Catalyst for decomposing nitrous oxide at low temperature and preparation method thereof
By using synergistic catalysis of fibrous cerium oxide support and strontium-modified Co3O4 active component in the catalyst, the problem of poor catalyst performance at low temperatures is solved, achieving efficient decomposition of nitrous oxide, which is suitable for industrial production.
Patent Information
- Application Number
- CN202411644595.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-18
- Publication Date
- 2025-01-07
AI Technical Summary
Existing catalysts have poor performance in catalytic decomposition of nitrous oxide at low temperatures (<400℃), making it difficult to effectively control N2O emissions.
A catalyst with high specific surface area was prepared by using fibrous cerium oxide as a support and introducing strontium-modified Co3O4 as an active component through liquid-phase mixing. The synergistic catalytic effect of cerium oxide and strontium-doped Co3O4 was utilized to promote the decomposition of N2O.
This improved the catalyst's reaction contact area and oxygen mobility, lowered the N2O decomposition temperature, and achieved efficient decomposition under low-temperature conditions, making it suitable for industrial production.
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Figure CN119259063A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of catalysts, and in particular to a catalyst for low-temperature decomposition of nitrous oxide and a preparation method thereof. Background Art
[0002] Nitrous oxide (N2O) is one of the greenhouse gases that has attracted much attention and is likely to cause a hole in the ozone layer. Currently, N2O emissions mainly come from: biomass combustion of various fossil fuels, chemical production of adipic acid, and motor vehicle exhaust. Effectively reducing the growing N2O emissions faces challenges, so emission reduction work is urgent.
[0003] Direct catalytic decomposition of N2O has the advantages of simple process, economic efficiency, etc. It mainly includes precious metal-loaded catalysts, metal oxide catalysts and molecular sieve catalysts. However, metal oxide catalysts have become the main research object due to their low price, good stability and good catalytic activity. Among them, cobalt-based spinel or cobalt-based perovskite catalysts have become the focus of research due to their lower activation energy.
[0004] In the manufacturing and transportation industries, the catalyst operating temperature is usually required to be lower than 400°C, but the existing catalysts have poor catalytic performance at low temperatures (<400°C). Summary of the invention
[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a catalyst for low-temperature decomposition of nitrous oxide and a preparation method thereof. The catalyst of the present invention has the advantages of high specific surface area, good activity and low activation temperature, and is of great significance for controlling the emission of N2O.
[0006] The technical solution adopted by the present invention is: A catalyst for low-temperature decomposition of nitrous oxide, comprising a catalyst carrier and an active component arranged on the catalyst carrier, wherein the catalyst carrier is a fibrous cerium oxide carrier, the active component is strontium-modified Co3O4, and the molar ratio of strontium to cobalt is 1:4-6.
[0007] Preferably, in the catalyst for low-temperature decomposition of nitrous oxide, the total mass ratio of the fibrous cerium oxide carrier to the catalyst is 1:2-6, and the active component has a spinel or perovskite-like structure.
[0008] The present invention also provides a method for preparing a catalyst for low-temperature decomposition of nitrous oxide, which comprises the following steps: Step S1, adding an appropriate amount of cerium nitrate and a complexing agent to a mixed solvent of ethanol and water, continuously dropping ammonia water under stirring conditions to adjust the pH to 2-4, and then continuously stirring to obtain a carrier precursor solution; Step S2, adding the carrier precursor solution obtained in step S1 into a high-pressure reactor and heating it to 100-160° C. for complexation, and then aging it at room temperature to obtain an intermediate product; Step S3, washing, drying and calcining the intermediate product obtained in step S2 to obtain a fibrous cerium oxide carrier; Step S4, weighing strontium nitrate and cobalt nitrate according to a molar ratio of strontium to cobalt of 1:4-6, then dissolving strontium nitrate in deionized water to obtain a strontium nitrate aqueous solution, and finally adding cobalt nitrate to the strontium nitrate aqueous solution, stirring for 1-3 hours, to obtain a first mixed solution; Step S5, adding the fibrous cerium oxide support obtained in step S3 to the first mixed solution, adjusting the pH to be greater than 7 with aqueous ammonia, and then stirring to obtain a second mixed solution; Step S6, heating the second mixed solution obtained in step S5 to 80-100° C., removing excess water, and obtaining a paste-like mixture; Step S7, continuing to roast the paste mixture obtained in step S6 to obtain a product.
