Preparation method of composition containing carbon nanotubes

Abstract

The invention belongs to the crossing field of a nanometer material preparation technology and a rubber industry composite material technology, and particularly relates to a preparation method of a composition containing a carbon nanotube. The invention aims to solve the problems of non-uniform dispersion of carbon black and carbon nanotubes, complex process and non-adjustable product components in the prior art. The method comprises the following steps: mixing high-dispersion silicon dioxide with iron (III), molybdenum (VI) and aluminum composite oxide (Fe: Mo: Al = 14: (1-5): (7-20)) to prepare a catalyst, shearing and mixing the catalyst and a liquid hydrocarbon raw material, injecting the mixture into a high-temperature reactor (1350-1800 DEG C), decomposing to generate carbon black and carbon nanotubes, rapidly cooling, and separating; by optimizing the catalyst and the process, the contents of the carbon black (85-98wt%) and the carbon nanotubes (0.6-9wt%) are regulated and controlled, and the performance of the rubber composite material is improved; the dispersity and the performance adaptability of the product in the rubber composite material are remarkably improved, and the method is suitable for industrial production of products such as tires and transmission belts.

Description

Technical Field

[0001] The present invention belongs to the cross - field of nanomaterial preparation technology and rubber industrial composite material technology, and specifically relates to a preparation method of a composition containing carbon nanotubes. Background Art

[0002] Carbon nanotubes (CNT) are widely used as reinforcing agents for rubber composites due to their excellent mechanical, electrical, and thermal properties. In the prior art, the following methods are mainly used to prepare compositions containing carbon nanotubes, but there are still significant defects:

[0003] Physical mixing method: As described in patent EP4286465 (IPC C08K3 / 04, publication date: December 6, 2023), carbon nanotubes are dispersed in a liquid medium and mixed with carbon black and then dried. Although this method is simple to operate, due to the surface energy difference between carbon black and carbon nanotubes, the dispersion is uneven and the interfacial binding force is weak, which limits the improvement of the mechanical properties of rubber products. In addition, agglomeration is likely to occur during the drying process, further exacerbating the performance fluctuations.

[0004] Suspension blending method: As described in the literature "Ηοвый метοд смешивания суспензии для пοлучения равнοмернοй дисперсии углерοдных нанοтрубοк в кοмпοзитахиз натуральнοгο каучука, Results in Physics,2019Volume 15,December 2019,102720", carbon nanotubes are added in batches to natural latex, combined with ultrasonic dispersion and mechanical mixing. Although the dispersion can be partially improved by step - by - step addition, the process involves multiple steps (such as multiple grindings, staged mixing, and long - time drying), the process is cumbersome and energy - consuming, and it is difficult to scale up industrially. In addition, the carbon nanotube content in the final product is limited by the addition method and cannot be flexibly adjusted.

[0005] Chemical vapor deposition method: As described in patent EP3305723 (IPC C01B 32 / 162, publication date: April 11, 2018), carbon nanotubes are grown on the surface of a catalyst by high - temperature pyrolysis of a carbon source gas (such as methane). Although this method can achieve high yields, the product composition is single (mainly carbon nanotubes), it is difficult to simultaneously generate carbon black, and small changes in the catalyst composition and reaction conditions (such as temperature, carrier gas flow rate) easily lead to uncontrollable product structures, and cannot meet the multi - scenario requirements of the carbon black / carbon nanotube ratio for rubber composites.

[0006] Coupling preparation method: As described in US Patent US20220227630A1 (IPC C01B 32 / 162, publication date: July 21, 2022), during the production of carbon black, by-product gas is used to synthesize carbon nanostructures. Although this process can prepare carbon black and carbon nanotubes synchronously, it requires multi-stage gas purification and the introduction of an additional catalyst reactor, with complex equipment and high costs. In addition, the generation processes of carbon black and carbon nanotubes are independent of each other, and the composition ratio of the products is limited by the cracking efficiency of the raw materials, making it difficult to accurately control.

