METHOD FOR REGENERATING METAL ZEOLITE CATALYST AND APPARATUS FOR REGENERATING METAL ZEOLITE CATALYST

Abstract

To provide a regeneration method and a regeneration apparatus which can easily improve catalytic performance of a metal zeolite-based NOx reduction catalyst such as deteriorated copper zeolite and iron zeolite.SOLUTION: Provided is a method for regenerating a metal zeolite catalyst that reduces nitrogen oxide in exhaust gas, where a deteriorated catalyst due to use is brought in contact with regeneration gas having the water vapor concentration of 75% or more under the temperature condition of 150 to 500°C. Then, the regeneration gas may further contain hydrogen or ammonia, or ammonia and nitrogen monoxide. Further, a regeneration apparatus supplies regeneration gas having the water vapor concentration of 75% or more to a reactor 47 housing a deteriorated catalyst 45 due to use, and heats the reactor 47 to the temperature of 150 to 500°C by an electric furnace 51, and allows the catalyst 45 and the regeneration gas to react with each other to regenerate a metal zeolite catalyst.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a catalyst for reducing nitrogen oxides in exhaust gas from stationary sources such as garbage incinerators and boilers, or mobile sources such as railways, ships, automobiles, especially automobiles driven by diesel engines, and particularly to a method and apparatus for regenerating a metal zeolite catalyst.

Background Art

[0002] Exhaust gas from stationary sources such as boilers or mobile sources such as automobiles contains nitrogen oxides (hereinafter referred to as NOx), which is a cause of air pollution. Conventionally, in order to reduce the emission of NOx into the atmosphere, a denitration technology has been adopted in which NOx in exhaust gas is decomposed into harmless nitrogen and water vapor by the action of a catalyst using ammonia or the like. For example, heavy vehicles driven by diesel engines such as buses and trucks are equipped with a purification catalyst system according to exhaust gas regulations. As a catalyst used for reducing such nitrogen oxides in exhaust gas, a catalyst based on metal zeolite (metal ion zeolite) such as copper zeolite or iron zeolite is particularly effective. However, the catalyst gradually deteriorates during use, and as the deterioration progresses, the catalyst performance decreases, so that the emission amount of NOx, which is a harmful component, increases.

[0003] In the above-mentioned heavy vehicle driven by a diesel engine, the catalyst is fixed inside a metal converter container. When problems such as performance degradation or damage of the catalyst occur, the entire converter container is replaced with a new one in order to prevent NOx emissions. However, if the same catalyst can be continuously used without replacing it with a new one in such a case, it is economically and resourcefully preferable. For example, Patent Document 1 discloses a method for regenerating a NOx reduction catalyst in which a vanadium-based NOx reduction catalyst is brought into contact with 10 to 50% water vapor in a temperature range of 250 to 390°C.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-534783 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The regeneration method described in Patent Document 1 makes it possible to improve the catalytic performance of a degraded vanadium-based NOx reduction catalyst. However, in recent years, environmental issues have become a major topic of discussion, and exhaust gas emission regulations have become stricter year by year. In this regard, vanadium-based NOx reduction catalysts, such as those described in Patent Document 1, cannot be said to be able to meet the increasingly stringent exhaust gas emission regulations. Currently, metal zeolite catalysts such as copper zeolite and iron zeolite, which can meet stringent exhaust gas emission regulations, are becoming the mainstream NOx reduction catalysts. Therefore, there is a need for a method that allows for easy regeneration of metal zeolite catalysts such as copper zeolite and iron zeolite.

[0006] The present invention was made to solve these problems and aims to provide a regeneration method and apparatus that can easily improve the catalytic performance of degraded metal zeolite-based NOx reduction catalysts such as copper zeolite and iron zeolite. [Means for solving the problem]

[0007] Generally, zeolite-based catalysts are known to degrade easily when exposed to water vapor at high temperatures, resulting in a shortened catalyst lifespan. Furthermore, unlike vanadium-based catalysts, copper zeolites in particular degrade even with water vapor in exhaust gas (approximately 10-13%), leading to a decrease in catalyst performance. However, the inventors focused on the fact that hydrothermal synthesis is used for zeolite synthesis and discovered that NOx reduction catalysts can be easily regenerated by incorporating a high concentration of water vapor into the gas used for catalyst regeneration, thus completing the present invention. Specifically, the present invention has the following configuration.

