CN111185153A

CN111185153A - MnO2Nanosheet catalytic material and preparation method and application thereof

Info

Publication number: CN111185153A
Application number: CN202010065558.3A
Authority: CN
Inventors: 江春立; 吴隐; 黄其佩
Original assignee: Guangzhou Spene Eco Friendly Technology Co ltd
Current assignee: Guangzhou Spene Eco Friendly Technology Co ltd
Priority date: 2020-01-20
Filing date: 2020-01-20
Publication date: 2020-05-22

Abstract

The invention relates to MnO₂A nano-sheet catalytic material, a preparation method and application thereof. The preparation method comprises the following steps: (1) preparing solution A by using 3-60 wt% of ammonium salt aqueous solution, 8-32 wt% of hydrogen peroxide aqueous solution and water; the volume ratio of the ammonium salt aqueous solution to the hydrogen peroxide aqueous solution to water is 5-10: 1-4: 10-40; (2) taking a manganese salt aqueous solution with the concentration of 0.02-0.10 g/mL as a solution B; (3) adding the solution A into the solution B for reaction, filtering and drying after the reaction is finished to obtain MnO₂A nanosheet catalytic material; the ammonium salt is selected from ammonium sulfate, ammonium bisulfate, ammonium chloride, ammonium nitrate, ammonium carbonate, ammonium bicarbonate, ammonium hydroxide, ammonium fluoride, ammonium iodide or ammonium bromide. MnO prepared by the method of the invention₂The nano-sheet catalytic material has good catalytic decomposition capability on indoor air pollutants at normal temperature.

Description

MnO2Nanosheet catalytic material and preparation method and application thereof

Technical Field

The invention relates to the technical field of environmental protection, in particular to MnO₂Nanosheet catalytic material and preparation method thereofAnd application.

Background

Today's society, people spend more than 80% of their time indoors. Indoor air quality has attracted a great deal of attention because it is closely related to human health. The formaldehyde released from furniture and building materials is a main pollutant of indoor air, and with the wide application and increasing high consumption of furniture and building materials, the problem of indoor formaldehyde pollution is inevitable. The formaldehyde pollution problem is particularly obvious in new or reconstructed buildings. The long-term exposure of human beings to formaldehyde can cause adverse effects on human bodies, such as dizziness, nausea, headache and the like, and serious even carcinogenesis. The concern that indoor formaldehyde emissions affect human health is increasing in china and even worldwide. The world health organization WHO classified formaldehyde as a class of carcinogens set the guideline value for indoor formaldehyde to 0.1mg m in 2010^-3(WHOGuidelines for index Air Quality: Selected polutants; World health organization Regional Office for Europe: Copenhagen, Denmark,2010.), China also used this guideline value as a standard value. As one of the most densely populated developing countries in the world, the formaldehyde levels in newly built buildings and rebuilt houses in china exceed 70%, far exceeding safety standards. Therefore, not only the development of economical and practical formaldehyde removal technology is required, but also the development of novel catalytic materials is urgently required. The utilization of novel catalytic materials to rapidly convert formaldehyde into carbon dioxide at room temperature is one of the technologies with great application prospects at present.

Highly effective formaldehyde removal materials have been developed with supported Pt catalysts, such as 1 wt% Pt/TiO₂，0.1wt％Pt/TiO₂，1wt％Pt/Fe₂O₃And 3 wt% Pt/MnO_x-CeO₂And the like. They all exhibit complete conversion of ppm-grade formaldehyde to CO at room temperature₂The ability of the cell to perform. To reduce costs, at present, the transition metal oxide MnO is inexpensive₂Have been applied to the oxidation of formaldehyde. First discovery of MnO by Sekine et al₂Is the most active of the 13 commercial transition metal oxides (Sekine,atmos. environ.2002,36, 5543-5547.). Zhang et al also reported delta-MnO₂MnO of 4 different phase structures₂The activity of medium catalytic oxidation formaldehyde is best, and the GHSV is 100L g cat at 80 DEG C^-1h^-1Almost 100% conversion rate was achieved (Catal. Sci. Technol.2015,5, 2305. 2313.).

However, since most non-noble metal catalysts require temperatures well above room temperature to catalyze the complete conversion of formaldehyde, the conversion of formaldehyde is greatly reduced as the temperature is lowered. Thus most non-noble metal catalysts have very low formaldehyde conversion at room temperature, which is not in line with the higher conversion rate required for indoor air purification.

