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CN-121990561-A - Method for continuously preparing single-walled carbon nanotubes and hydrogen based on methane pyrolysis

CN121990561ACN 121990561 ACN121990561 ACN 121990561ACN-121990561-A

Abstract

The invention relates to the technical field of carbon nanotube preparation, and discloses a method for continuously preparing single-walled carbon nanotubes and hydrogen based on methane pyrolysis. The method comprises the steps of (1) introducing a mixed gas I containing methane and argon into an arc reaction unit, (2) loading a catalyst in a catalyst injection unit into a cavity of an electrode cathode in the arc reaction unit, performing cracking reaction through arc discharge to obtain tail gas containing hydrogen and single-walled carbon nanotubes, (3) cooling the tail gas and the single-walled carbon nanotubes by a cooling device, then collecting the deposited single-walled carbon nanotubes by an iron wire gauze in the arc reaction unit, (4) introducing the tail gas into a tail gas separation and purification unit for separation and purification to obtain a mixed gas II and hydrogen, and circulating the mixed gas II into the arc reaction unit through a gas circulation unit to participate in the cracking reaction. The method provided by the invention can continuously prepare the single-walled carbon nanotube and hydrogen, and has high methane conversion rate.

Inventors

  • LI YONGFENG
  • XU CHONG

Assignees

  • 中国石油大学(北京)

Dates

Publication Date
20260508
Application Date
20251209

Claims (10)

  1. 1. A method for continuously preparing single-walled carbon nanotubes and hydrogen based on methane pyrolysis, which is characterized by comprising the following steps: (1) Introducing a mixed gas I containing methane and argon in a raw material feeding unit into an electric arc reaction unit, wherein the content volume ratio of the methane to the argon in the mixed gas I is 1:3-10; The electric arc reaction unit comprises an electrode anode, an electrode cathode, a product collecting device and a cooling device, wherein the electrode anode and the electrode cathode are coaxially arranged and have a gap, the electrode anode adopts a graphite electrode with a hollow channel, and a concave cavity is formed in the axial end, opposite to the hollow channel of the electrode anode, of the electrode cathode; (2) Loading the catalyst in the catalyst injection unit into a concave cavity of an electrode cathode in the arc reaction unit, then starting an arc power supply, and performing cracking reaction through arc discharge to obtain tail gas containing hydrogen and single-walled carbon nanotubes; The catalyst contains transition metal simple substance and rare earth metal simple substance in a mass ratio of 10-50:1; (3) Cooling the tail gas and the single-walled carbon nanotubes by a cooling device in an electric arc reaction unit, and then collecting the deposited single-walled carbon nanotubes by a wire gauze in the electric arc reaction unit; (4) Introducing the tail gas into a tail gas separation and purification unit for separation and purification to obtain mixed gas II and hydrogen with the purity of more than or equal to 99wt%, wherein the mixed gas II contains methane and argon, and the mixed gas II is circulated into an electric arc reaction unit through a gas circulation unit to participate in the cracking reaction.
  2. 2. The method according to claim 1, wherein in the step (1), the content volume ratio of methane to argon in the mixed gas I is 1:3-5.
  3. 3. The method according to claim 1, wherein the transition metal element is at least one selected from the group consisting of iron, cobalt, and nickel; And/or the rare earth metal simple substance is selected from at least one of yttrium, cerium and lanthanum.
  4. 4. The method according to claim 1, wherein the conditions of the cleavage reaction include an arc current of 60 to 100A, an arc voltage of 20 to 40V, a reaction pressure of 0.1 to 0.5MPa and a reaction temperature of 4000 to 6000K.
  5. 5. The method according to claim 1, characterized in that in the arc reaction unit the gap between the electrode anode and electrode cathode is 2-6mm.
  6. 6. The method according to any one of claims 1 to 5, wherein the electrode anode has an inner diameter of 3 to 7mm, an outer diameter of 12 to 18mm and a length of 60 to 80mm.
  7. 7. The method of any one of claims 1-5, wherein the electrode cathode is a graphite electrode having a cavity; And/or the diameter of the electrode cathode is 12-20mm, and the length is 60-80mm.
  8. 8. The method of any one of claims 1-5, wherein the cavity is a cylindrical cavity, The ratio of the depth of the concave cavity to the length of the electrode cathode is 1:15-20, and the ratio of the diameter of the concave cavity to the diameter of the electrode cathode is 0.5-0.8:1.
  9. 9. The method according to any one of claims 1 to 5, wherein in step (2), the catalyst is injected at a rate of 0.1 to 0.5g/min.
  10. 10. The method of any one of claims 1-5, wherein the single-walled carbon nanotubes have a diameter of 0.8-2.4nm and a length of 5-20 μm.