[0008] (1) A method for regenerating a metal zeolite catalyst that reduces nitrogen oxides in exhaust gas, wherein the catalyst that has deteriorated due to use is brought into contact with a regenerated gas having a water vapor concentration of 75% or more under temperature conditions of 150-500°C. (2) The method for regenerating a metal zeolite catalyst according to (1), wherein the regenerated gas further comprises hydrogen, or ammonia, or ammonia and nitric oxide. (3) A method for regenerating a metal zeolite catalyst as described in (1), wherein the temperature conditions are 150-350°C, the regenerated gas has a water vapor concentration of 75% or more, and the remaining gas is an inert gas. (4) The method for regenerating a metal zeolite catalyst as described in (1), wherein the temperature conditions are 150-300°C and the regenerating gas contains hydrogen. (5) The method for regenerating a metal zeolite catalyst as described in (1), wherein the temperature conditions are 200-450°C and the regenerating gas contains ammonia. (6) The method for regenerating a metal zeolite catalyst as described in (1), wherein the temperature conditions are 300-500°C and the regenerated gas contains ammonia and nitric oxide. (7) A method for regenerating a metal zeolite catalyst according to any one of (1) to (6), wherein the temperature is alternately changed at regular intervals between low temperature and high temperature within a certain temperature range among the temperature conditions. (8) The metal zeolite catalyst is copper zeolite. This is a method for regenerating a metal zeolite catalyst as described in any one of (1) to (7). (9) The exhaust gas is exhaust gas from a diesel engine. A method for regenerating a metal zeolite catalyst as described in any one of (1) to (8). In heavy vehicles driven by diesel engines, regenerating the catalyst reduces the cost and effort of replacing the catalyst with a new one. (10) A metal zeolite catalyst regeneration device for reducing nitrogen oxides in exhaust gas, comprising: a container for containing a catalyst that has deteriorated due to use; a regeneration gas supply unit for supplying regeneration gas with a water vapor concentration of 75% or more to the container; and a heater for heating the container to a temperature of 150-500°C. (11) The regeneration apparatus for a metal zeolite catalyst according to (10), wherein the regeneration gas further comprises hydrogen, or ammonia, or ammonia and nitric oxide. (12) The metal zeolite catalyst regeneration apparatus according to (10), wherein the temperature is 150-350°C, the regeneration gas has a water vapor concentration of 75% or more, and the remaining gas is an inert gas. (13) The regeneration apparatus for a metal zeolite catalyst according to (10), wherein the temperature is 150-300°C and the regeneration gas contains hydrogen. (14) The regeneration apparatus for a metal zeolite catalyst according to (10), wherein the temperature is 200-450°C and the regeneration gas contains ammonia. (15) The regeneration apparatus for a metal zeolite catalyst according to (10), wherein the temperature is 300-500°C and the regeneration gas contains ammonia and nitric oxide. (16) A metal zeolite catalyst regeneration apparatus according to any one of (10) to (15), which is provided with a control device that alternately changes the temperature of the heater between a low temperature and a high temperature within a certain temperature range at regular intervals. (17) The metal zeolite catalyst is a copper zeolite, and the regeneration device for the metal zeolite catalyst is one of the metal zeolite catalysts described in any one of (10) to (16). (18) The exhaust gas is exhaust gas from a diesel engine. (10) to (17) The metal zeolite catalyst regeneration device. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a regeneration method and regeneration apparatus that can easily improve the catalytic performance of metal zeolite-based NOx reduction catalysts such as copper zeolite and iron zeolite. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram showing an example of the configuration of an exhaust gas treatment system. [Figure 2] This is a diagram illustrating the configuration of a catalyst regeneration treatment device (catalyst performance testing device). [Figure 3] It is a configuration diagram of a catalyst deterioration treatment device. [Figure 4] It is a diagram showing the results of a catalyst performance test of deteriorated products.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described in detail while referring to the drawings. In the embodiments of the present invention, the gas concentration means volume concentration (vol%, ppmv). Also, when indicating a temperature range, a concentration range, etc., the upper limit value and the lower limit value are included.

[0012] FIG. 1 shows an example of the configuration of an exhaust gas treatment system. In the illustrated example, an exhaust gas treatment system 1 for a heavy vehicle driven by a diesel engine is shown. A heavy vehicle driven by a diesel engine has better fuel efficiency and less carbon dioxide emissions compared to a gasoline vehicle, so it is environmentally friendly. Also, as a long-distance transport vehicle such as a bus or a truck, or a special vehicle, long-term use is expected in the future.

