A co- scr catalyst, its preparation method and application

Abstract

The application discloses a CO-SCR catalyst, a preparation method and application thereof, and the CO-SCR catalyst comprises a cerium-based composite oxide carrier and a noble metal active component, and the noble metal active component is dispersed on the surface of the cerium-based composite oxide carrier by means of a surfactant. The CO-SCR catalyst utilizes the dispersion and loading of the noble metal assisted by the surfactant, so that the CO-SCR catalyst has higher metal dispersion and redox capacity. Meanwhile, the suitable pH value of the carrier surface is also beneficial to the adsorption of CO and NO, and the low-temperature catalytic activity and high-temperature stability of the catalyst are improved, and the CO-SCR catalyst has higher catalytic activity and nitrogen selectivity in the use temperature range of 250 DEG C to 400 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of flue gas purification and environmental protection technology, specifically relating to a CO-SCR catalyst, its preparation method, and its application. Background Technology

[0002] Nitrogen oxides (NO) x Nitrogen oxides (NOx) are one of the major air pollutants, with the combustion of fossil fuels and vehicle exhaust being the primary sources. NO is colorless and odorless, with only a mild irritant effect, but high concentrations can cause mild central nervous system disturbances. Furthermore, NO is easily oxidized in the atmosphere to toxic NO2. NO2 is a respiratory irritant and has a significant impact on human health. Besides its direct hazards, NO... x It is still a major component of acid rain. Meanwhile, NO... x Under ultraviolet light, it can undergo a series of complex photochemical reactions with HC, producing ozone and various compounds (including formaldehyde, acrolein, sulfuric acid, etc.), causing secondary pollution.

[0003] Traditional stationary source flue gas denitrification mainly uses ammonia selective catalytic reduction (NH3-SCR) technology, which uses NH3 to catalytically reduce nitrogen oxides (NOx) to achieve NOx elimination. However, ammonia itself is a harmful gas, and excessive NH3 emissions can also lead to environmental pollution. Therefore, how to eliminate NOx using only CO and NO naturally present in vehicle exhaust, without introducing other gases, is an important research direction. CO-SCR uses carbon monoxide (CO) as a reducing agent to reduce NO... x Catalytic reduction to N2. CO, as a reducing gas, is widely present in sintering and coking flue gas, as well as vehicle exhaust. The catalysts required for this reaction often contain precious metals, and rhodium (Rh) plays an irreplaceable role in eliminating nitrogen oxides. Meanwhile, catalysts with cerium dioxide (CeO2) and modified cerium dioxide as active components have attracted widespread attention from researchers due to their good redox capabilities, fewer side reactions, and environmentally friendly characteristics.

[0004] Currently, precious metal CO-SCR catalysts still face the problem of precious metal sintering and agglomeration at high temperatures during use, which greatly reduces the catalytic activity of the catalyst.

[0005] Therefore, improving the dispersion of precious metals in CO-SCR denitrification catalysts and mitigating metal agglomeration and sintering at high temperatures are crucial for extending catalyst lifespan and improving waste gas treatment efficiency. Summary of the Invention

[0006] In view of the above-mentioned problems existing in the prior art, the purpose of this invention is to provide a CO-SCR catalyst, its preparation method and application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a CO-SCR catalyst, the CO-SCR catalyst comprising a cerium-based composite oxide support and a noble metal active component, wherein the noble metal active component is dispersed on the surface of the cerium-based composite oxide support by means of a surfactant.

[0009] In the CO-SCR catalyst of this invention, since the noble metal active component is dispersed on the surface of the cerium-based composite oxide support with the assistance of a surfactant, the catalyst exhibits high metal dispersion and redox capability, significantly increasing the active sites and enhancing the catalytic activity. Furthermore, it reduces the sintering and agglomeration of noble metals to a certain extent, thereby improving the overall catalyst lifespan and catalytic activity. The CO-SCR catalyst of this invention exhibits high catalytic activity and nitrogen selectivity within an operating temperature range of 250°C to 400°C.