Description

Method for continuously preparing single-walled carbon nanotubes and hydrogen based on methane pyrolysis Technical Field The invention relates to the technical field of carbon nanotube preparation, in particular to a method for continuously preparing single-walled carbon nanotubes and hydrogen based on methane pyrolysis. Background The carbon nano tube has a broad application prospect in the fields of composite materials, electronic devices, energy storage and the like due to the unique structure and excellent mechanical, electrical and thermal properties. However, the large scale controllable preparation of high quality carbon nanotubes remains a key bottleneck limiting its commercial application. Currently, the main methods for preparing single-walled carbon nanotubes include arc discharge, laser evaporation and chemical vapor deposition. Among them, the arc discharge method is widely used because of its advantages such as simple equipment and good crystallinity of the product. The traditional arc discharge method mostly uses graphite electrodes as carbon sources, and has the problems of large electrode consumption, discontinuous process and the like. Although some researches try to replace graphite electrodes with gaseous carbon sources such as methane, the problems that the methane conversion rate is not high, tail gas is not effectively utilized and the like still exist. In addition, the hydrogen and unreacted methane generated in the reaction process are not recycled, so that the resource waste and the cost are increased. Therefore, development of a method capable of continuously preparing single-walled carbon nanotubes, synchronously producing hydrogen and realizing efficient recycling of resources is needed. Disclosure of Invention The invention aims to solve the problems of difficult continuous production, low raw material utilization rate and low methane conversion rate in the prior art. In order to achieve the above object, a first aspect of the present invention provides a method for continuously preparing single-walled carbon nanotubes and hydrogen based on methane pyrolysis, the method comprising the steps of: (1) Introducing a mixed gas I containing methane and argon in a raw material feeding unit into an electric arc reaction unit, wherein the content volume ratio of the methane to the argon in the mixed gas I is 1:3-10; The electric arc reaction unit comprises an electrode anode, an electrode cathode, a product collecting device and a cooling device, wherein the electrode anode and the electrode cathode are coaxially arranged and have a gap, the electrode anode adopts a graphite electrode with a hollow channel, and a concave cavity is formed in the axial end, opposite to the hollow channel of the electrode anode, of the electrode cathode; (2) Loading the catalyst in the catalyst injection unit into a concave cavity of an electrode cathode in the arc reaction unit, then starting an arc power supply, and performing cracking reaction through arc discharge to obtain tail gas containing hydrogen and single-walled carbon nanotubes; The catalyst contains transition metal simple substance and rare earth metal simple substance in a mass ratio of 10-50:1; (3) Cooling the tail gas and the single-walled carbon nanotubes by a cooling device in an electric arc reaction unit, and then collecting the deposited single-walled carbon nanotubes by a wire gauze in the electric arc reaction unit; (4) Introducing the tail gas into a tail gas separation and purification unit for separation and purification to obtain mixed gas II and hydrogen with the purity of more than or equal to 99wt%, wherein the mixed gas II contains methane and argon, and the mixed gas II is circulated into an electric arc reaction unit through a gas circulation unit to participate in the cracking reaction. Compared with the prior art, the invention has the following advantages: 1. the method provided by the invention can obviously improve the purity and crystallinity of the single-wall carbon nano tube, and the prepared carbon nano tube has concentrated diameter distribution (the diameter distribution is 1.2-1.8 nm) and good structural integrity. 2. The continuous production method provided by the invention can realize uninterrupted preparation of the single-walled carbon nanotube, and greatly improves the production efficiency. 3. And the comprehensive utilization of resources is realized by collecting hydrogen generated by the cracking reaction while preparing the single-walled carbon nanotubes and recycling unreacted methane and argon, so that the consumption and cost of raw materials are greatly reduced. 4. The preparation method is environment-friendly, realizes near zero pollutant emission in the whole process, ensures that the total utilization rate of methane is more than 90 percent, and meets the green manufacturing requirement. Drawings FIG. 1 is a process flow diagram for continuously preparing single-walled carbon nanotubes and