阅读说明：本技术 一种基于纳米木质素原位生长的纳米碳球及其制备方法 (Nano carbon spheres based on in-situ growth of nano lignin and preparation method thereof ) 是由 娄瑞 田杰 陈威 张斌 孔令波 张宏 刘钰 曹启航 于 2020-12-29 设计创作，主要内容包括：本发明属于碳纳米材料技术领域,公开了一种基于纳米木质素原位生长的纳米碳球及其制备方法。将农林生物质于DES溶液中进行分级分离处理,得到纳米木质素；将所得纳米木质素经热解处理,原位生长制得基于木质素原位生长的纳米碳球。其中,将农林生物质和DES溶液混合反应后,先采用真空抽滤进行固液分离再采用旋蒸进行挥发处理,然后在浓缩的滤液中加入水中沉析出固相产物,采用冷冻离心进行固液分离后进行真空冷冻干燥,得到纳米木质素；将所得纳米木质素进行烧结热解处理,制得基于纳米木质素原位生长的纳米碳球。该制备方法原材料易得环保、工艺简单、所得基于纳米木质素原位生长的纳米碳球形貌良好,粒径均一稳定,球形度良好,利于扩大化生产。(The invention belongs to the technical field of carbon nano materials, and discloses a nano carbon sphere based on in-situ growth of nano lignin and a preparation method thereof. Carrying out graded separation treatment on the agricultural and forestry biomass in DES solution to obtain nano lignin; and carrying out pyrolysis treatment on the obtained nano lignin, and carrying out in-situ growth to obtain the nano carbon spheres based on the in-situ growth of the lignin. After mixing and reacting agricultural and forestry biomass and DES solution, performing solid-liquid separation by vacuum filtration, performing volatilization treatment by rotary evaporation, adding water into the concentrated filtrate to precipitate a solid-phase product, performing solid-liquid separation by using refrigerated centrifugation, and performing vacuum freeze drying to obtain nano lignin; and sintering and pyrolyzing the obtained nano lignin to prepare nano carbon spheres based on in-situ growth of the nano lignin. The preparation method has the advantages of easily-obtained raw materials, environmental protection and simple process, and the obtained nano carbon spheres based on in-situ growth of the nano lignin have good appearance, uniform and stable particle size and good sphericity, and are beneficial to expanded production.)

1. A preparation method for in-situ growth of carbon nanospheres based on nano lignin is characterized by comprising the following steps: carrying out graded separation treatment on the agricultural and forestry biomass in DES solution to obtain nano lignin; and carrying out pyrolysis treatment on the obtained nano lignin to prepare nano carbon spheres based on in-situ growth of the nano lignin.

2. The method for preparing nano carbon spheres based on in-situ growth of nano lignin according to claim 1, wherein a DES solution is obtained by mixing choline chloride and lactic acid, and the ratio of the amounts of the choline chloride and the lactic acid is 1: 2-1: 10.

3. The method for preparing nano carbon spheres based on in-situ growth of nano lignin according to claim 1, wherein the particle size of the agricultural and forestry biomass is 60-80 meshes.

4. The method for preparing nano carbon spheres based on in-situ growth of nano lignin according to claim 1, wherein the particle size of the nano lignin is 30-160 nm.

5. The method for preparing nano carbon spheres based on in-situ nano lignin growth according to claim 1, wherein the fractionation treatment comprises the following operations:

mixing and reacting agricultural and forestry biomass with a DES solution, cooling to obtain a mixed solution, performing solid-liquid separation treatment on the obtained mixed solution, then taking filter residue, washing the obtained filter residue, then taking washing filtrate, concentrating the obtained washing filtrate to obtain a concentrated solution, separating out lignin precipitate from the obtained concentrated solution in water, performing freeze centrifugation on the obtained lignin precipitate, then taking a solid-phase product, washing the obtained solid-phase product to obtain colloidal nano lignin, and performing vacuum freeze drying treatment on the obtained colloidal nano lignin to obtain the nano lignin.

