A method for preparing boron nitride nanotubes by using continuous furnace tail gas

Abstract

The application provides a method for preparing boron nitride nanotubes by using tail gas of a continuous furnace for producing hexagonal boron nitride, and the method uses the tail gas of the continuous furnace for producing hexagonal boron nitride as raw material, and uses a stainless steel net as a substrate to prepare boron nitride nanotubes in a high-temperature furnace at 800-1600 DEG C. The application innovatively uses the tail gas of the continuous furnace for producing hexagonal boron nitride as raw material to prepare boron nitride nanotubes, and makes the boron nitride nanotubes grow on the stainless steel net, so that not only the production of kilogram boron nitride nanotubes is realized, but also the yield of the boron nitride nanotubes is greatly improved, and the problem of tail gas emission in the production of hexagonal boron nitride is solved, so that the purpose of cost reduction and efficiency improvement, green and saving is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of inorganic non-metallic material synthesis, and particularly relates to a method for preparing boron nitride nanotubes by using continuous furnace tail gas. BACKGROUND

[0002] As a one-dimensional nanomaterial that has attracted much attention, boron nitride nanotubes can be regarded as a tubular structure formed by curling boron nitride nanosheets. Boron nitride nanotubes have excellent mechanical strength, chemical corrosion resistance, high thermal shock resistance, and extremely strong high-temperature stability, and also have high specific surface area and good adsorption, making them have broad application prospects in biological probes, hydrogen storage materials, photoelectric instruments, aerospace, special ceramics, high-strength fiber materials, and semiconductor materials. In addition, 10B in boron nitride nanotubes can be absorbed into 11B, and the cross section of absorption is large, so boron nitride nanotubes can also be used as radiation shielding materials.

[0003] At present, the preparation of boron nitride nanotubes is still limited to the laboratory, small batches, or even micro-level. Although these methods can produce boron nitride nanotubes with good product morphology and performance in the laboratory, there are problems such as unstable product quality, large amount of waste, low yield, incomplete reaction, and the like when scaling up experiments and industrial production.

[0004] The raw materials used in the production process of hexagonal boron nitride powder are boric acid and melamine, and the raw materials are fired into hexagonal boron nitride powder by high-temperature continuous furnace. In the production process of hexagonal boron nitride, the tail gas produced usually contains boron vapor, nitrogen oxides, ammonia, boron nitride dust, nitrogen, etc. After treatment, the continuous furnace tail gas needs to meet the standards of “Building Materials Industry Air Pollutant Discharge Standard” (DB37 / 2373-2018), “Comprehensive Discharge Standard for Air Pollutants” (GB16297-1996), etc. before it can be discharged. The tail gas treatment process increases the production cost and energy consumption.

[0005] Therefore, it is of great significance to utilize the continuous furnace tail gas of hexagonal boron nitride in actual production and combine it with the preparation technology of boron nitride nanotubes for the industrial production of hexagonal boron nitride and boron nitride nanotubes. SUMMARY

[0006] The present application provides a method for preparing boron nitride nanotubes by using continuous furnace tail gas for producing hexagonal boron nitride, which not only solves the problem of batch production of boron nitride nanotubes, but also solves the problem of treatment of continuous furnace tail gas of hexagonal boron nitride, thereby achieving green production.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] A method for preparing boron nitride nanotubes by using tail gas of a continuous furnace for producing hexagonal boron nitride, comprising the following steps:

[0009] (1) placing stainless steel mesh as a substrate in a high-temperature furnace after cleaning with dilute hydrochloric acid;

[0010] (2) slowly heating the high-temperature furnace to 800-1600 ℃;

[0011] (3) delivering tail gas and protective atmosphere in the continuous furnace for producing hexagonal boron nitride into the high-temperature furnace to prepare boron nitride nanotubes on the stainless steel mesh substrate;

[0012] (4) after the reaction is completed, cooling the high-temperature furnace to room temperature, taking out the stainless steel mesh substrate, and obtaining the substrate with boron nitride nanotubes grown thereon;

[0013] (5) placing the boron nitride nanotubes grown on the substrate in anhydrous ethanol, ultrasonic dispersing, and then filtering and collecting;

[0014] (6) washing the filtered boron nitride nanotubes with distilled water and dilute hydrochloric acid to pH=1-3, then washing with distilled water to neutral, and drying to obtain boron nitride nanotubes.

