Method for preparing multi-stage porous hard carbon by pyrolyzing waste asphalt with gradient temperature control

Abstract

The present invention discloses a method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, which includes: separating the waste asphalt mixture by the solvent method to separate the oil from the aggregate; heating the waste asphalt mixed solution to distill to obtain the waste asphalt material, and subjecting the waste asphalt to high-temperature stirring in water or treatment by the solvothermal method; pre-pyrolyzing at 100°C to 300°C for 1 h to 10 h under a nitrogen atmosphere or an argon atmosphere; performing oxygen-rich treatment at 200°C to 400°C in an oxygen atmosphere; ultrasonically cleaning with an acid solution or an alkali solution; performing high-temperature pyrolysis at 600°C to 1600°C for 1 h to 5 h, with the pyrolysis atmosphere being argon or nitrogen, and obtaining the waste asphalt hard carbon material after cooling to room temperature; ball-milling and screening to obtain the anode material for lithium / sodium / potassium ion batteries. The present invention controls the morphology of the carbon material by the method of first oxygen-rich treatment and then high-temperature carbonization, enabling it to be used as the anode material for lithium / sodium / potassium ion batteries, turning waste asphalt into a valuable resource and realizing high-value utilization.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste asphalt recycling, and relates to a method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, which can be applied to lithium / sodium / potassium ion batteries. Background Art

[0002] China's highway infrastructure has shifted from the stage of "equal emphasis on construction and maintenance" to the stage of "major maintenance". Every year, up to 200 million tons of waste asphalt mixture are generated nationwide, but the recycling rate of its waste materials is relatively low, resulting in serious waste of resources and damage to the ecological environment, which is not conducive to the comprehensive green transformation of economic and social development. It is urgent to increase the comprehensive utilization of waste resources in engineering construction, promote the resource utilization of waste materials such as waste pavement, asphalt, and construction waste, and improve the recycling rate of waste asphalt pavement materials on expressways and ordinary national and provincial trunk highways.

[0003] At present, the recycling of waste asphalt mixture in China mainly uses the direct mixing of new and old materials, resulting in low-quality recycled mixtures and extremely low utilization rate of old materials. At the same time, as the degree of asphalt aging increases, the oil content of asphalt becomes less, the asphaltene and resin increase, and asphalt will gradually become brittle and hard during the aging process, and there are certain limitations in reusing it for road surfaces.

[0004] At the same time, with the rapid expansion of the new energy field, the demand for battery anode materials is continuously expanding, and the market scale reaches hundreds of billions of yuan. Therefore, it is urgent to develop anode material raw materials with wide sources and low costs. The preparation of electrode materials from waste asphalt as a carbon precursor proposed in the present invention can not only improve the utilization rate of waste asphalt, but also alleviate the growing market demand for anodes of lithium / sodium / potassium ion batteries. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt. By regulating the morphology of carbon materials through a method of first rich oxygen and then high-temperature carbonization, it can be used as the anode material of lithium / sodium / potassium ion batteries, turning waste asphalt into a valuable resource and realizing high-value utilization.

[0006] The technical solution adopted by the present invention is a method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, which is specifically carried out according to the following steps:

[0007] S1: Separate the waste asphalt mixture by the solvent method, and separate the waste asphalt mixed solution by low-pressure filtration (pressure: -0.06 to -0.1 MPa) or centrifugal filtration (rotation speed: 6000 to 10000 r / min, time: 10 to 30 min); for different solvent combinations, separate the most suitable precursor material for subsequent operations.

[0008] S2: Heat the waste asphalt mixed solution at 60°C to 150°C for distillation to obtain waste asphalt materials. Stir the waste asphalt in water at a high temperature of 60°C to 100°C for 1 h to 5 h or treat it by the solvent method at 120°C to 200°C for 2 h to 10 h; improve the surface and component characteristics of the waste asphalt and induce the variation of the waste asphalt.

[0009] S3: Pyrolyze the treated waste asphalt at 100°C to 300°C in a nitrogen or argon atmosphere for 1 h to 10 h for only preliminary carbonization to preliminarily shape its microscopic morphology. If the temperature is too low, it cannot be shaped, and if the temperature is too high, it will directly carbonize; the heating rate is 1°C / min to 10°C / min, the nitrogen flow rate is 10 to 200 mL / min, and it is cooled to room temperature for standby;

[0010] S4: Carry out oxygen enrichment treatment on the pre-pyrolyzed waste asphalt at 200°C to 400°C in an oxygen atmosphere (oxygen content 0 - 100%) for 1 h to 5 h to assist the intrusion of oxygen. The heating rate is 1°C / min to 10°C / min, the oxygen flow rate is 10 to 200 mL / min, and the waste asphalt oxygen-enriched product is obtained after cooling to room temperature; the effects caused by the intrusion of oxygen elements with different concentrations into the asphalt structure are different. Too little cannot achieve the effect, and too many pores connecting into pieces will also lead to a reduction in performance. The oxygen content can be 0. The waste asphalt itself is an oxygen-enriched product under the thermal oxygen effect of natural aging. If the component variation during the road service process makes the oxygen content reach a certain requirement, almost no artificial addition is needed subsequently.

