CN104891479A - Plant-based graphene and preparation method thereof - Google Patents

Abstract

The invention provides plant-based graphene and a preparation method thereof. The preparation method comprises the steps of liquefying and filtering plant raw materials to obtain biological oil; mixing the biological oil with a catalyst to obtain a mixture, placing the mixture into a self-pressurizing reactor, sealing the reactor, catalytically calcining for 1 to 12 hours at the temperature of 500 to 1200 DEG C, cooling, washing by utilizing hydrochloric acid to remove the catalyst, rinsing by utilizing deionized water, and drying to obtain the quasi-graphene. According to the preparation method, the plant raw materials are firstly liquefied into biological oil which mainly includes oligosaccharide and a phenolic substance, then the biological oil is mixed with the catalyst, and under the high temperature and high pressure, the biological oil is converted to quasi-graphene on the surface of the catalyst, so that a novel method for preparing the quasi-graphene material in a mass manner by virtue of cheap plant raw materials is provided.

Description

Plant-based graphene and preparation method thereof

technical field

The invention relates to a plant-based graphene-like material and a preparation method thereof, in particular to an industrialized method for preparing a supercapacitor activated carbon composite material through liquefaction and low-temperature catalytic calcination with plant resources.

Background technique

Graphene is a two-dimensional carbon material, which is a general term for single-layer graphene, double-layer graphene and few-layer graphene. Graphene is the thinnest and hardest nanomaterial known in the world. It also has the characteristics of large specific surface area, high electrical conductivity, and excellent thermodynamic properties. It can play an important role in the fields of life sciences and energy. At present, the methods for preparing graphene include graphite oxide reduction method, epitaxial growth method, chemical vapor deposition method, mechanical exfoliation method, and electrochemical method. The graphite oxide reduction method adopts the idea of first oxidation and then reduction. The specific steps are to prepare graphite oxide first, then use ultrasonic waves, thermal expansion and other methods to peel off graphene oxide as much as possible, and finally use a suitable reducing agent to convert graphene oxide into graphene. For example, hydrazine hydrate is used to reduce graphene oxide, and the carbon atoms whose hybridization mode is sp3 are changed into graphene composed of sp2 carbon network lattice. In the epitaxial growth method, carbon elements are doped into rare metals by high-temperature infiltration to form interstitial impurities, and then carbon is deposited on the surface of the metal substrate by low-temperature treatment to precipitate graphene crystal films. When the first layer of graphene has not completely covered the metal substrate, the second layer has begun to grow. Since the chemical bonds between the first layer and the second layer of graphene and the metal substrate are completely different, weak coupling and strong covalent bonds The gap between the roles makes it easy for the second layer of graphene to be peeled off. The chemical vapor deposition method uses a metal single crystal as the substrate, and achieves the purpose of precisely controlling the thickness of the graphene film by changing the temperature, adjusting the substrate, and controlling the exposure of the precursor. The specific method is to heat the 300mm thick Ni film to 1000 degrees Celsius and then expose it to methane atmosphere, so as to form a high-purity graphene film on the Ni surface. Micromechanical separation method Micromechanical separation method is the most original method of exfoliating graphene. During the specific operation, some method is often used to expand the graphite to facilitate separation, and the single-layer graphite will appear irregularly on the graphite surface. Compared with the chemical exfoliation method, this method is more difficult to control the graphene morphology, and is not suitable for high-precision industrial production.

Yang Rong and others disclosed a preparation method of a graphene-like conductive carbon material (application number: 201410134804.0), mixing sepiolite powder, sucrose and deionized water evenly, then ultrasonically dispersing, and then microwave heating. Place in a 98.3% concentrated sulfuric acid desiccator for 24-144 hours; in this step, the sucrose is transformed into caramel by microwave heating. Carbonization is carried out in a protective gas atmosphere, caramelized on the layered framework of sepiolite. The carbonized sepiolite is alternately acidified and washed with hydrofluoric acid and hydrochloric acid, and then the sepiolite is washed with deionized water and fully dried to obtain a conductive carbon material with a graphene-like structure.

