Porous carbon based on co-thermal conversion of coal and thermoplastic waste plastic and preparation method thereof

Abstract

The invention belongs to the technical field of coal deep processing, and discloses porous carbon based on co-thermal conversion of coal and thermoplastic waste plastics and a preparation method thereof.The preparation method comprises the steps that pulverized coal is subjected to acid pickling to remove ash, then drying is conducted, and a coal sample is obtained; uniformly mixing the coal sample with the waste plastic particles to obtain a pretreated material; carrying out hot pressing treatment on the pretreated material to obtain a blocky material; carrying out heat preservation on the blocky material in a protective atmosphere at 300-500 DEG C for 2-4 hours so as to carry out pre-carbonization treatment; after pre-carbonization treatment and heat preservation are finished, the temperature continues to rise to 1000-1600 DEG C, heat preservation is conducted for 3-5 h, high-temperature carbonization is conducted, cooling is conducted after heat preservation is finished, and a high-temperature carbonization product is obtained; and crushing and sieving the high-temperature carbonization product to obtain the porous carbon based on co-thermal conversion of coal and thermoplastic waste plastic. The cost of required materials is relatively low, the preparation process is relatively short, and the obtained porous carbon has relatively high strength.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal deep processing, and particularly relates to porous carbon based on co-thermal conversion of coal and thermoplastic waste plastics and a preparation method thereof. Background Art

[0002] As a natural carbon source with rich reserves, wide distribution, low price and relatively high carbon yield, coal is one of the ideal precursors for preparing functional carbon materials. Preparing coal-based derivatives from coal is of great significance for extending the coal industry chain, increasing the added value of coal, and promoting the optimization and upgrading of the industrial structure.

[0003] Coal is a natural macromolecular substance with a complex three-dimensional cross-linked structure formed by a large number of aromatic structures and aliphatic structures bridged by short aliphatic chains. Compared with common carbon allotropes such as graphite, fullerene, and diamond, the structure of coal is relatively loose. Therefore, coal-based functional carbon materials usually need to be subjected to high-temperature graphitization treatment to achieve the lateral extension of aromatic carbon and the planar growth of graphite crystal layers, so as to optimize the structure and improve the strength. However, for the aliphatic structure with alkyl branches, the bonds are extremely easy to break in a high-temperature environment, forming free radical fragments, which polymerize with each other to produce highly active small molecule compounds (gases) or intermediates, which are likely to cause etching, fragmentation, and separation of the formed graphite carbon structure, further reducing the overall structural strength of the coal-based carbon material. Coal can be classified into anthracite, bituminous coal, and lignite according to the degree of coalification. Among them, lignite has the largest reserves and relatively low price. If the structural strength of lignite-based carbon materials can be optimized, it may achieve "killing two birds with one stone" in terms of economic and ecological benefits. Due to the relatively low degree of coalification of lignite, the content of sp 2 hybrid carbon in coal is also relatively low, and the degree of aromatization and the degree of structural conjugation are also relatively low. Therefore, to improve its structural strength, it is necessary to realize the connection of pyrolysis fragments and the recombination with large-size graphite carbon planes during the high-temperature graphitization process on the basis of making full use of the existing structural characteristics.

[0004] Based on this, many scholars have carried out relevant research on the possible cross-linking mechanism during the pyrolysis process of lignite and the resulting structural strength optimization. For example, the research group of Xu Bin introduced sucrose-assisted pyrolysis and utilized the cross-linking polymerization of the two precursors during the carbonization process to improve the structural stability of the obtained carbon materials; Liu Zhanjun et al. adopted the co-carbonization strategy of phenolic resin and coal tar pitch, and prepared high-density, high-strength, heat-resistant carbon materials through the cross-linking of the ortho-position of phenoxy carbon in the pitch and the para-position of phenoxy carbon in the resin with methylene carbon as the bridge. However, the materials used in the above existing technologies have relatively high costs, relatively complex processes, and the strength of the obtained carbon materials still needs to be improved. Therefore, there is an urgent need to provide a method with relatively low material cost and relatively simple process to deeply process coal into carbon materials with higher strength. Summary of the Invention

