Reactor, reaction system and preparation method of single-walled carbon nanotube

Abstract

The invention belongs to the technical field of single-walled carbon nanotubes, and particularly relates to a reactor, a reaction system and a preparation method of a single-walled carbon nanotube. The reactor provided by the invention comprises a graphite pipe 2 and a medium-frequency induction heater 3 arranged on the outer surface of the graphite pipe 2, the medium-frequency induction heater 3 comprises a medium-frequency induction heating power supply 31 and a medium-frequency induction water cooling device 32; the cross section of the graphite pipe 2 is in a long square shape or an oval shape; the width of the rectangle ranges from 100 mm to 400 mm, and the length of the rectangle ranges from 500 mm to 2000 mm. The long diameter of the ellipse is 500-2000mm, the short diameter of the ellipse is 100-400mm, and the ellipticity is e, 0lt; lt, lt; 1; the height of the graphite pipe (2) ranges from 5000 mm to 8000 mm. By utilizing the reactor provided by the invention, the yield of the single-walled carbon nanotubes can be increased, and batch production of the single-walled carbon nanotubes is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of single-walled carbon nanotubes, and in particular relates to a reactor, a reaction system and a method for preparing the single-walled carbon nanotubes. Background Art

[0002] Single-walled carbon nanotubes are one-dimensional tubular materials with a huge aspect ratio composed of nearly perfect sp2 hybridized carbon atoms. Highly crystalline single-walled carbon nanotubes have few defects, and their tensile strength can reach 100GPa and thermal conductivity can reach 3000Wm -1 K -1 , resistivity as low as 5×10 -6 Ωcm. Single-walled carbon nanotubes (SWCNTs) have attracted extensive attention due to their excellent mechanical, thermal and optoelectronic properties and have broad application prospects. However, they are currently limited by the imperfect batch preparation technology and high costs, which restricts their large-scale application.

[0003] The existing methods for preparing single-walled carbon nanotubes mainly include laser ablation, arc discharge and chemical vapor deposition (CVD). Among them, laser ablation and arc discharge are difficult to be applied to large-scale production of single-walled carbon nanotubes due to the high impurities in the products, the difficulty in purification and the low yield. CVD technology is favored because of its low cost and easy control. CVD technology can be divided into high-pressure CVD (HIPCO), supported catalyst CVD (SCCVD) and floating catalyst CVD (FCCVD). The typical FCCVD process is to send the catalyst precursor and the carrier gas into the high temperature zone of the reactor together, and then decompose to form floating nanoparticles to catalyze the growth of carbon nanotubes. The process can be continuous, including catalyst particle nucleation, SWCNT growth and direct collection of SWCNT. Although the FCCVD process is considered to be the most scalable manufacturing route for producing high-yield, high-quality carbon nanotubes (CNTs) materials, there are still many challenges in the repeatability, uniformity and controllability of growth, which hinder the large-scale application of the prepared single-walled carbon nanotubes. In order to increase the output, expanding the diameter of the reactor has become the most direct choice. However, as the diameter of the reactor increases, due to the influence of factors such as the heating method and the heating rate, the temperature field inside the reactor cannot maintain the uniformity of the small-diameter reactor. In addition, as the amount of carrier gas increases, the temperature gradient increases, and the eddy effect is easily formed in the reactor, causing a recycling phenomenon, which seriously affects the nucleation of the catalyst and the growth of single-walled carbon nanotubes. Therefore, although increasing the size of the reactor is the most direct and effective way to increase the output of single-walled carbon nanotubes, the enlarged effect that follows, especially the existence of problems such as heat transfer efficiency and temperature gradient, has a serious impact on its preparation process. Therefore, only by solving these problems generated by the reactor amplification process can the mass production of single-walled carbon nanotubes be realized. Summary of the Invention

[0004] In view of this, the present invention provides a reactor, a reaction system and a method for preparing single-walled carbon nanotubes. The reactor provided by the present invention can efficiently prepare single-walled carbon nanotubes in large quantities.

