Porous carbon material based on synergistic activation of PVC and PET as well as preparation method and application of porous carbon material

Abstract

The invention relates to a porous carbon material based on synergistic activation of PVC (polyvinyl chloride) and PET (polyethylene terephthalate) as well as a preparation method and application thereof, and relates to the technical field of coal-based solid waste recycling. The porous carbon material is prepared by taking fine coal gasification slag as a carbon source and taking polyvinyl chloride and polyethylene glycol terephthalate as a synergistic activator and a supplementary carbon source through an acid pickling pretreatment and alkali co-activation process; the porous carbon material has a graded pore structure, the specific surface area is 700-950, the pore volume is 0.45-0.75, and the carbon dioxide adsorption capacity at 0 DEG C and 1 standard atmospheric pressure is greater than 45. According to the method, waste is treated by waste, three kinds of solid waste with heavy environmental burden are converted into products with high added value, and the problems of solid waste stockpiling pollution and resource utilization are synchronously solved.

Description

Technical Field

[0001] This application relates to the field of coal-based solid waste resource utilization technology, and in particular to porous carbon materials based on PVC and PET synergistic activation, their preparation methods and applications. Background Technology

[0002] With the global push towards the goal of "carbon peaking and carbon neutrality," the development of low-energy-consumption and high-efficiency carbon dioxide capture technologies is of paramount importance. Solid adsorption methods, based on solid adsorbents, have become a research hotspot due to their operational flexibility and convenient regeneration; the core of this approach lies in developing low-cost, high-performance adsorption materials.

[0003] Coal gasification fine slag (CGFS) is a large-scale industrial solid waste generated from coal gasification. It contains unburned carbon and can be used as an inexpensive carbon source for preparing porous carbon materials. Existing research mainly improves its porosity through physical or chemical activation, but the resulting materials generally suffer from low micropore ratios and limited improvement in specific surface area, making it difficult to meet the requirements for carbon dioxide adsorption capacity (especially at room temperature).

[0004] Meanwhile, the disposal of waste plastics such as polyvinyl chloride (PVC) and polyethylene terephthalate (PET) is also an environmental challenge. Studies have shown that PVC pyrolysis releases hydrogen chloride, which has the potential to act as an "in-situ pore-forming agent," significantly improving the specific surface area and carbon dioxide adsorption performance of the resulting activated carbon in synergistic effects with alkaline agents such as KOH. PET, with its high carbon content and unique structure, can serve as a supplementary carbon source.

[0005] Therefore, there is an urgent need for a method that can synergistically utilize three solid wastes—coal gasification slag, PVC, and PET—to prepare porous carbon materials for capturing and separating carbon dioxide. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide porous carbon materials based on the synergistic activation of PVC and PET, their preparation method and application. It solves the technical problems of raw material performance bottleneck, single solid waste disposal, and difficulty in synergistic optimization of pore structure in existing technologies.

[0007] To achieve the above objectives, the present invention provides the following technical solution: Porous carbon materials based on the synergistic activation of PVC and PET, their preparation methods, and applications are described. Using coal gasification slag as the carbon source, and polyvinyl chloride and polyethylene terephthalate as synergistic activators and supplementary carbon sources, the materials are prepared through an acid washing pretreatment and an alkaline co-activation process. The porous carbon materials possess a hierarchical pore structure and a specific surface area of ​​700-950 nm. The pore volume is 0.45-0.75. The carbon dioxide adsorption capacity at 0℃ and 1 standard atmosphere is greater than 45. .

[0008] Furthermore, the hierarchical pore structure includes micropores and mesopores, with micropore diameters less than 2 nm and mesopore diameters of 2-50 nm; the Raman spectral ID / IG value of the porous carbon material is less than 1.10, and the surface oxygen-containing functional group content measured by X-ray photoelectron spectroscopy is less than 5 at.

[0009] Furthermore, after 10 carbon dioxide adsorption-desorption cycles, the porous carbon material retains an adsorption capacity of no less than 97%.