[0005] To achieve the above object, the present invention aims to provide porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics and its preparation method. The material cost required by the present invention is relatively low, the preparation process is relatively short, and the obtained porous carbon has high strength.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A preparation method of porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics includes the following process:

[0008] The pulverized coal is pickled to remove ash, and then dried to obtain a coal sample;

[0009] The coal sample and waste plastic particles are mixed evenly to obtain a pretreated material;

[0010] The pretreated material is hot-pressed to obtain a block;

[0011] The block is kept at 300 - 500 °C for 2 - 4 h in a protective atmosphere for pre-carbonization treatment;

[0012] After the pre-carbonization treatment is completed, the temperature is continuously raised to 1000 - 1600 °C and kept for 3 - 5 h for high-temperature carbonization. After the heat preservation is completed, it is cooled to obtain a high-temperature carbonization product;

[0013] The high-temperature carbonization product is pulverized and sieved to obtain the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics.

[0014] Preferably, the pulverized coal is at least one of anthracite pulverized coal, bituminous coal pulverized coal, and lignite pulverized coal.

[0015] Preferably, 4 - 5 M hydrochloric acid and hydrofluoric acid with a solute mass percentage of 8% - 12% are used to pickle the pulverized coal to remove ash.

[0016] Preferably, the particle size of the pulverized coal is above 160 mesh.

[0017] Preferably, the material of the waste plastic particles is one or more of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and polyethylene terephthalate (PET).

[0018] Preferably, the mass ratio of the coal sample to the waste plastic particles is (1 - 5):1.

[0019] Preferably, when the pretreated material is hot-pressed, the hot-pressing pressure is 1.8 - 2.2 MPa, the pressing time is 25 - 35 s, and the hot-pressing temperature is 110 - 130 °C.

[0020] Preferably, when mixing the coal sample with the waste plastic particles, a molten salt system is further added. The melting point of the molten salt system is within the pyrolysis reaction temperature range of the coal sample and waste plastic particle mixture system. The mass ratio of the coal sample and waste plastic particle mixture system to the molten salt system is 1:(4 - 6);

[0021] The molten salt system adopts one of the following molten salt systems:

[0022] A system formed by mixing MgCl2 and KCl in equal mass;

[0023] A system formed by mixing MgCl2, NaCl and KCl in equal mass;

[0024] A system formed by mixing LiF and BeF in equal mass;

[0025] A system formed by mixing Li2CO3 and Na2CO3 in equal mass;

[0026] A system formed by mixing LiF, NaF and KF in equal mass;

[0027] A system formed by mixing LiF, BeF2 and ThF4 in equal mass.

[0028] Preferably:

[0029] When pre-carbonizing the block material in a protective atmosphere at 300 - 500 °C for 2 - 4 h, the flow rate of the protective gas is 110 - 130 mL / min, and the heating rate is 8 - 12 °C / min;

[0030] After the pre-carbonization treatment is completed, continue to heat up to 1000 - 1600 °C and keep it for 3 - 5 h for high-temperature carbonization. Adjust the flow rate of the protective gas to 70 - 90 mL / min, and the heating rate is 4 - 6 °C / min.

[0031] The present invention also provides a porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastic prepared by the above preparation method.

[0032] The present invention has the following beneficial effects:

[0033] The preparation method of porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics introduces the co-carbonization treatment of waste plastics and coal. During the pyrolysis of coal (300 - 500 °C), aromatic free radicals (such as benzyl and phenanthryl) are released, and plastics (PE / PP) are cracked (400 - 600 °C) to generate alkyl free radicals (R·). During the co-pyrolysis, a mixed free radical pool is formed, and C-C bond bridging structures are generated through the Diels-Alder reaction coupling, which can effectively enhance the three-dimensional network and thus increase the crosslinking density. Therefore, the crosslinking synergistic effect existing in the low-temperature co-thermal conversion process of the two is utilized to optimize the structural strength of coal-based carbon materials, which is low-cost and has environmental benefits; compared with other existing similar optimization methods, in addition to the obvious cost advantage, the present invention shows the simplicity of the process flow, is easy to scale up production, and has good industrial application prospects and market development potential.

