CN113443617B - Continuous carbon nanotube purifying device and process - Google Patents
Continuous carbon nanotube purifying device and process Download PDFInfo
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- CN113443617B CN113443617B CN202110956806.8A CN202110956806A CN113443617B CN 113443617 B CN113443617 B CN 113443617B CN 202110956806 A CN202110956806 A CN 202110956806A CN 113443617 B CN113443617 B CN 113443617B
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- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/158—Carbon nanotubes
- C01B32/168—After-treatment
- C01B32/17—Purification
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
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- C01B2202/30—Purity
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- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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Abstract
The invention discloses a continuous carbon nanotube purification device and a process, which belong to the technical field of nano material preparation, and consist of a plurality of hearths, wherein the hearths comprise an inlet hearth, a preheating hearth, a high-temperature hearth, a cooling hearth and an outlet hearth; the purification process comprises the following steps: s1, preheating a hearth to preheat and primarily purifying impurities in a carbon nano tube; s2, performing secondary purification treatment in a high-temperature area; and S3, cooling and purifying the cooling hearth again. The invention adopts a continuous purification process to realize continuous purification of the carbon nano tube, effectively removes metal or nonmetal impurities in the carbon nano tube, and has the advantages of large yield, short production period, good homogeneity and low cost.
Description
Technical Field
The invention belongs to the technical field of nano material preparation, and particularly relates to a continuous carbon nano tube purification device and process.
Background
Carbon Nanotubes (CNTs) are a class of nanomaterials consisting of a two-dimensional hexagonal lattice of Carbon atoms, which are bent in one direction and combined to form a hollow cylinder. Carbon nanotubes are one of the allotropes of carbon, between Fullerene (0-dimensional) and Graphene (2-dimensional).
In addition to these Single-wall carbon nanotubes (SWCNTs), the name is also used for multi-wall (MWCNT) variants consisting of two or more nested nanotubes, or for multi-layer graphene-like strips rolled up like a scroll. The individual nanotubes are naturally aligned by relatively weak van der waals forces into "ropes" that are held together. While one can construct nanotubes of other compositions, most research has focused on carbon nanotubes; the "carbon" qualifier is therefore generally implicit, with the names abbreviated to NT, SWNT and MWNT.
The carbon nano tube has special physical and chemical properties of high strength, high toughness, high conductivity, electromagnetic emission and the like, can be widely used for lithium battery conductive agents, conductive films, shielding materials and the like, and is an indispensable important strategic material for national defense and military industry, modern industry and high and new technology development. At present, the carbon nanotubes are prepared by a variety of methods, and the main techniques include arc discharge, laser evaporation, hydrocarbon catalytic pyrolysis, solid phase pyrolysis, chemical vapor deposition, and the like. However, in any of the carbon nanotubes prepared by any of the synthesis methods, in many processes for preparing carbon nanotubes, except some arc methods, catalysts are not required, and other methods require the participation of catalysts, and metal active components (such as iron, cobalt, nickel, manganese, etc.) are coated by a carbon layer along with the growth of the carbon nanotubes, thereby causing the deactivation of the catalysts, and various impurities such as amorphous carbon, carbon nanoparticles, carbon nanospheres, fullerenes, catalyst particles, etc. are mixed in the obtained product. The existence of these impurities greatly hinders the practical application of carbon nanotubes, for example, the rapid development of new energy automobiles greatly promotes the mass application of carbon nanotubes in lithium battery products, when carbon nanotubes are used as lithium battery conductive agents, the carbon nanotubes are required to have low ash content and magnetic substance content (especially, the content of Fe is less than 50 PPm), and the carbon nanotubes need to be purified before use, so that the application of carbon nanotubes in many fields is greatly restricted, and therefore, the research on the purification of carbon nanotubes is very necessary.