[0010] A method for preparing a porous carbon material as described above includes the following steps: S1. Mix the coal gasification fine slag with the acid solution, react at 50-70℃ for 4-6 hours, filter, wash until neutral, and dry to obtain the pickling slag; S2. Mixing and Batching: Mix the pickling residue, alkali activator, polyvinyl chloride powder and polyethylene terephthalate powder evenly at a mass ratio of 1:(2-4):(0.05-0.2):(0.5-1.5); S3. Activate the mixture in an inert atmosphere at 800-900℃ for 1-3 hours; S4. Neutralize the activated product with an acid solution, wash until neutral, and dry to obtain the porous carbon material.

[0011] Furthermore, in step S1, the acid solution is a hydrochloric acid solution and a hydrofluoric acid solution, and the acid washing pretreatment includes: first, mixing the coal gasification fine slag with a 20% mass fraction hydrochloric acid solution at a solid-liquid ratio of 1:8-12, and then mixing the solid with a 40% mass fraction hydrofluoric acid solution at the same solid-liquid ratio.

[0012] Furthermore, in step S2, the mass ratio of the pickling residue, alkali activator, polyvinyl chloride, and polyethylene terephthalate is 1:2:0.05:1 or 1:4:0.1:1.

[0013] Furthermore, in step S2, the alkali activator is potassium hydroxide or sodium hydroxide; the particle size of the polyvinyl chloride powder and polyethylene terephthalate powder is 80-200 mesh.

[0014] Furthermore, in step S3, the activation is carried out under a nitrogen atmosphere, with a heating rate of 3-10℃ / min, an activation temperature of 850℃, and an activation time of 2 hours.

[0015] Furthermore, in step S4, the acid solution is a hydrochloric acid solution with a mass fraction of 1-5%, and the drying is vacuum drying at 80°C for 8-12 hours.

[0016] An application of a porous carbon material as described in any of the preceding claims in carbon dioxide capture, wherein the porous carbon material is used as an adsorbent to capture carbon dioxide in flue gas, industrial exhaust gas or the atmosphere; the adsorption temperature is 0-50°C and the adsorption pressure is 0.1-2 bar.

[0017] In summary, the porous carbon materials based on the synergistic activation of PVC and PET, their preparation methods, and applications, as described in this application, offer at least the following beneficial technical effects: 1. This application utilizes coal gasification slag as the primary carbon source, and waste polyvinyl chloride (PVC) and polyethylene terephthalate (PET) as synergistic activators and supplementary carbon sources. By treating waste with waste, it transforms three environmentally burdensome solid wastes into high-value-added products, simultaneously solving the problems of solid waste storage pollution and resource utilization. 2. By employing a process of "acid pickling pretreatment" and "PVC / PET-KOH synergistic activation," a specific surface area of ​​700-950 m² was prepared. 2 / g, porous carbon materials with a microporous-mesoporous hierarchical structure. The HCl gas released during the thermal decomposition of PVC acts as an in-situ gas pore-forming agent, while PET serves as a supplementary carbon source and framework support, facilitating the formation of mesopores. Both, along with KOH chemical activation, synergistically enhance the adsorption affinity between the material and carbon dioxide molecules; 3. Porous carbon materials exhibit a carbon dioxide adsorption capacity greater than 45 at 0℃ and 1 atm. It still performs well at temperatures close to industrial flue gas temperature (25℃), solving the problem that existing adsorbents are effective at low temperatures but fail at room temperature. Attached Figure Description

[0018] Figure 1 The nitrogen adsorption-desorption isotherms and pore size distribution diagrams are shown for the examples and comparative samples.

[0019] Figure 2 Nitrogen adsorption-desorption isotherms and pore size distribution diagrams for samples with different PVC content.

[0020] Figure 3 Scanning electron microscope (SEM) images of samples at different processing stages.

[0021] Figure 4 Scanning electron microscope (SEM) images of samples with different PVC content.

[0022] Figure 5 Raman spectra of samples at different treatment stages.

[0023] Figure 6 The carbon dioxide adsorption isotherms for each sample at 0℃ and 25℃ are shown.

[0024] Figure 7The results are for the carbon dioxide cyclic adsorption performance test of HH-CGFS-2KOH-0.05PVC.

[0025] Figure 8 The X-ray photoelectron spectra of samples at different processing stages are shown in C1s and O1s spectra.

[0026] Figure 9 This is a schematic diagram of a molecular model constructed based on elemental analysis and XPS results.

