High-purity biomass-based carbon nanotubes and preparation method thereof

Abstract

The present invention discloses a high-purity biomass-based carbon nanotube and a preparation method thereof. The preparation method comprises the following steps: mixing biomass with an inducer 1 in a solvent to prepare a solution, wherein the inducer 1 is selected from one or more of dicyandiamide, melamine, urea and ammonium chloride; drying the solution to a constant weight to obtain a precursor; placing the precursor in a reaction vessel; a titanium sheet is provided on the inner side of the top cover of the reaction vessel; a solution of an inducer 2 is loaded on the titanium sheet; the inducer 2 is selected from one or more of ferric chloride, ferric nitrate, cobalt chloride, nickel chloride, nano-iron powder, nano-nickel powder and nano-cobalt powder; placing the reaction vessel in a pyrolysis vessel for in-situ pyrolysis reaction, thereby obtaining a biomass-based high-purity carbon nanotube material. The present invention achieves controllable synthesis of high-purity carbon nanotubes by optimizing the container configuration and adding the inducer. This process is both a high-value utilization of biomass resources and provides a new method for the preparation of high-purity carbon nanotubes.

Description

Technical field:

[0001] The present invention relates to the technical field of biomass high-value conversion and resource utilization, and in particular to high-purity biomass-based carbon nanotubes and a preparation method thereof. Background technology:

[0002] Carbon nanotubes (CNTs) are materials with nanometer-scale diameters and ultrathin walls. They possess large specific surface area, high thermal and electrical conductivity, and excellent mechanical properties. They are widely used in capacitors, electrodes, hydrogen storage, and magnetic materials. Existing methods for producing CNTs include arc discharge, laser evaporation, and chemical vapor deposition. Most of these methods use relatively pure industrial gases, resulting in demanding preparation conditions and high costs. Therefore, finding a new, simple, and cost-effective method for producing CNTs is a pressing issue.

[0003] Biomass pyrolysis technology uses biomass as a raw material to produce biochar through pyrolysis. Its low raw material cost, widespread availability, and ease of implementation make it a technological approach with both economic and environmental benefits. Producing carbon materials through biomass pyrolysis is one of the most efficient conversion methods, contributing to the achievement of the national "3060" dual carbon goals. Furthermore, as the sole renewable carbon source, biomass can also contribute to the sustainable development of carbon materials and reduce production costs. However, currently, the carbon materials obtained from biomass pyrolysis are primarily porous carbon. Some research has yielded carbon nanotubes (CNTs). For example, Yao Yunjin et al. prepared biomass CNTs via a two-step pyrolysis process involving alkaline treatment, carbonization, and post-treatment (ZL 201610137714.6). Liang Jiyuan et al. used natural biomass with a microtubule structure as a raw material and synthesized a hybrid carbon material of biomass microtubes and CNTs by pyrolysis after adding a metal catalyst (CN 108736012 A).

[0004] However, in these processes using biomass (assisted by chemical reagents) as raw materials, the resulting carbon materials are often mixed with non-tubular carbon particles, and the purity of carbon nanotubes is low. There are even fewer reports on the technology of preparing high-purity carbon nanotubes using biomass as raw materials. Therefore, how to achieve the conversion of biomass into high-purity carbon nanotubes through a simple and fast process is of great significance. Summary of the invention:

[0005] The present invention solves the problems existing in the prior art and provides a high-purity biomass-based carbon nanotube and a preparation method thereof. Based on the analysis of the tube formation mechanism of biomass-based carbon nanotubes, the present invention optimizes the preparation method, regulates the distribution of the inducer, optimizes the tube formation process, thereby promoting the growth of nanotubes, and realizes the controllable synthesis of high-purity carbon nanotubes. This process can not only realize the high-value utilization of biomass resources, but also provides a new method for the preparation of high-purity carbon nanotubes.

[0006] The present invention aims to provide a method for preparing high-purity biomass-based carbon nanotubes, comprising the following steps: mixing biomass with an inducer 1 in a solvent to prepare a solution, wherein the inducer 1 is selected from one or more of dicyandiamide, melamine, urea, and ammonium chloride; drying the solution to a constant weight to obtain a precursor; placing the precursor in a reaction vessel, a titanium sheet disposed on the inner side of the top cover of the reaction vessel, and loading the titanium sheet with a solution of an inducer 2, wherein the inducer 2 is selected from one or more of ferric chloride, ferric nitrate, cobalt chloride, nickel chloride, nano-iron powder, nano-nickel powder, and nano-cobalt powder; placing the reaction vessel in a pyrolysis vessel for an in-situ pyrolysis reaction, thereby obtaining a biomass-based high-purity carbon nanotube material. The titanium sheet on the inner side of the top cover is secured by a high-temperature resistant adhesive or other feasible means.