[0013] As shown in FIG. 1, the exhaust gas treatment system 1 is arranged in order from the upstream side of the flow path of the engine exhaust gas, and includes an oxidation catalyst (DOC) 11 that oxidizes nitrogen monoxide (NO), hydrocarbons (HC), and carbon monoxide (CO) in the exhaust gas, a diesel particulate filter (DPF) 13 that removes particulate matter (PM) in the exhaust gas, a NOx selective reduction catalyst (hereinafter referred to as an SCR (Selective Catalytic Reduction) catalyst) 15 that reduces NOx in the exhaust gas, an ammonia slip catalyst (ASC) 17 that oxidizes and removes ammonia in the exhaust gas, etc. Also, a reducing agent supply device 21 for supplying a reducing agent is arranged at the inlet of the SCR catalyst.

[0014] DOC11 is an oxidation catalyst supporting noble metals such as platinum and palladium. Before reaching the downstream DPF13, NO, HC, and CO contained in the exhaust gas are oxidized by the noble metals to become harmless carbon dioxide (CO2) and water vapor (H2O). Also, a part of NO is oxidized to nitrogen dioxide (NO2).

[0015] DPF13 is a filter device that collects and removes PM in the exhaust gas. By injecting extra fuel into DOC11 and forcibly raising the temperature by the oxidation heat generated when this fuel is catalytically oxidized in DOC11, PM is combusted (DPF regeneration) processed. Heat-resistant ceramics or metal porous bodies that can filter fine particles are used for the filter, and PM in the exhaust gas purified by DOC is collected when the exhaust gas passes through the fine pores of the filter.

[0016] The SCR catalyst 15 is a catalyst that reduces NOx in the exhaust gas. By the action of the SCR catalyst 15 and the reducing agent supplied from the reducing agent supply device 21, NOx in the exhaust gas is reduced to nitrogen and water vapor. The reducing agent supply device 21 can be configured to include a tank in which the reducing agent is stored, a pump, a valve, an injection nozzle, pipes, etc. As the reducing agent, ammonia (NH3) and urea (aqueous urea solution) are used. In the case of urea, it can be stored in the tank in the form of aqueous urea solution, so it is excellent in handling and preferable. And since the aqueous urea solution is hydrolyzed by the exhaust heat of the engine, it becomes ammonia gas when blown into the exhaust gas.

[0017] The reducing agent may be supplied either through the exhaust gas flow path between the DPF 13 and the SCR catalyst 15, or directly to the converter container in which the SCR catalyst 15 is located. The SCR catalyst 15 should preferably be an iron zeolite or copper zeolite, which consists of a zeolite support on which metal ions such as iron or copper ions are supported. Other metal ions include gallium ions, cobalt ions, silver ions, and palladium ions, but iron zeolite and copper zeolite are preferred because they are known to have high NOx reduction effects. Copper zeolite is particularly suitable because it exhibits high NOx reduction effects even at relatively low temperatures. Various catalyst shapes can be used, such as honeycomb, plate-like, or granular. The type of zeolite (crystal structure) is also arbitrary. For example, it may be type A (LTA), ferrielite (FER), MCM-22 (MWW), ZSM-5 (MFI), mordenite (MOR), type L (LTL), type X or Y (FAU), type beta (BEA), chabazite (CHA), etc., and may also be type CDO, type GON, etc. The structural codes are shown in parentheses.

[0018] In the presence of oxygen in the atmosphere, the exhaust gas undergoes selective reduction of NOx through the action of the reducing agent supplied from the reducing agent supply device 21 and the SCR catalyst 15, as shown in the following chemical reaction equations (1)-(3), mainly producing nitrogen and water vapor.

[0019] 4NO + 4NH3 + O2 → 4N2 + 6H2O (1) 2NO2 + 4NH3 + O2 → 3N2 + 6H2O (2) NO + NO2 + 2NH3 → 2N2 + 3H2O (3)

[0020] At this time, in order to completely react with the NOx present in the exhaust gas, an excess of reducing agent is supplied relative to the NOx. However, these reducing agents are oxidized by the downstream ASC17, and purified gas is produced. The ASC17 is an ammonia oxidation catalyst for oxidizing the unreacted reducing agent (ammonia) that passes through the SCR catalyst, and some contain metals such as copper, iron, platinum, and palladium on a support such as zeolite, titania, alumina, silica, or zirconia. In this way, NOx and other harmful gases are removed from the exhaust gas by the exhaust gas treatment system 1.

[0021] Furthermore, SCR catalysts gradually deteriorate during use, and as deterioration progresses, their catalytic performance (activity) decreases. For example, in exhaust gas treatment system 1 as shown in Figure 1, depending on the usage conditions, a new catalyst will experience a decrease in catalytic performance of approximately 10-50% after 1,000 to 10,000 hours of use. Therefore, according to this embodiment, the catalytic performance of a deteriorated catalyst can be improved by removing it from the converter container and performing a regeneration process. Specifically, a catalyst that has deteriorated due to reduced catalytic performance is brought into contact with an atmospheric gas containing a high concentration of water vapor (hereinafter referred to as the regeneration gas) under temperature conditions of 150-500°C.

