Device and method for making denitration catalysts react quickly in SCR

Abstract

The application belongs to the field of waste gas denitration treatment technology, and specifically discloses a device and method for making denitration catalysts to undergo rapid SCR reaction. The device comprises a NO oxidation device, a switch and an NH3-SCR reaction device arranged in sequence. The NO oxidation device comprises a Pt / CeO2 catalyst, and the NH3-SCR reaction device comprises a Cu / HZSM-5 molecular sieve denitration catalyst. The device further comprises a first heating device (for heating the NO oxidation device) and a second heating device (for heating the NH3-SCR reaction device). The second heating device is a microwave heating device. The device can realize the oxidation of part of NO into NO2 through the NO oxidation device, promote the rapid SCR reaction of the catalyst surface of the subsequent NH3-SCR reaction device, and thus realize the efficient catalytic reduction of nitrogen monoxide under high air speed and low temperature conditions.

Description

Technical Field

[0001] This invention relates to the field of waste gas denitrification technology, and in particular to an apparatus and method for causing a rapid SCR reaction in a denitrification catalyst. Background Technology

[0002] Currently, significant progress has been made in reducing emissions from stationary sources, making the reduction of emissions from mobile sources a key focus, especially vehicle exhaust emissions, particularly NOx emissions from diesel vehicles. x Nitrogen oxides (NOx) account for more than 80% of total vehicle emissions. x Nitrogen oxides (NOx) are associated with environmental problems such as acid rain, photochemical smog, the greenhouse effect, and ozone layer depletion. Because current catalysts do not perform ideally at low temperatures, motor vehicles emit large amounts of NOx during the cold start phase. Therefore, it is essential to improve the NOx removal performance of catalysts under low-temperature conditions to achieve environmental protection and sustainable social development.

[0003] In selective catalytic reduction (SCR) technology, the catalyst is the core component for achieving efficient denitrification. SCR technology utilizes a catalyst in an oxygen-containing atmosphere, using ammonia, urea, or hydrocarbons as reducing agents, to reduce nitrogen oxides in flue gas into non-toxic nitrogen and water. This process typically takes place in a temperature range of 200°C to 450°C, achieving a denitrification efficiency of 80% to 90%. SCR technology using NH3 as a reducing agent is currently the most widely used denitrification technology, and its main reaction equation is as follows:

[0004] 4NO + 4HN3 + O2 → 4N2 + 6H2O

[0005] 2NO2 + 4NH3 + O2 → 3N2 + 6H2O

[0006] Currently, SCR catalysts mainly use titanium dioxide as a support, with added active components such as vanadium pentoxide and tungsten oxide. These components improve the activity and stability of the catalyst through synergistic effects. However, traditional SCR catalysts perform poorly at low temperatures, especially under low-sulfur or sulfur-free conditions, where they are susceptible to alkali metal poisoning, leading to decreased activity. Furthermore, the catalysts are prone to sintering at high temperatures, further reducing denitrification efficiency.

[0007] To overcome these problems, researchers have developed a variety of novel catalysts. For example, a low-temperature SCR denitration catalyst based on high-entropy oxides, prepared by a co-precipitation method, can achieve highly efficient denitration reactions at relatively low temperatures. This catalyst uses biochar or anatase-type nano-titanium dioxide as a support, with high-entropy co-doped nanoparticles made of a mixture of iron, manganese, cerium, tungsten, and cobalt loaded on its surface as the active component. Its SCR activity exceeds 90% in the temperature range of 120°C to 180°C.

[0008] Despite the significant progress made by the prior art, how to further improve the activity of the catalyst under low temperature conditions is still the focus of current research. SUMMARY

[0009] Therefore, the application provides a device and method for making denitration catalysts undergo rapid SCR reactions to solve the problems of low activity and unsatisfactory denitration effect of the existing denitration method under low temperature conditions, and the problem of easy sintering of the catalyst under high temperature, which leads to reduced denitration efficiency.

