A preparation method of a reverse copper-based catalyst for selective catalytic oxidation of ammonia and application thereof

Abstract

The application belongs to the field of environment-friendly catalytic treatment technology, and discloses a preparation method of a reverse copper-based catalyst for selective catalytic oxidation of ammonia and application thereof. The catalyst is composed of two metal oxides of component I and component II, the component I is a copper oxide carrier phase with an active component, and the component II is a nano-oxide loading phase. The nano-oxide is dispersed on the surface of the copper oxide by using a one-step method, and the reverse copper-based catalyst with a specific structure is obtained by oxidation treatment under a reaction atmosphere. The catalyst can catalytically oxidize NH3 in the air into non-toxic and harmless N2 and H2O by using O2 in the air, has excellent ammonia selective catalytic oxidation activity and nitrogen selectivity, and the ammonia selective catalytic oxidation performance and nitrogen selectivity remain unchanged after stable operation for 1200 hours, which shows excellent stability and good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of environmentally friendly catalytic treatment technology, specifically relating to a reverse copper-based catalyst and its preparation method, as well as its application in the selective catalytic oxidation of ammonia to produce N2 and H2O. Background Technology

[0002] Human activities such as agricultural activities and large-scale vehicle exhaust emissions have led to an increase in NH3 emissions, causing a series of environmental problems that have drawn close attention. The best way to mitigate the negative impacts of excessive NH3 emissions is to convert the pollutants back into high-value-added chemicals. Among various NH3 emission reduction measures, selective catalytic oxidation of ammonia is considered the most promising technology, the core of which lies in the selection of catalysts. Therefore, considerable effort has been devoted to finding high-performance catalysts for ammonia oxidation.

[0003] The design of traditional NH3 oxidation catalysts for nitrogen production mainly revolves around supported catalysts formed by highly active metal oxides and oxide substrates. In traditional catalysts, oxides such as silica, cerium oxide, zirconium oxide, alumina, and titanium oxide are typically used as the bulk phase, with the active components better dispersed in the form of a support. Metal oxides with relatively high reactivity, such as copper, iron, cobalt, and nickel, are used as the catalyst support phase to provide active sites and promote intermolecular reactions. However, traditional normal-phase copper-based catalysts often exhibit low activity below 180°C, with ammonia conversion rates mostly below 20%. Furthermore, the active centers of supported copper nanoparticles tend to aggregate at high temperatures, further reducing reactivity. Although numerous studies have aimed to improve the catalytic activity of traditional non-noble metal supported catalysts, the limited content of active metal oxides and the low interfacial content between the metal oxide and the support are the main reasons for the low activity. Therefore, developing a low-temperature, high-efficiency catalyst for the selective oxidation of ammonia has broad application prospects.

[0004] This invention provides a reversed-phase copper-based catalyst with nano-oxide supported on an active component metal oxide and its preparation method. The reversed-phase copper-based catalyst prepared in one step exhibits performance exceeding that of most reported catalysts at a temperature of 180°C, significantly improving the low-temperature ammonia oxidation activity; and after stable operation for 1200 h, the NH3 catalytic performance and N2 selectivity remain unchanged, demonstrating excellent stability. Summary of the Invention

[0005] The present invention aims to provide a reversed copper-based catalyst, its preparation method, and its application. A one-step method is employed to disperse nano-oxide onto the surface of copper oxide to synthesize a catalyst with a specific structure, followed by oxidation treatment under a reaction atmosphere to obtain the reversed copper-based catalyst. The rod-shaped reversed copper-based catalyst prepared by this invention can efficiently and selectively oxidize ammonia to nitrogen at 180℃, with an ammonia conversion rate >50%, significantly improving the catalyst's low-temperature selective catalytic oxidation activity for ammonia. Furthermore, after 1200 h of stable operation, the selective catalytic oxidation performance for NH3 and the selectivity for N2 remain unchanged, exhibiting excellent reaction stability and promising application prospects.