[0007] In summary, the existing technologies generally have defects such as poor dispersion, complex processes, and uncontrollable composition, which limit the application of carbon nanotube-containing compositions in the rubber industry. Therefore, there is an urgent need to develop a preparation method with a simple process, adjustable composition, and excellent dispersion. Summary of the Invention

[0008] In view of the above problems, the present invention provides a method for preparing a composition containing carbon nanotubes, which simultaneously generates carbon black and carbon nanotubes by catalytic cracking of hydrocarbon raw materials, aiming to solve the problems of uneven dispersion of carbon black and carbon nanotubes, complex processes, and uncontrollable product composition in the existing technologies.

[0009] The present invention includes the following technical solutions:

[0010] A method for preparing a composition containing carbon nanotubes, comprising the following steps:

[0011] (a) Prepare a catalytic additive: Mix highly dispersed silica with a composite oxide of iron (III), molybdenum (VI), and aluminum in a mass ratio of 1:1 to 85:1, wherein the mass ratio of the metals in the composite oxide is Fe:Mo:Al = 14:(1–5):(7–20);

[0012] (b) In a hydrodynamic rotary disperser, mix the catalytic additive obtained in step (a) with a liquid hydrocarbon raw material by using shear stress and cavitation;

[0013] (c) Inject the mixture obtained in step (b) into the heating zone of the reactor through a nozzle. The temperature of the heating zone is 1350–1800 °C, and heat is provided by burning a gaseous fuel or a liquid fuel, so that the liquid hydrocarbon raw material decomposes to generate carbon black, and at the same time, the catalytic additive is activated to generate carbon nanotubes;

[0014] (d) Inject chemically pure water into the end of the reactor to rapidly cool the mixture to 600–650 °C and terminate the growth of carbon black particles;

[0015] (e) Further cool the cooled mixture to 260–300 °C through a cooler, and separate the composition containing carbon nanotubes through a gas-solid separation device.

[0016] Further, in the preparation method of the above carbon nanotube-containing composition, the mixing in step (a) is completed by a high-speed mixer, the stirring speed is 10,000–12,000 revolutions per minute, and the mixing time is 5–10 minutes.

[0017] Further, in the preparation method of the above carbon nanotube-containing composition, the particle size of the highly dispersed silica in step (a) is 10–50 nm, and the specific surface area is 150–300 m 2 / g.

[0018] Further, in the preparation method of the above carbon nanotube-containing composition, the molar ratio of iron (III), molybdenum (VI) and aluminum in the composite oxide in step (a) is 1:0.05–0.3:0.5–1.5.

[0019] Further, in the preparation method of the above carbon nanotube-containing composition, the liquid hydrocarbon raw material in step (b) is one of petroleum fractions, coal tar or biomass pyrolysis oil.

[0020] Further, in the preparation method of the above carbon nanotube-containing composition, the gaseous fuel in step (c) is one of natural gas, propane or hydrogen, and the liquid fuel is one of diesel or heavy oil.

[0021] Further, in the preparation method of the above carbon nanotube-containing composition, the heating zone of the reactor in step (c) is a fuel-rich combustion environment, and the remaining air volume fraction is 1–5%.

[0022] Further, in the preparation method of the above carbon nanotube-containing composition, the injection amount of the chemically pure water in step (d) is 5–15% of the total mass of the mixture.

[0023] Further, in the preparation method of the above carbon nanotube-containing composition, the gas-solid separation device in step (e) is at least one of a cyclone dust collector, a bag filter or an electrostatic precipitator.

[0024] Further, in the preparation method of the above carbon nanotube-containing composition, the carbon black content in the carbon nanotube-containing composition in step (e) is 85–98 wt%, and the carbon nanotube content is 0.6–9 wt%.

[0025] Compared with the prior art, the present invention has the following outstanding beneficial effects:

[0026] 1. Process simplification: Through the integrated design of catalytic cracking and carbon black generation, complex steps such as multi-stage purification and dispersant addition are omitted, the process steps are reduced by more than 50%, and the energy consumption is reduced by 30%.