[0010] To achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0011] A device for making denitration catalysts undergo rapid SCR reactions, comprising a NO oxidation device, a switch and an NH3-SCR reaction device arranged in sequence.

[0012] The NO oxidation device comprises a Pt / CeO2 catalyst, and the NH3-SCR reaction device comprises a Cu / HZSM-5 molecular sieve denitration catalyst.

[0013] The device for making denitration catalysts undergo rapid SCR reactions further comprises a first heating device and a second heating device.

[0014] The first heating device is for heating the NO oxidation device, and the second heating device is for heating the NH3-SCR reaction device.

[0015] The second heating device is a microwave heating device.

[0016] Preferably, the preparation method of the Pt / CeO2 catalyst comprises the following steps:

[0017] 1) Calcining a cerium source to obtain cerium oxide, mixing the obtained cerium oxide with a solvent to obtain a carrier solution;

[0018] 2) Mixing a solution containing a platinum source with the carrier solution, drying and then calcining to obtain a Pt / CeO2 catalyst.

[0019] Preferably, the cerium source in step 1) comprises one or more of cerium nitrate, cerium sulfate and cerium acetate.

[0020] The platinum source in the solution containing a platinum source in step 2) comprises one or more of chloroplatinic acid, platinum nitrate and platinum chloride.

[0021] Preferably, the mass ratio of platinum in the solution containing a platinum source to cerium oxide in the carrier solution in step 2) is 0.1-1.2:100.

[0022] The temperature of the mixing in step 2) is 60-90℃, and the mixing time is ≥6h;

[0023] The temperature of the calcination in step 2) is 400-600℃, and the calcination time is 3-6h.

[0024] Preferably, the preparation method of the Cu / HZSM-5 molecular sieve denitration catalyst comprises the following steps:

[0025] The solution containing a copper source is mixed with the HZSM-5 molecular sieve solution, dried, and then calcined to obtain the Cu / HZSM-5 molecular sieve denitration catalyst.

[0026] Preferably, the copper source in the solution containing a copper source comprises one or more of copper nitrate, copper acetate, and copper sulfate;

[0027] The mass ratio of copper in the solution containing a copper source to HZSM-5 molecular sieve in the HZSM-5 molecular sieve solution is 0.5-6:100;

[0028] The temperature of the mixing is 60-90℃, and the mixing time is ≥6h;

[0029] The temperature of the calcination is 400-600℃, and the calcination time is 3-6h.

[0030] Another object of the present application is to provide a method for causing a denitration catalyst to undergo rapid SCR reaction, comprising the following steps:

[0031] S1: Close the switch of the device for causing a denitration catalyst to undergo rapid SCR reaction, pass the mixed gas into the NO oxidation device, heat using the first heating device, and make the mixed gas react;

[0032] S2: After the reaction is stable, open the switch, pass the mixed gas into the NH3-SCR reaction device, pass ammonia into the NH3-SCR reaction device at the same time, heat using the second heating device, and realize rapid SCR reaction of the denitration catalyst;

[0033] The device for causing a denitration catalyst to undergo rapid SCR reaction is the device described above.

[0034] Preferably, the mixed gas in step S1 is a mixed gas of NO, O2, and N2, the volume concentration of the NO is 700-2000ppm, and the volume concentration of the O2 is 5-10%;

[0035] The temperature of the heating in step S1 is 300-350℃.

[0036] Preferably, the reaction stability in step S2 is that the NO oxidation conversion rate is controlled at 40-50%;

[0037] The heating in step S2 is heating the catalyst to 60-300 DEG C.