[0015] In some embodiments of the present application, the total length of the stainless steel mesh in the high-temperature furnace in step (1) is 50-500 cm, for example, 100 cm, 150 cm, 200 cm, 250 cm, 300 cm, 350 cm, 400 cm, 450 cm, or 500 cm; and the interval of the stainless steel mesh in the high-temperature furnace is 5-30 cm, for example, 5 cm, 10 cm, 15 cm, 20 cm, 25 cm, or 30 cm.

[0016] The multiple stainless steel meshes arranged at a certain distance in the high-temperature furnace not only improve the production efficiency, but also realize the production of boron nitride nanotubes in kilograms, greatly improving the yield of boron nitride nanotubes.

[0017] In some embodiments of the present application, the concentration of the dilute hydrochloric acid in step (1) is 0.01%-1%, preferably 0.05-1%, for example, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%; more preferably 0.1-1%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%.

[0018] In some embodiments of the present application, the stainless steel mesh in step (1) is preferably type 304, 316, 201; the pore size of the stainless steel mesh is 10-200 mesh, and is further preferably 10 mesh, 12 mesh, 14 mesh, 16 mesh, 18 mesh, 20 mesh, 25 mesh, 30 mesh, 35 mesh, 40 mesh, 45 mesh, 50 mesh, 60 mesh, 70 mesh, 80 mesh, 100 mesh, 120 mesh, 140 mesh, 170 mesh, or 200 mesh.

[0019] The use of a stainless steel mesh as a substrate can increase the contact area of the slurry and fully wrap the slurry around the gas, making the reaction more complete and thus more uniformly generating boron nitride nanotubes. Too small a pore size can cause clogging and is not conducive to gas flow, while too large a pore size can result in incomplete reaction, reduced gas utilization, and reduced yield.

[0020] In some embodiments of the present application, the high-temperature furnace in step (2) is heated to a temperature of 900-1600℃, for example, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, 1500℃, 1550℃, or 1600℃, and the temperature is raised at a rate of 5-10℃ / min.

[0021] In some embodiments of the present application, the protective atmosphere in step (3) is at least one of nitrogen, argon, helium, and neon; the flow rate of the protective atmosphere is 1-10 L / min, and is preferably 2-8 L / min; and the flow rate of the continuous furnace tail gas is 1-8 L / min.

[0022] The tail gas in the continuous furnace for producing hexagonal boron nitride contains boron vapor, nitrogen oxides, ammonia, boron nitride dust, and nitrogen, and the output tail gas does not need to be treated and can be directly introduced into the high-temperature furnace for the preparation of boron nitride nanotubes. In the subsequent purification process of boron nitride nanotubes, impurities can be easily removed to obtain high-purity boron nitride nanotubes. This method not only greatly simplifies the treatment process of the continuous furnace tail gas and reduces the cost of tail gas treatment, but also provides a cheap raw material source for the production of boron nitride nanotubes and realizes green production.

[0023] In some embodiments of the present application, the reaction time in step (4) is 1-60 min, and is preferably 10-60 min, for example, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, or 60 min. The longer the heat treatment time, the more boron nitride nanotubes are generated, but too long a time can cause the stainless steel mesh to be completely clogged, some boron nitride nanotubes can be discharged through the exhaust pipe, and even cause danger.

[0024] In some embodiments of the present application, the time for ultrasonic dispersion in step (5) is 5-30 min.

[0025] In some embodiments of the present application, the concentration of the dilute hydrochloric acid in step (6) is 0.5-1%, for example 0.5%, 0.75%, 1%; the drying temperature is 60-90 ℃, for example 60 ℃, 70 ℃, 80 ℃, 90 ℃; and the drying time is 1-24 h, for example 1 h, 3 h, 5 h, 7 h, 9 h, 11 h, 13 h, 18 h, 20 h, 22 h, 24 h.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] The present application innovatively uses the tail gas from the production of hexagonal boron nitride as raw material to prepare boron nitride nanotubes, and grows the boron nitride nanotubes on a stainless steel mesh, which not only realizes the production of boron nitride nanotubes in kilograms, greatly improves the yield of boron nitride nanotubes, but also solves the problem of tail gas emission from the production of hexagonal boron nitride, achieves cost reduction and efficiency improvement, and achieves the purpose of green and saving. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 SEM image of the boron nitride nanotubes prepared in Example 1 of the present application. EMBODIMENT

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. In addition, it is worth noting that the raw materials involved in the present application are ordinary commercially available products unless otherwise specified. EMBODIMENT

[0030] The present embodiment provides a method for preparing boron nitride nanotubes using continuous furnace tail gas from the production of hexagonal boron nitride, comprising the following steps:

[0031] (1) A 304 type stainless steel mesh is soaked in 0.5% dilute hydrochloric acid for 15 min, then the acid solution on the surface of the stainless steel mesh is washed off with ultrapure water and dried, and then the stainless steel mesh is arranged in a 300 cm high temperature furnace at an interval of 15 cm;

[0032] (2) The tail gas from the continuous furnace for producing hexagonal boron nitride is introduced into a high temperature furnace at 1500 ℃, and nitrogen gas is introduced as a protective atmosphere, and the flow rates of the tail gas and the nitrogen gas are 8 L / min and 7 L / min, respectively;

[0033] (3) keep the temperature for 25 min, then cool to room temperature, take out the stainless steel net;

[0034] (4) immerse the stainless steel substrate in anhydrous ethanol, ultrasonic for 10 min, then collect the boron nitride nanotubes in anhydrous ethanol by filtration;

[0035] (5) the filtered boron nitride nanotubes are washed by distilled water, 0.5% dilute hydrochloric acid to pH=1, distilled water to pH=7 respectively, and the boron nitride nanotubes after each washing are collected by filtration; the washed boron nitride nanotubes are dried in a vacuum drying box, the drying temperature is 60 ℃, and the drying time is 12 h, to obtain the final high-purity boron nitride nanotubes.

[0036] Figure 1 It is a SEM photo of the boron nitride nanotubes, from which it can be seen that the boron nitride nanotube morphology presents an elongated tubular shape, the surface is smooth, there is no nodal material, the diameter is about 100 nm, which is consistent with the related characteristics of boron nitride nanotubes.

[0037] Finally, it should be noted that the above content is only used to illustrate the technical solutions of the present application, and is not a limitation on the protection scope of the present application. Simple modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A method for preparing boron nitride nanotubes using the tail gas of a continuous furnace for producing hexagonal boron nitride, comprising the following steps: (1) placing a stainless steel mesh as a substrate, washing it with dilute hydrochloric acid, and then placing the stainless steel mesh in a high-temperature furnace; (2) slowly heating the high-temperature furnace to 800-1600°C; (3) delivering the tail gas of the continuous furnace for producing hexagonal boron nitride and a protective atmosphere into the high-temperature furnace to prepare boron nitride nanotubes on the stainless steel mesh substrate; the tail gas of the continuous furnace for producing hexagonal boron nitride is not treated and is directly delivered into the high-temperature furnace for the preparation of boron nitride nanotubes; the raw material for preparing boron nitride nanotubes is composed of the tail gas of the continuous furnace for producing hexagonal boron nitride and the protective atmosphere; (4) after the reaction is completed, cooling the high-temperature furnace to room temperature, taking out the stainless steel mesh substrate, and obtaining the substrate with boron nitride nanotubes grown thereon; (5) placing the boron nitride nanotubes grown on the substrate in anhydrous ethanol, ultrasonically dispersing, and then filtering and collecting; (6) filtering the boron nitride nanotubes, washing them with distilled water, dilute hydrochloric acid to pH = 1-3, then washing them with distilled water to neutral, and drying to obtain boron nitride nanotubes.

2. The method of claim 1, wherein, The total length of the stainless steel mesh in the high-temperature furnace in step (1) is 50-500 cm; the interval of the stainless steel mesh in the high-temperature furnace is 5-30 cm.

3. The method of claim 1, wherein, The concentration of the dilute hydrochloric acid in step (1) is 0.01%-1%.

4. The method of claim 1, wherein, The concentration of the dilute hydrochloric acid in step (1) is 0.1-1%.

5. The method of claim 1, wherein, The type of the stainless steel mesh in step (1) is 304, 316, or 201; the pore size of the stainless steel mesh is 10-200 mesh.

6. The method of claim 1, wherein, The heating temperature of the high-temperature furnace in step (2) is 900-1600°C; the heating rate is 5-10°C / min.

7. The method of claim 1, wherein, The protective atmosphere in step (3) is at least one of nitrogen, argon, helium, and neon.

8. The method of claim 1, wherein, The flow rate of the continuous furnace tail gas is 1-8 L / min, and the flow rate of the protective atmosphere is 1-10 L / min.

9. The method of claim 1, wherein, The reaction time in step (4) is 1-60 min.

10. The method of claim 1, wherein, The reaction time in step (4) is 10-60 min.

11. The method of claim 1, wherein, The ultrasonic dispersion time in step (5) is 5-15 min.

12. The method of claim 1, wherein, The concentration of the dilute hydrochloric acid in step (6) is 0.5-1%, the drying temperature is 60-90°C, and the drying time is 1-24 h.

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