[0027] 2. Precise Component Regulation: By adjusting the Fe / Mo / Al ratio (14:(1–5):(7–20)) in the catalytic additive and the raw material ratio, a flexible match of the carbon black (85–98 wt%) and carbon nanotube (0.6–9 wt%) contents is achieved to meet the performance requirements of different rubber products.

[0028] 3. Excellent Dispersibility: The catalytic additive and the liquid hydrocarbon raw material undergo shear-cavitation synergistic action in a hydrodynamic rotary disperser to form a homogeneous mixture. The carbon nanotubes and carbon black in the product are evenly dispersed, and the interfacial bonding force is increased by more than 40%.

[0029] 4. High Cost-Effectiveness: Using liquid hydrocarbon raw materials (such as petroleum fractions, biomass pyrolysis oil) to replace high-purity carbon source gases reduces the raw material cost by 25%; and no additional reactor is required, reducing the equipment investment by 20%.

[0030] 5. Strong Performance Adaptability: The obtained composition shows higher tensile strength (increased by 15–25%) and conductivity (the resistivity is reduced by 1–3 orders of magnitude) in the rubber matrix, and is suitable for high-value-added products such as tires and conveyor belts. Description of the Drawings

[0031] Figure 1 Comparison of the tensile strength (MPa) of the rubber products prepared from the compositions of Examples 1-6 and Comparative Examples 1-3;

[0032] Figure 2 Comparison of the elongation at break (%) of the rubber products prepared from the compositions of Examples 1-6 and Comparative Examples 1-3. Detailed Description of the Invention

[0033] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] The main raw materials used in the present invention are as follows:

[0035] High-dispersion silica Evonik 200.

[0036] Iron(III) oxide (Fe2O3): Sigma-Aldrich 310050 (purity ≥ 99%, particle size < 50 nm);

[0037] Molybdenum(VI) oxide (MoO3): Alfa Aesar 12365 (purity 99.95%, powder);

[0038] Aluminum oxide (Al2O3): Sasol SB (specific surface area 200–300 m 2 / g, γ phase);

[0039] The above single oxides need to be mixed in proportion and a composite oxide is formed by ball milling or coprecipitation method.

[0040] Petroleum fraction: ExxonMobil TM Light cycle oil (LCO, distillation range 200–350 °C).

[0041] Coal tar: Chemicals tar fraction (ASTM D490 standard).

[0042] Biomass pyrolysis oil: Ensyn RFPTM bio-oil (ASTM D7544 standard).

[0043] Natural gas: commercially available pipeline natural gas (methane content ≥ 85%).

[0044] Propane: Air Liquide Propane C3 (purity ≥ 99.5%).

[0045] Hydrogen: Linde H25.0 (purity 99.999%).

[0046] Diesel: Sinopec No. 0 diesel (GB 19147-2016 standard).

[0047] Heavy oil: Shell Marine IFO 380 (ISO 8217 standard).

[0048] Example 1

[0049] A method for preparing a composition containing carbon nanotubes, comprising the following steps:

[0050] (a) Mix 60 g of highly dispersed silica (particle size 20 nm, specific surface area 200 m 2 / g) with 40 g of composite oxide (Fe:Mo:Al = 14:1:7) in a mass ratio of 1.5:1 and mix in a high-speed mixer at 10,000 revolutions per minute for 8 minutes to obtain a catalytic additive.

[0051] (b) Shear-mix 100 g of catalytic additive with 400 liquid petroleum fraction in a hydrodynamic rotary disperser.

[0052] (c) Inject the mixture into the heating zone of the reactor (1800 °C, natural gas fuel, 3% excess air), decompose the liquid hydrocarbon to generate carbon black, and simultaneously catalytically generate carbon nanotubes.

[0053] (d) Inject pure chemical water (10% of the total mass) into the end of the reactor and rapidly cool down to 600 °C.

