Method for preparing metal / metal sulfide composite catalyst by ball milling method and application of metal / metal sulfide composite catalyst

Abstract

The invention discloses a method for preparing a metal / metal sulfide composite catalyst through a ball milling method and application. The method comprises the following steps: providing mixed powder containing metal powder and sulfur powder, and carrying out mechanochemical reaction on the metal powder and the sulfur powder in the mixed powder in an inert atmosphere in a ball milling manner to form a metal compound containing a metal / metal sulfide composite structure, so as to obtain the metal / metal sulfide composite catalyst. The mechanochemistry is utilized to enable sulfur powder and metal to react with each other to form metal sulfide on the surface of the metal, so that the combination efficiency of the metal main catalyst and the non-metal cocatalyst is improved; meanwhile, the particle size of the catalyst is reduced in the ball milling process, and the catalytic efficiency is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular 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 form, due to its excellent electrical, mechanical and thermal properties, has been widely used. Carbon nanotubes can also be understood as a curled 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 popular preparation method for carbon nanotube growth. The use of CVD method to grow nanotubes, especially carbon nanotubes, in a targeted manner must ensure the selectivity of the synthesis process, and 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, the combination mode and distribution of the metal main catalyst and the non-metallic co-catalyst, the size of the catalyst particles, etc. will affect the morphology and structure of carbon nanotubes, and are important influencing factors in the preparation of carbon nanotubes. However, in the existing preparation process of carbon nanotubes, the metal main catalyst and the non-metallic co-catalyst are often added separately (reducing the efficiency of the combination of the metal main catalyst and the non-metallic co-catalyst in the catalytic reaction) or the two are combined using a preparation process such as a hydrothermal method that is not conducive to amplified preparation. Therefore, it is difficult to achieve an increase in the yield of carbon nanotubes with the existing technology. Therefore, an effective method is needed to solve the problem that the metal main catalyst and the non-metallic co-catalyst cannot be efficiently combined to achieve high-yield carbon nanotube preparation. 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] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes: 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.

[0006] 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 bound to the surface of the active metal as a co-catalyst.

[0007] Another aspect of the present invention also provides the use of the above metal / metal sulfide composite catalyst in the preparation of carbon nanotubes.

[0008] Compared with the prior art, the technical solution of the present invention has at least the following advantages: 1) The present invention uses a mechanical ball milling method in an inert atmosphere to promote the mechanochemical reaction between iron powder and sulfur powder to form metal / metal sulfide composite catalyst particles, thereby improving the combination efficiency of the metal main catalyst and the non-metallic co-catalyst; at the same time, the ball milling process also reduces the catalyst particle size, further improving the catalytic efficiency; 2) The ball milling method used in the present invention is simple and convenient, and can be easily integrated into the continuous production process, which is conducive to expanding the production scale; 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 has a significantly higher yield of carbon nanotubes than that produced by directly mixing pure iron powder and sublimated sulfur powder at the same reaction time, up to 12 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0010] Figure 1 A photo of a ball mill and ball mill used in preparing a metal / metal sulfide composite catalyst in a typical embodiment of the present invention; Figure 2 This is an optical microscope photograph of pure iron powder before ball milling in Example 1 of the present invention; 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; Figure 4 This 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

[0011] The present invention will be more fully understood by reading the following specific embodiments. However, it should be understood that the specific embodiments disclosed below are only exemplary of the present invention, and the present invention can be embodied in various forms. Therefore, the specific functional details disclosed herein should not be interpreted as limiting, but only as the basis for the claims and as a representative basis for teaching those skilled in the art to adopt the present invention in different ways in any appropriate detailed embodiment.

[0012] 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.

[0013] 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.

[0014] In some embodiments, the metal powder includes, but is not limited to, iron powder.

[0015] In some embodiments, the particle size of the metal powder is 180-300 mesh.

[0016] In some embodiments, the sulfur powder includes, but is not limited to, sublimated sulfur powder.

[0017] In some embodiments, the particle size of the sulfur powder is 100-200 mesh.

[0018] In some embodiments, the inert atmosphere includes, but is not limited to, an argon atmosphere and / or a nitrogen atmosphere.

[0019] 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.

[0020] In some preferred embodiments, the mass ratio of the mixed powder to the ball milling balls is 1:5 to 1:20.

