A rod-shaped cerium dioxide-supported metal oxide nanocatalyst, its preparation method and application

Abstract

The present invention belongs to the technical field of catalysts, and specifically relates to a rod-shaped cerium dioxide supported metal oxide nanocatalyst, its preparation method and application. This catalyst has high catalytic activity and stability and can be used for the redox catalytic reaction of heavy metal ions in wastewater. During the preparation process, the active sites on the surface of the cerium dioxide support are modified to make its surface in a state with a large number of negative charges, copper oxide is loaded onto the surface of the support as metal oxide nanoparticles, and a supported nano-metal oxide catalyst is formed through calcination treatment. In the reduction process of metal ions, N-methylpyrrolidone is used as a solvent in this preparation method, and sodium polyacrylate and ethylene glycol are introduced as surfactants and reducing agents, which can control the morphology and size of the nanoparticles, improve the dispersion and stability of the nanoparticles, and thus improve the catalytic performance of the catalyst. At the same time, this method has the advantages of simple preparation, controllable process, low cost, etc.

Description

Technical Field

[0001] The present invention provides a preparation method and application of a cerium dioxide supported metal oxide nanocatalyst, belonging to the fields of heavy metal ion treatment of wastewater and environmental protection catalytic materials. Background Art

[0002] With the development of industry, more and more chemical reactions require the use of catalysts to improve the reaction rate and selectivity. At present, metal oxide catalysts have been widely used in various catalytic reactions, such as in the fields of organic synthesis, environmental treatment, and energy conversion. Therefore, treating heavy metal ions in wastewater has become an important field of environmental protection. At present, the commonly used heavy metal ion removal technologies mainly include methods such as chemical precipitation, adsorption, ion exchange, membrane separation, and biological technology. However, these methods have some problems, such as low treatment efficiency, high operating cost, and secondary pollution. Therefore, it is necessary to find new, efficient, and environmentally friendly removal technologies. Using metal oxide catalysts to adsorb heavy metal ions in wastewater and catalyze their reduction, oxidation, and other reactions to convert them into oxide precipitates that are not easily soluble in water, thereby achieving the removal of heavy metal ions. This method has the advantages of simple operation, high removal efficiency, and no secondary pollution, and is a promising wastewater treatment technology. Traditional metal oxide catalysts are usually made by preparing metal oxide powders and directly adding them to the reaction. However, this method has some problems, such as poor dispersion of the powder catalyst, small surface area, difficult exposure of active centers, and low catalytic efficiency. To overcome these problems, some scholars have proposed the concept of supported metal oxide nanocatalysts. Supported nanocatalysts achieve catalytic reactions by dispersing metal oxide nanoparticles on a high-surface-area support. This type of catalyst has the advantages of high specific surface area, high dispersion, and easy exposure of active centers. The existing supported nanocatalysts mainly load metal oxides on high-surface-area alumina supports. However, the thermal stability and chemical stability of the alumina support are insufficient, which will cause the loaded metal oxide nanoparticles to aggregate or deactivate under high temperature or high pressure. Therefore, developing a supported nanocatalyst with high stability and high catalytic efficiency is of great significance for improving the efficiency and economy of catalytic reactions. Summary of the Invention

[0003] The present invention provides a preparation method and application of a rod-shaped cerium dioxide supported metal oxide nanocatalyst for improving the efficiency and stability of catalytic reactions of heavy metal ions in wastewater.

[0004] The object of the present invention can be achieved by the following technical solutions:

[0005] The technical solution of the present invention is as follows: Cerium dioxide is used as the carrier in the present invention. It has a large specific surface area and good structural stability, and has high chemical stability and thermal stability. N-methylpyrrolidone is used as the solvent, which plays a role in dissolving the catalyst precursor, promotes the reaction, and can adjust the polarity and acidity and alkalinity of the solvent during the reaction. Copper oxide nanoparticles are loaded as the catalytic active component, which has good catalytic activity and can increase the reaction rate. Ethylene glycol is selected as the reducing agent, which can provide reducing electrons to reduce metal ions to a lower valence state and promote the formation of the morphology and structure of the catalyst. Sodium polyacrylate as the surfactant can adjust the surface properties of the reaction system, affect the dispersion and stability of the catalyst, and make it have better catalytic performance and stability.