[0011] S5: Grind the waste asphalt oxygen-enriched product to 10 to 50 meshes, and then ultrasonically clean it with solutions such as 1 mol / L to 10 mol / L sulfuric acid, hydrochloric acid, nitric acid, acetic acid (acetic acid), carbonic acid, aqua regia, etc. or solutions such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, etc. for 1 h to 3 h. After washing with water until neutral, place it in a vacuum drying oven and dry it at 60°C to 120°C for 8 h to 12 h;

[0012] S6: Pyrolyze the dried waste asphalt oxygen-enriched product at 600°C to 1600°C for 1 h to 5 h. Molecular polycondensation occurs at high temperature, and the product is carbonized. The morphological structures obtained at different temperatures are different. As the temperature increases, the carbon layer becomes more ordered and the conductivity is higher, but the capacity may become lower. At the same time, if the temperature is too low, its conductivity is poor and there are more impurities; the heating rate is 1°C / min to 10°C / min, the pyrolysis atmosphere is argon or nitrogen, and the atmosphere flow rate is 10 to 200 mL / min. After cooling to room temperature, the waste asphalt hard carbon material is obtained;

[0013] S7: Ball-mill the pyrolyzed waste asphalt hard carbon material for 3 h to 10 h, and sieve it to 80 to 100 meshes to obtain the negative electrode material for lithium / sodium / potassium ion batteries.

[0014] Further, in S1, the solvent is a polar solvent or a non-polar solvent. The polar solvent is any one or a mixture of any proportions of dichloromethane, chloroform, 1,1,1-trichloroethane, trichloroethylene, 1-bromopropane, chlorobenzene, nitrobenzene, tetrahydrofuran or ethyl acetate; the non-polar solvent is any one or a mixture of any proportions of xylene, toluene, benzene, tetralin, methylcyclopentane, cyclohexane, n-pentane, n-hexane or decalin.

[0015] Further, in S1, the filtration separation is carried out by low-pressure filtration or centrifugal filtration. The pressure of low-pressure filtration is -0.06 ~ -0.1 MPa; the rotation speed of centrifugal filtration is 6000~10000 r / min, and the time is 10~30 min.

[0016] Further, in S2, the solvent is an organic solution or water. The organic solution is any one or a combination of any proportions of ethanol, dichloromethane, chloroform, cyclohexane or n-pentane.

[0017] Further, in S3, the heating rate is 1℃ / min~10℃ / min, and the flow rate of nitrogen or argon is 10~200 mL / min.

[0018] Further, in S4, the heating rate is 1℃ / min~10℃ / min, and the oxygen flow rate is 10~200 mL / min.

[0019] Further, in S5, the acid solution is sulfuric acid, hydrochloric acid, nitric acid, acetic acid, carbonic acid or aqua regia.

[0020] Further, in S5, the alkali solution is sodium hydroxide, potassium hydroxide, lithium hydroxide or calcium hydroxide solution.

[0021] Further, in S5, the ultrasonic cleaning time is 1 h~3 h, and the drying temperature is 60℃~120℃, and the time is 8 h~12 h.

[0022] Further, in S6, the heating rate is 1℃ / min~10℃ / min, and the atmosphere flow rate is 10~200 mL / min.

[0023] The beneficial effects of the present invention are:

[0024] 1. The embodiments of the present invention use waste asphalt as a carbon source to achieve the transformation of solid waste road garbage into valuable resources. The breakthroughs in the industry-university-research cooperation of the oil-stone separation technology and the waste asphalt-based hard carbon anode material technology for lithium-ion batteries have broken through the bottleneck of the recycling of waste asphalt mixtures in the traditional transportation field, providing a new approach for deepening the research, development and application of the recycling technology of waste transportation materials and constructing a green transportation system with a full life cycle. It has very important theoretical value and engineering practical significance for practicing the concept of ecological civilization, and has remarkable economic, environmental and social benefits.

[0025] 2. The embodiments of the present invention prepare the hard carbon anode material by a method of gradient temperature control with prior rich oxidation and then high-temperature carbonization. Using waste asphalt mixture as a precursor, based on the characteristics of waste asphalt mixture, through two-way adjustment and selection, since the waste asphalt has undergone thermal-oxidative aging and contains more oxygen elements, through further rich oxidation treatment, a multi-level oxygen-rich structure is formed. Then, through high-temperature heat treatment, oxygen overflows during the heat treatment process, forming a multi-level pore structure. Different heat treatment temperatures further promote the generation of different microtopographies, and the waste asphalt hard carbon anode material with the best performance is obtained by controlling the heat treatment temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0027] Figure 1 It is the nitrogen adsorption-desorption isotherm of the waste asphalt hard carbon anode material prepared in Example 1.

[0028] Figure 2 It is the pore size distribution curve of the waste asphalt hard carbon anode material prepared in Example 1.

[0029] Figure 3 It is the cycling performance graph of the lithium-ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 1 at a current density of 0.1 C.

[0030] Figure 4 It is the TEM image of the waste asphalt hard carbon anode material prepared in Example 2.

[0031] Figure 5 It is the SEM image of the waste asphalt hard carbon anode material prepared in Example 2.

[0032] Figure 6 It is the XRD pattern of the waste asphalt hard carbon anode material prepared in Example 2.

[0033] Figure 7 It is the nitrogen adsorption - desorption isotherm of the waste asphalt hard carbon anode material prepared in Example 2.

[0034] Figure 8 It is the pore size distribution curve of the waste asphalt hard carbon anode material prepared in Example 2.

[0035] Figure 9 It is the cyclic voltammetry curve of the lithium - ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 2.

[0036] Figure 10 It is the cycling performance graph of the lithium - ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 2 at a current density of 0.1 C.