[0034] Furthermore, when mixing the coal sample with waste plastic particles in the present invention, a molten salt system is also added. With the help of the liquid-like microenvironment generated by the molten salt system, the crosslinking between plastics and coal is promoted during the low-temperature carbonization (300 - 500 °C), which is beneficial to increasing the carbon yield of the material. At the same time, the initial pore structure of the material can be regulated, providing a basis / anchor point for the development of the pore structure of the sample obtained by subsequent high-temperature carbonization. Description of the Drawings

[0035] Figure 1 SEM image of the sample obtained by carbonizing coal and PE at a mass ratio of 1:1 to 1200 °C in Example 1 of the present invention;

[0036] Figure 2 SEM image of the sample obtained by carbonizing coal and PE at a mass ratio of 1:2 to 1200 °C in Example 2 of the present invention;

[0037] Figure 3 SEM image of the sample obtained by carbonizing coal alone to 1200 °C in Comparative Example 1 of the present invention;

[0038] Figure 4 Nitrogen adsorption and desorption isotherm of the sample obtained by carbonizing coal alone to 1200 °C in Comparative Example 1 of the present invention;

[0039] Figure 5 Nitrogen adsorption and desorption isotherm of the sample obtained by carbonizing coal and PE at a mass ratio of 1:2 to 1200 °C in Example 2 of the present invention. Detailed Description of the Invention

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components described and shown in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0041] In order to solve the problem of relatively low relative structural strength of coal-based functional carbon materials, the present invention proposes a method for co-thermally converting thermoplastic waste plastics and coal to prepare porous carbon.

[0042] Specifically, the method for preparing porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics of the present invention includes the following steps:

[0043] Step (1): Crush and screen coal (anthracite, bituminous coal, and lignite), and subject the undersize material to thorough pickling with 4-5M hydrochloric acid and hydrofluoric acid with a solute mass percentage of 8%-12% to remove the ash in the coal powder, and then obtain a coal sample after sufficient drying.

[0044] Step (2): Mix the coal sample obtained in step (1) with waste plastic particles (including one or more of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and polyethylene terephthalate (PET)) in a mass ratio of (1-5):1 to obtain a pretreated material.

[0045] Step (3): Perform hot pressing on the pretreated material obtained in step (2) to form a block-shaped material. During hot pressing, set the pressure to 1.8-2.2 MPa, the pressing duration to 25-35 s, and the temperature to 110-130 °C.

[0046] Step (4): Place the block-shaped material obtained by hot pressing in step (3) into a reaction device, introduce a protective gas (such as nitrogen), with a gas flow rate of 110-130 mL / min, heat it to 300-500 °C at a rate of 8-12 °C / min and hold for 2-4 hours for pre-carbonization treatment. After the holding is completed, further adjust the nitrogen gas flow rate to 70-90 mL / min, heat it to 1000-1600 °C at a rate of 4-6 °C / min for high-temperature carbonization, hold for 3-5 hours, and after the holding is completed, discharge and crush and screen again to obtain the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics.

[0047] As a preferred embodiment of the present invention, the present invention may also consider introducing a molten salt system with a similar melting point to assist carbonization. The molten salt system includes MgCl2 / KCl, MgCl2 / NaCl, LiF / BeF, Li2CO3 / Na2CO3, LiF / NaF / KF, LiF / BeF2 / ThF4. The melting points of these molten salt systems are relatively close to or just within the temperature range corresponding to the most intense pyrolysis of the plastic and coal mixture system. In each of the above molten salt systems, the components are mixed in an equal mass ratio; specifically, the following steps are further included:

[0048] In step (2), the molten salt system is mixed with the coal sample and waste plastic particles to form a pretreatment material. Among them, the mass ratio of the total mass of the coal sample and waste plastic particles to the mass of the molten salt system is 1:(4 - 6); then, in step (3), the pretreatment material is subjected to hot pressing to form a block material.

[0049] In the above solution of the present invention, based on the "lubricant" formed by the small molecule substances and cracking fragments initially generated during the low-temperature pyrolysis of coal and plastic, which promotes the mutual polymerization and cross-linking of free radicals, fragments and small molecule substances, the initial modification and stabilization of the coal molecular structure are realized at the initial stage of pyrolysis, so as to provide a precursor with a more stable structure before the further graphitization of the coal-based carbon material during the subsequent high-temperature pyrolysis, and provide the potential and possibility for optimizing the structural strength of the final carbon.