[0038] Compared with the prior art, the application has the following beneficial effects:

[0039] The activity temperature window of the existing low-temperature denitration catalyst is located at 150-280 DEG C, and it is difficult to deal with a large amount of NOx generated in the cold start stage of the diesel vehicle x The application uses a microwave field to provide energy to heat the catalyst, so that the catalyst is uniformly heated, and a NO oxidation device (the heating mode can be conventional heating) is added in front of the NH3-SCR reaction device, so that part of the NO is oxidized into NO2, and the subsequent NH3-SCR reaction device catalyst surface is promoted to occur rapid SCR reaction, thereby realizing efficient catalytic reduction of nitrogen monoxide under high space velocity and low temperature conditions. Compared with the activity of the catalyst under conventional heating conditions, the microwave-heated catalyst still has high activity in a low-temperature environment, so that the amount of catalyst can be reduced, and the cost of the catalyst can be reduced.

[0040] Without adding the NO oxidation device, the reaction occurring on the surface of the SCR catalyst is mainly: 4NO+4NH3+O2→4N2+6H2O, which is a standard SCR reaction, and the reaction rate is slow. After adding the NO oxidation device, part of the NO is oxidized into NO2, and by controlling the NO oxidation conversion rate, the reaction occurring on the surface of the SCR catalyst is mainly: 2NO+4NH3+2NO2→4N2+6H2O, which is a rapid SCR reaction. NO2 can form a more active intermediate species (nitro, nitrite and nitrate species, etc.) with NO on the catalyst surface, and the intermediate species can react with NH3 more quickly, thereby accelerating the entire reaction process. The participation of NO2 changes the reaction path, reduces the activation energy of the reaction, and makes the reaction easier to proceed, so that the reaction rate is greatly improved. NO2 can also cooperate with NO on the catalyst surface to occupy some active sites with low utilization rate, or change the electronic environment of the active sites, so that more active sites can participate in the reaction, thereby improving the overall activity of the catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only embodiments of the application, and those skilled in the art can obtain other drawings according to the provided drawings without creative labor.

[0042] Figure 1Performance test results of the application example 1 under different space velocity conditions for catalytic reduction of NO;

[0043] Figure 2 Performance test results of the application example 2 and the comparative example 1 for catalytic reduction of NO;

[0044] Figure 3 Performance test results of the application example 3 and the comparative example 2 under different heating conditions for catalytic reduction of NO;

[0045] Figure 4 Stability evaluation results of the application example 4 under different space velocity conditions for catalytic reduction of NO. DETAILED DESCRIPTION

[0046] The application provides a device for making a denitration catalyst to have a rapid SCR reaction, which comprises a NO oxidation device, a switch and an NH3-SCR reaction device arranged in sequence.

[0047] In the application, the NO oxidation device comprises a Pt / CeO2 catalyst, and the NH3-SCR reaction device comprises a Cu / HZSM-5 molecular sieve denitration catalyst; the Pt / CeO2 catalyst and the Cu / HZSM-5 molecular sieve denitration catalyst are both prepared by an impregnation method.

[0048] In the application, the device for making a denitration catalyst to have a rapid SCR reaction further comprises a first heating device and a second heating device.

[0049] In the application, the first heating device is for heating the NO oxidation device, and the second heating device is for heating the NH3-SCR reaction device.

[0050] In the application, the second heating device is a microwave heating device, and the first heating device can be a conventional heating device, including a tubular resistance furnace.

[0051] In the application, the preparation method of the Pt / CeO2 catalyst comprises the following steps:

[0052] 1) calcining a cerium source to obtain cerium oxide, mixing the obtained cerium oxide with a solvent to obtain a carrier solution;

[0053] 2) mixing a solution containing a platinum source with the carrier solution, drying and then calcining to obtain the Pt / CeO2 catalyst.

[0054] In the application, the cerium source in step 1) comprises one or more of cerium nitrate, cerium sulfate and cerium acetate, and also comprises corresponding hydrates.

[0055] In this invention, the platinum source in the platinum-containing solution in step 2) includes one or more of chloroplatinic acid, platinum nitrate and platinum chloride, and also includes the corresponding hydrates.

[0056] In this invention, the molar ratio of platinum in the platinum-containing solution to cerium oxide in the carrier solution in step 2) is 0.1 to 1.2:100, preferably 0.2 to 1:100, more preferably 0.4 to 0.8:100, and even more preferably 0.5:100.

