1. A method for preparing graphene by taking heavy aromatic hydrocarbon as a raw material is characterized by comprising the following steps:

1) mixing and heating a carbon source and a carbonizing agent for a period of time by taking heavy aromatic hydrocarbon as the carbon source and sulfuric acid as the carbonizing agent, cooling, filtering and drying to obtain a graphene precursor;

2) mixing the graphene precursor obtained in the step 1) with a filler, and uniformly grinding; and under the protection of inert gas, stripping and thinning the obtained mixture powder at high temperature to obtain the graphene.

2. The method as claimed in claim 1, wherein the heating temperature in step 1) is 150 ℃ and 220 ℃, and the treatment time is 4-24 hours.

3. The method as claimed in claim 1, wherein the temperature of the high temperature stripping thinning process is between 600 ℃ and 1200 ℃ for 2-20 hours.

4. The method of claim 1, wherein the volume ratio of heavy aromatics to sulfuric acid is less than 1: 0.5.

5. The method as claimed in claim 1, wherein the filler is an inorganic salt having a melting point of 600-1000 ℃.

6. The method according to claim 5, wherein the filler is MgCl₂、KCl、K₂CO₃One of (1); or the filler is mixed salt selected from NaCl/KCl, KCl/LiCl and KCl/K₂CO₃、KCl/K₂SO₄、K₂CO₃/K₂SO₄、K₂SO₄/Na₂SO₄、NaF/CaF₂/MgCl₂、NaCl/KCl/ZnCl₂。

7. The method according to claim 1, wherein the weight ratio of the graphene precursor to the filler is 1:5 to 1: 100.

8. The process of claim 1, wherein the heavy aromatic hydrocarbon is a mixture of one or more of a monocyclic aromatic hydrocarbon and a bicyclic aromatic hydrocarbon.

9. The method according to claim 8, wherein the monocyclic aromatic hydrocarbon is selected from one or more of alkylbenzene, tetrahydronaphthalene, indane and indene; the bicyclic aromatic hydrocarbon is selected from one or more of naphthalene, acenaphthene and acenaphthylene.

10. The method of claim 1, wherein the concentration of sulfuric acid is 70-98%.

Background

Graphene is a two-dimensional carbon nanomaterial consisting of sp carbon atoms²The hexagonal shape formed by the hybrid tracks is in a honeycomb lattice structure. Since the british scholars prepared the single-layer graphene by the simple mechanical stripping method in 2004, due to the unique chemical bonding mode and the pi-pi conjugated carbon layer, the graphene has excellent thermal, electrical, mechanical properties, optical and unique structures and the like, and can be widely used in many fields such as energy, materials, electronics and biomedicine as a revolutionary material.

The existing graphene preparation methods mainly comprise a graphite method and a non-graphite method. The graphite method firstly oxidizes natural graphite with a strong oxidant to prepare graphene oxide, and then reduces the graphene oxide by a reduction means to obtain reduced graphene, but the preparation process is complex and the cost is too high, the performance of the graphene is reduced due to the damage to the graphene lamellar structure in the oxidation process, and the severe environmental problems caused by the use of corrosive strong acid in the preparation process hinder the realization of large-scale preparation. The non-graphite method, typically a CVD method, has a good morphology, but the equipment is complex and the synthesis cost is high. On the whole, the field of graphene industry is developed quickly, and the downstream application scene development is severely restricted due to the high manufacturing cost of graphene. On the other hand, the petrochemical industry in China is large in scale, the traditional industrial characteristics are obvious, oil products in various regions are low, and byproducts such as benzene series, naphthalene series and acenaphthene series are more and low in price. Therefore, how to efficiently utilize petrochemical byproducts to develop high-added-value graphene products, widening the selection of graphene raw materials and reducing the cost of graphene are the key points for accelerating the development of the graphene industry.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for preparing graphene by taking heavy aromatic hydrocarbon as a raw material, which aims to overcome the defects in the prior art, wherein a chemical primary product aromatic hydrocarbon with benzene rings is taken as a carbon source, and a solvothermal method is adopted to convert a liquid aromatic hydrocarbon raw material into a solid carbon material in one step without a catalyst; the prepared graphene has thin sheet layer and good crystallinity.