[0027] Figure 10 This is a comparison between the simulated 13C NMR spectrum of the molecular model and the experimental spectrum.

[0028] Figure 11 The results show the CO2 adsorption capacity of the prepared porous material at 0℃ and 25℃.

[0029] Figure 12 Nitrogen adsorption-desorption and pore size distribution tests were performed on porous materials.

[0030] Figure 13 Cyclic adsorption tests were performed on HH-CGFS-4KOH-PVC. Detailed Implementation

[0031] To facilitate a clear understanding of the technical means, creative features, objectives, and effects of this invention, the invention will be further described below in conjunction with specific embodiments.

[0032] The following is in conjunction with the appendix Figure 1-13 This application will be described in further detail.

[0033] This application discloses porous carbon materials based on the synergistic activation of PVC and PET, their preparation methods, and applications.

[0034] Example 1: Acid washing pretreatment and KOH activation Raw material processing: Weigh 50g of industrial coal gasification fine slag (CGFS, its industrial analysis is shown in Table 1), and add it sequentially to a 20 wt.% hydrochloric acid (HCl) solution and a 40 wt.% hydrofluoric acid (HF) solution at a solid-liquid ratio of 1:10 (g / mL). Stir each solution for 5 hours at 60℃ in a water bath. After the reaction is complete, filter the mixture and wash the filter cake repeatedly with deionized water until the filtrate is neutral. Dry the resulting solid in a 105℃ oven for 12 hours to obtain the acid-washed residue, denoted as HH-CGFS.

[0035] Table 1: Industrial Analysis of Gasification Fine Slag from Industrial Solid Waste

[0036] KOH activation: Dry HH-CGFS and potassium hydroxide (KOH) are mixed evenly at a mass ratio of 1:2. The mixture is placed in a tube furnace and heated to 850°C at a heating rate of 5°C / min under a nitrogen atmosphere, and maintained at this temperature for 2 hours for activation.

[0037] Post-processing: After activation, allow the furnace to cool to room temperature and remove the sample. Add dilute hydrochloric acid (approximately 5% by mass) at a solid-liquid ratio of 1:10 (g / mL) to neutralize the residual alkali. Filter and wash with deionized water until neutral. Place the final product in an 80℃ vacuum drying oven and dry for 10 hours to obtain a porous carbon material, denoted as HH-CGFS-2KOH.

[0038] Characterization: Its specific surface area is 483.34. The pore volume is 0.4469. Its nitrogen adsorption-desorption curve is a mixed type I / IV with an H4-type hysteresis ring. Figure 1 a) indicates the presence of micropores and mesopores ( Figure 1 b). SEM image ( Figure 3 c) This shows that its channel structure has been improved.

[0039] Example 2: Synergistic activation of KOH and PVC Raw material processing: Same as step 1 in Example 1, to obtain pickling residue HH-CGFS.

[0040] Mixing and Activation: HH-CGFS, KOH, and polyvinyl chloride (PVC) powder (approximately 150 mesh) were mixed uniformly at a mass ratio of 1:2:0.05. Subsequent activation and post-treatment steps were the same as steps 2-3 in Example 1. The resulting sample was designated as HH-CGFS-2KOH-0.05PVC.

[0041] Characterization: Its specific surface area was significantly increased to 723.29. The pore volume is 0.5144. The nitrogen adsorption-desorption curve is a type IV (with an H3-type hysteresis ring). Figure 2 a) Aperture distribution ( Figure 2 b) shows a significant increase in the number of micropores and mesopores. SEM image ( Figure 3 d, Figure 4 a) This shows the formation of a richer and more interconnected hierarchical pore structure. The Raman spectral ID / IG value decreased to 1.08 ( Figure 5 (d) indicates an increased degree of graphitization. The carbon dioxide adsorption capacity reaches 47.63 at 0℃ and 1 atm. ( Figure 6 After 10 adsorption-desorption cycles, the adsorption capacity retention rate exceeded 97%. Figure 7XPS analysis showed that the content of oxygen-containing functional groups on its surface was reduced (). Figure 8 e,f). Molecular models were constructed using elemental analysis and XPS (e,f). Figure 9 c), and verified by 13C NMR ( Figure 10 c), whose adsorption energy is calculated to be -15.5 kcal / mol.

