Iron-based oxide catalyst as well as preparation method and application thereof

Abstract

The invention discloses an iron-based oxide catalyst as well as a preparation method and application thereof. The iron-based oxide catalyst comprises a main catalyst body and a cocatalyst distributed on the main catalyst body, the main catalyst body comprises iron powder, and the cocatalyst comprises iron oxide. The preparation method comprises the following steps: in the presence of water vapor and oxygen, iron powder is subjected to an oxidation reaction in a reaction chamber, iron oxide is generated on the surface of the iron powder in situ, and the iron-based oxide catalyst is prepared. The iron-based oxide catalyst provided by the invention is good in stability and controllable in particle size, and the cocatalyst component and the main catalyst body have strong interaction, so that agglomeration and falling of the cocatalyst can be effectively prevented; when the catalyst is applied to catalytic preparation of carbon nanotubes, the yield is high, and the tube diameter is uniform.

Description

Technical Field

[0001] The invention belongs to the technical field of nano material preparation, and specifically relates to an iron-based oxide catalyst and a preparation method and application thereof. Background Art

[0002] Carbon nanotubes are divided into single-walled carbon nanotubes and multi-walled carbon nanotubes. They are a carbon allotrope with a one-dimensional cylindrical hollow structure. The carbon atoms are arranged in sp 2 Hybrid form, due to its excellent electrical, mechanical and thermal properties, has been widely used. The existing methods for preparing carbon nanotubes mainly include arc method, chemical vapor deposition and laser ablation. Among them, chemical vapor deposition (CVD) is the most widely used and most popular preparation method for carbon nanotube growth. In the process of growing carbon nanotubes by CVD, the catalyst plays the role of promoting the decomposition of organic matter to generate carbon atoms and adsorbing and dissolving activated carbon and allowing carbon atoms to precipitate on the surface to grow carbon nanotubes. Therefore, the preparation of the catalyst used in the CVD method is at the core of the technology. The existing catalysts for growing carbon nanotubes generally load the active components on the surface of the carrier, but the binding force between these active components and the carrier is insufficient and they are easy to agglomerate at high temperature, which makes the catalyst inactivated and affects the yield of carbon nanotubes. Therefore, a new catalyst for preparing carbon nanotubes is needed to solve the above problems. Summary of the invention

[0003] The main purpose of the present invention is to provide an iron-based oxide catalyst and a preparation method and application thereof, so as to overcome the deficiencies in the prior art.

[0004] 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 an iron-based oxide catalyst, which includes a main catalyst body and a co-catalyst distributed on the main catalyst body, wherein the main catalyst body includes iron powder and the co-catalyst includes iron oxide.

[0005] Another aspect of the present invention provides a method for preparing an iron-based oxide catalyst, which comprises: subjecting iron powder to an oxidation reaction in a reaction chamber in the presence of water vapor and oxygen, generating iron oxide in situ on the surface of the iron powder, and preparing an iron-based oxide catalyst.

[0006] Another aspect of the present invention also provides an iron-based oxide catalyst prepared by the above preparation method.

[0007] Another aspect of the present invention also provides use of the aforementioned iron-based oxide 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 iron-based oxide catalyst provided by the present invention has a special structure, and the co-catalyst (iron oxide) component is in-situ grown and distributed on the surface of the main catalyst (nano iron) body. On the one hand, the binding force between the metal oxide co-catalyst and the metal main catalyst is improved, and on the other hand, the presence of the metal oxide can prevent the coarsening of the iron-based catalyst particles at high temperatures; and the co-catalyst component interacts strongly with the main catalyst body, so that the co-catalyst component is evenly dispersed and not easy to agglomerate; 2) The preparation method provided by the present invention is simple, easy to expand, and suitable for industrial application. The structure and composition of the final catalyst can be controlled according to the steam introduction amount, reaction temperature and reaction time during the reaction. The content of the co-catalyst on the surface of the body can be regulated by the preparation method, especially in a high temperature environment, the co-catalyst can be effectively prevented from agglomerating and falling off; and the catalyst particle size can be controlled by the particle size of the added pure iron powder; 3) The iron-based oxide catalyst provided by the present invention has good stability and high yield in the preparation of carbon nanotubes, and the obtained carbon nanotubes have uniform diameters. 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 schematic diagram of an apparatus used in preparing an iron-based oxide catalyst in a typical embodiment of the present invention; Figure 2 This is an optical microscope photograph of the iron-based oxide catalyst prepared in Example 1 of the present invention; Figure 3 is a SEM image of the single-walled carbon nanotube prepared in Example 1 of the present invention; Figure 4 TEM image of the single-walled carbon nanotube prepared in Example 1 of the present invention; Figure 5a is the XRD pattern of the iron-based oxide catalyst prepared in Example 1 of the present invention; Figure 5b is the XRD pattern of the iron-based oxide catalyst prepared in Example 2 of the present invention; Figure 5c This is the XRD diagram of the catalyst prepared in Comparative Example 1 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, an iron-based oxide catalyst includes a main catalyst body and a co-catalyst distributed on the main catalyst body, wherein the main catalyst body includes iron powder and the co-catalyst includes iron oxide.

