A low-temperature and high-efficiency composite functional catalyst for removing CO and NO in flue gas and a preparation method and application thereof x A low-temperature and high-efficiency composite functional catalyst for removing CO and NO in flue gas and a preparation method and application thereof

Abstract

The application aims to provide a low-temperature high-efficiency composite functional catalyst for removing CO and NO in flue gas x The application relates to a preparation method of a hydrotalcite-like composite functional catalyst for removing CO and NO in flue gas and application of the catalyst, and belongs to the technical field of atmospheric pollution catalytic materials.The high-performance copper-manganese-iron hydrotalcite is prepared by a coprecipitation method at room temperature, using copper nitrate trihydrate, manganese nitrate and iron nitrate nonahydrate as raw materials, using sodium hydroxide as a precipitator, and combining hydrogen peroxide coupling hot air modification with solution rheological property adjustment.The copper-manganese-iron composite metal oxide obtained after calcination has high-efficiency CO and NO x conversion rates at low temperatures, can be used as a dual-functional catalyst to simultaneously purify steel sintering flue gas, reduce environmental pollution, save the cost and land space of CO treatment facilities, the catalyst uses simple raw materials, the preparation method is easy to master, and has high value for reducing flue gas pollutant emission in the steel and non-ferrous metallurgical industries.

Description

Technical Field

[0001] This invention belongs to the field of atmospheric pollution catalytic materials technology, specifically relating to a low-temperature, high-efficiency method for removing CO and NO from flue gas. x Preparation method and application of hydrotalcite-like composite functional catalyst. Background Technology

[0002] Industrial production processes, such as those in the steel and non-ferrous metallurgy industries, consume large amounts of fossil fuels and mineral resources, emitting significant amounts of air pollutants and placing considerable pressure on the environment. Industrial stationary sources, in particular, account for the largest emissions, containing highly complex pollutants. While flue gas dust removal and desulfurization technologies are relatively well-developed, NO... x CO and NO are major pollutants in flue gas, and removal technologies are still under development and improvement. The denitrification technology is a medium-low temperature NH3-SCR technology, with an operating temperature generally around 280~450℃. After desulfurization, the flue gas needs to be heated through heat exchange equipment and then externally heated to reach the target temperature. This not only increases the complexity of the system but also leads to higher overall investment and energy consumption. Furthermore, the flue gas still contains a large amount of CO after the denitrification process; direct emission would have serious impacts on the environment and human health. Therefore, it is crucial to develop a highly active bifunctional catalyst at low temperatures to simultaneously and efficiently remove CO and NO from flue gas. x It is of great significance.

[0003] Currently, catalysts studied in the laboratory are mainly divided into noble metal catalysts and non-noble metal catalysts. Traditional noble metal catalysts, such as Pt, Rh, and Au, have high catalytic efficiency and good water resistance, but they are expensive, have limited storage, and are not suitable for large-scale applications. Common non-noble metal catalysts, such as composite oxides of Cu, Mn, Co, and Ni, are not only inexpensive but also have high catalytic effects at low temperatures, but they suffer from problems such as susceptibility to poisoning and low catalytic activity.

[0004] Layered double hydroxides (LDHs) possess a large specific surface area, uniform dispersion of active components, and good thermal stability. Composite metal oxide catalysts synthesized based on these materials exhibit excellent stability. This synthesis method provides an effective approach to address the problems of poisoning and low catalytic activity in non-precious metal catalysts, improving their performance and lifespan, and achieving more environmentally friendly and efficient removal of CO and NO from industrial flue gas. x The catalytic process. Summary of the Invention

[0005] The purpose of this invention is to provide a low-temperature, high-efficiency method for removing CO and NO from flue gas. x The preparation method and application of hydrotalcite-like composite functional catalysts are mainly aimed at NO in steel sintering flue gas. xThe synergistic control of CO is of great significance for solving the problems of high denitrification reaction temperature and CO emission in existing catalysts.