6. The method for preparing nano carbon spheres based on in-situ growth of nano lignin according to claim 5, wherein the rotation speed of the freezing centrifugation is 4000-5000 r/min, the time is 5-10 min, and the temperature is-4-0 ℃.

7. The method for preparing nano carbon spheres based on in-situ growth of nano lignin according to claim 5, wherein the temperature of vacuum freeze drying treatment is-60 to-40 ℃, the pressure is 0.4 to 0.6MPa, and the time is 18 to 32 hours.

8. The method for preparing nano carbon spheres based on in-situ nano lignin growth according to claim 1, wherein the pyrolysis treatment is three-stage vacuum sintering and comprises the following steps:

the first stage is as follows: heating to 600-800 ℃ at a speed of 2-10 ℃/min, and keeping the temperature for 30-50 min; the second stage is as follows: heating to 1200-1400 ℃ at a speed of 5-10 ℃/min, and preserving heat for 30-50 min; the third stage is as follows: cooling to 600-800 ℃ at a speed of 5-10 ℃/min and then cooling along with the furnace.

9. The nano carbon spheres based on the in-situ growth of the nano lignin, which are prepared by the preparation method of any one of claims 1 to 8.

10. The nano-carbon spheres based on in-situ nano-lignin growth according to claim 9, wherein the nano-carbon spheres based on in-situ nano-lignin growth have a particle size of 150 to 800nm, and the nano-carbon spheres based on in-situ nano-lignin growth have a graphitization degree of 1.1 to 1.5.

Technical Field

The invention belongs to the technical field of carbon nano materials, and relates to a nano carbon sphere based on in-situ growth of nano lignin and a preparation method thereof.

Background

Lignin is a byproduct in pulping, papermaking and biomass refining processes, the production amount of the lignin is large, and at present, the lignin is usually used only as a low-grade fuel or a feed ingredient, so that the serious waste of lignin resources and environmental pollution are caused.

Lignin, one of three elements of lignocellulose, has higher energy density than cellulose, complex and compact structure and non-uniform molecular composition, which causes difficult separation, and the existing lignin preparation method has the defects of long consumption time, large and uneven particles and the like due to methods of dilute acid, dilute alkali, particle liquid and the like, so that the search and development of a green novel solvent with high solubility on lignin becomes a hotspot of study of researchers.

Meanwhile, the carbon element content in the lignin can reach as high as about 60 percent, and the lignin has the characteristics of wide sources, universality, accessibility, high heat value and the like, so that the preparation of fuel and high-quality carbon materials by using the characteristics of the carbon element content in the lignin as a carbon source becomes an important direction for research. At present, the nano lignin is concerned about the preparation of nano carbon spheres, and the nano carbon spheres can be used in the fields of medicines, wastewater treatment, catalysts and the like. However, the existing methods for preparing carbon nanospheres include electrostatic spinning, freeze drying, hydrothermal carbonization, activation and the like, but most of the methods have the defects of long time consumption, high equipment requirement, complex preparation process and the like, so that the development of lignin in the direction of preparing carbon nanospheres is restricted, and therefore, the simple and convenient method for converting lignin into carbon nanosphere materials is urgently sought.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide nano carbon spheres based on in-situ growth of nano lignin and a preparation method thereof, so as to solve the problems of large product particles, poor dispersibility, poor uniformity and complex preparation process when the nano carbon spheres are prepared by the existing lignin.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

the invention discloses a preparation method of nano carbon spheres based on in-situ growth of nano lignin, which comprises the following steps: carrying out graded separation treatment on the agricultural and forestry biomass in DES solution to obtain nano lignin; and carrying out pyrolysis treatment on the obtained nano lignin to prepare nano carbon spheres based on in-situ growth of the nano lignin.

Preferably, the DES solution is prepared by mixing choline chloride and lactic acid, and the ratio of the amounts of the choline chloride and the lactic acid is 1: 2-1: 10.

Further preferably, the mixing temperature of the choline chloride and the lactic acid is 60-80 ℃ and the time is 2-4 h.

Preferably, the solid-liquid mass ratio of the agricultural and forestry biomass to the DES solution is 1: 10.

