CN114471531B - Nano porous spherical birnessite, preparation method thereof and application thereof in formaldehyde degradation - Google Patents
Nano porous spherical birnessite, preparation method thereof and application thereof in formaldehyde degradation Download PDFInfo
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- CN114471531B CN114471531B CN202110523171.2A CN202110523171A CN114471531B CN 114471531 B CN114471531 B CN 114471531B CN 202110523171 A CN202110523171 A CN 202110523171A CN 114471531 B CN114471531 B CN 114471531B
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- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 title claims abstract description 212
- 238000002360 preparation method Methods 0.000 title claims abstract description 29
- 230000015556 catabolic process Effects 0.000 title claims description 21
- 238000006731 degradation reaction Methods 0.000 title claims description 21
- 238000006243 chemical reaction Methods 0.000 claims abstract description 79
- 239000000463 material Substances 0.000 claims abstract description 50
- 239000011572 manganese Substances 0.000 claims abstract description 25
- 239000007864 aqueous solution Substances 0.000 claims abstract description 23
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 20
- 239000000243 solution Substances 0.000 claims abstract description 19
- 238000003756 stirring Methods 0.000 claims abstract description 17
- 238000010438 heat treatment Methods 0.000 claims abstract description 7
- 238000007789 sealing Methods 0.000 claims abstract description 7
- 239000011259 mixed solution Substances 0.000 claims abstract description 6
- 239000011702 manganese sulphate Substances 0.000 claims description 18
- 235000007079 manganese sulphate Nutrition 0.000 claims description 18
- SQQMAOCOWKFBNP-UHFFFAOYSA-L manganese(II) sulfate Chemical compound [Mn+2].[O-]S([O-])(=O)=O SQQMAOCOWKFBNP-UHFFFAOYSA-L 0.000 claims description 18
- 239000012286 potassium permanganate Substances 0.000 claims description 17
- 229940099596 manganese sulfate Drugs 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 16
- 230000003197 catalytic effect Effects 0.000 claims description 12
- 230000035484 reaction time Effects 0.000 claims description 5
- 239000002135 nanosheet Substances 0.000 claims description 3
- JYLNVJYYQQXNEK-UHFFFAOYSA-N 3-amino-2-(4-chlorophenyl)-1-propanesulfonic acid Chemical compound OS(=O)(=O)CC(CN)C1=CC=C(Cl)C=C1 JYLNVJYYQQXNEK-UHFFFAOYSA-N 0.000 claims description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 2
- 229910021380 Manganese Chloride Inorganic materials 0.000 claims description 2
- GLFNIEUTAYBVOC-UHFFFAOYSA-L Manganese chloride Chemical compound Cl[Mn]Cl GLFNIEUTAYBVOC-UHFFFAOYSA-L 0.000 claims description 2
- 150000001875 compounds Chemical class 0.000 claims description 2
- 239000011777 magnesium Substances 0.000 claims description 2
- 229910052749 magnesium Inorganic materials 0.000 claims description 2
- 229940071125 manganese acetate Drugs 0.000 claims description 2
- 239000011565 manganese chloride Substances 0.000 claims description 2
- 235000002867 manganese chloride Nutrition 0.000 claims description 2
- 229940099607 manganese chloride Drugs 0.000 claims description 2
- UOGMEBQRZBEZQT-UHFFFAOYSA-L manganese(2+);diacetate Chemical compound [Mn+2].CC([O-])=O.CC([O-])=O UOGMEBQRZBEZQT-UHFFFAOYSA-L 0.000 claims description 2
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 150000003839 salts Chemical class 0.000 claims description 2
- 238000006555 catalytic reaction Methods 0.000 abstract description 6
- 230000000052 comparative effect Effects 0.000 description 32
- 238000001000 micrograph Methods 0.000 description 10
- 230000000593 degrading effect Effects 0.000 description 9
- 239000003054 catalyst Substances 0.000 description 8
- 239000000725 suspension Substances 0.000 description 8
- 230000008859 change Effects 0.000 description 6
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 6
- 238000001035 drying Methods 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 238000005406 washing Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 238000000227 grinding Methods 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 229910000314 transition metal oxide Inorganic materials 0.000 description 4
- 238000002425 crystallisation Methods 0.000 description 3
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- 229910000510 noble metal Inorganic materials 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 241000282414 Homo sapiens Species 0.000 description 2
- 238000003905 indoor air pollution Methods 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 description 2
- 235000010755 mineral Nutrition 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000012494 Quartz wool Substances 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 238000004887 air purification Methods 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000010170 biological method Methods 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 229910000428 cobalt oxide Inorganic materials 0.000 description 1
- IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical compound [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000005034 decoration Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 231100000053 low toxicity Toxicity 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 238000010525 oxidative degradation reaction Methods 0.000 description 1
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- B01J23/32—Manganese, technetium or rhenium
- B01J23/34—Manganese
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Abstract
The invention belongs to the technical field of formaldehyde catalysis, and particularly discloses a preparation method of nano porous spherical birnessite, which comprises the following steps: step (1): dropping a permanganate A aqueous solution into a divalent manganese source aqueous solution, and stirring to perform a first reaction; wherein the molar ratio of the permanganate A to the divalent manganese source is 0.5-2: 1, a step of; step (2): adding permanganate B into the solution system of the first reaction, then sealing the mixed solution in a container, heating to perform a second reaction, and separating to obtain a nano porous spherical birnessite product after the reaction is finished; the molar ratio of the permanganate B to the divalent manganese source is 0.5-3.5: 1, a step of; the temperature of the second reaction is 160-250 ℃. The material prepared by the invention has excellent formaldehyde catalysis performance.
Description
Technical Field
The invention belongs to the field of nano material manufacturing, and particularly relates to a preparation method of nano porous spherical birnessite for efficiently degrading formaldehyde.
Technical Field
With the development of science and technology and the progress of society, the requirements of human on interior decoration are higher and higher, and the problems are also generated. Most interior materials contain a certain amount of formaldehyde, and thus the released formaldehyde gas also passes through the polluted air in the room, thereby endangering the physical health of human beings. Thus, there is a need to solve the problem of indoor air pollution. The current means for treating indoor air pollution are adsorption method, biological method, plasma method, photocatalytic oxidation method and thermocatalytic oxidation method. Among them, the thermal catalytic oxidation method is favored because of its good formaldehyde removal effect and low operating cost.
The key to the thermocatalytic oxidation process is the choice of catalyst, which is largely divided into noble metals and transition metal oxides. Wherein, the noble metal catalyst has high catalytic activity and good catalytic effect. However, noble metal catalysts have limited further applications due to low reserves, high prices, and the like. Thus, scholars of all countries have been looking at the transition metal oxide. The transition metal oxide is mainly classified into manganese oxide, cobalt oxide or composite oxide. Compared with other transition metal oxides, the manganese oxide has the characteristics of low toxicity, high activity, stable structure, various shapes and the like, and attracts the eyes of scholars of various countries.
Birnessite, a kind of MnO 6 The layered manganese oxide mineral formed by stacking octahedron and water molecules of different cations has the characteristics of strong oxidizing capability, large specific surface area, high ion exchange capacity and the like. The change of the morphology of the birnessite can cause the physical and chemical properties of the birnessite to be greatly changed. The majority of birnessite reported in the literature is mainly in the form of flakes, petals and spheres. By changing the microscopic morphology of the birnessite, the specific surface area of the birnessite is changed, and the birnessite is promoted to meet the requirements of different fields.
However, the catalytic performance of the birnessite reported in the prior art for formaldehyde is still lower at room temperature, and formaldehyde removal can be realized at a higher temperature. The prior art also lacks materials that still exhibit good formaldehyde removal properties at ambient conditions.
Disclosure of Invention
The first aim of the invention is to provide a preparation method of nano porous spherical birnessite, which has low cost, simple operation and convenient treatment. The material has large specific surface area and can efficiently degrade formaldehyde gas in air.
The second aim of the invention is to provide the nano porous spherical birnessite prepared by the preparation method.