[0005] To solve the above technical problems, the present invention provides a reactor, comprising a graphite tube 2 and an intermediate frequency induction heater 3 arranged on the outer surface of the graphite tube 2; the intermediate frequency induction heater 3 comprises an intermediate frequency induction heating power supply 31 and an intermediate frequency induction water cooling device 32;

[0006] The cross-section of the graphite tube 2 is a long square or an ellipse; the width of the rectangle is 100 - 400 mm, and the length is 500 - 2000 mm; the major diameter of the ellipse is 500 - 2000 mm, the minor diameter is 100 - 400 mm, and the ellipticity is e, 0 < e < 1; the height of the graphite tube 2 is 5000 - 8000 mm.

[0007] Preferably, the wall thickness of the graphite tube 2 is 20 - 100 mm;

[0008] When the cross-section of the graphite tube 2 is a long square, the right angles of the graphite tube 2 are subjected to arc treatment, and the radian is 60 - 240°;

[0009] The output power of the intermediate frequency induction heating power supply 31 is 50 - 200 kW, and the oscillation frequency is 0.5 - 20 kHz.

[0010] The present invention further provides a reaction system, comprising a feeding unit, a reactor and a discharging and collecting device 4 connected in series in sequence;

[0011] The feeding unit comprises a liquid carbon source storage tank 14, an input device 12 with an inlet communicated with the outlet of the liquid carbon source storage tank 14, an auxiliary gas storage tank 13 and a preheater 11; the outlets of the input device 12 and the auxiliary gas storage tank 13 are respectively communicated with the inlet of the preheater 11;

[0012] The reactor is the reactor described in the above technical solution;

[0013] The outlet of the preheater 11 is communicated with the inlet of the graphite tube 2 in the reactor through a pipeline; the outlet of the graphite tube 2 is communicated with the inlet of the discharging and collecting device 4.

[0014] Preferably, the end of the pipeline at the outlet of the preheater 11 is led into the upper middle part of the graphite tube 2.

[0015] The present invention further provides a method for preparing single-walled carbon nanotubes by using the reaction system described in the above technical solution, comprising the following steps:

[0016] The liquid carbon source and the auxiliary gas are mixed and introduced into the preheater 11 for preheating to obtain a preheated mixture; the preheated mixture is introduced into a reactor for single-walled carbon nanotube growth to obtain the single-walled carbon nanotube.

[0017] Preferably, the liquid carbon source comprises a carbon source, a catalyst and a co-catalyst;

[0018] The carbon source includes ethanol, n-butanol, benzyl alcohol, toluene, xylene or cyclohexane;

[0019] The catalyst is an iron-containing compound;

[0020] The promoter is a sulfur-containing compound.

[0021] Preferably, the iron-containing compound includes ferrocene, carbonyl iron, ferric acetate, ferric ethoxide or ferric citrate;

[0022] The sulfur-containing compound includes thiophene, carbon disulfide or elemental sulfur;

[0023] The mass percentage of the catalyst in the liquid carbon source is 0.5-4.5%;

[0024] The mass percentage of the promoter to the total mass of the carbon source and the promoter is 0.5 to 4.5%;

[0025] The flow rate of the liquid carbon source entering the preheater (11) is 2 to 15 mL / min.

[0026] Preferably, the auxiliary gas is a mixed gas of an inert gas and a reducing gas; the inert gas includes argon or nitrogen; the reducing gas includes hydrogen;

[0027] The volume ratio of the inert gas to the reducing gas in the auxiliary gas is 0.8 to 1.2:2;

[0028] The flow rate of the auxiliary gas entering the preheater 11 is 150-250 L / min.

[0029] Preferably, the preheating temperature is 100-400°C.

[0030] Preferably, the temperature for growing the single-walled carbon nanotubes is 1200-1600°C.

