CN114162804B - Device and method for preparing single-walled carbon nanotube by expandable floating catalytic cracking - Google Patents

Abstract

The invention belongs to the technical field of nano material preparation, and relates to a device and a method for preparing a single-walled carbon nanotube by expandable floating catalytic cracking. The device includes: the device comprises a powder feeder, a product synthesis unit and a product collection unit, and also comprises a catalyst pretreatment unit for preheating and accelerating catalyst particles; the powder feeder is connected with one end of the catalyst pretreatment unit, the other end of the catalyst pretreatment unit is connected with one end of the product synthesis unit, the other end of the product synthesis unit is connected with the product collection unit, and a carbon source mixed gas inlet is formed in the end part of one end, connected with the catalyst pretreatment unit, of the product synthesis unit. The device and the method are easy to implement, are beneficial to realizing large-scale continuous preparation of the single-walled carbon nanotube, have great significance for the industrialization of the boosting single-walled carbon nanotube, have similar effects for other similar reactors and have certain universality.

Description

Device and method for preparing single-walled carbon nanotube by expandable floating catalytic cracking

Technical Field

The invention belongs to the technical field of nano material preparation, and relates to a device and a method for preparing a single-walled carbon nanotube by expandable floating catalytic cracking.

Background

As a novel nano material, the single-walled carbon nanotube (SWCNT) has excellent mechanical and electrical properties, a huge length-diameter ratio and a large specific surface area, and has potential application prospects in the aspects of electrochemical energy storage, catalysis, compounding, nano devices and the like. Many colleges, scientific research institutions and companies at home and abroad research how to combine the large-scale production of the single-wall carbon nanotube.

To date, there are three main ways of preparing single-walled carbon nanotubes: arc, laser ablation and plasma CVD chemical vapor deposition, compared to which Floating Catalytic Chemical Vapor Deposition (FCCVD) is an economical process and therefore the most common synthesis method has been in the last decade.

In the Floating Catalytic Chemical Vapor Deposition (FCCVD), a mixture of hydrocarbon containing a metal catalyst is injected into a high-temperature reactor when carrier gas is introduced, a carbon source forms SWCNT under the action of the catalyst, a large number of SWCNT are self-assembled to form an aerogel structure, aerogel can be blown to an outlet position to be collected under the action of the carrier gas, and the carbon nanotube aerogel is difficult to realize continuous collection.

There is a control of the yield by controlling the amount of sulphur, known in the prior art as Nanoscale,2019, 11, 18483-1849, by controlling the iron and sulphur (Fe/S) ratio to grow highly graphitic (G/D ratio of about 100) single-walled carbon nanotubes, under certain conditions if the Fe/S ratio is low enough the production can be scaled up to some extent, but the yield of single-walled carbon nanotubes is not sufficient to produce orders of magnitude variations.

The Chinese patent publication No. CN109437157A discloses a chemical vapor deposition method of a floating catalyst of a single-walled carbon nanotube, which adopts a horizontal tube furnace (the inner diameter of the furnace tube is 39 mm, the length of the reaction zone is 250 mm) with a 0.3 liter reaction cavity, the productivity of the horizontal tube furnace is 0.32 g/h, and the technical problem of the daily output of hectogram cannot be broken through.

The size factor of the reactor also restricts the capacity of preparing the single-walled carbon nanotube by the floating catalytic chemical vapor deposition method, and the Chinese patent publication No. CN111348642A further improves the reaction efficiency and the reaction capacity by increasing a reaction pipeline; a single vertical reaction pipeline (the inner diameter of a furnace tube is 50 mm, the length of a reaction zone is 250 mm) with a single reaction cavity of 0.5 liter is adopted, and the productivity is 1.1 g per hour; the ten vertical reaction pipelines (the inner diameter of the furnace tube is 50 mm, the length of the reaction zone is 250 mm) with 0.5L reaction cavities are arranged in an array mode, the productivity is 11 g/h, the productivity of daily kilogram-grade single-walled carbon nanotubes is difficult to break through, and the product collection continuity is uncontrollable.

