A diatomite-loaded carbon-doped manganese dioxide composite material and its preparation method and application

Abstract

The present invention relates to the technical field of mineral-supported composite catalytic materials, and relates to a diatomaceous earth-supported carbon-doped manganese dioxide composite material, and a preparation method and application thereof. The present invention provides a diatomaceous earth-supported carbon-doped manganese dioxide composite material, comprising diatomaceous earth and carbon-doped manganese dioxide supported on the surface and in the pores of the diatomaceous earth; the carbon-doped manganese dioxide has an oxygen vacancy structure. The diatomaceous earth-supported carbon-doped manganese dioxide composite material provided in the present invention has strong adsorption performance for formaldehyde, and the carbon-doped manganese dioxide has an oxygen vacancy structure. Therefore, compared with pure manganese dioxide, more active sites are exposed after loading and doping, thereby improving the catalytic oxidation performance for formaldehyde.

Description

Technical Field

[0001] The invention relates to the technical field of mineral-supported composite catalytic materials, and relates to a diatomaceous earth-supported carbon-doped manganese dioxide composite material, a preparation method and application thereof. Background Art

[0002] Formaldehyde gas is the main pollutant in indoor air, mainly from artificial boards used for indoor decoration, adhesives with formaldehyde as the main raw material, and other decorative materials that contain formaldehyde and may emit it to the outside, such as wall coverings, wallpapers, paints and coatings. Indoor formaldehyde has the characteristics of low concentration, wide sources, and long release cycle. Existing conventional air purification technology is difficult to use for efficient and long-term purification of formaldehyde in indoor air. Therefore, how to achieve sustainable purification of indoor gaseous formaldehyde has become a technical problem and research hotspot in this field.

[0003] At present, formaldehyde purification technologies mainly include adsorption, photocatalysis, thermal catalysis and room temperature catalytic oxidation, among which: the adsorption method has the problem of easy saturation and difficult circulation; although the photocatalytic technology and thermal catalytic technology have the advantages of wide applicability and recyclability, they have the problem of requiring additional energy input. The room temperature catalytic oxidation method has the advantages of no additional energy input, high efficiency and long duration, and shows good application prospects in the field of formaldehyde treatment in home environments. In the room temperature catalytic oxidation technology, the most widely studied catalyst is manganese dioxide. Compared with other more efficient precious metal catalysts, manganese dioxide catalysts have the advantages of simple preparation, low production cost and wide application. However, the existing manganese dioxide catalyst needs to be at a higher temperature (generally above 50°C) to quickly achieve complete oxidation of formaldehyde. In the indoor environment at room temperature (10-30°C), the efficiency of catalytic oxidation of formaldehyde (converting formaldehyde into carbon dioxide) is low (only 88.93%). Summary of the invention

[0004] In view of this, the present invention provides a diatomaceous earth loaded carbon doped manganese dioxide composite material and a preparation method and application thereof. The diatomaceous earth loaded carbon doped manganese dioxide composite material provided by the present invention can achieve efficient removal of indoor formaldehyde.

[0005] In order to achieve the above-mentioned purpose of the invention, the present invention provides a diatomite-loaded carbon-doped manganese dioxide composite material, comprising diatomite and carbon-doped manganese dioxide loaded on the surface and in the pores of the diatomite; the carbon-doped manganese dioxide has an oxygen vacancy structure.

[0006] Preferably, the carbon doping rate of the carbon-doped manganese dioxide is 5-20%.

[0007] Preferably, the mass ratio of the diatomaceous earth to the carbon-doped manganese dioxide is 1:0.4-0.7.

[0008] The present invention also provides a method for preparing the above-mentioned diatomite-loaded carbon-doped manganese dioxide composite material, comprising the following steps:

[0009] The slurry of high-calcined diatomite and an aqueous solution of potassium permanganate are mixed, and the obtained reaction material is dried and calcined in sequence under a protective atmosphere to obtain the diatomite-loaded carbon-doped manganese dioxide composite material;

[0010] The calcination temperature is 500-600° C., and the heat preservation time is 2-4 hours.

[0011] Preferably, the heating rate to the calcination temperature is 1 to 10° C. / min.

[0012] Preferably, the organic matter content of the high-loss-on-ignition diatomaceous earth is 15% to 50%.

[0013] Preferably, the mass ratio of the high-burnt diatomaceous earth to potassium permanganate is 1:0.75-1.25.

[0014] Preferably, the drying temperature is 100-110°C.

[0015] The present invention also provides the use of the above-mentioned diatomaceous earth-loaded carbon-doped manganese dioxide composite material as a catalyst.

[0016] Preferably, the catalyst is used for catalytic oxidation of formaldehyde.