[0022] The amount of high-concentration water vapor in the regeneration gas should be 75-100 vol% or 75-90 vol% (the remainder being balance gas). By setting the water vapor concentration within this range, the catalyst can be regenerated. The regeneration temperature should be 150-500°C, preferably around 150-350°C, where the reconstruction of the zeolite skeleton structure and activation of the catalyst components can be more effectively expected. A regeneration temperature of 150°C or higher can accelerate the catalyst regeneration reaction. Furthermore, from the viewpoint of the durability of the zeolite under high-concentration water vapor, a temperature of 500°C or lower is preferable.

[0023] Furthermore, the regeneration treatment time varies depending on the amount and temperature of water vapor, the flow rate, and other conditions, but is generally carried out in the range of 1 to 168 hours. Preferably, 5 to 50 hours is sufficient as contact time between the catalyst and the regeneration gas. In addition, during the catalyst regeneration treatment, the regeneration gas may be flowed while maintaining a constant temperature, or the temperature may be changed alternately between low and high temperatures within a certain temperature range at regular intervals. By changing the regeneration temperature between low and high temperatures, it is expected that the chemical equilibrium conditions will be altered, thereby promoting the activation of the catalyst. This temperature range can be any between 150 and 500°C, but if it is too wide, it will be difficult for the actual temperature of the catalyst itself to follow the temperature change, so it is sufficient to set it to around 100°C, preferably around 50°C, within the aforementioned temperature range. For example, if the regeneration time is 20 hours, it is conceivable to control the temperature to change between 200°C and 250°C or between 250°C and 300°C every 30 minutes or 1 hour. This control can be achieved by controlling the temperature of a heater (electric furnace 51, described later) that heats the reaction vessel (reactor 47, described later) containing the catalyst to be regenerated, using a control device (including a timer) not shown.

[0024] Furthermore, the regenerated gas may also contain hydrogen (H2), ammonia (NH3), or ammonia and nitric oxide (NO). For example, in the exhaust gas purification process, metals contained in iron zeolite or copper zeolite may be deactivated by oxygen (O2) in the exhaust gas by becoming metal oxides such as iron oxide or copper oxide. In this case, if the regenerated gas contains hydrogen, it can be said that it contributes to improving catalytic performance because hydrogen has the effect of reducing such metal oxides. The amount of hydrogen in the regenerated gas should be 0.1-10 vol%, preferably 0.25-2.5 vol%. If the hydrogen concentration is too low, the regeneration effect will be small, while if it is too high, the catalytic components will be excessively reduced, thus reducing the effect of improving activity.

[0025] Furthermore, since ammonia added to the regenerated gas, or ammonia and nitric oxide, are reactants in the SCR catalyst, it is thought that they have the effect of activating the SCR catalyst. When adding only ammonia, the concentration should be 100-10000 ppm, preferably 200-2000 ppm. When adding both ammonia and nitric oxide, the ammonia concentration should be 100-10000 ppm, preferably 200-2000 ppm, and the nitric oxide concentration should be 100-10000 ppm, preferably 200-2000 ppm. By setting the amounts of ammonia and nitric oxide within the above concentration ranges, the regeneration effect will be enhanced. Note that since ammonia and nitric oxide have a higher regeneration effect than hydrogen, the amount added can be less than that of hydrogen.

[0026] Figure 2 shows the catalyst regeneration apparatus and catalyst performance testing apparatus used in this embodiment. The catalyst regeneration apparatus 3 and the catalyst performance measuring apparatus are the same apparatus, and are configured to regenerate catalysts and measure the activity of regenerated or degraded catalysts. The apparatus mainly consists of flow controllers 31, 33, 35, 37, and 39 for each gas, a mixer 40 for each regeneration gas, a water vaporizer 43 for producing steam, a reactor 47 for containing catalyst samples 45 for regeneration, and a gas analyzer 49 for measuring and analyzing the gas concentration at the supply port (inlet) 47a and outlet 47b of the reactor 47 for regeneration gases. In the illustrated example, flow controllers are installed in each gas flow path (piping) 61, 63, 65, 67, and 69, and regeneration gas of the desired composition is obtained by appropriately mixing each gas. However, multiple types of compressed regeneration gases of the desired composition may be prepared in advance, and a single control device may be used to open and close solenoid valves (not shown) installed in specific regeneration gas flow paths to supply regeneration gases of different compositions.