Jiao Qifang (Jiao Qifang, Preparation and electrocatalytic performance of graphene-like carbon nano-fragments, [Dissertation], South China Normal University, 2013) used waste lithium-ion battery carbon anode as raw material, after a series of pretreatment- Chemical oxidation-ultrasonic pulverization-dialysis purification, etc., to obtain oxidized carbon nano-fragments. The results show that the oxidized carbon nano-fragments have a rough outline, a thickness of 1.5nm, a shape similar to graphene, a size ranging from 5nm to 2μm, and a large amount of Oxygen-containing functional groups and defects.

Zhu Runliang et al. disclosed a method for preparing a graphene-like structure nano-carbon material (publication number CN103058168A). The bentonite adsorbed with the dye is sequentially dried, pulverized, carbonized, acidified, washed, and dried to obtain a nano-carbon material with a graphene-like structure. The invention uses waste bentonite as a raw material to prepare a new type of nano-layered carbon material with a large specific surface area. At the same time, it provides a new way to solve the recycling of bentonite after dye adsorption, and realizes bentonite resources after wastewater treatment. Utilization, thus helping to promote the application of bentonite in dye/printing and dyeing wastewater treatment.

Zhou Xufeng disclosed a graphene preparation method and a graphene invention patent (publication number CN104477901A). Mix the metal catalyst with water to obtain an aqueous solution of the metal catalyst; mix the gel material with the aqueous solution of the metal catalyst to obtain a hydrogel material adsorbed with the metal catalyst, the gel material includes starch compounds, cellulose One or more of compounds and synthetic resins; the hydrogel material adsorbed with metal catalysts is heat-treated in a protective gas atmosphere or in a vacuum environment to obtain graphene.

Liang Xuelei et al. (Liang Xuelei, Li Wei, GuangJun C, etc. Effect of transfer process on the quality of CVD-grown graphene [J]. Science Bulletin, 2014, (33)) using chemical vapor deposition (CVD) to grow on metal substrates of graphene. Using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) to prove that the metal substrate corrosion solution will introduce pollution on the graphene surface during the transfer process, using our developed "modified RCA (radio corporation of America) cleaning (modified RCA clean) "The transfer process can effectively remove this pollution. This is of great significance for improving the performance of subsequent electronic devices

Guilin University of Technology Zou Zhengguang et al [Zou Zhengguang, Yu Huijiang, Long Fei, et al. Preparation of GO by ultrasonic-assisted Hummers method[J]. Journal of Inorganic Chemistry, 2011, 27(09):1753-1757.] studied the low temperature of Hummers method ( ≤10°C), medium temperature (38°C) and low-medium temperature stages were assisted by ultrasound at different powers, and the influence of ultrasound on the Hummers method was explored. They found that the GO layer spacing from large to small was low-medium temperature ultrasound-assisted, medium-temperature ultrasound-assisted, and low-temperature ultrasound-assisted. Not only that, the distance between graphene layers is positively correlated with the ultrasonic power, and the larger the distance is, the easier it is for the exfoliation of single-layer GO. Therefore, single-layer GO or intercalated GO can be prepared according to different experimental requirements.

[Jia Jina, Zhao Guangchao. Preparation of graphene solid-phase microextraction fiber and detection of polychlorinated biphenyls [J]. Journal of Analysis and Testing, 2013, 32(05):541-546.] Through solid-phase microextraction technology The titanium sol-gel added with graphene is made into fiber, so that the fiber has all the advantages of both graphene and gel, not only has a high specific surface area, strong thermal stability and excellent mechanical strength, but also Has a three-dimensional structure to provide more adsorption points.

Ren Xiaomeng et al [Ren Xiaomeng, Wang Yuansheng, He Te. The key process and reaction mechanism of graphene synthesized by Hummers method [J]. Materials Engineering, 2013 (01): 1-5.] explored the classic Hummers method, by changing the reaction temperature , temperature control time, the amount of reaction substances, etc., and detect each group of products separately. It is found that the optimum temperature of the low-temperature reaction stage of the Hummers method is close to 0°C, the reaction time can be increased appropriately, and the concentrated sulfuric acid and potassium permanganate in the low-temperature reaction stage can be added in excess, and the addition of sodium nitrate will basically not affect the reaction. It is best to adjust the temperature in the middle temperature stage to 30-45°C, and increase the reaction time by 90 minutes, so as to ensure that the oxidation of graphite is deeper and the flakes are more complete. However, it is in the heating stage that most affects the yield. The research team found that controlling the temperature within 90-100°C is the highest yield range. By adding deionized water in small amounts several times, the reaction time should be shortened as much as possible to prevent the product from reuniting.