[0017] The present invention provides a diatomite-loaded carbon-doped manganese dioxide composite material, comprising diatomite and carbon-doped manganese dioxide loaded on the surface and in the pores of the diatomite; the carbon-doped manganese dioxide has an oxygen vacancy structure. The diatomite-loaded carbon-doped manganese dioxide composite material provided by the present invention has strong adsorption performance for formaldehyde, and the carbon-doped manganese dioxide has an oxygen vacancy structure, so that compared with manganese dioxide, more active sites are exposed, thereby improving the catalytic oxidation performance for formaldehyde.

[0018] The present invention also provides a method for preparing the diatomite-loaded carbon-doped manganese dioxide composite material described above, wherein the slurry of high-burnt diatomite and an aqueous solution of potassium permanganate are mixed, and the resulting reaction material is dried and roasted in sequence under a protective atmosphere to obtain the diatomite-loaded carbon-doped manganese dioxide composite material; the roasting temperature is 500-600°C, and the heat preservation time is 2-4 hours. In the present invention, during the roasting process, the organic matter on the surface and pores of the high-burnt diatom is in-situ carbonized into amorphous carbon and potassium permanganate is reduced, and at the same time, the amorphous carbon is doped into the manganese dioxide crystal, causing lattice distortion, exposing Mn 4+ and oxygen vacancies, exposing more active sites and improving the catalytic oxidation performance of formaldehyde. DETAILED DESCRIPTION

[0019] The invention provides a diatomite-loaded carbon-doped manganese dioxide composite material, comprising diatomite and carbon-doped manganese dioxide loaded on the surface and in the pores of the diatomite; the carbon-doped manganese dioxide has an oxygen vacancy structure.

[0020] In the present invention, the diatomaceous earth in the diatomaceous earth-loaded carbon-doped manganese dioxide composite material preferably does not contain organic matter.

[0021] In the present invention, the carbon doping rate of the carbon doped manganese dioxide is preferably 5-20%, more preferably 10-15%. In the present invention, the mass ratio of the diatomite to the carbon doped manganese dioxide is preferably 1:0.4-0.7, more preferably 1:0.4-0.6.

[0022] In the present invention, part of the organic matter in the high-calcined diatomite will be burned and separated in a high-temperature inert gas atmosphere, and part of it will be transformed into amorphous carbon and doped into manganese dioxide crystals. Therefore, the organic matter content in the diatomite is not equal to the carbon doping rate.

[0023] The present invention also provides a method for preparing the above-mentioned diatomite-loaded carbon-doped manganese dioxide composite material, comprising the following steps:

[0024] The ore pulp of high-calcined diatomite and the aqueous solution of potassium permanganate are mixed, and the obtained reaction material is dried and roasted in sequence under a protective atmosphere to obtain the diatomite-loaded carbon-doped manganese dioxide composite material; the roasting temperature is 500-600° C., and the insulation time is 2-4 hours.

[0025] In the present invention, the organic matter content of the high-burned diatomite is preferably 15-50%, more preferably 20-40%. In the present invention, the diatomite slurry preferably includes diatomite and water, and the mass ratio of the high-burned diatomite to water in the high-burned diatomite slurry is preferably 1:90-110, more preferably 1:95-105. In the present invention, the mass concentration of potassium permanganate in the aqueous solution of potassium permanganate is preferably 0.90-1.95%, more preferably 0.95-1.90%.

[0026] In the present invention, the mass ratio of the high-loss-on-ignition diatomaceous earth to potassium permanganate is preferably 1:0.75-1.25, more preferably 1:1.

[0027] In the present invention, the mixing is preferably performed by dripping the aqueous solution of potassium permanganate into the diatomite slurry. In the present invention, the dripping speed is preferably 10 to 50 drops / min, more preferably 20 to 30 drops / min.

[0028] In the present invention, the drying temperature is preferably 100-110° C., more preferably 105° C. In the present invention, the drying can remove moisture from the reaction materials, preventing the moisture in the system and the organic matter in the high-burning diatomaceous earth from reacting at high temperature, thereby affecting the reaction between the organic matter and manganese dioxide.

[0029] In the present invention, the protective atmosphere is preferably nitrogen. In the present invention, the calcination temperature is preferably 400-800°C, more preferably 500-700°C, and most preferably 600°C; the holding time is preferably 2-4h, and more preferably 3h. In the present invention, the heating rate to the calcination temperature is preferably 1-10°C / min, more preferably 3-6°C / min, and most preferably 5°C / min. In the present invention, during the calcination process, the organic matter on the surface and pores of the high-burned diatom is in-situ carbonized into amorphous carbon and reduced to potassium permanganate, and at the same time, the amorphous carbon is doped into the manganese dioxide crystals, causing lattice distortion and exposing Mn 4+ and oxygen vacancies, which improves the catalytic activity of the composites.

[0030] The present invention also provides the use of the above-mentioned diatomaceous earth-loaded carbon-doped manganese dioxide composite material as a catalyst.