[0013] In some embodiments, the iron powder content in the iron-based oxide catalyst is 23.9-89.7 wt %, and the iron oxide content is 10.3-76.1 wt %.

[0014] As another aspect of the technical solution of the present invention, a method for preparing an iron-based oxide catalyst includes: subjecting iron powder to an oxidation reaction in a reaction chamber in the presence of water vapor and oxygen, generating iron oxide in situ on the surface of the iron powder, and obtaining an iron-based oxide catalyst.

[0015] In some embodiments, the oxidation reaction temperature is 200-800° C., and the time is 0.5-6 hours. If the reaction time is too long, Fe will be completely oxidized, so the present invention controls the reaction time within this range.

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

[0017] In some embodiments, the particle size of the iron powder is 50 nm to 50 µm. Carbonyl iron powder with a particle size that is too small has a high raw material cost and unstable performance. The present invention selects a particle size of 50 nm or more as more suitable. The particle size of the prepared catalyst is determined by the particle size of the added pure iron powder, and the co-catalyst iron oxide is generated in situ on the surface of the pure iron powder.

[0018] In some embodiments, the preparation method comprises: Provide an air compression device, a heating device, and a tube furnace that are interconnected; The iron powder is placed in the reaction chamber of the tube furnace, and the temperature is raised to the temperature required for the oxidation reaction, while the selected liquid on the heating device is heated to boiling; The air compression device is turned on to allow the steam above the boiling liquid to continuously flow into the reaction chamber of the tubular furnace to carry out the oxidation reaction.

[0019] In some preferred embodiments, the selected liquid includes, but is not limited to, pure water or oxygen-enriched water.

[0020] In some preferred embodiments, the heating temperature is 105-150°C.

[0021] In some preferred embodiments, the vapor of the selected liquid is introduced into one end of the reaction chamber of the tube furnace, and an alumina insulation assembly is placed at the other end.

[0022] In some preferred embodiments, the working pressure of the air compression device is 0.4-1.0 MPa. The amount of steam introduced into the tubular furnace is controlled by the pressure value of the air compressor, and the overall range is 0.4 to 1.0 MPa (usually the upper limit of the working pressure of commercially available air compressors is 1.0 MPa), and the type of iron oxide generated in situ on the surface of the pure iron powder can be controlled by the amount of steam introduced or the reaction temperature and time of the tubular furnace.

[0023] In some preferred embodiments, the air compression device includes but is not limited to an oil-free mobile air compressor.

[0024] In some preferred embodiments, the heating device includes but is not limited to an electric heating mantle.

[0025] In some more specific embodiments, the preparation method comprises: Step 1: Assemble the reaction equipment using an air compressor, electric heating jacket and tubular furnace to ensure smooth airflow inside the equipment.

[0026] Step 2: Pour pure iron powder (such as carbonyl iron powder) of the required particle size into a flat corundum boat and cover the bottom of the boat. Move the corundum boat into the tube furnace in step 1, set the tube furnace to increase the temperature, and heat the solution in the spherical flask on the electric heating jacket at the same time.

[0027] Step 3: When the tubular furnace in the equipment of step 2 reaches the specified temperature and the solution in the electric heating jacket boils, turn on the air compressor to allow the steam above the boiling liquid to continuously flow into the tubular furnace. After the reaction time is over, wait for the furnace to cool to room temperature, turn off the equipment, take out the corundum boat, weigh the weight of the catalyst after the reaction, and perform XRD test on the catalyst powder.

[0028] The heating mantle uses a three-necked round-bottom flask to hold a heating solution, the heating solution is pure water or oxygen-enriched water, and the heating temperature is 105-150 degrees Celsius. The three sockets of the three-necked round-bottom flask are respectively connected to an air compressor, a temperature probe and a tubular furnace.

