CN101597085B - Mesoporous manganese oxide nano granule and preparation method thereof - Google Patents

Abstract

The invention relates to a mesoporous manganese oxide nanomaterial and a preparation method thereof. Through the hydrothermal action of metal manganese, manganese acetate and ammonia water and subsequent roasting control, uniformly distributed mesoporous and particle sizes with a pore diameter of 2 to 10 nanometers are prepared. The mixture of manganese oxyhydroxide and trimanganese tetraoxide, the single crystal particle of pentamanganese octaoxide or the single crystal particle of manganese trioxide, which can be controlled in the range of 20-80 nanometers, can catalyze the combustion reaction of toluene. The preparation method of the invention is simple, the synthesis conditions are loose, easy to repeat, and the raw materials are cheap, so that large-scale production can be carried out.

Description

Mesoporous manganese oxide nanoparticles and preparation method thereof

technical field

The invention relates to a mesoporous manganese oxide nano material and a preparation method thereof, belonging to the field of inorganic porous materials and nano materials.

Background technique

Manganese oxide is an important chemical material widely used in the reduction of organic pollutants and electrode materials. At present, there are literatures to make manganese oxide into porous structure and nanoparticles in order to improve its catalytic activity and electrochemical performance. Papers published in Science 276 (1997) 926 and Chem.Commun. (1997) 1031 prepared mesoporous manganese oxide by using the surfactant template method, but the particles of the obtained material are usually micron-sized and irregular, and the surface activity used in the synthesis The agent needs to be removed after synthesis, and the operation process is cumbersome. Chinese patent CN1467159A discloses a porous manganese oxide nanosheet material, which is obtained by reacting equimolar amounts of potassium permanganate and long-chain alkyl quaternary ammonium salts, and has a large pore size distribution (4-50nm). Chinese patent CN1513767A discloses a preparation method of ultrafine manganese dioxide, which is prepared in a surfactant microemulsion system, and the obtained sample particles are small, but without mesoporosity. Chinese patent CN1438181A discloses a method for preparing nano-manganese dioxide. Potassium permanganate is used as a raw material, and alkyl alcohol polyoxyethylene ether is used as a reducing agent and a surface dispersant. The prepared manganese oxide particles also have no mesopority. We adopted a simple method to synthesize manganese oxide nanoparticles with uniformly distributed mesoporous pores in the absence of surfactants, and its phase can be obtained by controlling different calcination temperatures to obtain a mixture of β-MnOOH and Mn ₃ O ₄ , Mn ₅ O ₈ single crystal particles, and Mn ₂ O ₃ single crystal particles, they catalyze the combustion reaction of toluene.

Contents of the invention

The purpose of the present invention is to provide a mesoporous manganese oxide nanoparticle material and its preparation method, which can overcome the shortcomings of the prior art. The invention has simple synthesis equipment, convenient operation, loose conditions, less pollution, energy saving, simple and easy-to-obtain raw materials, low cost, large output and controllable crystal structure.

In order to achieve the above object, the present invention adopts the hydrothermal treatment method of metal manganese, manganese acetate and ammonia solution to prepare mesoporous manganese oxide nanoparticles. The experimental method can obtain mesoporous manganese oxide with different sizes by adjusting the ratio of metal manganese and manganese acetate, and the particle size can also be adjusted at the same time, and the crystal phase of manganese oxide can be controlled by roasting. The preparation process of the material includes the following schemes:

a) Mix and dissolve a certain amount of manganese powder and manganese acetate in ammonia solution, stir at room temperature for 30 to 60 minutes, transfer the mixture to a stainless steel reaction kettle containing a polytetrafluoroethylene liner, and conduct hydrothermal treatment at 170 to 180°C for 24 hours ; b) After cooling, filter, wash, and dry at 80°C to obtain a brown powder, which is then roasted at a certain temperature.

The molar ratio of manganese acetate to manganese flakes or manganese powder is 1-1.2, the concentration of ammonia water used is 25%, and the molar ratio of ammonia water to manganese is 50-100.

The calcination temperature is 80-800° C., the calcination time is 1-4 hours, and no inert gas protection is needed.

The synthesized brown powder sample is a mixture of manganese oxyhydroxide and trimanganese tetraoxide, and mesoporous manganese oxide nanoparticles with different crystal phases and different pore sizes can be obtained after roasting at different temperatures.

The synthesized brown powder sample is calcined at 400° C. for 3 to 4 hours to obtain pentamanganese octaoxide single crystal nanoparticles, and then calcined at 700° C. for 3 to 4 hours to obtain dimanganese trioxide single crystal nanoparticles.

The mesoporous manganese oxide nanoparticles play a catalytic role in the combustion reaction of toluene.

