Carbon nanomaterial pretreatment device and process thereof

Abstract

The invention discloses a carbon nanomaterial pretreatment device and a process thereof, and belongs to the technical field of carbon nanomaterial modification and application, the device comprises a pretreatment main body, a roller way conveying mechanism, a sagger and a collecting and releasing dust-free purification area, the roller way conveying mechanism penetrates through the purification area and the pretreatment main body, the pretreatment body is provided with a low-temperature area, a medium-temperature area, a high-temperature area and a cooling area in the material conveying direction, the temperatures of all the temperature areas are independently controlled, an exhaust and detection assembly is arranged, and the roller way conveying speed can be adjusted to control the material retention time. According to the process, carbon nanotubes are fed into a device through dust-free feeding, and the temperatures (300-600 DEG C) of a low-temperature area, a medium-temperature area, a high-temperature area and a cooling area and the protective gas and oxidant atmosphere are accurately regulated and controlled; according to the method, the pretreatment target of'modification but not destruction 'is achieved, the purity, surface activity and dispersity of the carbon nanotubes are synchronously improved, the defect structure is optimized, the specific surface area is increased to 600-1000 m < 2 > / g, and the core performance is remarkably enhanced.

Description

A carbon nanomaterial pretreatment device and its process Technical Field

[0001] This invention relates to the field of carbon nanomaterial modification and application technology, and in particular to a carbon nanomaterial pretreatment device and process. Background Technology

[0002] Carbon nanotubes (CNTs), as nanomaterials with excellent mechanical, electrical, and thermal conductivity, are typically prepared by the pyrolysis and growth of a carbon source in a high-temperature chamber under the action of a catalyst, essentially a transformation from gaseous carbon to solid carbon. However, existing carbon nanotubes suffer from significant technical defects: on the one hand, incomplete reaction processes lead to insufficient product purity, leaving behind amorphous carbon, carbon nanoparticles, and catalyst residues such as Fe, Co, and Ni; on the other hand, their tube walls are composed of sp... 2 Composed of hybrid carbon atoms, with a smooth surface and lack of active sites, it exhibits surface inertness, is prone to aggregation and poor dispersibility, and has insufficient compatibility with matrix materials such as polymers and metals, which prevents it from fully realizing its excellent performance and limits its application scenarios.

[0003] Carbon nanotube pretreatment is a key step in solving the above problems. Existing pretreatment technologies suffer from difficulties in controlling the oxidation intensity: excessive oxidation can easily lead to carbon nanotube wall fracture, reduced aspect ratio, or even complete oxidation failure; insufficient oxidation cannot effectively remove impurities or introduce sufficient active functional groups, making it difficult to meet the needs of industrial applications. Therefore, there is an urgent need for a pretreatment process that can precisely control the oxidation process and balance impurity removal with performance optimization. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides the following technical solution: a carbon nanomaterial pretreatment device, comprising a pretreatment body, a roller conveyor mechanism, saggers, and a dust-free collection and disposal area. The roller conveyor mechanism is connected end to end, and multiple saggers are arranged on the roller conveyor mechanism. The roller conveyor mechanism passes through the dust-free collection and disposal area and the pretreatment body. The dust-free collection and disposal area is equipped with a dust-free feeding mechanism and a vacuum receiving mechanism.

[0005] Preferably, the dust-free purification zone for receiving and storing is a sealed structure.

[0006] Preferably, the pretreatment body is provided with a low temperature zone, a medium temperature zone, a high temperature zone and a cooling zone in sequence along the material conveying direction.

[0007] Preferably, the low-temperature zone has a temperature of 50-80℃, the medium-temperature zone has a temperature of 100-300℃, the high-temperature zone has a temperature of 300-600℃, and the cooling zone has a temperature of room temperature.

[0008] Preferably, the roller conveyor mechanism uses high-temperature resistant ceramic rollers, and the conveying speed is adjustable through frequency conversion drive to ensure that the residence time of materials in each temperature zone is controllable.

[0009] Preferably, the top of the low-temperature zone, medium-temperature zone, high-temperature zone and cooling zone in the pretreatment body are each provided with an independent exhaust pipe. All exhaust pipes are connected to the exhaust gas treatment unit after being collected. A gas composition sensor is provided on the exhaust pipe.

