CN116603536A - Preparation method of carbon nano tube catalyst - Google Patents

Abstract

The invention discloses a preparation method of a carbon nanotube catalyst. The present invention aims at the shortcomings of the prior art and improves the catalyst preparation method in the process of making the catalyst. The method of spray drying is used to complete the dispersion of active components and the control of particle size in the instant drying process, so that the produced carbon nanotubes The particle size of the catalyst is uniform, and the active components are uniformly dispersed, so that the electrical conductivity of the carbon nanotubes produced by it has been greatly improved. The preparation method of the invention is simple, can effectively improve the production efficiency, reduce the production cost and shorten the preparation cycle.

Description

A kind of preparation method of carbon nanotube catalyst

technical field

The invention relates to the technical field of carbon nanotubes, in particular to a preparation method of a carbon nanotube catalyst.

Background technique

Catalysts are the starting materials for the production of carbon nanotubes. Catalysts with good performance can produce carbon nanotubes with good conductivity, high aspect ratio and excellent performance, which is of great significance to improve the performance of carbon nanotubes.

Most of the existing technologies use the hydrothermal method to prepare catalysts, which has the disadvantage of low yield; the prepared catalysts are prone to the problem of wide grain size range, and it is difficult to control the concentration of active substances loaded on the carrier in the later drying process, thus The quality of the carbon nanotubes produced by the catalyst is not high, and the electrical conductivity is poor. In addition, a large amount of wastewater will be generated during the preparation of catalysts by hydrothermal method, resulting in a large waste of resources.

Contents of the invention

The invention aims to provide a method for preparing a carbon nanotube catalyst to solve the problems of long production cycle, complicated process and low carbon tube graphitization degree of the existing hydrothermal catalyst.

In order to achieve the above object, the present invention will adopt the following technical solutions:

A preparation method of carbon nanotube catalyst, comprising the steps of:

S1. Vector preparation

S1-1. adding soluble magnesium salt and precipitating agent into water, adjusting pH to 6-14, and carrying out precipitation reaction under stirring condition;

S1-2. washing the obtained precipitate, and proportioning the washed precipitate with deionized water;

S1-3. Use a spray drying device to spray dry and shape to obtain micron-sized magnesium carbonate particles;

S1-4. Calcining micron-sized magnesium carbonate particles at high temperature to convert them into micron-sized mesoporous magnesium oxide particles;

S2. Preparation of catalyst

Add active material components and additive components to water to form an active component solution, add a carrier to the active component solution, mix and stir, and then granulate through a spray drying device to obtain a catalyst precursor, and obtain a catalyst after roasting product.

As an improvement, the soluble magnesium salt described in step S1-1 is one or more of magnesium nitrate, magnesium chloride, magnesium sulfate containing crystal water salt or not containing crystal water salt; of alkaline substances.

As an improvement, the concentration of the magnesium salt solution after the soluble magnesium salt is added to the water in step S1-1 is 5%-50%; the concentration of the precipitant solution after the precipitant is added to the water is 3%-50%.

As an improvement, the anion and cation molar ratio of the soluble magnesium salt to the precipitating agent in step S1-1 is 1:0.1-5, and the precipitation time is 0-30 min.

As an improvement, the stirring rate in step S1-1 is 100-400 r/min, the precipitation process is controlled at 0-60 minutes, and the stirring is continued for 0-60 minutes after complete precipitation.

As an improvement, the mass ratio of the precipitate to the deionized water in step S1-2 is 1:0.5-20.

As an improvement, the inlet temperature of the spray drying in step S1-3 is 150-300°C, and the outlet temperature is 80-125°C.

As an improvement, the high-temperature calcination method described in step S1-4 is: raise the temperature at 3-15°C/min to a calcination temperature of 500-1000°C, and then calcine the micron-sized magnesium carbonate particles for about 2-6 hours to convert them into It is micron-sized mesoporous magnesium oxide particles.

As an improvement, the active material components described in step S2 include ferric nitrate, ferric chloride, ferric sulfate, cobalt nitrate, cobalt chloride, cobalt sulfate, manganese chloride, manganese nitrate, manganese sulfate, nickel nitrate, nickel chloride and One or more of nickel sulfate, the concentration of the active component is 0.5-2.5mol/L;

The additive component includes one or more of ammonium heptamolybdate, ammonium metavanadate, ammonium metatungstate and compounds containing Cu/Mn, and the concentration of the additive component is 0.005-0.25mol/L ; The molar ratio between the active component and the auxiliary component is 10-300:1.

As an improvement, the spray drying conditions in step S2 are: inlet temperature 110-200°C, outlet temperature 80-120°C; the calcination temperature is 200-750°C.

Beneficial effects of the present invention:

1. The present invention aims at the shortcomings of the prior art and improves the method of catalyst preparation in the process of making the catalyst, adopts the method of spray drying, and completes the active component dispersion and particle size control in the instant drying process, so that the produced carbon The particle size of the nanotube catalyst is uniform, and the active components are uniformly dispersed, so that the conductivity of the carbon nanotubes produced by it has been greatly improved.

2. The preparation method of the present invention is simple, can effectively improve production efficiency, reduce production cost, and shorten the preparation cycle.