The present invention has following characteristics:

1. Use cheap, non-toxic manganese acetate and metal manganese powder or manganese flakes as reactants, without using any surfactant or template agent, which is beneficial to environmental protection.

2. Mesoporous manganese oxide nanocrystal particles with a particle size range of 20-80 nanometers and a pore diameter of 2-10 nanometers can be obtained by adjusting different manganese source ratios and reaction temperatures.

3. The preparation process and equipment are simple, and the particle size, mesopore distribution and crystal phase structure of manganese oxide can be controlled.

4. The prepared material has good catalytic performance for toluene combustion and has industrial application value.

Detailed ways

Example 1:

Mix and dissolve 0.55 g of manganese powder and 2.45 g of manganese acetate in 10 ml of 25% ammonia solution, and stir vigorously at room temperature for 30 to 60 minutes. The molar ratio of the mixed liquid is 1Mn:1Mn(CH ₃ COOH) ₂ :100NH ₃ ·H ₂ O. Then the mixed solution was transferred to a stainless steel reaction kettle containing a polytetrafluoroethylene liner, and subjected to hydrothermal treatment at 170° C. for 24 hours. After cooling, the sample was filtered, washed, and dried overnight at 80°C to collect a brown solid powder. The XRD test results show that the obtained powder sample is a mixture phase of β-MnOOH JCPDS#18-0804 and Mn ₃ O ₄ JCPDS#80-0382; SEM photos show that the particle size of the obtained material is 45nm; TEM shows that the material has an irregular medium Pores: The nitrogen adsorption-desorption isotherm and the corresponding pore size distribution diagram show that the material has a typical mesoporous structure, the BET specific surface area is 33m ² /g, and the mesopore diameter is 2nm.

Example 2:

The sample prepared in Example 1 was calcined in a muffle furnace at a heating rate of 2°C/min, and then calcined for 3 hours after reaching 400°C. The obtained sample structure is Mn ₅ O ₈ JCPDS 39-1218, C2/m, a=1.034nm, b=0.572nm, c=0.485nm, β=109.4°, particle size is about 20-80nm, BET specific surface area It is 15m ² /g, and the mesopore diameter is 4.2nm.

Example 3:

The sample prepared in Example 1 was calcined in a muffle furnace at a heating rate of 2°C/min, and then calcined for 3 hours after reaching 700°C. The obtained sample structure is Mn ₂ O ₃ JCPDS 71-0636, Ia-3, a=0.9414nm, the particle size is about 20-80nm, the BET specific surface area is 10m ² /g; the mesopore diameter is 6.3nm.

Claims (3)

1. A method for preparing mesoporous manganese oxide nanoparticles is characterized in that: 0.55 gram of manganese powder and 2.45 gram of manganese acetate are mixed and dissolved in 10ml of 25% ammonia solution, vigorously stirred at normal temperature for 30 to 60 minutes, mixed The molar ratio of the liquid is 1Mn: 1Mn(CH ₃ COOH) ₂ : 100NH ₃ ·H ₂ O, and then the mixed liquid is transferred to a stainless steel reaction kettle containing a polytetrafluoroethylene liner, hydrothermally treated at 170°C for 24 hours, and cooled After the sample was filtered, washed, and dried overnight at 80°C, a brown solid powder was collected. The XRD test results showed that the obtained powder sample was a mixture phase of β-MnOOH JCPDS#18-0804 and Mn ₃ O ₄ JCPDS#80-0382; SEM photos showed that The particle size of the material is 45nm; TEM shows that the material has irregular mesopores; the nitrogen adsorption-desorption isotherm and the corresponding pore size distribution diagram show that the material has a typical mesoporous structure, and the BET specific surface area is 33m ² /g , Mesopore diameter is 2nm. 2. A method for preparing mesoporous manganese oxide nanoparticles, characterized in that: the brown solid powder according to claim 1 is roasted in a muffle furnace at a heating rate of 2° C./min, and roasted for 3 hours after reaching 400° C. , the obtained sample structure is Mn ₅ O ₈ JCPDS 39-1218, C2/m, a=1.034nm, b=0.572nm, c=0.485nm, β=109.4°, particle size is 20-80nm, BET specific surface area It is 15m ² /g, and the mesopore diameter is 4.2nm. 3. A method for preparing mesoporous manganese oxide nanoparticles, characterized in that: the brown solid powder according to claim 1 is roasted in a muffle furnace at a heating rate of 2° C./min, and roasted for 3 hours after reaching 700° C. , the obtained sample structure is Mn ₂ O ₃ JCPDS 71-0636, Ia-3, a=0.9414nm, the particle size is 20-80nm, the BET specific surface area is 10m ² /g; the mesopore diameter is 6.3nm.