[0031] The present invention provides a reactor, which comprises a graphite tube 2 and an intermediate frequency induction heater 3 arranged on the outer surface of the graphite tube 2; the intermediate frequency induction heater 3 comprises an intermediate frequency induction heating power supply 31 and an intermediate frequency induction water cooling device 32; the cross-section of the graphite tube 2 is a long square or an ellipse; the width of the rectangle is 100 - 400 mm, and the length is 500 - 2000 mm; the major diameter of the ellipse is 500 - 2000 mm, the minor diameter is 100 - 400 mm, and the ellipticity is e, where 0 < e < 1; the height of the graphite tube 2 is 5000 - 8000 mm. In the present invention, the graphite tube has good electrical and thermal conductivity, can be used as a heating element, and can also be used as the main body of the reactor. Based on the "skin effect" of intermediate frequency induction, heat is first generated on the graphite surface, and the good thermal conductivity of the graphite enables the generated heat to be quickly radiated to the inside of the reactor, realizing rapid heating. At the same time, the cross-section of the reaction tube is designed to be square or elliptical, reducing the heat radiation distance while ensuring the cross-sectional area, improving the heat transfer efficiency, realizing the uniformity of the temperature in the reaction cavity, thereby solving the disadvantage of unstable temperature in the large cavity reactor, realizing the controllability of rapid heat transfer and uniform temperature field required in the growth process of single-walled carbon nanotubes, thereby improving the utilization rate of the catalyst, further increasing the yield of single-walled carbon nanotubes, and realizing the batch production of single-walled carbon nanotubes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic structural diagram of the reactor;

[0033] Figure 2 is a schematic structural diagram of the reaction system adopted in the embodiment;

[0034] Figures 1-2 In, 11 is a preheater, 12 is an input device, 13 is an auxiliary gas storage tank, 14 is a liquid carbon source storage tank, 15 is a liquid pipeline, 16 is a gas pipeline, 17 is a baffle, 18 is a nozzle, 2 is a graphite tube, 3 is an intermediate frequency induction heater, 31 is an intermediate frequency induction heating power supply, 32 is an intermediate frequency induction water cooling device, and 4 is a discharge collection device;

[0035] Figure 3 is the temperature rise curve of heating the graphite tube in Example 1;

[0036] Figure 4 is the Raman spectrum of the single-walled carbon nanotubes prepared in Example 1;

[0037] Figure 5 is the Raman spectrum of the single-walled carbon nanotubes prepared in Example 5;

[0038] Figure 6 is the TEM image of the single-walled carbon nanotubes prepared in Example 1;

[0039] Figure 7 TEM image of the single-walled carbon nanotubes prepared in Example 5. Detailed implementation manners

[0040] The present invention provides a reactor, which includes a graphite tube 2 and an intermediate-frequency induction heater 3 arranged on the outer surface of the graphite tube 2; the intermediate-frequency induction heater 3 includes an intermediate-frequency induction heating power supply 31 and an intermediate-frequency induction water cooling device 32.

[0041] In the present invention, the cross-section of the graphite tube 2 is a long rectangle or an ellipse; the width of the rectangle is 100 - 400 mm, and can be 200 - 300 mm; the length of the rectangle is 500 - 2000 mm, and can be 600 - 1800 mm, can also be 800 - 1500 mm, and further can be 1000 - 1300 mm; the major diameter of the ellipse is 500 - 2000 mm, and can be 800 - 1500 mm, can also be 1000 - 1300 mm; the minor diameter of the ellipse is 100 - 400 mm, and can be 200 - 300 mm; the ellipticity of the ellipse is e, where 0 < e < 1; the height of the graphite tube 2 is 5000 - 8000 mm, and can be 6000 - 7000 mm. As a specific implementation manner of the present invention, the wall thickness of the graphite tube 2 can be 20 - 100 mm, can also be 30 - 80 mm, and further can be 50 - 70 mm.

[0042] As a specific implementation manner of the present invention, when the cross-section of the graphite tube 2 is a long rectangle, chamfering can be performed on the right angles of the graphite tube 2, and the chamfering radian can be 60 - 240°, can also be 80 - 200°, and further can be 100 - 180°. The present invention limits the cross-section of the graphite tube 2 to a rectangle or an ellipse, which shortens the distance of heat radiation, and by using graphite, an excellent heat conductor, rapid heat transfer can be achieved, so that the temperature inside the reaction tube is uniform.

