Preparation method and application of cerium-doped cobalt-manganese spinel catalyst with layered structure
The preparation of cerium-doped cobalt-manganese spinel catalyst by co-precipitation method solves the problem of poor stability of existing catalysts in high water vapor and SO2 environments, and achieves the effect of efficient and stable catalyzing of CO oxidation under industrial conditions.
Patent Information
- Application Number
- CN202510287935.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-12
- Publication Date
- 2025-06-10
AI Technical Summary
The existing CO catalytic oxidation catalysts have poor thermal stability and ease of inactivation in high water vapor and SO2 environments, which are difficult to meet the needs of industrial applications.
The cerium-doped cobalt manganese spinel catalyst was prepared by co-precipitation method, and the oxalic acid solution was used as the precipitation agent, and the catalyst with a layered structure was prepared after low-temperature mixing, stirring, drying and calcining.
The prepared cerium-doped cobalt manganese spinel catalyst exhibits excellent catalytic properties and stability in the CO catalytic oxidation reaction, can completely oxidize CO at 130°C, and maintain a high conversion rate in water vapor and SO2 environment for 14 hours.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of material preparation and environmental purification, and specifically relates to a preparation method of cerium-doped cobalt manganese spinel and its application in the catalytic oxidation of low-concentration CO in flue gas containing high water vapor and SO 2 for the catalytic oxidation of low-concentration CO in flue gas containing high water vapor and SO Background Art
[0002] Carbon monoxide (CO) is one of the main components of air pollution, mainly originating from vehicle exhaust, waste gas emissions from coal-fired power plants, and the steel industry, etc., causing serious harm to the environment and human health. At present, catalytic oxidation technology is mainly used in industry to efficiently convert CO into CO 2 .
[0003] So far, many materials have been developed and applied to the catalytic oxidation of CO. For example, noble metal-based catalysts, and nano-gold particles highly dispersed on oxide supports exhibit excellent CO catalytic activity. However, the reserves of noble metals are limited and the cost is expensive, which is not conducive to industrial applications. In addition, the Hopcalite catalyst (composed of copper oxide and manganese oxide in a molar ratio of 1:2.2 - 3.0) has a low cost and high catalytic performance, but this catalyst has the disadvantages of poor thermal stability and being extremely prone to deactivation when exposed to water vapor and SO 2 . Therefore, there is an urgent need to develop highly efficient catalysts with excellent stability and resistance to water and sulfur. Summary of the Invention
[0004] The purpose of the present invention is to provide a preparation method of a cerium-doped cobalt manganese spinel catalyst and an application for enhancing the anti-SO 2 performance in the catalytic oxidation reaction of CO. The cerium-doped cobalt manganese spinel prepared by this method has an obvious layered structure, exposing more active sites, having excellent catalytic performance for the catalytic oxidation of CO, and still maintaining excellent stability in an environment containing water vapor and SO 2 .
[0005] To achieve the above purpose, the technical solution of the present invention is as follows: A preparation method of a cerium-doped cobalt manganese spinel with a layered structure, which includes the following steps: Mix a cerium source, a cobalt source, and a manganese source with deionized water, then add an appropriate amount of oxalic acid solution as a precipitant, stir at a low temperature for a period of time, filter and wash, place in an oven for drying, and then calcine in a muffle furnace to obtain the cerium-doped cobalt manganese spinel.
[0006] Further, the cerium source, cobalt source, and manganese source are cerium nitrate Ce(NO 3 ), cobalt nitrate Co(NO 3 ), and manganese nitrate Mn(NO 3 ), and manganese nitrate Mn(NO 2 ), and manganese nitrate Mn(NO 3 )2 , the amounts of cerium source, cobalt source, and manganese source are weighed according to the molar ratio Ce:Co:Mn = 0.01 - 0.1:0.10 - 0.20:0.80 - 0.90, and the molar ratio of the total metal amount (Ce + Co + Mn) to oxalic acid is 1:1.0 - 1.3.
[0007] Furthermore, the concentration of the oxalic acid solution is 0.5 - 1.5 mol / L.
[0008] Furthermore, the low-temperature mixing and stirring temperature is 0 - 10 °C, and the low-temperature mixing and stirring time is 1 - 8 h.
[0009] Furthermore, the drying temperature in the oven is 60 - 80 °C, and the time is 8 - 12 h.