Although the above methods have successfully prepared high-quality graphene, the preparation process is expensive, polluting, and difficult to industrialize. Therefore, macro-scale production and large-scale production are still the most important bottlenecks hindering the large-scale commercial use of graphene materials. At present, there is no report on the preparation method of plant-based graphene materials, and the large-scale liquefaction technology of biomass is mature. Therefore, using plant-based materials with a wide range of sources and low crystallinity as raw materials, graphene-like materials can be prepared by liquefaction and catalytic calcination , large-scale industrialization can be realized, the cost is greatly reduced, the environmental pollution is small, the product dispersibility is better, and it is easier to store.

Contents of the invention

In order to solve the existing problems in the prior art, such as difficult preparation process, serious pollution, and high price, the present invention provides a plant-based liquefaction catalytic preparation of graphene-like materials and a method thereof, which can realize large-scale industrialization and clean preparation process. , the steps are simple, the manufacturing cost is low, the product has better dispersion performance and is easier to store.

Technical scheme of the present invention is: the preparation method of plant-based graphene, comprises the steps:

The first step, plant liquefaction: liquefy the dried agricultural and forestry biomass raw materials with phenol, and obtain bio-oil after filtering to remove inorganic impurities;

The second step is to mix the bio-oil with the catalyst: the iron-based element nitrate is used as the catalyst, and the catalyst and the bio-oil are mixed according to the mass ratio (0.1-1.0): 1.0;

The third step, sealed pretreatment: put a certain amount of the above mixture in a self-generating pressure reactor, and the amount of material does not exceed 1/3 of the volume of the reactor, and perform airtight pretreatment;

The fourth step, calcining: put the self-generated pressure reactor with materials in a high-temperature furnace, heat up and calcined, after the calcining is completed, cool naturally, take out the sample, recover the catalyst by pickling, rinse with deionized water, and dry, That is, the plant-based graphene sample, the electrical conductivity of the plant-based graphene is 370 s/cm, the specific surface area is 760 m ² /g, and the thickness is 1-3 nm.

The plant raw materials described in the first step include wood chips, bamboo chips, and straws, which are used for drying.

The bio-oil described in the first step is filtered to remove solid impurities.

In the second step, the iron series elements include iron, nickel, and cobalt.

In the second step, when the nitrate of the iron series element is mixed with the bio-oil, uniform stirring is carried out.

In the fourth step, the calcination temperature is 500-1200°C, and the calcination time is 1-10h.

The graphene obtained by the method for preparing plant-based graphene has an electrical conductivity of 180-370 s/cm, a specific surface area of 420-760 m ² /g, and a thickness of 1-3 nm.

The yield, specific surface area, and thickness of the plant-based graphene-like material of the present invention can be controlled by catalyst loading, activation temperature, calcination temperature and time. Preparation of plant-based graphene-like materials: liquefy the dried plant material with phenol, and filter to remove inorganic impurities to obtain bio-oil. Mixing of bio-oil and catalyst: use iron-based element nitrate as catalyst, and mix with bio-oil according to the mass ratio (0.1～1.0)︰1.0. A certain amount of the above-mentioned mixture is placed in a self-generating pressure reactor, and the amount of material does not exceed 1/3 of the volume of the reactor, and airtight pretreatment is carried out. Place the self-generating pressure reactor filled with materials in a high-temperature furnace, raise the temperature to 500-1200°C at a certain heating rate, and keep it for 1-10h. After calcination, cool naturally, take out the sample, recover the catalyst by acid washing, rinse with deionized water, and dry to obtain the graphene-like sample. The electrical conductivity of plant-based graphene is 180-370 s/cm, the specific surface area is 420-760 m ² /g, and the thickness is 1-3 nm.

Beneficial effect:

1. Firstly, the plant-based raw material is liquefied and pretreated. Plant-based raw materials reduce the crystallinity of plant fibers through the liquefaction process to obtain oligosaccharides and phenolic substances, reduce the activation energy of graphitization, and increase the conversion rate of graphitization. Moreover, the liquefaction technology equipment has been industrialized, and the raw materials for preparing graphene can be obtained on a large scale.

