Method and synthesis reactor for producing carbon nanotubes

Abstract

A synthesis reactor for producing carbon nanotubes. The reactor includes a main reactor, a feeder, a settler, an air inlet device, and a product outlet. The main reactor communicates with the settler in the form of a communicating vessel. The feeder communicates with the settler via a catalyst inlet. The air inlet device is disposed under the settler. The wall of the main reactor is provided with a heat exchanger. The product outlet is disposed at the lower part of the main reactor. A method for producing a carbon nanotube, includes: 1) drying red mud for 1 to 4 hour(s) at the temperature of between 101 C. and 109 C.; 2) smashing and sieving the red mud through a 200-mesh sieve to yield a catalyst; and 3) adding the catalyst to a synthesis reactor.

Claims

1. A method for producing carbon nanotubes by utilizing a synthesis reactor, the reactor comprising a main reactor and a settler, wherein the main reactor is connected to the settler via communicating vessels to form a hollow square structure; the method comprising: 1) collecting red mud, and drying the red mud for 1 to 4 hour(s) at a temperature of between 101 C. and 109 C.; 2) smashing and sieving the red mud through a 200-mesh sieve to yield a catalyst; 3) adding the catalyst to the synthesis reactor via a catalyst inlet disposed on the settler; 4) heating the main reactor to a temperature of between 600 and 1000 C.; 5) adding a mixed gas of nitrogen and a carbon source comprising a hydrocarbon having less than 7 carbon atoms into the synthesis reactor via an air inlet device disposed under the settler, whereby the catalyst is carried by the mixed gas to the main reactor; 6) discharging the carbon nanotubes through a product outlet disposed at a lower part of the main reactor; 7) allowing a mixture comprising residual gases and the catalyst to flow from the main reactor to the settler, and insufflating the mixture into the main reactor by utilizing the mixed gas; and 8) discharging waste gas from a waste gas outlet disposed on a side wall of the settler.

2. The method of claim 1, wherein the red mud is a waste product generated in an industrial production of aluminum through Bayer process; a mass percentage of total iron in the red mud is more than 20%.

3. The method of claim 1, wherein the method further comprises introducing nitrogen to the synthesis reactor prior to reaction.

4. The method of claim 1, wherein the method further comprises introducing nitrogen into the synthesis reactor for 20 to 60 minutes prior to reaction.

5. The method of claim 4, wherein a volume ratio of nitrogen to the hydrocarbon in the mixed gas is between 1:0.5 and 1:1.

6. The method of claim 4, wherein a flow rate of the mixed gas is between 0.2 and 0.5 m/s.

7. The method of claim 1, wherein the residual gases comprise an unreacted carbon source.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a synthesis reactor for producing carbon nanotubes in accordance with one embodiment of the invention;

(2) FIG. 2 is an electron microscope image of nanotubes produced by a method and a synthesis reactor for producing carbon nanotubes in Example 1;

(3) FIG. 3 is an electron microscope image of nanotubes produced by a method and a synthesis reactor for producing carbon nanotubes in Example 2; and

(4) FIG. 4 is an electron microscope image of nanotubes produced by a method and a synthesis reactor for producing carbon nanotubes in Example 3.

(5) In the figures, the following reference numbers are used: 1. Main reactor; 2. Heat exchanger; 3. Feeder; 4. Catalyst inlet; 5. Waste gas outlet; 6. Settler; 7. Air inlet device; and 8. Product outlet.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(6) For further illustrating the invention, experiments detailing a method and a synthesis reactor for carbon nanotube production are described below. It should be noted that the following examples are intended to describe and not to limit the invention.

(7) A synthesis reactor comprises a main reactor 1, a feeder 3, a settler 6, an air inlet device 7, and a product outlet 8. The main reactor 1 communicates with the settler 6 in the form of a communicating vessel. The feeder 3 communicates with the settler 6 via a catalyst inlet 4. The air inlet device 7 is disposed under the settler 6. A wall of the main reactor 1 is provided with a heat exchanger 2. The product outlet 8 is disposed at a lower part of the main reactor 1.

(8) The main reactor 1 is combined with the settler 6 to form a hollow square structure. The main reactor 1 is a fluidized bed.

(9) One side wall of the settler 6 is provided with a waste gas outlet 5, and the waste gas outlet 5 is disposed above the catalyst inlet 4.

Example 1

(10) The red mud used in the example is a waste product generated in the industrial production by bayer process of aluminum. A mass percentage of the total iron in the red mud is 25.21%

(11) The red mud was dried for 2 hours at 105 C.; then the red mud was smashed and sieved by a 200-mesh sieve to yield a catalyst.

(12) N2 was introduced from the air inlet device 7 for 30 minutes before the reaction. 20 g of the catalyst was added into the feeder 3, and was introduced into the synthesis reactor from the catalyst inlet 4. A fluidized bed of the main reactor was heated to 700 C., and a mixed gas of propylene and nitrogen was introduced into the main reactor; the catalyst was insufflated into the main reactor 1 by the mixed gas to yield the carbon nanotubes. A ratio of nitrogen to propylene in the mixed gas is 1:0.5. A flow rate of the mixed gas is 0.3 m/s. The reaction lasted for an hour and produced 75 g of carbon nanotubes which were shown in FIG. 2.

Example 2

(13) The red mud used in the example is a waste product generated in the industrial production by bayer process of aluminum. A mass percentage of the total iron in the red mud is 36.69%

(14) The red mud was dried for 4 hours at 102 C.; then the red mud was smashed to yield a catalyst.

(15) N2 was introduced from the air inlet device 7 for 20 minutes before the reaction. 20 g of the catalyst was added into the feeder 3, and was introduced into the synthesis reactor from the catalyst inlet 4. A fluidized bed of the main reactor was heated to 900 C., and a mixed gas of methane and nitrogen was introduced into the main reactor; the catalyst was insufflated into the main reactor 1 by the mixed gas to yield the carbon nanotubes. A ratio of nitrogen to methane in the mixed gas is 1:0.8. A flow rate of the mixed gas is 0.5 m/s. The reaction lasted for an hour and produced 91 g of carbon nanotubes which were shown in FIG. 3.

Example 3

(16) The red mud used in the example is a waste product generated in the industrial production by bayer process of aluminum. A mass percentage of the total iron in the red mud is 44.71%

(17) The red mud was dried for 1.5 hours at 109 C.; then the red mud was smashed to yield a catalyst.

(18) N2 was introduced from the air inlet device 7 for 60 minutes before the reaction. 20 g of the catalyst was added into the feeder 3, and was introduced into the synthesis reactor from the catalyst inlet 4. A fluidized bed of the main reactor was heated to 850 C., and a mixed gas of ethylene and nitrogen was introduced into the main reactor; the catalyst was insufflated into the main reactor 1 by the mixed gas to yield the carbon nanotubes. A ratio of nitrogen to ethylene in the mixed gas is 1:0.6. A flow rate of the mixed gas is 0.4 m/s. The reaction lasted for an hour and produced 103 g of carbon nanotubes which were shown in FIG. 4.

(19) According to different requirements, the synthesis reactor for carbon nanotube production is also suitable for producing fiber, hydrogen, or other nanomaterials.

(20) While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.