The third purpose of the invention is to provide the application of the nano porous spherical birnessite prepared by the preparation method in formaldehyde degradation.
The morphology uniformity of the birnessite in the prior art is not ideal, and is usually a micron-sized material, the performance of the material in formaldehyde catalysis is to be improved, for example, the formaldehyde degradation performance at normal temperature is poor, the material is limited in practical application, and the following technical scheme is provided for aiming at the technical problem:
the preparation process of nanometer porous spherical birnessite includes the following steps:
step (1): dropping a permanganate A aqueous solution into a divalent manganese source aqueous solution, and stirring to perform a first reaction; wherein the molar ratio of the permanganate A to the divalent manganese source is 0.5-2: 1, a step of;
step (2): adding permanganate B into the solution system of the first reaction, then sealing the mixed solution in a container, heating to perform a second reaction, and separating to obtain a nano porous spherical birnessite product after the reaction is finished;
the molar ratio of the permanganate B to the divalent manganese source is 0.5-3.5: 1, a step of;
the temperature of the second reaction is 160-250 ℃.
The invention innovatively discovers that the permanganate A is dripped into the divalent manganese source aqueous solution in advance to perform a first reaction, then the permanganate B is added to perform a second reaction, the cooperation can be realized unexpectedly by further matching with the control of each condition based on the two-stage reaction thought, the material with porous, spherical and nano-size formed by assembling nano-sheets can be obtained, and more importantly, the material obtained by the method has unexpected degradation advantage in formaldehyde catalysis.
The research of the invention discovers that the stepwise two-stage reaction thought of permanganate, the addition proportion on the reaction thought and the joint cooperative control of the reaction temperature are key to improving the material structure, the morphology and the formaldehyde degradation performance.
In the invention, the divalent manganese source can ionize Mn 2+ Is a water-soluble compound of (2); preferably at least one of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate, or manganese ore extract. The divalent manganese source may be a commercial chemical source or may be derived from a mineral smelting material (e.g., leachate).
Preferably, in the aqueous solution of the divalent manganese source, mn 2+ The molar concentration of (2) is 0.1-2M; more preferably 0.1 to 0.5M.
The permanganate A and the permanganate B can ionize MnO 4 -a water-soluble salt, preferably at least one of potassium permanganate, sodium permanganate, magnesium permanganate.
Aqueous permanganate A solution (in MnO 4 -by mole) of 0.1 to 0.5M.
According to the invention, the permanganate A is added into the divalent manganese source solution in a dropwise manner, the dropping speed, the stirring rotation speed in the reaction stage and the reaction time are further controlled, the morphology of the material prepared under the two-stage reaction mechanism can be unexpectedly further improved, and the formaldehyde degradation performance is further improved.
Preferably, in step (1), the drop rate of the permanganate A aqueous solution is 0.001 to 0.005moL/min.
Preferably, the permanganate A in aqueous solution (in MnO 4 -by) a molar ratio relative to the divalent manganese source of 0.5 to 1:1; more preferably 0.5 to 0.6:1.
Preferably, in the step (1), the stirring speed in the first reaction process is 50 to 300r/min.
Preferably, in the step (1), the time of the first reaction process is 0.5-3 h; more preferably 1 to 2 hours.
In the present invention, an aqueous permanganate B solution is added to a first reaction system, and the mixed solution is placed in a pressure-resistant vessel, the vessel is closed, and a second reaction is performed by heating. It is found that controlling the amount of permanganate B added in the second reaction stage and the reaction temperature helps to further facilitate obtaining a material with better formaldehyde catalytic degradation performance.
In the present invention, permanganate B aqueous solution (in MnO form 4 -by mole) 0.1-1.5M; preferably 0.8 to 1M.
Preferably, the molar ratio of permanganate B to the divalent manganese source is 1-2:1.
Preferably, the temperature of the second reaction is 180 to 240 ℃.
Preferably, the second reaction time is 12-48 h; more preferably 15 to 24 hours.
In the invention, after the second reaction is finished, solid-liquid separation is carried out on the product, and washing and drying are carried out to obtain the product.