2. Catalytic graphitization to prepare graphene materials. The supported iron-based catalyst can significantly reduce the graphitization temperature and increase the yield of graphene under autogenous pressure. The electrical conductivity of plant-based graphene is 370 s/cm, the specific surface area is 760 m ² /g, and the thickness is 1-3 nm.

Description of drawings

Fig. 1 is the electron micrograph of plant-like graphene in Example 1 of the present invention.

Fig. 2 is the XRD figure of embodiment 1.

FIG. 3 is an atomic force micrograph of Example 1. FIG.

Figure 4 is a schematic diagram of an autogenous pressure reactor.

1 is a resistance furnace, 2 is a thermocouple, 3 is a resistance wire, 4 is an electric heating rod, 5 is a stainless steel sealed tank, and 6 is a vent.

Detailed ways

The present invention is as follows to the test method of prepared plant-based graphene material performance:

(1) Determination of specific surface area: the determination of nitrogen adsorption isotherm of activated carbon under liquid nitrogen conditions was used, and the specific surface area was calculated according to the BET formula.

(2) The surface morphology was tested by transmission electron microscope (TEM) and atomic force microscope (AFM).

(3) Conductivity measurement: SZT-C four-probe test bench measurement.

A preparation method for plant-based graphene, comprising the steps of:

The first step, plant liquefaction: liquefy the dried plant raw materials with phenol, and filter to remove inorganic impurities to obtain bio-oil. The conversion of plant material into bio-oil by liquefaction, mainly composed of oligosaccharides and phenolic substances. For this step, please refer to Wang Yuanyuan, Ye Lei, Shen Huyan, et al. Preparation of adhesive by phenol liquefaction and resinization of waste biomass from Zizania japonica[J]. Guangzhou Chemical Industry, 2014, (23).; Li Gaiyun, Zhu Xianchao, Zou Xianwu, Microwave-assisted rapid phenol liquefaction of poplar wood and product characterization[J]. Forestry Science, 2014, (11). DOI: doi: 10.11707/j.1001-7488.20141116.; Sun Fengwen, Li Xiaoke. Bamboo phenol liquefaction and adhesive preparation Technology [J]. Forest Products Chemistry and Industry, 2007,27(6):65-70.DOI:doi:10.3321/j.issn:0253-2417.2007.06.014.; Jie Shujun, Zhang Qiuhui, Li Jianzhang. Chinese fir phenol liquefaction Synthesis of Thermosetting Phenolic Resin[J]. Biomass Chemical Engineering, 2007,41(5):9-12.DOI:doi:10.3969/j.issn.1673-5854.2007.05.003.; Qin Tefu, Luo Bei, Li Gaiyun.Research on Phenol Liquefaction and Resinization of Plantation Wood Ⅱ.Preparation and Characterization of Liquefied Wood-based Phenolic Resin[J].Wood Industry,2006,20(5):8-10.DOI:doi:10.3969/ j.issn.1001-8654.2006.05.003.; Ma Xiaojun, Zhao Guangjie. Preliminary Discussion on Preparation of Carbon Fiber from Wood Phenol Liquefaction Products[J]. Forest Products Chemistry and Industry, 2007,27(2):29-32.DOI:doi:10.3321/ The method described in j.issn:0253-2417.2007.02.007.

The second step is to mix the bio-oil with the catalyst: the iron-based element nitrate is used as the catalyst, and the bio-oil is mixed according to the mass ratio (0.1-1.0): 1.0.

The third step, sealed pretreatment: put a certain amount of the above mixture in a self-generating pressure reactor, and the amount of material does not exceed 1/3 of the volume of the reactor, and perform airtight pretreatment.

The fourth step, calcining: put the self-generating pressure reactor filled with materials in a high-temperature furnace, raise the temperature to 500-1200° C. at a certain heating rate, and keep it for 1-10 hours. After calcination, cool naturally, take out the sample, recover the catalyst by acid washing, rinse with deionized water, and dry to obtain the graphene-like sample. The electrical conductivity of plant-based graphene is 370 s/cm, the specific surface area is 760 m ² /g, and the thickness is 1-3 nm.

The plant raw materials described in the first step include wood chips, bamboo chips, straw and other agricultural and forestry biomass raw materials, which need to be dried.