[0027] When used as a catalyst regeneration treatment device, steam is used as the regeneration gas. Therefore, the amount of water supplied is adjusted using a water flow rate controller 41 installed in the water flow path (piping) 71, and the water is converted into steam in the vaporizer 43 before being introduced into the gas flow path. The gas flow path 73 between the vaporizer 43 and the reactor 47 is maintained at approximately 100-130°C by heating pipes 53 arranged around it. The reactor 47 is maintained at a predetermined temperature, for example, 150-500°C, by an electric furnace 51 arranged around it.

[0028] For example, let's consider a catalyst regeneration apparatus where only water vapor is used as the regeneration gas and nitrogen is used as the balance gas. Note that the balance gas can be any inert gas, and helium or argon may also be used. First, a metal zeolite-based NOx reduction catalyst (catalyst sample 45), such as copper zeolite, which has deteriorated due to use, is placed inside the reactor 47. The reactor 47 is made of heat-resistant stainless steel or quartz reaction vessel. Then, the required amount of nitrogen is supplied by controlling the nitrogen flow control meter 39 installed in the nitrogen flow channel 69, and the required amount of water is similarly introduced into the vaporizer 43 by controlling the water flow control meter 41 to produce water vapor, thereby supplying a mixed gas of water vapor and nitrogen into the reactor 47. The reactor 47 is maintained at a predetermined temperature by an electric furnace 51, and by flowing the regeneration gas for a predetermined time, the regeneration gas reacts with the catalyst and the catalyst is regenerated. Alternatively, a control device (not shown) may be provided to control the temperature of the electric furnace 51, and the regeneration temperature and regeneration time may be controlled by a separately provided or built-in timer. For a metal zeolite-based catalyst, it is sufficient to flow the regeneration gas at a regeneration temperature of 150-500°C for approximately 20 hours.

[0029] Furthermore, when using hydrogen, ammonia, or nitric oxide as regenerating gases, the required amount can be supplied by controlling the hydrogen flow control meter 31 installed in the hydrogen flow path 61, the ammonia flow control meter 35 installed in the ammonia flow path 65, and the nitric oxide flow control meter 33 installed in the nitric oxide flow path 63, respectively. These gases are mixed in the gas mixer 40 and supplied to the reactor 47 from the supply port 47a along with water vapor that joins them midway through the flow path.

[0030] Furthermore, when evaluating the performance of a catalyst that has been regenerated for a predetermined time, the catalyst regeneration apparatus can also be used as a catalyst performance test apparatus by changing the type and flow rate of gas supplied to the reactor 47, the temperature of the electric furnace 51, etc. Therefore, catalyst performance testing can be performed immediately after the regeneration process, with the regenerated catalyst still in place. The method of using it as a catalyst performance test apparatus is described below.

[0031] The catalyst performance test can be performed by installing a regenerated catalyst or a degraded catalyst (catalyst sample 45) in the reactor 47, supplying a simulated exhaust gas to the reactor 47, injecting the simulated gas from the reactor 47's supply port 47a and the reactor 47's discharge port 47b into a gas analyzer 49, and measuring the NOx concentration in each simulated gas. The simulated gas can contain not only nitric oxide, the main component of exhaust gas, but also ammonia and oxygen as reducing agents, and the required amount can be flowed by controlling the ammonia flow controller 35 and the oxygen flow controller 37. Furthermore, by changing the catalyst sample 45, a new catalyst can also be tested in the same way. [Examples]

[0032] (Production of degraded products) First, a degraded product (degraded catalyst) for comparison was prepared using a catalyst degradation treatment apparatus. Figure 3 shows the configuration diagram of the catalyst degradation treatment apparatus 80. Two grams of new copper zeolite catalyst powder (copper content = 3.7 wt%, zeolite = chabazite, manufactured by Tosoh Corporation, H-SSZ-13, HSZ-D12HOA, Si / 2Al (molar ratio) = 16.6) was used as a sample. It was packed into a heat-resistant alumina boat (length 100 mm, width 15 mm, height 15 mm) 82 and placed in the center of a quartz tube (inner diameter 35 mm, length 600 mm) 84. Since the degree of degradation varies depending on the catalyst usage conditions and environment, in this example, the degradation treatment was carried out using the following method to simulate the degradation state in order to produce a uniformly degraded sample and to accelerate the degradation of the catalyst.

[0033] The electric furnace 86 was set to 750°C, and the heating pipe 88 was maintained at 130°C. The water supply was adjusted using the water flow controller 90 so that the water vapor concentration was 30 vol%, and the water was introduced into the vaporizer 92. Air was used as a balance gas, and the flow rate was adjusted using the air flow controller 94 so that the gas flow rate was 500 ml / min. The gas was then flowed for 10 hours to produce a degraded product.