[0010] Furthermore, the calcination temperature in the muffle furnace is 300 - 400 °C, and the time is 3 - 5 h.
[0011] The application of the cerium-doped cobalt-manganese spinel catalyst in the CO catalytic oxidation reaction includes: using the cerium-doped cobalt-manganese spinel as a catalyst, with CO and O 2 as reaction gases, in an environment containing water vapor and SO 2 , converting O 2 and CO into CO 2 ; the reaction temperature is 40 - 170 °C, the volume space velocity is 60000 mL·g -1 ·h -1 ; the catalytic oxidation reaction atmosphere of CO is 1% CO / 5% H 2 O / 200 ppm SO 2 / 10% CO 2 / 84% Air, the reaction gas flow rate is 100 mL / min; the cerium-doped cobalt-manganese spinel catalyst has the ability to resist water and sulfur.
[0012] The remarkable advantages of the present invention are as follows: (1) The preparation method of the present invention is simple, economical, energy-saving and efficient. The obtained cerium-doped cobalt-manganese spinel has an obvious layered structure, shows excellent catalytic performance for CO catalytic oxidation, can reach a CO conversion rate of 100% at 130 °C, and can maintain the complete conversion of CO for up to 14 hours under the conditions of containing water vapor and SO 2 .
[0013] (2) The present invention prepares an anti-water-vapor and anti-SO 2The cerium-doped cobalt-manganese spinel catalyst with excellent properties shortens the synthesis cycle and has important practical significance for realizing efficient and economical removal of CO in sintering flue gas. The metal oxide with spinel structure contains a large number of redox electron pairs, has certain hydrophobic properties and the ability to resist SO 2 poisoning, and doping cerium in the metal catalyst can regulate the surface acidity of the catalyst and inhibit SO 2 poisoning of the catalytic active sites, making it suitable as a CO catalytic oxidation material. Since SO 2 is an acidic gas, doping cerium can increase the surface acidity of the catalyst and weaken the adsorption of SO 2 on the metal oxide with spinel structure, thus improving the SO 2 resistance ability of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 XRD patterns of the cerium-doped cobalt-manganese spinel prepared in Examples 1-5; Figure 2 SEM images of the cerium-doped cobalt-manganese spinel prepared in Examples 1-5; Figure 3 CO conversion rate (a) and stability diagram (b) of the cerium-doped cobalt-manganese spinel prepared in Examples 1-5; Figure 4 NH 3 -TPD diagrams (a) and acid site content distribution diagrams (b) of the cerium-doped cobalt-manganese spinel prepared in Examples 1-5. DETAILED IMPLEMENTATION METHODS The following details the specific implementation methods of the present invention. The specific implementation methods described herein are only for explaining and understanding the present invention and are not used to limit the present invention. By adding an oxalic acid solution precipitant and through drying and calcination, the cerium-doped cobalt-manganese spinel catalyst is prepared. The method of the present invention is simple and efficient, and the prepared cerium-doped cobalt-manganese spinel catalyst exhibits excellent CO catalytic oxidation performance, as well as resistance to water vapor and SO 2 stability, and has broad application prospects.
[0016] Example 1: Weigh 0.402 g of Co(NO 3 ) 2 and 3.185 g of Mn(NO 3 ) 2Add it to 27.0 g of deionized water, stir to dissolve, then add 20 mL of oxalic acid solution with a concentration of 0.5 mol / L drop by drop. Then stir in an ice bath at 2 °C for 1.5 h. After stirring, wash and filter with deionized water. Then transfer the solid product to an oven and dry it at 60 °C for 12 h, and then transfer it to a muffle furnace and calcine it at 400 °C for 3 h. The obtained catalyst is denoted as Co1Mn8.
[0017] Example 2: Weigh 0.603 g of Co(NO 3 ) 2 and 5.185 g of Mn(NO 3 ) 2 , and additionally add 0.016 g of Ce(NO 3 ) 3 . Mix and dissolve in 50.0 g of deionized water, and stir until dissolved. Then add 40 mL of oxalic acid solution with a concentration of 1.5 mol / L drop by drop. Then stir in an ice bath at 4 °C for 2 h. After stirring, wash and filter with deionized water. Then transfer the solid product to an oven and dry it at 70 °C for 10 h, and then transfer it to a muffle furnace and calcine it at 380 °C for 4 h. The obtained catalyst is denoted as 0.1%CeCo1Mn8.