The bio-oil described in the first step needs to be filtered to remove solid impurities.

In the second step, the iron series elements include iron, nickel, and cobalt.

In the second step, when the nitrate of the iron series element is mixed with the bio-oil, uniform stirring is carried out.

The self-generated pressure reaction device is that the outer layer is a resistance furnace 1, and a stainless steel sealed tank 5 is arranged in the resistance furnace 1, and a resistance wire 3 is arranged in the resistance furnace 1, and the self-generated pressure reactor is heated by an electric heating rod 4, and the built-in The thermocouple 2 monitors the temperature, and the resistance furnace 1 is also provided with a vent 6 .

Example 1

(1) Plant liquefaction: liquefy the dried bamboo chips with phenol, and filter to remove inorganic impurities to obtain bio-oil.

(2) Mixing of bio-oil and catalyst: Nickel nitrate is used as a catalyst and mixed with bio-oil according to the mass ratio of 0.1︰1.0.

(3) Sealing pretreatment: a certain amount of the above mixture is placed in a self-generating pressure reactor, and the amount of material is 1/3 of the volume of the reactor, and airtight pretreatment is carried out.

(4) Calcination: put the self-generating pressure reactor filled with materials in a high-temperature furnace, raise the temperature to 500° C. at a certain heating rate, and keep it for 1 hour. After calcination, cool naturally, take out the sample, recover the catalyst by acid washing, rinse with deionized water, and dry to obtain the graphene-like sample. The electrical conductivity of plant-based graphene is 180 s/cm, the specific surface area is 420 m ² /g, and the thickness is 1-3 nm.

Example 2

(1) Plant liquefaction: liquefy the dried bamboo chips with phenol, and filter to remove inorganic impurities to obtain bio-oil.

(2) Mixing of bio-oil and catalyst: Nickel nitrate is used as catalyst and mixed with bio-oil according to the mass ratio of 1.0︰1.0.

(3) Sealing pretreatment: a certain amount of the above mixture is placed in a self-generating pressure reactor, and the amount of material is 1/3 of the volume of the reactor, and airtight pretreatment is carried out.

(4) Calcination: put the self-generating pressure reactor filled with materials in a high-temperature furnace, raise the temperature to 1200° C. at a certain heating rate, and keep it for 10 hours. After calcination, cool naturally, take out the sample, recover the catalyst by acid washing, rinse with deionized water, and dry to obtain the graphene-like sample. The electrical conductivity of plant-based graphene is 327 s/cm, the specific surface area is 590 m ² /g, and the thickness is 1-3 nm.

Example 3

(1) Plant liquefaction: liquefy the dried bamboo chips with phenol, and filter to remove inorganic impurities to obtain bio-oil.

(2) Mixing of bio-oil and catalyst: Nickel nitrate is used as catalyst, mixed with bio-oil according to the mass ratio of 0.7︰1.0.

(3) Sealing pretreatment: a certain amount of the above mixture is placed in a self-generating pressure reactor, and the amount of material is 1/3 of the volume of the reactor, and airtight pretreatment is carried out.

(4) Calcination: put the self-generating pressure reactor filled with materials in a high-temperature furnace, raise the temperature to 1100° C. at a certain heating rate, and keep it for 10 hours. After calcination, cool naturally, take out the sample, recover the catalyst by acid washing, rinse with deionized water, and dry to obtain the graphene-like sample. The electrical conductivity of plant-based graphene is 370 s/cm, the specific surface area is 760 m ² /g, and the thickness is 1-3 nm.

Example 4

(1) Plant liquefaction: liquefy the dried bamboo chips with phenol, and filter to remove inorganic impurities to obtain bio-oil.

(2) Mixing of bio-oil and catalyst: Nickel nitrate is used as catalyst, mixed with bio-oil according to the mass ratio of 0.7︰1.0.

(3) Sealing pretreatment: a certain amount of the above mixture is placed in a self-generating pressure reactor, and the amount of material is 1/3 of the volume of the reactor, and airtight pretreatment is carried out.

(4) Calcination: put the self-generating pressure reactor filled with materials in a high-temperature furnace, raise the temperature to 1200° C. at a certain heating rate, and keep it for 10 hours. After calcination, cool naturally, take out the sample, recover the catalyst by acid washing, rinse with deionized water, and dry to obtain the graphene-like sample. The electrical conductivity of plant-based graphene is 365 s/cm, the specific surface area is 730 m ² /g, and the thickness is 1-3 nm.