The diameter of the prepared carbon nano tube depends on the size of the metal crystal size of the catalyst, so that the catalyst nano particles with narrow size are controlled and distributed in the floating catalytic chemical vapor deposition, which is important for generating the single-walled carbon nano tube, the retention time of the catalyst is too long before the catalyst size meets a carbon source for growth, the catalyst particles continuously grow, and byproducts such as multi-walled carbon nano tubes, graphitized carbon and the like are easily generated.

The yield is a difficult problem for restricting the industrialization of the technical scheme for preparing the single-walled carbon nanotube by FCCVD. How to prepare a large amount of catalyst particles with narrow size distribution to react with a carbon source in a reaction zone is a key technology for realizing the bright preparation of single-walled carbon nanotubes by floating catalytic cracking.

Disclosure of Invention

The invention discloses a device and a method for preparing a single-walled carbon nanotube by expandable floating catalytic cracking, which are used for solving any one of the above and other potential problems in the prior art.

In order to achieve the purpose, the technical scheme of the invention is as follows: an apparatus for scalable floating catalytic cracking production of single-walled carbon nanotubes, the apparatus comprising: the device comprises a powder feeder, a product synthesis unit and a product collection unit, and also comprises a catalyst pretreatment unit for preheating and accelerating catalyst particles;

the powder feeder is connected with one end of the catalyst pretreatment unit, the other end of the catalyst pretreatment unit is connected with one end of the product synthesis unit, the other end of the product synthesis unit is connected with the product collection unit, and a carbon source mixed gas inlet is formed in the end part of one end, connected with the catalyst pretreatment unit, of the product synthesis unit.

Further, the catalyst pretreatment unit includes a main body, a gas preheater, and an acceleration unit,

the accelerating unit is arranged in the main body, and a catalyst inlet, a catalyst auxiliary agent inlet and a carrier gas injection port are arranged at one end of the main body inlet;

the side wall of the main body is also provided with a plurality of carrier gas injection ports, and the carrier gas injection ports on the side wall of the main body are communicated with the accelerating unit;

the gas preheater is disposed on each of the carrier gas injection ports.

Further, the volume of the reaction chamber of the product synthesis unit is 50 to 200 times the volume of the interior of the main body of the catalyst pretreatment unit, and the total volume of the catalyst pretreatment unit is 0.3L to 30L.

Furthermore, the acceleration unit comprises a plurality of acceleration units, and the plurality of acceleration units form a non-closed conical structure in an end-to-end nesting manner;

and each acceleration monomer is in a circular truncated cone shape, and the included angle between the axial direction of each acceleration monomer and the side edge is 3-60 degrees.

The non-closed conical structure comprises at least 3 accelerating monomers, and included angles among the accelerating monomers of a plurality of sections are the same or are sequentially increased in equal proportion. The accelerating monomer is made of 310S stainless steel, tantalum, tungsten or graphite.

Another object of the present invention is to provide a method for preparing single-walled carbon nanotubes using the above apparatus, the method comprising the steps of:

s1) placing a catalyst in a powder feeder, and introducing inert gas for emptying;

s2) starting the catalyst pretreatment unit and the product synthesis unit, preheating the catalyst pretreatment unit, and heating the product synthesis unit for later use;

s3) quantitatively injecting the catalyst into a catalyst pretreatment unit through a powder feeder, preheating carrier gas, injecting a catalyst auxiliary agent and the catalyst to form mixed gas flow, accelerating the mixed gas flow, and sending the accelerated mixed gas flow into a product synthesis unit;

and S4) injecting the preheated carbon source mixed gas into the product synthesis unit, reacting the carbon source mixed gas with the mixed gas flow in the product synthesis unit, enabling the generated product to enter a product collection unit along with the gas through a connecting pipeline, and separating to obtain a final product.

Further, the preheating temperature of the catalyst pretreatment unit in the S2) is 200-680 ℃; the product synthesis unit is heated to 800-1600 ℃;

the preheating temperature of the carrier gas in the S3) is 200-680 ℃; the iron/sulfur ratio in the catalyst and the catalytic promoter is 1; the gas flow rate at the outlet of the catalyst pretreatment unit is 5-50 meters per second;

the preheating temperature of the carbon source mixed gas in the step S4) is 300-550 ℃.