[0006] The present invention adopts the following technical solution: This invention synthesizes copper-manganese-iron hydrotalcite with a layered structure by using copper nitrate trihydrate, manganese nitrate solution, and ferric nitrate nonahydrate as raw materials, sodium hydroxide as precipitant, and deionized water as solvent through a co-precipitation method. The copper-manganese-iron composite metal oxide is then obtained by calcination.

[0007] Specifically, the steps include the following: The first step is to prepare a mixed salt solution: Weigh out copper nitrate trihydrate, manganese nitrate and ferric nitrate nonahydrate respectively, dissolve them in deionized water, and stir thoroughly at room temperature for 30 minutes to ensure complete dissolution; The second step is to prepare sodium hydroxide solution and sodium carbonate solution: Weigh sodium hydroxide and sodium carbonate, dissolve them separately in deionized water, and stir thoroughly at room temperature for 30 minutes to ensure complete dissolution; The third step is to prepare copper-manganese-iron hydrotalcite: Add the mixed salt solution to a beaker containing sodium carbonate solution and stir evenly with a magnetic stirrer. While introducing hot air, add hydrogen peroxide solution dropwise for oxidation modification. Stir for 1-3 hours to obtain a mixed solution. At the same time, add sodium humate and solution rheology modifier to the mixed solution and mix thoroughly. Then, slowly add sodium hydroxide solution dropwise to the beaker and observe the pH value of the solution with a pH meter to maintain the pH at 10±0.2. After the addition is complete, continue stirring for 25-35 minutes, and then age at room temperature for 12 hours. The fourth step involves filtering and washing the aged solution until it reaches neutrality, then drying it in a drying oven at 60°C to obtain a copper-manganese-iron hydrotalcite precursor, denoted as Cu3Mn. a Fe 1-a -LDHs; The fifth step involves placing the obtained copper-manganese-iron hydrotalcite precursor into a muffle furnace and heating it to 400-450°C. The mixture is then calcined in air at the corresponding temperature for 4-6 hours to finally obtain the copper-manganese-iron composite metal oxide, denoted as Cu3Mn. a Fe 1-a -LDO, ready for use.

[0008] Furthermore, the ratio of copper nitrate trihydrate, manganese nitrate, ferric nitrate nonahydrate, and deionized water used in the first step is 7.248g: 0.7158-2.1474g: 1.616-3.232g: 100mL.

[0009] Furthermore, in the second step, the ratio of sodium hydroxide to deionized water is 8g:100mL, and the ratio of sodium carbonate to deionized water is 1.06g:100mL.

[0010] Furthermore, in the third step, the oxidation modification temperature is 58-80℃, the temperature of the hot air is 60-80℃, the oxidation modification time is 1-3h, and the amount of hydrogen peroxide added is 1-5% of the volume of the mixed salt solution.

[0011] Furthermore, in the third step, the mass ratio of sodium humate to solution rheology modifier is (30~50):(70~50), and the amount of sodium humate and solution rheology modifier added is 5~7.5% of the mass of the mixed solution.

[0012] Furthermore, the solution rheology modifier mentioned in the third step is an elastic fluid composed of oxidized modified carbon nanomaterials, calcium stearate, and soluble polyvinyl alcohol, with a mass ratio of oxidized modified carbon nanomaterials, calcium stearate, and soluble polyvinyl alcohol of 40~45:40~50:5~20.

[0013] A hydrotalcite-like composite functional catalyst is used for the low-temperature, high-efficiency removal of CO and NO from flue gas. x .