Meanwhile, in practical application, the catalyst is usually in powder form, which is inconvenient in practical application. If the catalyst with a specific morphology can be synthesized in a large amount in a controllable manner, the practical application value of the catalyst is greatly promoted. Therefore, the catalyst which has a plurality of active sites and can keep higher activity and better stability at room temperature is developed and prepared, has great potential in the aspects of air purification such as formaldehyde conversion, ozone degradation and the like, and has potential application prospects in the fields of water treatment, supercapacitors, energy storage and the like.

Disclosure of Invention

Based on this, one of the objects of the present invention is to provide MnO₂Preparation method of nanosheet catalytic material and MnO prepared by method₂The nano-sheet catalytic material has good catalytic decomposition capability on indoor air pollutants at normal temperature.

The specific technical scheme is as follows:

MnO (MnO)₂The preparation method of the nanosheet catalytic material comprises the following steps:

(1) preparing solution A by using 3-60 wt% of ammonium salt aqueous solution, 8-32 wt% of hydrogen peroxide aqueous solution and water; the volume ratio of the ammonium salt aqueous solution to the hydrogen peroxide aqueous solution to water is 5-10: 1-4: 10-40;

(2) taking a manganese salt aqueous solution with the concentration of 0.02-0.10 g/mL as a solution B;

(3) adding the solution A into the solution B for reaction, filtering and drying after the reaction is finished to obtain MnO₂Nano meterA sheet catalytic material;

the ammonium salt is selected from ammonium sulfate, ammonium bisulfate, ammonium chloride, ammonium nitrate, ammonium carbonate, ammonium bicarbonate, ammonium hydroxide, ammonium fluoride, ammonium iodide or ammonium bromide.

In some embodiments, the concentration of ammonium salt in the ammonium salt aqueous solution is 5-50 wt%, and the concentration of hydrogen peroxide in the hydrogen peroxide aqueous solution is 10-30 wt%.

In some embodiments, the volume ratio of the solution A to the solution B is 25-45: 8 to 25.

In some of these embodiments, the ammonium salt is selected from ammonium hydroxide.

In some of the embodiments, the concentration of ammonium salt in the ammonium salt aqueous solution is 3-7 wt%; the concentration of hydrogen peroxide in the hydrogen peroxide solution is 25-32 wt%; the volume ratio of the ammonium salt aqueous solution to the hydrogen peroxide aqueous solution to the water is (6-10) to (2-3) to (28-32).

In some embodiments, the volume ratio of the solution A to the solution B is (35-45): (15-25).

In some of these embodiments, the mixing means for the reaction in step (3) is sonication, stirring, or ball milling.

In some of these embodiments, the conditions of the reaction in step (3) comprise: reacting for 0.5-24 h at room temperature.

In some of these embodiments, the reaction in step (3) is: stirring and reacting for 8-14 h at room temperature.

In some of these embodiments, the manganese salt of step (2) is manganese dichloride, manganese dichloride tetrahydrate, manganese carbonate, or manganese oxalate.

In some of these embodiments, the filtered reaction product of step (3) is washed and then dried, the washing comprising: washing with water for 2-3 times.

In some embodiments, the drying in step (3) comprises: drying at 60-120 ℃ for 12-36 h.

Another object of the present invention is to provide MnO prepared by the above preparation method₂A nanosheet catalytic material.

Another object of the present invention is to provide MnO as defined above₂The nanosheet catalytic material is applied to degrading formaldehyde, ozone or toluene.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, a specific kind of ammonium salt is matched with hydrogen peroxide to prepare solution A, then the solution A is slowly added into the solution B for reaction, the concentration of each component in the solution A and the solution B and the proportion of the components are controlled, and finally the prepared MnO is₂The nano-sheet catalytic material has high specific surface area and a plurality of active sites, and has good catalytic decomposition capability on indoor air pollutants at normal temperature.

Particularly, through a large number of experiments, the inventors of the present invention have found that: selecting ammonium salt as ammonium hydroxide, and reasonably controlling the concentration and the proportion of the ammonium hydroxide and the hydrogen peroxide to prepare the MnO₂The catalytic decomposition rate of the nanosheet catalytic material to formaldehyde, toluene and ozone is remarkably improved at normal temperature, the degradation rate to formaldehyde is more than 95%, the degradation rate to toluene is more than 82%, the degradation rate to ozone is more than 90%, the catalytic decomposition capability is very excellent, and the nanosheet catalytic material has a good application prospect.

MnO of the invention₂The nano-sheet catalytic material can keep higher activity and better stability at room temperature, has great potential in the aspects of air purification such as formaldehyde conversion, ozone degradation and the like, and has potential application prospects in the fields of water treatment, supercapacitors, energy storage and the like.

In addition, the method has mild preparation conditions, does not need heating treatment, is convenient and safe to operate, and is favorable for large-scale production.

