CN102627270A

CN102627270A - Method for preparing carbon nano-fiber by hydrogenating carbon dioxide by taking foamed nickel as catalyst

Info

Publication number: CN102627270A
Application number: CN2012101281075A
Authority: CN
Inventors: 李保山; 张�杰
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2012-04-28
Filing date: 2012-04-28
Publication date: 2012-08-08

Abstract

The invention provides carbon nano-fiber and a preparation method thereof. In the preparation method, carbon nano-fiber is prepared by taking a mixed gas formed by carbon dioxide and hydrogen as a raw material under the catalytic action of foamed nickel, and the volume ratio of the carbon dioxide to the hydrogen in the mixed gas is 0.1-1. CO2 for preparing carbon nano-fiber can be derived from emission of industrial waste gas, so that the generation of raw materials is reduced greatly; and the carbon nano-fiber is produced by taking the foamed nickel as a catalyst, so that the carbon nano-fiber has the characteristics of easiness in producing, convenience for separating and reduction in mass transfer energy consumption. The method has the advantages of saving in cost, reduction in energy consumption and convenience for operating.

Description

A kind of is the method that the catalyzer hydrogenation of carbon dioxide prepares carbon nanofiber with foaming nickel

Technical field

The present invention relates to the field of carbon nanofiber, be specifically related to a kind of preparation carbon nanofiber and preparation method thereof.

Background technology

CO ₂Be topmost greenhouse gases in the atmosphere, by CO ₂The Greenhouse effect that brought have produced huge threat to existent environment of people.Each national investigator accumulates in CO to sight in the world at present ₂Recycle on, hope through to CO ₂Be used to alleviate the disadvantageous effect of Greenhouse effect to environment.Current, with CO ₂For the useful chemical substance of feedstock production has become CO ₂A research focus of chemistry.Such as, with CO ₂For reactant prepares methyl alcohol, dme, carbon monoxide, carbon material, carbon monoxide and methyl-formiate etc., the production that is synthesized to the novel aq raw material from basic raw material for chemical industry can both be seen CO ₂Figure.Wherein, with CO ₂The hydrogenation preparing carbon nanomaterial is considered to a kind of very promising CO ₂The recycle approach.

Carbon nanofiber is a kind of new carbon with nanoscale, possesses good physical and chemical performance, in industry, has broad application prospects.According to current research, the catalyzer of preparation carbon nanofiber mainly contains nickel, cobalt, iron, copper and their alloy, and these catalyzer all are that form with nano particle exists, and has the characteristics of separation difficulty.Meanwhile, in existing research, the carbon source of preparation carbon nanofiber mainly is hydrocarbon polymer and CO.

Foaming nickel is a kind of metallic substance with the mesh structural porous structure of three-dimensional space, and voidage reaches more than 95%, and it is big to have specific surface area, good mechanical property, resistance to mass transfer little with characteristics such as thermal conductivity is good.The nickel that foams so far is widely used in fields such as strainer, battery electrode material, WWT electrode materials, high temperature filler, support of the catalyst.The good physics-chem characteristic of foaming nickel has as the Application of Catalyst prospect it.

Summary of the invention

In order to solve catalyzer and product separation difficulty in the traditional preparation process carbon nanofiber method, raw materials cost is high and resistance to mass transfer is big shortcoming, the invention provides a kind of preparation carbon nanofiber and preparation method thereof.

According to an aspect of the present invention; A kind of preparation method of carbon nanofiber is provided; The gas mixture that utilizes carbonic acid gas and hydrogen to form is raw material preparation carbon nanofiber under the katalysis of foaming nickel, and the volume ratio of carbonic acid gas and hydrogen is 0.1 ~ 1 in the gas mixture.