[0006] The technical solution of the present invention:

[0007] A method for preparing a reversed copper-based catalyst for the selective catalytic oxidation of ammonia includes the following steps:

[0008] (1) Bubble the deionized water with argon or helium to maintain an oxygen-free environment for the deionized water; prepare a metal salt solution with the oxygen-free deionized water, and then add the precipitant to the metal salt solution of the supported phase, and heat and stir.

[0009] (2) After dissolving the copper precursor salt of the support phase in deionized water, add it to the metal salt solution; carry out the reaction under heating reaction conditions, with a stirring temperature of 20-80℃, preferably 30-55℃, and a stirring reaction time of 0.5-5h; argon or helium gas is continuously introduced for protection throughout the reaction process.

[0010] (3) After the reaction is completed, age at room temperature for 0.5-4h, centrifuge the precipitate at 3000-10000r / min, wash with water or organic solvent, and dry the washed sample under vacuum at 60℃ for 5-18h.

[0011] (4) The dried sample is calcined at high temperature in an inert atmosphere under the following conditions: the temperature is increased from room temperature to 250-500℃ at a heating rate of 2-10℃ / min, and calcined for 1-6h, preferably 2-4h; then it is oxidized in a mixed reaction atmosphere of ammonia and oxygen at 250℃ for 30-90min to obtain the reverse copper-based catalyst.

[0012] The metal salt is one or a mixture of two or more of the following: silicate ester, zirconium chloride, zirconium nitrate, hydrated zirconium nitrate, cerium nitrate, cerium nitrate, hydrated cerium nitrate, aluminum nitrate, hydrated aluminum nitrate, aluminum chloride, titanium tetrachloride, tungsten nitrate, tungsten chloride, lanthanum nitrate, hydrated lanthanum nitrate, lanthanum chloride, manganese nitrate, hydrated manganese nitrate, and manganese chloride.

[0013] The copper precursor salt is one or a mixture of two or more of copper nitrate, hydrated copper nitrate, copper chloride, and hydrated copper chloride.

[0014] The precipitant is one or a mixture of two or more of the following: sodium hydroxide, oxalic acid, sodium carbonate, urea, ammonia, and tetrapropylammonium hydroxide.

[0015] The molar amount of the precipitant is 1-5 times the total molar amount of the metal salt and the copper precursor salt.

[0016] In the oxidation treatment using a mixed ammonia and oxygen reaction atmosphere, the ammonia concentration is 500–5000 ppm, and the oxygen content is 5–20 vol%.

[0017] In the reversed copper-based catalyst, the mass of the active copper oxide support phase is 50.01% to 94.9% of the catalyst mass.

[0018] The molar ratio of the metal salt to the copper precursor salt is >1:1 and <1:20.

[0019] A method for selectively oxidizing and eliminating ammonia in the atmospheric environment utilizes a reversed-phase copper-based catalyst, with ammonia and oxygen as reactants, in a fixed-bed or moving-bed reactor to convert NH3 into N2 and H2O via O2. Specifically, the reversed-phase copper-based catalyst is placed in a fixed-bed or moving-bed reactor, and a reaction gas is introduced. The ammonia concentration in the reaction gas is 500–5000 ppm, the oxygen content is 5–20 vol%, and the volume hourly space velocity is 9000–80000 h⁻¹. -1 .

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) This invention employs a one-step method to encapsulate or disperse different amounts of nano-oxides on the surface of an active copper oxide support. The preparation method is simple, environmentally friendly, and provides a safer and more stable catalyst with a reversed-phase interface structure. Throughout the preparation process, the solution maintains an oxygen-free environment. Simultaneously, drying under vacuum and calcination under an inert atmosphere result in a copper-based catalyst precursor with a higher concentration of monovalent copper. The presence of more monovalent copper at the interface is beneficial for ammonia oxidation activity. Oxidation treatment under a reaction atmosphere stabilizes the catalyst surface, ensuring structural stability during the reaction. This method successfully prepares a catalyst with a highly active interface structure. Compared to supported catalysts prepared by impregnation and co-precipitation methods, the one-step reversed-phase copper-based catalyst exhibits significantly improved performance.

