A method for preparing metal / metal sulfide composite catalyst by ball milling and its application

Abstract

The present invention discloses a method for preparing a metal / metal sulfide composite catalyst by ball milling and its application. The method comprises providing a mixed powder comprising metal powder and sulfur powder, and subjecting the mixed powder to a mechanochemical reaction in an inert atmosphere by ball milling to form a metal compound containing a metal / metal sulfide composite structure, thereby obtaining a metal / metal sulfide composite catalyst. The present invention utilizes mechanochemistry to cause the sulfur powder and metal to react with each other to form a metal sulfide on the metal surface, thereby improving the bonding efficiency between the metal main catalyst and the non-metallic co-catalyst. The ball milling process also reduces the catalyst particle size, further improving catalytic efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and particularly relates to a method for preparing a metal / metal sulfide composite catalyst by a ball milling method and application thereof. Background Art

[0002] Carbon nanotubes are a type of carbon allotrope with a one-dimensional cylindrical hollow structure. 2 Hybrid forms have been widely used due to their excellent electrical, mechanical and thermal properties. Carbon nanotubes can also be understood as a curled-up graphite sheet structure, which is divided into single-walled carbon nanotubes and multi-walled carbon nanotubes. Compared with multi-walled carbon nanotubes, single-walled carbon nanotubes have obvious advantages during use and the addition amount is also lower. The existing methods for preparing carbon nanotubes mainly include arc method, chemical vapor deposition and laser ablation. Among them, chemical vapor deposition (CVD) is currently the most widely used and most researched preparation method for carbon nanotube growth. The use of CVD method to grow nanotubes, especially carbon nanotubes, in a targeted manner requires ensuring the selectivity of the synthesis process. This kinetic selectivity depends on whether an effective carbon nucleus can be formed on the catalyst to trigger the growth of carbon nanotubes.

[0003] During the growth of carbon nanotubes (CNTs), the binding and distribution of the metal primary catalyst and non-metallic co-catalyst, as well as catalyst particle size, all influence the CNT morphology and structure, making them crucial factors in CNT production. However, existing CNT production processes often employ separate addition of the metal primary catalyst and non-metallic co-catalyst (reducing their efficient binding during the catalytic reaction) or combine them using hydrothermal methods, which are not ideal for scalable production. Consequently, existing technologies struggle to achieve increased CNT production. Therefore, an effective method is needed to address this issue of inefficient binding of the metal primary catalyst and non-metallic co-catalyst, enabling high-yield CNT production. Summary of the Invention

[0004] The main purpose of the present invention is to provide a method for preparing a metal / metal sulfide composite catalyst by ball milling and its application, so as to overcome the deficiencies in the prior art.

[0005] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0006] One aspect of the present invention provides a method for preparing a metal / metal sulfide composite catalyst by ball milling, which comprises: providing a mixed powder comprising metal powder and sulfur powder, and subjecting the metal powder and the sulfur powder in the mixed powder to a mechanochemical reaction by ball milling in an inert atmosphere to form a metal compound containing a metal / metal sulfide composite structure, thereby obtaining a metal / metal sulfide composite catalyst.

[0007] Another aspect of the present invention provides a metal / metal sulfide composite catalyst prepared by the aforementioned method, wherein the metal / metal sulfide composite catalyst is a metal compound containing a metal / metal sulfide composite structure, which includes an active metal as a main catalyst and a metal sulfide as a co-catalyst bound to the surface of the active metal.

[0008] Another aspect of the present invention also provides the use of the aforementioned metal / metal sulfide composite catalyst in the preparation of carbon nanotubes.

[0009] Compared with the prior art, the technical solution of the present invention has at least the following advantages:

[0010] 1) The present invention uses mechanical ball milling in an inert atmosphere to promote a mechanochemical reaction between iron powder and sulfur powder to form metal / metal sulfide composite catalyst particles, thereby improving the bonding efficiency between the metal main catalyst and the non-metallic co-catalyst. The ball milling process also reduces the catalyst particle size, further improving the catalytic efficiency.