Preferably, the agricultural and forestry biomass includes pine, wheat straw, poplar, and the like.

Preferably, the particle size of the agricultural and forestry biomass is 60-80 meshes.

Preferably, the particle size of the nano lignin is 30-160 nm.

Preferably, the fractionation process comprises the following operations: mixing and reacting agricultural and forestry biomass with a DES solution, cooling to obtain a mixed solution, performing solid-liquid separation treatment on the obtained mixed solution, then taking filter residue, washing the obtained filter residue, then taking washing filtrate, concentrating the obtained washing filtrate to obtain a concentrated solution, separating out lignin precipitate from the obtained concentrated solution in water, performing freeze centrifugation on the obtained lignin precipitate, then taking a solid-phase product, washing the obtained solid-phase product to obtain colloidal nano lignin, and performing vacuum freeze drying treatment on the obtained colloidal nano lignin to obtain the nano lignin.

Further preferably, the reaction temperature of the agriculture and forestry biomass and the DES solution is 130-150 ℃, and the reaction time is 6-24 h.

Further preferably, the rotation speed of the freezing centrifugation is 4000-5000 r/min, the time is 5-10 min, and the temperature is-4-0 ℃.

Further preferably, the temperature of the vacuum freeze drying treatment is-60 to-40 ℃, the pressure is 0.4 to 0.6MPa, and the time is 18 to 32 hours.

Preferably, the pyrolysis process is a three-stage vacuum sintering comprising: the first stage is as follows: heating to 600-800 ℃ at a speed of 2-10 ℃/min, and keeping the temperature for 30-50 min; the second stage is as follows: heating to 1200-1400 ℃ at a speed of 5-10 ℃/min, and preserving heat for 30-50 min; the third stage is as follows: cooling to 600-800 ℃ at a speed of 5-10 ℃/min and then cooling along with the furnace.

The invention also discloses a nano carbon sphere based on the in-situ growth of nano lignin, which is prepared by the preparation method.

Preferably, the particle size of the nano carbon spheres based on the in-situ growth of the nano lignin is 150-800 nm.

Preferably, the graphitization degree of the nano carbon spheres based on the in-situ growth of the nano lignin is 1.1-1.5.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a preparation method of nano carbon spheres based on in-situ growth of nano lignin, which is a green, environment-friendly and low-cost preparation method. The catalyst (Fe, Co and Ni) and the activator (NaOH, H) are mixed with the catalyst₂SO₄) Compared with the nano carbon spheres prepared by adding lignin, the preparation method of the invention adopts the agriculture and forestry biomass as the raw material and utilizes the grading separation treatment of the agriculture and forestry biomass and the DES solutionObtaining the nano lignin with good particle appearance, and further utilizing the nano lignin as a high-quality carbon source to pyrolyze and form nano carbon spheres in situ. The method has the advantages of wide raw material source, simple process and low preparation cost, and most importantly, the method solves the problem of influence on the appearance and performance of the nano carbon material due to difficulty in removing the catalyst and the activating agent, and fully considers the principles of energy conservation, environmental protection, economy and practicality, thereby having important significance on sustainable development of resources and environment.

Furthermore, by adjusting the ratio of the amounts of choline chloride and lactic acid substances in the DES solution, the obtained nano lignin can be ensured to have the characteristics of high yield, high purity and low molecular weight.

Furthermore, by adjusting the particle size range of the agricultural and forestry biomass, the high-yield nano lignin can be better separated from the agricultural and forestry biomass, and the agricultural waste is fully utilized.

Furthermore, the DES solution mixed in the colloidal nano lignin can be better removed through freezing, centrifuging, vacuum freezing and drying treatment, and the purity of the nano lignin is improved.

Furthermore, the structure and the appearance of the nano lignin can be better maintained through vacuum freeze drying treatment.