[0021] In some embodiments, the ball milling speed used in the ball milling is not less than 300 rpm.

[0022] In some embodiments, the ball milling time is 2.5 to 90 hours.

[0023] In some embodiments, the ball milling equipment used in the ball milling has a material hardness greater than or equal to the hardness of the metal powder, and is preferably made of stainless steel.

[0024] In some embodiments, the method further comprises: before ball milling, first removing the air in the ball milling device, and then introducing an inert gas.

[0025] In some more specific embodiments, the method comprises: Step 1: Control the ratio of adding metal powder (such as iron powder) with a mesh size of 180-300 and sublimated sulfur powder and mix them evenly; wherein the molar ratio of the metal element in the metal powder to the sulfur element in the sublimated sulfur powder is 2:1-30:1.

[0026] Step 2: Pour the mixed powder in step 1 into a stainless steel (or other material with a hardness greater than or equal to the added metal powder) ball mill with a gas filling hole, and add a certain amount of ball mills of different sizes (the material is consistent with the ball mill). Among them, the ball mill consists of three sizes: large, medium and small. The diameter of the large ball ranges from 10 to 20 mm; the diameter of the medium ball is 6 to 9 mm; the diameter of the small ball is 3 to 5 mm. The total mass ratio of the metal powder and sublimated sulfur powder in the ball mill to the mass ratio of the ball mill is 1:5 to 1:20. After passing inert gas into the ball mill for a certain period of time, seal the tank body, place the tank in a planetary ball mill, and set a certain ball mill speed and ball milling time. The ball mill lid is equipped with an air filling valve. The air in the tank must be discharged before the ball milling begins, so an inert gas such as argon, nitrogen, etc. is injected into the tank through the air filling valve. The mechanical ball milling time is set according to the molar ratio of metal element to sulfur element in the metal powder and sublimated sulfur powder. The higher the metal content, the shorter the ball milling time. Generally, the ball milling time ranges from 2.5 to 90 hours. The mechanical ball milling speed is set to not less than 300 rpm.

[0027] 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.

[0028] 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, 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.

[0029] In some embodiments, the particle size of the metal / metal sulfide composite catalyst is 2 μm-152 μm.

[0030] In some embodiments, the content of metal sulfide in the metal / metal sulfide composite catalyst is 5.2-70 wt %.

[0031] As another aspect of the technical solution of the present invention, it also involves the use of the above-mentioned metal / metal sulfide composite catalyst in the preparation of carbon nanotubes.

[0032] In summary, the present invention forms a metal / metal sulfide composite catalyst by mixing a certain proportion of metal powder and sulfur powder, and then reacting them by ball milling, so that the active metal and the catalyst promoter metal sulfide are closely combined. During the ball milling process, on the one hand, mechanochemistry is used to make the sulfur powder and the metal react with each other to form metal sulfide on the metal surface; on the other hand, the powder is cut by ball milling balls of different sizes to make the catalyst smaller. The above preparation method of the present invention is conducive to the combination of the catalyst promoter on the surface of the active metal particles to prevent the active metal from agglomerating, so that the catalyst remains in a small particle state, which is convenient for realizing the large-scale preparation of carbon nanotubes.

[0033] Specifically, the metal / metal sulfide composite catalyst prepared by the present invention is a metal compound containing a metal / metal sulfide composite structure, and the metal compound is screened and dried, and then decomposed into active carbon atoms in an inert gas using decomposed organic matter to prepare carbon nanotubes. In the process of preparing carbon nanotubes using the catalyst of the present invention, different metal / metal sulfide catalysts can be obtained by adjusting ball milling parameters, thereby improving the yield and quality of carbon nanotubes.

[0034] The present invention is further described below by way of examples, but the present 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 without specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturers.

[0035] Example 1 A method for preparing a metal / metal sulfide composite catalyst by ball milling, comprising the following preparation steps: S1, weigh 58.29 g of iron powder with a D50 of 180 mesh and 1.71 g of sublimated sulfur powder with a D50 of 100 mesh, and the molar ratio of Fe to S is 19.5:1. The particle morphology of the unmilled iron powder is shown in Figure 2 .