[0009] Preferably, in the method for preparing the catalyst for low-temperature decomposition of nitrous oxide, the temperature during continuous stirring in step S1 is 40-60° C. and the stirring time is 1-3 h.
[0010] Preferably, in the method for preparing the catalyst for low-temperature decomposition of nitrous oxide, the cerium nitrate in step S1 is selected from one of cerium nitrate hexahydrate and ammonium cerium nitrate, and the concentration of the cerium nitrate is 0.01-1 mol / L.
[0011] Preferably, in the method for preparing the catalyst for low-temperature decomposition of nitrous oxide, the complexing agent in step S1 is selected from one of ethylenediaminetetraacetic acid, citric acid, tartaric acid, and glycolic acid, and the concentration of the complexing agent is 0.01-1 mol / L.
[0012] Preferably, in the method for preparing the catalyst for low-temperature decomposition of nitrous oxide, the complexing time in step S2 is 6-8 hours and the aging time is 2-4 hours.
[0013] Preferably, in the method for preparing the catalyst for low-temperature decomposition of nitrous oxide, the calcination temperatures in step S3 and step S7 are both 400-600° C., and the calcination time is both 3-6 hours.
[0014] Preferably, in the method for preparing a catalyst for low-temperature decomposition of nitrous oxide, the length of the fibrous cerium oxide carrier in step S3 is 26-198 μm, the diameter is 3-14 μm, and the specific surface area is 5-30 m 2 / g.
[0015] Preferably, in the method for preparing the catalyst for low-temperature decomposition of nitrous oxide, the stirring time in step S5 is 1-2 hours.
[0016] Advantages of the present invention: (1) The catalyst for low-temperature decomposition of nitrous oxide and the preparation method thereof of the present invention are prepared by a solvothermal method. The fibrous cerium oxide carrier has a specific surface area of 2-10 m2 compared with the traditional granular cerium oxide. 2 / g increased to 5-30m 2 / g can increase the reaction contact area and carry active sites more effectively. The length of cerium oxide fiber is 26-198μm and the diameter is 3-14μm. The cerium oxide carrier with high aspect ratio can improve oxygen mobility and reduce reaction activation energy.
[0017] (2) The catalyst for low-temperature decomposition of nitrous oxide and the preparation method thereof of the present invention adopt a liquid phase mixing method to prepare a catalyst having a cobalt metal site as an active site, introduce strontium into the catalyst to inhibit the growth of the Co3O4 spinel structure, further increase the reaction contact phase, provide oxygen vacancies, and promote the N2O decomposition reaction.
[0018] (3) The catalyst for low-temperature decomposition of nitrous oxide and the preparation method thereof of the present invention effectively reduce the decomposition temperature of N2O through the synergistic catalysis between cerium oxide and strontium-doped Co3O4. The conditions are mild, the operation is convenient, and it is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 This is a scanning electron microscope image of the fibrous cerium oxide support in Example 1.
[0020] Figure 2 It is a N2O catalytic performance curve diagram of the catalysts prepared in Examples 1-2 and Comparative Examples 1-3. DETAILED DESCRIPTION
[0021] The present invention will be further described below in conjunction with specific embodiments.
[0022] Example 1 A catalyst for low-temperature decomposition of nitrous oxide comprises a catalyst carrier and an active component arranged on the catalyst carrier, wherein the catalyst carrier is a fibrous cerium oxide carrier, the active component is strontium-modified Co3O4, and the molar ratio of strontium to cobalt is 1:5; the total mass ratio of the fibrous cerium oxide carrier to the catalyst is 1:5, and the active component has a spinel structure.