Furthermore, the invention utilizes the vacuum high-temperature pyrolysis technology to pyrolyze the nano lignin to form nano carbon spheres by in-situ growth, thereby realizing high-value utilization of the nano lignin. The method is characterized in that the advantages of vacuum high-temperature sintering are utilized, nano carbon spheres are formed in situ in a distributed heating and heat preservation mode, nano lignin is uniformly heated at a low heating rate in the first stage and is pyrolyzed from inside to outside, so that the gasification of the nano lignin is reduced, and the generation of a high-yield nano lignin carbon sphere precursor is guaranteed.

The invention also discloses the nano carbon spheres based on the in-situ growth of the nano lignin prepared by the preparation method, and the nano carbon spheres obtained by pyrolysis in-situ growth by taking the nano lignin as a carbon source have the characteristics of good appearance, uniform and controllable size, good sphericity and the like.

Furthermore, the particle size distribution of the carbon nanospheres is between 150 nm and 800nm, the yield of the carbon nanospheres is 60 percent to 70 percent, and the graphitization degree is (relative intensity ratio I of a D peak to a G peak in a Raman spectrum)_D/I_GTo detect) 1.1 to 1.5. Therefore, the nano carbon spheres based on in-situ growth of the nano lignin have good electrochemical energy storage performance and can be used as a negative electrode material of a lithium ion battery and a super capacitor material.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) image of nano lignin prepared in step one of example 1 of the present invention;

FIG. 2 is a diameter distribution diagram of a laser particle size analyzer for nano-lignin prepared in step one of example 1 of the present invention;

FIG. 3 is a Scanning Electron Microscope (SEM) image of nano carbon spheres based on in-situ growth of nano lignin prepared in example 1 of the present invention;

fig. 4 is a Raman (Raman) graph of nano carbon spheres based on in-situ growth of nano lignin prepared in example 1 of the present invention.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The invention discloses a method for preparing nano carbon spheres based on in-situ growth of nano lignin, which comprises the following steps,

the method comprises the following steps: the DES solution prepared by mixing choline chloride and lactic acid is used for carrying out fractional separation on agricultural and forestry biomass to obtain 30-160 nm nano lignin.

The characteristics of small nano lignin particles, uniform size and good sphericity can be better utilized as a high-quality carbon source to prepare the nano carbon spheres with good appearance.

Step two: and (3) putting the prepared nano lignin into a graphite mold, vacuumizing, and carrying out vacuum sintering pyrolysis treatment under the protection of nitrogen to prepare the nano carbon spheres based on in-situ growth of the nano lignin. Wherein the particle size of the nano carbon spheres based on the in-situ growth of the nano lignin is 150-800 nm.

The first step specifically comprises the following operations:

1) the method comprises the steps of mixing choline chloride and lactic acid in a molar ratio of 1: 2-1: 10 to prepare a DES solution, drying the solution in an oven before weighing the choline chloride to prevent the choline chloride from absorbing a large amount of water, wherein the preparation temperature of the DES solution is 60-80 ℃, the preparation time is 2-4 hours, and the DES solution is transparent and uniform.

The method has the advantages that the uniform lignin with nanoparticles can be better separated from the agriculture and forestry biomass by adjusting the mixing ratio of choline chloride and lactic acid in the DES solution, and the DES solution is green and environment-friendly, low in cost and good in economic benefit; by adjusting the ratio of the amounts of choline chloride and lactic acid substances in the DES solution, the obtained nano lignin can be ensured to have the characteristics of high yield, high purity and low molecular weight.

2) Mixing the agriculture and forestry biomass raw materials and the DES solution according to the solid-liquid mass ratio of 1:10, putting the mixed solution into an oven, wherein the temperature of the oven is 130-150 ℃, and the reaction time is 6-24 hours, so as to obtain the mixed solution. Wherein, the agriculture and forestry biomass raw materials are dried, crushed and sieved, and 60-80 meshes are reserved.

The reaction temperature of the agriculture and forestry biomass and the DES solution has the characteristic of low energy consumption, and the nano lignin with high purity and high yield can be better separated at the temperature.

Specifically, the agricultural and forestry biomass is pine, wheat straw, poplar and the like.

3) And (3) carrying out solid-liquid separation on the mixed solution obtained in the step 2) by adopting vacuum filtration, washing the filter residue for 3-5 times by adopting absolute ethyl alcohol (98 percent) until the washing filtrate becomes clear, and collecting the washing filtrate.