[0043] As a specific implementation manner of the present invention, the intermediate-frequency induction heater 3 includes a stacked heat insulation layer, a heating induction coil, a water cooling coil and a sealed housing. As a specific implementation manner of the present invention, the output power of the intermediate-frequency induction heating power supply 31 can be 50 - 200 kW, can also be 80 - 180 kW, and further can be 100 - 150 kW; the oscillation frequency of the intermediate-frequency induction heating power supply 31 can be 0.5 - 20 kHz, can also be 1 - 15 kHz, and further can be 5 - 10 kHz. The present invention uses the intermediate-frequency induction heating method to perform magnetic induction heating on the graphite tube, and the temperature inside the graphite tube can be accurately controlled by controlling the output power and oscillation frequency of the intermediate-frequency induction heating power supply 31.

[0044] The present invention adopts graphite material with good electrical conductivity as the main reaction tube of the reactor, and a medium-frequency induction heating coil is wound around the periphery of the graphite tube. The graphite heating element is rapidly heated by the rapid heating of the medium-frequency induction, and then the efficient thermal conductivity is utilized to realize rapid heat transfer, reduce the area where the temperature gradient exists, effectively reduce the possibility of eddy current formation, and finally realize the uniform temperature inside the square or elliptical graphite tube. The present invention improves the heat transfer efficiency of the reaction tube by improving the shape, material and heating method, solves the problem of uneven temperature distribution in the reactor, and thus increases the yield of single-walled carbon nanotubes.

[0045] The present invention further provides a reaction system, comprising a feed unit, a reactor and a discharge collection device 4 connected in series in sequence; the reactor is the reactor described in the above technical solution.

[0046] As a specific embodiment of the present invention, the feeding unit includes a liquid carbon source storage tank 14, an input device 12 whose inlet is connected to the outlet of the liquid carbon source storage tank 14, an auxiliary gas storage tank 13 and a preheater 11; the outlet of the liquid carbon source storage tank 14 can be provided with a delivery pump; the outlet of the liquid carbon source storage tank 14 can be connected to the inlet of the input device 12 through a first stainless steel pipe, and the diameter of the first stainless steel pipe can be 0.5-3mm, and can also be 1-2mm. As a specific embodiment of the present invention, the outlet of the input device 12 and the outlet of the auxiliary gas storage tank 13 are respectively connected to the inlet of the preheater 11; the outlet of the input device 12 can be connected to the inlet of the preheater 11 through a second stainless steel pipe, and the diameter of the second stainless steel pipe can be 0.5-3mm, and can also be 1-2mm; the outlet of the auxiliary gas storage tank 13 can be provided with a gas flowmeter, and the outlet of the auxiliary gas storage tank 13 can be connected to the inlet of the preheater 11 through a third stainless steel pipe, and the diameter of the third stainless steel pipe can be 18-22mm, and can also be 20mm. The present invention can connect the input device 12, the auxiliary gas storage tank 13 and the preheater 11 through a three-way connection. As a specific embodiment of the present invention, the input device 12 can be a liquid pump, and the liquid pump can be a high-pressure pump or a peristaltic pump.

[0047] As a specific implementation of the present invention, the coil in the preheater 11 can be a fourth stainless steel pipe, and the diameter of the fourth stainless steel pipe can be 12 to 20 mm, or can be 15 to 18 mm.

[0048] As a specific embodiment of the present invention, the outlet of the preheater 11 is connected to the inlet of the graphite tube 2 in the reactor through a pipeline, which can be connected by a flange; the material of the pipeline can be a nickel-based alloy, and the nickel-based alloy can be Incoloy 800; the diameter of the pipeline can be 1-8 mm, and can also be 3-5 mm; a nozzle can also be provided at the outlet of the pipeline, and a baffle can be provided at the nozzle outlet; the end of the pipeline at the outlet of the preheater 11 can be connected to the middle and upper part of the graphite tube 2 (the high-temperature reaction zone of the graphite tube). As a specific embodiment of the present invention, the temperature that the preheater 11 can provide can be 100-400°C, and can also be 200-300°C.

[0049] As a specific embodiment of the present invention, the reactor can be arranged vertically on a horizontal plane, the feed unit is located at the upper end of the reactor, and the discharge collection device 4 is located at the lower end of the reactor.