[0023] The preparation method of the catalyst for low-temperature decomposition of nitrous oxide in this embodiment comprises the following steps: Step S1, adding 21.3 g of cerium nitrate and 37.9 g of ethylenediaminetetraacetic acid to a mixed solvent of 70 ml of ethanol and 30 ml of water, and continuously dropping ammonia water under stirring to adjust the pH to 3, and then continuously stirring to obtain a carrier precursor solution, the temperature during continuous stirring is 40° C., and the stirring time is 2 h; Step S2, adding the carrier precursor solution prepared in step S1 into a high-pressure reactor, heating to 110° C. for complexation for 6 hours, and then aging at room temperature for 2 hours to obtain an intermediate product; Step S3: Wash, dry and calcine the intermediate product obtained in step S2 to obtain a fibrous cerium oxide carrier. The calcination temperature is 500° C. and the calcination time is 4 h. The length of the fibrous cerium oxide carrier is 60-110 μm, the diameter is 3-9 μm, and the specific surface area is 25 m 2 / g; Step S4, dissolving 2.65 g of strontium nitrate in 40 ml of deionized water to obtain a strontium nitrate aqueous solution, adding 18.89 g of cobalt nitrate hexahydrate to the strontium nitrate aqueous solution, and stirring for 1 hour to obtain a first mixed solution; Step S5, adding 1.59 g of the fibrous cerium oxide support obtained in step S3 to the mixed solution and heating to , adjusting the pH to 7.2 with aqueous ammonia, and then stirring at 60° C. for 1 h to obtain a second mixed solution; Step S6, heating the second mixed solution obtained in step S5 to 100° C. for 0.5 h, removing excess water, and obtaining a paste-like mixture; Step S7, continue to roast the paste mixture obtained in step S6 to obtain a product, the roasting temperature is 550° C., and the roasting time is 4 hours.
[0024] Example 2 A catalyst for low-temperature decomposition of nitrous oxide comprises a catalyst carrier and an active component arranged on the catalyst carrier, wherein the molar ratio of strontium to cobalt is 1:5; the total mass ratio of the fibrous cerium oxide carrier to the catalyst is 1:5, and the active component has a spinel structure.
[0025] The preparation method of the catalyst for low-temperature decomposition of nitrous oxide in this embodiment comprises the following steps: Step S1, adding 30.2 g of ammonium cerium nitrate and 24.9 g of citric acid to a mixed solvent of 70 ml of ethanol and 30 ml of water, and continuously dropping ammonia water under stirring to adjust the pH to 3, and then continuously stirring to obtain a carrier precursor solution, the temperature during continuous stirring is 40° C., and the stirring time is 2 h; Step S2, adding the carrier precursor solution prepared in step S1 into a high-pressure reactor, heating to 110° C. for complexation for 6 hours, and then aging at room temperature for 2 hours to obtain an intermediate product; Step S3: Wash, dry and calcine the intermediate product obtained in step S2 to obtain a fibrous cerium oxide carrier. The calcination temperature is 500° C. and the calcination time is 4 h. The length of the fibrous cerium oxide carrier is 48-122 μm, the diameter is 3-11 μm, and the specific surface area is 26 m 2 / g; Step S4, dissolving 2.65 g of strontium nitrate in 40 ml of deionized water to obtain a strontium nitrate aqueous solution, adding 18.89 g of cobalt nitrate hexahydrate to the strontium nitrate aqueous solution, and stirring for 1 hour to obtain a first mixed solution; Step S5, adding 1.59 g of the fibrous cerium oxide support obtained in step S3 to the mixed solution, heating to 60° C., adjusting the pH to 7.2 with aqueous ammonia, and then stirring at 60° C. for 1 h to obtain a second mixed solution; Step S6, heating the second mixed solution obtained in step S5 to 100° C. for 0.5 h, removing excess water, and obtaining a paste-like mixture; Step S7, continue to roast the paste mixture obtained in step S6 to obtain a product, the roasting temperature is 550° C., and the roasting time is 4 hours.
[0026] Comparative Example 1 A catalyst for low-temperature decomposition of nitrous oxide comprises a catalyst carrier and an active component arranged on the catalyst carrier, wherein the catalyst carrier is a cerium oxide carrier, the molar ratio of strontium to cobalt is 1:5; and the total mass ratio of the cerium oxide carrier to the catalyst is 1:5.
[0027] The preparation method of the catalyst for low-temperature decomposition of nitrous oxide in this comparative example comprises the following steps: Step S1, dissolving 2.65 g of strontium nitrate in 40 ml of deionized water to obtain a strontium nitrate aqueous solution, adding 18.89 g of cobalt nitrate hexahydrate to the strontium nitrate aqueous solution, and stirring for 1 hour to obtain a first mixed solution; Step S2, adding 1.59 g of cerium oxide powder to the first mixed solution, heating to 60° C., adjusting the pH to 7.2 with ammonia water, and then stirring at 60° C. for 1 h to obtain a second mixed solution; Step S6, heating the second mixed solution obtained in step S5 to 100° C. for 0.5 h, removing excess water, and obtaining a paste-like mixture; Step S7, continue to roast the paste mixture obtained in step S6 to obtain a product, the roasting temperature is 550° C., and the roasting time is 4 hours.