4) Evaporating the absolute ethyl alcohol in the washing filtrate collected in the step 3) by adopting rotary evaporation to obtain a concentrated solution, then adding the obtained concentrated solution into 2mL of deionized water under a stirring state, standing for 12-24 h, and precipitating and separating out lignin.

5) And (3) performing solid-liquid separation on the lignin solution precipitated in the step 4) by adopting refrigerated centrifugation, pouring out supernatant, reserving a solid-phase product, washing the obtained solid-phase product by using an absolute ethyl alcohol/water (1:9, v/v) solution, and performing circulating centrifugal washing for 3-5 times to obtain the colloidal nano lignin. Wherein the rotation speed of the freezing centrifugation is 4000-5000 r/min, the time is 5-10 min, and the temperature is-4-0 ℃.

6) And (3) carrying out vacuum freeze drying on the colloidal nano lignin obtained in the step 5) by adopting freeze drying to obtain nano lignin powder with the particle size of 30-160 nm. Wherein the temperature of the vacuum freeze drying is-60 to-40 ℃, the pressure is 0.4 to 0.6MPa, and the time is 18 to 32 hours.

The first step specifically comprises the following operations:

filling the nano lignin prepared in the step one into a graphite mold, vacuumizing, and then carrying out nitrogen atmosphere protection treatment.

Secondly, performing pyrolysis treatment on the nano lignin prepared in the first step, wherein the pyrolysis treatment comprises the following steps: heating to 600-800 ℃ at a speed of 2-10 ℃/min, and keeping the temperature for 30-50 min; heating to 1200-1400 ℃ at a speed of 5-10 ℃/min, and preserving heat for 30-50 min; and then cooling to 600-800 ℃ at a speed of 5-10 ℃/min, and then cooling along with the furnace to obtain 150-800 nm nano carbon spheres based on in-situ growth of nano lignin.

The invention is further described in detail below with reference to the following figures and examples:

a preparation method of nano carbon spheres based on in-situ growth of nano lignin comprises the following steps:

example 1

The method comprises the following steps: DES (data encryption standard) fractionation treatment for preparing nano lignin

Mixing the dried choline chloride and the dried lactic acid at a molar ratio of (1:2) in an oven at 60 ℃ for 4 hours until the solution is transparent and uniform to obtain a DES solution. Mixing 60-mesh pine wood raw material and DES solution at a mass ratio of (1:10), and reacting in an oven at 130 deg.C for 24 hr. And after the reaction is finished, standing and cooling, then carrying out solid-liquid separation by adopting vacuum filtration, washing the filter residue for 3-5 times by adopting absolute ethyl alcohol until the washing filtrate becomes clear, and collecting the washing filtrate. And (3) volatilizing the absolute ethyl alcohol by using a rotary evaporator, adding the concentrated washing filtrate into 2mL of deionized water, standing for 12h, and precipitating after lignin is separated out. And (3) performing solid-liquid separation on the precipitated lignin on a freezing centrifugal machine (4000r/min, 0 ℃ and 5min), pouring out a supernatant, reserving a solid-phase product, washing the solid-phase product by using an absolute ethyl alcohol/water (1:9, v/v) mixed solution, performing circulating centrifugal washing for 3-5 times, and performing vacuum freeze drying (-40 ℃, 0.5MPa and 24h) on the centrifuged colloidal nano lignin in a vacuum freeze dryer to obtain nano lignin powder, wherein the particle size of the nano lignin is concentrated at 30-110 nm.

Step two: and (3) carrying out pyrolysis treatment on the nano lignin obtained in the step one by adopting a vacuum high-temperature pyrolysis technology to obtain nano carbon spheres based on in-situ growth of the nano lignin.