[0010] Preferably, heat insulation plates are provided between each pair of adjacent low-temperature zone, medium-temperature zone, high-temperature zone and cooling zone inside the pretreatment body, and temperature sensors and heating modules are independently provided in each of the low-temperature zone, medium-temperature zone, high-temperature zone and cooling zone.

[0011] A carbon nanomaterial pretreatment process, wherein (1) the carbon nanotubes to be treated are fed into the casket on the roller conveyor through the dust-free feeding mechanism in the material collection and disposal purification area; (2) the temperatures of the low temperature zone, medium temperature zone, high temperature zone and cooling zone of the pretreatment body are adjusted, the oxidation temperature is set to 300-600℃, and the residence time of a specific temperature range is controlled according to the type of impurities, wherein the amorphous carbon removal temperature range is about 300℃, and the metal oxide removal temperature range is 400-500℃; (3) a protective gas and a selected oxidant are introduced into the pretreatment body to maintain the stability of the atmosphere inside the cavity, the running speed of the roller conveyor is adjusted, and the carbon nanotube oxidation treatment time is controlled to be 1.5-6 hours; (4) after the treatment is completed, the pretreated carbon nanotubes are collected through the vacuum receiving mechanism to complete the pre-oxidation process.

[0012] Preferably, in step (2), by adjusting the oxidation temperature and time, defects in the carbon nanotube wall can be repaired or controlled etching can be achieved, thereby increasing the specific surface area of ​​the oxidized carbon nanotubes to 600-1000 m². 2 / g.

[0013] Preferably, the protective gas includes one or more of nitrogen and argon, and the gas flow rate is 0.5-5 L / min.

[0014] Beneficial effects: Compared with existing technologies, this invention achieves the pretreatment goal of "modification rather than destruction" through precise control of temperature in low-temperature, medium-temperature, high-temperature and cooling zones, as well as precise regulation of oxidant concentration and treatment time, avoiding problems of over-oxidation or under-oxidation; simultaneously, it improves the purity of carbon nanotubes, enhances surface activity, improves dispersibility and optimizes defect structures, significantly improving their core properties such as mechanical strength, electrical and thermal conductivity; process parameters can be customized according to different specifications of carbon nanotubes and end-use scenarios, covering multiple fields such as polymer composites, catalyst supports, energy storage, adsorption separation and biomedicine. Attached Figure Description

[0015] Figure 1 is a schematic diagram of the carbon nanomaterial pretreatment device of the present invention.

[0016] In the attached diagram: 1-Roller conveyor mechanism, 2-Sagger, 3-Dust-free cleanroom for receiving and discharging, 4-Pre-treatment main body, 401-Low temperature zone, 402-Medium temperature zone, 403-High temperature zone, 5-Dust-free feeding mechanism, 6-Vacuum receiving mechanism, 7-Exhaust pipe. Detailed Implementation

[0017] The technical solution of this patent will be further described in detail below with reference to specific embodiments. In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention, which mainly includes: a pretreatment device comprising a pretreatment body with heating, heat preservation, and exhaust functions; a roller conveyor mechanism for continuously conveying the saggers; saggers carrying carbon nanotubes; and a material collection and disposal purification zone for dust-free feeding and vacuum collection, which can avoid secondary pollution during the pretreatment process; pre-oxidation core parameters: precise temperature control using low-temperature, medium-temperature, high-temperature, and cooling zones, with a temperature range of 200℃-600℃; a protective gas is introduced into the cavity to maintain a stable atmosphere; and the roller conveyor speed can be flexibly adjusted according to the specifications of the carbon nanotubes and processing requirements, adapting to the processing needs of multiple varieties.