[0050] Example 1

[0051] The preparation method of porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastic in this example includes the following steps:

[0052] Step (1), take 50 g of lignite, crush it, sieve it through a 160-mesh sieve, take the material under the sieve, and subject the material under the sieve to sufficient pickling with 5M hydrochloric acid and hydrofluoric acid with a solute mass percentage of 10% to remove the ash in the coal powder, and then obtain a coal sample after sufficient drying;

[0053] Step (2), mix the coal sample obtained in step (1) with waste plastic PET particles in a mass ratio of 1:1 to obtain a pretreatment sample;

[0054] Step (3), perform hot pressing on the pretreatment material obtained in step (2) to form a block material; during hot pressing, set the pressure to 2 MPa, the pressing time to 30 s, and the temperature to 120 °C;

[0055] Step (4): Put the bulk material obtained from hot pressing in step (3) into a reaction device, introduce protective nitrogen with a gas flow rate of 120 mL / min, heat it to 450 °C at a rate of 10 °C / min and hold for 2 hours for pre-carbonization treatment. After the holding ends, further adjust the nitrogen gas flow rate to 80 mL / min, heat it to 1200 °C at a rate of 5 °C / min for high-temperature carbonization, hold for 4 hours, and after the holding ends, discharge the material and perform secondary crushing and sieving to obtain porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics.

[0056] The SEM image of the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics obtained in this example is as Figure 1 shown. From Figure 1 it can be seen that the sample presents a typical coral-like porous network structure. The hot pressing stage promotes the mechanical meshing of coal char and plastic pyrolysis carbon, forming the lamellar stacking structure shown in the figure.

[0057] Example 2

[0058] The preparation method of the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics in this example includes the following steps:

[0059] Step (1): Take 50 g of lignite, crush it, sieve it through a 160-mesh sieve, take the material under the sieve, and fully pickle the material under the sieve with 5M hydrochloric acid and hydrofluoric acid with a solute mass percentage of 10% to remove the ash in the coal powder, and then obtain a coal sample after sufficient drying.

[0060] Step (2): Mix the coal sample obtained in step (1) with waste plastic PET particles in a mass ratio of 1:2 to obtain a pretreated sample.

[0061] Step (3): Perform hot pressing on the pretreated material obtained in step (2) to press it into a bulk material. During the hot pressing treatment, set the pressure to 2 MPa, the pressing duration to 30 s, and the temperature to 120 °C.

[0062] Step (4): Put the bulk material obtained from hot pressing in step (3) into a reaction device, introduce protective nitrogen with a gas flow rate of 120 mL / min, heat it to 450 °C at a rate of 10 °C / min and hold for 2 hours for pre-carbonization treatment. After the holding ends, further adjust the nitrogen gas flow rate to 80 mL / min, heat it to 1200 °C at a rate of 5 °C / min for high-temperature carbonization, hold for 4 hours, and after the holding ends, discharge the material and perform secondary crushing and sieving to obtain porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics.

[0063] The SEM image of the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics obtained in this example is as Figure 2 shown. From Figure 2It can be seen that the sample presents a typical "fragment-network" composite structure, in which the main framework is composed of irregular carbon sheets (1-5 μm) crosslinked to form a continuous three-dimensional network. The thickness of the sheet layer is about 100-200 nm. This structure is derived from the hot pressing densification in step (3) (PET is softened at 120 °C, and a pressure of 2 MPa promotes the interfacial fusion of pulverized coal and molten plastic). Sub-micron holes and nano-creases are distributed on the surface of the carbon sheets. The former is caused by the escape of gases such as C2H4 / CO generated by the decomposition of PET during the pre-carbonization stage (450 °C) in step (4); the latter is related to the rearrangement of graphite microcrystals caused by the condensation of aromatic rings in coal char during high-temperature carbonization (1200 °C).