The method specifically comprises the following steps: filling the nano lignin obtained in the step one into a graphite mold, vacuumizing, and sintering under the protection of a nitrogen atmosphere: heating to 600 ℃ at a speed of 2 ℃/min, preserving heat for 30min, heating to 1200 ℃ at a speed of 5 ℃/min, preserving heat for 30min, cooling to 600 ℃ at a speed of 5 ℃/min, and then cooling along with the furnace, namely pyrolyzing the nano lignin to obtain 150-250 nm nano lignin in-situ growth-based nano carbon spheres, wherein the yield of the nano lignin in-situ growth-based nano carbon spheres is 69.3%, performing Raman (Raman) test on the obtained nano carbon spheres based on the nano lignin in-situ growth, and performing Raman spectrum according to the relative intensity ratio I of a D peak and a G peak_D/I_GThe graphitization degree of the material is detected, and the obtained nano carbon spheres based on the in-situ growth of the nano lignin are known as I_D/I_G＝1.1。

Referring to fig. 1, which is an SEM image of the nano lignin prepared in the first step of example 1, it can be seen from fig. 1 that the obtained nano lignin has small particles, uniform size, good dispersibility, and good sphericity, and can be used as a high-quality carbon source for preparing a nano carbon material.

Referring to fig. 2, which is a diameter distribution diagram of the laser particle size analyzer of nano lignin prepared in the first step of example 1, it can be seen from fig. 2 that the obtained nano lignin has a uniform particle distribution and is mainly concentrated between 50nm and 100 nm.

Referring to fig. 3, which is an SEM image of the nano carbon spheres based on in-situ growth of nano lignin prepared in example 1, it can be seen from fig. 3 that the obtained nano carbon spheres based on in-situ growth of nano lignin have small particles, uniform size, good dispersibility, and good sphericity.

Referring to fig. 4, it can be seen from fig. 4 that the nano carbon spheres based on in-situ growth of nano lignin prepared in example 1 have a graphite structure except amorphous carbon, have high graphitization degree and good conductivity, and thus can be used in the fields of lithium ion battery negative electrode materials, supercapacitors, electrochemical energy storage and the like.

Example 2

The method comprises the following steps: DES (data encryption standard) fractionation treatment for preparing nano lignin

Mixing the dried choline chloride and the dried lactic acid at a molar ratio of (1:5) in an oven at 70 ℃ for 3 hours until the solution is transparent and uniform to obtain a DES solution. Mixing 70-mesh wheat straw raw material and DES solution at a mass ratio of (1:10), and reacting in an oven at 140 deg.C for 18 h. And after the reaction is finished, standing and cooling, then carrying out solid-liquid separation by adopting vacuum filtration, washing the filter residue for 3-5 times by adopting absolute ethyl alcohol until the washing filtrate becomes clear, and collecting the washing filtrate. And (3) volatilizing the absolute ethyl alcohol by using a rotary evaporator, adding the concentrated washing filtrate into 2mL of deionized water, standing for 20h, and precipitating after lignin is separated out. And (3) performing solid-liquid separation on the precipitated lignin on a refrigerated centrifuge (4500r/min, -2 ℃ and 8min), pouring out supernatant, reserving a solid-phase product, washing the solid-phase product by using absolute ethyl alcohol/water (1:9, v/v) mixed solution, circularly centrifuging and washing for 3-5 times, and performing vacuum freeze drying (-50 ℃, 0.4MPa and 32h) on the centrifuged colloidal nano lignin in a vacuum freeze dryer to obtain nano lignin powder, wherein the particle size of the nano lignin is concentrated at 50-130 nm.

Step two: and (3) carrying out pyrolysis treatment on the nano lignin obtained in the step one by adopting a vacuum high-temperature pyrolysis technology to obtain nano carbon spheres based on in-situ growth of the nano lignin.