[0028] Comparative Example 2 A catalyst for low-temperature decomposition of nitrous oxide comprises a catalyst carrier and an active component arranged on the catalyst carrier, wherein the catalyst carrier is a cerium oxide carrier, and the total mass ratio of the cerium oxide carrier to the catalyst is 1:5.
[0029] The preparation method of the catalyst for low-temperature decomposition of nitrous oxide in this comparative example comprises the following steps: Step S1, dissolving 18.89 g of cobalt nitrate hexahydrate in 40 ml of deionized water, and stirring for 1 hour until the solution is completely dissolved to obtain a cobalt nitrate aqueous solution; Step S2, adding 1.5 g of cerium oxide powder to the aqueous cobalt nitrate solution obtained in step S1, heating to 60° C., adjusting the pH to 7.2 with aqueous ammonia, and then stirring at 60° C. for 1 h to obtain a first mixed solution; Step S3, heating the first mixed solution obtained in step S2 to 100° C. for 0.5 h, removing excess water, and obtaining a paste-like mixture; Step S4, continuing to roast the paste mixture obtained in step S3 to obtain a product, the roasting temperature is 550° C., and the roasting time is 4 hours.
[0030] Comparative Example 3 A catalyst for low-temperature decomposition of nitrous oxide is strontium-modified Co3O4, wherein the molar ratio of strontium to cobalt is 1:5.
[0031] The preparation method of the catalyst for low-temperature decomposition of nitrous oxide in this comparative example comprises the following steps: Step S1, dissolving 2.65 g of strontium nitrate in 40 ml of deionized water to obtain a strontium nitrate aqueous solution, adding 18.89 g of cobalt nitrate hexahydrate to the strontium nitrate aqueous solution, and stirring for 1 hour to obtain a first mixed solution; Step S2, heating the first mixed solution obtained in step S2 to 100° C. for 0.5 h, removing excess water, and obtaining a paste-like mixture; Step S3, continuing to roast the paste mixture obtained in step S2 to obtain a product, the roasting temperature is 550° C., and the roasting time is 4 hours.
[0032] Comparative Example 4 One catalyst used for the low temperature decomposition of nitrous oxide is the Co3O4 catalyst.
[0033] The preparation method of the catalyst for low-temperature decomposition of nitrous oxide in this comparative example comprises the following steps: Step S1, dissolving 18.89 g of cobalt nitrate hexahydrate in 40 ml of deionized water, and stirring for 1 hour until the solution is completely dissolved to obtain a cobalt nitrate aqueous solution; Step S2, heating the aqueous cobalt nitrate solution obtained in step S1 to 60° C., adjusting the pH value to 7.2 with aqueous ammonia, and then stirring at 60° C. for 1 h to obtain a mixed solution; Step S3, heating the mixed solution obtained in step S2 to 100° C. for 0.5 h, removing excess water, and obtaining a paste-like mixture; Step S4, calcining the paste mixture obtained in step S3 to obtain a product, the calcination temperature is 550° C., and the calcination time is 4 hours.
[0034] The catalysts prepared in Examples 1-2 and Comparative Examples 1-4 were passed through a 60-80 mesh sieve, pressed into tablets, and placed in a fixed bed reactor for performance evaluation testing.
[0035] The working conditions for performance testing are: 100 mg of catalyst is placed in a 5 mm quartz tube, N2O concentration is 800-1000 ppm, and the gas mass space velocity is 30000 ml g -1 ·h -1 , the balance gas is N2.
[0036] Figure 1 This is a scanning electron microscope picture of the fibrous cerium oxide support in Example 1. In the picture, the fibrous cerium oxide has a length of 60-110 μm and a diameter of 3-9 μm.