[0031] In the present invention, the catalyst is used for catalytic oxidation of formaldehyde; the external environment for catalytic oxidation of formaldehyde is preferably an indoor environment, the temperature is preferably room temperature, and the humidity is preferably 35-45%.

[0032] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] 1 g of high-burnt diatomaceous earth (organic matter content of 30%) was added to 100 mL of water and stirred evenly to obtain a slurry of high-burnt diatomaceous earth.

[0035] Add 1 g of potassium permanganate into 100 mL of water and stir evenly to obtain an aqueous solution of potassium permanganate.

[0036] The aqueous solution of potassium permanganate is added drop by drop into the slurry of high-burnt diatomite, stirred evenly, and dried at 105°C. After the dried product is ground, it is heated to 600°C at a heating rate of 5°C / min in a nitrogen atmosphere, and heat treated at 600°C for 3h to obtain the diatomite-loaded carbon-doped manganese dioxide composite material.

[0037] Example 2

[0038] The only difference from Example 1 is that the organic matter content of the high-burnt diatomaceous earth is 15%.

[0039] Example 3

[0040] The only difference from Example 1 is that the organic matter content of the high-burnt diatomaceous earth is 25%.

[0041] Example 4

[0042] The only difference from Example 1 is that the organic matter content of the high-burnt diatomaceous earth is 30%.

[0043] Example 5

[0044] The only difference from Example 1 is that the calcination temperature is 500°C.

[0045] Example 6

[0046] The only difference from Example 1 is that 0.75 g of potassium permanganate is added.

[0047] Example 7

[0048] The only difference from Example 1 is that 1.25 g of potassium permanganate is added.

[0049] Comparative Example 1

[0050] The only difference from Example 1 is that no high-calcined diatomaceous earth is added.

[0051] Comparative Example 2

[0052] The only difference from Example 1 is that the organic matter content in the diatomaceous earth is 0%.

[0053] Comparative Example 3

[0054] The only difference from Example 1 is that the organic matter content in the diatomaceous earth is 3%.

[0055] Comparative Example 4

[0056] The only difference from Example 1 is that 0.5 g of potassium permanganate is added.

[0057] Comparative Example 5

[0058] The only difference from Example 1 is that 1.5 g of potassium permanganate is added.

[0059] Comparative Example 6

[0060] The only difference from Example 1 is that the calcination atmosphere is air.

[0061] Comparative Example 7

[0062] The difference from Example 1 is that the calcination temperature is 400° C. and the calcination time is 6 hours.

[0063] Comparative Example 8

[0064] The difference from Example 1 is that the calcination temperature is 800° C. and the calcination time is 1 hour.

[0065] Comparative Example 9

[0066] Comparative Example 1 is a commercially available activated carbon adsorption product.

[0067] Comparative Example 10

[0068] Comparative Example 2 is a commercially available activated manganese decomposition felt (model: ZF-A10).

[0069] Test Case

[0070] 1. Instruments and Equipment

[0071] Reaction box: Dimensions are 50×50×50cm, with built-in fan, heating plate, object holder, and temperature and humidity sensors.

[0072] Micro syringe: specification is 25μL, accuracy is 0.1μL.

[0073] Infrared photoacoustic spectrometer: can monitor the concentration of gaseous formaldehyde and carbon dioxide in real time.

[0074] 2. Detection method

[0075] According to the national standard "GB / T16129-1995 Standard method for hygienic examination of formaldehyde in the atmosphere of residential areas - spectrophotometry", the carbon dioxide concentration in the reactor is monitored in real time by an infrared photoacoustic spectrometer.

[0076] 3. Test steps

[0077] 2.1 Weigh 1g of diatomaceous earth-loaded carbon-doped manganese dioxide composite material and spread it evenly on a glass container and place it on the temperature sensor. Then inject 2.5μL of formaldehyde solution onto the heating plate of the sealed box and seal the box.

[0078] 2.2 Turn on the heating plate, infrared photoacoustic spectrometer and fan. After the formaldehyde solution has completely evaporated, turn off the heating plate, start the first sampling, calculate the initial formaldehyde concentration, and record the initial carbon dioxide concentration measured by the infrared photoacoustic spectrometer.

[0079] 2.3 After reacting for 1 h at a temperature of 26°C and a relative humidity of 40% Rh, take a second sample, calculate the final formaldehyde concentration, and record the results measured by the infrared photoacoustic spectrometer, and calculate the final carbon dioxide concentration.

[0080] 4. Result calculation

[0081] (1) The removal rate is calculated according to Formula I:

[0082]

[0083] In Formula I, X 1 ——removal rate, %;

[0084] C 2 ——The initial concentration of formaldehyde, in milligrams per cubic meter (mg / m 3 );

[0085] C 3 ——Final formaldehyde concentration, in milligrams per cubic meter (mg / m 3 ).