[0054] (e) Cool down to 300 °C through a cooler, separate by a cyclone dust collector, and obtain a composition containing 98 wt% carbon black and 1.6 wt% carbon nanotubes.

[0055] Example 2

[0056] A method for preparing a composition containing carbon nanotubes, comprising the following steps:

[0057] (a) Mix 40 g of highly dispersed silica (particle size 20 nm, specific surface area 200 m 2 / g) with 40 g of composite oxide (Fe:Mo:Al = 14:2:10) in a mass ratio of 1:1, and mix in a high-speed mixer at 11,000 revolutions per minute for 8 minutes to obtain a catalytic additive.

[0058] (b) Shear-mix 100 g of the catalytic additive with 400 g of liquid petroleum fraction in a hydrodynamic rotary disperser.

[0059] (c) Inject the mixture into the heating zone of the reactor (1650 °C, natural gas fuel, 3% excess air), decompose the liquid hydrocarbon to generate carbon black, and simultaneously catalytically generate carbon nanotubes.

[0060] (d) Inject pure chemical water (10% of the total mass) into the end of the reactor and rapidly cool down to 600 °C.

[0061] (e) Cool down to 300 °C through a cooler, separate by a cyclone dust collector, and obtain a composition containing 93 wt% carbon black and 5.7 wt% carbon nanotubes.

[0062] Example 3

[0063] A method for preparing a composition containing carbon nanotubes, comprising the following steps:

[0064] (a) Mix 600 g of highly dispersed silica (particle size 20 nm, specific surface area 200 m 2 / g) with 40 g of composite oxide (Fe:Mo:Al = 14:4:15) in a mass ratio of 15:1, and mix in a high-speed mixer at 10,000 revolutions per minute for 8 minutes to obtain a catalytic additive.

[0065] (b) Shear-mix 100 g of the catalytic additive with 400 g of coal tar in a hydrodynamic rotary disperser.

[0066] (c) Inject the mixture into the heating zone of the reactor (1550 °C, natural gas fuel, 3% excess air), decompose the liquid hydrocarbon to generate carbon black, and simultaneously catalytically generate carbon nanotubes.

[0067] (d) Inject chemically pure water (10% of the total mass) into the end of the reactor and rapidly cool it to 600 °C.

[0068] (e) Cool it to 300 °C through a cooler, separate it through a cyclone dust collector, and obtain a composition containing 95 wt% carbon black and 1.25 wt% carbon nanotubes.

[0069] Example 4

[0070] A method for preparing a composition containing carbon nanotubes, comprising the following steps:

[0071] (a) Mix 120 g of highly dispersed silica (particle size 30 nm, specific surface area 250 m 2 / g) with 16 g of a composite oxide (Fe:Mo:Al = 14:2:12) in a mass ratio of 7.5:1 and mix them in a high-speed mixer at 12,000 revolutions per minute for 7 minutes.

[0072] (b) Shear-mix 100 g of a catalytic additive with 400 liquid petroleum fractions in a hydrodynamic rotary disperser.

[0073] (c) Inject the mixture into the heating zone of the reactor (1450 °C, diesel fuel, 2% excess air), decompose the liquid hydrocarbon to generate carbon black, and simultaneously catalytically generate carbon nanotubes.

[0074] (d) Inject chemically pure water (8% of the total mass) into the end of the reactor and rapidly cool it to 620 °C.

[0075] (e) Cool it to 280 °C through a cooler, separate it through a bag filter, and obtain a composition containing 89 wt% carbon black and 4.8 wt% carbon nanotubes.

[0076] Example 5

[0077] A method for preparing a composition containing carbon nanotubes, comprising the following steps:

[0078] (a) Mix 80 g of highly dispersed silica (particle size 40 nm, specific surface area 180 m 2 / g) with 40 g of a composite oxide (Fe:Mo:Al = 14:3:12) in a mass ratio of 2:1 and mix them in a high-speed mixer at 10,000 revolutions per minute for 10 minutes.

[0079] (b) Shear-mix 100 g of a catalytic additive with 400 g of biomass pyrolysis oil in a hydrodynamic rotary disperser.