[0018] Controllable introduction of active functional groups: Oxygen-containing functional groups such as carboxyl, hydroxyl, and epoxy groups are introduced by etching defect sites on the surface of carbon nanotubes using oxidants (air, O2, H2O2, etc.) or plasma / high-temperature heat treatment. Under special conditions (ammonia atmosphere oxidation), nitrogen-containing functional groups can be introduced. Hydrogen bonding and electrostatic repulsion between these functional groups break up agglomerations and provide sites for chemical reactions with the matrix material, enhancing interfacial bonding. Impurity removal and defect control: Utilizing the difference in oxidation temperature between impurities and carbon nanotubes (amorphous carbon ~300℃, metal oxides ~500℃, carbon nanotubes themselves ~600℃ and above), the oxidation temperature is controlled at 400-500℃ to achieve selective impurity removal. By adjusting the oxidation intensity, some irregular defects are repaired to make the tube wall structure more regular, or microporous / mesoporous structures are constructed, increasing the specific surface area from the original 200-400 m². 2 / g increased to 600-1000 m 2 / g; Application performance adaptation: Parameters are customized according to the end application scenario. For example, in the field of polymer composite materials, the focus is on improving compatibility; in the field of catalyst support, the focus is on increasing specific surface area and active sites; and in the field of energy storage materials, the focus is on optimizing electrolyte wettability and ion transport rate.

[0019] Example 1 A carbon nanomaterial pretreatment process, the specific steps are as follows: (1) 50g of multi-walled carbon nanotubes, which contain about 8wt% amorphous carbon impurities and about 5wt% metal catalyst residue, are fed into an alumina casket on the roller conveyor through a dust-free feeding mechanism in the material collection and disposal purification area.

[0020] (2) Adjust the temperature of the four temperature zones of the pretreatment body: Low temperature zone: set the temperature to 60℃, used for carbon nanotube preheating and moisture removal; Medium temperature zone: set the temperature to 280℃, used for preliminary oxidation and removal of low boiling point impurities; High temperature zone: set the temperature to 450℃, used for deep oxidation treatment, control the temperature of the amorphous carbon removal section to 300℃, stay for 40 minutes, the temperature of the metal oxide removal section to 450℃, stay for 60 minutes; Cooling zone: room temperature cooling (3) Introduce nitrogen into the pretreatment body as a protective gas, the gas flow rate is 2L / min; at the same time, introduce air as an oxidant, the air flow rate is 0.5L / min. Adjust the running speed of the roller conveyor mechanism to 0.5m / min, and control the total oxidation treatment time of carbon nanotubes to 3 hours.

[0021] (4) After the treatment is completed, the pretreated carbon nanotubes are collected under a negative pressure of 0.08 MPa through a vacuum collection structure to complete the pre-oxidation process.

[0022] The specific surface area of ​​the obtained carbon nanotubes was measured to be 740 m². 2 / g, the amorphous carbon content was reduced to 1.2wt%, and the metal impurity content was reduced to 0.8wt%.

[0023] Example 2 A carbon nanomaterial pretreatment process, the specific steps are as follows: (1) 100g of single-walled carbon nanotubes (containing about 12wt% amorphous carbon impurities and about 3wt% metal oxide impurities) are fed into a quartz sagger on a roller conveyor through a dust-free feeding mechanism.

[0024] (2) Adjust the temperature of the four temperature zones of the pretreatment body: Low temperature zone: set the temperature to 75℃ for uniform preheating of materials; Medium temperature zone: set the temperature to 250℃ for pre-oxidation treatment; High temperature zone: set the temperature to 520℃, control the temperature of the amorphous carbon removal section to 300℃ and stay for 50 minutes, and the temperature of the metal oxide removal section to 480℃ and stay for 90 minutes; Cooling zone: room temperature cooling.

[0025] (3) Argon gas is introduced into the pretreatment body as a protective gas at a flow rate of 3 L / min; at the same time, a mixture of carbon dioxide and oxygen (CO2:O2=4:1) is introduced as an oxidant at a flow rate of 1 L / min. The operating speed of the roller conveyor is adjusted to 0.3 m / min, and the total oxidation treatment time is controlled to 5 hours.

[0026] (4) After the treatment is completed, the pretreated carbon nanotubes are collected under a negative pressure of 0.1 MPa by a vacuum collection structure.

[0027] The specific surface area of ​​the obtained carbon nanotubes was measured to be 910 m². 2 / g, the amorphous carbon content was reduced to 0.9wt%, the metal oxide impurity content was reduced to 0.5wt%, the defects in the carbon nanotube wall were repaired, and the crystallinity was improved.