[0042] Figure 3 Scanning electron microscopy (SEM) analyses were performed on CGFS, HH-CGFS, HH-CGFS-2KOH, and HH-CGFS-2KOH-0.05PVC, respectively. As shown in the figure, after acid washing, a large amount of alkali metal minerals were removed from the carbon-rich slag, and the remaining residual carbon gradually formed a rich porous system. However, the pore size was too large and prone to collapse, which was not conducive to carbon dioxide adsorption. Through co-alkali activation with the addition of PVC, the pore system was reconstructed by supplementing the carbon source. The macropores further developed, resulting in a smaller overall pore size and an increased number of pores. Combined with pore size analysis, an interconnected hierarchical pore structure was found, with macropores and mesopores providing channels for the rapid diffusion of carbon dioxide gas.

[0043] Figure 4 SEM images of porous adsorbed carbon materials under different PVC co-alkali treatment conditions all show strip-shaped pore structures, which are the result of the synergistic effect of PVC pyrolysis gas expansion and inorganic mineral framework support. With increasing addition, the pore size first increases and then is disrupted, consistent with the pore optimization trend observed in the specific surface area and pore volume data. The coal gasification slag contains inorganic mineral components such as silicates and aluminates, some of which dissolve during acid washing. The remaining mineral framework remains relatively stable at high temperatures, providing rigid support for carbon activation and preventing pore collapse at high temperatures. Simultaneously, stress differences easily form at the interface between the mineral phase and the carbon phase, further promoting the formation and expansion of pores at the interface. KOH, as a strong alkali activator, undergoes the following typical reaction with the carbon matrix at high temperature (850 ℃):

[0044] Potassium metal and its compounds can intercalate between carbon layers and dissolve during subsequent water washing, forming abundant micropores and small-sized mesopores. This process establishes a uniformly distributed initial pore network in the acid-washed gasified slag (HH-CGFS). During heating, PVC undergoes pyrolysis, releasing HCl gas and low-carbon hydrocarbon fragments. These gases generate localized pressure within the carbon matrix, expanding existing channels and forming an interconnected mesoporous-macroporous structure. Due to the uniform mixing of PVC and KOH, the gas release process and the KOH activation reaction overlap in time and space, allowing the newly formed pores to interpenetrate with the existing micropores, forming open channels that permeate the entire structure.

[0045] Molecular models were established for HH-CGFS, HH-CGFS-2KOH, and HH-CGFS-2KOH-0.05PVC, respectively. Due to the extremely low content of other elements in the three samples, only C, H, O, and N were considered when constructing the molecular models. First, the atomic ratios of the elements in the samples were calculated based on the elemental analysis results in Table 2. Combined with XPS fitting of functional group proportions, the chemical formulas of the molecular models were established. Then, Materials Studio software was used to build the molecular models and perform geometric optimization to obtain their three-dimensional molecular models. Finally, the construction of the activated carbon molecular model was repeatedly adjusted and modified to maximize its ability to meet the requirements of various characterization results. Finally, the accuracy of the results was verified by comparing the 13C NMR simulation results with the actual values.

[0046] Table 2: Elemental Analysis of Samples

[0047] Table 3: Characteristics of porous carbon after activation treatment

[0048] Example 3: Effect of different PVC addition amounts The preparation process is the same as in Example 2, except that the amount of PVC added is changed.

[0049] HH-CGFS, KOH, and PVC were mixed in a mass ratio of 1:2:0.1, and the resulting sample was denoted as HH-CGFS-2KOH-0.1PVC. Its specific surface area was 705.25. The pore volume is 0.3871. (Table 4). SEM such as Figure 4 As shown in b.

[0050] HH-CGFS, KOH, and PVC were mixed in a mass ratio of 1:2:0.15, and the resulting sample was denoted as HH-CGFS-2KOH-0.15PVC. Its specific surface area was 684.13. The pore volume is 0.4819. (Table 4). SEM such as Figure 4 As shown in c.

[0051] Data shows that the best effect is achieved when the amount of PVC added is 0.05-0.1 g, and excessive addition may cause partial collapse of the pore structure.

[0052] Table 4: Characteristics of porous carbon after activation treatment

[0053] Example 4: Synergistic activation of KOH and PET Raw material processing: Same as step 1 in Example 1, to obtain pickling residue.