The technical scheme adopted by the invention for solving the problems is as follows:

a method for preparing graphene by taking heavy aromatics as raw materials comprises the following steps:

1) mixing a carbon source and a carbonizing agent by taking heavy aromatic hydrocarbon as the carbon source and sulfuric acid as the carbonizing agent, heating to 150-220 ℃, reacting for 4-24 hours, cooling to room temperature, filtering, washing and drying the obtained filter cake to obtain a graphene precursor (namely a graphene-like solid);

2) mixing the graphene precursor obtained in the step 1) with a filler, uniformly grinding, and carrying out high-temperature stripping and thinning treatment on the obtained mixture powder under the protection of inert gas to obtain graphene; wherein the temperature of the high-temperature stripping and thinning treatment is between 600 ℃ and 1200 ℃, and the time is 2-20 hours.

According to the scheme, the heavy aromatic hydrocarbon refers to a hydrocarbon containing a benzene ring and having nine or more carbon atoms, and can be selected from one or more of monocyclic aromatic hydrocarbon, bicyclic aromatic hydrocarbon and other heavy aromatic hydrocarbons. Further, the monocyclic aromatic hydrocarbon is selected from one or more of benzene (such as alkylbenzene), tetrahydronaphthalene, indane, indene (such as indene, indane and the like) and the like; the bicyclic aromatic hydrocarbon is one or more selected from naphthalene or naphthalenes (such as methylnaphthalene and the like), acenaphthene (such as acenaphthylene and the like), acenaphthylene (such as acenaphthylene and the like) and the like.

According to the scheme, the concentration of the sulfuric acid is 70-98%.

According to the scheme, the volume ratio of the heavy aromatic hydrocarbon to the sulfuric acid is less than 1: 0.5. Preferably, the volume ratio of the heavy aromatic hydrocarbon to the sulfuric acid is 1: 0.5-1: 2.

According to the scheme, the filler is inorganic salt with the melting point of 600-1000 ℃. Further, the filler is selected from MgCl₂、KCl、K₂CO₃One of the like; or the filler is mixed salt such as NaCl/KCl, KCl/LiCl, NaF/CaF₂/MgCl₂、NaCl/KCl/ZnCl₂And the like.

According to the scheme, the weight ratio of the graphene precursor to the filler is 1: 5-1: 100.

According to the scheme, the temperature is increased to the high-temperature stripping and thinning treatment temperature at the temperature increase rate of 4-6 ℃/min.

The method for preparing the graphene from the heavy aromatic hydrocarbon is a liquid-state to solid-state transition. Firstly, hydrogen atoms and oxygen atoms in heavy aromatic hydrocarbons are captured by utilizing the dehydration property of sulfuric acid to obtain a graphene precursor, namely a graphene-like solid; however, since the graphene precursor does not have the structure and properties of graphene, graphene is obtained by sufficiently grinding and mixing graphene and a filler, and then performing exfoliation and thinning treatment at a high temperature. The filler can be uniformly distributed among the generated graphene precursors along with the temperature rise to the melting point of the filler, so that the mutual agglomeration among the graphene precursors is prevented; in addition, during cooling, phase separation occurs between the fillers, thereby forming the shape of graphene.

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

the method takes chemical primary product aromatic hydrocarbon with benzene ring as a carbon source, adopts a solvothermal method to convert a liquid aromatic hydrocarbon raw material into a solid carbon material in one step, and does not need a catalyst; the prepared graphene has thin sheet layer and good crystallinity. Meanwhile, the method can reduce the manufacturing cost of the graphene and improve the high added value utilization of chemical byproducts.

Drawings

Fig. 1 is a scanning electron microscope image of a graphene precursor prepared in example 1 of the present invention.

Fig. 2 is an X-ray diffraction pattern of the graphene precursor prepared in example 1 of the present invention.

Fig. 3 is a scanning electron microscope image of graphene prepared in example 1 of the present invention.

Fig. 4 is an X-ray diffraction pattern of graphene prepared in example 1 of the present invention.

Fig. 5 is a raman spectrum of the graphene-like sheet prepared in example 1 of the present invention.

Detailed Description

In order to better understand the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.

Example 1

A method for preparing graphene by taking heavy aromatics as raw materials comprises the following steps:

(1) slowly adding 30mL of concentrated sulfuric acid (with the concentration of 98%) into 30mL of tetrahydronaphthalene, heating to 180 ℃ for reacting for 4 hours, cooling to room temperature, filtering the reaction solution, repeatedly washing, and drying to obtain a graphene precursor;

(2) mixing the graphene precursor obtained in the step with a filler (NaCl/KCl mixed salt is adopted as the filler, the mass ratio of the NaCl/KCl mixed salt to the filler is 1:1) according to the mass ratio of 1:10, and grinding the mixture into uniform fine powder; and under the protection of argon, heating the fine powder mixture to 800 ℃ at a heating rate of 5 ℃/min, carrying out high-temperature treatment, keeping for 2h, cooling, washing and drying to obtain the graphene.