[0028] Example 3 A carbon nanomaterial pretreatment process, the specific steps are as follows: (1) 80g of double-walled carbon nanotubes (containing about 5wt% amorphous carbon impurities and about 7wt% metal impurities) are fed into a silicon carbide sagger on a roller conveyor through a dust-free feeding mechanism.

[0029] (2) Adjust the temperature of the four temperature zones of the pretreatment body: Low temperature zone: set the temperature to 55℃ to remove adsorbed moisture; Medium temperature zone: set the temperature to 200℃ to activate the material; High temperature zone: set the temperature to 380℃, control the temperature of the amorphous carbon removal section to 300℃ and stay for 30 minutes, and the temperature of the metal oxide removal section to 380℃ and stay for 40 minutes.

[0030] Cooling zone: ambient temperature cooling (3) A mixture of nitrogen and argon (N2:Ar=3:1) is introduced into the pretreatment body as a protective gas, with a total gas flow rate of 4L / min; at the same time, water vapor is introduced as an oxidant, with a water vapor flow rate of 0.8L / min. The running speed of the roller conveyor is adjusted to 0.8m / min, and the total oxidation treatment time is controlled to 2 hours.

[0031] (4) After the treatment is completed, the pretreated carbon nanotubes are collected by a vacuum collection structure.

[0032] The specific surface area of ​​the obtained carbon nanotubes was measured to be 670 m². 2 / g, the amorphous carbon content was reduced to 0.7wt%, and the metal impurity content was reduced to 1.2wt%, achieving controllable etching and forming a uniform microporous structure on the surface of carbon nanotubes.

[0033] Comparative Example 1 A carbon nanomaterial pretreatment process, the specific steps are as follows: (1) 50g of multi-walled carbon nanotubes (the same batch of raw materials as in Example 1) are directly fed into the casket on the roller conveyor through the ordinary feeding port.

[0034] (2) The pretreatment body is set up with only a single high temperature zone: directly heated to 450℃, without low temperature preheating and medium temperature transition process, without cooling zone, and naturally cooled after treatment. (3) Only air is introduced into the pretreatment body as an oxidizing atmosphere, with an air flow rate of 5L / min, and no protective gas is introduced.

[0035] (4) After processing, carbon nanotubes are collected by ordinary open-top collection method.

[0036] The specific surface area of ​​the obtained carbon nanotubes was measured to be 310 m². 2 / g, the amorphous carbon content decreased to 4.6wt%, the metal impurity content decreased to 2.4wt%, and the carbon nanotube burn-off rate reached 28%, due to severe damage to the tube wall structure caused by thermal shock.

[0037] Comparative Example 2: A carbon nanomaterial pretreatment process, the specific steps are as follows: (1) 100g of single-walled carbon nanotubes (the same batch of raw materials as in Example 2) are fed into the roller conveyor through a dust-free feeding mechanism.

[0038] (2) The temperature settings of the four temperature zones of the pretreatment body are not appropriate: Low temperature zone: 120℃ Medium temperature zone: 350℃ High temperature zone: 450℃ Cooling zone: room temperature (3) The gas parameters are the same as those in Example 2.

[0039] Testing revealed that excessively high preheating temperatures caused premature oxidation of some carbon nanotubes, resulting in a specific surface area of ​​only 390 m². 2 / g, poor impurity removal effect, and damage to material structure.

[0040] Comparative Example 3: A carbon nanomaterial pretreatment process, the specific steps are as follows: (1) 80g of double-walled carbon nanotubes (the same batch of raw materials as in Example 3) are fed into the roller conveyor through a dust-free feeding mechanism.

[0041] (2) The pretreatment body lacks a low temperature zone: directly enter the medium temperature zone: 250℃ high temperature zone: 400℃ cooling zone: room temperature (3) Other process parameters are the same as in Example 3.

[0042] Testing revealed that due to the lack of a low-temperature preheating stage, the carbon nanotubes were heated unevenly, resulting in a specific surface area of ​​only 520 m². 2 / g, with low impurity removal rate and localized peroxidation of the material.