[0022] (2) In the catalyst prepared by this invention, the molar ratio of nano-oxide to copper oxide is >1:1 and <1:20, and the resulting reversed copper-based catalyst has a rod-shaped structure. Copper oxide serves as the rod-shaped support, and the nano-oxide is dispersed on the surface of the support, thus possessing a reversed interface structure.

[0023] (3) The rod-shaped reversed-phase copper-based catalyst prepared in this invention is used in the selective catalytic oxidation of ammonia. During the entire reaction process, bubbling under an inert atmosphere causes the surface of the rod-shaped copper oxide to exhibit a porous structure, increasing the specific surface area of ​​the catalyst. This porous rod-shaped support forms more reaction interfaces with the nano-oxide, exhibiting stronger interfacial interactions and enhancing the selective catalytic oxidation performance of ammonia. It efficiently and selectively oxidizes ammonia to nitrogen at 180℃, with an ammonia conversion rate >50%, significantly improving the catalyst's low-temperature selective catalytic oxidation activity and nitrogen selectivity. Furthermore, after running for 1200 h in the selective catalytic oxidation of ammonia, it exhibits excellent reaction stability and can be used for extended periods or in multiple cycles. Attached Figure Description

[0024] Figure 1 The powder X-ray diffraction pattern of the catalyst in one embodiment demonstrates the presence of a reverse copper-based catalyst structure with two metal oxides in the catalyst.

[0025] Figure 2 The image shows a TEM image of the catalyst in one embodiment, demonstrating that the structure of a reverse copper-based catalyst is rod-shaped.

[0026] Figure 3 The reaction results of the catalyst in one embodiment, showing the NH3 conversion and N2 selectivity over 1200 h, demonstrate that a reversed copper-based catalyst has excellent reaction stability.

[0027] Figure 4 The results of the comparison between the selective catalytic oxidation activity of the reversed copper-based catalyst and the forward catalyst in one embodiment demonstrate that a reversed copper-based catalyst has an ammonia conversion rate of >50% at 180°C and exhibits highly efficient low-temperature ammonia oxidation activity. Detailed Implementation

[0028] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0029] Traditional catalysts used in the selective catalytic oxidation of ammonia typically employ oxides such as silica, cerium oxide, zirconium oxide, alumina, and titanium oxide as the bulk phase, serving as a support to better disperse the active components, accounting for approximately 50% to 99.9% of the catalyst mass fraction. Metal oxides such as copper, iron, cobalt, and nickel, with relatively high reactivity, are used as the catalyst support phase to provide NH3 reaction active sites, accounting for approximately 0.01% to 30% of the catalyst mass fraction. However, traditional normal-phase copper-based catalysts often exhibit low activity below 180°C, with ammonia conversion rates mostly below 20%, and the active centers of the supported copper nanoparticles tend to aggregate at high temperatures, thus reducing reactivity. This invention provides a reverse-phase copper-based catalyst with a specific structure prepared in one step, exhibiting higher low-temperature activity. This catalyst uses copper oxides providing NH3 active sites as the bulk phase and one or more nano-oxides capable of generating oxygen vacancies or adsorbing and activating ammonia as the support phase. In one specific embodiment, the volume hourly space velocity is 40,000 h⁻¹. -1 At 180℃, the ammonia conversion rate is >50%, and the stability exceeds 1200h.

[0030] In this invention, the loading amount refers to the percentage of the mass of the supported phase nano-oxide on the copper oxide to the total mass of the catalyst. The formula for calculating the loading amount is: Loading amount = Mass of supported phase nano-oxide / Total mass of catalyst × 100%.