[0014] The beneficial effects of this invention are as follows: This invention uses copper nitrate trihydrate, manganese nitrate solution, and ferric nitrate nonahydrate as raw materials, and sodium hydroxide as a precipitant. Through hydrogen peroxide coupled with hot air modification and solution rheological property modulation, a high-performance copper-manganese-iron-based layered double hydroxide (TLH) is prepared at room temperature via a co-precipitation method. The resulting copper-manganese-iron composite metal oxide exhibits high efficiency in CO and NO dispersibility at low temperatures. x The conversion rate can serve as a dual-function catalyst to simultaneously purify flue gas from steel sintering, reducing environmental pollution. It can also save on the cost and space required for CO treatment facilities. The catalyst uses simple raw materials and its preparation method is easy to master, making it highly valuable for reducing flue gas pollutant emissions from the steel and non-ferrous metallurgical industries. Attached Figure Description

[0015] Figure 1 This is a scanning electron microscope (SEM) image of the copper-manganese-iron hydrotalcite precursor prepared in Example 1 of this invention.

[0016] Figure 2 Here is the X-ray diffraction (XRD) pattern of the copper-manganese-iron hydrotalcite precursor prepared in Example 1 of this invention: a is the precursor Cu3Mn 0.2 Fe 0.8 -LDHs; b represents Cu3Mn after calcination. 0.2 Fe 0.8 -LDO.

[0017] Figure 3 This is the FTIR image of the copper-manganese-iron hydrotalcite precursor prepared in Example 1 of this invention.

[0018] Figure 4 It is Cu3Mn in Embodiment 1 of the present invention 0.2 Fe 0.8 - Curves showing the CO and NO conversion rates and N2 selectivity of LDO as a function of temperature. Detailed Implementation

[0019] Example 1 (1) Weigh out 7.2480g of copper nitrate trihydrate, 0.7158g of manganese nitrate and 3.2320g of ferric nitrate nonahydrate respectively, dissolve them in 100mL of deionized water, and stir thoroughly at room temperature for 30min to ensure complete dissolution; (2) Weigh 8g of sodium hydroxide and 1.06g of sodium carbonate, dissolve them separately in 100mL of deionized water, and stir thoroughly at room temperature for 30min to ensure complete dissolution; (3) Add the mixed salt solution to a beaker containing sodium carbonate solution and stir evenly with a magnetic stirrer. Simultaneously add 3 mL of hydrogen peroxide solution in hot air and stir for 1.5 h. At the same time, add a certain amount of sodium humate and solution rheology modifier to the mixed solution, with a total proportion of 5%. The mass ratio of sodium humate to solution rheology modifier is 30:70. Mix them thoroughly. Slowly add sodium hydroxide solution to the beaker and observe the pH value of the solution with a pH meter to keep the pH at 10±0.2. After the addition is complete, continue stirring for 25~35 min and then age at room temperature for 12 h. (4) The aged solution was filtered and washed until neutral, and then dried in a drying oven at 60°C to obtain copper-manganese-iron hydrotalcite, denoted as Cu3Mn. 0.2 Fe 0.8 -LDHs; (6) Calcination: The copper-manganese-iron hydrotalcite precursor obtained above was placed in a muffle furnace and heated from room temperature to 400℃ at a heating rate of 2℃ / min. The mixture was then calcined at 400℃ for 5 hours to finally obtain the copper-manganese-iron composite metal oxide, denoted as Cu3Mn. 0.2 Fe 0.8 -LDO, ready for use.

[0020] (7) The calcined granular product is compressed into tablets and sieved into 40-60 mesh particles.

[0021] Figure 1 Cu3Mn prepared in Example 1 of this invention 0.2 Fe 0.8 The SEM image of -LDHs shows that the catalyst exhibits a plate-like morphology. Figure 2 Cu3Mn 0.2 Fe 0.8The XRD pattern of -LDHs shows that the catalyst exhibits diffraction peaks characteristic of hydrotalcite. Figure 3 Cu3Mn 0.2 Fe 0.8 The FTIR spectra of -LDHs also show the vibrational peaks characteristic of hydrotalcite. The above analysis confirms the successful synthesis of hydrotalcite.

[0022] The calcined samples were used in CO oxidation and NH3-SCR processes in sintering flue gas, with specific reactions simulating actual flue gas conditions: namely, oxygen content of 16% and NO content of 100%. x 400 ppm, NH3 400 ppm, CO 6000 ppm, space velocity 30000 h⁻¹ -1 .

