second supply route.

[0280] R3: Recycling route.

[0281] R4: Exhaust path.

[0282] U: Reaction tube.

[0283] V1: First on / off valve.

[0284] V2: Second on / off valve.

[0285] V3: Third on / off valve.

[0286] V4: Fourth on / off valve.

Claims

1. A unit for producing ammonia, wherein, The ammonia manufacturing unit has a manufacturing apparatus and a control device for controlling the manufacturing apparatus. The manufacturing apparatus includes: The reaction tube contains a catalyst material comprising precious metals; A first supply path is used to supply exhaust gas containing NOx and oxygen to the reaction tube; A second supply path is used to supply NOx-free reducing gas to the reaction tube; and A recovery circuit is provided for recovering the ammonia generated from the reaction tube. The control device causes the manufacturing apparatus to perform manufacturing processes. The manufacturing process includes: The first step involves supplying the exhaust gas to the catalyst material, causing the NOx in the exhaust gas to be adsorbed by the catalyst material; and The second step involves, after the supply of exhaust gas is stopped, supplying the reducing gas to the catalyst material, whereby the NOx adsorbed in the catalyst material is converted into ammonia and recovered. The reducing gas includes any one or more of H2, C3H6, C3H8, and CH4.

2. The ammonia manufacturing unit as described in claim 1, wherein, The manufacturing process is repeated.

3. A unit for producing ammonia, wherein, The ammonia manufacturing unit has a manufacturing apparatus and a control device for controlling the manufacturing apparatus. The manufacturing apparatus includes: There are N reaction tubes, each containing a catalyst material containing precious metals, where N is a natural number greater than 2. N first supply paths, which are used to supply exhaust gas containing NOx and oxygen to the N reaction tubes respectively; N second supply paths, which are used to supply NOx-free reducing gas to the N reaction tubes respectively; and There are N recovery paths, which are used to recover the generated ammonia from the N reaction tubes respectively. The control device causes the manufacturing apparatus to repeatedly perform the manufacturing process for each of the N reaction tubes. The manufacturing process includes: The first step involves supplying the exhaust gas into the reaction tube, causing the NOx in the exhaust gas to be adsorbed by the catalyst material; and The second step involves, after the exhaust gas supply is stopped, supplying the reducing gas into the reaction tube to generate ammonia from the NOx adsorbed in the catalyst material, which is then recovered. During the execution of the first step for K of the N reaction tubes, the second step is executed for (NK) reaction tubes, where K is a natural number less than N. During the execution of the second step for the K reaction tubes, the first step is executed for the (NK) reaction tubes. The reducing gas includes any one or more of H2, C3H6, C3H8, and CH4.

4. The ammonia manufacturing unit as described in claim 3, wherein, The manufacturing apparatus has: N first on / off valves, which respectively open and close the N first supply lines; and N second on / off valves, which respectively open and close the N second supply lines. In the first step, the control device opens the first on / off valve and closes the second on / off valve. In the second process, the control device makes the first on-off valve closed and the second on-off valve open.

5. The ammonia manufacturing unit as described in claim 3, wherein, The manufacturing apparatus has: There are N exhaust paths, which are used to discharge exhaust gas from the N reaction tubes respectively; N third-party on / off valves, which respectively open and close the N recovery paths; as well as There are N fourth on / off valves, which respectively open and close the N exhaust paths. For each of the N reaction tubes, in the first step, the control device closes the third on-off valve and opens the fourth on-off valve. In the second process, the control device, for each of the N reaction tubes, opens the third on / off valve and closes the fourth on / off valve.

6. A method for producing ammonia, wherein, The method for manufacturing ammonia includes: The first step involves supplying exhaust gas containing NOx and oxygen to a catalyst material containing precious metals, causing the NOx in the exhaust gas to be adsorbed into the catalyst material; and The second step involves, after the exhaust gas supply is stopped, supplying a NOx-free reducing gas to the catalyst material, whereby the NOx adsorbed in the catalyst material is converted into ammonia and recovered. The reducing gas includes any one or more of H2, C3H6, C3H8, and CH4.

7. A method for producing ammonia, wherein, In a manufacturing apparatus having N reaction tubes, each containing a catalyst material comprising a noble metal, a manufacturing process is repeatedly performed for each of the N reaction tubes, where N is a natural number greater than 2. The manufacturing process includes: The first step involves supplying exhaust gas containing NOx and oxygen into the reaction tube, causing the NOx in the exhaust gas to be adsorbed by the catalyst material; and The second step involves, after the exhaust gas supply is stopped, supplying a NOx-free reducing gas into the reaction tube, whereby the NOx adsorbed in the catalyst material is converted into ammonia and recovered. During the execution of the first step for K of the N reaction tubes, the second step is executed for (NK) reaction tubes, where K is a natural number less than N. During the execution of the second step for the K reaction tubes, the first step is executed for the (NK) reaction tubes. The reducing gas includes any one or more of H2, C3H6, C3H8, and CH4.

8. The method for producing ammonia as described in claim 6 or 7, wherein, The temperature of the exhaust gas and the reducing gas is at least one of the temperature of the catalyst material, which is between 150°C and 500°C.

9. The method for producing ammonia as described in claim 6 or 7, wherein, The catalyst material includes: the noble metal; at least one of the alkali metal and the alkaline earth metal; and an oxide support.

10. The method for producing ammonia as described in claim 6 or 7, wherein, The precious metal is one or more of platinum, palladium, rhodium, and iridium. The catalyst material as a whole is set at 100% by mass, and the content of the precious metal is 0.01% to 20.0% by mass of the catalyst material as a whole.

11. The method for producing ammonia as described in claim 9, wherein, The alkali metal is selected from one or more of lithium, potassium, sodium, and cesium. The alkaline earth metal is selected from one or more of calcium, magnesium, strontium, and barium. The catalyst material is set to 100% by mass, and the content of the alkali metal and the alkaline earth metal is 0.1% to 50.0% by mass of the catalyst material.

12. The method for producing ammonia as described in claim 9, wherein, The oxide support is any one or more of Al2O3, CeO2, TiO2, and ZrO2.

13. The method for producing ammonia as described in claim 9, wherein, The oxide support is Al2O3. The noble metal is contained within the Al2O3. The alkali metal and the alkaline earth metal are loaded onto Al2O3 containing the noble metal inside.

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