Most manufacturers adopt a periodic vacuum furnace to purify carbon nanotubes at present, the furnace is divided into a horizontal type and a vertical type, generally adopts a resistance or induction heating mode, and basically comprises a furnace body, a vacuum system, an electric control system, a gas circuit system, a water circuit system and the like. The furnace body is a double-layer metal shell and is provided with an operation door, refractory heat-insulating materials such as graphite felt and composite graphite felt are embedded in a furnace shell, a graphite crucible is fixed in the heat-insulating materials, the heating body is electrode graphite, and if the heating body is in a resistance heating mode, the heating is performed at low voltage and high current. When the materials are processed each time, the materials are loaded into the crucible, the furnace door is closed, the materials are sealed into the furnace shell, the materials are circularly vacuumized and inflated for a plurality of times, the temperature is raised according to the set process curve and vacuum pressure curve under the condition of basically no oxygen, and the materials are cooled and discharged after the processing is finished. The purification mechanism is that the boiling point of metal or nonmetal impurities is reduced by depending on a vacuum state, so that the impurities are volatilized and discharged in a steam mode, a periodic operation mode (3-5 days are a period) is adopted, the effective purification time of a product in a high-temperature state is very short in the purification process, 50% -60% of the time of each period is in the temperature reduction process, and the temperature reduction time mostly needs 1.5-3 days, so that the production period is long, the yield is small, and the energy consumption is high. If the mode of increasing the furnace body loading capacity is adopted to improve the production efficiency, the product can not be uniformly heated, the homogeneity of the product is poor, the large-scale popularization of the periodic furnace is limited, and the requirement of the rapid growth of the lithium battery industry market is difficult to adapt.
Disclosure of Invention
The invention aims to overcome the defects in the prior art of carbon nanotube purification, and the continuous purification treatment of the carbon nanotubes is realized by the continuous carbon nanotube purification device and the continuous carbon nanotube purification process, so that the yield is improved, and the cost is reduced.
One of the purposes of the invention is to provide a continuous carbon nanotube purification device, which consists of a plurality of hearths, wherein each hearth comprises an inlet hearth, a preheating hearth, a high-temperature hearth, a cooling hearth and an outlet hearth, the inlet hearth and the outlet hearths are both in normal temperature and normal pressure external environments, the preheating hearth, the high-temperature hearth and the cooling hearth are respectively provided with an independent vacuum and inflation system, and the inlet hearth and the preheating hearth, the preheating hearth and the high-temperature hearth, and the high-temperature hearth and the cooling hearth are respectively in sealed vacuum communication through a plurality of isolation chambers.
Preferably, in the continuous carbon nanotube purifying device, the preheating furnace chamber has a vacuum pressure of 5000-80000 Pa, the high-temperature furnace chamber has a vacuum pressure of 10-10000 Pa, and the cooling furnace chamber has a vacuum pressure of 2000-80000 Pa.
Preferably, in the continuous carbon nanotube purifying apparatus, the preheating furnace chamber is sealed and vacuum isolated by a plurality of isolation chambers to form a plurality of vacuum chambers-a, and the heating temperature range of all the vacuum chambers-a is 300-1800 ℃.
Preferably, in the continuous carbon nanotube purifying apparatus, the high-temperature furnace is a high-temperature region, and the heating temperature range is 1800 to 2800 ℃.
Preferably, in the continuous carbon nanotube purifying device, the cooling furnace is internally sealed and vacuum-isolated by a plurality of isolation chambers to form a plurality of vacuum chambers-B, and each vacuum chamber-B is further connected with a multi-section water cooling jacket.
Preferably, in the continuous carbon nanotube purifying apparatus, the isolation chamber is composed of a plurality of sealing doors.
The second objective of the present invention is to provide a process for purifying carbon nanotubes by using a continuous purification device, comprising the following steps:
s1, feeding carbon nano tubes to be purified into a preheating hearth from an inlet hearth, gradually decreasing all vacuum chambers-A arranged in the preheating hearth within the range of vacuum pressure of 80000-5000 pa, gradually increasing the heating temperature within the range of 300-1800 ℃, and primarily purifying impurities in the carbon nano tubes;
s2, the preheated carbon nano tubes in the S1 gradually enter all high-temperature regions arranged in a high-temperature hearth, and secondary purification treatment is carried out at the temperature of 1800-2800 ℃, the vacuum pressure of 10-10000 Pa and the pressure of the pressure lower than the pressure of all vacuum chambers-A;
s3, the carbon nano tubes subjected to high-temperature treatment in the S2 gradually enter a cooling hearth, and all vacuum chambers-B arranged in the cooling hearth are gradually increased within the vacuum pressure range of 2000-80000Pa and gradually decreased within the temperature range of 2800-1200 ℃ for secondary purification treatment; and cooling the obtained ultrapure carbon nanotube to 100 ℃, and discharging the ultrapure carbon nanotube from an outlet hearth.