[0080] (c) Inject the mixture into the heating zone of the reactor (1400 °C, hydrogen fuel, 4% excess air), decompose the liquid hydrocarbon to generate carbon black, and simultaneously catalytically generate carbon nanotubes.

[0081] (d) Inject chemically pure water (12% of the total mass) into the end of the reactor and rapidly cool down to 630 °C.

[0082] (e) Cool down to 270 °C through a cooler, separate by an electrostatic precipitator, and obtain a composition containing 87 wt% carbon black and 9 wt% carbon nanotubes.

[0083] Example 6

[0084] A method for preparing a composition containing carbon nanotubes, comprising the following steps:

[0085] (a) Mix 85 g of highly dispersed silica (particle size 50 nm, specific surface area 150 m 2 / g) with 1 g of composite oxide (Fe:Mo:Al = 14:3:18) in a mass ratio of 85:1, and mix in a high-speed mixer at 12,000 revolutions per minute for 6 minutes.

[0086] (b) Shear-mix 100 g of catalytic additive and 400 g of coal tar in a hydrodynamic rotary disperser.

[0087] (c) Inject the mixture into the heating zone of the reactor (1350 °C, propane fuel, 5% excess air), decompose the liquid hydrocarbon to generate carbon black, and simultaneously catalytically generate carbon nanotubes.

[0088] (d) Inject chemically pure water (15% of the total mass) into the end of the reactor and rapidly cool down to 650 °C.

[0089] (e) Cool down to 260 °C through a cooler, separate by a cyclone, and obtain a composition containing 88 wt% carbon black and 0.6 wt% carbon nanotubes.

[0090] Comparative Example 1

[0091] Prepared by physical mixing method, comprising the following steps: According to Patent EP4286465, disperse carbon nanotubes and carbon black in ethanol, and dry after mechanical stirring.

[0092] Defects: Serious agglomeration of carbon black and carbon nanotubes, only a 5% increase in tensile strength, and a resistivity fluctuation range of ±50%.

[0093] Comparative Example 2

[0094] Prepared by suspension blending method, comprising the following steps: According to the literature "Новыйметοдсмешиваниясуспензиидляпοлученияравнοмернοйдисперсииуглерοдныхнанοтрубοквкοмпοзитахизнатуральнοгοкаучука", add carbon nanotubes to natural latex in 20 portions, and vulcanize after ultrasonic dispersion.

[0095] Defect: The process takes 18 hours, the upper limit of the carbon nanotube content is only 3 wt%, and the uneven dispersion causes the elongation at break of the rubber to decrease by 20%.

[0096] Comparative Example 3

[0097] Prepared by chemical vapor deposition, including the following steps: According to Patent EP3305723, using methane as the carbon source, the Fe / Mo / Al catalyst grows carbon nanotubes at 1400 °C.

[0098] Defect: The proportion of carbon nanotubes in the product is 90 wt%, there is no coexistence of carbon black, and it cannot be directly used for rubber reinforcement. Additional carbon black needs to be added, resulting in a 30% increase in cost.

[0099] Test Example 1

[0100] Mechanical property test

[0101] 1. Sample preparation: Add the compositions of Examples 1–6 and Comparative Examples 1–3 to the natural rubber matrix at 5 wt%, mix and vulcanize (150 °C × 12 minutes).

[0102] 2. Test standards:

[0103] Tensile strength: ASTM D412, dumbbell-shaped specimen, tensile rate 500 mm / min.

[0104] Elongation at break: The elongation percentage at break of the same sample is tested.

[0105] The test results are shown in Table 1 and Figure 1 and 2 。

[0106] Table 1 Test results of mechanical properties.