[0029] Among them, the air compressor is an oil-free mobile air compressor, the ventilation rate can be adjusted by a pressure switch, and the working pressure range is selected from 0.4 to 1.0 MPa.

[0030] The constant temperature of the tubular furnace can be selected as a fixed value between 200 and 800 degrees Celsius, and its constant temperature holding time is related to the constant temperature. The higher the temperature, the shorter the required reaction time. The overall reaction time is 0.5 to 6 hours.

[0031] When the tube furnace reaches the constant temperature insulation stage, the air compressor is turned on to pass the steam in the round bottom flask into the tube furnace through the air flow for reaction. During the reaction, an alumina porous insulation furnace door plug is placed at the outlet of the tube furnace.

[0032] The particle size range of the selected pure iron powder is 50 nm to 50 µm. Since the reaction in the tubular furnace is in situ, the particle size of the catalyst obtained after the reaction is close to that of the initial pure iron powder.

[0033] The volume of the selected corundum boat can be selected from 10 to 200 mL, and the depth of the boat is less than 20 mm. Pure iron powder is spread on the bottom of the boat, and its weight ranges from 10 to 200 g. The corundum boat containing iron powder is placed in the middle section of the tube furnace.

[0034] When the tubular furnace reaches the cooling program section, the air compressor and the electric heating jacket are stopped. When the corundum boat is cooled to room temperature, it is taken out and weighed to obtain the weight of the iron powder after oxidation, and the type of iron oxide in the powder is detected by XRD.

[0035] As another aspect of the technical solution of the present invention, it also relates to an iron-based oxide catalyst prepared by the aforementioned preparation method.

[0036] The iron-based oxide catalyst provided by the present invention has a special structure, and the co-catalyst (iron oxide) component is in-situ grown and distributed on the surface of the main catalyst (nano iron) body. On the one hand, the binding force between the metal oxide co-catalyst and the metal main catalyst is improved, and on the other hand, the presence of the metal oxide can prevent the coarsening of the iron-based catalyst particles at high temperatures; and the co-catalyst component interacts strongly with the main catalyst body, so that the co-catalyst component is evenly dispersed and not easy to agglomerate.

[0037] As another aspect of the technical solution of the present invention, it also involves the use of the aforementioned iron-based oxide catalyst in the preparation of carbon nanotubes.

[0038] In some embodiments, the application includes: application of the aforementioned iron-based oxide catalyst in preparing carbon nanotubes by chemical vapor deposition (CVD).

[0039] Specifically, the iron-based oxide catalyst provided by the present invention has good stability and high yield in the preparation of carbon nanotubes, and the obtained carbon nanotubes have uniform diameters; taking a catalyst obtained from carbonyl iron powder with an initial particle size of 200 nm as a raw material as an example, when used for the CVD method to produce carbon nanotubes, a uniform tube diameter of 1-2 nm can be obtained.

[0040] In summary, the present invention combines an air compressor, an electric heating jacket and a tubular furnace, passes steam generated by heating a solution with the electric heating jacket into the tubular furnace through the air compressor, and utilizes the oxidation reaction of iron powder with water vapor and oxygen at high temperature to form iron oxide in situ on the surface of the iron powder to prepare an iron oxide-iron composite catalyst. The iron oxide is gradually converted into Fe3C in the carbon nanotube growth reaction, and then decomposed into Fe and graphite. This process can promote the growth of carbon nanotubes. In addition, the presence of metal oxide can enhance the chemical stability of metal nanoparticles and prevent them from coarsening so that the catalyst remains in a small particle state. The preparation method of the present invention is simple, can expand production, and is convenient for realizing the large-scale preparation of carbon nanotubes.

[0041] 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.

[0042] Example 1 This embodiment provides a method for preparing an iron-based oxide catalyst, which comprises the following preparation steps: S1: Take a 500 mL three-necked round-bottom flask, fill it with aqueous solution, and place it in an electric heating mantle. Assemble the air compressor, electric heating mantle and tube furnace as follows Figure 1 The reaction equipment shown ensures smooth airflow inside the equipment.