[0011] 2) The ball milling method used in the present invention is simple and easy to integrate into the continuous production process, which is conducive to expanding the production scale;

[0012] 3) The composite catalyst provided by the present invention has a high catalytic yield. The catalyst prepared with pure iron powder and sublimated sulfur powder as raw materials produces carbon nanotubes at a significantly higher yield of up to 12 times that of the catalyst prepared by directly mixing pure iron powder and sublimated sulfur powder under the same reaction time. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 This is a photo of a ball milling jar and ball milling balls used in preparing a metal / metal sulfide composite catalyst in a typical embodiment of the present invention;

[0015] Figure 2 This is an optical microscope photograph of pure iron powder before ball milling in Example 1 of the present invention;

[0016] Figure 3 This is an optical microscope photograph of the metal / metal sulfide composite catalyst obtained after the ball milling reaction in Example 1 of the present invention;

[0017] Figure 4This is a particle size distribution diagram of the metal / metal sulfide composite catalyst obtained after ball milling in Example 6 of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be more fully understood by reading the following detailed description. However, it should be understood that the detailed description disclosed below is merely exemplary of the present invention, and that the present invention may be embodied in a variety of forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as a basis for the claims and as a representative basis for teaching those skilled in the art to variously employ the present invention in virtually any appropriately detailed embodiment.

[0019] As one aspect of the technical solution of the present invention, a method for preparing a metal / metal sulfide composite catalyst by ball milling comprises: providing a mixed powder comprising metal powder and sulfur powder, and subjecting the metal powder and the sulfur powder in the mixed powder to a mechanochemical reaction by ball milling in an inert atmosphere to form a metal compound containing a metal / metal sulfide composite structure, thereby obtaining a metal / metal sulfide composite catalyst.

[0020] In some embodiments, the molar ratio of the metal element in the metal powder to the sulfur element in the sulfur powder is 2:1 to 30:1.

[0021] In some embodiments, the metal powder includes, but is not limited to, iron powder.

[0022] In some embodiments, the particle size of the metal powder is 180-300 mesh.

[0023] In some embodiments, the sulfur powder includes but is not limited to sublimed sulfur powder.

[0024] In some embodiments, the particle size of the sulfur powder is 100-200 mesh.

[0025] In some embodiments, the inert atmosphere includes, but is not limited to, an argon atmosphere and / or a nitrogen atmosphere.

[0026] In some embodiments, the ball milling balls used in the ball milling include a combination of large balls, medium balls, and small balls, wherein the diameter of the large balls is 10-20 mm, the diameter of the medium balls is 6-9 mm, and the diameter of the small balls is 3-5 mm.

[0027] In some preferred embodiments, the mass ratio of the mixed powder to the ball milling balls is 1:5 to 1:20.

[0028] In some embodiments, the ball milling is performed at a speed of not less than 300 rpm.

[0029] In some embodiments, the ball milling time is 2.5 to 90 hours.

[0030] In some embodiments, the ball milling equipment used in the ball milling has a hardness greater than or equal to that of the metal powder, and is preferably made of stainless steel.

[0031] In some embodiments, the method further comprises: before ball milling, removing air from the ball milling device and then introducing an inert gas.

[0032] In some more specific embodiments, the method comprises:

[0033] Step 1: Control the ratio of adding 180-300 mesh metal powder (such as iron powder) and sublimed sulfur powder and mix them evenly; wherein the molar ratio of the metal element in the metal powder to the sulfur element in the sublimed sulfur powder is 2:1-30:1.

