Method for preparing mesoporous carbon material by utilizing non-charring plastic through one-pot method

Abstract

The invention relates to a method for preparing a mesoporous carbon material by using non-charring plastic through a one-pot method, which comprises the following steps: uniformly mixing plastic and eutectic salt, carrying out carbonization reaction at 600-800 DEG C, soaking in olefine acid, washing with water, and drying to obtain the mesoporous carbon material. According to the method, non-charring waste plastic is used as a raw material, the mesoporous carbon material is prepared through a one-pot method, the process is simple, green and environment-friendly, the structure is controllable, and waste plastic treatment and high-value carbon material preparation can be achieved at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of waste resource utilization and relates to a method for preparing a mesoporous carbon material by using a non-carbon-forming plastic in a one-pot process. Background Art

[0002] As plastics are widely used, a large amount of waste plastics are generated and need to be dealt with. At present, the main methods of plastic treatment are incineration and landfill, which not only brings secondary pollution, but also wastes carbon resources. It is urgent to develop harmless and resource-based recycling technologies for waste plastics.

[0003] Plastics have a high carbon content and are ideal raw materials for preparing carbon materials. According to their pyrolysis properties, plastics can be divided into charring and non-charring. 56.1% of the total plastics are non-charring plastics, such as polyethylene (PE), polypropylene (PP), polystyrene (PS), etc. Non-charring plastics completely decompose into small molecular hydrocarbons during pyrolysis, do not produce pyrolytic carbon, and are difficult to pyrolyze and carbonize. The lack of a controllable preparation method for applicable carbon materials is a bottleneck problem that restricts the development of waste plastic carbonization technology.

[0004] At present, the main method for preparing carbon materials from non-carbon-forming plastics is chemical vapor deposition (Waste Management 2019, 87, 691-700). However, the preparation of catalysts for chemical vapor deposition is complex, costly, and difficult to recycle. Zhang et al. reported a self-generated pressure carbonization-KOH activation method to convert PE into porous carbon (ACS Sustainable Chemistry & Engineering 2019, 7 (4), 3801-3810). However, the two-step method is complicated to operate, and KOH activation will erode and destroy the graphite structure of the carbon material, reducing the electrical and mechanical properties of the material. Therefore, it is of great significance to develop a green, simple and feasible controllable carbonization method for non-carbon-forming plastics. Summary of the invention

[0005] The present invention aims to provide a method for preparing mesoporous carbon materials using a one-pot method of non-carbon-forming plastics, which can solve the problem of difficult controllable carbonization of non-carbon-forming plastics. It not only successfully prepares mesoporous carbon, but also solves the problem of resource application of waste plastics.

[0006] To achieve the above object, the technical solution of the present invention is as follows: A method for preparing mesoporous carbon material by a one-pot method using non-carbon-forming plastics comprises the following steps: evenly mixing the plastic with a eutectic salt, subjecting the plastic to a carbonization reaction at 600-800°C, then soaking the plastic in olefinic acid, washing the plastic with water, and drying the plastic to obtain the mesoporous carbon material.

[0007] Preferably, the particle size of the plastic is less than 10 mm.

[0008] Preferably, the mass ratio of the plastic to the eutectic salt is 1:4-10.

[0009] Preferably, the plastic is a non-charring plastic. More preferably, the non-charring plastic is one of low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP) or polystyrene (PS) or a mixture thereof in any proportion.

[0010] Preferably, the eutectic salt is a eutectic salt composed of metal chlorides with a melting point of 500-620° C. The eutectic salt is a eutectic salt composed of two or more of LiCl, NaCl, KCl, MgCl2, CaCl2, SrCl2, and BaCl2. More preferably, in the eutectic salt composed of KCl and CaCl2, the molar ratio of KCl to CaCl2 is 0.75:0.25.

[0011] Preferably, the carbonization reaction is carried out in a closed autoclave with a working pressure of >10 MPa, which is kept airtight during the reaction process, and high pressure is spontaneously generated by the decomposition of the plastic.

[0012] Preferably, the carbonization reaction time is 0.5~1h.

[0013] Preferably, the olefinic acid is hydrochloric acid.

[0014] Preferably, the soaking time is more than 12 hours.

[0015] The final product obtained by the reaction has a specific surface area of ​​100-600 m 2 / g of mesoporous carbon material. When the melting point of the selected eutectic salt is lower than 500°C, the product is mainly micron-sized carbon spheres; when the melting point of the selected eutectic salt is higher than 500°C, the product is mainly lamellar carbon material.

[0016] Compared with the existing technology, the present invention innovatively uses eutectic salt to regulate the structure of carbon materials during the autogenous pressure carbonization reaction, and converts non-carbon-forming plastics into mesoporous carbon materials in a one-pot method. Compared with the previous recycling and treatment methods, this method uses a one-pot method, can regulate the structure of carbon materials, has a simple process, low cost, and high product value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a scanning electron microscope photograph of the mesoporous carbon material prepared by using non-carbon-forming plastic and KCl / CaCl2 (0.75 / 0.25) eutectic salt in Example 1.

[0018] Figure 2This is a scanning electron microscope photograph of the mesoporous carbon material prepared in Example 2 using non-carbon-forming plastic and NaCl / CaCl2 (0.48 / 0.52) eutectic salt.

[0019] Figure 3 This is a scanning electron microscope photograph of the mesoporous carbon material prepared by using non-carbon-forming plastic and LiCl / MgCl2 (0.4 / 0.6) eutectic salt in Example 3;.

[0020] Figure 4 This is a scanning electron microscope photograph of the carbon material prepared in Comparative Example 1 using non-carbon-forming plastic and KCl / MgCl2 (0.7 / 0.3) eutectic salt.