[0007] The specific steps of cutting and cleaning the titanium sheet in the present invention are: cutting the titanium sheet into a rectangle of 2cm*4cm, and cleaning the surface of the titanium sheet with 1M hydrochloric acid and 1M hydrogen peroxide in sequence until the surface impurities are completely removed.

[0008] In the present invention, the reaction container is a crucible, and the pyrolysis container is a tubular furnace. The biomass raw materials are cracked at high temperature to release small molecular carbon-containing gases, which are then formed into nanotube morphology through vapor deposition reaction under the catalytic action of inducer 1. A titanium sheet loaded with inducer 2 is placed on the top of the crucible (inside the crucible cover) as a carrier for the growth of carbon nanotubes, thereby achieving the collection of high-purity carbon nanotubes.

[0009] Preferably, the addition amount of the inducer 1 is based on per gram of biomass, and the addition amount of nitrogen element in the inducer 1 is 0.05-0.50 mol.

[0010] Preferably, the biomass is selected from one or more of cellulose, royal bamboo grass and microalgae.

[0011] Preferably, the solvent is water or ethanol, and the mass volume ratio of biomass to solvent is 0.005-0.500 g / mL. Using ethanol as the solvent can speed up the drying process and reduce air oxidation.

[0012] Preferably, the amount of the inducer 2 loaded per square centimeter of the titanium sheet is 0.001-0.01 mmol.

[0013] The specific steps of fully mixing the inducer 2 and the solvent in the present invention are: ultrasonicating in an ultrasonic cleaning machine for 15 minutes, manually shaking every 3 minutes in the middle, to obtain a uniformly dispersed ethanol mixed solution of the inducer 2.

[0014] Preferably, the pyrolysis atmosphere is nitrogen or an inert gas, the pyrolysis temperature is 700° C.-1200° C., and the pyrolysis constant temperature time is 0.5-3.0 h. The inert gas is helium, argon, etc.

[0015] The present invention also protects high-purity biomass-based carbon nanotubes obtained by the above-mentioned preparation method. The carbon nanotubes have an outer diameter of 10-300 nm and a length greater than 50 μm. The carbon nanotubes are uniformly distributed on the titanium sheet in large quantities, with almost no particulate carbon impurities, and are of high purity.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The present invention uses biomass as raw material, which has a wide source, low cost, and has environmental and economic benefits.

[0018] 2. The present invention optimizes the configuration of the pyrolysis container, and the carbon nanotubes obtained through the collection device on the top are of higher purity and longer length. Description of the drawings:

[0019] Figure 1 This is a physical picture of the titanium sheet before and after pyrolysis in Example 1 of the present invention;

[0020] Figure 2 This is a scanning electron microscope image of the carbon nanotubes of Example 1 of the present invention;

[0021] Figure 3 This is a physical picture of the titanium sheet before and after pyrolysis in Example 2 of the present invention;

[0022] Figure 4 This is a scanning electron microscope image of the carbon nanotubes of Example 2 of the present invention;

[0023] Figure 5 This is a physical picture of the titanium sheet before and after pyrolysis in Example 3 of the present invention;

[0024] Figure 6 This is a scanning electron microscope image of the carbon nanotubes of Example 3 of the present invention;

[0025] Figure 7 This is a physical picture of the titanium sheet before and after pyrolysis in Example 4 of the present invention;

[0026] Figure 8 This is a scanning electron microscope image of the carbon nanotubes of Example 4 of the present invention;

[0027] Figure 9 This is a physical picture of the titanium sheet before and after pyrolysis in Example 5 of the present invention;

[0028] Figure 10 This is a scanning electron microscope image of the carbon nanotubes of Example 5 of the present invention;

[0029] Figure 11 This is a physical picture of the titanium sheet before and after pyrolysis in Example 6 of the present invention;

[0030] Figure 12This is a scanning electron microscope image of the carbon nanotubes of Example 6 of the present invention;

[0031] Figure 13 Physical pictures of the titanium sheet before and after pyrolysis in Example 7 of the present invention;

[0032] Figure 14 This is a scanning electron microscope image of the carbon nanotubes of Example 7 of the present invention;

[0033] Figure 15 This is a physical picture of the titanium sheet before and after pyrolysis in Example 8 of the present invention;

[0034] Figure 16 This is a scanning electron microscope image of the carbon nanotubes of Example 8 of the present invention;

[0035] Figure 17 This is a physical picture of the titanium sheet before and after pyrolysis in Example 9 of the present invention;

[0036] Figure 18 This is a scanning electron microscope image of the carbon nanotubes of Example 9 of the present invention. Specific implementation method:

[0037] The following examples are provided to further illustrate the present invention, but are not intended to limit the present invention.