[0010] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0011] Preferably, the cerium-based composite oxide support has the chemical formula CeMO. x Where M is a dopant element, which is at least one of an alkali metal or an alkaline earth metal, and x is the number of O atoms required to satisfy valence equilibrium. In the catalyst of this invention, the dopant element in the cerium-based composite oxide support is an alkali metal, which is beneficial to CO adsorption. Meanwhile, CeMO... x The presence of Ce-OM asymmetric oxygen vacancies within the memory can enhance NO. x Adsorption capacity.

[0012] Preferably, M is selected from at least one of Li, Na, K, Mg, Ca, Sr and Ba, and is more preferably Mg.

[0013] Preferably, the CeMO xIn this process, the molar ratio of Ce to M is (19–2):1, for example, it can be 19:1, 18:1, 17:1, 16:1, 15:1, 14:1, 13:1, 12:1, 11:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, or 2:1, etc. If the amount of dopant M is too large, it cannot successfully enter the CeO2 lattice to form a solid solution, and phase separation will occur, thus affecting the interaction between Ce and the dopant element, thereby affecting the catalytic performance. If the amount of dopant M is too small, it cannot adjust the basicity and redox ability of CeO2, thus affecting the catalytic performance.

[0014] Preferably, the noble metal active component includes at least one of rhodium, platinum, palladium, ruthenium, iridium and gold, with rhodium being the most preferred.

[0015] Preferably, based on the total mass of the CO-SCR catalyst (100%), the mass fraction of the noble metal active component is 0.1% to 20%, for example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%, etc., preferably 0.5% to 10%, and more preferably 0.5% to 2%.

[0016] In this invention, if the mass fraction of the precious metal active component is too small, the number of active sites will be too small, and they will not be able to react with all the gas to be purified, which will greatly reduce the catalytic efficiency of the catalyst. If the mass fraction of the precious metal active component is too large, the cost of the catalyst will be greatly increased, and it may also lead to poor dispersion of active sites and easy agglomeration, thereby affecting the catalytic ability.

[0017] Preferably, the surfactant comprises hexadecyltrimethylammonium bromide (CTAB). In a second aspect, the present invention provides a method for preparing a CO-SCR catalyst as described in the first aspect, the method comprising the following steps:

[0018] A cerium-based composite oxide, a first solvent, a surfactant, and a precursor of a noble metal active component are mixed to obtain a mixture. The mixture is then dried and calcined to obtain the CO-SCR catalyst.

[0019] The method of this invention is simple, the synthesis conditions are simple and mild, the raw materials are readily available, and the proportion of surfactants is easily adjustable. By changing the amount of surfactant used, the particle size and dispersion of the noble metal active component can be easily adjusted, thereby further improving the catalytic performance and stability of the catalyst. Moreover, the method of this invention produces no byproducts or pollution, and can significantly save on synthesis and raw material costs.

[0020] Preferably, the preparation method of the cerium-based composite oxide includes the following steps:

[0021] (1) Mix the cerium source, the doped element M source, and the second solvent to obtain a mixed solution;

[0022] (2) The mixture is added dropwise to ethanol and stirred, then stirred and evaporated to dryness, and then calcined at high temperature to obtain the cerium-based composite oxide.

[0023] The method of the present invention can adjust the surface acidity and alkalinity, redox capacity and noble metal dispersion of cerium-based composite oxides, thereby regulating the redox capacity of the catalyst and further improving the denitrification activity, nitrogen selectivity and stability of the catalyst.

[0024] Preferably, the cerium source in step (1) includes cerium nitrate.

[0025] Preferably, the dopant element M source in step (1) includes a nitrate of M.

[0026] Preferably, the temperature for stirring and drying in step (2) is 60℃~100℃, for example, it can be 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃.

[0027] Preferably, the high-temperature calcination temperature in step (2) is 400℃~600℃, for example, it can be 400℃, 410℃, 415℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃, etc.

[0028] Preferably, the high-temperature calcination time in step (2) is 3h to 4h, for example, it can be 3h, 3.2h, 3.5h, 3.7h or 4h.