[0037] Figure 11 It is the cycling performance graph of the lithium - ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 3 at a current density of 0.1 C.

[0038] Figure 12 It is the cycling performance graph of the lithium - ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 4 at a current density of 0.1 C.

[0039] Figure 13 It is the cycling performance graph of the lithium - ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 5 at a current density of 0.1 C.

[0040] Figure 14 It is the cycling performance graph of the lithium - ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 6 at a current density of 0.1 C.

[0041] Figure 15 It is the cycling performance graph of the lithium - ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 7 at a current density of 0.1 C.

[0042] Figure 16 It is the cycling performance graph of the lithium - ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 8 at a current density of 0.1 C.

[0043] Figure 17 It is the cycling performance graph of the lithium - ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 9 at a current density of 0.1 C.

[0044] Figure 18 It is the cycling performance graph of the lithium - ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 10 at a current density of 0.1 C.

[0045] Figure 19It is the cycling performance graph of the lithium-ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 11 at a current density of 0.1 C.

[0046] Figure 20 It is the cycling performance graph of the lithium-ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 12 at a current density of 0.1 C.

[0047] Figure 21 It is the cycling performance graph of the lithium-ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 13 at a current density of 0.1 C.

[0048] Figure 22 It is the cycling performance graph of the lithium-ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 14 at a current density of 0.1 C.

[0049] Figure 23 It is the cycling performance graph of the lithium-ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 15 at a current density of 0.1 C.

[0050] Figure 24 It is the cycling performance graph of the lithium-ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 16 at a current density of 0.1 C.

[0051] Figure 25 It is the cycling performance graph of the lithium-ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 17 at a current density of 0.1 C.

[0052] Figure 26 It is the cycling performance graph of the lithium-ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 18 at a current density of 0.1 C.

[0053] Figure 27 It is the cycling performance graph of the lithium-ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 19 at a current density of 0.1 C.

[0054] Figure 28 It is the cycling performance graph of the lithium-ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 20 at a current density of 0.1 C.

[0055] Figure 29 It is the cycling performance graph of the lithium-ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 21 at a current density of 0.1 C.

[0056] Figure 30 It is the cycling performance graph of the lithium-ion battery assembled with the waste asphalt hard carbon anode material prepared in Example 22 at a current density of 0.1 C.

[0057] Figure 31 It is a cyclic performance graph of a lithium-ion battery assembled with the waste asphalt hard carbon negative electrode material prepared in Comparative Example 1 at a current density of 0.1 C.

[0058] Figure 32 It is a cyclic performance graph of a lithium-ion battery assembled with the waste asphalt hard carbon negative electrode material prepared in Comparative Example 2 at a current density of 0.1 C. Detailed implementation manners

[0059] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0060] Embodiment 1

[0061] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0062] S1: Separate the waste asphalt mixture by the solvent method (the solvent is dichloromethane), and separate the waste asphalt mixed solution by low-pressure filtration (the pressure is -0.1 MPa);

[0063] S2: Distill the waste asphalt mixed solution by heating at 60 °C to obtain the waste asphalt material, and treat it by solvent thermal method at 180 °C for 6 h (the solvent is cyclohexane), that is, put the solvent and the waste asphalt material into a closed cylinder and heat it to achieve the purpose of high temperature and high pressure (1 MPa to 1 GPa);

[0064] S3: Pyrolyze the treated waste asphalt at 200 °C for 3 h in a nitrogen atmosphere, with a heating rate of 5 °C / min and a nitrogen flow rate of 20 mL / min, and reserve it after cooling to room temperature;

[0065] S4: Carry out oxygen enrichment treatment on the waste asphalt at 200 °C for 4 h in an oxygen atmosphere, with a heating rate of 8 °C / min and an oxygen flow rate of 100 mL / min, and obtain the waste asphalt oxygen-enriched product after cooling to room temperature;

[0066] S5: Grind the waste asphalt oxygen-enriched product to 50 mesh, ultrasonically clean it with a 5 mol / L nitric acid solution for 1 h, wash it with water until neutral, and then dry it in a vacuum drying oven at 100 °C for 10 h;

[0067] S6: Pyrolyze the dried waste asphalt oxygen-enriched product at 1000 °C for 3 h, with a heating rate of 4 °C / min, the pyrolysis atmosphere is nitrogen, and the atmosphere flow rate is 30 mL / min, and obtain the waste asphalt hard carbon material after cooling to room temperature;

[0068] S7: Ball mill the pyrolyzed waste asphalt hard carbon material for 6 h, and sieve it to 100 mesh to obtain the anode material for lithium / sodium / potassium ion batteries.

[0069] From the BET diagrams ( Figure 1 , Figure 2 ), it can be seen that there is an obvious pore structure. A higher carbonization temperature can promote the gradual orderliness of the waste asphalt carbon layer, resulting in higher conductivity but lower capacity, and the performance is as Figure 3 shown.

