CN1266018A

CN1266018A - Process of nickel catalytic cracking methane preparing carbon nanometer tube

Info

Publication number: CN1266018A
Application number: CN 00102824
Authority: CN
Inventors: 崔屾; 乔亚莉; 崔兰; 吕成章
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2000-03-07
Filing date: 2000-03-07
Publication date: 2000-09-13
Anticipated expiration: 2020-03-07
Also published as: CN1140448C

Abstract

A preparation method of carbon nanometer tube uses nickel oxide as catalyst mother material, and includes the following steps: placing the nickel oxide with a definite quantity in reactor, heating it to a certain temp., using hydrogen gas to make reduction reaction for a certain time, then introducing reaction gas to make it undergo cracking reaction to prepare carbon nanoemeter tube. Said invention is characterized by thatthe reaction gas is a mixed gas containing methane, and said mixed gas is made up by mixing methane and hydrogen gas or by mixing methane, hydrogen gas and inactive gas including argon gas. Said invention features high yield, simple technological process, stable reaction and low cost.

Description

Method for preparing carbon nano tube by catalytically cracking methane with nickel

The invention relates to a method for preparing a carbon nano tube by cracking methane by taking nickel as a catalyst, belonging to the preparation technology of the carbon nano tube.

The carbon nano tube has excellent comprehensive mechanical properties such as high elastic modulus, high Young modulus and low density, and excellent electrical properties, thermal properties and adsorption properties, so the carbon nano tube can play an important role in the fields of microelectronics, nano composite materials, energy, environmental protection, catalysis, biomedicine, national defense, aerospace and the like.

At present, some patents and literature reports on a method for preparing carbon nanotubes by cracking methane with a catalyst, such as a CN1170631A patent, disclose that an oxide of a transition metal is used as a catalyst to crack methane to prepare carbon nanotubes, the reaction temperature is 600 ℃, the space velocity for introducing methane is 2400/h, the reaction time is 20 minutes, and 33 mg of carbon nanotubes are obtained after a product is purified; the document "A.M.Cassell, et a1., J.Phys.chem.B 1999, 103, 6484-: preparing a single-walled carbon nanotube by catalytically cracking methane by using a Fe/Mo bimetallic supported catalyst, wherein the reaction temperature is 900 ℃, the reaction time is 30 minutes, and the maximum yield is about 2%; the document "V.B.Fenelonov, et al., Carbon 1997, 35(8), 1129-: the Ni/Cu bimetallic supported catalyst is used for catalytically cracking methane to prepare the carbon nano tube, the reaction temperature is 565 ℃, and the reaction time can reach 38 hours at most.

The main technique of the carbon nanotube preparation method reported in the above patent and literature is to select a catalyst and then perform a methane cracking reaction by using a single methane gas or a single carbon monoxide gas.

The invention aims to provide a method for preparing a carbon nano tube by catalytically cracking methane with nickel. The method has the characteristics of high yield, simple process, stable reaction and low cost.

In order to achieve the above object, the present invention is realized by the following technical solutions. The nickel oxide prepared by adopting the known coprecipitation method is used as a catalyst matrix, firstly, quantitative nickel oxide is placed in a reactor, after the nickel oxide is heated to the temperature of 550 ℃ and 650 ℃, hydrogen is used for reducing for 0.5 to 1.5 hours, and then reaction gas is introduced to crack the nickel oxide to prepare the carbon nano tube, and the method is characterized in that: the introduced reaction gas is mixed gas containing methane, the flow rate of the mixed gas is 50-300 ml/min, and the reaction temperature is 500-800 ℃.

The mixed gas containing methane is a mixed gas of methane and hydrogen, and the ratio of the mixed gas containing methane to hydrogen is 20: 1-1: 1 (volume ratio); or the mixture of methane, hydrogen and inert gas including argon in the volume ratio of 4-6 to 1-2 to 3-5.

The optimal reaction temperature for the preparation reaction is 550-650 ℃.

When the reaction gas is a mixed gas of methane and hydrogen, the optimal CH₄And H₂The ratio of (A) to (B) is 10: 1-3: 1 (volume ratio).

The present invention will be described in detail below.

The reaction process expression of the invention is as follows: the catalyst is a nickel catalyst.