[0021] Figure 5 This is a scanning electron microscope photograph of the carbon material prepared in Comparative Example 2 using non-carbon-forming plastic and KCl / NaCl (0.49 / 0.51) eutectic salt.

[0022] Figure 6 This is a scanning electron microscope photograph of the carbon material prepared using non-carbon-forming plastic and ZnCl2 in Comparative Example 3. DETAILED DESCRIPTION

[0023] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0024] Example 1 After the waste PE plastic was crushed into particles less than 10 mm in size, it was mixed and ground with KCl / CaCl2 (molar ratio 0.75 / 0.25, melting point 600°C) eutectic salt at a mass ratio of 1:10. The mixture was added to a high-pressure reactor, sealed and placed in a muffle furnace, heated to 700°C and kept warm for 30 min. After the reaction was completed, it was cooled to room temperature and the solid product was collected. The product was soaked in excess 1 M hydrochloric acid overnight and then washed with water until the pH was neutral. After filtration, it was dried in an oven at 80°C to obtain a carbon material.

[0025] Scanning electron microscope photos of carbon materials Figure 1 As shown in the figure, a clear pore structure can be observed. The physical adsorption instrument results show that the specific surface area is 415 m 2 / g, average pore size 5.2 nm. Example

[0026] The mixture of waste PE, PP, and PS (1:1:1) was crushed into particles less than 10 mm in size, and then mixed and ground with NaCl / CaCl2 (molar ratio 0.48 / 0.52, melting point 504°C) eutectic salt in a mass ratio of 1:4. The mixture was added to a high-pressure reactor, sealed, and placed in a muffle furnace, heated to 800°C and kept warm for 1 h. After the reaction was completed, it was cooled to room temperature and the solid product was collected. The product was soaked in excess 1M hydrochloric acid overnight and then washed with water until the pH was neutral. After filtration, it was dried in an oven at 80°C to obtain a carbon material.

[0027] Scanning electron microscope photos of carbon materials Figure 2 As shown in the figure, a clear pore structure can be observed. The physical adsorption instrument results show that the specific surface area is 160 m 2 / g, average pore size 10.2 nm. Example

[0028] After the waste PP was crushed into particles less than 10 mm in size, it was mixed and ground with LiCl / MgCl2 (molar ratio 0.4 / 0.6, melting point 570°C) eutectic salt at a mass ratio of 1:10. The mixture was added to a high-pressure reactor, sealed and placed in a muffle furnace, heated to 600°C and kept warm for 1 h. After the reaction was completed, it was cooled to room temperature and the solid product was collected. The product was soaked in excess 1 M hydrochloric acid overnight and then washed with water until the pH was neutral. After filtration, it was dried in an oven at 80°C to obtain a carbon material.

[0029] Scanning electron microscope photos of carbon materials Figure 3 As shown in the figure, a clear pore structure can be observed. The physical adsorption instrument results show that the specific surface area is 453 m 2 / g, average pore size 5.5nm.

[0030] Comparative Example 1 Compared with Example 1, most of the above are the same, except that in this example, the eutectic salt is KCl / MgCl2 (0.7 / 0.3) with a melting point of 423°C. Figure 4 As shown, it is mainly micron-sized carbon spheres with a specific surface area of ​​1.3 m 2 / g.

[0031] Compared with Example 1, most of the above are the same, except that in this example, the eutectic salt is KCl / NaCl (0.49 / 0.51), and the melting point is 657°C. Figure 5 As shown, it is mainly a lamellar carbon material with a specific surface area of ​​4.2m 2 / g.

[0032] Compared with Example 2, most of them are the same, the only difference is that in this example, the eutectic salt uses NaCl / ZnCl2 (0.24 / 0.76)2, whose melting point is 270°C. The morphology of the carbon material is as follows Figure 6 As shown, it is mainly micron-sized carbon spheres with a specific surface area of ​​2.1 m 2 / g. The melting point of ZnCl2-based molten salt is lower than that of ZnCl2 (318°C), and even lower than that of the eutectic salt required by this method (500-620°C). When other ZnCl2-based molten salts are used, such as LiCl / ZnCl2 (0.09 / 0.91, 294°C), KCl / ZnCl2 (0.36 / 0.64, 230°C), and CsCl / ZnCl2 (0.48 / 0.52, 263°C), the products are all micron-sized carbon spheres.

Claims

1. A method for preparing mesoporous carbon materials using a one-pot method of non-carbon-forming plastics, characterized in that: The plastic and the eutectic salt are uniformly mixed, carbonized at 600-800°C, then immersed in olefinic acid, washed with water and dried to obtain the mesoporous carbon material.

2. The method according to claim 1, characterized in that The particle size of the plastic is less than 10 mm.

3. The method according to claim 1, characterized in that The mass ratio of the plastic to the eutectic salt is 1:4-10.

4. The method according to claim 1, characterized in that The plastic is a non-charcoal-forming plastic.

5. The method according to claim 4, characterized in that The non-carbon-forming plastic is one of low-density polyethylene, high-density polyethylene, polypropylene or polystyrene, or a mixture in any proportion.

6. The method according to claim 1, characterized in that The eutectic salt is a eutectic salt composed of metal chloride salts with a melting point of 500-620°C.

7. The method according to claim 6, characterized in that The eutectic salt is a eutectic salt composed of two or more of LiCl, NaCl, KCl, MgCl2, CaCl2, SrCl2, and BaCl2; more preferably, in the eutectic salt composed of KCl and CaCl2, the molar ratio of KCl to CaCl2 is 0.75:0.

25.

8. The method according to claim 1, characterized in that: The carbonization reaction time is 0.5~1h.

9. The method according to claim 1, characterized in that: The olefinic acid is hydrochloric acid.

10. The method according to claim 1, characterized in that The soaking time is more than 12 hours.

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