Further, the carrier gas in the step S3) is a mixed gas of argon and hydrogen;

the catalyst is ferrocene;

the catalytic auxiliary agent is thiophene, dimethyl sulfoxide, carbon disulfide or other sulfur-containing compounds;

s4), the volume of the carbon source gas mixture including the carbon source gas is 5-45%; 10-50% of reducing gas, 0.1-5% of water vapor and the balance of inert gas.

Further, the carbon source gas is at least one of methane, ethylene and propylene, the reducing gas is at least one of hydrogen, carbon monoxide or ammonia gas, and the inert gas is argon, nitrogen or helium.

The single-walled carbon nanotube is prepared by the method.

The invention has the beneficial effects that: by adopting the technical scheme, the catalyst nano particles with narrow size distribution are prepared firstly, and then the catalyst particles with narrow size distribution are sent into the reaction cavity for reaction with the carbon source mixed gas by the catalyst pretreatment unit before further growth, so that a large amount of catalyst particles with narrow size distribution are kept in the reaction cavity, a road is paved for the large-scale production of the single-walled carbon nano tubes by the floating catalytic cracking, and the expandability is shown.

The powdered catalyst ferrocene is melted and sublimated to form a gas state by preheating the carrier gas, and meanwhile, a sulfur-containing liquid catalyst assistant such as thiophene is introduced, and the two substances are mixed more uniformly in a gas state after being gasified by the preheating carrier gas, so that the catalyst nano-particles with narrower and more uniform size distribution can be obtained. The catalyst nanoparticles used in the preparation have an average size of less than 30nm, preferably catalytic in the range of 1 to 8nm,

the carbon source mixed gas is preheated and then injected into the reaction cavity, so that the carbon source mixed gas and the catalyst nano particles coming out of the catalyst pretreatment unit are combined more uniformly, the load of a heater is reduced, the uniformity of a temperature field of the reaction cavity is kept, and the aim of preparing a large number of single-walled carbon nano tubes in an expandable manner is fulfilled finally.

The device and the method can be beneficial to continuously and effectively obtaining macro single-walled carbon nanotubes. Meanwhile, the reactor has similar effect on other similar reactors and has certain universality.

With regard to the nanostructures obtained using the described methods and apparatus, they are involved in many of the most promising directions in material science, nanotechnology, nanoelectronics, applied chemistry and others.

For example, carbon nanotubes can be used to make adsorbents, catalyst materials, and various composite materials. The application is attributed to its large specific surface area, high strength, high electrical and thermal conductivity properties.

The unique electrical properties of carbon nanotubes make them one of the basic materials in nanoelectronics. A prototype of field effect transistor based on single walled nanotubes has been developed.

Single-walled carbon nanotubes are used in the computer industry. For example, prototypes for thin flat panel displays operating on nanotube substrates have been created and tested. The pixel size of such a display will be of the order of microns.

Ultra-thin films of single-walled carbon nanotubes are used to fabricate sensors, biochips in electronics, to monitor activity and to target drug delivery fields. In the future development trend, the development of biosensors and application in nanotechnology will allow the design and fabrication of micro-analyzers for clinical applications. It should be noted that only a small number of applications are mentioned here, and the application prospects are broad.

Drawings

FIG. 1 is a schematic structural diagram of an apparatus for preparing single-walled carbon nanotubes by scalable floating catalytic cracking according to the present invention.

Fig. 2 is a schematic structural diagram of the acceleration unit shown in fig. 1 according to the present invention.

FIG. 3 is a side view of a portion of the catalyst pretreatment unit shown in phantom in FIG. 2 according to the present invention.

FIG. 4 is a front view of the accelerating cell of FIG. 2 according to the present invention.

FIG. 5 is a schematic scanning electron microscope of the single-walled carbon nanotube prepared in example 3 of the present invention.

FIG. 6 is a schematic diagram of thermogravimetric characterization of single-walled carbon nanotubes prepared by the apparatus of the present invention in example 3 of the present invention.

Fig. 7 is a raman spectrum of the single-walled carbon nanotube prepared in example 3 of the present invention.