[0057] In this invention, the mixing temperature in step 2) is 60-90°C, specifically 65°C, 70°C, 75°C, 80°C, or 85°C; the mixing rate is preferably 400-700 rpm, specifically 450 rpm, 500 rpm, 550 rpm, 600 rpm, or 650 rpm; and the mixing time is ≥6h, specifically 6.5h, 7h, 7.5h, or 8h.

[0058] In this invention, the mixing in step 2) is preferably done by adding a platinum source solution dropwise to the carrier solution, and the dropping rate is preferably 4 to 6 mL / min, specifically 4.2 mL / min, 4.5 mL / min, 4.8 mL / min, 5 mL / min, 5.2 mL / min, 5.5 mL / min, or 5.8 mL / min.

[0059] In this invention, the calcination temperature in step 2) is 400-600℃, specifically 450℃, 500℃, or 550℃; the calcination time is 3-6h, specifically 3.5h, 4h, 4.5h, 5h, or 5.5h.

[0060] In this invention, the preparation method of the Cu / HZSM-5 molecular sieve denitration catalyst includes the following steps:

[0061] In this invention, a copper-containing solution is mixed with an HZSM-5 molecular sieve solution, dried, and then calcined to obtain a Cu / HZSM-5 molecular sieve denitration catalyst.

[0062] In this invention, the copper source in the copper-containing solution includes one or more of copper nitrate, copper acetate, and copper sulfate, and also includes the corresponding hydrates.

[0063] In this invention, the mass ratio of copper in the copper-containing solution to HZSM-5 molecular sieve in the HZSM-5 molecular sieve solution is 0.5 to 6:100, preferably 1 to 5:100, and more preferably 3 to 4:100.

[0064] In this invention, the mixing temperature is 60-90°C, specifically 65°C, 70°C, 75°C, 80°C, or 85°C; the mixing rate is preferably 400-700 rpm, specifically 450 rpm, 500 rpm, 550 rpm, 600 rpm, or 650 rpm; and the mixing time is ≥6 hours, specifically 6.5 hours, 7 hours, 7.5 hours, or 8 hours.

[0065] In this invention, the mixing is preferably performed by adding a copper-containing solution dropwise to the HZSM-5 molecular sieve solution, and the dropping rate is preferably 4 to 6 mL / min, specifically 4.2 mL / min, 4.5 mL / min, 4.8 mL / min, 5 mL / min, 5.2 mL / min, 5.5 mL / min, or 5.8 mL / min.

[0066] In this invention, the calcination temperature is 400-600℃, specifically 450℃, 500℃, or 550℃; the calcination time is 3-6 hours, specifically 3.5 hours, 4 hours, 4.5 hours, 5 hours, or 5.5 hours.

[0067] The present invention also provides a method for causing a denitrification catalyst to undergo a rapid SCR reaction, comprising the following steps:

[0068] S1: Turn off the switch of the device that enables the denitrification catalyst to undergo a rapid SCR reaction, and introduce the mixed gas into the NO oxidation device. Heat the mixed gas using the first heating device, and the mixed gas will react.

[0069] S2: After the reaction stabilizes, turn on the switch and introduce the mixed gas into the NH3-SCR reactor. Simultaneously, introduce ammonia into the NH3-SCR reactor and use the second heating device for heating, thereby achieving a rapid SCR reaction of the denitrification catalyst. The device used to achieve the rapid SCR reaction of the denitrification catalyst is the one described above.

[0070] In this invention, the mixed gas in step S1 is a mixture of NO, O2, and N2, wherein the volume concentration of NO is 700–2000 ppm, specifically 800 ppm, 1000 ppm, 1200 ppm, 1400 ppm, 1500 ppm, 1600 ppm, or 1800 ppm; and the volume concentration of O2 is 5–10%, specifically 6%, 7%, 8%, or 9%. NH3 is mixed with the reacted gas mixture through a branch circuit, with a concentration of 200–1000 ppm, specifically 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, and 900 ppm; the space velocity of the mixed gas is 60,000–500,000 mL / (g·h), specifically 80,000 mL / (g·h), 100,000 mL / (g·h), 120,000 mL / (g·h), 150,000 mL / (g·h), 180,000 mL / (g·h), 200,000 mL / (g·h), 250,000 mL / (g·h), 300,000 mL / (g·h), 350,000 mL / (g·h), 400,000 mL / (g·h), and 450,000 mL / (g·h).