[0043] S2: Weigh 1 portion of 50 g of carbonyl iron powder with a particle size of 200 nm and pour it into a flat corundum boat with a length, width and height of 80×30×10 mm, covering the bottom of the boat. Move the corundum boat into the tube furnace in S1, and set the temperature of the tube furnace to increase from room temperature 25 degrees Celsius to 200 degrees Celsius in 1 hour, keep it at 200 degrees Celsius for 2 hours, and then cool it to room temperature. At the same time, set the target temperature of the electric heating mantle to 120 degrees Celsius, and start heating the solution in the round-bottom flask.

[0044] S3: When the tubular furnace in the equipment of step S2 reaches 200 degrees Celsius, the solution in the electric heating jacket is already in a boiling state. Turn on the air compressor and the pressure gauge shows 0.6 MPa, so that the steam above the boiling liquid is continuously passed into the tubular furnace. After the reaction time is over, wait for the furnace to cool to room temperature, turn off the equipment, take out the corundum boat, and weigh the iron-based oxide catalyst (referred to as catalyst 1) obtained after the reaction to obtain a weight of 54.24 g. For an optical micrograph of catalyst 1, see Figure 2 The XRD test was performed on the catalyst 1 powder. The test results are shown in Figure 5a It was found that Fe on the catalyst surface was in situ oxidized to Fe3O4.

[0045] Catalyst 1 was added to the reactor. Argon was first introduced into the reactor to exhaust the air. Then ethanol was bubbled with 4200 sccm hydrogen and the steam was introduced into the reactor. The center temperature of the reactor was adjusted to 1200°C by programmed temperature increase and the growth was carried out for 60 min. The bubbling was stopped and the equipment was cooled to room temperature under the protection of 2000 sccm argon to obtain carbon nanotubes with a yield of 0.59 g / h.

[0046] The morphology of carbon nanotube samples was observed by scanning electron microscopy and transmission electron microscopy. Figure 3 (SEM images) and Figure 4 As shown in (TEM image), the obtained carbon nanotubes are relatively long, all greater than 1 μm, and have uniform diameters, all between 1 and 2 nm.

[0047] Example 2 This embodiment provides a method for preparing an iron-based oxide catalyst, which comprises the following preparation steps: S1: Take a 500 mL three-necked round-bottom flask, fill it with aqueous solution, and place it in an electric heating mantle. Assemble the air compressor, electric heating mantle and tube furnace as follows Figure 1 The reaction equipment shown ensures smooth airflow inside the equipment.

[0048] S2: Weigh 50 g of carbonyl iron powder with a particle size of 200 nm and pour it into a flat corundum boat with a length, width and height of 80×30×10 mm, covering the bottom of the boat. Move the corundum boat into the tube furnace in S1, and set the temperature of the tube furnace to rise from room temperature 25 degrees Celsius to 600 degrees Celsius in 2 hours, keep it at 600 degrees Celsius for 1 hour, and then cool it to room temperature. At the same time, set the heating target temperature of the electric heating mantle to 120 degrees Celsius, and start heating the solution in the round-bottom flask.

[0049] S3: When the tubular furnace in the equipment of step S2 reaches 600 degrees Celsius, the solution in the electric heating jacket is already in a boiling state. Turn on the air compressor and the pressure gauge shows 0.8 MPa, so that the steam above the boiling liquid is continuously passed into the tubular furnace. After the reaction time is over, wait for the furnace to cool to room temperature, turn off the equipment, take out the corundum boat, and weigh the iron-based oxide catalyst (referred to as catalyst 2) obtained after the reaction to obtain a weight of 60.28 g. XRD test was performed on the catalyst 2 powder. The test results are shown in Figure 5b It was found that Fe on the catalyst surface was in situ oxidized to Fe2O3 and Fe3O4.

[0050] Catalyst 2 was added to the reactor. Argon was first introduced into the reactor to exhaust the air. Then 4200 sccm of hydrogen was used to bubble ethanol, and the steam was introduced into the reactor. The center temperature of the reactor was adjusted to 1200°C by programmed temperature increase, and the growth was carried out for 60 min. The bubbling was stopped, and the equipment was cooled to room temperature under the protection of 2000 sccm of argon to obtain carbon nanotubes with a yield of 0.89 g / h.

[0051] Example 3 This embodiment provides a method for preparing an iron-based oxide catalyst, which comprises the following preparation steps: S1: Take a 500 mL three-necked round-bottom flask, fill it with aqueous solution, and place it in an electric heating mantle. Assemble the air compressor, electric heating mantle and tube furnace as follows Figure 1 The reaction equipment shown ensures smooth airflow inside the equipment.