Drawings

FIG. 1 shows MnO prepared in example 1₂SEM images of the nanosheet catalytic material;

FIG. 2 shows MnO prepared in example 2₂TEM images of the nanosheet catalytic material;

FIG. 3 shows MnO prepared in example 2₂TEM images of the nanosheet catalytic material (further magnified magnification image of fig. 2);

FIG. 4 shows MnO prepared in example 3₂SEM images of the nanosheet catalytic material;

FIG. 5 shows MnO prepared in example 5₂TEM images of the nanosheet catalytic material.

Detailed Description

In order that the invention may be more readily understood, reference will now be made to the following more particular description of the invention, examples of which are set forth below. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The invention provides MnO₂The preparation method of the nanosheet catalytic material comprises the following steps:

(3) adding the solution A into the solution B for reaction, filtering and drying after the reaction is finished to obtain MnO₂A nanosheet catalytic material;

Further, the concentration of ammonium salt in the ammonium salt aqueous solution is 5-50 wt%, and the concentration of hydrogen peroxide in the hydrogen peroxide aqueous solution is 10-30 wt%; the volume ratio of the solution A to the solution B is 25-45: 8 to 25.

The inventors of the present invention found out in their studies that the selection of the kind of ammonium salt and the concentration and ratio of each reactant to MnO₂The catalytic effect of the nano-sheet catalytic material has larger influence and can ensure that MnO is not present₂The decomposing capacities of the nano-sheet catalytic material to three indoor air pollutants of formaldehyde, toluene and ozone are different. Even if the same ammonium salt is used, when the concentration and the ratio of the raw materials are greatly changed, the MnO prepared is₂The catalytic effect of the nanosheet catalytic material will also be affected. On the basis, the inventor finally finds out through a large number of experimental researches that: the ammonium salt is ammonium hydroxide, the concentration of the ammonium salt in an ammonium salt aqueous solution is 3-7 wt%, the concentration of hydrogen peroxide in a hydrogen peroxide aqueous solution is 25-32 wt%, and the volume ratio of the ammonium salt aqueous solution to the hydrogen peroxide aqueous solution to water is (6-10): 2-3): 28-32, so that the prepared MnO is formed₂The nano-sheet catalytic material has transverse size less than 0.5 mu m, longitudinal size less than 2 mu m, high specific surface area and more active sites, remarkably improves the catalytic decomposition rate of formaldehyde, toluene and ozone at normal temperature, has the degradation rate of more than 95 percent for formaldehyde, more than 82 percent for toluene and more than 90 percent for ozone, and has good application prospect.

Further, the concentration of ammonium salt in the ammonium salt water solution is 4-6 wt%; the concentration of hydrogen peroxide in the hydrogen peroxide solution is 28-32 wt%; the volume ratio of the ammonium salt aqueous solution to the hydrogen peroxide aqueous solution to the water is (7-9): 2-3): 29-30. At this time, MnO was prepared₂The degradation rate of the nanosheet catalytic material to formaldehyde is more than or equal to 98%, the degradation rate to toluene is more than or equal to 85%, the degradation rate to ozone is more than or equal to 90%, and the nanosheet catalytic material has more excellent catalytic decomposition capability.

Further, a stirring mixing mode is selected, and the reaction time is controlled to be 6-16 h. Further, the reaction time is preferably 8-14 h, more preferably 9-12 h, and the prepared MnO is₂The nanosheet catalytic material is of a suitable size. When the reaction time is too long, MnO obtained by the preparation method₂The nano-sheet catalytic material has larger size, and the catalytic effect is reduced.

The present invention will be described in further detail with reference to specific examples.

Example 1

(1) mixing 7mL of ammonium bicarbonate solution (7 wt% aqueous solution) and 3mL of hydrogen peroxide solution (30 wt% aqueous solution) and adding the mixture into 30mL of water, and mixing and uniformly stirring to obtain solution A;

(2) weighing 1g of manganese dichloride (A.R.99.0%) and dissolving in 20mL of pure water to obtain solution B;

(3) slowly adding the solution A into the solution B, stirring and reacting for 6h at room temperature, filtering, washing with pure water for three times, and drying at 100 ℃ for 13h in air atmosphere to obtain MnO₂A nanosheet catalytic material.

Example 1 MnO prepared₂An SEM image of the nano-sheet catalytic material is shown in figure 1, wherein the transverse dimension of the nano-sheet catalytic material is 5-8 μm, and the longitudinal dimension of the nano-sheet catalytic material is 2-3 μm.