[0023] Among them, [CO] in NO x ] in and [NH3] in These refer to CO and NO respectively. x Inlet concentrations of NH3 (ppm) and [CO] out NO x ] out [NH3] out and [N2O] out These refer to CO and NO respectively. x The outlet concentrations (ppm) of NH3 and N2O.

[0024] Figure 4 Cu3Mn prepared in Example 1 of this invention 0.2 Fe 0.8 The results of the LDO NH3-SCR synergistic CO oxidation activity test at different temperatures show that the catalyst has a high conversion rate at 125-200℃. It can efficiently remove CO and NO from flue gas at low temperatures. x .

[0025] Example 2 (1) Weigh out 7.2480g of copper nitrate trihydrate, 1.4316g of manganese nitrate and 2.4240g of ferric nitrate nonahydrate respectively, dissolve them in 100mL of deionized water, and stir thoroughly at room temperature for 30min to ensure complete dissolution; (2) Weigh 8g of sodium hydroxide and 1.06g of sodium carbonate, dissolve them separately in 100mL of deionized water, and stir thoroughly at room temperature for 30min to ensure complete dissolution; (3) Add the mixed salt solution to a beaker containing sodium carbonate solution and stir evenly with a magnetic stirrer. Simultaneously add 4 mL of hydrogen peroxide solution in hot air and stir for 2 hours. At the same time, add a certain amount of sodium humate and solution rheology modifier to the mixed solution, with a total proportion of 6%. The mass ratio of sodium humate to solution rheology modifier is 40:60. Mix them thoroughly. Slowly add sodium hydroxide solution to the beaker and observe the pH value of the solution with a pH meter to keep the pH at 10±0.2. After the addition is complete, continue stirring for 25~35 min and then age at room temperature for 12 h. (4) The aged solution was filtered and washed until neutral, and then dried in a drying oven at 60°C to obtain copper-manganese-iron hydrotalcite, denoted as Cu3Mn. 0.4 Fe 0.6 -LDHs; (6) Calcination: The copper-manganese-iron hydrotalcite precursor obtained above was placed in a muffle furnace and heated from room temperature to 400℃ at a heating rate of 2℃ / min. The mixture was then calcined at 400℃ for 5 hours to finally obtain the copper-manganese-iron composite metal oxide, denoted as Cu3Mn. 0.4 Fe 0.6 -LDO, ready for use.

[0026] (7) The calcined granular product is compressed into tablets and sieved into 40-60 mesh particles.

[0027] Example 3 (1) Weigh out 7.2480g of copper nitrate trihydrate, 2.1474g of manganese nitrate and 1.6160g of ferric nitrate nonahydrate respectively, dissolve them in 100mL of deionized water, and stir thoroughly at room temperature for 30min to ensure complete dissolution; (2) Weigh 8g of sodium hydroxide and 1.06g of sodium carbonate, dissolve them separately in 100mL of deionized water, and stir thoroughly at room temperature for 30min to ensure complete dissolution; (3) Add the mixed salt solution to a beaker containing sodium carbonate solution and stir evenly with a magnetic stirrer. Simultaneously add 2.5 mL of hydrogen peroxide solution in hot air and stir for 2.5 h. At the same time, add a certain amount of sodium humate and solution rheology modifier to the mixed solution, with a total proportion of 7.5%. The mass ratio of sodium humate and solution rheology modifier is 50:50. Mix them thoroughly. Slowly add sodium hydroxide solution to the beaker and observe the pH value of the solution with a pH meter to keep the pH at 10 ± 0.2. After the addition is complete, continue stirring for 25-35 min and then age at room temperature for 12 h. (4) The aged solution was filtered and washed until neutral, and then dried in a drying oven at 60°C to obtain copper-manganese-iron hydrotalcite, denoted as Cu3Mn. 0.6 Fe 0.4 -LDHs; (6) Calcination: The copper-manganese-iron hydrotalcite precursor obtained above was placed in a muffle furnace and heated from room temperature to 400℃ at a heating rate of 2℃ / min. The mixture was then calcined at 400℃ for 5 hours to finally obtain the copper-manganese-iron composite metal oxide, denoted as Cu3Mn. 0.6 Fe 0.4 -LDO, ready for use.