[0052] S2: Weigh 1 portion of 50 g of carbonyl iron powder with a particle size of 200 nm and pour it into a flat corundum boat with a length, width and height of 80×30×10 mm, covering the bottom of the boat. Move the corundum boat into the tube furnace in S1, and set the temperature of the tube furnace to rise from room temperature 25 degrees Celsius to 800 degrees Celsius in 2 hours, keep it at 800 degrees Celsius for 1 hour, and then cool it to room temperature. At the same time, set the heating target temperature of the electric heating mantle to 120 degrees Celsius, and start heating the solution in the round-bottom flask.

[0053] S3: When the tubular furnace in the equipment of step S2 reaches 800 degrees Celsius, the solution in the electric heating jacket is already in a boiling state. Turn on the air compressor and the pressure gauge shows 0.8 MPa, so that the steam above the boiling liquid is continuously passed into the tubular furnace. After the reaction time is over, wait for the furnace to cool to room temperature, turn off the equipment, take out the corundum boat, and weigh the iron-based oxide catalyst (referred to as catalyst 3) obtained after the reaction, which is 61.97 g. XRD test of catalyst 3 powder found that Fe on the catalyst surface was in situ oxidized to Fe2O3.

[0054] Catalyst 3 was added to the reactor. Argon was first introduced into the reactor to exhaust the air. Then ethanol was bubbled with 4200 sccm hydrogen and the steam was introduced into the reactor. The center temperature of the reactor was adjusted to 1200°C by programmed temperature increase and the growth was carried out for 60 min. The bubbling was stopped and the equipment was cooled to room temperature under the protection of 2000 sccm argon to obtain carbon nanotubes with a yield of 0.75 g / h.

[0055] Example 4 This embodiment provides a method for preparing an iron-based oxide catalyst, which comprises the following preparation steps: S1: Take a 500 mL three-necked round-bottom flask, fill it with aqueous solution, and place it in an electric heating mantle. Assemble the air compressor, electric heating mantle and tube furnace as follows Figure 1 The reaction equipment shown ensures smooth airflow inside the equipment.

[0056] S2: Weigh 50 g of carbonyl iron powder with a particle size of 50 nm and pour it into a flat corundum boat with a length, width and height of 80×30×10 mm, covering the bottom of the boat. Move the corundum boat into the tube furnace in S1, and set the temperature of the tube furnace to rise from room temperature 25 degrees Celsius to 200 degrees Celsius in 1 hour, keep it at 200 degrees Celsius for 6 hours, and then cool it to room temperature. At the same time, set the target temperature of the electric heating mantle to 120 degrees Celsius, and start heating the solution in the round-bottom flask.

[0057] S3: When the tubular furnace in the equipment of step S2 reaches 200 degrees Celsius, the solution in the electric heating jacket is already in a boiling state, and the air compressor is turned on and the pressure gauge shows 0.4 MPa, so that the steam above the boiling liquid is continuously passed into the tubular furnace. After the reaction time is over, wait for the furnace body to cool to room temperature, turn off the equipment, take out the corundum boat, and obtain the iron-based oxide catalyst obtained after the reaction.

[0058] The obtained iron-based oxide catalyst was added into the reactor, argon was first introduced into the reactor to exhaust the air, then 4200 sccm hydrogen was used to bubble ethanol, and steam was introduced into the reactor. The center temperature of the reactor was adjusted to 1200°C by programmed temperature increase, and the growth was carried out for 60 min. The bubbling was stopped, and the equipment was cooled to room temperature under the protection of 2000 sccm argon to obtain carbon nanotubes.

[0059] Example 5 This embodiment provides a method for preparing an iron-based oxide catalyst, which comprises the following preparation steps: S1: Take a 500 mL three-necked round-bottom flask, fill it with aqueous solution, and place it in an electric heating mantle. Assemble the air compressor, electric heating mantle and tube furnace as follows Figure 1 The reaction equipment shown ensures smooth airflow inside the equipment.

[0060] S2: Weigh 50 g of carbonyl iron powder with a particle size of 50 µm and pour it into a flat corundum boat with a length, width and height of 80×30×10 mm, covering the bottom of the boat. Move the corundum boat into the tube furnace in S1, and set the temperature of the tube furnace to rise from room temperature 25 degrees Celsius to 800 degrees Celsius in 2 hours, keep it at 800 degrees Celsius for 0.5 hours, and then cool it to room temperature. At the same time, set the heating target temperature of the electric heating mantle to 120 degrees Celsius, and start heating the solution in the round-bottom flask.