[0031] In this invention, the particle size of the reverse copper-based catalyst is 10-200 mesh (20 mesh, 40 mesh, 60 mesh, 80 mesh, 100 mesh, 150 mesh).

[0032] The following examples and comparative examples illustrate the implementation of this application in more detail.

[0033] Example 1

[0034] 500 mL of deionized water was bubbled under an argon atmosphere for 1 hour, and this solution was designated as solution A. 1.09 g of cerium nitrate hexahydrate was dissolved in 40 mL of water, stirred until completely dissolved, and then added dropwise to solution A. 2.08 g of sodium hydroxide was dissolved in 52 mL of water, dissolved until completely dissolved, and then added dropwise to solution A. 4.832 g of copper nitrate trihydrate was dissolved in 200 mL of water, dissolved until completely dissolved, and then added dropwise to solution A at a reaction temperature of 40 °C, with stirring at 40 °C for 2 hours. The resulting precipitate was further aged at room temperature for 2 hours and then washed with ethanol and deionized water until the filtrate was neutral. The obtained material was dried overnight under vacuum at 60 °C, and then calcined at 300 °C under an argon atmosphere for 2 hours. After calcination, it was pretreated at 250 °C for 1 hour in a reaction atmosphere to obtain a cerium oxide / copper oxide catalyst (20 wt% CeO2 / CuO) with a cerium oxide content of 20 wt%.

[0035] The solid catalyst was granulated to a particle size of 20–40 mesh and placed in a fixed-bed reactor for ammonia oxidation. The specific reaction conditions were: 1000 ppm NH3, 10 vol% O2, with He as the equilibrium gas, and a reaction space velocity of 40,000 h⁻¹. -1 The reaction temperature is 150–220℃.

[0036] Example 2

[0037] 500 mL of deionized water was bubbled under an argon atmosphere for 1 hour, and this solution was designated as solution A. 1.86 g of zirconium nitrate pentahydrate was dissolved in 40 mL of water, stirred until completely dissolved, and then added dropwise to solution A. 2.49 g of sodium hydroxide was dissolved in 52 mL of water, dissolved until completely dissolved, and then added dropwise to solution A. 4.832 g of copper nitrate trihydrate was dissolved in 200 mL of water, dissolved until completely dissolved, and then added dropwise to solution A at a reaction temperature of 40 °C, with stirring at 40 °C for 2 hours. The resulting precipitate was further aged at room temperature for 2 hours and then washed with ethanol and deionized water until the filtrate was neutral. The obtained material was dried overnight under vacuum at 60 °C, and then calcined at 300 °C under an argon atmosphere for 2 hours. After calcination, it was pretreated at 250 °C for 1 hour in a reaction atmosphere to obtain a zirconium oxide / copper oxide catalyst (20 wt% ZrO2 / CuO) with a zirconium oxide content of 20 wt%.

[0038] The solid catalyst was granulated to a particle size of 20–40 mesh and placed in a fixed-bed reactor for ammonia oxidation. The specific reaction conditions were: 1000 ppm NH3, 10 vol% O2, with He as the equilibrium gas, and a reaction space velocity of 40,000 h⁻¹. -1 The reaction temperature is 150–220℃.

[0039] Example 3

[0040] Except for the precursor salts being aluminum nitrate nonahydrate and copper nitrate trihydrate, everything else was the same as in Example 2. An alumina / copper oxide catalyst (20wt% Al2O3 / CuO) with an alumina content of 20wt% was obtained.

[0041] Example 4

[0042] Except for the precursor salts being manganese chloride and copper nitrate trihydrate, everything else was the same as in Example 2. A manganese oxide / copper oxide catalyst (20wt% MnO2 / CuO) with a manganese oxide content of 20wt% was obtained.

[0043] Example 5

[0044] Except for the precursor salts being aluminum nitrate nonahydrate and cerium nitrate hexahydrate, everything else was the same as in Example 1. A cerium oxide-alumina / copper oxide catalyst (20wt% CeAlO) was obtained with 20wt% alumina and cerium oxide. x / CuO).