[0034] (Performance test) Performance testing (catalytic activity testing) of the degraded sample was performed using the apparatus shown in Figure 2 in the following manner. 10 mg was weighed out from the degraded sample prepared by the method described above, and 0.8 g of granular quartz sand (diameter 0.3-0.5 mm) was added to ensure gas permeability. The mixed sample 45 was then fixed in the center of reactor 47 (inner diameter 10 mm, length 310 mm) sandwiched between quartz wool. As conditions for simulating exhaust gas, the standard SCR reaction of equation (1) above was performed using a gas that simulated the following diesel gas composition. Simulated gas composition: 200 ppm NO, 220 ppm NH3, 1% H2O, 10% O2, N2 balance Flow rate 400ml / min

[0035] The catalyst temperature was lowered from 430°C to 230°C in 40°C increments for 30 minutes each using an electric furnace 51. At each temperature (6 points: 430°C, 390°C, 350°C, 310°C, 270°C, and 230°C), the gas at the supply port 47a and the gas at the outlet 47b of the reactor 47 were analyzed using a gas analyzer 49 (FT-IR with gas cell, manufactured by Thermo Fisher Scientific Inc., iS-10, resolution 0.5 cm²). ―1 The NOx conversion rate was measured by injecting the gas into the sample (i.e., the inlet and outlet gases were measured six times for one sample 45). The measurement conditions were as follows. NOx conversion rate=[(NOx)inlet-(NOx)outlet] / (NOx)inlet x 100(%) (4)

[0036] Figure 4 shows the results of measuring the NOx conversion rate of the degraded product. Of the six temperatures mentioned above, the average value (average of 4 points) of the NOx conversion rate at 270°C-390°C, which corresponds to the catalyst temperature range during actual vehicle operation, was used as the catalyst performance index (catalytic activity value) to be evaluated. In this case, the NOx conversion rate of the degraded product was 76.7% (Table 1). For reference, the NOx conversion rate of a new product is approximately 99%. Similarly, in subsequent examples, the average value of the NOx conversion rate at 270°C-390°C was used as the catalyst performance index (catalytic activity value).

[0037] (Regeneration process) (Example 1) The catalyst that had deteriorated using the method described above was regenerated using the following method. 10 mg was weighed out from the prepared degraded sample, and 0.8 g of granular quartz sand (diameter 0.3-0.5 mm) was added to ensure gas permeability. The mixed sample 45 was then fixed in the center of the reactor 47 (inner diameter 10 mm, length 310 mm) sandwiched between quartz wool. The regeneration temperature was set to 200°C by adjusting the temperature of the electric furnace 51, and the water vapor concentrations were set to 1%, 30%, 50%, 75%, and 90%, with nitrogen used as a balance gas (i.e., the regeneration gas components were only water vapor and nitrogen). The regeneration time was set to 20 hours. The nitrogen flow controller 39 and water flow controller 41 were adjusted so that the total flow rate of the regeneration gas was 75 ml / min. The holding temperature of the heating pipe 53 was set to 100-130°C (100°C in Experimental Example 1 (H2O 1%), and 130°C in Experimental Examples 2-5) to prevent condensation of water vapor. The regenerated samples obtained in this way were subjected to catalyst activity tests using the same method as the performance tests for the degraded products described above. The results are shown in Table 1. [Table 1]

[0038] From the results in Table 1, a clear improvement in NOx conversion rate was observed when the water vapor concentration in Experimental Examples 4 and 5 was set to a high concentration of 75% or more. Therefore, further investigations were conducted under the same conditions, with the water vapor concentration set to 75% and the regeneration temperature changed, while other conditions remained the same. In addition to maintaining a constant regeneration temperature, a method of alternating between low and high temperatures at regular intervals was also implemented. The method of sample preparation and installation in the reactor was the same as described above (Experimental Examples 1-5). The regenerated samples obtained in this way were also subjected to catalyst activity tests in the same manner. The results are shown in Table 2. In Experimental Example 9, the temperature was changed between 250°C and 300°C every 30 minutes, and in Experimental Example 10, the temperature was changed between 300°C and 350°C every 30 minutes. This temperature change was performed by adjusting the set temperature and time of the temperature controller of the electric furnace 51. The total flow rate of the regenerated gas was the same as in Experimental Examples 1-5, and the same flow rate was used in all the examples shown below. Similarly, the use of nitrogen as the balance gas and the 20-hour regeneration time are also noteworthy.