Preferably, in S1, the impurities are metallic or non-metallic impurities.
Preferably, the metal impurities comprise one or more of Fe, co, zn, mg, mn, ca, mo, K and Ni, and the non-metal impurities comprise one or more of Si, S, be, cl and P.
Preferably, in S2, the time of the secondary purification treatment is 1 to 8 hours.
Compared with the prior art, the invention has the following beneficial effects:
1. compared with the existing intermittent processing mode, the invention adopts a continuous purification process to realize continuous purification of the carbon nano tube, effectively removes metal or nonmetal impurities of the carbon nano tube, has large yield, short production period, good homogeneity of products and low cost, and can be suitable for large-scale production.
Drawings
FIG. 1 is a schematic structural diagram of a continuous carbon nanotube purification apparatus according to the present invention;
description of reference numerals:
1. an inlet hearth 2, a preheating hearth 3, a high-temperature hearth 4, a cooling hearth 5, an outlet hearth 6, vacuum chambers-A and 7, vacuum chambers-B and 8 and an isolation chamber.
Detailed Description
In order that those skilled in the art will better understand the technical solutions of the present invention to be implemented, the present invention will be further described with reference to the following specific embodiments and accompanying drawings.
Example 1
A continuous carbon nanotube purifying device is composed of a plurality of hearths.
The plurality of hearths comprise an inlet hearth 1, a preheating hearth 2, a high-temperature hearth 3, a cooling hearth 4 and an outlet hearth 5. The carbon nanotube product is discharged after being treated by an inlet hearth 1, a preheating hearth 2, a high-temperature hearth 3, a cooling hearth 4 and an outlet hearth 5, wherein the inlet hearth 1 and the outlet hearth 5 are both in normal-temperature and normal-pressure external environments, and the preheating hearth 2, the high-temperature hearth 3 and the cooling hearth 4 are all provided with independent vacuum and inflation systems; the inlet hearth 1 and the preheating hearth 2, the preheating hearth 2 and the high-temperature hearth 3 and the cooling hearth 4 are in sealed vacuum communication through a plurality of isolation chambers 8;
an isolation chamber 8 is arranged between the inlet hearth 1 and the preheating hearth 2 to realize the transition from the atmospheric air environment to the vacuum inert gas protection environment; a plurality of vacuum chambers-A6 are formed in the preheating hearth 2 by sealing and vacuum-isolating a plurality of isolation chambers 8, the pressure between the adjacent vacuum chambers-A6 is also adjusted by one isolation chamber 8 in a mode of gradually reducing the pressure, equalizing the pressure and increasing the pressure so as to realize the gradual reduction of the pressure and gradual increase of the temperature of the vacuum inert gas protective environment, and then the isolation chambers 8 are hermetically connected with the inner wall of the preheating hearth 2; an isolation chamber 8 is also arranged between the preheating hearth 2 and the high-temperature hearth 3 so as to realize the transition from the low-vacuum inert gas protection environment to the high-vacuum inert gas protection environment; a plurality of high-temperature heating zones can be arranged in the high-temperature hearth 3 to realize evaporation and gasification of residual impurities of the carbon nano tubes in a high-vacuum environment; an isolation chamber 8 is also arranged between the high-temperature hearth 3 and the cooling hearth 4 so as to realize the transition from the high-vacuum inert gas protection environment to the low-vacuum inert gas protection environment; a plurality of isolation chambers 8 are sealed and vacuum isolated in the cooling hearth 4 to form a plurality of vacuum chambers-B7, the pressure between the adjacent vacuum chambers-B7 is also adjusted through one isolation chamber 8 in a mode of gradually reducing the pressure, equalizing the pressure and increasing the pressure so as to realize the gradual increase of the pressure and gradual reduction of the temperature of the vacuum inert gas protective environment, and then the isolation chambers 8 are hermetically connected with the inner wall of the preheating hearth 2; an isolation chamber 8 is also arranged between the cooling hearth 4 and the outlet hearth 5 so as to realize the transition from the vacuum inert gas protection environment to the normal pressure air environment; the isolation chamber 8 consists of a plurality of sealing doors, and two interlocked gates are arranged in the plurality of sealing doors, so that the inlet hearth 1 and the preheating hearth 2, the preheating hearth 2 and the high-temperature hearth 3, and the high-temperature hearth 3 and the cooling hearth 4 are connected in a vacuum manner;