The method specifically comprises the following steps: filling the nano lignin obtained in the step one into a graphite mold, vacuumizing, and sintering under the protection of a nitrogen atmosphere: heating to 700 ℃ at a speed of 5 ℃/min, preserving heat for 40min, heating to 1300 ℃ at a speed of 7 ℃/min, preserving heat for 40min, cooling to 700 ℃ at a speed of 8 ℃/min, and then cooling along with the furnace, namely pyrolyzing the nano lignin to obtain 180-350 nm nano lignin in-situ growth-based nano carbon spheres, wherein the yield of the nano lignin in-situ growth-based nano carbon spheres is 62.3%, performing Raman test on the obtained nano carbon spheres based on the nano lignin in-situ growth, and performing Raman spectrum according to the relative intensity ratio I of a D peak and a G peak_D/I_GThe graphitization degree of the material is detected, and the obtained nano carbon spheres based on the in-situ growth of the nano lignin are known as I_D/I_G＝1.3。

Example 3

The method comprises the following steps: DES (data encryption standard) fractionation treatment for preparing nano lignin

Mixing the dried choline chloride and the dried lactic acid at a molar ratio of (1:10) in an oven at 80 ℃ for 2 hours until the solution is transparent and uniform to obtain a DES solution. Mixing 80-mesh poplar raw materials and DES solution in a mass ratio of (1:10), and then reacting in an oven at 150 ℃ for 6 hours. And after the reaction is finished, standing and cooling, then carrying out solid-liquid separation by adopting vacuum filtration, washing the filter residue for 3-5 times by adopting absolute ethyl alcohol until the washing filtrate becomes clear, and collecting the washing filtrate. And (3) volatilizing the absolute ethyl alcohol by using a rotary evaporator, adding the concentrated washing filtrate into 2mL of deionized water, standing for 24h, and precipitating after lignin is separated out. And (3) performing solid-liquid separation on the precipitated lignin on a refrigerated centrifuge (5000r/min, -4 ℃ and 10min), pouring out a supernatant, reserving a solid-phase product, washing the solid-phase product by using an absolute ethyl alcohol/water (1:9, v/v) mixed solution, circularly centrifuging and washing for 3-5 times, and performing vacuum freeze drying (-60 ℃, 0.6MPa and 18h) on the centrifuged colloidal nano lignin in a vacuum freeze dryer to obtain nano lignin powder, wherein the particle size of the nano lignin is concentrated at 70-160 nm.

Step two: and (3) carrying out pyrolysis treatment on the nano lignin obtained in the step one by adopting a vacuum high-temperature pyrolysis technology to obtain nano carbon spheres based on in-situ growth of the nano lignin.

The method specifically comprises the following steps: filling the nano lignin obtained in the step one into a graphite mold, vacuumizing, and sintering under the protection of a nitrogen atmosphere: heating to 800 ℃ at a speed of 10 ℃/min, keeping the temperature for 50min, heating to 1400 ℃ at a speed of 10 ℃/min, keeping the temperature for 50min, cooling to 800 ℃ at a speed of 10 ℃/min, and then cooling with a furnace, namely, the nano lignin is pyrolyzed and then cooled with the furnace to obtain nano carbon spheres based on the in-situ growth of the nano lignin, wherein the average size of the nano carbon spheres is about 800nm, the yield of the nano carbon spheres based on the in-situ growth of the nano lignin is 60.2%, the obtained nano carbon spheres based on the in-situ growth of the nano lignin are subjected to Raman test, and the relative intensity ratio I of a D peak to a G peak in a Raman_D/I_GThe degree of graphitization of the material was examined and the basis for the examination was found to beI of nano carbon spheres grown in situ by nano lignin_D/I_G＝1.35。

Specifically, in the embodiment of the present invention, the pyrolysis treatment is performed using a vacuum high-temperature sintering furnace, and the vacuum freeze-drying treatment is performed in a vacuum freeze-dryer.

Therefore, the nano carbon spheres with good appearance, uniform size, good sphericity, high graphitization degree, good conductivity and high yield are formed in situ by adopting the vacuum high-temperature sintering pyrolysis technology by taking the nano lignin as a carbon source, and the nano carbon spheres are used as a lithium ion battery cathode material, a super capacitor, a carbon material which is superior to other lignin-prepared carbon materials in performances such as electrochemical energy storage, adsorption separation, ion exchange and the like, and have good use value and market potential.

Specifically, in particular embodiments of the present invention, the agricultural and forestry biomass used includes pine, wheat straw, poplar, and the like.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.