[0061] S3: When the tubular furnace in the equipment of step S2 reaches 800 degrees Celsius, the solution in the electric heating jacket is already in a boiling state, and the air compressor is turned on and the pressure gauge shows 1.0 MPa, so that the steam above the boiling liquid is continuously passed into the tubular furnace. After the reaction time is over, wait for the furnace body to cool to room temperature, turn off the equipment, take out the corundum boat, and obtain the iron-based oxide catalyst obtained after the reaction.

[0062] The obtained iron-based oxide catalyst was added into the reactor, argon was first introduced into the reactor to exhaust the air, then 4200 sccm hydrogen was used to bubble ethanol, and steam was introduced into the reactor. The center temperature of the reactor was adjusted to 1200°C by programmed temperature increase, and the growth was carried out for 60 min. The bubbling was stopped, and the equipment was cooled to room temperature under the protection of 2000 sccm argon to obtain carbon nanotubes.

[0063] Comparative Example 1 Weigh 50 g of carbonyl iron powder with a particle size of 200 nm and pour it into a flat corundum boat with a length, width and height of 80×30×10 mm, cover the bottom of the boat, and spray 5 mL of pure water into the corundum boat. Move the corundum boat into a constant temperature oven and set the temperature to 200 degrees Celsius. Keep it warm for 2 hours, and keep spraying 5 mL of water into the corundum boat every 30 minutes. After the reaction time is over, wait for the oven to cool to room temperature, turn off the equipment, take out the corundum boat, and weigh the catalyst obtained after the reaction (referred to as catalyst D1) to obtain a weight of 50.89 g. XRD test was performed on the catalyst D1 powder. The test results are shown in Figure 5c It was found that a small amount of Fe on the catalyst surface was in situ oxidized to Fe3O4. Catalyst D1 was added to the reactor, and argon was first introduced into the reactor to exhaust the air. Then 4200 sccm of hydrogen was used to bubble ethanol, and steam was introduced into the reactor. The center temperature of the reactor was adjusted to 1200°C by program heating, and the growth was carried out for 60 min. The bubbling was stopped, and the equipment was cooled to room temperature under the protection of 2000 sccm argon to obtain carbon nanotubes with a yield of 0.09 g / h.

[0064] Comparative Example 2 Compared with Example 2, the difference is that when the tubular furnace in the equipment reaches 600 degrees Celsius, the air compressor pressure gauge is turned on to show 0.3 MPa, so that the steam above the boiling liquid is continuously passed into the tubular furnace. After the reaction time is over, wait for the furnace body to cool to room temperature, turn off the equipment, take out the corundum boat, and weigh the catalyst obtained after the reaction (referred to as catalyst D2) to be 56.11 g. XRD test was performed on the catalyst D2 powder, and it was found that compared with Example 2, the Fe on the catalyst surface was in situ oxidized to Fe2O3 and Fe3O4, but the iron oxide content was reduced. Catalyst D2 was added to the reactor for the preparation of carbon nanotubes, and its yield decreased to 0.56 g / h compared with Example 2.

[0065] Comparative Example 3 Compared with Example 1, the difference is that the temperature of the tubular furnace is set to rise from room temperature 25 degrees Celsius to 150 degrees Celsius in 1 hour, and kept at 150 degrees Celsius for 2 hours. When the tubular furnace in the equipment reaches 150 degrees Celsius, turn on the air compressor to continuously pass the steam above the boiling liquid into the tubular furnace. After the reaction time is over, wait for the furnace body to cool to room temperature, turn off the equipment, take out the corundum boat, and weigh the catalyst obtained after the reaction (referred to as catalyst D3) to be 51.59g. XRD test was performed on the catalyst D3 powder, and it was found that the iron oxide content in the catalyst decreased compared with Example 1. Catalyst D3 was added to the reactor for the preparation of carbon nanotubes, and its yield decreased to 0.19 g / h compared with Example 1.