Description of drawings

Figure 1 is a process flow diagram of carrier preparation.

Figure 2 is a flow chart of the process for preparing catalysts using supports.

Fig. 3 is a process flow chart for preparing carbon nanotubes using a catalyst.

FIG. 4 is the appearance of carbon nanotubes prepared in Example 1.

FIG. 5 is the diameter of carbon nanotubes prepared in Example 1.

Figure 6 is the appearance of the catalyst prepared in Example 1.

Detailed ways

In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

Example 1

This embodiment discloses a method for preparing a carbon nanotube catalyst, comprising the following steps:

S1. Vector preparation

S1-1. Stir sodium carbonate in water to prepare a 1mol/L sodium carbonate solution, stir magnesium chloride in water to prepare a 1mol/L magnesium chloride solution; slowly add 110ml of sodium carbonate solution dropwise to 100ml stirred at a speed of 200rpm In the magnesium chloride solution, continue to stir for 20 minutes to precipitate after the dropwise addition is completed, and continue to stir for 20 minutes after complete precipitation;

S1-2. After the precipitation is completed, perform solid-liquid separation, wash the obtained precipitate with water and ethanol, mix the washed precipitate with deionized water in a ratio of 1:15, stir and mix evenly;

S1-3. Use a spray drying device for spray drying and shaping. The spray conditions are: inlet temperature 250°C, outlet temperature 80°C, flow rate 20ml/min, nozzle size 1mm, after spray drying, micron-sized magnesium carbonate particles, carbonic acid The particle size of magnesium particles is 4-16 μm;

S1-4. Calcining micron-sized magnesium carbonate particles at high temperature, heating up to 600°C at 5°C/min, and calcining the magnesium carbonate particles at a temperature of 600°C for 2 hours to obtain mesoporous magnesium oxide particles;

S2. Preparation of catalyst

Completely dissolve 28g Co(NO ₃ ) ₂ ·6H ₂ O, 0.35g (NH ₄ )6Mo ₇ O ₂₄ , and 1.16g NH ₄ VO ₃ in beaker A of 100ml of pure water to configure an active component solution; Add 20g of mesoporous magnesium oxide to the component solution, heat, mix and stir in a water bath at a temperature of 100°C, and then granulate through a spray drying device. The spraying conditions are inlet temperature 160°C, outlet temperature 80°C, flow rate 10ml/min, nozzle The size is 1mm, and the catalyst precursor is obtained;

Using a muffle furnace, the temperature was raised to 650° C. (heating rate 20° C./min), and the catalyst precursor was calcined for 180 minutes to obtain a finished catalyst.

Comparative example 1

Comparative Example 1 Using the method of Example 1 to prepare a mesoporous magnesia carrier, then 28g Co(NO ₃ ) ₂ ·6H ₂ O, 0.35g (NH ₄ )6Mo ₇ O ₂₄ , 1.16g NH ₄ VO ₃ were completely dissolved in In beaker A with 100ml of pure water, configure an active component solution; add 20g of mesoporous magnesium oxide carrier to the active component solution, heat and mix in a water bath at a temperature of 100°C. After heating and stirring, put it into a vacuum evaporation device and rotate it for 60 minutes (temperature 90°C); put the evaporated material into a muffle furnace for 60 minutes (temperature 650°C) and roast for 180 minutes (heating rate 20°C/min) to obtain a finished catalyst .

Comparative example 2

Comparative example 1 uses the hydrothermal method to prepare magnesium hydroxide carrier, and then 28g Co(NO ₃ ) ₂ ·6H ₂ O, 0.35g (NH ₄ )

6Mo ₇ O ₂₄ , 1.16g NH ₄ VO ₃ are completely dissolved in beaker A of 100ml of pure water to configure the active component solution; add 28.78g of magnesium hydroxide carrier to the active component solution, and at a temperature of 100°C Heat in a water bath to mix and stir. After heating and stirring, put it into a vacuum evaporation device and rotate it for 60 minutes (temperature 90°C); put the evaporated material into a muffle furnace for 60 minutes (temperature 650°C) and roast for 180 minutes (heating rate 20°C/min) to obtain a finished catalyst .

Comparative example 3

Dissolve 28g Co(NO ₃ ) ₂ 6H ₂ O, 10g Fe(NO ₃ ) ₂ 9H ₂ O, 0.35g (NH ₄ )6Mo ₇ O ₂₄ , 1.16g NH ₄ VO ₃ in a 100ml pure water beaker In A, configure the active component solution; add 20g of mesoporous magnesium oxide to the active component solution, heat, mix and stir in a water bath at a temperature of 100°C, and then granulate through a spray drying device. The spraying condition is an inlet temperature of 160°C , the outlet temperature is 80°C, the flow rate is 5ml/min, the nozzle size is 1mm, and the catalyst precursor is obtained;

Using a muffle furnace, the temperature was raised to 650° C. (heating rate 20° C./min), and the catalyst precursor was calcined for 180 minutes to obtain a finished catalyst.