Fig. 8 is a schematic view of the absorption spectrum of the single-walled carbon nanotube prepared in example 4 of the present invention.

Fig. 9 is a schematic diagram of a transmission electron microscope of the single-walled carbon nanotubes prepared in example 5 of the present invention.

Fig. 10 is a schematic view of a transmission electron microscope of the single-walled carbon nanotube prepared in example 5 of the present invention.

In the figure:

10. a catalyst pretreatment unit, 101, a main body, 102, an acceleration unit, 103, an acceleration monomer, 11, a powder feeder, 12, a catalyst auxiliary injection port, 14, 16 and 18, a carrier gas injection port, and 15, 17, 19 and 22 are explosion-proof gas preheaters; 20. a product synthesis unit, 21, a carbon source mixed gas injection port, 22, an explosion-proof gas preheater and 25, a reaction cavity; 30. and a product collecting unit.

Detailed Description

The technical solution of the present invention is further explained with reference to the accompanying drawings and specific embodiments.

As shown in fig. 1, the present invention provides an apparatus for preparing single-walled carbon nanotubes by scalable floating catalytic cracking, the apparatus comprising: the device comprises a powder feeder, a product synthesis unit and a product collection unit, and also comprises a catalyst pretreatment unit for preheating and accelerating catalyst particles;

the powder feeder is connected with one end of the catalyst pretreatment unit, the other end of the catalyst pretreatment unit is connected with one end of the product synthesis unit, the other end of the product synthesis unit is connected with the product collection unit, and a carbon source mixed gas inlet is formed in the end part of one end, connected with the catalyst pretreatment unit, of the product synthesis unit.

As shown in fig. 2 to 4, the catalyst pre-treatment unit includes a main body, a gas preheater and an acceleration unit,

the accelerating unit is arranged in the main body, and a catalyst inlet, a catalyst auxiliary agent inlet and a carrier gas injection port are arranged at one end of the main body inlet;

the side wall of the main body is also provided with a plurality of carrier gas injection ports, and the carrier gas injection ports on the side wall of the main body are communicated with the accelerating unit;

the gas preheater is arranged on each carrier gas injection port;

the acceleration unit comprises a plurality of acceleration monomers, and the acceleration monomers form a non-closed conical structure in an end-to-end nesting mode; and each accelerating monomer is uniformly communicated with one carrier gas injection port in a matching way, then is accelerated and discharged from an outlet of the accelerating monomer, and after the accelerating monomers are sequentially superposed, the gas flow velocity of the carrier gas is increased to 5-50 meters per second.

Each acceleration monomer is in a round table shape, the included angle A between the axial direction of each acceleration monomer and the side edge is 3-60 degrees,

the volume of the reaction chamber of the product synthesis unit is 50-200 times of the volume of the interior of the main body of the catalyst pretreatment unit, and the total volume of the catalyst pretreatment unit is 0.3L-30L.

As shown in fig. 3, the non-closed conical structure includes at least 3 accelerating monomers, and the included angles between the accelerating monomers are the same or are sequentially increased in equal proportion. The accelerating monomer is made of 310S stainless steel, tantalum, tungsten or graphite.

A method for preparing single-walled carbon nanotubes by adopting the device comprises the following steps:

s1) placing a catalyst in a powder feeder, and introducing inert gas for emptying;

s2) starting the catalyst pretreatment unit and the product synthesis unit, preheating the catalyst pretreatment unit, and heating the product synthesis unit for later use;

s3) quantitatively injecting the catalyst into a catalyst pretreatment unit through a powder feeder, preheating carrier gas, injecting a catalyst auxiliary agent and the catalyst to form mixed gas flow, accelerating the mixed gas flow, and sending the accelerated mixed gas flow into a product synthesis unit;

and S4) injecting the preheated carbon source mixed gas into the product synthesis unit, reacting the carbon source mixed gas with the mixed gas flow in the product synthesis unit, enabling the generated product to enter a collection unit along with the gas through a connecting pipeline, and separating to obtain a final product.