[0054] Mixing and Activation: The pickling residue, KOH, and polyethylene terephthalate (PET) powder (approximately 150 mesh) were mixed evenly at a mass ratio of 1:4:1. Activation was carried out under a nitrogen atmosphere by heating to 850°C at a rate of 5°C / min and holding at that temperature for 2 hours.

[0055] Post-processing: Same as step 3 in Example 1.

[0056] Characterization: The obtained sample was designated HH-CGFS-4KOH-PET. Its specific surface area was 914.28 m². 2 / g, with an average pore size of 3.11 nm and a pore volume of 0.71 (Table 1). The nitrogen adsorption-desorption curve is type IV, with a type H1 hysteresis loop ( Figure 11 This indicates a regular mesoporous structure. The maximum adsorption capacities for carbon dioxide at 0℃ and 25℃ are 47.63 and 47.63, respectively. and 31.28 ( Figure 12 Cyclic adsorption tests showed that it has excellent stability. Figure 13 ).

[0057] KOH, PVC, and PET are synergistically activated. This example demonstrates the synergistic effect of PVC and PET.

[0058] Raw material processing: Same as step 1 in Example 1, to obtain pickling residue.

[0059] Mixing and activation: The pickling residue, KOH, PVC powder, and PET powder are mixed evenly at a mass ratio of 1:4:0.1:1. The activation and post-treatment processes are the same as in Example 4.

[0060] Characterization: The obtained sample combines the advantages of Examples 2 and 4. The pyrolysis gas pore-forming effect of PVC and the synergistic effect of PET, combined with a high KOH ratio, achieve a specific surface area of ​​900-950 m² while maintaining the carbon dioxide adsorption capacity. 2 / g.

[0061] Comparative examples: original and acid-washed samples Raw coal gasification fine slag (CGFS): specific surface area only 152.19 pore volume 0.1909 (Table 3). SEM showed that its structure was dense ( Figure 3 a).

[0062] Acid-washed sample only (HH-CGFS): Specific surface area increased to 281.22. pore volume 0.401 (Table 3). SEM showed the formation of large pores, but the structure was prone to collapse. Figure 3 b). The Raman ID / IG value is 1.14 ( Figure 5 b). Low carbon dioxide adsorption capacity ( Figure 6 ).

[0063] Figure 5 The Raman spectra of different samples are shown. Analysis revealed that the degree of graphitization of the samples changed systematically with each processing step, with the calculated ID / IG values ​​being 1.18, 1.14, 1.09, and 1.08 respectively. Figure 5 As shown in (a), the Raman spectrum of the original gasified slag (CGFS) exhibits typical D and G peaks at 1340 cm⁻¹ and 1580 cm⁻¹, respectively, with a high intensity ratio (ID / IG), indicating that its structure is dominated by disordered carbon and has a low degree of graphitization. The D and G peaks of the sample obtained after acid washing (HHCGFS) show increased intensity, but the ID / IG value does not change significantly, indicating that the acid washing process mainly removes impurities such as ash and has limited impact on the graphitization structure of the carbon framework. Figure 5 As shown in (b).

[0064] Subsequently, the sample treated with KOH (HH-CGFS-2KOH) showed a significant increase in the intensity of the G peak and a marked decrease in the ID / IG value, indicating that the chemical activation of KOH effectively promoted the ordering of graphite microcrystals in carbon materials and reduced structural defects. Figure 5 (c). Further introduce PVC as an auxiliary carbon source for co-activation treatment, such as... Figure 5 The Raman spectrum of sample (d) shows further sharpening of the G peak and a continued decrease in the ID / IG value, indicating that the carbon produced by the decomposition of PVC at high temperature participated in the construction of the graphitized structure, further enhancing the graphitization degree and structural order of the material. Therefore, acid washing pretreatment mainly plays a purification role, while the synergistic activation of KOH and PVC significantly promotes the formation of the graphitized structure of the carbon material, which helps to improve its structural stability and provides a favorable structural basis for its carbon dioxide adsorption.