[0036] S2, mix the powders in step S1 together, add Figure 1 304 stainless steel 500 ml ball mill jar with gas valve as shown. Weigh 900 g of 304 stainless steel ball 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. Add all the ball milling balls to the ball mill jar, seal the jar, open the two gas valves, and fill one of the valves with argon gas. Select the flow rate of 500 cm 3 / min, and close the two valves after 5 minutes of aeration. Put two ball milling jars of the same weight into the planetary ball mill and fix them, set the speed to 320 rpm, and the ball milling time to 9.5 h.

[0037] 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 it 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 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%.

[0038] The obtained metal / metal sulfide composite catalyst is used to prepare carbon nanotubes. The specific steps are: placing the mixed catalyst powder in a powder feeder and allowing it to evenly enter a 1800°C high-temperature furnace, and growing carbon nanotubes in hydrogen, methane and inert atmosphere, with a yield of 0.6 g / min.

[0039] Example 2 A method for preparing a metal / metal sulfide composite catalyst by ball milling, comprising the following preparation steps: S1. Weigh 48.83 g of iron powder with a D50 of 180 mesh and 11.16 g of sublimated sulfur powder with a D50 of 200 mesh. The molar ratio of Fe to S is 2.5:1.

[0040] S2, mix the powders in step S1 together, add Figure 1 304 stainless steel 500 ml ball mill jar with gas valve as shown. Weigh 900 g of 304 stainless steel ball 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. Add all the ball milling balls to the ball mill jar, seal the jar, open the two gas valves, and fill one of the valves with argon gas. Select the flow rate of 500 cm 3 / min, and close the two valves after 5 minutes of aeration. Put two ball milling jars of the same weight into the planetary ball mill and fix them, set the speed to 320 rpm, and the ball milling time to 20 h.

[0041] 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 in the ball mill into an 80-mesh sieve and shake it continuously to separate the milled powder from the ball mill. The collected powder was weighed to obtain 57.6 g, and the calculated yield was 96%. The particle size of the obtained metal / metal sulfide composite catalyst was 65 μm, and the content of metal sulfide was 62.9 wt%.

[0042] The obtained metal / metal sulfide composite catalyst is used to prepare carbon nanotubes. The specific steps are: placing the mixed catalyst powder in a powder feeder and allowing it to evenly enter a 1800°C high-temperature furnace, and growing carbon nanotubes in hydrogen, methane and inert atmosphere, with a yield of 0.9 g / min.

[0043] Example 3 A method for preparing a metal / metal sulfide composite catalyst by ball milling, comprising the following preparation steps: S1. Weigh 58.88 g of iron powder with a D50 of 180 mesh and 1.12 g of sublimated sulfur powder with a D50 of 150 mesh. The molar ratio of Fe to S is 30:1.

[0044] S2, mix the powders in step S1 together, add Figure 1 304 stainless steel 500 ml ball mill jar with gas valve as shown. Weigh 900 g of 304 stainless steel ball 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. Add all the ball milling balls to the ball mill jar, seal the jar, open the two gas valves, and fill one of the valves with argon gas. Select the flow rate of 500 cm 3 / min, and close the two valves after 5 minutes of aeration. Put two ball milling jars of the same weight into the planetary ball mill and fix them, set the speed to 320 rpm, and the ball milling time to 72 h.

[0045] 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 in the ball mill into an 80-mesh sieve and shake it continuously to separate the milled powder from the ball mill. The collected powder was weighed to obtain 59.07 g, and the calculated yield was 98.5%. The average particle size of the obtained metal / metal sulfide composite catalyst was 152 μm, and the content of metal sulfide was 5.2 wt%.

[0046] The obtained metal / metal sulfide composite catalyst is used to prepare carbon nanotubes. The specific steps are: placing the mixed catalyst powder in a powder feeder and allowing it to evenly enter a 1800°C high-temperature furnace, and growing carbon nanotubes in hydrogen, methane and inert atmosphere, with a yield of 0.48 g / min.

[0047] Example 4 A method for preparing a metal / metal sulfide composite catalyst by ball milling, comprising the following preparation steps: S1. Weigh 58.88 g of iron powder with a D50 of 250 mesh and 1.12 g of sublimated sulfur powder with a D50 of 200 mesh. The molar ratio of Fe to S is 30:1.