[0038] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the experimental materials and reagents herein are conventional commercial products in the art.

[0039] A method for preparing high-purity biomass-based carbon nanotubes comprises the following steps: mixing biomass with inducer 1 in a solvent to prepare a solution, stirring the solution evenly, drying it in a 50°C oven to constant weight to obtain a precursor, and placing it in a crucible. After thoroughly mixing inducer 2 with anhydrous ethanol, the precursor is loaded onto a cut and cleaned titanium sheet, dried at room temperature, and fixed to the inner side of the crucible lid. The crucible is placed in a tubular furnace, heated to 700°C-1200°C in an inert atmosphere, and subjected to an in-situ pyrolysis reaction for 0.5-3.0 hours. The solution is cooled, the crucible is removed, and the carbon nanotube material on the titanium sheet is collected to obtain the high-purity biomass-based carbon nanotubes.

[0040] In the following preferred embodiments, inducer 1 is selected from at least one of dicyandiamide, melamine, urea, and ammonium chloride. The amount of inducer 1 added is based on the amount of nitrogen added in inducer 1 of 0.05-0.50 mol per gram of biomass. The biomass is selected from at least one of cellulose, Pennisetum, and microalgae. The solvent is water or ethanol, and the mass-to-volume ratio of biomass to solvent is 0.005-0.500 g / mL.

[0041] In the following preferred embodiments, the inducer 2 is selected from at least one of ferric chloride, ferric nitrate, cobalt chloride, nickel chloride, nano iron powder, nano nickel powder, and nano cobalt powder. The amount of the inducer 2 loaded per square centimeter of the titanium sheet is 0.001-0.01 mmol.

[0042] In the following embodiments, preferably, the pyrolysis atmosphere is nitrogen or an inert gas, and the inert gas is helium, argon, etc.

[0043] Example 1

[0044] A method for preparing high-purity biomass-based carbon nanotubes comprises the following steps:

[0045] S1. Mix 1 g of powdered microcrystalline cellulose and 1.05 g of dicyandiamide in 50 mL of anhydrous ethanol. Stir the mixed solution at room temperature for 12 h, dry it in a vacuum drying oven at 50 ° C, and collect the powdered precursor into a crucible.

[0046] S2. Cut the titanium sheet into 2cm*4cm rectangles, clean the surface with 1M hydrochloric acid and 1M hydrogen peroxide, and dry at room temperature;

[0047] S3, take 4.48mg nano iron powder and dissolve in 0.1mL anhydrous ethanol, shake well and use ultrasonic cleaning instrument ultrasonic 15min, during every 3min take out and shake well once, obtain iron ethanol solution. Use a brush to brush the iron ethanol solution after being fully mixed on the aforementioned titanium sheet (to verify the necessity of derivant 2 nano iron powder, only brush part of the area), dry at room temperature, and then fix the titanium sheet on the crucible top cover (the side with derivant 2 is facing the crucible).

[0048] S4. Place the crucible containing the precursor in a tube furnace, and in an inert atmosphere, heat it to 1000°C at a heating rate of 20°C / min, keep the temperature constant for 1 hour, and take it out after cooling.

[0049] The obtained materials were observed and their growth was as follows Figure 1 As shown in the figure, a carbon layer grows only on the titanium sheet coated with inducer 2. Further tunnel scanning electron microscopy tests show that Figure 2 As shown, a large number of carbon nanotubes are evenly distributed on the titanium sheet coated with inducer 2, and no non-tubular impurities are observed. The diameter of the carbon nanotubes is about 50 nm and the length is greater than 50 μm.

[0050] Example 2

[0051] The same as Example 1, except that the biomass raw material is royal bamboo grass, and in order to verify the necessity of the inducer 2 nano iron powder, the coating method adopts the spot coating method. The obtained material was observed, and its growth condition is as follows Figure 3As shown in the figure, the carbon layer grows only on the part coated with inducer 2. Further tunnel scanning electron microscopy test shows that Figure 4 As shown, a large number of carbon nanotubes are evenly distributed on the titanium sheet coated with inducer 2, and no non-tubular impurities are observed. The diameter of the carbon nanotubes is about 200 nm and the length is greater than 50 μm.