[0039] [Table 2] These results showed a stable improvement in the NOx conversion rate over a wide temperature range from 150°C to 350°C. Therefore, it was confirmed that a relatively high NOx conversion rate can be obtained stably by using high-concentration water vapor as a regenerating gas. Furthermore, when the temperature was changed between low and high temperatures, a NOx conversion rate of approximately 80% was achieved, demonstrating an effect of improving the NOx conversion rate.

[0040] (Example 2) Next, to investigate the effect of hydrogen addition, the amount of hydrogen added was adjusted using the hydrogen flow controller 31, and a small amount of hydrogen was added to the regenerated gas to perform the regeneration process. The method of sample preparation and installation in the reactor was the same as in Example 1. The regeneration temperature was set by adjusting the temperature of the electric furnace 51, the water vapor concentration was set to 75%, nitrogen was used as a balance gas, and the regeneration time was set to 20 hours. Two conditions were used for the amount of hydrogen added: 0.25 vol% and 2.5 vol%. In addition, the hydrogen flow controller 31, nitrogen flow controller 39, and water flow controller 41 were adjusted so that the total flow rate of the regenerated gas was 75 ml / min. The regenerated sample obtained in this way was subjected to a catalyst activity test in the same manner as in Example 1. The results are shown in Table 3. [Table 3]

[0041] From the above results, it was found that, particularly in the intermediate to low temperature range below 300°C, using regenerated gas obtained by adding hydrogen to high-concentration water vapor gas significantly improved the NOx conversion rate. Furthermore, it was confirmed that even a small amount of added hydrogen, such as about 0.25 vol%, contributed to improving the NOx conversion rate. In particular, as shown in Experimental Examples 12 and 17, a significant functional recovery of over 90% was observed with the addition of hydrogen.

[0042] (Example 3) Furthermore, to investigate the effect of ammonia addition, the amount of ammonia added was adjusted using the ammonia flow controller 35, and a small amount of ammonia was added to the regenerated gas to perform the regeneration treatment. The method of sample preparation and installation in the reactor was the same as in Example 1. The regeneration temperature was set by adjusting the temperature of the electric furnace 51, the water vapor concentration was set to 75%, nitrogen was used as a balance gas, and the regeneration time was set to 20 hours. In addition, the ammonia flow controller 35, nitrogen flow controller 39, and water flow controller 41 were adjusted so that the total flow rate of the regenerated gas was 75 ml / min. The regenerated samples obtained in this way were subjected to catalyst activity tests in the same manner as in Example 1. The results are shown in Table 4. [Table 4]

[0043] From the above results, it was observed that using regenerated gas obtained by adding ammonia to high-concentration water vapor gas improved the NOx conversion rate, particularly in the intermediate temperature range of 200-450°C. Although the difference in conversion rate between the regenerated gas and the degraded gas at 450°C was only about 2.5%, even this small difference can be considered a significant recovery of activity.

[0044] (Example 4) Furthermore, to investigate the effect of adding nitric oxide, the amount of ammonia added was adjusted using the ammonia flow controller 35, and the amount of nitric oxide added was adjusted using the nitric oxide flow controller 33. A small amount of ammonia and nitric oxide was added to the regenerated gas, and the regeneration process was performed. The method of sample preparation and installation in the reactor was the same as in Example 1. The regeneration temperature was set by adjusting the temperature of the electric furnace 51, the water vapor concentration was set to 75%, nitrogen was used as a balance gas, and the regeneration time was set to 20 hours. In addition, the ammonia flow controller 35, nitric oxide flow controller 33, nitrogen flow controller 39, and water flow controller 41 were adjusted so that the total flow rate of the regenerated gas was 75 ml / min. The regenerated sample obtained in this way was subjected to a catalyst activity test in the same manner as in Example 1. The results are shown in Table 5. [Table 5]

[0045] From the above results, it was found that, particularly in the high-temperature range of 300-500°C, using a regenerated gas obtained by adding ammonia and nitric oxide to high-concentration water vapor gas consistently resulted in a high improvement in the NOx conversion rate. In the examples, copper zeolite was used as the metal zeolite catalyst, but since the mechanism of performance degradation and functional recovery of the metal zeolite catalyst is thought to be mainly due to the destruction and repair of the zeolite structure, it can be said that other metal types of zeolites will exhibit similar regenerative action and effects.