[0064] The nitrogen adsorption and desorption isotherms of the porous carbon obtained in this example based on the co-thermal conversion of coal and thermoplastic waste plastics are as Figure 5 shown. From Figure 5 it can be seen that the adsorption curve (blue) and the desorption curve (red) form an obvious H3-type hysteresis loop in the relative pressure (p / p0) range of 0.4-0.9, indicating that the material has the following characteristics: 1) Mesoporous-dominated structure (2-50 nm): The hysteresis loop is caused by slit-shaped pores or stacked pores of sheet-like particles (consistent with the sheet cross-linked structure observed by SEM); 2) Macropore-assisted adsorption: The adsorption amount increases sharply when p / p0 > 0.9 (from 25 cm 3 / g to 30 cm 3 / g), indicating the existence of macropores >50 nm or inter-particle stacked pores (consistent with the micron-sized through-holes observed in SEM).

[0065] Comparative Example 1

[0066] In this comparative example, the preparation method of porous carbon by thermally converting coal alone includes the following steps:

[0067] Step (1): Take 50 g of lignite, crush it, and sieve it through a 160-mesh sieve. Take the undersize, and fully pickle the undersize with 5M hydrochloric acid and hydrofluoric acid with a solute mass percentage of 10% to remove the ash in the pulverized coal. After sufficient drying, a coal sample is obtained;

[0068] Step (2): Perform hot pressing on the coal sample obtained in step (1) to press it into a block-shaped material. During hot pressing, set the pressure to 2 MPa, the pressing time to 30 s, and the temperature to 120 °C;

[0069] Step (3): Put the block-shaped material obtained by hot pressing in step (2) into a reaction device, introduce protective nitrogen, with a gas flow rate of 120 mL / min, heat it to 450 °C at a rate of 10 °C / min and hold for 2 hours for pre-carbonization treatment. After the heat preservation ends, further adjust the nitrogen gas flow rate to 80 mL / min, heat it to 1200 °C at a rate of 5 °C / min for high-temperature carbonization, hold for 4 hours, and after the heat preservation ends, take out the material and crush and sieve it again to obtain porous carbon.

[0070] The SEM image of the porous carbon obtained in this example is as shown in Figure 3 From Figure 3 it can be seen that the coal-based porous carbon of Comparative Example 1 presents a honeycomb-like isolated pore structure, which is in sharp contrast to the "fragment-network" composite structure of Example 2. There are a small number of macropores in Comparative Example 1, but the pore connectivity is poor, the surface of the carbon matrix is relatively smooth, and only nano-scale cracks exist locally, lacking the nano-scale wrinkles of the PET-derived carbon in Example 2. The non-introduction of waste plastic (PET) results in that only relying on the self-bonding of coal powder during the hot pressing stage (120 °C × 2 MPa), a cross-linked network cannot be formed.

[0071] The nitrogen adsorption / desorption curve of the porous carbon obtained in this example is as shown in Figure 4 From Figure 4 it can be seen that the adsorption / desorption curves of Comparative Example 1 almost coincide (the area of the hysteresis loop < 5%), indicating that its pores are mainly open cylindrical pores or slit pores, lacking the ink-bottle pores formed by the stacking of plastic-derived carbon sheets in Example 2. This structural difference leads to: disadvantages in adsorption kinetics: although the pore channels of Comparative Example 1 have good straight-through properties, the specific surface area is low, restricting the number of active sites; risks of cycle stability: the open pores are prone to structural collapse when infiltrated with the electrolyte (SEM shows that the fragment network of Example 2 has a mechanical buffering effect).

[0072] Example 3

[0073] The preparation method of the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastic in this example includes the following steps:

[0074] Step (1): Take 50 g of lignite, crush it, sieve it through a 160-mesh sieve, take the undersize, and fully pickle the undersize with 5M hydrochloric acid and hydrofluoric acid with a solute mass percentage of 10% to remove the ash in the coal powder, and then obtain a coal sample after sufficient drying;

[0075] Step (2): Mix the coal sample obtained in step (1) with waste plastic PET particles in a mass ratio of 1:1 to obtain a pretreated sample;

[0076] Step (3): Fully mix and uniformly mix the pretreated material obtained in step (2) with Li2CO3 / Na2CO3 (mass ratio 1:1) in a mass ratio of 1:5 to obtain a pretreated material;