Example 2

(1) mixing 8mL of ammonium hydroxide solution (5 wt% aqueous solution) and 3mL of hydrogen peroxide solution (30 wt% aqueous solution) and adding the mixture into 30mL of water, and mixing and uniformly stirring to obtain solution A;

(3) slowly adding the solution A into the solution B, stirring at room temperature for 10h, filtering, washing with pure water for three times, and drying at 80 deg.C for 24h in air atmosphere to obtain MnO₂A nanosheet catalytic material.

EXAMPLE 2 MnO preparation₂TEM images of the nano-sheet catalytic material are shown in FIG. 2 and FIG. 3, the transverse dimension of the nano-sheet catalytic material is less than 0.5 μm, and the longitudinal dimension is less than 2 μm.

Example 3

(1) mixing 6mL of ammonium bisulfate solution (25 wt% aqueous solution) and 2mL of hydrogen peroxide solution (20 wt% aqueous solution) and adding the mixture into 30mL of water, and mixing and uniformly stirring to obtain solution A;

(2) weighing 0.7g of manganese (II) chloride tetrahydrate (A.R.99.0%) and dissolving in 20mL of pure water to obtain solution B;

(3) slowly adding the solution A into the solution B, ball-milling for 8h at room temperature, filtering, washing with pure water for three times, and drying for 36h at 120 ℃ in the air atmosphere to obtain MnO₂A nanosheet catalytic material.

Example 3 MnO prepared₂An SEM image of the nanosheet catalytic material is shown in FIG. 4, wherein the catalytic material has a transverse dimension of 3-5 μm and a longitudinal dimension of 1-2 μm.

Example 4

(1) mixing 9mL of ammonium bromide solution (50 wt% aqueous solution) and 2mL of hydrogen peroxide solution (30 wt% aqueous solution) and adding the mixture into 20mL of water, and mixing and uniformly stirring to obtain solution A;

(2) weighing 0.7g of manganese (II) chloride tetrahydrate (A.R. 99.0%) and dissolving in 10mL of pure water to obtain solution B;

(3) slowly adding the solution B into the solution A, ball-milling for 9h at room temperature, filtering, washing with pure water for three times, and drying at 110 ℃ for 34h in an air atmosphere to obtain MnO₂A nanosheet catalytic material.

Example 5

(1) mixing 8mL of ammonium hydroxide solution (7 wt% aqueous solution) and 3mL of hydrogen peroxide solution (25 wt% aqueous solution) and adding the mixture into 30mL of water, and mixing and uniformly stirring to obtain solution A;

Example 5 MnO prepared₂The TEM image of the nano-sheet catalytic material is shown in FIG. 5, the transverse dimension of the nano-sheet catalytic material is less than 0.5 μm, and the longitudinal dimension of the nano-sheet catalytic material is less than 2 μm.

Comparative example 1

(1) mixing 8mL of ammonium hydroxide solution (10 wt% aqueous solution) and 4mL of hydrogen peroxide solution (30 wt% aqueous solution) and adding the mixture into 30mL of water, and mixing and uniformly stirring to obtain solution A;

Comparative example 2

(1) mixing 8mL of ammonium hydroxide solution (15 wt% aqueous solution) and 4mL of hydrogen peroxide solution (30 wt% aqueous solution) and adding the mixture into 30mL of water, and mixing and uniformly stirring to obtain solution A;

MnO₂Evaluation of catalytic Effect of nanosheet catalytic Material

MnO-MnO₂Evaluation of catalytic effect of nanosheet catalytic material on formaldehyde

Self-made two 0.125m³One glass experiment box is used for placing a test sample and is a sample box; the other was placed with a blank glass plate as a comparison box. And each joint of the glass experiment box is treated by Vaseline and sealant. An air collecting port is reserved in the center of the side wall of the experiment box, and a small fan is arranged on the left side of the experiment box and used for homogenizing air in the box.

0.3g of MnO prepared in example and comparative example, respectively₂The nano-sheet catalytic material is uniformly sprayed on 80 multiplied by 80cm²At a temperature of 25 ℃ and a relative humidity of (50. + -. 10)% after 24h of drying the experiment was carried out.

And respectively putting the prepared experimental sample plate and the blank glass plate with the same area into an experimental box and a comparison box, and sealing the experimental box. mu.L (3 +/-0.25) of analytically pure formaldehyde is taken by a micro syringe, dropped into a blank glass dish preset in an experimental box and a comparison box through an injection hole, and the injection hole is sealed.

The gas in the collection box is collected after being sealed for 1h to test the concentration of the gas, and the concentration is the initial concentration n₀. Collecting gas in the box after 24h and testing the concentration of the gas, wherein the concentration is termination concentration n₁. The fan is turned on for 30min before gas collection and turned off during sampling.