The invention discloses a preparation method of porous spherical birnessite for efficiently degrading formaldehyde, which comprises the following steps:
(1) Preparing a manganese sulfate aqueous solution for later use:
(2) Will be put onAdding potassium permanganate (MnO 4-relative to added Mn) into the prepared manganese sulfate aqueous solution 2+ The molar ratio of (2) is 0.5-2: 1) Stirring at room temperature, and performing a first-stage reaction to obtain a first reaction solution;
(3) Continuously adding potassium permanganate (the mol ratio of MnO 4-relative to added Mn2+ is 0.5-3.5:1) into the mixed solution and the mixed solution in the step (2), and stirring and reacting for 0.5-3 h to obtain a suspension;
(4) Transferring the suspension into a pressure-resistant container, sealing the reactor, and crystallizing at 160-240 ℃ for 12-48 hours;
(5) Washing with absolute ethyl alcohol and deionized water to neutrality, filtering with a vacuum pump, drying at 40-90 deg.c and grinding to obtain birnessite powder.
The invention also provides the nano porous spherical birnessite prepared by the preparation method, which is formed by interlacing birnessite nano sheets.
The invention also provides application of the nano porous spherical birnessite prepared by the preparation method in catalytic degradation of formaldehyde.
Advantageous effects
1. The invention provides a permanganate two-stage reaction idea, and further discovers that based on the two-stage reaction idea, the material proportion and the temperature and other conditions are further matched to realize the cooperation unexpectedly, so that the nanometer spherical material with good structure and morphology can be obtained, and more importantly, the material with the morphology structure obtained in the aspect has excellent performance in formaldehyde catalysis;
2. the nano porous spherical birnessite for efficiently degrading formaldehyde is simple in preparation process, low in cost, free of addition of surfactant or modifier and environment-friendly. The birnessite prepared by the method has rich pore canal structure, good stability and higher specific surface area, and can have important application value in various fields such as adsorption, catalysis, oxidative degradation materials, air purification materials and the like.
Drawings
FIG. 1A scanning electron microscope image of nano porous spherical birnessite with high formaldehyde degrading capacity is prepared in example 1;
FIG. 2. X-ray diffraction pattern of nano porous spherical birnessite with high formaldehyde degrading capacity is prepared in example 1;
FIG. 3 is a graph showing the change of formaldehyde conversion rate with temperature of nano porous spherical birnessite prepared in example 1 and having the capability of efficiently degrading formaldehyde;
FIG. 4 is a graph of normal temperature formaldehyde tolerance over time for the preparation of nanoporous spheroidal birnessite with efficient formaldehyde degradation capability in example 1;
FIG. 5 is an SEM image of the comparative example 1 preparation material;
FIG. 6 XRD patterns of the comparative example 1 preparation material;
FIG. 7 is a graph showing formaldehyde conversion as a function of temperature for the comparative example 1 preparation material;
FIG. 8 is a scanning electron microscope image of comparative example 2 for preparing nanoporous spherical birnessite with high formaldehyde degrading ability;
FIG. 9 is a graph showing the change of formaldehyde conversion rate with temperature of nano porous spherical birnessite prepared in comparative example 2 and having an ability to efficiently degrade formaldehyde;
FIG. 10 is a scanning electron microscope image of the material prepared in comparative example 3;
FIG. 11 is a graph showing formaldehyde conversion as a function of temperature for the comparative example 3 preparation material;
FIG. 12 scanning electron microscope image of a nanoporous spherical birnessite prepared in example 2 with high formaldehyde degrading capacity;
FIG. 13A graph of formaldehyde conversion over temperature for the preparation of nanoporous spherical birnessite with efficient formaldehyde degradation capability in example 2;
FIG. 14 is a scanning electron microscope image of the material prepared in comparative example 4;
FIG. 15 is a graph showing formaldehyde conversion as a function of temperature for the comparative example 4 preparation material;
FIG. 16 scanning electron microscope image of nano porous spherical birnessite prepared in example 3 with high formaldehyde degrading capacity;