[0050] As a specific implementation of the present invention, the outlet of the graphite tube 2 is connected to the inlet of the discharge collection device 4; the connection can be made in the form of a sealing flange.

[0051] The present invention also provides a method for preparing single-walled carbon nanotubes using the reaction system described in the above technical solution, comprising the following steps:

[0052] The liquid carbon source and the auxiliary gas are mixed and passed into a preheater 11 for preheating to obtain a preheated mixture;

[0053] The preheated mixture is introduced into a reactor to grow single-walled carbon nanotubes to obtain the single-walled carbon nanotubes.

[0054] In the present invention, the liquid carbon source and the auxiliary gas are mixed and introduced into the preheater 11 for preheating to obtain a preheated mixture. As a specific embodiment of the present invention, the reaction system can be purged before the liquid carbon source and the auxiliary gas are introduced, and the purging gas can be argon or nitrogen.

[0055] As a specific embodiment of the present invention, the liquid carbon source may include a carbon source, a catalyst and a co-catalyst; the carbon source may include ethanol, n-butanol, benzyl alcohol, toluene, xylene or cyclohexane; the catalyst is an iron-containing compound, and the iron-containing compound may include ferrocene, carbonyl iron, iron acetate, ethanol iron or iron citrate; the co-catalyst is a sulfur-containing compound, and the sulfur-containing compound may include thiophene, carbon disulfide or sulfur. As a specific embodiment of the present invention, the mass percentage of the catalyst in the liquid carbon source may be 0.5-4.5%, and may be specifically 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%. As a specific embodiment of the present invention, the mass percentage of the co-catalyst to the total mass of the carbon source and the co-catalyst may be 0.5-4.5%, and may be specifically 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%;

[0056] The invention uses a specific catalyst to effectively control the nucleation process of the catalyst and increase the utilization rate of the catalyst.

[0057] As a specific embodiment of the present invention, the flow rate of the liquid carbon source entering the preheater 11 can be 2-15 mL / min, can be 3-10 mL / min, and can further be 4.5-5 mL / min.

[0058] As a specific embodiment of the present invention, the auxiliary gas is a mixture of an inert gas and a reducing gas; the inert gas includes argon or nitrogen; the reducing gas includes hydrogen; the volume ratio of the inert gas to the reducing gas in the auxiliary gas can be 0.8-1.2:2, specifically 1:2; the flow rate of the auxiliary gas entering the preheater 11 can be 150-250L / min, specifically 150L / min, 180L / min, 200L / min, 230L / min or 250L / min.

[0059] As a specific embodiment of the present invention, the preheating temperature may be 100-400°C, or 200-300°C.

[0060] After obtaining the preheated mixture, the present invention introduces the preheated mixture into a reactor to grow single-walled carbon nanotubes to obtain the single-walled carbon nanotubes. As a specific embodiment of the present invention, the temperature for growing the single-walled carbon nanotubes can be 1200-1600°C, specifically 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, 1550°C or 1600°C.

[0061] In the present invention, the liquid carbon source is mixed with the auxiliary gas after entering the preheater 11, and the auxiliary gas carries the carbon source, the catalyst and the co-catalyst into the high temperature zone of the reactor; after the catalyst enters the high temperature zone, it immediately decomposes into nuclei. Since it is in the high temperature zone, its saturated vapor pressure is relatively large, so it forms catalyst particles with a small particle size (2 to 3 nm) and uniformity suitable for the growth of single-walled carbon nanotubes. At the same time, the carbon source entering the high temperature zone is also immediately decomposed to generate carbon atoms, and the carbon atom adsorption-dissolution-precipitation-cap lifting process occurs on the catalyst particles, and finally single-walled carbon nanotubes are formed.

[0062] The single-walled carbon nanotubes grow in the high temperature constant temperature zone of the reactor, and after growth, the products are collected in the tail end discharge collection device 4 with the airflow and under the action of gravity, and the tail gas is treated as waste gas.