[0037] The catalyst performance evaluation test results are as follows Figure 2 As shown by Figure 2 It can be seen that the performance of the strontium-doped Co3O4 catalyst (Comparative Example 3) is improved compared with the Co3O4 catalyst (Comparative Example 4). 50 The temperature of N2O decreased from 410℃ to 385℃, which benefited from the introduction of strontium to inhibit the growth of Co3O4 spinel structure, provide oxygen vacancies, and promote the decomposition reaction of N2O. The introduction of granular cerium oxide as a carrier (Comparative Example 2) formed a synergistic catalysis with Co3O4, which effectively reduced the decomposition temperature of N2O, T 50 360℃; Sr-doped Co3O4 did not hinder the synergistic catalysis between the active component and the carrier (Comparative Example 1). Thanks to the strong interaction between cerium oxide and Co3O4, the contact loading was performed preferentially. 50 340℃; using fibrous cerium oxide instead of traditional granular cerium oxide as a carrier (Examples 1 and 2), the performance is further improved, T 50 The temperature at which the catalyst is heated to 320°C is better than that of the catalyst in the comparative example. The N2O conversion rate reaches 100% at around 380°C. The fibrous cerium oxide provides a larger supporting site, and the high aspect ratio brings a higher oxygen mobility, thereby reducing the activation energy of the reaction. In addition, the present invention adopts a solvothermal method to prepare the carrier and a liquid phase mixing method to prepare the catalyst, and the preparation process is simple and easy to industrialize.
[0038] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.
Claims
1. A catalyst for low temperature decomposition of nitrous oxide, characterized in that: The invention comprises a catalyst carrier and an active component arranged on the catalyst carrier. The catalyst carrier is a fibrous cerium oxide carrier, the active component is Co3O4 modified with strontium, and the molar ratio of strontium to cobalt is 1:4-6.
2. The catalyst for low-temperature decomposition of nitrous oxide according to claim 1, characterized in that: The total mass ratio of the fibrous cerium oxide carrier to the catalyst is 1:2-6, and the active component has a spinel or perovskite-like structure.
3. The method for preparing a catalyst for low-temperature decomposition of nitrous oxide according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step S1, adding an appropriate amount of cerium nitrate and a complexing agent to a mixed solvent of ethanol and water, continuously dropping ammonia water under stirring conditions to adjust the pH to 2-4, and then continuously stirring to obtain a carrier precursor solution; Step S2, adding the carrier precursor solution obtained in step S1 into a high-pressure reactor and heating it to 100-160° C. for complexation, and then aging it at room temperature to obtain an intermediate product; Step S3, washing, drying and calcining the intermediate product obtained in step S2 to obtain a fibrous cerium oxide carrier; Step S4, weighing strontium nitrate and cobalt nitrate according to a molar ratio of strontium to cobalt of 1:4-6, then dissolving strontium nitrate in deionized water to obtain a strontium nitrate aqueous solution, and finally adding cobalt nitrate to the strontium nitrate aqueous solution, stirring for 1-3 hours, to obtain a first mixed solution; Step S5, adding the fibrous cerium oxide support obtained in step S3 to the first mixed solution, adjusting the pH to be greater than 7 with aqueous ammonia, and then stirring to obtain a second mixed solution; Step S6, heating the second mixed solution obtained in step S5 to 80-100° C., removing excess water, and obtaining a paste-like mixture; Step S7, continuing to roast the paste mixture obtained in step S6 to obtain a product.
4. The method for preparing a catalyst for low-temperature decomposition of nitrous oxide according to claim 3, characterized in that: The temperature during continuous stirring in step S1 is 40-60° C., and the stirring time is 1-3 h.
5. The method for preparing a catalyst for low-temperature decomposition of nitrous oxide according to claim 3, characterized in that: In step S1, the cerium nitrate is selected from one of cerium nitrate hexahydrate and ammonium cerium nitrate, and the concentration of the cerium nitrate is 0.01-1 mol / L.
6. The method for preparing a catalyst for low-temperature decomposition of nitrous oxide according to claim 3, characterized in that: In step S1, the complexing agent is selected from one of ethylenediaminetetraacetic acid, citric acid, tartaric acid, and glycolic acid, and the concentration of the complexing agent is 0.01-1 mol / L.
7. The method for preparing a catalyst for low-temperature decomposition of nitrous oxide according to claim 3, characterized in that: In step S2, the complexing time is 6-8 hours, and the aging time is 2-4 hours.
8. The method for preparing a catalyst for low-temperature decomposition of nitrous oxide according to claim 3, characterized in that: In step S3 and step S7, the calcination temperature is 400-600° C., and the calcination time is 3-6 hours.
9. The method for preparing a catalyst for low-temperature decomposition of nitrous oxide according to claim 3, characterized in that: The length of the fibrous cerium oxide carrier in step S3 is 26-198 μm, the diameter is 3-14 μm, and the specific surface area is 5-30 m 2 / g.
10. The method for preparing a catalyst for low-temperature decomposition of nitrous oxide according to claim 3, characterized in that: The stirring time in step S5 is 1-2h.