In the reaction, a plurality of factors influence the yield (or methane conversion rate) of the carbon nano tube and the appearance and crystallinity of the carbon nano tube, and experiments prove that the hydrogen with a certain concentration is kept in the feed gas, so that the carbon nano tube can be ensured to stably and continuously grow, the yield (or methane conversion rate) of the carbon nano tube is improved, and the appearance of the carbon nano tube is improved; experiments also prove that the yield of the carbon nano tube (or the methane conversion rate) can be obviously increased by adding proper inert gas into the feed gas. In addition, the reduction reaction temperature is increased, and the catalyst with different amounts is adopted, so that the effects of improving the yield of the product and improving the appearance are influenced.

The carbon nanotube product has outer diameter of 10-80nm, inner diameter of 2-15nm and length of micron-mm level.

Compared with the prior art, the method has the characteristics that the carbon nano tube can stably and continuously grow, the product yield is high, generally 25-35%, and the maximum can reach 40%; low cost, high efficiency and simple method.

The invention is further illustrated by the following examples and comparative examples.

The first embodiment is as follows:

transferring 0.3g of catalyst into a quartz reaction tube, heating to 600 ℃, and reducing for 1 hour by using hydrogen; then introducing mixed gas with the ratio of methane to hydrogen being 20: 1, wherein the total flow rate is 110 ml/min; the reaction was carried out for 1 hour, and the product yield was 2%.

Example two:

the reaction was carried out for 1 hour with the same conditions and procedure as in the example one except that the ratio of methane to hydrogen was changed to 10: 1, and the product yield was 25%.

Example three:

the reaction was carried out for 1 hour with the same conditions and procedure as in the example one except that the ratio of methane to hydrogen was changed to 4: 1, and the product yield was 21%.

Example four:

the reaction was carried out for 1 hour with the same conditions and procedure as in the example one except that the ratio of methane to hydrogen was changed to 3: 2, and the product yield was 5%.

Example five:

the reaction was carried out for 1 hour with the same conditions and procedure as in the example one except that the ratio of methane to hydrogen was changed to 1: 1, and the product yield was 0.4%.

Example six:

the reaction was carried out for 1 hour under the same conditions and in the same manner as in the example-except that the ratio of methane to hydrogen to argon was 5: 1: 4, and the yield of the product was 40%.

Example seven:

transferring 0.3g of catalyst into a quartz reaction tube, heating to 600 ℃, and reducing for 0.5 hour by using hydrogen; then introducing mixed gas with the ratio of methane to hydrogen being 10: 1, wherein the total flow rate is 110 ml/min; the reaction was carried out for 1 hour, and the product yield was 18%.

Example eight:

the reaction was carried out for 2 hours under the same conditions and procedures as in example seven, and the product yield was 19%.

Example nine:

the reaction was carried out for 3 hours under the same conditions and in the same manner as in the seventh example, giving a product yield of 18%.

Example ten:

the reaction was carried out for 4 hours under the same conditions and in the same manner as in example seven, and the product yield was 19%.

Comparative example one:

the reaction temperature was 800 ℃ as in the other conditions and steps of the example, and only a very small amount of carbon nanotubes were produced, and the morphology was very poor.

Comparative example two:

the same procedure as in example one, except that CH was introduced₄The reaction time is 2 hours, the product yield is less than 1 percent, and the nano carbon particles are more.

Claims

1. A method for preparing carbon nano tube by catalytic cracking methane with nickel, which adopts nickel oxide prepared by a known coprecipitation method as a catalyst matrix, firstly, putting a certain amount of nickel oxide in a reactor, heating to 550-650 ℃, then reducing for 0.5-1.5 hours with hydrogen, and then introducing reaction gas to crack the nickel oxide to prepare the carbon nano tube, and is characterized in that: the introduced reaction gas is mixed gas containing methane, the flow rate of the mixed gas is 50-300 ml/min, and the reaction temperature is 500-800 ℃.

2. The method of preparing carbon nanotubes by catalytically cracking methane with nickel according to claim 1, wherein: the optimal preparation reaction temperature is 500-650 ℃.

3. The method of preparing carbon nanotubes by catalytically cracking methane with nickel according to claim 1, wherein: the mixed gas containing methane is a mixed gas of methane and hydrogen, and the mixing ratio of the mixed gas and the hydrogen is 20: 1-1: 1 (volume ratio).

4. The method of preparing carbon nanotubes by catalytically cracking methane with nickel according to claim 1, wherein: the mixed gas containing methane is a mixed gas of methane, hydrogen and an inert gas including argon, and the mixed gas is mixed in a ratio of (4-6) to (1-2) to (3-5) (volume ratio).

5. The method of preparing carbon nanotubes by catalytically cracking methane with nickel according to claim 3, wherein: the optimal mixing ratio of the methane and the hydrogen is 10: 1-3: 1 (volume ratio).