when the carbon nano tube enters the first vacuum chamber-A6 of the preheating hearth 2 from the inlet hearth 1, the middle isolation chamber 8 is two interlocked gates, is vacuumized and filled with inert protective gas through the isolation chamber 8 between the hearth 1 and the preheating hearth 2 to be treated, achieves the same pressure as the first vacuum chamber-A6 of the preheating hearth 2 and the same inert protective atmosphere, and enters the first vacuum chamber-A6 of the preheating hearth 2; when the carbon nano tube entering the first vacuum chamber-A6 of the preheating hearth 2 passes through the next same vacuum chamber-A6 for vacuumizing and inert gas filling treatment, the carbon nano tube also achieves the same pressure and inert protective atmosphere with the next adjacent vacuum chamber-A6, then enters the next vacuum chamber, and so on, enters a plurality of vacuum chambers-A6 with the temperature increasing and the pressure decreasing continuously, then enters the high-temperature heating area 3 with the pressure constant and minimum and the temperature increasing or constant, and then is treated by the cooling area 4 with the pressure increasing and the temperature decreasing gradually; all the preheating hearth 2, the high-temperature hearth 3 and the cooling hearth 4 are always isolated from the outside air, so that the outside air is effectively prevented from entering, the vacuum pressure of the preheating hearth 2 is 80000-5000 Pa, the vacuum pressure of the high-temperature hearth 3 is 10-10000 Pa, and the vacuum pressure of the cooling hearth 4 is 2000-80000 Pa;
at least one vacuum chamber-A6 is arranged in the preheating hearth 2, a resistance or induction heating mode is adopted, all the vacuum chambers-A6 are heated by resistance wires, silicon-carbon rods, silicon-molybdenum rods, graphite pipes and the like, the heating temperature range is 300-1800 ℃, the hearth is compositely insulated by graphite felt, zirconia fibers, alumina fibers, aluminum silicate fibers and other materials, and the temperature is measured by a thermocouple and an infrared thermometer; the high-temperature hearth is of a double-layer water-cooled furnace shell structure, composite heat-insulating materials such as graphite felt, zirconia fiber, alumina fiber, aluminum silicate fiber and the like are sealed in a sealed cavity, and a thermocouple and an infrared thermometer are adopted for measuring temperature; one or more high-temperature regions are arranged in the high-temperature hearth 3, a graphite tube resistance or induction heating mode is adopted, the heating temperature range is 1800-2800 ℃, and a thermocouple and an infrared thermometer are adopted for measuring temperature; the multi-section water is connected to each vacuum chamber-B7 in a plurality of vacuum chambers-B7 separated and formed in the cooling hearth 4 for cooling, the imported hearth 1 and the preheated hearth 2 are connected with the preheated hearth 2 and the high-temperature hearth 3, the high-temperature hearth 3 and the cooling hearth 4 are communicated in a sealing mode through a plurality of isolation chambers 8, each isolation chamber 8 is composed of a plurality of sealing doors, the connection of the plurality of vacuum chambers is achieved, the adjacent isolation chambers 8 are communicated through step-by-step pressure reduction, isobaric pressure increase, and finally enter the exported hearth 5, and the whole purification processing process is completed.
Example 2
The process for purifying carbon nanotubes using the continuous purification apparatus of example 1 comprises the following steps:
the carbon nano tube to be purified enters a preheating hearth 2 from an inlet hearth 1, sequentially passes through all vacuum chambers-A6 arranged in the preheating hearth 2, and is preheated and primarily purified by metal or nonmetal impurities in the carbon nano tube in a gradually increasing mode under the pressure of 5000Pa and at the heating temperature of 300-1800 ℃ by all the vacuum chambers-A6, so that the temperature of the carbon nano tube in the last temperature preheating zone vacuum chamber-A6 reaches 1800 ℃; the preheated and primarily purified carbon nano tubes enter a high-temperature area 3, the temperature of all the high-temperature areas is 1800 ℃ for the carbon nano tubes, after the secondary purification treatment is carried out for 1h under the vacuum pressure of 15Pa, the carbon nano tubes after the secondary purification enter a cooling area 4, the carbon nano tubes sequentially pass through all vacuum chambers-B7 arranged in the cooling area 4, the temperature is respectively reduced and purified again in a gradually decreasing mode under the vacuum pressure of 2000Pa and at the temperature of 1800-1200 ℃, and the obtained ultrapure carbon nano tubes are discharged from an outlet hearth 5.