Using the catalysts prepared in Example 1 and Comparative Examples 1-3 to prepare carbon nanotubes, the specific preparation method is as follows:

A tube furnace was selected for CVD reaction, with propylene as the carbon source and nitrogen as the protective gas. Among them, the gas velocity ratio of propylene and nitrogen is 1:3, the propylene is 500 sccm, the reaction time is 50 min, and the reaction temperature is 680°C.

The properties of the carbon nanotubes prepared by the reaction are as follows:

Table 1 Properties of carbon nanotubes

serial number Example 1 Comparative example 1 Comparative example 2 Comparative example 3 Conductivity s/m 9122 5299 3564 7217 Yield% 1200 600 400 900 carrier Mesoporous MgO Mesoporous MgO Mg(OH)2 Mesoporous MgO Calcination temperature ℃ 650 650 650 650

Comparing Example 1 with Comparative Example 1, it can be seen that the catalyst prepared by the spray drying method has a better catalytic effect than the catalyst prepared by the traditional hydrothermal method, the electrical conductivity of the prepared carbon nanotubes is improved by 72.15%, and the yield is improved by 100%.

Comparing Example 1 with Comparative Example 2 and Comparative Example 3, it can be concluded that the use of different carriers has a greater impact on the yield and conductivity, and the difference in their active substances will also affect the yield and conductivity of carbon nanotubes to a certain extent. sex.

In summary, the selection of carriers and active substances in Example 1 is the optimal solution.

The specific embodiments of the present invention have been described in detail above, but they are only examples, and the present invention is not equivalent to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, equivalent changes and modifications made without departing from the spirit and scope of the present invention shall fall within the scope of the present invention.

Claims (10)

1. a preparation method of carbon nanotube catalyst, is characterized in that, comprises the steps: S1. Vector preparation S1-1. adding soluble magnesium salt and precipitating agent into water, adjusting pH to 6-14, and carrying out precipitation reaction under stirring condition; S1-2. washing the obtained precipitate, and proportioning the washed precipitate with deionized water; S1-3. Use a spray drying device to spray dry and shape to obtain micron-sized magnesium carbonate particles; S1-4. Calcining micron-sized magnesium carbonate particles at high temperature to convert them into micron-sized mesoporous magnesium oxide particles; S2. Preparation of catalyst Add active material components and additive components to water to form an active component solution, add a carrier to the active component solution, mix and stir, and then granulate through a spray drying device to obtain a catalyst precursor, and obtain a catalyst after roasting product. 2. the preparation method of a kind of carbon nanotube catalyst according to claim 1 is characterized in that, the soluble magnesium salt described in step S1-1 is magnesium nitrate, magnesium chloride, magnesium sulfate containing crystal water salt or not containing crystal water One or more salts; the precipitation agent is an alkaline substance containing carbonate or bicarbonate. 3. the preparation method of a kind of carbon nanotube catalyst according to claim 1, is characterized in that, the concentration of magnesium salt solution after adding the soluble magnesium salt described in step S1-1 in water is 5%-50%; After the precipitating agent is added into water, the concentration of the precipitating agent solution is 3%-50%. 4. The preparation method of a carbon nanotube catalyst according to claim 1, characterized in that the anion and cation molar ratio of the soluble magnesium salt to the precipitating agent in step S1-1 is 1:0.1～5, and the precipitation time 0 to 30 minutes. 5. The method for preparing a carbon nanotube catalyst according to claim 1, characterized in that, the stirring rate in step S1-1 is 100-400r/min, the precipitation process is controlled at 0-60min, and after complete precipitation Continue to stir for 0-60 minutes. 6 . The method for preparing a carbon nanotube catalyst according to claim 1 , wherein the mass ratio of the precipitate to deionized water in step S1-2 is 1:0.5-20. 7 . The method for preparing a carbon nanotube catalyst according to claim 1 , wherein the inlet temperature of the spray drying in step S1-3 is 150-300° C., and the outlet temperature is 80-125° C. 7 . 8. The preparation method of a carbon nanotube catalyst according to claim 1, characterized in that, the high-temperature calcination method described in step S1-4 is: heating up to 500-1000°C at 3-15°C/min calcining temperature, and then calcining the micron-sized magnesium carbonate particles for about 2-6 hours to convert them into micron-sized mesoporous magnesium oxide particles. 9. The preparation method of a kind of carbon nanotube catalyst according to claim 1, is characterized in that, active material component described in step S2 comprises iron nitrate, iron chloride, iron sulfate, cobalt nitrate, cobalt chloride, One or more of cobalt sulfate, manganese chloride, manganese nitrate, manganese sulfate, nickel nitrate, nickel chloride and nickel sulfate, the concentration of the active component is 0.5-2.5mol/L; The additive component includes one or more of ammonium heptamolybdate, ammonium metavanadate, ammonium metatungstate and compounds containing Cu/Mn, and the concentration of the additive component is 0.005-0.25mol/L ; The molar ratio between the active component and the auxiliary component is 10-300:1. 10. The method for preparing a carbon nanotube catalyst according to claim 1, wherein the spray drying conditions in step S2 are: inlet temperature 110-200°C, outlet temperature 80-120°C; The calcination temperature is 200-750 degrees Celsius.