[0018] Example 3: Weigh 0.804 g of Co(NO 3 ) 2 and 6.185 g of Mn(NO 3 ) 2 , and additionally add 0.032 g of Ce(NO 3 ) 3 . Mix and dissolve in 50.0 g of deionized water, and stir until dissolved. Then add 40 mL of oxalic acid solution with a concentration of 1.5 mol / L drop by drop. Then stir in an ice bath at 4 °C for 2 h. After stirring, wash and filter with deionized water. Then transfer the solid product to an oven and dry it at 70 °C for 10 h, and then transfer it to a muffle furnace and calcine it at 380 °C for 4 h. The obtained catalyst is denoted as 0.25%CeCo1Mn8.
[0019] Example 4: Weigh 1.022 g of Co(NO 3 ) 2 and 7.396 g of Mn(NO 3 ) 2 , and additionally add 0.064 g of Ce(NO 3 ) 3, Mix and dissolve in 60.0 g of deionized water, and stir until dissolved. Then, gradually add 45 mL of oxalic acid solution with a concentration of 1.5 mol / L drop by drop. Then, stir in an ice-water bath at 6 °C for 2 h. After stirring, wash and filter with deionized water. Then, transfer the solid product to an oven and dry it at 75 °C for 10 h. Then, transfer it to a muffle furnace and calcine it at 380 °C for 4 h. The obtained catalyst is denoted as 0.5%CeCo1Mn8.
[0020] Example 5: Weigh 1.205 g of Co(NO 3 ) 2 and 8.489 g of Mn(NO 3 ) 2 , and additionally add 0.128 g of Ce(NO 3 ) 3 . Mix and dissolve in 70.000 g of deionized water, and stir until dissolved. Then, gradually add 50 mL of oxalic acid solution with a concentration of 1.5 mol / L drop by drop. Then, stir in an ice-water bath at 7 °C for 2 h. After stirring, wash and filter with deionized water. Then, transfer the solid product to an oven and dry it at 80 °C for 10 h. Then, transfer it to a muffle furnace and calcine it at 400 °C for 4 h. The obtained catalyst is denoted as 1%CeCo1Mn8.
[0021] Application Example Use a fixed-bed reactor to test the CO conversion rate and its stability in water-vapor- and SO 2 -containing gas. Weigh 0.1 g of the catalyst and place it in a quartz reaction tube for programmed temperature treatment; the flow rate of the mixed gas is 100 mL / min, controlled by a mixed-gas mass flowmeter. The mixed gas consists of 1% CO, 10% CO 2 , and 89% Air. When performing the catalyst stability test, 2000 ppm of SO 2 gas and 5% water vapor (the water vapor content is controlled by controlling the water temperature) are introduced into the reaction gas. At this time, the mixed gas is 1% CO / 5% H 2 O / 200 ppm SO 2 / 10% CO 2 / 84% Air, and the reaction space velocity is 60000 mL·h -1 ·g -1 . After the gas passes through the reaction tube, it enters an infrared detector to detect the CO concentration of the outlet gas. A condensation device is set before the gas enters the infrared detector to remove the water vapor in the pipeline; the gas after condensation treatment enters the infrared detector to obtain the concentration changes of the products and reactants.
[0022] CO conversion rate calculation formula Among them, X is the CO conversion rate, is the concentration of CO at the reactor inlet, is the concentration of CO at the reactor outlet.
[0023] Figure 1 is the XRD pattern of cerium-doped cobalt-manganese spinel, where x% is the molar ratio of the doped cerium species to the two metal species of cobalt and manganese. It can be seen that the characteristic peaks of the sample synthesized in Example 1 are basically consistent with the PDF standard card (JCPSD No. 32-0927) of cobalt-manganese spinel. After doping with cerium species, the characteristic peaks of the sample remain unchanged, and no characteristic peaks of CeO 2 are observed, indicating that the cobalt-manganese spinel structure remains intact.
[0024] Figure 2 is the SEM image of the prepared sample. Among them, (a-b) is 0.1%CeCo1Mn8, (c-d) is 0.25%CeCo1Mn8, (e-f) is 0.5%CeCo1Mn8, (g-h) is 1%CeCo1Mn8, and (i-j) is Co1Mn8. It can be seen that the Co1Mn8 sample without cerium doping has a layered morphology of micron-scale sheet stacking. After cerium doping, the morphological structure of the catalyst remains unchanged, indicating that a certain amount of cerium doping has no significant effect on the surface morphology of cobalt-manganese spinel.