Example 3
The process for purifying carbon nanotubes using the continuous purification apparatus of example 1 comprises the following steps:
the carbon nano tube to be purified enters a preheating furnace 2 from an inlet furnace 1, and is preheated and primarily purified by gradually increasing the carbon nano tube in all vacuum chambers-A6 arranged in the preheating furnace 2 under the pressure of 6000Pa and the heating temperature of all the vacuum chambers-A6 within the range of 300-1800 ℃ so as to ensure that the temperature of the carbon nano tube in the last vacuum chamber-A6 in a temperature preheating area reaches 1800 ℃; and the carbon nano tubes after preheating and preliminary purification enter a high-temperature area 3, all the high-temperature areas continue to heat the carbon nano tubes to 2100 ℃ and perform secondary purification treatment for 1h under the vacuum pressure of 100Pa, the carbon nano tubes after secondary purification enter a cooling area 4, sequentially pass through all vacuum chambers-B7 arranged in the cooling area 4, are cooled and purified again in a gradually decreasing mode respectively under the vacuum pressure of 3000Pa and the temperature of 2100-1200 ℃, and the obtained ultrapure carbon nano tubes are discharged from an outlet hearth 5.
Example 4
The process for purifying carbon nanotubes using the continuous purification apparatus of example 1 comprises the following steps:
the carbon nano tube to be purified enters a preheating furnace 2 from an inlet furnace 1, and is preheated and primarily purified by gradually increasing the carbon nano tube in all vacuum chambers-A6 arranged in the preheating furnace 2 under the pressure of 5000Pa and the heating temperature of 300-1800 ℃ of all the vacuum chambers-A6 respectively, so that the temperature of the carbon nano tube in the last vacuum chamber-A6 in a temperature preheating area reaches 1800 ℃; and the carbon nano tubes after preheating and preliminary purification enter a high-temperature area 3, all the high-temperature areas continue to heat the carbon nano tubes to 2000 ℃ and perform secondary purification treatment for 1.5h under the vacuum pressure of 100Pa, the carbon nano tubes after secondary purification enter a cooling area 4, all vacuum chambers-B7 are arranged in the cooling area 4 in sequence, and cooling and secondary purification treatment are performed in a gradually decreasing mode respectively under the vacuum pressure of 2000Pa and the temperature of 2000-1200 ℃, so that the obtained ultrapure carbon nano tubes are discharged from an outlet hearth 5.
Example 5
The process for purifying carbon nanotubes using the continuous purification apparatus of example 1 comprises the following steps:
the carbon nano tube to be purified enters a preheating furnace hearth 2 from an inlet furnace hearth 1, sequentially passes through all vacuum chambers-A6 arranged in the preheating furnace hearth 2, and is preheated and primarily purified of metal or nonmetal impurities in the carbon nano tube in a gradually increasing mode at the heating temperature of 300-1800 ℃ under the pressure of 7000Pa by all the vacuum chambers-A6, so that the temperature of the carbon nano tube in the last temperature preheating zone vacuum chamber-A6 reaches 1800 ℃; and the preheated and primarily purified carbon nano tubes enter the high-temperature area 3, all the high-temperature areas continue to heat the carbon nano tubes to 2250 ℃, after secondary purification treatment is carried out for 2 hours under the vacuum pressure of 1000Pa, the secondarily purified carbon nano tubes enter the cooling area 4, sequentially pass through all vacuum chambers-B7 arranged in the cooling area 4, are respectively cooled and purified again in a gradually decreasing mode under the vacuum pressure of 3000Pa and at the temperature of 2250-1200 ℃, and the obtained ultrapure carbon nano tubes are discharged from the outlet hearth 5.