[0029] As a preferred embodiment of the preparation method of the CO-SCR catalyst of the present invention, the surfactant includes hexadecyltrimethylammonium bromide.

[0030] Preferably, the precursor of the noble metal active component includes a noble metal nitrate.

[0031] Preferably, the mass ratio of the surfactant to the cerium-based composite oxide is 1:(1 to 4), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4, etc.

[0032] Preferably, the concentration of the surfactant in the mixture is 0.005 g / mL to 0.1 g / mL, for example, it can be 0.005 g / mL, 0.008 g / mL, 0.01 g / mL, 0.015 g / mL, 0.02 g / mL, 0.025 g / mL, 0.03 g / mL, 0.035 g / mL, 0.04 g / mL, 0.045 g / mL, 0.05 g / mL, 0.055 g / mL, 0.06 g / mL, 0.065 g / mL, 0.07 g / mL, 0.075 g / mL, 0.08 g / mL, 0.085 g / mL, 0.09 g / mL, 0.095 g / mL, or 0.1 g / mL, etc., preferably 0.005 g / mL to 0.02 g / mL. In this invention, by adding the surfactant in the above-mentioned amount, it is helpful to improve the dispersion of precious metals, increase the active sites of the catalyst, and thus enhance the catalytic activity of the catalyst.

[0033] Preferably, the roasting temperature is 500℃ to 700℃, for example, it can be 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, 625℃, 650℃, 670℃ or 700℃, etc.

[0034] Preferably, the heating rate of the calcination is 1℃ / min-10℃ / min, for example, it can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min, etc.

[0035] Preferably, the roasting time is 3h to 6h, for example, it can be 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h.

[0036] As a preferred embodiment of the preparation method of the CO-SCR catalyst according to the present invention, the preparation method of the CO-SCR catalyst includes the following steps:

[0037] (I) A mixture of cerium salt, M-containing nitrate and solvent is added dropwise to an ethanol solution to obtain a mixture. The mixture is stirred and evaporated to dryness at 70℃~90℃. Then, the temperature is increased to 400℃~600℃ at a heating rate of 1℃ / min~10℃ / min and calcined for 3h~10h to obtain cerium-based composite oxide.

[0038] (II) The cerium-based composite oxide and surfactant are dispersed in a solvent, mixed and stirred for 20-40 min, then mixed with a noble metal precursor, and then dried at 60℃~110℃. Then, the temperature is raised to 400℃~600℃ at a heating rate of 1℃ / min~10℃ / min for 3h~10h to obtain the CO-SCR catalyst.

[0039] In a second aspect, the present invention provides an application of the CO-SCR catalyst as described in the first aspect, wherein the CO-SCR catalyst is used for the selective catalytic reduction of NO by CO.

[0040] Preferably, the operating temperature of the CO-SCR catalyst is 100℃ to 600℃, for example, it can be 100℃, 150℃, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃ or 600℃, and preferably 250℃ to 400℃.

[0041] Thirdly, the present invention provides a CO-SCR reactor, the CO-SCR reactor comprising the CO-SCR catalyst as described in the first aspect, the CO-SCR reactor being used in at least one of a mobile source gas vehicle exhaust treatment device, a stationary source gas vehicle exhaust treatment device, and a stationary source gas denitrification device.

[0042] Preferably, the stationary source gas vehicle exhaust treatment device includes a simulated vehicle exhaust treatment device.

[0043] Preferably, the mobile source gas denitrification device includes any one or a combination of at least two of a diesel engine, a gas turbine, or an aircraft engine.

[0044] Preferably, the stationary source gas denitrification device includes an industrial kiln and / or a calcining kiln.