[0086] (2) The conversion rate is calculated according to Formula II:

[0087]

[0088] X 2 ——conversion rate, %;

[0089] C 1 ——The initial concentration of formaldehyde, in milligrams per cubic meter (mg / m 3 );

[0090] C 3 ——The initial concentration of carbon dioxide, in milligrams per cubic meter (mg / m 3 );

[0091] C 4 ——Final concentration of carbon dioxide, in milligrams per cubic meter (mg / m 3 ).

[0092] Tables 1 and 2 are statistical results of formaldehyde removal rate and conversion rate of the products obtained from Examples 1 to 7 and Comparative Examples 1 to 10, respectively.

[0093] Table 1 Results of removal and conversion rates of formaldehyde by the products obtained in Examples 1 to 7

[0094]

[0095] Table 2 Results of removal rate and conversion rate of formaldehyde by the products obtained in comparative examples 1 to 10

[0096]

[0097] From Tables 1 to 2, it can be seen that Comparative Examples 1 to 3 show that diatomaceous earth with different organic matter contents can improve the catalytic activity of manganese dioxide, and diatomaceous earth with strong adsorption performance enriches formaldehyde, which greatly improves the formaldehyde removal rate. Comparative Examples 4 and 5 show that too low or too high a mass ratio of diatomaceous earth to potassium permanganate will reduce the catalytic performance of the catalyst; if the mass ratio is too high, the manganese oxide crystal growth is poor, the active sites are fewer, and the catalytic effect is reduced, while if the mass ratio is too low, the diatomaceous earth organic matter doping effect becomes poor, which also reduces the catalyst active sites and the catalytic performance is not ideal. Comparative Example 6 shows that the activity of the composite material obtained under air atmosphere is reduced, because the organic matter in diatomaceous earth under air atmosphere is difficult to be converted into amorphous carbon and doped into manganese oxide crystals. Comparative Examples 7 to 8 show that if the reaction temperature is too low or too high, and the reaction time is too short or too long, it will affect the crystal growth of manganese oxide and the doping of organic matter, thereby reducing the removal rate and conversion rate of formaldehyde. Comparative Examples 7 to 8 show that commercially available activated carbon and commercially available manganese dioxide formaldehyde removal products are difficult to completely remove formaldehyde and efficiently decompose formaldehyde under the conditions of a temperature of 26° C. and a relative humidity of 40% Rh.

[0098] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A diatomite-loaded carbon-doped manganese dioxide composite material, characterized in that: It comprises diatomite and carbon-doped manganese dioxide loaded on the surface and in the pores of the diatomite; the carbon-doped manganese dioxide has an oxygen vacancy structure; The method for preparing the diatomite-loaded carbon-doped manganese dioxide composite material comprises the following steps: The slurry of high-calcined diatomite and an aqueous solution of potassium permanganate are mixed, and the obtained reaction raw material liquid is dried and calcined in sequence under a protective atmosphere to obtain the diatomite-loaded carbon-doped manganese dioxide composite material; The calcination temperature is 500-600°C and the holding time is 2-4h; The organic matter content of the high-burnt diatomaceous earth is 15% to 50%; The mass ratio of the high-burnt diatomaceous earth to potassium permanganate is 1:0.75-1.

25.

2. The diatomite-loaded carbon-doped manganese dioxide composite material according to claim 1, characterized in that: The carbon doping rate of the carbon-doped manganese dioxide is 5-20%.

3. The diatomite-supported carbon-doped manganese dioxide composite material according to claim 1 or 2, characterized in that: The mass ratio of the diatomaceous earth to the carbon-doped manganese dioxide is 1:0.4-0.

7.

4. The method for preparing the diatomite-supported carbon-doped manganese dioxide composite material according to any one of claims 1 to 3, characterized in that: The following steps are involved: The slurry of high-calcined diatomite and an aqueous solution of potassium permanganate are mixed, and the obtained reaction raw material liquid is dried and calcined in sequence under a protective atmosphere to obtain the diatomite-loaded carbon-doped manganese dioxide composite material; The calcination temperature is 500-600°C and the holding time is 2-4h; The organic matter content of the high-burnt diatomaceous earth is 15% to 50%; The mass ratio of the high-burnt diatomaceous earth to potassium permanganate is 1:0.75-1.

25.

5. The preparation method according to claim 4, characterized in that: The heating rate to the calcination temperature is 1-10°C / min.

6. The preparation method according to claim 4, characterized in that: The drying temperature is 100-110°C.

7. Use of the diatomaceous earth-loaded carbon-doped manganese dioxide composite material according to any one of claims 1 to 3 as a catalyst.

8. The use according to claim 7, characterized in that The catalyst is used for catalytic oxidation of formaldehyde.

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