[0066] Comparative Example 4 Compared with Example 3, the difference is that the temperature of the tubular furnace is set to 2 hours from room temperature 25 degrees Celsius to 900 degrees Celsius, and kept at 900 degrees Celsius for 1 hour. When the tubular furnace in the equipment reaches 900 degrees Celsius, turn on the air compressor to continuously pass the steam above the boiling liquid into the tubular furnace. After the reaction time is over, wait for the furnace body to cool to room temperature, turn off the equipment, take out the corundum boat, and weigh the catalyst obtained after the reaction (referred to as catalyst D4) to be 62.57g. XRD test was performed on the catalyst D4 powder, and it was found that the iron oxide content in the catalyst increased compared with Example 3. Catalyst D4 was added to the reactor for the preparation of carbon nanotubes, and its yield decreased to 0.49 g / h compared with Example 3.

[0067] Comparative Example 5 Compared with Example 1, the difference is that the tubular furnace in the equipment is kept at 200 degrees Celsius for 0.3 hours, and the air compressor is turned on to continuously pass the steam above the boiling liquid into the tubular furnace. After the reaction time is over, wait for the furnace to cool to room temperature, turn off the equipment, take out the corundum boat, and weigh the catalyst obtained after the reaction (referred to as catalyst D5) to be 50.33 g. XRD test was performed on the catalyst D5 powder, and it was found that the iron oxide content in the catalyst decreased compared with Example 1. Catalyst D5 was added to the reactor for preparing carbon nanotubes, and its yield decreased to 0.12 g / h compared with Example 1.

[0068] Comparative Example 6 Compared with Example 3, the difference is that when the tubular furnace in the equipment reaches 800 degrees Celsius and is kept warm for 6.5 hours, the air compressor is turned on to continuously pass the steam above the boiling liquid into the tubular furnace. After the reaction time is over, wait for the furnace to cool to room temperature, turn off the equipment, take out the corundum boat, and weigh the catalyst obtained after the reaction (referred to as catalyst D6) to be 63.91 g. XRD test was performed on the catalyst D6 powder, and it was found that the iron oxide content in the catalyst increased significantly compared with Example 3, and the characteristic peak of Fe element disappeared completely. Catalyst D6 was added to the reactor for the preparation of carbon nanotubes, and its yield decreased to 0.32 g / h compared with Example 1.

[0069] In summary, the carbon nanotubes prepared by the CVD method using the iron-based oxide catalyst of the present invention have uniform tube diameters and high yields, indicating that the iron-based oxide catalyst of the present invention has high activity and excellent performance.

[0070] 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.

[0071] 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. An iron-based oxide catalyst, characterized in that It comprises a main catalyst body and a co-catalyst distributed on the main catalyst body, wherein the main catalyst body comprises iron powder and the co-catalyst comprises iron oxide.

2. The iron-based oxide catalyst according to claim 1, characterized in that The content of iron powder in the iron-based oxide catalyst is 23.9-89.7 wt %, and the content of iron oxide is 10.3-76.1 wt %.

3. A method for preparing an iron-based oxide catalyst, characterized in that: include: In the presence of water vapor and oxygen, iron powder is subjected to oxidation reaction in a reaction chamber, iron oxide is generated in situ on the surface of the iron powder, and an iron-based oxide catalyst is prepared.

4. The preparation method according to claim 3, characterized in that: The temperature of the oxidation reaction is 200-800° C., and the time is 0.5-6 hours.

5. The preparation method according to claim 3, characterized in that: The iron powder includes carbonyl iron powder; and / or the particle size of the iron powder is 50 nm~50 µm.

6. The preparation method according to claim 3, characterized in that: include: Provide an air compression device, a heating device, and a tube furnace that are interconnected; The iron powder is placed in the reaction chamber of the tube furnace, and the temperature is raised to the temperature required for the oxidation reaction, while the selected liquid on the heating device is heated to boiling; The air compression device is turned on to allow the steam above the boiling liquid to continuously flow into the reaction chamber of the tubular furnace to carry out the oxidation reaction.

7. The preparation method according to claim 6, characterized in that: The selected liquid includes pure water or oxygen-enriched water; and / or the heating temperature is 105-150°C.

8. The preparation method according to claim 6, characterized in that: The vapor of the selected liquid is introduced into one end of the reaction chamber of the tubular furnace, and an alumina heat insulation assembly is placed at the other end; And / or, the working pressure of the air compression device is 0.4~1.0 MPa; and / or, the air compression device comprises an oil-free portable air compressor; And / or, the heating device comprises an electric heating jacket.

9. An iron-based oxide catalyst prepared by the preparation method according to any one of claims 3 to 8.

10. Use of the iron-based oxide catalyst according to any one of claims 1, 2 and 9 in the preparation of carbon nanotubes.

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