[0048] S2, mix the powders in step S1 together, add Figure 1 304 stainless steel 500 ml ball mill jar with 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. Add all the ball milling balls to the ball mill jar, seal the jar, open the two gas valves, and fill one of the valves with argon gas. Select the flow rate of 500 cm 3 / min, and close the two valves after 5 minutes of aeration. Put two ball mills of the same weight into the planetary ball mill and fix them, set the speed to 600 rpm, and the ball milling time to 2.5 h.

[0049] 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 in the ball mill into an 80-mesh sieve and vibrate continuously to separate the milled powder from the milling balls. Collect the powder to obtain the metal / metal sulfide composite catalyst.

[0050] The obtained metal / metal sulfide composite catalyst is used to prepare carbon nanotubes. The specific steps are: placing the mixed catalyst powder in a powder feeder and allowing it to evenly enter a 1800°C high-temperature furnace, and growing carbon nanotubes in hydrogen, methane and inert atmosphere, with a yield of 0.42 g / min.

[0051] Example 5 A method for preparing a metal / metal sulfide composite catalyst by ball milling, comprising the following preparation steps: S1. Weigh 48.83 g of iron powder with a D50 of 300 mesh and 11.16 g of sublimated 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 1 304 stainless steel ball milling jar with a volume of 500 ml and a gas valve as shown. Weigh 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. Add all the ball milling balls to the ball milling jar, seal the jar, open the two gas valves, and fill one of the valves with argon gas, with a flow rate of 500 cm 3 / min, and close the two valves after 5 minutes of aeration. Put two ball milling jars of the same weight into the planetary ball mill and fix them, set the speed to 320 rpm, and the ball milling time to 90 h.

[0053] 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 in the ball mill into an 80-mesh sieve and vibrate continuously to separate the milled powder from the milling balls. Collect the powder to obtain the metal / metal sulfide composite catalyst.

[0054] The obtained metal / metal sulfide composite catalyst is used to prepare carbon nanotubes. The specific steps are: placing the mixed catalyst powder in a powder feeder and allowing it to evenly enter a 1800°C high-temperature furnace, and growing carbon nanotubes in hydrogen, methane and inert atmosphere, with a yield of 0.87 g / min.

[0055] Example 6 A method for preparing a metal / metal sulfide composite catalyst by ball milling, comprising the following preparation steps: S1. Weigh 56.75 g of iron powder with a D50 of 180 mesh and 3.24 g of sublimated sulfur powder with a D50 of 100 mesh. The molar ratio of Fe to S is 10:1.

[0056] S2, mix the powders in step S1 together, add Figure 1 304 stainless steel 500 ml ball mill jar with gas valve as shown. Weigh 900 g of 304 stainless steel ball 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. Add all the ball milling balls to the ball mill jar, seal the jar, open the two gas valves, and fill one of the valves with argon gas. Select the flow rate of 500 cm 3 / min, and close the two valves after 5 minutes of aeration. Put two ball milling jars of the same weight into the planetary ball mill and fix them, set the speed to 320 rpm, and the ball milling time to 19 h.

[0057] 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 it continuously to separate the milled powder from the ball mill. The collected powder was weighed to obtain 51.96 g, and the calculated yield was 86.6%. The particle size distribution diagram of the obtained metal / metal sulfide composite catalyst can be found in Figure 4 , with an average particle size of 15.4 μm, of which D V (10)=2.11 μm.

[0058] The obtained metal / metal sulfide composite catalyst is used to prepare carbon nanotubes. The specific steps are: placing the mixed catalyst powder in a powder feeder and allowing it to evenly enter a 1800°C high-temperature furnace, and growing carbon nanotubes in hydrogen, methane and inert atmosphere, with a yield of 0.93 g / min.

[0059] Comparative Example 1 Compared with Example 1, the difference is that the weighed iron powder and sublimated sulfur powder are directly mixed to prepare carbon nanotubes, and the yield of carbon nanotubes is 0.07 g / min.

[0060] Comparative Example 2 Compared with Example 1, the difference is that only large balls and medium balls are used, including 500 g of large balls with a diameter of 10 mm and 400 g of medium balls with a diameter of 6 mm. After the same reaction time, the catalyst particle size is larger, averaging 230 μm. The obtained catalyst is used to prepare carbon nanotubes, and the yield of carbon nanotubes is 0.39 g / min.