[0045] Example 6

[0046] Except that the molar ratio of CeO2:CuO is 1:20, the rest is the same as in Example 1. A cerium oxide / copper oxide catalyst (10wt% CeO2 / CuO) with a cerium oxide content of 10wt% is obtained.

[0047] Example 7

[0048] Except that the stirring temperature is 50°C, the rest is the same as in Example 1. A cerium oxide / copper oxide catalyst (20wt% CeO2 / CuO - 50°C) with a cerium oxide content of 20wt% is prepared.

[0049] Example 8

[0050] Except that the stirring temperature is 70°C, the rest is the same as in Example 1. A cerium oxide / copper oxide catalyst (20wt% CeO2 / CuO - 70°C) with a cerium oxide content of 20wt% is prepared.

[0051] Example 9

[0052] Except that the precipitating agent is sodium hydroxide, the rest is the same as in Example 1. A cerium oxide / copper oxide catalyst (20wt% CeO2 / CuO - NaOH) with a cerium oxide content of 20wt% is obtained.

[0053] Example 10

[0054] Except that the precipitating agent is sodium carbonate, the rest is the same as in Example 1. A cerium oxide / copper oxide catalyst (20wt% CeO2 / CuO - Na2CO3) with a cerium oxide content of 20wt% is obtained.

[0055] Example 11

[0056] Except that the calcination temperature is 250°C, the rest is the same as in Example 1. A cerium oxide / copper oxide catalyst (20wt% CeO2 / CuO - 250°C) is prepared.

[0057] Example 12

[0058] Except that the calcination temperature is 500°C and the calcination time is 1h, the rest is the same as in Example 1. A cerium oxide / copper oxide catalyst (20wt% CeO2 / CuO - 500°C) is prepared.

[0059] Example 13

[0060] Except that the stirring reaction time is 5h, the rest is the same as in Example 1. A cerium oxide / copper oxide catalyst (20wt% CeO2 / CuO - 3h) is prepared.

[0061] Comparative Example 1

[0062] Except for the CeO2:CuO molar ratio of 1:0.3, everything else was the same as in Example 1. A cerium oxide / copper oxide catalyst (90wt% CeO2 / CuO) with a cerium oxide content of 90wt% was obtained.

[0063] Comparative Example 2

[0064] Except for the CeO2:CuO molar ratio being 1:1, everything else was the same as in Example 1. A cerium oxide / copper oxide catalyst (70wt% CeO2 / CuO) with a cerium oxide content of 70wt% was obtained.

[0065] Comparative Example 3

[0066] 4.832 g of copper nitrate hexahydrate and 1.009 g of cerium nitrate trihydrate were weighed and dissolved in 350 mL of deionized water, and stirred at room temperature to disperse them. 4.35 g of oxalic acid dihydrate was weighed and dissolved in 70 mL of deionized water, and added dropwise to the above mixed solution. The mixture was stirred at room temperature for 1 h. The resulting precipitate was further aged at room temperature for 2 h, and then washed with ethanol and deionized water until the filtrate was neutral. The obtained material was dried in air at 80 °C overnight, and then calcined in static air at 400 °C for 2 h. After calcination, a cerium oxide / copper oxide catalyst (20 wt% CeO2 / CuO) with a cerium oxide content of 20 wt% was obtained.

[0067] The solid catalyst was granulated to a particle size of 20–40 mesh and placed in a fixed-bed reactor for ammonia oxidation. The specific reaction conditions were: 1000 ppm NH3, 10 vol% O2, with He as the equilibrium gas, and a reaction space velocity of 40,000 h⁻¹. -1 The reaction temperature is 150–250℃.