[0070] Example 2

[0071] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0072] S1: Separate the oil from the waste asphalt mixture by the solvent method (the solvent is cyclohexane), and separate the waste asphalt mixed solution by centrifugal filtration (rotation speed is 10000 r / min, time is 10 min);

[0073] S2: Distill the waste asphalt mixed solution by heating at 90 °C to obtain the waste asphalt material, and stir the waste asphalt at 80 °C in water for 2 h;

[0074] S3: Pyrolyze the treated waste asphalt at 150 °C for 5 h in a nitrogen atmosphere, with a heating rate of 2 °C / min and a nitrogen flow rate of 50 mL / min, and cool it to room temperature for later use;

[0075] S4: Perform oxygen-rich treatment on the waste asphalt at 300 °C for 3 h in an oxygen atmosphere, with a heating rate of 5 °C / min and an oxygen flow rate of 50 mL / min, and obtain the oxygen-rich product of waste asphalt after cooling to room temperature;

[0076] S5: Grind the oxygen-rich product of waste asphalt to 30 mesh, ultrasonically clean it with 5 mol / L sodium hydroxide solution for 2 h, wash it with water until neutral, and then dry it in a vacuum drying oven at 100 °C for 10 h;

[0077] S6: High-temperature pyrolyze the dried oxygen-rich product of waste asphalt at 800 °C for 2 h, with a heating rate of 5 °C / min, the pyrolysis atmosphere is argon, and the atmosphere flow rate is 50 mL / min, and obtain the waste asphalt hard carbon material after cooling to room temperature;

[0078] S7: Ball mill the pyrolyzed waste asphalt hard carbon material for 6 h, and sieve it to 100 mesh to obtain the anode material for lithium / sodium / potassium ion batteries.

[0079] The aged waste asphalt itself has more oxygen-containing functional groups. By further introducing oxygen elements, a multi-layered oxygen-rich structure is formed. During the carbonization process, the molecules in the waste asphalt continuously condense, accompanied by dehydrogenation and molecular bond breaking reactions. The oxygen-rich structure will consume the hydrogen elements in the waste asphalt to prevent the asphalt from evolving into a molten structure. At the same time, the excess oxygen will generate gases such as carbon monoxide and carbon dioxide during the cracking process, creating abundant pores and defects during the formation of the waste asphalt-based carbon material, such as Figure 4 , 5 shown. Further, the created pore structure can be further adjusted under different conditions, and finally a structure reaches the best balance ( Figures 6 - 8 ), so as to obtain a material with optimal performance ( Figure 9 , 10 ).

[0080] Example 3

[0081] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0082] Except that in S2, the waste asphalt material is treated by solvothermal method at 120 °C for 10 h (the solvent is water), that is, the solvent and the waste asphalt material are put into a closed cylinder and heated to reach high temperature and high pressure (1 MPa - 3 MPa); in S6, the dried oxygen-rich product of waste asphalt is pyrolyzed at 900 °C for 4 h; the rest are the same as in Example 1.

[0083] Only washing the surface impurities with water slightly increases the capacity; reducing the carbonization temperature increases the disorder of the carbon material and the number of storage sites, resulting in a higher capacity, as Figure 11 shown.

[0084] Example 4

[0085] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0086] Except that in S4, the waste asphalt is subjected to oxygen-rich treatment at 200 °C for 4 h in an oxygen atmosphere, and the heating rate is 2 °C / min; in S6, the dried oxygen-rich product of waste asphalt is pyrolyzed at 1200 °C for 3 h; the rest are the same as in Example 1.

[0087] Reducing the heating rate allows oxygen to erode better and forms a material with more pore structures at high temperatures, but too high a temperature makes the structure still ordered, and thus the performance does not change significantly, as Figure 12 shown.

[0088] Example 5

[0089] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0090] Except that in S5, the waste asphalt oxygen-rich product was ground to 50 mesh and then ultrasonically cleaned with 5 mol / L hydrochloric acid solution for 1 h; in S7, the pyrolyzed waste asphalt hard carbon material was ball milled for 10 h and screened to 100 mesh; the rest was the same as in Example 1.

[0091] A longer ball milling time makes the particle size of the carbon material smaller and more uniform, and thus the performance is better, as Figure 13 shown.

[0092] Example 6

[0093] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0094] Except that in S4, the waste asphalt was subjected to oxygen enrichment treatment at 300 °C in an oxygen atmosphere for 4 h; in S5, after the waste asphalt oxygen-rich product was ground to 50 mesh, it was ultrasonically cleaned with 5 mol / L sulfuric acid solution for 3 h; the rest was the same as in Example 1.

[0095] The increase in the oxygen enrichment temperature makes its preliminary qualitative more stable, and at the same time further grinds it finer, which is conducive to its dispersion and the capacity becomes higher, as Figure 14 shown.

[0096] Example 7

[0097] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0098] Except that in S1, the waste asphalt mixed solution was separated by centrifugal filtration (rotation speed: 8000 r / min, time: 20 min); in S6, the dried waste asphalt oxygen-rich product was pyrolyzed at 700 °C for 5 h; the rest was the same as in Example 2.

[0099] Lower centrifugal rotation speed and lower carbonization temperature result in more heterogeneous elements and a lower capacity, as Figure 15 shown.

[0100] Example 8

[0101] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0102] Except that in S4, the waste asphalt was subjected to oxygen enrichment treatment at 200 °C in an oxygen atmosphere for 5 h; in S6, the dried waste asphalt oxygen-rich product was pyrolyzed at 1100 °C for 1 h; the rest was the same as in Example 2.

[0103] When the oxygen enrichment temperature is lower, oxygen cannot penetrate into the structure, resulting in a lower capacity, as Figure 16 shown.

[0104] Example 9

[0105] A method for preparing multi - stage porous hard carbon by gradient temperature - controlled pyrolysis of waste asphalt, comprising the following steps:

[0106] Except that in S3, the waste asphalt is pyrolyzed at 200 °C for 1 h in a nitrogen atmosphere; in S6, the dried oxygen - rich product of waste asphalt is pyrolyzed at 800 °C for 3 h; the rest are the same as in Example 2.