[0061] Comparative Example 3 Compared with Example 1, the difference is that only medium balls and small balls are used, including 500 g of large balls with a diameter of 6 mm and 400 g of medium balls with a diameter of 3 mm. After the same reaction time, the catalyst particle size distribution is wide, and the average particle size is larger, averaging 275 μm. The obtained catalyst is used to prepare carbon nanotubes, and the yield of carbon nanotubes is 0.40 g / min.

[0062] Comparative Example 4 Compared with Example 2, the difference is that 43.44 g of iron powder and 16.55 g of sublimated sulfur powder are weighed, and the molar ratio of Fe to S is 1.5: 1. Because the S element content in the catalytic system is high, the catalyst is deactivated, and the obtained catalyst is used to prepare carbon nanotubes, and the yield of carbon nanotubes is 0.02 g / min.

[0063] Comparative Example 5 Compared with Example 3, the difference is that 58.94 g of iron powder and 1.05 g of sublimated sulfur powder are weighed, and the molar ratio of Fe to S is 32: 1. Because the S element content in the catalytic system is too low, the catalyst activity is too low, and the obtained catalyst is used to prepare carbon nanotubes, and the yield of carbon nanotubes is 0.01 g / min.

[0064] Comparative Example 6 Compared with Example 1, the difference is that a total of 240 g of 304 stainless steel ball milling balls are weighed, 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 catalyst obtained contains unreacted S powder, and the content of metal sulfide is 4.1% (7.8% in Example 1). The obtained catalyst is used to prepare carbon nanotubes, and the yield of carbon nanotubes is 0.24 g / min.

[0065] Comparative Example 7 Compared with Example 1, the difference is that a total of 1320 g of 304 stainless steel ball milling balls are 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 particle size of the catalyst obtained becomes larger, and the refined powder is fused into larger particles with an average particle size of 305 μm. The obtained catalyst is used to prepare carbon nanotubes, and the yield of carbon nanotubes is 0.33 g / min.

[0066] Comparative Example 8 Compared with Example 1, the difference is that two ball mills of the same weight are placed in a planetary ball mill and fixed, and the rotation speed is set to 120 rpm. After the same reaction time, the particle size of the catalyst obtained becomes larger, and the average particle size is larger, averaging 295 μm. The obtained catalyst is used to prepare carbon nanotubes, and the yield of carbon nanotubes is 0.38 g / min.

[0067] It can be seen from Examples 1-2 and Comparative Example 1 that the catalyst prepared by the preparation method of the present invention has an output of carbon nanotubes that is 8.5 to 12.8 times higher than that of the blank control group of directly mixing iron powder and sublimated sulfur powder under the same reaction time.

[0068] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0069] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a metal / metal sulfide composite catalyst by ball milling, characterized in that: include: A mixed powder containing metal powder and sulfur powder is provided, and the metal powder and sulfur powder in the mixed powder are subjected 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.

2. The method according to claim 1, characterized in that 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.

3. The method according to claim 1, characterized in that The metal powder includes iron powder; and / or the particle size of the metal powder is 180-300 meshes; and / or the sulfur powder includes sublimated sulfur powder; and / or the particle size of the sulfur powder is 100-200 meshes.

4. The method according to claim 1, characterized in that: The inert atmosphere includes argon atmosphere and / or nitrogen atmosphere; and / or, the ball milling balls used in the ball mill include a combination of large balls, medium balls and small balls, 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.

5. The method according to claim 4, characterized in that The mass ratio of the mixed powder to the ball milling balls is 1:5-1:

20.

6. The method according to claim 1, characterized in that The ball milling speed is not less than 300 rpm; and / or the ball milling time is 2.5 to 90 hours.

7. The method according to claim 1, characterized in that The hardness of the material of the ball milling equipment used in the ball mill is greater than or equal to the hardness of the metal powder, and is preferably made of stainless steel.

8. The method according to claim 1, characterized in that The method further comprises: before ball milling, firstly exhausting the air in the ball milling device, and then introducing the inert gas.

9. A metal / metal sulfide composite catalyst prepared by the method according to any one of claims 1 to 8, 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; Preferably, the particle size of the metal / metal sulfide composite catalyst is 2 μm-152 μm; Preferably, the content of metal sulfide in the metal / metal sulfide composite catalyst is 5.2-70wt%.

10. Use of the metal / metal sulfide composite catalyst according to claim 9 in the preparation of carbon nanotubes.

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