[0034] Step 2: Pour the mixed powder from Step 1 into a stainless steel (or other material with a hardness equal to or greater than the metal powder being added) ball mill jar equipped with gas injection holes. Add a predetermined number of milling balls of varying sizes (made of the same material as the jar). The milling balls come in three sizes: large, medium, and small. The diameters of the large balls range from 10 to 20 mm; the medium balls from 6 to 9 mm; and the small balls from 3 to 5 mm. The mass ratio of the total mass of the metal powder and sublimated sulfur powder in the mill to the mass of the milling balls is 1:5 to 1:20. After passing an inert gas through the mill for a specified period of time, seal the jar, place it in a planetary ball mill, and set the mill speed and milling time. The mill lid is equipped with a gas valve. Before milling begins, the air must be expelled from the jar. Therefore, an inert gas, such as argon or nitrogen, is introduced through the gas valve. The mechanical milling time is set based on the molar ratio of metal to sulfur in the metal powder and sublimated sulfur powder. The higher the metal content, the shorter the milling time. Generally, the milling time ranges from 2.5 to 90 hours. The mechanical milling speed should be set to no less than 300 rpm.

[0035] Step 3: After the ball mill is finished working, remove the ball mill jar, open the vent on the jar body first, wait for the gas to be discharged, open the ball mill jar, use an 80-mesh sieve to separate the ball milling balls from the powder, collect the ball milling powder, and weigh it to calculate the yield.

[0036] As another aspect of the technical solution of the present invention, it also relates to a metal / metal sulfide composite catalyst prepared by the aforementioned method. The metal / metal sulfide composite catalyst is a metal compound containing a metal / metal sulfide composite structure, which includes an active metal as a main catalyst and a metal sulfide as a co-catalyst bound to the surface of the active metal.

[0037] In some embodiments, the metal / metal sulfide composite catalyst has a particle size of 2 μm to 152 μm.

[0038] In some embodiments, the content of metal sulfide in the metal / metal sulfide composite catalyst is 5.2-70 wt%.

[0039] As another aspect of the technical solution of the present invention, it also involves the use of the aforementioned metal / metal sulfide composite catalyst in the preparation of carbon nanotubes.

[0040] In summary, the present invention forms a metal / metal sulfide composite catalyst by mixing a certain ratio of metal powder and sulfur powder, then reacting them using ball milling. This creates a tightly bound metal / metal sulfide catalyst, tightly binding the active metal and the co-catalyst metal sulfide. The ball milling process utilizes mechanochemical forces to cause the sulfur powder and metal to react, forming metal sulfide on the metal surface. Furthermore, milling balls of varying sizes are used to reduce the powder size of the catalyst. This preparation method facilitates the co-catalyst binding to the surface of the active metal particles, preventing active metal aggregation and maintaining the catalyst in a small particle size, facilitating the mass production of carbon nanotubes.

[0041] Specifically, the metal / metal sulfide composite catalyst prepared in the present invention is a metal compound containing a metal / metal sulfide composite structure. After screening and drying, the metal compound is then decomposed into activated carbon atoms in an inert atmosphere using decomposed organic matter to produce carbon nanotubes. During the carbon nanotube production process using the catalyst of the present invention, different metal / metal sulfide catalysts can be produced by adjusting ball milling parameters, thereby improving carbon nanotube yield and quality.

[0042] The present invention is further illustrated by way of examples below, but the invention is not limited to the scope of the examples. The reagents and raw materials used in the following examples are commercially available, and the experimental methods where specific conditions are not specified are generally carried out under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0043] Example 1

[0044] A method for preparing a metal / metal sulfide composite catalyst by ball milling, comprising the following preparation steps:

[0045] S1, weigh 58.29 g of iron powder with a D50 of 180 mesh and 1.71 g of sublimed sulfur powder with a D50 of 100 mesh, with a molar ratio of Fe to S of 19.5:1. The particle morphology of the unmilled iron powder is shown in Figure 2 .

[0046] S2, mix the powders in step S1 together, add Figure 1Place the 500 ml 304 stainless steel milling jar with a gas valve as shown. Weigh 900 g of 304 stainless steel milling balls, including 500 g of large balls with a diameter of 10 mm, 300 g of medium balls with a diameter of 6 mm, and 100 g of small balls with a diameter of 3 mm. Place all the milling balls in the milling jar, seal the jar, open the two gas valves, and introduce argon gas into one of the valves at a flow rate of 500 cm / s. 3 / min, and close both valves after 5 minutes of aeration. Place two ball mill jars of the same weight into the planetary ball mill and secure them. Set the speed to 320 rpm and the ball milling time to 9.5 h.