[0006] The specific technical solution of the present invention is as follows:

[0007] A rod-shaped cerium dioxide-supported metal oxide nanocatalyst, which is prepared from the following components: N-methylpyrrolidone is used as the solvent, cerium dioxide is used as the carrier, copper oxide nanoparticles are loaded as the catalytic active component, ethylene glycol is used as the reducing agent, and sodium polyacrylate is used as the surfactant.

[0008] In the technical solution of the present invention: Based on the mass of the carrier, the mass percentage content of the active component copper oxide is 2% to 8%.

[0009] In the technical solution of the present invention: The particle size of the catalyst is 0.5 to 5 nm.

[0010] A rod-shaped cerium dioxide-supported metal oxide nanocatalyst, and the preparation method includes the following steps:

[0011] (1) Add the cerium dioxide precursor to N-methylpyrrolidone, after ultrasonic treatment for 30 to 60 minutes, add sodium carbonate, and stir for 0.5 to 1 hour at a temperature of 40 to 60 °C to obtain a uniform cerium dioxide carrier sol;

[0012] (2) Dissolve copper oxide in ethanol, place it in a quartz tube for a reduction reaction to reduce copper oxide to metallic copper powder; then add the metallic copper powder to a mixed solution of sodium polyacrylate and ethylene glycol and stir for 20 to 30 minutes to prepare a pretreated sol;

[0013] (3) Slowly drop the pretreated sol into the cerium dioxide carrier sol to obtain a mixed sol, and at the same time perform ultrasonic treatment, and the ultrasonic treatment time is 1 to 3 hours. Place the mixed sol in an oven for drying, and then transfer the mixed sol to a tube furnace for calcination to obtain the cerium dioxide-supported metal oxide nanocatalyst.

[0014] In the above method: The cerium dioxide precursor in step (1) is cerium nitrate hexahydrate.

[0015] In the above method: in step (1), the mass ratio of the cerium dioxide precursor to N-methylpyrrolidone is 1:(10 - 15), and the mass ratio of the cerium dioxide precursor to sodium carbonate is 1:(2 - 5).

[0016] In the above method: in step (2), in step (2): in the reduction reaction, the mass ratio of copper oxide to ethanol is 1:(15 - 20); in the pretreated sol, the mass ratio of copper oxide, sodium polyacrylate and ethylene glycol is 1:(3 - 6):(20 - 30); the temperature of the reduction reaction is 500 - 600 °C, and the time of the reduction reaction is 1 - 3 hours.

[0017] In the above method: in step (3), the mixed sol is dried, the drying temperature is 100 - 150 °C, and the time is 3 hours.

[0018] In the above method: in step (3), the heating rate of the mixed sol under nitrogen protection is 5 - 10 °C / min. The calcination temperature is 480 - 520 °C, and the heat preservation time is 3 - 5 hours.

[0019] In the technical solution of the present invention, the application of the catalyst in the removal of heavy metal ions in wastewater.

[0020] Beneficial effects:

[0021] The advantages of the present invention are that N-methylpyrrolidone can act as a solvent to dissolve the catalyst precursor, promote the reaction, and can adjust the polarity and acid-base properties of the solvent during the reaction, thereby affecting the morphology and structure of the catalyst. And ethylene glycol can provide reduction electrons as a reducing agent to reduce metal ions to a lower valence state and promote the formation of the morphology and structure of the catalyst. Sodium polyacrylate can adjust the surface properties of the reaction system as a surfactant, affect the dispersion and stability of the catalyst, and make it have better catalytic performance and stability. The active component of the catalyst uses supported copper oxide nanoparticles, which have good catalytic activity and can increase the reaction rate. The catalyst uses cerium dioxide as a carrier, which has a large specific surface area and good structural stability, can improve the dispersion of the active component, and has high chemical stability and thermal stability, can maintain good catalytic performance under high temperature and high pressure, and extend the service life of the catalyst. Description of the drawings

[0022] Figure 1 Scanning electron microscope picture of the catalyst prepared in Example 1.