Example 6
The process for purifying carbon nanotubes using the continuous purification apparatus of example 1 comprises the following steps:
the carbon nano tube to be purified enters a preheating furnace 2 from an inlet furnace 1, sequentially passes through all vacuum chambers-A6 arranged in the preheating furnace 2, and is preheated and preliminarily purified from metal or nonmetal impurities in the carbon nano tube in a gradually increasing mode at the heating temperature of 300-1800 ℃ under the pressure of 8000Pa so that the temperature of the carbon nano tube in the last vacuum chamber-A6 in a temperature preheating region reaches 1800 ℃; the carbon nano tubes after preheating and preliminary purification enter a high-temperature area 3, all the high-temperature areas continue to heat the carbon nano tubes to 2350 ℃, after secondary purification treatment is carried out for 2 hours under the vacuum pressure of 3000Pa, the carbon nano tubes after secondary purification enter a cooling area 4, sequentially pass through all vacuum chambers-B7 arranged in the cooling area 4, are respectively cooled and purified again in a gradually decreasing mode under the vacuum pressure of 3000Pa and the temperature of 1800-2350 ℃, and the obtained ultrapure carbon nano tubes are discharged from an outlet hearth 5.
Example 7
The process for purifying carbon nanotubes using the continuous purification apparatus of example 1 comprises the following steps:
the carbon nano tube to be purified enters a preheating furnace 2 from an inlet furnace 1, and is preheated and primarily purified by gradually increasing the carbon nano tube in all vacuum chambers-A6 arranged in the preheating furnace 2 under the pressure of 5000Pa and the heating temperature of 300-1800 ℃ of all the vacuum chambers-A6, so that the temperature of the carbon nano tube in the last vacuum chamber-A6 in a temperature preheating area reaches 1800 ℃; and the preheated and primarily purified carbon nano tubes enter the high-temperature area 3, all the high-temperature areas continue to heat the carbon nano tubes to 2250 ℃, after secondary purification treatment is carried out for 4 hours under the vacuum pressure of 5000Pa, the carbon nano tubes sequentially pass through all vacuum chambers-B7 arranged in the cooling area 4, and are cooled and purified again in a gradually decreasing mode respectively under the vacuum pressure of 2000Pa and at the temperature of 2250-1200 ℃, so that the ultrapure carbon nano tubes are obtained and discharged from the outlet hearth 5 to be cooled, and the ultrapure carbon nano tubes are obtained.
Example 8
The process for purifying carbon nanotubes using the continuous purification apparatus of example 1 comprises the following steps:
the carbon nano tube to be purified enters a preheating furnace 2 from an inlet furnace 1, and is preheated and primarily purified by gradually increasing the carbon nano tube in all vacuum chambers-A6 arranged in the preheating furnace 2 under the pressure of 5000Pa and the heating temperature of 300-1800 ℃ of all the vacuum chambers-A6, so that the temperature of the carbon nano tube in the last vacuum chamber-A6 in a temperature preheating area reaches 1800 ℃; and the preheated and primarily purified carbon nano tubes enter the high-temperature area 3, all the high-temperature areas continue to heat the carbon nano tubes to 2400 ℃, after the carbon nano tubes are subjected to secondary purification treatment for 2.5 hours under the vacuum pressure of 5000Pa, the carbon nano tubes sequentially pass through all vacuum chambers-B7 arranged in the cooling area 4, and are subjected to cooling and secondary purification treatment in a gradually decreasing mode respectively under the vacuum pressure of 2000Pa and at the temperature of 2400-1200 ℃, so that the obtained ultrapure carbon nano tubes are discharged from the outlet hearth 5.
Example 9
The process for purifying carbon nanotubes using the continuous purification apparatus of example 1 comprises the following steps:
the carbon nano tube to be purified enters a preheating furnace 2 from an inlet furnace 1, and is preheated and primarily purified by gradually increasing the carbon nano tube in all vacuum chambers-A6 arranged in the preheating furnace 2 under the pressure of 9000Pa and the heating temperature of all the vacuum chambers-A6 within the range of 300-1800 ℃ so that the temperature of the carbon nano tube in the last vacuum chamber-A6 in a temperature preheating area reaches 1800 ℃; and the preheated carbon nano tubes enter the high-temperature area 3, all the high-temperature areas continue to heat the carbon nano tubes to 2800 ℃, after secondary purification treatment is carried out for 3 hours under the vacuum pressure of 10000Pa, the carbon nano tubes after secondary purification enter the cooling area 4, and are sequentially subjected to cooling and secondary purification treatment in all vacuum chambers-B7 arranged in the cooling area 4 in a gradually decreasing mode under the vacuum pressure of 3000Pa and the temperature of 1800-1200 ℃, so that the obtained ultrapure carbon nano tubes are discharged from an outlet hearth 5.