[0047] S3. Wait for the planetary ball mill to stop running, remove the ball mill, open one of the two gas valves, discharge the gas generated by the reaction, and then open the ball mill. Pour all the contents of the ball mill into an 80-mesh sieve and shake continuously to separate the milled powder from the milling balls. The collected powder weighed 58.39 g, and the calculated yield was 97.3%. The morphology of the catalyst obtained after ball milling is shown in Figure 2. Figure 3 The average particle size of the obtained metal / metal sulfide composite catalyst was 115 μm, and the content of metal sulfide was 7.8 wt%.

[0048] The obtained metal / metal sulfide composite catalyst was used to prepare carbon nanotubes. The specific steps were as follows: the mixed catalyst powder was placed in a powder feeder and evenly introduced into a high-temperature furnace at 1800°C. The carbon nanotubes were grown in a hydrogen, methane and inert atmosphere with a yield of 0.6 g / min.

[0049] Example 2

[0050] A method for preparing a metal / metal sulfide composite catalyst by ball milling, comprising the following preparation steps:

[0051] S1. Weigh 48.83 g of iron powder with a D50 of 180 mesh and 11.16 g of sublimed sulfur powder with a D50 of 200 mesh. The molar ratio of Fe to S is 2.5:1.

[0052] S2, mix the powders in step S1 together, add Figure 1 Place the 500 ml 304 stainless steel milling jar with a gas valve as shown. Weigh 900 g of 304 stainless steel milling balls, including 500 g of large balls with a diameter of 10 mm, 300 g of medium balls with a diameter of 6 mm, and 100 g of small balls with a diameter of 3 mm. Place all the milling balls in the milling jar, seal the jar, open the two gas valves, and introduce argon gas into one of the valves at a flow rate of 500 cm / s. 3 / min, and close both valves after 5 minutes of aeration. Place two ball mill jars of the same weight into the planetary ball mill and secure them. Set the speed to 320 rpm and mill for 20 h.

[0053] S3. Wait for the planetary ball mill to stop running, remove the milling jar, open one of the two gas valves to release the reaction gases, and then open the milling jar. Pour the entire contents of the milling jar through an 80-mesh sieve and continuously vibrate to separate the milled powder from the milling balls. The collected powder weighed 57.6 g, with a calculated yield of 96%. The resulting metal / metal sulfide composite catalyst had a particle size of 65 μm and a metal sulfide content of 62.9 wt%.

[0054] The obtained metal / metal sulfide composite catalyst was used to prepare carbon nanotubes. The specific steps were as follows: the mixed catalyst powder was placed in a powder feeder and evenly introduced into a high-temperature furnace at 1800°C. The carbon nanotubes were grown in a hydrogen, methane and inert atmosphere with a yield of 0.9 g / min.

[0055] Example 3

[0056] A method for preparing a metal / metal sulfide composite catalyst by ball milling, comprising the following preparation steps:

[0057] S1. Weigh 58.88 g of iron powder with a D50 of 180 mesh and 1.12 g of sublimed sulfur powder with a D50 of 150 mesh. The molar ratio of Fe to S is 30:1.

[0058] S2, mix the powders in step S1 together, add Figure 1 Place the 500 ml 304 stainless steel milling jar with a gas valve as shown. Weigh 900 g of 304 stainless steel milling balls, including 500 g of large balls with a diameter of 10 mm, 300 g of medium balls with a diameter of 6 mm, and 100 g of small balls with a diameter of 3 mm. Place all the milling balls in the milling jar, seal the jar, open the two gas valves, and introduce argon gas into one of the valves at a flow rate of 500 cm / s. 3 / min, and close both valves after 5 minutes of aeration. Place two ball mill jars of equal weight into the planetary ball mill, secure them, set the speed to 320 rpm, and mill for 72 h.