Fig. 1 shows a scanning photograph of a graphene precursor, which shows a lamellar stacked bulk structure, and the XRD spectrum of fig. 2 shows that after concentrated sulfuric acid treatment, liquid-phase heavy aromatic hydrocarbons are primarily converted into a graphene precursor having a graphite phase structure.

As shown in fig. 3(a) and (b), the graphene obtained in this example is a distinct lamellar structure, and the thickness of the lamellar layer is less than 10 nm.

The graphene obtained in the embodiment shows a typical characteristic peak of graphene, as shown in fig. 4; and FIG. 5 shows at 1374cm^-1And 1590cm^-1There are 2 characteristic peaks corresponding to the D peak and the G peak of graphene.

Example 2

A method for preparing graphene by taking heavy aromatics as raw materials comprises the following steps:

(1) slowly adding 30mL of sulfuric acid solution (with the concentration of 50%) into 30mL of tetrahydronaphthalene, mixing, heating to 180 ℃, reacting for 4 hours, cooling to room temperature, filtering the reaction solution, repeatedly washing, and drying to obtain a graphene precursor;

(2) mixing the graphene precursor obtained in the step with a filler (NaCl/KCl in a mass ratio of 1:1) according to a mass ratio of 1:10, and grinding the mixture into uniform fine powder; and under the protection of inert gas argon, the fine powder mixture is heated to 800 ℃ at a heating rate of 5 ℃/min, is subjected to high-temperature treatment, is kept for 2 hours, and is washed and dried after being cooled, so that the graphene is obtained.

Example 3

A method for preparing graphene by taking heavy aromatics as raw materials comprises the following steps:

(1) adding 30mL of concentrated sulfuric acid (with the concentration of 70%) into a mixed solution of 30mL of alkylbenzene and indan according to the volume ratio of 1:1, heating to 200 ℃ for reacting for 4 hours, cooling to room temperature, filtering the reaction solution, repeatedly washing and drying to obtain a graphene precursor;

(2) mixing the graphene precursor obtained by the reaction in the step with a filler (NaCl/KCl in a mass ratio of 1:1) according to a mass ratio of 1:10, and grinding the mixture into uniform fine powder; and under the protection of inert gas argon, the fine powder mixture is heated to 800 ℃ at a heating rate of 5 ℃/min, is subjected to high-temperature treatment, is kept for 2 hours, and is washed and dried after being cooled, so that the graphene is obtained.

Example 4

A method for preparing graphene by taking heavy aromatics as raw materials comprises the following steps:

(1) adding 30mL of concentrated sulfuric acid (with the concentration of 98%) into a mixed solution of 30mL of tetrahydronaphthalene and indane according to the volume ratio of 1:1, heating to 200 ℃ for reaction for 12 hours, cooling to room temperature, filtering the reaction solution, repeatedly washing and drying to obtain a graphene precursor;

(2) mixing the graphene precursor obtained by the reaction in the step with a filler (NaCl/KCl in a mass ratio of 1:1) according to a mass ratio of 1:100, and grinding the mixture into uniform fine powder; and under the protection of inert gas argon, the fine powder mixture is heated to 800 ℃ at a heating rate of 5 ℃/min, is subjected to high-temperature treatment, is kept for 2 hours, and is washed and dried after being cooled, so that the graphene is obtained. The graphene sheets obtained were thinner and dispersed better than in example 1.

Example 5

A method for preparing graphene by taking heavy aromatics as raw materials comprises the following steps:

(1) taking 30mL of petrochemical refinery byproduct heavy aromatic hydrocarbon (such as heavy aromatic oil and reformed heavy aromatic hydrocarbon, wherein the content of the heavy aromatic hydrocarbon is more than 80%), slowly adding 30mL of concentrated sulfuric acid (with the concentration of 98%), heating to 180 ℃ for reaction for 4 hours, cooling to room temperature, filtering the reaction solution, repeatedly washing and drying to obtain a graphene precursor;

(2) mixing the graphene precursor obtained by the reaction in the step with a filler KCl/LiCl (mass ratio, 1:1) according to a mass ratio of 1:10, and grinding into uniform fine powder; and under the protection of inert gas argon, the fine powder mixture is heated to 800 ℃ at a heating rate of 5 ℃/min, is subjected to high-temperature treatment, is kept for 2 hours, and is washed and dried after being cooled, so that the graphene is obtained.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, many modifications and changes can be made without departing from the inventive concept of the present invention, and these modifications and changes are within the protection scope of the present invention.