FIG. 17A graph of formaldehyde conversion over temperature for the preparation of nanoporous spherical birnessite with efficient formaldehyde degradation capability in example 3;
FIG. 18 is a scanning electron microscope image of the material prepared in comparative example 5;
FIG. 19 is a graph showing formaldehyde conversion as a function of temperature for the comparative example 5 preparation material;
FIG. 20 is a scanning electron microscope image of the material prepared in comparative example 6;
FIG. 21 is a graph showing formaldehyde conversion as a function of temperature for the comparative example 6 preparation material;
FIG. 22 is a scanning electron microscope image of the material prepared in comparative example 7;
FIG. 23 is a graph showing formaldehyde conversion as a function of temperature for the comparative example 7 preparation material;
FIG. 24 is a scanning electron microscope image of the material prepared in comparative example 8;
FIG. 25 is a graph showing formaldehyde conversion as a function of temperature for the comparative example 8 preparation material;
FIG. 26 is a graph showing formaldehyde conversion as a function of temperature for the example 4 preparation material;
FIG. 27 is a graph showing formaldehyde conversion as a function of temperature for the example 5 preparation material;
the specific embodiment is as follows:
describing a formaldehyde catalytic degradation step and a data measurement method:
catalyst catalytic Activity determination for HCHO (80 ppm): 0.1g of catalyst powder having a particle size of 200 to 250 μm was placed in the middle (inner diameter 6 mm) of the reactor and supported by quartz wool at atmospheric pressure. The total flow rate was 100ml min-1, corresponding to a Gas Hourly Space Velocity (GHSV) of 60 L.h-1.g-1. Once the given reaction temperature was reached, the catalyst was stable for 1 hour. The reaction products were detected on-line using a gas chromatograph-mass spectrometer equipped with a thermal conductivity detector. The catalytic activity of the catalyst was evaluated by converting HCHO to CO 2. The HCHO conversion of the sample was calculated using the following formula
Wherein [ HCHO ] in and [ CO2] in are respectively the inlet HCHO and the CO2 concentration [ CO2] out represent the outlet CO2 concentration.
The room temperature according to the invention is, for example, 20 to 35 ℃.
Example 1
(1) Preparing a 0.2M manganese sulfate aqueous solution for later use:
(2) Dropwise adding 0.4M potassium permanganate solution (dropwise adding rate is 0.004mol/min and dropwise adding molar quantity is 0.1 mol) into the prepared manganese sulfate aqueous solution (1L), stirring at room temperature (stirring speed is 80 r/min), and carrying out first-stage reaction for 60min to obtain a first reaction solution;
(3) Continuously adding 0.8M potassium permanganate solution (the addition molar quantity is 0.2mol, the dropping speed is the same as that in the step (2)) into the first invention solution, and uniformly stirring to obtain a suspension;
(4) Transferring the suspension into a pressure-resistant reactor, sealing the reactor, heating to 180 ℃ and performing a second-stage reaction for 20 hours;
(5) Washing with absolute ethanol and deionized water to neutrality, filtering with a vacuum pump, drying at 60deg.C, and grinding to obtain birnessite powder.
The nano porous spherical birnessite material with high formaldehyde degradation efficiency prepared in the embodiment has a scanning electron microscope picture shown in figure 1, an X-ray diffraction spectrum shown in figure 2, a curve of the conversion rate of formaldehyde along with the temperature change shown in figure 3, and the tolerance of the catalyst to formaldehyde at normal temperature shown in figure 4.
Comparative example 1
The only difference compared with example 1 is that the potassium permanganate of step (2) is relative to Mn 2+ The molar ratio of the addition is 0.4;
the scanning electron microscope picture of the prepared material is shown in figure 5, the X-ray diffraction spectrum is shown in figure 6, and the curve of the conversion rate of formaldehyde with temperature is shown in figure 7.
Comparative example 2
The only difference compared to example 1 is that in step (3) (second reaction), the molar ratio of potassium permanganate to manganese sulfate is 4.
The nano porous spherical birnessite material with high formaldehyde degradation efficiency prepared in the embodiment has a scanning electron microscope picture shown in figure 8, and a curve of the conversion rate of formaldehyde with temperature change shown in figure 9.