[0023] Figure 2 Scanning electron microscope picture of the catalyst prepared in Comparative Example 1. Detailed implementation manners

[0024] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with examples, but the content of the present invention is not limited to the following embodiments.

[0025] Example 1:

[0026] (1) Preparation of cerium dioxide support sol

[0027] Take 10 g of cerium nitrate hexahydrate and 100 ml of N-methylpyrrolidone, mix and stir, perform ultrasonic treatment for 30 minutes, then add 20 g of sodium carbonate, and stir for 1 hour at a temperature of 40 °C to obtain a uniform cerium dioxide support sol.

[0028] (2) Preparation of pretreatment sol

[0029] Take 0.32 g of copper oxide, add it to 6 ml of ethanol and mix evenly, add it to a quartz tube, and react at a high temperature of 500 °C for 1 h to reduce it to metallic copper powder. Then add the metallic copper powder to a mixture of 0.96 g of sodium polyacrylate and 5.8 ml of ethylene glycol, and stir for 20 minutes to prepare a pretreatment sol.

[0030] (3) Preparation of catalyst

[0031] Slowly drop the pretreatment sol into the cerium dioxide support sol while performing ultrasonic treatment for 3 hours. Place the mixed sol in an oven at 120 °C and dry for 3 hours, then transfer the mixed sol to a tubular furnace, heat it to 500 °C at a rate of 5 °C / min under nitrogen protection, and hold for 5 hours to obtain a rod-shaped cerium dioxide-supported copper oxide nanoparticle catalyst.

[0032] (4) Catalyst effect test

[0033] Take appropriate amounts of lead nitrate, cadmium chloride, and mercury chloride to prepare simulated wastewater, adjust the concentration so that the Pb 2+ concentration is 50 mg / L, the Cd 2+ concentration is 100 mg / L, the Hg 2+ concentration is 10 mg / L, add 1 mol / L sodium hydroxide solution to adjust the pH of the wastewater to 7. Add 2% of the rod-shaped cerium dioxide-supported copper oxide nanoparticle catalyst based on the total amount of the wastewater, and stir at room temperature for 2 hours. By measuring the concentrations of Pb 2+ , Cd 2+ and Hg 2+ in the wastewater, the removal rates of Pb 2+ , Cd 2+ and Hg 2+ can be calculated to be 92%, 89%, and 75% respectively.

[0034] Example 2:

[0035] (1) Preparation of cerium dioxide support sol

[0036] Take 10 g of cerium nitrate hexahydrate and 150 ml of N-methylpyrrolidone, mix and stir, sonicate for 60 minutes, then add 50 g of sodium carbonate, and stir at 60 °C for 1 hour to obtain a uniform cerium dioxide support sol.

[0037] (2) Preparation of pretreated sol

[0038] Take 0.08 g of copper oxide, add 2 ml of ethanol and mix evenly, add it into a quartz tube, react at 600 °C for 2 h to reduce it to metallic copper powder. Then add the metallic copper powder to 0.48 g of sodium polyacrylate and 2.2 ml of ethylene glycol, and stir for 30 minutes to prepare the pretreated sol.

[0039] (3) Preparation of catalyst

[0040] Slowly drop the pretreated sol into the cerium dioxide support sol while performing sonication for 3 hours. Place the mixed sol in an oven at 150 °C and dry for 3 hours, then transfer the mixed sol to a tubular furnace, heat it to 500 °C at a rate of 5 °C / min under nitrogen protection, and hold for 5 hours to obtain a rod-shaped cerium dioxide-supported copper oxide nanoparticle catalyst.