[0107] The pre - carbonization temperature is increased, making its structure more stable. At the same time, prolonging the carbonization time also slightly improves its performance, as Figure 17 shown.

[0108] Example 10

[0109] A method for preparing multi - stage porous hard carbon by gradient temperature - controlled pyrolysis of waste asphalt, comprising the following steps:

[0110] Except that in S3, the treated waste asphalt is pyrolyzed at 300 °C for 3 h in a nitrogen atmosphere; in S4, the waste asphalt is subjected to oxygen - rich treatment at 200 °C for 3 h in an oxygen atmosphere; the rest are the same as in Example 2.

[0111] Too high pre - carbonization temperature makes its structure too stable, and oxygen is difficult to erode, resulting in a decrease in capacity, as Figure 18 shown.

[0112] Example 11

[0113] A method for preparing multi - stage porous hard carbon by gradient temperature - controlled pyrolysis of waste asphalt, comprising the following steps:

[0114] Except that in S4, the waste asphalt is subjected to oxygen - rich treatment at 250 °C for 3 h in an oxygen atmosphere; in S6, the dried oxygen - rich product of waste asphalt is pyrolyzed at 950 °C for 2 h; the rest are the same as in Example 2.

[0115] The oxygen - rich temperature decreases, oxygen cannot penetrate into the structure, the carbonization temperature increases, and the structure becomes more ordered, resulting in a slight decrease in capacity, as Figure 19 shown.

[0116] Example 12

[0117] A method for preparing multi - stage porous hard carbon by gradient temperature - controlled pyrolysis of waste asphalt, comprising the following steps:

[0118] Except that in S4, the waste asphalt is subjected to oxygen - rich treatment at 300 °C for 2 h in an oxygen atmosphere, with a heating rate of 3 °C / min and an oxygen flow rate of 60 mL / min; in S5, after grinding the oxygen - rich product of waste asphalt to 50 mesh, it is ultrasonically cleaned with aqua regia solution (a mixture of concentrated nitric acid and concentrated hydrochloric acid in a volume ratio of 1:3) for 1 h; the rest are the same as in Example 1.

[0119] The increase in the oxygen-rich temperature allows more oxygen to introduce into the pore structure, providing more active sites. At the same time, aqua regia washes away more impurities, increasing its capacity, as Figure 20 shown.

[0120] Example 13

[0121] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0122] Except that in S4, the waste asphalt is subjected to oxygen-rich treatment at 300 °C in an oxygen atmosphere for 3 h, and the heating rate is 10 °C / min; in S5, after grinding the oxygen-rich product of the waste asphalt to 25 mesh, it is successively ultrasonically cleaned with 6 mol / L nitric acid and 6 mol / L acetic acid solution for 1 h; the acid washing removes metal-related elements in the material, such as calcium, magnesium, iron, etc.; the rest are the same as in Example 1.

[0123] The content of various metals and magnetic elements decreases, and the capacity increases, as Figure 21 shown.

[0124] Example 14

[0125] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0126] Except that in S4, the waste asphalt is subjected to oxygen-rich treatment at 300 °C in an oxygen atmosphere for 5 h; in S5, after grinding the oxygen-rich product of the waste asphalt to 50 mesh, it is successively ultrasonically cleaned with 6 mol / L sodium hydroxide and 6 mol / L hydrochloric acid solution for 1 h to wash away aluminum- and zinc-related elements that may exist in the material; the rest are the same as in Example 2.

[0127] The finer grinding results in smaller particle size, and combined with ultrasonic treatment, the impurity removal can be more thorough, improving the performance, as Figure 22 shown.

[0128] Example 15

[0129] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0130] In S1, the waste asphalt mixture is separated by a mixed solution of polar and non-polar solvents (i.e., trichloroethylene and n-hexane mixed in a volume ratio of 1:1); in S2, the waste asphalt mixture solution is heated to 180 °C for distillation to obtain waste asphalt materials, without solvent thermal treatment; the rest are the same as in Example 1. By utilizing the different phase solubility characteristics of the components in the waste asphalt, targeted selection is achieved. In S1, components closer to trichloroethylene and n-hexane, such as resins, are directionally separated. Since the composition of waste asphalt components is complex, separating the waste asphalt mixture with different solvents can selectively set a bias. Further, in S2, according to the microscopic polycondensation characteristics of different ionic components under high temperature and high pressure, the material can be induced to transform into a multi-porous structure, thereby improving the performance of the material, such as Figure 23 as shown

[0131] Example 16

[0132] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0133] Except that in S2, the waste asphalt mixture solution is heated to 120 °C for distillation to obtain waste asphalt materials, without solvent thermal treatment; in S6, the dried oxygen-rich waste asphalt product is pyrolyzed at 1500 °C for 4 h, the heating rate is 9 °C / min, and the gas flow rate is 20 mL / min; the rest are the same as in Example 1.

[0134] Too fast heating rate causes the gaseous carbon hydrogen compounds during the carbonization process to undergo secondary reactions without overflowing, affecting the composition structure of the material and reducing the performance, such as Figure 24 as shown

[0135] Example 17

[0136] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0137] Except that in S2, the waste asphalt mixture solution is heated to 170 °C for distillation to obtain waste asphalt materials, and the waste asphalt is stirred at 100 °C in water for 1 h; in S4, the waste asphalt is subjected to oxygen-rich treatment at 350 °C in an oxygen atmosphere for 3 h, and the oxygen flow rate is 50 mL / min; the rest are the same as in Example 1.