[0045] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0046] Compared with existing technologies, the present invention has the following beneficial effects:

[0047] (1) In the CO-SCR catalyst of the present invention, since the noble metal active component is dispersed on the surface of the cerium-based composite oxide support with the assistance of surfactant, the catalyst has high metal dispersion and redox capability, which can significantly increase the active sites of the catalyst and improve its catalytic activity. Moreover, it reduces the sintering and agglomeration of noble metals to a certain extent, thereby improving the overall service life and catalytic activity of the catalyst. The CO-SCR catalyst of the present invention exhibits high catalytic activity and nitrogen selectivity within the operating temperature range of 100℃ to 400℃. Furthermore, the doping element in the cerium-based composite oxide support is an alkali metal, which is beneficial for CO adsorption. Simultaneously, CeMO... x The presence of Ce-OM asymmetric oxygen vacancies within the memory can enhance NO. x This enhances the adsorption capacity, thereby improving the performance of the catalyst.

[0048] (2) The method of the present invention is simple, the synthesis conditions are simple and mild, the raw materials are readily available, and the proportion of surfactants is easy to adjust. By changing the amount of surfactant used, the particle size and dispersion of the noble metal active components can be easily adjusted, thereby further improving the catalytic performance and stability of the catalyst. Moreover, the method of the present invention has no by-products or pollution, and can significantly save synthesis costs and raw material costs. Attached Figure Description

[0049] Figure 1 This is a TEM image of the CO-SCR denitrification catalyst prepared in Example 1 of this invention. Detailed Implementation

[0050] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0051] The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0052] Example 1

[0053] This embodiment provides a CO-SCR denitrification catalyst, and the preparation method of the CO-SCR denitrification catalyst is as follows:

[0054] (1) Dissolve 2g of cerium nitrate hexahydrate and 0.0641g of magnesium nitrate in 10mL of water, mix well, and then add dropwise to 45mL of ethanol. Stir and evaporate to dryness at 85℃, and then calcine at 500℃ for 3h to obtain Ce. 0.95 Mg 0.05 O x Composite oxide carrier;

[0055] (2) Disperse 0.5g of the composite oxide carrier and 0.25g of CTAB in 5mL of water and stir rapidly for 40min to obtain a stable emulsion with a concentration of 0.05g / mL of CTAB in the emulsion.

[0056] (3) Dissolve 0.0025 g Rh in 1 mL of dilute nitric acid solution and sonicate for 5 min to obtain a uniform and transparent solution;

[0057] The transparent rhodium nitrate solution was added dropwise to a stable emulsion, mixed and stirred for 30 minutes, and then evaporated to dryness in an oven at 80°C. The powder obtained after evaporation was ground and then placed in a muffle furnace and calcined at 550°C for 6 hours at a heating rate of 5°C / min to obtain the CO-SCR denitration catalyst.

[0058] In the CO-SCR catalyst prepared in this embodiment, the mass fraction of the noble metal active component rhodium is 0.5%.

[0059] TEM image of the CO-SCR denitrification catalyst prepared in this embodiment is shown below. Figure 1 As shown in the figure, the catalyst is amorphous, and the precious metal rhodium is uniformly dispersed on the catalyst.

[0060] Example 2

[0061] This embodiment provides a CO-SCR denitrification catalyst, and the preparation method of the CO-SCR denitrification catalyst is as follows:

[0062] (1) Dissolve 1.953 g of cerium nitrate hexahydrate and 0.1282 g of magnesium nitrate in 10 mL of water, mix well, and then add dropwise to 45 mL of ethanol. Stir and evaporate to dryness at 85 °C, and then calcine at 500 °C for 3 h to obtain Ce. 0.9 Mg 0.1 O x Composite oxide carrier;

[0063] (2) Disperse 0.5g of the composite oxide carrier and 0.25g of CTAB in 5mL of water and stir rapidly for 40min to obtain a stable emulsion with a concentration of 0.05g / mL of CTAB in the emulsion.

[0064] (3) Dissolve 0.0025 g Rh in 1 mL of dilute nitric acid solution and sonicate for 5 min to obtain a uniform and transparent solution;

[0065] The transparent rhodium nitrate solution was added dropwise to a stable emulsion, mixed and stirred for 30 minutes, and then evaporated to dryness in an oven at 80°C. The powder obtained after evaporation was ground and then placed in a muffle furnace and calcined at 550°C for 6 hours at a heating rate of 5°C / min to obtain the CO-SCR denitration catalyst.