The preheating temperature of the catalyst pretreatment unit in the S2) is 200-680 ℃; the product synthesis unit is heated to 800-1600 ℃;

the preheating temperature of the carrier gas in the S3) is 200-680 ℃; the iron/sulfur ratio in the catalyst and the catalytic promoter is 1; the gas flow rate at the outlet of the catalyst pretreatment unit is 5-50 meters per second;

the preheating temperature of the carbon source mixed gas in the step S4) is 300-550 ℃.

The carrier gas in the S3) is a mixed gas of argon and hydrogen;

the catalyst is ferrocene;

the catalytic promoter is thiophene, dimethyl sulfoxide, carbon disulfide or other sulfur-containing compounds;

s4), the volume of the carbon source gas mixture including the carbon source gas is 5-45%; 10-50% of volume of reducing gas, 0.1-5% of water vapor and the balance of inert gas.

The carbon source gas is at least one of methane, ethylene and propylene, the reducing gas is at least one of hydrogen, carbon monoxide or ammonia gas, and the inert gas is argon, nitrogen or helium.

The single-walled carbon nanotube is prepared by the method.

Example 1:

preheating carrier gas to 280 ℃, starting a catalyst pretreatment unit, and simultaneously heating a product synthesis unit to 900 ℃; and then injecting ferrocene into a catalyst pretreatment unit with the total volume of 0.5L by a powder feeder, simultaneously injecting a catalyst auxiliary agent thiophene, preheating a carrier gas pair, mixing the catalyst and the catalyst auxiliary agent, and then feeding the mixture into the catalyst pretreatment unit, wherein the molar ratio of iron to sulfur in the catalyst and the catalyst auxiliary agent is controlled to be 1. Introducing carbon source mixed gas into a reaction cavity with the volume of 25L for synthesis reaction, enabling the generated product to enter a product collecting unit along with the gas through a connecting pipeline, and obtaining a final product in a filtering and separating mode.

The carbon source mixed gas comprises carbon source gas 10% of methane, reducing gas with the volume of 32% of hydrogen and 2% of water vapor, and the balance argon inert gas, wherein the carbon source mixed gas is preheated to 300 ℃.

The catalyst pretreatment unit contained angle adopt 4 groups of equal ratio 1 for 1 to make up the mutual nested non-closed toper structure of acceleration unit, the axial is 15 degrees with the contained angle of side, the distance is 3 millimeters, adopts 310S stainless steel for acceleration unit material. The final catalyst pretreatment unit outlet gas flow rate was 18 meters per second.

As is clear from Table 1, the average G/D ratio of the product obtained in example 1 was 14, the TG residue of the product was 37.6%, and the yield was 0.12kg/h.

Example 2

The apparatus and process used in example 1 differ in that the carrier gas is preheated to 400 ℃ and the product synthesis unit is warmed to 1170 ℃;

the total volume of the catalyst pretreatment unit is 8L, and the volume of the reaction cavity is 400L;

the product collecting unit obtains a final product by a moving scraper mode.

The carbon source mixed gas comprises carbon source gas 12% of methane, reducing gas 35% of hydrogen and carbon monoxide 5% of mixed gas, water vapor is 3%, and the balance is nitrogen inert gas. Wherein the carbon source mixed gas is preheated to 430 ℃.

The included angle of the accelerating monomer of the catalyst pretreatment unit adopts 3 groups of combined accelerating units which are nested in a non-closed conical structure in an equal ratio of 1. And a tungsten high-temperature-resistant material is adopted, and the gas flow rate at the outlet of the final catalyst pretreatment unit is 35 meters per second.

As is clear from Table 1, the average G/D ratio of the product obtained in example 2 was 23, and the TG residue of the obtained product was 38.5%, and the yield was 0.15kg/h.

Example 3

The apparatus and process used in example 2 differ in that the carrier gas is preheated to 660 ℃ and the product synthesis unit is warmed to 1370 ℃;

the total volume of the catalyst pretreatment unit is 18L, and the volume of the reaction cavity is 2000L;

the iron/sulfur ratio is controlled to be 1;

the collection unit obtains a final product in a cyclone separation mode.

The carbon source mixed gas comprises 15% of carbon source gas methane, 50% of reducing gas hydrogen, 5% of water vapor and the balance of nitrogen inert gas. Wherein the carbon source mixed gas is preheated to 480 ℃.