The average values of the measurements of the metal or nonmetal impurities in the carbon nanotubes were obtained from the raw material carbon nanotubes and the purified carbon nanotubes of examples 1 to 8, respectively, at random for 5 times, and the results were as follows:
TABLE 1 comparison of purity and metallic impurity content of carbon nanotubes and purified carbon nanotubes
TABLE 2 comparison of purity and non-metallic impurity content of carbon nanotubes and purified carbon nanotubes
As shown in tables 1 and 2, the purity of the carbon nanotubes is significantly improved to 99.95% or more by the continuous carbon nanotube purification apparatus and process of the present invention, and the metal or nonmetal impurities in the carbon nanotubes are effectively removed, wherein the content of each metal or nonmetal impurity is significantly reduced.
It should be noted that, the connection relation of the components not specifically mentioned in the present invention is the default of the prior art, and the connection relation of the structures is not described in detail since it does not relate to the invention point and is a common application of the prior art.
It should be noted that, when the present invention relates to a numerical range, it should be understood that two endpoints of each numerical range and any value between the two endpoints can be selected, and since the steps and methods adopted are the same as those in the embodiment, in order to prevent redundancy, the present invention describes a preferred embodiment. While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (5)
1. The process for purifying the carbon nanotubes by the continuous purification device is characterized in that the continuous purification device consists of a plurality of hearths, each hearth comprises an inlet hearth (1), a preheating hearth (2), a high-temperature hearth (3), a cooling hearth (4) and an outlet hearth (5), the inlet hearth (1) and the outlet hearth (5) are both in normal-temperature and normal-pressure external environments, and the inlet hearth (1) is in sealed vacuum communication with the preheating hearth (2), the preheating hearth (2) is in sealed vacuum communication with the high-temperature hearth (3), and the high-temperature hearth (3) is in sealed vacuum communication with the cooling hearth (4) through a plurality of isolation chambers (8);
a plurality of vacuum chambers-A (6) are formed in the preheating hearth (2) by sealing and vacuum isolating a plurality of isolation chambers (8), and the heating temperature range of all the vacuum chambers-A (6) is 300-1800 ℃;
a plurality of vacuum chambers-B (7) are formed in the cooling hearth (4) by sealing and vacuum isolating a plurality of isolation chambers (8), and each vacuum chamber-B (7) is also connected with a multi-section water cooling jacket;
the process for purifying the carbon nano tube by the continuous purification device comprises the following steps:
s1, feeding carbon nanotubes to be purified into a preheating furnace (2) from an inlet furnace (1), decreasing all vacuum chambers-A (6) arranged in the preheating furnace (2) within the vacuum pressure range of 80000-5000 Pa, increasing the heating temperature within the range of 300-1800 ℃, and performing primary purification treatment on impurities in the carbon nanotubes;
s2, the preheated carbon nano tubes in the S1 gradually enter all high-temperature regions arranged in a high-temperature hearth (3), and secondary purification treatment is carried out at the temperature of 1800-2800 ℃ and the vacuum pressure of 10-10000 Pa, wherein the pressure of the secondary purification treatment is lower than that of all vacuum chambers-A (6);
s3, the carbon nano tubes subjected to high-temperature treatment in the S2 gradually enter a cooling hearth (4), and are subjected to secondary purification treatment by gradually increasing all vacuum chambers-B (7) arranged in the cooling hearth (4) within the range of vacuum pressure of 2000-80000Pa and gradually decreasing the temperature within the range of 2800-1200 ℃; after the ultra-pure carbon nano tube is obtained, the temperature is reduced to 100 ℃, and then the ultra-pure carbon nano tube is discharged from the outlet hearth (5).
2. The process for purifying carbon nanotubes by a continuous purification device according to claim 1, wherein the isolation chamber (8) is composed of several sealing doors.
3. The process for purifying carbon nanotubes by using a continuous purification apparatus as claimed in claim 1, wherein in S1, the impurities are metallic or non-metallic impurities.
4. The continuous carbon nanotube purifying process according to claim 3, wherein the metal impurities comprise one or more of Fe, co, zn, mg, mn, ca, mo, K, ni, and the non-metal impurities comprise one or more of Si, S, be, cl, P.
5. The process for purifying carbon nanotubes by using the continuous purification device as claimed in claim 1, wherein the secondary purification treatment time in S2 is 1 to 8 hours.
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