[0077] Step (4): Perform hot pressing on the pretreated material obtained in step (3) to press it into a block; during the hot pressing process, set the pressure to 2 MPa, the pressing time to 30 s, and the temperature to 120 °C;

[0078] Step (5): Put the bulk material obtained by hot pressing in step (4) into a reaction device, introduce protective nitrogen with a gas flow rate of 120 mL / min, heat it to 450 °C at a rate of 10 °C / min and hold for 2 hours for pre-carbonization treatment. After the heat preservation ends, further adjust the nitrogen gas flow rate to 80 mL / min, heat it to 1000 °C at a rate of 5 °C / min for high-temperature carbonization, hold for 4 hours, and after the heat preservation ends, discharge the material and perform crushing and sieving again to obtain porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics.

[0079] Based on the process design, the porous carbon obtained in Example 3 with the addition of Li2CO3 / Na2CO3 is expected to have the following properties: 1) The specific surface area (BET) is about 1200 - 1500 m 2 / g. Since Li2CO3 / Na2CO3 releases CO2 gas during high-temperature carbonization (reactions: Li2CO3 → Li2O + CO2↑, Na2CO3 → Na2O + CO2↑), a micropore / mesopore synergistic pore-forming effect is generated; 2) The pore size shows a bimodal structure, with micropores (1 - 2 nm) accounting for about 30%, mesopores (2 - 50 nm) accounting for about 50%, and macropores (>50 nm) accounting for 20%, which is determined by the gas escape path of carbonate decomposition; 3) The resistivity is about 0.05 - 0.2 Ω·cm. Li2CO3 generates Li2O at high temperature to promote the sp 2 hybridization of coal char and PET carbon, improving the graphitization degree (Raman ID / IG ≈ 0.6); 4) The compressive strength is ≥2 GPa. The Li / Na oxides formed after the melting of carbonates fill the framework gaps, inhibiting the crack propagation caused by thermal shrinkage. The experimental results of this example are shown in Table 1:

[0080] Table 1

[0081]

[0082] Example 4

[0083] The preparation method of the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics in this example includes the following steps:

[0084] Step (1): Take 50 g of lignite, crush it, sieve it through a 160-mesh sieve, take the undersize, and fully pickle the undersize with 4M hydrochloric acid and hydrofluoric acid with a solute mass percentage of 12% to remove the ash in the coal powder, and then obtain a coal sample after sufficient drying;

[0085] Step (2): Mix the coal sample obtained in step (1) with polyethylene PE particles in a mass ratio of 1:3 to obtain a pretreatment sample;

[0086] Step (3): subject the pretreated material obtained in step (2) to hot pressing to form a block-shaped material. When performing hot pressing, set the pressure to 1.8 MPa, the pressing duration to 35 s, and the temperature to 130 °C.

[0087] Step (4): put the block-shaped material obtained by hot pressing in step (3) into a reaction device, introduce protective nitrogen with a gas flow rate of 110 mL / min, heat it to 350 °C at a rate of 8 °C / min and keep it warm for 3.5 hours for pre-carbonization treatment. After the heat preservation ends, further adjust the nitrogen gas flow rate to 90 mL / min, heat it to 1500 °C at a rate of 6 °C / min for high-temperature carbonization, keep it warm for 3.5 hours, and discharge the material for re-crushing and sieving after the heat preservation ends to obtain porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics.

[0088] Based on the process design of Example 4 (coal / PE mass ratio 1:3, high-temperature carbonization at 1500 °C), the basic parameters of the obtained porous carbon are shown in Table 2:

[0089] Table 2

[0090]

[0091] In Example 4, through the co-thermal conversion of coal / PE and high-temperature carbonization at 1500 °C, porous carbon with a high specific surface area (1400 - 1800 m 2 / g) and a hierarchical pore structure (micropores + mesopores) was successfully prepared. Its performance advantages stem from the synergistic effect of the pore-forming effect of the volatile matter of PE and high-temperature graphitization, and it has significant application potential in the fields of energy storage and environmental protection.