[0063] Figure 1 is a schematic diagram of the structure of the reactor. Figure 2 Schematic diagram of the structure of the reaction system used in the embodiment, wherein 11 is a preheater, 12 is an input device, 13 is an auxiliary gas storage tank, 14 is a liquid carbon source storage tank, 15 is a liquid pipeline, 16 is a gas pipeline, 17 is a baffle, 18 is a nozzle, 2 is a graphite tube, 3 is a medium frequency induction heater, 31 is a medium frequency induction heating power supply, 32 is a medium frequency induction water cooling device, and 4 is a discharge collection device.

[0064] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0065] Example 1

[0066] use Figure 2 The reaction system shown is used to prepare single-walled carbon nanotubes. The cross-section of the graphite tube in the reactor is rectangular, and the dimensions of the graphite tube are: length×width×height are 1000×200×5000mm, the thickness of the graphite tube is 50mm, and the chamfer radius is 180°; the catalyst in the liquid carbon source is ferrocene, the carbon source is ethanol, the co-catalyst is thiophene, and the mass ratio of ethanol, thiophene and ferrocene is 96:2:2; the auxiliary gas is a mixed gas of argon and hydrogen in a volume ratio of 1:2; the outlet of the liquid carbon source storage tank is connected to the inlet of the input device through a stainless steel pipe with a diameter of 2mm; the outlet of the input device is connected to the inlet of the preheater through a stainless steel pipe with a diameter of 2mm; a gas flowmeter is set at the outlet of the auxiliary gas storage tank, and the outlet of the auxiliary gas storage tank is connected to the inlet of the preheater through a stainless steel pipe with a diameter of 20mm; the outlet of the preheater is connected to the inlet of the graphite tube in the reactor through a nickel alloy pipe with a diameter of 4mm and made of Incoloy 800, and is connected in the form of a flange;

[0067] The reaction system was purged with inert gas Ar to exhaust the air inside the reaction system, and then the medium frequency induction heater was started, and the output power of the medium frequency induction heating power supply was adjusted to 80 kW, the oscillation frequency was 5 kHz, and the temperature inside the graphite tube was controlled to 1250°C;

[0068] The liquid carbon source is introduced into the preheater through an input device (peristaltic pump) at a flow rate of 5 mL / min by a delivery pump, mixed with an auxiliary gas (the auxiliary gas is delivered to the preheater at a flow rate of 200 L / min), and then preheated to 300° C. to obtain a preheated mixture;

[0069] The preheated mixture is introduced into a reactor to grow single-walled carbon nanotubes at 1250°C, and the obtained single-walled carbon nanotubes are collected in a discharge collection device;

[0070] Figure 3 is the temperature rise curve of heating the graphite tube in Example 1, Figure 3 It can be seen that the heating rate of the medium frequency induction furnace is very fast, and the temperature distribution in the furnace is uniform with a small temperature gradient.

[0071] Example 2

[0072] Single-walled carbon nanotubes were prepared according to the method of Example 1, except that the dimensions of the graphite tubes were: length×width×height: 800×300×5000 mm.

[0073] Example 3

[0074] Single-walled carbon nanotubes were prepared according to the method of Example 1, except that the size of the graphite tubes was: length×width×height: 500×500×5000 mm.

[0075] Example 4

[0076] Single-walled carbon nanotubes were prepared according to the method of Example 1, except that the output power of the medium-frequency induction heating power supply was 160 kW, the oscillation frequency was 8 kHz, and the temperature inside the graphite tube was controlled to be 1400°C.

[0077] Example 5

[0078] Single-walled carbon nanotubes were prepared according to the method of Example 1, except that the output power of the medium-frequency induction heating power supply was 160 kW, the oscillation frequency was 2 kHz, and the temperature inside the graphite tube was controlled to be 1400°C.

[0079] Comparative Example 1

[0080] Single-walled carbon nanotubes were prepared according to the method of Example 1 (the liquid carbon source was a mixed solution of ethanol, thiophene and ferrocene in a mass ratio of 96:2:2; the auxiliary gas was a mixed gas of argon and hydrogen in a volume ratio of 1:2), except that a cylindrical quartz tube with an outer diameter of 500 mm, a wall thickness of 50 mm and a height of 5000 mm was used as a reaction tube, and the quartz tube was heated by a silicon-molybdenum rod to maintain a heating temperature of 1400°C; the liquid carbon source was mixed in the quartz tube at a flow rate of 5 mL / min and the auxiliary gas at a flow rate of 200 L / min to grow single-walled carbon nanotubes, thereby obtaining single-walled carbon nanotubes.