[0065] Figure 6 The carbon dioxide adsorption isotherms for each sample at atmospheric pressure are shown. At 0 °C and 25 °C, the carbon dioxide adsorption capacities of the samples ranged from 7.53 to 47.63, respectively. and 7.63-31.28 Within the range, the HH-CGFS-2KOH-0.05PVC sample exhibited the highest adsorption capacity, at 47.63 g / mL. (0℃) and 23.65 (25℃), compared to the original carbon-rich slag, the efficiency was increased by 40.1%. and 23.75 The results showed that the carbon dioxide adsorption capacity of samples treated only by acid washing was only slightly improved; however, after alkali activation, the adsorption capacity was significantly enhanced compared to the fine slag, and the addition of PVC further increased the adsorption capacity even more significantly. The HH-CGFS-2KOH-0.05PVC sample exhibited the best carbon dioxide adsorption performance among all samples; however, when PVC was added in excess, such as in the HH-CGFS-2KOH-0.15PVC sample, its adsorption capacity decreased significantly. The addition of PVC is equivalent to introducing an additional gas template and carbon source into the activation system. Through the synergistic effect of its thermally decomposed gas and KOH, it significantly enhances pore development and expansion, thereby increasing the specific surface area and pore volume. Excessive PVC may lead to partial pore collapse or blockage; therefore, the optimal PVC content is achieved at a ratio of 0.05–0.1 g.

[0066] Figure 7 After 10 cycles of adsorption, the amount of carbon dioxide adsorbed showed almost no significant decrease, and the carbon dioxide desorption efficiency was also high. The results also indicate that the adsorption of carbon dioxide on this adsorbent material is reversible, and it exhibits high stability and regenerability during the adsorption process, making it highly promising for practical applications of carbon dioxide adsorption.

[0067] Figure 8 To fit the XPS spectrum to a curve, such as Figure 8 As shown, the C1s spectrum of the acid-washed sample (HH-CGFS) is... Figure 8 a) It can be fitted with characteristic peaks such as C=C, CO, and C=O / OC=O, indicating that there are a certain amount of oxygen-containing functional groups on its surface. The corresponding O 1s spectrum ( Figure 8 b) This further confirmed the presence of oxygen-containing structures such as CO and C=O, consistent with the C1s analysis results. After activation with KOH (HH-CGFS-2KOH), its C1s spectrum ( Figure 8 In (c), the relative intensity of the sp2 C=C peak is significantly enhanced, while the peak intensity corresponding to oxygen-containing functional groups is significantly weakened, indicating that KOH activation at high temperatures effectively promotes the graphitization of the carbon structure and partially reduces the surface oxygen-containing groups. Meanwhile, the O1s spectrum ( Figure 8 The proportion of the corresponding oxygen-containing components in d) also decreased. When PVC was further introduced for co-activation (HH-CGFS-2KOH-0.05PVC), the C1s spectrum ( Figure 8 (e) shows that the sp2 C=C peak continues to dominate, and the signal of oxygen-containing functional groups is further reduced, indicating that the addition of PVC provides an additional carbon source, promotes the formation of a more complete carbon skeleton during activation, and further reduces the surface oxidation state. The corresponding O 1s spectrum ( Figure 8The content of oxygen species bonded to carbon in f) also decreased accordingly, consistent with the trend of C 1s. During the treatment process from acid washing and KOH activation to KOH / PVC co-activation, the chemical state of the material underwent a systematic evolution: oxygen-containing functional groups gradually decreased, and the graphitized sp2 carbon structure was significantly enhanced. This trend is consistent with the increased degree of graphitization reflected in Raman spectroscopy, jointly indicating that the synergistic activation effect of KOH and PVC effectively optimized the surface chemical properties of the carbon material and improved its adsorption capacity.