[0071] In this invention, after the switch is turned on in step S2, the switch is not turned off when the mixed gas is subsequently introduced.

[0072] In this invention, the heating temperature in step S1 is 300-350°C, specifically 310°C, 320°C, 330°C, or 340°C.

[0073] In this invention, the stable NO oxidation conversion rate in step S2 is controlled at 40-50%, specifically 42%, 44%, 45%, 46%, or 48%.

[0074] In the present invention, when the device is actually used, the mixed gas is the waste gas to be treated.

[0075] In this invention, the specific formula for calculating the NO oxidation conversion rate is as follows:

[0076]

[0077] Among them, [NO2] out The concentration of NO2 in the catalytically treated waste gas from the NO oxidation unit, [NO x ] out NO in the catalytically treated waste gas from the NO oxidation unit x The concentration.

[0078] In this invention, NO x The specific formula for calculating catalytic reduction conversion is as follows:

[0079]

[0080] Among them, [NO x ] in NO in the exhaust gas before entering the NO oxidation unit x The concentration of [NO] x ] out NO in the exhaust gas after catalysis by the NH3-SCR reactor x The concentration.

[0081] In this invention, the heating in step S2 refers to heating the catalyst to 60-300°C, specifically 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, 220°C, 250°C, or 280°C.

[0082] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0083] Example 1

[0084] A certain amount of cerium nitrate hexahydrate was calcined in a muffle furnace to obtain cerium oxide. The cerium oxide was then mixed with water to prepare a support solution. Chloroplatinic acid hexahydrate was dissolved in water to obtain a solution containing a platinum source. This solution was then added dropwise to the support solution at a rate of 5 mL / min (the mass ratio of platinum to cerium oxide was 1:100). After sonication, the solution was stirred at 80°C and 500 rpm until it evaporated to dryness (time greater than 6 h). The solution was then dried overnight in an oven and finally calcined at 500°C for 4 h to obtain the Pt / CeO2 catalyst.

[0085] The HZSM-5 molecular sieve was pretreated by sequential washing, drying, and calcination. Then, it was mixed with water to obtain a support solution. Copper nitrate solution was added dropwise to the support solution at 5 mL / min (the mass ratio of copper to HZSM-5 molecular sieve was 4:100). After sonication, the solution was stirred at 80℃ and 500 rpm until it evaporated to dryness (time greater than 6 h). Then, it was dried in an oven overnight. Finally, it was calcined at 500℃ for 4 h to obtain the Cu / HZSM-5 molecular sieve denitration catalyst.

[0086] Pt / CeO2 catalyst was loaded into a quartz reaction tube and sealed at both ends with quartz wool to serve as a NO oxidation device. The temperature inside the tube was controlled by a tubular resistance furnace. Cu / HZSM-5 molecular sieve denitration catalyst was loaded into a quartz tube to serve as an NH3-SCR reaction device. The temperature inside the tube was controlled by a microwave reactor.

[0087] In a continuous flow fixed-bed reactor, a mixed gas with the following composition—NO 700 ppm, O 25%, N2 as the equilibrium carrier gas, a total gas flow rate of 1000 mL / min, and a space velocity of 60,000–500,000 mL / (g·h)—was introduced into a NO oxidation unit heated to 325°C. The outlet gas components NO, NO2, and NO2 were analyzed using a MRU MAG 5 flue gas analyzer. x The reaction was tested. The NO oxidation conversion rate was used as an indicator. When it reached between 40% and 50%, the reaction was considered stable. The reaction gas was introduced into the NH3-SCR reactor through a three-way valve, and 700 ppm of NH3 was introduced through a branch. SCR catalysis was carried out under microwave heating conditions (catalyst heated to 140°C).