The included angle of the accelerating monomer of the catalyst pretreatment unit adopts 6 groups of non-closed conical structures which are embedded into each other by combining the accelerating units with the equal ratio of 1. And a graphite high-temperature-resistant material is adopted, and the gas flow velocity at the outlet of the final catalyst pretreatment unit is 48 meters per second.

From FIG. 5, the Raman spectrum of the sample prepared in example 3 has a distinct RBM characteristic absorption peak, and the G/D ratio is 67, i.e. the product is a single-walled carbon nanotube with high graphitization degree; from the thermogravimetric graph of the single-walled carbon nanotube prepared in example 3 of fig. 4, it can be seen that the residual mass is 19.3%, no obvious decomposition is seen at 400 ℃, and the purity of the single-walled carbon nanotube is high; as can be seen from the scanning electron microscope of FIG. 2, the surface impurities of the sample of example 3 are less, and the yield is 1.8kg/h, which is significantly higher than those of examples 1 and 2.

Example 4

The apparatus and process used in example 3 were distinguished in that the product synthesis unit was warmed to 1450 ℃ with the carrier gas preheated to 550 ℃;

the total volume of the catalyst pretreatment unit is 25L, and the volume of the reaction cavity is 3000L;

the carbon source mixed gas comprises a carbon source gas of 20% of methane, a reducing gas of 55% of hydrogen and 5% of carbon monoxide, water vapor of 5% and the balance of nitrogen inert gas. Wherein the carbon source mixed gas is preheated to 520 ℃.

The included angle of the catalyst pretreatment unit adopts a non-closed conical structure in which 3 groups of combined accelerating monomers with the difference of 10 degrees are nested with each other, the included angles are respectively 20 degrees, 30 degrees and 40 degrees, and the distance is 30 millimeters. The gas flow rate at the outlet of the final catalyst pretreatment unit was 45 meters per second.

It can be seen from table 1 that the average G/D ratio of the product obtained in example 2 was 78, the TG residue of the product was 8.5%, and the yield was 2.3kg/h, and from the absorption spectrum of the sample single-walled carbon nanotube prepared in example 4 of fig. 6, the product was a single-walled carbon nanotube and had a high purity.

Example 5

The apparatus and process of example 4 are used except that the carrier gas is preheated to 650 deg.C and the product synthesis unit is warmed to 1350 deg.C;

the total volume of the catalyst pretreatment unit is 15L, and the volume of the reaction cavity is 1600L;

the carbon source mixed gas comprises carbon source gas 5% of methane and 5% of ethylene mixed gas, reducing gas 56% of hydrogen, water vapor 5%, and the balance nitrogen inert gas. Wherein the carbon source mixed gas is preheated to 520 ℃.

The catalyst pretreatment unit included angle adopts 5 groups of combined accelerating monomers with difference of 5 degrees to nest into a non-closed conical structure, the included angles are respectively 10 degrees, 20 degrees, 30 degrees, 40 degrees and 50 degrees, and the distance is 15 millimeters. And a 310S stainless steel high-temperature-resistant material is adopted, and the gas flow rate at the outlet of the catalyst pretreatment unit is 36 meters per second finally.

As shown in fig. 7, the transmission electron microscope characterization of the single-walled carbon nanotube prepared in example 5 shows that the prepared catalyst has a uniform particle size distribution, and fig. 8 shows the characterization result with high resolution shows that the prepared catalyst has a particle size of about 3nm. As is clear from Table 1, the average G/D ratio of the product obtained in example 2 was 74, and the TG residue of the obtained product was 21.3%, and the yield was 1.3kg/h.

Comparative example 1

The same method and apparatus were used as in example 4, except that no accelerating elements were used to nest the non-closed conical structures with each other. It can be seen from table 1 that the average G/D ratio of the product obtained in example 2 is 15, the yield is 0.06kg/h, and therefore the TG residue of the product is increased to 67.3%, which is not only significantly lower than that of example 4 in quality and purity, but also has a yield difference of 2 orders of magnitude, and fails to break through the target of single-walled carbon nanotubes of kilogram-level daily output. The non-use of a catalyst pretreatment unit leads to the inactivation of a large amount of prepared nano iron particles before the nano iron particles enter a reaction cavity and are combined with a carbon source to form large nano particles, and the objective condition of forming single-walled carbon nanotubes is not met, so the purity of the product is low.