Comparative example 3
The only difference compared with example 1 is that the potassium permanganate of step (3) is relative to Mn 2+ The molar ratio of the addition is 0.3;
a scanning electron microscope picture of the material prepared in the comparative example is shown in fig. 10, and a curve of the conversion rate of formaldehyde with temperature is shown in fig. 11.
Example 2
The only difference compared to example 1 is that in step (2), the molar ratio of potassium permanganate to manganese sulphate of step (1) is 2:1.
The nano porous spherical birnessite material with high formaldehyde degradation efficiency prepared in the embodiment is shown in fig. 12, and the curve of the conversion rate of formaldehyde with temperature is shown in fig. 13.
Comparative example 4
The difference compared to example 1 is only that the crystallization temperature in step (4) is 130 ℃.
A scanning electron microscope picture of the material prepared in the comparative example is shown in fig. 14, and a curve of the conversion rate of formaldehyde with temperature is shown in fig. 15.
Example 3
The only difference compared to example 1 is that in step (3), the molar ratio of potassium permanganate to manganese sulphate of step (1) is 2:1.
The nano porous spherical birnessite material with high formaldehyde degradation efficiency prepared in the embodiment is shown in fig. 16, and the curve of the conversion rate of formaldehyde with temperature is shown in fig. 17.
Comparative example 5
The difference compared with example 1 is only that the first reaction time of step (2) is 20min;
a scanning electron microscope picture of the material prepared in the comparative example is shown in fig. 18, and a curve of the conversion rate of formaldehyde with temperature is shown in fig. 19.
Comparative example 6
The difference from example 1 is that the two ranges are not adopted, and the total molar amount of potassium permanganate to be added and other treatment parameters are the same as those in example 1;
a scanning electron microscope picture of the comparative example material is shown in FIG. 20, and a curve of the conversion rate of formaldehyde with temperature is shown in FIG. 21.
Comparative example 7
The difference from example 1 is that in step (3), the molar ratio of potassium permanganate to manganese sulfate to be added is 25:1, and the other conditions are the same as in example 1.
The nano porous spherical birnessite material with high formaldehyde degradation efficiency prepared in the comparative example is shown in figure 22, and the curve of the conversion rate of formaldehyde with temperature is shown in figure 23.
Comparative example 8
The difference compared to example 1 is only that the treatment temperature (crystallization temperature) of step (4) is 80 ℃.
A scanning electron microscope picture of the material prepared in the comparative example is shown in fig. 24, and a curve of the conversion rate of formaldehyde with temperature is shown in fig. 25.
Example 4
(1) Preparing a 0.2M manganese sulfate aqueous solution for later use:
(2) Dropwise adding 0.5M potassium permanganate solution (the dropwise adding rate is 0.004mol/min, and the adding mole ratio is 0.5 relative to manganese sulfate) into the prepared manganese sulfate aqueous solution (1L), stirring at room temperature (the stirring rotating speed is 100 r/min), and carrying out first-stage reaction for 120min to obtain a first reaction solution;
(3) Continuously adding 0.8M potassium permanganate solution (equivalent to the adding molar ratio of the manganese sulfate in the step (1) being 2, and the dropping speed being the same as that in the step (2)) into the first invention solution, and uniformly stirring to obtain suspension;
(4) Transferring the suspension into a pressure-resistant reactor, sealing the reactor, heating to 220 ℃ and performing a second-stage reaction for 24 hours;
(5) Washing with absolute ethanol and deionized water to neutrality, filtering with a vacuum pump, drying at 60deg.C, and grinding to obtain birnessite powder.
The nano porous spherical birnessite material with high formaldehyde degradation efficiency prepared in the scheme has a curve of formaldehyde conversion rate with temperature shown in figure 26.