[0041] (4) Catalyst performance test

[0042] Take appropriate amounts of lead nitrate, cadmium chloride and mercury chloride to prepare simulated wastewater, adjust the concentration so that the concentration of Pb 2+ is 50 mg / L, the concentration of Cd 2+ is 100 mg / L, the concentration of Hg 2+ is 10 mg / L, add 1 mol / L sodium hydroxide solution to adjust the pH of the wastewater to 7. Add 2% of the rod-shaped cerium dioxide-supported copper oxide nanoparticle catalyst based on the total amount of the wastewater, and stir at room temperature for 2 hours. By measuring the concentrations of Pb 2+ , Cd 2+ and Hg 2+ in the wastewater, the removal rates of Pb 2+ , Cd 2+ and Hg 2+ can be calculated to be 90%, 85% and 78% respectively.

[0043] Example 3:

[0044] (1) Preparation of cerium dioxide support sol

[0045] Take 5 g of cerium nitrate hexahydrate and mix it with 60 ml of N-methylpyrrolidone, stir, and ultrasonically treat for 30 minutes. Then add 25 g of sodium carbonate and stir at 50 °C for 1 hour to obtain a uniform cerium dioxide support sol.

[0046] (2) Preparation of pretreatment sol

[0047] Take 0.09 g of copper oxide, add 1.94 ml of ethanol, mix evenly, add it to a quartz tube, and react at a high temperature of 550 °C for 3 h to reduce it to metallic copper powder. Then add the metallic copper powder to a mixture of 0.45 g of sodium polyacrylate and 2.26 ml of ethylene glycol and stir for 25 minutes to prepare the pretreatment sol.

[0048] (3) Preparation of catalyst

[0049] Slowly drop the pretreatment sol into the cerium dioxide support sol while performing ultrasonic treatment for 3 hours. Place the mixed sol in an oven at 130 °C and dry for 3 hours. Then transfer the mixed sol to a tubular furnace, heat it to 500 °C at a rate of 5 °C / min under nitrogen protection, and hold for 5 hours to obtain a rod-shaped cerium dioxide-supported copper oxide nanoparticle catalyst.

[0050] (4) Catalyst effect test

[0051] Take appropriate amounts of lead nitrate, cadmium chloride, and mercury chloride to prepare simulated wastewater, adjust the concentration so that the Pb 2+ concentration is 50 mg / L, the Cd 2+ concentration is 100 mg / L, and the Hg 2+ concentration is 10 mg / L. Add 1 mol / L sodium hydroxide solution to adjust the pH of the wastewater to 7. Add 2% of the rod-shaped cerium dioxide-supported copper oxide nanoparticle catalyst based on the total amount of wastewater and stir at room temperature for 2 hours. By measuring the concentrations of Pb 2+ , Cd 2+ and Hg 2+ in the wastewater, the removal rates of Pb 2+ , Cd 2+ and Hg 2+ can be calculated to be 91%, 90%, and 72% respectively.

[0052] Comparative example 1:

[0053] (1) Preparation of catalyst

[0054] Except that N-methylpyrrolidone is not added in step (1) during the catalyst preparation, other conditions are the same as in Example 1;

[0055] (2) Catalyst effect test

[0056] Take an appropriate amount of lead nitrate, cadmium chloride and mercury chloride to prepare simulated wastewater, and adjust the concentration so that the concentration of Pb 2+ is 50 mg / L, the concentration of Cd 2+ is 100 mg / L, the concentration of Hg 2+ is 10 mg / L, and add 1 mol / L sodium hydroxide solution to adjust the pH of the wastewater to 7. Add 2% of the total amount of wastewater of the rod-shaped cerium dioxide supported copper oxide nanoparticles catalyst, and stir for 2 hours at room temperature. By measuring the concentrations of Pb 2+ , Cd 2+ and Hg 2+ in the wastewater, the removal rates of Pb 2+ , Cd 2+ and Hg 2+ can be calculated to be 62%, 47% and 49% respectively.

[0057] (3) Comparison effect:

[0058] Compared with Example 1, when preparing the catalyst, N-methylpyrrolidone is not added in step (1), and it cannot play the role of dissolving the catalyst precursor in the catalyst, thus affecting the morphology and structure of the catalyst and resulting in a decrease in the performance of the catalyst.