[0059] S3. Wait for the planetary ball mill to stop running, remove the milling jar, open one of the two gas valves to release the reaction gases, and then open the milling jar. Pour the entire contents of the milling jar into an 80-mesh sieve and continuously vibrate to separate the milled powder from the milling balls. The collected powder weighed 59.07 g, with a calculated yield of 98.5%. The resulting metal / metal sulfide composite catalyst had an average particle size of 152 μm and a metal sulfide content of 5.2 wt%.

[0060] The obtained metal / metal sulfide composite catalyst was used to prepare carbon nanotubes. The specific steps were as follows: the mixed catalyst powder was placed in a powder feeder and evenly introduced into a high-temperature furnace at 1800°C. The carbon nanotubes were grown in a hydrogen, methane and inert atmosphere with a yield of 0.48 g / min.

[0061] Example 4

[0062] A method for preparing a metal / metal sulfide composite catalyst by ball milling, comprising the following preparation steps:

[0063] S1. Weigh 58.88 g of iron powder with a D50 of 250 mesh and 1.12 g of sublimed sulfur powder with a D50 of 200 mesh. The molar ratio of Fe to S is 30:1.

[0064] S2, mix the powders in step S1 together, add Figure 1 Place the mill in a 500 ml 304 stainless steel ball mill jar with a gas valve as shown. Weigh 1200 g of 304 stainless steel ball milling balls, including 600 g of large balls with a diameter of 15 mm, 400 g of medium balls with a diameter of 8 mm, and 200 g of small balls with a diameter of 4 mm. Place all the balls in the mill jar, seal the jar, open the two gas valves, and introduce argon gas into one of the valves at a flow rate of 500 cm / s. 3 / min, and close both valves after 5 minutes of aeration. Place two ball mill jars of the same weight into the planetary ball mill and secure them. Set the speed to 600 rpm and mill for 2.5 h.

[0065] S3. Wait for the planetary ball mill to stop running, remove the milling jar, open one of the two gas valves to release the reaction gases, and then open the milling jar. Pour the entire contents of the milling jar into an 80-mesh sieve and continuously vibrate to separate the milled powder from the milling balls. Collect the powder to obtain the metal / metal sulfide composite catalyst.

[0066] The obtained metal / metal sulfide composite catalyst was used to prepare carbon nanotubes. The specific steps were as follows: the mixed catalyst powder was placed in a powder feeder and evenly introduced into a high-temperature furnace at 1800°C. The carbon nanotubes were grown in a hydrogen, methane and inert atmosphere with a yield of 0.42 g / min.

[0067] Example 5

[0068] A method for preparing a metal / metal sulfide composite catalyst by ball milling, comprising the following preparation steps:

[0069] S1. Weigh 48.83 g of iron powder with a D50 of 300 mesh and 11.16 g of sublimed sulfur powder with a D50 of 200 mesh. The molar ratio of Fe to S is 2.5:1.

[0070] S2, mix the powders in step S1 together, add Figure 1 Place the mill in a 500 ml 304 stainless steel ball mill jar with a gas valve as shown. Weigh 300 g of 304 stainless steel ball milling balls, including 150 g of large balls with a diameter of 20 mm, 100 g of medium balls with a diameter of 9 mm, and 50 g of small balls with a diameter of 5 mm. Place all the balls in the mill jar, seal the jar, open the two gas valves, and introduce argon gas into one of the valves at a flow rate of 500 cm / s. 3 / min, and close both valves after 5 minutes of aeration. Place two ball mill jars of the same weight into the planetary ball mill and secure them. Set the speed to 320 rpm and the ball milling time to 90 h.

[0071] S3. Wait for the planetary ball mill to stop running, remove the milling jar, open one of the two gas valves to release the reaction gases, and then open the milling jar. Pour the entire contents of the milling jar into an 80-mesh sieve and continuously vibrate to separate the milled powder from the milling balls. Collect the powder to obtain the metal / metal sulfide composite catalyst.

[0072] The obtained metal / metal sulfide composite catalyst was used to prepare carbon nanotubes. The specific steps were as follows: the mixed catalyst powder was placed in a powder feeder and evenly introduced into a high-temperature furnace at 1800°C. The carbon nanotubes were grown in a hydrogen, methane and inert atmosphere with a yield of 0.87 g / min.