[0052] Example 3

[0053] The same as Example 1, except that the biomass raw material is microalgae. The obtained material was observed and its growth was as follows Figure 5 As shown, further tunnel scanning electron microscopy tests were performed as shown in Figure 6 As shown, the carbon nanotubes are evenly distributed on the titanium sheet, and no non-tubular impurities are observed.

[0054] Example 4

[0055] The same as Example 1, except that ammonium chloride was selected as inducer 1 (i.e., 2.68 g of ammonium chloride was added per gram of biomass raw material). The obtained material was observed, and its growth was as follows. Figure 7 As shown, further tunnel scanning electron microscopy tests were performed as shown in Figure 8 As shown, the carbon nanotubes are evenly distributed on the titanium sheet, and no non-tubular impurities are observed.

[0056] Example 5

[0057] The same as Example 1, except that: the inducer 2 is nano-cobalt (ie, 4.712 mg of nano-cobalt is loaded on the titanium sheet). The obtained material is observed, and its growth is as follows Figure 9 As shown, further tunnel scanning electron microscopy tests were performed as shown in Figure 10 As shown, the carbon nanotubes are evenly distributed on the titanium sheet, and no non-tubular impurities are observed.

[0058] Example 6

[0059] The same as Example 1, except that: the inducer 2 is nano nickel (ie, 4.696 mg of nano nickel is loaded on the titanium sheet). The obtained material is observed, and its growth is as follows Figure 11 As shown, further tunnel scanning electron microscopy tests were performed as shown in Figure 12 As shown, the carbon nanotubes are evenly distributed on the titanium sheet, and no non-tubular impurities are observed.

[0060] Example 7

[0061] The same as Example 1, except that the inducer 2 is ferric chloride. The obtained material was observed, and its growth was as follows Figure 13 As shown, further tunnel scanning electron microscopy tests were performed as shown in Figure 14 As shown, the carbon nanotubes are evenly distributed on the titanium sheet, and no non-tubular impurities are observed.

[0062] Example 8

[0063] The same as Example 1, except that the pyrolysis temperature is 700°C. The obtained material was observed, and its growth was as follows Figure 15 As shown, further tunnel scanning electron microscopy tests were performed as shown in Figure 16 As shown, the carbon nanotubes are evenly distributed on the titanium sheet, and no non-tubular impurities are observed.

[0064] Example 9

[0065] Same as Example 1, except that the loading amount of nano-iron on the titanium sheet is 0.001 mmol / cm 2 (i.e. 0.448 mg of nano-iron is loaded on the titanium sheet). The obtained material was observed and its growth was as follows Figure 17 As shown, further tunnel scanning electron microscopy tests were performed as shown in Figure 18 As shown, the carbon nanotubes are evenly distributed on the titanium sheet, and no non-tubular impurities are observed.

[0066] The description of the above embodiments is only used to help understand the technical solution and core ideas of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention. These improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing high-purity biomass-based carbon nanotubes, characterized in that: The method comprises the following steps: mixing biomass with an inducer 1 in a solvent to prepare a solution, wherein the inducer 1 is selected from one or more of dicyandiamide, melamine, urea and ammonium chloride; drying the solution to constant weight to obtain a precursor; placing the precursor in a reaction container; a titanium sheet is provided on the inner side of a top cover of the reaction container; a solution of an inducer 2 is loaded on the titanium sheet; the inducer 2 is selected from one or more of ferric chloride, ferric nitrate, cobalt chloride, nickel chloride, nano-iron powder, nano-nickel powder and nano-cobalt powder; placing the reaction container in a pyrolysis container for in-situ pyrolysis reaction; the pyrolysis atmosphere of the pyrolysis reaction is nitrogen or an inert gas; the pyrolysis temperature of the pyrolysis reaction is 700°C-1200°C; and the pyrolysis constant temperature time is 0.5-3.0 h, thereby obtaining a biomass-based high-purity carbon nanotube material.

2. The preparation method according to claim 1, characterized in that The addition amount of the inducer 1 is based on per gram of biomass, and the addition amount of nitrogen element in the inducer 1 is 0.05-0.50 mol.

3. The preparation method according to claim 1 or 2, characterized in that The biomass is selected from one or more of cellulose, royal bamboo grass and microalgae.

4. The preparation method according to claim 1 or 2, characterized in that The solvent is water or anhydrous ethanol, and the mass volume ratio of biomass to solvent is 0.005-0.500 g / mL.

5. The preparation method according to claim 1 or 2, characterized in that The amount of inducer 2 loaded per square centimeter of titanium sheet is 0.001-0.01 mmol.

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