TABLE 1 comparison of material Properties of an apparatus and method for preparing single-walled carbon nanotubes by scalable floating catalytic cracking in examples and comparative examples

	Average G/D ratio	TG residual mass (%)	Yield (kg/h)
				Example 1	14	37.6	0.12
Example 2	23	38.5	0.15
				Example 3	67	19.3	1.8
Example 4	78	23.5	2.3
				Example 5	74	21.3	1.3
Comparative example 1	15	67.3	0.06

Description of the principle:

the diameter of the prepared carbon nano tube depends on the size of the metal crystal size of the catalyst, so that the catalyst nano particles with narrow size are controlled and distributed in the floating catalytic chemical vapor deposition, which is important for generating the single-walled carbon nano tube, the retention time of the catalyst is too long before the catalyst size meets a carbon source for growth, the catalyst particles continuously grow, and byproducts such as multi-walled carbon nano tubes, graphitized carbon and the like are easily generated.

How to prepare a large amount of catalyst particles with narrow size distribution to react with a carbon source in a reaction area is a key technology for realizing the macroscopic preparation of the single-walled carbon nanotube by floating catalytic cracking.

According to the invention, the catalyst nano particles with narrow size distribution are prepared, and then the catalyst pre-treatment unit is used for sending the catalyst nano particles with narrow size distribution into the reaction cavity to react with the carbon source before the catalyst nano particles do not grow further, so that a large amount of catalyst nano particles with narrow size distribution are kept in the reaction cavity, thus a road is paved for the large-scale production of single-walled carbon nano tubes by floating catalysis, and the expandability is demonstrated.

The invention can control the catalyst particle size through iron/sulfur ratio control to prepare high-quality single-walled carbon nanotube, and the invention leads powdered catalyst ferrocene to be melted and sublimated to form gas state through preheating carrier gas, and simultaneously introduces sulfur-containing liquid catalyst auxiliary agent such as thiophene, and the two substances are mixed more uniformly in the gas state after being gasified by preheating carrier gas. The catalyst pretreatment unit is used for preparing a large amount of catalyst nano particles with controllable sizes and narrow distribution by controlling the air flow rate and the temperature field, and quickly sending the optimized catalyst nano particles with narrow sizes into the reaction cavity to react with the preheated carbon source mixed gas in time. Finally, the aim of massively preparing the single-walled carbon nanotube is achieved. The catalyst nanoparticles used for preparation have an average size of less than 50nm, preferably catalytic particle size of 1-8nm, to grow high quality single-walled carbon nanotubes. As can be seen from the transmission electron microscope of the single-walled carbon nanotube prepared in fig. 9, the size distribution of the prepared catalyst particles is relatively uniform, and as can be seen from the characterization results of fig. 10 with high resolution, the size of the prepared catalyst particles is about 3nm.

The above provides an apparatus and a method for preparing single-walled carbon nanotubes by scalable floating catalytic cracking, which are provided by embodiments of the present application and are described in detail. The above description of the embodiments is only for the purpose of helping to understand the method of the present application and its core ideas; meanwhile, for a person skilled in the art, according to the idea of the present application, the specific implementation manner and the application scope may be changed, and in summary, the content of the present specification should not be construed as a limitation to the present application.

As used in the specification and claims, certain terms are used to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. "substantially" means within an acceptable error range, and a person skilled in the art can solve the technical problem within a certain error range to substantially achieve the technical effect. The following description is of the preferred embodiment for carrying out the present application, but is made for the purpose of illustrating the general principles of the application and is not to be taken in a limiting sense. The protection scope of the present application shall be subject to the definitions of the appended claims.

It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a good or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such good or system. Without further limitation, an element defined by the phrases "comprising one of 8230; \8230;" 8230; "does not exclude the presence of additional like elements in articles of commerce or systems including such elements.

It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter associated objects are in an "or" relationship.