[0081] The single-walled carbon nanotubes prepared in Examples 1 and 5 were detected using a Raman spectrometer to obtain Raman spectra. Figure 4 and Figure 5 As shown, Figure 4 This is the Raman spectrum of the single-walled carbon nanotubes prepared in Example 1. Figure 5 This is the Raman spectrum of the single-walled carbon nanotubes prepared in Example 5. Figure 4 , 5 It can be seen that there are obvious sharp RBM peaks (100~300cm -1 ), indicating that the product contains high-quality single-walled carbon nanotubes. The RBM peak is related to the radial breathing vibration mode of single-walled carbon nanotubes (SWCNTs). The RBM peak is a unique characteristic peak of single-walled carbon nanotubes. The presence of the RBM peak indicates the presence of single-walled carbon nanotubes. The sharper the RBM peak, the more uniform the diameter of the single-walled carbon nanotubes.

[0082] The single-walled carbon nanotubes prepared in Examples 1 and 5 were observed using a transmission electron microscope to obtain TEM images. Figure 6 , 7 As shown, Figure 6 This is a TEM image of the single-walled carbon nanotubes prepared in Example 1. Figure 7 This is a TEM image of the single-walled carbon nanotubes prepared in Example 5. Figure 6 , 7 In the figure, the single-walled carbon nanotube bundles are clearly visible, with a tube diameter of 1 to 2 nm and a uniform size distribution. There is basically no amorphous carbon around the single-walled carbon nanotube wall.

[0083] The yields of the single-walled carbon nanotubes prepared in Examples 1 to 5 and Comparative Example 1 were measured and listed in Table 1; the purity of the single-walled carbon nanotubes prepared in Examples 1 to 5 and Comparative Example 1 was tested by thermogravimetry, and the results are listed in Table 1; the single-walled carbon nanotubes prepared in Examples 1 to 5 and Comparative Example 1 were tested by Raman spectrometer to obtain the G / D value of the carbon material, and the results are listed in Table 1.

[0084] Table 1 Yield and purity of single-walled carbon nanotubes prepared in Examples 1 to 5 and Comparative Example 1

[0085] Example Output (g / h) purity(%) G / D value Example 1 43 75 112 Example 2 32 72 82 Example 3 12 60 58 Example 4 29 80 132 Example 5 49 90 152 Comparative Example 1 7.9 50 34

[0086] Comparing the test results of Example 1 and Example 3 in Table 1, the yield and quality of the single-walled carbon nanotubes in Example 3 are lower than those in Example 1. The reason is that due to the increase in the width of the reaction graphite tube and the influence of the airflow, the temperature inside the reaction tube is slightly uneven, which affects the effective nucleation of the catalyst and causes a decrease in yield and quality.

[0087] Comparing the test results of Example 1 and Examples 4 and 5 in Table 1, Example 4 improves the quality of single-walled carbon nanotubes compared with Example 1. The reason is that the reaction temperature is increased, which is conducive to the graphitization of carbon nanotubes, and the single wall produced also produces partial induction heating due to its excellent conductivity. The temperature rise further improves the graphitization degree of carbon tubes, reduces defects and impurity carbon, and improves the quality of carbon tubes. Example 5 reduces the oscillation frequency compared with Example 4, which is conducive to uniform heating of the heating element, thereby making the temperature inside the entire reactor more uniform, thereby promoting the nucleation of the catalyst and the growth of carbon nanotubes, thereby increasing the yield.

[0088] Comparing the test results of Example 1 and Comparative Example 1 in Table 1, due to the silicon-molybdenum rod heating method, the heating rate is lower than the medium frequency induction heating. As the auxiliary gas is introduced into the reactor, the temperature gradient inside the reaction tube is obvious, and the eddy effect significantly affects the effective nucleation of the catalyst, which has a serious impact on the growth of carbon nanotubes, reducing its yield, increasing the impurity content, and reducing its quality.