[0066] In the CO-SCR catalyst prepared in this embodiment, the mass fraction of the noble metal active component rhodium is 0.5%.

[0067] Example 3

[0068] This embodiment provides a CO-SCR denitrification catalyst, and the preparation method of the CO-SCR denitrification catalyst is as follows:

[0069] (1) Dissolve 1.736 g of cerium nitrate hexahydrate and 0.2564 g of magnesium nitrate in 10 mL of water, mix well, and then add dropwise to 45 mL of ethanol. Stir and evaporate to dryness at 85 °C, and then calcine at 500 °C for 3 h to obtain Ce. 0.8 Mg 0.2 O x Composite oxide carrier;

[0070] (2) Disperse 0.5g of the composite oxide carrier and 0.25g of CTAB in 5mL of water and stir rapidly for 40min to obtain a stable emulsion with a concentration of 0.05g / mL of CTAB in the emulsion.

[0071] (3) Dissolve 0.0025 g Rh in 1 mL of dilute nitric acid solution and sonicate for 5 min to obtain a uniform and transparent solution;

[0072] The transparent rhodium nitrate solution was added dropwise to a stable emulsion, mixed and stirred for 30 minutes, and then evaporated to dryness in an oven at 80°C. The powder obtained after evaporation was ground and then placed in a muffle furnace and calcined at 550°C for 6 hours at a heating rate of 5°C / min to obtain the CO-SCR denitration catalyst.

[0073] In the CO-SCR catalyst prepared in this embodiment, the mass fraction of the noble metal active component rhodium is 0.5%.

[0074] Example 4

[0075] This embodiment provides a CO-SCR denitrification catalyst, and the preparation method of the CO-SCR denitrification catalyst is as follows:

[0076] (1) Dissolve 1.519 g of cerium nitrate hexahydrate and 0.3846 g of magnesium nitrate in 10 mL of water, mix well, and then add dropwise to 45 mL of ethanol. Stir and evaporate to dryness at 85 °C, and then calcine at 500 °C for 3 h to obtain Ce. 0.7 Mg 0.3 O x Composite oxide carrier;

[0077] (2) Disperse 0.5g of the composite oxide carrier and 0.25g of CTAB in 5mL of water and stir rapidly for 40min to obtain a stable emulsion with a concentration of 0.05g / mL of CTAB in the emulsion.

[0078] (3) Dissolve 0.0025 g Rh in 1 mL of dilute nitric acid solution and sonicate for 5 min to obtain a uniform and transparent solution;

[0079] The transparent rhodium nitrate solution was added dropwise to a stable emulsion, mixed and stirred for 30 minutes, and then evaporated to dryness in an oven at 80°C. The powder obtained after evaporation was ground and then placed in a muffle furnace and calcined at 550°C for 6 hours at a heating rate of 5°C / min to obtain the CO-SCR denitration catalyst.

[0080] In the CO-SCR catalyst prepared in this embodiment, the mass fraction of the noble metal active component rhodium is 0.5%.

[0081] Example 5

[0082] This embodiment provides a CO-SCR denitrification catalyst, and the preparation method of the CO-SCR denitrification catalyst is as follows:

[0083] (1) Dissolve 2.0625 g of cerium nitrate hexahydrate and 0.041 g of calcium nitrate in 10 mL of water, mix well, and then add dropwise to 45 mL of ethanol. Stir and evaporate to dryness at 85 °C, and then calcine at 500 °C for 3 h to obtain Ce. 0.95 Ca 0.05 O x Composite oxide carrier;

[0084] (2) Disperse 0.5g of the composite oxide carrier and 0.25g of CTAB in 5mL of water and stir rapidly for 40min to obtain a stable emulsion with a concentration of 0.05g / mL of CTAB in the emulsion.