[0028] (7) The calcined granular product is compressed into tablets and sieved into 40-60 mesh particles.

Claims

1. A hydrotalcite-like composite functional catalyst for the efficient removal of CO and NO from flue gas at low temperature x The application of this technology is characterized by: The catalyst is used for CO oxidation and NH3-SCR in flue gas. The catalyst preparation method includes the following steps: The first step is to prepare a mixed salt solution: Weigh out copper nitrate trihydrate, manganese nitrate and ferric nitrate nonahydrate respectively, dissolve them in deionized water, and stir thoroughly at room temperature for 30 minutes to ensure complete dissolution; The second step is to prepare sodium hydroxide solution and sodium carbonate solution: Weigh sodium hydroxide and sodium carbonate, dissolve them separately in deionized water, and stir thoroughly at room temperature for 30 minutes to ensure complete dissolution; The third step is to prepare copper-manganese-iron hydrotalcite: Add the mixed salt solution to a beaker containing sodium carbonate solution and stir evenly with a magnetic stirrer. While introducing hot air, add hydrogen peroxide solution dropwise for oxidation modification. Stir for 1-3 hours to obtain a mixed solution. At the same time, add sodium humate and solution rheology modifier to the mixed solution and mix thoroughly. Then, slowly add sodium hydroxide solution dropwise to the beaker and observe the pH value of the solution with a pH meter to maintain the pH at 10±0.

2. After the addition is complete, continue stirring for 25-35 minutes, and then age at room temperature for 12 hours. The mass ratio of sodium humate to solution rheology modifier is 30-50:70-50, and the amount of sodium humate and solution rheology modifier added is 5-7.5% of the mass of the mixed solution. The solution rheology modifier is an elastic fluid composed of oxidized modified carbon nanomaterials, calcium stearate and soluble polyvinyl alcohol, with a mass ratio of oxidized modified carbon nanomaterials, calcium stearate and soluble polyvinyl alcohol of 40~45:40~50:5~20. The fourth step involves filtering and washing the aged solution until it reaches neutrality, then drying it in a drying oven at 60°C to obtain a copper-manganese-iron hydrotalcite precursor, denoted as Cu3Mn. a Fe 1-a -LDHs; The fifth step involves placing the obtained copper-manganese-iron hydrotalcite precursor into a muffle furnace and heating it to 400-450°C. The mixture is then calcined in air at the corresponding temperature for 4-6 hours to finally obtain the copper-manganese-iron composite metal oxide, denoted as Cu3Mn. a Fe 1-a -LDO, ready for use.

2. The hydrotalcite-like composite functional catalyst according to claim 1 for the low-temperature and high-efficiency removal of CO and NO from flue gas. x The application of this technology is characterized by: The ratio of copper nitrate trihydrate, manganese nitrate, ferric nitrate nonahydrate, and deionized water used in the first step is 7.248g: 0.7158-2.1474g: 1.616-3.232g: 100mL.

3. The hydrotalcite-like composite functional catalyst according to claim 1 for the low-temperature and high-efficiency removal of CO and NO from flue gas. x The application of this technology is characterized by: In the second step, the ratio of sodium hydroxide to deionized water is 8g:100mL, and the ratio of sodium carbonate to deionized water is 1.06g:100mL.

4. The hydrotalcite-like composite functional catalyst according to claim 1 for the low-temperature and high-efficiency removal of CO and NO from flue gas. x The application of this technology is characterized by: The oxidation modification temperature in the third step is 58-80℃, the temperature of the hot air introduced is 60-80℃, the oxidation modification time is 1-3h, and the amount of hydrogen peroxide added is 1-5% of the volume of the mixed salt solution.

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