[0068] Carbon atoms constitute the main macromolecular framework of porous carbon, with other groups connected to the carbon atom framework in different ways. Based on XPS results, the proportions of different types of carbon atoms (aliphatic carbon, aromatic carbon, etc.) and oxygen atoms are calculated. Molecular models are then built using Materials Studio (MS) software based on the atomic and functional group ratios. Figure 9 As shown, the molecular formulas of the HH-CGFS, HH-CGFS-2KOH, and HH-CGFS-2KOH-0.05PVC samples are C200H17O6N, C90H9O3N, and C361H30O29N, respectively. After activation, the number of oxygen-containing functional groups (such as CO and C=O) on the material surface is significantly reduced, while the proportion of graphitized carbon is greatly increased. This enhances the hydrophobic properties of the adsorbent material, allowing the hydrophobic surface to interact more effectively with the adsorbate through van der Waals forces, thereby increasing the adsorption capacity. The reduction of oxygen-containing functional groups lowers the chemical instability of the material under acidic or oxidizing environments. The graphitized carbon-based surface, with its higher chemical stability, is less prone to structural degradation or functional group loss during repeated adsorption-desorption cycles, helping to maintain long-term adsorption performance and improve the cycle life of the material. The increased proportion of graphitized sp2 carbon signifies an enhancement of the delocalized π-electron system in the material. Simultaneously, the abundant π-electron system also enhances the polarized adsorption of carbon dioxide. The process from acid washing to KOH / PVC activation involves controlling the surface chemistry to transform it from "rich in oxygen-containing functional groups" to "highly graphitized and low in oxygen content," which endows the final porous carbon material with properties such as high hydrophobicity, a strong π-electron system, and excellent chemical stability. These properties enhance the adsorption of carbon dioxide and its adsorption stability.

[0069] like Figure 10As shown, the comparison results show that the 13C NMR peak of the constructed sample macromolecular model is basically consistent with the experiment, and it can well reflect the macromolecular structure of the prepared porous carbon. The density functional theory (DFT) calculation was performed using the DMol 3 module in Material Studio 2020. The Perdew-Burke-Ernzerhof (PBE) function in the generalized gradient approximation (GGA) method was used to describe the interaction between the core electron and the valence electron. All calculations included spin polarization and DFT half-core pseudopotential. For the adsorption process, van der Waals forces are crucial, so the Tkatchenko-Scheffler (TS) method was used for DFT-D correction. The basis set was selected as the dual numerical polarization (DNP) function. The convergence criteria for force and energy were set to 0.002 Hartley / Å and 10-5 Hartley, respectively. After optimization, the binding energy (ΔE, kcal / mol) of carbon dioxide adsorbed by the material was calculated by formula (2):

[0070] in It is about optimizing the system's energy. It is the energy of the material. This refers to the energy of carbon dioxide. The adsorption energy of different samples was evaluated using density functional theory calculations, and the results are shown in Table 5.

[0071] Table 5: Adsorption energies calculated by DFT for different samples

[0072] The carbon dioxide adsorption energy of the acid-washed sample (HH-CGFS) was -8.4 kcal / mol, indicating that the adsorption between its surface and carbon dioxide was mainly due to weak physical adsorption. After KOH activation, the adsorption energy of the sample (HH-CGFS-2KOH) significantly increased to -13.6 kcal / mol. This was mainly attributed to the fact that the KOH activation process greatly increased the specific surface area and micropore volume of the material, while the increased degree of surface graphitization and the electron-rich π system formed enhanced the polarization of carbon dioxide, thereby strengthening the adsorption affinity. Further introduction of PVC for synergistic activation (HH-CGFS-2KOH-0.05PVC) further increased the adsorption energy to -15.5 kcal / mol, reaching the highest value among the three. This enhancement can be attributed to PVC acting as an external carbon source, promoting the formation of a more developed hierarchical pore structure and optimizing the surface electron distribution during the high-temperature activation process. XPS analysis revealed that the sample surface exhibited a higher sp2 carbon ratio and a lower content of oxygen-containing functional groups. This highly graphitized and hydrophobic surface facilitated interaction with carbon dioxide molecules through enhanced dispersion forces. The adsorption energy order HH-CGFS-2KOH-0.05PVC>HH-CGFS-2KOH>HH-CGFS indicates that KOH activation effectively enhanced the carbon dioxide adsorption strength, while the introduction of PVC further optimized the pore structure and surface properties through a synergistic effect, thus achieving the strongest adsorption force.

[0073] like Figure 11 As shown, Performance comparison and application verification The carbon dioxide adsorption performance of the samples from Examples 1-4 and the comparative examples was tested. Figure 6 , Figure 12 The results showed that simple pickling or KOH activation had limited effect on performance improvement. The introduction of PVC (Example 2), through the HCl gas released during its thermal decomposition, served as a pore-forming agent and supplemented the carbon source, significantly increasing the number of micropores and mesopores, as well as the carbon dioxide adsorption capacity. The introduction of PET (Example 4), with a high KOH ratio, achieved a higher specific surface area and pore volume.