[0059] Comparative Example 2:

[0060] (1) Catalyst preparation

[0061] Except that sodium polyacrylate and ethylene glycol are not added in step (2) when preparing the catalyst, other conditions are the same as in Example 2;

[0062] (2) Catalyst effect test

[0063] Take an appropriate amount of lead nitrate, cadmium chloride and mercury chloride to prepare simulated wastewater, and adjust the concentration so that the concentration of Pb 2+ is 50 mg / L, the concentration of Cd 2+ is 100 mg / L, the concentration of Hg 2+ is 10 mg / L, and add 1 mol / L sodium hydroxide solution to adjust the pH of the wastewater to 7. Add 2% of the total amount of wastewater of the rod-shaped cerium dioxide supported copper oxide nanoparticles catalyst, and stir for 2 hours at room temperature. By measuring the concentrations of Pb 2+ , Cd 2+ and Hg 2+ in the wastewater, the removal rates of Pb 2+ , Cd 2+ and Hg 2+ can be calculated to be 41%, 38% and 33% respectively.

[0064] (3) Comparison effect:

[0065] Compared with Example 2, when preparing the catalyst, sodium polyacrylate and ethylene glycol are not added in step (1), and the catalyst cannot form a regular rod-like morphology, resulting in a decrease in the performance of the catalyst.

Claims

1. A preparation method of a rod-shaped cerium dioxide-supported metal oxide nanocatalyst, characterized in that, The catalyst is prepared from the following components: using N-methylpyrrolidone as a solvent, cerium dioxide as a carrier, loading copper oxide nanoparticles as a catalytic active component, using ethylene glycol as a reducing agent, and using sodium polyacrylate as a surfactant; Its preparation method includes the following steps: (1) Add the cerium dioxide precursor to N-methylpyrrolidone, after ultrasonic treatment for 30 - 60 minutes, add the precipitant sodium carbonate, and stir for 0.5 - 1 hour at a temperature of 40 - 60 °C to obtain a uniform cerium dioxide carrier sol; (2) Dissolve copper oxide in ethanol, place it in a quartz tube for a reduction reaction to reduce copper oxide to metallic copper powder; then add the metallic copper powder to a mixed solution of sodium polyacrylate and ethylene glycol, and stir for 20 - 30 minutes to obtain a pretreated sol; (3) Slowly drop the pretreated sol into the cerium dioxide carrier sol to obtain a mixed sol, while performing ultrasonic treatment, and the ultrasonic treatment time is 1 - 3 hours; place the mixed sol in an oven for drying, then transfer the mixed sol to a tube furnace and calcine to obtain the cerium dioxide-supported metal oxide nanocatalyst.

2. The preparation method according to claim 1, characterized in that: Based on the mass of the carrier, the mass percentage content of the active component copper oxide is 2% - 8%.

3. The preparation method according to claim 1, characterized in that: The particle size of the catalyst is 0.5 - 5 nm.

4. The preparation method according to claim 1, characterized in that: The cerium dioxide precursor in step (1) is cerium nitrate hexahydrate.

5. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of the cerium dioxide precursor to N-methylpyrrolidone is 1:(10 - 15), and the mass ratio of the cerium dioxide precursor to sodium carbonate is 1:(2 - 5).

6. The preparation method according to claim 1, characterized in that: In step (2): In the reduction reaction, the mass ratio of copper oxide to ethanol is 1:(15 - 20); in the pretreated sol, the mass ratio of copper oxide, sodium polyacrylate, and ethylene glycol is 1:(3 - 6):(20 - 30); the temperature of the reduction reaction is 500 - 600 °C, and the time of the reduction reaction is 1 - 3 hours.

7. The preparation method according to claim 1, characterized in that: In step (3), the mixed sol is dried, the drying temperature is 100 - 150 °C, and the time is 1 - 3 hours.

8. The preparation method according to claim 4, characterized in that: In step (3), the heating rate of the mixed sol under nitrogen protection is 5 - 10 °C / min; the calcination temperature is 480 - 520 °C, and keep the temperature for 3 - 5 hours.

9. Application of the catalyst prepared by the method according to claim 1 in the removal of heavy metal ions in wastewater.

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