Further, above-mentioned preparation method comprises: 1) before the reaction, the nickel that will foam earlier places retort furnace at 350 ~ 1000 ℃, and calcination time is 0.5 ~ 5h; 2) nickel that will foam places reactor drum and is heated to 200 ~ 700 ℃ activation temperature, in microreactor, charges into hydrogen activation foaming nickel; 3) temperature of reactor is reduced to 300 ~ 1000 ℃, and in reactor drum, charge into gas mixture, obtain carbon nanofiber behind 2 ~ 10h.

Further, above-mentioned steps 3) in the speed of charging into of gas mixture be 5 ~ 150 mL/min.

The speed of charging into of the hydrogen further, above-mentioned steps 2) is 10 ~ 80 mL/min, and the soak time of foaming nickel is 0.5 ~ 5h.

Further, in above-mentioned steps 1) before, comprise that also pre-treatment comprises: A is 5cm with area to the pre-treatment of foaming nickel ²Foaming nickel with salt soak 5min, the volumetric concentration of hydrochloric acid is 0.1 ~ 5mol/L; The foaming nickel that B will pass through processing of step A cleans 3 ~ 5 times with thermokalite water, absolute ethyl alcohol and deionized water successively repeatedly.

Further, the thermokalite water of above-mentioned steps B is that 80 ℃ volumetric concentration is the NaOH solution of 0.1 ~ 1mol/L.

According to another aspect of the present invention, a kind of carbon nanofiber is provided, this carbon nanofiber is prepared from above-mentioned preparation method.The carbon nanofiber for preparing through method of the present invention is the matrix growth with the foaming nickel skeleton, and diameter is between 200 ~ 300 nm.The foaming nickel of the responsible carbon nanofiber of the inventive method preparation can have the advantage of the Separation and Recovery of being easy in the carrier of catalyzer; In mass transfer process, because the special skeleton structure of foaming nickel, pressure drop is little, helps cutting down the consumption of energy.

Description of drawings

Fig. 1 shows the space structure SEM figure according to the used foaming nickel of the embodiment of the invention 2.

Fig. 2 shows the SEM figure according to the reaction post-foaming carbon nanofiber that nickel surface generates of the embodiment of the invention 2.

Fig. 3 shows the amplification SEM figure according to the reaction post-foaming carbon nanofiber that nickel surface generates of the embodiment of the invention 2.

Embodiment

Below in conjunction with embodiment and contrast accompanying drawing the present invention is done further explain, but not therefore and restriction the present invention.

Embodiment 1

With area is 5cm ²Foaming nickel with the salt soak of 1mol/L 5 minutes, use 80 ℃, concentration to clean 3 times afterwards respectively as the NaOH solution of 1mol/L, use absolute ethyl alcohol and washed with de-ionized water 3 times at last again, dry for use naturally.After foaming nickel dries, place retort furnace to calcine 1 hour down at 700 ℃ earlier, put into microreactor then, be warmed up to 500 ℃, activation is 2 hours in the hydrogen stream of 40 ml/min.Drop to 300 ℃ to temperature after the activation, feed the gas mixture (CO of carbonic acid gas and hydrogen ₂: H ₂=1:3, volume ratio) react, the reaction gas flow velocity is 30 ml/min, the reaction times is 5 hours.After the reaction, carbon nanofiber is in the surface growth of foaming nickel, and the space-time yield of CNFs is 0.005g _CarbonG ^-1 _Cat.H ^-1

Embodiment 2

With area is 5cm ²Foaming nickel with the salt soak of 1mol/L 5 minutes, use 80 ℃, concentration to clean 3 times afterwards respectively as the NaOH solution of 1mol/L, use absolute ethyl alcohol and washed with de-ionized water 3 times at last again, dry for use naturally.After foaming nickel dries, place retort furnace to calcine 1 hour down at 700 ℃ earlier, put into microreactor then, be warmed up to 500 ℃, activation is 2 hours in the hydrogen stream of 40 ml/min.After the activation temperature maintenance at 500 ℃, feed the gas mixture (CO of carbonic acid gas and hydrogen ₂: H ₂=1:3, volume ratio) react, the reaction gas flow velocity is 30 ml/min, the reaction times is 5 hours.After the reaction, carbon nanofiber is in the surface growth of foaming nickel, and the space-time yield of CNFs is 0.01g _CarbonG ^-1 _Cat.H ^-1