Example 5

(1) Plant liquefaction: liquefy the dried bamboo chips with phenol, and filter to remove inorganic impurities to obtain bio-oil.

(2) Mixing of bio-oil and catalyst: use iron-based element nitrate as catalyst, and mix with bio-oil according to the mass ratio of 1.0︰0.7.

(3) Sealing pretreatment: a certain amount of the above mixture is placed in a self-generating pressure reactor, and the amount of material is 1/3 of the volume of the reactor, and airtight pretreatment is carried out.

(4) Calcination: put the self-generating pressure reactor with materials in a high-temperature furnace, raise the temperature to 1200° C. at a certain heating rate, and keep it for 5 hours. After calcination, cool naturally, take out the sample, recover the catalyst by acid washing, rinse with deionized water, and dry to obtain the graphene-like sample. The electrical conductivity of plant-based graphene is 355 s/cm, the specific surface area is 718 m ² /g, and the thickness is 1-3 nm.

Example 6

The bamboo chips in Example 3 were changed to Chinese fir chips, and the rest were the same as in Example 3 to obtain a plant-based graphene with an electrical conductivity of 369 s/cm, a specific surface area of 751 m ² /g, and a thickness of 1-3 nm.

Example 7

Change the bamboo chip raw material in embodiment 3 into coconut shell, all the other are the same as embodiment 3, obtain the electrical conductivity of plant-based graphene 325s/cm, specific surface area 728m ² /g, thickness 1-3nm.

Example 8

The nickel nitrate in Example 3 was changed to iron nitrate, and the rest were the same as in Example 3, to obtain a plant-based graphene with a conductivity of 285 s/cm, a specific surface area of 672 m ² /g, and a thickness of 1-3 nm.

Example 9

The nickel nitrate in Example 3 was changed to cobalt nitrate, and the rest were the same as in Example 3, so that the electrical conductivity of plant-based graphene was 370 s/cm, the specific surface area was 760 m ² /g, and the thickness was 1-3 nm.

Claims (7)

1. the preparation method of plant base class Graphene, is characterized in that, comprises the steps:

The first step, plant is liquefied: the agricultural-forestry biomass raw material of oven dry and phenol are liquefied, and filters after removing inorganic impurity and obtains bio oil;

Second step, bio oil and catalyst mix: with iron group nitrate for catalyzer, (0.1 ~ 1.0) ︰ 1.0 mixes according to mass ratio for catalyzer and bio oil;

3rd step, sealing pre-treatment: be placed in spontaneous pressure reactor by a certain amount of said mixture, inventory is no more than 1/3 of reactor volume, carries out airtight pre-treatment;

4th step, calcining: the spontaneous pressure reactor that material is housed is placed in High Temperature Furnaces Heating Apparatus, heat up calcining, after calcining terminates, naturally cooling, take out sample, reclaim catalyzer, by rinsed with deionized water through pickling, after drying, be described plant base class Graphene sample, the specific conductivity 370s/cm of plant base class Graphene, specific surface area 760m ²/ g, thickness 1-3nm.

2. the preparation method of plant base class Graphene as claimed in claim 1, it is characterized in that, the plant material described in the first step comprises wood chip, and bamboo is considered to be worth doing, stalk, dries and uses.

3. the preparation method of plant base class Graphene as claimed in claim 1, it is characterized in that, the bio oil described in the first step removes solid impurity after filtration.

4. the preparation method of plant base class Graphene as claimed in claim 1, it is characterized in that, in second step, iron group comprises iron, nickel, cobalt.

5. the preparation method of plant base class Graphene as claimed in claim 1, is characterized in that, at the uniform velocity stir when iron group nitrate mixes with bio oil in second step.

6. the preparation method of plant base class Graphene as claimed in claim 1, it is characterized in that, in the 4th step, calcining temperature is 500 ~ 1200 DEG C, calcination time 1-10h.

7. the Graphene that obtains of the preparation method of the arbitrary described plant base class Graphene of claim 1 ~ 6, is characterized in that, specific conductivity 180 ~ 370s/cm, specific surface area 420 ~ 760m ²/ g, thickness 1-3nm.