[0085] (3) Dissolve 0.0025 g Rh in 1 mL of dilute nitric acid solution and sonicate for 5 min to obtain a uniform and transparent solution;

[0086] The transparent rhodium nitrate solution was added dropwise to a stable emulsion, mixed and stirred for 30 minutes, and then evaporated to dryness in an oven at 80°C. The powder obtained after evaporation was ground and then placed in a muffle furnace and calcined at 550°C for 6 hours at a heating rate of 5°C / min to obtain the CO-SCR denitration catalyst.

[0087] In the CO-SCR catalyst prepared in this embodiment, the mass fraction of the noble metal active component rhodium is 0.5%.

[0088] Example 6

[0089] The only difference between this embodiment and Example 1 is that, in the preparation process of the composite oxide support, magnesium nitrate is replaced with barium nitrate, and the molar ratio of Ce:Ba is kept at 95:5. All other conditions and parameters are exactly the same as in Example 1.

[0090] Example 7

[0091] The only difference between this embodiment and Embodiment 1 is that in step (3), rhodium nitrate is replaced with palladium nitrate containing 0.0025g Pd, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0092] In the CO-SCR catalyst prepared in this embodiment, the mass fraction of the noble metal active component palladium is 0.5%.

[0093] Example 8

[0094] The only difference between this embodiment and Example 1 is that in step (3), rhodium nitrate is replaced with platinum nitrate containing 0.0025g Pt. All other conditions and parameters are exactly the same as in Example 1.

[0095] In the CO-SCR catalyst prepared in this embodiment, the mass fraction of the noble metal active component platinum is 0.5%.

[0096] Example 9

[0097] The only difference between this embodiment and Embodiment 1 is that in step (3), rhodium nitrate is replaced with rhodium nitrate containing 0.01g Rh, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0098] In the CO-SCR catalyst prepared in this embodiment, the mass fraction of the noble metal active component rhodium is 2%.

[0099] Comparative Example 1

[0100] The only difference between this comparative example and Example 1 is that magnesium is not added in step (1), the carrier is cerium oxide, and the other conditions and parameters are exactly the same as in Example 1.

[0101] Comparative Example 2

[0102] The only difference between this comparative example and Example 1 is that in step (1), magnesium is replaced with zirconium, and the Ce:Zr element ratio is kept at 95:5. All other conditions and parameters are exactly the same as in Example 1.

[0103] Comparative Example 3

[0104] The only difference between this embodiment and embodiment 1 is that no precious metal is added in step (3), while the other conditions and parameters are exactly the same as in embodiment 1.

[0105] Comparative Example 4

[0106] The only difference between this embodiment and Example 1 is that the surfactant CTAB is replaced with PVP (polyvinylpyrrolidone). All other conditions and parameters are exactly the same as in Example 1.

[0107] Performance testing:

[0108] The catalysts prepared in Examples 1-9 and Comparative Examples 1-4 were used to conduct denitrification activity experiments on simulated automobile exhaust gas. The simulated flue gas contained 1500 ppm CO and 1500 ppm NO, with argon as the balance gas. 60 mg of the above CO-SCR denitrification catalyst was mixed evenly with 300 mg of quartz sand and placed in a quartz tube with an inner diameter of 0.6 mm for catalytic activity testing.

[0109] The test results are shown in Table 1:

[0110] Table 1

[0111]

[0112]

[0113] As can be seen from Table 1, based on Examples 1-4, when the composite oxide support is CeMgO x At that time, the optimal cerium:magnesium ratio was 95:5. With the addition of alkali metal magnesium, the catalyst's T... 90 As the temperature gradually increases, both the NO conversion rate and nitrogen selectivity gradually decrease, indicating that the acidity or alkalinity of the composite oxide support has a direct impact on the catalyst activity. Excessive alkalinity on the support surface may hinder the desorption of carbonates, thereby leading to a decrease in catalytic activity and nitrogen selectivity.

[0114] A comparison of Examples 1 and 5-6 shows that as the alkaline metal element in the composite oxide support changes, its catalytic activity and nitrogen selectivity also change. This indicates that the pH of the composite oxide support has a direct impact on the catalyst activity, and the interaction between the elements in the support and the noble metal may also have a direct impact on the catalyst activity.