[0089] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A reactor, characterized in that: It includes a graphite tube (2) and an intermediate frequency induction heater (3) disposed on the outer surface of the graphite tube (2); the intermediate frequency induction heater (3) includes an intermediate frequency induction heating power supply (31) and an intermediate frequency induction water cooling device (32); The cross-section of the graphite tube (2) is a long square or an ellipse; the width of the rectangle is 100 - 400 mm, and the length is 500 - 2000 mm; the major diameter of the ellipse is 500 - 2000 mm, the minor diameter is 100 - 400 mm, and the ellipticity is e, where 0 < e < 1; the height of the graphite tube (2) is 5000 - 8000 mm.

2. The reactor according to claim 1, characterized in that: The wall thickness of the graphite tube (2) is 20 - 100 mm; When the cross-section of the graphite tube (2) is a long square, the right angles of the graphite tube (2) are rounded, and the radian is 60 - 240°; The output power of the intermediate frequency induction heating power supply (31) is 50 - 200 kW, and the oscillation frequency is 0.5 - 20 kHz.

3. A reaction system, characterized in that: It includes a feeding unit, a reactor, and a discharging and collecting device (4) connected in series in sequence; The feeding unit includes a liquid carbon source storage tank (14), an input device (12) with an inlet communicating with the outlet of the liquid carbon source storage tank (14), an auxiliary gas storage tank (13), and a preheater (11); the outlet of the input device (12) and the outlet of the auxiliary gas storage tank (13) are respectively communicated with the inlet of the preheater (11); The reactor is the reactor described in claim 1 or 2; The outlet of the preheater (11) is communicated with the inlet of the graphite tube (2) in the reactor through a pipeline; the outlet of the graphite tube (2) is communicated with the inlet of the discharging and collecting device (4).

4. The reaction system according to claim 3, characterized in that: The end of the pipeline at the outlet of the preheater (11) leads into the upper middle part of the graphite tube (2).

5. A method for preparing single-walled carbon nanotubes using the reaction system according to claim 3 or 4, characterized in that: It includes the following steps: Mix the liquid carbon source and the auxiliary gas and then introduce them into the preheater (11) for preheating to obtain a preheated mixture; introduce the preheated mixture into the reactor for single-walled carbon nanotube growth to obtain the single-walled carbon nanotubes.

6. The method for preparing single-walled carbon nanotubes according to claim 5, characterized in that: The liquid carbon source includes a carbon source, a catalyst, and a promoter; The carbon source includes ethanol, n-butanol, benzyl alcohol, toluene, xylene, or cyclohexane; The catalyst is an iron-containing compound; The promoter is a sulfur-containing compound; 7. The method for preparing single-walled carbon nanotubes according to claim 6, characterized in that: The iron-containing compound includes ferrocene, iron carbonyl, iron acetate, iron ethanolate, or iron citrate; The sulfur-containing compound includes thiophene, carbon disulfide, or sulfur; The mass percentage of the catalyst in the liquid carbon source is 0.5 - 4.5%; The mass percentage of the promoter in the total mass of the carbon source and the promoter is 0.5 - 4.5%; The flow rate of the liquid carbon source introduced into the preheater (11) is 2 - 15 mL / min.

8. The method for preparing single-walled carbon nanotubes according to claim 1 or 7, characterized in that: The auxiliary gas is a mixed gas of an inert gas and a reducing gas; the inert gas includes argon or nitrogen; the reducing gas includes hydrogen; The volume ratio of the inert gas to the reducing gas in the auxiliary gas is 0.8 - 1.2:2; The flow rate of the auxiliary gas introduced into the preheater (11) is 150 - 250 L / min.

9. The method for preparing single-walled carbon nanotubes according to claim 5, characterized in that: The temperature of the preheating is 100 - 400 °C.

10. The method for preparing single-walled carbon nanotubes according to claim 5, characterized in that: The temperature for growing the single-walled carbon nanotubes is 1200-1600°C.

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