Example 5
(1) Preparing a 0.2M manganese sulfate aqueous solution for later use:
(2) Dropwise adding 0.1M potassium permanganate solution (the dropwise adding rate is 0.004mol/min, and the adding mole ratio is 0.5 relative to manganese sulfate) into the prepared manganese sulfate aqueous solution (1L), stirring at room temperature (the stirring rotating speed is 80 r/min), and carrying out first-stage reaction for 60min to obtain a first reaction solution;
(3) Continuously adding 1M potassium permanganate solution (the adding molar ratio relative to manganese sulfate is 2, the dropping speed is the same as that in the step (2)) into the first invention solution, and uniformly stirring to obtain suspension;
(4) Transferring the suspension into a pressure-resistant reactor, sealing the reactor, heating to 240 ℃ and performing a second-stage reaction for 15 hours;
(5) Washing with absolute ethanol and deionized water to neutrality, filtering with a vacuum pump, drying at 60deg.C, and grinding to obtain birnessite powder. The nano porous spherical birnessite material with high formaldehyde degradation efficiency prepared in the scheme has a curve of formaldehyde conversion rate with temperature change shown in figure 27.
The conversion data of formaldehyde at various temperatures for examples 1-5 and comparative examples 1-8 are shown in Table 1
It can be seen from table 1 that by adopting the two-stage reaction of the present invention, in combination with the addition amounts of the first-stage reaction and the second-stage reaction and the cooperative control of the crystallization temperature of the second-stage reaction, the properties of the prepared material can be unexpectedly improved, the low-temperature and high-temperature catalytic properties can be further improved, and particularly, the catalytic properties at room temperature can be effectively improved, and the present invention has a larger practical application prospect.
Claims (12)
1. The preparation method of the nano porous spherical birnessite is characterized by comprising the following steps:
step (1): dropping a permanganate A aqueous solution into a divalent manganese source aqueous solution, and stirring to perform a first reaction; wherein the molar ratio of the permanganate A to the divalent manganese source is 0.5-2: 1, a step of; the first reaction time is 1-2 h;
step (2): adding permanganate B into the solution system of the first reaction, then sealing the mixed solution in a container, heating to perform a second reaction, and separating to obtain a nano porous spherical birnessite product after the reaction is finished;
the molar ratio of the permanganate B to the divalent manganese source is 1-2: 1, a step of;
the temperature of the second reaction is 160-250 ℃.
2. The method for preparing nano porous spherical birnessite according to claim 1, wherein the divalent manganese source is Mn capable of ionization 2+ Is a water-soluble compound of (a).
3. The method for preparing nano-porous spherical birnessite according to claim 2, wherein the divalent manganese source is at least one of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate.
4. The method for preparing nano-porous spherical birnessite according to claim 1, wherein in the aqueous solution of divalent manganese source, mn 2+ The molar concentration of (2) is 0.1-2M.
5. The method for preparing nano-porous spherical birnessite according to claim 1, which is characterized in thatCharacterized in that the permanganate A and the permanganate B can ionize MnO 4 -a water-soluble salt.
6. The method for preparing nano porous spherical birnessite according to claim 5, wherein the permanganate A and the permanganate B are at least one of potassium permanganate, sodium permanganate and magnesium permanganate.
7. The method for preparing nano porous spherical birnessite according to claim 1, wherein the molar concentration of permanganate a aqueous solution is 0.1-0.5M;
the molar concentration of the permanganate B aqueous solution is 0.1-1.5M.
8. The method for producing a nanoporous spherical birnessite according to claim 1, wherein in the step (1), the drop rate of the permanganate a aqueous solution is 0.001 to 0.005mol/min.
9. The method for preparing nano porous spherical birnessite according to claim 1, wherein in the step (1), the stirring rotation speed in the first reaction process is 50-300 r/min.
10. The method for preparing nano porous spherical birnessite according to claim 1, wherein the reaction time of the step (2) is 12-48 hours.
11. A nano porous spherical birnessite prepared by the preparation method of any one of claims 1-10, characterized in that the nano porous spherical birnessite nanosheets are interlaced to form a spherical material with porous and nano size.
12. The use of the nanoporous spherical birnessite prepared by the preparation method of any one of claims 1 to 10, characterized in that it is used for the catalytic degradation of formaldehyde.
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