[0115] A comparison of Examples 1 and 7-8 shows that when the noble metal active component changes from rhodium to palladium and platinum, the catalyst activity and nitrogen selectivity decrease accordingly. Meanwhile, the NO conversion rate and nitrogen conversion rate of palladium are slightly better than those of platinum. This may be due to the different adsorption capacities of the noble metal active sites for NO; the active sites on rhodium are more prone to adsorbing NO, thus facilitating the entire reaction. Numerous studies have also shown that rhodium plays an irreplaceable role in the adsorption and conversion of NO, and its activity is superior to that of palladium and platinum.

[0116] A comparison of Examples 1 and 9 shows that when the loading of the noble metal active component is greater than or equal to 2%, the catalyst activity decreases. This indicates that when the amount of noble metal used is too high, the surfactant cannot help disperse a large amount of noble metal, leading to noble metal agglomeration, some active sites are not exposed, and the utilization rate of active sites is low.

[0117] As can be seen from the comparison between Example 1 and Comparative Examples 1-2, the basic element magnesium plays an important role in improving the low-temperature activity and nitrogen selectivity of the catalyst. After removing magnesium or replacing it with other elements such as zirconium, the redox ability of the catalyst decreases, and both the low-temperature activity and nitrogen selectivity decrease.

[0118] As can be seen from the comparison between Example 1 and Comparative Example 3, when there is no noble metal on the catalyst surface, the effective active sites of the catalyst are greatly reduced, and the catalytic activity and nitrogen selectivity of the catalyst are greatly reduced. Therefore, the noble metal active sites are crucial to the entire catalytic reaction.

[0119] As can be seen from the comparison between Example 1 and Comparative Example 4, after replacing the surfactant CTAB in the preparation process with PVP, the low-temperature activity and nitrogen selectivity of the catalyst are greatly reduced. This may be due to the different surfactants, which lead to poorer dispersion of noble metals, fewer active sites, and poorer redox ability of the catalyst, thus resulting in poorer low-temperature activity and nitrogen selectivity of the catalyst.

[0120] The applicant declares that the detailed method of the present invention is illustrated by the above embodiments, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A CO-SCR catalyst, characterized in that, The CO-SCR catalyst comprises a cerium-based composite oxide support and a noble metal active component, wherein the noble metal active component is dispersed on the surface of the cerium-based composite oxide support with the assistance of a surfactant. The chemical formula of the cerium-based composite oxide support is CeMO. x Where M is a doping element selected from Mg, and x is the number of O atoms required to satisfy valence balance.

2. The CO-SCR catalyst according to claim 1, characterized in that, The CeMO x In this case, the molar ratio of Ce to M is (19~2):

1.

3. The CO-SCR catalyst according to claim 1, characterized in that, The precious metal active component includes at least one of rhodium, platinum, palladium, ruthenium, iridium, and gold.

4. The CO-SCR catalyst according to claim 3, characterized in that, The noble metal active component is rhodium.

5. The CO-SCR catalyst according to claim 1, characterized in that, Based on the total mass of the CO-SCR catalyst being 100%, the mass fraction of the noble metal active component is 0.1% to 20%.

6. The CO-SCR catalyst according to claim 5, characterized in that, Based on the total mass of the CO-SCR catalyst being 100%, the mass fraction of the noble metal active component is 0.5% to 10%.

7. The CO-SCR catalyst according to claim 6, characterized in that, Based on the total mass of the CO-SCR catalyst being 100%, the mass fraction of the noble metal active component is 0.5% to 2%.

8. The CO-SCR catalyst according to claim 1, characterized in that, The surfactant includes hexadecyltrimethylammonium bromide.

9. A method for preparing a CO-SCR catalyst according to any one of claims 1-8, characterized in that, The preparation method includes the following steps: A cerium-based composite oxide, a first solvent, a surfactant, and a precursor of a noble metal active component are mixed to obtain a mixture. The mixture is then dried and calcined to obtain the CO-SCR catalyst.