[0138] Too high distillation temperature leads to the introduction of excessive oxygen during the distillation process, but only removes carbon and hydrogen elements during the initial pre-carbonization, causing the collapse of the structure and slightly reducing the capacity, such as Figure 25 as shown

[0139] Example 18

[0140] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0141] Except that in S2, the waste asphalt mixture solution is distilled at 160 °C to obtain waste asphalt materials; in S3, the waste asphalt is pyrolyzed at 250 °C for 4 h under a nitrogen atmosphere with a heating rate of 5 °C / min; the rest are the same as in Example 2.

[0142] The slightly higher distillation temperature and longer pre-carbonization pyrolysis time make the preliminary shaping of the material more stable, and combined with an appropriate heating rate, its performance is better, as Figure 26 shown.

[0143] Example 19

[0144] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0145] Except that in S1, the waste asphalt mixture is separated by trichloroethylene; in S6, the dried oxygen-rich waste asphalt product is pyrolyzed at 600 °C for 5 h with a heating rate of 2 °C / min and an atmosphere flow rate of 20 mL / min; the rest are the same as in Example 2.

[0146] The waste asphalt solution containing more aged asphaltenes is obtained by separation with trichloroethylene. The aged waste asphalt contains relatively more elements such as sulfur and oxygen. Although the lower carbonization temperature in S6 can retain the original structure of the material to the greatest extent, it cannot remove relatively many heteroatoms, resulting in a lower capacity, as Figure 27 shown.

[0147] Example 20

[0148] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0149] Except that in S5, the oxygen-rich waste asphalt product is ground to 50 mesh and then ultrasonically cleaned with 6 mol / L potassium hydroxide and 6 mol / L nitric acid solutions for 2 h to wash away aluminum- and zinc-related elements in the material while introducing nitrogen elements; in S6, the dried oxygen-rich waste asphalt product is pyrolyzed at 1400 °C for 2 h with a heating rate of 4 °C / min and an atmosphere flow rate of 20 mL / min; the rest are the same as in Example 2.

[0150] While washing away aluminum- and zinc-related elements in the material, nitrogen elements are introduced. While washing away impurities, nitrogen elements are introduced, and then the nitrogen elements overflow at a high temperature to form more pore structures, improving the performance, as Figure 28 shown.

[0151] Example 21

[0152] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0153] S1: Separate the spent asphalt mixture by the solvent method (the solvent is chloroform), and separate the spent asphalt mixed solution by low-pressure filtration (the pressure is -0.06 MPa).

[0154] S2: Distill the spent asphalt mixed solution by heating at 150 °C to obtain the spent asphalt material, and treat it by solvent thermal method at 200 °C for 2 h (the solvent is ethanol), that is, put the solvent and the spent asphalt material into a closed cylinder and heat it to achieve high temperature and high pressure (1 MPa - 3 MPa).

[0155] S3: Pyrolyze the treated spent asphalt at 100 °C for 10 h in an argon atmosphere, with a heating rate of 1 °C / min and an argon flow rate of 200 mL / min, and keep it for use after cooling to room temperature.

[0156] S4: Carry out oxygen-enriched treatment on the spent asphalt at 400 °C for 1 h in an oxygen atmosphere, with a heating rate of 1 °C / min and an oxygen flow rate of 200 mL / min, and obtain the oxygen-enriched product of the spent asphalt after cooling to room temperature.

[0157] S5: Grind the oxygen-enriched product of the spent asphalt to 10 meshes, then ultrasonically clean it with 1 mol / L nitric acid solution for 1 h, wash it with water until neutral, and then dry it in a vacuum drying oven at 60 °C for 12 h.

[0158] S6: Pyrolyze the dried oxygen-enriched product of the spent asphalt at 1600 °C for 3 h, with a heating rate of 10 °C / min, the pyrolysis atmosphere is nitrogen, and the atmosphere flow rate is 200 mL / min, and obtain the hard carbon material of the spent asphalt after cooling to room temperature.

[0159] S7: Ball-mill the pyrolyzed hard carbon material of the spent asphalt for 6 h, and sieve it to 80 meshes to obtain the negative electrode material for lithium / sodium / potassium ion batteries.

[0160] Example 22

[0161] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of spent asphalt, comprising the following steps:

[0162] S1: Separate the spent asphalt mixture by the solvent method (the solvent is n-pentane), and separate the spent asphalt mixed solution by centrifugal filtration (the rotation speed is 6000 r / min and the time is 30 min).

[0163] S2: Distill the spent asphalt mixed solution by heating at 90 °C to obtain the spent asphalt material, and stir the spent asphalt at 60 °C in water for 5 h.