[0074] The core of this invention is the synergistic activation of PVC and PET. Through the complementary effects of the two plastics in pyrolysis behavior, products and surface chemical regulation, and the synergistic effect with KOH activation, porous carbon materials with ultra-high specific surface area, ideal hierarchical pore structure and excellent surface chemical properties can be controllably prepared, thereby obtaining high carbon dioxide capture performance.

[0075] Porous carbon materials can be used as adsorbents and filled into fixed-bed or fluidized-bed adsorption devices to capture carbon dioxide in scenarios such as power plant flue gas (temperature about 50-150℃), cement plant tail gas, or direct air capture (ambient temperature). They can work effectively in the range of atmospheric pressure (0.1 MPa) to low pressure (0.2 MPa).

[0076] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A porous carbon material based on the synergistic activation of PVC and PET, characterized in that, The porous carbon material is prepared using coal gasification slag as the carbon source, and polyvinyl chloride and polyethylene terephthalate as synergistic activators and supplementary carbon sources, through acid washing pretreatment and alkali co-activation processes. The porous carbon material has a hierarchical pore structure and a specific surface area of ​​700-950 nm. The pore volume is 0.45-0.

75. The carbon dioxide adsorption capacity at 0℃ and 1 standard atmosphere is greater than 45. .

2. The porous carbon material based on the synergistic activation of PVC and PET according to claim 1, characterized in that, The hierarchical pore structure includes micropores and mesopores, with micropore diameters less than 2 nm and mesopore diameters ranging from 2 to 50 nm; the Raman spectral ID / IG value of the porous carbon material is less than 1.10, and the surface oxygen-containing functional group content measured by X-ray photoelectron spectroscopy is less than 5 at.

3. The porous carbon material based on the synergistic activation of PVC and PET according to claim 1, characterized in that, After 10 carbon dioxide adsorption-desorption cycles, the porous carbon material retains an adsorption capacity of no less than 97%.

4. A method for preparing a porous carbon material as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Mix the coal gasification fine slag with the acid solution, react at 50-70℃ for 4-6 hours, filter, wash until neutral, and dry to obtain the pickling slag; S2. Mixing and Batching: Mix the pickling residue, alkali activator, polyvinyl chloride powder and polyethylene terephthalate powder evenly at a mass ratio of 1:(2-4):(0.05-0.2):(0.5-1.5); S3. Activate the mixture in an inert atmosphere at 800-900℃ for 1-3 hours; S4. Neutralize the activated product with an acid solution, wash until neutral, and dry to obtain the porous carbon material.

5. The preparation method according to claim 4, characterized in that, In step S1, the acid solution is a hydrochloric acid solution and a hydrofluoric acid solution. The acid washing pretreatment includes: first, mixing the coal gasification fine slag with a 20% hydrochloric acid solution at a solid-liquid ratio of 1:8-12, and then mixing the solid with a 40% hydrofluoric acid solution at the same solid-liquid ratio.

6. The preparation method according to claim 4, characterized in that, In step S2, the mass ratio of the pickling residue, alkali activator, polyvinyl chloride and polyethylene terephthalate is 1:2:0.05:1 or 1:4:0.1:

1.

7. The preparation method according to claim 4, characterized in that, In step S2, the alkali activator is potassium hydroxide or sodium hydroxide; the particle size of the polyvinyl chloride powder and polyethylene terephthalate powder is 80-200 mesh.

8. The preparation method according to claim 4, characterized in that, In step S3, the activation is carried out under a nitrogen atmosphere, with a heating rate of 3-10℃ / min, an activation temperature of 850℃, and an activation time of 2 hours.

9. The preparation method according to claim 4, characterized in that, In step S4, the acid solution is a hydrochloric acid solution with a mass fraction of 1-5%, and the drying is vacuum drying at 80°C for 8-12 hours.

10. An application of a porous carbon material as described in any one of claims 1-3 in carbon dioxide capture, wherein the porous carbon material is used as an adsorbent to capture carbon dioxide in flue gas, industrial exhaust gas or the atmosphere; the adsorption temperature is 0-50°C and the adsorption pressure is 0.1-2 bar.

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