10. The method for preparing the CO-SCR catalyst according to claim 9, characterized in that, The preparation method of the cerium-based composite oxide includes the following steps: (1) The cerium source, the doped element M source, and the second solvent are mixed to obtain a mixed solution; (2) The mixture is added dropwise to ethanol and stirred, then stirred and evaporated to dryness, and then calcined at high temperature to obtain the cerium-based composite oxide.

11. The method for preparing the CO-SCR catalyst according to claim 10, characterized in that, The cerium source in step (1) includes cerium nitrate.

12. The method for preparing the CO-SCR catalyst according to claim 11, characterized in that, The dopant element M source in step (1) includes nitrate of M.

13. The method for preparing the CO-SCR catalyst according to claim 10, characterized in that, The temperature for stirring and drying in step (2) is 60℃~100℃.

14. The method for preparing the CO-SCR catalyst according to claim 10, characterized in that, The high-temperature calcination temperature in step (2) is 400℃~600℃.

15. The method for preparing the CO-SCR catalyst according to claim 10, characterized in that, The high-temperature calcination time in step (2) is 3h~4h.

16. The method for preparing the CO-SCR catalyst according to claim 9, characterized in that, The surfactant includes hexadecyltrimethylammonium bromide.

17. The method for preparing the CO-SCR catalyst according to claim 9, characterized in that, The precursor of the noble metal active component includes a noble metal nitrate.

18. The method for preparing the CO-SCR catalyst according to claim 9, characterized in that, The mass ratio of the surfactant to the cerium-based composite oxide is 1:(1~4).

19. The method for preparing the CO-SCR catalyst according to claim 9, characterized in that, The concentration of the surfactant in the mixture is 0.005 g / mL to 0.1 g / mL.

20. The method for preparing the CO-SCR catalyst according to claim 19, characterized in that, The concentration of the surfactant in the mixture is 0.005 g / mL to 0.02 g / mL.

21. The method for preparing the CO-SCR catalyst according to claim 9, characterized in that, The roasting temperature is 500℃~700℃.

22. The method for preparing the CO-SCR catalyst according to claim 9, characterized in that, The heating rate of the roasting is 1℃ / min-10℃ / min.

23. The method for preparing the CO-SCR catalyst according to claim 9, characterized in that, The roasting time is 3 to 6 hours.

24. The method for preparing the CO-SCR catalyst according to claim 9, characterized in that, The preparation method of the CO-SCR catalyst includes the following steps: (I) A mixture of cerium salt, M-containing nitrate and solvent is added dropwise to an ethanol solution to obtain a mixture. The mixture is stirred and evaporated to dryness at 70℃~90℃. Then, the temperature is increased to 400℃~600℃ at a heating rate of 1℃ / min~10℃ / min and calcined for 3h~10h to obtain cerium-based composite oxide. (II) The cerium-based composite oxide and surfactant are dispersed in a solvent, mixed and stirred for 20-40 min, then mixed with a noble metal precursor, and then dried at 60℃~110℃. Then, the temperature is increased to 400℃~600℃ at a heating rate of 1℃ / min~10℃ / min for 3h~10h to obtain the CO-SCR catalyst.

25. The application of a CO-SCR catalyst as described in any one of claims 1-8, characterized in that, The CO-SCR catalyst is used for the selective catalytic reduction of NO by CO.

26. The application of the CO-SCR catalyst according to claim 25, characterized in that, The operating temperature of the CO-SCR catalyst is 100℃~600℃.

27. The application of the CO-SCR catalyst according to claim 26, characterized in that, The operating temperature of the CO-SCR catalyst is 250℃~400℃.

28. A CO-SCR reactor, characterized in that, The CO-SCR reactor includes the CO-SCR catalyst as described in any one of claims 1-8, and the CO-SCR reactor is used in at least one of a mobile source gas vehicle exhaust treatment device, a stationary source gas vehicle exhaust treatment device, and a stationary source gas denitrification device.

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