The formaldehyde concentration was determined by AHMT spectrophotometry according to GB/T16129.

Second, MnO₂Evaluation of catalytic effect of nanosheet catalytic material on toluene

0.3g of MnO prepared in example and comparative example, respectively₂The nano-sheet catalytic material is uniformly sprayed on 80 multiplied by 80cm²The test was carried out after drying one surface of the glass plate at a temperature of 25 ℃ and a relative humidity of (50. + -. 10)% for 24 hours.

And respectively putting the prepared experimental sample plate and the blank glass plate with the same area into an experimental box and a comparison box, and sealing the experimental box. mu.L (3 +/-0.25) of analytically pure toluene is taken by a micro-syringe, dropped into a blank glass dish preset in an experimental box and a comparison box through an injection hole, and the injection hole is sealed.

Test analysis of the toluene concentration gas chromatography was used in accordance with GB/T11737.

MnO, III₂Evaluation of catalytic effect of nanosheet catalytic material on ozone

And respectively putting the prepared experimental sample plate and the blank glass plate with the same area into an experimental box and a comparison box, and sealing the experimental box. Quantitative standard ozone is introduced into the experiment box and the comparison box through the micro-flow controller, and the injection hole is sealed.

The ozone concentration was measured and analyzed by GB/T T15437 sodium indigo disulfonate spectrophotometry.

TABLE 1 MnO₂Evaluation results of catalytic Activity of nanosheet catalytic Material

As is clear from Table 1, MnO prepared in the examples of the present invention₂The nano-sheet catalytic material has good catalytic decomposition capability on indoor air pollutants, and the degradation rate of the indoor air pollutants at normal temperature is obviously improved.

The inventor finds that in the field of nano materials, the process parameters have very important influence on the properties and performances of the nano materialsAnd (6) sounding. In the embodiments 2 and 5 of the invention, ammonium salt is selected as ammonium hydroxide, the concentration of an ammonium hydroxide aqueous solution is controlled to be 3-7 wt%, the concentration of hydrogen peroxide is controlled to be 25-32 wt%, and the volume ratio of the ammonium hydroxide aqueous solution, the hydrogen peroxide aqueous solution and water is (6-10): 2-3): 28-32, so as to prepare the MnO₂The lateral dimension of the nanosheet catalytic material is < 0.5 μm, lower than in the other examples. And MnO prepared in examples 2 and 5₂The degradation rate of the nanosheet catalytic material to formaldehyde is more than 95% at normal temperature, the degradation rate to toluene is more than 82%, the degradation rate to ozone is more than 90%, and the catalytic decomposition rates to formaldehyde, toluene and ozone at normal temperature are all very good and are far higher than those of other embodiments and comparative examples.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. MnO (MnO)₂The preparation method of the nanosheet catalytic material is characterized by comprising the following steps:

2. The preparation method of claim 1, wherein the concentration of ammonium salt in the ammonium salt aqueous solution is 5-50 wt%, and the concentration of hydrogen peroxide in the hydrogen peroxide aqueous solution is 10-30 wt%; the volume ratio of the solution A to the solution B is 25-45: 8 to 25.

3. The method of claim 1, wherein the ammonium salt is selected from ammonium hydroxide.

4. The preparation method according to claim 3, wherein the concentration of the ammonium salt in the ammonium salt aqueous solution is 3 to 7 wt%; the concentration of hydrogen peroxide in the hydrogen peroxide solution is 25-32 wt%; the volume ratio of the ammonium salt aqueous solution to the hydrogen peroxide aqueous solution to the water is (6-10) to (2-3) to (28-32).

5. The preparation method according to claim 3, wherein the volume ratio of the solution A to the solution B is (35-45): (15-25).

6. The production method according to claim 3, wherein the reaction in step (3) is: stirring and reacting for 8-14 h at room temperature.

7. The method according to any one of claims 1 to 6, wherein the manganese salt in the step (2) is manganese dichloride, manganese dichloride tetrahydrate, manganese carbonate or manganese oxalate.

8. The method according to any one of claims 1 to 6, wherein the reaction product after filtration in step (3) is washed and then dried; the washing comprises the following steps: washing with water for 2-3 times;

and/or, the drying process in the step (3) comprises the following steps: drying at 60-120 ℃ for 12-36 h.

9. MnO obtainable by the process according to any one of claims 1 to 8₂A nanosheet catalytic material.

10. The MnO of claim 9₂The nanosheet catalytic material is applied to degrading formaldehyde, ozone or toluene.