[0046] As described above, by contacting the degraded catalyst with a regenerated gas containing 75% water vapor and performing a regeneration treatment, an improvement in catalyst performance was observed. Furthermore, according to this embodiment, the regenerated gas can be easily prepared by simply adding a small amount of water vapor (and nitrogen), or hydrogen, ammonia, or ammonia and nitric oxide to water vapor, making it a simple regeneration method and apparatus. [Industrial applicability]

[0047] The present invention is not limited to stationary sources such as waste incinerators and boilers, or mobile sources such as railways, ships, and automobiles, but may also be applicable to a catalyst regeneration method and regeneration apparatus for reducing nitrogen oxides in exhaust gas from various other combustion devices. [Explanation of Symbols]

[0048] 1. Exhaust gas treatment system 3. Catalyst regeneration treatment device (catalyst performance testing device) 11 DOC 13 DPF 15 Catalyst 17 ASC 21 Reducing agent supply device 31, 33, 35, 37, 39, 41 Flow rate controller 40 mixer 43. Vaporizer 45 Catalyst Samples 47 Reactor 49 Gas analyzer 51 Electric Furnace 53 Heating piping 61, 63, 65, 67, 69, 71, 73 channel 80 Catalyst degradation treatment device 82 Alumina Boat 84 Quartz tube 86 Electric Furnace 88 Heating piping 90 Water flow control meter 92 Vaporizer 94 Air flow control meter

Claims

1. 1. A method for regenerating a metal zeolite catalyst that reduces nitrogen oxides in exhaust gas, comprising: A method for regenerating a metal zeolite catalyst, comprising contacting a catalyst deteriorated with use with a regeneration gas having a steam concentration of 75% or more at a temperature of 150-500°C.

2. 2. The method for regenerating a metal zeolite catalyst according to claim 1, wherein the regeneration gas further contains hydrogen, ammonia, or ammonia and nitric oxide.

3. 2. The method for regenerating a metal zeolite catalyst according to claim 1, wherein the temperature condition is 150-350°C, the regeneration gas has a water vapor concentration of 75% or more, and the remainder is an inert gas.

4. 2. The method for regenerating a metal zeolite catalyst according to claim 1, wherein the temperature condition is 150-300° C. and the regeneration gas contains hydrogen.

5. 2. The method for regenerating a metal zeolite catalyst according to claim 1, wherein the temperature condition is 200-450° C. and the regeneration gas contains ammonia.

6. 2. The method for regenerating a metal zeolite catalyst according to claim 1, wherein the temperature condition is 300-500° C. and the regeneration gas contains ammonia and nitrogen monoxide.

7. A method for regenerating a metal zeolite catalyst according to any one of claims 1 to 6, characterized in that the temperature is alternately changed between low and high temperatures within a certain temperature range among the temperature conditions at regular intervals.

8. 8. The method for regenerating a metal zeolite catalyst according to claim 1, wherein the metal zeolite catalyst is a copper zeolite.

9. 9. The exhaust gas of claim 1, wherein the exhaust gas is exhaust gas from a diesel engine.

10. A method for regenerating a metal zeolite catalyst according to claim 9.

10. A regenerator for a metal zeolite catalyst that reduces nitrogen oxides in exhaust gas, comprising: a container for storing a catalyst that has deteriorated due to use; a regeneration gas supply unit that supplies a regeneration gas with a water vapor concentration of 75% or more to the container; a heater for heating the vessel to a temperature of 150-500°C; A regeneration device for a metal zeolite catalyst, comprising:

11. 11. The apparatus for regenerating a metal zeolite catalyst according to claim 10, wherein the regeneration gas further contains hydrogen, ammonia, or ammonia and nitric oxide.

12. 11. The apparatus for regenerating a metal zeolite catalyst according to claim 10, wherein the temperature is 150-350°C, the regeneration gas has a water vapor concentration of 75% or more, and the remainder is an inert gas.

13. 11. The apparatus for regenerating a metal zeolite catalyst according to claim 10, wherein the temperature is 150-300° C. and the regeneration gas contains hydrogen.

14. 11. The apparatus for regenerating a metal zeolite catalyst according to claim 10, wherein the temperature is 200-450° C. and the regeneration gas contains ammonia.

15. 11. The apparatus for regenerating a metal zeolite catalyst according to claim 10, wherein the temperature is 300-500°C and the regeneration gas contains ammonia and nitric oxide.

16. A regeneration device for a metal zeolite catalyst described in any one of claims 10 to 15, characterized in that a control device is provided that alternately changes the temperature of the heater between low and high temperatures within a certain temperature range at regular intervals.

17. 17. The apparatus for regenerating a metal zeolite catalyst according to claim 10, wherein the metal zeolite catalyst is a copper zeolite.

18. 18. The apparatus for regenerating a metal zeolite catalyst according to claim 10, wherein the exhaust gas is exhaust gas from a diesel engine.

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