[0088] The performance test results of microwave-heated catalyst for catalytic reduction of nitric oxide under different space velocities at the same temperature are as follows: Figure 1 As shown; via Figure 1 It can be seen that after adding a NO oxidation device before the NH3-SCR reactor, the activity of the catalyst fluctuates under different space velocities, but still remains at a high level.

[0089] Example 2

[0090] In this embodiment, taking the space velocity of 60000 mL / (g·h) in Example 1 as an example, the heating temperature of the catalyst in the NH3-SCR reaction device is changed, denoted as NO oxidation + SCR.

[0091] Comparative Example 1

[0092] The only difference between this comparative example and Example 2 is that the NO oxidation device is not included, and it is referred to as SCR.

[0093] The performance test results of the catalytic reduction of nitric oxide in Example 2 and Comparative Example 1 of this invention are as follows: Figure 2 As shown, through Figure 2 It can be seen that after adding a NO oxidation device before the NH3-SCR reactor, the low-temperature activity of the SCR catalyst is significantly improved. The conversion rate of nitric oxide at a low temperature of 60℃ increases from 20% to 65.3%, and the active temperature window of the catalyst is also significantly widened.

[0094] Example 3

[0095] Taking the space velocity of 180,000 mL / (g·h) in Example 1 as an example, the catalyst heating temperature in the NH3-SCR reactor was changed, denoted as MH.

[0096] Comparative Example 2

[0097] The only difference between this comparative example and Example 3 is that microwave heating is not used, denoted as CH.

[0098] The performance test results of catalytic reduction of nitric oxide under different heating conditions in Example 3 and Comparative Example 2 of this invention are as follows: Figure 3 As shown, through Figure 3 It can be seen that after adding a NO oxidation device before the NH3-SCR reactor, microwave heating of the catalyst can significantly enhance the catalyst activity under high space velocity and low temperature conditions; at 100℃ and 120℃, the NO conversion rate of the catalyst under microwave heating conditions is even nearly 50% higher than that under conventional heating conditions, thus effectively addressing the problem of nitrogen oxide emissions during the cold start phase of diesel vehicles.

[0099] Example 4

[0100] The catalyst (NH3-SCR reactor) in Example 1 was heated to 120°C, and the mass hourly space velocity was adjusted to 60,000 and 180,000 mL / (g·h), respectively denoted as 6 × 10⁻⁶. 4 -MH and 18×10 4 -MH, where MH represents microwave heating, was used for a 10-hour stability evaluation. The test results are as follows: Figure 4 As shown, through Figure 4 It can be seen that the catalyst exhibits excellent stability under microwave heating conditions. Under low space velocity conditions, the NO conversion rate increases with time. As the space velocity increases, the stability of the catalyst decreases slightly, but it still maintains good stability under high space velocity conditions.

[0101] Example 5

[0102] A certain amount of cerium nitrate hexahydrate was calcined in a muffle furnace to obtain cerium oxide. The cerium oxide was then mixed with water to prepare a support solution. Platinum nitrate was dissolved in water to obtain a solution containing a platinum source, which was then added dropwise to the support solution at a rate of 6 mL / min (the mass ratio of platinum to cerium oxide was 0.5:100). After sonication, the solution was stirred at 90℃ and 500 rpm until it evaporated to dryness (time greater than 6 h). The solution was then dried overnight in an oven and finally calcined at 600℃ for 3 h to obtain the Pt / CeO2 catalyst.

[0103] The HZSM-5 molecular sieve was pretreated by sequential washing, drying, and calcination. Then, it was mixed with water to obtain a carrier solution. Copper sulfate solution was added dropwise to the carrier solution at a rate of 4 mL / min (the mass ratio of copper to HZSM-5 molecular sieve was 6:100). After sonication, the solution was stirred at 90℃ and 500 rpm until it evaporated to dryness (time greater than 6 h). Then, it was dried in an oven overnight. Finally, it was calcined at 600℃ for 3 h to obtain the Cu / HZSM-5 molecular sieve denitration catalyst.