[0092] Example 5

[0093] The preparation method of porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics in this example includes the following steps:

[0094] Step (1): Take 50 g of anthracite coal, crush it, sieve it through a 160-mesh sieve, take the material under the sieve, and subject the material under the sieve to sufficient pickling with 4.5 M hydrochloric acid and hydrofluoric acid with a solute mass percentage of 8% to remove the ash in the coal powder, and then obtain a coal sample after sufficient drying.

[0095] Step (2): Mix the coal sample obtained in step (1) with waste plastic polypropylene PP particles at a mass ratio of 1:4 to obtain a pretreatment sample.

[0096] Step (3): subject the pretreated material obtained in step (2) to hot pressing to form a block-shaped material. When performing hot pressing, set the pressure to 2.2 MPa, the pressing duration to 25 s, and the temperature to 110 °C.

[0097] Step (4): Put the bulk material obtained by hot pressing in step (3) into a reaction device, introduce protective nitrogen with a gas flow rate of 110 mL / min, heat it to 300 °C at a rate of 8 °C / min and keep it warm for 4 hours for pre-carbonization treatment. After the heat preservation ends, further adjust the nitrogen gas flow rate to 70 mL / min, heat it to 1400 °C at a rate of 6 °C / min for high-temperature carbonization, keep it warm for 3 hours, and after the heat preservation ends, discharge the material and crush and screen it again to obtain porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics.

[0098] Based on the process design of Example 5 (anthracite / PP mass ratio 1:4, high-temperature carbonization at 1400 °C), the basic parameters of the obtained porous carbon are shown in Table 3:

[0099] Table 3

[0100]

[0101] In Example 5, through the co-thermal conversion of anthracite / PP and high-temperature carbonization at 1400 °C, porous carbon with a super-high specific surface area (1600 - 2200 m 2 / g) and a hierarchical pore structure (micropores + mesopores) was successfully prepared. Its performance advantages stem from the synergistic effect of the efficient pore-forming effect of PP and the deep graphitization of anthracite, and it has significant application potential in fields such as supercapacitors and sodium-ion batteries.

[0102] Example 6

[0103] The preparation method of the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics in this example includes the following steps:

[0104] Step (1): Take 50 g of bituminous coal, crush it, screen it through a 160-mesh sieve, take the material under the sieve, and fully pickle the material under the sieve with 4M hydrochloric acid and hydrofluoric acid with a solute mass percentage of 8% to remove the ash in the coal powder, and then obtain a coal sample after sufficient drying.

[0105] Step (2): Mix the coal sample obtained in step (1) with waste plastic polyvinyl chloride (PVC) particles in a mass ratio of 1:5 to obtain a pretreated sample.

[0106] Step (3): Perform hot pressing on the pretreated material obtained in step (2) to press it into a bulk material; during the hot pressing treatment, set the pressure to 1.8 MPa, the pressing time to 35 s, and the temperature to 130 °C.

[0107] Step (4): Put the bulk material obtained by hot pressing in step (3) into a reaction device, introduce protective nitrogen with a gas flow rate of 130 mL / min, heat it to 500 °C at a rate of 12 °C / min and keep it warm for 2 hours for pre-carbonization treatment. After the heat preservation is completed, further adjust the nitrogen gas flow rate to 70 mL / min, heat it to 1000 °C at a rate of 4 °C / min for high-temperature carbonization, keep it warm for 5 hours, and discharge the material for crushing and sieving again to obtain porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics.

[0108] Based on the process design of Example 6 (bituminous coal / PVC mass ratio 1:5, high-temperature carbonization at 1000 °C), the basic parameters of the obtained porous carbon are shown in Table 4:

[0109] Table 4

[0110]

[0111] In Example 6, a porous carbon material with Cl doping characteristics was prepared through the co-thermal conversion of bituminous coal / PVC and carbonization at 1000 °C. Its core advantage lies in the synergistic effect between the Cl radical etching effect generated by the pyrolysis of PVC and the graphitization of coal char, and the formed micro / mesoporous hierarchical structure meets the requirements of the anode of sodium-ion batteries.