[0068] Comparative Example 4

[0069] 0.3784 g of cerium nitrate hexahydrate was weighed and dissolved in a small amount of deionized water, and then ultrasonically dispersed and dissolved. 0.6 g of copper oxide powder was added to the solution and allowed to stand for 24 h. The remaining solution was evaporated to dryness in air at 80 °C, and then calcined in static air at 300 °C for 2 h. After calcination, a cerium oxide / copper oxide catalyst (20 wt% CeO2 / CuO) with a cerium oxide content of 20 wt% was obtained.

[0070] The solid catalyst was granulated to a particle size of 20–40 mesh and placed in a fixed-bed reactor for ammonia oxidation. The specific reaction conditions were: 1000 ppm NH3, 10 vol% O2, with He as the equilibrium gas, and a reaction space velocity of 40,000 h⁻¹. -1 The reaction temperature is 150–260℃.

[0071] Comparative Example 5

[0072] 0.7762 g of copper nitrate trihydrate was dissolved in a small amount of deionized water and ultrasonically dispersed. 0.6 g of cerium dioxide powder was added to the solution and allowed to stand for 24 h. The remaining solution was evaporated to dryness in air at 80 °C, and then calcined in static air at 300 °C for 2 h. After calcination, a copper oxide / cerium oxide catalyst (20 wt% CuO / CeO2) with a copper oxide content of 20 wt% was obtained.

[0073] The solid catalyst was granulated to a particle size of 20–40 mesh and placed in a fixed-bed reactor for ammonia oxidation. The specific reaction conditions were: 1000 ppm NH3, 10 vol% O2, with He as the equilibrium gas, and a reaction space velocity of 40,000 h⁻¹. -1 The reaction temperature is 150–260℃.

[0074] Table 1 shows the loading and reaction conditions for the methods described in Examples 1-10 and Comparative Examples 1-6.

[0075] Table 1 Catalyst loading and reaction conditions

[0076]

[0077]

[0078] To better illustrate the ammonia catalytic oxidation effect of the reversed copper-based catalyst of the present invention, the catalyst reaction performance was evaluated. Table 2 shows the NH3 conversion rate of each catalyst at different temperatures in the NH3 catalytic oxidation reaction.

[0079] Table 2. NH3 conversion rates of various catalysts in the NH3 catalytic oxidation reaction.

[0080]

[0081]

[0082] Table 2 shows that, compared with the impregnation and co-precipitation methods, the reverse-phase copper-based catalyst prepared by the one-step method exhibits superior selective catalytic oxidation activity for ammonia. The catalyst in Example 1 showed the highest activity, with an NH3 conversion rate as high as 50.01% at 180℃, significantly improving the poor activity of ammonia at low temperatures. In contrast, Comparative Example 3, due to continuous contact with oxygen during preparation, drying, and calcination, failed to generate more active interfaces with monovalent copper, resulting in an ammonia conversion rate of <20% at 180℃ and relatively poor selective catalytic oxidation activity for ammonia.

[0083] Table 2 shows that the rod-shaped catalysts prepared by the one-step method exhibit high selective catalytic oxidation activity for ammonia when the molar ratio of nano-oxide to copper oxide is within the range of 1:1 to 1:20. In contrast, the catalysts described in Comparative Examples 1 and 2, with a molar ratio of nano-oxide to copper oxide ≤1:1, do not exhibit a rod-shaped structure and show relatively poor activity.

[0084] As shown in Table 2, the one-step reversed-phase copper-based catalyst exhibits higher selective catalytic oxidation activity for ammonia compared to traditional normal-phase supported copper-based catalysts. In Example 1, ammonia was completely converted at 200°C, and the ammonia conversion rate was >50% at 180°C, while in Comparative Example 5, the ammonia conversion rate was <80% at 200°C and <20% at 180°C.

[0085] Figure 1 Powder X-ray diffraction patterns of Example 1 and Comparative Example 7 are given. Example 1 shows a strong copper oxide diffraction peak.

[0086] Figure 2 The TEM image of Example 1 is provided, showing that nano-oxide clusters are dispersed on the surface of porous rod-shaped copper oxide, indicating that rod-shaped reverse copper-based catalysts were successfully prepared by a one-step method.