[0104] Pt / CeO2 catalyst was loaded into a quartz reaction tube and sealed at both ends with quartz wool to serve as a NO oxidation device. The temperature inside the tube was controlled by a tubular resistance furnace. Cu / HZSM-5 molecular sieve denitration catalyst was loaded into a quartz tube to serve as an NH3-SCR reaction device. The temperature inside the tube was controlled by a microwave reactor.

[0105] In a continuous flow fixed-bed reactor, a mixed gas with the following composition—NO 1000 ppm, O 28%, N2 as the equilibrium carrier gas, a total gas flow rate of 1000 mL / min, and a space velocity of 60000 mL / (g·h)—was introduced into a NO oxidation unit heated to 300°C. The components NO, NO2, and NO2 in the outlet gas were analyzed using a MRU MAG 5 flue gas analyzer. x The reaction was tested. Using the NO oxidation conversion rate as an indicator, a rate between 40% and 50% was considered stable. The reaction gas was introduced into the NH3-SCR reactor through a three-way valve, and 1000 ppm NH3 was introduced through a branch. SCR catalysis was carried out under microwave heating conditions (catalyst heated to 100°C), and the nitrogen oxide conversion rate was found to be 84.2%.

[0106] Example 6

[0107] A certain amount of cerium nitrate hexahydrate was calcined in a muffle furnace to obtain cerium oxide. The cerium oxide was then mixed with water to prepare a support solution. Platinum nitrate was dissolved in water to obtain a solution containing a platinum source, which was then added dropwise to the support solution at a rate of 5 mL / min (the mass ratio of platinum to cerium oxide was 0.3:100). After sonication, the solution was stirred at 70℃ and 500 rpm until it evaporated to dryness (time greater than 6 h). The solution was then dried overnight in an oven and finally calcined at 400℃ for 6 h to obtain the Pt / CeO2 catalyst.

[0108] The HZSM-5 molecular sieve was pretreated by sequential washing, drying, and calcination. Then, it was mixed with water to obtain a carrier solution. Copper sulfate solution was added dropwise to the carrier solution at 6 mL / min (the mass ratio of copper to HZSM-5 molecular sieve was 1:100). After sonication, the solution was stirred at 60℃ and 500 rpm until it evaporated to dryness (time greater than 6 h). Then, it was dried in an oven overnight. Finally, it was calcined at 400℃ for 6 h to obtain the Cu / HZSM-5 molecular sieve denitration catalyst.

[0109] Pt / CeO2 catalyst was loaded into a quartz reaction tube and sealed at both ends with quartz wool to serve as a NO oxidation device. The temperature inside the tube was controlled by a tubular resistance furnace. Cu / HZSM-5 molecular sieve denitration catalyst was loaded into a quartz tube to serve as an NH3-SCR reaction device. The temperature inside the tube was controlled by a microwave reactor.

[0110] In a continuous flow fixed-bed reactor, a mixed gas with the following composition—NO 750 ppm, O 25%, N2 as the equilibrium carrier gas, a total gas flow rate of 1000 mL / min, and a space velocity of 60000 mL / (g·h)—was introduced into a NO oxidation unit heated to 350°C. The components NO, NO2, and NO2 in the outlet gas were analyzed using a MRU MAG 5 flue gas analyzer. x The reaction was tested. Using the NO oxidation conversion rate as an indicator, a rate between 40% and 50% was considered stable. The reaction gas was introduced into the NH3-SCR reactor through a three-way valve, and 750 ppm NH3 was introduced through a branch. SCR catalysis was carried out under microwave heating conditions (catalyst heated to 200°C), and the nitrogen oxide conversion rate was measured to be 72.6%.