[0025] Figure 3 is the catalytic activity and stability diagram of the prepared sample. As Figure 3 shown in a, with the increase of cerium doping amount, the CO conversion rate first increases and then decreases. When the cerium doping amount is 0.25%, the catalytic activity of cobalt-manganese spinel is the highest, and CO can be completely oxidized at 130 °C. Further introducing 10% water vapor and 200 ppm of SO 2 into the reaction system to test the stability of the catalyst. As Figure 3 shown in b, the complete conversion of CO of Co1Mn8 without Ce doping can be maintained for about 6 h, and at about 7.3 h, the conversion rate drops to 73%. The stability of the cerium-doped cobalt-manganese spinel catalyst is significantly improved. Among them, the 0.25%CeCo1Mn8 catalyst can maintain a stable time of 18.4 h, and this performance is better than most of the reported non-noble metal catalysts. The spinel structure has a hydrophobic property, making the prepared series of catalysts exhibit excellent anti-water vapor performance.
[0026] Figure 4 is the NH 3 -TPD diagram and the relative desorption content diagram of NH 3 of cobalt-manganese spinel catalysts with different cerium doping amounts. According to Figure 4As can be seen from a, the catalyst has a desorption peak in the weak acid region (50 - 200 °C) and a stronger peak and a weaker peak in the strong acid region (400 - 650 °C). Combining Figure 4 As can be seen from b, the weak acid content of the catalyst is close. With the increase of cerium doping amount, the strong acid sites gradually increase. However, excessive cerium doping leads to a decrease in the dispersion of cerium species and a reduction in the acid amount. The number of strong acid sites of the 0.25% CeCo1Mn8 catalyst is relatively high. Appropriate cerium doping can effectively improve the surface acidity of the catalyst, which is beneficial to reducing the adsorption of SO 2 and weakening the poisoning effect of SO 2 on the active sites of the catalyst, thereby improving the stability.
[0027] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.
Claims
1. A method for preparing a cerium-doped cobalt-manganese spinel catalyst having a layered structure, characterized in that: The following steps are involved: The cerium source, cobalt source and manganese source are mixed with deionized water, and then a proper amount of precipitant is added. After mixing and stirring at low temperature for a period of time, the mixture is filtered and washed, placed in an oven for drying, and then placed in a muffle furnace for calcination at a certain temperature to obtain the cerium-doped cobalt-manganese spinel.
2. The preparation method according to claim 1, characterized in that: The cerium source is cerium nitrate, the cobalt source is cobalt nitrate, and the manganese source is manganese nitrate.
3. The preparation method according to claim 1, characterized in that: The precipitant is oxalic acid solution with a concentration of 0.5-1.5 mol / L.
4. The preparation method according to claim 1, characterized in that: The amounts of cerium source, cobalt source and manganese source are weighed according to the molar ratio of Ce:Co:Mn = 0.01~0.1:0.10~0.20:0.80~0.
90.
5. The preparation method according to claim 3, characterized in that: The ratio of the total molar amount of metal species Ce+Co+Mn to oxalic acid is 1:1.0~1.
3.
6. The preparation method according to claim 1, characterized in that: The low-temperature mixing and stirring temperature is 0-10°C, and the low-temperature mixing and stirring time is 1-8 h.
7. The preparation method according to claim 1, characterized in that: The drying temperature is 60-80 ℃ and the time is 8-12 h.
8. The preparation method according to claim 1, characterized in that: The calcination temperature is 300-400 ℃ and the time is 3-5h.
9. A cerium-doped cobalt-manganese spinel catalyst having a layered structure obtained according to the preparation method according to any one of claims 1 to 8.
10. The use of the cerium-doped cobalt-manganese spinel catalyst in CO catalytic oxidation reaction according to claim 9, characterized in that: Using cerium-doped cobalt-manganese spinel as catalyst, CO and O2 as reaction gases, in a water vapor and SO2 environment, O2 and CO are converted into CO2; the reaction temperature is 40-170 °C, and the volume space velocity is 60000 mL·g -1 ·h -1 ; The cerium-doped cobalt-manganese spinel catalyst has the ability to resist water and sulfur.