[0087] Figure 3 The stability test results of Example 1 within the range of 200℃ and 1200h are given. There is no significant change in NH3 conversion rate and N2 selectivity.

[0088] Figure 4 The reaction results of Examples 1 and 6 and Comparative Examples 1 and 2 are presented to compare the selective catalytic oxidation activity of ammonia by reversed copper-based catalysts with different molar ratios in a one-step process. Example 1 shows better activity.

[0089] Where there is no conflict, the above embodiments and features described herein can be combined with each other.

[0090] The above embodiments are provided merely for the purpose of describing the present invention and are not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims. Various equivalent substitutions and modifications made without departing from the spirit and principle of the invention should be covered within the scope of the invention.

Claims

1. A method for preparing a reversed copper-based catalyst for the selective catalytic oxidation of ammonia, characterized in that, Includes the following steps: (1) Bubble the deionized water with argon or helium to maintain an oxygen-free environment for the deionized water; prepare a metal salt solution with the oxygen-free deionized water, and then add the precipitant to the metal salt solution of the supported phase, and heat and stir. (2) After dissolving the copper precursor salt of the support phase in deionized water, add it to the metal salt solution; carry out the reaction under heating reaction conditions with stirring at a temperature of 20-80 ℃ and a reaction time of 0.5-5 h; argon or helium gas is continuously introduced for protection throughout the reaction process; the molar amount of the precipitant is 1-5 times the total molar amount of the metal salt and the copper precursor salt. The molar ratio of the metal salt to the copper precursor salt is 1:1 to 1:20, excluding endpoint values; (3) After the reaction is completed, age at room temperature for 0.5-4 h, centrifuge the precipitate at 3000-10000 r / min, wash with water or organic solvent, and dry the washed sample under vacuum at 60 ℃ for 5-18 h. (4) The dried sample was calcined at high temperature under an inert atmosphere. The conditions were: heating from room temperature to 250-500 ℃ at a heating rate of 2-10 ℃ / min for 1-6 h; then oxidized in a mixed reaction atmosphere of ammonia and oxygen at 250 ℃ for 30-90 min to obtain the reverse copper-based catalyst; in the reverse copper-based catalyst, the mass of the support phase was 50.01%~94.9% of the mass of the reverse copper-based catalyst.

2. The preparation method according to claim 1, characterized in that, The metal salt is one or a mixture of two or more of the following: silicate ester, zirconium chloride, zirconium nitrate, cerium nitrate, cerium nitrate, aluminum nitrate, aluminum chloride, titanium tetrachloride, tungsten nitrate, tungsten chloride, lanthanum nitrate, lanthanum chloride, manganese nitrate, and manganese chloride.

3. The preparation method according to claim 1, characterized in that, The copper precursor salt is one or both of copper nitrate and copper chloride.

4. The preparation method according to claim 1, characterized in that, The precipitant is one or a mixture of two or more of the following: sodium hydroxide, oxalic acid, sodium carbonate, urea, ammonia, and tetrapropylammonium hydroxide.

5. The preparation method according to claim 1, characterized in that, In the oxidation treatment using a mixed ammonia and oxygen reaction atmosphere, the ammonia concentration is 500~5000 ppm and the oxygen content is 5~20 vol.

6. The application of the reversed copper-based catalyst obtained by any of the preparation methods described in claims 1-5 in the selective catalytic oxidation of ammonia to produce nitrogen and water.

7. The application according to claim 6, characterized in that, The reverse copper-based catalyst is used to convert ammonia and oxygen into nitrogen and water by O2 in a fixed bed or a moving bed, and the specific method is as follows: the reverse copper-based catalyst is placed in a fixed bed or a moving bed reactor, the reaction gas is introduced, the ammonia concentration in the reaction gas is 500-5000 ppm, the oxygen content is 5-20 vol%, the volume space velocity is 9000-80000 h -1 .

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