[0043] Comparative Analysis of Effects

[0044] As can be seen from the above embodiments and comparative examples, the present invention, through temperature control in the low-temperature zone, medium-temperature zone, high-temperature zone, and cooling zone, the synergistic effect of protective gas and oxidant, and the optimization of specific process parameters, can effectively remove amorphous carbon and metallic impurities from carbon nanotubes, significantly improve the specific surface area, and maintain the structural integrity of the carbon nanotubes. In contrast, the comparative examples, due to the lack of key process steps or improper parameters, suffer from poor purification effects, limited improvement in specific surface area, or severe carbon nanotube burn-off.

[0045] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

[0046] It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this invention can be combined with each other. In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0047] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

Claims

1. A carbon nanomaterial pretreatment device, characterized in that: It includes a pretreatment body (4), a roller conveyor mechanism (1), a sagger (2), and a dust-free collection and disposal area (3). The roller conveyor mechanism (2) is connected end to end. Multiple saggers (2) are provided on the roller conveyor mechanism (1). The roller conveyor mechanism (1) passes through the dust-free collection and disposal area (2) and the pretreatment body (4). The dust-free collection and disposal area (3) is provided with a dust-free feeding mechanism (5) and a vacuum receiving mechanism (6).

2. The carbon nanomaterial pretreatment device according to claim 1, characterized in that: The dust-free purification area (3) is a sealed structure.

3. The carbon nanomaterial pretreatment device according to claim 1, characterized in that: The pretreatment body (4) is provided with a low temperature zone (401), a medium temperature zone (402), a high temperature zone (403) and a cooling zone (404) in sequence along the material conveying direction.

4. The carbon nanomaterial pretreatment device according to claim 1, characterized in that: The low-temperature zone (401) has a temperature of 50-80℃, the medium-temperature zone (402) has a temperature of 100-300℃, the high-temperature zone (403) has a temperature of 300-600℃, and the cooling zone (404) is at room temperature.

5. The carbon nanomaterial pretreatment device according to claim 1, characterized in that: The roller conveyor mechanism (1) adopts high-temperature resistant ceramic rollers, and the conveying speed is adjustable through frequency conversion drive, so as to ensure that the residence time of materials in each temperature zone is controllable.

6. The carbon nanomaterial pretreatment device according to claim 1, characterized in that: Independent exhaust pipes (7) are provided at the top of the low temperature zone (401), medium temperature zone (402), high temperature zone (403) and cooling zone (404) in the pretreatment body (1), and all exhaust pipes (7) are connected to the waste gas treatment unit after being collected.

7. The carbon nanomaterial pretreatment device according to claim 1, characterized in that: The pretreatment body (1) has heat insulation plates installed between each pair of adjacent low temperature zone (401), medium temperature zone (402), high temperature zone (403) and cooling zone (404), and each of the low temperature zone (401), medium temperature zone (402), high temperature zone (403) and cooling zone (404) is independently equipped with a temperature sensor and a heating module.

8. A carbon nanomaterial pretreatment process based on the apparatus of any one of claims 1-7, characterized in that: (1) The carbon nanotubes to be treated are fed into the sagger (2) on the roller conveyor (1) through the dust-free feeding mechanism (5) of the receiving and discharging purification zone (3); (2) The temperatures of the low temperature zone (401), medium temperature zone (402), high temperature zone (403) and cooling zone (404) of the pretreatment body (4) are adjusted, and the oxidation temperature is set to 300-600℃. The residence time of a specific temperature range is controlled according to the type of impurities. The temperature range for removing amorphous carbon is about 300℃, and the temperature range for removing metal oxides is 400-500℃; (3) Protective gas and selected oxidant are introduced into the pretreatment body (4) to maintain the stability of the atmosphere inside the cavity. The running speed of the roller conveyor (1) is adjusted to control the carbon nanotube oxidation treatment time to 1.5-6 hours; (4) After the treatment is completed, the pretreated carbon nanotubes are collected through the vacuum receiving mechanism (6) to complete the pre-oxidation process.

9. The carbon nanomaterial pretreatment process according to claim 8, characterized in that: In step (2), by adjusting the oxidation temperature and time, defects in the carbon nanotube wall are repaired or controlled etching is achieved, thereby increasing the specific surface area of ​​the oxidized carbon nanotubes to 600-1000 m². 2 / g.

10. The carbon nanomaterial pretreatment process according to claim 8, characterized in that: The protective gas includes one or more of nitrogen and argon, with a gas flow rate of 0.5-5 L / min.

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