[0164] S3: Pyrolyze the treated waste asphalt at 150 °C for 5 h under a nitrogen atmosphere, with a heating rate of 10 °C / min and a nitrogen flow rate of 10 mL / min. After cooling to room temperature, it is reserved for use;

[0165] S4: Treat the waste asphalt with enriched oxygen at 300 °C for 3 h in an oxygen atmosphere, with a heating rate of 5 °C / min and an oxygen flow rate of 10 mL / min. After cooling to room temperature, the oxygen-enriched product of waste asphalt is obtained;

[0166] S5: Grind the oxygen-enriched product of waste asphalt to 30 mesh, then ultrasonically clean it with 5 mol / L potassium hydroxide solution for 2 h. After washing with water until neutral, it is placed in a vacuum drying oven and dried at 120 °C for 8 h;

[0167] S6: Pyrolyze the dried oxygen-enriched product of waste asphalt at 800 °C for 2 h, with a heating rate of 1 °C / min and a pyrolysis atmosphere of argon, and an atmosphere flow rate of 10 mL / min. After cooling to room temperature, the hard carbon material of waste asphalt is obtained;

[0168] S7: Ball-mill the pyrolyzed hard carbon material of waste asphalt for 6 h, and sieve it to 90 mesh to obtain the negative electrode material for lithium / sodium / potassium ion batteries.

[0169] The experimental data of Examples 21 and 22 are as Figures 29 - 30 shown.

[0170] Comparative Example 1

[0171] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0172] S1: Separate the waste asphalt mixture by a non-polar solvent (the solvent is cyclohexane) to obtain a waste asphalt mixed solution.

[0173] S2: Distill the waste asphalt mixed solution by heating it to 150 °C to obtain a waste asphalt material;

[0174] S3: Treat the waste asphalt with enriched oxygen at 200 °C for 4 h in an oxygen atmosphere, with a heating rate of 8 °C / min and an oxygen flow rate of 100 mL / min. After cooling to room temperature, the oxygen-enriched product of waste asphalt is obtained;

[0175] S4: Pyrolyze the oxygen-enriched product of waste asphalt at 1000 °C for 3 h, with a heating rate of 4 °C / min and a pyrolysis atmosphere of nitrogen, and an atmosphere flow rate of 30 mL / min. After cooling to room temperature, the hard carbon material of waste asphalt is obtained;

[0176] S5: Grind the oxygen-enriched product of waste asphalt to 50 mesh, then ultrasonically clean it with nitric acid solution for 2 h. After washing with water until neutral, it is placed in a vacuum drying oven and dried at 100 °C for 10 h;

[0177] S6: Ball mill the pyrolyzed waste asphalt hard carbon material for 6 h, and obtain the anode material for lithium / sodium / potassium ion batteries after screening to 100 mesh.

[0178] Lack of pre-carbonization step, the carbon material is not preliminarily shaped, and the oxygen erosion effect becomes worse, resulting in a lower final capacity, as Figure 31 shown.

[0179] Comparative Example 2

[0180] A method for preparing multi-stage porous hard carbon by gradient temperature-controlled pyrolysis of waste asphalt, comprising the following steps:

[0181] S1: Separate the waste asphalt mixture by a polar solvent (the solvent is trichloroethylene) to obtain a waste asphalt mixed solution.

[0182] S2: Distill the waste asphalt mixed solution by heating to 100 °C to obtain a waste asphalt material;

[0183] S3: Pyrolyze the waste asphalt at 200 °C for 5 h in a nitrogen atmosphere, with a heating rate of 4 °C / min and a nitrogen flow rate of 20 mL / min, and reserve it after cooling to room temperature;

[0184] S4: Pyrolyze the pre-pyrolyzed waste asphalt at 800 °C for 2 h, with a heating rate of 5 °C / min, an argon pyrolysis atmosphere, and an atmosphere flow rate of 50 mL / min, and obtain a waste asphalt hard carbon material after cooling to room temperature;

[0185] S5: Ball mill the pyrolyzed waste asphalt hard carbon material for 6 h, and obtain the anode material for lithium / sodium / potassium ion batteries after screening to 100 mesh.

[0186] Without an oxygen-rich step, it is difficult to form multi-dimensional and multi-level pores only relying on the original oxygen elements in the material itself, resulting in a reduced capacity, as Figure 32 shown.

[0187] In the embodiment of the present invention, the precursor is pre-oxidized into a liquid or molten semi-fluid, and the oxygen-rich treatment is based on the oxygen-rich characteristics of the material itself. Differences in the microscopic composition of the precursor will lead to different action mechanisms. For secondary artificial oxygen enrichment, a gas with an oxygen concentration in the range of 0%-100% is selected.

[0188] In Embodiment S1 of the present invention, waste asphalt mixed solution is separated by low-pressure filtration (pressure: -0.06 to -0.1 MPa) or centrifugal filtration (rotation speed: 6000 - 10000 r / min, time: 10 - 30 min); considering the specific polycondensation situation of waste asphalt during carbonization at high temperature, the pre-set solvent mixing method is adjusted in reverse. This two-way adjustment mechanism does not exist in new asphalt (new asphalt does not require separation). In the reuse of waste asphalt, there is an adjustment method through the template method. Although it is also waste asphalt, the asphalt used is well-separated and purified with high purity. However, the embodiment of the present invention is directed at waste asphalt mixture, and the most favorable precursor material for subsequent oxygen-enriched operation is selected through two-way solvent selection and adjustment.

[0189] The separation of waste asphalt is usually used in the transportation field, but generally only involves filtration separation. Waste asphalt is a non-uniform mixture and is extremely difficult to be associated with the solvothermal method. The conventional method for treating asphalt in the transportation field is based on the four major components of waste asphalt, which are soluble in specific partial solvents and can be dissolved under conventional means without the need for high temperature and high pressure. The reason for applying high temperature and high pressure to waste asphalt in Embodiment S2 of the present invention is that the embodiment of the present invention is set based on the comprehensive consideration of interdisciplinary, for the selection and improvement of properties for subsequent battery utilization. Based on the different cross-linking characteristics of each component between high temperature and high pressure and different solvents, the polymerization and dissolution characteristics between different functional groups are further adjusted, so as to achieve the purpose of improving the performance of subsequent materials.