[0107] Sample Tensile strength (MPa) Elongation at break (%) Example 1 28.5 580 Example 2 30.2 560 Example 3 26.8 570 Example 4 27.3 550 Example 5 32.0 540 Example 6 24.0 590 Comparative Example 1 18.2 520 Comparative Example 2 20.1 480 Comparative Example 3 22.5* 500*

[0108] (*For Comparative Example 3, additional carbon black needs to be added to 5 wt%, resulting in performance fluctuations)

[0109] 3. Data analysis

[0110] The tensile strength of Examples 1 - 6 ranges from 24.0 to 32.0 MPa, and the elongation at break ranges from 540 to 590%; the tensile strength of Comparative Examples 1 - 3 ranges from 18.2 to 22.5 MPa, and the elongation at break ranges from 480 to 520%. The tensile strength and elongation at break of the examples are significantly better than those of the comparative examples as a whole, indicating that the composition prepared by the present invention can provide better mechanical properties in the rubber matrix. In Example 5, the carbon nanotube content is the highest (9 wt%), and its tensile strength reaches 32.0 MPa, which is the highest value among the examples, indicating that carbon nanotubes have a significant effect on rubber reinforcement, and the tensile strength shows an increasing trend with the increase of the carbon nanotube content. In Example 6, the carbon nanotube content is the lowest (0.6 wt%), but the carbon black content is high (88 wt%), and its tensile strength is still 24.0 MPa, and it is better than Comparative Example 1 (pure physical mixture), indicating that even with a low carbon nanotube content, the method of the present invention can improve the mechanical properties of rubber through good dispersion and synergy.

[0111] In Comparative Example 1, due to the use of the physical mixing method, the carbon black and carbon nanotubes agglomerated severely, resulting in the lowest tensile strength of only 18.2 MPa, and the resistivity fluctuated greatly, indicating that uneven dispersion seriously affected the performance of the material.

[0112] In Comparative Example 2, the suspension blending method was used, and the process took as long as 18 hours. The upper limit of the carbon nanotube content was only 3 wt%, and uneven dispersion led to a 20% decrease in the elongation at break of the rubber, indicating that this method is not only complex in process but also difficult to obtain high-performance compositions. In Comparative Example 3, the chemical vapor deposition method was used. The carbon nanotubes accounted for 90 wt% in the product, and there was no carbon black coexistence, so it could not be directly used for rubber reinforcement. Additional carbon black needed to be added, resulting in a 30% increase in cost. At the same time, the process complexity was high, and the interfacial bonding was weak.

[0113] Test Example 2

[0114] Verification of composition controllability

[0115] 1. Sample preparation: Take 1 g of the product powders of Examples 1–6 and Comparative Examples 1–3 respectively.

[0116] 2. Test conditions:

[0117] Thermogravimetric analysis (TGA): In a nitrogen atmosphere, the heating rate is 10 °C / min, and the temperature range is 25–800 °C.

[0118] Carbon black content: The residual mass percentage at 600 °C (carbon black has high thermal stability).

[0119] Carbon nanotube content: Through semi-quantitative analysis of Raman spectroscopy (ID / IG peak area ratio).

[0120] The test results are shown in Table 2.

[0121] Table 2: Component Controllability Verification Table

[0122] Sample Carbon black content (wt%) Carbon nanotube content (wt%) Deviation (carbon black / CNT) Example 1 98.0 1.6 ±0％ / ±0.1％ Example 2 93.0 5.7 ±0％ / ±0.2％ Example 3 95.0 1.25 ±0％ / ±0.1％ Example 4 89.0 4.8 ±0％ / ±0.2％ Example 5 87.0 9.0 ±0％ / ±0.3％ Example 6 88.0 0.6 ±0％ / ±0.05％ Comparative Example 1 95.0 0.0 - Comparative Example 2 97.0 3.0 ±5％ / ±1.0％ Comparative Example 3 0.0 90.0 -

[0123] 3. Data Analysis

[0124] The carbon black content of Examples 1 - 6 ranges from 87.0 - 98.0 wt%, and the carbon nanotube content ranges from 0.6 - 9.0 wt%. The deviation of the carbon black and carbon nanotube content is < ±1.5%. This indicates that by adjusting the Fe / Mo / Al ratio (14:(1 - 5):(7 - 20)) in the catalytic additive and the raw material ratio, the method of the present invention can accurately control the content of carbon black and carbon nanotubes in the product to meet the performance requirements of different rubber products.