[0073] Example 6

[0074] A method for preparing a metal / metal sulfide composite catalyst by ball milling, comprising the following preparation steps:

[0075] S1. Weigh 56.75 g of iron powder with a D50 of 180 mesh and 3.24 g of sublimed sulfur powder with a D50 of 100 mesh. The molar ratio of Fe to S is 10:1.

[0076] S2, mix the powders in step S1 together, add Figure 1 Place the 500 ml 304 stainless steel milling jar with a gas valve as shown. Weigh 900 g of 304 stainless steel milling balls, including 500 g of large balls with a diameter of 10 mm, 300 g of medium balls with a diameter of 6 mm, and 100 g of small balls with a diameter of 3 mm. Place all the milling balls in the milling jar, seal the jar, open the two gas valves, and introduce argon gas into one of the valves at a flow rate of 500 cm / s. 3 / min, and close both valves after 5 minutes of aeration. Place two ball mill jars of equal weight into the planetary ball mill and secure them. Set the speed to 320 rpm and mill for 19 h.

[0077] S3. Wait for the planetary ball mill to stop running, remove the ball mill, open one of the two gas valves, exhaust the gas generated by the reaction, and then open the ball mill. Pour all the contents of the ball mill into an 80-mesh sieve and vibrate continuously to separate the milled powder from the milling balls. The collected powder weighed 51.96 g, with a calculated yield of 86.6%. The particle size distribution diagram of the obtained metal / metal sulfide composite catalyst can be found in the table below. Figure 4 , with an average particle size of 15.4 μm, of which D V (10)=2.11 μm.

[0078] The obtained metal / metal sulfide composite catalyst was used to prepare carbon nanotubes. The specific steps were as follows: the mixed catalyst powder was placed in a powder feeder and evenly introduced into a high-temperature furnace at 1800°C. The carbon nanotubes were grown in a hydrogen, methane and inert atmosphere with a yield of 0.93 g / min.

[0079] Comparative Example 1

[0080] Compared with Example 1, the difference is that the weighed iron powder and sublimed sulfur powder are directly mixed to prepare carbon nanotubes, and the yield of carbon nanotubes is 0.07 g / min.

[0081] Comparative Example 2

[0082] Compared to Example 1, only large and medium spheres were used, including 500 g of large spheres with a diameter of 10 mm and 400 g of medium spheres with a diameter of 6 mm. After the same reaction time, the resulting catalyst particles had a larger average particle size of 230 μm. The resulting catalyst was used to prepare carbon nanotubes, with a yield of 0.39 g / min.

[0083] Comparative Example 3

[0084] Compared with Example 1, only medium and small spheres were used, including 500 g of large spheres with a diameter of 6 mm and 400 g of medium spheres with a diameter of 3 mm. After the same reaction time, the resulting catalyst had a wide particle size distribution, with a larger average particle size of 275 μm. The resulting catalyst was used to prepare carbon nanotubes, with a yield of 0.40 g / min.

[0085] Comparative Example 4

[0086] Compared with Example 2, the difference was that 43.44 g of iron powder and 16.55 g of sublimed sulfur powder were weighed, and the molar ratio of Fe to S was 1.5:1. Due to the high sulfur content in the catalytic system, the catalyst was deactivated. The resulting catalyst was used to prepare carbon nanotubes, and the yield of carbon nanotubes was 0.02 g / min.

[0087] Comparative Example 5

[0088] Compared with Example 3, the difference was that 58.94 g of iron powder and 1.05 g of sublimed sulfur powder were weighed, and the molar ratio of Fe to S was 32:1. Because the S content in the catalytic system was too low, the catalyst activity was too low. The resulting catalyst was used to prepare carbon nanotubes, and the carbon nanotube yield was 0.01 g / min.