The foregoing description shows and describes several preferred embodiments of the present application, but as aforementioned, it is to be understood that the application is not limited to the forms disclosed herein, but is not to be construed as excluding other embodiments and is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the application as described herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the application, which is to be protected by the claims appended hereto.

Claims (7)

1. An apparatus for scalable floating catalytic cracking production of single-walled carbon nanotubes, the apparatus comprising: the device comprises a powder feeder, a product synthesis unit and a product collection unit, and also comprises a catalyst pretreatment unit for preheating and accelerating catalyst particles;

the powder feeder is connected with one end of the catalyst pretreatment unit, the other end of the catalyst pretreatment unit is connected with one end of the product synthesis unit, the other end of the product synthesis unit is connected with the product collection unit, and a carbon source mixed gas inlet is formed in the end part of one end, connected with the catalyst pretreatment unit, of the product synthesis unit; characterized in that the catalyst pretreatment unit comprises a main body, a gas preheater and an acceleration unit,

the accelerating unit is arranged in the main body, and a catalyst inlet, a catalyst auxiliary agent inlet and a carrier gas injection port are arranged at one end of the main body inlet;

the side wall of the main body is also provided with a plurality of carrier gas injection ports, and the carrier gas injection ports on the side wall of the main body are communicated with the accelerating unit;

the gas preheater is arranged on each carrier gas injection port;

the acceleration unit comprises a plurality of acceleration monomers, and the acceleration monomers form a non-closed conical structure in an end-to-end nesting mode; and each accelerating monomer is in a circular truncated cone shape, and the included angle between the axial direction of each accelerating monomer and the side edge is 3-60 degrees.

2. The apparatus of claim 1, wherein the volume of the reaction chamber of the product synthesis unit is 50-200 times the volume of the interior of the body of the catalyst pretreatment unit.

3. The device of claim 1, wherein the non-closed conical structure comprises at least 3 accelerating cells, and the accelerating cells are made of 310S stainless steel, tantalum, tungsten, or graphite.

4. A method for preparing single-walled carbon nanotubes using the apparatus of any one of claims 1 to 3, wherein the method comprises

The method specifically comprises the following steps:

s1) placing a catalyst in a powder feeder, and introducing inert gas for emptying;

s2) starting the catalyst pretreatment unit and the product synthesis unit, preheating the catalyst pretreatment unit, and starting heating the product synthesis unit for later use;

s3) quantitatively injecting the catalyst into the catalyst pretreatment unit through the powder feeder, preheating the carrier gas, injecting the preheated carrier gas into the catalyst pretreatment unit to form mixed gas flow with the injected catalyst auxiliary agent and the catalyst, accelerating the mixed gas flow, and sending the accelerated mixed gas flow into the product synthesis unit;

s4) then injecting the preheated carbon source mixed gas into a product synthesis unit, wherein the carbon source mixed gas and the mixed gas flow are synthesized in the product

The resultant product enters a product collecting unit along with the airflow through a connecting pipeline, and the final product is obtained after separation.

5. The method according to claim 4, wherein the preheating of the catalyst pretreatment unit in S2)

The temperature is 200-680 ℃; the product synthesis unit is heated to 800-1600 ℃;

the preheating temperature of the carrier gas in the S3) is 200-680 ℃; the iron/sulfur ratio in the catalyst and the catalytic promoter is 1; the gas flow rate at the outlet of the catalyst pretreatment unit is 5-50 meters per second;

the preheating temperature of the carbon source mixed gas in the S4) is 300-550 ℃.

6. The method as claimed in claim 5, wherein the carrier gas in S3) is a mixed gas of argon and hydrogen;

the catalyst is ferrocene; the catalytic auxiliary agent is thiophene, dimethyl sulfoxide, carbon disulfide or other sulfur-containing compounds;

s4), the volume of the carbon source gas mixture including the carbon source gas is 5-45%; 10-50% of reducing gas, 0.1-5% of water vapor and the balance of inert gas.

7. The method of claim 6, wherein the carbon source gas is at least one of methane, ethylene, and propylene, the reducing gas is at least one of hydrogen, carbon monoxide, or ammonia, and the inert gas is argon, nitrogen, or helium.

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