[0125] Comparative Example 1 only contains carbon black and cannot generate carbon nanotubes. Its composition is single and cannot meet the multi-scenario requirements of the carbon black / carbon nanotube ratio for rubber composites. In Comparative Example 2, due to the stepwise addition method, the carbon nanotube content fluctuates greatly (±1.0%), and the component controllability is poor. In Comparative Example 3, the product is single (only carbon nanotubes), and carbon black needs to be mixed secondly, which increases the process complexity and cost, and it is difficult to ensure the uniformity and performance stability after secondary mixing.

[0126] In summary, through the systematic comparison of Examples 1 - 6 and Comparative Examples 1 - 3, the significant advantages of the present invention in process simplification, component controllability, and performance improvement are verified. The test data shows that by optimizing the catalytic additive and reaction conditions, the ratio of carbon black and carbon nanotubes can be flexibly controlled to meet the diverse needs of rubber composites, and it has the value of industrial promotion.

[0127] The above are only several limited preferred embodiments of the present invention, and its description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for preparing a composition containing carbon nanotubes, characterized in that: The following steps are involved: (a) preparing a catalytic additive: mixing highly dispersed silica with a composite oxide of iron (III), molybdenum (VI) and aluminum in a mass ratio of 1:1 to 85:1, wherein the mass ratio of the metals in the composite oxide is Fe:Mo:Al=14:(1-5):(7-20); (b) mixing the catalytic additive of step (a) with the liquid hydrocarbon feedstock in a hydrodynamic rotary disperser by utilizing shear stress and cavitation; (c) injecting the mixture of step (b) into a heating zone of a reactor through a nozzle, wherein the temperature of the heating zone is 1350-1800° C., using gas fuel or liquid fuel combustion to provide heat, so that the liquid hydrocarbon feedstock is decomposed to generate carbon black, and the catalytic additive is activated to generate carbon nanotubes; (d) injecting chemically pure water into the end of the reactor to rapidly cool the mixture to 600-650°C to terminate the growth of carbon black particles; (e) The cooled mixture is further cooled to 260-300° C. by a cooler, and separated by a gas-solid separation device to obtain a composition containing carbon nanotubes.

2. The preparation method according to claim 1, characterized in that: The mixing in step (a) is accomplished by a high-speed stirrer, with a stirring speed of 10,000-12,000 rpm and a mixing time of 5-10 minutes.

3. The preparation method according to claim 1, characterized in that: The particle size of the highly dispersed silicon dioxide in step (a) is 10-50 nm, and the specific surface area is 150-300 m 2 / g.

4. The preparation method according to claim 1, characterized in that: The molar ratio of iron (III), molybdenum (VI) and aluminum in the composite oxide in step (a) is 1:0.05-0.3:0.5-1.

5.

5. The preparation method according to claim 1, characterized in that: The liquid hydrocarbon raw material in step (c) is one of petroleum fractions, coal tar or biomass cracking oil.

6. The preparation method according to claim 1, characterized in that: In step (c), the gaseous fuel is one of natural gas, propane or hydrogen, and the liquid fuel is one of diesel or heavy oil.

7. The preparation method according to claim 1, characterized in that: The heating zone of the reactor in step (c) is a fuel-rich combustion environment, and the residual air volume fraction is 1-5%.

8. The preparation method according to claim 1, characterized in that: The injection amount of the chemically pure water in step (d) is 5-15% of the total mass of the mixture.

9. The preparation method according to claim 1, characterized in that: The gas-solid separation device in step (e) is at least one of a cyclone dust collector, a bag dust collector or an electrostatic precipitator.

10. The preparation method according to claim 1, characterized in that: In step (e), the carbon black content of the carbon nanotube-containing composition is 85-98 wt %, and the carbon nanotube content is 0.6-9 wt %.

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