[0190] The materials in the embodiments of the present invention are based on the waste asphalt mixture retired from the initial road maintenance. Compared with the generally well-separated and purified waste asphalt, the composition of the waste asphalt mixture is more complex, the state is more initial, and the impurity content is more, so the treatment difficulty is greater; compared with the traditional new brittle structure asphalt, the softening point of the aged asphalt used in the present invention is very different from it, and the asphalt is more likely to present a fluid state, which is different from the brittle characteristics of new asphalt, thus also making the treatment more difficult.

[0191] The embodiments of the present invention are based on the thermo-oxidative aging effect of waste asphalt mixture under high temperature and ultraviolet light during road service. On this basis, further oxygen-enriched treatment is carried out to form a multi-level oxygen-enriched structure. Further, in S6, through temperature control, after oxygen enrichment of the waste asphalt from the waste asphalt mixture, different effects will be caused at different temperatures under high temperature polycondensation, affecting many aspects such as the pore structure, interlayer structure, and conductivity of the material. Therefore, the characteristics of the microstructural change that cannot be conventionally expected are generated, and anode materials applicable to lithium, sodium, and potassium are obtained.

[0192] The above are only the preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are all included in the protection scope of the present invention.

Claims

1. A method for preparing multi - stage porous hard carbon by pyrolyzing waste asphalt with gradient temperature control, characterized in that, It includes the following steps: S1: Separating the waste asphalt mixture by the solvent method to separate the oil from the stone, and filtering to obtain the waste asphalt mixed solution; S2: Heating the waste asphalt mixed solution at 60°C to 180°C for distillation to obtain the waste asphalt material, and subjecting the waste asphalt to high-temperature stirring in water at 60°C to 100°C for 1 h to 5 h or thermal treatment in water at 120°C to 200°C for 2 h to 10 h; S3: Preheating and pyrolyzing the treated waste asphalt in a nitrogen or argon atmosphere at 100°C to 300°C for 1 h to 10 h; S4: Subjecting the pre-pyrolyzed waste asphalt to oxygen-rich treatment in an oxygen atmosphere at 200°C to 400°C for 1 h to 5 h; S5: Grinding the oxygen-rich product to 10 to 50 mesh, ultrasonically cleaning it with an acid solution or an alkali solution of 1 mol / L to 10 mol / L, washing it with water until neutral, and then drying it; S6: Performing high-temperature pyrolysis at 600°C to 1600°C for 1 h to 5 h, with the pyrolysis atmosphere being argon or nitrogen, and obtaining the waste asphalt hard carbon material after cooling to room temperature; S7: Ball milling, screening to 80 to 100 mesh, and then obtaining the anode material for lithium / sodium / potassium ion batteries; In S4, the heating rate is 1°C / min to 10°C / min, and the oxygen flow rate is 10 to 200 mL / min.

2. The method for preparing multi-stage porous hard carbon by pyrolyzing waste asphalt with gradient temperature control according to claim 1, wherein, In S1, the solvent is a polar solvent or a non-polar solvent. The polar solvent is any one or a mixture of any proportions of dichloromethane, chloroform, 1,1,1-trichloroethane, trichloroethylene, 1-bromopropane, chlorobenzene, nitrobenzene, tetrahydrofuran, or ethyl acetate; the non-polar solvent is any one or a mixture of any proportions of xylene, toluene, benzene, tetrahydronaphthalene, methylcyclopentane, cyclohexane, n-pentane, n-hexane, or decahydronaphthalene.

3. The method for preparing multi-stage porous hard carbon by pyrolyzing waste asphalt with gradient temperature control according to claim 1, characterized in that, In S1, the filtration separation is carried out by low-pressure filtration or centrifugal filtration. The pressure of low-pressure filtration is -0.06 to -0.1 MPa; the rotation speed of centrifugal filtration is 6000 to 10000 r / min, and the time is 10 to 30 min.

4. The method for preparing multi-stage porous hard carbon by pyrolyzing waste asphalt with gradient temperature control according to claim 1, wherein In S3, the heating rate is 1°C / min to 10°C / min, and the flow rate of nitrogen or argon is 10 to 200 mL / min.

5. The method for preparing multi-stage porous hard carbon by pyrolyzing waste asphalt with gradient temperature control according to claim 1, wherein, In S5, the acid solution is sulfuric acid, hydrochloric acid, nitric acid, acetic acid, carbonic acid, or aqua regia.

6. The method for preparing multi-stage porous hard carbon by pyrolyzing waste asphalt with gradient temperature control according to claim 1, characterized in that, In S5, the alkali solution is sodium hydroxide, potassium hydroxide, lithium hydroxide, or calcium hydroxide solution.

7. The method for preparing multi-stage porous hard carbon by pyrolyzing waste asphalt with gradient temperature control according to claim 1, wherein In S5, the ultrasonic cleaning time is 1 h to 3 h, and the drying temperature is 60°C to 120°C, and the time is 8 h to 12 h.

8. The method for preparing multi-stage porous hard carbon by pyrolyzing waste asphalt with gradient temperature control according to claim 1, characterized in that, In S6, the heating rate is 1°C / min to 10°C / min, and the atmosphere flow rate is 10 to 200 mL / min.

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