[0089] Comparative Example 6

[0090] Compared to Example 1, the difference lies in weighing a total of 240 g of 304 stainless steel ball milling balls, including 130 g of large balls with a diameter of 10 mm, 80 g of medium balls with a diameter of 6 mm, and 30 g of small balls with a diameter of 3 mm. After the same reaction time, the resulting catalyst contained unreacted sulfur powder and had a metal sulfide content of 4.1% (compared to 7.8% in Example 1). The resulting catalyst was used to prepare carbon nanotubes, with a yield of 0.24 g / min.

[0091] Comparative Example 7

[0092] Compared to Example 1, the difference is that a total of 1320 g of 304 stainless steel ball milling balls were weighed, including 730 g of large balls with a diameter of 10 mm, 440 g of medium balls with a diameter of 6 mm, and 150 g of small balls with a diameter of 3 mm. After the same reaction time, the resulting catalyst particle size increased, and the refined powder fused into larger particles with an average particle size of 305 μm. The resulting catalyst was used to prepare carbon nanotubes, with a yield of 0.33 g / min.

[0093] Comparative Example 8

[0094] Compared to Example 1, two ball mill jars of equal weight were placed in a planetary ball mill, fixed securely, and the rotational speed was set at 120 rpm. After the same reaction time, the resulting catalyst particles became larger, with an average particle size of 295 μm. The resulting catalyst was used to prepare carbon nanotubes, with a yield of 0.38 g / min.

[0095] It can be seen from Examples 1-2 and Comparative Example 1 that the catalyst prepared by the preparation method of the present invention produces 8.5 to 12.8 times more carbon nanotubes than the blank control group of directly mixing iron powder and sublimated sulfur powder under the same reaction time.

[0096] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0097] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. Application of a metal / metal sulfide composite catalyst in the preparation of carbon nanotubes, including: The metal / metal sulfide composite catalyst powder is placed in a powder feeder and evenly fed into a high-temperature furnace at 1800°C to grow carbon nanotubes in a hydrogen, methane, and inert atmosphere. The metal / metal sulfide composite catalyst is prepared by a ball milling method, specifically comprising: providing a mixed powder comprising metal powder and sulfur powder, and subjecting the metal powder and the sulfur powder in the mixed powder to a mechanochemical reaction by ball milling in an inert atmosphere to form a metal compound containing a metal / metal sulfide composite structure, thereby obtaining the metal / metal sulfide composite catalyst; The molar ratio of the metal element in the metal powder to the sulfur element in the sulfur powder is 2:1 to 30:1; the metal powder is iron powder, and the particle size of the metal powder is 180 to 300 meshes; the sulfur powder is sublimated sulfur powder, and the particle size of the sulfur powder is 100 to 200 meshes; The ball milling balls used in the ball mill are a combination of large balls, medium balls and small balls, the diameter of the large balls is 10 to 20 mm, the diameter of the medium balls is 6 to 9 mm, and the diameter of the small balls is 3 to 5 mm; the mass ratio of the mixed powder to the ball milling balls is 1:5 to 1:20; the ball milling speed used in the ball mill is not less than 300 revolutions per minute; and the ball milling time is 2.5 to 90 hours.

2. The use according to claim 1, characterized in that The inert atmosphere includes an argon atmosphere and / or a nitrogen atmosphere.

3. The use according to claim 1, characterized in that The hardness of the material of the ball milling equipment used in the ball milling is greater than or equal to the hardness of the metal powder.

4. The use according to claim 3, characterized in that The ball milling equipment used in the ball milling is made of stainless steel.

5. The use according to claim 1, characterized in that The preparation method of the metal / metal sulfide composite catalyst further comprises: before ball milling, first removing the air in the ball milling equipment, and then introducing inert gas.

6. The use according to claim 1, characterized in that: The metal / metal sulfide composite catalyst is a metal compound containing a metal / metal sulfide composite structure, which includes an active metal as a main catalyst and a metal sulfide as a co-catalyst bound to the surface of the active metal; the particle size of the metal / metal sulfide composite catalyst is 2μm-152μm; the content of metal sulfide in the metal / metal sulfide composite catalyst is 5.2-70wt%.

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