Embodiment 3

With area is 5cm ²Foaming nickel with the salt soak of 1mol/L 5 minutes, use 80 ℃, concentration to clean 3 times afterwards respectively as the NaOH solution of 1mol/L, use absolute ethyl alcohol and washed with de-ionized water 3 times at last again, dry for use naturally.After foaming nickel dries, place retort furnace to calcine 1 hour down at 700 ℃ earlier, put into microreactor then, be warmed up to 500 ℃, activation is 2 hours in the hydrogen stream of 40 ml/min.After the activation temperature maintenance at 500 ℃, feed the gas mixture (CO of carbonic acid gas and hydrogen ₂: H ₂=1:2, volume ratio) react, the reaction gas flow velocity is 30 ml/min, the reaction times is 5 hours.After the reaction, carbon nanofiber is in the surface growth of foaming nickel, and the space-time yield of CNFs is 0.003g _CarbonG ^-1 _Cat.H ^-1

Embodiment 4

With area is 5cm ²Foaming nickel with the salt soak of 2mol/L 5 minutes, use 80 ℃, concentration to clean 3 times afterwards respectively as the NaOH solution of 1mol/L, use absolute ethyl alcohol and washed with de-ionized water 3 times at last again, dry for use naturally.After foaming nickel dries, place retort furnace to calcine 1 hour down at 900 ℃ earlier, put into microreactor then, be warmed up to 500 ℃, activation is 2 hours in the hydrogen stream of 40 ml/min.After the activation temperature maintenance at 500 ℃, feed the gas mixture (CO of carbonic acid gas and hydrogen ₂: H ₂=1:2, volume ratio) react, the reaction gas flow velocity is 30 ml/min, the reaction times is 5 hours.After the reaction, carbon nanofiber is in the surface growth of foaming nickel, and the space-time yield of CNFs is 0.009g _CarbonG ^-1 _Cat.H ^-1

Claims

1. the preparation method of a carbon nanofiber; It is characterized in that; The gas mixture that utilizes carbonic acid gas and hydrogen to form is raw material said carbon nanofiber of preparation under the katalysis of foaming nickel, and the volume ratio of carbonic acid gas and said hydrogen described in the said gas mixture is 0.1 ~ 1.

2. preparation method according to claim 1 is characterized in that, said preparation method comprises:

1) before the reaction, the nickel that will foam earlier places retort furnace at 350 ~ 1000 ℃, and calcination time is 0.5 ~ 5h;

2) said foaming nickel is placed reactor drum and be heated to 200 ~ 700 ℃ activation temperature, in said microreactor, charge into the said foaming nickel of mixed gas activation of hydrogen or hydrogen;

3) said temperature of reactor is reduced to 300 ~ 1000 ℃, and in said reactor drum, charge into said gas mixture, obtain said carbon nanofiber behind 2 ~ 10h.

3. preparation method according to claim 1 is characterized in that, the speed of charging into of the gas mixture in the said step 3) is 5 ~ 150 mL/min.

4. preparation method according to claim 1 is characterized in that, said step 2) in the speed of charging into of hydrogen be 10 ~ 80 mL/min, the soak time of said foaming nickel is 0.5 ~ 5h.

5. preparation method according to claim 1 is characterized in that, before said step 1), also comprises the pre-treatment to said foaming nickel, and said pre-treatment comprises:

A uses the salt soak with said foaming nickel, and the volumetric concentration of said hydrochloric acid is 0.1 ~ 5mol/L;

The foaming nickel that B will pass through said processing of step A cleans 3 ~ 5 times with thermokalite water, absolute ethyl alcohol and deionized water successively repeatedly;

C will pass through foaming nickel calcining 0.5 ~ 5h under 350 ~ 1000 ℃ that said step B handles.