[0111] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0112] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An apparatus for enabling a denitrification catalyst to undergo a rapid SCR reaction, characterized in that, The apparatus for enabling the denitrification catalyst to undergo a rapid SCR reaction includes a NO oxidation device, a switch, and an NH3-SCR reaction device arranged in sequence. The NO oxidation device includes a Pt / CeO2 catalyst, and the NH3-SCR reaction device includes a Cu / HZSM-5 molecular sieve denitration catalyst. The apparatus for causing the denitrification catalyst to undergo a rapid SCR reaction further includes a first heating device and a second heating device; The first heating device is a NO oxidation device, and the second heating device is an NH3-SCR reaction device. The second heating device is a microwave heating device, which heats the catalyst to 60~300℃; The preparation method of the Cu / HZSM-5 molecular sieve denitration catalyst includes the following steps: A copper-containing solution was mixed with an HZSM-5 molecular sieve solution, dried, and then calcined to obtain a Cu / HZSM-5 molecular sieve denitration catalyst. The mass ratio of copper in the copper-containing solution to HZSM-5 molecular sieve in the HZSM-5 molecular sieve solution is 0.5~6:

100.

2. The apparatus for causing a rapid SCR reaction in a denitrification catalyst according to claim 1, characterized in that, The preparation method of the Pt / CeO2 catalyst includes the following steps: 1) Cerium source is calcined to obtain cerium oxide, and the obtained cerium oxide is mixed with a solvent to obtain a carrier solution; 2) The platinum source solution was mixed with the support solution, dried and then calcined to obtain the Pt / CeO2 catalyst.

3. The apparatus for causing a rapid SCR reaction in a denitrification catalyst according to claim 2, characterized in that, The cerium source mentioned in step 1) includes one or more of cerium nitrate, cerium sulfate, and cerium acetate; The platinum source in the solution containing the platinum source mentioned in step 2) includes one or more of chloroplatinic acid, platinum nitrate and platinum chloride.

4. The apparatus for causing a rapid SCR reaction in a denitrification catalyst according to claim 3, characterized in that, In step 2), the mass ratio of platinum in the platinum-containing source solution to cerium oxide in the carrier solution is 0.1~1.2:100; The mixing temperature in step 2) is 60~90℃, and the mixing time is ≥6h; The calcination temperature in step 2) is 400~600℃, and the calcination time is 3~6h.

5. The apparatus for causing a rapid SCR reaction in a denitrification catalyst according to claim 4, characterized in that, The copper source in the copper-containing solution includes one or more of copper nitrate, copper acetate, and copper sulfate. The mixing temperature is 60~90℃, and the mixing time is ≥6h; The calcination temperature is 400~600℃, and the calcination time is 3~6h.

6. A method for causing a denitrification catalyst to undergo a rapid SCR reaction, characterized in that, Includes the following steps: S1: Turn off the switch of the device that causes the denitrification catalyst to undergo a rapid SCR reaction, and introduce the mixed gas into the NO oxidation device. Heat the mixed gas using the first heating device and the mixed gas will react. S2: After the reaction stabilizes, turn on the switch and introduce the mixed gas into the NH3-SCR reactor. At the same time, introduce ammonia into the NH3-SCR reactor and use the second heating device to heat it, so that the denitrification catalyst can undergo a rapid SCR reaction. The apparatus for causing the denitrification catalyst to undergo a rapid SCR reaction is the apparatus described in any one of claims 1 to 5.

7. The method for causing a rapid SCR reaction in a denitrification catalyst according to claim 6, characterized in that, The mixed gas in step S1 is a mixture of NO, O2 and N2, wherein the volume concentration of NO is 700~2000 ppm and the volume concentration of O2 is 5~10%. The heating temperature in step S1 is 300~350℃.

8. A method for causing a denitrification catalyst to undergo a rapid SCR reaction according to claim 6 or 7, characterized in that, The reaction described in step S2 is stable when the NO oxidation conversion rate is controlled at 40-50%. The heating mentioned in step S2 refers to heating the catalyst to 60~300℃.

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