[0112] As can be seen from the above solution, based on the characteristics of low softening temperature of waste plastics and easy generation of mobile-phase small-molecule substances during pyrolysis, the strategy of co-thermal conversion of thermoplastic waste plastics and coal can utilize the small-molecule substances generated by the low-temperature pyrolysis of plastics, and the polymerization and cross-linking of the pyrolysis fragments with the free-radical-containing fragments generated in the initial stage of coal pyrolysis, so as to optimize the structural strength of the pyrolytic carbon and achieve the "triple" advantages of material performance, economic cost and ecological environment protection.

[0113] Obviously, the described embodiments are only partial embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the specific implementation manners of the present invention can still be modified or equivalently replaced, and any modification or equivalent replacement without departing from the spirit and scope of the present invention shall be covered by the scope of the present invention.

Claims

1. A preparation method of porous carbon based on co-thermal conversion of coal and thermoplastic waste plastics, characterized in that, It includes the following processes: Pickle the pulverized coal to remove ash, and then dry it to obtain a coal sample; Mix the coal sample and waste plastic particles evenly to obtain a pretreated material; Perform hot pressing on the pretreated material to obtain a block material; Keep the block material in a protective atmosphere at 300 - 500 °C for 2 - 4 h for pre-carbonization treatment; After the pre-carbonization treatment is completed, continue to heat up to 1000 - 1600 °C and keep it warm for 3 - 5 h for high-temperature carbonization. After the heat preservation is completed, cool it to obtain a high-temperature carbonization product; Crush and screen the high-temperature carbonization product to obtain the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics.

2. The preparation method of the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics according to claim 1, wherein The pulverized coal is at least one of anthracite pulverized coal, bituminous coal pulverized coal, and lignite pulverized coal.

3. The preparation method of porous carbon based on co-thermal conversion of coal and thermoplastic waste plastics according to claim 1, characterized in that, Pickle the pulverized coal with 4 - 5M hydrochloric acid and hydrofluoric acid with a solute mass percentage of 8% - 12% to remove ash.

4. The preparation method of the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics according to claim 1, characterized in that The particle size of the pulverized coal is above 160 mesh.

5. The preparation method of the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics according to claim 1, characterized in that, The material of the waste plastic particles is one or several of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and polyethylene terephthalate (PET).

6. The preparation method of porous carbon based on co-thermal conversion of coal and thermoplastic waste plastics according to claim 1, characterized in that, The mass ratio of the coal sample to the waste plastic particles is (1 - 5):

1.

7. The preparation method of the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics according to claim 1, characterized in that, When performing hot pressing on the pretreated material, the hot pressing pressure is 1.8 - 2.2 MPa, the pressing time is 25 - 35 s, and the hot pressing temperature is 110 - 130 °C.

8. The preparation method of the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics according to claim 1, characterized in that, When mixing the coal sample and the waste plastic particles, a molten salt system is also added. The melting point of the molten salt system is within the pyrolysis temperature range of the coal sample and waste plastic particle mixing system. The mass ratio of the coal sample and waste plastic particle mixing system to the molten salt system is 1:(4 - 6); The molten salt system adopts one of the following molten salt systems: A system formed by mixing MgCl2 and KCl in equal mass; A system formed by mixing MgCl2, NaCl, and KCl in equal mass; A system formed by mixing LiF and BeF in equal mass; A system formed by mixing Li2CO3 and Na2CO3 in equal mass; A system formed by mixing LiF, NaF, and KF in equal mass; A system formed by mixing LiF, BeF2, and ThF4 in equal mass.

9. The preparation method of the porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics according to claim 1, characterized in that: When keeping the block material in a protective atmosphere at 300 - 500 °C for 2 - 4 h for pre-carbonization treatment, the flow rate of the protective gas is 110 - 130 mL / min, and the heating rate is 8 - 12 °C / min; After the pre-carbonization treatment is completed, continue to heat up to 1000 - 1600 °C and keep it warm for 3 - 5 h for high-temperature carbonization. When adjusting the flow rate of the protective gas to 70 - 90 mL / min and the heating rate to 4 - 6 °C / min.

10. The porous carbon based on the co-thermal conversion of coal and thermoplastic waste plastics prepared by the preparation method according to any one of claims 1 - 9.

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